SP30

NATIONAL ELECTRICAL CODE

BUREAU OF IND IAN STANDARDSMANAK BHAVAN. 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

SP 30:1984

First Published August 1985

First Reprint April 1990

Second Reprint September 1992

Third Reprint September 1993

Fourth Reprint November 1998

0 BUREAU OF INDIAN STANDARDS

UDC 621.3 : 006.78

The National Electrical Code was adopted by the Bureau of Indian Standards(then Indian Standards Institution) on 15 June 1984, after the draft finalized bythe National Electrical Code Sectional Committee had been approved byElectrotechnical Division Council

PRICE Rs 600.00

Printed in India at Central Electric Press, A-12/1, Naraina Industrial Area, Phase-l,New Delhi 110028 and Published by the Bureau of Indian Standards, New Delhi 110002.

INTRODUCTION

Development programmes are interwoven to a large extent with electricalenergy. Realizing the need for harnessing this most useful form of energyavailable, a great amount of emphasis is being laid on the implementation ofthe programmes for electrical power generation and a substantial portion ofthe national budget is being allotted for the purpose. The main feature of thiseffort is to plan for and execute the economic selection, installation andmaintenance of electrical equipment employed in the generation, transmission,distribution and utilization of electric power.

The design and practices being followed by the various agencies engaged inthis type of activity could be rationalized in the light of newer equipment andprocesses. to remove any extraneous safety and other factors. Realizing theneed for standardizing the requirements of the various Electricity Boards andother bodies; the Electrotechnical Division Council under the Code ofPractice for Power Installation and Maintenance Sectional Committee hasbeen formulating Indian Standard Codes of practice on the various aspects ofhandling the power equipment. These codes have been revised from time totime to align wtth the latest technology made available as well as toincorporate the experience gained in the implementation of these codes.

However, time and again the need has been felt for a cogent Electrical Codecovering unified practices and procedures and safety requirements to becomplied with in the design, execution, inspection and maintenance ofelectrical installation in different locations. The lndiun E/ecrrici;.v Rules, 1956contain specific regulations to be adhered to in the supply and use of electricalenergy in the interest of safety. Nevertheless, there are several areas whichneed amplification and complementing. The National Electrical Code isformulated primarily to elaborate the Indian Electricity Rules which arestatutory in nature and serve as a comprehensive document an electricalpractices in our country.

The task of the preparation of the Code is entrusted with the NationalElectrical Code (NEC) Sectional Committee (ETDC 56). This guidingcommittee and the expert groups under the same have a broad basedrepresentation from central and state government organizations, privatebodies and professional institutions having wide experience in the field ofelectrotechnology, particularly in the field of installation engineering.

The object of the National Electrical Code (NEC) is given below :

The object of the National Electrical Code is to complement the lndiunE/ectricif~v Rules,. 1956 by way of elaborating as well as recommendingpractices to comply with their requirements. This code is to provideinformation in a consolidated form to electrical engineers and contractors inthe country who are concerned with the design and operation of electricalinstallations.

The presentation of information in the Code has been broadly organized inthe following manner :

Part I General and Common Aspects

Part 2 Electrical Installation in Standby Generating Stations andSub-stations.

Part 3 Electrical Installations in Non-Industrial Buildings

Part 4 Electrical Installations in Industrial Buildings

Part 5 Outdoor Installations

Part 6 Electrical Installations in Agricultural Premises

Part 7 Electrical Installations in Hazardous Areas.

The National Electrical Code Sectional Committee (ETDC 56) has decidedupon the above format as best suited for a compendium like this afterconsiderable deliberations, as it presents a method of identifying informationthat is classified on the basis of type of occupancy, a method considered bestmeeting the needs of practising engineers.

The information relating to each type of installation identified above isfurther classified and presented in the following manner :

a) Assessment of the general characteristics of the occupancy from thepoint of view of the electrical installation therein.

b) Heavy current installation in the occupancy :

1)2)3)

4)

5)

6)7)

Power supply and distribution system,

Cables and accessories for power circuit.

Protective equipment,

Metering of consumption,

Emergency electric supply,

Reactive power compensation as applicable, and

Guidance on electrical aspects of building services (lighting,air-conditioning and lifts).

c) Light current installation in the occupancy :

1) Electric bells and clock systems,

2) Electrical audio systems. and

3) Fire protection signalling systems.

d) Specific requirements for protection and safety.

It should be brought out, however, that the approach of the NationalElectrical Code has been primarily to cater to system engineers. Individualproduct codes are available on specific power equipment for the use ofproduct application engineer. In the preparation of NEC, the efforts ofproduct groups had been taken into account while consolidating t;heinformation in a handbook form.

The Code, though elaborate, excludes requirements coming under thepurview of utilities, namely, the large generating stations and distribution sub-stations. Considering the variety of practices being followed by the ElectricityBoards and the need to collect data on the same, it had been felt that at thisstage, such installations should be -excluded from the scope of the Code.Product details are also excluded from the compilation work for the timebeing. The Code also does not cover electrical installations in undergroundmines.

Users of IVEC, who are also familiar with the National Building Code ofIndia 1983, would find that a one-to-one correspondence does not existbetween the building classification made in them. The NBC classification 01buildings/occupancies is based on fire-safety considerations and, NEC, whileclosely following the same, adogts a modified approach to this classificationtaking into account the following broad guidelines :

a) The classification of electrical installations should take into accountthe skill and capabilities of the occupants utilizing the installation; and

b) Further classification should be based on the degree of sophisticationof the electrical requirements of the building, rather than the occupancy.

The NEC is basically a compilation document taking assistance fromdetailed codes already available, and does not constitute fundamentalstandardization work. To a limited extent, however, efforts have been made tofill certain gaps in consultation with the relevant Technical Committees of ISI.

The compilation work\ such as the one envisaged for the National ElectricalCode. apart from the fact that all the required information may not be

vi

available in a ready format, is made difficult by the need to make a judiciouschoice of what is to be reproduced in the Code and what is to be referred to inthe parent standard. On the one hand is the need to make the Code self-contained as a reference document and on the qther hand is the need to keepit less voluminous. The individual parts of the Code. which deal with specificoccupancies, should also preferably be self-contained to the extent possible,without calling for too many references to Part I dealing with general andcommon aspects.

It had been possible, therefore, in many instances, to only draw attention tothe relevant standard, while in others the relevant provisions have beenextracted and reproduced. In all cases, for detailed guidance, reference shouldbe made to the individual standard and should any contradiction be observedbetween the provisions in individual code and those reproduced herein. theprovisions of the former shall be considered accurate.. As a general rule,technological innovations such .as better materials or new and better methodalso proved as ‘good practice’ would first be introduced in the individualstandard as appropriate than in the National Electrical Code. In order to keeppace with such changes and to incorporate the additional knowledge that willbe gained through the implementation of the Code, a continuous programmeof review is envisaged. A complete revision of the Code is also intended in duecourse of time.

The National Electrical Code (hereafter referred to as the Code) is intendedto be advisory. It contains guidelines, which framed in unison with thestatutory provisions of IE Rules 1956, can be immedia,tely adopted for use bythe various interests concerned; with minimum elaboration for their specificpurpose. Its provisions will not be mandatory but will serve as a model foradoption in the interest of safety and economy.

vii

ACKNOWLEDGEMENTS

The contributions made by the following individuals/groups and their organizationsin respect of the part/sections of the National Electrical Code prepared in collaboration with themare greatly acknowledged.

Member Organization

Electrical Contractors Asso-ciation of Maharashtra,Bombay

Siemens India Ltd, Bombay

Chief Electrical Engineer toGovernment of Maharashtra,Bombay

Fact Engineering & DesignOrganization, Udyogamandal

Central Public Works Depart-ment, New .Delhi

Part/Section of NEC

1. Shri D. N. Purandare

Shri V. S. Bhatia

Shri M: A. Khan.

Shri K. P. R. Pillai

2. Chief Engineer (Elect)-1

3. Shri D. N. Purandare Electrical Contractors Asso-ciation of Maharashtra,Bombay

4. Shri M. J. Anandamurthv Chief Electrical Insnector.

5. Shri M. L. Dongre

6. Shri V. S. Bhatia

Shri A. N. Dutt

Shri A. Chatterjee

7. Shri G. N. Thadani

8. Chief Engineer (Elect)-1

Government of Ta’mil Nadu,Madras

Bombay Electric Supply &Transport Undertaking,Bombay


Electrical Contractors Asso-ciation of Eastern India,Calcutta

Part II Electrical Installationsin Standby Generating Stationsand Captive Substations

Part 111 Electrical Installationsin Non-industrial Buildin s : )Section I Domestic f.Dwe lmgs

Part 111 Electrical Installations inNon-industrial Buildings : Sec-tion 2 Office Buildings, Shop-ping and Commercial Centresand Institutions

Part 111 Electrical Installations inNon-industrial Buildings : Sec-tion 3 Recreational, Assembl;Buildings

Part I I1 Electrical Installations inNon-industrial Buildings : Sec-tion 4 Medical Establish-ments Section 5 Hotels

Part V Outdoor InstallationsSection 1 Public Lighting Ins-tallations and Section 2 Tem-porary Outdoor Installations

Part IV Electrical Installationsin Industrial Buildings

General Insurance Corporationof India, Bombay

Engineers India Ltd, New Part VII Electrical InstallationsDelhi in Hazardous Areas

Central Public Works -Depart- Appendix to Part III Specificment, New Delhi Requirements for Electrical

Installations in MultistoreyedBuildings.

Shri M. J.

Electrical

Shri V. G.

NATIONAL ELECTRICAL CODESECTIONAL COMMITTEE, ETDC 56

C-214

Members

Anandamurthy

ChairmanShri M. L. Dongre

Casuarina Cooperating Housing SocietyBest Nagar, Ghatkopar East

Bombay.

Representing

Chief Electrical Inspector, Governmentof Tamil Nadu, Madras

Inspector (Technical)(Alternate)

Bapat

Shri K. S. Joshi (Alternate)Shri V. S. Bhatia

Shri M. M. Shethna (Alternate)Shri ‘D. K. Biswas

Chief Engineer (Elect)-1

Surveyor of Works (Elect)-1(Ahernate)

Shri P. J. DamanyShri J. H. Pate1 (A/female)

Shri K. Dasgupta

Shri P. Neogi (AIternare)Director of Mines Safety, Dhanbad

Director of Mines Safety, Sitapur(A Iternate) ’

Shri A. N. Dutt

Shri Abani Dutta (Alternate)Shri G. L. Dua

Shri S. K. Sethi (Ahernafe)Deputy Chief Electrical Engineer (G)

Shri K. C. GuptaShri N. Raghavan (Alternate)

Brig L. G. Ketkar

Lt-Co1 G. R. Mahadevan(Alternate)

Shri M. A. Khan

Superintending Engineer(inspection) (AIternafe)

Shri S. K. Kundu

Shri S. R. Chakrabarty (Alfernare)

Federation of Electricity Undertakings ofIndia, Bombay


Department of Science and Technology(National Committee on EnvironmentalPlanning and Coordination),New Delhi

Central Public Works Department, New Delhi

Gujarat Electricity Board, Vadodara

Calcutta Electric Supply CorporationCalcutta

Directorate General of Mines Safety,

Electrical Contractors Association ofEastern India, Calcutta

Ltd,

Dhanbad

Rural Electrification Corporation Ltd, New Delhi

Railway Board, Ministry of Railways New Delhi

h’ational Safety Council, Bombay

Directorate General of Inspection,Ministry of Defence, New Delhi

Chief Electrical Engineer to Governmentof Maharashtra, Bombay

Chief Electrical Inspector to Governmentof West Bengal, Calcutta

Shri S. V. Madgavkar

Shri R. K. Sehgal (Ahcw7ate)

Shri B. S. Landalika

Shri H. R. Khan (Alternate)Shri K. K. Mondal

Shri I. N. Khushu (A/female)Member (Hydroelectric)

Director (H ED)-1 (AIIei’nare)Shri M. Muniram

Shri S. N. Narasinga Rao

Shri M. Ramatar (Alternate)Shri V. H. Navkal

Shr i M. R . Iv. Menon (Ahernure)Dr G. M. Phadke

Shri K. P. R. Pillai

Shri D: N. Purandare

Shri S. S. Jhaveri (Ahernute)Shri T. RamachandranShri B. M. ReddyShri T. V. Shankaranarayana

Shri V. Venkateshaiah (Alternate)Shri P. D. Sharma

Shri S. C. Jain (Alternate)Shri G. N. Thadani

Shri S. G. Gokhale (Alrernure)

Representative

Shri S. Govindaraj (Alternate 1)Shri A. S. R. Sastry (Ahernure II)

Shri S. P. Sachdev,Director (Elec tech)

Bombay Suburban Electric Supply Ltd,Bombay

Armv Headouarters. Ministry of Defence,h’ew Delhi.

General InsuranceBombay

Central Electricity

Corporation of India,

Authority, New Delhi

Karnataka Electricity Board,Bangalore

Power Project Engineering Division,Department of Atomic Energy, Bombay

The Bombay Electric Supply andTransport Undertaking, Bombay

Indian Electrical Manufacturers’Association, Bombay

Fact Engineering & Design Organization,Udyogamandal

Electrical Contractors Associations ofMaharashtra, Bombay

Planning Commission, New DelhiCentral Electricity Authority, New DelhiChief Electrical Inspector to

Government of Karanataka, Bangalore

Delhi Electric Supply Undertaing, New- Delhi

Engineers India Ltd, b!ew Delhi

Bharat Heavy Electricals Ltd, Hyderabad

Director General, IS1 (Ex-officio Member)

SecretaryShri K. Ganesh

Deputy Director (Elec tech), ISI

CONTENTS

INTRODUCTION

PART I GENERAL AND COMMON ASPECTS

0. Foreword

SECTION I SCOPE OF THE NATIONAL ELECTRICAL CODE

SECTION 2 DEFINITIONS

0.1.2.3.

SECTION 3

0.I.2.3.4.

SECTION 4

0.I.2.

Foreword 5Scope 5Definitions 5List of Indian Standards on ElectrotechnicalVocabulary IO

GRAPHICAL SYMBOLS FOR DIAGRAMS,LETTER SYMBOLS AND SIGNS

ForewordS c o p eGraphical SymbolsList of Indian Standards on Graphical SymbolsLetter Symbols and signs

GUIDE FOR PREPARATION OF DIAGRAMS,CHARTS AND TABLES, AND MARKING

ForewordScopePreparation of Diagrams, Charts and Tables

202020

SECTION 5 UNITS AND SYSTEMS OF MEASUREMENT

0. ForewordI. Scope2. Units and Systems of Measurement

SECTION 6 STANDARD VALUES

0. ForewordI. Scope2. Standard Values of voltages3. Preferred Current Ratings4. Standard System Frequency

SECTION 7 FUNDAMENTAL PRINCIPLES

0.I.2.3.

SECTION 8

0.

Foreword 28Scope 28Fundamental Principles 28Design of Electrical Installation 29

ASSESSMENT OF GENERALCHARACTERISTICS OF BUILDINGS

Foreword 32

3

4

242424

2626262727

I. S c o p e2. Assessment of General Characteristics of Buildings

APPENDIX A Types of System Earthing

SECTlOh’ 9 SELECTION OF EQUIPMENT

0. Foreword1. Scope2. Selection of Equip ment

SECTlOh’ 10 ERECTIOh’ AND INITIAL TESTING OFINSTALLATION

0. ForewordI. Scope2. Erection3. Inspection and Testing

SECTION I I WIRING INSTALLATIONS

0. ForewordI. Scope2. Equipment, Fittings and Accessories3. Construction4. Methods of Internal Wiring

SECTlOT’! I2 E A R T H I N G

0. ForewordI. Scope2. General Remarks3. Earth Electrodes4. Earth Bus and Earth Wires5. Measurement of Earth Electrode Resistance6. Earthing of Installations in Buildings7. Measurement of Earth Loop ,Impedance

APPENDI’X A Representative Values of Soil Resistivity inVarious Parts of India

APPENDIX B Additional Rules for Earthing

323238

404040

41414141

4646464851

5757575962636364

6566

SECTION I3 SHORT-CIRCUIT CALCULATIONS

( Under Consideration) 69

SECTION I4 ELECTRICAL ASPECTS OF BUILDING SERVICES

0. Foreword 71I. S c o p e 712. General Guidelines 71

SECTION l4A LIGHTING

3. Aspects of Lighting Services 71

SECTION l4B VENTILATION

4. Aspects of Ventilation 72

SECTION l4C AIR-CONDITIONING AND HEATING

5. Aspects of Air-Conditioning and Heating Services 72

SECTION l4D LIFTS AND ESCALATORS

‘6. Electrical Aspects of Lifts and Escalator Services 73

xii

SECTION 14E AUDIO SYSTEMS

7. Electrical Aspects of Audio System Services

SECTION 14F FIRE ALARM SYS-lEMS

8. Electrical Aspects of Fire Alarm Systems

SECTION l4G MISCELLANEOUS SERVICES

75

77

9. Electrical Call Bell Services 78IO. Clock Systems 79

SECTION I5 LIGHTNING PROTECTION

0. Foreword 81I. Scope 812. Terminology 813. Exchange of Information 814. Characteristices of Lightning Discharges 825. Determination of the Need for Protection 826. Zone of Protection 837. Materials and Dimensions 838. Design 839. Isolation and Bonding 86

IO. Protection of Special Structures 87I I. Inspection and Testing 87

SECTION I6 SAFETY IN ELECTRICAL WORK

0. Foreword 88I. Scope 882. Permit-to-work System 883. Safety Instructions 884. Safety Practices 915. Safety Posters 916. Accidents and Treatment for Electric Shock 91

SECTION I7 GUIDELINES FOR POWER-FACTOR IMPROVEMENT

0. ForewordI. Scope2. General3. Power Factor4. Use of Capacitors5. Power Factor Improvement and Capacitor Rating

SECTION I8 TABLES

929292929394

0. Foreword 95

PART 2 ELECTRICAL INSTALLATIONS -IN STANDBYGENERATING STATIONS AND CAPATIVE

SUBSTATIONS

0. Foreword IO1I. Scope 1022. Terminology 1023. General Characteristics of Station installation 1024: Exchange of Information 1025. Layout and Building Construction Aspects 1026. Selection of Equipment 102

. . .XIII

7.8.9.

IO.I I.12.13.14.15.16.17.

PART

Generating Sets 102Transformer Installations 103High Voltage Switching Stations 103Low Voltage Switching Stations and Distribution Panels 103Station Auxiliaries 103Wiring in Station Premises 104Earthing 104Building Services 104Fire Safety Requirements 104Lightning Protection 104Testing and Inspection 104

3 ELECTRICAL INSTALLATIONS IN NON-INDUSTRIAL BUILDINGS

0. Foreword 107

SECTION 1 DOMESTIC DWELLINGS

0. Foreword I08I. Scope I082. Terminology I083. Classification I084. General Characteristics of- Installation I085. Supply Characteristics and 1 Parameters 1096. Switchgear for Control and Protection I IO7. Service Lines I l l8. Metering Ill9. Earthing in Domestic Installations II I

IO. Building Services II2I I. Fire Protection II312. Testing of Installation 11313. Miscellaneous Provisions II3

APPENDIX A Particular Requirements for Locations Containinga Bath Tub or Shower Basin II3

SECTlOIS 2 OFFICE BUILDINGS, SHOPPING AND COMMERCIALCENTRES AND 1NSTITUTIOtiS

Q. Foreword 117I. S c o p e II72. Terminology II73. Classification II74. General Characteristics of Installations II75. Supply Characteristics and Parameters II86. Testing of Installation 1217. Miscellaneous Provisions I21

SECTION 3 RECREATIONAL, ASSEMBLY BUILDINGS

0.I.2.3.4.5.6. .7.

Foreword 123Scope 123Terminology 123Classification 123General Characteristics of Installations 123Supply Characteristics and Parameters 124Testing of Installation 126Miscellaneous Provisions 126

xiv

SECTION 4 M,EDICAL ESTABLISHMENTS

0. ForewordI. Scope2. Terminology3. Classification4. General Characteristics of Medical Establishments5. Safety Considerations6. Supply Characteristics and Parameters7. Additional Requirements for Hazardous

Locations in Hospitals8. Building Services9. Testing of Installation

IO. Standby and Special Safety Supply SystemI I. Measures against Interference Provision12. Miscellaneous Provisions

APPENDIX A Zones of Risk in the Operating Theatre WhenUsing Flammable Anaesthetic Mixtures ofAnesthetic Gases and Cleaning Agents

APPENDIX B Patient EnvironmentAPPENDIX C Example of an Electrical Installation in a

Medical EstablishmentAPPENDIX D Schematic Representation of Protective Conductors

and Equipotential Bonding in Operating TheatersAPPENDIX E Safety Supply SystemsAPPENDIX F Safety Supply System of a Hospital (Example)

127127126129129130131

138139140140141142

144145

146

147148151

SECTION 5 HOTELS

0. ForewordI. Scope2. Terminology3. Classification4. General Characteristics of Installation5. Supply Characteristics and Parameters6. Testing of Installation7. Miscellaneous Provisions

APPENDIX A Particular Requirements for Swimming Pools

152152152152152153155155156

SECTlOh’ 6 SPORTS BUILDINGS

0. ForewordI. Scope2. Terminology3. Classification of Sports Buildings4. General Characteristics of Sports Buildings5. Supply Characteristics and Parameters6. Testing of Installation7. Miscellaneous Provisions

APPENDIX TO PART 3 Specific Requirements for ElectricalInstallations in Multi-Storeyed Buildings

159-1.59159159160160163163

164

PART 4 ELECTRICAL lNSTALLATlONS ININDUSTRIAL BUILDINGS

0. Foreword 171I . Scope 172

XV

2. Terminology3. Classification of industrial Buildings4. General Characteristics of Industrial Buildings5. Supply Characteristics and Parameters6. Emergency] Standby Power Supplies7. System Protection8. Building Services9. Miscellaneous/ Special Provisions

APPENDIX A Examples of Industries Based on Fire SafetyAPPElVDlX B Selection of Wiring SystemsAPPENDIX C Requirements for Fire Safety in Specific IndustriesAPPElVDlX D Recommended Values of Illumination and Limiting

Values of Glare Index-Industrial BuildingsAPPENDIX E Power Factor in Industrial Installations

PART 5 OUTDOOR INSTALLATIONS

0. Foreword

SECTION I PUBLIC L.IGHTING INSTALLATIONS

0. Foreword‘I. Scope2. Terminology3. Classification4. General Principles5. Designs6. Selection of Equipment7. Guidelines for Specific Location8. Power Installation Requirements9. Miscellaneous Considerations

APPEFDIX A Terminology of Road Types

SECTION 2 TEMPORARY OUTDOOR INSTALLATIONS

0.. ForewordI. Scope2. Terminology3. Classification4. General Characteristics of Temporary Installations5. General Requirements for Temporary Outdoor

Installations6. Additional Requirements for Temporary Outdoor

Installations7. Protection and Safety8. Testing dnd Commissioning

SECTION 3 OUTDOOR INSTALLATIONS

0. ForewordSECTION 3A GENERAL

I. Scope2. Terminology3. Types of Permanent Outdoor lnstallatiops4. General Characteristics of Permanent Outdoor

Installations

SECTION 3B EQUIPMENT AND AUXILIARIES

5. Rules for Equipment and Auxiliaries

\vi

172172173174I78I78I79I 791801x1183

184I91

I95

196196196I98I98199207209210212215

216216216216216

217

2172192:3

220

220220221

222

222

WC t tOS 3C‘ PRO It-C 1 t’OS t - O R SAF-E’IY

h. (iencral Rulc~ lor Protect ion in Outdoor Instal lat ion

S1IC.t IO?. 31) RPQ\IIREMt:N t S FO!i INS-I-At.l.A’l‘IONS

7. Requirement\ for Permanent Outdoor Installations

StICTtON ?tJ AI)t)t-I’IONAL GUIDEL INES FOR SPECIF ICAREAS

8. Additional Guidelines for Installations in Specific Areas

PART 6 ELECTRICAL 1NSTALLATlONS 1NAGRICULTURAL PR.EMlSES

0. Foreword 235I. scope 2362. Terminology 2363. Classification 2364. General Characteristics of Agricultural Premises 2365. Supply Characteristics and Parameters 2376. Services in Agricultural Premises 2397. Testing of Installation 2398. Miscellaneous Provisions 239

PART 7 ELECTRlCAL INSTALLATIONS INHAZARDOUS AREAS

0. ForewordI. Scope2. Terminotogy3. Statutory Regulations4. Fundamental Concepts5. Classification of Hazardous Areas6. Specific Guidelines for Electrical Installations in

Ha;rardous Areas7. Testing of Installation

APPENDIX A Indian Standards for Electrical Equipment for Usein Hazardous Atmospheres

APPENDtX B Recommendations for the Protection of DieselEngines for Permanent Installation in HajrardousAreas

APPENDIX C Recommendations for Storage Batteries for Usein Zone 2 Areas

APPENDIX D Examples of Industries and their Working Placeswhich Require Considerations in Regard toHazardous Locations

APPENDIX E Lightning Protection of Structures with Explosiveor Highly Flammable Contents.

INDEX

225

227

231)

243244244245245246

248261

261

262

263

264

265

267

N A T I O N A L E L E C T R I C A L C O D EP A R T 1

As in the Original Standard, this Page is Intentionally Left Blank

PART 1 GENERAL AND COMMON ASPECTS

0 . F O R E W O R D

0.1 Each part/section of the National Electrical Code covers the requirementsrelating to electrical installations m specific occupancies. It is. however, feltessential to bring out the fundamental and general principles governing electricalinstallation practice together with common aspects applicable to all types ofinstallations in a separate part to serve as a reference document on such matters.

0.2 The details enumerated in this part are generally applicable to all types ofoccupancies and are to be read as modified or supplemented with the informationprovided in the relevant Parts of the Code.

0.3 This part of the Code is basically a compilation of guidelines available inseveral Indian Standards dealing with the various general aspects relating toelectrical installation practice. Individual sections of this part would therefore haveto be read in conjunction with the relevant Indian Standards from whichinformation has been condensed. These Indian Standards are listed at theForewords to each Section.

0.4 Effort has been made to make this part self-contained, so that users of the Codecan derive utmost advantage in using it for application in the field even foroccupancies not explicitely covered by the scope of subsequent Parts of the Code.Efforts have also been made to ensure that all the relevant details required for theunderstanding of the Code are available to the extent possible within Part I andreferences of individual standards have been kept to the minimum.

SECTION 1 SCOPE OF THE NATIONAL ELECTRICAL CODE

1. SCOPE g) Sports buildings;1.1 This Section of the Code describes the scopeof the National Electrical Code.

2. SCOPE OF THE NATIONAL ELECTRICALCODE

h) Industrial premises;j) Temporary and permanent outdoor

installations;

2.1 The National Electrical Code covers thefollowing:

k) Agricultural premises; andm) Installations in hazardous areas.

4

b)

c)

4

Standard good practices for selection ofvarious items of electrical equipmentforming part of power systems;Recommendations concerning safety andrelated matter in the wiring of electricalinstallations of buildings or industrialstructures, promoting compatibilitybetween such recommendations and thoseconcerning the equipment installed;General safety procedures and practices inelectrical work; andAdditional precautions to be taken for useof electrical equipment for specialenvironmental conditions like explosive andactiv.e atmosphere.

2.2 The Code applies to electrical installationssuch as those in:

a)

b)c)

4d

0

Standby/emergency generating plants andbullding substations;Domestic dwellings;Office buildings, shopping and commercialcentres and institutions;Recreational and other public premises;Medical establishments;Hotels;

NOTE I - Any type of installation not covered by the aboveshall be classified in the group which most nearly resembles itsexisting or proposed use.

NOTE 2 - Where change in the occupancy places it underthe scope of a different section of the Code, the sameinstallation shall be made to comply with the requirements ofthe Code for the new occupancy.

2.3 Theinternal

2.4 The

Code applies to circuits other than thewiring of apparatus.Code does not apply to traction, motor

vehicles, installations in rolling-stock, on board-ships, and aircraft or installations in undergroundmines.2.5 The Code covers only electrical aspects oflightning protection of buildings and in so far asthe effects of lightning on the electricalinstallations are concerned. It does not coverlightning protection aspects from structural safetypoint of view.2.6 The Code is also not intended to apply to:

a) Systems of distribution of energy to public;and

b) Power generation arid transmission for suchsystems.

2.7 The Code also does not cover guidelines onthe payment for electrical work done ininstallations.

.

4 NATIONAL ELECTRICAL CODE

SECTION 2 DEFINITIONS

O . F O R E W O R D

0.1 Each part of the Code gives, where necessaqdefinitions of terms and phrases relevant for the

comprehensions of the requirements stipulatedtherein. Users may find it convenient to refer to adetai led l ist of terms and their def in i t ionscontained in this section that are relevant toelectrical installation practice. It may however benoted that for further guidance, recourse shouldbe made to IS : 1885 (series) on electrotechnicalvocabulary containing a compendium of terms inthe field.

0.2 The definitions contained in the Code, havebeen drawn up by the relevant expert groupsunder the Electrotechnical Division Council withthe object of striking a correct balance betweenabsolute precision and simplicity. The principalobject of this exercise is to provide definitionswhich are sufficiently clear so that each term isunderstood wi th the same meaning by al lconcerned. It does not however constitute atreat ise on electr ical engineering. I t maysometimes be felt that the definitions are notsufficiently precise do not include all cases. do nottake account of certain exceptions or are notidentical with those which may, be found in otherpublications designed with different objectivesand for other readers. Such differences areinevitable and should be accepted in the interestof uniformity and clarity.

1. SCOPE

1.1 This Section of the Code covers definitions ofterms.

2. DEFINITIONS

2.0 For theP

urposes of the National ElectricalCode, the de Initions given below shall apply. inaddition to those contained in individual partssections.

N OTE ~ A list of ‘Indian Standards on clcctrotcchnicc~lvocabulary relevant for the purposca of the Code i\ gkcn in 3.

2.1 Fundamental Definitions

2.1.1 Capacitor A system of two conductors(plates) separated over the extent of their surfacesby an insulation medium which is capable ofstoring electrical energy as electrical stress.

2.1.2 Cotltluc~rol A substance or body whichallows current of electricity to pass continuously.

2.1.3 Dielectrics ~- A material medium in whichan electric field can exist in a stationary state.

2.1.4 Elecrrotle ~~ A conducting element usedfor conveying current to and from a medium.

2.1.5 Currenr ~~ The elementary quantity ofelectricity flowing through a given section of a

PAR-I’ I GENERAI. AND COMMON ASPECTS

conduc to r d i v i ded by t he co r respond ingindefinitely small time.

2.1.6 Elec-tric Circuit ~- An arrangement ofbodies or media through which a current canflow.

2.1.7 Electric Current ~ The movement’ ofelectricity in a medium or along a circuit. Thedirection of the current is accepted as opposite tothat of the motion of negative electricity.

2.1.8 Voltage, Potential D(/fkretwP ~~~ The lineof integral from one point to another of anelectric field. taken along a given path.

2.1.9 Arc A luminous discharge of electricityacross a gas, characterized by a large current anda low voltage gradient. often accompanied bypartial volatilization of the electrodes.

2.1 .lO Flasho\!et The passage of a disruptivedischarge round an insulating material.

2.1.1 I Spark A brillinntlv luminous phcno-mcnon of shol-t d u r a t i o n wII_ich charactcri/cs adisruptive discharge.

2.1 .I2 Cot?t?rc’tiotl (,I’ Cirr~Lrirs

Series ~~~ An arrangement of elements so thatthey all carry the same current or flux. _

Parallel ~-~ Electric or magnetic circuits are saidto be in parallel (or shunt) when current or flux isd i\ idcd between them.

Series Parallel- An arrangement of elementsof which some are connected in series and othersin parallel.

2.1.13 Earth Fault --- Accidental connection 01a conductor to earth. When the impedance isnegligible, the connection is called a dead earth.

2.1 .I4 Earlh Leakage Crtrrettl The currentf lowing to ear th on account of imperfectinsulation.

2.1.15 It~sulation Faltll A n abnormaldecrease in insulation resistance.

2.1.16 O\wloatl Operating conditions in anelectrically undamaged circuit which causes anovercurrent.

2.1.17 Short-Circrrit -~ The intentional oraccidental connection of two points of a circuitthrough a negligible impedance. The term is;oftenapplied _to the group of phenomena whichaccompany a short circuit between points atdifferent .potentials.

2.2 Equipment

2.2.1 Electrical Equipnlenl - The electricalmachines. apparatus and circuits forming part ofan electrical installation or a power system.

NIIJI- I Outdoor electrical equipment are those \uitablcor installation in open air.

5

Na7W2 ~~ For the purposes of this Code. the term electricalequipment can in general be used to any item used for suchpurposes as gtneration, conversion. transmission, distributionor utilization of electrical energy such as machines,transformers. apparatus. measuring instruments, protectivedevices, wiring material and appliances.

2.2.2 Current Using Equipmenr - Equipmentintended to convert electrical energy into anotherform of energy, for example, light, heat or motivepower.

2.2.3 Portable Equipment - Equipment whichis moved while in operation or which can easily bemoved from one place to another while connectedto the supply.

2.2.4 Hand- Held Equipment - Portableequipment intended to be held in the hand duringnormal use, in which the motor, if any, forms anintegral part of the equipment.

2.2.5 Stationary Equipment - Either fixedequipment or equipment not provided with acarrying handle and having such a mass that itcannot easily be moved.

2.2.6 Fixed Equipmenr - Equipment fastenedto a support or otherwise secured in a specificlocation.

2.2.7 Generator - A machine for convertingmechanical energy into electrical energy.

2.2.8 Electric Motor - A machine forconverting electrical energy into mechanicalenergy.

2.2.9 Induction Motor - An alternatingcurrent motor without a commutator in whichone part only, the rotor or a stator, is connectedto the supply network, the other working byinduction.

2.2.10 Motor Generator Set - A machinewhich consists of an electric motor mechanicallycoupled to a generator.

2.2.11 Auto- Transformer - A transformer inwhich the primary and secondary windings havecommon part or parts.

2.2.12 Transformer - A piece of apparatus,without continuously moving parts, which byelectromagnetic induction transforms variablevoltage and current in one or more other windingsusually at different values of voltage and currentand at the same frequency.

2.2:13 Reia.,, (Including GUS-OperaledRelal!) - A device designed to produce suddenpredetermined changes in one or more phjvsicalsystems on the appearance of certain conditions inthe phJsica/ system controlling it.

2.2.14 S~c.i~chgcar antI Conlro~~eur Ageneral term covering switching devices and theircombination with associated control. measuring,protective and regulating equipment, alsoassemblies of such devices and equipment withassoc ia ted in te r -connec t ions , accessor ies ,enclosures and supporting structures intended inprinciple for use in connection with generation,

transmission, distribution and conversion ofelectric energy. Controlgears are switching devicesintended in principle for the control of electricalenergy consuming equipment.

2.2.15 Switch (Mechanicat) - A mechanicalswitching device capable of making, carrying andbreaking currents under normal circuit conditionswhich may include specified operating overloadconditions and also carrying for a specified timecurrents under specified abnormal circuitconditions such as those of a short-circuit.

2.2.16 Switch-Fuse-A switch in which one ormore poles have a fuse in series in a compositeunit.

2.2.17 Fuse-Switch - A switch in which a fuse-link or a fuse-carrier with fuse-link forms themoving contact of the switch.

2.2.18 Circuit- Breaker ( Mechanic*al) -~~ Amechanical switching device capable of making,carrying and breaking currents under normalcircuit conditions and also making, carrying for aspecified time and breaking currents underspecified abnormal circuit conditions such asthose of a short-circuit.

.2.2.19 Fuse- A switching device that by themelting of one or more of its specially designedand proportioned components, opens a circuit inwhich it is inserted and’ breaks the current whenthis exceeds a given value for a sufficient time.

2.2.20 Enclosed Distribution Fuse-Board - Anenclosure containing bus-bars, with fuses, for thepurposes of protecting, controlling or connectingmore than one outgoing circuit fed from one ormore incoming circuits.

2.2.21 Carrridge Fuse-Link - A fuse-linkhaving a totally enclosed container, usuallycylindrical, ‘provided at its two ends with metalcontacts, the shape of which varies according tothe type of the fuse.

2 .2 .22 Fuse-Link -The part of the fuseincluding the fuse-element which requiresreplacement by a new fuse-link after the fuse hasoperated and before the fuse can be put back toservice.

2.2.23 Miniature Circuit- Breaker - A compactmechanical device for making and breaking acircuit both in normal conditions and in abnormalconditions, such as those of overcurrent andshort-circuit.

2.2.24 D- ljpe Fuse - A non-interchangeablefuse comprising a fuse-base a screw type fuse-.carrier, a gauge piece and a fuse-link.

2.2.25 Distribution Pillar - A totally enclosedstructure,‘cubicle containing bus-bars connectedto incoming and outgoing distribution feederscontrolled through links/fuses.

2.2.26 Interconnecting Bus-Bar - A conductorother than cable, used for external connectionbetween &rminals ‘of equipment.


2.2.27 Bimetallic Connector - A connectordedgned for the purpose of connecting togethertwo or more conductors of different materials(normally copper and aluminium) for preventingelectrolytic corrosion.

2.2.28 Fuse-Element (Fuse- Wire in RehirableFuse)- That part of a rewirable fuse, which isdesigned to melt and thus open the circuit.

2.2.29 Fuse-Base- The fixed part of a fuseprovided with terminals for connection to thesystem. The fuse-base comprises all the partsnecessary for insulation.

2.2.30 Fuse-Carrier-The movable part of afuse designed to carry a fuse-link. The fuse-carrierdoes not include any fuse-link.

2.2.31 Lightning Arrester (Surge Diverter) - Adevice designed to protect electrical apparatusfrom high transient voltage and to limit theduration and frequently the amplitude of follow-current. The term ‘lightning arrester’ includes anyexternal series gap which is essential for theproper functioning of the device as installed forservice, regardless of whether or not it is suppliedas an integral part of the device.

2.3 Wiring Practice

2.3.1 Accessory - Any device, associated withthe wiring and electrical appliance of aninstallation, for example, a switch, a fuse, a plug,a socket-outlet, a lampholder, or a ceiling rose.

2.3.2 Apparatus -- Electrical apparatusincluding all machines, appliances and fittings inwhich conductors are used for of which they mayform a part.

2.3.3 Aerial Conductor - Any conductorwhich is supported by insulators above theground and is directly exposed to the weather.

NOTE - Four classes of aerial conductors are recognized:

a) Bare aerial conductors,b) Covered aerial conductors,c) Insulated aerial conductors, andd) Weatherproof neutral-screened cable.

2 . 3 . 4 B u n c h e d - Cables are said to be‘bunched’ when two or more are contained withina single conduit, duct or groove or. if notenclosed, are not separated from each other.

2.35 Cable - A length of single-insulatedconductor (solid or stranded), or (Ho or more suchconductors, each prov ided wi th i t s owninsulation, which are laid up together. Theinsulated conductor or conductors may or maynot be provided with an overall mechanicalprotective covering.

2.3.6 &ble. Armoured- A cable providedwith a wrapping of metal (usually in the form oftape or wire),serving as a mechanical protection.

23.7 Cable, Flexible -A cable containing one-:-or more cores, each formed of a group of wires,

the diameters of the cores and of the wires beingsufficiently small to afford flexibility.

P A R T I C;JN”RAl, A N D C O M M O N A S P E C T S

2.3.8 Circuit - An arrangement of conductoror conductors for the purpose of conveyingenergy and forming a system or a branch of asystem.

2.3.9 Circuit, Final, Sub - An outgoing circuitconnected to one-way distribution fuse-board andintended to supply electrical energy at one ormore points to current-using appliances, withoutthe intervention of a further distribution fuse-board other than a one-way board. It includes allbranches and extensions derived from thatparticular way in the board.

2.3.10 Cleat - An insulated incombustiblesupport normally used for insulated cable.

2.3.11 Conductor, Bare - A conductor notcovered with insulating material.

2.3.12 Conductor, Earthed - A conductorwith no provision for its insulation from earth.

2.3.13 Conductor, Insulated - A conductoradequately covered with insulating material ofsuch quality and thickness as to prevent danger.

2.3.14 Connector Box or Joint Box- A boxforming a part of wiring installation provided tocontain joints in the conductors of cables of theinstallation.

2.3.15 Conductor for Portable Appliankes - Acombination of a plug and socket arranged forattachment to a portable electrical appliance or toa flexible cord.

2.3.16 Consumer’s Terminals - The ends ofthe electrical conductors situated upon anyconsumer’s premises and belonging to him atwhich the supply of energy is delivered from theservice line.

2.3.17 Cord, Fkxible - A flexible cable havingconductor of small cross-sectional area. Twoflexible cords twisted together are known as ‘TwinFlexible Cord’

NOTE - For the maximum diameter and minimum numberof wires for flexible cord. SCP relevant standard.

2.3.18 GUI-0~ Any appliance forautomatically interrupting the transmission ofenergy through any conductor when the currentrises above a predetermined amount, for example,fusible cut-out.

2.3.19 Dead - At or about earth potentialand/or disconnected from any live system.

2.3.20 Direct Earthing System - A system ofearthmg in which the parts of an installation areso earthed as specified but are not connectedwithin the installation to the neutral conductor ofthe supply system or to earth through the trip coilof an earth leakage circuit-breaker.

2.3.21 Distribution Fuse- Board - Anassemblage of parts including one or more fusesarranged for the distribution of electrical energyto final sub-circuits.

7

2.3.22 Earth --A connection to the generalmass of earth by means of an earth electrode. Anobject is said to be ‘earthed’ when it is electricallyconnected to an earth electrude; and a conductoris said to be .‘solidly earthed’ when it is electricallyconnected to earth electrode without a fuse,switch, circuit-breaker, resistance or impedance inthe earth connection.

2.3.23 Earth Continuity Conductor -Theconductor. including any clamp, connecting to theearthing lead or to each other those parts of aninstallation which are required to be earthed.

2.3.24 Earth Electrode-A metal plate, pipeor other conductor electrically connected to thegeneral mass of the earth.

2.3.25 Earthing Lead - The final conductor bywhich the connection to the earth electrode ismade.

2.3.26 Fitting, Lighting - A device forsupporting or containing a lamp or lamps (forexample, fluorescent or incandescent) togetherwith any holder, shade, or reflector, for example,a bracket, a pendant with ceiling rose, anelectrolier, or a portable unit.

2.3.27 Flammable - A material capable ofbeing easily ignited.

2.3.28 Disconnector - A device used to open(or close) a circuit when either negligible currentis interrupted (or established) or when thesignificant change in the voltage across theterminals of each of the pole of the disconnectoroccurs; in the open position it provides anisolating distance between the terminals of eachpole.

2.3.29 Insulation Double

b)

Of a conductor - A conductor is said tohave double insulation when insulatingmaterial intervenes not only between theconductor and its surrounding envelope (if acable) or immediate suport (if bare), but alsobetween the envelope or support and earth.

Of an appliance - An appliance havingaccessible metal part is doubly insulatedwhen protective insulation is provided inaddition to the normal functional insulation,in order to protect against electric shock incase of breakdown of the functionalinsulation.

2.3.30 Live or Alive-Electrically charged soas to have a potential difference from that ofearth.

2.3.31 Multiple Earthed Neutral System - Asystem of earthing in which the parts of aninstallation, specified, to be earthed are connectedto the general mass of earth and, in addition, areconnected within the installation to the neutralconductor of the supply system.

2.3.32 Neutral or Neutral Conductor -Includes the neutral conductor of a three-phase

8

four-wire system, the conductor of, a single-phaseor dc installation which is earthed by the supplyundertaking (or otherwise at the source of thesupply), and the middle wire or common returnconductor of a three-wire dc or single-phase acsystem.

2.3 .33 Point-A point shall consist of thebranch wiring from the branch distribution board,together with a switch as required, as far as andincluding the ceiling rose or socket;outlet orsuitable termination. A three-pin socket-outletpoint shall include. in addSon, the connectingwire or cable from the earth pm to the earth studof the branch distribution board.

2.3.34 Service -- T h e conductors andequipment required for delivering energy from theelectric supply system to the wiring system of thepremises served.

2.3.35 Socket-Outlet and Plug - A deviceconsisting of two portions for easily connectingportable lighting fittings and other current-usingappliances to the supply. The socket-outlet isdesigned as a fixed member and the plug portioncarries multiple metal contacts which connectwith corresponding metal contacts in socketportion.

2.3.36 Switchboard - An assemblage ofswitchgear with or without instruments but theterm does not apply to a group of local switchesor a final sub-circuit where each switch has itsown insulating base.

2.3.37 Voltage, Low - The voltage which doesnot normally exceed 250 volts.

2.3.313 Voltage, Medium - The voltage whichnormally exceeds 250 volts but does not exceed650 volts.

2.3.39 Volrage, High - The voltage whichnormally exceeds 650 volts (but less than 33 kV).

2.3.40 Voltage, Extra- High - The voltageexceeding 33 kV under normal conditions.

NOTE-The definitions given in 2.3.37 to 2.3.40 are basedon the provisions of IE Rules. It may however, be noted thatvoltage ranges as defined internationally are at variance withthe above definitions.

2.4 Miscellaneous Terms

2.4.1 Building - Any structure for whatsoeverpurpose and of whatsoever materials constructedand every part thereof whether used as humanhabitation or not and includes foundation, plinth,walls, floors, roofs, chimneys, plumbing andbuilding services, fixed platforms, verandah,balcony, cornice or projection, part of a buildingor anything affixed thereto or any wall enclosingor intended to enclose any land or space and signsa n d o u t d o o r d i s p l a y s t r u c t u r e s . T e n t s ,SHAMIA NA HS. tarpaulin shelters, etc, erectedfor temporary and ceremonial occasions with thepermission of the Authority shall not beconsidered as building.


2 . 4 . 2 O c c u p a n c y o r U s e G r o u p - T h eprincipal occupancy for which a building or a partof a building is used or intended to be used; forthe purposes of classification of a buildingaccording to occupancy, an occupancy shall bedeemed to include the subsidiary occupancieswhich are contingent upon it.

2.4.3 Room Height-The vertical distancemeasured from the finished floor surface to thefinished ceiling surface. Where a finished ceiling isnot provided, the underside of the joints or beamsor tie beams shall determine the upper point ofmeasurement ‘for determining the head robm.

2.4.4 Impulse - Usually an aperiodic transientvoltage or current which rises rapidly to a peakvalue and then falls, generally more slowly, tozero. Ideally it appioximates a double exponentialform. Other forms are sometimes’used for specialpurposes.

2.4.5 Clearance -The distance between twoconducting parts along a string ~ stretched theshortest way between these conducting parts.

2.4.6 Creepage Distance - The. shortestdistance between two conducting parts along thesurface of the insulating material or along thejoint of two insulatihg bodies.

2.4.1 Simultn~eousl~~ Access ib l e Par t s -Conductors or conduciiveb parts that can betouched Bsimultaneously by a person or whereapplicable by livestock.

NCTE - Simultaneously accessible parts may be:-live parts,-exposed conductive parts,-extraneous conductive parts,-protective conductors, and-earth electrodes.

2.4.8 Arm’s Reach’- A zone extending fromany point on a surface where persons usuallystand or move about to the limits which a personcan reach with the hand in any direction withoutassistance.

2.4.9 Enclosure - A part providing protectionof equipment against certain external influencesand, in any direction, protection against directcontact.

2.4.10 Barrier - A part providing protectionagainst direct contact from any usual direction Ofa c c e s s .

2.4.11 Obstacle - A .part preventing uninten-tional direct contact, but not preventing dehberateaction.

2.4.12 Leakage Current (in an Installation) ~~~ Acurrent which flows to earth or to extraneousconductive parts in a circuit in the absence of afault.

N OTE -This current may have a capacitive componentincluding that resulting from the deliberate use of capacitors.

2.4.13 Nominal Voltage (of an Installation) -Voltage by which an installatio or part of aninstallation is designated.

N O T E-The actual voltage may differ from the nominalvoltage by a quantity within permitted tolerances.

2.4.14 Supply Terminals-The point at whicha consumer received energy.

2.4.15 Service Line, Service - A line forconnecting a current consuming installation to thedistribution network.

2.4.16 Distribution Undertaking - The partysupplying electricity to consumers entirely fromextrernal sources of power via a distributionnetwork.

2.4.17 Consumer or. Customer-The partywho receives electricity from the supply ordistribution undei-taking for his own needs or forfurther distribution.

2.4.18 Demand - The magnitude of electricitysupply, expressed in kW or kVA.

2.4.19 Instailed Load-The sum of the ratedinputs of the electrical apparatus installed on theconsumer’s premises.

2.4.20 Connected Load-The part of theinstalled load of consumer supplied by the supplyundertaking.

2.4.21 Kilowatthour Rate (kWh , R&e)-- Theamount to be paid per unit of energy (kWh)consumed.

2.4.22 Meter Rent - An amount to be paid fora specified period for metering, and associatedequipment installed.

2.4.23 Tari$f - A statement setting. out thecomponents to be taken into account and themethods to be employed in calculating theamounts to be charged by the supply/distributionundertaking to the consumer, according to thecharacteristics of the supply.

2.4.24 Domestic Tariff - A tariff applicableparticularly or exclusively to domestic consumers.

2.4.25 ‘Industrial Tariff - A tariff applicableexclusively to industrial consumers.

2.4.26 Lighting TariJf - A tariff applicab!: toelectricity supplies taken mainly for lighting andother small appliances, for example, fans andradios.

2.4.27 Heating Tar$f - A tariff applicable toelectricity supplies taken for space heating or forthermal applications or for both.

2.4.28 Power Factor Clause - A clause settingout increase in charges to be applied if the ratio ofthe kWh to kVAh consumed by a consumerduring a specified period below a set limit; thesame clause may provide for a decrease in chargesin the opposite case.

NOTE -The power factor is generally measured by the ratioof. kWh to kVAh consumed during the specified period.

2.4.29 Load Factor - The ratio, expressed as anumerical value or as a percentage, of the energyconsumption within a specified period (year,

PART I GENERAL AND COMMON ASPECTS 9

month, day, etc) to the energy consumption thatwould resu l t f rom cont inuous use of themaximum kW demand occurring within the sameperiod.

NOTE -The load factor for a given demand is also equal tothelratio of the utilization time to the time in hours within thesame period.

3. LIST OF INDIAN STANDARDS ONELECTROTECHNICAL VOCABULARY

IS : 1885 Electrotechnical vocabulary:IS : 1885 (Part I)-1961 Fundamental defini-

tionsIS : 1885 (Part 8)-1965 Secondary cells and

batteriesIS : 1885 (Part 9)-1966 Electrical relaysIS : 1885 (Part IO)-1968 Electrical power system

protectionIS : 1885 (Part I I)-1966 Electrical measure-

mentsIS : 1885 (Part l4)-1967 Nuclear power plantsIS : 1885 (Part l5)-1967 Primary cells and

batteriesI S : 1 8 8 5 ( P a r t 16/Set I)-1968 L i g h t i n g ,

Section I General aspectsIS : 1 8 8 5 ‘ ( P a r t I6/Sec 2)-1968 L i g h t i n g ,

Section 2 General illumination lightingf i t t ings and l igh t ing for t ra f f ic andsignalling

IS : 1885 * ( P a r t l6/ Set 3)-1967 L i g h t i n g ,Section 3 Lamps and auxiliary apparatus

IS : I885 (Part I 7)- I979 Switchgear and control-gear (/irst revision)

IS : 1885 (Part 27)-1969 Static power convertorsIS : 1885 (Part 28)-1972 Ins t rument t r ans -

formersIS : 1885 (Part 29)-1971 Mining termsIS : 1885 (Part 30)-1971 O v e r h e a d , t r a n s -

mission and distribution of electricalenergy

IS : 1885 (Par t 32)-1972 Cables. conduc-tars and accessories

IS : 1885 (Part 34)-1972IS : 1885 (Part 35)-1973IS :. 1885 (Part 37)-1974IS : l&5 (Part 3X)-1977

(&r’s/ re\ri.sion)IS :

IS :

IS :

1s :

IS :

IS :

IS :IS :

1885 (Part 42)-19771885 (Part 43)-1977 E lec t r i ca l equ ip -ment used in medical practice1885 (Part 49)1978 Indus t r i a l p rocessmeasurement and control1885 ( P a r t 5I1Sec I)-1979 I n d u s t r i a lelectro-heating, Section I General termsI885 (Part 5 I Set 2)-1979 I n d u s t r i a lelectro-heating, Section 2 ResistanceheatingI885 (Part 53)- 1980 Mica (superseding1s : 1174)1885 (Part 54)-1980 Insulators1885 (Part 55)-1981 Electric fans

for electricity supplyCinematographyRotating machineryTariffs for electricityTransformers

Power capacitors

NO T E- Other Parts/Sections of the IS : 1885 series coverterminology relating to the field of electronics andtelecommunications.


SECTION 3 GRAPHICAL SYMBOLS FOR DIAGRAMS, LETTERSYMBOLS AND SIGNS

0. FOREWORD

0.1 The purpose of the Section of the Code is :osummarize a list of graphical symbols which areto be used for installation diagrams. Considerableamount of standardization had been achieved inthe field of symbols for electrotechnology that it isnow possible to device electrical networkschematics using them so that these schematicdiagrams could be uniformly understood by allconverned.

0.2 The symbols contained in this Section of theCode have been drawn up by individual expertgroups under the Electrotechnical DivisionCouncil. They represent a consensus of opinion inthe discipline and are recommended for directadoption. For additional symbols in the subjectreference should be made to IS : 2032 (series) ongraphical symbols used in electrotechnology.

0.3 It has also been felt essential for the purposesof this Section to draw the attention of practisingengineers to standardized letter symbols andsigns. For further details, the following IndianStandards could be referred to:

IS : 3722 Letter Symbols and Signs used inElectrical Technology(Pa r t I)-1983 Genera l Guide l ines onsymbols and subscripts.(Pa r t 2 ) -1983 Refe rence Tab le s fo rsymbols and subscripts.

1. SCOPE

1.1 This Section of the Code covers graphicalsymbols for diagrams, letter symbols and signs.

2. GRAPHICAL SYMBOLS

2.0 For the purposes of the Code, the graphicalsymbols given below shall apply.

NO T E-A list of Indian Standards on graphical symbolsused in electrotechnology relevant to the Code is given in 3.

2.1 Fundamental Symbols

2.1.1 Direct Current

2.1.2 Alternating current, General Symbol

a) Alternating Current, Single-Phase,50 Hz

-5OHz


b) Alternating Current, Three-Phase,415 V, 50 Hz

3wf,15 ”OHz,

c) Alternating Current, Three-Phase withneutral. 50 Hz

3Nw50Hz

2.1.3 Neutral

N

2.1 A Positive Polaritj~

+

2.1.5 Negatilv Polarity

2.1.6 Direct Current, 2 Conductors, 110 V

2 110 v

2. I .7 Dirwt Current, 3 Conductors includingNeutral. 220 V

2N 220v

2.1.8 Underground Cable

2.1.9 Overhead Line

2.1.10 Winding, Delta

A2.1.11 Winding, Star

2.1.12 Terminals

0

I2

2.1.13 Resistance, Resistor, Variable Resistor

k#

2.1.14 Impedance

*

2.1.15 Inductance, Inductor

+ LF_

2.1 r16 Winding

2.1.17 Capacitance, Capacitor

- - i t -

2.1.m Earth

li2.1,19 Fault

2.2 Equippent

2.2.1 Flexible Conductor

2.2.2 Generator

0G

AC generator

0G

DC generator

0G

2.2.3 Motor

0M

2.2.4 Synchronous Motor

0MS

2.2.5 Mechanically Coupled Machines

2.2.6 Induction Motor, Three-Phase,Squirrel Cage

Induction Motor with Wound Rotor

00M

2.2.7 Transformers withWindings

8

2.2.8 Auto- Transformer

Two Separate

$2.9 II-Phase Transformer with ThreeSeparate Windings-Star-Star-Delta

NATIONAL ELECI-RICAL CORE

2.2.10 Starter 2.2.18 Isolator

2.2.11 LX;z;on- Line Starter for Reversing

2.2.12 Star-Delta Starter

rlA2.2.13 Auto- Transformer Starter

2.2.14 Rheostatic Starter

2.2.15 Snitch

1t

2.2.16 Contactor

2.2.17 Circuit-Breaker

2.2.19 Fuse

2.2.20 Signal Lamp

2.2.21 Link

2.2.22 Distribution Board, Cubicle Box, MainFuse Board with Switches

2.2.23 Socket Outlet, SA,

YoR (4Socket Outlet, 1SA

An2.2.24 Plug

PART 1 GENERAL AND COMMON ASPECTS 13

2.2.25 Voltmeter 2.2.34 Watthour Meter

0V

2.2.26 Ammeter

0A

2.2.27 Wattmeter

0W

2.2.28 Varmeter

0VCN

2.2.29 Power Factor Meter

0coscp

2.2.30 Ohmmeter

0R

2.2.31 Indicating Instrument (general symbol)

02.2.32 Recording Instrument (general symbol)

cl2.2.33 Integrating Meter

tlWh

2.2.35 Clock

0L

2.2.36 Master Clock

0L

2.2.37 Current Transformer

EI2.2.38 Voltage Tran$ormer

LJJM

2.2.39 Wiring on the Swface

2.2.40 Wiring in Conduit

0

2.2.41 Lamp

X2.2.42 Lamp Mounted on a Ceiling


2.2.43 Emergency Lamp 2.2.52 Fan Regulay

2.2.44 spot Light

c =X2.2.45 Flood Light

CXY\2.2.46 Heater

I III-2.2.41 S t o r a g e T,pe Water Heaters

2.2.53 Aerial

2.2.54 Radio Recviling Set

2.2.55 Television Receiving Srt

2.2.56 ManualI,? Operated Fire Alarm2.2.48 Bell

A2.2.49 Buzzer

R2.2.50 Ceiling Fan

2.2.51 Exhaust Fan

PART I CENERAI. AND COMMON ASPECTS

,, i,. ,.“. ,. U/_,, _

II02.2.57 Automatic Fire Detector Sh?tch

clI0

3. 1,IST O F I N D I A N S T A N D A R D S O NGRAPHICAL SYMBOLS

IS : 2032 Graphical symbols used in elcctro-technology:

IS : 2032 (Part 2)-I962 Kind of current distri-bution system and methods of connection

IS : 2032 (Part 3)-1962 Circuit elements andvariability

IS : 2032 (Part 4)-1964 Rotating machines andtransformers

IS : 2032 (Part 5)-I965 Generating stations andsub-stations

IS : 2032 (Part 6)-1965 Motor startersIS : 2032 (Part 7)-1974 Switchgear and auxi-

liaries (first revision)

IS

IS : 2032 (Part IO)-1969 Measuring instru-ments

IS : 2032 (Part I I)-1970 Electrical instal-lations in buildings

IS : 2032 (Part IS)-1976 Aircraft electricalsymbols

IS : 2032 (Part l8)-1976’Symbolsand connectiondiagrams for integrating meters

Es : 2032 (Part 19)-1977 Electrical equipmentused in medical practice

IS : 2032 (Part 21)-1977. Electric weldingequipment

IS : 2032 (Part 22)-1978 Irlstrument t rans -formers

IS : 2032 (Part 23)-1978 Instruments for processmeasurement and control

IS : 2032 (Part 25)-1980 Electrical instal-lations ;n ships

4. LETTER SYMB0I.S AND SIGNS4.0 General

4.0.1 Quantities and units used in electro-technology cover in addition to electricity andmagnetism. other subjects such as radiationand light, geometry. kinematics, dynamics andthermodynamics. Several disciplines interact with

the result that terminolobecomes clc~sely ?

y used’in one disciinterre ated with that oP

linethe

other. In order to enable uniform understandingof t.he meamng they represent. the letter symbolsand .signs used in abbreviatibns for denotingquantltles, thtir functions and units shall contormto those recommended in. IS : 3722 (Part I)-l983*and IS : 3722 (Part 2)-1983*.

4.0.2 Guidance on the choice of alphabet andtheir type, representation of vector quantities,synibols of units, numerical values, and guidanceon the use of subscripts are covered in IS : 3722(Part I)-l983*

Ready reference tables for symbols andsubscripts are contained in IS : 3722 (Part 2)-1983*. For the purposes of this Code, a list ofsymbols, names of quantities and of constants andsubscripts referred to frequently is given in 4.1.

4.1 Symbols and Subscripts

4.111 Table I gives a reference likt of symbolsand subscripts used in electrotechnology.

l L.eltcr symbols and signs used in Electrotcchnology:Parr I General guidance on symbols and subscripts.Part 2 Rcfcrcncc lables for symbols and subscripts.

TABI,E I R E F E RE N C E GABLE FOR wmoLs AND S U B S C R I P T S

Ilk>! NAMt OkNo. QI,ANTII\

(1) (2)

I. angle (plane angle)

SI UN I T

c hNaie Symbol ’

(4) (5)

radian rad

5,

m

m

m

m

m

m

Other units aredegree minuteand second

2. wlld angle

3 length

4. breadth

5. hclpht. dcprh

6 Ihlchnc\\

7. I-adlu\. radial

X. d8;imcrcr

9. ua\clcn~lh

IO. arc;,. \urt;KY ;,rca

I I \otumc

12. tlmc

stcradian

met re

met rc

mcl rc

met rc

mcl rc

met rc

mcI rc

\qu.,,L’ rnc,,c

cuhlc mc,,c

WYontl Olhcr unit\ iircmlnutc .Ind haul

‘,

tr/

kg

AlbO. C!ClC perwcond

Ihc WI m kIlogram-Vorcc (kgl’) t’or Heightis .a140 gl\cn a\hiloponc (hp)

I6 \ ‘L\TIONAI. EI.EC’TRI(‘AI. C O D E

TRUE I REFERENCE TABLE FOR SYMROLS AND SU~RIPTS-ConrdITEM NAME OFNo. @hW’lTlTY

(1)1 6 .

(2)density (mass density)

CHIEFREMARKS

(3)

P

F

T

P

W

E

P

r)

T

I

a

V

u

E

CL

c

I

J

e

R

P

G

Y

Z

X

6

P

QsAtlN

ttK

(4)

kilogram. percubic IlwR‘hewton

newton metrc

newton persquaremetre(Pascal)

joule

jouk

watt

(6)

17. force

IS. torque

19. pressure

N

N.m

Pa

20.

21.

22.

23.

work J

J

W

energy

power

efficiency Also expressedin percent

2 4 . Kthermodynamictemperature. absolutetemperature

temperature (Celsius)

kelvin

25. degree Celsius

I per kelvin

OC TemperatureInterval of )K

26. K“::xzY(clccrric) potential

potential difference..tension. voltage

electromotive force

electric flux

capacitance

(electric) current

current density

27.

28.

volt

volt

volt

coulomb

farad

ampere

ampere persquare mctrc

webcr

ohm

ohm mctre

siemens

sicmcns per metre

ohm

ohm

radian

watt

var

voltampere

V

V

29.

30.

31.

32.

33.

V

C

F

A

A, rn’

34.

35.

36.

37.

38.

39.

40.

41.

magnetic flux

r&tancc

rcsistivity

Wb

n

fI.m

s

S/m

R

n

rad

W

var

V A

conductance

conductivity

impedance

reactance

loss angle

active power

reactive power

42.

43.

44.

45.

46.

47.

apparent power

power factor

dissipation factor

number of lurns Ina winding

turns ratio

transformation ratioof an instrumenttransformer

48.

49.


TABLE I REFERENCE TABLE FOR SYMBOLS AND SURSf?RIPTS-Conrd

I T E M N AME OF

NO. Q U A NT ITY

(1) (2)

50. transformation ratioof a voltagetransformer

CHIEFSYMIWI.

(3)

K

St UNITA \ REMAUKS

Name Symbol(4) (5) (6)

I

51. transformation ratioof a currentlranbformer

52. number of phases

53. number of pairsof poles

54. luminous intensity

55. luminous flux

candela

lumen

I

II

cd

Im

56. luminance

57. illuminance.illumination

1.

E

candela persquare metre

lux

cd rn’

Ix

NOTE I - For alternatiw symbols and other units of designation. .we IS : 3722 (Part 2)-19X3*

NOTE 2 - Wherever symbol for the unit is I. the corresponding quantity IS numeric and its value is written as a numberwithout the unit symbol.

‘Letter symbols and signs used in Electrotechnology : Part 2 Reference tables for symbols and subscripts.

Ill NATIONAI. ELECTRICAl. ( ‘ O D E

SECTION 4 GUIDE FOR PREPARATION OF DIAGRAMS,CHARTS AND TABLES, AND MARKING

O . F O R E W O R D

0.1 Various types of diagrams and charts arerequired to be prepared during the planning andexecution stages of an electrical installation work.It is therefore necessary to define the differenttypes of diagrams. charts and tables, theirpurposes and -format and the guiding principlesfor preparing them for the sake of uniformity,

0.2 This Section of the Code covers generalguidelines on the subject. The contents of thisSection are based primarily on the followingpublications:

IS : 8270 Guide for the preparation of dia-grams. charts and tables for electrotech-nology :(Part I)-1976 Definitions and classi-fication(Part 2)-1976 Item designation(Part 3)- 1977 General requirementsfor diagrams(Part 4)-1977 Circuit diagram(Part 5)-1976 Interconnection diagramsand tables

0.3 The guidelines for marking of conductorsgicen in 2.6. Table I of the Section are in line withthe guidelines accepted internationally on suchmatters. l-he) provide for a common basis f o runderstanding and identifying conductors andtipparatus terminal\: but more important, ensuresafety to operating. maintenance personnel.

I. SCOPE

1 .I This Section of the Code covers guidelines forpreparation of diagrams, charts and tables inelectrotechnology and for marking of conductors.

2. PREPARATION OF DIAGRAMS,CHARTSAND TABLES

2.0 General

2.0.1 Diagram -~ A diagram may show themanner in which the various parts of a network.installation. group 01 apparatus or items of anapparatus are interrelated and or interconnected.

2 .0 .2 Char1 - A c h a r t m a y s h o w t h einterrelation between:

a) different operations.

b) operations and time.

c) operations and physical quantities. and

d) the states of several items.

2.0.3 Tab/e - A table replaces or supplementsa diagram or a chart.


2.1 Classification According to Purpose

2.1.0 The main classifications are:

a) explanatory diagrams,

b) explanatory charts or tables,

c) wiring diagrams or wiring tables, and

d) location diagrams or tables.

2.1. I Erplottator~~~ Diagrams - Explanatorydiagrams are intended to facilitate the study andunderstanding of the funct ioning of aninstallation or equipment. Three types are definedbelow:

a)

b)

cl

Blocli diagram - Relatively simple diagramto facilitate the understanding of theprinciple of operation. It is a diagram inwhich an installation or equipment togetherwith its functional interrelationships arerepresented by symbols. block symbols orpictures without necessarily showing all theconnections.

Circuit diagram - Explanatory diagramintended to facilitate the understanding ofthe functioning in detail. It shows bysypbols an installation or part of an instal-lation and the electrical connections andother links concerned with its operation.

Equi\~alenr circuir diagram - Special typof circuit diagram for the analysis and cal-culation of circuit characteristics.

2.1.2 Explanaktry~ Charrs . Tables -Explanatory charts or tables arz’ intended tofacilitate the study of diagrams and to giveadditional information. Two examples are givenbelow:

a) S e q u e n c e chart or rahle - gives thesuccessive operation in a specified order,and

b) Time seywnce charr or rahk - is one whichin addition takes account of the timeintervals between successive operations.

2.1.3 Wiring Diagrams or Wiring Tables -Wiring diagrams are intended to guide themaking and checking of the connection of aninstallation or equipment. For an equipment, theyshow the inteknal or external connections or both.The diagrams may sometimes show the layout ofthe different parts and accessories, such asterminal blocks and the wiring between them.

2.1.3.1 Unit H,iring diagram - D i a g r a mrepresenting all connections within a unit of aninstallation.

2.1.3.2 Inrerconnection diagram - Diagramrepresenting the connections between the differentunits of an installation.

19

2.1.33 Terminal diagram - Diagram showingthe terminals and the internal and/or externalconductors connected to them.

NOI I Any of the wiring diagrams may be replaced oraupplcmcnted by a table.

2.1.4 Localion Diagrams or Tables - Alocation diagram or table contains detailedinformation about the location of parts of theequipment, for example. terminal blocks, plug-inunits, sub-assemblies, modules, etc. It shows theitem designations used in related diagrams andtabler.

NOTE I -A location diagram need not necessarily be toscale.

NOTE 2 -Several typer of diagrams may be combined Intloa single diagram. forming a mixed diagram. The samedrawing may form both an explanator) and wiring diagram.

2.2 Classification According to MethodRepresentation

2.2.1 The method of representationdistinguished bv:

a) The number of conductors. deviceselements represented by a single symbol (see2.2.1.1);

b) the arrangement of the symbols representingthe elements or parts of an item ofapparatus (for example, detached o rassembled) (see 2.2.1.2); and

cl the placing of the symbols to correspondwith the topographical layout of the devices(see 2.2.1.3).

Of

is

Or

2.2.1.1 Number of conducrors - According tothe number of conductors, devices or elementsrepresented by a single symbol, the two methodsof representation as given below may bedistinguished:

a) Single-line representation -- Two or moreconductors are represented by a sirigle line.In particular, a single line may represent:I) circuits of a multiphase system,2) circuits which have a similar electrical

function,3) circuits or conductors which belong to

the same signal path,4) circuits which follow the same physical

route, and5) conductor symbols which would follow

the same route on the diagram.

Several similar items of apparatus mayaccordingly be represented by a singlesymbol.

b) Multi-line representation - Each conductoris represented by an individual line.

2.2.1.2 Arrangemen/ c$ swlbols - Accord ingto the arrangement of the symbols representingthe elements or parts of an item of apparatus on

20

rhe diagram. the methods of representation aregiven below:

a) Assembled representatiorr -- The symbolsfor the different parts of an item ofapparatus or of an installation or equipmentare drawn in c lose proximity on thediagram.

b) Semi-assembled representation -~~ Thesymbols for the different parts of an item ofapparatus or of an installation are separatedand arranged in such a way that the symbolsfor mechanical linkages between the partswhich work together may be drawn easily.

c) Dctachecl r~~pre:8erltatiorl The symbols forthe different parts of an item of apparatusor of an installation are :,cparated andarranged in such a uay that the circuits ma!’easily be followed.

2.2.1.3 Topo~yraphic~al repwserttatiort - T h epos i t i ons o f t he 5)mbols on the d iag ramcorrespond wholly, or partly to the topographical(ph\,sical) location of items represented.

T h e f o l l o w i n g arc e x a m p l e s w h e r etopographical representation may bc used:

a) Wiring diagrams.

b) Architectural diagrams, and

c) Network diagrams.

NOI I- Se\crtil of the\e method\ of repruentatlon ma! heused on the umc dugwm.

2.3 Item Designation

2.3.1 Item is a term used for component.equipment. plant. unit, etc. which is representedby a graphical symbol on a diagram. The itemdesignation is shown at an appropriate place nearthe graphical symbol of the item. This designationcorrelates the Item on different diagrams. partslist. circuit descriptions and in the equipment.

2.3.2 An item designation may be used folgeneral or special ptirposes depending on the kindo f i n f o r m a t i o n r e q u i r e d . Cu,Lclines o nassignment of item designation, groups togetherwith standard letter codes for the same arecovered in IS : 8270 (Part 2)-l976*

2.4 General Rules for Diagrams

2.4.1 Paper sizes_ for drawings shall preferabl!be according to the international A-series (XVIS : 1064-196lt). The choice of drawing sizesshould be decided after taking into account thenecessary factors enumerated in 2.2 of IS : 8270(Part 2):l976*

2.4.2 In IS : 2032:. different kinds of symbolsas well as symbols of different forms are shown.

*GUI& Ior preparation 01 dugram\. chart, a n d tahle~ lorelectrotcchnolog! Part 2 Item de\lgnation.

+SpeclCwatlon ior paprr \IICS.$(;raphwal symbols used in clectrotcchnolog! ( P a r t \

to ‘25).

NATIOSAI. ELECTRICAl. CODt.

All the powbre examples are also not coveredthere. Any symbol may be composed using theguidanc:e from relevant Part of IS : 2032 andSection 3 Part I of the Code. The basic rules forthe choice of symbols shall be:

a) to use the simplest form of symbol adequatefor the particular purpose,

b) to use a preferred form wherever possible,and

c) to use the chosen form consistentlythroughout the same set of documentation.

2.4.3 Specific guidelines on the application ofIS : 2032 from the point of view df choice ofalternative symbols, symbol sizes, line thinkness,orientation of symbols and met:hods of indicatingsymbol location are ‘covered In IS : 8270 (Part?)-1977*

2.5 Interconnection Diagrams and Tables

2.5.1 Interconnection diagrams and tablesprovide information on the external electricalconnections between equipment in an installation.They are used as ari aid in the fabrication ofwir ing and for maintenance purposes.Information on the internal connections of unitsare normally not provided but references to theappropriate circuit diagram [SEC IS : 8270 (Part4)-1977*1 may be provided.

2.5.2 The diagrams may employ single ormultiple representation and may be combinedwith or replaced by tables, provided clarity ismaintained. The latter are recommended when thenumber of interconnections is large.

2.5.3 Guidance on layout, identification andtypes of interconnection diagrams and tables aregiveri in IS : 8270 (Part 5)-l97h*

2.6 Marking and Arrangement of Conductors

2.6.0 General

2.6.0.1 l-he purpose of marking is to pro\,idc a.meanb whereby conductors can be id!xntified in acircuit and also after they hake been detachedfrom the terminals to which they ar-e connected.Main marking is a system of markingcharactcri7ing each conductor or group ofconductors irrespective of their electrlcal function.Supplementary marking is used as supplement to

*Guide lor preparatton of dlagramb. chart\ and table\ forelectroteclln~~lop~:

Part 3 General requlrrmPnt\ for diagramsPar1 4 CIKUII diagrams.Parr 5 lntcrconnwmn diagrams and tablea.

a main marking based on the electrical functiortofeach conductor or group of conductors.

2.6.0.2 The various methods of markingapplicable to electrical installations and theequipment which form part of them are coveredin IS : 5578-l970*

2.6.1 I d e n t i f i c a t i o n o f I n s u l a t e d a n d Bprekonducrors - For the .durposes of this code, theprovisions of Table I below shall apply for thegeneral application of marking conductors ininstallation. The rules also apply for markingconductors in assembies, equipment andapparatus. Reference is -also drawn to theprovisions contained in relevant Indian Standard.

2.6.2 Arrangement qf Conductors

2.6.2.0 Bus-bars and main connections whichare substantially in one plane shall be arranged inthe order given in either 2.6.2.1 or 2.6.2.2according to the system. The relative orderremains applicable even if any poles of the systemare omitted.

.2.6.2.1 AC .41wernIs - The order of phaseconnection shall be. red, yellow and blue:

a)

b)

C)

d)

When the run of the conductors ishorizontal. the red shall be on the top or onthe left or farthest away as viewed from th’ef r o n t .

When the run of the conductors is vertical,the red shall be on the left or farthest awayas viewed from the front.

When the system has a neutral connection inthe same place as the phase connections, theneutral shall occupy an outer position.

Unless the neutral connection can be readilydistinguished from the phase connections.the order shall be red. yellow. blue andblack.

2.6.2.2 DC .vr.\rena -~ Ihe arrangement shallbe as follows:

b)

c)

When the run of the conducto-rs ishorizontal. the red shall be on the top or onthe left or farthest away is viewed from thefront. .

When the run of the conductors is vertical.the red shall be on the left or farthest awayas viewed from the front.

When the system is 3-wire with theconductors in the same place. the neutralshall occupy the middle position.

*Guldc lor marktng of insulated conductors


TABLE I ALPHANUMERIC NOTATION, GRAPHICAL SYMBOLS AND COLOURS

(Clause 2.6. I)

DE>IGNATION OF C O N D U C T O R S I~JENTIFICATI~N w

(1)

Supply acsystem

Apparatusac system

SUPPlYdc system

Supply acsystem

(single phase)

Protective

Earth

IPhase IPhase 2Phase 3Neutral

I

Phase IPhase 2Phase 3Neutral

I

PositiveNegativeMidwire

Phaseseutral

conductor

A1 \

Alphanumeric Graphical ColourNotation Symbol

(2) (3) (4)

L I RedL2 YellowL3 BlueN Black

U RedV YellowW BlueN Black

L+ + RedL- BlueM Black

L RedN Black

PE

E

Green andYellow

No colourother than thecolour of thebare conductor

Noiseless (clean earth) TE

Frame or chassis M M

Equipotential Terminal C C

Underconsideration.


SECTION 5 UNITS AND SYSTEMS OF MEASUREMENT

0 . F O R E W O R D

0.1 The International System of Units (Sl) havereceived worldwide acceptance and in’ everycountry legislation for their adoption either existsor is being introduced. It has been introduced inIndia under the Weights and Measures Act, 1976.Use of Sl Units in matters relating to electricalengineering practice has many advantages.

0.2 This Section of the Code, for reasons ofbrevity, is restricted to electrical units only.Reference may therefore be necessary toIS : 10005-1980*.

1. S C O P E

1.1 This Section of the Code covers units andsystems of measurement in electrotechnology.

2. ITNITS AND SYSTEMS OFMEASUREMENT

2.1 Absolute Units

2.1.1 A m p e r e (unit of electric current) Aconstant current which. maintained i n t w oparallel straight conductors of infinite Icngth, ofnegligible circular CI-W\ section and placed at adistance of one mctrc apart In a vacuum willproduct a force ol 2 X IO ’ newton per metrelength between the conductors.

2.1.2 ~‘cllilol,ll~ (unit 01 quantlt\ ofelectricity) The quantit! of elcctricitlj conveyedin one second by a current of o n e a m p e r e .

2.1.3 r~rot/ (unit of ctectric capacitance) Thecapacitance of an electric capacitor having adifference of elect;-ic potential of one LOII hct\+een

the plates, when it is charged with a quantit; ofelectricity of one coulomb.

2.1.4 Henry (unit of electric inductance) - Theinductance of a closed circuit in which an emf ofone volt is produced when the current in thecircuits varies at the uniform rate of one ampereper second.

2.1.5 Ohm (unit of electrical resistance) l-heelectrical resistance between two points of aconductor when a constant potential difference ofone volt, applied to thehc points. produces acurrent of one ampere in the conductor. providedno emf is generated in the conductor.

2.1.6 Volt (unit of electric potential differenceatid emf) - The difference of electric potentialwhich exists between two points of a conductorcarrying a constant current of one ampere. whenthe power dissipated between these points is onewatt.

2 . 1 . 7 Weber (unit .of magne t i c f l ux ) Themagnet ic f lux which, l inked wi th a c i rcui tcomposed of a single turn produces in it an emf ofone volt if it is uniformly reduced to zero in onesecond.

2.1 .8 Wurf (unit of electric power) -~ Thepower which results in the production of energy atthe rate of IJ,‘s.

2.1.9 Siemens (unit of electric conductance) -The conductance of a conductor of resistance Iohm and is numerically equal to I ohm-‘.

2.1.10 Teslu (unit of magnetic flux density) -The tesla is a magnetic flux density of I Wb/m’.

2.2 The electrical units defined in 2.1, togetherwith their expression in terms of other units,recommendations on the selection of theirmultiples and submultiple\ and supplementaryremarks (if any) are enumerated in Table I.


QUANTITY

(1)

Electric current

Power

Quantity of clectri-city, electricc h a r g e

Electric potential,potential difference,electromotive force

Capacitance

Electrical resistance

Conductance

Magnetic flux

Magnetic fluxd e n s i t y

Inductance

Conductivity

Electric ticld.strength

Permeability

Permittivity

Reluctance

Resistivity

NAME

(2)

a.mpere

watt

coulomb

Volt

Farad

ohm

siemens

wcber

tesla

henry

siemens/mctrc

volt/metre

henry/ metre

farad permetre

I per henry

ohm. mctrc

~(ClOUSP 2.2)

SpOlOL

(3)

A.

W

C

V

F

n

S

Wb

T

H

S/m

V/m

H/m

F/m

H-’

f3.m

TABLE I ELECTRICAL UNITS OF MEASUREMENT

EXPRESSIONIN TERMS O FOTHER UNITS

(4)

-

J/s

.-

WI.4

c/v

V/A

NVV.S

Wb/ m’

Wb/A

EXPRESSIONm TERMS

OF SIBASE Uhs

(9

-

m*.kg.s“

s.A

m*.kg.s-‘.A-’

m’.kg.s-‘.A“

m’.kg.s-‘.A-*

rn-‘.kg-‘.s-‘.

mz.kg.s~z.A-’

kgs’.A-’

m3.kg-‘.S’.A’

m.kg.i’A’

m~‘.kg~‘.s*.A*

m’.kg.s-‘.A-’

SELECTION OFMIILTIPLES

(6)

kA. mA. WA.nA. PA

GW. MW, kW.mW, .PW

kc. PC. nC,PC

MV, kV, mV,Ir V

mF. rrF, nF,PF

GR, Mf-l, Kfl.mR, .J~R

kS, mS, PS

mWb

mT. PT. nT

mH. PH. nH,PH

MS/m. kS/m

MV/m, kV/m01 V/mm, V/m,mV/m. rV/m

rH/m. nH/m

pF/m, nF/m.pF/m

-

GfTm, MfLm,k0.m. fkm.mfIm. Itflm.nflm.


SECTION 6 STANDARD VALUES

0.1 Standardization of basic parameters such asvoltage, currents and frequency is one of theprimary exercises undertaken at the national level.This standardization helps in laying a soundfoundation for further work reiating to product orinstallation engineering. The values of voltagesrecommended as standard in this SeAon arebased on the contents of IS : 585-1962*.

0.2 This history of standardization of systemvoltages nart;Pl*I.-rly those of systems operatingbelow medium voltage levels is enumerated inIS : 585.

1. SCOPE

1.1 This Section of the Code covers standardvalues of ac and dc distribution voltages,preferred values of current ratings and standardsystem frequency.

2. STANDARD VALtiES OF VOLTAdES

2.0 General

2.0.1 For the sake of completeness. all thestandard values of voltages given in IS : 585-1962* relating to ac transmission and distributionsystems are reproduced in this Section. However.it is noted that for most of the types ofinstallations covered in subsequent parts of theCode. only the lower voltage values would berelevant.

2.0.2 For medium and low voltage distributionsystem.\. the original recommended. standarcJvalues of nominal voltages were 230 V for single-phahc and 230 400 V for three-phase system.Howclcr. during 1959. to al ign with IECrccommcndation\ and in view of’ the economicadbantageh thry offered. values of 240 V si’ngle-phase atid 240 415 V *three-phase had beenadopted.

2.0.3 In the case of voltages above I kV, theimportance of highest system voltage. which aregeneralI!, IO percent above the correspondingnominal voltages given in 2.1.2.1. is recognizedand product standards relate the voltage.rating ofequipment with respect to highest system voltagesonly.

2.1 Standard Declared Voltage

2.1 .I Sitl~lc- Phasr. Trcvo- Wire System - Thestandard voltage shall be 240 V.

2.1.2 Three- Phase S_wem

-*Vol~gc\ and frequency for tran\mi\\wn and distribution

systcmb


2.1.2.1 The standard voltages for three-phasesystem shall be as under:

415 v3.3 kV6.6 kVI I kV

f: K

(voltage to neutral - 22 $

II0 kV132 kV220 kV400 kV

N OTE I - These boltages refer to the Ime-Id-line voltage.

NOIE 2 I IO kV is not a standard voltage for transmissionpurposes but this value has been included for the sake ofequipment thal are required for use on the I IO kV systemsalready in existence. It is realized that. because of economicand other co+iderations. extensions to existing systems at thisvoltage may have to be made at the same vbltage.

2.1.3 The standard dc distribution ,voltage shallbe 2201440 v.

2.2 .Voltage Limits for AC Systems

2.2.1 The voltage at any point of the systemunder normal conditions shall not depart from thedeclared voltage by more than the values givenbelow:

a) 6 percent in the case of low or mediumvoltage; or

b) 6 percent on the higher side or 9 percenton the lower side in the case of highvoltage; or

c) 12.5 percent in the case of extra highvoltage.

NO T E-The permissible variations given above are inaccordance *vith Indian Electricity Rules, 1956. and areapplicable to the supply aurhorities.

2.2.2 For installation design purposes, thelimits of boltage between which the system andthe equipment used in the system shall bc capableof operating continuously are as follows:

240 V 264 v415 v 457 v3.3 kV 3.6 kV6.6 kV 7.2 kVI I kV I2 kV22 kV 24 kV33 kV 36 kV66 kV 72.5 kV

132 kV I45 kV220 kV 245 kV400 kV 420 kV

HighestVoltage

(Uln)

LOWSIVohage

‘216 V374 v3.0 kV6.0 kVIO kV20 kV30 kV60 kV

I20 kV200 kV380 kV

Noit This variation in voltage should not be confusedwith the permissible variarion from the declared voltage asgiven in 2.2.1.

25

3. PREFERRED CURRENT RATINGS 4. STANDARD SYSTEM FREQUENCY

3.1 The preferred current ratings shall be selectedfrom. the R5 series. If intermediate values are 4.1 The standard system frequency shall be 50required, the same shall be selected from RIO H7.series (see IS : lO76-1967*).

4.2 The limits within which the frequency is to bemaintained are governed by the IE Rules.

NATIONAL EI.ECTRICAI. CODE

SECI’ION 7 FUNDAMENTAL PRINCIPLES

O . F O R E W O R D

0.1 This Section contains the fundamentalprinciples for electrical installation. The basiccriteria in the design of electrical installation areenumerated in this Section which could be takennote of in the planning stages. The specific natureof each occupancy cal ls for addit ionalinformation which are summariired in therespective Sections of the Code.

0.2 The fundamental principles for protection forsafetv f rom various hazards in the use ofelectricity. enumerated in 3.1 ate based on IECPub : 364-2 ‘Electrical installations of buildings.Part 2 Fundamental principles’ issued by theInternational Electrotechnical Commission.Measures for achieving protection against thevarious hazards are under consideration by theNational Electrical Code Sectional Committee. Itmay be added that subsequent requirements of theCode would. however. provide sufficientguidelines in respect of achieving the desired levelof safety.

1. SCOPE

1.1 This -Section of the Code enumerates thefundamental principles of design and execution ofelectrical installations.

2. FUNDAMENTAL PRINCIPLES

2.0 General

2 . 0 . 1 Co~~ornrir.r~ H*ith I n d i a n E1ecrricir.vRules - The installation shall generally becarried out in conformity with the requirements ofthe IE Rules (1956) as amended from time totime. and also the relevant regulations of theelectric supply authority concerned.

2 .0 .2 Materials Al l materials. f i t t ings.equipment and their accessories, appliances, etc.used in an electrical installation shall conform toIndian Standard Specifications wherever theyexist. In case an Indian Standard does not exist.the materials and other items shall be thoseapproved by the competent authority.

2.0.3 b+‘orktmn.ship Good workmanship isan essential requirement for compliance with thisCode. Unless otherwise exempted under the IERules. the work on electrical installations shall becarried out under the supervision of a personholding a certificate of competency issued by, arecognized authority. The workmen shall alsohold the appropriate certificate of competency.

2.1 Coordination

2 .1 . I E.rchange q/ It@mation

2.1.1.1 Proper coordination and collaborationbetween the architect. building engineer and the

PART t GENERAI. AND COMMON ASPECTS

electrical engineer shall be ensured from theplanning stage of the installation. The provisionsthat would have to be made for theaccommodation of substation, transformerswitchgear rooms, lift wells and other spacesrequired to be provided for service cable ducts.openings, etc. in, the civil work. and such otherrelevant data shall be specified in advance.

2.1.1.2 In all cases, that is. whether theproposed electrical work is a new installation oran extension to the existing one, or amodification. the relevant authority shall beconsulted. In all such cases. it shall also beensured that the current carrying capacity and thecondition of the existing equipment andaccessories are adequate.

2.1.1.3 Sufficient coordination shall beensured with the civil architect in the initial stagesitself to ensure that sufficient building space beallotted for electrical installation purposes such asthose required for sub-station installation, fromthe point of safety

2.1.1.4 The building services plan shall alsoinclude at the early stages all the details ofservices that utilize electrical energy and therequirements of the electrical installation in orderto enable the designers and others involved todecide the coordination to be ensured.

2.2 Distance from Electric Lines No buildingshall be allowed to be erected or re-erected. or anyadditions or alterations made to the existingbui lding. unless the fol lowing mtnimumclearances are orovided from the overhead electricsupply lines: ’

a) 1.o~ a n d medwm \olt;~grIlne\

h) High\ 0ltagcIlnes

Up IO andmcludmg11000 v

Abwc I I kVup IO a n dmcludmg33 kV

c) Fxtra high voltage l ines

Verricol Horizonralm m

2.5 I 23.1 I.2

3.7 2.0

3.7 2.0( s e e NOTE) (SW NOTE)

Nolr For extra high voltage l ines apart j rom themlnimum clearances indicated. a rertical and horizontalclearance of 0.30 m for ever) additional 33 kV or part thereofshall he prwided

2.3 Lighting and Ventilation - From the point ofview of conserving e.rergy, it is essential toconsider those aspects of design of buildings asvital, which would enable use of natural lightingand ventilation to the maximum. Attention is.however. drawn to the general requirementsstipulated in Section 14; Part I.

27

2.4 Heat Insulation

2.4.1 For information regarding recommendedlimits of thermal transmit^&nce of roofs and wallsand transmission losses due to differentconstructions, reference shall be made toIS : 3792-1978’.

2.4.2 Proper coordination shall be ensured toprovide for necessary arrangements to install andserve the electrical equipment needed for theairconditioning and heating services in thebuilding.

2.5 Lifts and Escaiators- Fdr information df theelectrIcal engineer, the lift/escalator manufacturerin consultation with the building planners,. shalladvise of the electrical requirements necessary forthe lifts and escalators to be installed in thebuilding. G&era1 provisions are outlined inSection 14, Part I.2.6 Location and Space for ElectricalEquipment - Even though specific provisionsregarding the choice of location and spacerequirements for electrical installation in buildingshave been provided in the relevant parts of theCode the following asp&s shall be taken note ofin general while planning the building design:

a)

b)

c)4e)

r)g)

Need for and location and requirements ofbuilding substation,Load centre and centre of gravity ofbuildings,

Layout,Room/spaces required for electrical utility,

Location and requirements of switchrooms,

Levels of illumination, and

Fannage.

3. DESIGN OF ELECTRICALINSTALLATION

3.0 General

.3.0.1 The design of the electrical installationshall take into account the following factors:

a) The protection of persons, livestock andproperty in accordance with 3.1. and

b) The proper functioning of the electricalinstallation for the use intended.

3.0.2 The following factors shall therefore bekept in view:

a) Characteristics of the :available supply orsupplies,

b) Nature of demand,

c) Emergency supply or supplies,

d) Environmental conditioni,

e)r)

f3)h)j)k)

ml

Cross-section of conductors,Type of wiring and methods of installations,Protective equipment,Emergency control,Disconnecting devices,Preventing of mutual influence betweenelectrical and noneiectrical installations,and

Accessibility.

3.1 Protection for Safety

3.1.0 The requirements stated in 3.1.1 to 3.1.6are intended to ensure’ the safety of persons,livestock’ and property against dangers anddamage which may arise in the reasonable use ofelectrical intitallations.

NOTE - In electrical installations. two major types of risksexist:

a) shock currents; and

b) excessive temperatures likely lo cause burns, fires andorher injurious effects.

3.1.1 Protection Against Direct Contact -Persons and livestock shall be protected againstdanger that may arise from contact with live partsof the installation.

This protection can be achieved by one of thefollowing methods:

4

b)

Preventing a current from passing throughthe body of any p’erson or any livestock,and.

Limiting the current which can pass througha body to a value lower than the shockcurrent.

3.1.2 Protection Against lndirhct Contact -Persons and livestock shall be protected against

dangers that may arise from contact with exposedconductive parts.


a)

b)

C.)

Preventing a fault current from ‘passingthrough the body of any person or anylivestock.

Limiting the fault current which can passthrough a body to a value lower than theshock current,

Automatic di&onnection of the supply onthe occurrence of a fault likely to cause acurrent to flow through a body in contactwith exposed conductive parts, where thevalue of that current is equal to’ or greaterthan the shock current.

3 .1 .3 P r o t e c t i o n Agpinst Thermal EJfects inNormal Ser\Vce - The ,electrical installation shallbe so arranged that there is no risk of ignition offlammable materials due to high temperature or


electric arc. Also, during normaLoperation of theelectrical equipment, there shall be no risk ofpersons or livestock suffering burns.

3.1.4 Protection Against Overcurrent -Persons or livestock shall be protected againstinjury, and property shall be protected againstdamage due to excessive tempeatures orelectromechnical stresses caused by anyovercurrents likely to arise in live conductors.


a) Automatic disconnection on the occurrenceof an overcurrent before this overcurrentattains a dangerous value taking intoaccount its duration, and

b) Limiting the maximum overcurrent to a safevalue and duration.

3.1.5 Protection Against Fault Currents -Conductors, other than live conductors, and anyother parts intended to carry a fault current shallbe capable of carrying that current withoutassuming excessive temperature.

NOTE I - Partxular attention should be given to earth faultcurrents.

NOPE 2 - For hve conductors, compliance with 3.1.4assures their protectron against any fault currents. includrngovercurrents caused by faults.

3.1.6 Profecrion Againsr Overvolrage -Persons or livestock shall be protected againstinjury and property shall be protected against anyharmful effects of a fault between *live parts ofcircuits supplied at different voltages.

Persons or livestock shall be protected againstinjury and property shall be protected againstdamage from ‘any excessive voltages likely to arisedue to other causes (for example, atmosphericphenomena or switching voltages).

3.1.7 Methods for Prorecrion for Safer,! -While the general principles of protection againsthazards in an electrical installation are given in3.1.1 to 3.1.6 guidel ines on the methods f o rachieving protection and the choice of a particularprotective measure are under consideration.

3.2 Other Factors of Design3.2.1 Characteristics qf the Available Supply or

Yupplies

aj Nature of current: ac -and/or dc,

b) Nature and number of conductors:

1) For ac:

i) phase conductor(s),

ii) neutral conductor, and

iii) protective conductor.

2) For dc:i) conductors equivalent to those listed

above.

c) Values and tolerances:I) voltage and voltage tolerances

(see Section 6 of Part I),2) frequency and frequency tolerances

(see Section 6 of Part I),3) maximum current allowable, and4) prospective short-circuit .current

(see Section 13 of Part I).d) Protective measures inherent in the sup ly,

for example, earthed (grounded) neutra P ormid-wire.

e) Particular requirements of the supplyundertaking.

3.2.2 Nature of Demand-The number -andtype of the circuits required for lighting, heating,power, control, signalling, telecommunication,etc, are to be determined by:

a) location of points of power demand,b) loads to be expected on the various circuits,c) daily and yearly variation of demand;d) any special conditions,e) requirements for control, signalling,

telecommunication, etc.3.2.3 Emergency Supply or Supplies (see also

Part 2 of the Code)a) Source of supply (nature, characteristics),

andb) Circuits to be supplied by the emergency

source.3.2.4 Environmental Conditions (see Section 8

of Part I)3.2.5 Cross Section of Conductors -the cross

section of conductors shall be determinedaccording to:

a) their admissible maximum temperature,b) the admissible voltage drop,c) the electromechanical stresses likely to occur

due to shortcircuits,d) other mechanical stresses to which the

conductors may be exposed, -ande) the maximum impedance with respect to the

functioning of the short-circuit. protection.NOTE - The above listed items concern primarily the safety

of electrical installations. Cross-sectional areas greater thanthose required for safety may be desirable for economicoperation.

3.2.6 T)qpe o f W i r i n g arid M e t h o d s o fInstallations - The choice of the type of wiringand the methods of installation depend on:

a) the nature of the location,b) the nature of the walls or other parts of the

building supporting the wire,


cl

4e)

0

accessibility of wiring to persons andlivestock,

voltage,

the electromechanical stresses likely to occurdue to short-circuits, and

other stresses to which the wiring may beexposed during the erection of the electricalinstallation or in service.

3.2.7 Protective Equipment - The characteris-tics of protective equipment shall be determinedwith respect to their function which may be, forexample, protection against the effects of:

a) overcurrent (overload. short-circuit),

b) earth-fault current,

c) overvoltage, and

d) undervoltage and no-voltage.

The protective devices shall operate at values ofcurrent, voltage and time which are suitablyrelated to the characteristics of the circuits and tothe possibilities of danger.

3.2.8 Emergency Control- Where in case ofdanger, there is necessity f o r i m m e d i a t e

interruption of supply, in interrupting device shallbe installed in such a way that it can be easilyrecognized and effectively 2nd rapidly operated.

3.2.9 Disconnecting Delkes -~ Disconnectingdevices shall be provided so as t0 pe rmi tdisconnection of the electrical installation. circuitsor individual items of apparatus as required fOJmaintenance, testing, fault detection OJ repair.

3.2.10 Prevention ej’ Mutual Injluencv BetH,eellElectrical ud .‘l’oll-rkt~c,t~ic,al Iu\~uIIu~~o:?: Theelectrical instaiiatlon shall be arranged in such away that no mutual detrimental influence willoccur between the electrical installation and non-electrical installations of the building.

32.11 Accessihilit~~ of Electrical Equipment ~~The electrical equipment shall be arranged so asto afford as may be necessary:

4

b)

sufficient space for the initial installationand later replacement of individual items ofelectrical equipment, and

accessibility for operation, testing.inspection, maintenance and repair.


SECTION 8 ASSESSMENT OF GENERAL CHARACTERISTICSOF BUILDINGS

O . F O R E W O R D

0.1 An assessment of the general characteristicsof buildings is essential before planning for theneeds of an electrical installation. Based on thework of the International ElectrotechnicalCommission (IEC) under IECjTC 64 “ElectricalInstallations of Buildings’ this section covers acheck l i s t o f va r ious fac to rs tha t r equ i reassessment.

0.2 This Section follows the internationallyrecommended method of identification of theexternal influences on the electrical installationsuch as environment, utilization and method ofconstruction of the building. Out of theseinfluences, those which are specifically importantfor specific occupancies are listed at the relevantSections of the Code. However, it is hoped thatthis Section would also enable understanding ofinstallations not explicitly covered by the Code.

0.3 The contents of this Section are primarilyintended for installations inside buildings thoughto the extent possible they could be utilized foroutdoor sites. However mqe severe conditionsmay prevail at outdoor sites and these requirespecial considerations.

I. SCOPE

1.1 This Section of the Code covers guidelines forassessing the characteristics of buildings and theelectrical installation therein.

2. ASSESSMENT OF GENERALCHARACTERISTICS OF BUILDINGS

2.0 An assessment of the general characteristicsof buildings as enumerated below is essential fromthe point of view of design and protection forsafety of the electrical installa!ion. T h e s echaracteristics when assessed shall also be takeninto consideration in the selection and erection ofequipment.

2.1 Identification of General Characteristics

2.1 .O Purposes, Supplies and Structure - Thefollowing shall be assessed:

4

b)

c)

Maximum demand and diversity from thepoint of view of economic and reliabledesign (see 3.2.2 of Section 7, Part I).

Type of distribution system, which include,types of systems of live conductors and typesof system earthing.

NOIF.- For t y p e s o f system earthing, WEAppendix A.

Supply characteristics such as nature ofcurrent, nominal voltage, prospective short-circuit currents.


NOTE - This assessment shall include those charac-teristics of main, standby and safety supply services.

d) Diversion of installation from the point ofview of control, safe operation, testing andmaintenance.

2.2 Identification of External Influences on theElectrical Installation

2.2.1 The characteristics of the followingexternal influences shall be assessed:

I) Environments

a) Ambient temperature,

b) Atmospheric humidity,

c) Altitude,

d) Presence of water,

e) Presence of foreign solid bodies,

f) Preserce o f c o r r o s i v e o r p o l l u t i n gsubstances,

g) Mechanical stresses,

h) Presence of flora and/or mould growth,

j) Presence of fauna,

k) Electromagnetic, electrostatic or ionizinginfluences,

m) Solar radiation,

n) Seismic effects,

p) Lightning, and

q) Wind.

2) Utilization

a) Capability of persons,

b) Electrical resistance of human body,

c) Contact of persons with earth potential,

d) Conditions of evacuation in an emergency,and

e) Nature of processed or stored material.

3) Construction of Buitdings

a) Constructional materials, and

b) Building design.

2.2.2 Table I suggests the classification andcodification of external influences which requireassessment in the design and erection of electricalinstallation.

NOTE I - Each condition of external influence is designatedby a code comprising 2 group of two capital letters and anumber as follows:

31

The jirsr let terexternal injluence

A = environment

B = utilization

C = construction

relates IO the general category of

of buildings

T h e s e c o n d l e t t e r relares t o the na ture o f theexrernal injuenre

A

B

c

T h e n u m b e r relates to r h e c l a s s w i t h i n e a c hexternal inJluence

I

2 . .

3

For example, the code AC 2 signifies:

A = environment

AC = environment altitude

AC2 = environment altitude > 2 000 m

The code given here is not intended to be usedfor marking equipment.

NOTE 2 -The characterist ics defined for electr icalinstallations are those accepted by the IEC and as applicablefor electrical installations in buildings. Influences on outdoorinstallations are separately defined in the respective parts ofthe Code.

For the time being, the characteristics of influences (co1 2.Table I) are given in descriptive language only. Codificationfor the same (see NOTE I above), as recommended by IEC aregiven in co1 4 for information. It is hoped that in due coursethe. users of the Code would be familiar with the codificationin terms of which the requirements would be stated in futureeditions.

2.3 Compatibility - An assessment shall be madeof any characteristics of equipment likely to haveharmful effects upon other electrical equipment orother services or likely to impair the supply.Those characteristics include, for example:

a) transient overvoltages,

b) rapidly fluctuatirig

c) starting currents

d) harmonic currents,

e) dc feedback,

loads,

2.4 Maintainability - An assessment shall bemade of the frequency and quality of maintenancethe installation can reasonably be expected toreceive. during its intended life. Where anauthority is to be responsible for the operation ofthe installation, that authority shall be consulted.Those characteristics are to be taken into accountin applying the requirements of this code so that,having regard to the frequency and quality ofmaintenance expected:

a) any periodic inspection and testing andmaintenance and repairs like1 to benecessary during the intended li e can befyreadily and safely carried out,

the effectiveness of. the protective measuresfor safety during the intended life is ensured,and

c) the reliability of equipment for properfunctioning of the installation is appropriateto the intended life.

f) high-frequency oscillations, and

g) earth leakage currents.

TABLE 1 ASSESSMENT OF GF.NERAI. CHARACTERISTICS OF BI’II.DINGS

\

CLASS DESIGSI IO\

(1)

(ClNl/\<’ 2 2.2)

CII\K.\(‘II~KISI,~‘\ Awl I( \, IO\\ \\I) COIN

I-\ \\ll’l I \

(2) (3) (4)

Environment

I) Ambienttemperature

l-he ambient temperature 10 heconsidered for the cqulpment is thetemperature at the place where theequipment is to he installed resultingfrom the influence of all otherequipment in the hame location. uhcnoperating. not taking into accountthe thermal contrthution of theequipment to he installed.

Lower and upper limits of ranges 01ambient temperature:

-WC +50 c A A I-400 c +5”c AA2-2YC +5oc AA3

- 5 ° C +40” c A A 4+5”c +400 c AA5t5oc +6ooc AA6

(Conrinued)


TABLE 1 ASSESSMENT OF GENERAL CHARACTERISTICS OF’ BUILDINGS - Comd

(‘I \\\I h\IGSArIO”;

(1)

CHAI~A~TE~I~TICS

(2)

The average temperature over a 24 hourperiod must not exceed 5°C below theupper limits.

A PPLICATIONS AND CODE

EXAMPLES

(3) (4)

Combination of two ranges to definesome environments may be necessary.Installations subject to temperaturesoutside the ranges require specialconsideration.

2) Atmospherichumidity

under consideration

3) Altitude <2OOOm>ZOOOm

4) Presence of water

Negligible Probability of presence ofwater is neghgible

Free-fallingdrops

Sprays

Splashes

Jets

Waves

lmmeralon

Submersion

5) Presence of foreignsolid bodies:

Negligible

Small Objects

Very smallobjects

Possibility of verticallyfalling drops

Possibility of water falling as spray Locations in which sprayed waterat an angle up to 60’C from the forms a continuous film on floorsVertlCal and ior walls.

Possibility of splashes from anydirection

Locations where equipment may be A D 4subjected lo splashed water, thisapplies. for example, 10 certainexternal lightmg fittings. constructionsite equipment, etc.

Possibility of .jets of water fromany dIrectIon

PosGbihty of water waves

Possibility of intermittent partialor total covering by water.

Possibility of permanent and totalcoverlng by water

The quantity of nature ot dust orforeign sohd bodies i\ notslgmficant.

Presence of foreign solid hodItwhere the smallest dlmenslonis not less than 2.S mm

Presence of foreign solid hodieswhere the smallest dimension isnot Ins than I mm.

NOI I. In conditions AEI andAE3. dust may be present but isnot slgmficant to operation ofthe electrical equipment.

AC1AC2

ADI

A D 2

Locations in which the wallsdo not generally show tracesof water but may do so forshort periods, for example!in the form of vapour whichgood, ventilation dl les rapidly.

Locations in which water vapouroccasionally condenses as dropsor where steam may occasionallybe present.

AD3

Locations where hosewater is usedregularly (yards. car-washing bays).

A D 5

Seashore locatIon\ huch as piers.heache\ quays. etc.

A D 6

LocatIon\ which may be flooded AD7and or uhere water may be at leastI50 mm ahove the highest point ofequipment. the lowest part ofequipment being not more than I mbelou the water surface.

Locations such as iwlmming poolsuhere electrical equipment is per-manently and totally covered withwater under a pressure greater than0.1 har

A D 8

A E I

1001s and small objects are examples AE2of foreign solid bodies of which thesmallest dimension is at least 2.5 mm.

Wires are examples of foreign solidbodies of which the smallest dimen-slon is not less than I mm.

AE3

P A R T 1 GENERAI. A N D C O M M O N A S P E C T S 33

34

TABLE 1 ASSESSMENT OF GENERAL CHARACTERISTICS OF BUILDINGS Conrrl

CI \ss DI+I<;\ .\ I IOX CII .,w~,~‘l-i WiS~II(‘S APPLI(‘ATIOYS AK,,EXAMPLM

(1) (2) (3)

DtJst Presence of dust in significantquantity.

6) Presence of corrosiveor polluting substances:

Negligible The quantity or nature of corrosiveor polluting substances is not signi-

Atmospheric

Intermittentor accidental

Continuous Continuously subject to corrosiveor polluting chemical substancesin substantial quantity.

7) Mechanical Stresses:

a)’ Impact

Low severity

Medium severity

High severityNOTE - Provisional classification.

Quantitative expression of impactseverities is under consideration.

b) Vibration

Low severity

ficant

The presence of corrosive orpolluting substance of atmosphericorigin is significant.

Intermittent or accidental subjectionto corrosive or polluting chemicalsubstances being used or produced

Medium severity

High severity

Installations situated by the sea orindustrial zones producing seriousatmospheric pollution, such aschemical works and cement works;this type of pollution arises especiallyin the production of abrasive, insu-lating or conductive dusts.

AF2

Locations where some chemicalproducts are handled in smallquantities and where these productsmay come only accidentially intocontact with electrical equipment; suchconditions are found in factory,laboratories, other laboratories or inlocations where hydra-carbons areused (boiler-rooms, garages, etc).

AF3

For example, chemical works. AF4

coot

(4)

AE4

A F I

Household and similar conditions.

Usual industrial conditions.

Severe industrial conditions.

AGI

AG2

AC3

Household and similar conditions where AHIthe effects of vibration are generallynegligible.

Usual industrial conditions.

Industrial installations subjectto severe conditions.

A H 2

A H 3

NOW - Provisional classification.Quantitative expression of vibrationseverities is under consideration.

c) Other mechanicalstresses

Under consideration

8) Presence of fungusand/or mould growth

AJ

No hazard No hazard of fungus and/ormould growth

AK1

Hazard hazard of fungus and/or mouldgrowth

9) Presence of vermin

No hazard No hazard

The hazard dcpcnda on local conditions AK2and the nature of fungus. IXstrnctionshould bc made bctvvccn harmfulgrowth of vcgctatton or condittonsfor promotion of mould grovvth.

(Conrinued)


TABLE 1 ASSESSMENT OF GENERAL CHARACTERISTICS OF BUILDINGS - Conrd

C LASS D ESIGNATION C%A~AUTERI~~I~~ APPLICATIONS AND CODEEXAMPLES

(1) (2) (3) (4)

Hazard Hazard from fauna (insects, birds, The hazard de nds on the nature ofsmall animals) the vermin. gstinction should

AL2

he made between:

- presence of insects in harmfulquantity or of an aggressive nature.

IO) Electromagnetic,electrostattc orionizing influences

Negligible

Stray currents Harmful hazards of stray currents.

Electromagnetics Harmful presence of electromagneticradiation.

loni7ation

Electrostatics

Induction

I I) Solar radiation

Negligible

Significant

12) Seismic effects

Negligible

Low severity

Medium severity

High severity

13) Lightning

- presence of small animals or birdsm harmful quantity or of an aggres-sive nature.

No harmful effects from stray currents,electromagnetic radiation, electrostaticfields. ioni7ing radiation orinduction.

Harmful presence of ionizing radiation.

Harmful presence of electrostatic fields.

Harmful presence of induced currents.

Solar radiation of harmful intensityand/or duration.

AMI

A M 2

A M 3

A M 4

A M 5

A M 6

ANI

AN2

Up to 30 Gal (I Gal = I cm/s’) A P I

over 30 up to and including 300 Gal AP2

over 300 up to and including 600 Gal AP3

greater than 600 Gal Vibration which may cause the AP4destruction of the building is outsidethe classification.

Frequency is not taken into accountin the classification; however, if theseismic wave resonates with thebuilding, seismic effects must bespecially considered. In general,the frequency of seismic accelerationis between 0 and IO H z .

Negligible

Indirectexposure

Directexposure

14) Wind

AQIHazard from supply arrangements Installations supplied by overhead AQ2

lines.

Hazard from exposure of equipment Parts of installation> located outside AQ3buildings. The risks AQ2 and AQ3relate to regions with a particularlyhigh level of thunderstorm activity.

(Under consideration)

Utilization

I) Capability of Persons

Ordinary Uninstructed persons BAI

Children Children in locations intended for Nurseries BA2their occupation.

( COrIliflUPd)


TABLE I ASSESSMENT OF GENERAL CHARACTERISTICS OF BUILDINGS - Con/d

Handicapped

Instructed

Skilled

2) Electrical Resistanceof the Human Body

Classification(Underconsideration)

3) Contact of Personswith Earth Potential

None

Low

Frequent

Continuous

4) Conditions ofEvacuation inan Emergency

5) Nature of Processedor Stored Materials

No signifiantrisks

Fire risks Manufacture. processing or

Explosionrisk

Contaminationrisks

CII 4K \(‘trKISTI(‘S

(2)

Norm ~- This class does not necessarilyapply to family dwellings.

A P P L I C A T I O N S AND CODEEXAMPUS

(3) (4)

Persons not in command of all their Hospitalsphysical and intellectual abilities(sick persons, old persons)

BA3

Persons adequately advised or Electrical operating areassupervised by skilled persons toenable them to avoid dangers whichelectricity may create (operating andmaintenance staff)

BA4

Persons with technical knowledge or Closed electrtcal operating areas.sufficient experience to enable themto avoid dangers which electricitymay create (engineers and technicians)

BA5

Persons in non-conducting situations

Persons do not in usual conditionsmake contact with extraneousconductive parts or stand onconducting surfaces.

Persons are frequently in touch withextraneous conductive parts orstand on conducting surfaces.

Persons are in permanent contactwith metallic surroundings andfor whom the possibility of inter-rupting contact is limited.

Low density occupation, easy con-ditions of evacuation.

Low density occupation. difficultconditions of evacuation.

High density occupation. easy condi-tions of evacuation.

High density occupation, difficultconditions of evacuation.

storageof flammable materials includingpresence of dust.

Processing or storage of explosiveor low flashpoint materials includ-ing presence of explosive dusts.

Presence of unprotected foodstuffs,pharmaceutics, and similarproducts without protection.

BB

Norr-conducting locations. BCI

BC?

Locations with extraneous conductiveparts. either numerous or of largearea.

BC3

Metallic surroundings such as boilersand tanks.

BC4

Buildings of normal or low heightused for habitation.

High-rise buildings.

Locations open to the public(theatres. cinemas).

High-rise buildings open to thepublic (hotels. hospitals, etc.)

Barns. wood-working shops. paperfactories.

Oil refineries. hydrocarbon stores.

BDI

BD2

BD3

BD4

BEI

BE2

BE3

Foodstuff industries. kitchens,NOT E - Certain precautions may be

necessary, in the event of fault, toprevent processed materials beingcontaminated by electrical equipment.for example, by broken lamps.

(Conrinued)


TABLE 1 ASSESSMENT OF GENERAL CHARACTERISTICS OF BUILDINGS- Conld

CLASS DESIGNATIOK

I) ConstructionalMaterials

Non-combustible

Combustible

2) Building Design

Negligible risk

Prtortgation of

Movement

Flexible orunstable

CHARAUERISTI~S APPLICATIONS AND CODEEXAMPLES

(2) (3) (4)

.Constructions of Building

-

Buildings mainly constructedof combustible materials

Buildings of which the shape anddimensions facilitate the spreadof fire (for example, chimneyeffects).

Risks due to structural movement(for example, displacement betweena building and the ground, orsettlement of ground .or buildingfoundations).

Structures which are weak or sub-jects to movement (for example.oscillation)

Wooden buildings

CA1

CA2

_ CBI

High-rise buildings. Forced ventilation CB2systems.

Buildings of considerable lengthor erected on unstable ground.

Contraction or expansion joints.

CB3

Tents, air-support structures. falseceilings. removable partitions.

CB4

Flexible wiring. Installations needingsupport.

A P P E N D I X A

(Clause 2. I .O)

TYPES OF SYSTEM EARTHING

The folloGng types of system earthing are independent of the earth electrodes oftaken into account in this Code. the p o w e r s y s t e m ,

a) TN Systems-TN power systems have onepoin t d i rec t ly ea r thed , then exposedconductive parts of the installation beingconnected to that point by protectiveconductors. Three types of TN systems arerecognized, according to the arrangement ofneutral and protective conductors as

c) IT qstem -~ The IT system has no directconnec t ion b e t w e e n l i v e p a r t s a n dearth, the exposed conductive parts ofthe electrical installation being earthed.

NOTE I - Figures I to 5 show examples of commonly usedthree-phase systems.

NOTE 2 -The codes used have the following meanmgs:follows:

TN-S system:

TN C-S system:

TN-C system:

having separate neutraland protective conduc-tors throughout thesystem,

in which neutral andprotective functionsa re combined in asingle conductor in apart of the system,and

in which neutral andprotective functionsare combined in asingle conductor thro-ughout the system.

b) TT s.llstem -- The TT power system has onepoin t d i rec t ly ea r thed , the exposedconductive parts of the installation beingconnected to earth electrodes electricallv


First letter indicates relationship of the power system toearth:

T = direct connection of one point to earth, and

I = all alive parts isolated from earth, or one pointconnected to earth through an impedance.

Second letter indicates relationship of the exposedconductive parts of the installation to earth:

T = direct electrical connection of exposed conductiveparts to earth, independently of the earthing of anypoint of the power system, and

N = direct electrical connection of the exposed conductiveparts to the earthed point of the power system, (in acsystem, the earthed point is normally the neutralpoint).

Subsequent letter(s) (if any) indicate arrangement of neutraland protective conductors:

s=

c=

neutral and protective functions provided by separateconductors,

neutral and protective functions combined in a singleconductor (PEN conductor).

37

SYSTEMEARTH S E D C O N D U C T I V E

P&R1 S

P O W E RS Y S T E M

E A R T H C O N D U C T I V EP A R T S

F I G. I T N - S S Y S T E M S E P A R A T E N E U T R A L A N D F I G. 2 T N - C - S S Y S T E M N EUTRAL AND PROTEC-P R O T E C T I V E C O N D U C T O R S THRO~JGHOIJI TIVE FIJN~TIONS CO M B I N E D I N A S I N G L E

I III: SJ~SIIXI CONDIKV~R IN A P A R T O F T H E S Y S T E M

P O W E RS Y S T E ME A R T H C O N D U C T I V E

P A R T S

F I G. 3 7-N-C SYSTFM. NEUTRAI. A N D PROI.E(.YIW~Ii~;(‘l’IONS C O M B I N E D I N A SING1.FC‘~NDI:~T~R ‘TIIROIIGIIOI:T I III: SI.SMM

L20L30Nt v

- A -‘ =

:-)) -o -* b---lI hPEL-_- -_-A

P O W E RS Y S T E M f

&E X P O S E D

E A R T H C O N D U C T I V EPART

S Y S T E ME A R T H C O N D U C T I V E

F I G. 4 TT SYSTEM

PART

FIG. 5 IT S~.S~M


SECTION 9 SELECTION OF EQUIPMENT

0 . F O R E W O R D

0.1 A series of product codes have been broughtout in the field of electrotechnology which coversdetails of selection, installation, and maintenanceof electric power equipment. This Section of theCode is prepared in such a manner as to bring outonly the essential criteria for selection ofequipment, and users of the Code arerecommended to make reference to individualproduct codes for detailed guidelines.

1. SCOPE

1.1 This Section of the Code covers generalcriteria for selection of equipment.

NOTE -This Section shall be read in conjunction with theIndian Standard codes on individual equipment.

2. SELECTION OF EQUIPMENT

2.1 Conformity to Indian Standards L- Everyi tem of e lec t r i ca l equ ipment used in theinstallation shall conform to the relevant IndianStandard specifications wherever available.

2.2 Characteristics - Every item of electricalequ ipment s e l e c t e d s h a l l h a v e s u i t a b l echaracteristics appropriate to the values andconditions on which the design of the electricalinstallation (see 3.2 of Section 7 of Part I) isb a s e d a n d s h a l l , i n p a r t i c u l a r , fulfil t h erequirements given in 2.2.1 to 2.2.4.

2.2.1 Voltage - Electrical equipment shall besuitable with respect to the maximum steadyvoltage (rms value for ac). likely to be applied, aswell as overvoltages likely to occur.

NOTE - For certain equipment, it may be necessary to takeaccount of the lowest voltage likely to occur.

2.2.2 Current - All electrical equipment shallbe selected with respect to the maximum steadycurrent (rms value for ac) which it has to carry innormal service, and with respect to the currentlikely to be carried in abnormal conditions and

the period (for example, operatingprotective devices, if any) during whichexpected to flow.

2.2.3 Frequency - If frequencyinfluence on the characteristics of

time ofit may be

has anelectrical

equipment, the rated frequency of the equipmentshall correspond to the frequency likely to occurin the circuit.

2.2.4 Power - All electrical equipment to beselected on the basis of its power characteristics,shall be suitable for the duty demanded of theequipment, taking into account the load factorand the normal service conditions.

2.3 Con.Iitions of Installation - All electricalequipment shall be selected so as to withrtandsafely the stresses and the environmentalconditions (see 3.2 of Section 7 of Part I)characteristic of its location to which it may beexposed. The general characteristics of buildinginstallat ions are assessed according to theguidelines given in Section 8, of Part 1 of theCode. If, however, an item of equipment does nothave by design the properties corresponding to itslocation it may be used on condition thatadequate additional protection provided as partof the completed electrical installation.

2.4 Prevention of Harmful effects - All electricalequipment shall be selected so that it will notcause harmful effects on, other equipment orimpair the supply during normal service includingswitching operations. In this context, the factorswhich may have an influence include:

a) power factor,

b) inrush current,

c) asymmetrical load, and

d) harmonics.

2.5 Guidelines on the selection of specificequipment are covered in the relevant IndianStandard codes of practice.


SECTION 10

0. F O R E W O

0.1 Testing and ensurmg that

ERECTION AND INITIAL TESTINGOF INSTALLATION

R D

the installationconforms to the predetermined conditions beforethe installation could be energized, is a necessaryprerequisite under the Giutory -provisions. ThisSection lists the aspects/parameters that arerequired to be verified before an installation couldbe certified as ready for energizing and use.

0.2 While a complete check list of items to bechecked and necessary tests to be done areincluded in this Section, individual productstandards cover more detailed guidelines onprecommissioning c h e c k s f o r i n d i v i d u a lequipment.

0.3 In addition to initial testing, periodic testingand preventive maintenance checks are necessary,the nature and frequency of such measuresdepending on the nature of the electricalinstallation in question. Guidelines on suchaspects are outside the purview of the Code.However, a reference could be made to individualequipment codes which cover maintenanceschedules:

0.4 The contents of this Section are based oniS_: 732 (Part 3)-1982*

1. SCOPE

1.1 This Section of theprinciples of erectionguidelines on initial testing

2. ERECTION

Code covers generalof installation andbefore commissioning.

2.1 For the erection of the electrical installation,good workmanship by su i tab ly qua l i f iedpersonnel and the use of proper materials shall beensured.

2.2 The characterist ics of the electricalequipment, as determined in accordance withSection 9 of Part I shall not be impaired in theprocess of erection.

2.3 Protective conductors and neutral conductorsshall be identifiable at least at their terminationsby colouring or other means. These conductors inflexible cords or f lexible cables shall beiden t i f i ab le by co lour ing or o ther meansthroughout their length (see 2.6 of Section 4 ofPart I).

2.4 Connections between conductors and betweenconductors and other electrical equipment shall bemade in such a way that safe and reliable contactsire ensured.

*Code of practice for electrical wiring installations: Part 3inspection and testing of installation.

40

2.5 All electrical equipment shall be installed insuch a manner that the designed coolingconditions are not impaired.

2.6 All electrical equipment likely to cause hightemperatures or electric arcs shall be placed orguarded so as to eliminate the risk of ignition offlammable materials. Where the temperature ofany exposed parts of electrical equipment is likelyto cause injury to persons, these parts shall be solocated as to prevent accidental contact therewith.

2.7 Attention is also drawn to the provisionscontained in relevant Indian Standard codes oninstallation of specific equipment which shall beadhered to during erection of the installation.

3. INSPECTION AND TESTING

3.1 General Requirements

3.1.1 Before the completed installation, or anaddition to the existing installation. is put intoservice, inspection and testing shall be carried outin accordance with the Indian Electricity Rules,1956. In the event of defects being found, theseshall be rectified, as soon as practicable. and theinstallation retested.

3.1.2 After putting the installation intoservice periodic inspection and testing shall becarried out in order to maintain the installation ina sound condition.

3.1.3 Where an addition is to be made to thefixed wiring of an existing installation the latters h a l l b e e x a m i n e d f o r c o m p l i a n c e withrecommendations of this Code.

3.2, Inspection of the Installation

3.2.0 General- At the completion of wiring, ageneral inspection shall be carried out bycompetent personnel to verify that the provisionsof this Code and that of Indian Electricity Rules,1956 have been complied with. This, among otherthings, shall include checking whether allequipment, fittings, accessories, wires and cables,used in the installation are of adequate rating andquality to meet the requirements of the load.General workmanship of the electrical wiring withregard to the layout and finish shall be examinedf o r n e a t n e s s t h a t w o u l d f a c i l i t a t e e a s yidentification of circuits of the system. adequacyof clearances, soundness of termination withrespect to tightness, contact prcssui-e and contactarea. A complete check shall also be made of allthe protective devices, with respect to the rating,range of settings and for co-ordination betweenthe various protective devices.

NATIONAL EI.ECTRICAI. CODE

3.2.1 Substation Installations ~~ in substationinstallation it shall be checked whether:

1)

2)

3)

the installation has been carried out inaccordance with the approved drawings,

phase-to-phase and phase-toearth clear-ances are provided as required,

handle interlock for safe and reliableoperation in all panels and cubicles,

clearances in the front, rear and sides of theswitthboards, are adequate,

the gap in the horngap fuse and the size offuse adequate,

all equipments are efficiently earthed andproperly connected to the required numberof earth electrodes,

21)

22)

23)

4)

5)

6)

the required ground *clearance to liveterminals is provided,

the switch operates freely, all the bladesmake contact at the same time. The arcinghorns contact in advance, and tlie handlesare provided with locking arrangements,

Insulators .are free from cracks, and areclean,

suitable fencing is provided with gatewith lockable arrangements, in the case of transformers, there is any oil

leak,

7)

the required number of caution boards,fire-fighting equipments, operating rods,rubber mats, etc, are kept in the substation,

in case of indoor substation, sufficientventilation and draining arrangements aremade,

connections to bushings in transformers aretightened and have good contact,

bushings are free from cracks and areclean,

8) all cable trenches are provided with non-flammable covers,

9)

10)

free accessibility is provided for all equip-ment for normal operation,

all na.me-plates are fixed and the equipmentare fully painted,

24)

25)

26)

27)

28)

29)

30)

31)

accessories of transformers like breathers,vent pipe, buchholz relay, etc, are in order,

connections to gas relay in transformersare in order,

11) all construction materials and temporaryconnections are removed,

oil and winding temperature are set forspecific requirements in transformers,

in case of cable cellars, adequate arrange-ments to pump out water that has entereddue to seepage or other reason is provided,and

12) oil levels, bus bar tightness, transformer tapposition, etc, are in order, 32)

13)

14)

15)

earth pipe troughs and cover slabs areprovided for earth electrodes/earth pits.Neutral and lightning arrester earth pits aremarked for easy identification,

earth electrodes are of GI pipes or CI pipesor copper plates. For earth connections,brass bolts and nuts with lead washers areprovided in the pipes/ plates,

earth pipe troughs, oil sumps/pits are freefrom rubbish and dirt and stone jelly andthe earth connections are visible and easilyaccessible,

all incoming and outgoing circuits of panelsare’clearly and indelibly labelled for identi-fications both at the front and at the rear.

3.2.2 Installation at Voltage not exceeding 650V- It shall be checked whether:

2)

3)

16)

all blocking materials that are used for safetransportation in switchgears, contactors,relays, etc, are removed,

all connections to the earthing system arefeasible for periodical inspection,

sharp cable bends are avoided and cablesare taken in a smooth manner in thetrenches or alongside the walls andceilings using suitable support clamps atregular intervals,

17)

18)

4) suitable linked switch or circuit-breaker orlockable push button is provided near themotors/apparatus for controlling supplyto the motor/apparatus in an easily acces-sible location,

19)

Panels and switchgears are all vermin anddamp proof and all unused openings orholes are b!ocked properly,

the earth bus bars for tightness and forcorrosion free joint surface,

control switchfuses are provided at anaccessible height from ground,

adequate head room is available in thetransformer room for easy topping up ofoil, maintenance, etc.

5)

20) safety devices, horizontal and verticalbarriers, bus bar covers/ shrouds, auto-matic safety shutters/doors interlock,

two separate and distinct earth connectionsare provided for the motor/apparatus,

control switchfuse is provided at an acces-sible height from ground for controllingsupply to overhead travelling crane hoists,overhead bus bar trunking,

PAHT I GENERAL AND COMMON ASPECTS Jl

8)

9)

IO)

II)

12)

13)

14)

15)

16)

the metal rails on which the crane travelsare electrically continuous and earthed andbonding of rails and earthing at both endsare done,

four core cables are used for overheadtravelling crane and portable equipments,the fourth core being used for earthing, andseparate supply for lighting circuit istaken,

if flexible metallic hose is used for wiringto motors and equipments, the wiring isenclosed to the full lengths, and the hosesecured properly,

the cables are not taken through areaswhere they are likely to be damaged orchemically affected,

the screens and armours of the cables areearthed properly,

the belts of the belt driven equipment areproperly guarded,

adequate precautions are taken to ensurethat no live parts are so exposed as to causedanger,

ammeters and voltmeters are tested andcalibrated,

the relays are inspected visually by movingcovers for deposits or dusts or other foreignmatter, and

in the case of air circuit-breakers, provi-sions of arc chutes in their respective polesare made.

3.2.3 Lighting- The lighting circuits shall bechecked whether:

1) wooden boxes and uanels

3.3 Testing of Installation

factories for mounting theand switch controls, etc,

are avoided inlighting boards

2) neutral links are provided_ in double poleswitch fuses which are used for lightingcontrol, and no fuse is provided in theneutral,

3.3.0 Gerwtd- After inspection, the followingtests shall be carried out, before an installation oran addition to the existing i. tallation is put intoservice, any testing of the electrical installation inan already existing installation shall commenceafter obtaining permit to work from the engineer-incharge and after ensuring the safety provisions.

3) the plug points in the lighting circuit are allof 3-pin type, the third pin being suitablyearthed,

3.3.1 Switchboards - Switchboards shall betested in the manner indicated below:

4) tamper-proof interlocked switch socketoutlets are used for locations easilyaccessible,

5) lighting wiring in factory area is takenenclosed ir. conduit and conduit properlyearthed, or alternatively, armoured cablewiring is used,

all switchboards shall be tested for di-electric test in the manner recommendedin IS : 8623 (Part I)-l977*,

all earth connections shall be checked forcontinuity,

the operation of all protective devices shallbe tested by means of secondary or primaryinjection tests,

6) a separate earth wire is run in the lightinginstallation to provide earthing for plugpoints, fixtures and equipment,

1)

2)

3)

4) the operation of the circuit-breakers shallbe tested from all control stations,

7) proper connectors and junction boxes areused wherever joints are to be made in

*Factory built assemblies of switchgear and controlgear:Part I General requirements.

.42 NATIONAL ELECTRICAL CODE

conductors or cross over of conductorstake place,

8) cartridge fuse units are fi t ted withcartridge fuses only,

9) clear and permanent identification marksare painted in all distribution boards,switchboards, sub-main boards andswitches, as necessary,

IO) the polarity is checked and all fuses andsingle pole switches are connected on thephase conductor only and wiring is corre-ctly connected to socket outlets,

I) spare knockouts provided in distributionboards and switchfuses are blocked,

2) ends of conduits enclosing the wiring leadsare provided with suitable bushes,

13)

14)

15)

16)

17)

the fittings and fixtures used for outdooruse are all of weather proof construction,and similarly, fixtures, fittings and switch-gears used in the hazardous area are offlame proof application,

proper terminal connectors are used fortermination of wires (conductors and earthleads) and all strands are inserted in theterminals,

flat ended screws are used for fixingconductor to the accessories,

flat washers backed up by spiring washersare used for making end connections, and

number of wires in a conduit conform toprovisions of this Code.

5) indication/ signalling lamps shall bechecked for working,

6) the operation of the circuit-breakers shallbe tested for all intedock,

7) the closing and opening timings of theciicuit-breakers shall be tested whereverrequired for autotransfer schemes,

8) contact resistance of main and isolator con-tacts shall be measured, and

9) the specific gravity of the electrolyte andthe voltage of the control battery shall bemeasured.

3.3.2 ~;.u,~.\/~),.I)I~~~.s All commissioning testsas l isted in IS : 1002X (Part 2)-1981* shall becar-ricd out.

3.3.3 C’cihlc~s Cable installations shall bechcckcd ah laid doun in IS : 125%19X3+.

3.3.4 Motors and Other Equipment - Thefollowing tests are made on motor and otherequipment:

a)

b)

The insulation resistance of each phasewinding against the frame and between thewindings shall be measured. Megohm-meter of 500 V or 1 000 V rating shall beused. Star points should be disconnected.Minimum acceptable value of the insulationresistance varies with the rated power andthe rated voltage of the motor.

The following relation may serve as areasonable guide:

2 0 X E,R1 = I 000 + 2P

where

R, = Ksuptibn resistance in MR at0

E, = Rated phase-to-phase voltage,and

P = Rated power kW.

If the resistance is measured at a tempera-ture different from 25OC, the value shallbe corrected to 25°C.

The insulathon resistance as measuredat ambient temperature does not alwaysgive a reliable value, since moisturemight have been absorbed during shipmentand storage: When the temperature of sucha motor is raised, the insulation resistancewill init ially drop considerably, evenbelow the acceptable minimum. If any suspi-cion exists on this score, motor windingshall be dried out.

*Code of practice for selection. installation and maintenanceof transformers: Part 2 Installation.

+Code of practice for installation and maintenance of powercables up to and Including 33 kV (/ir.vr r~\~ision).

PART I GE:NERAI. A N D C O M M O N A S P E C T S

3.3.5 Wiring Installation - The following testsshall

a)

b)

c)

d)

e)

be done:

The insulation resistance shall be measuredby applying between earth and the wholesystem of conductor or any section thereofwith all fuses in place and all switchesclosed, and except in earthed concentricwiring, all lamps in position or both poles ofinstallation otherwise electrically connectedtogether, a dc voltage of not less than twicethe working voltage, provided that it does notexceed 500 volts for medium voltagecircuits. Where the supply is derived fromthree-wire (ac or dc) or a polyphase systemthe neutral pole of which is connected toea r th e i the r d i rec t o r th rough addedresistance, the working voltage shall bedeemed to be that which is maintainedbetween the outer or phase conductor andthe neutral.

The insulation resistance in megohms of anin?tallation measured as in (a) shall be notless than 50 divided by the number of pointson the circuit, provided that the wholeinstallation need not be required to have aninsulation resistance greater than IMR.

Control rheostats, heating and powerappliances and electric signs, may, if desired,be disconnected from the circuit during thetest, but in that event the insulationresistance between the case or framework,and all live parts of each rheostat, applianceand sign shall be not less than that specifiedin the relevant Indian Standard specificationor where there is no such specification shallbe not less than 0.5 MR.

The insulation resistance shall also bemeasured betwetn all conductors connectedto one pole or phase conductor of the >upplyand all the conductors connected to themiddle wire to the neutral on to the otherpole of phase conductors of the supply.Such a test shall be made after removingall metallic connections between the twopoles of the installation and in these cir-cumstances the insulation resistance betweenconductors of the installation shall be notless than that specified in (b).

On completion of an electrical installation(or an extension to an installation) acer t i f i ca te sha l l be fu rn i shed by thecontractor, countersigned by the certifiedsupervisor under whose direct supervisionthe installation was carried out. Thiscertificate shall be in a prescribed form asrequired by the local electric supplyauthority.

3.3.6 Earthing - For checking the efficiency ofearthing the following tests are recommended (seeIS : 3043-1966*).

*Code of practice for earthing.

43

_ I’/

I.ii

..> .

a) The earth resistance of each electrode ismeasured.

b) The earth resistance of earthing grid ismeasured.

the earth resistance of the entire earthingsystem is measured.

These tests shall preferably be done during thec) All electrodes are connected to the’grid and summer months.


SECTION 11 WIRING INSTALLATIOlVS

0 . F O R E W O R D

0.1 A major portion of fixed installation design ina building relates to wiring installation. ThisSection of the Code is primarily intended to coverguidelines on design and construction of wiringinstallations which are commonly applicable to alltypes of occupancies. The requirements specifiedin this Section are based on safety and reliabilityconsiderations.

2.2.4 Ordinary socket outlet may be fixed atany convenient place at a height above 20 cmfrom the floor level and shall be away fromdanger of mechanical injury.

NOTE ~ In situations where a socket outlet is accessible tochildren, it is necessary to install an interlocked plug andsocket or alternatively a socket outlet which automatically getsscreened by the withdrawal of plug.

0.2 It may be mentioned that the general designguidelines for wiring given in this Section have tobe carefully considered while applying them tospecific occupancies and a proper selection of themethod is to be decided depending on localconditions. Guidance on such matters are coveredin respective Sections of the Code.

0.3 The contents of this Section are based onIS : 732 (Part 2)-1982*

2.2.5 In an earthed system of supply, a socketoutlet with plug shall be of three-pin type with thethird terminal connected to the earth. When suchsocket outlets with plugs are connected to anycurrent+onsuming device of metal or any non-i n s u l a t i n g m a t e r i a l o r b o t h , c o n d u c t o r sconnecting such current-consuming devices shallbe of flexible cord with an earthing core and theearthing core shall be secured by connectingbetween1 the earth terminal of plug and the,bodyof current-consuming devices.

2.3 Lighting Fittings1. SCOPE

1.1 This Section of the Code covers the essentialdesign and constructional requirements forelectrical wi,ring installations.

2. qQUIPMENT FITTINGS ANDACCESSORIES

2.3.1 A switch shall be provided for the controlof every lighting fitting or a group of lightingfittings. Where control at more than one point isnecessary as many two-way or intermediateswitches may be provided as there are controlpoints.

2.1 Ceiling Roses and Similar Attachments

2.1 .1 A ceiling rose or any other similarattachment shall not be used on a circuit thevoltage of which normally exceeds 250 V .

2.1.2 Normally, only one flexible cord shall beattached to a ceiling rose. Specially designedceiling roses shall be used for multiple pendants.

2.1.3 A ceihng rose shall not embody fuseterminal as an integral part of it.

2.3.2 Where necessary lighting fittings shall besupported by suitable pipe/conduits, bracketsfabricated from structural steel, steel chains, etc,depending upon the type and weight of thefittings. Where a lighting fitting is supported byone or more flexible cords, the maximum weight!o which the twin flexible cords may be subjectedshall be as follows:

Nominal Cross-Sectional Area

of TwinFlexible

Cordmm*

Number andDiameterin mm of

Wires

MaxrmumPermissible

Weightkg

2.2 Socket Outlets and Plugs

2.2.1 Each 15A socket outlet provided inbuildings for the use of domestic appliances sychas air-conditioner, water cooler, etc, shall beprovided with its own individual fuse, withsuitable discrimination with back-up fuse orminiature circuit-breaker provided in- thedistribution/sub-distribution board. The socket-outlet shall not necessarily embody the fuse as anintegral part of it.

0.5 l6/0.2 20.75 2410.2I .o 3210.2 :1.5 4810.2 5.32.5 8010.2 8.8

4 12810.2 14.0

2.3.3 No flammable shade shall form a part oflighting fittings unless such shade is well protectedagainst all risks of fire. Celluloid shade or lightingfitting shall not be used under any circumstances.

2.2.2 Each socket outlet shall also be controlledby a switch which shall preferably be locatedimmediately adjacent thereto or combinedtherewith.

2.2.3 The switch controlling the socket outletshall be on the live side of the line.

*Code of practice for electrical wiring iE.takitiOnS: Part 2,Design and consiruction.

2.4 Fitting-Wire - The use of fittings-wire shallbe restricted to the internal wiring of the lightingfittings. Where fittings-wire is used for wiringfittings, the sub-circuit leads shall termmate In aceiling rose or box with connectors from whichthey shall be carried into the fittings.

2.5 Lampholders - Lampholders for use withflexible pendants shall be provided with co rdgrips. ,A11 lampholders shall be provided with


shade carriers. Where centrecontact Edison screwlampholders are used, the outer or screw contactsshall be connected to the ‘middle wire’, theneutral, the earthed conductor of the circuit.

2.6 Outdoor Lamps - Lamps fitted outdoor shallhave weather-proof fittings so as to effectivelyprevent the ingress of moisture and dust. Flexiblecord and cord grip lampholders shall not be usedwhere exposed to weather. In verandahs andsimilar exposed situations where pendants areused, they shall be of fixed rod type.

2.7 Lamps - All lamps unless otherwise requiredand suitably protected, shall be hung at a heightof not less than 2.5 m above the floor level.

4

b)

c)

d)

Portable lamps shall be wired with flexiblecord. Hand lamps shall be equipped with ahandle of moulded composition or othermaterial approved for the purpose. Handlamps shall be equipped with a substantialguard attached to the lamp holder orhandle. Metallic guards shall be earthedsuitably.

A bushing or the equivalent shall beprovided where flexible cord enters the baseor stem of portable lamp. The bushing shallbe of insulating material unless a jackettedtype or cord is used.

Ali wiring shall be free from short-circuitsand shall be tested for these defects prior tobeing connected to the circuit.

Exposed live parts within porcelain fixturesshall be suitably recessed and so located asto make it improbable that wires will comein contact with them. There shall be aspacing of at least 125 mm between liveparts and the mounting plane of the fixture.

2.8 Fans, Regulators and Clamps

2.8.1 Ceiling Fans-Wiring for ceiling fansshall

a)

b)

c)

46

conform to the following requirements:

Control of a ceiling fan shall be through itsown regulator as well as a switch in series.

All ceiling fans shall be wired with normalwiring to ceil ing roses or to specialconnector boxes to which fan rod wires shallbe connected and suspended from hooks orshackels with insulators between hooks andsuspension rods. There shall be no joint inthe suspension rod, but if joints areunavoidable then such joints shall bescrewed to special couplers of 5 cmminimum length and both ends of the pipesshall touch together within the couplers, andshall in addition be secured by means of splitpins; alternatively the two pipes may bewelded. The suspension rod shall be s;adequate strength to withstand the dead andimpact forces imposed on it.

Fan clamps shall be of suitable designaccording to the nature of construction of

4

e)

f)

ceiling on which these clamps are to befitted. In all cases fan clamps shall befabricated from new metal of suitable sizesand they shall be as close fitting as possible.Fan clamps for reinforced concrete roofsshall be buried with the casting and due careshall be taken that they shall serve thepurpose. Fan clamps for wood beams shallbe of suitable flat iron fixed on two sides ofthe beam and according to the size andsection of the beam one or two mild steelbolts passing through the beam shall holdboth flat irons together. Fan clamps for steeljoint shall be fabricated from flat iron to fitrigidly to the bottom flange of the beam.Care shall be taken during fabrication thatthe metal does not crack while hammeringto shape. Other fan clamps shall be made tosuit the position, but in a:1 cases care shallbe taken to see that they are rigid and safe.

NOTE - All fan clamps shall be so fabricated thatfans revolve steadily.

Canopies on top and bottom of suspensionrods shall effectively hide suspensions andconnections to fan motors, respectively.

The lead-in-wire shall be of nominal cross-sectional area not less than 1.0 mm’ copperor 1.5 mm* aluminium and shall beprotected from abrasion.

Unless otherwise specified, the clearancebetween the bottom-most point of the ceilingfan and the floor shall be not less than 2.4 m.The minimum clearance between the ceilingand the plane of the blades shall be not !essthan 300 mm.

2.8.2 Exhaust Fans - For fixing of an exhaustfan, a circular hole shall be provided in the wall tosuit the size of the frame which shall be fixed bymeans of &-bolts embedded in the wall. Thehole shall be neatly plastered with cement andbrought to the original finish of the wall. Theexhaust fan shall be connected to exhaust fanpoint which shall be wired as near to the hole aspossible by means of a flexible cord, care beingtaken that the blades rotate in the properdirection.

2.9 Attachment of Fittings and Accessories

2.9.1 In wiring other than conduit wiring, allceiling roses, brackets, pendants and accessoriesattached to walls or ceilings shall be mounted onsubstantial wooden blocks twice varnished afterall fixing holes are made in them. Blocks shall notbe less than 4 cm deep. Brass screws shall only beused for attaching fittings and accessories to theirbase blocks.

2.9.2 Where teak or hardwood boards are usedfor mounting switches, regulators, etc, theseboards shall be well varnished with pure shellacon all four sides (both inside and outside),irrespective of being painted to match thesurroundings. The size of such boards shall


depend on the number of accessories that couldconveniently and neatly be arranged. Where t.heteis danger of attack by termite, the boards shall bepainted with suitable, antitermite paint. on theunderside instead of pure shellac.

3. CONSTRUCTION

3.1 Reception and Distribution of Main Supply

3.1.1 Control at the Point of Commencementof SUPPlY

3.1.1.1 There shall be ctrcuit-breakei or alinked switch with fuse on each live conductor ofthe supply mains at the point of entry. The wiringthroughout the installation shall be such thatthere is no break in the neutral wire in the form ofthe switch or fuse unit.

3.1.1.2 The main switchgear shall be easilyaccessible and shall he situated as near aspracticable to the termination of service line.

3.1.1.3 On the main switchgear, where.the conductors include an earthed conductor of atwo-wire system or an earthed neutral conductorof a multi-wire system or a conductor which is tobe connected thereto, an indication of apermanent nature shall be provided to identity theearthed neutral conductor.

3.1.2 Main Sn’itches and S~citc~hhoards

3.1.2.1 All main switches shall be either ofmetal-clad enclosed pattern or of any insulatedenclosed pattern which shall be fixed at closeproximity to the point of entry of supply.

3.1.2.2 Location

b)

cl

4

e)

f-l


The location of the main board should besuch that it is easily accessible for firemanand other personnel to quickly disconnectthe supply in case of emergencies.

Main switchboards shall be installed inrooms or cupboards having provisions forlocking arrangement so as to safeguardagainst operation by unauthorized per-sonnel.

Open type switchboards shall be placed onlyin dry situations and in ventilated roomsand they shall not be placed in the vicinityof storage batteries or exposed to chemicalfumes.

In a damp situation or where flammable orexplosive dust, vapour or gas is likely to bepresent, the switchboard shall be totallyenclosed or made flameproof as may benecessitated by the particular circumstances.

Switchboards shall not be erected above gasstoves or sinks, or within 2.5 m of anywashing unit in the washing rooms.

In case of switchboards unavoidably fixed inplaces likely to be exposed to weather, todrip or to abnormal moist atmosphere. theouter casing shall be weatherproof and shall

be provided with glands or bushings oradopted tb receive screwed conduit,according to the manner in which the cabksare run.

g) Adequate illumination shall be provided forall working spaces about the switchboardswhen installed indoors.

3.1.23 Metal-clad switchgear shall preferablybe mounted on any of the following types ofboards:

a)

b)

cl

Hinged-type metal ‘boards - These shallconsist of a box made of sheet metal not lessthan 2 mm thick and shall be provided witha hinged cover to,enable the board to swingopen for examination ‘of the wiring at theback. The joints shall be welded. A teakwood board, thoroughly protected bothinside and outside with insulating varnishand of not less than 6.5 mm in thickness,shall bc provided at the back for attachmentof incoming and outgoing cables. Thereshall be a clear distance of not less than2.5 cm between the teak wood board andthe cover, the distance being increas-ed for larger boards in order that on clos-ing of the cover, the insulation of thecables is not subjected to damage and noshort length of cables is subjected toexcessive twisting or bending in any case.The board shall be securely fixed to thewall by means of rag bolts, plugs, orwooden Gutties and shall he provided witha locking arrangement and an earthing stud.All wires passing through the metal boardshall be bushed. Alternatively, hinged-typemetal boards shall be made of sheet coveringmounted on channel or angle iron frame.

NOTE - Such type of boards are parlicularly suit-able for small switchboards for mounting metal-cladswitchgear connected to supply at low voltages.

Fixed-type metal boards - These shallconsist of an angle or channel iron framefixed on the wall. or on the floor andsupported on the wall at the top if necessary.There shall be a clear distance of I m infront of the switchboard. If there are anyattachments of bare connections at the backof the switchboard, Rule 5 I(t)(c) of IndianElectricity Rules, 1956 shall apply.

NOTE-Such type of boards are particularly suit-able for large switchboards for mountmg large numberof switchgears or higher capacity metal-clad switchgearor both.

Wooden boards - For small installationsconnected to a single-phase 240 volts supply,woode? hoards may be used as main-boardsor sub-boards. These shall be of seasonedteak or other suitable quality timber with alljoints dovetailed.

3.1.2.4 Recessing q/ hoards-- W h e r e S O

specified. the switchboards shah be recessed in thewall. The front shall be fitted with a hinged panelof teak wood or other suitable material. such asbakclite. or with unbreakable glass doors in teak

17

wood frame with locking arrangement. the outersurface of the doors being flush with the walls.Ample room shall be provided at the back forconnec t ion and a t the *front be tween theswitchgear mountings.

3.1.2.5 In large installations of mediumvoltage, before proceeding with the actualconstruction of the boards. a proper drawingshowing the detailed dimensions and design,including the disposition of the .mountings. whichshall be symmetrically and neatly arranged forarriving at the overall dimensions, shall beprepared and incorporated in the buildingdrawing.

3.1.2.6 Arrangemetlr o/’ apparatus

4

b)

cl

4

e)

0

Equipment which is on the front of aswitchboard shall be so arranged thatinadvertent personal contact with live partsis unlikely during the manipulation ofswitches, changing of fuses like operation.

No apparatus shall project beyond any edgeof the panel. No fuse body shall be mountedwithin 2.5 cm of any edge of the panel andno hole other than the holes by means ofwhich the panel is fixed shall be drilledcloser than 1.3 cm from any edge of thepanel.

The. various live parts, unless they areeffectively screened by substantial barriers ofnon-hygroscopic, non-flammable insulatingmaterial, shall be so spaced that an arccannot maintain between such parts andearth.

The arrangement of the gear shall be suchthat they shall be readily accessible and theirconnec t ions to a l l ins t ruments andapparatus shall also be easily identifiable.

In every case in which switches and fuses arefitted on the same pole, these fuses shall beso arranged that the fuses are not live whentheir respective switches are in off position.

No fuses other than fuses in instrumentcircuit shall be fixed on the back of orbehind a switchboard panel or frame.

3.1.2.7 Identification and marking

a) Marking shall be done as given in Table I ofSet 41 Part I of the Code.

b) Where a board has more than one switch,each such switch shall be marked to indicatewhich section of the installation it controls.The main switch shall be marked as suchand where there is more than one mainswitch in the building, each such switch shallbe marked to indicate which section of theinstallation it controls.

c) All markings shall be clear and pe.rmanent.

3.1.3 .Iltritt trtiil Brutli~h I~i.\lrihirriort Hourcl\

411

3.1.3.1 Main and branch distribution boardsshall be of any type mentioned under 3.1.2.3.

3.1.3.2 Main distribution board shall beprovided with a circuit-breaker on each circuit, ora switch with a fuse on the phase or liveconductor and link on the neutral or earthedconductor of each circuit. The switches shallalways be linked. Looping by cable connections atincoming and outgoing of these devices should beavoided.

3.1.3.3 Branch distribution hoards

a)

b)

c)

Branch distribution boards shall be providedwith a fuse or a miniature circuit-breaker orboth of adequate rating/setting, on the liveconductor of each sub-circuit and theear thed n .eu t ra I conduc to r sha l l beconnected to a common link and be capableof being disconnected individually fortesting purposes. At least one spare circuitof the same capacity shall be provided oneach branch distribution board.

Lights and fans may be wired on a commoncircuit. Such sub-circuit shall not have morethan a total of ten points of lights, fans and5-A ,ocket outlets. The load of such circuitshall be restricted to 800 watts. If a se aratefan circuit is provided, the number of ans inPthe circuit shall not exceed ten. Power sub-circuits shall be designed according to theload but in no case shall there be more thantwo 15-A outlets on each sub-circuit.

In installations requiring the use of groupcontrol for switching operation, circuits forsocket outlets may bc kept separate fromfans and lights. Normally, fans and lightsmay be wired on a common circuit ,however, if need is felt separate circuits maybe provided for the I W O. The load on anylow voltage sub-circuit shall not exceed3 000 watts. In case of new installation. allcircuits and sub-circuits shall be designed bymaking a provision of 20 percent increase inload due to any future modification. Powersub-circuits shall be designed according tothe load but in no case shall there be morethan four outlets on each sub-circuit.

3.1.3.4 Installation on distribution boards

a) The distribution fuse-boards shall be locatedas near as possible to the centre of the loadthey are intended to control.

b) These shall be fixed on suitable stanchion orwall and shall be accessible for replacementof fuses. and shall not bc more than 2 mfrom floor level.

c) These shall be of either metal-clad type, orall-insulated type. But, if exposed to weatheror damp situations, they shall be of theweatherproof type. In corrosive atmos-pheres. they shall be trcatcd with anti-cor-rosivc prcservativc. or co\cred with \uit:thlcplastic compound.

N A T I O N A L EI.C:(‘TWI<‘AI. <‘ODE

d)

d

Where two or more distribution fuse-boardsfeeding low voltage circuits are fed from asupply of medium voltage, these distributionboards shall be:

I) fixed not less than 2 m apart; or2) arranged so that it is not possible to o

the two at the same time, namely, t %n

eyare interlocked, and the metal case ismarked ‘Danger 415 volts’ and identifiedwith proper phase marking and dangermarks.

NOTE-The wiring of such low voltage distri-bution boards shall be segregated from each otherand not run in the same condvk

3) instal led in a room or enclosureaccessible to only authorited persons.

All distribution boards shall be markedLighting’ or ‘Power’, as the case may be,

and also marked with the voltage andnumber of phases of the supply. Each shallbe provided with a circuit .list giving detailsof each circuit which it controls and thecurrent rating of the circuit and size offuse-dlement.

3.1.3.5 Wiring qf tlivrrihurion boards:

a)

b)

c)

4

e)

1)

PAR1

In wiring a branch distributioh board, totalload of the consuming devices shall bedivided. as far as possible evenly betweenthe number of ways of the board, leaving thespare circuit for future extension.

All connections between pieces of apparatusor between apparatus and terminals on aboard shall be neatly arranged in a definitesequence. following the arrangements of theapparatus mourited thereon. avoidingunnecessary crossings.

Cables shall be connected to a terminal onlyby soldered or welded or crimped lugs usingsuitable sleeve, lugs or ferrules unless theterminal is of such a form that it is possibleto securely clamp them without the cuttingaway of cable strands. Cables in each circuitshall be bunched together.

All bare conductors shall be rigidly fixed insuch a manner that a clearance of at least2.5 cm is maintained between conductors ofopposite polarity or phase and between theconductors and any material other thaninsulating material.

If required, a pilot lamp shall be fixed andconnected through an independent single-pole switch and fuse to the bus-bars of theboard.

In a hinged type board, the incoming andoutgoing cables shall be fixed at one ormore points according to the number ofcables on the back of the board leavingsuitable space in between cables. .and shallalso, if possible. be fixed at the corres-ponding points on the switchboard panel.

I GENERAL ANS) COMMON ASPECTS

The cables between these points shall be ofsuch length as to allow, the switch-board panel to swing through an angleof not less than 900

3.1.3.6 Fuses

a) A fuse carrier shall not be fitted with a fuse-element of higher rating than that for whichthe carrier is designed (see Set 18, Part I c?fthe Code).

b) The current rating of a fuse shall not exceedthe current rating of the smallest cable in thecircuit protected by the fuse.

c) Every fuse shall have in its own case orcover, or in an adjacent conspicuousposition, an indelible indication of itsappropriate current rating for the protectionof the circuit which it controls.

3.1.4 Selection of Size qf Conductor (see SetI8 Part I of the Code).

3.1.4.1 The sizes d conductors of circuitsshall be so selected that the drop in voltage fromconsumer’s terminals in a public supply (or fromthe bus-bars of the main switchboard controllingthe various circuits in a private generation plant)to any point on the installation does not exceed 3percent of the voltage at the consumer’s terminals(or at two bus-bars as the case may be) when theconductors are carrying the maximum currentunder the normal conditions of service.

3.1.4.2 If the .cable size is increased to avoidvoltage drop in the circuit, the rating of the cableshall be the current which the circuit is designedto carry. In each circuit or sub-circuit the fuseshall be selected to match the cable rating toensure the desired protection.

3.1.43 All conductors shall be of copper oraluminium. Conductor for final sub-circuit for fanand light wiring shall have a nominal cross-sectional area not less than 1.00 mm2 copper and1.50 mm? aluminium. The cross-sectional areas ofconductors for power wiring shall be not less than2.5 mm?. copper, 4.00 mm? aluminium. Theminimum cross-sectional area of conductors offlexible cord shall be 0.50 mm? copper.

3.1.5 Branch Switches - Where the supply isderived from a three-wire or four-wire source, anddistribution is done on the two-wire system, allbranch switches shall be placed in the outer or liveconductor of the circuit and no single-phaseswitch or fuse shall be inserted in the middle wire.earth or earthed neutral conductor of the circuit.Single-pole switches (other than for multiplecontrol) carrying current of not more than I5 Amay be of tumbler tybe or flush type which shallbe ‘on’ when the handle or knob is ,down.

3.1.6 Passing Through Walls and Floors

3.1.6.1 Where cond:uctors pass through walls.one.of the following methods shall be employed.Care shall be taken to see that wires pass very

49

freely through protective pipe or box and that thewires pass through in a straight line without anytwist or cross in wires, on either ends of suchholes:

a)

b)

c)

A teak wood box extending through thewhole thickness of the wall shall be buriedin the wall and casings or conductors shallbe carried so as to allow 1.3 cm air spaceon three sides, of the casing or conductor.

The conductor shall be carried either in arigid steel conduit or a rigid non-metallicconduit or in a porcelain tube of such asize which permits easy drawing-in. The endof conduit shall be neatly bushed withporcelain, wood or other suitable material.

Insulated conductors while passing throughfloors shall be protected from mechanicalinjury by means of rigid steel conduit to atieight not less than I.5 cm above the floorsand flush with the ceiling below. This steelconduit shall be earthed and securelybushed.

3.1.6.2 Where a wall tube passes outside abuilding so as to be exposed to weather, the outerend shall be bell-mouthed-and turned downwards.and properly bushed on the open end.

3.1.7 Fixing to Walls and Ceilings - Plugs forordinary wails or ceilings shall be of well-seasonedteak or other suitable hardwood not less than 5cm long and 2.5 cm square on the inner end and 2cm square on the outer end They shall becemented into walls to within 6.5 cm of thesurface, the remainder being finished according tothe nature of the surface with plaster or limepunning.

3.1.7.1 Where owing to irregular coursing orother reasons the plugging of the walls or ceilingwith wood plugs presents difficulties, the woodcasing, wood, batten, metal conduit or cleat (asthe case may) shall be attached to the wall orceiling in a suitable manner that would conformto the requirements given in the Code. In the caseof new buildings. wherever possible, teak woodplugs shall be fixed in the walls before they areplastered

3.1.7.2 To achieve neatness. plugging of wallsor ceilings may be done by a suitable type ofasbestos, metallic or a fibre fixing plug.

4. METHODS OF INTERNAL WIRING

4.1 Cleated Wiring System

4.1.1 General- This system shall not beemployed for wiring on damp walls or ceilingsunless suitable precautions in an approvedmanner are adopted to effectively preventdampness from affecting the insulation ofconductors.

4.1.2 Accessihi/ir\* - All cleated wiring shall berun, as far as pra&icable, in such a manner so asto be visible except in positions where they would

be liable to mechanical injury and where they areless than I.5 m above the floor, in which casesthey shall be adequately protected.

4.1.3 Class q/ Cables - Vulcanized rubberinslulated cables; plastic (PVC and polyethylene)insulated cables, braided or unbraided; shall beused without any further protection.

4.1.4 Cleats - All cleats shall be of apprqveddesign and shall consist of two parts. a base pieceand a cap. A special pattern of cleat may be used,if necessary. where conductors pass roundcorners, so that there may be no risk of theconductors touching the wall owing to sagging orstretching. Cleats shall be fixed at distances notgreater than 60 cm apart and at regular intervals.

4.1.5 Where cleated wiring is laid along ironjoists or any metal. spacing between such metaland porcelain cleats shall be inserted either withvarnished wood fillet or varnished wood clampsecurely fixed so as to prevent conductors comingin contact with such metal along which they arepassing.

4.1.6 Fixing qf Cleats

a)

b)

In ordinary cases, cleats shall be attached toplugs arranged in the manner specifiedunder 4.1.7.Where practicable the same method shall beadopted in the cases of stone walls, butwhen owing to irregular coursing or otherreasons it is impracticable to fix the cleatsin a regular and workman like manner, awood batten shall be provided and fixedwith not less than one plug per 1.25 m run.The batten shall be of seasoned teak orother suitable seasoned hardwood 2 cmthick and 2.5 cm wider than the cleat used,it shall be chamfered on the edges, wroughtall over and varnished with two coats ofvarnish or painted as may be required.

4.1.7 Distance Between Wires - For circuitvoltages up to 250 volts, cleats shall be of suchdimensions that in the case of branch loads,conductors shall not be less than 2.5 cm apartcentre-tocentre and in the case of sub-mains notless than 4 cm apart centre-to-centre, providedthat this rule shall not apply, if the cable used intwin-core. Care shall be taken in selecting size ofcleats particularly for branch distribution wiringwhere two-way and three-way porcelain cleats areessential. and the difference in size shall bereasonable. Care shall also be taken that graovesof porcelaicl cleats do not compress the insluationnor be too wide to give a very loose fit. Under nocircumstances two wires shall be placed in onegroove of porcelain cleats.

4.lJ Crossing yf’ Conductors

a) Where cleated conductors cross each otherthey shall be separated by an insulatingbiidging piece, which will rigidly maintaina distance of at :least 1.3 cm between the


conductors except when the cabk used istwincore.

b) In open type wiring, joint cut-outs or.fusecut-outs shall not be inserted for any pur-pose, but where joints are required forconnecting or bifurcating the wires, junctionboxes of wooden or other insulating mater-ial with porcelain connectors inside shalf beused.

4.1.9 Prorecrion Near Floor

a) No cleated wiring shall be left unprotectedup to I.5 m.above floor level. When broughtthrough the floor it shall be enclosed incOnduit in the manner specified’ in 4.2.9.

b) As far as possible. no open type of wiringshall run within floors. walls. partitions. cei-lings, roof spaces or other concealed spacesin which they are not normally open to view;in such case conductors shall be carriedthrough steel conduit with all screwed acces-sor ies, keeping mechanical cont inui tythroughout the entire layout, and such pipework shall be earthed and properly bushedon all open ends to prevent abrasion ofcables.

c) At the time of laying and drawing of con-ductors, care shall be taken to keep’the wiresstraight, tight and rigid without any twist.

d) All wooden fittings. such as boards, blocks,etc. shall be of well-seasoned teak wood orof suitable insulating material and shall beof double type. that is, separate base andtop. The wooden boards shall be well var-nished on all sides (both inside and outside)and may be mounted with suitable porcelainInsulators behind the boards.

4.2 Wood C&g Wiring System

4.2.1 General- This system of wiring is suit-able for low voltage installation where vulcanizedrubber insulated cables, plastic insulated cables orother suitable insulated cables are used in thewiring work and carried within wood casingenclosure. Wood casing wiring system shall not beused in damp places or in illventilated places.unless suitable precautions are taken.

4 .2 .2 Mureriol atltl Buftcrtl 91’ C a s i n g ~- Allcasing shall be of seasoned teak wood or anyother suitable hardwood. free from knots, shakes.saps, or other defects. all sides plaqed withsmooth finish and all sides well varnish’ed, (bothinside and outside) with pure shellac varnish. Thecasing shall have grooved~ body with beaded orplain moulded cover as desired.

4.2.3 Dimensions qf Casing - The sizes ofcasing and capping for various sizes of 250 voltsgrade insulated cables in a groove shall be inaccordance with those specified in Table 2 of Set18! Part I of the Code.

4.2.4 Bunching q/ Circuits - Conductors ofopposite polarity or different phases shall not be

bunched in one groove in wood casing.

NOTE--Lengths of conductors of the same polarity orphase, and free joints, may be bunched. if so desired.

4.2.5 Attachment qf Casing to Wall andCeihng - All casing shall be fixed by means ofsuitable countersunk head wood screws to plugsat an interval not exceeding 90 cm for sizes up to64 mm casing and not exceeding 60 cm for sizesabove 64 mm casing. Screw heads shall becountersunk within the dividing wall of thegrooves (in the case of three-grooved casing, twoscrews shall be inserted on the two dividing wallsin a workmanlike manner). All casing shall bespaced from the wall or ceiling by means ofporcelain disc insulators not less than 6.5 mmthick. Casing shall be used only on dry walls andceilings avoiding outside walls. as far as possible.and shall not be buried in walls or ceilings underplaster. nor fixed in proximity to gas. steam orwater pipes or immediately below the latterCasing under steel joists shall be securt;d by hoop-iron or by of wood clamps. and spaced with discinsulators,.

4.2.6 At/acVwwnl of Capping - All cappingshall be attached to the casing (after all insulatedwires are laid inside grooves) by round-headscrews (rust resisting) fixed on edges and screwedto outer wails of the casing at an interval notexceeding 15 cm crosswise (that is, 30 cm betweentwo successive screws on each side) for all sizes upto 64 mm casing and capping. For sizes above 64mm similar additional round-head screws shall befixed on the centre-wall (or alternative walls incases of 3 grooves) at an interval of 45 cm.

NOIV Care shall bc taken in llxing screws on cupping\ wthat they do nol picrcr through Ihe walls of casing and damagethe insulation.

4.2.7 Join/s in Casing and Capping - Casingand capping shall be run in lengths as long aspossible. All joints shall be scarfed or cutdiagonally ‘in longitudinal section and shall besmoothed down by fitting to make joints a veryclose fit as far as possible. They shall be securedat joints with two or more screws as would benecessary. Joints in capping shall not overlapthose in the casing.

4.2.8 Ly~wur c?/’ Wood Cuing Wiring I.ay~Lltof wood casing wiring shall he such as to avoidcorners as far as possible and avoid crossing ofconductors inside the casing. Where conductorshave to cross corners. teak wood solid cornerpieces of a radius not less than 7.5 cm and 01same width as that of casing with same tini%h ;t\that of capping shall be used with grooves at thebottom for conductors. Where crossing of wire\ isunavoidable and a junction box is not used. ;Ibridge piece of casing shall be fixed on the top ofcasing with neat finish and shall pass conductor\avoiding crossing.

4.2 .9 P a s s i n g Thsou~h Fioor.s Whereconductors pass through floors. they shall hecarried in an approved heavy gauge conduitproperly bushed at both ends. The conduit shall


be carried 1.5 m above floor level and 2.5 mbelow ceiling level and neatly entered into thehasing, which shall, if so required, be suitablyprotected at the floor level. The conduit shall besecurely earthed.

4.2.10 Casing Round Mouldings or Decor-a/ions -- This shall be considered as specialdecoration work and carried out in consultationwith the architect or the engineer-in-charge ofconstruction work and with this approval.

4.3.4.1 In cases where there are chances of anydamage to the wiring such wiring shall be covendwith sheet metal protective covering, the base ofwhich is made flush with the plaster or brickwork,as the case may be, or the wiring shall be drawnthrough a conduit complying with all require-ments of conduit wiring system.

4.3.4.2 Such protective covering shall in allcases be fitted or all downdrops within 1.5 m fromthe floor.

4.2.11 Painting and Varnishing - All casingand capping shall be given before erection,internally and on the back. two coats of varnish.In addition all casing together with capping aftererection shall be painted or varnished to thedesired finish. 4

4.3.5 Bends in Wiring -,The wiring shall notin any circumstances be bent so as to form a rightangle but shall be rounded off at the corners to aradius not less than six times the .overall diameterof the cable.

4.3 Tough Rubber-Sheathed or PVC-SheathedWiring System

4.3.0 Genera/- Wiring with tough rubber-sheathed cables is suitable for low voltageinstallations. and shall not be used in placesexposed to sun and rain nor in damp places. wiresare l sheathed in protective covering againstatmosphere and well protected to withstanddampness. Wiring with PVC-sheathed cables issuitable for medium voltage’installation and maybe installed directly under exposed conditions ofsun and rain or damp places. This system ofwiring is suitable in situations where acids andalkalis are likely to be present. Where attack fromtermite is’prevalent, antitermite treatment shall begiven.

4.3.6 Passing Through Floors - All cablestaken through floors shall be enclosed in aninsulated heavy gauge steel conduit extending I.5m above the floor and flush with the ceilingbelow, or by means of any other approved type ofmetallic covering. The ends of all conduits orpipes shall be neatly bushed with porcelain, woodor other approved material.

43.1 Passing Through Walls - The method tobe adopted shall be that laid;down in 3.1.6. In thelatter case there shall be one or more conduits ofadequate size to carry the cables. The conduitsshall be neatly arranged so that the cables enterthem straight without b_ending.

4.3.1 All sheathed cables on brick walls. stone,or plaster walls and ceilings. steel joists. or anystructural steel work shall he run on well-seasonedaqd varnished. straight teak wood battens of notless than IO mm finished thickness and the widthof which is such as to suit total width of cableslaid on the batten. Prior to’erection. these shall bepainted \;;ith one coat of varnish or suitable paintmatching with the surroundings. These battensshall be secured to the walls and ceilings bycountersunk head wood screws to coed plugs orother plugs at an interval pot exceeding 75 cm;the flat-head wood screws shall be countersunkwithin wood batten and smoothed down with file.

4.3.8 Buried Cables-The tough rubbersheathed cables shall not be buried directly inplaster; where so specified, they may be taken inteak wood channelling of ample capacity orcement chases or conduit buried in the wall.

4.3.3 Link Clips -- Link clips shall be soarranged that one single clip shall not ho&morethan two twin-core TRS or PVC-sheathed cablesup to I.5 mm?. above which a single clip shallhold a single twin-core cable. The clips shall befixed on varnished wood battens with any rust-resisting pins or screws and spaced at intervals ofIO cm in the case of horizontal runs and I5 cm inthe case of vertical runs. For the wiring and runsof mains exposed to heat and rain. clips speciallymade for dutdoor use from a durable metal.resistant to weather and atmospheric corrosion.shall be used.

4.3.9 Stripping of Outer Covering - Whilecutting and stripping of the outer covering of thecables, care shall be taken that the stiarp edge ofthe cutting instrument does not touch the rubberor PVC sheathed insulation of conductors. Theprotective outer covering of the cables shall bestripped off near connecting terminals, and thisprotective covering shall be maintained up to theclose proximity of connecting terminals as far aspracticable. Care shall be taken to avoidhammering on link clips with any metalinstruments, after the cables are laid. Wherejunction boxes are provided, they sh‘8il be mademoisture-proof 1 with suitable plastic compound.

4.3.10 Painting - If so required, the toughrubber sheathed wiring shall, after erection. bepainted with one coat of oil-free paint ordistemper of suitable colour over a coat of oil-freeprimer, and the PVC-sheathed wiring shall bepainted with a synthetic enamel paint of quickdrying type.

4.3.4 Protection of TRS or PVC-SheathedWiring .from Mechanical Damage

4.4 Metal-Sheathed Wiring System

4.4.0 General- Metal-sheathed wiring systemis suitable for low voltage. installations, and shallnot be used in situations where acids and alkalisare likely to be present. Metalsheathed wiringmay be used in places exposed to sun and rain


provided no joint of any description is exposed;this system may be installed in damp places withprotection against ingress of dampness providedat the open ends of the cables.

4.4.1 Link Clips - These shall be so arrangedthat one single clip shall not hold more than twotwin-core metal-sheathed. cables up to 1.5 mm2above which a single clip shall hold a single twin-core cable. The clips shall be fixed on varnishedwood battens with brass pins or brass screws andplaced at intervals of IO cm in the case ofhorizontal runs and 15 cm in the case of verticalruns. For the wiring and runs of mains exposed toheat and rain, clips specially made for the outdooruse from a durable metal, resistant to weather andatmospheric corrosion, shall be used.

4.4.2 Arrachment to Walls and Ceilings - Allmetal-sheathed cables on brick walls, stone wallsor plastered walls and ceilings, steel joists or anystructural steel work shall be run on well-seasonedand perfectly straight teak wood battens of notless than IO mm finished thickness, which havebeen well varnished on four sides. The width ofteak wood battens shall be such as to suit the totalwidth of cables -laid on the batten. Prior toerection these shall be painted with one coat ofvarnish or suitable paint of colour to match withthe surroundings. These battens shall be securedto the wills and ceilings by counter sunk headwood screws to wood plugs or other approvedplugs a.t an interval not exceeding 75 cm; thewood screws shall be counter sunk within woodb a t t e n a n d s m o o t h e d d o w n w i t h f i l e .Alternatively, metal-sheathed cables can be runon metallic saddles.

4.4.3 Wiring on Rolled Steel Joists - Wherewiring is to be carried along the tace of rolledsteel joists, a batten shall first be laid on the joistsand clipped to it as in,onspicuously as possible.The wiring shall be fixed to the batten in theordinary way.

4.4.4 ProtecGon of Wiring from MechanicalDamage

4.4.4.1 In cases where there are chances of anydamage to the wiring, such wiring shall becovered with sheet metal protective covering, thebase of which is made flush with the plaster orbrickwork, as the case may be, or the wiring shallbe drawn through a steel conduit pipe bycomplying with all requirements of conduitsystem of wiring.

4.4,4.2 The protective covering shall in allcases be carried right through the entire length ofsuch doubtful positions.

4.4.5 Join/s - Where joint-box system isspecified, joints shall be made by means ofconnectors, insulated with porcelain. or otherapproved material and enclosed in joint-boxes.The joint-boxes shall be so constructed as toprevent insects from entering them and to allowthe white-washing of the walls without waterhaving access to the connectors. All cables shall

be bonded through, or across these boxes.Bonding connections shall be so arranged as notto come in contact with plaster.

4.4.6 Stripping of Insulation and OuterCovering

4.4.6.1 When rubber or PVC insulation has tobe stripped for joints, the metal sheathing shall benicked only, not cut, and the insulation betweenthe metal sheath and the conductors shall be ofrubber or PVC sheath only. All tape shall be.stripped off. Where paper-insulated metal-sheathed cable is used, all openings in the sameshall be sealed.

4.4.6.2 While cutting and stripping of theouter covering of the cables, care shall be takenthat .the sharp edge of cutting instrument does nottouch the rubber or PVC insulat ion ofconductors. While connecting conductors to theconnecting terminals of accessories. care shall betaken to remove cotton !ape covering from thetop of rubber insulation of cable. The cotton tapecovering shall always remain inside lead coveringof cables.

4.4.7 Passing Through Floors - All cablestaken through floors shall be enclosed in aninsulated steel conduit extending 1.5 m above thefloor and flush with the ceiling below. orprotected by means of any other approved type ofmetallic covering. The ends of all conduits orpipes shall be neatly bushed with porcelain, woodor other suitabk material.

4.4.8 Passing Through Walls -The method tobe adopted shall be that laid down in 3.1.6. In thelatter case there shall be one or more conduits ofadequate size to carry the cables. The conduit(s)shall be neatly arranged so that the cables enterthem straight without bending.

4.4.9 Buried Cables Metal-sheathed cablesshall in no case be buried directly in the plaster orunder any masonry work.

4.4.10 Earthing ~ Precautions shall be takento ensure that all metal sheathing includingportable appliance with exposed metal parts,together with all joint-boxes and other similarreceptacles are efficiently earthed in accordancewith the requirements laid down under 5.3 andmade electrically continuous throughout theirlengths by means of soldered joints or approvedsuitable clamps or alternatively, with earthcontinuity conductors (each bonded cables)especially manufactured for the purpose. Theearthing shall extend to all main switches,distribution boards, etc. in comph&nce withIndian Electricity Rules, 1956, as. well asmanufacturers design and inst+uctions inconnection with earthing of all insulated m,icrogapmainswitches or similar fittings.

4.4.11 Testing - The electrical resistance of themetal sheathing together with the resistance of theearthing lead, measured from the connection withthe earth electrode to any other position in thecompleted installation shall not exceed IfI.

PART t tiENERAL AND COMMON ASPECTS 53

4.4.12 Puinring - Where required, all metal-sheathed wiring or its protective covering whensuch is fitted, shall be neatly painted after erectionwith two coats of any suitable paint.

4.5 Conduit Wiring System4.5.1 Surfacp Conduit Wiririg System with

Rigid Steel Conduits

4.5.1.1 7)pe and size of conduit - Allconduit pipes shall be finished with stoveenamelled surface. All conduit accessories shall beof threaded type and under no circumstances pingrip type or clamp type .accessories be used. Nosteel conduit less than 16 mm in diameter,shall beused. The number of insulated conductors thatcan be drawn into rigid steel conduit are given inTable 3 of set 18/Part I of the Code.

4.5.1.2 Bunching of cables - Unless otherwisespecified, insulated conductors of ac supply anddc supply shall be bunched in separate conduits.For lighting and small power outlet circuits phasesegregation in separate conduits is recommended.

4.5.13 Conduir jo ints-Conduit shall bejoined by means of screwed couplers and screwedaccessoeries only. In long distance straight runs ofconduit, inspection type couplers at reasonableintervals Shall be provided or running threadiwith couplers and jam-nuts shall be provided.Threads on conduit pipes in all cases shall bebetween I I mm to 27 mm long sufficient toaccommodate pipes to full threaded portion ofcouplers or accessories. Cut ends df conduit pipesshall have no sharp edges nor any burrs left toavoid damage to the insulation of conductorswhile pulling them’ through such conduits.

4.5.1.4 Prorection against dampness - Inorder to minimize condensation or sweating insidethe conduit all outlets of conduit system shall beproperly drained and ventilated, but in such amanner as to prevent the entry of insects as far aspossible.

4.5.1.5 Prortction of conduit against rust -The outer surface of ‘the conduit pipes, includingall bends. unions, tees, junction boxes, etc.forming part of the conduit system shall beadequately protected against rust particularlywhen such system is exposed to weather. In alIcases, no bare threaded portion of conduit pipeshall be allowed unless such bare threaded portionis treated with anti-corrosive preservative orcovered with suitable plastic compound.

4.5.1.6 Fixing of conduit - Conduit pipesshall be fixed by heavy gauge saddles,‘secured tosuitable wood plugs or other plugs with screws inan approved manner at an interval of not morethan I m. but on either side of couplers or bendsor similar fitting, saddles shall be fixed at adistance of 30 cm from the centre of such fitting.

4.5.1.7 Bends in conduit - All necessarybends in the system including diversion shall bedone by bending pipes; or by inserting suitable

54

a)

b)

solid or inspection type normal bends, elbows orsimilar fittings; or fixing cast-iron inspectionboxes whichever is more suitable. Conduit fittingsshall be avoided as far as possible on conduitsystem exposed to weather; where necessary, solidtype ‘fittings shall be used. Radius of such bendsin conduits shall be not less than 7.5 cm. Nolength of conduit shall have more than theequivalent of four quarter-bends from outlet tooutlet, the bends at the outlets not being counted.

4.5.1.8 Ourlets - All outlets . f&r fit t ings,switches, etc, shall be boxes of suitable meta. orany other approved outlet boxes for either surfacemounting or flush mounting system.

4.5.1.9 Conductors - All conductors used inconduit wiring shall preferably be stranded. Nosingle-core cable of nominal cross-sectional areagreater than 130 mm* enclosed alone in a conduitand used for alternating current.

4.5.1 .lO Erecrion and earthing of con&t -The conduit of each circuit or section shall becompleted before conductors are drawn-in. Theentire system of conduit after erection shall betested for mechanical and electrical continuitythroughout and permanently connected to earthby means of suitable earthing clamp, efficientlyfastened to conduit in a .wo’rkman like manner fora perfect continuity between each wire andconduit. If conduits are liable to mechanicaldamage, they shall be a‘dequately protected.

4.5.1.11 Inspection type conduit fittings suchas inspection boxes, draw boxes, bends, elbowsand tees shall be so installed that they remainaccessible for such purposes as withdrawal ofexisting cable< or installation of additional cables.

4.5.2 Recessed Conduit Wiring S,-srem withRigid Steel Conduits - Recessed conduit wiringsystem shall comply with’all the requirements forsurface conduit wiring system specified in 4.5.1.1to 4.5.1.11 and in tidditional, conform to therbquirements specified below.

Making of chase-The chase in the wallshall be neatly made and be of ampledimensions to p,ermit the conduit to be fixedin the manner desired. In the case of build-ings under construction. chases shall beprovided in the wall, ceiling, etc. at the timeof their construction and shall be filled upneatly after erection of conduit and broughtto ,the original finish of the wall.

Fixing qf conduir in chase -The conduitshall be fixed by means of staples or bymeans of saddles not more than 60 cmapart. Fixing of standaid bends or elbowsshall be avoided as far as practicable and allcurves maintained by bending the aonduitpipe itself with a long radius which willpermit easy drawing-in of conductors. Allthreaded joints of rigid steel conduit shallbe treated with some,approved preseivativecompound to secure protection against rust.


cl

d)

e)

Inspection boxes - Suitable inspectionboxes shall be provided to permit periodicalinspection and to facilitate removal of wires,if necessary. These shall be mounted flushwith the wall. Suitable ventilating holesshall be provided in the inspection boxcovers. The minimum sizes of inspection boxesshall be 75 X 15 mm.Types of accessories to be used - All out-lets. such al switches and sockets, may beeither of flushmounting type.

mounting type or of surface

9

ii)

Flush mounting type - All flush mount-ing outlets shall be of cast-iron or mildsteel boxes with a cover of insulatingmaterial or shall be a box made of asuitable insulating material. The switchesand other outlets shall be mounted onsuch boxes. The metal box shall be eff-ciently earthed with conduit by.a suitablemeans of earth attachment.Surface mounting type - If surfacemounting type.outlet box is specified, itshall be of any suitable insulatingmaterial.

When -crossing through expansion joints inbuildings, the conduit sections -across thejoint may be through flexible conduits of thesame size as the rigid conduit.

45.3 Conduit Wiring System with Rigid Non-metallic Conduits - Rigid non-metallic conduitsare used for surface, recessed and conceakdconduit wiring.

4.5.3.1 Qpe and sire-The conduit may beeither threaded type or plain type and shall beused with the corresponding accessories.

4.532 Btinching of cables - Conductors ofac supply and dc supply shall be bunched inseparate conduits. For !ighting and small poweroutlet circuits phase segregation in separatecircuits is recommended. The number of insulatedcables that may be drawn into the conduits aregiven in Table 4 of Set 18/Part I of the Code.

4.5.33 Conduit joints - Conduits shall bejoined by means of screwed or plain couplersdepending on whether the conduits are screwed orplain. Where there are long runs of straightconduit, inspection type couplers shall beprovided at intervals.

4.5.3.4 Fixing of Conduits - The provisionof 4.5.1.6 shall apply except that the spacingbetween saddles or supports is recommended tobe 60 cm for rigid non-metallic conduits.


4.5.3.5 Bends in conduit - Wherevernecessary, bends or diversions may be achieved bybending the conduits (see 45.3.9) or by employingnormal bends, inspection bends, inspection boxes,elbows or similar fittings.

4.536 Conduit fittings shall be avoided, asfar as possibk, on outdoor systems.

4.5.3.1 Outletsswitches

-all the outlets for fittings,etc. shall be boxes of substantial

constru&ion. In order to minimize condensationor sweating inside the conduit, all outlets ofconduit systems shall be properly drained andventilated, but in such a manner as to prevent theentry of insects, etc, as far as possible.

4.5.3.g For use with recessed conduit wiringsystem the provisions of 4.5.2(a) to (d) shallapply.

4.53.9 Heat may be used to soften theconduit for bending and forming joints in case ofplain conduit. As the material softens ‘whenheated, positioning of conduit in close proximityto hot surfaces should be avoided. Cautton shouldbe exercised in the use of this conduit in locationswhere the ambient temperature is 5oOC or above.

NOTE - Rigid PVC conduits are not.suitable for use wherethe normal w&king te.npcrature of the conduits and fittingsmay exceed WC. Certain types of ri

gid PVC conduits and

their associated fittings are unsuitibe for use where theambient temperature is likely to fall below -5°C.

4.53.10 Non-metallic conduit systems shall beused only where it is ensured that they -are:

a) suitable for extremes of ambient tem-

b)

cl

perature to which they are likely to besubjected in service,resistant to moisture and chemicalatmospheres, andresistant to low temperature and sunlighteffects.

For use underground, the material shall beacceptably resistant to moisture and corrosiveagents.

4.5.4 Conduit Wiring Systems wiih FlexibkNon-metallic Conduits - Where flexible non-metallic conduits are unavoidabk, they shall besecured at intervals not exceeding I.5 m andwithin 300 mm ‘on each side of every outkt box orfittmg. However thts provision is not applicabkwhere flexible conduit 1s fished and for lengths ofnot over 900 mm at terminals where flexibility isnecessary.

SECTION 12

O . F O R E W O R D

0.1 Earthing provides safety of persons andapparatus against earth faults. Any system ischaracterised by the type of distribution system,which include types of systems of live conductorsand types of system earthing. The different typesof earthing sSet I/Part r

stems are listed in Appendix A toof the Code. The choice of one

system or the other would detl”

nd on severalconsiderations as each offer di ferent degree ofperformance/ safety.0.2 This Section of the Code summarises theessential requirements associated with earthing inelectrical installations. These relate to generalconditions of soil resistivity, design parameters ofearth electrode, earth bus and earth wires andmethods of measurements . Par t icularrequirements for earthing depending on the typeof installation are covered in respective Sectionsof the Code.0.3 Additional rules applying to earth leakagecircuit-breaker systems are covered in AppendixB.0.4 The contents of this Section are based onfollowing:

IS : 732 (Part 2)-1982 Code of practice forelectrical wiring installations, Part 2 Design andconstruction

IS : 3043-1966 Code of practice for earthing.

1. SCOPEI.1 This Section of the Code covers generalrequirements associated with earthing in electricalinstallations. Specific requirements for earthing inindividual installations are covered in respectiveParts of the Code.NOTE - This section shall be read in conjunction with the

provisions of IS : 3043-1966.

2. GENERAL REMARKS

2.0 General2.0.1 The subject of earthing covers the

problems relating to the conductidn of electricitythrough earth. The terms earth and earthing havebeen used in this Code, irrespective of reliancebeing placed on the earth itself, to denote a lowimpedance return path of the fault current. As amatter of fact, the earth now .rarely serves as a

Part of the return circuit but is being used mainlyor fixing the voltage of system neutrals. The

earth connection improves service continuity andavoids damage to equipment and danger tohuman lives.

2.0.2 The object of an earthing system is toprovide as nearly as possible a surface under and

51

EARTHING

around a station which shall be at a uniformpotential and as near1 zero or absolute earthpotential as possibk. xe purpose of this is toensure thqt in general811 parts of apparatus, otherthan live parts, shall be at earth potential, as wellas to ensure that operators and attendants shall beat earth potential at all times. Also by providingsuch an earth surface of uniform potential underand surrounding the station, as neatly as possible,there can exist no difference of ,potential in ashort distance big enough to shock or injure anattendant when short-circuits or other abnormaloccurrences take place.

2.0.3 Earthing associated with current-carryingconductor is normally essential to the security ofthe system and is generally known as systemearthing, while earthing of noncurrent carryingmetal work and conductor is essential to thesafety of human life, of animals and of propertyand is generally known as equipment earthing.

2.0.4 Earthing shall generally be carried out inaccordance with the requirements of IndianElectricity Rules, 1956 as amended frdm time totime, and the relevant regulations of the electricitysupply authority concerned. The following IndianElectricity Rules are particularly applicable:

32, 5 1, 61, 62, 67, 69, 88 (2) and 90.

2.0.5 All medium voltage equipment shall beearthed by two separate and distinct connectionswith earth through an earth electrode. In the caseof high and extra high voltashall be ea,rthed by not less tgh

es the neutral pointsan two separate and

distinct conriections with earth each having itsown electrode at the generating station orsubstation and may be earthed at any other pointprovided no interference is caused by suchearthing. If necessary, the neutral may be earthedthrough a suitable impedance;

2.0.5.1 In cases where direct earthing mayprove harmful rather than provide safety (forexample, high frequency and mains frequencycorekss induction furnaces), relaxation may beobtained from the competent authority.

2.0.6 Earth electrodes shall be provided atgenerating stations, substations and consumerpremises in accordance with the requirements.

2.0.7 As far as possible all earth terminals shallbe visible.

2.01 All connections shall be canfully made; ifthey are poorly made or inadequate for thepurpose for which they are initnded, loss of life orserious personal injury may result.

2.0.9 Each earth system shall be so devised thatthe testing of individual earth ekctrode ispossible. It is recommended that the value of anyearth system resistance shall not be more than5 n, ynless otherwise specified.

NATIONAL ELEflRICAL CODE

2.0.10 It is recommended that a drawingshowin the main earth connection and earth

o!electr es be prepared for each installation.2.0.11 No addition to the current-carrying

system either temporary or permanent, shall bemade, which will increase the maximum availableearth fault current or’its duration until it has beenascertained that the existing arrangement of earthelectrodes, earth bus-bar, etc. ate capable ofcarrying the new value of earth fault currentwhich may be obtained by this addition.

2.0.12 No cut-out, link or switch other than alinked switch arranged to operate simultaneouslyon the earthed or earthed neutral conductor andthe live conductors shall be inserted on any supplysystem. This however, does not include the case ofa switch for use in controlling a generator or atransformer or a link for test purposes.

2.0.13 All materials, fittings, etc, used inearthing shall, conform to Indian Standardspecifications wherever these exist. In the case ofm a t e r i a l s f o r w h i c h l n d i a n S t a n d a r dspecifications do not exist, the material shall beapproved by the competent authority.

2.1 Design Considerations

2.1.1 System %Irrhing

2.1.1.1 The ngulations that every medium,high and extra high voltage equipment shall beearthed by not less than two separate and distinctconnections with earth is designed primarily topreserve the security of the system by ensuringthat the voltage on each live conductor isrestricted to such a value with respect to thepotential of the general mass of the earth as isconsistent with the levels of insulation applied.

2.1.1.2 The earth system resistance should besuch that when any fault occurs against whichearthing is designed to give” protection, theprotective gear will operate to make the faultyportions of plant harmless. In most cases suchoperation involves isolation of the faulty main orplant by circuit-breaker or fuses. In the case ofunderground system there may be no difficulty,but in the case of overhead line sonly by fuses there may be J

stem protectedifficulty in so

arranging the value of the earth resistance that aconductor falling and making good contact withearth shall cause the fuses in the supply tooperate.

NOTE -Earthing may notf

ive protection against faultswhich are not csrntially earth auks. For example, if a phaseconductor of an overhead spur litic*brcaks, -and the‘ partremote from the SUDD~Y falls to the nround. it is unlikelv thatany protective gcar’iziying on carth%tg wili operate sin& ihemajor fault is the open-circuit against which urthing gives noprotection.

2.1.2 Equipment Earthing - The object ofequipment earthing is to ensure effectiveoperation of the protective gear in the event ofleakage through such metal work, the potential ofwhich with respect to neighbouring objects may


attain a value which would cause danger to life orrisk of fire.

2.13 Soil Resistivity

2X3.1 The resistance to earth of an electrodeof givep dimensions is dependent on the ekctricalresistivny of the soil in which it is installed. Itfollows, therefore, that an overr id ingconsideration in deciding which of the alternativemethod of protection is to be adopted for aparticular system or location is the soil resistivityin the area concerned.

2.1.3.2 The type of soil largely determines itsresistivity and representative values for s’oilsgenerally found in India are given in Appendix A.Earth conductivity is, however, essentiallyelectrolytic in natun and is affected therefore bymoisture .content of the soil and its chemicalcomposition and concentration of salts dissolvedin the contained water. Grain sire and distributionand closeness of packing ate also contributoryfactors since they control the manner in which themoisture is held in soil. Many of these factorsvary locally and some seasonally and, therefore,the values given in Appendix A should be takenonly as a general guide. Local values should beverified by actual measurement and this isspecially important whete the soil is stratified, asowing to the disposition of earth current, theeffective resistivity depends not only on thesurface layers but also on the underlyinggeological formation.

2.1.33 The soil temperature also has someeffect on soil resistivity but is important only nearand below freezing point, necessitating theinstallation of earth electrode at depths to whichfrost ~111 not penetrate.

2.1.3.4 While the fundamental nature andproperties of a soil in a given area cannot bechanged, use can be made of purely localconditions in choosing suitable electrode sites andof methods of oreoaring the site sekcted. tosecure optimum t%tivit< Reference is drawn to1s : 3043-1966.

2.1.4 Potential Gradients - It is necessary LOensure, especially in case of large electricalinstallations, that a person walking on the groundor touching an earthed objects, in or around thepremises shall not have large dangerous potentialdifferences impressed across his body in case of afault within or outside the premises. Such dan ermay arise if steep potential gradients exist witffinthe premises or between boundary of the premisesand an accessible point outside. For this the steppotential and touch potential should beInvestigated and kept withm safe limits. Within anearthing grid, the .step and touch potentials maybe lowered to any value by reducing the meshinterval of the grid. The situation is more difficultin the zone immediately outside the peripherywhere the problems may exist even for thetheoretical case of a singk plate covering thesubstation area. This problem may be serious insmall stations where the grid may cover only a

57

limited area. Attempts shot& be made to design asubstation so as to eliminate the possibility oftouch contact beyond the earth-system periphery.when the limitations on step potential become lessexacting. While assessing the touch potential, the

method of earthing of the object touched, forexampk, whether it is earthed directly below orremotely should be kept in view in order, toconsider the possibility of occurrence of largepotential differences.

Special attention should be paid to the pointsnear the operating handles of apparatus, and, ifnecessary, potential equaliser grillages of closermesh securely bonded to the structure and theoperating handle’ should be buried below thesurface where the operator may stand whenoperting the switch.

2.1.~ At consumer’s premises where theapparatus is protected by fuses, the total earthcircuit impedance shall not be more than thatobtained by graphs given in Fig. I.

3. EARTH ELECTRODES

3.1 Material

3.1.1 Although electrode material does notaffect initial earth resistance, care should be takento select a material which is resistant to corrosionin the type of soil in which it will be used

3.1.2 Under ordinary conditions of soil, use ofcopper, iron or mild steel electrodes isreco:umended.

3.1.3 In cases where soil conditions point toexcessive corrosion of the electrode and the

60

m 5oiiLz 40

L0f 30d

z!a

20

10

connections, it IS recommended to use eithercopper electrode or copper clad ekctrode or zinccoated (galvanized) iron electrodes.

3.1.4 In direct current system, however, due toelectrolytic action which causes serious corrosion,it is recommended to use only copper ekctrodes.

3.1.5 The ,electrode shall be kept free frompaint, enamel and grease.

3.1.6 It is recommended to use similar materialfor earth electrodes and earth conductors orotherwise precautions should be taken to avoidcorrosion.

3.2 Current Loading

3.2.1 An earth electrode should be designed tohave a loading capacity adequate for the system inwhich it forms a part, that is, it should be capableof dissipating without failure, energy in the earthpath at the point at which-it is installed under anycondition of operation of the system. Failure ISfundamentally due to excessive rise of temperatureat the surface of the electrode and is thus afunction of current density and duration as well aselectrical and thermal properties of soil.

32.2 Two conditions of operation requireconsideration, namely:

a) Long duration overloading as with normalsystem opertion, and

b) Short time overloading as under faultconditions in directly earthed system.

( 1) CURVE A - TOTAL EARTH CIRCUIT WPEDANICE

(2) CURVE R-RESISTANCE OF CONSUMER’SEARTH ELECTRODE

(ASSUMING SUG- STATIDN ELECTRODE OFEQUAL RESISTANCE AN0 2 OHMS IMPEDANCEIN REMAINDER OF CIRCUIT)

(2) IN BOTH CASES A SUPPLY VOLTAGE OF24OV HAS BEEN ASSUMED

2 4 6 8 13 12 11 16

IMPEDANCE OR RESISTANCE IN OHMS

FIG. I RECOMMENDED EARTH CIRCUIT IMPEDANCE OR RESISTANCEFOR DIFFERENT VALUES OF FUSE RATING


33 Voltage Gradient

33.1 Under fault conditions the earth electrodeis raised to a potential with respect to the generalmass of the earth. This results in the existence ofvoltages in the soil around the electrode whichmay be injurious to telephone and pilot cableswhose cores are substantially at earth potentialowing to the voltage to which the sheaths of suchcables are raised. The voltage gradient at thesurface of the earth may also constitute danger tolife.

33.2 Earth electrodes should not be installed inproximity to a metal fence to avoid the possibilityof the fence becoming live, and thus dangerous atpoints remote from the substation, oralternatively giving rise to danger within theresistance area of the electrode Chich can bereduced only by introducing a good connectionwith the general mass of the karth. If the’ metalfence is unavoidable, it should be earthed.3.4 Types of Earth Electrodes-The followingtypes of earth electrodes are considered standard:

a) Rod and pipe electrodes,b) Strip or conductor electrodes,c) Plate electrodes, andd) Cable sheaths.

For details regarding their design, reference shallbe made to IS : 3W3-I966*3.5 Design Data on Earth Electrodes

3.5.1 The design data on the various types ofearth electrodes is given in Table I.


3.5.2 Effect of S h a p e o n Elecrro&Resistance - The resistance of any electrodeburied in the earth is in fact related to thecapacitance of that electrode and its image in freespace. The relationship is given by:

100 PR=-

4nCwhere

R = resistance in an infinite medium,P = resistivity of the medium .(soil) in ohm-

metre, and ’C = capacitance of the electrode and its image

in free space.

In practical case, the capacitance is divided intotwo by the plane of earths surface so that,

loo PR=_27rc

a) For rod or pipe ekctrodes, the formula isloo P

R = 2 log, y ohms72

whereI = length of rod or pipe in cm, and

d = diameter of rod or pipe in cm.b) For strip or round conductor ekctrodes,

Rloo P 212 p

=‘G log y ohms

<’ TABLE I DESIGN DATA ON EARTH QLECTRODES

MEASCIREMEI~ ,TYPE OF ELECTRODES

Rod Pipe Strip - Round PlateConductor (WC NOTE 2)

(1) (2)(Wc N$TE 1)

(4) (5) (6)

Diameter 16 mm* 38 mm*(not less than) 12.5 mm? IO0 mm:

L=if@;;pL;“‘” (Ideal 2.5 m 2.5 m 0.5 m I5 m I.5 m3

(not less than) to 3.5 m)

Size - - 25 X 1.60 mmt 3.0 mm*7 60X60 cm25X4 mm* 6 mm’*

Thickness - - - - 6.30 mm?3.15 mm+

NOTE I - A typical illustration of pipe earth electrode is given in Fig. 2.

NOTE 2 - A typical illustration of plate ekctrode is given in Fig. 3. If two or more plates are used in parallel, they shall beseparated by not less than 8.0 m. Ideal area is 3.50 m*.

*Steel or galvanized iron.tCoppcr.:Cast iron.

PART 1 GENERAL AND COMMON ASPECTS 59

-

Cl COVER HINGED‘4 us ROD7 f TO Cl FRAMEsC E

I a.3 rCI COVER HINGED

MEN1 CONCRETETO Cl FRAME

(WI))\I_ ~~- JygOafcME

- ::. . ’

f

/MIRE MESH

;’ rCEMENt CONCRETE r912.7 GI PIPE

I

t

LA

i150

1

75

80

II, It 200&300#-4SdlO 01 PIPC 2J I

1500(min.1

ENLARGED DE

‘-0 12.7 GI PIPE

a t

F!iKoAL

i

_.I-ALTERNATE LAYER

OF CHARCOAL OR-@- COKE AND SALT

HOLE,0 12-t

~6OOx600x6*3 GI PLATE bR6OOx6OOx3~15 COPPER YLAIE

SECltbN X X

All dimensions in miilimctres. All dimensions in millimetres.

NOTE -Three or four buckets of water to be poured intosump every few days to keep the soil surrounding the earth

NOTE -Three and four buckets 6f water to be poured into

pipe permanently moist.sump every few days to keep the soil surrounding the earthplate permanently moist.

FIG. 2 A TYPICAL ILLUSTRATION OF PIPE EARTH FIG. 3 A TYPICAL ILLUSTRATION OF PLATE EARTHELECTRODE ELECTRODE

whereI = length of the strip in cm,

w = depth of burial in cm, andt = width (strip) or twice the diameter

(conductors) in cm.c) For plate electrodes,-

R = 4 a ohms

whereA = area of both sides of plate in m2.

35.3 Effect of Depth of Burial - To reducethe depth of burial without increasing theresistance, a number of rods or pipes shall beconnected together in parallel (see Fig. 4). Theresistance in this case is practically prdortionalto the reciprocal of the number of electfydes usedso along as each is situated outside the resistancearea of the other. The distance between twoelectrodes in such a case shall preferably be notless than twice the length of the electrode.

4. EARTH BUS AND EARTH WIRES

4.0 G e n e r a l

4.0.1 The mimmum allowable size of earth wireis determined principally by mechanicalconsideration for they are more liable tomechanical injury and should therefore be strong

enough to resist any strain that is likely to be putupon them.

4.0.2 All earth wires and earthcontinuityconductors shall be of copper, galvanized iron, orsteel or aluminium.

NOTE - Aluminium shall not bc used underground.

4.0.3 They shall be either stranded or solid barsor flat rectangular strips and may be bareprovided due care is taken to avoid corrosion andmechanical damage to it. Where required, theyshall be run inside metallic conduits.

4.0.4 Interconnections of earth-continuityconductors and main and branch earth wires shallbe made in such a way that reliable and goodelectrical connections are permanently ensured.

NOTE - Welded. bolted and clamped joints are permissible.For stranded conductors, sleeve connectors (for example,indented, riveted or bolted connectors) are permissible. Boltedconnectors and their screws shall be protected against anypossible corrosion.

4.0.5 The path of the earth wire shall, as far aspossible, be out of reach of any person.

4.0.6 If the metal sheath and armour have beenused as an earth continuity conductor the armourshall be bonded to the metal sheath and theconnection between the earth wire and earthingelectrode shall be made to the metal sheath.

4.0.7 If a clamp has been used to provideconnection between the earth wire and the metalsheath and armour, it shall be so designed and

6

INDIVIDUAL RESISTANCE IN OHMS

F I G, 4 RE S I S T A N C E OF EL E C T R O D E S A T

D E P T H S A N D S O I L RESISTIVITIESVARIOGS

P A R T 1 GEKI:RAL A N D C O M M O N A S P E C T S 61

16 18

lnstaikd as to provide reliable connection without 5.1.2 The source of current shall be isolateddamage to the cable. from the supply by a double wound transformer.

4.0.8 The neutral conductor shall not be usedas earth wire.

4.0.9 The minimum sizes of earth-continuityconductors an4 earth wires shall be as given in therelevant part of the Code.

5.1.3 At the time of test, wheri possibk, thetest electrode shall be separated from the earthingsystem.

5.1.4 The auxiliary electrodes usually consist of12.5 mm diameter mild steel rod driven up to I minto the ground.

5. MEASUREMENT OF EARTH ELECTRODERESISTANCE

5.1 Fall of Potential Method - In this methodtwo auxiliary earth electrodes, besides the testelectrode, tire placed at suitable distances from thetest electrode (see Fig. 5). A measured current ispassed between the electrode ‘A’ to be tested andan auxiliary current electrode ‘C’ and thepotential difference between the electrode ‘A’ andthe auxiliary potential electrode ‘B’ is measured.The resistance of the test electrode ‘A’ is thengiven by:

5.1.5 Ail the test electrodes and the currentelectrodes shall be so placed that they areindependent of the resistance area of each other.If the test electrode is in the form of rod, pipe orplate, the auxiliary current electrode ‘C’ shall beplaced at least 30 m away from it and theauxiliary potential electrode ‘B’ shall be placedmidway between them.

5.1.6 Unless three consecutive readings ot testelectrode resistance with different spacings ofelectrodes agree, the test shall be repeated byincreasing the distance between electrodes ‘A’ and‘C’ up to 50 m and each time placing the electrode‘B’ midway between them.p$

whereR =V=F

I =

resistance of the test electrode in ohms,reading of the voltmeter in volts, andreading of the ammeter in amperes.

AMMETER-

A\+TEST

ELECTRODE

8”POTENTIAL

ELECTRODE

X+lmCVJ._

CURRENTELECTROOE

F I G. 3 METHOD O F M E A S U R E M E N T O F E A R T H

E L E C T R O D E R E S I S T A N C E

5.1.1 If the test is made at power frequency,that is. 50 Hz, the resistance of the voltmetershould be high compared to that of the auxiliarypotential electrode ‘B’ and in no case should beless than 20 000 ohms.

NOTE - In most cases there will be stray currents flowing inthe soil and unless some steps are taken to eliminate theircffecc, they may prodlice serious errors in the measuredvalue.lf Ihe testing current is of the same I* uency as thestray current. this elimination becomes very dl ~cult and it aI?betrer lo use an earth tester incorporating a handdrIvengeneralor. I hese earth testers usually generare direct currentand have rotary current-reverser and synchronous rectifiermounted on rhc generator shaft so that alternating current issupplied 10 the lest circuit and the resulting potentials arerectified for measurement by a direct-reading moving-coil ohmmeter. The uresence ot strav currents in the soil is indicated bv

a wtndcring of the instrument pointer. but an increase 0;decrease of generator handle speed will cause thi? lo disappear.

62

5.2 Alternative Method

5.2.1 The method described in 5.1 may not givesat.isfactory results if the test electrode is of verylow impedance (I ohm or less). .This appliesparticularly while measuring the combinedresistance of large installations. In these cases, thefollowing method may. be adopted.

. 5.2.1.1 Two suitable directions, at least 90degrees apart. arr: first selected. The potential Leadis laid in one direction and an electrode is’placed250 to 300 metres from the fence. The current leadis taken in the other direction and the currentelectrode located at the same distance as thepotential electrode. A reading is taken under thiscondition. The current electrode is then movedout in 30-m steps untik the same reading isobtained fdr three consecutive locations. Thecurrent electrode is then left in the last foregoingposition and the potential electrode is moved outin 30-m steps until three consecutive readings areobtained without a change in value. The lastreadings then correspond to the true value ofearth resistance.

6. EARTHING OF INSTALLATIONS INB U I L D I N G S

6.1 The eaithing arrangements of the consumer’sinstallation shall be such that on occurre,nce of afault of negligible impedance from a phase ornon-earthed conductor to adjacent exposed metal,a current corresponding to not less than three-and-a-half iimes the rating of the fuse or one-and-a-half times the setting of the overload earthleakage circuit-breaker will flow except wherevoltage operated earth leakage circuit-breakersare used and make the faulty circuit dead. Wherefuses are used to disconnect the faulty section ofan installation in the event of an earth fault. theto/q!, permissjble impedance of the earth faultpath may bc computed from the following


formula (for a normal three-phase system withearthed neutral).

z = Phase-toearth voltage of systemMinimum Factorfusing current X ofof fuse safety

where

2 = permissible impedance in ohms.NOII .~~ The factor of safety in calculating the permissible

Impedance should be left to the discretion of the de‘signer.

6.1.1 The factor of safety in the above formulaensures that in most cases the fuse will blow in atime which is sufficiently short to avoid dangerand allowing for a number of circumstances, suchas the grading of fuse ratings, increase ofresistance due to drying out of the earthelectrodes in dry weather. inevitable extensions toinstallations involving, increase in length of thecircuit conductors and the earth-continuityconductors, etc.

6.1.2 It will be observed that this requirementdetermines the overall impedance and does notcontain a specific reference to any part of thecircuit such as the conduit or other earth-continuity conductor together with the earthinglead. In fact. in large installations the overallimpedance permissible may be less than I ohm, sothat considerably less than this might be allowablefor the earth-continuity system.

6.2 ‘It is desirable when, planning an installationto consult the supply authority or an electricalcontractor having knowledge of local conditions,in order to ascertain which of the two. namely,the use of fuses or overload circuit-breakers, forprotection against earth-leakage currents is likelyto prove satisfactory.

6.3 It is recommended ,that the maximumsustained vol tage deve loped under fau l tconditions between exposed metal required to beearthed and the consumer’s earth terminal shallnot exceed 32 volts rms.

6.4 Only pipe or rod earth electrodes arer e c o m m e n d e d and they shall satisfy therequirements of 3.5.

6.5 Earth-Continuity Conductors

6.5.1 Connection to earth of those parts of aninstallation which require to be earthed shall bemade by means of an earth-continuity conductorwhich may be a separate earth conductor, themetal sheath of the cables or the earth-contin Yityconductor contained in a cable, flexible cable orflexible cord.

6.5.2 Earth-Conrinuit.\a Conductors and EarthWires not Contained in the Cables ~- The size ofthe earth-continuity conductors should becorrelated with the sire of the current carryingconductors, that is, the &es of earth-continuityconductors should not be less than half of the


largest current carrying conductors, provided theminimum size of earth-continuity conductors isnot less than 1.5 mm? for copper and 2.5 mm? .foraluminium and need not be greater than 70 mm*for copper and 120 mm? for aluminium. Asregards the sizes of galvanized iron and steelearth-continuity conductors, they may be equal tosize of current-carrying conductors with whichthey are used. The size of earth-continuityconductors to be used along with aluminiumcurrent-carrying conductors should be calculatedon the basis of equivalent size of the coppercurrent-carrying conductors.

65.3 Earth-Conlinuit!, Conductors and EarthWires Contained in the Cables - For flexiblecables, the size of the earth-continuity conductorsshould be equal to the size of the current-carrying-conductors and for metal sheathed, PVC andtough rubber sheathed cables the sizes of thee a r t h - c o n t i n u i t y c o n d u c t o r s s h a l l b e i naccordance with relevant Indian Standards.

6.5.4 Cable Sheaths Used as Earth-ContinuitjxConduc/ors -~ Where the metal sheaths of cablesare used as earth-continuity conductors, everyjoint in such sheaths shall be so made that itscurrent-carrying capacity is not less than that ofthe sheath itself. Where necessary. they shall beprotected against corrosion.

Where non-metallic joint boxes are used, meansshall be provided to maintain the continuity, suchas a metal strip having a resistance not greaterthan that of the sheath of the largest cableentering the box.

6.5.5 Metal Conduit Pipe Used as on Earrh-Continui ty Conducror - Metal conduit pipeshould generally not be used as an earth-continuity conductor but where used a very highstandard of workmanship in installation isessential. Joints shall be so made that theircurrent-carrying capacity is not less than that ofthe conduit itself. Slackness in joints may result ihdeterioration and even comple te loss o fcontinuity. Plain slip or pin-grtp sockets areinsufficient to ensure satisfactory electricalcontinuity of joints. In the case of screwedconduit, lock nuts ,should also be used.

6.5.6 Pipes and Structural Steel Work - Pipes,such as water pipe, gas pipe, or members ofstructural steel work shall not be used as earth-continuity conductor.

7. MEASUREMENT OF EARTH LOOPIMPEDANCE

7.1 The current which will flow under earth faultconditions and will thus be available to operatethe overload protection depends upon theimpedance of the earth return loop. This includesthe line conductor, fault , earth-continuityconductor and earthing-lead, earth electrodes atconsumer’s premises and substations and any

63

parallel metallic return to the transformer neutral been connected this shall be done by the use of anas tiell, as the transformer winding. To test theoverall earthing for any installation depending for

earth loop impedance tester as shown in Fig. 6.The neutral is used in place of the phase

protection on the operation of dvercurrentdevices, for example, fus& it is necessary to

conductor for the purpose of the test. The open-circuit voltage of the loop tester should not

measure the impedance of this loop underpractical fault conditions. After the supply has

exceed 32 volts.

L-+-J

A = ammeterB = neon indicatorC = main switchD = test switchE = consumer’s earth electrode

F = supply fusesP = polarity switchs = substation earth electrodeV = voltmeter

At FF, jacks are provided for insertion of plugs for connection to external neutral and/or earth conductors. if desired.

NOTE I -Arrows show current flow in neutral/earth loop.

NOTE 2 -Supply system is shown dotted.

FI G. 6 C IRCUIT D IAGRAM OF EARTH LOOP IMPEDANCE TESTER

A P P E N D I X A(Clause 2.1.3.2)

REPRESENTATIVE VALUES OF SOIL RESISTIVITY IN VARIOUS PARTS OF INDIA.SLNo.

LOCALITY TYPE OF SOIL ORDER OFREHSJIVITYohm-metre

1, Kakarapar, Distt Surat,Gujarat

2. Taptee Valley

3 Narmada Valley

Clayey black soil 6-23

Alluvium 6-24

Alluvium 4-i I

4. Purna Valley(Deogaon)

5. Dhond, Bombay

6. Bijapur Distt,Karnataka

7. Garimenapenta,Distt Nellore

Andhra Pradesh

8 . Kartee

9. Delhia) Najafgarh

Agricultural 3-6

Alluvium

a) Black cottons o i l

b) Moorm

Alluvium(highly clayey)

a) Alluvium 3-5 Underlying bedrock-sand-b) Alluvium 9-2 I stone, trap or gneisses

a) Alluvium(dry sandy soil)

b) Loamy to clayeysoil

c) Alluvium (saline)

6-40

2-10

I O-50

2

75-l 70 do

38-50 do

1.5-9 do

REMARKS

Underlying bedrock-Deccan trap

doUnderlying bedrock-sand-

stones, shale and lime-stones, Deccan trap andgneisses

Underlying bedrock-Deccantrap

do

do

do

Underlying be&ck-gneisses

(Conrinued)


SL LOCALITYNo.

b) Chhatarpur

IO. Korba , MP

I I. Cossipur,Calcutta

12. Bhagalpur, Bihar

13. Kerala (TrivandrumDistt.)

14. Bharatpur

15. kalyadi, Mysore

16. Koiar Gold F ie lds

17. Wajrakarur,Andhra Pradesh

18. Koyna, SataraDistt.

19. Kutch-Kandla(Amjar Area)

20. Villupuram,Madras

21. Ambaji. BanaskanthaGujarat

22. RamanathapuramDistt Madras

T Y P E OF SO I L

Dry soil

a) Moist clayb) Alluvium soil

Alluvium

a) Alluviumb) Top soil

Lateritic clay

Sandy loam(Saline)

Alluvium

Sandy surface

Alluvium

Lateritic

a) Alluvium(clayey)

b) Alluvium(sandy) ’

Clayey sands

Alluvium

a) Alluvium

b) Lateritic soil

O RDER O FRESISTIVITYohm-metre

36-109

2-3

>I O-20

2 5bvrmx)

9-1424-46

6-14

60-150

45-185

50- I50

800-l 200(dry)4-50

60-200

II

170

2-5

ia:prox)

REMARKS

Underlying bedrock-quartzites

Underlying bedrock-sand-stone or shale

Underlying bedrock-traps,sand-stones or gneisses

Underlying bedrock-laterite, charnockite orgranites

Underlying bedrock-gneisses

do

do

Underlying bedrock-sand-laterite or trap

Underlying bedrock-sand-stone, shale or trap

do

Underlying bedrock-granite

Underlying bedrock-granites and gneisses

Underlying bedrock-sand-stones and gneisses

do

NOTF ~~ The soil resistivities are subject to wide seasonal variation as they depend very much on the moisture content

A P P E N D I X B

( C l a u s e 0 . 3 )

ADDITIONAL RULES FOR EARTHINGS

B-l. ADDITlONAL RULES APPLYING TOTHE DIRECT EARTHING SYSTEM

B-l .1 Where a’ driven or buried elstrode isused, the earth resistance shall be as low aspossible.

Nort. The value of earth resistance is under consideration.

B-2. ADDITIONAL RULES APPLYING TOTHE MULTIPLE EARTH NEUTRALSYSTEM

B-2.1 This system shall be used only where theneutral and earth is low enough to preclude thepossibility of a.dangerous rise of potential in theneutral.


B-3. ADDITIONAL RULES APPLYING TOTHE EARTH LEAKAGE CIRCUIT-BREAKER SYSTEM

B-3.1 Installation of the Earth Leakage Circuit-Breaker System, General ( see Fig. 7) - All partsrequired to be earthed shall be connected to anearth electrode through the coil of an earthleakage circuit-breaker which controls the supplyto all those parts of the installation which are tobe protected; and to a separate earth electrode.

B-3.2 Selective Protection - If selectiveoperation of earth leakage circuit-breaker isrequired, the circuit-breaker, electrodes andearthing conductors shall be installed in one ofthe follbwing ways:

65

a) Arrangement Giving Complete SelectivitJ3(see Fig. 8) - All metal frames, condutts,earthing conductors, etc, which are to beprotected as a unit shall be electricallyseparated from all other such parts and fromany other earthed metal. Each part to beprotected ‘as a unit shall be connected to an

earth electrode through the coil of an earthleakage circuit-breaker.

Ali the separately protected portions ofthe installations may be connected to oneelectrode to the earth leakage circuit-breaker.

P L U GOUT L

F’I N S U L A T E D

C O N D U C T O R

E ARTH,INGCONDUCTORSM A Y B E B A R E

E ARfH E L E C T R O D E S

F I G. 7 CONNECTION OF E A R T H L E A K A G E CIRCIJIT-BREAKER SI M P L E I N S T A L L A T I O N

INSULATE0 CdNOLtClOR

ELECTRODE

\INSULAlED CONDUCTOR

REINFORCEME

4EARTHELECTRODE

8A By complete separation of the exposed metal of oneinstallation from that of othger installations

88 By use of a double-insulated wiring system, where thereare no conduits to be earthed

F I G. 8 ‘ CO N N E C T I O N S O F E A R T H L E A K A G E CIRWIT- BREAKERS FOR C O M P L E T E SELE~TIVIT\


b) Arrangement Giving Partial Se1ectivir.v(Complete Selectivit)’ MYth Respect to Faultsin Apparatus, but no Selectivity M’ith Respectto Falls in Wiring in Conduit) (see Fig. 9) -All the conduits and associated fittings shallbe bonded together and connected to an earthelectrode, all shall also be connected toanother earth electrode through an earthleakage circuit-breaker which controls allthe active conductors supplying the whole orportions of the installations concerned. Eachpart to be protected as a unit shall beconnected to an earth electrode through

the coil of a separate earth leakage circuit-breaker which controls al l the activeconductors supplying that portion of theinstallation only. All these portions may beconnec ted to one e lec t rode , bu t th i selectrode shall be separated from theelectrode to which the condui t s a reconnected.

NOTL I -- A double-Insulated wiring system is used. e.g.,tough rubber-sheathed cables. Any conduit used does not thenneed to be earthed.

NOTE 2 ~ The earthing conductor is insulated from theconduit.

f-INSULATEDCONDUCTOR

MAY BE 0ARE M A I N E . L . C . B .

ARTHING CONDU-MAY BE BARE

CONDUCTOR

PLUG-SOCKETOUTLETS ELECTRODES

f+p-EQUIPMENT

F I G. 9 CONNEC‘TIONS OF E A R T H L E A K A G E CIIKIJIT-BREAKERS FOR P A R T I A L S E L E C T I V I T Y


‘SECTION 13 SHORT-CIRCUIT CALCULATIONS(Under Consideration)

SECTION 14 ELECTRICAL ASPECTS OF BUILDING SERVICES

O.FOREWORD

0.1 Most of the modern day services in buildingsdepend on electrical energy. These services,broadly; are:

a) Lighting and ventilation,b) Air-conditioning, andc) Lifts and escalators.From the point of view of conservation of

energy and safety in its use, it is found essential SOdraw attention to essential design principles forbuilding services.0.2 Apart from the three major power consumingservices in a buildin

athere are other

functional/safety services t at are basically lightcurrent installations, whose proper functioning isimportant. These are:

a) Electrical audio-systems,b) Electric call-bell systems,c) Electric clock systems, andd) Fire-alarm systems.

0.3 This Section of the Code draws attention tothe requirements to be complied with in thedesign and construction of building services. Forreasons of restricting the volume of the text, thisSection is restricted to only the electrical aspectsof building services. Non-electrical design aspectsare not covered in the Code, for which referenceshall be made to the relevant part of SP : 7-1983‘ National Building Code of India ‘.

1. SCOPE

1.1 This Section of the Code covers requirementsfor installation work relating to building servicesthat use electric *power.

2. GENERAL GUIDELINES2.1 Extensive guidelines on building designaspects have been covered from the point of viewof ensuring economic services in an ,occupancy inSP : 7 (Part 8)- 1983. These shall be referredto from the point of view of ensuring good designof building services and early coordinationamongst all concerned.

2.2 Orientation of Building

2.2.1 The chief aim of orientation of buildingsis to provide physically and psychologicallycomfortable living inside the buildings by creatingconditions which suitably and successfully wardoff the undesirable effects of severe weather to aconsiderable extent by judicious use of therecommendationsfactors.

PART I GENERAL

and _ knowledge of climatic

AND COMMON ASPECTS

2.2.2 From the point of view of lighting andventilation, the following climatic factorsinfluence the optimum orientation af thebuildings:

a) Solar* radiation and temperature,b) Clouds,c) Relative humidity, andd) Prevailing winds.Reference shall be made to IS : 7662 (Part I)-

1974* on orientation of buildings.SECTION 14A LIGHTING

3. ASPECTS OF LIGHTING SERVICES3.1 Principles of Good Lighting

3.1.1 Good lighting is necessary for allbuildings and has three primary aims. The first isto promote the work and other activities carriedon within the buildings; the second is to promoiethe safety of people using the building; and thethird is to create, in conjunction with the structureand decoration, a pleasing environment conduciveto interest and a sense of well-being.

Realization ot these aims involves:

4

b)

4

4

4

Careful planning of the brightness andcolour patterns within the working area andthe surroundings so that attention is drawnnaturally to the important areas, detail isseen quickly and accurately and the room isfree frog any sense of gloom or monotony,Using directional lighting, .whereappropriate, to assist preception of taskdetail and to give good modelling,Controlling direct and reflected glare fromlight sources to eliminate visual discomfort,In artificial lighting installations, minimizmgflicker from certain types of lamp andpaying attention to the cdlour renderingproperties of the light,Correlating lighting throughout the buildingto prevent excessive differences betweenadjacent areas and so as to reduce the risk ofaccidents, andInstalling emergency lighting systems wherenecessary.

3.1.2 Good lighting design shall take intoaccount the following:

a)

b)

Planning the brightness pattern from thepoint of view of visual performance, safetyand amenity and surroundings,Form and texture in the task area andsurroundings,

*Recommendations for orientation of building:Part I Non-industrial buildings.

71

C)

4e)fl

g)

Cornrolling glare, stroboscopic effect andflicker,

Colour rendering,

Lighting for movement,

Provision for emergency,

Maintenance factors in lighting installation,and

Maximum energy effectiveness of thelighting system used consistent with thespecific needs of visual tasks performed.

3.1.3 Guidelines on principles of good lightingdesign can be had from IS : 3646 (Part I)-1966*.

3.2 Design Aspects

3.2.1 Illumination Levels -- The level ofillumination for a particular occupation dependson the following criteria:

4 Adequacy for preventing both strain inseeing and liability to accidents caused bypoor visibility,

b)

c)

Adequacy for realizing maximum visualcapacity,

Adequacy for the performance of visualtasks at satisfactory high levels of efficiency,and

4 Adequacy for pleasantness or amenity.

The schedule of recommended values ofillumination and limiting values of glare index aregiven in IS : 3646 (Part 2)-1966t. For specificoccupancies covered in the Code see relevantPart/Section.

3.2.2 Designing for Daylight - Reference shallbe made to IS : 2440-19752.

3.2.3 Lighting Problems and Economics -Reference is drawn to Appendices C and D ofIS : 3646 (Part I)-1966*

SECTION 14B VENTILATION

4. ASPECTS OF VENTILATION

4.0 General

4.0.1 Ventilation of buildings is required tosupply fresh air for respiration of occupants, todilute inside air to prevent vitiation by bodyo d o u r s a n d t o r e m o v e a n y p r o d u c t s o fcombustion or other contaminants in air and toprovide such thermal environments as will assist

*Code of practice for interior illumination: Part I Principlesof good lighting and aspects of design.

tCode of practice for interior illumination: Part 2 Schedulefor values of illumination and glare index.

iGuide for daylighting of buildings (secund revision).

72

the’ maintenance of heat balance oaf the body inorder to prevent discomfort and injury to healthof the occupants.

4.0.2 The following govern designconsiderations:

a)b)

cl

4

Supply of fresh air for respiration,

Removal of combustion products or othercontaminants and to prevent vitiation bybody odours,

Recommended schedule of values of airchanges for various occupancies, and

The limits of comfort and heat tolerance ofthe occupants.

4.1 Methods of Ventilation - General ventilat’oninvolves providing a building with relatively Ila gequantities of outside air in order to improvegeneral environment of building. This may beachieved in one of the following ways:

a) Natural supply and natural exhaust of air,

b) Natural supply and mechanical exhaust ofair,

c) Mechanical supply and natural exhaust ofair, and

d) Mechanical supply and mechanical exhaustof air.

4.2 Mechanical Ventilation - Reference shouldbe made to IS : 3103-1975* and IS : 3362-19777which cover methods of mechanical ventilation.

SECTION 14C AIR-CONDITIONING ANDHEATING

5. ASPECTS OF AIR-CONDITIONING ANDHEATING SERVICES

5.0 General

5.0.1 Where desired temperatures andhumidities cannot be obtainted by ventilation, air-conditioning is resorted to. In the case ofbuildings to be air-conditioned, provisions for,electrical requirements for the system shall bemade at the planning stage itself.


5 . 1 . 1 The design of the system and its\associated controls should take into account thefollowing:

a) The nature of the application,

b) The type of construction,

c) External and internal load patterns,

d) Desired space conditions,

*Code of practice for industrial ventilation firs/ revision).tCode of practice for natural ventilation of residential

buildings lfirsr revision).


e)f)

g)h)

Permissible control limits,

Control methods for minimizing use ofprimary energy,

Opportunities for heat recovery, and

Economic factors (including probable futurecost and availability of power).

51.2 The operation of the system in thefollowing circumstances should be consideredwhen assessing the complete design:

a) In summer,

b) In winter,

c) In intermediate seasons.

d) At night.

e) At weekends,

f) Under frost conditions, where applicable,

g) If electricity supply failure occurs and whenthe supply is restored, and

h) If extended low voltage conditions persist.

5.1.3 Consideration should be given to changesin building load and the system designed so thatmaximum operatianal efficiency_ is maintainedunder part, load conditions. Similarly, the totalsys tem should be separa ted in to smal le rincrements having similar load requirements sothat each area can be separately controlled tomaintain optimum operating conditions.

5.2 Electrical Requirements

5.2.1 Conduits - Where conduits are used forcarrying insulated electrical conductors and,whensuch conduits pass from a non-air-condmonedarea into an air-conditioned area or into a fanchamber of duct, a junction box shall be installedor other means shall be adopted to break thecontinuity of such conduit at the point of entry, orjust outside, and the conduit should be sealedround the conductors to prevent air being carriedfrom one area into the other through the conduitand thereby giving rise not only to leakage andinefficiency but also to the risk of condensation ofmoisture inside the conduits. The same methodapplies equally to other types of wiring, like woodsheathing or ducts which allow air to passthrough around the conductors

5.2.2 In case of air-conditioning plants wherere-heating is used, a safety device shall bei n c o r p o r a t e d i n t h e instal~lation to cut offautomatically the source of heating, such as steamor electricity by means of a theremostat or someother device, as soon as the temperature of theroom reaches a predetermined high level notexceeding 44”C, unless a higher temperature isrequired for an industrial process carried on in theair-conditioned enclosure.

5.2.3 In case of air-conditioning plants whereheating by means of an electric heater designed tooperate in an air current is used, a safety device


shall be incorporated in the instailation to cut offthe supply of electricity to the heating devicewhenever there is failure of the air current inwhich the heater is required to operate. Seriousharm to the plant and sometimes fires may becaused by negligence in this respect.

The surface temperature of all electric heatersused in an air-conditioned . ..plant should belimited, preferably to 400°C and in any case itshall not exceed 538OC, when measured in stillair.

5.2.4 Air-conditioning and ventilatingsystems circulating air to,more tnan one floor ortire area shall be provided with dampers designedto close automatically in case of fire and therebyprevent spread of fire or smoke. Such system shallalso be provided with automatic controls to stopfans in case of fire, unless arranged to removesmoke from a fire, in which case these shall bedesigned to remain in operation.

5.2.5 Air-cdnditioning system serving largeplaces of assembly (over I 000 persons), largedepartmental stores or hotels with over 100 roomsin a single block shall be provided with effectivemeans for preventing circulation of smokethrough the system in the case of a fire in airfilters or from other sources drawn into thesystem even though there is insufficient heat toactuate heat sensitive devices controlling fans ordampers. Such means shall consist of suitablephoto-electric or other effective smoke sensititvecontrols, or may be manually operated controls.

SECTION 14D LIFTS AND ESCALATORS

6. ELECTRICAL ASPECTS OF LIFTSAND ESCALATOR SERVICES

6.0 General

6.0.1 For the information of the electricalengineer, the lift/escalator manufacturer shouldadvise the architect/engineer of the building of hiselectrical requirements. This should be availableearly in the planning stage to ensure properelectrical provisions to be made for the service.

6.0.2 The following aspects shall be taken intoaccount to decide the electrical requirements forlifts:

a) N u m b e r o f lifts, size capacity andposition.

b) Nu’mber of floors served by the lift.

c) Height between floor levels,

d) Provisions for machineroom,

e) Provisions for ventilation and lighting,

f) Electric supply required,

g) Details of wiring and apparatus required,

h) Quantity/quality of service;

73

j) Occupant load factors,

k) Car speed,

m) Control system, and

n) Operation and maintenance.

6.1 Design and Operation- Reference is drawnto IS : 1860-1980* and IS : 4666-1980t

6.2 Electrical Installation Requirements

6.2.1 General - The requirements for mainswitches and wiring with reference to relevantregulations are given in IS : 4666-19807. The liftmaker should specify, on a schedule, particularsof full load current, starting current, maximumpermissible voltage drop, size of switches andother details to suit requirements. For multiplelifts a diversity factor may be used to determinethe cable size and should be stated by the liftmanufacturer.

It is important that the switches at the intakeand in the machine room which are provided bythe electrical contractor are of correct size, so thatcorrectLy rated fuses can be fitted. No form of‘ N O ’ VCJLT’ trip relay should be includedanywhere in the power supply of the lift.

The lift, maker should provide overcurrentprotection for power and controi circuits, eitheron the controller or by a,circuit-breaker, but thefollowing are not included in the contract.

4

b)

4

Pmver Supp(v Mums - The lift sub-circuitfrom the intake room should be separatefrom other building service.

Each lift should be capable of being isolatedfrom the mains supply, This means ofisolation should be lockable.

For banks of interconnected lifts, a separatesub-circuit is required for the commonsupervisory system, in order that any carmay be shut down without isolating thesupervisory control of the remainder.

Lightiqg- Machine rooms and all otherrooms containing lift equipment should beprovided with adequate illumination andwith a switch fixed adjacent to.the entrance.At least one socket outlet, suitable for lampsor tools, should be provided in each room.

The supply to the car light should be from aseparate circuit. and controlled by a switch in themachine room. For multiple lifts with a commonmachine room a separate supply should beprovided for each car. The car lighting supplyshould be independent of the power supply mains.

Pits should be provided with a light, the switch

*Code of practice for instal lat ion, operat ion andmaintenance of electric passenger and goods lifts (secondrwision).

TSpecification for electric passenger and goods lifts (/S-.$Irevision).

74

for which should be in the lift well, and accessiblefrom the lower terminal floo’r entrance.

When the alarm system is connected to atransformer or trickle-charger, the supply shouldbe taken from the machine room lighting.

6.2.2 Electrical Wiring and Apparatus

6.2 .2 .1 All electrical’ supply l ines andapparatus in connection with the lift installationshall be so constructed and shall be so installed,protected, worked and maintained that there maybe no danger to persons therefrom.

6.2.2.2 All metal casings or metallic coveringscontaining or protecting any electric supply linesof apparatus shall be efficiently earthed.

6.2.2.3 No bare conductor shall be used in anylift car as may cause danger to persons.

6.2.2.4 All cables and other wiring inconnection with the lift installation shall be ofsuitable grade for the voltage at which these areintended to be worked and if metallic covering isused it shall be efficiently earthed.

6.2.2.5 Suitable caution notice shall be affixednear every motor or other apparatus operating ata voltage exceeding 250 volts.

6.2.2.6 Circuits which supply current to themotor shall not be included in any twin ormulticore trailing cable used in connection withthe control and safety devices.

6.2.2.7 A trailing cable which incorporatesconductors for’ the control circuits shall bes e p a r a t e a n d d i s t i n c t f r o m t h a t w h i c hincorporates lighting and signalling circuits in thecase of buildings less than 30 metres in height. tnthe case of building more than 30 metres in heightor where high speed lifts (I .52 m/s or more) areemployed, use of single travelling cable forlighting and control circuits is permitted. Allconductors should be insulated for the maximumvoltage found in the cable.

6.2.2.8 Emergency signal or telephone - It isrecommended that lift car be proylded either withan emergency signal that is operattve from the liftcar and audible outside the lift well or with atelephone.

When an alarm bell is to be provided, each caris fitted with. an alarm push which is wired to aterminal box in the lift well at the ground floor bythe lift maker. This alarm bell, to be supplied bythe lift maker (with indicator for more than onelift), should be fixed in an agreed position andwired to the lift well. The supply may be from abattery (or transformer) fixed in the machineroom or, when available, from the building firealarm supply.

‘When a telephone is to be provided in the liftcar, the lift maker should fit the cabinet in the carand provide wiring from the car to a terminal boxadjacent to the lift well.

NATIONAL ELECTRICAL CuDE

6 . 2 . 2 . 9 E a r t h i n g - The terminal for theearthing of the frame of the motor, the windingmachine, the frame of the control panel, the casesand covers of the tappet switch and similarelectric appliances which normally carry the maincurrent shall be at least equivalent to a 10 mmdiameter bolt, stud or screw. The cross-sectionalarea of copper earthing conductor shall be nots’maller than those specified in 5.2.2 of Part 1 /Set12 of the Code.

The terminal for the earthing of the metalliccases and covers of doors interlocks, doorcontacts, call and control buttons, stop buttons,car switches, limit switches, junction boxes andsimilar electrical fittings which normally carryonly the control current shall be. at leastequivalent to a 5 mm brass screw, such terminalbeing specially provided for this purpose.

The earthing conductor shall be secured toearthing terminal in accordance wi th therecommendations made in IS : 3043-1966* andalso in conformity with the provisions of IndianElectricity Rules.

Where screwed conduit screws into electricfittings carrying control current and making thecase and cover electrically continuous with theconduit, the earthing of the conduit may beconsidered to earth the fitting. Where flexible.conduit is, used for leading into_ a fitting, thefitting and such length of flexible conduit shall beeffectively earthed.

One side of the secondary winding of belltransformers and their cases shall be earthed.

6.3 Additional Requirements for Escalators

6.3.1 Connection Between Driving Machineand Main Drive Shqft - The driving machineshall be connected to the main drive shaft bytoothed gearing, a coupling, or a chain.

6.3.2 Driving Motor- An electric motor shallnot drive more than one escalator.

6.3.3 Brake - Each escalator shall be providedwith an electrically released, mechanically appliedbrake capable of stopping the up or downtravelling escalator with any load up to ratedload. This brake shall be located either. on thedriving machine or on the main drive shaft.

Where a chain is used to connect the drivingmachine to the main drive shaft, a brake shall beprovided on this shaft. It is not required that thisbrake be of the electrically released type if anelectrically released brake is provided .on thedriving machine.

6.3.4 No bare conductor shall be used in anyescalator as may cause danger to persons.

6.3.5 Electrical conductors shall be encased inrigid conduits. e l ec t r i ca l tubings or wirewayswhich shall be securely fastened to the supportingstructure.



6.3.6 All electrical supply. lines and apparatusin the ezcalator shall be of suitable constructionand shall be so installed, protected, worked andmaintained that there is no danger to personsfrom them.

All metal casings or metall ic coverings,containing or protecting any electric supply lineor apparatus shall be efficiently connected withearth.

6.3.7 Disconnect SLititch - An enclosed, fusedswitch or a circuit-breaker shall be mstalled andshall be connected into the power supply line tothe driving machine motor. Disconnectingswitches or circuit-breakers shall be of themanually closed multi-pole type. The switch shallbe so placed that it is close to and visible from theescalator machine to which the supply iscontrdlled.

With dc power supplies the main disconnectingswitch and any circuit-breaker shall be soarranged and connected that the circuit -of brakemagnet coil is opened at the same time that themain circuit is opened.

6.3.8 Enclosure qf Electrical Parts -- A l lelectric safety switches and controllers shall beenclosed to protect against accidental contact.

6.3.9 Caution Notice - Suitable ‘CAUTION’notice shall be affixed near every motor or otherapparatus operating at a voltage exceeding 250volts.

6 .3 .10 Jnsulation - The electrical parts ofstarting and stopping devices, other operating andsimilar devices, controllers and similar other partsshall be efficiently insulated and the insulationshall be capable of withstanding for a period ofone minute the continuous application of a ac testvoltage equal to ten times the voltage at whichthese electrical parts are energised, subject to amaximum voltage of 2 000 V when the testvoltage is applied between contacts or similarparts in the open position, and between suchcontacts and earthed parts.

SECTION 14E AUDIO SYSTEMS

7 . E L E C T R I C A L A S P E C T S O F A U D I OSYSTEM SERVICES

7.0 General

7.0.1 This Section covers essential installationdesign -aspects of electrical audio systems forindoor and outdoor use both for temporary andpermanent installations.

7.0.2 This applies to sound distribution systemsand public address systems but does not coverinstallations in conference halls where bothmicrophones and loudspeakers are distributedamongst the audience.

7.0.3 Specific requirements if any, forindividual occupancies are covered in individualSections of the Code.

75

7.0.4 For guidance on selection of equipmentand their installation and maintenance, referenceshall be made to IS : 1881-196t* and IS : 1882-19611.

7.1 Exchange of Information

7.1.1 The initial and ultimate requirements ofthe installat ions should be ascertained asaccurately as possible by prior consultations.Plans shall show:

a) details of the installation proposed,

b) the accommodation and location of thecentral amplifier equipment, and

c) the ducts are overhead lines required forwiring.

7.2 Design Requirements

7.2 .0 The ou tpu t f rom the microphone ,gramophone, tape-recorder or radio receiver orfrom a sound film is amplified and presentedthrough a system of loudspeakers installed atchosen locations. The design of this installationshall ,be such that, depending on the nature ofoccupancy, the quality of reproduction is asdesired. Reference is drawn to 5.2 of IS : 1881-1961* and IS : 1882-19617 on the qual i ty ofreproduction suitable for different purposes, andthe acoustic power requirements therein. Thechoice of equipment such as these for inputsignals, ampl i fy ing equipment / sys tem andl o u d s p e a k e r s s h a l l b e g o v e r n e d b y t h econsiderations enumerated in IS : 1881-1961* andIS : 1882-1961 t.

7.2.1 Wiring for Audio System

7.2.1‘0 All equ ipment sha l l be secure lyinstalled in rooms gatirded against unauthorizedaccess. -Precautions shall be taken ‘to keep dustaway.

7.2.1.1‘ All present controls should bemounted behind cover plates and designed foradjustment only with the help of tools. Allcontrols shall be mechanically and electricallynoiseless.

7.2.1.2 The positioning of equipment shall besuch that the lengths of the interconnecting cable’sis kept to the minimum.

7.2.13 In case the number of the equipment islarge, they shall be mounted on racks of suitabledimensions of metal or wood, in such a mannerthat the controls are within easy reach. The patchcords shall be neatly ,arranged.

7.2.1.4 In determining the positioning of themicrophones and loudspeakers in the installation,

*Code of practice for the’ installation of indoor amplifyingand sound distribution syskems.

tCode of practice for outdoor installation of public addresssystems.

76

advice of an acoustical expert shall be sought forbest accuracy and reproducibility.

7.2.1.5 For outdoor installations, the line-matching transformers shall be mounted inweather-proof junction boxes.

7.2.1.6 In large open grounds such as anoutdoor stadium, care shall be taken to ensurethat the .sound heard from different loudspeakersdo not have any noticeable time lag.

7.2.1.7 The plugs and sockets used ine l e c t r i c a l a u d i o s y s t e m s shall n o t b einterchangeable with those meant for powercurrents.

7.2.1.8 Microphone and gramophone cablesshall preferably use twisted pairs of conductorswith sufficient insulation screened continuouslywith a close mesh of tinned-copper braid. Thecopper braiding should be sheathed with aninsulating covering. These shall be isolated frompower, loudspeaker and telephone cables. Jointsin the cables shall be avoided. Microphone cablesshall be laid without sharp bends. Indoor cablescan be laid on the floor along the walls or underthe carpet. When laid in the open, they shall beeither buried in the ground at a depth not lessthan 20 cm, or inside an iron-pipe at that depth if

heavy mechanical movement is expected above.This may also. be laid overhead at a height not lessthan 3.5 m, clipped securely to a bearer wire. Anywiring required to be run along corridors oroutside walls below 1.8 m’shall be protected by aconduit.

7.2.1.9 The loudspeaker cables shall be sochosen that the line losses do not exceed thevalues given. in Table I of IS : 1882-1961*

7.2.2 PoMjer Supplies

7.2 .2 .1 The equipment should normallyoperate from 240 V. single phase 50 Hz ac mainssupply. A voltage regulating device shall beprovided if the regulation is poorer than * 5percent. In the absence of ac mains supply thesystem shall be suitable for operating from astorage battery.

7.2.2.2 The supply mains shall be controlledby a switch-fuse of adequate capacity.

7.2.3 Earrhing - Proper e a r t h i n g o f theequipment shall be made in ar:?rdance with goodpractice.

7.3 Inspection and Testing - The completedinstallation shall be inspected and tested by theengineer to ensure that the work has been carriedout in the manner specified.

7.4 Miscellaneous Provisions - Where necessary,that is in installations where the breakdown of thesound distribution systems should be restoredinstantaneously or within a limited time, thestand-by equipment shall be readily available.

*Code of practice for outdoor installation of public addresssystems.


.,

SECTION 14F FIRE ALARM SYSTEMS

8. ELECTRICAL A S P E C T S O F FIREALARM SYSTEMS

8.0 General

8.0.1 This Section is intended to cover theelectrical aspects of the installation of firealarm/protection systems in buildings.

8.0.2 This Section is applicable in genera1 to alltypes of occupancies, while specific requirementsif any or individual situations are covered in therespective sections of the Code.

8.0.3 For total requirements for fire protectionof buildings, including non-electrical aspects suchas choice and disposition of fire-fightingequipment, depending on the nature of occupancyinstallation and maintenance aspects, etc,reference shall be made to Part 4 of SP : 7-1983*and the relevant Indian Standards.

8.1 Fire Detectors

8.1.1 The following types of fire detectors areavailable for installation in buildings:

a) Heat detectors (IS : 217519771):

i) ‘Point’ or ‘spot’ type detector

ii) Line type detector.NOTF ~~~ These may be of fixed temperature detector

or rate of rise detector.

b) Smoke detectors:

i) Optical detectors.

ii) loniration chamber detector.

iii) Chemically sensitive detector.

c) Flame detectors.

8.1.2 For guidance on their choice and siting inthe installation, see Appendix B, Part 4 ofSP : 7-1983*8.2 Wiring for Fire Alarm Systems

8.2.1 The equipment and wiring of the firealarm system shall be independent of any otherequipment or wiring, and shall be spaced at least5 cm away from each other and other wiring. Thewiring of the fire alarm systems shall be inmetallic conduits. The wiring shall be kept awayfrom lift shafts. stair cases and other flue-likeopening.

8.2.2 Alarm sounders shall be of the same kindin a particular installation.

8.2.3 For large or intricate premises. it isnecessary that the origin of a call be indicated.For this, the premises shall be divided intosections’Tones. All call points in a section shall beconnected to the same indicator. The various

*National Building Code.tHeat WISIIIV~ lire-dctcctors for- UK I” autonx~l~ fire alarm

systems.

PART I GKNERAI. AND COMMON ASPECTS

drops or lamp indicators shall be groupedtogether on the main indicator board or controlpanel. When the premises are extensive, a numberof main indicator boards may be used coveringdifferent sectors. These shall be supplemented bysector indicators for the various sectors at acentral control point.

8.2.4 At the control point the main indicatorboard or the Tone and section indicating boardsa n d a l l c o m m o n control appa ra tus andsupervisory equipment shall be located. For everyinstallation a control point shall be provided,where it can be under constant observation. Themain control centre shall be located on theground floor and should be segregated from therest of the building by fire-break wall.

8.2.5 No section shall have more than 200 fire-detectors connected together.

8.2.6 The origin of the calls may be indicatedby the use of lamp indicators. Each indicator shallinclude:

a)

b)

two lamps connected in parallel associatedwith each indication, so arranged thatfailure of either of the lamps -is readilyapparent, or

one lamp glowing during normal operationof the system for each section and the alarmindicated by the extinguishing of the lampfor the section where the call originates.Alarms should not sound on the failure ofthe indicator.

8.2.7 The arrangement of the circuits and theelectrical connections shall be such that a call orfault in any circuit does not prevent the receipt ofcalls on any other circuit.

8.2.8 The indicating device associated with thevarious call points and sections shall be groupedtogether on the main indicator board. If necessaryremote indicating panel, with audible alarms inthe night quarters of the caretaker of the buildingshould be provided.

8.2.9 The silencing switches/push buttons intheir off position shall give an indication of thisfact on the main control panel. Operation ofsilencing switches shall not prevent sounding ofalarm from any other zone simultaneously, orcancel the other indications of the alarm or fault.

8.2.10 For fire alarm systems, cables of thefollowing types shall be used:

a) Mineral insulated aluminium sheathedcables;

b) PV.C insulated cables,

c) Rubber insulated braided cables,d) PVC or rubber insulated armoured cables,

and

e) Hard metal sheathed cables.The laying of the cables shall be done in

accordance with Part I Set I of the Code.

77

8.2.11 The source of supply for the alarmsystem shall be a secondary battery continuouslytrickle/float charged from ac mains, with facilitiesfor automatic recharging in 8 hours sufficiently tosupply the maximum alarm load at an adequatevoltage for at least 2 hours. The capacity ofbattery shall ‘be such that it is capable ofmaintaining the maximum alarm load on thesystem at an adequate voltage for at least I hourplus the standing load or losses for at least 48hours. Suitable overload protective devices shallbe provided to prevent discharging of the batteriesthrough the charging equipment.

8.3 Fire Fighting Equipment

8.3.0 The choice of fire fighting equipment andtheir installation details shall be governed by therequirements specified in Part IV of SP : 7-1983*

8.3.1 Requirements ,for Electrical Drives ,forPumps in H_vdrant and Sprinkler S,wems

8.3.1.1 Full details of the electric supply shallbe furnished together with details of generatorplant to the appropriate authorities.

8.3.1.2 Sufficient power shall be madeavailable for the purpose and the power sourceshall be entirely independent of all otherequipment in the premises and shall not beinterrupted at any time by the main switchcontrolling supply to the premises. An indicatorlamp shall continuously glow in a prominentposition to indicate this, in the substation and inthe fire-pump room.

8.3.1.3 Pumping sets shall be direct coupledtype, arid shall work satisfactorily at varying load.

8.3.1.4 All motors and electrical equipmentshall be continuously rated, drip-proof with airinlets and outlets protected with meshed wirepanels where required motors shall have a suitablefixed warming resistance to maintain them in drycondition.

8.3.1.5 1 he starting equipment of the set shallincorporate an immeter and clearly marked toshow full load current. They shall not incorporateno-volt trips.

8.3.1.6 The electric circuit for fire fightingsystem shall be provided at its origin with asuitable switch for isolation, but overload and no-volt protection shall not be provided in theswitch.

SECTION 14G MISCELLANEOCJS SERVICES

9. ELECTRICAL CALL BELL SER%‘lCES

9.0 General9.0.1 Guidance on installation of electric bells

and call systems are covered in IS : 8884-1978t.

*National Building Code,+Code of practice for the installation of electric bells and

call systems.

78

9.0.2 On the basis of information collected onthe extent of installation of electric bells andbuzzers, or indicator call system in the building,the following, aspects shall be ascertained incollaboration with the parties concerned:

a) Accommodation required for controlapparatus, locatIon and distribution points;and

b) Details of chases, ducts and condliitsrequired for wiiing.

9.1 Equipment and Materials9.1.1 If wooden bases are used for bells and

buzzers, the component parts shall be rigidly heldtogether independently of the base, so that theyare unaffected by any warping.

9.1.2 Bells and buzzers which have a make orbreak contact shall be provided with means ofadjustir.g the contact gap and pressure and meansfor locking the arrangement.

9.1.3 Equipment for outdoor use shall besuitably protected against the environmentalconditions.

9.1.4 Bell push switches shall be of robustconstruction. Terminals shall be of adequate sizeand should be so arranged that the loosening of aterminal screw does not disturb the contactassembly. Any flexible’chordslattached to themshould be covered with hard wearing braid.

9.1.4.1 Pela sY

mayfollowing sltua Ions:

be requ i red fo r the

a) Where mains operated device is to becontrolled by a circuit operating at a voltagenot exceeding 24 V,

b) For repeating a call indication at a distantpoint or points, and

c) For maintaining a call indication until anindication is reset.

9.1.5 The indications shall be one of thefollowing types:

a) L a m p t!‘pe - where sound of bell isundesirable; for example in hospitals or innoisy locations such as forges, mills, etc.

b) Flag t.l’pe ~~ where positive indication isrequired which remain in position untilrestored.

c) Pendulum type - for small installationshaving up to 20 call points.

9.2 Choice of Call-Bell System-The followingguidelines are recommended:

a) Simple Call Bell S~~stcrn --- For dwellingsand small offices (see Fig. 1).

b) Multiple Call Be/l S,!stem ~~ Hotels, hospi-tals or similar large buildings where call,points are numerous (see Fig. 2).

C) Time Bell Sjtstem - Factories, schools.

NATIONAL ELECTPICAL CODE

RESET KNO8

L

SUPPLY

F I G. I SI M P L E E L E C T R I C C ALL B ELL S Y S T E M

BELL PUSHSWllcHES

INDIC ATOR

/llooloRCENTRAL SWlTCbtUOOY WITN

FIG..~ MULTIPLE C ALL B ELL S Y S T E M


9.3 Power Supply - The system may be operatedat the normal mains voltage. though it ispreferable for the control circuit to be operated ata\ voltage not exceeding 24 V

9.4 Wiring- The wiring shall be done in.accordance with Part l/Set I I of the Code.10. CLOCK SYSTEMS


10.1.1 Reference’is drawn to 5.1 of IS : 8969-1978*. A schematic is shown in Fig. 3.

10.1.2 The enclosure of the clocks shall have noopenings giving access to live parts or functionalinsulated parts or functional insulation other thanthe openings necessary for the use and working ofthe clocks. Where such openings are necessary,sufficient protection against accidental contactwith live parts shall be provided.

10.1.3 To ensure necessary continuity ofsupply. direct connection of the system to thesupply mains is not recommended. Batteriesshould always be provided. The capacity of thebattery shall be at least sufficient to supply theinstallation for 48 hours, not less than IO Ah.

10.1.3.1 Where the supply is ac, single batteryon ‘constant trickle charge is recommended, meansbeing provided for charging at a higher rate whennecessary.

10.1.3.2 Where the supply is dc, two batteriesshould be provided with changeover switch.

10.2 Location of Clocks

10.2.1 The master clock shall be placed in aroom not smaller than 2.4 X 3.6 m.

10.2.2 The location and size of slave clocksm a y f r e q u e n t l y d e p e n d u p o n a e s t h e t i crequirements. but from the point of view ofreadability, a ration of 0.30 m diameter of dial toevery 2.7 m of height is acceptable. The followingis adequate:

Dia qf Clock Height ,from Floor

0.30 m 2.70 m0.45 m 3.30 m0.60 m 4.50 m

10.3 Wiring- The wiring shall be done inaccordance with Part I /Set I I of the CodeSpecial conductor shall be provided. or theconduit may be colour coded for distinction fromother circuits.

*Code of practice for the installation and maintenance ofimpulse and electronic master and slave clock systems.

79

A S T E R C L O C K

R E L A Y

A V E C L O C K S

T R I C K L E C H A R G E

pk \ t\

a c S U P P L Y

F I G. 3 IMPULSE M ASTER CLO<.K SY S T E M

ti:ATIONAL ELECTRICAL CODE

SECTION 15 LIGHTNING PROTECTION

O.FOREWORD

0.1 For the purposes of the National ElectricalCode, the fixed installation for lightningprotection is considered part of the electricalinstallation design and constitutes a major areawhere the installation design enginegr has toensure proper coordination.

0.i This Section covers the essential design andconstruction details of lightning protectivesystems. It is, however, intended to serve qnly as aguide of general nature on the principles andpractices in the protection of structures againstlightning, and account has to be taken of severalother local conditions such as variati’ons in thearchitecture, t o p o g r a p h y o f t h e r e g i o n ,atmospheric conditions, etc.

0.3 Lightning p r o t e c t i o n o f industrialinstallations which are categorized as hazardous,require s p e c i a l consideratians. These a resummarised in Part 7 of the Code.

0.4 The contents of this Section are based onIS : 2309-1969 ‘Code of pract ice for theprotection of buildings and allied -structuresagainst lightning’.

1. SCOPE

1.1 This Section of the Code covers guidelines onthe basic electrical aspects of lightning protectivesys tems for bu i ld ings and the e lec t r i ca linstallation forming part of the system.

1.2 Additional guidelines if any, for specificoccupancies from the point of lightning protectionare covered in respective sections of the Code.

2. TERMINOLOGY

2.0 For the purposes of this section, the followingdefinitions shall apply.

2.1 Air Termination (Lightning Conductor) orAir Termination Network --Those parts of alightning protective system that are intended tocollect the l ightning discharges from theatmosphere.

2.2 Bonds Electrical connection between thelightning protective system and other metal work.and between various portions of the latter.

2.3 Down Conductors Conductors whichconnect the air terminations with the earthterminations.

2.4 Earth Terminations or Earth TerminationsNetwork ~~ Those part of the lightning protectivesystem which are intended lo distribute thelightning discharges into the general mass of the


earth. Ali parts below the testing point in a downconductor are included in this term.

2.5 Earth Electrodes -- A metal plate. pipe orother conductor or an array of conductorselectrically connected to the general mass of theearth; these include those portions of the earthterminations that make direct electrical contactwith the earth.

2.6 Fasteners Devices used to fasten theconductors to the structures.

2.7 Isoceraunic Level - It is the number of daysin a year on which the thunder is heard in theparticular region averaged over, a number ofyears.

2.8 Joints - The mechanical and electricaljunctions between two or more portions of thelightning protective system or other metal bbndedto the system or both.

2.9 Lightning Protective System - The wholesystem of interconnected’ conductors used toprotect a structure from the effects of lightning.

2.10 Metal-Clad Building -~ A building with sidesmtide of or covered with sheet metal.

2.11 Metal-Roofed Building -- A building withroof made of or covered with sheet metal.

2.12 Side Flash -- A spark occurring betweennearby metallic objects or between such objectsand the lightning protective system or to earth.

2.13 Testing Points ~~ Joints in down conductorsor in bonds or in earth conductors connectingearth electrodes, so designed and situated as toenable resistance measurements to be made.

2.14 Zone of Protection The space withinwhich the lightning cotiductor is expected toprovide protection against a direct lightningstroke.

3. EXCHANGE OF INFORMATION

311 The architect should exchange informationwith the engineer concerned when the buildingplans are hejng prepared. The primary object ofsuch an exchange is to obtain informationregarding the architectural features of thestructure so that due provision may be made toretain the aesthetic features of the building whileplanning the location of the lightning conductorsand down conductors of the’ lightning protectivesystem. Information may also be obtained at anearly stage regarding other services, such aselectrical installation. gas and water pipes as wellas climatic and soil conditions

81

3.2 Scale drawings showing plans and elevationsof the structure shduld be obtained, and thenature. size and position of. all the metalcomponent parts of the lightning protectivesystem should be indicated on them. In addition,a ground plan should show all the tall objects,such as, buildings, masts, transmission lowers, talltrees, etc. within the zone of protection.

4. C H A R A C T E R I S T I C S O F L I G H T N I N GDISCHARGES

4.1 The principal effects of lightning discharge tostructure are electrical, thermal and mechanical.These effects are determined by the current whichis discharged into the structure. These currents areunidirectional and may vary in amplitude from a _few hundred amperes to about 200 kA. Thecurrent in any lightning discharge rises steeply toits crest value in a few microseconds and decaysto zero in a few milliseconds. Many lightningdischarges consist of a single stroke but someothers involve a sequence of strokes which followthe same path and which discharge separatecurrents of amplitude and duration as mentionedabove. A complete lightning discharge may thuslast a second or even longer.

4.2 Electrical Effects -- The principal eletricaleffects of a lightning discharge are two-fold.

4.2.1 The lightning current which is dischargedto earth through the resistance of the lightningconductor and earth electrode provided for alightning protective system. produces a resistivevoltage drop whtch momentarily raises thepotential of the protective system with respect lothe absolute earth potential to a very high value.The lightning current also produces, around theearth electrode. a high voltage gradient whichmay be dangerous to persons and animals.

4.2.2 The lightning current rises steeply lo itscrest value (approximately at the rate. of IOkA, ps) and as a first approximation may beregarded as equivalent to high f requencydischarge. A vertical conductor of the dimensionsgenerally used in a lightning protective system hasan inductance of about 16 X IO-‘H/ 100 m. Therate of rise of current in conjunction with theinductance of the discharge path produces aninductive voltage drop which would be added.with due regard to the time relationship, to theresistive (ohmic) voltage drop across the earthingsystem.

4.3 Thermal Effects The thermal effect oflightning discharge results in rise in temperatureof the conductor throligh which the lightningcurrent is discharged to the earth. Although theamplitude of the lightning current may be verbhigh. its duration IS so short that the thermal effecton a lightning protective system is usuallynegligible. This ignores the fusing or weldingeffects which occur locally consequent upon therupture of a conductor which was previousiydamaged or was of inadequate cross-sectional

82

area. .In practice the cross-sectional area of alightning conductor is determined primarily bymechanical considerations.

4.4 Me&a&al Effects - When a high ekctriccurrent is discharged through parallel conductorswhich are in close proximity to each other, theseare subjected to large mechanical forces Thelightning conductors should, therefore; ‘beprovided with adequate mechanical fixings.

4.4.1 A different mechanical effect exerted by alightning discharge is due lo the fact that the airchannel, that is, the space between the thundercloud and the lightning conductor, along whichthe discharge is propagated, is suddenly raised loa very high temperature. This results in a.strongair pressure wave which is responsible fordamages to buildings and other structures. It isnot possible to provide protection against such .aneffect.

5. DETERMINATION OF THE NEED FORPROTECTION

5.1 Risk Index - .In determining how fai to go inproviding lightning protection for specific cases orwhether or not it is needed at all, it is necessary totake into account the following factors:

a) Usage of structure.

b) Type of construction.

c) Contents or consequential effects,

d) Degree of isolation,

e) Type of terrain,

f-l Height of structure, and

g) Lightning prevalance.

5.2 With many structures, however, there will bedoubt as to the need for lightning protectibn.little

The

a)

examples of such structures are:

those in or near which large number ofpeople congregate,

b)

c)

d)

e)

r)

those concerned with ‘the maintenance ofessential public services,

those in areas where lightning strokes areprevalent.very tall or isolated structures,

structures of historic or cultural importance,and

structures containing explosives and highlyflammable materials.

5.1.1 Appendix C of IS : 2309-1969 gives thedetails of various factors that affect the risk of thestructure being struck and the consequentialeffects of a stroke. Certain values called ‘indexfigures’, have been assigned lo these factors whichhelp in arriving at an overall ‘risk index’ to seyeas an aid to judging whether lightning protectlonis necessary or not.


6. ZONE OF PROTECTION

6.1 The zone of protectionconductor denotes the space

of a lightnmgwithin which a. . . . . .hghtnmg conductor provides protection against a

direct lightning stroke by diverting the stroke toitself. Examples of the protection of differenttypes and shapes of buildings along with zone ofprotection provided by their lightning protectivesystems are given in Appendix A of IS : 2309-1969.

7. MATERIALS AND DIMENSIONS

7.1 Materials - The materials of lightningconductors, down conductors, earth terminationnetwork, etc, of the protective system shall bereliably resistant to corrosion or be adequatelyprotected against corrosion. The fo l lowingmaterials are recommended:

a)

b)

c)

d)

Copper - When solid or stranded copperwire or flat copper strips are used, they shallbe o f g rade o rd ina r i l y requ i red f o rcomniercial electrical work, generallydes igna ted as be ing o f 98 pe rcen tconductivity when annealed: They shallconform to re levant Indian Standardspecifications.

Copper-clad SW/ - Where copper-clad steelis used. t he coppe r coverlng shall bepermanently and effectively welded to thesteel core. The proportion of copper andsteel shall be such that the conductance ofthe material is not less than 30 percent of theconductance of solid copper of the sametotal cross-sectional a’rea.

Gal\qnizd Steel- Where steel is used itshall be thoroug,hly p ro tec ted aga ins tcorrosion by a 71nc coat ing which wi l lsatisfactorily withstand the test specified inAppendix D of IS : 2309-1969. Copper ispreferred to galvanized iron where corrosivegaich. industrial p o l l u t i o n or saltladenatmospheric condition\ ;trc ,cncountcrcd.

.Illrt~~irlilrt~r Aluminlum ~irc :I& strips arcincreasingly linding fa\our for u\e a slightning conductor\ in \ic.\\ of the fact thataluminium has ;I conduct~\~t!~ almost doublethat of copper mahs for no\\. When used, itshall be at least 09 perccnr pul-e. (:f sufficientm e c h a n i c a l s t r e n g t h :Ind eflccti\elyprotected against corrosion.

e) A1lo.1~~ -- Where a l loys o f meta ls a reused they shall .be substantially as rchistantt o co r ros ion as coppe r unde r similarconditions.

7.2 Shapes and Sizes The recommended shapeand minimum sizes--o& conductors for USC aboveground and below ground are given in Table Iand Table 2 rc\pcctl\cly.

P A R T I CENERAI. AND C O M M O N ASPEUTS

TABLE 1 SHAPES AND MINIMUM SIZES OFCONDUCTORS FOR USE ABOVE GROUND

;:.I,

2.

::

5.

7?

(Clause 7.2)

MATERIAL AND SHAPE MINIMUM SIZE

Round copper wire orcopper-clad steel wire

Stranded copper wire

Copper stripRound galvanized iron

wireCWvanized iron stripRound aluminium wire

Aluminium strip

6 mm diameta

$0 mm.* (or 7/3.(10 m mdiameter)

20X3 mm8 mm diameter

20X3 mm9 mm diameter25 X.3.15 mm

TABLE 2 SHAPES AND MINIMUM SIZES OFCONDUCTORS FOR USE BELOW GROUND

((-louse 7.2)

2M A T E R I A L A N D S H A P E MlNlMClM SIZE

r). Round copper wire or 8 mm diametercopper-clad steel wire

2. Copper strip 32X6 mm3. Round galvanized iron IO mm diameter

wire4. Galvanized iron strip 32X6 mm

7.3 Corrosion - Where corrosion due toatmospheric, chemical, electrolytic or other causesis likely to impair any part of the lightningprotective system, suitable precautions should betaken to prevent its occurrence. The.contact ofdissimilar metals is likely to initiate and acceleratecorrosion unless the contact surfaces are keptcompletely dry and protected against the ingressof moisture.

7.3.1 Dissimilar metal contacts can exist wherea conductor is held by fixing devices or againstexternal metal surfaces. Corrosion can arise alsowhere water passing over one metal comes intocontact with another. Run-off water from copper,copper alloys and lead can attack altiminiumalloys and zinc. The metal of the lightningprotective system should be compatible with themetal ‘or metals used externally on the structureover which the system passes or with which it maymake contact.

8. DESIGN

8.0 General l.ightning protective systemsshould be installed with a view to offering leastimpedance to the passage of lightning currentbetween air-t_erminalh and earth. There shall be aticast two parts. and more if practicable. This isd:lne bv connecting the conductors to form a cagecnc!osing the building. The bas i c des ignconsiderations for lightning protective systems aregiven in 9.2 of IS : 2309-1969.

The pr inc ipal component of a l ightn ingprotective system are:

a) air terminations,

b) down conductors,

83

c) joints and bends,

d) testing points,

e) earth terminations,

f) earth electrodes, and

g) fasteners.

8.1 Air Terminations - For the purpose oflightning protection, the vertical and horizontalconductors are considered equivalent and the useof pointed air terminations or vertical finials is,therefore, not regarded as essential except whendictated by practical considerations. An airtermination may consist of a vertical conductor asfor a spire, a single horizontal and verticalconductors for the protection of bigger buildings.

8.1.1 A vertical air termina’tion need not havemore than one point and shall project at least 30cm above the object, salient point or network onwhich it is fixed,

8.1.2 Horizontal air terminations should be sointerconnected that no part of the roof is morethan 9 m away from the nearest horizontalconductor except that an additional 30 cm may beallowed for each 30 cm by which the part to beprotected is below the nearest protectiveconductor. For a flat roof, horizontal airterminations along the outer perimeter of the roofare used. For a roof of building with largerhorizontal dimensions a network of parallelhorizontal conductors should be installed asshown in IS : 2309-1969.

NOTC Salient points even if less than 9 m apart shouldeach be provided with an air termination.

8.1.3 Horizontal air terminations should becoursed along contours, such as ridges, parapetsand edges of flat roofs, and where necessary overflat surfaces in such a way as to join each airtermination to the rest and should themselvesform a closed network.

8.1.4 The layout of the network may bedesigned to suit the shape of the roof andarchitectural features of the buildings.

8.1.5 The air termination network should coverall salient points of the structure.

8.1.6 All metallic finials, chimneys. ducts. ventpipes, railings, gutters and the like. on or abovethe main surface of the roof of the structure shallbe bonded to, and form part of, the airtermination network. If portions of a structurevary considerably in height, any necessary airtermination or air termination network of thelower portions should, in addition to their ownconductors, be bonded to the down conductors ofthe taller portions.

8.1.7 All air terminals shall be effectivelysecured against overturning either by attachmentto the object to be protected or by means ofsubstantial braces and fixings. which shall bepermanently and rigidly attached to the building.

84

The method and nature of the fixings should besimple, solid and permanent, due attention beinggiven to climatic conditions and possiblecorrosion.

8.2 Down Conductors - The number andspacing of down conductors shall largely dependupon the size and shape of the building and uponaesthetic considerations. The minimum number ofdown conductors may, however, be decided onthe following considerations:

4

b)

C)

A structure having a base area not exceeding100 m* may have one down conductor onlyif the height of the air termination providessufficient protection. However, it isadvisable to have at least two down con-d.uctors except .for very small buildings.

For structures having a base area exceeding100 m*, the number of down conductorsrequired should be worked out as follows:

i) One for the first 100 m* plus one morefor every additional 300 m* or partthereof, or

ii) One for every 30 m of perimeter.

The smaller of the two shall apply.

For a structure exceeding 30 m in heightadditional consideration as given inIS : 2309-1969 shall apply.

8.2.1 Down conductors should be distributedround the outside walls of the structure. Theyshall preferably be run along the corners andother projections, due consideration being givento the location of air terminations and earthterminations. Lift shafts shall not be used forfixing down conductors.

8.2.2 It is very important that the downconductors shall follow the most direct pathpossible between the air termination and the earthtermination. avoiding sharp bends, upturns andkinks. Joints shall as far as possible be avo&d indown conductors. Adequate protection may beprovided to the conductors against machanicaldamage. Metal pipes should not be used asprotection for the conductors.

8.2.3 Metal pipes leading rainwater from theroof to the ground may be connected to the downconductors but cannot replace them. Suchconnections shall have disconnecting joints fortesting purposes.

8.2.4 Where the provision of suitable externalroutes for down conductors is impracticable orinadvisable, as in buildings of cantileverconstruction, from the first floor upwards, downconductors may be used in an air space providedby a non-metallic non-combustible internal duct.Any covered recess not smaller than 75 X I5 mmor any vertical service duct running the full heightof the building may be used for this purpose,provided it does not contain an unarmoured ornon-metal-sheathed cable.


8.2.5 Any extended metal running verticallythrough the structure should be bonded to thelightning conductor at the top and the bottomunless the clearances are in accordance withIS : 2309-1969 for tall structures.

8.26 A structure on bare rock, should beprovided with at least two down conductorsequally spaced.

8.2.7 In deciding on the routing of the downconductor, its accessibility for inspection, testingand maintenance should be taken into account.

8.3 Joints and Bonds

8.3.1 Joinrs - The lightning protective systemshall have as few joints in it as necessary. In thedown conductors below ground level these shallbe mechanically and electrically effective and shallbe so made as to exclude moisture completely.The joints may be clamped. screwed, bolted,crimped, riverted or welded. With overlappingjoints the length of the overlap should not be lessthan 20 mm for all types of conductors. Contactsurfaces should first be cleaned and then inhibitedfrom oxidation with a suitable non-corrosivecompound. Joints of dissimilar metal should besuitably protected against bimetallic action andcorrosion.

8.3.1.1 In general, joints for strips shall betinned, soldered, welded or brazed and at leastdouble-riveted. Clamped or bolted joints shallonly be used on test points or on bonds ,toexisting metal, but joints shall only be of theclamped or screwed type.

8.3.2 Bonds - External metal on or formingpart of a structure may have to discharge the fulllightning current. Therefore. the bond to thelightning protective system shall have a cross-sectional area not less than that employed for themain conductors. On the other hand, internalmetal is not so vulnerable and its associatedbonds are, at most, only likely to carry a portionof the total lightning current, apart from theirfunction of equalizing potential. These latterbonds may, therefore, be smaller in cross-sectional area than those used for the mainconductors. All the bonds should be suitablyprotected against corrosion. Bonds shall be asshort as possible.

8.4 Testing Points- Each down conductor shallbe provided with a testing point in a positionconvenient for testing but inaccessible forinterference. No connection, other than one directto an earth electrode, shall be made below atesting point. Testing points shall bephosphorbronze. gunmetal, copper or any othersuitable material.

8.5 Earth Terminations - Each down conductorshall have an independent earth termination. Itshould be capable of isolation for testingpurposes. Suitable location for the earthtermination shall be selected after testing and


assessing the specific resistivity of the soil andwith due regard to reliability of the sub-soil waterto ensure minimum soil moistness.

8.5.1 Water pipe system should not be bondedto the earth termination system. However, ifadequate. clearance between the two cannot beobtained, they may be effectively bonded and thebonds should be capable of isolation and testing.The gas pipes, however, should in no case bebonded to the earth termination system.

8.5.2 It is recommended that all earthterminations should be interconnected. Commonearthing, besides equalizing the voltage at variousearth terminations also minimizes any risk to it ofmechanical damage. The condition for limitingearthing resistance given in 11 does nobapply andin such a case no provision need be made forisolation in earth. e

8.5.3 A structure standing on bare rock shouldbe equipped with a conductor encircling and fixedto the structure at ground level and followingreasonably closely the contour of the ground. Thisconductor should be installed so as to minimizeany risk to it of mechanical damage.’ Thecondition for limiting earthing resistance given in11 does not apply and in such a case no provisionneed be made for isolation in earth terminationfor testing. Where there is a risk to persons or tovaluable equipment. expen advice should besought.

8.6 Earth Electrodes - Earth electrodes shall beconstructed and installed in accordance with PartI /Set I2 of the Code.

8.6.1 Earth electrodes shall consist of rods,strips or plates. Metal sheaths of cables shall notbe used as earth electrodes.

8.6.2 When rods or pipes are used they shouldbe driven into the ground as close as practicablebut qutside the circumference of the structure.Long lengths in sections coupled’ by screwedconnectors or socket joints can be built up wherenecessary to penetrate the substrate of lowresistivity. Where ground conditions are morefavourable for the use of shorter lengths of rods inparallel, the distance between the rods shouldpreferably be not less than twice the length of therods. The arrangement of earth electrodes aregiven in Fig. 6 of IS.: 2309-1969.

8.6.3 When strips are used, these should beburied in trenches or beneath the structure at asuitable depth, but not less than 0.5 m deep toavoid damage by building or agriculturaloperations. The strips should preferably be Laidradially in two or more directions from the pointof connection to a down conductor. But if this isnot possible they may extend in one directiononly. However, if the space restriction requires thestrips to be laid in parallel or in grid formationthe distance between two strips should not be lessthan 2 m.

8.6.4 When plate electrodes are-used they shall

85

oc ourled mto the ground so that the top edge ofthe plate is at a depth not less than 1.5 m from thesurface of the ground. If two plate electrodes areto be used in parallel the distance between the twoshall not be less than 8 m.

8.6.5 In the neighbourhood of structure wherehigh temperatures are likely to be the encounteredin the sub-soil, for example brick kilns, the earthelectrodes may have to be installed at such adistance from the structure where the ground isnot likely to be dried out.

8.7 Fasteners - Conductors shall be securelyattached to the building or other object to beprotected by fasteners which shall be-Substantialm construction. not subject to bi’eakage. and shallbe made of galvanized steel or other suitablematerial. If fasteners are made of steel, theyshould be galvanilcd to protect them againstcorrosion. If they are made of any other materialsuitable precautions shou!, be taken to avoidcorrosion. Some samples of fasteners are shownin IS : 2309-1969.

8.8 Earth Resistance - Each earth terminationshould have a resistance in ohms to earth notexceeding numerically the product of IO and thenumber of earth terminations to be provided. Thewhole qf the lightning protective system shouldhave a combined resistance to earth not exceedingIO ohms before any bonding has been effected tometal in or on the structure or to surface belowground.

9. ISOLATION AND BONDING

9.0 When a.lightning protective system is struckwith a lightning discharge. its electrical potentialwith respect to earth is raised. and unless suitableprecautions are taken. the discharge may seekalternative paths to earth by-side flashing to othermetal in the structure. Side flashing may beavoided by the following two methods :

a) Isolation. and

b) Bonding.

9.1 Isolation - Isolation requires large clearancesbetween the lightning protective system and othermetal parts in the structure. To find out theapproximate clearances. the following two factorsshould be taken into account :

a) The resistive voltage drop in the earthtermination. and

b) The inductive voltage drop in the downconductors.

9.1.1 The resistive voltage drop require> aclearance of ‘0.3 m,‘ohm of earthing resistancewhile the inductive _,voltage drop requires aclearance of I m for each I5 m of structure height.For two or more down conductors with acommon air termination this distance should bedivided by the number of down conductors. The

86

total clearance required is the sum of the twodistances and may be expressed by the followingsimple equation :

D=0.3Ri Kl5n

where

D =R=

H =n=

9.1.2

required clearance in metres,the combined earthing resistance of theearth termination in ohms,structure height in metres, andnumber of down conductors connected to acommon air termination.The above clearance may be halved if a. ^ . - .

slight risk ot occurence ot a side Hash c a n b eaccepted.

9.1.3 The drawback of isolation lies inobtaining and maintaining the necessary safeclearances and in ensuring that isolated metal hasno connection via the water pipes or otherservices with the earth. In general, isolation canbe practised only in small buildings.

9.2 Bonding - In structures which containelectrically continuous metal. for example, a roof.wall. floor or covering, this metal, suitablybonded, may be used as part of the lightningprotective system. provided the amount andarrangement of the metal render it suitable for usein accordance with 8.

9.2.1 If a structure is simply a continuous metalframe without external coverings it mrfy notrequire any air termination or down conductorsprovided it can be ensured that the conductingpath is electrically continuous and the base of thestructure is adequately earthed.

9.2.2 -A reinforced concrete structure or areinforced concrete frame structure may havesufficiently low inherent resistance to earth toprovide protection against lightning and ifconnect ions are brought out f rom thereinforcement at the highest points derringconstruction. a test may be made to varify this atthe compktion of the structure.

9.2.3 If the resistance to earth of the steel frameof a structure or the reinforcement of a reinforcedconcrete structure is found to be satisfactory, asuitable air termination’should be installed at thetop of the structure and bonded to the steel frameor to the reinforcement. Where regular inspectionis not possible. it is recommended that a corrosionresistant material be used for bonding to t%e steelor to the reinforcement and this should bebrought out for connection to the air termination.Down conductor and earth terminations will, otcourse. be required if the inherent resistance ofthe structure is fdund to be unsatisfactory whentested.

9.2.4 Where metal exists in a structure asreinforcement which cannot be bonded into acontinuous conducting network, and which is notor cannot be equipped with external earthing


connections, its presence should be disgarded. Thedanger inseparable from the presence of suchmetal can. lx mipimized by keeping it entirelyisolated from the lightning protective system.

9.2.5 Where the roof structure is wholly orpartly covered by metal, care should be taken thatsuch metal is provided with a continuousconducting path to earth.

9.2.6 In any structure. metal which is attachedto-the outer surface or projects through a wall ora roof and has insufficient clearance from thelightning protective system, and is unsuitable foruse as pa0 of it, should preferably be bonded asdirectly as possible to the lightning protectivessystem. If the metal has considerable length (forexample, cables, pipes, gutters, rain-water pipes,stair-ways, etc) and runs approximately parallel toa down conductor or bond, it should be bondedat each and but not below the test point. If themetal is in discontinuous lengths, each portionshould be bonded to the lightning protectivesystem; alternatively, where the clearance permits,the presenee of the metal may be disregarded.

9.2.7 Bonding of metal entering or leaving astructure in the form of sheathing or armouring ofcable, electric conduit, telephone, steam,compressed air or other services with earthtermination system, should be avoided. However,if they are .required to be bonded. the bond&should be done as directly as possible to the earthtermination at the point of entry or exist outsidethe structure on the supply side of the service. Thegas pipes should in no case be bonded with othermetal parts. However. water pipes may be bondedto other metal parts, if isolation and adequateclearance cannot be obtained. In this operation allthe statutory rules or regulations which may be inforce should be followed and the competentauthority should be consulted for providinglightning protection in such cases.

9.2.8 Masses of metal in a building, such asbell-frame in a t6wer. should be bonded to thenearest down conductor by the most direct routeavailable.

9.2.9 Metal clading or curtain walling having acontinuous conducting path in all directions maybe used as part of a lightning protective system.

9.2.10 In bonding adjacent metalwork to thelightning protective system careful considerationshould be given lo the possible effects suchbonding would have upon metalwork which maybe cathodically protected..10. PROTECTION OF SPECIAL

STRUCTURES10.1 For guidance on design of lightningprotection systems for special structures, referenceshall be made to IS : 2309-1969. Guidance for theappropriate authorities shall also be obtained.

11. INSPECTION AND TESTING

II.1 Inspection - All lightning protective


systems shall be exammed by a coinpetentengineer after completion, alteration orextensions, in order to verify that they are inaccordance with the recommendations of theCode. A routine inspection shall be made at leastonce a year.

11.2 Teathg

11.2.1 On completion of the installation or ofany modification, the resistance of each earthtermination or section thereof, shall. if possible,be measured and’the continuity of all conductorsand the efficiency of all bonds and joints shall beverified.

11.23 Normally annual measurement of earthresistance shall be carried out but Localcircumstances in the light of experience mayjustify increase or decrease in this interval but itshould not be less than once in two years. In thecase of structures housing explosives orflammable materials, the ‘interval shall be sixmonths.

11.23 Earth resistance shall be measured inaccordance with Part I/Set I2 of the Code.

11.2.4 The actual procedure adopted for thetest shall be recorded in detail so that future testsmay be carried out under similar conditions. Thehighest value of resistance measured shall benoted as the resistance of the soil and details ofsalting or other soil treatment, should berecorded.

11.2.5 The record shall also contain particularsof the engineer. contrzictor or owner responsiblefor ‘the installation or upkeep or both of thelightning protective system. Details bf additionsor alterations to the system, and dates of testingtogether with the test results and reports, shall becarefully recorded.

11.3 Deterioration - If the resistance to earth ofa lightning protective system or any section of itexceeds the lowest value obtained at the firstinstallation by more thah 100 percent, appropriatesteps shall be taken to ascertain the causes and toremedy defects, if any.

1.1.4 Testing Continuity and Efficacy ofConductors and Joints

11.4.1 The ohmic resistance of the lightningprotective system complete with air termination,but without the earth’ connection should bemeasured and this should be a fraction of an ohm.If it exceeds I ohm, then there shall be some faulteither electrical or mechanical, which shall beinspected and the defect rectified.

11.4,2_For this system .is best hivided intoconvement sectlons at testmg oints by suitablejoints. A continuous curre.nt oPabout IO A shallbe passed through the portion of the system undertest and the resistance verified) against its--calculated or recorded value. Suitable portableprecision testing sets for this purposes should beused.

87

SECTION 16 SAFETY IN ELECTRICAL WORK

O . F O R E W O R D

0 . 1 T h i s Sect;on i s i n t e n d e d t o c o v e rrecommendatiops on safety procedures andpractices in electrical work. It covers basicapproaches to-electrical work from the point ofview of ensuring safety which include inbuiltsafety in procedures such as permit-to-worksystem, safety insturctions and safety practices.

0.2 It is essential that safety should be preachedand practiced at all times in the installation,operation and maintenance work. The real benefitto be derived from the guidelines covered in thisSec!‘!on will be realized only when the safetyinstructions it contains are regarded as normalroutine duty and not as involving extra andlaborious operations.

03 This Section of the Code shall be read inconjunction with the following standards :

IS : 5216 Recommendat ions on safetyprocedures and practices in electrical work.

Part I 1982 GeneralPart 2 1982 Life saving techniques

IS : 2!5 I-1982 Specification for danger noticeplates

IS : 8923-1978 Warning symbol for dangerousvoltages

1. SCOPE

1.1 This Section of the Code covers guidelines onsafety procedures and practices in electrical work.

2. PERMIT-TO-WORK SYSTEM

2.1 All work on major electrical installations shallbe carried out under permit-to-work system whichis now well established. unless standinginstructions are issued by the competent authorityto follow other procedures. In extenuatingcircumstance, such as for the purpose of savinglife or tjme in the event of an emergency, it maybecome necessary to start the work without beingable to obtain the necessary permit-to-work; insuch cases, the.action taken shall be reported tothe person-in-charg: _,as soon as possible. Thepermit-to-work certlflcate from the person-in-charge of operation to the person-in-charge of themen selected to carry out any particular workensure that the portion of the installation wherethe work is to be carried out is rendered dead andsafe for working. All work shall be carried outunder the personal supervision of a competentperson. If more than one department is workingon the same apparatus, a permit-to-work shouldbe issued to the person-in-charge of eachdepartment.

N O T E- The words permit-to-work’ and ‘permit’ areBynonymous for the purpose of this Section.

aa

2.2 No work shall be commenced on live mainsunless it is specifically intended to be so done byspecially trained staff. In such cases all possibleprecautions shall be taken to ensure the safety ofthe staff engaged for such work, and also ofothers who may be directly or indirectlyconnected with the work. Such work shall only becarried out with proper equipment provided for_the purpose and, after taking necessaryprecautions. by specially trained and experiencedpersons who are aware of the danger that existswhen working on or near live mains or apparatus.

‘23 On completion of the work for which thepermit-to-work is issued, the person-in-charge ofthe maintenanqe staff should return the permitduly discharged to the issuing authority.

2.4 In all cases, the issue and return of permitsshal! bc recorded in a special register provided forthat purpose.

2.5 Thestaff of tR

ermits shall be issued not only to thee supply under takings, but also to the

staff of other departments, contractors, engineers,etc. who might be required to work adjacentto live electrical mains or apparatus.

2,6 A model form of permit-to-work certificate isgiven in IS : 5216 (Part I)-1982 ‘Recommenda-tions on safety procedures and practices inelectrical work : Part I General’.

NOTE I -~ The permit is to be prepared in duplicate by theperson-inxharge of operation on the basis of message. dulylogged, from the person-in-charge of the work.

NOTE 2 The original permit will be issued to the person-in-charge of work and the duplicate will be retained in thepermit book. For further allocation of work by the permitreceiving officer. tokens may be issued to the workersauthorizing them individually to carry out the prcscribcdwork.

NOTE 3 On completion of the work, the original shall bereturned to the issuing officer duly discharged for cancellation.

2.7 Permit books should be treated as importantrecords. All sheets in the permit books and thebooks themselves should be seriaily numbered.No page should be detached or used for any otherexcept bonafide work. If any sheet is detached, adated and initialled statement shall then and therebe recorded in the book by the person responsiblefor it.

i.8 Permit books shall be kept only by theperson-in-charge of operation who shall maintaina record of the receipts and issues made by him.

3. SAFETY INSTRUCTIONS

3.1 Safety Instructions for Working on Mainsand Apparatus up to and including 650 V

3.1.1 Work on Dead LOHI and Medium VoltageMains and Apparatus - Unless a person isauthorized to work on live imains and apparatusall mains and apparatus to be worked upon shall

N-ATIONAL ELECTRICAL CODE

be isolated from all sources of supply beforestarting the work, proved dead, earthed andshort-circuited. For earthing and short-circuiting,only recognized methods should be used.Measures shall be taken against, the inadvertentenergizing of the mains and apparatus.

3.1.2 Work on Live Mains and Apparatus -Only competent, experienced and authorizedpersons shall work on live mains and apparatus,and such persons should take all safety measuresas may be required.

Warning boards shall be attached on oradjacent to the live apparatus and at the limits ofthe zone in which work may be carried out.

Immediately before starting work, rubbergauntlets, if used, shall be thoroughly examinedto see whether they are in sound condition. Underno circumstances shall be person work withunsound gauntlets, mats, stools, platforms orother accessories and safety devices.

No live part should be within’unsafe distang ofa person working on live low at&medium voltagemains so that he does not come in contact with itunless he is properly protected.

3.1.3 Testing of Mains and Apparatus-Noperson shall apply test voltage to any mains unlesshe has received a permit-to-work and has warnedall persons working on the mains of the proposedapplication of test voltage. If any part which willthus become alive is exposed, the person-in-charge of the test shall take due precautions toensure that the exposed live portion does notconstitute danger to any person. It should also beensured before the application of test voltage, thatno other permit-to-work has been issued forworking on this mains.

3.1.4 Connecting Dead Mains to Live MainsWhen dead mains are connected to live mains, ahconnections to the live parts shall be made last,and in all cases the phase sequence should bechecked to ensure that only like phases areconnected together. Before inserting fuses or linksin a feeder or distribution pillar controlling thecable on which a fault has been cleared, eachphase shall first be connected through a testswitch fuse.

3.2 Safety Instructions for Working on Mainsand Apparatus at Voltages Above 650V

3.2.1 General - All mains and apparatus shallbe regarded as live and a source of danger andtreated accordingly, unless it is positively knownto be dead and earthed.

a) No person shall work on, test or earth mainsor apparatus unless covered by a permit-to-work and after proving the mains dead,except for the purpose of connecting thetesting apparatus, etc. which is speciallydesigned for connecting to the live parts,

b) The operations of proving dead, earthingand short-circuiting of any mains shall be

PAW t GENERAL AND COMMON ASPECTS

carried out only by an authorized personunder the instructions of the person-in-chargeof maintenance;

c) While working on mains, the followingprecautions shall be taken :

1)

2)

3)

3.2.2

No person, after receiving a permit-to-work, shall work on, or in any wayinterfere with, any mains or conduits orthrough containing a live mains exceptunder the persotutl instructions andsupervision, on the ‘site of work, ofcompetent person,When any live mains is to be earthed, theprocedure prescribed in 3.2.4 shall bescrupulously followed, andThe earths and short-circuits, specifiedon the permit-to-work shall not beremoved or interfered with except byauthority from the person-in-charge ofthe work.Minimum Working Distance - No_ __ . _ .person shall work within the minimum working

distance from the exposed live mains andappartus. The minimum working distancedepends upon the actual voltages. It does notapply to operations carried out on mains andapparatus which are so constructed as to permitsafe operation within these distances. Exposedlive equipment in the viscinity shall be cordonedoff so that persons working on the releasedequipment in service. The cardoning off shall bedone in such a way that it does not hinder themovement of the maintenance personel. Ifnecessary, a safety sergent could be posted.

‘3.23 Isolation of Mains - Isolation of mainsshall

4

be effected by the following methods :

The electrical circuits shall be broken onlyby authorized persons by disconnectingswitches, isolating links, unbolting connec-tions or switches which are racked outWhere possible, the isolation should bevisibly checked, and

b) Where the means of isolation areprovided with a device to prevent theirreclosure by unauthorized persons, such adevice shall be used.

3.2.4 . Devices .for Proving Mains andApparatus Bead

3.2.4.1 High voltage neon lamp contactindicato& rods are often used for proving exposedmains and apparatus dead. Each rod is fitted withan indicating neon tube or other means whichglows when the contact end of the rod comes incontact with exposed live parts. Each rod isclearly marked for the maximum voltage ,onwhich it may be safely used and shall not, underany circumstances, be used on higher voltapes.

3.2.4.2 Contact indicator and phasing rods areprovided-for phasing and proving exposed mainsand apparatus dead. A ,set consists of two rods

a9

connected in series by a length of insulated cables.Both rods are fitted with contact tips andindicating tubes. When the contact tip of one rod.is applied to ixposed live parts and that of theother to earth or other exposed live partsprovided there is sufficient voltage differencebetween the. two, the indicating tubes shouldglow. Each set of rods is normally marked for themaximum voltage on .which it may be used andshall not, under any circumstances. be used onhigher voltages.

3.2A.3 Use of Conrocr Indicator and PhasingRods - While using the high voltage contactindicator and phasing rods for proving the mainsor apparatus dead, following precautions shouldbe taken :

a)W

cl

4

Ensure that the rod is clean and dry,

Check the rod by applying it to known liveparts of the correct voltage, the indicatingtube shall glow,

Apply the rod to’each phase required lo beproved dead, the indicating tube shall notglow. Be very careful lo be in a position tosee the glow. if any, appearing in theindicating tube, and

Again check the rod by applying it to liveparts as in (2) above, agam the indicatingtubes shall glow.

NOTE I -All the above iperations shall be carried out atrhe same place and at the same time. if no live parts areavailable on the site, rods up to II kV may be tested byapplying them to the top of the spark plug in a running motorcar cngme. If the rod is in order the indicating tube will gloweach time the plug sparks. Therefore, the glow will tointermittent, but the Indicating tube should glow on this test ortlFa;od is.useleu as a means of proving the mains or apparatus

L

NOTE 2-The rod should be tested both before and afterthe use.

3.2.4.4 Testing ond morking of devices -- Itshill be ensured that all devices for proving highvoltage mains and apparatus dead are markedclearly with the maximum voltage for which theyare intended and should be tested periodically.

3.2.4.5 Idcnt~ficotion of cables to be workedupon - A cable shall be identified as that havingbeen proved dead prior to cutting or carrying outatiy operation which may involve work on ormovement of the cable. A non-contact indicatingrod, induction testing set or spiking device may beused for proving the cable dead.

3.2.4.6 Earthing and short-circuiting mains

a) High voltage mains shall not be workedu on unless they are discharged to earthaPter making them dead and are earthed andshort-circuited with earthing and short-circuiting equipment is adequate to carrypossible short-circuit currents and speciallymeant for the purpose. All earthingswitches wherever installed should be lockedup.

90

b) If a cable is required to be cut, a steel wedgeshall be carefully driven through it at the

d

4

d

point where it is to be cut or preferably bymeans of a spiking gun of approved design.

After testing the cable with dc voltage, thecable shall be discharged through a 2megohms resistance and not directly, owingto dielectric absorption which is particularlyprominent in the dc voltage testing of highvoltage cables. The cable shall be dischaigedfor a sufficiently long period to prevent re-building up of voltage.

The earthing device when used shall be firstconnected lo an effective earth. The otherend of the device shall then be connected tothe conductors lo he earthed.

Except for the purpose of ‘testing. phasing,etc. the earthing and short-circuiting devicesshall remain connected for the duration ofthe work.

3.2.4.8 Sqfety precautions ,for earthing - Theprecautions mentioned below should be adoptedto the extent applicable and possible :

a)

b)

Examine earthing devices periodically andalways prior lo their use.

Use only earthing switches or any. otherspecial apparatus where provided forearthing,

c) Verify that the circuit is dead by means ofdischarging rod or potential indicator. Theindicator itself should first be tested on alive circuit before and after the verification.

d) Earthing should be done in such a mannerthat the persons doing the job are protectedby earth connections on both sides of theirworking zone. and

d All the three phases should he effectivelyearthed and short-circuited though workmay be proceeding on one phase only.

3.2.4.7 Removing the eorth conntictions - Oncompletion of work, removal of the earthing andshort-circuiting devices shall be carried out in thereverse order to that adopted for placing them(see 3.2.4.6). that is, the end of the earthingdevice attached to the conductors of the earthedmains or apparatus shall be removed first and theother and connected lo earths shall be removedlast. The conductor shall not be touched after theearthing device has been removed from it.

3.2.4.9 Working on mains H*hew visibleisolation connot be carried out - Where theelectrical.circuit cannot be broken visibly as setout in 3.2.3 the circuit may be broken by twocircuit opening devices, one on each side of thework zone. where duplicate feed is available andby one circuit opening device where duplicate feedis not available provided the following conditionsare fulfilled :

a) The position of the contacts of the circuitoF~ning device(s) -- ‘open’ or ‘closed’- is


W

cl

4

d

clearly indicated by the position of theoperating handle or by signal lights or byother means,

The circuit opening device(s) can be locked’mechanically in the open position,

The mains and apparatus to be worked onare adequately earthed and short-circuitedbetween the circuit opening device and theposition of the work,

In cases where duplicate feed is available,both the circuit opening devices are in seriesbetween the mains and apparatus to beworked on and any source of supply.

In cases where duplicate feed is notavailable. the circuit opening device isbetween the mains to be worked on and anysource of supply.

The circuit opening devices mentioned .aboveshall be locked in the open position before thework on the mains and apparatus is commenced.The locking devices shall be removed only by acompete_nt person and not until the work has beencompleted. any short-circuiting and earthingremoved and’ the permit-to-work form dulyreturned and cancclled.

3.2.4.10 W o r k o n tttains wilh mw or moresecrions - When the mains to be worked uponare to be divided into two or more sections, theprovisions of 3.2.3 and 3.2.4.6 and 3.2.4.9 shall beobserved with regard to each section.

FART I CENERAI. AND COMMON ASPECTS

4. SAFETY PRACTICES

4.1 In all electrical works, it is very necessary thatcertain elementary safety practices are observed.It has been fc.md that quite a large number ofaccidents occur due to the neglect of thesepractices. The details of such practices are givenm Appendix C of IS: 5216 (Part I)-1982.

4.2 Equipment, Devices and Appliances -General guidelines regarding the same as given inl’S : 5216 (Part 1)~1,982.

5. SAFETY POSTERS

5.1 The owner of every medium, high and extrahigh voltage installation is required to fixpermanently, in a conspicuous positi0.n a dangernotice in Hindi or English and the local languageof the district on every motor, generator,transformer, all supports or high and extra highvoltage etc. The danger notice plate shall conformto IS : 2551-1982 ‘Specification for danger noticepla te.s (first revision)‘.

5.2 It is also recognized as good practice toindicate by means of the symbol recommended inIS : 8923-1978 ‘Warning symbol for dangerousvoltages’ on electrical equipment where thehalards arising out of dangerous voltage exist.

6 . A C C I D E N T S A N D T R E A T M E N T F O RELECTRIC SHOCK - (see IS : 5216 (Part 2)-1982. Recommendation on safety procedures andpractices in electrical work: Part 2 Life savingtechniques.

91

SECTION 17 GUIDELINES FOR POWER-FACTORIMPROVEMENT

& F O R E W O R D

0.1 This Section has been prepared with a viewto providing guidance to the consumers ofelectrical energy who take supply of low andmedium vbltage for improvement of power factorat the installation in their premises.

0.2 The various advantages of maintaining a highpower factor of a system reflects on the nationaleconomy of a country. The available resources areutilized to its fullest possible extent. More usefulpower is available for transmission and utilizationwithout any extra cost. Moreover, the life ofindividual apparatus is considerably increased andthe energy losses reduced.

0.3 1 he guidelines provided in this Section arebasically intended for installation operating atvoltages below 650 V. For higher voltageinstallations. additional or more specific rulesapply.

0.4 The contents of this Section are based onI S : 7752 (Part I)-1975 “Guide for t ticimprovement of power factor in consumers’installations: Part I Low and medium suppIvoltages”.

1. SCOPE

1.1 This Section of the Code covers causes forlow power fac to r and guIdelines for use ofcapacitors to improve the same in consumersinstallations.

1.2 Specific guidelines, if anr*

for individualinstallation on improvement 0 power factor arecovered in the respective sections of the Code.

2. GENERAL

2.1 Conditions of supply of electricity boards orlicensees stipulate the lower limit of power factorwhich is generally 0.85 and consumer is obliged toimprove and maintain the power factor of hisinstallation to. conform to these conditions.

2.1.1 When the tariffs of Electricity Boards andthe licensees are based on kVA demand or kWdemand with suitable penalty, rebate for lowi highpower factor, improvetient. in the power factorwould effect savings in the energy bills.

2.2 Power factor is dependent largely onconsumers apparatus and partly on systemcomponents such as transformers. cables,transmissioti lines. etc. System components havefixed parameters of inductance. capacitance andresistance. The choice of these components tobring up fhe power factor depends on economics.

92

23 In case of ac supply, the total c_urrent takenby almost every item of electrical equipment,except that of incandescent lighting and mostforms of resistance heating, is made up of twoparts, namely :

a) the in-phase component of the current(active or useful current) which is utilizedfor doing work or producing heat; and

b) the quadrature component of the current(also called ‘idle’ or ‘reactive’ current) andused for creating magnetic field in themachinery or apparatus. This component isnot convertible mto useful output.

3. POWER FACTOR

3.1 The majority of ac electrical machines andequipment draw from the supply an apparentpower (kVA) which exceeds the required usefulpower (kW). This is due to the reactive power(LVAR) necessary for alternating magnetic field.The ratio of usefol power (kW) to apprarentpower (kVA) is termed the power factor of theload. The reactive power is indispensable andconstitutes an additional demand on the system.

3.2 The power factor indicates the portion of thecurrent in the system performing useful work. Apower factor of unity (100 percent) deiotes 100percent utilisation of the total current for usefulwork whereas a power factor of 0.70 shows thatonly 70 percent of the current is performing usefulwork.

3.3 Principal Causes of Lower Power Factor

3.3.1 The following electrical equipment andapparatus have a lower factor :

a)

b)

cl

4

e)

f-l

Induction motors of all types particularlywhen they are underloaded.

Power transformers and voltage regulators,

Arc welders.

Induction furnaces and heating coils,

Choke coils and magnetic systems,

Fluorescent and discharge lamps. neon.signs, etc.

3.3.2 The principal cause of a low power factoris due to the reactive power flowing in the circuit.The reactive power depends on the inducta;lceand capacitance of the apparatus.

3.4 Effect of Power Factor to Consumer

3.4.1 The disadvantages of low power factorare as follows :

a) OvtJoading of cables and transformer.


b) Decreased line voltage at point ofappiicatioll,

c) inefficient operation of plant. and

d) Penal power rates.

3.4.2 The advailtages of high power factor areas follows :

4b)c)

d)

e)

Reduction in the current,

Reduction in power cost,

Reduced losses in the transformers andcables,

Lower loading of transformers, switchgears.cables. etc.

Increased capability of the ‘power system(additional load can be met withoutadditional equipment).

Improvement in voltage conditions andapparatus performance, and

Reduction in voitagc dips caused by weldingand slmiiar ‘equipment.

3.5 Economics of Power Factor Improvement

3.5.1 Static caGacitors. also called staticcondensers. when installed at or near the point of‘consumption. provide necessary Capacitivereactive power. relieve distribution system before

the point of its installation from carrying theinductive reactive power to that extent.

3.5.2 The use of the static capacitors is aneconomical way of improving power factor onaccount of their comparatively-low cost. ease ofinstallation loss maintenance. low losses and theadvantage of extension’ by addition of requisiteunits to meet. the load growth. installation ofcapacitors also improve the voltage. regulationand reduces amperes loading and energy losses inthe supply apparatus and lines.

3.5.3 When considering the economicsconnected with power factor correction. it is mostimportant to remember that any power factorimproving equipment will. in general. compensatefor losses and lower the loadings on supplyequipment. that is. cables, transformers.switchgear. generating plant. etc.

3.5.4 The minimum permissible .power factorprescribed in the conditions of supply ofElectricity Boards or Licensees and the reductionin charges offered in supply tariffs fortfurtherimprovement of power factor shall, along withorher considerations such as reduction of losses,etc. determine the kVAR capacity of thecapacitors to be installed. - _

3.5.5 In case of two port tariff with kVAdemand charged. the value of economic improvedpower factor (Cos & ) may be obtained asfoliows :

Let th: tariff be Rs A per kVA of maximumdemand per annum plus Rs P per kWh

PART I GENERAL AND COMMOh A S P E C T S

cos qbl is the imttal power factor,

Cos $Q is the improved power factor afterinstalling the capacitors

The economic power factor Cos & is obtainedfrom the expression

where

B is the total cost per kVAR per year ofcapacitor installation ihclusive of interest,depreciation and maintenance.

NOTE - The explanation for the derivation of the formulafor economic power factor Cos $17 is given in Appendix A ofIS : 7752 (Part I)-1975 ‘Guide for improvement of power-factor in consumers’ installation: Part I Low and medtumsupply voltages.

4. USE OF CAPACITORS

4.1 In order to improve the power factor, theconsumer shall install capacitors where thenatural power factor of this installation is low.

4.2 The average values of the power factor fordifferent types of 3 phase electrical installationsas measured by one of major utilities in thecountry are given in respective Sections of theCode.

43 Capacitors for power factor improvementmay be arranged as described in IS : 7752 (PartI)-1975. The successful operation of power factorimprovement depends very largel-y on thepositioning of the capacitor on the system. Idealconditions are achieved when the highest powerfactor is maintained under all load conditions.

4.4 Individual Compensat ion Whereverpossible the capacitor should be connecteddirectly across the terminals of the low powerfactor appliance or equipment. This ensures thecontrol to be automatic through the sameswitching devices of the apparatus of applianct.

4.5 Group Compensation - In industries where alarge number of small motors or other appliancesand machines are installed and whose operation isperiodical it is economical to dispense withindividual installation of capacitors. A bank ofcapacitors may be installed to connect them to thedistribution centre of main bus-bars of the groupof machines.

4.6 Central Compensation - Capacitors mayalso be installed at a central point, that is. at theincoming supply or service position. In order toovercome problems of drawing leading currentson light loads. these capacitors may be operate!manually or automatically as required. Theautomatic control is preferred as it eliminateshuman errors. Automaiic operation may bearranged by means of suitable relays in which a

93

contactor controls the capacitors bank anamaintains the correct amount of, kVAR in thecircuit.4.7 The methods of connecting power factQrcapacitors to supply line and motors is given inFig. 1 and 2.

5. POWER FACTtlR 1MPROYEMENT:ANDCAPACITOR RATING

5.1 For calculating the siqe of the capacitor forpower factor improvement ref&cacc rhould bemade to Table 5 of Part 1 /Sac 18 of the Code.

TO STAR DELTASTARTER

F I G. I ME T H O D S OF C O N N E C T I N G C A P A C I T O R S F O R IM P R O V E M E N T O FPOWER FACTOR TO MOTORS

CIRCUIT BREAKER,CONTACTOR.ORFUSE SWITCH, ASRECOMMENDEDtSUIlABLE FORGROUP OPERATION1

F I G. 2 METHODS OF CONNECTING CAPACITORS FOR IMPROVEMENT ofPOWER FACTOR TO SUPPLY L I N E


SECTION 18 TABLES

0 . F O R E W O R D

0.1 In electrical engineering work, frequent needarises to make reference to certain data, which,when made available in the form of readyreference tables facilitates the work. This Sectionof Part I gives in one place such of those tableswhich basically provide fundamental data notnecessarily required for the understanding of theCode that they should appear along with relevanttext, but are required to be referred to indesigning the installation.

0.2 The recommended current rating of cables arecovered in the form of tables in the followingIndian Standards.

IS 3961 Recommended current ratings forcables(Part I)-1967 Paper insulated lead sheathedcables(Part 2)- 1967 PVC insulated and PVC sheat-hed heavy duty cables(Part 3)-1968 Polyethylene insulated cables(.:.a, 4)-1968 PVC insulated light duty

In view of ihe fact that this data is voluminousand are themselves being extensively reviewed forpossible up-dating by the concerned expert group,this Section merely draw a reference to IS : 3961(series). The data when finalized will form part ofthe Code.

TABLE 1 DIAMETER AND MAXIMUM ALLOWABLERESISTANCE OF FUSE-WIRES, TINNED COPPER

RATC~ NOMINAL T O L E- PERMISSIRLE RESlSrANcECLlRREhT D I A M E T E R RANCE AT 20°COF Fr:tr-

WlRFMax Min

(A) (2) (3) (4) (5)mm mm Dim flim

6 0.20 t 0.003 0.564 4 0.525 0

t: 0.35 0.50 + ? 0.004 0.005 0.089 0.183 4 8 0.173 0.084 0 820 0.63 f 0.006 0.056 6 0.053 5

:: 0.75 0.85 t t 0.008 0.009 0.031 0.040 0 I 0.037 0.029 6 340 I .25 t 0.011 0.014 3 0.013 6

:: 1 I so .80 _t t 0.015 O.Oi8 0.009 0.006 9 9 0.009 0.006 4 5100 2.00 f 0.020 0.005 6 0.005 3


TAPLE 2 SIZE OF WOOD CASING AND CAPPINb.AND NUMBER OF CABLES THAT MAY BE DRAWN IN

ONE GROOVE OF THE CASING

Width of casing ofcapping, mm

No. of grooves

Width of grooves. mm

Width of dividingfillet, mm

Thickness of outerwall. mm

Thickness of casing. mm

Thickness ofcapping. mm

Thickness of the backunder thegroove. mm

Length. m

SIZE OF CAHLE

Nominal Number andCross- Diameter

Sectional (in mm)Area, mm’ of Wires

I.0 l/1.12*

1.5 l/l.40

2.5 lil.8031 I .60’

4 I/2.2471 I .85*

6 I/2.8071 I .06

IO I / 3.j5t711.40

16 7/ 1.70

25 712.24

35 712.50

50 7/3.OOt191 1.80

38 44 51 64 76 89 102

2 2 2 2 2 2 2

6 6 9 13 16 16 19

12 12 I3 18 24 35 38

7 IO IO IO IO I I 1:

16 16 19 19 25 32 32

6 6 IO IO Ill 13 13

6 6 6 IO IO 10 I3

2.5 to 3.0

NI’MRER O F C A R L E S T H A T M A Y H E

D R A W N IN ON E GROOVE

2 2

I II I

- -

- -

- -- -

- -

*For copper conductors only.tFor aluminium conductors only

3

2

2

2

I

i----

9

8

5

5

4

:

IIII

I2

12

IO

8

6

I2

12

IO

9

6

!n

TABLE 3 MAXIMUM PERMISSIBLE NUMBER OF 1.1 kV GRADE CABLESTHAT CAN BE DRAWN INTO RIGID STEEL CONDUITS

SIZE OF CABLE SnE OF CO N D U I T , m m

50 63 \-Nominal N u m b e r and. ’ 16Cross- Diameter

io 25 32 40NUMBER OF CABLES, MUX

Sectional (in mm) -+-Area of Wires Smm2(1)t.01.52.3

4

6

(2) (3)

I/ 1.12. 5

l/l.40 4

l/l.80 33/1.06*

l/2.24 37/0.85*

10

1;\;.6” 2.

I6

25

35

50

w;wgr --711.70 -

712.24 -

712.50 -

19/1.80 -7/3.oot

B

(4)432

2’

-

--_-

---

S

(5)7

7

0

4

3

:-

-

-

-

. .B S

(6) (7)

5 1 3

5’ I2

5 IO

3 7

2 6

- 5- 4

- 2- -

- -

- -

B‘

(8)

I O

IO

8

0

5

43-

-

S

(9)

20

20

I8

B

(10)I4

14

I2

I2 IO

IO 8

:

3

2-

-

S

(11)---

s7

5

4

2

B‘

(12)-

-

-

:

6

4

3-

S

(13)-

-

-

B‘

(14)-

-

-

- -

-

- -

8 6

7 5

5 4

-

-

-

9

8

9

NOTE - The table shows the maximum capacity of conduits for the simulataneous drawing of cables. The table applies toI: I kV grade cabks. The columns headed S apply to runs ot conduit which have distance not exceedlnp 4.25 m between draw-in-boxes, and which do not deflect from the straight by an angle of more than IS”. The columns headed B apply to runs ofconduit which deflect from the straight by an angle of more than ISo

*For copper conductors only.tFor aluminium conductors only.

TABLE 4 MAXIMUM PERMISSIBLE NUMBER OF 1.1 kV GRADE SINGLE-CORECABLES THAT MAY BE DRAWN INTO RIGID NON-METALLIC CONDUITS

SIZE OF CABLE S I Z E O F C O N D U I T , m m/

Nominal Number and. ,

I6 20 25 32 40 50 .Cross- Diameter N U M R E R O F C A B L E S , M a x

SectionalAreamm*

(inwm,:; of

I.0 l/l.129

I.5 111.40

2.5 l/l.8031 I.060

4 I(2247/0.85*

6 r/2.8071 I.400

IO I /3.55t711.40.

16 711.70

25 712.24

35 712.50

50 7/3.oot19/1.80

*For .copper conductors only.?For, rluminium conductors only.

5 7 I3 20 - -

4 6 IO I4 - -

3 5 IO I4 - -

2 3 6

- 2 5

- 4

- - 2--

-- -

IO I4 -

9 II -

7 9 -

4 5 I2 .

2 2 6

2 5

2- 2 :

w NATIONAL ELECTRICAL CODE

TABLE 5 CAPACITOR SIZES FOR POWER FACTOR IMPROVEMENT

EXIST-,IMPROVED POWER FA C T O R

INGPOWERFA(.TOR

(1)

0.80 0.85 0.90 0.91 0.96 0.97 0.98 0.99 1.00 -

(2) (3) (4) (5)

0.92 0.93 0.94 0.95

@?6) (7) (a) (9)

MULTIPLI~NG FKTOR

(10) (11) (12) (13) (14)

I.861I.7981.7381.680

t-z I.924

I:771I.8601.800

I.713 1.7421.647 1.6771.592 1.6261.533 1.567I.485 I.5191.430 1.4641.386 1.4201.337 1.369

KB I::;:I:205 1.237I.164 I.196I.124 I.1361.085 I.117,I.047 I.079I.010 1.0420.973 1.0050.939 0.971

0.904 0.9360.870 0.9020.838 0.8700.805 0.8370.774 0.8060.743 0.775a.713 0.7450.684 0.7160.654 0.6860.625 0.657

0.597 0.6290.568 0.6000.541 0.5730.514 0.5460.487 0.5190.460 0.4920.434 0.4660.408 0.4400.381 0.4130.355 0.387

0.400.410.420.43

8.:0.460.470.480.490.50

0.510.520.530.540.550.560.570.580.590.60

0.610.620.630.640.650.660.670.680.690.70

0.710.720.730.740.750.760.770.780.790.80

0.810.820.830.840850.860.870.880.890.90

0.910.920.930.940.950.960.970.980.99

1.5371.474I.413I.356I.2901.230I.179I.1301.076I.0300.982

0.9360.8940.8500.8090.7690.7300.6920.6550.6180.584

0.5490.5150.483014500.4190.3880.3580.3290.2990.270

0.2420.2130.1860.1590.1320.1050.0790.0530.026-

--

._

__

_..

__

It!I.544I.487I.421

1:g

1.zI:160I.112

I.8051.742I.6811.624I.558I.501I.446

1.::11297I.248

1.8321.7691.709I.6511.5851.5321.473I.4251.3701.3261.276

,614,561,502,454

:z,303

1.0661.0240.9800.9390.899

8:E0.7850.7480.714

1.202 1.230I.160 I.188I.116 I.1441.075 I.1031.035 1.0630.996 1.0240.958 0.9860.921 0.9490.884 0.9120.849 0.878

I ,257,215.I71,130

I :!?I.0130.9760.9390.905

0.679 0.815 0.843 0.8700.645 0.781 0.809 0.8360.613 0.749 0.777 0.8040.580 0.716 0.744 0.7710.549 0.685 0.713 0.7400.518 0.654 0.682 0.7090.488 0.624 0.652 0.6790.459 0.595 0.623 0.6500.429 0.565 0.593 0.6200.400 0.536 0.564 0.591

0.3720.3430.3160.2890.2620.2350.2090.1830.1560.130

0.1040.0780.0520.026-

0.508 0.536 0.5630.479 0.507 0.5340.452 0.480 0.5070.425 0.453 0.4800.398 0.426 0.4530.371 0.399 0.4260.345 0.373 0.4000.319 0.347 0.3740.292 0.320 0.3470.266 0.294 0.321

8:;:0.1880.1620.1360.1090.0830.0540.028

0.2680.2420.2160.1900.1640.1400.1140.0850.0590.031

0.2950.2690.2430.2170.1910.1670.1410.1120.0860.058

-

-

0.027

-

-_._

0.329 0.3610.303 0.3350.277 0.3090.251 0.2830.225 0.2570.198 0.2300.172 0.2040.143 0.1750.117 0.1490.089 0.121

0.058 0.0900.027 0.063- 0.032

I.959 1.998 2.037 2.085 2.146 2.2881.896 1.935 1.973 2.021 2.082 2.2251.836 I.874 I.913 I.961 2.022 2.1641.778 I.816 1.855 I.903 1.964 2.107I.712 I.751 1.790 1.837 I.899 2.0411.659 1.695 1.737 1.784 1.846 1.988I.600 1.636 1.677 1.725 1.786 1.9291.552 1.588 1.629 1.677 1.758 I.8811.497 1.534 1.575 1.623 1.684 1.8261.453 1.489 I.530 1.578 1.639. 1.782I.403 I.441 I.481 1.529 1.590 1.732

1.357 1.395 1.435 1.483 1.544 1.686I.315 1.353 1.393 I.441 1.502 1.644I.271 1.309 1.349 1.397 I ,458 1.6001.230 1.268 1.308 1.356 I.417 1.559I.190 1.228 1.268 1.316 1.377 I.519I.151 I.189 1.229 1.277 1.338 I.480I.113 I.151 I.191 1.239 1.300 1.4421.076 I.114 I.154 1.202 1.263 1.4051.039 1.077 I.117 I.165 1.226 I.3681.005 1.043 1.083 I.131 I.192 1.334

0.970 1.008 1.048 1.096 I.157 1.2990.936 0.974 I.014 1.062 I.123 1.2650.904 0.942 0.982 1.030 I.091 1.2330.871 0.909 0.949 0.997 1.058 1.2000.840 0.878 0.918 0.%6 1.027 I.1690.809 0.847 0.887 0.935 0.996 1.1380.779 0.817 0.857 0.905 0.966 I.1080.750 0.788 0.828 0.876 0.937 1.0790.720 0.758 0.798 0.840 0.907 1.0490.691 0.729 0.769 0.811 0.878 1.020

0.663 0.701 0.741 0.785 0.850 0.9920.634 0.672 0.712 0.754 0.821 0.9630.607 0.648 0.685 0.727 0.794 0.9360.580 0.618 0.658 0.700 0.740 0.9090.553 0.591 0.631 0.673 0.713 0.8820.526 0.564 0.604 0.652 0.687 0.8550.500 0.538 0.578 0.620 0.661 0.8290.474 0.512 0.552 0.594 0.634 0.8030.447 0.485 0.525 0.567 0.608 0.7760.421 0.459 0.499 0.541 0.582 0.750

0.395 0.433 0.4730.3669 0.407 0.4470.343 0.381 0.4210.317 0.355 0.3950.291 0.329 0.3690.264 0.301 0.3430.238 0.275 0.3170.209 0.246 0.2880.183 0.230 0.2620.155 0.192 0.234

0.5150.4890.4630.4370.4170.390

::E0.3090.281

0.556 0.7240.530 0.6980.5Og 0.6720.478 0.6450.450 0.6200.424 0.5930.395 0.5670.395 0.5380.369 0.5120.341 0.484

0.124 0.1610.097 0.1340.066 0.1030.034 0.071- 0.037-

0.2030.1760.1450.1130.0790.042-

--

0.250 0.3100.223 0.2830.192 0.2520.160 0.2200.126 0.1860.089 0.1490.047 0.107- 0.060-

0.4530.4260.3950.3630.3290.2 2%0.2

:::rl:

NOTE - The consumer a advised to make proper allowance for lower supply voltages where these exist during thworking hours and may choose slightly higher kVAR than recommended in the table for such cases.


PART 2,ELECTRICAL INSTALLATIONS IN ST iNDBYGENERATING STATIONS AND CAPTI\ E

SUBSTATIONS

O . F O R E W O R D

0.1 This part of the National Electrica! Code is primarily intend+_ to cover therequirements relating to standby generating stations and capttve substationsintended for serving an individual occupancy. As the general provisions relating tosuch installations are common and are themselves elaborate in nature, it was feltessential to cover them in a separate part preceeding the other parts which cover therequirements for specific installations.0.2 Generating stations covered by this Part are the standby or emergency supplyand captive substations normally housed in or around the building in question. ThisPart does not include the switching stations and other large generating plantscoming solely under the pet-view of the electric supply authority of a metropolis,even though to some extent the requirements stipulated herein could also beapplicable to them.U.3 Specific requirements, if any, for generating and switching substations forindividual buildings that might vary depending on the nature of the occupancy orthe size of the building are enumerated in the respective Sections of the Code.0.4 In the preparation of this Part, note has been taken of the requirementsstipulated in installation codes of individual equipment as well,as the fire-safetycodes for generating stations and substations. It is generally not feasible to drawvery strict guidelines for the design and layout for such installations owing to thecomplexity of the needs of building installations and hence only the essential safetyconsiderations are listed out for compliance. It is essential to take recourse to theassistance of local authorities for further details.0.5 Specific requirements pertaining to standby generating stations and captivesubstations for multistoreyed/high-rise buildings are covered in Appendix to PartIII of the Code.0.6 This Part shall be read in conjunction with the following publications :

IS : 1641-1960 Code of practice for fire-safety of buildings (general) : Generalprinciples and fire grading

IS : 1646-1982 Code of practice for fire-safety of buildings (general) : Electricalinstallations

IS : 2309-1969 Code of practice for the protection of buildings and alliedstructures against lightning

IS : 3034-1981 Code of practice for fire-safety of industrial buildings : Electricalgenerating and distributing stations (/i’r.sr revision)

IS : 3043-1966 Code of practice for earthingIS : 10028 (Part 2)-I981 Code of practice for selection, installation and

maintenance of transformers : Part 2 InstallationsIS : IO1 I8 (Part 3)-l 982 Code of practice for selection, installation and

maintenance of switchgear : Part 3 installations

1. SCOPE

I.1 This Part of .the Code covers e ssen t i a lrequirements for electrical standby generatingstations and captive substations intended to servea building or group of buildings.

I.2 This part is not intended to cover ‘captivegenerator sets’ of very large capacities which-aremain or supporting mode of power supply. ThisPart covers only the standby generating sets up tothe capacity & I MW. Similarly the substatlonsup to the capacities of 5 MVA and 33 _kV ‘arecovered. This Part also does not apply to stationscoming under the jurisdiction of the electricsupply authority in a city or metropolis.

:2. TERMINOLOO\Y

2.1 For the purposks of this Part, the definitiongiven in Part I/Set 2 of the Code shall apply.

3. GENERAL CHARACTERISTICS OFSTATION INSTALLATIONS

3.1 In determining the general characteristics ofstandby generating plants and buildingsubstations in a building, the assessment .ofcharacteristics of the buildings based on itsoccupancy shall be taken note of as specified inindividual Parts/Sections of the C&je.

3.2 Depending on the exact location of thestation in the building premises, and dependingon whether the equipment are installed indoor oroutdoor, the degree of external influence of theenvironme.nt shall be determihed based on theguidelines provided in Part 1’/Sec 8 of the Code.

3.3 It is generally presumed that generatingstations and substations are rest,ricted areas notmetint fo r unau thor i sed persons , and suchelectrical operating areas fall under the categoryof BA4 utilisation for instructed Frsonnel (seePart I /Set 8), which are adequately advised orsupervised by skilled persons to avoid dangersthat may arise owing to the use of electricity.

4. EXCHAF*I;E OF INFORMATION

4.1 Information shall be exchanged amongst thepersonnel involved regarding the size and natureof substation and supply station requirements tobe provided for an occupancy So that the type ofequipment and their choice, as well as theirinstallation shall be governed by the same. Anassessment shall also be made of the civilconstruction needs of the station equipmentkeeping in view a possible expansion in future.

4.2 Before ordering the equipment, informationshall be exchanged, regarding the installation andlocation conditions, including such buildingfeatures as access doors, lifting beams, oil pumps,cable trenches, foundation details for heavyequipment, ventilating arrangement, etc.

102

5. LAYOUT AND BUILDING CONS-TRUCTION ASPECTS

5.1 The constructional features of all buildingshousing the sta_tion installations shall comply withIS : 164l-1960* and IS : 3034-1981t. Locating ofsubs ta t ion in basements i s genera l ly no trecommended.

5.2 Switchgears, o i l c i r c u i t - b r e a k e r a n dtransformers (except outdoor types) shall behoused preferably in detached single storeybuildings of Type 1 construction. In the case ofbuilt up areas in cities, multistoreyed constructionmay also be adopted. Construction of suchbuildings shall conform to IS : ‘l&6-1982$.

5.3 Construction of fire separation walls shallcunform with the requirements of relevant IndianStandards. Doorway openings in seperating wallsof transformer or switchgear rooms shall beprovided with sills not less than 15 -cm in height.Reference is drawn to IS : 3034-1981t where risksof spread of possible fire exists, interconnectingdoors should be of fireproof construction.

NOTE - Noise level limitation for generator sets are understudy.

5.4 The foundation of the standby generating setsshall preferably be isolated from that of the otherstructures of the building so that vmrations arenot carried over.


6.1 The selection of equipment shall be done inaccordance with the guidelines provided in PartI /Set 9 of the Code.

7. GENERATING SETS

7.0 Stationary generating sets of about. 5 kVAand above are normally driven by diesel engine asthis drive is most economical. Smaller sets aredriven by petrol. During the planning of thebuilding, the dimensioni of the power plant ,roomand the transport ways shall be agreed to betweenthe architect and electrical contractor.

7.1 In case of large capacity sets which generateappreciable heat; t l ie rooms shall be wellven t i l a ted and prov ided wi th a i r exhaus tequipment.

7.2 The capacity of the standby set for aninstallation should be such that in an event- ofpower failure, the essential loads can be suppliedpower. For instance in case of hospitals suchloads comprise operation theatres and theirsupporting auxiliaries; intensive care units, Icoldstorage in laboratories, emergency lifts, etc. In thecase of industries having continuous processes,

*Code of practice for fire-safety of buildings (general)‘:General principles and fire grading.

tCode of practice for fire-safety of industrial buildings;Electrical generating and distributing stations f&r revision).

tCode for fire-safety of. buildings (general): Electricalinstallations.


such loads are required to be supplied with powerall the time. In commercial premises and high-risebuildings, a few lifts and circulation area lightsand fire-fighting equipment have to be keptworking by supply from standby sets. Similar isthe case of essential loads in large hotels. Suchsets can either be manually started and switchedon to essential loads with the use of changeoverswitches or they could be auto-start on mainsfailure and loads autochanged over to generatorsupply.

7.3 In case of large electrical installation in whichessential loads are widely scattered it becomesnecessary to run the generating set supply cablesto these essential loads and in the event of mainsfailure, changeover to generator supply, eithermanually or through auto-ctiangeover contactors.

7.4 The fuel oil storage requirements. shallconform to 73 of IS :3034-1981*.

7.5 The requirements for oil and gas firedinstallations shall conform to IS : 3034-1981*.

7.6 All equipment of prime mover shall conformto relevant Indian Standard for construction,temperature risk, overload and performance.

8. TRANSFORMER INSTALLATIONS

8.1 Reference is drawn to the requirements inIS : 10028 (Part 2)-19817.

8.2 Transformer of capacity up to 1 MVA may behoused indoor or outdoor. The larger ones,because of their size, are usually of outdoor type.8.3 Transformer housed in cabins will requireadequate ventilation to take away as much heat aspossible. Oil drainage facilities and partition wallsbetween transformers and between transformerand other equipment such as oil circuit-breakers isnecessary to reduce the risk of spread of fire.

8.4 As a transformer station normally has a highvoltage and a low voltage switchgear, all suchequipment should be adequately separated.

9. HIGH VOLTAGE SWITCHING STATIONS

9.,I Reference is drawn to the requirementsstipulated in IS : 101 18 (Part 3)-1982:.

10. LOW VOL?AGE SWITCHING STATIONSAND DISTRIBUTION PANELS

10.1 Reference is drawn to’ the requirementsstipulated in IS : 10118 (Part 3)-1982:.

*Code of practice for fire-safety in industrial buildings:Electrical generating and distrihuting stations CjTrsr revision).

tCode ot practice for selection, installation and maintenanceof transformers: Part 2 Installation.

:Code of practice for selection, installation and maintenanceof switchgear and controlgear: Part 3 installation.

11. STATION AUXILIARIES

11.0 Station auxiliaries could consist of:

W batteries for standing diesel sets,

b) batteries for short time emergency lighting,

cl battery charging equipment,

4 fuel oil pumps,

e) ventilating euipment, and

0 fire-fighting equipment.

11.1 Batteries

11.1.1 Batteries shall have containers of glassor any other non-corrosive, non-flammablematerial.

11.1.2 Batteries shall be installed in a separateenclosure away from any other auxilliaryequipment or switchgear. The enclosure shall befree from dust and well ventilated. Care shall betaken to ensure that direct sunlight does not fallon the batteries.

NOTE - Provision shall be made for sufficient diffusion andventilation of gases from the. battery to prevent theaccumulation of an explosive mixture.

11.1.3 The’ batteries shall stand directly ondurable, non-ignitable, non-absorbent and non-conducting material, such as glass, porcelain orglazed earthenware. These materials shall rest ona bench which shall be kept dry and insulatedfrom earth. If constructed of wood it shall beslatted and treated with anti-sulphuric enamel.

11.1.4 The batteries shall be so arranged on thebench that a potential difference exceeding 12 Vshall not exist between adjoining cells. Thebatteries not exceeding 20 V shall not be bunchedor arranged in circular formation.

11.1.5 All combustible materials within adistance of 60 cm measured horizontally from, orwithin 2.0 m measured vertically above, anybattery shall be protected with hard asbestossheets.

11.2 Battery Charging Equipment

11.2.1 Motor generator sets and converters orrectifiers together with necessary switch andcontrol gear shall be mounted separately andaway from the batteries.

11.2.2 The charging circuit shall be providedwith double or triple pole switches and fuses.Where a motor generator is employed, the motorshall be provided with double or triple poleswitches and fuses and an automatic battery andcut-out shall be placed in the generator circuit.Any subcircuit shall be provided with a fuse ineach live conductor.

11.2.3 The charging control panels shall be ofdurable, non-ignitable, non-absorbent, non-conducting material and together with rectifiers,transformers and supports for resistance of lamps,

PART 2 GENERATING STATIONS AND CAPTIVE SUBSTATIONS I03

shall be on a bench which shall be kept dry andinsulated from earth. If constructed of wood, itshall be slatted and treated with anti-sulphuricenamel.

11.2.4 l,f batteries are charged throughresistance or lamps, such resistance or lampsunless enclosed in metallic enclosure, shall be atleast 60 cm away from the nearest battery.

I I.3 Fuel Oil Pump

11.3.1 Fuel oil pump shall be installed close tothe engine room or inside the engine room.

11.3.2 The electric cable provided to run thepump motor shall be protected with oil-resistantouter sheath.

11.4 Ventilating Equipment

11.4.1 The engine room shall be fitted withhot-air extractors.

11.4.2 The battery room shall be fitted withexhaust fans. The exhaust gases shall be let off toatmosphere where no other equipment is installed.

12. WIRING IN STATION PREMISES

12.1 All cabling and electrical wiring insidegenerating’ or substation premises shall be done inaccordance with the practice recommended inPart I /Set I I of the Code.

13. EARTHING

13.1 The provision of 17 of IS : 3043-1981* shallapply (see also Part 1 I Set 12).

14. BUILDING SERVICES

14.1 Lighting

14.1.1 The general principles of good lightingfor any occupancy shall be as given in Part I/Set 14 of the Code. For the purposes of stationinstallations the values of illumination andlimiting ‘value of glare index shall be as given inTable I.

*Code of practice for fire-safety of industrial buildings;Electrical generating and distributing stations yirsr revision).

104

TABLE 1 RECOMMENDED VAtUEs OFILLUMINATION AND GLARE INDEX

bCATION ILL.UMI- LIMINTINGNATION GLARE INDEX

(1) (2) (3)lux

indoor Locationsa) Standby generator hall 200 2sb) Auxilliary equipment; battery 100 -

room, blowers, switchgearand transfdrmer chambers

c) Basements 70 -d) Control rooms :

i) Vertical conlrol panelsii) Control desks _

iii) Rear of control panel

Our&or Locationsa) Fuel oil storage areab) Transformers, outdoor

switchgear

200-300 I9300I50 ix

-1;

14.2 The luminaires used shall be of dust-proofconstruction.

15. FIRE-SAFETY REQUIREMENTS

15.1 The provisions of IS : 3034-I 98 I* shall applyfor station installations.15.2 All wiring for automatic fire-fightinginstallation shall be of fire-resistant outer sheath.

16. LIGHTNING PROTECTION

16.1 The provisions of 138 of IS : 230%19697shall apply.

17. TESTING AND INSPECTION

17.1 The guidelines provided in Part I /Set 10 ofthe Code shall apply. In the case of diesel. setswhich come into operation only in emergency asstandby sets, it is necessary that such sets. areregularly checked run up and the mechanical andelectrical system tested to ensure that the set isjnoperable condition all the time.

*Code of practice for fue-safety of industrial buildings,electrical generating and distribution stations uir.rr wvision).

t&de of practice for the protection of building and alliedstructures against lightning @r.rr m+.sion).


PART 3 ELECTRICAL INSTALLATIONSIN NON-INDUSTRIAL BUILDINGS

0 F O R E W O R D

0.1 For the purposes of the Code, electrical installations in buildings have beenbroadly classified as those in non-industrial and industrial buildings. While amajority of installations could be categorically classified as non-industrial, anindustrial complex would necessarily incorporate sub-units such as offices,residential quarters and support services which are housed or fall in the category ofnon-industrial buildings. The requirement stipulated in Part 3 and Part 4 of theCode would therefore require judicious application.0.2 With the current trend in power utilization, it would also be extremely difficultto classify electrical installations based on power requirement or the voltage ofsupply as large buildings of non-industrial use consume sufficient power to considerthem at par with the consumption of light industrial establishments. It is thereforenecessary to consider for initial assessment of the installation the guidelines given inPart l/Set 8 of the Code, which are better defined than the earlier terminologyused for classifying installations.0.3 Part 3 of the Code, therefore covers requirements for major types of non-industrial occupancies. It is felt that a large number of occupancies would fall inone of the categories, and for typical buildings which do not strictly fall into any ofthese, recourse shall be made to the general guideliines stipulated in Part 1.0.4 The various Sections of Part 3 cover requirements applicable to buildingswhich are of nominal heights less than 15 m. It is recognized that from the point ofview fire-safety of buildings more than 15 m height require specific considerations.These are summarised in Appendix to Part 3.

SECTION 1 DOMESTIC DWELLINGS

0 . F O R E W O R D

0.1 Electrical installations in domestic dwellingsand in buildings providing living accommodationfor people are by far the simplest form ofinstallation. Use of ekctrical appliances, bothportable and fixed has now become very commonand popular even in slngk family dwejlings. Theoptimum benefits from the use of electricity canbe obtained onl if the installation is of suffkientcapacity and axords enough fkxibility.

10.2 ‘The primary considerations in planning theelectrical layout in domestic dwellings areeconomy and safety. Besides these, otherconsiderations such as efficiency and reliability,convenience and provisions for future expansionare also valid.

shall include any private dwelling which isoccupied by members of a single family andhas a total sleeping accommodation for notmore than 20 persons.

20NOTE - If accommodation is provided for more than

pqsons, such buildings are considered lodging orrootntng hottscs.,(dormitorics) and the provistons ofPart 3/See 5 sgall apply.

b) Apartment Houses (Flats) - These shallinclude any building or structure in whichliving quarters are provided for three ormore families, living independently of eachother and with independent cooking facili-ties. For example apartment houses, mans-ions and chawls.

0.3 Domestic installations are characterizedmainly by a circuit voltage of 250 V to earthexcept in thecase of large power consumers wherethree-phase supply is given. A brief description ofthe type of installations covered in this Section isgiven m 3. It may, however, be noted that lodgingand ro.oming houses, though uti)ized as livingaccommodation for short periods of time (bydifferent occupants) are covered under the scopeof Part 3/Set 5 of the Code.

4.’ GENERAL CHARACTERISTICS OFINSTALLATIONS

4.0 General guidelines on the assessment ofcharacteristics of installations in buildings aregiven in Part I /Set 8 of the Code. For thepurposes of installations falling under the scope ofthis Section, the characteristics defined belowspecifically apply.

0.4 Specific requirements for installations inrooms containing a bath tub or shower ‘basin,namely, bathrooms are separately covered inAppendix A to this Section. These requirementsalso apply to similar locations in otheroccupancies, such as hotels. For convenience,these requirements form part of Section I.

4.1 Environment - The following environmentalfactors shall apply to electrical installations indomestic dwellings:

Environmennr Characrerrsrics(1) (2)

Presence of water Probability ofpresence of wateris negligible

1. SCOPE

1.1 This Section of the Code covers requirementsfor electrical installations in domestic dwellings.

Presence of foreign The quantity orsolid bodies nature of dust or

foreign solid bodiesis not signiticant

2. TERMINOLOGY

2.1 For the purposes of this section, thedefinitions given in Part I/Set 2 of the Code shallapply.

Presence ofcorrosive orpollutingsubstances

The quantity and Applicable for mostnature of of the locationscorrosive orpolluting subs-

except for dwell-ings situated by

tancer is not sea or in industrialsignificant zone in which case

categorizationAF2 applies(see Part I /SW 8)

3. CLASSIFICATION

3.1 The electrical installations covered in thisSection, are those in buildings intended for thefollowing purposes:

Domestic Dwellings/ Residential Buildings -These shall include any buildings in whichsleeping accommodation is provided for normalresidential (domestic) purposes with cooking anddining facilities.

Such buildings shall be further classified asfollows:

Mechanical Impact and vibra- Household andstresses tion of low similar conditions

severity

Siesmic effectand lighting

Depends on thelocation of thebuilding

4.2 Utilization -The following aspects of utili-ration shall apply:

Ulilizarion Characrerisrics Remarksf-1) (2) (3)

Capablity of Uninstructed Applies to ailpersons persons domestic installa-

tions

Contact of persons Persons innormally con-

a) One or Two Family Private Dwelling -These ducting situations

II NATIONAL ELECTRICAL CODE

R e m a r k s(3)

Conditions of Low dcmity occu- Building of normalevacuation during ption, easy con- or low heightemergency. ditions of used for one or two

evacuation. family dwellings

Low dcnsit occu- Apartment houses.hpstion. dl Icult including high-

conditions of rise flatsevacuation

Nature of proce- No significant riskssscd or storedmaterial

5. SUPPLY CHARACTERISTICS ANDPARAMETERS

5.0 Exchange of Information5.0.1 General aspects to be taken note of before

des ign ing the elect r ica l ins ta l la t ion areenumerated in Part I/Set 7 of the Code.However, the following points shall be notedparticularly in respect of domestic dwellings.

5.0.2 Before starting wiring and installation offittings and. accessories, information should beexchanged between the owner of the building orarchitect or electrical contractor and the locdlsupply authority in respect of tariffs applicable,types of aeach P

paratus that ma be connected undertarif ? requirement o? space for mstallmg

meters, switches, servicelines, etc, and for totalload requirement of lights, fans and power.

5.0.3 While planning an installation,consideration should be given to the anticipatedincrease in the use of electricity for lighting,general purpose socket+utlet, kitchen, heating,etc. It is essential that adequate provision shouldbe made for all the services which may berEqutred immediately and during the intendeduseful life of the building, for the householdermay otherwise be tempted to carry out extension

i of the installation himself or to rely upon use ofmultiplug adaptors and long flexible cords, bothof which are not recommended. A fundamentallysafe installation may be rendered dangerous, ifextended in this way.

5.0.4 Electrical installation in a new buildingshould normally begin immediately on thecompletion of the main structural building work.For conduit wiring system, the work should startbefore finishing woik like plaster.ing has begun.For surface wiring system, however, work shouldbegin before final finishing work like whitewashing, painting, etc. Usually, no installationwork should start until the building is reasonablyweatherproof, but where electric wiring is to beconcealed withirl the structures, the necessaryconduits and ducts should be positioned after theshuttering is in place and before the concrete ispoured, provision being made lo protect conduitsfrom damage. For this purpose, sufficientcoordination shall be ensured amongst thecoqcerned parties.

5.1 Branch Circuits

5.1 .l fitimation of Load Requirements - Theextent and form of electrical installation indomestic dwellings is basically designed to caterto light and fan loads and for electrical appliances‘and gadgets. In estimating the.. current to becarried by any branch circuit unless the actualvalues are known, these shall be calculated basedon the following recommended ratings:

Irem RetwmmendedRaring (in Watts)

Incandescent lamps 60

60loo

Fl~ore&ent tubes: ’Length 600mm 25

I2OOmmI5OOmm ;

Power socket outlcc (I5A) loo0

5.1.2 Number of Points in Branch Circuits -The recommended yardstick for dwelling units fordetermining the number of points is given inTable I.

T A BL E I NUMBER OF POINTS FOR DWELLING UNITS

SL DESCRIPTION A REA OF THE M A I N

No. D W E L L I N G U N I T (ml) .*35 45 55 85 140

(1) (2) (3) (4) (5) (6) t7)

I. Light points2. Ceiling fans 2-i 3_; ;_; ;: ;_;

(see Nom below)3. 5A Socket outlets 2 3 4 5 74. ISA Socket outlets - I 2 3 $5. Call-bell (buzzer) - - I I I

N~TE-T~~ tigures in table against SI No. 2 indicate therccommcnded number of points and the number of fans.

Exumple - For main dwelling unit of 55 m2. 4 points with3 fans are reco?mended.

5.1.3 Number of Socket Outlets-The re-commended schedule of socket-outlets for thevarious sub-units of a domestic dwelling are-givenin Table 2.

TABLE 2 RECOMMENDED SCHEDULE OFSOCKET-OUTLETS

DESCRIPTION NUMBER OF SOCKET-OUTLETS

’ 5A*I

ISA ’(1)

BedroomLiving roomKitchenDining roomGarageFor refrigeratorFor air-conditioner

VarandahBathroom

(2) (3)

2 to 32 to 3 :

:2

I i-- 1

(for each)I per IU m2

I f

PART 3 ELECTRICAL INSTALLATIONS IN NON-INDUSTRIAL BUILDINGS

5 . 1 . 4 Select ion of Size of Conductors-Provisions of 3.1.4 of Part I /Set I I of the Codeshall apply.

5.1.5 ‘Power’ sub-circuits shall be kept separateand distinct from ‘lighting-and-fan’ sub-circuit.All wiring shall be done on the distributionsystem with main and branch distribution boardslocated at convenient physical and electrical loadcentres. All types of wiring, whether recessed orsurface should be capable of easy inspection. Thesurface wiring when run along the walls should beas near the ceiling as possible. In all types ofwirings due consideration shall be given forneatness and good appearance and safety.

5.1.6 Balancing of circuits in three-wire orp o l y p h a s e i n s t a l l a t i o n s h a l l b e p l a n n e dbeforehand. In each case, it is recommended thatall socket-outlets in a room are connected to onephase. The conductors shall be so enclosed inea r thed meta l o r incombus t ib le insu$tingmaterial that it is not possible to have readyaccess to them. If the points between which avoltage exceeding 250 volts is present are 2 m ormore apart, the covers or access doors shall beclearly marked to indicate the voltage present.

5.1.7 It is recommended to provide at least twolighting sub-circuits in each house. It is alsorecommended that a separate lighting circuit beu t i l i zed’ fFr all external l ighting of steps,walkways, driveways, porch. carpark. terrace, etc,with a master double-pole switch for the sub-circuit in addition to the individual switches.

5.1.8 Wherever the load to be fed is more thanI kW, it shall be controlled by an isolator switchor miniature circuit-breaker.

5.2 Selection of Wiring - Any one of thefollowing types of wiring may be used in aresidential building (see Set I I, Part I of theCode).

a) Tough rubber sheathed or PVC insula-ted PVC sheathed wiring on wood batten,

b) PVC insulated wiring in steel/non-metallicsurface conduits, and

c) PVC insdlated wiring in steel/non-metallicrecessed conduits.

However, if aesthetics is the mainconsideration, recesged conduit wiring system maybe adopted.

The wiring for 15 A plug outlets (powerGircuits) shall invariably be carried out either insurface/ recessed conduit wiring system wheregenera1 wiring is on wood batten.

Wiring for staircase lights and garage lightsmay be done in recessed conduit wiring systems.

6. SWITCHGEAR FOR CONTROL ANDPROTECTION

6.1 Location

6.1.1 All main switches or miniature circuit-

110

breakers shall be either of metal-clad enclosedpattern or of any insulated enclosed pattern whichshall be fixed at close proximity to the point ofentry of supply.

6.1.2 Open type switch boards shall be placedonly in dry situation and in well ventilated rooms.They shall not be placed in the vicinity of storagebatteries and exposed to chemical fumes.

6.1.3 Main switch boards shall be installed inrooms or cupboards having provision for lockingso a s t o s a f e g u a r d a g a i n s t opera t ion byunauthorized persons.

6.1.4 In a damp s i tua t ion o r whereinflanimable or explosive dust, vapour or gas islikely to be present, the swi!ch boards shall betotally enclosed or made flame-proof as may benecessitated by the particular circumstances.

6.1.5 Switch boards shall not be erected abovegas stoves or sinks or within 2.5 m of any washingunit in the washing room.

6.1.6 Switch boards, if unavoidably fixed inplaces likely to be exposed to weather, to drip, orto abnormal moist atmosphere, their outer casingshall be weatherproof and shall be provided withglands or bushings or adopted to receive screwedconduit according to the manner in which cablesare run. PVC and double flanged bushes shall befitted in the holes of the switches for entry andexit of wires.

6.1.7 A switch board shall not be installed sothat its bottom is within I.25 m alone the. floor,unless the front of the switch board is completelyenclosed by a door, or the switch board is locatedin a position to which only authorized personshave access.

6.1.8 Where so required, the switch boardsshall be recessed in the wall. The depth of recessprovided at the back for connection and the spaceat the front between the switchgear mountingsshall be adequate.

6.1.9 Equipments which are pn the front of aswitchboard shall be so arranged that inadvertantpersonei contact with live parts is unlikely duringthe manipulation of switchgears, changing offuses or similar operations.

6.1.10 No mounting shall be mounted within2.5 cm of any edge of the panel and no hole otherthan the holes by beans ~,f which the panel isfixed shall be drilled closer than 1.3 cm from aPyedge of the panel.

6.2 General Requirements of Switchboards

6.2.1 The various live parts, unless they areeffectively screened by insulating material shall beso spaced that an arc cannot be maintainedbetween such parts and earth.

The arrangement of the gear shall be such that’they sha l l be read i ly access ib le and theirconnections to all instruments and apparatus shallalso be traceable.


6.2.2 In every case in which switches and fusesare fitted on the same pole, these fuses shall be soarranged that the fuses are not alive when theirrespective switches are in the ‘off’ position.

6.2.3 No fuse other than fuses in instrumentcircuit shall be fixed on the back of or behind aswitchboard panel or frame.

6.2.4 All metal switchgears and switchboardsshall be painted prior to erection.

6.2.5 All switchboards connected to mediumvoltage and above. shall be installed in accordancewith 3.1.3.4 of Part 1 /Set 11 of the Code.

6.2.6 The wiring throughout the installationshall be such that there is no break in the neutralwire in the form of a switch or fuse unit.

6.2.7 The neutral shall also distinctly marked.

6.2.8 The main switch shall be easily accessible.

6.3 Types of Switchboards (see also Part I Setll)

6 . 3 . 1 In dwel l ing un i t s , the meta l c ladswitchgears shall preferably be mounted on any ofthe following types of boards:

a)

b)

cl

Hinged-t)pe metal boards ~ Such boardsshall be suitable for mounting of metal cladswitchgear consisting of not more than oneswitchgear and ICDB 4 way or 6 way, I5 Aper way.

Fixed t.\‘pe metal board.y - Such boardsshall be suitable for large switchboards formounting large number of switchgearsand: or higher capacity switchgear.

Wooden hoards --~~ For small installationsconnected to a single phase 240 volts supply,these boards may be used as main board orsub-boards. These shall be of seasoned anddurable wood with solid back impregnatedwith varnish with joints dove-tailed.

Where a board has more than one switchgear,each such switchgear shall be marked to indicatethe section of the installation it controls. Themain switchgear shall be ma’rked as such. Wherethere is more than one main switchboard in thebuilding, each switchboard shall be marked toindicate the section of the installation andbuilding it controls.

6.4 Distribution Boards

6.4.1 Distribution boards shall preferably’ be ofmetal clad type.

6.4.2 Main distr ibution boards shall becontrolled by a linked switchfuse or circuit-breaker. Each outgoing circuit shall be providedwith a fuse on the phase or live conductor.

6.4.3 Branch distribution boards shall becontrolled by a linked switchfuse or circuit-breaker. Each outgoing circuit shall be providedwith a fuse or on the phase or live conductor. The

earthed neutral conductor shall be connected to ac o m m o n l i n k a n d b e c a p a b l e o f b e i n gdisconnected individually for testing purposes. Atleast one spare circuit of the same capacity shallbe provided on each branch distribution board.

6.4.4 Triple pole distribution boards shall notgenerally be used for final circuit distribution.Where use of triple pole distribution boards isinevitable, they shall be of HRC fuse type only.

6.4.5 All distribution boards shall be marked‘Lighting’ or ‘Power’ as the case may be and alsowith the voltage and number of phases of thesupply.

6.4.6 The distribution boards tor light andpower circuits shall be different.

7. SERVICE LINES

7.1 The relevant, provisions of IS : 8061-1976‘Code of practice for design, installation andmaintenance of service lines up to and including650 V’ shall apply.

8. METERING

8.1 It is recommended to have two distinctcircuits, one for lights and fans and the other forhigh wattage (power) appliances particularly whenthe tariff is different for light and power.

8.2 Energymeters shall be installed at such a placewhich is readily accessible to both the owner ofthe building and the authorized representatives ofthe supply authority. These should be installed ata height where it is convenient to note the meterreading, it should preferably not be installed at aheight less than I m from the ground. Theenergymeters should either be provided with aprotective covering, enclosing it completely.except the glass window through which thereadings are noted 01 should be mounted inside acompletely enclosed panel provided with a hingedor sliding doors with arrangement for locking it.

8.3 Means for isolating the supply to the buildingsha l l be p rov ided immedia te ly a f te r theenergymeter.

9. EARTHING IN DOMESTICINSTALLATIONS

9.0 Means shall be provided for proper earthingof all apparatus and abpliances in accordancewith Part I lSec 12 of the Code.

9.1 Plugs and Sockets .- All plugs and socketsshall be of three-pin type. one of the pins beingconnected to earth.

9.2 Lighting Fittings If the bracket type lampholders are of metall ic construction, i t isrecommended that they should be earthed. Allpedestal lamp fittings of metallic constructionshall be earthed.

PART 3 ELECTRICAL INSTALLATIONS IN NON-INDL'STRIAL Bl'ILDINGS III

9.3 Fans and Regulators - Bodies of all tablefans, pedestal fans, exhaust fans, etc, shall beearthed by the use of three-pin plugs. The coversof the regulators, if of metallic construction shallbe earthed by means of a separate earth wire.

TABLE 3 RECOMMENDED LEVELS OFILLUMINATION FOR DIFFERENT PARTS OF

DOMESTIC DWELLINGS

9.4 Domestic Electric Appliances - Bodies ofhot-plates, kettles, toasters, heaters, ovens andwater boilers shall all be earthed by the use ofthree-pin plugs. However, if fixed wiring has beenused, then a separate earth wire shall be used forearthing these appliances.

LCWZAT~ON ILLUMINATIONLEVEL

IUX

9.5 Bath Room -The body of automatic electricwater heaters shall be earthed by the use of athree-pin plug or by a separate earth wire, if fixedwiring has been done. All non-electrical metalwork including the bath fub, metal pipes, sinksand tanks shall be bonded together and earthed.

9.6 Radio Sets - From the point of view of goodreception it is recommended that radio sets shouldbe earthed through an electrode different fromthat of the main earth system for other electricalappliances. However, if it is not possible to haveseparate earth electrode, radio sets may beearthed through the main earth system.

Entrances, hallwaysL.;~mg roomDming roomBedroom :GeneralDressing tables, bed heads

Games or recreation roomTable gamesKitchenKitchen sinkLaundryBathroomBathroom mirrorSewingWorkshopStairsGarageStudy

::150

300200100

E300200

:Ez

::100

70300

10.2 Ak-Conditioning

9.7 Miscellaneous Apparatus - Where appli-ances utilizing gas and electricity are in use,for example, gas-heated electricity-driven washingmachines, the inlet end of the gas supply shall beeither fitted with a strong insulating bush,substantial enough to stand a flash test of 3 500 Vand so designed as to be difficult to detach, or,where it is desirable or necessary that metal workin proximity to electrical apparatus be bonded toihe earthed metal work of the latter, as forexample, in kitchens, the gas supply shall beintroduced through a non-conducting plastic pipefrom a point not in proximity to earthed metalwork. Where separation is not easily achieved, forexample, as in cases of direct-coupled motor-driven 4as boosters and motorized gas valves, themetal work of the electrical equipment, shall bebonded to the metal or pipework of. gasequipment. In such cases the addition to themotor control gear of a differential or current-balance type of circuit-breaker, designed tooperate at low values of fault current, wouldafford a desirable safeguard against fault currenttransfer specially where the rating of the plant isof a s ize and capaci ty which enta i lscorrespondingly high ratings for the normaloverload protective devices.

10.2.1 The general rules laid down in Partl/Set 14 of the Code shall apply. For domesticdwellings, by and large, the following types of air-cooling equipment are used:

a) Evaporative cooler>,b) Packaged air-conditioners, andc) Room airconditioners.10.2.2 The power requirements, layout and

design of electrical installation shall take intoaccount the number and type of such equipment.10.3 Lifts

10.3.1 Whenever lifts are required to beinstalled in residential buildings, the general ruleslaid down in Part 1 /Set 14 of the code shallapply. However, the design of lifts shall take intoaccount the following recommendations.

10.3.1.1 Occupant load - For residential(domestic) dwellings, the occupant load (thenumber of persons within any floor area)expressed in gross area in mZ/person shall not beless than 12.5.

The refrigerators, air-conditioners and coolers,electric radiators, electric irons, etc, shall all beearthed by the use. of three-pin plugs.

103.1.2 Passenger handling capacity (H) -Expressed ;ts the estimated population that has tobe handled m the buildings in the S-minute peakperiod, the passenger handling capacity forresidential’ buildings shall be 5 percent.

103.13 Car speed-Car speed for passengerlifts shall be as follows:

‘10. BUILDING SERVICES a) In low and medium class flats 0.5 m/s,and

10.1 Lighting- The general rules laid down inPart l/‘&c 14 of the-Code shall apply. The choiceof lamps, lighting fittings shall be based on therecommended values of illumination given inTable 3.

b) Large flats (No. of floors served 6- 12) 0.75-I .5ml s.

10.3.2 Where a lift is arranged to serve two,three or four flats per floor, the lift may be placed


adjoining the staircase, with the lift entrancesserving direct on to the landings. Where the lift isto serve a considerable number of flats havingaccess to balconies or corridors, it may beconveniently placed in a *well ventilated toweradjoining the building.

II. FIRE PROTECTION

11.1 The following protection systems arerecommended:

a) One or Two Family Private Dwellings Firedetection: extinguishing systems notrequired.

b) Apurtment Houses/ Flats

i) C/p to 2 storeys N o t r e q u i r e d .

ii) 3 sroreys and ahove

I) Floor area less than 300 m? ~ No trequired.

2) F loo r a r e a m o r e t h a n 3 0 0 m2 --Manually operated electric fire alarm.

12. TESTING OF THE INSTALLATION

12.1 The provisions of Part I /Set IO of the Codeshall apply.

13. MISCELLANEOUS PROVISIONS

13.1 TeleR

honewiring

Wiring ~~ Facilities for telephones all be provided in al l residential

buildings where telephones are likely to beinstalled. In high rise residential buildings, 30cm X I5 cm riser shall be provided for telephonewiring cables.

13.2 Safe ty Requ irements --~ Some of theimportant safety requirements in electricalins ta l l a t ions i n d o m e s t i c d w e l l i n g s a r esummarized below:

a)

b)

cl

d)

e)

f-l

g)

h)

All outlets for domestic electrical appli-antes shall be of three-pin socket type, thirdsocket being connected to the earth.

All the single pole switches shall be on phaseor live conductor only.

The electrical outlets for apphances in thebathrooms shall be away from the shower orsink (see Appendix A).

Wiring for power outlets in the kitchen shallbe preferably done in metallic conduitwiring.

The electrical outlets shall not be locatedabove the gas stove.

The clearance between the bottom mostpoint of the ceiling fan and the floor shallbe not less than 2.4 m.

The metallic body of the fan regulator ifany, shall be earthed effectively.

It is preferable to provide earth leakagecircuit-breaker at the intake of power supplyat the consumer’s premises (see Part I SetI2 of the Code).

13.3 Guidelines on Power Factor Improvement inDomestio Dwellings - General guidelines onprincipal causes of low power factor and methodsof compensation are given in Part I: Set I7 of theCode. For guidance on ‘natural power factoravailable for single phase. appliances andequipment used in domestic dwellings, see Table 3.

TAB1.E 4 POWER FACTOR FOR SINGLE PHASE ELECTRICALAPPLIANCES AND EQUIPMENT

(Clau.\r 13.3)

Sl. APPLIANCL EQUIPMENTNO.(1) 0)

I . N e o n s,gn

2. Wmdow type air-conditioners

3. Hair dryers

4. Liquidiser

5. Mixer

6. Coffee grinder

7. Refrigerator

8. Free7er

9. Shaver

10. Table fan

I I. Ceiling fan

POWFK OUTPllT, h

Minimum Maximum.

(3) (4)(W) (W)

500 5 000

750 2 000;

I50

I 50

I50

200

200

600

x0

25

60

2000

450

350

400

x00

I 000

250

I20

100

AVERAGE N A T U R A L

P O W E R FAC.TOR(5)

0.5 to 0.55

0.75 to 0.850.68 to 0.820.62 to 0.65

0.7 to 0.8

0.8

0.8

0.75

0.65

0.7

0.6

0.5 to 0.6

0.5 to 0.7

(Conrim&)

*Start dropping when compressor motor not in circuit.

PART 3 ELECTRICAL INSTALLATIONS IN NON-INDUSTRIAL BUILDINGS II3

SLNo.(1)

12. Cabin fan13. Exhaust fan14. Sewing machine

IS. Washing machine

16. Radio

17. Night lamp

18. Vac,uum cleaner

19. Tube light

20. Clock

TABLE 4 POWER FACTOR FOR SINGLE PHASE ELECTRICALAPPLIANCES’ AND EQUIPMENT - Conrd

(C/uuse I 3.3)

APPLIANCE/EQUIPMENT

(2)

P OWER O U T P U T

’ Minimum M a x i m u m ’(3) (4)(W) (W)

75 100

I50 350

80 120

300 450

25 100

IO I5

200 450

40 100

5 IO

A V E R A G E NATURAIPOWER FA C T O R

(5)

0.5 to 0.6

0.6 to 0.7

0.7 to 0.8

0.6 to 0.7

0.8

0.6

0.7

0.5

0.9

A P P E N D I X A[Clauses 0.4 and 13.2(c)]

PARTICULAR REQUIREMENTS FOR LOCATIONS CONTAININGA BATH TUB OR SHOWER BASIN

A-l. SCOPE

A-I.1 The part icular requirements of t h i sAppendix apply to bath tubs, shower basins andthe surrounding zones where susceptibility ofpersons to electric shock is likely to be increasedby a reduction in body resistance and contact withearth potential.

A-2. CLASSIFICATION OF ZONES

A-2.1 The requirements given. in this Appendixare based on the dimensions of four zones asdescribed in Fig. I and 2.

Z o n e 0 - is the interior of the bath tub orshower basin.

Zone I -- is limited:

a) by the vertical plane circumscribring thebath tub or shower basin, or for a showerwithout basin, by the vertical plane 0.6 mfrom the shower head; and

b) by the floor and the horizontal plane.2.25 mabove the floor.

Zone 2 - is limited:

a) by Zone I and the vertical parallel plane0.60 m external to Zone I. and

b) by the floor and the horizontal plane 2.25 mabove the floor.

Zone 3 -- is limited:

a) by Zone 2 and the paraltel vertical plane2.40 m external to Zone 2, and

b) by the floor and the horizontal plane 2.25 mabove the floor.

N OTE -The dimensionswalls and fixed partition.

A-3. PROTECTION

are measured taking account of

FOR SAFETY

A-3.1 Where safety extra low voltage is used,whatever the nominal voltage, protection againstdirect contact shall be provided by:

a) barriers or enclosures affording at least thedegree of protection IP2X, or

b) insulation capable of withstanding a testvoltage of 500 V for I minute.

A-3.2 A local supplementary equipotentialbounding shall connect all extraneous conductiveparts in Zones I, 2 and 3 with protectiveconductors of all exposed conductive partssituated in these zones.

A-4. SELECTION OF EQUIPMENT

A-4.1 Electrical equipment shall have at least thefollowing degrees of protection:

ZoneO: IPX7

Zone I: IPX5

Zone21 I P X 4

Z o n e 3 : 1PX I>

IP X 5 in public baths.

A-4.2 In Zones 0, I and 2, wiring systems shall belimited to those necessary to the supply ofappliances situated in those zones. Junction boxesare not permitted in Zones 0, I and 2. In Zone 3,they are permitted if the necessary degree ofprotection is available.

A-4.3 In Zones 0, I and 2 no switchgear andaccessories shall be installed.

NATIONAI. ELECTRICAl. C O D E

A-4.4 In Zone 3, socket-outlets are permittedonly if they are either:

a) supplied individually by an isolatingtransformer, or

b) supplied by safety extra-low voltage, orc) protected by a residual current protective

device.A-4.5 Any switches and socket outlets shall be at

Bath Tub

a distance of at least 0.60 m from door of theshower cabinet.

,A46 In Zone 0, only electrical appliancesspecially intended for use in the bath tub arepermitted.

In Zone 1 only water heaters may be installed.In Zone 2 only water heaters and Class I1

luminaires may be installed.

Z O N E 3

ZONE 1 2.40 m

Shower Basin

[ZONE 1 i ZONE 2 ZONE 3

Shower without Basin but with Fixed Partition

LFIXED PARTITION WALLFIG. 1 ZONE DIMENSIONS (Elevation)

PkRT 3 ELECTRICAL INSTALLATIONS IN NON-INDUSTRIAL BUILDINGS

a) Bath Tub

?f.ffffffff f

IZONEI Z O N E 3

2 IIIII

2.LOn

1’/

_/-_--

c) Shower Basin

e) Shower without Basin

HEAD \

ZONE 3\

YO9

b) Bath Tuh with Fixed Partition

Z O N E 1 Z O N E 3

d) Shower Basin with Fixed Partition

f) Shower without Basin but with, Fixed Partition

fS H O W E R H E A D

FI G. 2 ZONE D IMENSIONS (Plan)


SECTION 2 OFFICE BUILDINGS, SHOPPING AND COMMERCIAL’CENTRES AND

0. F O R E W O R D

INSTITUTIONS

0.1 Office buildings, shopping and commercialcentres can be of various types depending on thesize of the civil structure or the extent of activityinvolved in the building. High-rise buildingshousing office complexes are common, calling fora coordinated planning while designing theelectrical services therein.

0.2 In small buildings with comparativelymoderate loads, supply is normally at mediumvoltage and the distribution of power is lesscomplex. However, in the case of multistoreyedoffice-cum-commercial complex, where the largenumber of amenities is to be provided calls for amore complex distribution system. Some of suchbuildings has to incorporate a standby/emergencypower plant for essential service needs.

0.3 For editorial convenience, and keeping inview the similarity with the type of buildingscovered in this section, educational and otherinstitutional buildings are also covered here.Should any special provisions apply to them, theyare identified at the relevant clauses.

0.4 It is not .possible to define strictly the type ofbuildings covered in this Section except in broadterms, an attempt has been made to identify thena ture of the occupancy . Reference may,however, be made to 3 wherein a description isprovided for the various types of installationscovered in this Section.

1. S C O P E

I.1 This Section of the Code covers requirementsfor electrical installations in office buildings,shopping and commercial centres and educationaland similar institutional buildings.

2. TERMINOLOGY

2.1 For the purpose o f th i s Sec t ion , thedefinitions given in Part I Il Set 2 of the Code shallapply.

3. CLASSIFICATiON

3.1 The electrical installations covered in thissection. are those in buildings intended for thefollowing purposes:

a) Qffice Buildings] Business BuildingsThese include buildings for the transactionof business. for the keeping of accounts andrecords and similar purposes, professionalestablishments, offices, banks. research esta-blishments data processing installations, etc.

b) Shopping/ Comtnercial Centresj Mercantile6uiltling.s ~~ These include buildings used as

cl

shops, stores, market, for display and sale ofmerchandise, wholesale or retail, depart-mental stores, etc.

Educational Buildings - These includebuildings used for schools, colleges and day-care purposes for more than 8 hours perweek involving assembly of people for ins-truction and education (including incidentalrecreation), etc.

NOTE Larger assembly buildings recreationaloccupancies are covered in Part 3 Set 3 of theCode.

4. GENERAL CHARACTERISTICS OFINSTALLATIONS

4.0 General guidelines on the assessment ofcharactuistics of installations in buildings aregiven in Part I /Set 8 of the Code. For thepurpose of installations falling under the scope ofthis Section the characteristics defined b e l o wgenerally apply.

4.1 Environment - The following environmentalfactors shall apply to office buildings, shoppingand commercial centres and educational/institu-tional fluildings:

Presence ofwater

Presence offoreign solidbodies

Presence ofcorrosive orpolluting subs-tances

Mechanical>t rc5\e\

C‘horacrerrsrrc.~ Remarks(2) (3)

Probability ofpresence ofwater isnegligible

The quantity ornature of dust orforeign solidbodies IS notsignificant

The quantity and Locations wherenature of corro- some chemicalsive or nollutine oroducts aresubstances is not handled in smallsignificant quantities. (for

example. labo-ratories in schoolsand colleges) willbe categorired asAF3. For officeand other buildingscovered by thisSection situated b)the se;, or in indus-trial Tones. produc-ing serious pollu-tion. the categoric-ation A F 2 applies(WP Part 3 See 8).

Impact and vlbra-tion of IOULererlt!

Sekmlc effect andlightning

Depends on thelocation ol thebuilding

PART 3 EI.C:CTRICAI. INSTALLATIONS IN NON-INDUSTRIA’L BUILOIN(;S II7

4.2 Utilization - The following aspects of utili-zation shall apply:

Urilizorion Chorocrerisrics Remarks(1) (2) (3)

Capability of Uninstructed A major percentagepersons persons of occupants

Children Applies to schoolsPersons adequa- Applies lo areastely advised or such as buildingsupervised by substations and forskilled persons operating and

maintenance staff

Contact ofpersons

Persons in non-conductingsituations

Conditions ofevacuationduring emer-gency

Low density occu- Small offices andpation. easy shopsconditions ofevacuation

High density Departmentaloccupation. diffi- storescult conditionsof evacuation

High density High rise officeoccupation. diffi- commercial centres.cult conditions of undergroundevacuation shopping arcades.

etc

Nature of proces- No significant risk Small shopssed or storedmaterial Existance of fire In view of large

risk volume of paperand furniture (forexample, officebuildings. furni-ture shops. etc)

5. SUPPLY CHARACTERISTICS A N DPARAMETERS


5.0.1 Proper coordination shall be ensuredbetween the architect. building contractor and theelectrical engineer on the various aspects ofinstallation design. From the point of view of thedesign of the various installations. the followingshall be considered:

a)

b)

Cl

4

e)

f-l8)h)

Maximum demand and diversity,

Type of distribution system. mains andsub-mains,

Nature of supply (current, frequency, nomi-nal voltages),

Prospective short-circuit current at thesupply intake point.

Division of the installation,

Nature of the external influences (see 4),

Maintainability of the installation.

Nature and details of building services,

I ) Lighting.

5.1.3 In offices and showrooms, the interiordecoration normally include false ceiling, carpetsand curtains. Any wiring laid above the falseceiling should be adequately protected such as bydrawing the wires in metallic conduits and not runin open. Wires shall not be covered by carpets.They shall be run at skirting level and encased formechanical protection.

5.1.4 Adequate number of socket-outlets shallbe provided for electrically operated officemachines such as electric typewriter, calculators,etc. to avoid trailing of wires and use of multipleoutlets from one socket.

5.1.5 Areas where corrosive or pollutingsubstances a re p re sen t in te rmi t ten t ly orcontinuously, such as school laboratories andother buildings located in high industrialpollution zones, socket-outlets shall preferably beof metal clad weatherproof type with covers.

2) Air-conditioning. and

3) Lifts.5.1.6 Lighting circuits shall preferably be

combined in switched groups so that lighting can

118 N A T I O N A L EI.Efl R ICA; . CODE

j)

k)

m)n)

P)A

Other details as relevant such as, pumps forfire fighting, lighting, fire-alarm systems,telephones, call-bells, clock systems, etcN OTE -- Five protection system shall include suchdetails such as locations of detectors, zonal indicators,central conrrol console, public address system for firefighting, cable runs and their segregation from theother cable system.

Telephone circuits including extensions andintercom. facilities,

CCTV for information display and security,

zb;pu;;d installation facility where appli-

Metering system for different loads.

complete drawing of layout of the electrical.installation shall be prepared together withassociated floor plans indicating the detailsmentioned in (a) to (p) above. The wiring diagramshall include outlets for lights. sockets, bells,ceiling fans, exhaust fans, location of section-alized control switches, distribution boards,etc. In special occupancies such as school orcollege laboratories, the dc circuits be identifiablein the layout diagram.

5.1 Branch Circuits5.1.1 The general design of wiring of branch

circuits shall conform to those laid down in Partl/Set II of the Code. However, for special casessuch as for communication networks, fire-alarmsystem and wiring for data-processing equipment,the recommendations of the manufacturer shallapply.

5.1.2 The branch circuit calculations shall bedone according to the general provisions laiddown in Part 3/Set I of the Code. However, thespecific demands of the lighting, appliance andmotor loads as well as special loads encourtpredin the types of buildings covered in this Sectionshall be taken into account.

be limited to desks which are occupied.

5.2 Service Lines -The general provisions laiddown in IS : 8061-1976* shall apply.

5.3 Building Substations

5.3.0 General- The designer of power supplyfor office buildings and commercial centres shalltake into account the great concentration ofpower demand of the electrical loads. Air-conditioning in office buildings absorbs anespecially high proportion of the total powerused. Consequently, such occupancies have to beprovided with their own substation with verticaland horizontal forms of power distribution.

5.3.1 If the load demand is high, requiringsupply at high voltage, accommodation forsubstation equipment will be #required. Mainswitch room will serve feeders to various lpadcentres such as air-conditioning plant, elevators,water pumps, etc. Other loads are taken to localdistribution boards.

5.3.2 The transformer power rating for thesupply of the building shall be sufficient to caterto the highest simultaneous power requirementsof the building. Typical proportions of powerusage are given below:

Purl of Elerrrrc~alin ~rallaritin

Parr qf the DiversirjToral Power FactorRequirement

Percent

Ventilation. heating 45 I .o(air-conditioning)

Power plant (drives) 5 0.65Lighting 0.95Lifts :: I.0

5.3.3 The location and layout of buildingsubstation shall conform to the general rules laiddown in Part 2 of the Code. The substation roomshall be well ventilated and inaccessible to birdsand reasonably reptile-, rodent- and insect-proof.Only authorized persons be allowed to enter thesubstation for operations/maintenance of anykind.’ Cables leading from the substation to themain-building shall preferably be carriedunderground through ducts or pipes of adequatedimensions. Such pipes shall be properly sealed atboth ends to reduce the possibility of rain waterflowing through the pipes and flooding thetrenches.

5.3.4 E m e r g e n c y Supply - Whereveremergency supply is considered necessary,, it canbe in the form of separate and independent feederfrom the undertaking terminated in equipmentisolated from the regular supply line. In case ofstandby supply from diesel generator sets, a wellventilabed cabin segregated from the utility’ssupply shall be provided.

5.3.4.1 In office buildings, certain safety andessential services shall be supplied even in the case

*Code of practice for design. installation and maintenanceof service lines up to and including 650 V

of mains failure. These are governed by the rulesand regulations of the respective authorities.Essential services include amongst others, water-pressure pumps, ventilation installations, essentiallighting and lifts. The power requirement of theseessential loads is generally about 25 percent of thetotal power requirement of the building.

5.3.5 Switchboard9 and Panel. Boards - Allcurrent carrying equipment ishall he totallyenclosed, ‘dust- and vermin-proof and if mountedoutdoor, Shall be of weatherproof onstruction or

1housed in weatherpro0.f k ios or cabin.Switchboards shall be of open type or cubicletype. Cubicle type boards shall be with hingeddoors interlocked with switch-operatingmechanisms. All switches shall bear labelsindicating their, functions. Switchboards shall belocated away from areas (likely to be crowded bythe public.

5.3.6 Selection of equipment shall be madeaccording to the guidelines laid down in Part I/Set 9 of the Code. For the purposes of officebuildings, shopping and commerctal centres,miniature circuit-breakers of adequate capacityshall be preferred to switchfuse units. They canalso be effectively used in place of fuses in adistribution board.

5.4 MeterinB- In multistoreyed buildiggs, a

number of o rices, and commercial centres occupyvarious areas. Electrical load for each of themwould have to be metered separately; the-meter-room normally is situated in the ground floor.

5.5 System Protection

5.5.0 Genera/ - The general rules .forprotection for safety laid down in Part I/Set 7 ofthe Code shall apply. Reference is also drawn toSP : 7-1983 on guidelines for fire protection ofbuildings. The general rules given below shallapply.

5.5.1 The type of buildings covered in. thisSection fell under Group B (educattonalbuildings), Group E (business buildings) andGroup F (mercantile buildings) from the point ofview of fire safety classification (see SP : 7-1983).Typical fire fighting installation requirements arealso covered therein. The electrical needs for theappropriate type of installation shall, therefore, bedecided accordingly.

5.5.1 .I Educational buildings (Group B) -Educational buildings above 2-storeys having anarea of more than 500 ml per floor shall havebesides fire-fighting equipment, manuallyoperated electrical fire alarm and automatic firealarm systems.

5.5.1.2 Business buildings (tiroup E) -Besides fire-fighting equipment. automatic firealarm systems are recommended for offices,banks, professional establishments. etc. where thebuildings are more than 2 storeys with floor areaabove 500 rn? per floor, and for laboratories with

PART 3 ELECTRIC-AI. INSTALLATIONS IN NON-INDUSTRIAL BUILDINGS II9

1 f. “.

de l i ca te ins t ruments as we l l as compute rinstallations.

5.5.1.3 Mercantile buildings (Group n’ ~Besides f i re- f ight ing eyuipment, automat icsprinklers and automatic fire alarm systems arerecommended for wholesale establishments,warehouses, transport booking agencies, etc. aswell as for shopping areas inside buildings witharea more than 500 rn? on each floor. For otherpremises and shopping lines with central corridorsopen to sky, automatic fire-alarm systems shall beinstalled. Underground shopping centres shall beprovided with atitomatic sprinklers.

5.6 Building Services

5.6.1 Lighting

5.6.1.1 -The general rules laid dotin in Part

I/Set I4 of the Code shall apply. The choiceof lamps. lighting fittings and general lightingdesign together with power requirement shall beplanned based on the recommended values ofil!umination ;lnd l im i t ing values of plarc i n d e xgiven in Table I.

5.6.1‘2 In commercial premises, a fairly highlevel of glare free lighting on working planes andsubdued l i gh t i ng i n circulat ion areas arenecessary. Asthetics and interior decoration alsoplay a part. L.ighting des ign i n showroomsincludes high level c,f lighting in the vertical andhorizontal planes. depending on the merchandiseexhibited. and their layout. Colour temperaturecharacteristics of the light source shall also betaken into account in the case of showroomlighting.

TABLE I RECOMMENDED VALUES OF l1.1~UMINATlON

S L BUILI)INGNo.(1) (2)

I. Banks :a) Counters. typing accounting book areasb) Public areas

2. Libraries :a) Shelvesb) Reading rooms (newspaper. magazines)c) Readirig tablesd) Bodk repair and bindinge) Catalogging. sorting. stock rooms

3. Offices :a) Entrance halls and reception areab) Conference rooms, executive officesc) General officesd) Business machine operatione) Drawing officesf) Corridors and lift carsg) Stairsh) Lift landingsj) Telephone exchanges:

i).Manual exchange rooms (on desk)ii) Main distributton frame room

4. Schools and collenes :a)

b)

Assembly halls-i) General

ii) When used for examsiii) PlatformsClaSs and lecture rooms :

i) Desksii) Black boardEmb&idery and sewing roomsArt roomsLibrariesManual training

OfficesStaff rooms. common roomsCorridorsStairs

A N D G L A R E INDKX

ILLUMINATION ~.IMl?lNGGI ARt. INIWX

(3) (4)IUX

300 I9IS0 I9

70 to 150150 to 300 19300 lo 700 22300 lo 700 22I50 to 300 I9

I50300 19300 I9450 I9450 16

70 -IFl - -

200I50 ::

I50 I6

:zz It

300 I6200 to 300

:: lo 16(see SI No. 2 above)

(see appropriate trades in1:&3&G? (Part 2)-19y9*)

150 I9

1; - -

5. Shops and Storest :a) General areas I50 to 300b) Stock rooms 200 ::

*Code of practice for interior illumination: Part 2 Schedule for value of illumination and glare index.tDoes not cover display (showroom lighting).

NATIONAL ElJX-TRICAl, CODE

56.2 Air-Conditioning 6. TESTING OF INSTALLATION

5.6.2.1 The general rules laid down in Partl,‘Sec 14 of the Code shall apply. The design ofthe air-conditioning system, shall take intoaccount the requirements st ipulated in thefollowing clauses.

6.1 The various tests on the installation shall becarried out as laid down in Part I See IO of theCode.

7. MISCEI,LANEOUS PROVISIONS5.6.2.2 In case of large air-conditioning

installations (So0 tonnes and ahove) it is advisableto have a separate isolated equipment roomtogether with electrical controls. All equipmentrooms shall have provision for mechanicalventilation.

7.1 Group Control

5.6.3 Lifts and Escalators

5.6.3.1 The general rules laid down in PartIiSec 14, of the Code shall apply. However, thedesign of l ifts shall take into account thefollowing recommendations.

5.6.3.2 Occupant load- These shall be asfollows:

7.1.1 The lighting circuits shall preferably becombined in swi tched g roups as we l l a scoordinated to functional groups of desks in anopen plan office. The switching points may becombined centrally at the entrance, passageways.In order to ensure proper coordination withdesign of the building for daylight use of devicessuch as photoelectric switches shall be encouragedfor controlling lighting groups near windows.

7.2 Telephones/Intercoms

7.2.1 Adequate coordination shall be ensuredright from the planning stages with the telephoneauthorit ies to determine the needs for thetelephone system catering to the various units inoffice buildings. For private intercom systems,entirely under the control of the user, it isnecessary to preplan the coordination of externaland intercom systems.

a) Educational

b) Business

4

IO

c) Mercantile :i) Ground floor and sales

ii) Upper sale floor

5.6.3.3 Passenger handling capacit.\, ( H) --These are expressed in terms of percent of theestimated population that has to be handled inthe building in the 5 minute peak period asfollows:

Ouupanc~t II

a) Diversified (mixed) ol’f~ce IO-15 percentoccupancy

b) Single purpose office 15-25 pcrccntoccupancy

5.6.3.4 Car speed -. These shall be as follows:

0tTice bullding

Shops and depart-mental atorea

4-56- I 2

13-20

0.5-0.750.75-1.5above I.5

2-2.5

5.6.3.5 For office buildings.’ it is desirable tohave at least a battery of 2 lifts at two or moreconvenient points. If this is not possible. it isadvisable to have at least two lifts side by side atthe main entrance and one lift each at differentsections of the building for inter-communication.When two lifts are installed side by side, themachine room shall be suitably planned. Allmachines and switchgear may be housed in onemachine room.

7.3 Electric Call Bell System

7.3.1 The general guidelines laid down in PartI/ Set 14. regarding installation of electric bellsand call system shall be referred to. Depending onthe final requirements of the type of occupancy,the type of equipment to be used, wiring andother details shall be agreed to.

7.3.2 A simple call bell system is suitable forsmall offices whereb,y service staff may be calledto a particular position by the caller. A visible-cum-audible indicator/bell panel shall be used.When call points are too numerous on a singleindicator panel, such as in large offices, multiplecall system shall be preferred. The layout in sucha case would be determined by the size of buildingand staff. Time bell systems shall be installed inschools to give Start-work and Stop-work signals.

7.4 Clock Systems

7.4.1 The general guidelines contained in Partl/Set I4 shall apply regarding installation andmaintenance of master and slave clock systems.

7.4.2 In simple installations, impulse clocksdesigned to operate at the same current may beconnected in one series circuit, with a batteryhaving sufficient voltage to ensure satisfactoryoperation. In a more complex installation likemultistoreyed office buildings with large numberof slave clocks, the impulse clocks may bearranged in number of series circuits. Each ofwhich is connected to a pair of contact on a relaywhich is operated from the contacts of masterclock.

PART 3 ELECTRICAl INSTALLATIONS IN NON-INDIISTRIAL Bl:II.DINGS 121

7.4.3 Master clock shall be placed in a dust free following purposes:location, readily accessible for maintenance at alltimes. a) Security, and

b) Information display.

7.5 Closed Circuit T V Educational/institutional buildings may useCCTV as a teaching aid for pre-recorded

7.5.1 Commercial buildings may require the educational programmes. Reference shall be madeinstallation of CCTVs for one or more of the to good practice for installation of such facilities.


SECTION 3 RECREATIONAL, ASSEMBLY BUILDING!5

& F O R E W O R D

0.1 A variety of buildings are being used forpublic a s s e m b l y f o r p u r p o s e s t h a t a r erecreational, amusement. social or religious.These include cinema halls, theatres, auditoriaand the l ike. the primary feature being acongregation of people of all age groups for ashort period of ‘time during a day or a group ofdays. Buildings such as those catering to displayof regular programmes demands a continuouspower supply. In view of the nature of use of suchoccupancies. certain specific safety and reliabilityconsiderations become necessary for the electricalinstallation.

0.2 The lighting design of such buildings aregenerally sophisticated, required to be properlycoordinated with the electro-acoustic demands.On the physical aspects of lighting and soundsystems in rec rea t iona l bu i ld ings , it isrecominended that assistance should be derivedfrom specialists as such details are beyond thescope of this Code.

0.3 Sports buildings. which are also basicallyassembly buildings. are covered separately underPart 3’ Sec. 6 of the Code, in view of their uniquenature. The type of buildings covered in thisSection are enumerated in 3. It shall also be notedthat assembly buildings forming part of otherbuilding complex, say, educational or office-commercial-curzl-cinema complex sha l l a l socomply with this Section.

1. SCOPE

1.1 This Section of the Code covers requirementsfor electrical installation in buildings, such asthose meant for recreational and assemblypurposes.

I.2 This Section does not cover sports buildings.

2. TERMINOLOGY

2.1 For the purposes of this Sec t ion , thedefinitions given in Part I ‘Set 2 of the Code shallapply.

3. CLASSIFICATION

3.1 The electrical installations covered in thisSection, are those in buildings intended for thefollowing purposes:

Assetnhl!~/ Recreational Buildings ~~ These shallinclude any building where groups of peoplecongregate or gather for amusement, recreation,social, religious, patriotic, civil and similarpurposes, for example, theatres, motion-picture(cinema) houses, assembly halls, auditoria,exhibition halls, museums, restaurants, places ofworship, dance halls, clubs, etc.

4.1 Environment - The following environmentalfactors shall apply to recreational an’d assemblybuildings:

&n~Vro,1meJ,r(1)

Presence ofwater

Characrerbrics(2)

Probability ofpresence ofwater negli-gible

Remarks(3)

Presence offoreign solidbodies

The quantityor nature ofdust or foreignsolid bodies isnot significant

-

Presence ofcorrosive orpolluting sub-stances

The quantityand nature ofcoirosiveor pollutingsubstances isnot significant

Mechanicalstresses

Impact and vib-ration of lowseverity

Seismic effectand lighting


NOTE -- Theatres .are also classified further as permanent(air-conditioned and non-airconditioned), temporary ortravclling depending on the nature or construction of thepremises. Temporary installations shall also conform lo theadditional provisions laid down in Part S/SK 2 of the Code.


4.0 General guidelines on the assessment ofcharacteristics of installations in buildings aregiven in Section 8, Part 1 of the Code. For t h epurpose of installations falling under the scope ofthis section the characteristics defined belowgenerally apply.

4.2 Utilization - The following a s p e c t s o futilization shall apply:

Uriliiarion(1)

Capacity o fpersons

Condition\ ofevacuation du-ring emer-gency

Nature ofprocessed orstored material

Characteri.stics(2)

Uninstructedpersons

Persons ade-quately advi-sed or super-vised by skilledpersons

High densityoccupation.easy conditionsof evacuation

High density. Multiple cinemadifficult con- halls, cultural

dltions o f and theatricalevacuation buildings

Existence offire risk

Remarks(3)

Majority of the0ccupant.s

Electrical ope-rating areas

Small thcatresand cinemas

In view of largequantum offurniture anddrapings

PART 3 ELECTRICAL INSTALLATIONS IN NON-INDI:STRIAL BUILDINGS 123


5.0. Exchange of Information

5.0.1 Proper coordination shall be ensuredbetween the architect, building contractor and theelectrical engineer on the various aspects of theinstallation design in a building intended forrecreational or assembly purposes. For largeprojecis, the advice of the appropriate specialistsshall be obtained, in particular on the followingaspects:

a) Audio-visual systems,

b) Stage lighting and control, and

c) General auditorium lighting and otherspecial service needs.

5.0.2 The installation work shall conform tothe provisions of Indian Electricity Rules as wellas other Rules applicable for assembly buildingsformulated by the State Authorities.5.1 Branch Circuits

5.1.0 The branch circuits shall-in general caterto the following individual load groups:

a) Power installation:

i) Stage machinery,

ii) Ventilation and air-conditioninginstallation,

iii) Lifts, and

iv) Additional power connections.

b) Lighting:

i) In front of the theatre, such as generallighting of outdoor, foyer, corridors andstairs, and auditorium; and

ii) In the rear of the theatre for stage, workplace dressing rooms. workshops andstorehouses.

c) Emergency supply.

5.1.1 The electrical l ighting of the mainbuilding shall have atleast three separate anddistinct main circuits as follows:

a) For the enclosures (cabin) and hencethrough a dimmer regulator to the centrallighting of the auditoriurp;

b) For one half of the auditorium, passageways. stairways, exit and parts of thebuilding open to the public; and

c) For the remaining half of the auditorium,passage ways, stairways, exit and parts ofthe building open to the public.

5.1.2 The control of the circuits in respect ofthe two halves of the auditorium referred toin 5.1.1 shall be remote from each other.

5.1.3 The cabin shall be provided with twoseparate circuits . o n e f e e d i n g t h e c a b i n

equipments and the other lights and fans.

5.1.4 Wiring shall be of the conduit type. Endsof conduits shall enter and be mechanicallysecured to the switch. control gears, equipmentterminal boxes. etc. Ends of conduits shall beprovided with screwed bushes. Within theenclosure, all cables shall be enclosed in screwedmetal conduits adequately earthed. PVC conduitsmay be used in the auditorium and other places.

5.1.5 Temporary wiring shall not be allowed incabin, rewinding room, queue sheds and similarplaces.

5.1.6 The cabin equipment shall be accessibleat all times. Nothing shall impede access to anypart of the equipment or its controls.

5.1.7 Linked tumbler switches shall not be usedfor the control of circuits.

5.1.8 Branch and main distribution boardsshall be mcunted at suitable height not higherthan 2 m from the floor level. A front clearance ofI m ‘should alsd be provided.

5.1.9 Wood work shall not be used ‘for t‘hemounting of or construction of the framework foriron-clad switch and distribution boards andcontrolgear.

5.1.10 All the lighting fittings shall be at aheight of not less than 2.25 m.

5.1.11 The single pole switches for theindividual lights and fans shall be mounted onsheet steel boards suitably earthed.

5.1.12 Suitable socket outlets with controlsshall be provided on the side walls near the stagefor tapping supply to screen motor; stagefocussing lights, audio systems and portablelights.

5.1.13 In the queue sheds. bulk head fittingsshall be used.

5.1.14 For outdoor lighting, water-tight fittingsshall be used and fittings may be so mountedwithout spoiling the aesthetic view of therecreation buildings.

5.1.15 The installation in a travelling cinemashould genera l ly c o n f o r m t o t h e a b o v erequirements a n d t h e b u i l d i n g s h o u l d b esufficiently away from the near? conductor ofpower lines (.Y(Y 2.2 of Part I I Set 7 of the Code).

5.1.16 The plug points shall be provided at aheight of about 1.5 m from the floor, in assemblybuildings.

5.1.17 In case of travelling cinemas, the wiringfor the ‘open yard lighting shall be done withweather-:proof cables threaded through porcelainreel insulators suspended by earthed bearer wireat a height of not less than 5 m from ground level.The reel insulators shall be spaced 0.5 metresfrom each other.

5.1.18 When a tapping is taken from the openyard wiring, it should be taken only at a point of


support through-porcelain connectors housed in ajunction box, fixed to the supporting pole.

5.2 Feeders

5.2.1 Feeder circuits shall generally conform tothe requirements laid down in Part I /Set I1 ofthe Code.

5.2.2 Separate feeders shall be taken to air-conditioning units, lifts and the lighting and fancircuits.

5.3 Service Lines - Service lines shall conform tothe provisions laid down in IS : 8061-1976*

5.4 Building Substation

5.4.0 The electrical power demand of anassembly building can vary from 30 kVA to morethan I 000 kVA according to the, size of thebuilding. Usually, supply at voltages above I kV isgiven for large theatres and auditoria. Buildingsubs ta t ions sha l l conform to the genera lrequirements specified in Part 2 of the Code.

5.4.1 The following aspects shall be taken .noteof while deciding the location of substation:

a)

b)

c)

As the re wi l l be concen t ra t ion andmovement of people. the substation shouldbe located away from the area where peopleand vehicles move about, preferably at therear of the building.

The substation should not be in the way ofpeople and fire-fighting vehicles andpersonnel where they are -likely to attend toan emergency,

It is desirable that the transformer whichcontains a large quantity of oil is not locatedin the basement as there is risk of fire.


5.5.0 The rules for protection for safety laiddown in Part !/Set 7 of the Code shall apply.Reference may also be made to SP : 7-19837 onguidelines for fire protection of buildings. Thegeneral rules given below shall apply.

5.5.1 Tile type of occupancies covered in thisSection fall under Group D (assembly buildings)from the point of view of fire safety classification.Such occupancies can’ be further classified intogroups depending on the capac i ty o f thetheatre/auditorium to hold the congregation (seeSP : 7-1983*). Typical fire-fighting installationrequirements are also covered therein. Thefollowing shall be provided besides fire-fightingequipment:

a) Buildings having atheatrical stage andfixed seats

*Code of practice for design installation and maintenance ofservice lines~ up to and including 650 V

+National Building Code.

i) Stage Automatic sprinkler

ii) Auditoria, corri- Automatic fire-dor, green rooms, alarm systemcanteen andstorage

b) Buildings without a Automatic firestage but no alarm systempermanent seatingarrangement

c) All other structures Manualy operateddesigned for electrical fire-alarmassembly system


5.6.1 Lighting - The general rules laid down inPart I /Set 14 of the Code shall apply. The choiceof lamps, lighting fittings and /Igeneral lightingdesign together with power r&$nrement shall beplanned based on the recommended values ofillumination and glare index given in Table I.

TABLE 1 RECOMMENDED VALUES OFILLUMINATION AND GLARE lNDEX

SL P A R T OF BU I L D I N G

NO.

(1) (2)I. Assembly and concert:

a) Foyers, auditoriab) Platformsc) Corridorsd) Stairs

2. Cinemas:a) Foyersb) Auditoriac) Corridorsd) Stairs

3. Museums:a) Generalb) Display

4. Art Galleries:a) Generalb) Paintings

5. Theatres:a) Foyersb) Auditoriac) Corridorsd) Stairs

ILLUMI- L I M I T I N G

NATION VALUE OFlux G.LARE INDEX(3) (4)

100-1504 5 0

7 0 -

I00 -

I50

::I00

I50SpecialLighting

I6I6

:iI OI O

I50 -

::-

100 -

NOTE - The above is meant for general guidelines apd doesnot include special lighting effects.

5.6.2 Air-Conditioning

5.6.2.1 The general rules laid down in Part I/Set I4 of the Code shall apply.

5.6.2.2 In air-conditioned assembly buildings,inside temperature shall be 25.5 k 2.75”C.

5.6.2.3 Provisions shall be made to record thetemperature inside the auditorium.

5.6.2.4 In the event of a breakdown of the air-conditioning plant, alternate arrangements shouldbe available for ventilation and air circulation.

PART 3 ELECTRICAL INSTALLATIONS IN NON-INDlJSTRIAL BUILDINGS 125

5.6.3 Lifts and Escalators -The general ruleslaid down in Part I /Set 14 of the Code shallapply. However, the design of the lifts shall takeinto account the following recommendations:

a) Occupant load- This shall be as follows:

Occupancy, Occupant Load,Gross Area in

m2/ Person

Assembly halls with fixedor loose seats and dancefloors

0.6

Without seating facilities 1.5including dining rooms

b) Passenger handling capacity and carspeed - As given in Part 3/Set 2.

6. TESTING OF INSTALLATION

6.1 The various tests on the installation shall becarried out as laid down in Part l/Set IO of theCode.


7.1 Emergency Supply - See also Part 2 of theCode.

7.3 Group Contro l --The l ighting in theauditorium shall be suitably combined intocontrol groups to facilitate group switching. Inthe special case of stage lighting control, thelighting operator shall have a good view of thestage in order to be able to follow theperformance. Therefore, the control-room shall besituated in a convenient position.

7 .1 .1 In a l l r ec rea t iona l and assembly 7.4 Audio-Visual ofbuildings, sufficient number of emergency lights

System - Installation

fed from independent source or sources, with theamplifying and sound distribution systems shallconform.to the guidelines contained in Part I,/ Set .

provision for automatic switching-on in case of 14 of the Code.

failure of main’ supply shall be provided.

7.1.2 Depending on the total capacity requiredfor-standby supply for the occupancy. suitablestandby generator set shall be installed. Thelocation of the standby supply shall preferably beon the ground level away from the auditorium sothat noise from the generator reaching theaudience could be minimised. The changeover ofsupply arrangements should be reliable and easyto operate.

7.2 Stage Lighting -On the stage of a theatre, agreat number of spotl ights, border l ights,projectors, etc, are required for illumination,including portable light sources. The variouspossibilities of switching each fittings shall be keptin view while designing the lighting circuits. Forsame lighting schemes, dimmer-control equipmentmay be required.


SECTION 4 MEDICAL ESTABLISHMENTS

0 . F O R E W O R D

0.1 Hospitals in the country vary in size fromsimple premises used for medical purposes invillages to a wekquip’ped, multidisciplinaryhospital in big cities. The latter type will haveseveral units functioning simultaneously with avariety of support services to cater to the needs ofdoctors and patients.

0.2 Safety requirements for electrical equipmen!used in medical practice are covered in IS : 8607(in Parts)*. Additional safety provisions in theelectrical installations of medically used roomsand medical establishments are covered in thisSection of the Code. This Section is based on thefollowing considerations:

b)

c)

d)

d

The patient may not be in a condition’ toreact normally to the effects of hazardousevents;

The electrical resistance of the skin, which isnormally an important protection againstharmful electric currents is bypassed incertain examinations or treatments;

Medical electrical equipment may often beused to support or substitute vital bodyfunctions. the breakdown of which maycause a dangerous situation;

Specific locations in medical establishmentswhere flammable atmosphere exists. callfor special treatment; and

Electric and magnetic interference maydisturb certain medical examinations ortreatments.

0.3 The basic aspects of the safety philosophy forinstallations in hospitals have been standardizedat the IEC Level. These are enumerated in 4. Inthe preparation of this Section considerableassistance has also been derived from IEC 62A(Secretariat) 55 ‘Requirements for electricalinstallations in medical practice’ issued by theInternational Electrotechnical Commission.

1. SCOPE

1.1 This Section of the Code applies to’ theelectrical installations. in medical establishments.This Section is also applicable to rooms forveterinary medicine and dental practice.

2. TERMINOLOGY

2.0 In addition to the definitions contained inPart I/Set 2 of the Code the following shallapply.

*General and safety requirements for electrical equipn nt.d in medical practice (Parts I to 3).

2.1 Rooms

2.1.1 Anaesthetic Room - Medically usedroom in which general inhalation anaesthetics areintended to be administered.

NOTE - Anaesthetic room comprises for instance the actualoperating theatre. operating preparation room. operatingplaster room and surgeries.

2.1.2 Angiographic Examinat ion Room -Room intended for displaying arteries or veins,etc. with contrast media.

2.1.3 Central Monitoring Room - Room inwhich the output signals of several patientmonitors are displayed, stored or computed.

NOTE - A central monitoring room is considered to be partof a Room Group. if a conductive connectlon (for example, bysignal transmission lines) between the rooms of such a groupexists.

2.1.4 Central Sterilization Room - Room, notspatially connected to a medically used room, inwhich medical equipment and utensils aresterilized.

2.1.5 Deliver,* Room - Room in which theactual birth takes place.

2.1.6 Endoscopic Room - Room intended forapplication of endoscopic methods for theexamination of organs through natural orartificial orifices.

Examples o f endoscopic methods arebronchoscopic. laryngoscopic. cystoscopic.gastroscopic and similar methods. if necessary,performed under anaesthesia.

2 .1 .7 Heart Catheterizarion Rooter -~- R o o mintended for the examination or treatment of theheart using catheters.

Examples o f a p p l i e d procedures aremeasurement of ac t ion po ten t ia l s o f thehaemodynamics of the heart. drawing of bloodsamples. in jec t ion of con t ras t agen ts o rapplication of pacemakers.

2 . 1 . 8 Hemoclial~~sis R o o m ---. Room in .amedical establishment intended to connectpatients to medical electrical equipment in orderto detoxicate their blood.

2 . 1 . 9 H.\drorherap.v Roonr -- Koom in n hichpatients are treated by hydrotherapeutlc mcthodh.

Examples of such methods are therapeutictreatments with water. brine. mud. slime. clay.steam, sand. water with gases. brine with gases.inhalation therapy. electrotherapy in water*.massage thermotherapy and thermothcrap!, inwater*

Swimming pools for general use and normalbath-rooms are not considered as hydrotherap!,rooms

‘With or wIthout addfitl\cr

PART 3 ELECTRICAL INSTAI.I.ATlONS IN NON-INDI’STRIAI; Bl’ILDlNGS 127

2.1.10 Intcwsi\v Care Room - Room in whichbed patients are monitored independently of anoperation by means of electromedical equipment.Body actions may be stimulated if required.

2.1.1 I Intensi~~e E.ramination Room - R o o min which patients are connected for the purpose ofintensive examination. but not for the purpose oftreatment, simultaneously to severalelectromedicai measuring or monitoring devices.

2.1.12 Intett.si\y Monitoring Room R o o m i nwhich operated patients are monitored. usingelectromedical equipment. Body actions (forexample. heart circulation. respiration) may bestimulated. if required.

2.1113 Lahour R o o m - R o o m i n w h i c hpatients are prepared (waiting) for delivery.

2.1 .I4 Medical Estahlishmenr -- Establishmentfor medical care (examination. treatment,monitoring, transport, nursing, etc) of humanbeings or animals.

2.1 .I5 Medicall.,, Used Room - Roomintended to be used for medical, dental orveterinary examination, treatment or monitoringof persons or animals.

2.1.16 Minor Surgical Thearre - Room inwhich minor operations are performed onambulant or non-ambulant patients. if necessaryusing anaesthetics or analgesics.

2.1.17 Operating Plaster Room -- Room inwhich plaster of Paris or similar dressings areapplied while anaesthesia is maintained.

NOI1 Such a room helong~ IO the operating room groupand I\ u~uall! \patiall) connected to I I

2.1.18 Operating Preparation Room .- Roomin which patients are prepared for an operation.for example, by administering anaesthetics.

NoIt Such a room belong, to the operaring room groupa n d I\ ,parlally connected IO i t .

2.1.19 Operating Recover,l, Room - Room inwhich the patient under observation recoversfrom the influence of anaesthesia.

NOT k Such a room IS usually very close IO the operatingroom group but not necessarily part of it.

2.1.20 Operating Sterilization Room - Roomin which utensils required for an operation aresterilized.

Nork Such a room belongs 10 the operating room groupand is spatially connected to it.

2.1.21 Operating Thearre - Room in whichsurgical operations are performed.

2.1.22 Operating Wash Room - Room inwhich medical staff at an operation can wash fordisinfection purposes.

Nort Such a room belongs 10 the operating room groupand is spatially connected IO It.

2.1.23 Ph.vsiotherapj, Room - Room in whichpatients are treated by physiotherapeuticmethods.

2.1.24 Radiological Diagnostic Room - Roomintended for the use of ionizing radiation fordisplay of internal structures of the body by.means of radiography or fluoroscopy or by theuse of radio-active isotopes or for other diagnosticpurposes.

2.1.25 Radiologkal Therapy R o o m - R o o mintended for the use of ionizing radiation toobtain therapeutic effects on the surface of thebody or in internal organs by means of X-radiation. gamma radiation or corpuscularradiation or by the use of radio-active isotopes.

2.1.26 Room Group Group of medicallyused rooms linked with each other in theirfunction. by their designated medical purpose orby intcrconnectcd medical electrical equipment.

2.1.27 Urolog.\, Room - R o o m i n w h i c hdiagnostic or therapeutic procedures areperformed on the urogenital tract usingelectromedical equipment. such as X-rayequipment, endoscopic equipment and high-frequency surgery equipment.

2.1.28 Ward - Medically used room or roomgroup in which patients are accommodated’forthe duration of their stay in a hospital, or in anyother medical establishment.

2.2 Zones of Risk --(see also Appendix A).

2.2.1 OFlantntahle Anaesthetic A t m o s p h e r e -Mixture of a flammable anaesthetic vapour

and or a vapour of a flammable disinfection orcleaning agent with air in such a concentrStionthat ignition may occur under specifiedconditions.

2 . 2 . 2 F l a m m a b l e Anaeslheric Mi.rture -Mixture of a flammble anaesthetic vapour with

oxygen or with nitrous oxide in such aconcentration that ignitign may occur underspecified conditions.

2.2.3 Zone G - Volume in a medically usedroom in which continuously or temporarily smallquantities of flammable anaesthetic mixtures maybe produced, guided or used including thesurroundings of a completely or partly enclosedequipment or equipment part up to a distance of 5cm from parts of the equipme,nt enclosure whereieakage may occur because such parts are:

- unprotected and liable to be broken,- subject to a high rate of deterioration, or- liable to inadvertent disconnection.

Where the leakage occurs into anotherenclosure which is not sufficiently (naturally orforcedly) ventilated and enrichment of the leakingmixture may occur, such an enclosure \ andpossibly the surroundings of it (subject to possibleleakage) up to a distance of 5 cm from saidenclosure or part of it is regarded as a Zone G.

2.2.4 Zone M -~ Volume in a medically usedroom in which small quantities of flammableanaesthet ic atmospheres of f lammable

128 NATIONAL ELECTRICAL COL)E

anaestneucs with air may occur. A Zone M maybe caused by leakage of a flammable anaestheticmixture from a Zone G or by the application offlammable disinfection or cleaning agents. Wherea Zone M is caused by leakage, it comprises thespace srrounding the leakage area of a Zone G upto a distance of 25 cm from the leakage point

2.3 Special Terms

2.3.1 Equipotenrial Bonding - Electricalconnection intended to bring exposed conductiveparts or extraneous col’ductive parts to the sameor approximately the hame potential.

2.3.2 Essenrial Circuir ~- Circuit for supply ofequipment which is kept in operation duringpower failure.

NOTE Provisions f o r s u p p l y o f such arcuat wparatcl!f rom the remainder o f the electrical lnbtallation arc prcwnr

2.3.3 Generalor Se, - Self-contained energyconvertor including all essential components toSupply electrical power (for example. enginedriven generator).

2.3.4 Hazard Currenr - Total current for agiveh set of connections in an isolated powersystem that would flow through a low impedanceif it were connected between either- isolatedconductor and earth.

NOTE ~ Th is current is expressed in milliampere\.

The following hazard currents are recognized:

Tolal hazard current - Hazard current of anisolated system with all supplied equipment.including the line isolation monitor, connected.

Fauh hazard curren! - Hazard current of anisolated system with all supplied equipment,except the line isolation monitor, connected.

Moniror hazard current - Hazard current ofthe line isolation monitor.

2.3.5 Insularion Impedance Monitor ingDevice - A device measuring the ac impedance atmains frequency from either of the conductors ofan isolated circuit to earth and predicting thehazard current that will flow when an earth faultoccurs and providing an alarm when a presetvalue of that current is exceeded.

2.3.6 Insulat ion Monitor ing Device -Instrument indicating the occurrence of aninsulation fault from a live part of an isolatedelectr ical supply system to the protect iveconductor of the installation concerned.

2.3 .7 I nsu la t ion , Resislance MoniroringDellice - Instrument measur ing the ohmicresistance between the monitored isolated circuitand earth providing an alarm when the value ofthis resistance becomes less than a given limit.

2 .3 .8 Medica l I so la t ing Tran.yfijrmer --Electrical equipment used in medical practiceintended to supply isolated power to medicalelectrical equip.ment in order to minimize the

likelihood of discontinuity of supply in case of afailure tb earth in the isolated power source or inequipment connected to it.

2.3.9 Medical Safe07 Extra- LoHv Vol tage(Mselv) - Voltage not exceeding a nominal valueof 25 V ac or up to and including 60 V dc or peakvalee at rated supply voltage on the transformeror convertor between conductors is an earth-freecircuit isolated from the supply mains by amedical safety extra-low voltage transformer orby a convertor with separate windings.

2.3.10 Operaring Residual Current - Value ofa residual current causing a protective device tooperate under specified conditions.

2.3.11 Patient Environmen! - Any a rea up to

I.5 m distance from the intended location of thepaticnl in which intentional or unintehtionalcontact between patient and equipment or someother person touching the equipment can occur(sre Appendix H).

2.3.12 Touch Volrage Voltage appearing,d u r i n g a n i n s u l a t i o n f a u l t , b e t w e e nsimultaneously accessible parts.

3. CLAGSIFICATION

3.1 The electrical installations covered in thissection are those in buildings inten,ded for thefollowing purposes:

a) Ho.vpira1.v a n d Sonaloria This includesany building or group of buildings. which is

used for housing treating persons suf fer ingfrom physical limitations because of health.age. injury or disease. This also includesinfirmeries. sanatoria and nursing homes.

Cusrodial In,s~i~utions - This includes anybuilding or,group of buildings which is usedfor the custody and care of persons, such aschildren -(excluding schools), convalescentsand the aged. for example. home for theaged and inf i rm. convalescent homes,orphanages, mental hospitals. etc.

4. GENERAL CHARACTERISTICS OFMEDICAL ESTABLISHMENTS

4.0 General guidelines on the assessment ofcharacteristics of installations in buildings areg iven in Part I/Set X. of the C o d e . F o r t h epurpose of installations falling under the scope ofthis section, the characteristics given below apply.

4.1 Environment ~~~ The following environmentalfactors shall apply to hospitals:

PART 3 ELECTRICAL INSTALLATIONS IN NON-INDIbTRIAI. Bl:ILDINGS I29

Environmen: Characteristics(1) (2)

Remarks(3)

Presence offcci~; solid

The quantity or -nature of dust orforeign solid bodiesis not significant

Presence ofcorrosive orpolluting sub-stances

The quantity andnature of corro-sive or pollutingsubstances is notsignificant

Mechanical stress Impact and vibra-tion of lowseverity.

Seismic effectand lightning

4.2 Utilization - The followingzation shall apply:

Utili:arion(1)

Capabthty ofpersons

Contact of per-sons with earthpotential

Conditions ofevacuationduring emer-gency

Nature of processor storedmaterials

I30

Characrerrtrtrs(2)

Children in loca-tions intendedfor their occupa-tion

Handicapped

Locations wheresome chemicalproducts are hand-led (for example;laboratories inhospitals) will becategorized as inPart l/Set 8

Persons adequ-ately advised orsupervised byskilled persons

Persons do not inusual condttionsmake contact withextraneom conduc-tive part\ or standon conductmgsurfaces

Difficult condttionrof evacuation

-


Fire or risk

aspects of utili-

Remarks(3)

Applies to child-carehomes. orphanages.etc

Applies to hospitalsin general, sana-toria. nursinghomes, etc. wherethe occupants arenot in command ofall their physicaland intellectualabihties

Applies to areassuch as buildingsubstations. opera-tions and matn-tenance staff

Apphes in general toho\pual\ and stmt-lar buildings. irreb-pectivc of denbttyof occupation

M a n y locarton\ rnhospnal butldtngstn gcncral uouldfall under categoryBE I of no stgnifi-cant fire or explo-sion risk. spcctficlocations like.operation thcatre.casualit) mcdtcinestore. X-Ray blockfall under BE 2 andBE 3(.wc~ Par t 1 St2 Xol the Code)

5. SAFETY CONSIDERATIONS

5.0 General

5.0.0 In the context of this Section ‘installation’means any combination of interconnectedelectrical equipment within a given space orlocation intended to supply power to electricalequipment used in medical practice.

5.0.1 As such, some parts of the installationmay be present in the patient’s environment,where potential differences. that could lead toexcessive currents through the patient, must beavoided. For this purpose a combination ofearthing of equipment and potential equalizationin the installation seems to provide the bestsolution. A disadvantage of.such a system is thatin the case of an insulation fault in circuitsdirectly connected to supply mains, the faultcurrent may cause a considerable voltage dropover the protective earth conductor of the relevantcircuit. Since a reduction of such a voltage dropby the application of increased cross-sectionalareas of protective conductors is usuallyimpractical. available solutions are the reductionof the duration of fault currents to earth byspecial devices or the application of a powersupply which is isolated from earth.

5.0.2 Generally a power supply systemincluding a separated protective conductor isrequired (TN-S-system).

In addition the following provisions may berequired. depending upon the nature of theexaminations or treatments performed:

a ) A d d i t i o n a l requirements concerninp.

b)

cl

d)

protective conductors and protective devicesto restrict continuous voltage differences.

Restriction of voltage differences bysupplementary equipotential bonding.During the application of equipment withdirect contact to the patient. at least apotential equalized zone around the patientshall be provided with a patient centrebonding bar to which the protective andfunct ional earth conductors of theequipment are connected. Ail accessibleextraneous conductive parts in the zoneshall be connected to this potentialequalization bar.

Restriction of the potential equalizationzone to the /one around one patient,meaning pi-;tctic:tll! around one operationtable or around one bed in an intensive careroom.

If more than one patlent is present in an‘a rea . connection 01 lhc Iarious po ten t ia lequalization ccnIrc\ to ‘a central potentialequali/nrion hu4har. w h i c h s h o u l dprcferahl! he connected to the protectiveearth >!.~tcrn 01 the po\\er supp ly fo r thegl\cn ;irc;t.

In its completed lorm the equipotential

sAl-Ios.\i. E L E C T R I C A L CODE

4

r)

l3)

h)

j)

k)

bonding network may consist partly of fixedand permanently installed bonding and partlyof a number of separate bondings which aremade when the equipment is set up near thepatient. The necessary terminals for thesebonding conne**ions should be present onequipment and in the installation.

Restriction of the duration of transientvoltage difference by the application ofresidual current operated protective devices(earth leakage circuit-breakers).

Continuity of power supply to certainequipment in the case of a first insulationfault to earth and restriction of transientvoltage differences by application ofisolating transformers.

Monitoring of a first insulation fault toearth in an IT-system (the secondary side ofan isolating transformer) with sufficientlyhigh impedance to earth.

Prevention of ignitions and tire in roomswhere flammable anaesthetics or flammablecleaning or disinfection agents are used byventilation, anti-static precautions andcareful layout of the installation.

Safety supply system for major parts of thehospital,. usually a diesel-powered generator.Recommendations for essential cirouits to beconnected to it.

Special safety supply system for criticalequipment as life-supporting equipment andoperating room lamps.

The power supply is taken over by thesedevices in a short time. The device mayconsist of rechargeable batteries possiblycombined with convertors or specialgenerating sets.

Suppression of electroma netic interferenceachieved by the layout o fg the building andwiring a n d p r o v i s i o n o f s c r e e n i n garrangements.

Limits for magnetic fields of mainsfrequency are necessary tor a number ofsensitive measurements.

5.1 Safety Provisinw

$1.1 Safety measureS a re d iv ided in to anumber of provisions as given in Table I.

5.1.2 Provision PC, shall be applicable to allbuildings containing medically used r o o m s .Provision P, shall be applicable for all medicallyused rooms.

Other requirements of this Section, need not becomplied with if:

a) a room is not intended for the use ofmedical electrical equipment, or

b) patients do not come intentionally in contactwith medical electrical equipment during

diagnosis or treatment, or

c) only medical electrical equipment is usedwhich is internally powered or of protectionClass II.

The rooms mentioned under (a), (b) and (c)may be massage rooms. general wards, doctor’sexamining room (office, consulting room), wheremedical electrical equipment is not used.

5.1.3 Guidance on the application of theprovisions are given in Table 2.

5.1.4 A typical example of an installation in ahospital is given in Appendix C.



6.0.1 Proper coordination shall be ensuredbetween the architect, building contractor and theelectrical engineer or the various aspects ofinstallation design. The necessary special featuresof installations shall be ascertained beforehandwith reference to Table 2.

6.1 Circuit Installation Measures for SafetyProvisions -(See Table I. co1 3.)

6.1.1 Provision PO : General

6.1.1.1 All buildings in the hospital areawhich contain medically used rooms shall have aTN-S, T-T or IT power system. The conventionaltouch voltage limit (UL) is fixed at 50 V ac.

N O T E- The use of TN-C-S system (in which the PEn-conductor may carry current in normal condition) can causesafety hazards for the patients and interfere with the functionof medical electrical equipment. data processing equipment.signal transmission lines, etc.

6.1.2 Provision PI : Medical TN-S system

6.1.2.1 The conventional touch voltage limit(LIL) is fixed at 25 V ac.

6 .1 .2 .2 P ro tec t ive conduc to r s inside amedically used room shall be insulated: theirinsulation shall be coloured green-yellow (seePart I 1 Set 4 of the Code).

6.1.2.3 Exposed c o n d u c t i v e p a r t s o fequipment being part of the electrical installationused in the same room shall be connected to acommon protective conductor.

6.1.2.4 A main equipotential bonding with amain earthing bar shall be provided near the mainservice entrance. Connections shall be made to the-following parts by bonding conductors :

4

‘b)

c)d)

lightning-conductor;

earthing systems of the electric powerdistribution system;

the central heating system;

the conductive water supply line;

PART 3 ELECTRICAL INSTALLATIONS IN NON-INDUSTRjAL BUILDINGS 131

PllovlsloNs

(1)

PO

PI

S

I

p1

A

P6

P7

G E

El

4

A.

I ~

TABLE I SAFETY PROVISIONS

(Cbusr 5.1.1)

PRINCIPAL R~QUIRHUIENT~ INSTALLATION Msluurn

(2) (9

Dupm~f touch voltages ratricted to 8 TN-S, m or IT system

As I?0 but 8dditiorully : touch volt8ga inp8tient environment restricted to 8 s8fe limit

Addition81 to p0 : Supply system with additionalrequirements for protective cuthing. etc

As PI but 8dditiotully : Resist8nce betweenextmn&us conductive parts md the

Additiorul to PI : Suppkmentrry quipotenti8lbonding

protective conductor bus b8r of the roomnot exceeding 0.1 fl

A s PI or Pz but 8ddition8Uy : Potenti As P, or Pz : Meuurement neccas8ry. correctivedifference between expo&d conductive p8rts, rtion possibly neccssuyexttmneous aDnductiw p8rts md the protectiveconductor bus brr not exceeding t0 mV innormal condition (WC Note b&w)

As PI or A. Addition81 protection ryinstckctric shock by ,limit8tion of dironncctingtime

Continuity of the timins su ply m8intllined incue of 8 rurt insuktion rult to earth andPcurrents to euth restricted

Reduction of f8ult currents 8nd touchvolt8ges in case of 8 f8ult in ths b8sicinsuktion

Prevention of dangerous touch voltages innorm81 condition rnd in singk f8ultcondition (WC Note below)

No interruption of the power sup ly of theessential circuits of the hospit8l or morePth8n 15 seconds

N? interruption of ,the power supply of\;e-ss%po$mg qurpment for more th8n

No in~rruption of the power supply of theoper8tmg kmp for more thur 0.5 seconds

Prevention of cxpbsions. fue and ekctrostaticc barges

No excessive interference from ekctric andnugnetic folds

Additions1 to PI or P2 : Residual current oper8tedprotective device

Addition81 to PI, 4, or Pa : kol8ted supply systemwith isol8tion monitoring

Additional to P, or P2 : Medical isolatingtransformer supplying one individually piece ofequipment

Additioilal toS8fCty. extra

PI or P2 : Supply with medicallow voltage

spfety supply system

Special safety supply system

Special s8fety supply system for operating lamp

Measures concerning explosion and fire hazards

Layout of building nnd installation, scmning

NOW - Normal condirlon means .without any fault’ in the installation.

SL

(0I.

2.

3.

4.

5.

6.

TABLE 2 EXAMPLES OF APPLICATION OF SAFETY PROVISIONS

(Clausr 5. I .3)

Ms0ICAL.Lv P~~TE~w~E MEASURES SAFETY SUPPLY EXPLOSIONS M EASURESUSED SYSTEM AND F I R E AGAWSTR00M * h EM FIELDS

, I .P./A Pa P, P4 Ps P6 A GE EI El A I

(2) (3) (4) (5) (6) (7) (8) (9) (lo) (11) (12) (13) (14)

Murage room M 0 0 x-

Operating w8sh M X 0 xroom

w8rd general M 0 0 x

Delivery room M x x 0 0 x 0 x 0 0

ECG. EEG, Q4G M X X 0 x Xroom

Endoscopic room M X X 0 x 0(Conrinued)


TABLE 2 EXAMPLES OF APPLlCATlON OF SAFETY PROVISIONS-Conrd

SL MEDICALLYNo. USED

RoOM

PROTECTIVE MEWIRES SAFEN SUPPLYSYSTEM

E XPLOSIONS U EAWRESAND FIRE AGAINST

EM F IELDS

(1) (2)

p.1 PI

(3)

7. Examination ortratmcnt room

8. hbour room

9 . Opcmting rtixi-liition room

10. Urology room (notbeing an operatingtheotre)

I I. Radiological diag-nostic and therapyroom, other thanmentioned underSI No. 20 and 24

12. Hydrotherapyroom

13. Physiotherapyroom

14. Anaesthetic room

15. Operating theatre

16. Operating prepa-ration room

17.

18.

19.

20.

21.

22.

23.

24.

25. Hemodialysis room

26. Central monito-ring room(see Note)

Operating plasterroom

Operating reco-very room

Outpatient opera-ting theatre

Heart catheteri-zation room

Intensive careroom

Intensive exami-nation room

Intensive monito-ring room

Angiographicexamination room

M

M

M

M

M

M

U

UUU

U

U

U

U

U

M

U

U

M

M

S

(4)

0

X

0

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

P3

(5)

XXX

X

X

0

0

0

0

X0

P.

(6)X

XX

X

X

X

X

Xl

Xl

Xl

X,

XI

X,

XI

Xl

X

Xl

XI

Xl

XI

6

(7)

0

0

0

X

X

X

X

X

X

X

X

X

X

X

X

X

P6 Pl

(8) (9)

0

0

0

0

0

0’ 0

0

0

0

0

0

0

0

0

0

0

0

0

0

GE El &(10) (11) (12)X 0

XX

X

X

X

X

XXX

X

X

X

X

X

X

X

X

XX

0

X

X

X

X

X

X

X

X

0

X

0

X

X

X

X

X

X

X

X

0

X

0

A I

(13) 04)

0

0 0

X X

X X

X 0

X X

X X

X

X

0

X

0

0

NOTE - Only if such a room is part of a medical room group and therefore m\talled III the same way as an intensivemonitoring room. Central momtoring room having no conductive connection 10 the medically used room (for example.by use ol isolating coupling devices for \~gnal tran\m~\von) ma) hc ln\talled ab non-mcdlcally used room (provl,lon PU only).

Explanation: M = Mandatory measure.X = Recommended measure

X, = As X, but only lor equlpmenr de\crlhed III 6 .1 .6 .7 .0 = AdditIonal measure. ma! he con\ldered desirable.

e) the conductive parts of the waste water Ilne: Main euuipotential bonding conductors shall

f, the conductive parts of the gas supply; andhave cross:se&tional areas not-less than half thecross-sect ional area of the largest protect ive

g) the structural metal f ramework of the conductor of the insta l lat ion, -subjict to abuilding, if applicable. minimum of 6 mm?. The cross-sectional area need

PART 3 ELECTRICAL INSTAI.I.ATIONS IN NON-INDIISTRIAL BUILDINGS 133

not, however, exceed 25 mm* if the bondingconductor is of copper or a cro~s-s&ctional areaaffording equivalent current-carrying capacity inother metals.

6.1.2.5 Each medically used room or roomgroup shall have its own protective conductor busbar. which should have adequate .mechanical andelectciCal properties and resistance againstcorrosion.

This bus bar may be located in the relevantpower distribution box. The leads connected toterminals of such a protective conductor bar shallbe identified and shall be similarly designated ondrawings of the installation system. .

6.1.2.6 The impedance (Z) between theprotective conductor bar and each connectedprotective conductor contact in wall sockets orterminals should not exceed 0.2 n. if the ratedcurrent of the overcurrent protective device is 16A or less. In case of a rated current exceeding I6A the impedance should be calculated using theformula:

Z+ fl, in all cases Z shall not exceed.0.2 0.. I

whereI , = r a t e d c u r r e n t o f o v e r c u r r e n t

protective device in amperes.Non -- The measurement of the protective conductor

impedance should be performed with an ac current not lessthan IO A and not exceeding 25 A from a’source of currentwith a no-load voltage not exceeding 6 V. for a period of atleast 5 seconds.

6.1.2.7 The cross-sectional a r e a o f theprotective conductor shall be not less than theappropriate value shown in Table 3.

TABLE 3 CROSS-SECTIONAL AREA OF CONDUCTORS

CRCKS-SEUIONAL MISIMI!M CROSS-SM.-A R E A OF PIME TIONAL AREA OF TllE

COND~UW S. mm’ CORRESWNDING PRO-TWTIVE CONMKTOR.

PE. mm?

Sd 1616 < S G 35

s > 35

;

-r

N O T E- If the application of this table produces normstandard si7es. conductors having the nearest standard cross-sectional area are to be used.

The values in Table 3 are valid only if theprotective conductor is made of the same metal asthe phase conductors. If this is not so. the cross-sectional area of the protective conductor is tobe determined in a manner which produces aconductance equivalent to that which results fromthe application of Table 3.

The cross-sectional area of every protectiveconductor which does not form part of the supplycable or cable enclosure shall be, in any case, notless than:

134

- 2.5 mm2 if mechanical protection isprovided, and

- 4 mm2provided.

i.f mechanical protection is not

6.1.28 It may be necessary to run theprotective conductor separate from the phaseconductors. in order lo avoid measuring probkmswhen recording bioelectric potentials.

6.1 .3 Provision P2 : SupplemenraryEquiporenrial Bonding

6.1.3.1 In order to minimize the touchvoltage, all extraneous conductive parts shall beconnected lo the system of protective conductors.

An equipotential conductor bar shall beprqvided. It should be located near the protectiveconductor bar (see aho 6.1.2.5). A combinedprotective conductor and equipotential bondingbar may be used, if all conductors are clearlymarked according to 6.1.2.5 and 6.133 (e).

6.1.3.2 Connections shall be provided fromthe- equitiotential bonding bar to extraneousconductive parts, such as pipes for fresh water.heating. gases. vacuum and other parts with a&onductive surface area larger than 0.02 rn? or alinear dimension exceeding 20 cm. or smallerparts that may be grasped by hand.

Additionally the foilowing requirements supply:

a) Such connections need not be made to:

I) Extraneous conductive parts inside ofwalls (for example structural metalframe work of buildings) having no directconnection to any accessible conductivepart inside the room. and

2) conductive parts in a non-conductiveenclosure.

b) In locations where the position of thepatient can be predetermined this provisionmay be restricted to extraneous conductiveparts within the patient environment (seeAppendix B)

c) In operating theatres. intensive care rooms,heart catheterization rooms and roomsintended for the recording of bioelectricalactiol potentials all parts should beconnected to the equipotential bonding barvia direct and separate conductors.

6.1.33 The following requirements shall befulfilled:

a)

b)

The impedance betwe’en extraneousconductive parts and the equipotentialbonding bar shall not exceed 0.1 fI. I

N OTE - The measurement of this impedanceshould be performed with a current not less thinIO A and not exceeding 25 A during not less than5 seconds from a current source with a no-loadpotential not,exceeding 6 V ac.

All equipotential bonding conductors shallbe insulated. the insulation being colouredgreen/ yellow.


cl

4

e)

NorI.cqnduclor4

lnbulation of the equipotential bondingIS necessary. lo avoid loops by contact

and 10 avoid picking up of stray currents.

Equipotcntial conductors betweenpermanently installed extraneous conductiveparts and the equipotential bonding barshall have a cross-sectional area of not lessthan -4 mm’ copper or copper equivalent.

The equipotential bonding bar. if any,should have adequate mechanical andelectrical properties. and resistance againstcorrosion.

T h e c o n d u c t o r s c o n n e c t e d t o t h eequipotential bonding bar shall be markedand shall be similarly designated ondrawings of the installation system.

A separate protective conductor bar and anequipotential bonding bar in a medicallyused room or in a room group shall beinterconnected with a conductor having across-sectional area of not less than 16 mm?copper or its equivalent (see also 6.1.3.1).

An adequate number of equipotentialbonding terminals other than these forprotective conductor contacts or pins ofsocket outlets should be provided iq eachroom for the connection of an additionalprotect& conductor of equipment or forreasons of functional earthing of equipment.

6 . 1 . 4 Pro\si.siorl PJ : R e s t r i c t i o n of TouchVoltage irr Roon~ Equipped ,fiw Direct CardiacApplication

6.1.4.1 The continuous current through aresistance of I 000 R connected between theequipotential bonding bar and any exposedconductive part as well as any extraneousconductive part in the patient environment shallnot exceed IO PA in normal condition forfrequencies from dc to I kH7.

For a description of patient environment. seeAppendix B. Where the measuring device has animpedance and a frequency characteristics asgiven in Appendix D, the current may also beindicated as a continuous voltage with a limit ofIO mV between the parts mentioned above.

- During the test it is assumed that fixed andpermanently installed medical electricalequipment is operating.

-- ‘Normal conbitions* means ‘without airy faultin the installation and in the medicalelectrical equipment’.

N OTE -- To comply with this requirement it pay benecessary lo apply one or more of the following methods:

Extraneous* conductive parts may be:

a) connected to the equipotential bonding barby a conductor of a large cross-sectionalarea in order to reduce the voltage dropaccross sueh a conductor.

b)

d

insulated so that it is not possible to touchthem unintentionally, and

provided with isolating joints at those placeswhere they enter and leave the room.

Exposed conductive parts of permanentlyinstalled equipment may be isolated from theconductive building construction.

6.1.5 Provision PJ : Application tif Residual-Current Prohrive Devices

6.1.5 .1 The use of a residual-currentprotective device is not r&ognized as a sole meansof protection and does not obviate the need toapply the provisions P I and Pz.

6.1.5.2 Each room or each room group shallbe provided with at least one residual-currentprotective device.

6.1.5.3 A residual-current protective deviceshall have a standard rated operating residual-current I A N < 30 mA.

6.1.5.4 A medical isolating transfbrmer andthe circuits supplied,from it shall not be protectedby a residual-current -protective device.

6.1.5.5 Electrical equipment such as generallighting luminaries. installed more than 2.5 mabove floor level need not bc protected by aresidual-current protective device.

6.1.5.6 Fixed and permanently installedelectromedical e q u i p m e n t .wit h a powerconsumption requiring an overcurrent protectivedevice of more than 63 A rated value may beconnected to the supply mains by use of aresidual-current device withI A N d 300 mA’.

protective

6 . 1 . 6 Pro\isiou P5 : Metlicul IT-S,wem

6.1.6.0 The use of a medical IT-system for thesupply, of medically used rooms for exampleoperatmg theatres. may be desirable for differentreasons :

a)

b)

cl

PART 3 ELECTRICAL INSTAI.LATIOP;S IN NON-INDUSTRIAL

A medical IT-system increases the reliabilityof power supply in areas where aninterruption of power supply may cause ahalard to patient or user;

A medical IT-system reduces an earth faultcurrent to a low value and thus also reducesthe touch voltage across a protectiveconductor through which this earth faultcurrent may flow;

A medical IT-system reduces leakagecurrents of equipment to a low value. wherethe medical IT-system is approximatelysymmetrical to earth.

It is necessary to keep the impedance toearth of the medical IT-system as high aspossible. This may be achieved by:

I) restriction of the physical dimensions oft\he medical isolating transformer.

Bl;ILDINCS 135

4

3)

restriction of the system supplied by this checking the response of the monitor to atransformer, fault condition as described in 6.1.6.4.

restriction of the number of medicalelectrical equipment connected to such asystem, and

4) high internal impedance to ‘earth of theiinsulation monitoring device connectedto such a circuit.

If the primary reason for the use of medical IT-system is the reliability of the power supply, it isnot possible to define for such a system a hazardcurrent and an insulation resistance monitoringdevice should be used.

If,on the other hand the restriction of leakagecurrent of equipment is the main reason for theuse of the medical IT-system. an insulationimpedance monitoring device should be used.

6.1.6.1 For each room or each room group atleast one fixed and permanently installed medicalisolating transformer shall be provided.

6.1.6.2 A medical isolating transformer shallbe protected against short circuit and overload.

In case of a short circuit or a double earth faultin parts of opposite polarity of the medical IT-system the defective system shall be disconnectedby the relevant overcurrent protective device.

If more than one item of equipment can beconnected to the same secondary winding of thetransformer. at least two separately protectedcircuits should be provided for reasons ofcontinuity of supply.

6. I .6.7 lnsulorion resi.wonc*e monitoringdevice-The ac resistance of ,an insulationresistance monitoring device shall be at least 100kR The measuring voltage of the monitoringdevice shall be dc exceeding 25 V. and themeasuring current (in case of a short circuit of ancxtcrnal conductor to earth) shall not exceed ImA. The alarm shall operate if the resistancebctwccn the monitored isolated circuit and earthis 50 kfI or less. setting to a higher value isrecommended.

6. I .6.8 lnsulolion impedance moni to r ingdevice - An insulation impedance monitoringdevice shall give readings calibrated in totalhazard current with the value of 2 mA near thecentre of the meter scale.

The device shall not fail to alarm for totalhazard currents in excess of 2 mA. In no case.however. shall the alarm be activated until thefault hazard current exceeds 0.7 mA.

6.1.63 Overcurrent protective devices shall beeasily accessible and shall be marked to indicatethe protected circuit.

N O T E-The v a l u e s o f 2 mA or 0.7 mA a re based onpractical experience with I10 IO I20 V power supplies. For a220-240 V power supply it may be necessary IO in’crease thesevalues to 4 mA and 1.4 mA because of the higher leakagecurrent of equipment.

6.1.6.4 An insulation monitoring device shallbe provided to indicate a fault of the insulation toearth of a live part of the medical IT-system.

6.1.6.5 Fixed and permanently installedequipment with a rated power input of more than5 kVA and all X-ray equipment (even with a rated

1ower input of less than 5 LVA) shall be protectedy provision Pd. Electrical equipment such as

general lighting, more than 2.5 m above floorlevel. may be connected directly to the sup’plymains.

During the checking of the response of themonitor to a fault condition the impedancebetween the medical IT-system and earth shall notdecrease.

6. I .7 Pro vision Pf. : Medical lndividuolElecrricol Seporor ion

6.1.7.0 Individual electrical separation of acircuit is intended to prevent shock currentsthrough contact with exposed conductive partsWhich muy be energized by a fault in the basicinsulation.

6.1.6.6 General requiremenrs ./or insulorionmohiroring devices - A separate insulationresistance or impedance monitoring device shallbe provided for each secondary system. It shallcomply with the requirements given below:

a) It shall not be possible to render such adevice inoperative by a switch. It shallindicate visibly and audibly if the resistanceor impedance of the insulation falls belowthe value given Gn 6.1.6.7 and 6.1.6.8.

The arrangement may be provided with astopbutton for the audible indication only.

b) A test button shall be provided to enable

6.1.7.1 The source of supply. shall be amedical isolating transformer.

6.1.7.2 Only one item of equipment shall beconnected to one source of supply.

6.1.73 The voltage of the secondary circuitshall not exceed 250 V.

6.1.7.4 Live parts of the separated circuit shallnot be connected at any point to any other circuitor to earth.

6.1.75 To avoid the risk of a fault to earth,particular attention shall be paid to the insulationof such circuits from earth. especially for flexiblecables and cords.


cl

d)

The visible indication mentioned in (a) ofthe insulation monitoring device shall bevisible in the monitored room or roomgroup.

The insulation monitoring device should beconnected symmetrically to the secondarycircuit of the transformer.

6.1.7.6 Flexible cables and cords shall bevisible throughout any part of their length wherethey are liable to mechanical damage.

6.1.7.7. All conductors shall be physicallyseparated from those of other circuits.

6.1.8 Pt-m*isiorl P, : Medical Sqfkts Errra-LowVu/rage (MSELV)

6.1.8.1 Medical safety extra-low voltage shallnot exceed 25 V ac or 60 V dc peak value.

6.1.8.2 A supply transformer for medicalsafety extra-low voltage shall comply withrelevant Indian Standards.

6.1.83 A source of medical safety extra-lowvoltage other than ,a transformer shall have atleast the same separation and insulation to othercircuits and earth as required for the transformerunder 6.1.8.2.

6.1.8.4 Live parts at medical safety extra-lowvoltage shall not be connected to live parts orprotective conductors forming part of othercircuits or to earth.

6.1.8.5 Exposed conductive parts shall notintentionally be connected to:

a)

b)

c)

earth. or

protective conductors or exposed conductiveparts of another system. or

extraneous conductive parts except that,where electrical equipment is inherentlyrequired to be connected to extraneousconductive parts, it is ensured that thoseparts, cannot attain a voltage exceedingmedtcal safety extra-low voltage.

6.1.8.6 Live parts of circuits at medical safetyextra-low voltage shall be electrically separatedfrom other circuits. Arrangements shall ensureelectrical separation not less than requiredbetween the input and output of a medical safetyextra-low voltage transformer.

In particular. electrical separation not less thanthat provided between the input and outputwindings of a medical safety extra-low voltagetransformer shall be provided between the liveparts of electrical equipment such as relays.conductors. auxiliary switches and any part of acircuit with ;I higher \,oltagc.

6.1.8.7 Medical safety extra-low voltagecircuit conductors. shall either be physicallyseparated from those of any other circuit or wherethis is impracticable. one of the followingarrangements is required:

a) Medical safety extra-low voltage circuitconductors shall be enclosed in a non-metallic sheath additional to their basicinsulation.

b) Conductors of circuits at different voltagesshall he separated by an earthed metallicscreen or an earthed metallic sheath.

d

NOTI+- In he above arranBcments. basr-insulationof any conducto-r should comply only with the requim-ments for the voltage of the circuit of which :t isa part.

Where circuits at different voltages arecontained in a multi-conductor cable orother grouping of conductors, medical safetyextra-low voltage circuits shall be insulated,individually or collectively, for the highestvoltage present.

6.1.8.8 Plugs and socket-outlets shall complywith the following requirements:

a) Supply systems ot different voltages ordifferent kinds or nature shall not haveinterchangeable plugs and sockets, and

b) Socket-outlets shall not have a protectiveconductor contact.

6.2 Wiring

6.2.1 The general design of wiring shallconform to Part I /Set I I of the Code.

6.2.2 All panel boards and switchboards shallpreferably be of dead front type, enclosed in metalcabinet. Where locked cabinets are provided, alllocks should be keyed alike. Switchboard andpanel boards shall be installed in non-hazardouslocations.

6.2.3 Circuit -breakers are preferred toswitchfuse units in power and lighting feeders.

6.2.4 Inside the wards only silent type waHmounted switches should be used to reduce noise.The lighting points shall be so grouped so thatminimum lighting may be switched on duringnight time.

6.2.5 Separate circuits shall be provided for X-ray. electrotherapy, diathermy, electrocardio-graph, etc. Advjce of equipment manufacturersshall also be sought in their installation.

6.2.6 In corridors and spaces accessible topublic provisions shall be made for lighted signs.

6.2.7 Special convenience outlets in corridorsspaced about I2 m apart are desirable forportable treatment equipment and cleaningmachines.

6.3 Feeders-The general provisions laid downin Part I ;Sec I I of the Code shall apply.

6.4 Service Lines

6.4.1 The general provisions laid down inIS : 806l-1976* shall apply.

6.4.2 The main supply. conductors shallpreferably be brought into the bui ldingunderground to reduce the possibility ,ofinterruption of power supply.

*Code of practice for design. installation and maintenanceof service lines up IO and including 650 V.

PART 3 ELECTRICAL INSTALLATIONS IN NON-INDUSTRIAL BUILDINGS 137

6.5 Euilding Substation

65.0 General- The design of power supplyfor hospital and similar buildings shall take intoaccount the concentration of power demand forthe various electrical loads. If the load demand is

aceommrr X:,Bof su station eauipment will ehigh 2 * * su PlYg at high voltaT

required. Emergency and standby -power-supplyneeds of hospital buildings shall also be taken intoaccount in designing the building substation.

6.5.1 While calculatinf

the power requirement,the diversity factor or different electricalappliances and installations shall be considered.For guidance,, Table 4 giv,es reference values ofpower requirement and drversity factor for thedifferent parts in a hospital installation.

TARLE 4 POWER REQUIREMENTPART OF EL~C:CTRICAL

INSTALLATIONP~;~XI;~N D;A~7~:’ 5

PowerREQUIREMENT

(1) (2) (3)Pcrcclit

Lgtrting. .&;We;dtttoning

Sterilizer

kKdvEkctromcdical installationsand other loads

6.5.2 The location and layout of buildingsubstation shall conform to the general rules laiddown in Part 2 of the Code. The main supplypoint shall be located in the main building of thehospital.


6.6.OGeneral- The general rules forprotection for safety laid down in Part I of the

Code shall apply. Reference should be made toSP : 7-1983* for guidelines for fire-protection ofbuildings. The additional rules given below shallapply.

6.6.1 The type of buildings covered in thissection fall under Group Cl (hospitals andsanatoria), C2 (custodial institution) and C3(panel institutions - fo;ro~nta\h~ospitals. andsimilar buildings) fire-safetyclassification point of view.

-6.6.2 In hospitals and similar buildings, besidesfire-fighting equipment manually operatedelectrical fire alarm system and automatic fire-alarm system shall be provided. Restricted pagingsystem arrangement with sound alarm/ indicatorsin the duty rooms/nurses rooms shall be made.

6.6.3 For guidelines on selection of firedetectors. see Appendix B of SP : 7-1983*, Thewiring for fire-fighting systems shall be segregated

*National Building Code.

Effective ventilation and the application .of asuction system on anaesthesia equipmentassists in reducing llammable concentrationsof flammable anaesthetic mixtures in thepatient environment. the anaesthetistsworking-place and the operating table. Theeffectiveness of a ventilation:system may besubjected to National Regulations.

I3g NATIONAL ELECTRICAL CODE

from other wiring- to reduce risk of damage tothem in the case of fire. For high-rise buildings.the fire-fighting pump motors are generally largeand they draw heavy current. Sufficient care shallbe taken to ensure that the supply to such motorsis maintained properly.

6.7 Fire-Protection - Where electrical equipmentcontains pipes or tubes of combustion supportinggases, such as oxygen or nitrous oxide, thefollowing additional requirements apply:

4

b)

cl

4

e)

Gas outlets shall be located at least 20 cmaway from electrical components which, innormal use or in case of a fault,could generate sparks.

The gas-flow shall not be directed towardssuch electrical components.

Electrical wiring shall only be allowed to berun in a .common enclosure, for example ina common conduit for channel, with tubesfor combustion supporting gases. such asoxygen or nitrous oxide if in the relevantcircuit the p,roduct of the no-load voltage involts and the short-circuit current inahtperes does not exceed IO.

If the requirements in (c) cannot be. fulfilledgas-tight separation shall be providedbetween the electrical wiring and the tubesfor gases.

T h e g a s - t i g h t s e p a r a t i o n s,haII beelectrically conducting and shall beconnected to the protective earth busbar.

Where electrical leads are close to a pipelineguiding ignitable gases or oxygen, a short-circuit of these leads or a short-circuit of onelead with a metal duct or pipeline shall notresult in a temperature which may causeignition.

7. ADDITIONAL REQUIREMENTSFOR HAZARDOUS LOCATIONSIN HOSPlTALS

7.1 Provision A : Explosion and Fire Protection

7.1.1 Explosion Protection : General

a)

b)

When the administration of flammableanaesthetic atmospheres or flammableanaesthetics or flammable cleaning and/ordisinfection agents with air or oxygen andnitrous oxide is intended, special measuresto avoid ignitions and fire are necessary.These measures include mainly the use ofantistatic flooring.

d

4

e)

Limits of zones of risk are given inAppendix A.

Zones of risk exist only when flammableanaesthetics or flammable cleaning and/ordisinfection agents are used.

Requirements on construction. marking anddocumenta t ion of medical electricalequipment of category AP or APG are givenin IS : 8607 (Part I)-1978*.

Allocation of equipment of the categoriesAP or APG. to zones of risk in operatingtheatres or other anaesthetic rooms. a r eunder consideration.

Mains plug connections, switches, powerdistribution boxes and similar devices,which may cause ignition shall be keptoutside zones of risk.

7.2 Antistatic Floor

7.2.1 Antistatic floors shall be used in roomswhere zones of risk occur.

Where antistatic floors are used in cotijunctionwith non-antistatic floors marking should beprovided, which should be described in theapplication code.

7.2.2 The resistance of an antistatic floor shallnot exceed 25 MR at any time during the lifetimeof the floor when measured according toIS : 7689-1974t.

NO T E- The fact that during the lifetime of the floor theresistance may change should be taken into consideration. Theresistance of teraz7o floors increases. while that of PVC floorsdecreases with time.

7.2.3 If floors of low resistance (< 50 kR) areused, Provisions Ps and/or Ps shall be used to‘effectively limit the effects of fault currents.

8.’ BUILDING SERVICES

8.1 Lighting

8.1.1 The general rules laid down in Part I/SetI4 of the Code shall apply. The choice of lamps,lighting fittings and the general lighting designtogether with the power requirement shall beplanned based on the recommended values ofillumination and glare index given in Table 5.8.2 Air-Conditioning - The-provisions of Part ISet I4 of the Code shall apply. Provision shallbe made to induct fresh air to avoid entry ofexplosive gases from one room ‘to another.

8.3 Lifts

8.3.1 The general rules laid down in Part I /Set-14 of the Code shall apply. However, the designof lifts in hospitals and similar buildings shall bemade taking into account the criteria given below

*General and safety requirements for electrical equipmenlused in medical practice: Part I General.

Guide for contrdl of undesirable static electricity.

TARLE S R E C O M M E N D E D V A L U E S O F I L L U -MINATION AND LIMITING GLARE INDEX

(Clouw 8. I. I)

SLNo.

(1)

I.

4.

5.

BUlLDtNCS

(2)

Hospitalsa) Receptioo and waiting

r o o m sb) Wards

i) Generalii) Beds

c) Operating thcatrcs/Dental surgeries

i) Generalii) Tables/chairs

. d) Laboratoriese) Radiology department1) Casualty and out-

patient departmentg) Stairs. corridorsh) Dispensaries

Doctors S Surgeriesa) Consulting roomsb) Corridorsc) Sight testing (acuity)

wall charts and nearvision types

bundries/ Dry-Ck=aningWorks

a) Receiving. sorting,washing. drying

b) Dry-cleaning, bulkmachine work

c) Ironing, pressing.mending. spotting.despatch

Kirchens 2oot 25

ILLU-MINATION

!i?

L I M I T I N G

GLARE INDEX

(4)

I50 I6

looIS0

13.

( Sgiallighting)

300

I:

::

I5070

450

200

200

300

25

25

25

(SQQ Part 3iSec 2of the Code)

*Care shall be taken to screen all bright light and areas fromview of patients in bed.

tSpecial local lighting required over kitchen equipment.

8.3.2 Di&nsions - The outline dimensions of .’hospitals lifts shall conform to those laid down inTable 3 of IS : 3534-l976*

8.3.3 Occupant Load - For the types o f‘Gldings covered in this Section, the occupantload expressed ;IS gross area in m* per person,shall be 15.

8.3.4 Car Speed - These shall be as follows:

T,pe qf Lift No. qf Floors Car Speed. Served mfsec

Hospital passenger 13-20 Above I.5I(ft 4-5 .0.5 to 0.75

Hospital bed IlftsShort travel lifts in - 0.25

small hospitalsNormal -Long travel lifts in - OK5general hospitals

*Outline dimensions. for electric lifts (firsr rivision).

PART 3 ELECTRICAL INSTALLATIONS IN NON-INDUSTRIAL BUILDINGS I39

83.5 Position - It is convenient to positionthe hospital passenger lifts near the staircases.Hospital bed lifts shall be situated convenientlynear the ward and operating theatre enterances.There shall be sufficient space near the landingdoor for easy movement of stretcher/trolley.


9.1 The various tests on the installation shall becarried out as laid down in Part I /Set IO of theCode.9.2 The initial testing of the installation shall-alsoinclude:

a)

b)

Testing of the effectiveness of protectivemeasures (provisions PO to P7);

Testing of the resistance of protectiveconductors and of the qquipotentialbonding;

4 Testing of the insulation resistance betweenlive conductors and earth in each separatelyfused circuit;

4e)

Testing of the resistance of antistatic floors;Testing of the general safety supply system;and

0 Testing, of the special safety supply system.

10. STANDBY, SAFETY AND SPECIALSAFETY SUPPLY SYSTEM

10.1 Provision GE : Standby and Safety SupplySystem

10.1.1 Electrical systems for medicalestablishments shall comprise essential circuitscapable. of supplying a limited amount of lightingand power service which is considered essentialfor safety, life support and basic hospitaloperation during the time the normal electricalservice is interrupted (see also Appendix E).

10.1.2 All medical establishments containinglifelsupporting equipment shall be provided witha safety supply system.

10.1.3 Essential circuits shall provide facilitiesfor charging batteries of a special safety supplysystem.

10.1.4 Operation of a safety supply system shallnot impair the function of protective measures.

10.1.5 All parts of essential circuits shall bemarked.

10.1.6 An example of safety supply systems ofa hospital is given in Appendix F

10.1.7 A safety supply system shall be capableof automatically taking over the load of essentialcircuits in the event of a failure of the normalpower supply.

10.1.8 The taking-over procedure shall notstart earlier than after a period of 2 seconds has

elapsed during which the system voltage hasdropped below 90 V of the nominal value, andshall be completed within 15 seconds after thestarting of the taking-over procedure.

Return to normal power supply should bedelayed. For diesel-generators the delay should beat least 30 minutes.

10.1.9 To prevent simultaneous damage, themain feeders for the safety supply system shall besegregated from the normal system whereverpossible.10.2 Provisions EI and EI : Special Safety SupplySysteq

10.2.1 Provision EI : Special Sqfet.l* Supp!~*System, Medium Break

10.2.1.1 .A special safety supply system shallautomatically take over the load within I5seconds after a failure of the power supply at themedical establishment containing life-supportingequipment.

10.2.1.2 It shall be possible to resumeoperation of equipment for maintainingimportant body functions, in particular breathingequipment, or equipment for resuscitation, withinI5 seconds and to maintain operation for a periodof 3 hours subsequently, for exam.ple. via a-batterywith inverter or via a motor driven generator.

10.2.1.3 Where the rating of the special safetysupply system issufficient the circuits of a medicalIT-system according to 6.1.6 may be connected toit.

10.2.1.4 Where not all socket outlets in amedically used room are connectled to the specialsafety supply system the c0nnecte.d socket outletsshall be marked clearly as such..

10.2.2 Provision EZ : Special Sqfety Supp!~System. Short Break

10.2.2.1 A special safety supply system shallautomatically take over the load within 0.5 secondafter a failure of the power supply at theoperating lamp.

10.2.2.2 Operation of at least one operatinglamp shall be resumed after a switchover time notexceeding 0.5 second and operartion shall bemaintained tor at least 3 hours.

10.23 Common Recommendations for theProvisions EI and Ez.

10.2.3.1 The rated power of the source of aspecial safety supply system shall not be less thanrequired by the connected functions. At least theload which require continuity of supply shall beconnected to the special supply system.

10.2.3.2 Operation of a special safety supplysystem shall not impair the function of protectivemeasures.

For diesel-generators the requirements of 10.1.8shall apply.


10.2.3.3 Voltage deviations under normalconditions shall be less than IO percent forperiods of time exceeding 5 seconds.

10.2.3.4 Frequency deviations shall be lessthan I percent for periods of time exceeding 5seconds.

10.2.3.5 The special safety supply ‘systemsource shall be located outside the medically usedrooms, if possible close to the relevantdistribution point, so that physical damage to thecables connecting the source to the distributionpoint is unlikelv.

10.2.3.6 Operation of the special safety supplysystem shall be indicated by visual means in allrooms concerned.

NOTE--- It is recommended to provide additionally a totalload indicator in each room connected to the same specialsafety supply system.

10.2.3.7 Automatic means shall be providedto keep batteries optimally charged.

10.2.3.8 The charging device shall be designedso that,starting from the fully charged conditions,it is possible to discharge continuously during 3hours at nominal output, and subsequently torechange during 6 hours after which it shall bepossible to discharge once more for 3 hours underthe conditions mentioned above.

10.2.3.9 It’ shall be possible to supply .thecharging circuit of a special safetv supply systemfrom the safety supply system, so that the specialsafety supply system batteries can be charged evenduring a failure of the normal power supply.

11. MEASURES AGAINST INTERFERENCE:PROVISION I

11.1 Measures Against AC Interference

11.1.1 In rooms where measurements ofbioelectric potentials are performed measuresagainst interference in the room and in thesurrounding area should be effected if suchinterference may cause incorrect measurements.Such rooms are:

a)

b)c)d)e)0

rooms intended for measurement of bio-electric potentials (EEG, ECG, etc),intensive examination rooms,intensive care and monitoring rooms,catheterization rooms,angiographic examination rooms, andoperating theatres.

11.2 Measures Against Interference Caused byMains-Induced Electric Fields

11.2.1 The electrical wiring on both sides of orinside walls, floor and ceiling of the roomsconcerned should be screened by means of metalshielding of cables or by metal conduits for cablesand wiring.

If such metal shielding is applied it should beconnected to protective earth at one point only.

11.2.2 Metal enclosures or parts of enclosuresof fixed. and permanently installed electricalequipment of Class 11 and Ill (such as of lightingfittings) should be connected. to the equipotentialbonding system.

11.2.3 Where adequate measures accordingto 11.1 cannot be applied and ECG and EEGmonitoring is to be undertaken, it is recom-mended to shield the room or a part of the roomagainst electric fields by installing a room screen-ing within the wall structure.i 1.3 Measures Against Interference Caused byMains-Induced Magnetic Fields

11.3.1 It is recommended to provide sufficientdistance between electrical components andequipment which may, cause magnetic interferenceand the place for the examination of patients. Inpractice the following values of magnetic. fieldstrength have been found to be sufficiently low toavoid magnetic interferance:

4 X lO’T,, for ECG recording, and2 X lO’T,, for .EEG recording.

NOTE - Ballasts incorporated in fluorescent lamp fittingsgenerate an alternating magnetic field; those on the ceiling of:the room immediately below the examination room are theones most likely to cause interference. In some cases it may benecessary to remove ballasts of a certain type from the lightingfitting and to mount them at sufficient distance.

11.3.2 Sufficient distance should be providedwhen installing units with strong stray magneticfields such as transformers and motors. Thisapplies also to the isolating transformer ofprovision Ps. The distance should be 3 m or more.

11.3.3 The rooms listed in 11.1 should not havelarge power cables passing through or adjacent tothem. Suggested minimum distances are:

Conductor Cross- Distance,Sectional Area Min

IO to 70 mm2 3,m95 to I85 mm2 6 m240 mm2 29 mNOTE I -Cables, either single phase or three phase. will,

have a negligible external field if _the load is correctlydistributed between phase or between phase and neutral but inpractice faults between neutral and earth or incorrectlydistributed loads between lines and neutral, and kakagecurrents will cause alternating magnetic fields’in the vicinity ofpower cables.

NOTE 2 -The values apply only to twisted cables. Whenbar systems or separated single cables are used, the distancesmay have to be substantially larger.

11.4 Measures Against Interference from RadioFrequency Electromagnetic Fields

11.4.0 Powerful radio frequency fields maycause interference in sensitive electromedicalequipment.

11.4.1 Normally such fields exist only whereshort-wave diathermy or surgical diathermy

PART 3 ELECTRICAL INSTALLATIONS IN NON- INDUSTRIAL BUILDINGS 141

equipment is used and close to transmittingaerials used for such purposes as staff locationand amb(ulance communications. The simplestmeasure against such interference is to locate

“xuipment’which causes it kell away from areas

w ere sensitive equipment is used. Additionalmeasures are t* inclusion of r.f. rejection circuitsin sensitive equrpment and the use of short-wavec&!~;rmy equipment with a low modulation

.~If ‘the measures described here are not

sufficiently effective it may be necessary to usesensitive equipment with a screened room.

N~TE-T~~ construction of such a screened room shouldbe entrusted to a s cialist. An attenuation of 40 dB over thefrequency range I 0 kHz to 30 MHz is considered to be5”adequate.

11.5 Electric Heating Cables

11.5.0 The following requirement applies toelectric heating cables embedded in or attachedto surfaces in buildings. It does not apply toremovable appliances which may be mounted onthe surface of walls.

il.51 Electric heating cables of any typeshould not be used in rooms where’ bioelectricpotentials are recorded.

Nois - Due to the construction of such heating cables it isvery likety,, that the electric and magnetic fields will interferewith the recording of bioelectric potentials. Appropriatemeasures according to 11.2 and 11.3 should be taken.


12.1 Call Systems12.1.0 Electrical call and signal system when

provided in hospitals should comply with therequirements given in 12..i.l to 12.1.7. Thefollowing are the important call and signalsystem: ,

a) Nurses call,b) Doctors’ paging, and ’

c) In-and-out register.NOTE - It is recommended that electrtcal call and signal

system should be provided in all hospitals so that patients mayreceive prompt servia and the doctors. nurses and attendantsmay work more efficiently.

12.1.1 Nrirses’ Cd Sysrem - T h e nurses c a l lsystem should be a wired electrical systemwhereby patients may signal for a nurse from thebed site. Two types of systems are recommended:

a) A simple one-way’signal system which con-nects the bed side call stations with a signalat the nurses’ station, untility room andfloor pantry of the nursing unit. It simul-taneously lights a dome light over the doorof the room_from_.which the call orginated.The signal at the nurses station may be inthe form of an annunciator with a buzzer ora single light with a buzzer. Two or morelights in the ceiling’of the corridor at the

b)

nurses’ station to indicate the direction fromwhich the call came are desirable for thelatter arrangement.A central control panel should be set up pre-ferably on the ground floor incorporating aset of indicating panels according to thenumber of wards. Each indicating panelshould have a number of small lampsaccording to the number of beds. At eachbed there could be 4 push buttons. Firstfor. ‘Calling Nurses’, second for ‘i?lursePresent’, third for ‘Setting Combination’ andfourth for ‘Call for Doctor’. When anypatient presses the push button the indi-cation is at the central control room fromwhere intimation to nurses can be sent.After reaching the bed site the nurse pressesthe ‘Nurse Present’ button which gives anindication to operator at the central controlpanel that the nurse is available near theparticular bed. After attending the patient,the nurse presses the resetting button whichputs the whole equipment to the originalcondition. If the patient needs further helpof a doctor then the nurse again presses thefourth push button and the central.controlpanel operator sends, message to the doctorfor that particular bed.

12.1.1.1 For emergency call of nurse by thepatient when he/she is inside a bath or water-closet, suitable pull cord switches shall beprovided inside bath and water-closet. Theseswitches when operating will give an indication atthe central control panel from where intimation tonurse can be sent.

12.1.1.2 Nurses call system may also be of theintercommunicating type with a microphone andloudspeaker at the bed connected to the nurses’station. The patient can signal for a nurse orspeak to her and receive an answer. Formaximum benefit and service, this system shouldinclude all the features described in 12.1.1 for theone-way signal system in addition to theintercommunicating features.

12.1.2 Doctors Paging Sysrem - this mayconsist of loudspeakers located throughout thehospital, clinics on which doctors’ numbers can besounded or the flasher type which indicates thedoctors’. numbers. The loudspeaker and otheraudible calls should not be used as they maydisturb the patients and attendants. The flashersystem- consists of a keyboard and flasher at thetelephone switchboard. The’ telephone operatormay set the board to flash as many as threedoctors’ numbers automatically in rotation. Thenumber appear on annunciators located in allsections of the corridors. The same number ofnumerals at least three, should be used for eachdoctor so that a burnt out lamp may be located.

*<2.1.2.1 These paging systems could be usedfor calling interns, admintstrators, heads ofdepartments and their assistants and engineers.These flashers may also be used for other generalcalls such as ‘fire’ with a red ‘F’ and buzzer. The


flasher call system has its shortcomings as theindividual may fail to see the numbers whenflashed. For this reason the flasher system shouldbe supplemented with loudspeakers at pointswhere interns, heads of departments and doctorsmay congregate, that is, in doctors’ lounge, staffdining room, laboratory and engineers’ office andsuch other areas where the calls may not disturbthe patients.

12.1.3 VHF Paging System -This systemconsists of a low powered transmitting stationfrom which calls are broadcast throughout thehospital to miniature receiving sets which thedoctors and others may carry in their pockets.

12.1.4 In-and-Out Register - The doctors’*in-and-out register permits the doctor to register ‘IN’and ‘OUT’ with the minimum of effort and delay.The register consists of a board, at one or moreentrances, on which all staff doctor, upon enteringor leaving, operates a switch opposite his namewhich indicates whether or not he is in thebuilding. The switch controls a light at or back ofthe name on all boards connected in the system.

12.1.4.1 Except in very small hospitals, it isrecommended to install register system with aboard at two or more entrances and at thetelephone switchboard. Such a system shouldinclude a recall feature which consists of a flasherunit, having a motor driven interruptor. Thisf lasher un i t , con t ro l l ed a t the t e lephoneswitchboard. will actuate a flashing light at thedoctors’ name on all register boards whichindicates there is a massage for the doctors, andattracts the attention of doctor upon entering orleaving the building. Call back systems are usedfor nurses’ and interns’ bedrooms: With suchsystem the nurses and interns can be awakened,called for duty, or called to the telephone bypush-buttons in the office which operate buzzersin the rooms. The room called can answer bypushing a bu t ton which reg i s te r s on anannunciator in the office. The main office buzzersmay be connected through a selector switch sothat serial rooms or sections may be called by onebutton.12.2 Telephones

12.2.0 Interconnecting telephones should be

12.4.1 The list of other special circuits ininstallations in hospitals are given below:

a)

b)cl

Closed-circuit television in surgery depart-ment (for teaching purposes),

Television sets in wards,

Short-wave, ultraviolet rays or sterile raylamps in ceilings of operating and deliveryrooms around the operating light, to reducethe bacteria count; and

d) Luminous signs.

provided for all heads of departments, assistants,operating and delivering suites, nurses’ station,offices, housekeeper, doctors’ rooms. recordrooms and diet kitchens. These may be connectedon a d ia l sys tem which permi t s in te rna lcommunication through the hospital switchboardwithout the assistance of the operato- At allspecial and important beds, telepholie jacksshould be installed so that a telephone may beplugged in any time.

12.2.1 In case of operation theatre and roomswhere surgical operations and dressing is done,concealed wiring should be provided to avoid riskof contamination. In other places, any ty.pe ofgeneral wiring may be acceptable.

12.2.2 The concealed wiring and switch-socketoutlets in the operation theatres shall be kept at aminimum height of 1.5 m from the floor asanaesthetic gases are heavier than air andgravitate to the floor.

12.3 C l o c k s ~~ Electric clock system whet?provided, should have clocks at nurses’ stations,main lobby, telephone switchboard, kitchen,laundry, dining room and boiler room, as well asin the operating and delivery rooms. The clocksshould be of the recessed type, preferably with anarrow frame. Clocks in operating and deliveryrooms should have sweep second hands. Thegeneral guidance provided in Part I iSec I4 of theCode shall apply.

12.4 Other Special Installations

f’AR1 3 b:l.l-.< TRIC’.\I. INSTALI.ATIONS IN NON-INDl:STRIAL BlMJ,DINCS 143

A P P E N D I X A(Clauses 2.2 and 7.1.1)

ZONE OF RISK IN THE OPERATING THEATRE WHEN USING FLAMMABLEANAESTHETIC MIXTURES OF ANAESTHETIC GASES AND CLEANING AGENTS

ZONE G

ZONE M

LegendI. Ventilation syste’m.2. Ceiling outlet with sockets for electric power,

gases (for example, oxygen), vacuum andexhaust ventilation system for medical electri-cal equipment.

3. Operation lamp.4. Equipment. ,

5. Operating table.6. Foot switch.7. Additional Zone M due to use of flammable

disinfection and/or cleaning agents.8. Anaesthesia apparatus.9. Exhaust system for anaesthesia gases.

IO. Exhaust ventilation system.I I. Parts unprotected and likely to the broken.


A P P E N D I X B

(Clauses 2.3.1 1, 6.1.3.2(b) and 6.1.4)

PATIENT ENVIRONMENT

/-----------.// ‘\

/ a.

I I\\\\ ,I’\ /

l \ --- __ w--w* A’

01 OPERATION TABLE

02 M E D I C A L E L E C T R I C A LE Q U I P M E N T

PART 3 ELECTRICAL INSrALLATIONS IN NON-INDUSTRIAL BUlLDINGS 145'

EXAMPLE OF AN ELECTRICAL INSTALLATION IN A MEDICAL ESTABLISHMENT

A P P E N D I X C(Clause 5.1.4)

a

L e g e n d

::

25.

78:9.

IO.1 I.12.

Heating popesWater supplyGas supplyDistribution boardGeneral wardHospital bedHeating and water pipesMedical IT- system for Operation TheatreInsulation monitoring device. .Medical tsolatmg transtormerSocket .outletMain distribution board

13.14.

1?17:18.19.20.

Main earthing barJointWater meterGas meterWaste waterEarth electrodeLightning protective systemFrom public electric power system

L2, L ==

EC =PE =

Phase conductorsNeutral conductorsBonding conductorProtective conductor


A P P E N D I X D(Clause 6.1.4.1)

SCHEMATIC PRES E NT A T IO N 0~ PROTECTIVE CONDUCTORS AND EQUIPOTENTIALBONDING IN OPERATING THEATRES.

!P j’.-.---i

t :L3PE

Legend1.

:.4:5.6.7.

98.10:

1'::13.14.

Feeder from the main service entrance (maindistribution board)Distribution of the floorOperating thea!re distribution panelSafety supply systemMedical isolating transformerInsulation monitoring deviceSpecial safety supply system, EZSpecial safety supply system, ElCentral heatingMetal- window-frame

15.

Metal cabinet for instrumentsMetal washing-basin and water supplyCeiling stand with outlets for gas supplyCeiling stand with mains socket outlets (withterminals for equipotential bonding, enclosureconnected to the protective conductor bar)Alarm device for the insulation monitoringdevice (example)

16. Operating tabte (electrically driven)

17.18.

19.20.21.22.23.

:;:

;;.28.29.30.31.

Operating lampAmpere meter for special safety supplysystemX-ray equipmentSterilizerResidual-current protective deviceProtective conductor barEquipotential conductor barTerminals for equipotential bondingOperationWarningGreenRedBuzzerStopbutton for buzzerTestbutton

= Protective conductor= Equipotential bonding

L,, Lz, L3 = Phase conductorsN = Neutral conductor


A P P E N D I X E(Clause JO. 1. I)

SAFETY SUPPLY SYSTEMS

E-O. GENERAL

E-0.1 This appendix contains recommendationsfor the design of the safety supply system inmedical establishme.nts.

Priority is given to all aspects ensuring safeworking conditions in medically used rooms.

Interruption of normal electrical service inmedical establishments may cause hazardoussituations. Therefore, it is necessary to provide forcontinuity of power supply for vital services at alltimes.

In some medically used rooms a special safetysupply system should be provided additionally. Itsupplies life supporting equipment and theoperating table lighting for 3 hours only, that is,for a relatively short time if the mains supply orthe safety supply system fails or the switch-overtime cannot be tolerated.

The safety supply system is intended to supplyelectrical energy for a longer period of time toessential circuits of the medical establishment ifthe mains supply fails by external causes.

E-l. ESSENTIAL SERVICES - LIGHTING

E-l.1 Essential lighting requirements will varyconsiderably in different locations. depending onthe importance and nature of the work. In someinstances, for example, operating table lighting inoperating suites, and the crItIcal working areas inthe delivery room and recovery rooms. the degreeand quality of emergency lighting should beapproximately equal to that of the normall igh t ing . Even in these a reas , however ,considerable reduction in the general lighting maybe acceptable. Ample socket-outlets connected toessential circuits should be available to enableportable lighting fittings to be used for any tasksoutside the critical working area,which require ahigher standard of lighting.

E-1.2 No general recommendations can be madefor the emergency lighting arrsngements for stairsand corridors as needs will differ considerablyaccording to the design and size of the hospital.As a general guide, safety lighting should beprovided to enable essential movement of staffand patients to be carried out in reasonablesafety. Safety lighting should also be provided inpublic waiting spaces, at entrances and exits, andin corridors used by members of the public,ambulance staff, etc. External emergency lightingwill normally be restricted to the accident andemergency entrance areas.

E-1.3 Three grades of emergency lighting aresuggested, namely:

a) Grade A lighting of intensity and qualityequal or nearly equal to that provided under

148

normal supply condition&

b) Grade B reduced stanqard of lighting, forexample, about half the normal standard,sufficient to enable essential activities to beproperly carried out, and

c) Grade C safety lighting of a m&h reducedstandard but sufficient to allow the freemovement of persons, trolleys, etc.

Levels for Grades A, B and C are underconsideration.

E-l.4 Table 6 is intended as a general guide.Emergency lighting may be needed in areas notmentioned in the table.

TABLE 6 EMERGENCY LIGHTING

( C/OUSP E-I .4)

D E P A R T M E N T ORLO<‘ATION

Major Operating Sires

ARkA GRADt OFLIGIITING

Operating theatre Critical working area Grade AOperating theatre General working area Grade BAnaesthetic rooms General working area Grade APost operative General working area Grade AIntensive care Circulating areas Grade Croom

Deliver,, SuitesCrltical working area Grade A

Delivery rooms Other nursing areas Grade BCirculating areas Grade C

Awidenr and fher~enc~~DeparrmmrsOperating theatreslntenslve carerooms

Our-ParlmrL~epartnwntOperating theatresTreatment roomsConsulting rooms

Pathologicaldepartment

Diagnostic X-raydepartment

Radiotherapydepartment

Pharmacy

Critical working area Grade ACritical working area Grade AGeneral working areas Grade BCirculating areas Grade C

Critical working area Grade AGeneral working areas Grade BGeneral working areas Grade BCirculating areas Grade C

Essential working Grade Bareas

Blood bank Grade ATransfusion Grade A

laboratory

General working area Grade H(where portable X-raymachines may beused)

Circulation areas Grade C

Treatment areas Grade APublic circulatmg Grade Careas

Dispensing areas Grade BLaboratory Grade B

(Conrrnued)

NATIONAL ELECTRICAL. CODE

TABLE 6 EMERGENCY LIGHTING-Conrd. TABLE 7 SOCKET-OUTLETS IN ESSENTIAL CIRCUITS

( Ckruw E-I .4)

DEPARTMENT OR

LOCATION

Wurd AreasIntensivetherapy units

AREA GRADE OF

LIGHTING

intensive nursing Grade Aarea

Other nursing areas Grade BNurses’ station or Grade Bduty room

(Clause E-2. I)

DEPARTMENT NUMBER O F SOCKETOUTLETS CONNEVTED

TO ESSENTIALCm-rrm (see NOTE)

Operating suites Al l

Intensive care room and operatingrooms in accident and emergencydepartment

All

Special. &by Core UnitsNurseries General working area Grade BPsychiatric wards General working area Grade BTreatment rooms General working area Grade AOther nursing General working area. Grade C

areas (night-lighting)

Delivery rooms

Post-anaesthetic recovery rooms

Intensive therapy units

Cenrrol Sterile Sup&l General working area Grade BDeperrmenr

Operattws Robm

Li/rSLift carsEntrance and efiit of elevators

General CirculatingA rea3

Public entrances -and exits

Corridors andstaircases formingrecognized means

o f e s c a p e

Corridors and cir-culating spaces ofdeep planneddesigns

Elepphone Exhnges Essential working area Grade B

Grade B

Grade AGrade A

Grade C

Grade C

Grade C

Radiological diagnostic room

Ward accommodation set aside forpatients dependent on electricallydriven equipment, for example.respirators. rocking beds, artificialkidney machines, etc.

All

All

All

All

All

Special baby care units Ail

Pathology laboratories 2

Wards where essential equipmentsuch as suction apparatus will beused

2 sockets outlets forwards containingI to 4 beds and.pro rata. wherethe number ofbeds exceeds 4.

No~t -~ It is reasonable to assume that only essentialequtpment ~111 be used in these areas during periods of powerfailure. The recommendation that all sockets.are connected tothe Essentral Circuits provide the most convenient choice ofsockets outlets at any time. and to simplify installation.

Assemb!v AreasAssembly rooms Grade Cand associatedexits

Public waiting _~ Grade Cspace

Plant rooms Working area Grade Bhousing essentialplant

Kitchens Essential working Grade Ba r e a s

E-2.4 Blood banks and other clinical refrigeratorsare usually equipped with temperature retainingfacilities which will satisfactorily sefeguard againstpower failures of several hours’ duration.Nevertheless, they shall be supplied from anessential circuit.

E-2.5 Motors of surgical suction plant should beconnected to an essential circuit. It is desirablethat the motors should be so arranged that oncet h e y a r e s w i t c h e d o n t h e y w i l l r e s t a r tautomatically, following an interruption ofsupply.

E-2. ESSENTIAL CIRCUITS-SOCKET-OUTLETS

E-2.1 Socket-outlets should be so distributed thatin each area where essential equipment will beused, socket-outlets connected to at least twoseparate sub-circuits are available.

Table 7 is intended as a general guide.

E-2.2 Socket outlets’in operating rooms for theconnection of X-ray .equipment for fluoroscopy.should be supplied from an essential circuit.

E-2.3 Electrical services, including automaticcontrols, which are essential for the safe operationof sterilizing equipment in operating theatre andthe central sterile supply department should besupplied from an essential circuit.

E-2.6 Safety supply systems for facilities forventilation and air-conditioning purposes willusually apply only to plants which serve areaswhich are entirely dependent on mechanicalventilation and have no facilities for naturalventilation or where mechanical ventilationservices areessential for clinical reasons. Whereventilation requirements are met by duplicateplants it will usually only be necessary for one ofthe plants to be supplied from the emergencys o u r c e , t h u s e n s u r i n g a i r s u p p l i e s o fapproximately 50 percent of the normal rate.Changeover swi tches , however , shou ld beprovided, to enable either of the plants to beconnected to the emergency service.

E-2.7 Any mains-energized alarm and controlcircuits should be so arranged that they are


automatically connected to the safety supplysystem in the event of a power failure.

E-2.8 In biochemical laboratories and in thepharmacy about 50 percent of the normal loadshould be supplied from essential circuits.

E-3. PARTS OF ESSENTIAL CIRCUITS

E-3.1 peep-freeze refrigerators and food storagerefrigerators will normally operate within atemperature range of -10 to -23°C and befitted with a temperature alarm device to give awarning when the refrigerator temperatureapproaches the upper safety limit. It may bedesirable for one deep-freeze refrigerator at eachhospital to be supplied from the essential circuitswhere this can be conveniently arranged.

E-3.2 In milk kitchen, all refrigerators should besupplied from an essential circuit.

E-3.3 Where electrically operated pumps are usedto maintain essential water supplies (includingthat for fire fighting purposes) it will be nec’essaryto make suitable arrangements for the pumps tobe connected to the safety supply system.

E-3.4 Telephone exchange equipment, is usuallyenergized from float charged batteries having

sufficient capacity for at least 24 hours normalworking.

E-3.5 Where lifts are provided for the movementof patients it is desirable that one lift in eachseparate section of the hospital should be soarranged that it is normally connected to theessential circuits of the installation havingautomatic changeover facilities. These lifts will beregarded as emergency or fire lifts, and should besuitably indicated by markings at each landing.

Suitable manually-operated switchingarrangements should be provided to enable thegeneral safety supply system to be switched fromthe emergency lift to each of the other lifts in turnto eliminate the possibility of occupants beingtrapped in the lifts during power failures. Undernormal supply conditions the emergency lifts onlywill be connected to the essential circuit of theinstallation.

E-3.6 Communication equipment should beconnected to essential circuits.

E-3.7 All boiler house supplies should .be fedfrom essentia! circuits.

E-3.8 Emergency supplies for computers shouldbe examined in each case.


SECTION 5 HOTELS

0. F O R E W O R D

0.1 Hotels lodging or rooming houses are of awide variety, ranging from simple dormitory typeaccommodation for guests, where only a commonbath i s provided with no faci l i ty fordining/kitchen to the sophisticated star hotels.Increasing competition in the hotel industry assuch, coupled with the demand by guests for avariety of comforts, calls for an electricalinstallation in a hotel wi th increasedsophistication.0.2 The electrical needs of a hotel depend on thetype and extent of facilities being provided andthe rating of the hotel:The system design wouldin general be identical with that of any other largebuilding, the actual power requirement expressedin terms of per-unit area or per guest room.03 Specific requirements for installations inswimming pool are covered in Appendix A to thissection. These requirements also apply toswimming pools in other occupancies, say sportsbuildings. For editorial convenience, these specificrequirements form part of this section of theCode.

1. SCOPE

1.1 This Section of the Code covers requirementsfor electrical installations in buildings such ashotels and lodging houses.

2. TERMINOLOGY

2.1 Forthe purposes of this section, the definitionsgiven in Part I /Set 2 of the Code shall apply.

3. CLASSIFICATION

3.1 The electrical installations covered in thisSection are those in buildings intended for thefollowing purposes:

a)

b)

rn

Lodging or Rooming Houses - These includeany building or group of buildings in whichseparate sleeping accommodation for a totalof not more than 15 persons on either tran-sient or permanent basis with or withoutdining facilities, but without cookingfacilities for individuals, is provided.

N OTE -The above is, distinct from single or twofamily private dwellings which are covered inPart’3/Sec I of the Code.

Hotels -These include any building orgroup of buildings in which sleeping accom-modation is provided with or withoutdining facilities for hire to more than 15 per-sons,-who are primarily transienthotels, inns, clubs and motels.

such as

NO T E- For the purpose of this Code, restaurant?other than those forming part of a large hotel aretreated as assembly buildings and are covered inPart 3/Set 3 of the Code.

3.2 The electrical installations in hotels covered inthis Section include the following services:

4b)cl44r)g)h)j)ki

n-44P)4)r)s)t)

u)

v)

Supply intake,Mam distribution centre,Ventilation and exhaust systems,Kitchen,Laundry,Cold Storage,Health club,Swimming pool and filtration plants,Restaurants and bars,Interior lighting,Telephones,Channelized music,Service lifts and passenger lifts,Offices,Fire protection and alarm systems,Banquet halls and conference facilities,Gardens and parking lots and illuminationsystems therein,Illuminated signs, display lights and decora-tive illuminations, andEmergency system.


4.0 General guidelines on the assessment ofcharacteristics of installations in buildings aregiven in Part I /Set 8 of the Code. For thepurposes of installations falling under the scope ofthis Section, the characteristics defined belowgenerally apply.

4.1 Environment

4.1.1 The following environmental factorsapply to Hotels:

Environmenr Characrerisrics Remarks(1) (2) (3)

Presence of water Probability of pre- Majority of loca-sence of water tions in hotels.negligible Traces of water

appearing forshort periods aredried rapidly bygood ventilation


Environmenr(1)

Presence of, foreign solid

bodies

Presence of The quantity and For hotels. situatedcorrosive or nature of corro- by the sea orpolluting sub- sive or polluting industrial zones.stances substances not other cateaori-

significant zation applies(see Part i/Set 8of the Cede)

Mechanicalstresses


Chara;;ri>tirs Remarks(3)

Possibility of jets Applies 10 gardensof water fromany direction.

Possibility of per- Locations suctr.asmanent and total swimming pools

*covering by water

The. quantity ornature of dust orforeign solid bodiesis not significant

Impact and vibra-tion of low severity.

DepepJs on thelocation of thebuilding.

4.2 Utilization

4.2.1 The following aspects of utilization shall

apply:Utilizarion

(1)

Capability ofpersons

Characreri.v/ic:r Re:nurk.s(2) (3)

Ordinary. uninst- A major propor-rutted persons tion of occupants

in Hotels

Persons adequa- Applies lo areas.tely advised or such as buildingsupervised by substation andskllled persons for operating

and maintenancestaff

Contact ofpersons withearth potential

Persons in non-conductingsituations

Condition of. Low, density occu- Applies lo lodgingevacuation auring parlon, easy con- nousesemergency ditlons of evacu-

ation.

High density Large hotels,occupation diffi- high-rise build-cult conditions ings.of evacuation

Nature of No significant riskprocessed orstored material Contamination Applies to

risks due to kitchenspresence of un-protected foodsrulfs



5.0.1 Proper coordination shall be ensuredbetween the architect, building contractor and theelectrical engineer on the various aspects ofinstallation design. In addition to the generalaspec t s which requ i re coord ina t ion and

indentified in other sections. information shall beobtained on the following services :

4

b)

C.)

d)

Whether central air-conditioning system isintended. If so, layout of air handling units,fan coil units, ducting, false ceiling andchilled water lines should be obtained.

Whether centrally controlled fire-fighting isintended. If so, layout of fire-fightinginstallation should be obtained.

Whether telephone and TV facilities areintended. in each room. If so, layout of thetelephone installation and TV circuitsshould be obtained.

Whether centrally heated hot water system isintended. If so, layout of hot water pipe-linebe obtained.

5.1 Branch Circuits

5.1.1 The general provisions for th-c design ofwiring of branch circuits shall conl‘orm to thoselaid down in Part l/Set I I of the Code. However,for ‘special cases such as for .communicationnetworks, fire-alarm system, etc. ;I\ well as inareas s u c h a s k i t c h e n . laundr!,. e t c . therecommenda!ion of the manufacturer shall apply.

5.1.2 The branch circuit calculations shall bedone as laid down in Part 3/Set I of the Code.The specific demands of the lighting, applianceand motor loads. as well as special loadsencountered in hotel building shall be taken intoaccount.

5.1.3 In hotel buildings, the interior decornormally includes false ceiling, carpets andcurtains. Any wiring laid above the false ceilingshould be adequately protected, such as bydrawing the wires in metallic conduits and not runin open. Wires shall not be laid under carpets.They shall be run at skirting level and encased formechanical protection.

5.1.4 Panel Boards and S\c.ir~~ll-hoards -Theprovisions of Part I Set I I 01 the Code sha l lapply.

5.1.5 Socket-outlets trtltl I’llcp\

5.1.5.0 These should hc pro\lded in all placeswhere plug-in service I\ I~hcl! to be required, toreduce the need for altcr:\tlonh and extensions ofwiring after the hotel building is completed.Duplex or other suitable outlets should beprovided as required in the offices and workplaces for fans, lamps and appliances. The socket-outlets shall preferably have covers. Corridorsand staircases shall be provided with sufficientsocket-outlets for floor cleaning appliances. Theseshall be connected in a circuit separate from thecircuits for the guest rooms.

5.1.5.1 If provided, use of a central radioreceiving system wired with multi-channels pipedmusic system to each room is recommended sotha t the occupa?t may choose one of thebroadcasts. For such reception, special aerials and


related wiring arerooms are reauired

required. Aerial outlets atfor ttortable radios in arqas

and buildings’ where re;eption is poor but ingeneral the aerial buht in the set may be adequate.

5.1.5.2 Special convenience outlets incorridors at suitable locations are desirable for

fuse o portable equipment such as floor cleaningappliances. They should be of the 3-pin type.suitably rated with one-pin earthed.

Heavy duty sockets should also be provided inpantries, kitchens, toilets and utility rooms for useof appliances.

Adequate plug-in sockets at proper locationsshould be provided in banquet halls and othermeeting places for flood lights and otherappliances.

5.2 Feeders — the general provisions laid downin Pan 3/See 11 of the Code shall apply.

5.3 Service Lines— The general provisions laiddown in IS :806”1-1976* shall apply.


5.4.1 H the load demand is high which requiressupply at voltage above 650 V a separate indooraccommodation, as near the main load centre offhe hotel as possible shall & provided toaccommodate switchgear equipment of supplyundertaking and Indoor/outdoor accommodationfor the transformers. The main distributionequipment of the hotel shall preferably be locatednext to the substation. Separate feeders shall beprovided ~,for major lbads like central air-conditionlng, kitchen. laundry, swimming pool,lighting of main building and other essential.loads.

5.4.2 The supply line should preferably bebrought into the building underground to reducethe possibility of interruption of power supply.The accommodation for substation equipment aswell as for main distribution panel shall beproperly enclosed so as. to prevent access to anyunauthorized ~son. It shall be provided withproper ventilation and lighting arrangement.

5.5 SystemProtection

5.5.1 Genera/ — The general rules forprotection “for safety laid down in Part 1/ Sec 7 ofthe Code shall a ply. Reference should ti made

1’to SP :7-19831 or guidelines for fire protectionof buildings.

5.5.2 For lodging and rooming houses of 3storeys and above, with a floor area more than200 m~ with central corridor and rooms on eitherside, besides fire fighting equipment, manuallyoperated electric fire-alarm system shall be

*Code of practice for design, installation and maintenanceof service lines up to and including 650 V.

tNational Building Code.

154

provided. Both manually operated and automaticfire-alarm systems shall be provided in largefiotels,


5.6.1 Lighling

5.6.1,1 The general rules laid down in PartI /%c 14 of the Code shall apply. The choice oflighting fittings and general lighting designtogether with power requirements shall beplanned based on the recommended values ofillumination and limiting values of glare indexgiven in Table 1.

SLNo.

(1)

1.

2,

3.

4.

5.

6.

7.

EL

9,

10.

!1.

12.

13.

14.

TABLE 1 RECOMMENDED VALUES OFILLUMINATION AND GLARE INDEX

FOR HOTELS

BUILDING “ILLuhfb LIMITINGNATION GLARE

INDEX(2) (3) (4)

hlx

Entrance halls. lobby 150

Receptionand accounts 300

Dining rooms (tables) 100 .

Lounges 150 —

Bedrooms:a) General 100 —

b) Dressing tables, bed 200 —

heads, etc

Writing tablks 300

Corridors 70 —

Stairs 100

Laundries 200 25

Kitchens 200 25

Goods/ passenger lifts 70 —

Cloakrooms/ toilets 100 —

Bathrooms 100 —

Shops/stores 150 to 300 22

N6TE — The lighting of some of these locations isdetermined primarily by aesthetic considerations and theubovc viilues should be taken as a guide only.

5.6.1.2 In guest bedrooms, it shall be possibleto switch the general lighting not only from theentrance but also-from the bedside (see aho 7.4.2).

5.6,1.3 In bathrooms, the lights should bemounted at head level on both sides of the mirror.Care shall be taken to ensure that there is nogla[e.

5.6.1.4 Lighting in banquet halls shall begiven special consideration in view of itsmultipurpose utility such as fairs, dances. fashionshows, conferences, exhibition or concerts.Sufficient number of controlled socket-outletcircu’its sha~l be combined in a switching stationfrom which the entire hall shall be visible.

NATIONAL ELE~RICAL CODE

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5 .6 .1 .5 In des ign ing ou tdoor l igh t inginstallations, care shall be taken to ensure thatdisturbing glare does not reach the rooms of theguest’s.

5.6.2 Air-condirioning --- The provisions ofPart l/Set 14 of the Code shall apply.

5.6.3 L,$ts and Escalarors

5.6.3.0 The general rules laid down in Part I /Set 14 of the Code shall apply. However, thedesign of l ifts shall take into account thefollowing recommendations.

5.6.3.1 Occupant load - For hotel buildings,an occupant load of 12.5 gross area in m2 perperson is recommended.

5.6.3.2 Passenger handling capacity - Thepassenger handling capacity expressed in percentof the estimated population that has ‘to behandled in the 5 minute peak period shall be5 percent for hotel buildings.

5.6.3.3 Car speed- This shall be as follows :

Occupancy FloorsServed

Car Speedm/s

Passenger lifts -for low andmedium classlodging houses

0.s

Hotels 4-5 0.5-0.75

5.6.3.4 For hotel buildings, it is desirable tohave at least a battery of two lifts at convenientpoints of a building. If this is not possible, it isadvisable to have at least two lifts side by side atthe main entrance, and one lift at differentsections of the building for intercommunication.


6.1 The various tests on the installation shall becarried out as laid down in Part l/Set IO of theCode.


7.1 Call System -The general provisions forelectrical bells and call system shall conform tothose laid down in Part I /Set I4 of the Code. Thecall system should be a wired electrical systemwhereby customer may signal for attendance fromh i s r o o m . T w o t y p e s o f s y s t e m s a r erecommended :

a) A simple one-watt signal system whichconnects the room side call sfatims with as igna l a t t h e a t t e n d a n t s t a t i o n . ltsimultaneously lights a dome light over thedoor of the room from which the call isoriginated. The signal at the attendantstation may be in the form of anannunciator with a bu77er or a light with abuzzer.

b) A central control panel shall, be set uppreferably on the ground floor incorporatinga set of indicating panels according to thenumber of wings. Each indicating panelshould have a set of small lamps accordingto the number of rooms. After.attending thecustomer, the attendant presses the resettingbutton which puts the whole equipment tothe original condition.

7.2 Telephones - For internal communicatiofi.telephones may be required to be provided. Thesemay be connected on a dial system which permitsinternal communication through the hotelswitchboard without the assistance of theoperator. At all the rooms, telephone jacks shallbe installed so that a telephone may be plugged inany time at any convenient location. Paralleltelephones may be provided in the bedrooms.7.3 Clock Systems- The general provisions forclock systems shall conform to those laid down inPart 1 /Set 14. The following locations may beprovided with clocks:

a) Guest rooms,

b) Main lobby ,

c) Telephone switchboard,

d) Dining room,

e) Banquet halls,f) Kitchen, and

g) Restaurant and bar rooms.

7.4 Emergency Supply - (see a/so Part 2 of theCode).

7.4.1 In the event of a failure of supply, a largestandby power supply usually a diesel drivengenerating set could be used to partly or entirelysupply the loads in the hotel. Emergency lightingshall be confined to essential areas, and thestandby power supply shall feed essential andsafety installations in the hotel.

7 .4 .2 Par t o f the k i t chen , s to rage andrefrigeration rooms in the hotel shall also besupplied by the emergency supply.. A part of thelighting in each room, cdrridor, staircases andother circulation areas shall be connected toemergency supply.

7.5 Other Special Installations -The list of suchinstallations is given below:

a) TV sets at main assembly areas and in guestrooms,

b) Lighting in banquet halls,

c) Fire-fighting system,

d) Swimming pool (see Appendix A), and

e) Cold storage.

7.6 For particular requirements’ foi locationscontaining a bathtub or shower basin, seeAppendix A of Part 3/Set I of the Code.


A P P E N D I X A(Clauses 0.3 and 7.6)

PARTICULAR REQUIREMENTS FOR SWIMMING POOL

A-l. SCOPE

A-l.1 This appendix applies to the basins ofswimming pools and paddling pools and theirsurrounding zones where susceptibility to electricshock is likely to be increased by the reduction ofbody resistance and contact with earth potential.

A-2. CLASSIFICATION OF ZONES

A-2.1 Reference is drawn to Fig. 1 and 2.

Zone 0 -is the interior of the basin, and

Zone 1 - is limited by a vertical plane 2 mfrom the rim of the basin by the floor or thesurface expected to be occupied by persons andthe horizontal plane 2.50 m above the floor of thesurface.

NOTE - Where the pool contains diving boards, springboards, starting blocks or a chute, Zone I comprises the zonelimited by a vertical plane situated 1.50. m around the divingboards, spring boards and starting blocks, and by thehorizontal plane 2.50 m above the highest surface expected tobe occupied by the persons.

Zone 2 - is limited by the vertical planeexternal to Zone 1 and a parallel plane 1.50 mfrom the former, by the floor or surface expectedto be occupied by persons and the horizontalplane 2.50 m above the floor or surface.

A-3. PROTECTION FOR SAFETY

A-3.1 Where safety extra-low voltage is used,whatever the nominal voltage, protection againstdirect contact shall be provided by barriers orenclosures affording at least a protection of IP2X,or insulation capable or withstanding a testvoltage of 500 V for I minute.

A-3,2 All extraneous conductive parts in Zones 0,1 and 2 shall be bonded with protectiveconductors of all exposed conductive partssituated in these Zones.

A-4. SELECTION OF EQUIPMENTA-4.1. Electrical equipment shall have at least thefollowing degrees of protection:

Zone 0 : IP X 8

Zone 1: IPX4

Zone 2 : IP X 2 for inside swimming pools.IP X 4 for outside swimming pools.

A-5. WIRING SYSTEMS

A-5.1 In zones 0 and 1 wiring systems shall belimited to those necessary to the supply ofappliances situated in those zones.

A-5.2 Junction boxes are not permitted in Zones0 and 1. In Zone 2, they are permitted providedthey have the necessary degree of protection asgiven in A-4.1.

A-5.3 In Zones 0 and 1 no switchgear andaccessory shall be installed. In Zone 2 socket-outlets are permitted only if they are either :

4

b)cl

supplied individually by an isolatingtransformer, or

supplied by safety extra low voltage, or

protected by a residual current protectivedevice.


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SECTION 6 SPORTS BUILDINGS

0. F O R E W O R D

0.1 The design and erection of e l e c t r i c a linstallation in a sports building have to take intoaccount a multitude of factors. that are unique tothe type of use to which it is put. In a way theelectrical power needs and the external influencesin a sports building are quite identical to those fortheatres and other multipurpose buildings forcultural events excepting that for internationalevents exacting standards of services andflexibility had to be provided in a multipurposesports stadia.

0.2 Several stadia, especially those of the indoortype are meant for staging a variety of gameswhich between themselves require varyingstandards of lighting levels. The design ofillumination system in a sports building thereforerequires consultations with a specialist and theguidelines provided in this Section are purelyrecommendatory in nature in this respect.

0.3 In indoor stadia where large number ofpeople congregate i t is essential to inbuildadequate fire precautioris from the point of viewof safety. Assessing the need for adequate strengthof a standby supply for essential services requiresspecial considerations.

0.4 It is to be noted that a sports stadia shouldpreferably be designed for use for other purposesas well, such as the staging of cultural events andthis aspect shall be borne in mind while designingthe electrical needs of the complex so as to ensureoptimum utilization of the facilities.

0.5 With the advent of sophisticated stadia in thecountry as well as keeljing in view the accent onsports, this Section of the Code has been set asideto cover such of those specific requirementsapplicable to sports buildings from the electricalengineering point of view. Taking note of the f&tthat the type of buildings and their needs for thepurposes of sports and games would be quitedifferqnt between them, only broad guidelines areoutlined in this Section. It is recommended thatassistance of experts shall be sought in the designof the installation at the early stages itself:

1. SCOPE

1.1 This Section of the Code covers requirementsfor electrical installations in sports buildings andstadia, indoor and outdoor.2. TERMINOLOGY

2 . 1 For the purpdses of th i s Sec t ion , thedefinitions given in Part I/Set 2 of the Code shall

~-- apply.

3. CLASSIFICATION OF SPORTSBUILDINGS

3.1 The buildings for the purposes of conducting

sports and games are characterized by the criteriathat large number of people congregate. Sportscomplexes not basically meant for exhibitionpurposes, and not likely to be utilized for otherpurposes, such as -for staging special or culturalevents, shall however conform to the specialrequirements of this Section. The type of buildingshall therefore be classified as follows:

a) Based on Type of Building:

i) Indoor stadia

ii) Outdoor stadia : Stadia meant for usein daylight

Stadia meant for useduring night underartificial lighting

b) Based on Type of Game/Sport

i) Single game spprts hall/stadia.

ii) Multigames hall/stadia.

c) Based on utilit_v

i) Stadia meant for games only.

ii) Multipurpose stadia for oth&.r amuse-ments as well.

d) Based on Audience-factor

i) Stadia/halls meant for exhibition pur-poses-where groups of people con-gregate.

ii) Stadia/halls meant for training and pass-time -,where audience may not normal-ly be present.

NOTE ~ Classification d(i) includes stadia meait for stagingtournaments and events and d(ii) includes games halls ineducational institutions and the like where normally noexhibition is intended.

3.1.1 Reference should be made to 5.5.1.2 forclassification from lighting consideration.

3.2 The electrical installation needs in sportsbuildings would therefore be governed by the typeof use indicated in 3.1(a) to (d) above. A largesports complex may include the following sub-units:

a)b)

c)4

e)

f)

Supply intake/voltage of supply;

Main -substation and satelite substations, ifany;Central control room/ switch rooms;

Electrification of restaurant, health, clubs;hospitals, offices and other support struc-tures;

Communicationtelegraph, datapress facilities);

Fire protection

facilities (telephbne, telex,processing TV, radio and

services;

159PART 3 ELECTRICAL INSTALLATIONS IN NON-INDUSTRIAL BUILDINGS

.g)

h)

_i)k)

ml

n)

External electrification ot gardens and park-ing lots, service routes, lake fountains (ifany);Emergency electric, supply system includinguninterrupted power requirements;

Audio systems, public address/security;

Dewatering arrangements, sewage disposal,water supply systems;

Gas/oil arrangements for sports flame ifrequired; and

Miscellaneous requirements for power-socket, microphone outlets, score-boards,etc.

4. GENERAL CHARACTERISTICS OFSPORTS BUILDINGS

4.0 Genera1 guidelines on the assessment ofcharacteristics of installations in buildings aregiven in Part 1 /Set 8 of the Code. For thepurposes of installations falling under the scope ofthis Section, the characteristics given below shallapply.

4.1 Environment

4.1.1 The following environmental factorsapply to sports buildings:

Environment(1)

Presence of water

Presence of for-e i g n s o l i d b o d i e s

Presence of corro-sive of pollutingsubstances

Lightning

Characteristics Remarks(2) (3)

Submersion. pos- Locations such assibility of perma- swimming poolsnent and total where electricalcovering by equipment is per-water manently and

totally covered withwater under pres-sure greater than0.1 bar.

The quantity or Indoor stadia.nature of dust orforeign solid bodiesis not significant

Presence of dust Outdoor stadia.in significantquantity

Negligible. Covers majority ofcases. Stadia andgames cbmplexessituated by thesea or industrialzones requirespecial considera-tion.

Negligible. Covers category d(ii)(see 3.1) type ofinstallations.

Indirect exposure Installations supp-to lightning. lied by overheadwhere hazard lines.from supplyarrangementsexists.

Direct exposure Lighting towers inor hazard from outdoor stadia.exposure of equip-ment is present.

160

4.2 Utilization4.2.1 The following aspects of utilization shall

apply:Utilization

(1)

Characteristics(2)

Remarks(3)

Capability of Uninstructedpersons persons.

In sports stadia thesportsmen andspectators fallunder thiscategory.However. electricaloperating areas areaccessible toinstructed personsonly.

Conditions of 1.0~ density occu- Training halls andevacuation in an pation, easy con- the like whereemergency. ditions of evacu- people do not

ation. congregate.

High density -Large multipurposeoccupation, diffi- stadia for exhi-

*cult conditions of bition purposesevacuation.

Nature of proces- Existence of fire- Due to furnituresed or risks. and false floor forstored material playing area.


5.0 Exchange of Information5.0.1 Proper coordination shall be ensured

between the architect building contractor and ;theelectrical engineer on the various aspects of theinstallation design. In addition to the genera1aspects which require coordination and identifiedin other sections, the following data shallspecifically be obtained:

4

b)

c)

d)

e)

0

The total electric power needs of thestadium including the standby power arran-gements, which will decide the voltage ofsupply, number of substations and theirpreferred locations, capacity of diesel enginegenerating sets for standby supply, trans-formers, switchgear, voltage stabilisers,uninterrupted power supply requirements,etc;

In case of indoor stadia, whether air-condi-tioning is required and if so, the capacityand locations of main plants, air-handl-ing units, pumps, ducting, layout, route ofchilled water lines, etc. In case of outdoorstadium, the covered portions like offices,restaurants, are to be air-conditioned ornot and their details as above;

Details of fire fighting system/fire alarmsystem envisaged;

Details of water supply arrangements, stormwater drainage, sewage disposals and thepump capacities, locations, etc;

Locations of substations, switchrooms, dis-tribution boards, etc;

Requirements, of audio-communication


g)

h)

j)

k)

ml

system for the stadium which includes publicaddress system, car calling system, ambu-lance call, fire service call, intercom stations,wireless paging system, inter-stadia commu-nication facilities, computer-aided resultsinformation, etc;

Details of score-boards -that is whethermanual or automatic, etc, and their powerneeds, voltage stability, etc’, centralizedclock system, etc;Special requirements of press, TV, radio,telecommunication, games federations,. etc;Requirements of lighting, the location oflighting luminaires, type of light source,l&e1 of illumination required for variousstages like training, TV (black and white drcolour) coverage, etc;Requirements for power outlets, speakeroutlets, microphone outlets, etc, in playingarena and field;Other micellaneous items like electrificationof ancillary buildings in the sports complex,restaurants, gas/oil requirements for flameand their controls, fountain lighting system,car park,, path way and external electrifi-cation.

5.0.2 The following drawings are recommendedto be prepared before commencing the installa-tions work:

4

b)

c)

d)

e)

0

Single line diagram for electrical distri-bution;Complete layout drawings indicating typeand mounting .of luminaires and conduit/cable installations for various services.This shall be prepared in coordination withcivil and structural engineers;Wiring diagrams showing &itching sequenceof luminaires, tirealarm system, publicannouncement, systems, etc;In Zase of air-conditioning, layout of pln,1t5,chilled water piping routes, ducts/grill lay-out, etc;Layout of public address system envisaged;andSite plan ‘indicating the location of pumphouses for storm water drains, water supply,sewage and fire fighting systems, with theproposed source and route of power supply.

5.1 Branch Circuits

51.1 The general rules as laid down for otherlarge assembly buildings (see Part 3/Set 3) and aslaid down in Part I of the Code shall .apply.

5.1.2 Wiring installations for general purposelighting and ventilation needs of the sportsbuildings shall conform to the requirements laiddown in Part 1 /Set I of the Code. It is preferable

to avoid temporary wiring in electrical centralcontrol room.

Whenever floodlight luminaires of more thanI 000 W are installed, it is preferable to haveindividual branch. circuits to each of theluminaires after considering the economic aspects.

Junction boxes shall be installed near theluminaires from which connection to the lightsource may be taken by flexible conduits. This.will help maintenance work to be carried outwithout disturbing the positioning of the lightingfittings.

5.1.3 Panel Boards and Switchboards - Theprovision of Part I /Set 1 I of the Code shallapply. In large stadia, the areas covered by theservices shall be segregated into zones and thesubdistribution and distribution boards shall beso arranged and marked keeping in view theiraccessibility in times of need.

5.1.4 Socket-outlets and Plugs - For smallstadia] halls, the provisions of Part 3/Set 3 of theCode shall apply. The need for specialconvenience outlets shall be considered forservices enumerated in 3.2(e). Utility socket out-lets shall be provided at a height of about 0.3 mfrom the floor exce t in field/arena. These shallbe of weather-pro0 P type.

5.2 Feeders

5.2.1 The Utility shall be consulted as to thetype of service available, whether primary orsecondary, single-phase or three-phase star ordelta.

5.2.2 Outdoor floodlighting installations can bemade with either overhead or undergrounddistribution feeders. From the pqint of view ofappearance and minimum interference, theunderground system is more desirable where largeplaying areas are involved.

5.2.3 The underground system shall either becables directly buried or cables in conduits.5.3 Building Sdbstation

5.3.1 The electrical needs of sports stadia mayvary from 30 kVA to 1 000 kVA, according to thesize of the Installation. Usually HV supply is usedfor large multipurpose stadia where powerdemand is in excess of 500 LVA. The design ofsubstation shall conform to the requirementsspecified in Part 2 of the Code.

5.3.2 The main substation for a sports buildingshall prefereably be located in such a place thatdoes not interfere with the movement of peoplecongregating. All electrical operating areas, andcontrol rooms shall preferably be segregated frompublic routes for the sporting events.

5.3.3 Some installations may justify a separatetransformer on each pole of the floodlightingtower with primary wiring to each tower. Insmaller installations, it may be more economicalto reduce the number of transformers by serving


several locations from a single transformer of sport play into general areas for more than onethrough secondary wiring. sport and areas for particular sport.

5.3.4 For buildings staging national or General areas include, field houses,international sport events, it shall be ascertainedwhether duplicate power supply would be

gymanasiums, community centre halls and other

required together with its capacity, and the loadsmultipurpose areas. For the purposes of lightingdesign, the nature of sports shall be divided as

it is intended to serve. follows:


5.4.0 The general rules for the protection ofsafety laid down in Part I/Set 7 of the Code shallapply.

5.4.1 Sports buildings are classified as‘assembly buildings’ (Group D) from fire-safetypoint of view (see SP : 7-1983*). Besides firef ight ing equipment f i re-detect ion andextinguishing system. shall be provided asrecommended below:

a) Aerial sports (sports Badminton, basketball,which are aerial in handball, squash,part or whole) tennis and

volleyball.b) Low level (games Archery, billiards,

which are close to bowling, fencing,the ground level) hockey, swimming

and boxing.

Description F i r e Derecrion System

dig halls for over 5 000 Automatic sprinkler andpersons. alarm system.

Small halls. health clubs. Automatic sprinkler.arena. gymnasiums. etc.indoor with or without Automatic firealarm system.fixed seats corridors forabout I 000 persons.

Same as above. occupancy Same as above.for less than 1000 persons.

5.5.1.3 Levels of illumination - For somerepresentative types of sport, the recommendedvalues of illumination are as given in Table I.

5.5.1.4 Sekction of light sources - For sportslighting, the following light sources areadvantageous together with the considerationsindicated against each:

a)

Small indoor games halls Automatic firealarm system.for less than 300 persons. b)

Grandstands, stadia foroutdoor gathering.

Ma:rually operated firealarmsystems. in offices and auto-matic firealarm system inrtndia. mitchinc room. controlroom. ctc

Incandescent lamps (including tungstenhalogen) - Where necessary, overvoltageoperation can be used to advantage especi-ally as in sports installations, the lightingsystems are used for less than 500 h a year.Fluorescent lamps - Advantageous wheremounting heights are low and short projec-tion distances are acceptable - for exam-ple tennis, bowling, trampoline and a varietvof indoor sports.

cl


5.5.1 Lighting

5.5.1,0 The general rules laid down in Part I ISet I4 of the Code shall apply.

5.5.1.1 Special design .,features - Design ofsports lighting, especially m large stadia requireconsiderations of not only the objects to be seen,the background brightness, etc. but the observer’slocation in the grandstand as well. The following

High intensity discharge lamps - These arecharacterized by long life and high lumanefficiency. However, the inherent time delayfor full glow when first energized or whenthere is power interruption may neces-sitate use of incandescent lighting systemto provide emergency standby illuminationin spectator areas.

For sports events, where colour rendition isimportant, use of fluorescent mercury lamps isrecommended.

5.5.1.5 Miscellaneous considerations forlighting

shall

a)

b)

c)

be taken Into account:Observers have no fixed visual axis or fieldof view. During the shifting of sight, eventhe ceiling and luminaires are likely to comeinto the line of vision.While the game is in play, the objects ofregard are not fixed, and mostly moving in athree-dimensional space.It is important for observers to be able toestimate accurately the object velocity andtrajectory.

5.5.1.2 For’ the purposes of artificial lightingdesign, it is recommended to divide the location

*National Building Code.

162

a)

b)

While selecting and installing high intensitydischarge or fluorescent lamps in multipur-pose stadia, it is necessary to connect lampson alternate phases of supply to avoid flic-ker on rapidly moving objects. Where a quitesurroundmg is required in order to avoidballast hum, remote mounting of .ballastsshall be considered.Efforts shall be required to coordinate thelighting design for sports events with theillumination requirements for TV or filmcoverage. A horizontal illumination inexcess of 300 lux is considered adequate foroperation of black and white TV and filmrecording. Colour recording calls for more


TABLE 1 RECOMMENDED VALUES OFILLUMINATION(Clause 5.5.1.3)

SPORT

(I)

ArcheryTargetShootinn line

BadmintonBasketballBilliards (on table)Boxing and wresthngFo~(a”,“1, (see NOTES I and 2)

:I,I V

GymnasiumsMatchesGeneral exercising

Hockey (field)Racing

BicycleHorse

Rifle (outdoor)T a r g e t sFiring pointRange

Swimminga ) /r&or Exhibirion

Underwater*

b) Our&or E.khihirionUnderwater*

Tennis (lawn) IndoorOutdoor

Table tennisVolleyball

540220320540540540

Separate switching for lighting outsidethe stadia,

Requirement. of lighting for trainingpurpose,

1 100540320220

the

i)

ii)

iii)

iv)

Requirement of lighting for tournamentswith film and TV coverage, and

Separate switching for playing arenas.

540320220

5.5.2 Air-conditioning

320220

552.1 The requirements for air-conditioningand ventilation as laid down in Part I /Set 14 ofthe Code shall apply.

540 (vertical) 5.5.3 L[fts and Escalators-The general rules1 IO laid down in Part I/Set 14 of the Code shall54 apply.

540100 W/m’ of

surface area220

60 ;;yo6’;t of

540320540220

NOTE 1 - It is generally conceded that the distance betweenthe spectators and the play is primary consideration forfootball, as well as the potential seating capacity of the stand.The following classification is therefore described:

Class 1 - 30 000 spectators. over 30 m minimumdistance.

Class 11 ~~ 10 000-30 000 spectators, over 15-30 m mini-mum distance.

Class III ~~ 5 000-10000 spectators, over IO-15 mminimum distance.

C lass IV -~ 5 000 .spectators, o v e r I O m m i n i m u mdistance.

NOT; 2 - For football. unifgrm illumination shall beprovided at ground level as well as vertically for 15 m aboveground.

*Levels recommended are for incandescent lamps. Fordischarge lamps W/m’ would be reduced depending upon theefficiency of light source. In order that the installed flux is notwasted the walls of the pool basin shall be given a highreflectance surface finish.

stringent requirements. Colour filming mayalso need lamps having correlated colourtempera tu re o f be tween 3 000 K to7 000 K.

7.2 Control Room - The various communica-tion needs of a large stadia is normally met withby electronic equipment centrally controlled,requiring specific power supply, and otherinstallation conditions. This would call for specialwiring systems with sychronizing systems. Thetechnica l requ i rements fo r these sys temsconcerning voltage and frequency stability arevery high. These shall be considered beforedesigning the electrical services of the same.

7.3 Electrical/Electronic Score Board - Thepower requirements for such equipment woulddepend on the type of equipment to be installed.Guidelines of the manufacturer shall be adheredto.

For film/TV coverage, data on the following 7.4 Clock System - Reference shall be made toshall be necessary: the provisions in Part I iSec 14 of the Code.

9 Camera senitivity,ii) Exposure time, and

iii) Effective aperture.c) Grouu switching - Group switching of

luminaires is recommended t o h a v emaximum energy saving, after considering

following factors as well:


6.1 The various tests on the installation shall becarried out as laid down in Part I /Set IO of theCode.


7.1 Electrical Audio Systems - The generalprovisions for the installation of public addresssystems shall be as laid down in Part l/Set 14 ofthe Code.

In large grandstand stadia, the effect of time.delay for the sound from the loudspeakers toreach different sections of the audience would besignificant. This shall be avoided in taking properprecautions in the design of electrical audiosystems.


APPENDIX TO PART 3SPECIFIC REQUIREMENTS FOR ELECTRICAL

INSTALLATIONS IN MULTISTOREYED BUILDINGS

O . F O R E W O R D

0.1 The design and construction of electricalinstallations in multistoreyed buildings call forspecial attention to details pertaining to fire-safetyof the occupancy. While on the one hand, the civildesign aspects are more stringent for high-risebuildings than for buildings of low heights, theelectrical design engineer, on his part had toensure that the fire hazards from the use ofelectric power is kept to the lowest possible limit.

0.2 In drafting the requirements of electricalinstallations in various occupancies it was felt thata separate compendium giving the specificrequ i rements app l icab le to mul t i s to reyedbuildings should be brougnt out. For editorialconvenience, such details have been stated in thisAppendix where the major non-industrialoccupancies have been covered.

0.3 In applying the provisions of this Appendix,note shall also be taken of the nature ofoccupancy of the high-rise buildings and ajudicious choice of alternative features shall bemade.

1. SCOPE

1.1 This Appendix is intended to cover specificrequ i rement s for electrical installations inmultistoreyed buildings.

I.2 The requirements specified here are inaddition to those specified in respective sectionsof the Code, and are specifically applicable forbuildings more than 15 m in height.

2. TERMINOLOGY

2.1 For the purposes of this Appendix, thedefinitions given in Section 2, Part 1 /Sec. 2 of theCode shall apply.

3. SPECIAL CONSIDERATIONS

3.1 Special considerations shall have to be givenin respect of the following requirements for theelectrical installations in multistoreyed buildings:

4

b)cl4e)

fl

164

Internal wiring for lighting, ventilation,call bell system, outlets for appliances, powerand control wiring for special equipments likelifts, pumps, blowers, etc;

Distribution of electric power;

Generators for standby electric supply;

Telephone wiring;

Fire safety;

L.ightning protection;

g) Common antenna system;

h) Clock system; and

j) CCTV.

4. EXCHANGE OF INFORMATION4.1 The detailed requirements of the owner shallbe assessed at the planning stage.

4.2 It is necessary that right at the planningstages, t h e r e q u i r e m e n t s o f s p a c e f o raccommodating the distribution equipment forthe various electrical services and openingsrequired in slabs for vertical risers for suchservices are assessed and incorporated in drawingsin due coordination with the architect andstructural designer. Care shall be taken to provideadequate and where necessary, independentspaces for the equipment for electrical services fordifferent functions.

4.3 Multistoreyed buildings are usually in frameddesign. Coordination with the architect is requiredin evolving suitable layout of lights, fans andother outlets and the position for their switchcontrols to take care of functional utility andflexibility.

4.4 While designing the electrical services, dueconsideration should be given for conservation ofenergy.

4.5 The voltage of supply and location of energymeters (especially in multistoreyed buildingsmeant for residential purposes) shall be agreed tobetween the utility and the owner of the building.Spaces for accommodating the distribution andmeter ing equipment o f u t i l i ty should beaccordingly provided for by coordinating with thearchitect and licensee.

4.6 The telephone authorities shall be consultedfor the requirements of space for accommodatingthe distribution equipment, battery, etc. for thetelephone services.

4.7 The local fire brigade authorities shall beconsulted in the matter of system layout for firedetection and alarm systems to comply with localbye-laws. The locations of control panel andindication panel shall be decided in consultationwith the owner.

4 . 8 R u n s o f r o o f c o n d u c t o r s a n d d o w nconductors for lightning protection shall becoordinated with the architects of the building.The requirements as laid down in Part I/Set I5of the Code shall be complied with.,

5. ASSESSMENT OF CHARACTERISTICSOF MULTISTOREYED BUILDINGS

5.0 The general characteristics of buildingsdepending on the type of occupancy are assessed

NATIONAL ELECTRICAL CODE.

based on the guidelines given in relevant sectionsof the Code, together with those given in PartI/Set 8.

5.1 For the purposes of rnultistoreyed buildingsin addition to other external influences dependingon .the type of occupancy , the e lec t r ica linstallation engineer shall specifically take note ofcharacteristics BD2, BD4 and CB2 given in TableI of Part I /Set 8 of the Code.

6. DISTRIBUTION OF ELECTRIC POWER

6.0 Load Assessment and Equipment Selection6.0.1 The electrical load shall be assessed

considering the following:

a)b)

c)

Lighting and power loads;

Special loads of equipments as in laborato-ries, hodpitals, data processing areas, etc;

Air-conditioning/evaporative cooling/ heat-ing services;

4 Water supply pumps;

d Fire fighting pumps;

r) Electric lifts; and

g) Outdoor and security lighting.

The anticipated increase in lpad shali also begiven due consideration.

6.0.2 Suitable demand factors and diversityfactors shall be applied depending on theoperational and functional requirements. Thedistribution equipments shall be selected byadopting, standard rat ings. Adequate sparecapacity should be provided for every componentin the distribution system.

6 . 0 . 3 T h e f a u l t l e v e l a t t h e p o i n t o fcommencement of supply should be obtainedfrom the licencee and fault levels at salient pointsin the distribution system assessed. Distributionsystem component should be selected to satisfythe same.


6.1.1 The provisions contained in Part 2 of theCode shall apply.

6.1.2 A substation or a switch-station withapparatus having .more than 2 000 litres of oilshall not ordinarily be located in the basemlntwhere proper oil drainage arrangements cannot beprovided. If transformers are housed in thebuilding below the ground level, they shallnecessarily be in the first basement in a separatefire-resisting room of 4-hour rating. The roomshall necessarily be at the periphery of, thebasement. The entrance to the room shall ‘beprovided with a fire-resisting door of 2-hour firerating. A curb (sill) of a suitable height shall beprovided at the entrance in order to prevent theflow of oil from a ruptured transformer into other

parts of ttie, basement. Direct access to thetransformer mom shall be provided, preferablyfrom outside. The switchgears shall be housed in aroom separated from the transformer bays by afire-resisting wall with fire resistance of not lessthan 4 hours.

6.1.3 The transformer, if housed in basement,shall be protected by an automatic high velocitywater spray system. The transformer may beexempted from such protection if their individualoil capacity i’s less than 5 000 litres.

6.1.4 In case the transformers are housed in thebasements, totally segregated from other areas ofthe basements by 4-hour fire-resisting wall/ wallswith an access directly from outside, they may bep r o t e c t e d b y c a r b o n d i o x i d e o r B C F(bromochloro d i f lu ro methane) o r BTM(bromotrifluro methane) fixed installation system.

6.1.5 When housed at ground floor level,it/they shall be cut off from the other portion ofpremises by fire-resisting walls of 4-hour fireresistance.

6.1.6 Oil-filled transformers shall not behoused on any floor above the ground floor.

6.1.7 Soak pit of approved design shall beprovided where the aggregate oil capacity of theapparatus does not exceed 2 000 litres. Where theoil capacity exceeds 2 000 litres, a tank of RCCc o n s t r u c t i o n o f c a p a c i t y c a p a b l e o faccommodating entire oil of the transformersshall be provided at a lower level to collect the oilfrom the catch-pit in case of emergency. The pipeconnecting the catch-pit to the tank shall be ofnon-combustible construction and shall beprovided with a flame-arrester [see LS : 10028(Part 2)-19811.

6.2 Distribution System

6.2 .0 Capaci ty and number of sys temcomponents and the electrical distibution layoutshould be decided considering the likely futurerequirements, security, grade of service desiredand economics. The choice between cables andmetal rising mains for distribution of powershould be done depending on the load and thenumber of floors to be fed.

6.2.1 In multisloreyed buildings where largenumber of people gather (for example officebuildings), the.re shall be at least two rising mainslocated in separate shafts. Each floor shall have achangeover switch for connection to either of thetwo mains.

6.2.2 When cables are used for distribution todifferent floors, it may be desirable that cablesfeeding adjacent floors are interconnected for usewhen distribution cables in either of the floorsfail.

6.2.3 It is essential to provide independentfeeders for installations such as fire lift, fire alarm,fire pumps, etc.

PART 3 ELECTRICAL INSTALLATIONS IN NON-INDUSTRIAL BUILDINGS 165_.

6.2.4 In the case of residential buildings.submain wiring to the flats/apartments shall beindependent for each flat/apartment.

6.2.5 Twin earthing leads of adequate size shallbe provided along the vertical runs of risingmains.

63 Siting OT Distribution Equipment

6.3.1 The following aspects shall be consideredin deciding the location of electric substation formdtistoreyed buildings:

a)

b)cl4

e)

r)

g)

Easy access for purpose of movement ofequipment in and out of the substationincluding fire fighting vehicles;

Ventilation;

Avoidance of flooding by rain water;

Feasibility of provision of cable ducts (keep-ing in view the bending radius of the cable),oil soak pits (for large transformers) andentry of utility’s cable(s);

Transformer hum (and noise and vibrationfrom diesel generating sets where providedas part of the substation);

Where a separate building for substation isnot possible, the same should preferably beat ground floor level of the multistoreyedbuilding itself. In the case of a complexwith a number of buildings, the substationshould be located, as far as possible, near theload centre; and

In the cases of certain high rise buildings,provision of substation at intermediatefloors may be necessary for case of distri-bution. In such cases, non-inflammablecooling medium shall be used for sub-station equipment from the point of viewof fire safety.

6.3.2 The vertical distribution mains should belocated considering the following aspects:

4b)

c)

4

Proximity to load centre;

Avoiding excess lengths of wiring for finalcircuits and points;

Avoiding crossing of expansion joint, if any,by horizontal runs df wiring;

Avoiding proximity to water bound. areaslike toilets, water coolers, sanitary/air-conditioning shafts, etc;

Easy maintainability from common areaslike lobbies, corridors, etc; and

Feasibility to provide distribution switch-boa& in individual floors vertically oneover the other.

6.4 Wiring Installation

6.4.1 The electrical wiring shall be carried outin conformity with Part I /Set I I of the Code.

166

6.4.2 Normally aluminium conductor is usedfor wiring cables, but copper conductor may berequired for fire-alarm, telephones, controlcircuits, etc.

6.4.3 Where excessively long lengths of wiringruns are inevitable to suit the building layout, theconductor sizes shall be suitably designed to keepthe voltage drop within limits (see Part I /Set I Iof the Code).

6.4.4 The type and capacity of control switchesshall be selected to suit the loading, such as roomair-conditioners, water coolers, group contol offluorescent lights, etc.

6.4.5 All switchgear equipment used for main-distribution in multistoreyed buildings shall bemetal enclosed. Woodwork shall not be used forthe construction. of switchboards.

6.4.6 The electric distribution cables/ wiringshall be laid in a separate duct. The duct shall besealed at every alternative floor with non-combustible materials having the same fireresistance as that of the duct. Low’ and mediumvoltage wiring running in shaft and in false ceilingshall run in separate conduits.

6.4.7 Water ,mains, telephone lines, inter-cornlines, gas pipes or any other service line shall notbe laid in the duct for electric cables.

6.4.8 Separate circuits for water pumps, lifts,staircases and corridor lighting and blowers forpressurising system shall be provided directlyfrom the main switchgear pane1 and these circuitsshall be laid in separate conduit pipes, so that firein one circuit will not affect the others. Masterswitches controlling essential service circuits shallbe clearly labelled.

6.4.9 The inspection panel doors and any otheropening in the shaft shall be provided with air-tight fire doors having the fire resistance of notless than 1 hour.

6.4.10 Medium and low voltage wiring runuihgin shafts, and within false ceiling shall run inmetal conduit. Any 230 V wiring for lighting orother services, above false ceiling, shall have 660V grade insulation. The false ceiling, including allfixtures used for its suspension, shall be of non-combustible material.

6.411 An independent and well-ventilatedservice robm shall be provided on the groundfloor with direct access from outside or from thecorridor for the purpose of termination of electricsupply from the licensees, service and alternativesupply cables. The doors provided for the serviceroom shall have fire resistance of not less than 2hours.

6.412 If the utility agree to provide meters onupper floors, the uti l i ty’s cables shall besegregated from consumers’ cable by providing apartition in the duct. Meter rooms on upperfloors shall not open into staircase enclosures andshall be ventilated directly to open air outside.

\\


64.13 The staircase and corridor lighting shallbe on separate circuits and shall be independentlyconnected so as it could be operated by oneswitch installation on the ground floor easilyaccessible to fire fighting staff. at. any timeirrespective of the position of the individualcontrol of the light points, if any. It should be ofMCB type of switch so as to avoid replacement offuse in case of crisis.

6.4.14 Staircase and corridor lighting shall alsobe connected to alternative supply as defined in7.1 for buildings exceeding 24 m in height. Forassembly institutional buildings of height less than24 m, the alternative source of supply may beprovided by battery continuously trickle chargedfrom the electric mains.

6.4.15 Suitable arrangements shall be made byinstalling double throw switches to ensure that thelighting installed in the staircase and the corridordoes not get connected to two sources of supplysimultaneously. Double throw switch shall beinstalled in the service room for terminating thestandby supply.

6.4.16 Emergency lights shall be provided inthe staircase/corridor.

7. PROVISION OF STANDBY GENERATINGS E T

7,l The following loads shall be fed from thestandby generating set, to enable continuity ofsupply in the event of failure of mains :

a)

b)c)

4e)f-lg)h)

Lighting in common areas, namely corridors,staircases, lift lobbies, entrance hall,common toilets, etc;Fire lift;Fire fighting pump, smoke extraction anddamper systems;Fire alarm control panel;Security lighting;Obstruction light(s);Water supply pump; andAny other functional and critical loads.

8. TELEPHONE WIRING SYSTEM

8.1 On the basis of assessment of demand ofdirect telephones and PBX lines, the conduit runsfor telephone wiring should be designed inconsultation with telephone department. Wheretelephone wiring is intended to be taken on anyother method, this should be coordinated with thearchitect and the telephone department.8.2 Lighting, ventilation and flooring in batteryrooms should be designed in accordance with theguidelines in Part 2 of the Code.8.3 Suitable provisions should be made for cableentry and spaces for distribution components.

8.4 Where the layout of intercom telephones isknown in advance, provisions for wiring for thesame may also be made.

9. FIRE SAFETY

9.1 Consideration in respect of the followingprovisions is necessary from fire safety point ofview:

a) Fire detectors and alarm system;b) Fire fightingc) ‘Fire lift;d) First-aid firee) Construction

main shafts,

a r r a n g e m e n t s ; .

fighting appliances;of lift shafts, cable and risinglobbies, substation, etc, from

fire safety consideration% andf) Provision for pressurisation of stairwells, lift

shafts, fobbies, etc.9.2 Provisions contained in Part I/Set 14 of theCode and SP : 7,-1983* shall be applicable inrespect of theabove aspects. Any regulations offire safety by 1also be ?c

al municipal/fire authorities shallcamp ied with.

9.3 The following specific guidelines shall be keptin view.

9.3.1 All buildings with heights of more than15 m shall be equipped with manually operatedelectrical fire alarm (MOEFA) system andautomatic fire alarm system. However, apartmentand office buildings between 15 m and 24. m inheight may beexempted from the installation ofautomatic fire alarm system provided the localfire brigade is suitably equipped for dealihg withfire above I5 m height and in the opinion of theAuthority, such building does not constitutehazard to the safety of the adjacent property orthe occupants of the building itself.

9.3.1.1 Manually operated electrical fire alarmsystem shall be installed in a building with one ormore call boxes located at each floor. The ,callboxes shall conform to the following :

b)

The location of call .boxes shall bedecided after taking into consideration thefloor plan with a view to ensuring that oneor the other call box shall be readily acces-sible to all occupants of the floor withouthaving to travel more than 22.5 m.The call boxes shall be of the ‘break-glass’type where the call is transmitted automati-cally to the control room without any otheraction on the part of the person operatingthe call box. The mechanism of operation ofthe call boxes shall pceferably be withoutany moving parts. However, where anymoving part is incorporated in the design ofthe call box, it shall be of an approved type,

*National Buikiing Code.


so that there shail be no malfunctioning ofthe call box.

c) All call boxes shah be wired in a closed cir-cuit to a control panel in the control roomin accordance with good practice so locatedthat the floor number/zone where the callbox is actuated is clearly indicated on thecontrol panel. The circuit shall also includeone or more batteries with a capacity of 48hours normal working at full load. Thebattery shall be arranged to be continuouslytricklecharged from the electric mains. Thecircuit may be connected to alternativesource of electric supply.

d) The call boxes shall be arranged to soundone or more sounders so as to ensure thatall appropriate occupants of the desiredfloor(s) shall be warned whenever any call _box is actuated.

e) The call boxes shall be so installed that theydo not obstruct the exit-ways and yet their

location can eastly be noticed from eitherdirection. The base of the call box shall beat a height of I m from the floor level.

9.3.1.2 The installation of call boxes in hostelsaod such other places where these are likely to bemisused, shall as far as possible be avoided.Location of call boxes in dwelling units shallpreferably be inside the building.

NOTE I - Several types of tire detectors are available in themarket, but the application of each type is limited and has tobe carefully considered in relation to the type of risk and thestructural features of the. building where they are to beinstalled. For guidelines for selection of tire detection referencemay be made to relevant Indian Standard.

N OTE 2 -No automatic detector shall be requtred in anyroom or portion of building which is equipped with anapproved installation of automatic sprinklers.

10. LIGHTING PROTECTION10.1 Provisions of l ightning protection ofmultistoreyed buildings shall be made inconformity with Part I /Set I5 of, the Code.


PART 4 ELECTRICAL INSTALLATIONS ININDUSTRIAL BUILDINGS

O . F O R E W O R D

0.1 Electrical networks in industrial buildings serve the urpose of distributing therequired power to the consuming points where it is used or a multitude of purposesPin the, industry. The design of electrical installation in industrial premises istherefore more complicated than those in non-industrial buildings.0.2 Industrial installation has to take care of load requirements and sup ly.limitations in a simple and economic manner, ensuring at the same time Pullprotection to human life and loss of property by fire. The network layout shouldalso facilitate easy maintenance and fault localisation. Keeping in view the tariffstructures as also the economic necessity of conserving power to the maximumextent, power’ factor compensation assumes special importance.0.3 A particular feature of electrical installations in industrial buildings is thereliability of supply to essential operations for which .standby and emergency supplysources/networks had to be designed. The needs of such systems would depend onthe type and nature of the industrial works.0.4 Locations in industrial buildings which are by their nature hazardous, requirespecial treatment in respect of design .of electrical installations therein. Such specialrules for hazardous areas are covered, in Part 7 of the Code and these shall becomplied with in addition to the general rules specified in this Part 4 (see alsoAppendix D, Part 7 of the Code).0.5 In clause 3 of this Part, an attempt has been made to classify industrialinstallations depending on the specified eriteria therein. Such a classification, it ishoped-would help identify the specific nature of each industry and the locationstherein, assisting the design engineer in the choice of equipment and methods.

1. SCOPE cl1.1 This Part of the Code covers the guidelinesfor design and construction of electricalinstallations in industrial buildings.1.2 This Part does not cover specific areas inindustrial sites, such as office buildings, workersrest rooms, medical facilities, canteen annexe, etc,for which requirements stipulated in the relevantsections of Part 3 of the Code apply.

1.3 This Part also does not cover locations inindustrial sites that are by nature hazardous forwhich the provisions of Part 7 of the Code apply.

NOTE -- SP 7 : 1983; includes Group J buildings for suchlocations where storage. handling, manufacture or processing ofhighly combustible or explosive materials or products arebeing carried out. Such installations including such highhazard locations in Group G classification shall comply withthe special rules of Part 7 of the Code.

2. TERMINOLOGY

2.1 Far the purpose of this Part, the definitionsgiven in Part l/Set 2 of the Code shall apply.

3. CLASSIFICATION OF INDUSTRIALBUILDINGS

3.1.2 Examples - See Appendix A.

3.2 Classification Based on Power Consumption

3.2.1 Industrial buildings are also classifieddepending on the quantum of electric powerrequirements for its services as given in Table I.

3.0 Industrial buildings by definition include anybuilding or part of buildjng or structure, in whichproducts or materials of all kinds and propertiesare stored, fabricated, assembled, manufacturedor processed, for example, assembly plants,laboratories, dry cleaning plants, pumpingstations, refineries, dairies, saw mills, chemicalplants, workshops, distilleries, steel plants, etc.

Industrial installations are of various types andin a single industrial site, electrical loads ofvarying requirements are to be met. For thepurpose of this part, industries are classifiedbased on three criteria as given in 3.1 to’ 3.3.

TABLE 1 CLASSIF ICATION BASED ON POWERCONSUMPTION

DESCRIPTION * AVERAGE POWER EXAMPLES

Lightindustries

3.1 Classification Based on Fire Safety

3.1.1 Industrial buildings are classified intoGroup G from the fire safety point of view inSP 7 : 1983*. Buildings under Group G arefurther subdivided as follows:

Averageindustries

Heavyindustries

a) Subdivision G-l-Buildings used for lowhazard industries - Includes any building inwhich the contents are of such lowcombustibility and the industrial processesor operations conducted therein are of sucha nature that there are no possibilities forany self-propagating fire to occur and theonly consequent danger to life and propertymay arise’ from panic, fumes or smoke, orfire from some external source.

N O T E- Average factory installations are set apart fromheavy industries in that the former has no coriditions requiringspecialized or exceptional treatment.

b) Subdivision G-2- Buildings used formoderate hazard industries - Includes anybuilding in which the contents or industrialprocesses of operations conducted therein areliable to give rise to a fire which will burnwith moderate rapidity and give off a con-siderable volume of smoke but from whichneither toxic fumes nor explosions are to befeared in the event of fire.

*Terminology based on IS : 732 (Part 2)-1982 Code ofPractice for electrical wiring installations: Part 2 Design andConstruction (second revision).

3.2.2 Loads within the industrial site could bedivided depending on their nature and size. Forguidance, the.classification given in Table 2 shallbe referred to.

*National Building Code.3.3 Classification Based on Pollution - (Underconsideration).

172

Subdivision G-3-Buildings used for highhazard industries - Includes any building inwhich the contents or industrial processes oroperations conducted therein are liable to giverise to a fire which will burn with extremerapidity or from which poisonous fumes orexplosions are to be feared in the event offire.

(1)REQUIREMENT

(2)kVA

(3)

up to 50 Hosiery, tailoringand jewellery

Machinery, engine“,“:g 5a up tQ fitting. motor cars,

a i rc ra f t , l i gh t p res -sings, furniture,pottery, glass,tobacco, electricalmanufacturing andtextile (see NOTEbelow)

Above 2 000 Heavy electricalequipment, rollingmills. steel works,boilers. structuralsteel works, tubemaking, foundries,locomotives, ship-building and re-pairing. chemicalfactories, factoriesfor metal extrac-tion from ores. etc


TABLE 2 LOAD GROUPS IN INDUSTRIALBUILDINGS

(Clause 3.2.2)

SRotiPs T Y P E OF LOAD EXAMPLES POWERFACTOR

(4:

Repair shop, 0.6automatic lathe,workshop, spinn-ing mill, weav-ing mill

I Small and largeloads fairly evenlydistributed overthe whole areaand loaded cons-tantly during theworking day(precision mec-hantcal engi-neering)

2 Loads fairly even-ly distributed overthe whole area,but varying loadsand with peakload at differenttimes (for examplemetal workingindustry)

Tool making 0.6Press shop 0.4Machine shop 0.6Welding shop 0.7

3 Loads having veryhigh power re-quirement in con-junction withsmaller loads ofnegligible sizecompared to thetotal load (forexample, rawmaterial industry)

Heat treatmentshop, steel works,rolling mills

0.9

4. GENERAL CHARACTERISTICS OFINDUSTRIAL BUILDINGS

4.0 Gineral guidelines on the assessment ofcharacteristics of installations in buildings aregiven in Part I of the Code. For the purposes ofinstallations falling under the scope of this Part,the characteristics given below shall apply.

4.1 Environment

4.1.1 The following environmental factors shallapply to industrial installations:

Environmenr Characrerisrics Remarks

(1) (2) (3)

Presence of water Presence of water Depends on thenegligible, or location. For

Possibilities of further detailsree falling drops see Part l/Set 8

or sprays of the Code

Presence of These conditions Depends on theforeign solid include possibi- location. Forbodies lities of presence further details

of foreign solid see Part I/%X 8bodies of various of the Codesizes likely toaffect electricalequipment (such astools, wires,dust. etc)

Presence of corro- Negligible pollu-sive tion

(Conrinued)

Enviyymenr Characlerisrics(2)

Remarks(3)

polluting sub-s t a n c e s

Atmosphericwhere the pre-sence of corrosive the sea. chemical

Intermittent oraccidental subjec-tion to corrosiveor pollutingchemical sub-stances being usedor produced

works, cementworks where thepollution arisesdue to abrasive,insulati?g. orconductmg ducts

Factory laboratoriesboiler rooms. etc

Continuouspollution

Chemical works

Machanical stress Impact/vibration Usual industrialof medium conditionsseverity

Impact/vibration Industrial instal-of high severity lations subject to

severe conditions


- Depends on thelocation of thebuildings

4.2 Utilization

4.2.1 The following aspects of utilization shallapply:

Ulilizarion(1)


Characrerisbcs Remarks(2) (3)

lnsttatcted persons,adequately ad-vised or super-vised by skilledpersons (operat-mg and mainten-ance staffl

Majority of personsuttlising the indu‘s-trial installationsare in this cate-gory. Howeverspecific zones oroperations involv-ing uninstructedpersons shall alsobe kept in view


Conditions ofevacuation

PART 4 ELECTRICAL INSTALLATIONS IN INDUSTRIAL BUILDINGS

Persons with tech-nical knowledgeand sufficientexperience (engi-neers and techni-cians)

Persons are fre-quently in touchwith extraneousconductive partsor stand on con-ducting surfaces

Persons are in

Closed operatingareas

Locations withextraneous con-ducting parts,either numerousor large area

Metallic surround-permanent contact ings such aswith metallic sur- boilers and tanksroundings and forwhom the possibi-bility of interup-ting contact islimited

Low density occu- This categorypation. easy applies to build-conditions of ings of normalevacuations or low height

(Continued)

173

l.JMgtio Charatgrdics Remarks(3)

Nature of Existance of fire- Wood-workingprocessed or risks. where shop, paperstored materials manufacture. pro- factories, textile

cessinF

or stor- mills. etcage o flammablematerials. includingpresence of dust

Processing or stor- Oil refineries.age of low-tlash- hydrocarbonpoint materials storesincluding pre-sence of explosivedust

4.3 Compatibility - In industrial installations, anassessment shall also be made of anycharacterist ics of equipment like’ly to haveharmful effects upon other equipme.nt or otherservices (SCP Part I /Set 8 of the Code).

4.4 Maintainability - An assessment shall alsobe made of the f requency and qual i ty ofmaintenance the installation shall be receiving (seePart I /Set 8 of the Code).


5.0 General

5.0.1 ,The arrangement of the electrical systemin industrial plants and the selection of electricalequipment depends largely on the type ofmanufacturing process. the greatest possiblereliability of supply and adequate reserve ofelectrical capacity are the most important factorsto avoid interruption of supply.

5.0.2 All electrical apparatus shall be suitablefor the voltage and frequency of supply available.

5~0.3 In case of connected load of 100 kVA andabove, the relative advantage of high voltagethree-phase supply should be considered. Thoughthe use of high vohage supply en ta i l s theprovision of space ahd the capital cost ofproviding a suitable transformer substation on theconsumer’s premises, the following advantages aregained:

4b)

c)

4

Advantage in tariff,

More effective earth fault protection forheavy current circuits.

Elimination of interference with .suppliesto other consumers permitting the use oflarge size motors, welding plant, etc, and

Better control .of voltage regulation andmore constant supply voltage.

5.0.4 In very large industrial buildings whereheavy electric demands occur at scatteredlocations, the economics of electrical distributionat high voltage from the main substation to othersubsidiary transformer substations or to certainitems of plant, such as large motors, furnaces, etc,should be considered. The relative economyattainable by use of medium or high voltage

174

distribution and high voltage plant is a matter forexpert judgement and individual assessment in thelight of experience by a professionally qualifiedelectrical engineer.

5.1 Industrial Substations

5.1.0 The general requirements for substationinstallations given in Part 2 of the Code shallapply in addition to those given below.

5.1.1 If the load demand is high, which requiressupply at voltages above 650 V, a separatesubstation should be set up. For an outdoorsubstation general guidelines as given in Part 2 ofthe Code shall apply. For bringing the supply intot h e f a c t o r y b u i l d i n g , a s e p a r a t e i n d o o raccommodation, as close as possible to the mainload centre. should be provided to house theswitchgear equipment.

5.1.2 The supply conductors should preferablybe brought into the building underground toreduce the possibility of interruption of powersupply. The accommodation for substationequipment as well as for main distribution panelshall be properly chosen so as to prevent access byany unauthorised person. It shall be providedwith proper ventilation and lighting.

5.1.3 In cases where the load currents are veryhigh, and the transformers are located .just outsidethe building, a bus-trunking arrangement may bedesirable. These trunkings should. however. bestraight, as far as possible, and also as short aspossible on economic grounds. It would also bedesirable to locate the LV switchgear directlyabove the transformer.

5.1.4 Localion qf Transfbrnlers andSHitchgear - A s p e r convent\onal prictice,transformers being oil-f i l led apparatus, arepreferably located outdoors while the associatedswitchgear is located in a room of the buildingne%t to the transformers.

For reasons of safety, however. it may beconsidered desirable to locate the transformer alsoinside 1 the room. The transformer could beconnected to the switchgear by cables for smallloads, however it may often be found desirabte toavoid cable joints and connect the transformerdirectly to the switchgear placed on either side ofthe transformer. For oil-filled transformer, specialmeans should be available for remote operation oft h e m a i n switches/circuit-Breakers i n a nemergency created by explosion/fire in thetransformers.

5.1.5 In order to ensure the reliability andsafety expected of industrial substations, it isdesirable to have circuit-breakers as the mainswitching e lements on bo th s ides o f thetransformer. However, where load currents areless than 100 A on high voltage side and 600 A onlow voltage side, switches and fuses may also beused for this purpose.

5.1.6 F o r s m a l l s u b s t a t i o n s up to 1 6 0 0kVA/ I I kV capacity, it is also possible to locate

NATIONAL ELECTRICAL C O D E

the substation at the load centre, without aseparate room. This y i e l d s considerableeconomies in cost. In such cases, the transformershall be of the non-flammable synthetic oil type(these oils need care in handling).

5 . 1 . 7 I s o l a t i o n qf Switchgear - Forinstallations where the system voltage exceeds650 V, the typical circuits and the recommendedlocation ot lsolatlng switches-in such circuits areillustrated in IS : 732 (Part 2)-1982*. Referenceshould be made to the same for guidanceregarding isolation depending on the type ofsupply system.

5.2 Distribution of Power

5.2.1 From the main receiving station, power istaken to the loads, either directly as in the case ofsmall factories. or through further load centresubstations as would be the case with biggerinstallations.

Distribution is done on HV or LV dependingon the quantum of load to be transferred, distanceto be covered, and on other similar factors.Distribution is possible through one of thefollowing:

a) Wall-mounted distribution boards,

b) Floor mounted distribution boards,

c) Local fuse distribution boards, and

d) Overhead bus bar system with tap-off holes.

5.2.2 In every layout, however, specific careshall be taken for:

a) Human safety,

b) Fire/explosion hazards,

c) Accessibility for repair/checking,

d) Easy identification, and

e) Fault localisation.

5.2.3 Switchgear

5.2.3.0 All switchgear equipment used inindustrial installations shall be metal enclosed.Woodwork shall not be used for mounting offswitchboards.

5.2.3.1 lsolation and protection of out.goingcircuits forming main distribution system may beeffected by means of circuit-breakers, or fuses ors w i t c h f u s e u n i t s m o u n t e d o n t h e m a i nswitchboards. The choice between alternativetypes of equipment may be influenced by thefollowing considerations:

a) In certain installations where supply is fromremote transformer substations, it may benecessary to protect main circuits withcircuit-breakers operated by earth leakagetrips, in order to ensure effective earthfault protection.

*Code of practice for electrical wiring installations: Part 2Design and construction (second revision).

b)

c)

Where large electric motors, furnaces orother heavy electrical equipment is installed,the main circuits shall be protected bymetal-clad circuit-breakers or contactors ofair-break or oil-immersed type fitted withsuitable instantaneous and time delay overcurrent devices together with earth leakageand back-up protection where necessary.In installations other than those referred toin (a) and (b) or where overloading of cir-cuits may be considered unlikely to occur,H RC type fuses will normally afford adequateprotection for main circuits. Where means forisolating main circuits’is required, fuse switchor switch fuse units shall be used or fuses withswitches forming part of the mean switch-board shall be used:

5.3.1 For power distribution from a substationor main switchboard to a number of separatebuildings, use shall preferably be made of:

4

b)

metal-sheathed, bedded and armoured cable,served, installed overhead/underground, or

mineral-insulated metal-sheathed cable,served with PVC, laid overhead/direct in theground, or

cl PVC-insulated, arm’oured and PVC-sheath-ed cable installed overhead/ underground,or

4 X L P E i n s u l a t e d , armoured and PVC-sheathed cable installed overhead/under-ground.

5.2.3.2 It may be necessary to provide forconnection of capacitors for power-factorcorrection; and when capacitors are to be installedadvice of capacitor and switchgear manufacturersshall be sought.

5.2.3.3 Adequate passageways shall be allowedso that access to all switchboards for operation andmaintenance is available. Sufficient additionalspace shall be provided for anticipated futureextensions.

5.2.3.4 Switchboards should, preferably, belocated in separate control rooms to ensure:

a) adequate protection against weatherelemknts like heat, dust, corrosion, etc; and

b) protection against entry of factory materiallike cotton, wood dust, water during clean-ing, etc.

Where necessary the control rooms should bedesigned to avoid wide fluctuations in ambienttemperature. and against entry of excessive dust orcorrosive gases.

5.2.3:s Certain applications may necessitatelocation of the switchboards on the factory flooritself, without separate rooms. In suchlcases, theswitchboards shall be specifically designed andprotected against hazards mentioned above.

5.3 Main Distribution

PART 4 ELECTRICAL INSTALLATIONS IN INDUSTRIAL BUILDINGS 175

5.3.1.1 Cables shall not be laid in the sametrench or alongside a water main.

5.3.1.2 Cable trenches shall be made. withsufficient additional space to provide foranticipated future extensions.

5.3.2 Cables at different voltage levels shouldbe laid with adequate separation, and clearlyidentified. Cables at voltages above 1 000 Vshould be laid at the lowest level in trenches, andat the highest level on walls, keeping in view therequirements of human safety. The cable routeswhere buried should be properly identified byroute markers, as a precaution against accidents.The marker should necessarily indicate thevoltage level. Cables laid unde’rground or at lowworking levels, should either be with armouring,or should be adequately protected againstmechanical damage, for example, by the use ofconduits.

5.4 Subcircuits

5.4.0 The subcircuit wiring shall conform ingeneral to the. requirements in Section 2 ofIS : 732 (Part 2)-1982*.

5.4.1 In 3-phase distribution systems, a neutralconductor may preferably be provided in all sub-main circuits even when there is no immediaterequirement for the supply of single-phasecircuits. Control devices are often designed forconnection between one phase and neutral andconsiderable extra cost may be involved if a four-wire sub-main has to be installed i?. place of athree-wire sub-main previously installed.

5.4.2. In workshops and factories wherealterations and additions are frequent, it may beeconomical and convenient to install wiring inducts or trunking. Alternatively, cables may beconveniently run or perforated metal cable trays.In this case earth continuity conductor shall bebonded to each section of ducts or trunking toprovide permanancy of the electrical continuity ofthe joints of the ducts.

5.4.3 In machine shops and factories wherealterations i n layout may repeatedly occur,consideration shall be given to the replacement oflocal distribution boards by overhead bus-bar orcable systems, to which subcircuit are connectedthrough fused plugs in tapping boxes whereverrequired.

5.4.4 In industrial installations, the branchdistribution boards shall be totally segregated forsingle phase wiring.

5.4.5 Where more than one distribution systemis necessary, the socket outlets shall be so selectedas to obviate inadvertent wrong connections.

5.4.6 In industrial premises, 3-phase andneutral socket outlets shall be provided with earthterminal either of pin type or scrapping type in

*Code of practice for clcctrical wiring installations: Part 2Design and construction (zcw~rtl rrlGiotl).

176

addition to the main pins required for thepurpose.

In industrial installations, socket outlets ofrating 30 A and above shall be provided withinterlocked type switch. These shall be of metalclad type.

5.4.7 Where non-luminous heating appliance isto be used, pilot lamps shall be arranged toindicate when the circuit is live.

5.4.8 Final subcircuits for lighting shall be soarranged that all the lighting points for a givenarea are fed from more than one final subcircuit.

5.4.9 In some installations, the u,se of ring-circuit system of wiring is usually advantageousfrom the point of view of providing an adequatemember of outlets, where demand presentssufficient diversity.

5.4.10 Individual sub-mains shall be installedto suppl’)~ passenger and goods lifts from the mainor sub-main switchgear, and the lift manufacturershall be consulted as to the appropriate rating ofcables to be employed.

The supply to small hoists and service lifts shallnot be taken from a distribution board controllingfinal sub-circuits for lighting, unless the maximumcurrent, including the starting and acceleratingcurrent, of the motor i_s less than 20 percent of thetotal rating of all the ways of the distributionboards. Where the supply is taken from such adistribution board, the motor circuit shall beclearly labelled.5.5 Selection of Wiring Systems -The selectionof a wiring system to be adopted in a factorydepends upon the factors enumerated in part1 /Set 11 of the Code.

The wiring system available for general use areIi&ted in Appendix B. Selection from a group ofalternative systems shall be made in accordancewith Appendix B, keeping in view the particularcircumstances of each ciiht having regard to:

a)

b)

c)

d)

location, structural conditions, liability tomechanical damage and the possibility ofcorrosion,

protection against corrosion, nature of thecorrosive elements being taken into accountin conjunction with the protective coveringsavailable,

occupancy of the building, and

presence of dust, fluff. moisture and tem-perature conditions.

5.6 Earthing in Industrial Premises

5.6.0 In factories and workshops all metalconduits. trunking, cable sheaths, switchgear,distribution fuse boards, starters, motors and allother parts made of metal shall be bondedtogether and connected to an efficient earthsy~ Em. The electricity regulations made under theFa tories Act require that adequate precautions


. . .

shall be taken to prevent non-current-carryingmetal work of the installation from becomingelectrically charged.

In larger installations, having one or moresubstations, it is recommended to parallel allearth-continuity system.

5.6.1 Earth Electrodes- Any of the earthelectrodes as mentioned in Part I of the Codeexcept cable sheath, may be used in industrialpremises.

5.6.2 Earth Continuity Conductor

5.6.2.1 Earth-continuity conductors and earthwires not contained in the cables -The size ofthe earth-continuity conductors should becorrelated with the size of the current carryingconductors, that is, the sizes of earth-continuityconductors should not be less than half of thelargest current-carrying conductor, provided theminimum size of earth-continuity conductors isnot less than 1.5 mm2 for copper and 2.5 mm2 foraluminium and need not be greater than 70 mm2for copper and 120 mm2 for aluminium. Asregards the sizes of galvanized iron and steelearth-continuity conductors, they may be equal tothe size of the current carrying conductors withwhich they are used. The size of earth-continuityconductors to be used along with aluminiumcurrent-carrying conductors should be calculatedon the basis of equivalent size of the coppercurrent-carrying conductors.

5.6.2.2 Earth-continuity conductors and earthwires contained in the -cables - For flexiblecables, the size of the earth-continuity conductorsshould be equal to the size of the currentsarryingconductors and for metal sheathed, PVC andtough rubber sheathed cables the sizes of theearth-continuity conductors shall be inaccordance with relevant Indian Standard.

5.6.2.3 Conduits may be used as ‘earth-continuity conductors provided they arepermanently and securely connected to the earthsystem. However, where by nature of the process,metal conduits cannot be used as earth-continuityconductor on account of corrosion, etc, the toughrubber or PVC sheathed cables may be used inwhich case they shall incorporate an earth-continuity conductor.

5.6.2.4 Flexible conduits shall not be used asearth-continuity conductors. A separate earthwire shallFe p’rovided either inside or outside theflexible conduits which shall be connected bymeans of earth clips to the earth system at oneend and to the equipment at the other end.

5.6.2.5 Earth leakage protection - Use ofearth leakage protection shall be made wheregreater sensitivity than provided by overcurrentprotection is’ necessary. With a good earthelectrode, overload protective devices may be usedas earth leakage protective device.

In addition to the advantage of sensitivitygained by such methods, the circuits may be

relieved of the thermal and mechanical socksassociated with the ‘clearance of heavy faults.

Some degree of discrimination may, in certaincases, be introduced with advantage by providingthe delay in the operation of an earth-leakage trip,so that earth faults on smaller subsidiary circuitsprotected by fuses have time to clear and preventthe opening of the circuit-breaker, controlling alarger part of the installation.

5.6.3 Earthing of Portable Appliances andTools

5.6.3.0 Portable appliances and tools havingreinforced or double insulation need not beearthed.

5.6.3.1 Good electrical continuity between thebody of a portable appliance and the earth-continuity conductor shall always be maintained.

5.6.3.2 It shall be ascertained that the fixedwiring at the appliance inlet terminals has beendone correctly and in accordance with relevantIndian Standard.

5.6.3.3 A single pole switch shall not beconnected in the earth conductor.

5.6.3.4 No twisted or taped joints shall beused in earth wires.

5.6.3.5 Additional security may be obtainedby arranging the earth-continuity conductor in theflexible cable between the socket outlet and theportable appliance in the form of a loop throughwhich a light circulating current provided by asmall low-voltage transformer is passed when theappliance is in use. Any discontinuity in this loopwill interrupt the circulating current and can thusbe caused to operate a relay and disconnect thesupply from the portable appliance.

5.6.4 Earthing of Electrically! Driven MachineTools- Irrespective of’ the size or type ofmachine tools, the bed plate of the machine shallbe earthed by means of a strip or conductor ofcross-sectional area not less than 6.5 mm? if ofcopper, IO mm? if of aluminium, and I6 mm’ if ofgalvanized iron or steel. The strip or conductorshall be securely fastened to the bed plate bymeans of a. bolt.

5.6.5 Earthing of Electric Arc WeldingE q u i p m e n t

5.6.5.1 All components of electric arc weldingequipment shall be effectively bonded andconnected to earth. The transformers and separateregulators forming multioperator sets andcapacitors for power factor correction, if used,shall be included in the bonding.

5.6.5.2 All terminals on the output side of amotor generator set shall be insulated from thecar case and control panel, as the generator is notconnected electrically to a motor and thereforethe welding circuit is electrically separate from thesupply ctrcuit including the earth.


5.6.5.3 In case of transformer sets, which forwelding purpose are double wound, an ‘earth andwork’ terminal,shall be provided. In single phasesets this terminal shall be connected to one end ofthe secondary winding and in case of three-phasesets this shall be connected to the neutral point ofthe secondary winding.

5 . 6 . 6 Earrhing qf Industrial ElectronicApparatus

_~

5.6.6.0 The earthing of these apparatus shallfollow normal practice but attention shall be paidto the points discussed below.

5.6.6.1 Any industrial electronic apparatuswhich derives its supply from two-pin plugsincorporates small capacitors connected betweenthe supply and the metal case of the instfument tocut down interference. This capacitor shall besecurely earthed.

5.6.6.2 When an oscilloscope is being used toexamine the wave-form of a high frequencysource, the oscilloscope shall be earthed by aconductor entirely separate from that used by thesource of high frequency power. However, whenan oscilloscope is being used on a circuit wherethe negative is above earth potential and alsoconnected to its metallic case, ihe earthing of theoscilloscope is not possible. Precautions shall betaken that in such a case the oscilloscope issuitably protected from other apparatus.

5.6.6.3 High frequency induction heatingapparatus shall be earthed by means of separateearth wire by as direct a route as possible.

5.6.6.4 Dielectric loss heating equipment workat frequencies between IO MHz to 60 MHzaccording to its use. These should not be directlyearthed. At 30 MHz, for example, a quarterwavelength is nearly 250 cm and an earth wire ofthis length or odd multiples of it is capable ofbeing at earth potential at one end but severalhundred volts at the other end. This is due to thepresence of s tand ing waves on the ear thconductors which besides being dangerous canresult in energy being radiated to the detriment ofcommunication services. In such a case it isrecommended to mount the equipment ori a largesheet of copper or copper gauze, the earthconductor being connected to it at several points.

5.6.6.5 In case where direct earthing mayprdve harmful rather than provide safety, forexample, high’ frequency and mains frequencycoreless induction furnaces, special precautionsare necessary. The metal of the furnace charge isearthed by electrodes connected at the bottom Ofthe charge, and the furnace coils are connected tothe mains supply but are unearthed. A relay isconnected by a detection circuit which itself isearthed to the coils. The object is to preventdangerous break-through of hot metal throughthe furnace lining, the earth detection circuitgibing a continuous review of the conditions forthe furnace lining. When leakage current attains acertain set maximum it becomes necessary to take

the furance out of service and to re-line.

6. EMERGENCY/STANDBY POWERSUPPLIES

6.1 The provisions of Part 2 of the Code shallapply.

7. SYSTEM PROTECTION

7.1 Protection of Circuits

7.1.1 Appropriate protection shall be providedat switchboards and distribution boards for allcircuits and subcircuits against overcurrent andearth faults, and the protective apparatus shall becapable of interrupting any short-circuit current.that may occur, without danger. The ratings andsettihgs of fuses and the protective devices shall beco-ordinated so as to afford selectivity inoperation where necessary.

7.1.2 Where circuit-breakers are used forprotection pf a main circuit and of the subcircuitsderived therefrom, discrimination in operationmay be achieved by adjusting the protectivedevices of the sub-main circuit-breakers tooperate at lower current settings and shorter time-lag than the main circuit-breaker.

7.1.3 Where HRC type fuses are used for back-up protection of circuit-breakers, or where HRCfuses are used for protection of main circuits andcircuit-breakers for the protection of subcircuitsderived therefrom, in the event of short circuitsexceeding the breaking capacity of the circuit:breakers, the H RC fuses shall operate earlier thanthe circuit-breakers; but for smaller overloadswithin the breaking capacity of the circuit-breakers, the circuit-breakers shall operate earlierthan the HRC fuse.

7.1.4 If rcwirable type fuses are used to protectsubcircuits derived form a main circuit protectedby HRC type fuses, the main circuit fuSe shallnormally blow in the event of a short-circuit orearth fa’ult occurring on a subcircuit, althoughdiscrimination may be achieved in respect ofoverload currents. The use of rewirable fuses isrestricted to the circuits with short-circuit level of4 kA; for higher level either cartridge or HRCfuses shall be used.

7.1.5. Provision shall also be made for controlof general lighting and other emergency servicesthrough separate main circuits and distributionboards from the power circuits.

7.1.6 If necessary, independent source ofsupply for emergency service in particularinstallations may be provided.

7.2 Fire-safety Requirements

7.5.1 Besides fire fighting equipment, thefollowing fire detection and extinguishing systemsare recommended for industrial buildings:

a) Buildings for lowhazard industries - Not required


b) Buildings for moderate hazard industries:i) Area up to - Automatic ‘fire-

750 m* alarm systemii) Area above - Automatic sprin-

750 m* kler or automaticfire alarm system

7.2.2 Reference is also drawn to 1s : 1646-1961* regarding rules and regulations relating toelectrical installations from the point of firesafety. Appendix C covers specific requirementsfor fire safety for representative industries.

8 . BUILDXNC SERVlCES

8.1 Lighting8.1.0 Industrial lighting encompasses seeing

tasks, operating conditions and economy. Witheach of the various visual task conditions, lightingshould be suitable for adequate visibility. Physicalhazards exist in many manufacturing processes,therefore, lighting contribute to the utmost as’ asafety factor in preventing accidents. The speed ofmany manufacturing operations might alsd behampered due to poor lighting. The generalconsiderations for design of lighting in industrialareas are enumerated in .IS : 6665-19727.

8.1.1 Equipment for Lighting -The choice oflight sources and luminaries shall be governed bythe guidelines given in IS : 6665-19727. T h erecommended values of illumination and limitingva!ues of glare index are given in Appendix D forguidance.

8.2 Air-conditioning, Heating and Ventilation

8.2.1 The electrical installation meant for theservices such as air-conditioning heating andventilation in industrial buildings shall conform tothe requirements given in Part 1 /Set 14 of theCode. The specific needs of individual locationsreqliiring these services in each factory shall beascertained in consultation with the concernedpersonnel before designing the electrical system.Reference should be made to the guidelines givenin SP : 7-1983:.

8.3 Lifts

‘8.3.1 The general rules laid down in Part 1 /Set14 of the Code shall apply regarding liftinstallations. However:. the design of lifts inindustrial buildings shall1 take into account thefollowing requirements:

*Code of practice for fire safety of buildings (general):Electrical installations.

tCode of practice for industrial lighting.

$Nationa’l Building Code.

a) Occupant load-the occupant load ex-pressed in terms of gross area in m*/personshall be 10 for industrial buildings.

b) Car-speed,for goods Ilfts - These shall be asfollows:

Normal load carrying lifts-2-2.5 m/sLifts serving many floors -1 m/s

8.3.2 The location of lifts in factories,warehouses and similar buildings should beplanned to suit the progressive movement ofgoods through the buildings having regard to thenature of processes carried out, position ofloading platform, railway slidings, etc. Theplacing of a lift in a fume or dust ladenatmosphere, or where it may be ‘exposed toextreme temperatures shall be avoided. Where itis impossible to avoid extreme environmentalconditions. The selection of electrical equipmentshall be such that they are suitable to meet theconditions involved.

9. MISCELLANEOUS/SPECIALPROVISIONS

9.1 Control of Static Electricity - Referenceshould be made to IS : 7689-1974* regard ingrecommendations for controlling static electricitygenerated incidentally by processes in industrieswhich may pose a hazard or inconvenience.Specific control methods are also given for someindustries therein.

9.2 Safety in Electra-Heat . Installations -lndustrial process include in many instances,

electro-heat installations such as:

4b)c)

d)

e)0

Arc furnaces,

Induction furnaces,

Appliances for direct and indirect resistanceheating,

Medium and high frequency inductionheating, r.f. heating and dielectric heatingappliances,

Infra-red radiatum heating appliances, and

Microwave heating.

For safety requirements in such ‘electro-heatinstallations referrence shall be made to IS : 9080(Pa r t s 1 to IV)t.

9.3 Power Factor Compensation

9.3.1 ‘The provisions of Part 1 /Set 17 of theCode ‘shall apply. For specific guidance forinstallations covered by this part, See AppendixE.

*Guide for the control of undesirable static electricity.

tSafety requirements in electro-heat installations.


,,

; .. .

179

A P P E N D I X A(Clause 3. I .2)

EXAMPLES OF INDUSTRIES BASED ON FIRE-SAFETY

A-l. The following is a representative list ofindustries classified according to the degree of firehazard enumerated in 3.1 .l:

a) Low Hazard tndustriesAbrasive manufacturing premisesAerated water factoriesAgarbatti manufacturing premisesAluminium copper and zinc factoriesAsbestos steam packing and lagging

manufacturersBattery manufacturersBone millsBreweriesCanning factoriesCarbon dioxide plantsCardamom factoriesCement factoriesCement and /o r a sbes tos o r concre te

products manufacturing premisesCeramic and crockery factoriesClay worksClock and watch manufacturing premisesConfectionery manufacturersElectric generating housesE l e c t r i c l a m p s a n d fluorescent t u b emanufacturers

Electronic goods manufacturing premisesElectroplating workshopsEngineering workshopsFruit products and condiment factoriesGold thread factories/gilding factoriesGlass factoriesGum and glue factoriesIce candy and ice cream manufacturingpremises

Ice factoriesInk factories (excluding printing inks)Milm pasteurising plants and dairy farmsMica products manufacturing premisesPotteries/tiles and brick worksRice millsRefractoriesiworks and firebrick kilnsSalt crushing factories and refineriesSilicate (other than sodium silicate) factoriesSoap and. detergent factoriesSugar candy manufacturersSugar factoriesTanneries

b) Moderate HazardArecanut/ betelnut factoriesAtta and cereal grinding premisesBakeries and/or biscuit factoriesBeedi factoriesBook binders and paper cutting premisesBook sellers and stationers’ shopsBoot and shoe factories and other leather

180

Tea colouring factoriesUmbrella factoriesVermicelli factoriesWire drawing works

goods factoriesBoat builders and ship repairing docksButton factoriesCandle worksCanvas sheet manufacturersCardboard box manufacturersCarbon paper manufacturing premisesCarpet and durries factoriesCarpenter’s workshopsCamphor boiling premisesCashew nut factories (using open fire)Gnmng and pressing factoriesCloth processing worksCoffee curing premisesCoffee roasting and grinding worksColouridyes mixing and/or b lend ingfactories

Coir factoriesCork factoriesCork stopper and other cork products

manufacturing premisesCollieriesChemical manufacturersCotton millsDyeing and dry cleaning worksElectric wire and cable manufacturingpremises

EnameJ. factoriesEssential oil distillation plantsFlour millsGarment makersGhee manufacturing premisesGinning and pressing factoriesGrains and/or seeds disintegrating factoriesGrease manufacturing worksHat and topee factoriesHosiery factoriesIncandescent gas mantle manufacturersJute mills and jute pressesMineral oil blending and processing worksMutton tallow manufacturersManure and/or fertilizer works(blending, mixing and granulating only)

Mattresses and pillow making premisesOxygen plantsPaper millsPencil factoriesPlastic goods manufacturersPrinting press premisesPulverising and crushing mills (hazardousmaterials)

Rice millsRope factoriesRubber goods manufacturersSheliac factoriesSpray painting worksStarch factoriesSynthetic fibre manufacturing premisesTea factoriesThermalTobacco

power stations(chewing), zarda, kimam and pan


C)

B-1.

4

b)

4

4

eS

musalu making premisesTobacco grinding and crushing and snuff

manufacturing premisesTobacco’ curing and redrying factoriesTobacco pressmg worksUpholsterersWeaving factoriesWooilen millsWool cleaning/pressing factoriesYam gassing plants.

High HazardAcetylene plantsAlcohol distillersAluminium and magnesium powder plantsBi tuminished paper / hessian clothmanufacturing premises

Bobbin factoriesCinematograph film production studiesCalcium carbide plantsCotton waste factoriesCoal/coke/charcoal ball and briquettesfactories

Celluloid goods manufacturersCigarette filter manufacturersCotton seed cleaning or deliniting premisesDuplicating and stencil paper manufacturersFertilizer plants

Explosive manufacturersFireworks factoriesFoam plastics and foam rubber goodsmanufacturers

Grass, hay, fodder and bhoosa (chaff)pressing’ factories

Match factoriesOil millsOil extraction plantsOil and leather cloth factoriesPaint (including nitrocellulose paints) andvarnish factories

Petrochemical plantsPlywood factoriesPrinting ink manufacturersResin and lamp black manufacturersRubber substitute. manufacturersSurgical cotton manufacturersTar distilleriesTar felt manufacturing premisesTarpauplin and canvas proofing factoriesTimber and woodworkers’ premisesTin printers (where more than 50 percent offloor area is occupied as engineeringworkshop this may be taken as moderatehazard risk)

Terpentino distilleriesTyre retreading and resoling factoriesWoodmeal manufacturers

A P P E N D I X B( Clause 5.5)

SELECTION OF WIRING SYSTEMS

WIRING SYSTEMS FOR GENERALAPPLICATIdNBare solid or tubular conductors supportedon insulators in metal or incombustiblestructural ducts or chases (main connec-tions).Tough rubber-sheathed or PVC-sheathedcables protected as necessary againstmechanical damage, say, buried in plasteror installed in concrete ducts.

NOTE - Polythene-insulated PVC-sheathed cableprovides an alternative having the advantage of highinsulation-resistance.

Rubber-insulated braided and compoundedor PVC-insulated cable installed in heavy-gauge screwed conduit.

NOTE,-- The use of galvanized conduit and PVC-insulated cable is to be preferred where the situationmay be damp or long hfe is required.

Rubber-insulated braided’ and compoundedor PVC-insulated cable installed in light-gauge steel conduit with lug grip.Rubber-insulated braided and compoundedor PVC-insulated cable installed in PVC,orother insulated conduit and provided with abare copper or copper-alloy earth-continuityconductor as necessary.

g)

h)

3

k)

Grid suspension wiring system comprisingrubber-insulated or PVC. insulated cableslaid around a galvanized steel catenarywire, braided overall or otherwise protectedto withstand corrosive conditions wherenecessary.Rubber-insulated braided and compoundedor PVC-insulated cable installed in metaltrunking or ducts.

NOTE - Incombustible insulated trunking and ductsprovide an alternative and where these are used a barecopper or copper-alloy earth-continuity conductor maybe required.

Rubber-insulated braided and compoundedor PVC-insulated cable installed on cleats,with appropriate protection where cablepasses through floors or walls.LRubber-insulated lead-alloy-sheathed cablesincorporating an earth continuity conductor,or rubber-insulated aluminium-sheathedcable, protected as necessary against mecha-nical damage and corrosion.

NOTE- Where a lead-sheathed cable has plumbedjoints a separate earth-continuity conductor may notbe required.

Mineral-insulated metal-sheathed cable withor without protective shearhing with suitablewatertight glands.

?ART 4 ELECTRICAL INSTALLATIONS IN INDUSTRIAL BUILDINGS 181

ml Paper - insu la ted , l ead-or a lumin ium-sheathed cable with steel wire or tapearmour as necessary.

N O T E- Precautions should be taken against thedrainage of oil and in certain instances cables ofthe non-draining type are required.

B-2. ADDITIONAL WIRING SYSTEMSPARTICULARLY SUITABLE FOR USEIN FACTORIES AND THE LIKE

a)

b)

c)

d)

e)

g)

h)

Paper-insulated, lead-alloy-sheathed oraluminium-sheathed, steel tape or wirearmoured, served and impregnated cable orPVC-insulated and steel tape or wire armo-ured and PVC-sheathed cable buried direc-tly in the ground or used in special condi-tions.

Paper-insulated, lead-alloy sheathed oraluminium-sheathed, steel tape or wirearmoured cable or PVC-insulated steel tapeor wire armoured and PVC-sheathed cablewith cleat or hook suspensions.

Paper-insulated lead or lead-alloy or alumi-nium-sheathed cable or PVC-insulated andPVC-sheathed cable, installed in under-ground earthenware ducts or metal pipes.

Paper, rubber-insulated, Itad-or aluminium-sheathed cable or PVC-insulated and PVC-sheathed cable, mounted on porcelain orhardwood cleats or in trenches or ducts,and so installed as to be protected againstmechanical damage.Tough rubber-sheathed or PVC-sheathedcable mounted on insulating non-hygro-scopic cleats affixed to treated, teak battensby screws of corrosion-resisting material,such as Monel metal or phosphor-bronze.

Rubber-insulated braided and compoundedor PVC-insulated cable installed in galva-nized solid-drawn screwed conduit withflameproof couplings and inspection fittings.

Varnished-cambric insulated, lead-alloy oraluminium-sheathed cable.

Rubber-insulated, tough rubber-sheathedcable, steel wire armoured.

NOTL -. Varnished cambric insulated cables withoutmetal sheath should be used only for short connectionson switchboards and the like in dry situations.

B-3. SELECTION OF WIRING SYSTEMSFOR FACTORIES

B-3.1 Wiring systems suitable for installationsin different categories of factories are given i nTable 3.

B-4. SPECIAL RESTRICTIONS

B-4.1 Even though guidance may be takenfrom the selection chart (Table 3) for wiringsystems, the following restrictions to their useapply:

182

WiringSystem (seeB-l, B-2)

tb) and (g)

(c)

(h) and fs)

ci)(m). (n).(P) and (v)

Restrictions

If the ducts are in the form of under floortrenches then the following provisions shouldbe observed:

i) Cables shall preferably be so mounted oninsulated racks or other supports as to beat least 75 mm above the bottom.

ii) Top of trenches shall be covered withchequered plates or concrete slabs.

iii) In case of long trenches, it is recommendedthat trenches of more than I 000 cm2cross-

iv)

v)

sectional area be divided by incombustiblebarriers at intervals not exceeding 45 m.The barriers shall be at least 50 mm inthickness and of the same height as ofcable trench. The cables shall be carriedthrough holes in the barriers. which shallbe made good thereof to prevent the pass-age of tire beyond the barriers.The combined cross-sectional area of allconductors or cables shall not as far aspossible exceed 40 percenl of the internalcross-sectional area of the trench, andThe cable trenches shall be kept ‘free fromaccumulation of water. dusts and wastematerials.

Trunking or ducting systems for cables aboveground shall not be used where:

i) They are exposed to physical damage.ii) They are exposed to corrosive vapours,iii) Where atmosphere is likely to -contain

flammable gases or vapours.iv) Where wet processes are carried out, orv) In concealed spaces.

Ordinary steel conduits shall not be permittedin areas where flammable vapour may bepresent. unless it is of type conforming withwiring system (1) and shall not be permittedin locations:

i) Where wiring height is less than 2.5 mabove working floor level, unless pro-tected against mechanical damage,

ii) Where ambient temperature is likely to beabove 55°C at sometime or other durmgthe year.

iii) In concealed spaces of combustibleconstruction,

iv) Where atmosphere is likely to containflammable gases or vapours. or

v) Where conductor operates at voltage above650 V.

It shall be permitted only where voltage is below650 V and in locations where the atmosphere isunlikely to contain any flammable vapours orgases.

Same as in case of wiring system (d). Thissystem shall not be permitted in locations:

i) where exposed to severe physical damage.ii) where exposed to corrosive vappurs.iii) where wet processes are carried out, oriv) in concealed places.

These systems should only be permitted forvoltage below 250 V and that too only if useof such system is essential.

Same as in case of wiring system (d).Armoured cables shall not be permitted. infollowing locations unless the cable is ofPVC-sheathed type. and shall not be per-mitted in locations exposed to corrosive fumesor vapour; and battery rooms.


TABLE 3 SELECTION CHART FOR WIRING SYSTEMS FOR INSTALLATIONS IN FACTORIES

( C l a u s e s 5.5.1 a n d Bf4. I )

S EC T I O N O F I N S T A L L A T I O N , C ATEGORY OF FACTORY.

Average Heavy Light Chemical Facto-Factory Industry industry industry ries

7_ Involv-

2nd I St 2nd 1st 2nd 1st 2ndChoice Choice Choice

YeChoice Choice Choice Choice inG?e

(1) (2) (3) (4) (6) (7) (8) (9) (10)Main distribution at medium a aor low voltage ; : 5

P Sk k V ;

k

ki G q i rt

4 Lr

Y

Sub-main distribution lo a g a g C h f b klocal distribution boards C C V f S q t

:fk ff

r

P P PV r V

Sub-circuit wiring C::

C g b C kf f h f t

fj k j s

VV

N O T E- For description of a, b, c....v see B-l and B-2.

A P P E N D I X C(Clause 7.2.2)

REQUIREMENTS FOR FIRE SAFETY IN SPECIFIC INDUSTRIES

T+PE O F INDUSTRY(1)

J&e spinning andweavmg. juterope, carpetmaking factories

Cotton ginningcotton seeddelintering andpressing factories

Plants makingviscose rayonyarn or staplefibre or both

Textile millsusing cotton,cotton wasteregeneratedcellulose. manmade Ji bres orany grouping ofthese

R E F. ISS(2)

IS : 3836

MOTORS OTHER EQUIPMENT

(3) (4)

All motors shall All equipmentbe totally enclosed shall be metaltype and in wet clad, dust-tightlocations shall bedrip-proof

IS : 2726 -do-

IS .3079

Places where paints IS : 9109and varnishes arestored or pro-cessed

All equipment inthe Xanthationarea and finisheddisulphide plant

.shall comply withPart VII of theCode

Totally enclosed Metal clad andtype, the ‘cooling dust-tight. Equip-air for variable ment shall bespeed motor taken flamqproof in gasfrom outside the smgemg rooms.building. Stop motion

devices providedon frames snailbe dust-tight

FITTINGS MISCELLANEOUS

(5) (6)

Li hting fittingss all1 be dust-tight

Sup ly shall be at< 4SO V in jutegodowns

Vapour-prooflighting fittingsin areas wherecorrosive gasesare evolved

Dust-tight light-ing fittings atwillowing, lapbreaking, wasteopening, mixing,blow and ra.isingrooms

Wiring in steelconduits. Light-

ing fittings ofenclosed type


All current carryingparts, contactsliable for corrosionshall be cadmiumplated

Machines for singe-ing yarn shall beprotected lo ensurethat heating ele-ments are notswitched on whileyarn is stationary

Provisions shall bemade for switchingoff the wholefactory at morethan one controlpoint.

183

T YPE OF INDUSTRY RE F. 1% MOTORS OTHER EQUIPMENT FITTINGS h’t IsCELLANEOUS(1) (2) (3) (4) (5) (6)

Factories where.powders ofaluminium.magnesium andtheir alloys areprocessed or used

IS : 4226 Motors shall be All equipment Wiring in steel -do-flameproof dust- of the conduits. Enclosedprotected enclosed type lighting fittings(see Part 7 ofthe Code)

Coal, pulverisingmills, as alsoequipment.therein for powergeneration coleor briquettemaking

IS : 3595 Totally enclosed,flameproof, dust-proof (see Part 7of the Code)

Lighting fittingsshall be dust-tight. Only con-duits; armouredor mineral insu-lated type ‘ofwiring

Use of flexiblecables to be kept_to the minimum

Tea factories IS : 4886 Where. practicable,totally enclosed

type

Godowns, ware- IS : 3594houses, outdoorstorage sitesformmg part ofindustrtal comp-lexes or others:cold storagebuildings

Saw mills. furni- IS : 6329ture factories.coach and bodybuild works, up-holsteries andother woodworking shops.Plywood hard-wood. wood wool,insulation boards,wood flour. etc

-

Driving motorsfor overheadcranes totally

. e n c l o s e d

All switchgear Screwed steel cbn-equipment metal duits mineralenclosed. Formains operatedelectrical stackers,switch and socketshall be water-tight. Flexibleconnection to thestacker throughrubber compoundsheathed trailingcable with hardcord braiding

insulated, copperor aluminiumsheathed cable.Lighting fittingsto be

Positioned

not be ow 45 cmbelow roof. Aclearanoe of notless than 75 cmto be providedfrom higheststacking level.Flexible lightingpendants orportable lampsnot allowed

Motors shall be All equipment shalltotally enclosed be dust-tight andor pipe venti- where spray paint-lated ing is done shall

comply with Part7 of the Code

Fan motors ofdryers and wither-

.,ing troughs andother controlaquipment shall bedust proof type.Temperature ofeqqipment IO’Covq normal work-ing ,temperatureallowed

All control equip-ment switches, etc,outside godownwhere fibrousgoods, flammableliquids, nitro-cellulose, fire worksor explosives arestored

Electrical heatersshall be metalcased, totally en-closed, immersiontype or totallyenclosed low tem-perature type withexternal surfacebelow 92°C

A P P E N D I X D(Clause 8.1.1)

RECQMMENDED VALUES OF ILLUMINATION AND LIMITING VALUESOF G&ARE INDEX-INDUSTRIAL BUILDINGS

SL INDMTRIAL RtItLotNGs A N D PRO~‘ESSE.Q I AVERAGE L IMITINGNo. ILLUMINATION GLARE INDEX

lux

I. General factor areas:a) Canteensb) Cloakroom;’c) Entrances. corridors. stairs

2. Factory outdoor areas:Stockyards. main entrances, exit roads, car parks, internal factory roads

I50 -100 -100 -

20 -


I% INDUSTRIAL BUILDINGS AND PROCFSSE~

3. Aircraft factories and mainmnance hangers:a) Stock parts productionsb) Drilling. riveting, screw fastening, sheet aluminium layout and template

work. wing sections. cowling welding, sub-assembly. final assembly,inspection

c) Maintenance and repairs (Hangers)

4. Assembly shops:a) Rough work, for example, frame assembly. assembly of heavy machineryb) Medium work, for example, machined parts, engine assembly. vehicle

c) Fine work, for example, radio and telephone equipment. typewriterbody assembly

and office machinery-assemblyd) Very fine work. for example, assembly of very small precision mechanisms,

instruments

5. Bakeries:a) Mixing and make-up rooms, oven rooms, wrapping roomsb) Decorating and icing

6. Boiler houses (industrial):a) Coal and ash handlingb) Boiler rooms:

i) Boiler fronts and operating areasii) Other areas

c) Outdoor plants:i) Catwalks

ii) Platforms

7. Bookbinding:

8.

a) Pasting, punching and stitching.b) Binding and folding; miscellaneous machinesc) Finishing, blocking and in laying

Boot and shoe factories:a) Sorting and gradingb) Clicking and closing, preparatory operationsc) Cutting table and presses. stitchingd) Bottom stock preparation. lasting and bottoming, finishinge) Shoe rooms

9.

IO.

I I .

12.

13.

14.

Breweries and distilleries:a) General working areasb) Brewhouse. bottling and canning plantsc) Bottle inspection

Canning and preserving factories:a) Inspection of beans, rice, barley, etcb) Preparation: kettle areas. mechanical cleaning, dicing, trimmingc) Canned and bottled goods: retortsd) High speed labelling linese) Can inspection

Carpet factories:a) Winding, beamingb)- Designing. jacquard and cutting, setting pattern, tufting, topping, cutting,

hemming, fringingc) Weaving. mending, inspection

Ceramics -see pottery and clay products

Chemical works:a) Hand furnaces, boiling tanks, stationery driers, stationery or gravity

crystalizers. mechanical driers, evaporators, filtration plants, mechanicalcrystalizing bleaching. extractors, percolators, nitrators, electrolytic cells

b) Controls. gauges, values, etc

c) Control rooms:i) Vertical control panels

ii) Control desks

Chocolate’ and confectionery factories:a) Mixing. blending. boilingb) Chocolate husking, winnowing, fat extraction, crushing and refining.

feeding, bean cleaning. sorting, milling, cream makingc) Hand decorating, inspection, wrapping, packing

*Opiical aids should be used’ where necessary.TSupplementary local hghtlng may be requtred lor gauge lasses and instrument panels.$pecial attention should be paid to the colour quality o,B the light.

OVERAGE~LIUMINATION

lux

450300

300

IS0 28

300 25

700 22

I &lo* I9

100

w20 to 25

2050

I 000:700

IO00

:3

iiiSpecial lighting


450

:E300450

200

450450

-

IS0w

200 to 300300

LIMITINGGLARE INDEX

2525

25

::

-

--

--

::22

:;

::22

2s25-

::

::-

25

::

-

28-

28

::

SI. INDUSTRIAL BUILDINGS AND PROCESSES

No.

15. Clothing factories:a) Matching-upb) Cutting sewing:

i) Lightii) Mediumiii) Darkiv) Pressing

c) Inspection:i) Lightii) Mediumiii) Dark

d) Hand tailoring:~’ i) Light -

ii)dediumiii) Dark

16. Collieries (surface buildings):a) Coal preparation plant:

i) Working areasii) Other areas.iii) Picking beltsiv) Winding houses

b) Lamp rooms:i) Main areasii) Repair sectionsiii) Weigh cabine

c) Fan houses

17. Dairies:a

fGeneral working areas

b Bottle inspectionc) Bottle filling

18. Die sinking:a) Generalb) Fine

19. Dye works:a) Reception, ‘grey’ perchingb) Wet processesc) Dry processesd) Dyers’ offices‘e) Final perching

20. Electricity generating stations: Indoor locationsa) Turbine hallsb) Auxiliary equipment; battery rooms, blowers auxiliary generators,

switchgear and transformer chambersc) Boiler houses (including operating floors) platforms, coal conveyors,

pulverizers, feeders, preciprtators. soot and slag blowersd) Boiler house and turbine housee) Basementsf) Conveyor houses, conveyer gantries. junction towersg) Control rooms:

i) Vertical control panelsii) Control desks

iii) Rear of control panelsiv) Switch houses

h) Nuclear reactors and steam raising plants:i) Reactor areas, boilers, galleriesii) Gas circulator daysiii) Reactor charge/discharge face

2 I. Electricity generating stations: Outdoor locationsa) Coal unloading areasb) Coal storage areasc) Conveyorsd) Fuel oil delivery headerse) Oil storage tanksf) Catwalksg) Ptatforms. boiler and turbine decksh) Transformers and outdoor switchgear

22. Engraving:a) Handb) Machine (see Die sinking)

AVERAGEILLUMINAT!~N

IUX

4502

:z

:z

4501000I 500

4501000I 500

I50

::I50

lo0I50I50100

2001Special lighti;;

IE

750lW2w

,g:

200

100

70 to loo10070

70 to loo

200 lo :zI50I50

I50I50200

1000-

LIMITINGGLARE INDEX

I9

::2222

I9I9I9

I9I9I9

25

25

25

-

-

-

I9I9

;;

::25

_

I9-

l Spectal attention should be paid to the colour quality of the light.tSupplementaty local lighting may be required for gauge glasses and instrument panels.


SLNo.

23.

IN D U S T R I A L B U I L D I N G S A N D ‘PROCESSES

Farm buildings (dairies)a) Boiler housesb) Milk roomsc) Washing and sterilizing roomsd) Stablese) Milking parlours

24. Flour mills:a) Roller, purifier, sifting and packing floorsb) Wetting tables

25.

26.

Forges: General I50 28

Foundries:a) Charging floors, tumbling cleaning. pouring, shaking out, rough moulding

and rough core makingb) Fine moulding and core making, inspection

21. Garages:a) Parking areas (interior)b) Washing and polishing, greasing, general servicing, pitsc) Repairs

28. Gas works:a) Retort houses, oil gas plants, water gas plants, purifiers, coke screening and

coke handling plants (indoor)b) Governor, meter, compressor, booster and exhaustor housesc) Open type plants:

i) Catwalksii) Platforms

29.

30.

Gauge and tool rooms: General

Glass works and processes:a) Furnace rooms, bending, annealing lehrsb) Mixing rooms, forming (blowing. drawing. pressing, rolling)c) Cutting to size, grinding, polishing, tougheningd) Finishing (bevelling. decorating. etching. silvermg)e) Brilliant cuttingf) Inspection:

i) Generalii) Fine L

31. Glove mating:a) Pressing, knjtfing, sorting, cuttingb) Sowing:

i) Lightii) Medium

iii) Dark

32. Hat makinga) Stiffening, braiding, cleaning, refining forming, sizing, pouncing, flanging,

finishing ironing.b) Sewing:

i) Lightii) Medium

iii) Dark

33.

34.

Hosiery and knitwear:a) Circular and flat knitting machines universal winders, cutting out,

folding and pressingb) Lock stitch and overlocking machines:

i) Lightii) Medium

iii) Darkc) Mendingd) Examining, and hand finishing. liglit, medium, darke) Linking or running-on

Inspection shops (Engineering)a) Rough work. for example, counting, rough checking of stock parts, etcb) Medium work, for example. ‘Go’ and ‘No-go’ gauges, sub-assembliesc) Fine work. for example, radio and telecommunicat.ion equipment,

hllTlNGG L A R E INDEX

-

u25

150 25300 25

I50 28300 25

1:: :i300 25

30 to 50.100

:;:

7oot

2828

::I9

I9I9

22

::22

I50 22

iii700

::22

calibrated scales. precision mechanisms, instrumentsd) Very fine work. for example, gauging and inspection of small intricate partse) Minute work. for example. very small instruments

300

300450

I :g700450

22

::22I9I9I9

I50300

‘700

:z$

2825

*Supplementary local lighting should be used at important points.tSupplementary local lighting and optical aids should be used where necessary:Optical aids should be used where necessary. \

187PART 1 ELECTRICAL INSTALLATIONS IN INDUSTRIAL BUILDINGS

LIMITINGG LARE I N D E X

AVERAGEILLUMINATION

IUX

SL INDUSTRIAL B UILDINGS AND Pttoc~~!imNo.

35. Iron and steel. worksa) Marshalling and outdoor stockyardsb) Stairs. gan,gw ays basement< quarries, loading docks!c) Slab yards, melting shops. ingot stripping soaking pits, blast furnace

working areas, picking and cleaning lines. mechanical plants, pump hausesd) Mould preparation, rolling and wtre_mills, mills motors rooms, power

blower housese) Slab inspection andsonditioning, cold strip mills. sheet and plate

finishing, tinning. galvanizing, machine and roll shopsf) Plate inspectiong) Tinplate inspection

36. Jewellery and watchmakinga) Fitte processesb) Minute processes

38.

c) Gem cutting, polishing. settingLaboratories and test roomsa) General laboratories. balance roomsb) Electrical and instrument laboratories

Laundries and drycleaning worksa) Receiving, sorting, washing, drying, ironing (calendering), despatchb) Drycleaning bulk machine workc) Fine h&d ironing, pressing, inspection mending, spotting

39.

40.

Leather dressinga) Vats, cleaning. tanning, stretching, cutting, fleshing and stuffingb) Finishing, staking, splitting and strafing

.Leather workinga) Pressing and glazingb) Cutting, scarfing sewingc) Grading and matching

41.

42.

Machine and fitting shopsa) Rough bench and machine workb) Medium bench and machine work, ordinary automatic machines, rough

grinding. medium buffing andP

olishingc) Fine bench and machine work, me automatic machines, medium grinding.

fine buffing and polishing

Motor vehicle plantsa) General sub-assemblies, chassis assembly. car assemblyb) Final inspectionc) Trim shops. body sub-assemblies, body assemblyd) Spray booths

43.

44.

Paint worksa) General automatic processesb) Special batch mixingc) Colour matching

,Paint shops and spraying booths:a) Dipping. firing rough sprayingb) Rubbing, ordinary painting. spraying and finishingc) Fine painting. spraying and finishingd) Retouching and matching

45. Paper-works:a) Paper and board making:

i) Machine houses, calendering pulp mills, preparation plants, cutting,finishing, trimming

ii) Inspection and sorting (over hauling)b) Paper converting processes:

i) Corrugated board, cartons. containers and paper sack manufacture.coating and laminating processes

ii) Associated printing

46. Pharmaceuticals and fine chemicals works:a) Raw material storageb) Control laboratories and testingc) Pharmaceuticals manufacturing: grinding. granulating, mixing and drying.

tableting, sterilizing and washing, preparation of solutions andfilling. labelling. cap ing, cartoning and wrapping, inspection

d) Fine chemical Pmanu acture:i) Plant processingii) Fine chemical ftnishing

28

28

28_

150

200300

Special lighting

,g:I Soot

I9IO

300450

I9I9

iiz ::300 25

I50 28200 28

450700

1000*

2222I9

28

25

22700

300450300450

::25

200450700’

I50300450mt

::25I9

200300

2522

200 28W I9

300

%

25

::

*Optical aids should be used where necessary.*Special attention to colour quality of light may be neassary. ,

188 NA’FIONAL ELECTRICAL CODE

St. INDUSTRIAL . BUILDINGS AND PROCESSES

No.AVERAGE

ILL~~~~NA~!oNIUX

LIMITINGGLARE INDEX

47. Plastics works:a) Manufacture (see Chemical works)b) Processing:

i) Calendering, extrusionii) Moulding-compression, injection

iii) Sheet fabrication:I) Shaping2) Trimming. machining. polishing3) Cementing

48. Plating shops:a) Vat and baths, buffing. polishing, burnishingb) Final buffing and polishing

49. Pottery and clay products:a) Grinding. filter pressing, kiln rooms, moulding, pressing, cleaning.

trimming, glazing. firingb) Enamelling. colouring, decorating

-.

-z ::

::25

200300200

I50 25Special lighting _.

I50 28450. I9

50. Printing works:a)

b)

d

d)

e)

Type foundries:i) Matrix making, dressing type, hand and machine casting

ii) Front assembly, sortingPrinting plants:

i) Machine composition. imposing stonesii) Pressesiii) Composing room .iv) Proof readingElectrotyping:

i) Block-making, electroplating. washing, backingii) Moulding. finishing, routingPhoto-engraving:

i) Block-making, etching. maskingii) Finishing. routing

Colour printing:Inspection area

2522:ii

:ii450300

200300

200300

700*

::I9I9

::

2525

I9

5 I. Rubber processing:a) Fabric preparation creelsb) Dipping. moulding, compounding calendarsc) Tyre and tube making

52. Sheet metal works:a) Benchwork. scribing. pressing. punching shearing. stamping,

spinning. foldingb) Sheet inspection

200 2 5I50 25200 25

25200Special lighting

53. Soap factories:a) Kettle houses and ancillaries, glycerine evaporation and distillation.

b)

c)

d)

continuous indoor soap making, plants:i) General areas

ii) Control panelsBatch or continuous soap cooling. cutting and drying. soap milling.plodding:

i) General areasii) Control panels, key equipment

Soap stamping. wrapping and packing. granules making. granules storageand handling, filling and packing granules:

i) General areasii) Control panels. machinesEdible products processing ‘and packing

::I50

200 to 300

I50200 to 300 ::

I50

200 to :E! u25

54. Structural steel fabrication plants:a) Generalb) Marking off

I50300

55. Textile mills’ (cotton or linen):Bale breaking, blowing, carding, roving. slubbing. spinning (ordinarycounts), winding, heckling, spreading. cablingWarping, slashing, dressing and dyeing. doubling (fancy). spinning(fine counts)Healding (drawing-in)

25

25-

I;I9-

Weaving -i) Patterned cloths. fine counts dark

ii) Patterned cloths, fine counts lightiii) Plain ‘grey’ clothCloth inspection

-*Special attention should be paid to the colour quality of the light.


l%.INDUSTRIAL B UILDINGS A N D P R O C E S S E S

56. Textile mills (silk or synthetics):a) Soaking, fugitive tinting. coliditioning or setting of twistb) Spinningc) Winding, twisting, rewinding and coning, quality slashing:

i) Light threadii) Dark thread

d ) W a r p i n ge) Healding (drawing-in)f) W.eavingg) Inspection

57. Textile mills (woollen):a)

b)

dc;e)

Scouring, carbonizing, teasing, preparing, raising, brushing. pressing.back-washing, gilhng, crabbing and blowingBlending, carding, combing (white), tentering. drying, croppingSpinning, roving, winding, warping, combing (coloured). twlstmgHealding (drawing-in)Weaving:

i) Fine worsteds

r)Lx)

ii) Medium worsteds, fine woollensiii) Heavy woollensBurling and mendingPerching:

i) Greyii) Final

58. Textile mills (jute):a) Weaving, spinning, flat, jacquard carpet looms, cop windingb) Yarn calender

59. Tobacco factoriesAll processes

60. Upholstering,. furniture and vehicles

61. Warehouses and bulk stores:a) Large material, loading baysb) Small material, racksc) Packing and despatch

62. Welding and soldering:a) Gas and arc welding, rough spot weldingb) Medium soldering. brazing and spot welding. for example, domestic

hardwarec) Fine soldering and spot welding, for example, instruments. radio set

assembly - _d) Very fine soldering and spot welding. for example. radio valves

63. Woodworking shops:a) Rough sawing and bench workb) ‘Sizing. planning. rough sanding, medium machine, and bench work.

gluing, veneering. cooperagec) Fine bench and machine work. fine sanding and finishing

A VERAGE

ILLUMINATIONlux

I50iOO450700

700450

:z

2z*

200 25I50 25

3001

300

Iii 2”:I50 25

150 28

300 25

700 22150 19

I50

:E

L IMITING

G L A R E INDEX

2525

25

::

19I9

252525-

--

22

22

22

::

*Special attention should be paid to the Solour quality of the light.tSpecial attention should be paid to the colour quality of the light in all processing areas.


A P P E N D I X E(C/uuse 9)

POWER FACTOR IN INDUSTRIAL INSTALLATIONS

The general guidelines for power factor in Table 4. The recommended capacitor ratings atcompensation is giver in Part I /Set 17 of the rated voltage, for direct connection to acCode. For guidance, the natural power factor for induction motor in industries are given in Table 5.some three phase electrical installations are given

SLN o(1)

::3.4.5.6.7.

;:IO.I I.12.13.14.15.16.17.

TABLE 4 POWER FACTOR FOR THREE PHASE ELECTRICAL INSTALLATIONS

TYPE OF IN S T AL LATION N ATIIRAI. POWER St. TYPE OF INSTALLATION NATI’HAL. POWtRFACTOR No. FACTOR

(2) (3)

Cold storage and fisheries 0.76 to 0.80Cinemas Or78 to 0.80Metal pressing 0.57 to 0.72Confectionery 0.77Dyeing and printing (textile) 0.60 to 0.87Plastic moulding 0.57 to 0.73Film studios 0.65 to 0.74Newspapers 0.58Heavy engineering works 0.48 to 0.75Rubber extrusion and moulding 0.48Pharmaceuticals 0.75 to 0.86Oil and paint manufacturing 0.51 to 0.69Silk mills 0.58 to 0.68Biscuit factory 0.60Printing press 0.65 to 0.75Food products 0.63Laundries 0.92

(1) (2) (3)

18. Flour mills 0.6119. Gas works 0.8720. Textile mills 0.8621. Oil mill 0.51 to 0.5922. Woollen mills 0.7023. Potteries 0.6124. Cigarette manufacturing 0.8025. Cotton press 0.63 to 0.6826. Foundries 0.5927. Tiles and mosaic 0.6128. Structural engineermg 0.53 to 0.6829. Chemicals 0.72 to 0.8730. Municipal pumping stations 0.65 to 0.7531. Oil terminals 0.64 to 0.8332. Telephone exchange 0.66 to 0.8033. Rolling mills 0.72 to 0.6034. Irrigation pumps 0.52 to 0.70

TABLE 5 CAPACITOR RATINGS AT RATED VOLTAGE

RATED

OI’TPIT OF

CAPA(.ITOR RA T I N G IN kVAR tom Moron Srttn

I*

3 000 I 500 I 000 750 600 500MOTORS

(11kW

2.253.75.77.5

I l .2

G.722.53757

I::150I87

rev min rev min rev min rev min rev min re\ min(2) (3) (4) (5) (6) (7)

i2.5345

sI I

I23456

;12.5

::334250

I.52.53.54.56

9IOI62126364553

23.54.55.57.59

10.5I2IXi32x384755

2.54568.5

I I13IS2j29354x606X

2.545.56.59

Ii.5

::3240556776

No~I- I - The reference to speed of motor ha\ been made 51ncc the manufacturer\ pro\ idc inlnrmat~on on that bawls.

NOTI: 2 The capacitive current supplied bv condenser\ directl! connected acre\\ Induction motor terminal\ should notexceed the magnetising current of the induciion motors. to guard ‘against c\cc\\ tramlent torque\ and o\cr\olt+!c\.

NOTE 3 Should a consumer desire to impBo,e the power factor bqond a \aIuc which ih limited b! con\idcration\ 01magnetising kVAR of the motor as stated in Note 2. then he may install the calculated capacitor LVAR a\ a \cparate cltcultwith its independent controlgear.

PART 4 ELECTRICAL INSTALLATIONS IN INDUSTRIAL B U I L D I N G S I91


0. .F 0 R E W 0 R Da

0.1 As compared to the various types of indoor installations covered in other partsof the Code, outdoor installations ati distinct in nature by virtue of their- beingexposed to moderate to heavy environmental conditions. In addition, electric powerin outdoor installations is normally utilized for specific purposes such as, lighting orfor meeting the needs of heavy machinery (example, open cast mines). In the case ofthe latter, the duties would be more onerous than those normally encountered inindoor situations, thereby calling for special considerations in their design.0.2 Keeping the above in view, Part 5 of the Code has been set aside to deal withinstallations erected outdoor. This part basically deals-with two types of outdoorinstallations, namely, temporary and permanent. Temporary installations are thosewhich are erected to serve for a small duration of time after which.they are meantto be dismantled. For convenience, and keeping other aspects of safety provisionsin view, this duration is defined as not exceeding six months. Permanent outdoorinstallations are those which are generally ‘in use for longer periods of time.0.3 Even though, installations for lighting of public thoroughfares are permanent innature, they are dealt With separately in Section I.0.4 It may, however, be noted that small outdoor locations around buildinginstallations (example, gardens around hotel installations or storage yards inindustries) do not fall under the scope of Part 5. For requirements pertaining tothis, Merence should be made to relevant parts of the Code.

SECTION 1 PUBLIC LIGHTING INSTALLATIONS

0 . F O R E W O R D

0.1 One of the most common forms of permanentoutdoor installations is the public l ightinginstallations intehded for lighting of publicthoroughfares. With the availability of variety oflight sources for such insfallations and the needfor proper illumination of a variety of trafficroutes and city centres, i t has been foundnecessary to lay down guidelines fo.r cesigning onefficient and economical lighting Installation.

0.2 This Section of the Code is intended to covergeneral principles governing the lighting of publicthoroughfares and to lay down recommendationson the quantity and quality of lighting to beprovided. The actual details of design wouldentirely depend on the local circumstances.

0.3 The requirements given in this Section are.as far as prac t i cab le a l igned wi th [herecommendations of the International Com-mission on Illumination (CIE) modified tosuit the local conditions and regulations.

2.1.4 D u a l Curriugewu.v - A layout of theseparated carriageways, each reserved for trafficin one direction only.

2.1.5 Central Reserve - A longitudinal spacedividing a dual carriageway.

2.1.6 Service Road- A subsidiary roadbetween a principal road and buildings orproperties facing thereon and connected only atselected points with the principal road.

2 . 1 . 7 Cjxcle Truck - A way or part of ahighway for use by pedal cycles only.

2 . 1 . 8 FOO~N~U.I- That portion of a roadreserved exclusively for pedestrians.

2.1.9 Verie - The unpaved area flanking acarriageway, forming part of the highway andsubstantially at the same level as the carriageway.

2.1.10 Shoulder - A strip of highway adjacentto and level with the main carriageway to providean oppor tun i ty fo r veh ic les to l eave thecarriageway in an emergency.

1. SCOPE

1.1 This Section of the Code covers requirementsof public lighting installations in order to provideguidance to those concerned with the preparationof public lighting schemes, their installation andmaintenance.

2.1.11 Rqfuge -- A raisedguarded area so sited in thedivide the streams of trafficsafety area for pedestrians.

2.1.12 Kerb - A border ofother rigid material formedcarriageway.

p la t fo rm or acarriageway as toand to provide a

stone, concrete orat the edge of a

1.2 This Section deals onl with electric lightinsources and does not incluJ fe gas or other types olighting.

2.2 Terms Relating to Lighting Installation

1.3 This Section also does not cover exteriorlighting installations, such& those which applyfor parks, shopping enclaves, flood lighting ofroutes and structures of architectural importance,etc.

2.2.1 Lighting Installation -The whole of theequipment provided for lighting the highwaycomprising the lamps, luminaires, means ofsupport and electrical and other auxiliaries.

2. TERMINOLOGY

2.0 For the purpose of this Section, the followingterms together with those provided in IS : 1885(Part 16: Set 2)-1968* shall apply.

2.1 Terms Relating to Highways

2.1.1 High\csj. - A way for the passage ofvehicular traffic over which such traffic maylawfully pass.

2.2.2 Lighting Sj’stenl -- A n array ofluminaires h a v i n g a characteristic lightdistribution. sited in a manner concordant withthis distribution. (Lighting systems are commonlydesignated, by the name of the characteristic lightdis!ribution, for example, cut-off, semicut-off,etc.)

2.2.3 Luminuire - A. housing for one or morelamps, comprising a body and any refractor,reflector, diffuser or enclosure associated with thelamp(s).

2.1.2 Lu~wt All those physical features of ah i g h w a y .other than the sur fac ing of thecarriageway. which have to be taken into accountin planning a lighting installation.

2 . 1 . 3 Carriage,\,a\* - Tha t por t ion of ahighway intended primarily for vehicular traffic.

2.2.4 Outreach - The distance measuredhorizontally between the centre of the column orwall face and the centre of a luminaire (see Fig.1).

l Electrotechnical vocabulary : Part 16 Lighting. Section 2General illumination lighting fittings and lighting for trafficand signalling.

2.2.5 Overhung -The distance measuredhorizontally between the centre of a luminairemounted on a bracket and the adjacent edge ofthe carriageway (see Fig.1).

2.2.6 Mounting Height - The vertical distancebetween the centre of the luminaire and thesurface of the carriage (see Fig.1).


illumination is the lumen per square metre (lux).

2.3.5 Luminance (at a Point of Surface and ina Given -Direction)- The lumil, IS intensity perunit projected area of a surface. If a very smallportion of a surface has an intensity I candelas ina pa r t i cu la r d i rec t ion and i t s o r thogona lprojection (that is, its projection on a planeperpendicular to the given direction) has an areaD, the luminance in this direction is l/D candelasper unit area. The usual unit is the candela persquare metre (cd/ mz).

2.3.6 Luminosity - The attribute of visualsensation according to which an area appears toemit more or less light. It is some time calledbrightness.

NOTE - Luminosity,is the visual sensation which correlatesapproximately with the photometric quantity ‘luminance’.

2.3.7 Ligh t Ou tpu t -The luminous f luxemitted by a luminaire.

2.3.8 Light Distribution - The distribution ofluminous intensity from a luminaire in variousdirections in space.

2.2.7 Spacing -The distance, measured alongthe centre line of the carriageway, betweensuccessive luminaires in an installation (see Fig. I).

NOTES In a staggered arrangement. ‘the distance ismeasured, along the centre line of the carriageway, between aJuminaire on one side of the carriageway and the nextluminaire, which is on the other side of the carriage. It is notthe distance measured on the diagonal joining them; nor thedistance between successive luminaires on the same side of thecarriageway.

2.2.8 Span -That part of the highway lyingbetween successive luminaires in an installation.

‘2.2.9 Width of Carriagewav - The distancebetween kerb lines measured at right angles to thelength of the carriageway (see Fig. 1).

2.2.10 Arrangement --The pattern accordingto which luminaires are sited on plan, forexample, staggered, axial, opposite.

2.2.11 Geometry (of a Lighting System) - Theinter-related linear dimensions and characteristicsof the system, namely the spacing, mountingheight, width, overhang and arrangement.2.3 Photometric Terms

2.3.1 Luminous Nux - The light given by a 2.3.9 Svmmetrical (Converse As.vmmetrical)light source or a luminaire or receivtd by a Distribution - A distribution of luminoussurface irrespective of the directions in which it is intensity which is substantially symmetricaldistributed. The unit of the luminous flux is the (conversely asymmetrical) about the vertical axisl u m e n ( l m ) . of the luminaire.

23.2 Lower Hemispherical Flux or Dotinward 2.3.10 Axial (Converse Non-axial)Flux-The luminous flux emitted by a luminaire Distribution - An assymmetrical dist.riPution I inin all directions below the horizontal. w h i c h t h e dlrections o f m a x i m u m l u m i n o u s

2.3 .3 L u m i n o u s Intensitv -The q u a n t i t yintensity lie (do not lie) in vertical planes

which describes the light-giving power of asubs tan t ia l ly para l le l to the ax i s o f the

luminaire in any particular direction. The unit ofcarriageway.

luminous intensity is. the candela (cd): 2.3.11 Peak Intensity Ratio - The ratio of the

2.3..4 Illuhination - The luminous f luxmaximum intensity to the mean hemispherical

incident on a. surface per unit area. The unit ofintensity of the light emitted below the horizontal.

2.3.12 Mean Hemispherical .‘ntensitv - Thedownward. flux divided by 6.28 (2 7r ). (This isthe average intensity in the lower hemisphere.)

2.3.13 1ntensit.l. Ratio (in a ParticularDirection) -T The ratio of an actual intensity fromthe luminaire (in a particular direction) to themean hemispherical inrensity.

2.3.14 Beam -- The portion of the light outputof the luminaire contained by the solid anglesubtended at the effective centre of the luminaire

. conta in ing the maximum in tens i ty , bu t nointensity less. than 90 percent of the maximumintensity.

2.3.15 Beam Centre- A direction midwaybetween the directions for which the intensity is

0 = Location of columns90 percent of the maximum in a vertical plane

h = Mounting height of luminairesthrough the maximum and on a conical surface

d = Width of the carriage waythrough the maximum.

p = Outreachs = Overhang

2.3.16 Isocandela Curve -- A curve traced onc = Clearance an imaginary sphere with a source at its centre

and joining.all the points corresponding to thoseF I G. 1 SITING OF I.(.MISAIRI:S: CII.~K:\(.T~:,KIS.I.I(. directions in which the luminous intensity is the

DIMENSIOSS same or a plane projection of this curie.

I’\HT 5 0I’TI)OOH I\S’I \ I I \‘UIOUS IV7

2.3.17 Isocandela Diagram - An array ofisocandela curves.

2.3.18 Polar Curve - Curve of iightdistribution using polar co-ordinates.2.4 Terms Relating to Luminaires

2.4.1 Street Lighting Luminaire - A housingfor a light source or sources. together with anyrefractor, reflector, dispersive surround or otherenclosure which may be associated with thesource in order to modify the light distribution ina desired man&r and protect the light sourcefrom weather conditions and insects and/or forthe sake of appearance, brightness and otherlighting characteristic the source. _

2.4.2 Cut-off Luminaire - Luminaireemploying the techmque used for concealinglamps and surfaces of high luminance from directview in order to reduce glare.

2.4.3 Semi-out-off Luminaire - Luminaireemploying the techmque for concealing lamps andsurfaces of high luminance from direct view inorder to reAuce glare but to a lesser degree thancut-off luminaire.

2.4.4 Integral Luminaire - Lumina’ire with allits accessories such as ballasts, starters, igriiters,capaciters. etc. However integrally with the bodyof the luminaire.

2.4.5 Post Top Luminaire - Lummaire witha r r a n g e m e n t f o r m o u n t i n g t h e s a m esvmmetrically on the top of the coloumn.

3. CLASSIFICATION

3.0 Ideally. both from the points of view of trafficsafety and comfort, a high standard of lighting isadvisable on all roads. The system of lighting,from good engineering point of view as well aseconomy should take into account all the relevantfactors. suth as the presence of factories, places ofpublic resort, character of the street (whether ashopping area or a ring-road in non-built-uparea), aesthetic considerations, the properties ofthe carriageway surface, the existence of lumps,bends or long straight stretches and overhangingtrees.

3.1 The classification of lighting installations inpublic thoroughfares given in 3.2 is based onvolume, speed and composition of the trafficusing them. It is left to the local engineer todecide upon the category of the lighting for thegiven road. Further amplification of the types ofthoroughfares can be had from Appendix A,wherein description bf terms are given forguidance.

3.2 Types of Roads - For the purposes of thisSection, roads are classified as given in Table I.

4. GENERAL PRINeIPLES

4.1 Aims of Public Lighting Installations

4.1.1 Main Roads - The aim of public lighting

198

TABLE 1 ROAD CLASSIFICATION

GROUP DESCRIPTION

(as in IS : 1944)(1) (2)

A Main Roads :Subgroup A I Very important routes with rapid and

dense traffic where safety, speed oftraffic and comfort to drivers are theonly consideration.

Subgroup A2 Other main roads with considerablemixed traffic like main city streets,arterial roads ,etc.

B Secondary roads-Roads which do notrequire lighting up to Group Astandard.

Subgroup BI Secondary roads of considerable trafficsuch as principal local traffic routes,shopping streets, etc.

Subgroup BZ Secondary roads with comparatively lighttraffic.

C Residential and unclassified roads.These are roads not included in Groups’Aand B.

D Grade separated junctions, bridges andelevated roads (see NOTE 2).

E Town and city centres and areas of civicimportance (see NOTE 2).

F Roads with special requirements (seeNOTE 3).

G Tunnels (roads underground).

NOTE I - - For the purposes of lighting installations, bridgesare classified short or long when their lengths are less than orgreater than 60 metres.

NOTE 2 --Such areas are set apart in view of the fact thattheir standard of lighting is different from and higher than thatdescribed for other groups. Group E also includes importantshopping streets. boulevards. promenados and such otherplaces which are the focus of special activities after dark.

NOTE 3 -Grouo F includes roads in the vicinitv of aero-dromes. railways: docks and navigable waterways;. wherespecial lighting requirements are to be met in addition tocompliance with general principles.

along main roads bridges and flyovers (Groups A,B and Dj is to permit users of the roads at nightto move about with greatest possible safety andcomfort so that the traffic capacity of the road atnight is as much equal to that planned for daytime as possible. Towards this end considerationhas to be given while designing the lighting onroad junctior)s and pedestrian crossings so thatthese can be easily identified by the drivers.

4.1.2 Roads in Residential Areas- T h eprinciple aim of public lighting along roads inresidential areas (Group C) is to provide lightalong the stretch of carriage way and footpath forsafety and comfort of road users mainly thepedestrians; consideration has to be given toensure that the lighting is soft and does not causeglare.

4.1.3 Roads in Cit,. Centres- The mainconsideration while designing the lighting in citycentres (Group E) :Is proper illumination offootpaths for pedestrians, besides the comfort of


the drivers. Also care is required to easily identifyflow of traffic and road deviders, islands,roundabouts, etc.

4.1.4 Roads Mith Special Requirements(Group F) - Separate considerations are requiredto be given for each of the following:

4

b)

Airports ~ The main consideratton tndesigning lighting. of roads in the vicinity ofairports is to ensure that under nocircumstances, would a pilot mistake thestretch of the road as airport landing strip atnight time. Also the lamps should not causeglare to the pilot either while taking off ormore specifically while landing. which mayinterfere with his judgement.

Rail~~a~~s and Docks - The driver of therailway is required to observe a number ofsignals along the tracks in the course of hiswork. It is necessary that none of the streetlamps cause either glare to the driver or ismistaken by the driver for track signals.Similar considerations are applicable tonavigators in the vicinity of docks.

4.2 Principles of Vision in Public Lighting

4.2.0 Though public lighting has to satisfy bothdrivers and pedestrians, it is in practice therequirements of the drivers which are morestringent. The following principles are consideredessential [see also IS : 1944 (Parts I & 2)-1970*].

4.2.1 Requirements qf Drivers - These are asfollows :

a) Visibility of the whole of the road and itsdetails such as entry of side-roads, trafficsigns, etc;

b) Visual guidance on the alignment of theroad;

c) Clear visibility of objects in time;

d) Good seeing condition by silhouette vision;

e) Continuity and uniformity of lighting; and

f) General or special lighting of signs.

4.2.2 Visual Field qf the Driver-The visual~,et_~~a~~gt~~p~~t~~~e. comprises, in order of

a) The carriageway;

b) The surrounds to the road, including signs;and

c) The sky, including the bright luminaires.

4.2.3 Visibility - The phenomenon of visibilityis directly related to contrast. Good contrastshould always be produced:

a) Between the carriageway and all objectswhich indicate its boundaries: and

*Code of practice for lighting of public thoroughfares yirsrre\Vsion). .

PART 5 OUTDOOR IkTALLATlONS

b) Between any obstacles which may be presentand the background against which i tappears; since the characteristics of theobstacles may vary over a very wide range,any factor which tends to increase contrastshould be exploited.

4.24 Glare and Visual Comfort -Glare inpublic lighting is generally caused by theluminaires. Other factors that can lead to glareare presence of undersirable large surface of highreflection factor, specular surfaces, excessivelybright shop windows, advertisement signs or roaddirection signs.

4.3 Criteria of Quality

4.3.0 The following four factors contribute tothe fundamental criteria of quality of publiclighting :

a) The level of illuminance,

b) The uniformity of luminance,

c) The limitation of glare, and

d) The optical guidance.

4 .3 .1 Leve1.s qf L u m i n a n c e - T h e level ofluminance should be adequate to provide visibilitywhich guarantee for the user a maximum of safetyand sufficient visual comfort. It is obvious that itis the road surface luminance rather than theillumination level which provides for an accuratemeasure of the effective light in a street lightinginstallation. However, with the present state oftechnique and the knowledge of reflectionproperties of road surfaces, the calculation andmeasurement of luminance are likely to presentdifficulties. Reference may be made to 7.1regarding illumination values to be provided onthe road surfaces.

4.3.2 Uniformity of Luminance - Thisprovides visual comfort for the driver.

4.3.3 Limitation of Glare - It is required tocontrol the glare due to luminaires at a valuewhich keeps the visual d&omfort below a,,acceptable level.

4.3.4 Visual Guidance - A good visualguidance is required especially in long stretches ofthe road and even ‘more on compl ica tedintersections, roundabouts, etc. Most of the longrange guidance is offered by the luminaires.

5. DESIGN

5.1 Layout for Roads-The design, spacing andcolumn heights are governed by the road-widthand the classification of the roads. Typical layoutsfor various road width are given in Table 2.

5.2 Layout for Flyovers- The design andcolumn heights for flyovers are governed by thelayout of flyovers, height above normal groundlevel and the width of the low level roads. Thespacing may be governed by the.structuraI design

199

L6 TO 9 m

L9 TO 12m

2B

s

w-m __________

I’----------- ------------

_-- -__________6 ----------- -----------

Ll2 T O 2Om

2 c

h8 TO 206

2D

~--------~ c~-------cI _ _____w_____ A _ _ _ _

-‘c-35 _____________________--_______ __----------- -w-e-,O c &

F I G. 2 S TANDARD L AYOUTS FOR R OADS (Cormi)

200 NATIONAL EL,ECI;RICAL CODE

T-___-_-___--I_-,-_________

--

mm -or= = = a =, = z~YL-_-_~-c_-_-~= z--z= =E --_ e-m --- w--es Q, _ -9, _ _ a----a-_-_xc - _ Le. _ - -QA1 _- ‘p-,-,-,a~-_..~~~2 ~-_-z_--_~--_ = = 92-_=--

.L_---_____--_____-_----___-2F

S = Spacing between columns 0 = Location of columns

F I G. 2 STANDARD LAYOUTS FOR ROADS ( SIX ALTERNATIVES )

of the flyovers. I’he layout of typical flyovers isgiven in Fig. 3A to 3D.

5.2.1 The layout with recommendedarrangements, column heights and spacing forvarious road widths on flyover are given in theTable 3.

5.2.2 The layouts with recommended arran-gements, column heights and .spacing for variousroad widths of low level road are given inTable 4.

5.3 Junctiods - Spacing of the junction columnsshould be 50 to 75 percent of the normal spacingof, columns on the main roads. These columnsmay be installed on the traffic islands located atthe junctions.

53.1 The level of illumination of the junctionshould be substantially different from the nearby .I

‘2 12 r

3D :

TABLE 2 CLASSIFICATION OF ROADS ANDRECOMMENDED ARRANGEMENT OF COLUMNS

SPACING

s

(5)

2%o~H

2.5-3.0.H.2.5 H

2SH2.5 H

3.0 H

2.5 H

3.0 H

3.0 H

2.0 H

3.0 H

3.5 H

3.5 H

W IDTH OF

CARRIAGE-WAY

CROUP A R R A N G E- CO L U M N

MENT AS IN H E I G H T

FIG..H

(3) (4)(1)m

24

(2)m

E9-149

AlA2

Al18-20 2D 9-142c 9

A2

BI 2c. 9

A2 2c 9

BI 2c 9

82 28 9

C 2B Y

B2 28 9

C ‘28 7

C 2c 7

12 3 c

3A) II < 10 m

4-z:3B) r: < 10 m

l2 < 10 m11 < 10 m

3C) IO < ; 2 ;OO ;2

3D) IO < I, < 20 m1~ < 20 m

F I G. 3 S T A N D A R D LAYOUTS FOR F L Y O V E R S

( FOUR A L T E R N A T I V E S)

PART 5 OllTDOOR INSTALLATIONS 201

.,. ., , “,.,_ x

TABLE -3 RECOMMENDED ARRANGEMENT OFCOLUMNS ON FLYOVERS.

(Cluuse 5.2.1)

W IDTH OF GROUP A R R A N G E- CO L U M N SPACINGCARRIAGE- MENT AS IN H E I G H T*

WAY FIG.

(1) (2) (3) (‘4: &In m

12 D 3c 9 2-2.5 H

D 38 9 2.H

9 D 3A 9 2 H

*Above the flyover road level.

TABLE 4 RECOMMENDED ARRANGEMENT OFCOLUMNS ON FLYOVERS (LOW LEVEL ROADS)

IClause 5.2.2)

W IDTH OF GROuP A R R A N G E- COLUMN . SP A C I N GCARRIAGE- MENT AS IN HE I G H T*

WAY FIG.(1) (2) (3) (Z (S)In m

Over 2C D 9 2.5 HIO to 20 :“D 14 1.5 Hup lo IO : 3A 9 2.5 H

*Above low level road.

roads. The junctions may be lighted by either ofthe following methods :

4

b)

Higher level of illumination - In casethis scheme is adopted the level of illumina-tions should be 150 percent of that of theroads.

Change in height c$ column: - The sizeof columns adopted at the junction shouldbe higher than those adopted on roads.Recommended sizes are given in Table 5.

TABLE 5 RECOMMENDED VARIATION IN HEIGHT OFCOLUMNS OF JUNCTIONS

HEIGHT OF COLIJMNS RECOMMENDED HEIGHT OFO N ROADS COLUMNS AT JUNCTIONS

m m

7 9

9 14

14 High mast

c) Change .in the colour of the light source -In case the main road is lit by HPMV lamps,the junction could be lit by HPSV lamps orvice versa

5.3 .2 The d i f fe ren t types of junc t ionscommonly encountered are discussed below indetails as they require special consideration :

4

202

.,..”

Simple tM)o road juncrion -This type ofjunction should. be illuminated by locatingthe columns in such configuration that theiunction is noticed by fast moving traffic.

b)

The design would depend upon existence of -traffic islands at the junctions. Typicallayout of such junctions a1.e shown inFig. 4A to 4C.

Juncfion of IWO m a j o r r o a d s - T h e s ejunctions would generally’ be proiided withtraffic island at suitable locations to regulate

7--!

__-___- _____ --...._r-mm-* e-v----

._______.:_. 1;1_4A

__-_-__-_

I

4B

0 = Location of columns

F I G. 4 S I M P L E T w o RO A D J U N C T I O N S

( TH R E E A L T E R N A T I V E S )


flow of traffic. The lighting columns couldbe located in the islands to advantage.However, if the junctions are too wide or, theislands do not permit planting of poleswi th in the des i red spac ing , spec ia lconsiderations are required.

Typical layout of such junctions are shown inFig. 5A to SC.

c) Mtiltiple road junctions -The lighting ofmultiple road junction would depend uponthe geographical layout of the roads, thewidth of the various roads and mostimportant, the traffic conditions. At suchjunctions invariably entry for traffic may notbe permitted.on all the roads. Similarly, thetraffic islands design would change fromlocation to location. Special considerationwill have to be given to the design of lightingo f s u c h j u n c t i o n .

Typical layout of such junctions are shown inFig. 6A to 6C.

5.4 Roundabouts

5.4.0 Multiple road junctions with roundaboutsare much easier to design as a definite centralroundabout is available to locate the columns.Two

a)

b)

types of roundabouts are discussed below.

Islands which are clear or have on1.v parkingl o t s - T h e l igh t ing of these could beadvantageously achieved by use of high mastas given in Fig. 7A and 7B or semi-high mastlighting as in Fig. 7C and 7D.

lslan,ds which have gardens or otherconstruction which would be obstruction toline of vision of traffic - The lighting ofthese could be either by semi-high mast asin Fig. 8A or conventional lighiing as in Fig.8B and 8C.

5.5 Road Lighting in the Vicinity of Aerodrome

5.5.1 General Requirements -- When aproposed road lighting scheme is within 5 km ofthe boundary of an aerodrome it is essential thatappropriate aviation authority is consultedregarding any restrictions and precautions to beobserved that may be necessary.

5.5.2 The aviation authority may have aspecific interest in the pattern of the layout. themounting height, the colour and in tens i ty ,d i s t r ibu t ion of i igh t emmit ted above thehorizontal so that lighting installation does notpresent anv danger to the air navigation. Thefollowing points should, therefore, be kept in viewwhile designing lighting scheme in the vicinity ofthe aerodromes:

a) The light provided in the vicinity of anaerodrome shall be properly screened soas -to avoid any glare which may otherwiseendanger safety of an aircraft arriving anddeparting from an aerodrome.


-7in0

- - - - - - - - - - - - ._ _ _ _ _ _ _ _ _ _ _ -s

0u3

5c

0 = Location of columns

F I G. 5 J UNCTION OF T w o MA J O R R O A D S

( THREE ALTERNATIVES )

203

204 NATIONAL ELEtXRICAL CODE

6 C 6D.

0 = Location of Columns

FIG.'~ MULTIPLE ROAD JUNCTIONS ( FOUR ALTERNATIVES)

MAST LUMINAIRES

F I G. 7 US E OF HI G H M A S T, SE M I- HI G H- MA S T LU~INAIRESIN R O U N D A B O U T S ( FO U R A L T E R N A T I V E S)


205

206

\SEMI-HIGH MAST LUMINAIRES

1 aI

ia

~SEbll-HIGH MAST LUMINAIRES

I 8C

FI G. 8 USE OF, SE M I- MAST OR C ONVENTIONAL LIGHTING

IN R OUNDABOUTS ( THREE A L T E R N A T I V E S)


i

b) Lights m o u n t e d o n the electricpoles: pylones shall not c a u s e a nobstruction to the arriving and departingaircraft from an aerodrome in terms ofobstacle limitation specified by the airportauthorities.

c) It is particularly important to ensure thatlighting of the road cannot ever be confusedwith the ground lighting of the flight pathsby the pilots. Following conditions shouldbe ensured :

i) In case roads are not parallel to landingstrips,

1) Uniform design and spacing ofcolumns is not recommended.

2) Arrangement of mounting columns onopposite as in Fig. 2D is notrecommended.

ii) In case roads are parallel to landingstrips, no lighting should be provided onthe stretch of road near the landing strip.

5.6 Road Lighting in Vicinity of Railways, Docksand Navigable Waterways

5.6.0 General- In lighting for roads in thevicinity of railways, docks and navigablewaterways, because of the colour of the lightsource may iriterfere with the proper recognitionof signal svstem. it is essential that thisinterference is avoided, but local conditions varyso widely that it is not possible to lay down anyrigid code applicable to all circumstances.

5 . 6 . 1 Requireyenrs - The followingrequirements are likely to apply in all placeswhere roads are so located that their lightinginstallation may affect the operation of railways,docks and navigable waterways.

5.6.2 Consultafions --. It is essential that priorconsultation is made with the appropriateauthorities regarding any special provision thatmay be necessary. These provisions should be metin a way that is mutually acceptable so that theymay be incorporated at the design stage.

5 .6 .3 C o l o u r --~ Where any form of roadlighting is emploved there is a risk of confusionwith signal light. This may necessitate carefulselection of light SOUXCC, siting of luminaires orthe use of appropriate screened luminaire atcertain points arid heights.*

5.6.4 Glare and Masking- The position ofindividual light source on the road may fall in linewith signal lights and even when fairly remotemay mask them or make them difficult torecognize or may hamper the vision because ofglare. If these cannot be avoided by re-siting, itmay be necessary to employ screening to obviatethe interference even though the colour of thelight source is not objectionable.

5.6.5 Screening ~~ In all cases where screeningof a light source is required this should preferably

PART 5 OUTDOOR INSTAI.I.ATIONS

be achieved by means of properly designedluminaires and not by addition of unsightlyscreens to normal luminaires.

56.6 Siring -..- If the road is bordered by water(lake, river or canal) and if the lighting is singlesided, it is recommended that the columns besited, if possible. on the waterside.


6.1 Electric Light Sources

6.1.0 The choice of source for public lighting isguided by the following considerations :

a) Luminous flux,

b) Economy (determined by lumens/watt andlife),

c) Dimensions of the light sources, and

d) Colour characteristics.

6.1.1 The sources normally used in publiclighting are :

a)

b)

c)

d)

e)f-l8)

Incandescent lamps,

Mixed incandescent and high pressuremercury vapour lamps,

High pressure mercury vapour lamps withclear or fluorescent bulbs,

Tubular fluorescent lamps,

Sodium vapour lamps,

Mercury-halide lamps, and

High pressure sodium vapour lamps

6.1.1.1 Incandescenr lamps - For newinstallations the employment of incandescentlamps is very limited in practice. They aresometimes used for residential streets when initialcost is to be kept low. They are not usuallyemployed in traffic routes.

6.1 .1.2 Mixed incandescent and mercur.vlamps - These lamps may sometimes beemployed in modernizing an installation to obtainhigher levels without the need for ballastsrequired for discharge lamps.

6.1.113 High pressure mercur>> vapour lamp3(HPMV) - These -lamps have higher luminousefficiency and longer life than mixed incandescentand mercury lamps. These are suitable forinstallations where colour rendering is lessimportant and where high powers are needed.High pressure mercury vapour lamps withfluorescent bulbs are suitable for installationswhere colour appearance and colour rendering areimportant.

6.1 .1.4 Tubular fluorescent lamps -- Theselamps have high luminous efficiency and long life.They are suitable for installations where colourappearance and colour rendering are importantand where large multiplelamp luminaires areacceptable. The choice between high pressure

207

mercury vapour fl*uorescent lamps and fluorescenttubes is in general determined by local consi-derations of aesthetics and cost of installation.

6.1.1.5 Sodium vapour lamps --The use ofsod ium lamps i s convenient when colourrendering is not important and when a highluminous efficiency is desired. Their colour issometimes useful to provide visual guidance. It isalso particularly suitable under foggy conditions.

6.1.1.6 Mercur)) h. lide lamps - These lampsare improved versions of HPMV lamps andhaving very much higher efficiencies in the orderof 80 Im/W combined wi th good’ co lourcharacteristics.

6.1.1.7 High pressure sodium vapour lamps -These lamps are improved versions of sodiumvapour with efficiency of the order of to 100 Imi Wwith colour rendering satisfactory and ofdimensions suited to fittings of small size andaccurate light control.

6.2 Luminaires

6.2.0 The luminaire has double role ofprotecting the light source from the weather andredistributing the luminous flux of the source.

In the choice of the luminaire the followingpoints should be considered :

4

b)

c)

d)

e)f-l

8)h)j)k)

Nature and power of the source or sources;

Nature of the optical arrangements and thelight distribution which they provide;

Light output ratio;

Whether the luminaire Is open or closedtype;Resistance to heat, soiling and corrosion;

Protection against collection of dust and.insects;

Resistance to atmospheric conditions;

Ease of installation and maintenance;

Presence or absence of auxiliaries; and

Fixing arrangements, the weight and areaexposed to wind pressure.

The influence of all these factors variesaccording to local circumstances and it is difficultto recommend one solution rather than another,but the attention of lighting designers may bedrawn to the fact that the most economicali_nstallation can be achieved only by the choice ofthe most suitable luminait‘e, selected according tothe relative importance of the above mentionedfactors. There is , however, one essentialcharacteristic of luminaires the choice of whichdirectly influences the quality of the lighting, thatis, the general form of its distribution curves ofluminous intensity pai%icularly in directions nearthe usual directions of vision.

6.2.1 The following three fundamental forms of

208

light distribution are considered according to thedegree of glare which is acceptable :

a) Post top integral luminaires,

b) Post top non-integral luminaires,

c) Cut-off integral luminaires,

d) Cut-off non-integral luminaires.

e) Semi-cut-off integral.

f) Non-cut-off tubular luminatres, and

g) Flood-lighting luminaires.

6.2.1.1 Cut-c![f luminarie - A luminairewhose light distribution is characterized by arapid reduction of luminous intensity in theregion between 80” and the horizontal. Theintensity at the horizontal should not exceed IO cdper I 000 Im of flux from the light sources andthe intensity at 80° is of the order of 30 cd per1 000 Im. The direction of. the maximum intensitymay vary but should be below 65’.

The principal advantage of the cut-off system isthe reduction of glare and its use is favouredunder the following conditions :

4 Matt carriageway surfaces;

b) Absence of buildings;

cl Presence of large trees;

d) Long straight sections;

e) Slight humps, bridges; and

f-l Few intersections and obstructions.

6.2.1.2 Semi-cut-of luminaire -- A luminairewhose light distribution is characterized by a lesssevere reduction in the intensity in the region 80”to 90”. The intensity at the horizontal should notexceed 50 cd per I 000 Im of flux from the lightsources! and the intensity at 80’ is of the order of1 000 cd per I 000 lm. The direction of themaximum intensity may vary but should be below75”. The principal advantage of the semi-cut-offsystem is a greater flexibility in siting, and its useis favoured under the following conditions :

a) Smooth carriageway surfaces;

b) Buildings close to carriageway, especiallythose of architectural interest; and

c) Many intersections and obstructions.

6.2.1.3 Non-cur-@ luminaire - A luminairewhose luminous intensity in directions making anangle equal to or greater than 80” from thedownward vertical is not reduced materially andthe intensity of which at the horizontal mayexceed the values specified for the semi-cut-offdistribution. but should not nevertheless exceedI 000 cd. Non-cut-off luminaires are permissibleon/J, k,hen a certain amount qf glare may beaccepted and when the luminaires are @-large size

*Subject to a maximum value of I 000 cd whatever is theluminous flux emitted.


clnd of reduced brightness. In certain cases theyhave some advan tages in inc reas ing theillumination of facades.

6.2.1.4 Inclination -- Attention shou ld begiven to the inclination of luminaires. An upwardinclination which is generally called for reasons ofaesthetics. should be employed with care. Toogreat an inclination of.the luminaire may modify,particularly in certain directions, the cut-offqualities of the luminaires and in certainsituations (for example, when there are roads atseveral levels. bends, roundabouts, etc) thisinclination may lead to unexpected glare.

7. GUIDELINES FOR SPECIFICLOCATIONS

7.1 Several factors contribute to good publiclighting and those are enumerated for guidance invarious parts of IS : 1944*. Recommendations aremade on the various components of design ofpublic lighting installations and those requiredetailed calculations of the level and uniformity ofillumination on the road surface and of glare.Several criteria may not be satisfied for want ofdata such as characteristics of surface, etc. To getsome idea of the extent to which the installationwould perform, it may be preferable to make a

temporary trial installation of a few luminaires ona stretch of road to be lighted.

7.2 Tables 6 to 8 give a summary ofrecommendations on the various types ofthoroughfares. These shall be used as readyreckoners, though for a detailed guidancereference should be made to the relevant part ofIS : 1944*.

NOTE ~ Recommendations for Groups C. F and (Ii lightingare under consideration.

8. POWER INSTALLATIONREQUIREMENTS

8.1 The electrical design aspects of public lightinginstallations not only take into account thei!lumination principles, but also economicconsiderations giving allowance for cost ofelectrical control units, cable ducts, switching, etc.

8.1.1 Lamps and Luminaires

8.1.1.1 All’ lamps and luminaires and otherfittings used in public lighting installations shallconform to the relevant Indian Standards.

*Code of practice for lighting in public thoroughfares.

TABLE 6 LIGHTING INSTALLATION IN GROUP A AND B ROADS

(Clauses 4.3.1 and 7.2)

SI D~SC.RIPTIO~:No

(1) (2)

I Average Ifvel of illuminationon road surface. lux

GROI’P A l GROUP A2

(3) (4)

30 I5

2. Ratio minimum, averageillumination ratio

3 Transverse variation ofillumination, percent

4. Type of lumlnaire :

5. Mounting height. m

0.4 0.4

33 33

Cut-off

Semi-cut-off

9-10

Cut-off

Semi-cut-of1

9-10

GROI‘P BI GKOI‘P HZ

(5) (6)

8 4

0.3 0.3

20 20

Cut-off orSemi-cut-offNon-cut-off

7.5 - 9

Cut-off orSemi-cut-offNon-cut-off

7.5-9

6. Maximum spacing ofluminaire height ratio Cut-off = 3

Semi-cut-off = 3.5Cut-off = 3

Semi-cut-off = 3.5Non-cut-off = 4

No1t I III Group A lighting. the level and uniformity of illumination shall be as high as possible and the glare strictlyreduced.

Nor1 2 In Group B lighting. greater tolerances on uniformity and glare arc admitted. which may be justified by thecharacter of the road\ and by the presence of facades.

NOII 3 Mounting heights less than 7.5 m are undesirable except in special cases. such as lighting of residential roads orroad\ bordered by trees.

P A R T 5 0l:TDOOR I N S T A L L A T I O N S 209

TABLE 7 LIGHTING INSTALLATIONS IN TABLE 8 LIGHTING INSTALLATIONS INGROUP D ROADS GROUP E ROADS

A.

i)

(Cbuse 7.2)

DESGZIPTION(1)

Grade Separared Junctions

Lighting by conventionalstreet lighting technique

Complex junctions:

I) General principles

2) Mounting height, m3) Luminaire4) Light sources

ii) Lighting by tigh-mastlighting

I) Minimum servicelevel value (lux)

2) Uniformity ratio $Sd\L

3) Height of masts. m4) Choice of luminaire

B. Bridges

i) Short bridges (> 60m)

11)

Iii)

iv)

L.ong bridges (> 60m)

Bridges of historicalimportance

Parapet lighting:

REMARKS

(2)

Mountmg height. mSeparation betweenrows of lighting. mChoice of lamps

v) Foot-bridges

I) Illumination. _tux

C. EIevored Roads

I) General lighting2) Choice of luminaire

As in IS : 1944(Parts I & 2)-l970*IO-12cut-offHPMV or HPSV lamps

30

0.4

Not less than 20see IS : 1944(Parts I & 2)-1970’

Normal street lighting techni-ques with minor adjustments[.\ee IS : 1944 (Part 5)-19X1+]

.yeB IS : 1944 (Part 5)-19Xlt

Special considerations apply

Not greater than INot greater than I2

Tubular fluorescent lamps.HPSV lamps or other linearsources of luminanceweatherproof. dustproof.verminproof. robust

Not less than 6

Similar to heavy traffic road\Cut-off

*Code of practice for lighting of public thoroughfares:Part 1 General prmclple>. Part L Lighting of main roadsfirs1 revision)

tCode of’ practice for lighting of public thoroughfares:Part 5 Lighting of grade separated junctions. bridges andelevated road (Group D).

8.2 Cables

8.2.1 Underground cables shall be laid forpower supply !o the street lamps. For roads undergroups A, B and D, separate mains shall be laidfor group control of lamps on these roads. Thestreet lighting cables shall be terminated iaseparate junction boxes or street lighting pillars.The pillars shall be provided with electricallyoperated contactors of suitable current rating.Auxiliary terminals of these contactors couldprovide facility of return indication in case of


(Clause 7.2)

D ESCRIPTION

(1)

A. i) Main squares [seeIS : 1944 (Part 6)-1981’]:

I) Average level ofillumination, lux

2) Mounting height. m

ii ) Sho/IL>inR srree/.s/promenar1e.s

i il) Pedtwrial p recinc’ts

REMARKS

(2)

20

IO-15

Special consideratlohs.

I ) Average horizontalilluminance (footwaylevel). lux

2) Average horizontalilluminancc (undercanopies), lux

3) Mounting height. m

4) Luminaires

i v ) Public, c’ar parh.s(above grotind)

20

50

5-6

Special considerations

I) Average hoti/-ontalilluminance. Iux

2) Luminalres preferred

IO

Floodlight luminaires onhigh masts

I) Average level ofilluminance (surfaceof footbridge). lux

2) Average level ofilluminance (sub-ways). lux

4 6

Q IO

*Code of practice for lighting of public thoroughfares:Part 6 Lighting of town and city centres and areas ofcivic importance (Group E).

supervisory remote control. The contactor circuitsshall be provided with externally mountedswitches for local manual operation. A typicalstreet lighting pillar with control circuit is shownin Fig. 9.

8.2.2 The cable circuits for each section of theroads shall be so designed as to prevent importantsection of the roads from being completely off incase of a fault on the underground cables. Forroads under groups A I, A2 and D. each stretch ofroad shall ,be lit by two independent circuits,preferably emanating frop two separate streetlighting pillars. For junctions also. the lamps shallbe divided into at least two circuits in such a waythat in case of fault on one circuit the entirejunction, or a section of it does not becomecompletely dark.

8.2.3 in case of roads in groups A, B and D.the cables shall preferably be terminated into thecolumn .iunction boxes by looping rather than ‘T’joints.

8.2.4 Underground cables of suitable sizesshould be utilized for the purpose of control. Therecommended sifes of the cables for variousinstallatidn are shown in Table 9.

TABLE 9 RECOMMENDED TYPES AND SIZESOF CABLES

R OAD G R O U P SIZE OF CAHLES

(1) (2)mm?

A”:16-2516-25

BI 16-2582 IO-25

c IO-25

D 16-25

T Y P E O F CAHl.ES

(3)

3-phase. rt-core3-phase. 4-core3-phase. 4-toreSingle phase;q-phase.

4-coreSingle phase, 3-phase.

4-tore3-phase. 4-tore

8.2.5 The junction boxes with suitable sizedcontactors with independent fuses shall beprovided for each phase. The contactors shall becontrolled by electrically operated switchesmounted for external manuali local operation.

8.3 Power Supply - The supply to the .streetlights may be either through overhead wires 01underground cables. The supply to lamps onroads under groups A. B and D. shouldpreferably be by underground cables laid speciallyfor street lighting purposes. In case overheadwires are employed these should also be speciallyfor street lighting purposes.

8.4 Control of Street Lighting Installations

8.4.1 The contactors may be provided withadditional circuitry for remote/automatic control.Following schemes for remote control arerecommended:

a)

b)

Special Re/aj% C o n t r o l - T h i s m a y b eachieved by special control cables laid up tothe street lighting pillar. Special relaysoperated by normal supply or electronicimpulses may be provided. This schemeenables return indication of the operationby auxiliary contacts of the contactors.

Ripple Control -- This may be achievedby injecting audio frequency impulse throughsuitable power supply network and install-ing suitable sensors at control points.

8.4.2 Automatic* Control - The contactorsmay, alternately, be controlled automatically byuse of auto-control devices. The fqllowingcontrols are recommended.

a)

b)

Photoelectric control - This may beachieved by installing suitably mountedphotoelect&c switches near the controlpoints. The photoelectric switch shall bemounted so as to be free from the glarecaused by head-lights of motor vehicles andprotected from the weather.

T i m e SM,itc*hes - The local electricallyoperated contractors may be controlledthrough time switches. The time switchesmay be manually spring wound or electri-cally operated. In case of electrical operationthe time switches should be of electrically-wound mechanically-operated variety so as

PART J 0l:TDOOR INSTALLATIONS

to prevent their being affected by variationsin supply frequency. However, these wouldneed to be regulated from time to time dueto seasonal variations.

C) Electronic Control Suitches - It should bepossible to instail pre-programmed electro-nic micro-processors, with one year seasonalvariations. These could be installed for eachindividual lamp. With suitable design thesecould also be utilised to switch off un-wanted lights after peak traffic hours areover.

8.4.3 Black-out Control - Black-out controlmay be required to be adopted in case of war invulnerable areas. This could be achieved by eitherof the following schemes:

4

b)

4

Remote Control - Special control cablesare laid (alternatively, use of telephonecables) to give control impulse to groupcontrol points. The control could then beutilized to switch off the lamps instantane-ously on demand by civil deferice authori-ries.

Ripple Control-- In case special controlcables are not available, ripple controlequipment could be used with suitable sen-sing devices at the control points. When theneed arises, the entire area could be switchedoff by ripple control impulse.

UHF Control - Electronic relays respond-ing to predetermined control frequencycould be installed at each switching point.This could be programmed to switch off ondemand by a pre-determined control fre-quency signal.

8.4.4 BroMsn-out Control - Brown-out ,controlis necessary in vulnerable cities with heavyvehicular traffic at the time of war, wherecomplete black-out is not practicable. Even insuch cases. complete black-out would benecessary at the time of possible air raids.Following alternatives for brown-out control arerecommended:

a)

b)

voltage Control -- This could be advanta-geously adopted in areas where the source oflighting is filament lamp. Applying reducedvoltage to such lamps would automaticallyreduce the illumination to any desired level.In case of discharge lamps this schemewould not be suitable.

Ripple Control- In case ripple control isadopted, it would be possible to programmealternate (or any other combination) lampsto respond to specified ripple control sig-nals. In case of necessity. brown-out couldbe effected by switching off alternate lamqsand complete black-out by switching off allthe lamps.

Mult iple Lamp Luminaire5 --- -On mainroads the luminaires adopted could havetw,o or more lamps, each controlled either

211

d)

by different phase or by separate ripplecontrol signals. In case of necessity, eitherone or two phases could be switched off. oralternately alternate lamps be switched offby suitable ripple control signals.

Replacement qf Lamps -- In case of pro-longed brown-out operations, the wattage ofthe lamps could be reduced by replacing thesame with lower wattage lamps. This,though could not be achieved on shortnotice is recommended in case of prolongedoperations.

9. MISCELLANEOUS CONSIDERATIONS9.1 Aesthetics-The aesthetics of a lightinginstallation are principally judged by day. Half of

the time. the lighting installation serves no useful !purpose; an attractive or at least a non-disturbingdaytime appearance which harmonizes well withthe surroundings is , therefore, of greatimportance. Aesthetic considerations shouldrelate to the unit formed by the luminaire and itssupport and the situation in which it is placed.

Firstly, the unit formed by the luminaire and itssupport should be considered. Secondly. the sitingof the luminaires in the scene may lead tounpleasant effects even if the luminairesthemselves considered in isolation, are aesthetic.

There are no simple or universal rules foraesthetically satisfactory design and layout sinceevery city. town and village has its own character


/CANOPY

/

HINGE

HANDLE WELDEDTO DOOR

\

CDOUEILE HINGEDDOORS

/ L O C K

9A Street Lighting Pillar

F I G. 9 A T Y P I C A L S TR EET LIGHTIN‘~; PILLAR-ccmfd.

FUSEWAYS

FUSEWAYS

FUSEWAYS

I CONTACTOR1

9B Inside Layout

NKaCD

5 11m

8L2

KIL L3

9C Typical Contactor.Wiring (Manual)

FIG. 9 A TYPICAL STREET LIGHTING PILLAR-CO&.

PART 5 OUTDOOR INSTALLATIONS 213

ROTARYS W I T C H

( E X T E R N A L )ROTARYS W I T C H

( INTERNAL 1R E L A Y‘r’

9D Typical Wiring for Remote/ Auto Control

F I G. 9 A T YPICAL S TREET L I G H T I N G P I L L A R

and what may look well in one place may bein&ngruous in another.

The points of general application are:

a) Design and siting;

b) Columns and surroundings:

cl Size and type of luminaire;

4 Form of bracket;

e) Assembly of column, bracket and luminaire;

n Arrays of luminaires; and

8) Material and colour.

9.2 Lighting Columns as Hazards - A motorvehicle involved in an accident frequently leavesthe carriageway and the probabijity of thishappening increases with the speed of the vehicle.If the vehicle collides with a lighting column theseverity of injuries to the occupants is likely to beincreased. Ther6 is evidence to suggest that thenumber of such collisions decreases with theincrease of distance of the column from the edgeof the carriageway.

Normally the clearance between column andcarriageway should be at least 1.5 m. Where thereis a footway close to the carriageway, the columns h o u l d b e s i t e d b e h i n d t h e footway. I nexceptional cases a smaller clearance may be used.


TLRM(1)

Road

Street

Motorway

Express road

All purpose road

Trunk road!Major road

Minor road.

Ring road

A P P E N D I X A(Clause 3. I)

TERMINOLOGY FOR ROAD TYPES

Dts(,KIP7loh ot TY P E O F KOAD(2)

A general term denoting any public wayfor purposes of vehicular traffic

A road which has become partly orwholly defined by buildings along oneor both frontages

A road reserved for’motor trafiic. acces-sible only from interchanges and onwhich. in particular, stopping and park-ing are prohibited. Roads of this typeshould have two or several separate andone-way carriageways ’

A road similar to. but lacking some fea-ture of a motorway. for example:~~ not dual-carriageway__ not fully access-controlled_~ not all intersections grade-separated

Road usable by all traffic (includingpedestrians and cyclists)Used to distinguish other roads frommotorways.

A main route in the through communica-tion system of a country

A road which has. or IO which is assigned.a lesser traffic value than that of a majorroad

A road round an urban area enablingtraffic tc avoid the urban centre

P A R T 5 0I:TDOOR INSTAI.I.ATIONS

TE R M

(1)

Radial road

Commercial street

Shopping street

Residential street

Collector roadDistributor road

Local street

Service road

Footway

Cycle track

DESCRIPTION p2; TYPF: OF R O A D

A road providing direct communicationbetween the centre of an urban area andthe outer districts

Street with frontages comprising a highproportion of commercial premises(usually unlit at night), and with a highproportion of heavy goods vehicles inthe traffic stream

Street with frontages comprising a highproportion of shops or other premiseswhich may be lit at night and with heavypedestrian (and possibly pedal cycle)traffic

Street with the majority of froritages com-prising private houses

A link between the radial or ring roadsand the local access streets

Street giving direct access to buildingsand land with a minimum of throughtraffic

A subsidiary road. usually pirallel to themajor road. and giving access to pre-mises

That portion of a road reserved exclusi-vely for pedestrians

A way, or part of a road. reserved for useonly by bicycles

SECTION 2 TEMPORARY OUTDOOR INSTALLATIONS

0 . F O R E W O R D

0.1 Electrical installations are often required tobe designed and erected for use for short periodsof time ranging from a few hours to few monthsalld are connected to the supply source in openground. Such ins ta l l a t ions a re genera l lyunprotected from environmental hazards ascompared to installations in buildings.

0.2 The major risks in the use of power in suchinstallation arise from short circuit resulting infire accidents and exposure to live wire resultingin shock. It is, therefore, imperative to lay downthe necessary precautions to be observed for suchinstallations from the point of view of safety.

0.3 Temporary installations covered in thissection are enumerated in 3 and are classifiedbased on the duration of their existence in use. Itmay be noted that this section basically intends tolay down additional safety measures to beadopted in the design of temporary installations,a n d t h e g e n e r a l g u i d e l i n e s f o r o u t d o o rinstallations under heavy conditions from thepoint of view of selection and use of equipmentgiven in Part S/Set 3 shall also be referred to.

1. SCOPE

1.1 This sec t ion o f the Code covers therequirements for outdoor electrical installations bf,temporary use.

2. TERMINOLOGY

2.0 For the purposes of this Section, thefollowing definitions in addition to those given inPart I /Set 2 of the Code shall apply.

2.1 Temporary Installations (Outdook) - Anelectrical installation open to sky or partiallycovered, intended to be used for a temporaryperiod not exceeding 6 months.

NATE - In special cases, the guidelines specified in thisSection shall be applicable for longer durations subject tofresh inspection and tests with the prior app!oval of the supplyauthority (see a/so 8.3).

3. CLASSIFICATION3.1 The temporary outdoor electrical installationscovered in this Section are those intended for thefollowing purposes:

a) Temporary Installations for Durations notExceeding6 Months -Outdoor installations

‘open to sky or partially covered, erected inthe vicinity of construction sites solely forthe purposes of supplying the electricalneeds of building construction work such aslighting and power loads.

N OTE I -Construction site installations for verylong periods of times, where the equipment are quitesimilar to those in heavy conditions shall con,form tothe requirements in Part S/&c 3 of the Code.

216

b)

cl

4

NOTE 2 -- Construction site irstallatlons arc thobewhich include sites where the following are carried out:

a) Construction of new building;

b) Works of repair. alternation. extension or demoh-lion of existing buildings: and

c) Public engineering works.

The construction site installations are alsocharacterised by frequent modifications.

Temporary, Installations .for Durations notExceeding 45 Da,b,s -- These include fairlylarg loads such as for exhibitions, fairs, etc.

NOTE ~ Exhibition or fair site lighting installationsof the permanent type shall conform to the require-ments specified in Part 5 Set I of the Code.

Temporary, Installations ,/or Durations notExceeding 7 Dajcy ~ These include installa-tions site of temporary nature intended fora week long public function or outdoorlighting installations of buildings and partsin view of festival and other reasons.

Temporarll Installations ,for Durations notExceeding 24 Hours - These include tempa-rary installations which cater to loads forthe purposes of marriages, reception, religi-ous and other public function, etc.

4. GENERAL CHARACTERISTICS OFTEMPORARY INSTALLATIONS

4.0 General guidelines on the assessment ofcharacteristics of installations in buildings aregiven in Part I /Set 8 of the Code. For thepurposes of installations falling under the scope ofthis section. the characteristics defined belowgenerally apply.

1.1 Environment

4.1.1 The following environmental factors shallapply to temporary outdoor installations:

En\ironnWnr Characterrrsrics Remarks(1) (2) (3)

Presence of water Possibility of External lightingsplashes from fittings. constru-any direction ction site equip-

ment. etc

Possibility of jets Temporary installa-of water in any tions in partsdirection

Partial or totalcovering by water

Presence of foreign Presence of smallsolid bodies objects

Presence of dust insignificant quantity

Impact High severity Construction.demolition sites

N A T I O N A L ELEaRICAL C O D E

Environment(1)

Chorocteristics(2)

Remorks(3)

Vibrations Medium severity Constructions.demolitions sites

Presence of flora! No harmfulmould growth hazard

Presence of fauna Hazard from fauna(insects, birds.small animals)

5.2 If the equipment used in temporary andprovisional places of work in the open, such a sbuilding sites are similar to those used in surfacemining applications, references shall be. made tothe guidelines contained in Part S/Set 3 of theCode.

Solar radiation Solar radiation of 6. ADDITIONAL REQUIREMENTShbrmful intensity FOR TEMPORARY OUTDOORand/or duration INSTALLATIONS

Seismic effects Depends on thelocation of theinstallation

6.1 Supply Intake Arrangements

Lightning Hazard fromexposure ofequipment

Generally applicablefor installationslocated outdoors

6.1.0 The type of outdoor itMallations willdepend on the magnitude and duration of theinstallation. Depending on the availability ofs are ca acity, of the existing distribution system,tR Pe supp y intake arrangements could be througheither of the following:4.2 Utilization

4.2.1 The following factors of utilization apply:Uiilization

(1)


Characteristics Remarks(2) (3)

Uninstructed Majority of occu-persons pants say in an

exhibition circusfairs

Instructed persons Asy;p&es to operatingadequatelyadvised orsupervised byskilled persons

Contact of per- Frequent Construction sitessons with earthpotential

Conditions of Low density Small gatherings.evacuation dur- occupation easy such as for marri.ing emergency conditions of ages and similar

evacuation functions

Hieh densitv bccu- Circus. laree oublicpation. difiicult gatherings- inSideconditions of an enclosure, etcevacuation

Nature of Fire riskprocessed

Construciion of Combustiblestructure

5.

Structural designflexible orunstable

Shamianahs. tents

The nature of cons-truction materialsused in temporaryinstallations maybe combustible.Such as woodencloth structures intents

Structures which areweak or .subject tomovement such astents. removablepartitions etc

GENERAL REQUIREMENTSFOR TEMPORARY OUTDOORINSTALLATIONS

5.1 Temporary, installation shall in generalconform to the requirements stipulated in therelevant Section of Part I of the Code. in respectof wiring of circuits, location and installation of

PART 5 OUTQOOR INSTALLATIONS

equipmrnt, etc. Additional requirements are giver.in 6.

a) A HV feeder,

b) A HV feeder and step-down transformer,

c) A service line at voltages below 250 V, or

d) A tapping form one of the existing servicecon-nection.

One construction site may be served by severalsources of supply, including fixed or mobilepower generators. All the circuits supplied fromthe same point of supply comprise one installationand it is impoy.tant to clearly differentiate them; inparticular, a smgle distribution point, cabinet ord i s t r ibu t ion board sha l l cons i s t o f on lycomponents belonging to one and the sameinstallation except for circuits for standbysupplies, signalling or control.

6.1.1 Commissioning of Substation - In casethe loads at construction sites or to exhibitions,c’ircuses, etc, are large and the power supplyauthority has no network in the vicinity of thetemporary installation that could be utilized thenit would be necessary to establish a temporarysubstation where the switchgear and transformercan be installed. The substation site shall be soselected that it is as close to the load centre aspossible.

The power supply authority’s line should bebrought up to the substation in a separateenclosure. If overhead line is laid up to thetemporary substation, then the ‘supporting poles,conductors, materials of the line, insulation andthe method of stringing the conductors and themechanical strength of the line as a whole shallconform to the relevant provisions of IS : 5613(Part I /Set I)-1970* and IS : 5613 (Part l/Set 2)-197lt. In case supply at voltages above 650 V-

*Code of practice for design, installation and maintenanceof overhead power lines: Part I Lines op to and including I IkV, Section I Design.

tCode of practice for design, installation and maintenanceof overhead power lines: Part I Lines up to and including IIkV, Section 2 Installation and maintenance.

217

is required, a suitable enclosure to install theswitchgear and the metering arrangement shallalso be erected.

6.1.2 Power Distribution

6.1.2.1 At the origin of each installation a unitcontaining the main controlgear and the principalprotective device shall be provided. The mainswitch shall be installed in an enclosure or awooden cupboard and as close to the meteringpoint as possible (see also 6.2.1.1).

6.1.2.2 Means of emergency switching shall beprovided on the supply to all current usingequipment on which it may be necessary todisconnect all live conductors in order to removea hazard.

6.i.2.3 The enclosure or the cupboard inwhich the main-switch is installed shall be suchthat the equipment within shall be unaffected bythe environmental conditions (see 4.1).

6.1.2.4 The main switch on the installationshall be connected to the point of supply bymeans of an armoured cable and the terminationof this cable shall be adequately protected fromrain water.

6.1.2.5 The main switches shall be located at aheight not exceeding 1.5 m so as to be accessiblein emergencies.

6.1.2.6 The cable shall be laid ei therunderground or supported in the air. Precautionsshall be taken to ensure that this cable when laidunderground is done so with the same meticulouscare as is done for a permanent installation. Incase the cable passes underneath the passages, itshall be laid in whole or split pipes. When laidoverground, the cables shall either be cleated withsaddles of proper sire along the walls of apermanent structure if available, or alternatively,it shall be supported on rigid poles. The height ofthe cable shall not be less than 2 m when runinside the compound and at least 5 m when runalong or across road. Crossing of the road shallpreferably be avoided. An independent earthingshall be established inside the installat ionpremises. In case overhead wires are used in theinstallation they should conform to the relevantIndian Standards mentioned in 6.1.1.

6.1.2.7 In selecting the equipment and cables,t h e r a t i n g s h a l l b e d e c i d e d t a k i n g t h eenvironmental conditions into account.

6.1.28 The supply intake point shall be placedoutside the periphery of area which is accessibleto the general public.

6.1.2.9 In cities, towns and thickly populatedlocalities, it is advisable to wire up the installationwith insulated wires including for main circuits inopen compounds or running along or acrossroads. For main circuits, cables shall be used,preferably laid underground. Alternatively, theyshall be cleated along the walls of structures withproper saddles. When laid underground, the cable

218

6.1.2.11 In cities and towns, if the premiseswhere temporary electric supply required isisolated, then:

4

b)

In

mixed wiring of insu la ted and bareconductor - overhead wiring, and

mixed wiring, partly underground andpartly overhead may be used.

such an event, the underground part of the

shall be laid at a depth of 900 mm, covered withsand, bricks and earth for providing mechanicalprotection.

6.1.2.10 For temporary installations in citiesand towns for. purposes described under 3,1(b),(c) and (d), bare conductors shall not be used.Only in the case of load for purposes mentionedunder 3.1(a) especially outside cities and townbare conductors are permitted.

installation and the overhead part of theinstallation shall separately conform to therequirements as mentioned in this Section.

6.2 Control of Circuits

6.2.1 Main Circuit

6.2.1.1 A device shall be provided on theincoming cable to each supply unit and eachdistribution unit for switching and isolating. Withthis type of arrangement it shall be possible toswitch off the supply at the intake point or at thedistribution point.

6.2.1.2 The main switch shall be adequatelyprotected from ingress of water. The incomingand outgoing cable/wires of the main switch shallbe firmly supported so that cable and wire endsconnected to the main switch shall not besubjected to any mechanical force, transmitted toit from any portion of the cables and wires.

6.2.1.3 The main switch shall be installed on afirm and vertfcal surface, which can withstand themechanical vibrations created at the installationsite as well as the wind pressure at the location.

6.2.1.4 There shall be adequate ventilation inthe room where main switches are installed andthere shall be operational space around the switchin accordance with good practice. The switch roomshall be accessible at any time of the day or nightto authorised persons.

6.2.2 Subcircuit

6.2.2.1 On large temporary installations likethose on construction sites, at exhibitions,circuses, etc, the outgoing end of the main switchshall be connected to busbar of adequate size andvarious subcircuits shall be connected to thisbusbar through double or triple pole switches,depending upon whether they are single phase or3 phase circuits. The switches shall be mounted ona firm support and shall be at a height between I

‘m and 2 m from the floor level. The subcircuitswitch shall be so spaced that there shall be aminimum clear distance of 60 mm “--tween the


6.2.2.2 Ihe outgoing wires from the subcircuit\\+itches inside the enclosure shall be cleatedfirmly on wooden battens’ or taken throughcc)nduits which are fixed by means of,saddles tothe masonry wall or wooden partition wall. TheIcad wires connected to the subcircuits switchesshall be suitably supported on wall with clips andshall not be left hanging. Spans more than 2 mshall have guide wire support.

6.2.23 The distribution boards the subcircuits

6.2.2.4 Ta ed

shall be at an accessible height but not less than I

joints shall not be used at

m. The distribution boards shall be fixed on firm

heights less t R

supports or on pole firmly planted in the ground.

an 3 m. The taped joints shall beproperly supported and preferably clamped oneither side of the joint so that the joint is notsubject to a strain. For series lights used f o rdecorative purposes no taped joint shall be used.

insulated wire and shall be connected to the locabearth plate and taken along the cable connectingthe supply intake point and the mainswitch on theinstallation. The ronnection from this earthcontinuity wire shall be taken to various sub-distribution boards and terminated on a busbar.All appliances and equipment connected to sub-distribution board, shall get their duplicate earthconnection from the earth continuity busbar onthe sub-distribution board.

7. PROTECTION AND SAFETY

7.2 Temporary supply is generally used at publicplaces and for public functions and, therefore,extreme care shah be taken to ensure that there isno risk of any type of hazard either from electrical

7.1 The installation as a whole shall be protected

shock or fire.

against overload, short circuit and earth leakageby suitable protective devices.

6.2.2.5 A broken bulb of a lamp in a seriescircuit is a risk and therefore series lamps shallnot be strung or hung at heights less than 3metres. A defective series lamp shall not beallowed to remain in its position and shall beimmediately removed.

6.2.2.6 Installation at construction sites -The enttre area where the temporary supply willbe used, shall be indicated beforehand and in casethe electric supply is required at construction sitefor pipe lines, then a drawing may also be given tothe electric supply authority. On this drawingvarious points from where differentappliances/equipment are intended to be used,may also be indicated. All switches, sockets andfixed appliances shall be protected from rain byenclosing these in cubicles. Subcircuit distributionboard shall be installed, at a place where it is safefrom atmospheric conditions. If such a place isnot available, the distribution board shall beplaced in a cubicle. In a 3 phase circuit the loadson the 3 phases shall be balanced. At the point ofsupply the load on the neutral shall not be morethan 20 percent of the computed value of the loadin the phases.

6.2.3 Earthing

6.2.3.1 All appliances and equipment ontemporary installation shall be connected to asystem of duplicate earthing one of the PowerSupply Authority and one local. Whereverarmoured cables are used, the armouring shall beconnected to earthing arrangement of PowerSupply Author i ty . For loca l ea r th ing , anindependent earth continuity wire stiall be used.

6.2.3.2 For local earthing the earth electrodeshall be burried near the supply intake point. Theearth continuity wire shall be a single core

No flammable material shall be stored near theservice intake point or the operational area ofelectrical equipment or appliances. For largepublic functions, exhibitions, etc, suitable fireextinguishers shall be kept at the supply intakepoint and near the main switch of the installation.

In construction sites, protection of personsagainst indirect contact shall be assured byautomatic disconnection of supply appropriate tothe system of earthing. Socket outlet shall eitherbe protected by residual current devices havingoperating current not exceeding 30 mA or besupplied by safety extra-low voltage or electricalseparation of circuit each socket outlet beingsupplied by a separate transformer.

8. TESTING AND COMMISSIONING

8.1 Supply to all temporary installations shouldbe connected by a specific date for the user andtherefore the installation work meant for types ofinstallations in 3.1(a), (b) and (c) shall be ready atleast 24 hours prior to connection of supply, so asto properly test the installation and find the loadsin different subcircuits. In the case of installationdescribed’ in 3.1(c) there should be a period of atleast 6 hours after compl&ion of the work andprior to connecting supply for the purpose oftesting the installation and visual inspection.

8.2 The various tests on the installation shall becarried out as laid down in Part I /Set IO of theCode.

8.3 When the specified duration of use of theinstallation as defined in 2.1 is required to beextended beyond the stipulated period of 6months, the guidelines specified in this Sectionshall be applicable subject to fresh inspection andtests as above, with the, prior approval of thesupply authority.


.,::i

SECTION 3 PERMANENT OUTDOOR INSTALLATIONS

O . F O R E W O R D

0.1 Outdoor installations of the permanent naturerequire special t reatment as compared totemporary installations of short durations (lessthan 6 months) primarily owing to the continucusexposure of the former installation and equipmentforming part of it to heavy conditions of service atsite. The design and selection of equipment andcomponents have to take into consideration theexpected loading, operating characteristics andcycle duty, as well as the special and arduousenvironmental, operational. transportation andstorage conditions.

0.2 This Section of the Code attempts to coverthe general requirements applicable to equipmentand auxiliaries for a variety of permanent outdoorsite installations which are enumerated in 3. It isintended to provide necessary guidelines for suchinstallations in this Section for the purposes of thepractising engineers and the relevant authorities.

0.3 The general characteristics of permanentoutdoor installations are enumerated in 4. Theobject of this Section is to set out the guidingprinciples so as to ensure the safety of persons,livestock, property and the proper functioning.

0.4 In the prepara t ion o f th i s Sectionconsiderable assistance has been derived fromIEC Publication 62 I ‘Electrical installations foroutdoor sites under heavy conditions (includingopen-cast mines and quarries), issued by theInternational Electrotechnical Commission.

SECTION 3A GENERAL

1. SCOPE

1.1 This Section of the Code covers requirementsfor permanent ou tdoor ins ta l l a t ions , fo roperations of equipment and machinery thereinused

a)

b)

c)

d)

e)

9

Jz)

for the purposes such as: _

Winning, stacking and primary processing,

Secondary processing,

Transport conveying,

Associated pumping and water supply sys-tems,Haulage trucks,

h)

Power generating and distribution systems,

Control, signal supervisory and communi-cation system, and

Ancillaries.

1.2 This Section does not cover temporary andprovisional places of work of durations less than 6months for which reference shall be made to PartS/Set 2 of the Code.

220i

Nwt ~~ However this Section shall be applicable to buildingsites and earth-moving sites as far as the equipment usedtherein are similar to those used in surface mining application.

2. TERMINOLOGY

2 . 0 For the purpose o f th i s Sec t ion , thedefinitions given in Part I together with thosegiven below shall apply:

2.1 Operations (Electrical) - The process ofper forming work th rough the con t ro l ledapplication of electrical power. This processincludes:

Operaring : which means. switching, adjusting,controlling and supervision,

Servicing : which means maintenance,alterations, removal of faults and testing.

2.2 Operating. Area - An area accessible tooperating personnel in the normal performance oftheir duties.

2.3 Electrical Operating Area - An areaaccessible only by the opening of a door or theremoval of a barrier. The area shall be clearly andvisibly marked by appropriate signs.

2.4 Closed Electrical Operating Area - An areaaccessible only through the use of a tool or key.the area shall be clearly and visibly marked byappropriate signs.

2.5 Working Level (Bench)- That part of anopen-cut mine or quarry on which machineryand/or rolling stock are in operation. Theworking level and/or working area may changelocation with the progress of .operations.

2.6 Winning and Stacking Machinery - Winningand stacking machines are used in the process ofuncovering or detaching materials from theearth’s surface or stacking such material. Thesemachines are designed to be able to changelocation according to operational requirements.

They include the following:

a)

b)c)d)

e)

9I31

Excavators, namely: bucket-wheelexcavators, bucket-chain excavators,draglines, shovels and other excavators,reclaimers, ditch bunker loaders, etc,

Spreaders and stackers,

Mobile conveyor bridges,

Mobi le conveyors , inc lud ing t r ippercarriages,

Loading stations, including hoppers andsurge bins,

Floating dredgers, and

Mobile electric drills.

2.7 Transport Conveying System - A movable orstationary mechanical item of plant designed for


the conveying of materials continuously from onelocation to another.

They include the following:a) Belt conveyors,b) Cham conveyors,

c) Bucket conveyors,

d) Paddle or scraper conveyors.

e) Screw conveyors, and

f) Hydraulic conveyors systems.

2.8 Primary Processing Machinery - Anymachinery necessary to prepare material wonfrom the earth prior to its transport to the finalprocessing or utilization areas.

2.9 Secondary Processing Machinery - Anymachinery necessary to process at a point remotefrom the open cut or quarry, material won fromthe earth.

2.10 Fixed Apparatus - An apparatus orassembly of apparatus which is permanentlyinstalled in a determined place and which is notnormally moved during or between periods of use.

2.11 Portable Apparatus - An apparatus orassembly of apparatus intended to be normallyheld in the hand during use and which can becarried by ‘a person.

No’rE Cables are net included as part of apparatus.

2.12 Mobile Apparatus - An apparatus orassembly of apparatus which is too heavy to brportable but which is capable of being movedwithout discontinuity of electric power during use.

2.13 Movable Apparatus- An apparatus orassembly of apparatus which is too heavy to beportable, but which is moved between periods ofuse, with its electric power source disconnected.

2.14 Haulage Truck - An electrically poweredvehicle usually operating on rubber tyres used fortransport of materials and which may have a self-.contained or external power supply.

2.15 Movable Railway System 2 i4 railwaysystem which is designed to be tiovable toanother location without dismantling.

2 .16 Se l f -Conta ined Power Supply - Anelectrical installation in which the generation andutilization plants are housed within the sames t r u c t u r e .

2.17 External Power Supply - An electricalins ta l l a t ion in which the genera t ion andutilization plants are not housed within the samestructure.

2.18 Exposed Conductive Part -A conductivepart which can be touched readily and whichnormally is not live but which may become liveunder fault conditions.

NOTE .--Typical. exposed conductive parts are walls ofenclosures. operating handles. etc.

PART 5 OlJTDOOR INSTALLATlONS

2.19 Earthable Point - That point of the powersystem, for example, of the transformer and/orgenerator, which would be connected to earth ifthe system were to be earthed.

NOTI- l-he earthable point may be the neutral pointdepending on the type of power system.

2.20 Insulation Monitoring and WarningDevice - A device which causes a signal to begiven in the event of reduced insulation resistanceto earth.

2.21 Movable Distribution Cable - An insulatedcable that may be moved from time to timeaccording to the operation without necessarilyfollowing the movements of the machinery.

2.22 Drum Cable -- An insulated cable speciallydesigned to be frequently reeled on and off a cabledrum or reeler mounted on a mobile machine.

2.23 Trail ing Cable - An insulated cablespecially designed to be towed by a mobilemachine.

2.24 Overhead Traction (Trolley) Wire - Anelectric line having bare conductors used forsupplying vehicles (for example. locomotives) bymeans of a collector or pantograph.

2.25 Overhead Traction Distribution Line(Feeder) ‘-~~ An electric line having bareconductors used for the interconnecting linebetween the power source and traction wire.

2.26 Overhead Collector Wire - An electric lineused for supplying moving machinery, such as areclaimer, by means of a collector.

2.27 Overhead Distribution Line (Feeder) - Aninterconnecting electric line between distributionsubstation and load point.

2.28 Return Conductors - Conductors (whichmay be rails) used for carrying the. return current.

2.29 Safety Circuits and Devices - Circuits anddevices designed to prevent danger to personnelor livestock and damage to plant in the event ofabnormal or unintentional operation.

3. T Y P E S O F P E R M A N E N T O U T D O O RINSTALLATIONS

3.0 The types of permanent outdoor installationscovered by this Section are given in 3.1. Thegeneral characteristics and service conditionsenumerated in 4.1 cannot be made uniformlyapplicable to all such installations. Depending onthe site conditions and the nature of the operationinvolved, a judicious estimate has to be made ofthe environmental factors that influence theperformance of- the installation.

3.1 The following are the types of permanentoutdoor install.ations covered by this Section:

a) Open-cuf or Open-cast Mine - An openair sire for the extraction of materials orminerals such as coal, bauxite, iron-ore, etc.

221

b)

cl

e)

NOTE ~ Underground mines are excluded from thescope of this Section. However surface installations ofunderground mines are covered by this Section. to theextent that the operations therin are identical withthose described in 1.1.

Quarry - An open air site for the extractionof materials such as limestone, gravel, clay,etc.

Dockyards - includes loading and unioad-ink areas, container terminal, railway yards,repair docks, passenger berths, jetty’s,etc.

Airport Aprons - A defined area on a landaerodrome, intended to accommodate air-craft for the purposes of loading and un-loading passengers, mail or cargo, refueiiingparking or maintenance.

Railwyav Marshalling Yards - A yard withfacilities for receiving classifying and dis-patching railway roiling stock ( see alsoSection 3E).

4. GENERAL CHARACTERISTICSOF PERMANENT OUTDOORINSTALIJATIONS

4.0 The design and the selection of componentsshall be on the basis of expected loading,operating characteristics and cyclic duty takinginto consideration the protection required inspecial and arduous environmental, operational,transportation and storage conditions:

4.1 Some of these conditions, are listed belowwhich may differ from their normal values:

a)

b)c)d)e)r)g)

h)

j)

kSml

Altitude,

Low and/or high ambient temperature.

Supply voltage variations,

Supply frequency variations,

Insecure powrt supply and transients,

High or low humidity,

Environment (dust, wind pressure, marineatmosphere, etc).

Flammable and/or explosive material/oratmosphere,

Vermin, including rodents or other smallanimals,

Localities prone to natural calamities, and

Ecological impact.

SECTION 3B EQUIPMENT A N DAUXILIARIES

5. RULES FOR EQUIPMENT A N DAUXILIARIES

5.0 General

5.0.1 Exchange qf Information - Before

222

ordering electrical equipment for outdoor sites,information regarding the duties, location andinstallation conditions under which they wouldoperate, should be gathered by the engineersresponsible for their procurement. installation andmaintenance so that the electrical equipment orapparatus is procured to suit those conditions.Necessity for special measures may be decided inconsultation with ail concerned.

5.0.2 Relevant Standards - The electricalspecifications of ail components shall be not lessthan that required by the relevant IndianStandard.

5.0.3 Materials ~ Materials used in componentconstruction shall be appropriate f o r t h eenvironmental conditions, including temperature.altitude, moisture, etc.

5 . 0 . 4 Pro tec t ion - - Pro tec t ion sha l l beprovided against damage and/or overheatingduring normal operation..or in expected faultconditions.

5.0.5 Operating Conditions - Componentsshall be des.igned to meet such conditions asvibration, acceleration, deceleration, siewing andangles of inclination (tilting and mounting) whichmay occur under expected operational conditions.

5.0.6 Site Conditions - Components shall beinstalled so that design features such as coolingsystems shall not be impaired by external factorssuch as position, blocking of ventilation ducts,hostile environment, etc.

5.0.7 Combustible Materials ~ If combustiblematerial (for example. gas, dust or liquid) ispresent in such quantity as to create a hazard andcontact is possible between any exposed part ofthe component and the combustible material, thetemperature of the exposed part shall not exceedthe limits specified in Part 7 of t.he Code.

5.0.8 Noise Limitations ~ Consideration shallbe given in the design to limit the noise level inaccordance with local rules.5.1 Selection of Equipment and Ancillaries

5.1.1 Rotating Machines - Rotating machinesused in applications where high acceleration,overspeed , r evers ing o r b rak ing may beemployed shall be so selected that they arecapable of withstanding the expected stresses onparts such as rotor windings or cages. stators,stator end windings, shafts and couplings.rotating machines shall be so located or guardedto prevent inadvertant contact with moving parts.

5.1.2 Transfi~rmers - Transformers shall be soselected that:

4 the bracing of the core, coils. internal leadsand the tank of transformers on mobile andmovable installations are capable of with-standing vibrations,

b) they are totally enclosed, and

c) diy type transformers including cooling

NAT-IONAL ELECTRICAL CODE

system are protected against harmfulingress of dust.

The following additional protective measuresare suggested from fire:

a) Use of dry type transformers,

b) Use of flame-retardant cooling medium, and

c) Protective measures as specified in15 : 10028 (Par t 2)-1982* for transfor-mers with flammable cooling medium.

Adequate precautions shall be taken to preventspillage of the cooling medium causing pollution.

5.1.3 Static Converters ---- The followingprecautions are recommended:

a)

b)

c)

d)

e>fl

Protection against harmful effects of over-voltage, and transient overvoltage condi-tions;

Protection against interference with commu-nication or electrical control equipment;

Protection against spurious operation due toelectrical coupling with other apparatus;

Protection against interaction betweenearthing systems of the input, output andcontrol circuits;

Feedback supervision. where necessary; and

Measures to limit harmonics.

5.1.4 Switching Devices --- The followingmeasures are recommended for switching devicesfor outdoor sites:

a)

b)

cl

d)

Selection of proper design that no uninten-tional switching may be caused under ex-pected operational and risk conditions,

Ensuring, where required suitable means toenable isolators to be locked,

Suitable labelling of switching devices whichare not meant for interrupting load or faultcurrents, and

Suitable installation precautions to preventhazards to personnel from electric areas,automatic movement of the mechanism, etc.

5.1.5 Cables

5.1.5.1 Phase conductors - Selection of phaseconductor size should take into consideration theexpected load current, short-circuit current andduration of faul t , vo l tage d rop and themechanical strength required for the expectedmethod of handling. The voltage drop should becalculated for both starting and maximum loadconditions. Where supplying cyclic loads, thecurrent-carrying capacity should be based on thelong time (for example, (0 minutes) rms currentexpected.

5.1.5.2 Protective conductor - All multicore

*Code of practice for selection, installation and maintenanceof transftirmers: Part 2 Installation.

PART S OUTDOOR INSTALLATIONS

cables of the movable distribution. drum andtrail ing types. s h a l l c o n t a i n a protectiveconductor. In high voltage systems, specialmeasures shall be taken to guard againstdeterioration of the earthing circuit. This may beachieved by either:

4

b)

monitoring the protective conductor againstincrease in resistance by the use of pilotcores, high frequency monitoring or othermeans, or

cables should be specially designed and usedin accordance with the requirements of re-levant Indian Standard whether or not theyare used on a drum.

The protective conductor may be in the form ofcore(s) and/or screen(s).

For certain classes of movable distributioncables, the armouring may, subject to therequirements of 5.1.5.3, form the protectiveconductor.

5.1.53 Armouring as protective conductor -Where : the cross-sectional area of a singlecomposite strand of the armouring is greaterthan 6 mm2, the metallic armouring of a movabledistribution cable may be used as a protectiveconductor provided that the security againstbreakage of the armouring (taking irito accountstrength, elongation, lay, etc ) is at least equal tothat of all the conductors; and provided that thearmour conductivity is at least equal to that of aprotective conductor of the required nominalcross-sectional area which would otherwise berequired.

5.1.5.4 Limiting temperatures under shortcircuit -~ Cables shall be selected so as to ensuret h a t t h e m a x i m u m a l l o w a b l e c o n d u c t o rtemperature, considering the type of insulation, isnot exceeded under expected short-circuit faultconditions.

5.1.5.5 Protection against partial discharge --For flexible cables having nominal voltages

greater than 4 000 V, measures shall be providedto minimize internal partial discharge or to rendersuch effects harmless (for example, field gradientcontrol).

Suitable protective measures shall be applied toreduce the touch and step voltages. Suchmeasures may consist of

a) metallic screens, or

b) substantial semiconductive elements incontact with the protective conductor.

5.1.5.6 Semiconducting la.Lvrs -- Where cablesa r e f i t t e d w i t h s u b s t a n t i a l l o n g i t u d i n a lsemiconducting layers for the purpose ofproviding a current path to the protectiveconductor in the event of a fault, the resistancebetween the semiconducting element and theprotective conductor should be :ested to ensurethat it is suitable to carry the prospective faultcurrent.

223

5.1.5.1 Plo~~ision (?f .wreen.s and/or atmouringfiw ~ahle.s aho\v I 000 I/‘~ Where flexible cablesare handled manuaily while energized, they shallhave metallic screens and:‘dr armouring or shallbe provided with conducting elastomeric screensof substantial cross-sectional area and so placedas to limit the touch and step voltages that mayarise in the event of a cable fault.

conditions.

Cables having extruded metallic sheaths, forexample, cables with lead alloy or aluminiumsheaths or mineral-insulated metal-sheathedcables, shall not be used where fatigue may occur.due to vibration. frequent handling or groundmovement.

In cases where cables are handled only bymeans o f special insulated tools. theserequirements shall apply only for voltages above4 000 v.

5.1.5.13 Segregation of’ pobcler and controlcores

a)

5.1.5.8 Identification ofcwnd~rc~tor Unless o t h e r w i s k

protrc,tiL~cJrequired. the

following applies:

Single-cure cables Single-core cableswhich are installed in a common duct. con-duit or sleeving may be used for severalcircuits. both power and control.

a) For cables rated at ap to and iticludingI 000 V. in which the protective conductoris insulated, such insulation. or outer taping,shall be distinctly and indelibly colourcdgreen and yellow also see Part I : Set 4 of theCode over its whole length so that in anyI5 mm length one of these colours shallcover at least 30 percent and not more than70 percent of the surface, the other colourcovering the remainder of the surface, and

All such cables (except bare earthing con-ductors) shall be insulated for the maximumvoltage applied to any cable in the duct.conduit or sleeving.

When using single-core cables for alter-nating current circuits. all conductors of agiven circuit shall follow the same magneticpath to neutralire the resultant magneticflux.

b)

b) For cables rated at above I 000 V. in which,the protective conductor is insulated, suchinsulation or outer taping shall at least beidentified at each end by the green yellowcolour combination applied in accordancewith the foregoing paragraph. Suitablesupplementary identification may also beused.

Mlrlticore cables -~ For voltages up to andincluding I 000 V, multicore cables may beused for several circuits, both power andcontrol.

For voltages above I 000 V, the onlycontrol core(s) which may be includedin a multicore cable, shall be the earth con-tinuity check pilot.

5 . 1 .5 .9 Part ia l dischar~qe pet~fowiance Fo rcables rated at above 4 000 V each productionlength (minimum length I50 m) of movabledistribution cable, drum cable and trailing cableshall be tested by the cable manufacturer forpartial discharge.

Multicore cables containing power andcontrol cores shall comply with the follow-ing requirement as appropriate:

Any cable containing pilot, control andsupervisory cores shall have such coresinsulated from all other conducting ele-ments of the cable,

5.1.5.10 Terminat ions of ’ fle.rihle c,ahksFlexible cables shall be terminated in such a waythat their ends are not under stress or undertension effects, and that excessive bending andcompressing are avoided.

5.1.5.11 Pwar cable tbl,i.st lin7itation Wherethe normal mode of operation of the machinerequires infrequent rotation through an arc of upto 360” in either direction, the distance betweenthe clamping supports of the cable shall be notless than 50 times the largest cable diameter in thecable run. Where the normal mode of operationof the machine requires frequent rotation throughan arc of up to 360’ in either direction, thedistance between the clamping supports of thecable shall be not less than 100 times the largestcable diameter in the cable run. Where cablesdesigned specially for this purpose are used, theabove. ratios may be reduced to 25 and 50 timesrespectively.

1)

2)

3)

4)

Cables operating at above I 000 V in anunearthed system shall have either metal-lic screens or individual conductiverubber screens separating the powercores from the pilot core(s),

Cables operating at above I 000 V in anearthed system shall have metallic screensseparating the power cores from the pilotcore(s), and

Cables operating at up to and includingI, 000 V shall have pilot, control or super-visory cores separated from power coresby conductive rubber screens if on anunearthed system or metallic screens if onan earthed system. Alternatively, foreither system, the pilot, control or super-visory cores shall be insulated to a volt-age level equal to that of the power cores.

cl5.1.5.12 Sheathing- Cables may be laid

directly on or in the ground provided that tteouter sheath is designed for the operating

Composire multicore cables on reelingdrums - Multicore cable which containpower, pilot, control or supervisory coresmay be used for reeling drum applications,


subject to the voltage limitations given in(b) above provided that the cable is speci-ally designed for such reeling duty.

5.1.5.14 Separation of cables in racks -Where power and control cables. multicore ar?dsingle-core are used on a common rack, tray orduct, the degree -of mutual interference shall beconsidered.

5.1.5.15 Bending radius for jlexible cablesover 2.5 mm diameter-The recommendedminimum bending radius for flexible cablesduring installation and handling in service is sixtimes the cable diameter for cable not constructedin accordance with 5.1.5.5(a) or (b,), and eighttimes the cable diameter for cables which areconstructed in accordance with 5.1.5.5(a) or (b).

5.1.6 Cable Connectors

5.1.6.1 Use of plug/socket connectors -Where plug and socket connectors are used atvoltages above 1 000 V, measures shall be takento prevent the plug from being engaged with, ordisengaged from, the socket while the’circuit isenergized.

The measures shall consist of one o,r both of thefollowing:

4

b)

The provision of isolating switches whichare interlocked with the plug/socket so as toprevent connection or disconnection whilethe circuit is energized and to preventswitching the circuit when the plug/socketconnection is incomplete.The provision of protective conductor moni-toring by means of either a pilot core, byhigh frequency monitoring, or by othermeans.

The measures under (b) are intended as a safetyfeature and should not be used for normalisolation purposes.

5.1.6.2 Use qf bolted plug/socket connectorsand bolted connections - Where boltedplug/sdcket connectors or bolted connections areused, interlocking is not required providedsuitable and adequate operational procedures areimplemented.

5.1.7 Control Circuits and Control Devices -Control circuits and control devices shall notautomatically reset after tripping unless resettingof the control device either does not causeautomatic restarting of the device or there i,s nohazard to personnel created by automaticrestarting. or fire.

For unearthed control circuits, measures shallbe taken to limit the leakage and capacitance

--currents that they shall not exceed 70 percent ofthe drop-out currents. For unearthed controldelrices, an insulation monitoring device shall alsobe provided for safety.

5.1.8 Safety Circuits and Safety Devices - Anysafety circuits shall incorporate fail-safe principle


as far as reasonably possible. Some of theprinciples suggested are:

a) closed circuit principle,b) proving function operation principle, andc) fail-safe principles with solid state switching

devices.

SECTION 3C PROTECTION FOR SAFETY

6. GENERAL RULES ,FOR PROTECTIONIN OUTDOOR INSTALLATIONS

6.0 The general rules for protection for electricalinstallation inside buildings. as enumerated inPart I /Set 7 of the Code are applicable foroutdoor installations of permanent nature coveredby the scope of this Section. The additionalrequirements applicable for permanent outdoorinstallations are given in the following clauses.

6.1 Protection Against Direct Contact

6.1.1 Complete Protection by Means ofBarriers or Enclosures

6.1.1.1 The minimum electrical clehrances inair between field installed bare conductors andbetween such conductors and earthed paris (suchas barriers and enclosures) Shall.be in accordancewith Tables I or 2.

NATE I -These tables need not apply within electricalapparatus wiring devices or manufactured assemblies norwhen the installation is covered by other sections of the Code.

NATE 2 -Tables I and 2 take into consideration the factthat the system voltage may vary up to 20 percent from therated operating voltage.

NOTE 3 - Tables I and 2 may be used to indicate clearancedistances between conductors and earth in a TN or TT systemby using the phase-to-earth. voltage.

NOTE 4 -These minimum clearance distances in Tables Iand 2 do not take into consideration such factors as creepage

distances. diffeient voltage levels in the same area nor extremeenvironmental conditiorq, etc.

6.1.1.2 All live parts shall be inside enclosuresor behind barriers providing at least the degreesof protection’ in accordance with Table 3.

6.1.13 Barriers and enclosures shall be firmlysecured in place, and taking into account theirnature, size and arrangement, they shall havesufficient stability and durability to resist thestrains and -stresses likely to occur in outdoorconditions.

6.1.1.4 Where access to the install&ion isnecessary by removal of barriers, opening ofenciosurrs, etc. these shall:

a) necessitate the use of key or tool; orb) involve provision of an interlocking device

such that the removal, opening or with-drawal without the use of a key .or toolnecessitates previous switching off ofall live parts; or

225

TABLE I CLEARANCE DISTANCES FOR INDOOR INSTALLATIONS

(Clause 6. I. I. I )

Maximum rms value of rated 1 3 6 IO 20 30 45 60 110operating voltage, kV

Minimum distance for instal- 40 65 90 115 21s 325 520 700 I loolations subject to over-voltages, mm

Minimum distance for instal- 40lations protected againstovervol tages or connectedto cables, mm

60 70 90 160 270 380 520 950

TABLE 2 CLEARANCE DISTANCES FOR OUTDOOR INSTALLATIONS

(Clause 6.1.1.1)

Maximum rms value of ratedoperating voltage, kV

I O 20 30 45 60 110 150 220

Minimum distance for instal- 150 21s 325; 520 700 I 100 I 550 2200lations subject to over-voltages, mm

Minimum distance for instal-lations protected against - IS0 160 270 380 520 950 1 350 I 850overvoltages or connectedto cables, mm

TABLE 3 MINIMUM PROTECTION AGAINST DIREKT CONTACT BY BARRIERS OR ENCLOSURES(APPLICABLE TO LIVE PARTS ONLY)

(Clauses 6.1.1.2)

VOLTAGE WITIII~: OPERATING A R E A S WITHIK ELECTHIC.AI. OP E R A T I N G W ITHIN C~.ostn EL E C T R I C A LBAND ( A C ) AREAS OP~HATISG AR E A S

(1) (21 (3) (4)50 < I/G 1 000 V Complete protection IP2X* Partial protection IP IX*

or IP4X for top surfaces or if UG 660 V or no simal-No protection IPOX if

L1<6m Vbarriers or enclosureswhich are readily access-

taneously accessible parts

ible. This applies in parti-at different voltages are Partial protection IPOX* ifsituated within arm’s u > 660 V or no simul-

cular to those parts of pathenclosures which might

taneously accessible parts

serve as a standing surfaceat different voltages are

Complete protection IP2X if situated within arm’s reachCJ> 660 V or IWX if

See Note I U > 660 V for top surfaces See Note Ior barriers or enclosnreswhich are readily accessible

This applies in particularto those parts of enclosureswhich might serve as astanding surface

See Note I

LI>loooV Complete protection IPSXwithin arm’s reach

Complete protection IPSX Partial protectiofi IPIX*within arm’s reach

Partial protection IPZXbeyond arm’s reach

Partial protection IP 1 X*

U = rated voltage of the installation between linesbeyond arm’s reach

NOTE I - The use of floor plug and socket connector is not precluded but such sockets shall be covered when not in use.

NATE 2 - For details on IP classifications. see IS : 2147-1962 ‘Design of protection provided by enclosures for low voltageswitchgear controlgear’. As used in the present standard, the IP classification is intended to specify only the degree ofprotection required to protect persons from contact with live /!arts Additional protection may be required for protection. .from contact with moving parts or to prevent ingress of so Id foreign bodies, such as dust.

NOTE 3 - In the case of dc voltages. the voltage bands in the above table may be increased In the ratio of I : I .S. namely. upto I 500 V and above.

*For electrical operating areas and closed electrical operating areas. protection equivalent to IPIX is also considered to beachieved by placing out of reach or by the interposition of obstacles, for example, by means of protective barriers orhandrails.


c) ensure automatic disconnection when re-moval, opening or withdrawal withoutthe use of a key or tool is attempted.

6.1.2 Partial Protection by Placing Live PartsOut qf Reach -see Table 3.

6.1.3 Partial Protection by the Provision ofObstacles - see Table 3.

7.1.6 Electricconsideration.

Hand Lamps - Under

7.1.7 Drives ~-.- The following recommenda-tions apply to drives with a periodic or cyclic dutyas well as to certain other drives with acontinuous duty.

6.2 Protection Against Indirect Contact

6.2.1 The provisions of Part I /Set 7 of theCode shall apply.

7.1.7.1 -Effect on voltage levels - The effectsof equipment starting and of the duty cycle onvoltage levels, which may result ir. damage or themalfunction of equipment, shall be taken intoconsideration to ensure the safety of personneland equipment.

SECTION 3D REQUIREMENTS FORINSTALLATIONS

7. REQUIREMENTS FOR PERMANENTOUTDOOR INSTALLATIONS

7.1 Winning, Stacking and Primary ProcessingMachinery

7.1.1 Mounting qf’ Components - For themounting of motors, limit switches, sockets. etc,special protective connections to the structuralparts of the installation are not required if theconnecting surfaces between the electricalequipment housing and structural parts providean adequate conducting area. In such cases, thenormal mounting bolt or screw connection isadequate.

7.1.7.2 Supp(v systems -The effect of loadfluctuations on the supply system shall beconsidered, taking account any restrictionsimposed by the electricity supplier.

7.1.8 External Pok’er Supply Systems

7.1.8.1 $\,stem design - The supply systemshall meet the requirements of cyclic or periodicloads, motor starting, and inherent ac motoroscillations due to transient load changes. Forprotection requirements see 6.

7.1.8.2 Overcurrent protection --- Overloadand short-circuit protection for transformers,cables, etc, shall take into consideration thestarting requirements and cyclic nature of theload.

This is also applicable for the mounting of alltypes of electrical equipment in cubicles,termination boxes, etc.

Where the equipment is required to operateunder- corrosive atmospheric conditions orex t reme v ib ra t ing cond i t ions , a separa teprotective conductor shall be connected tomotors, limit switches. etc.

7.1.83 Automatic reclosing or transferring -Where regeneration may delay the oneration ofundervoitage devices, automatic reclosing ortransferring devices should not be used in thepower distribution system unless such device hassufficient time delay to allow motordisconnection, the device is fitted with ‘out ofstep’ protection, or the combination of supplysystem and motor design characteristics is such asto permit automatic re-energization.

7.1.2 QJ,f’Board Mobile and MovableAuxiliary, Equipment - For mobile and movableoff-board auxiliary equipment (such as weldingequipment, vulcanizing transformer<, etc) wherethe protective conductor is not monitored norvisible, a visible main equipotential bondingconductor shall be provided between suchauxiliary equipment and plant.

7.1.8.4 S.I,.stem voltage - It is important thatthe equipment manufacturer and user mutuallyunderstand whether the voltage specified is underno-load or full load conditions.

7.1.9 Self-Contained Power S_vstems

7.1.3 Insulation Monitoring Device jar ITS.\stems -- In the case of an IT system, aninsulation monitoring device is not required forpower circuits which are supplied by a. powersource from within the machine, such as by atransformer having electrical isolated windings orby a generator or storage battery.

7.1.9.1 S,,l.~tem design - the power generationsystems shall meet the requirements of motorstarting, regeneration, peak load, rms load andfrequency stability.

7.1.9.2 Fire protection - Considerationshould be given to the need for special and/oradditio.nal fire protection due to the fuels used[see 51.

7.1 A Insrrlation Monitoring Devices forVulcanizing Heating Platens - In IT systems,insulation monitoring devices are not required forvulcanizing heating platens where the powercircuit is supplied from a transformer havingelectrically isolated windings.

7 .1 .9 .3 Earthing - When the supply ofelectrical energy is self-contained withinstationary, mobile, o r movable i t ems ofequipment and there is no external supply, suchequipment need not be connected to the generalmass of the earth.

7.1 .S Electricconsideration.

Tools .- Under7.1.9.4 Supplr, t o off’hoartl eyiiip~)t~‘tIt

When power 1s suppiled to off-board nroh~lt~ ;indmovable equipment conditions given in 7.1.2 ;trl‘

PART 5 0l:TDOOR INSTAl.I.ATIONS 2P?

applicable.7.1.10 Cable Tvpes - Under consideration.7.1.11 Control Circuits and Control Devices

7.1.11.1 Shock, vibration and voltagefluctuations-The effect of shock, vibration orvoltage fluctuations on control devices shall betaken into consideration, ensuring that safety ofpersonnel and equipment is not endangered byinadvertant operation of control devices.

When mechanically latched control devices areused and re-energization following loss of supplypower would endanger personnel or equipment,means shall be provided to automatically trip thelatched control device on loss of supply p’ower.The device shall also be tripped on operation ofprotective devices.

7.1 .11.2 Synchronous motor control

a) Automatic field removal - Where synchro-nous motors are used to drive any part ofthe installation, automatic motor fieldremoval on disconnection is required.

b) Automatic field excitation controi - Wheresynchronous motors are used to drive perio-dic or cyclic loads, an automatic field excita-tion control is recommended.

c) Power toss protection - Where synchron-ous motors are used to drive loads whichmay be regenerative, means shall be pro-vided to trip the motor starting switch orincoming line switch upon loss of powersupply. Frequency sensitive devices arerecommended. When automatic reclosingor transferring devices are used in the dis-tribution system, conditions given in 7.1.8.3are applicable.

7.1 .11.3 Stop control - The devices describedin the following paragraphs shall not be used forpurposes of isolation or immobilisation to allowwork to be carried out on parts which wouldotherwise be electrically energized or moving:

a)

b)

c)

d)

221

Stop control circuits -The circuits of stopcontrol and of other safety protection de-vices should be as simple, reliable and directacting as is practical.Location of stop controls - A stop controlshall be located near each start control,except for lift call control. Additional stopcontrols may be provided.Locking of stop controls - Where required,provision shall be made to guard againstunauthorized starting. Acceptable methodsinclude locking of stop controls in the ‘offposition or ensuring that only the personoperating the stop control has access to thestart control.Pullwlire stop controls - Stop controlsope.rated by a pullwire shall be arranged sothat a pull on the wire in any direction willstop the controlled equipment. The stop

controls shall be of a type in which the cont-acts are opened by a positive mechanicalaction and can only be reclosed by a furthermechanical action.

7.1.11.4 tnterlocking of start controls -Where equipment can be started from more thanone location, the control system shall permitoperation from only one nominated location atany one time, unless start-up alarms are used, theequipment is in sight from all starting locations,or the equipment is .guarded against madvertantaccess.

7.1.12 Emergency? Stopping and EmergencyDevices

7.1.12.1 Emergency stopping - Disconnectionof power or other equally effective means shall beprovided for stopping the drive under emergencyconditions. The power disconnect device may be amanually or remotely operated powercircuit-breaker. contactor, etc.

Emergency stopping can be accomplished bymeans other than disconnection of power,provided that such means otherwise comply withthe intent of 7.1.11.3. For example, when rotationconverters are used, disconnection of the externalexcitation is permitted if protection against self-excitation is provided.

7.1.12.2 Emergency, devices - Where thecutout devices are actuated remotely they will bearranged as series tripping system. However,shunt tripping devices may be used providing thetripping device and its stored energy trippingsupply are monitored and regularly maintained.

Emergency devices may be arranged to operatesimultaneously in a number of different circuits.A number of emergency devices may be arrangedin groups; each group may operate in single ormultiple circuits.

Where several circuits are divided the respectivecontact elements shall be connected in series.However. shunt tripping systems may be usedproviding the above-mentioned conditions aremaintained.

The emergency device may use remote controlsystems. for example, audio-frequency of time-multiplex operations, providing at least the sameprotective measures as for the above devices areapplied to ensure positive and reliable operations.However, the simultaneous existence of two ormore faults within the remote controls systemneed not be expected.

7.1.13 Provision for Supply Isolation - Ameans of mains supply isolation shall be providedto isolate the power circuits from the equipmentor parts thereof mclusive of control and motorcircuits.

However, separate means of isolation may beprovided for control circuits, which may remainenergized after disconnection of power circuits,provided special measures for the safety ofpersonnel and equipment have been implemented.


7.2 Secondary Processing Machinery - Underconsideration.

7.3 Transport Conveyor Systevs

7.3.1 Mounting cJf Components -see 7.1.1.

7.3.2 Eyuipotential Bonding Conductor andClJrldlcl~til~it~~ (!f Structural Parts - Whereelectrical equipment supplied at a voltage inexcess of 50 V is mounted on a conveyor structureand the cable to the equipment does not include aprotective conductor, an equipotential bondingconductor shall be provided to the electricalequipment unless the structural parts of theconveyor are mechanically fastened and/ orelectrically bonded together. The c6nductivity ofthe metallic structural parts of the conveyor andits fastenings shall be at least equal to that of theotherwise necessary equipotential bondingconductor.

t.3.3 @F-hoard Mobile and MovableAu.riliar~~ Equiiwlent - s e e 7.1.2.

7.3.4 Insulation Monitoring Device ,for ITS.wenis - see 7.1.3.

7.3.5 Insulation Monitoring D e v i c e s .forVulcanizing Heating Platens - see 7.1.4.

7.3.6 Electricconsideration,.

Hand Tools - Under

7.3.7 Electricconsideration.

Hand Lamps - Under

7.3.8 Cables

7.3.8.1 General - Where cables withoutsemiconductive sheaths, metallic screens orarmouring are suspended from structures orframes of movable conveyors, such structures andframes shall be considered as extraneousconductive parts and shall be included as part ofthe whole plant in the design of .the protectivemeasures against indirect contact, that is, byensuring that al l metall ic parts are l inkedtogether.

7.3.8.2 Poccvr supp!,~ cables - Underconsideration.

7.3.9 Slop Controls -- The devices described inthe following clauses shall not be used forpurposes of isolation or immobilisation to allowwork to be carried out on parts which wouldotherwise be electricatly e’nergized or moving.

7.3.9.1 Stopping sequence -- The operation ofa stop control on a conveyor shall stop thatconveyor and:

a) aI1 upstream conveyors to a controlledloading point.

b) cause the material from all upstream con-veyors to be diverted to an alternativeroute.

c) initiate braking to stop the conveyoriti safe time. and

d) prevent run-back.

On very long conveyor systems, however, theoperation of a stop control within one stop zoneneed not stop all upstream conveyors beyond thatzone, provided that the conveyor upstream of thezone is proved to be unloaded, such as by sensors.

Although the stop control may be resetautomatically, restart ing shall be init iatedmanually.

7.3.9.2 Location of stop controls --- S t o pcontrols shall be provided. It is recommended thatstop controls be located at the head and tail endsof a conveyor and that pullwire stop controls beused along the length of the conveyor. Allaccessible points along the pullwire operated stopcontrol are considered as stop controls. Whereindividual stop controls are used, they shall belocated not more than 15 m from any accessiblepoint along the conveyor. Stop controls shall beaccessible from any side of a conveyor to whichthere is access.

NOTE Manually operated stop controls may also providethe function of an emergency stop.

7.3.10 S t o p p i n g of Dokwhill Con\vJws -Under consideration.

7.4 Pumping and Water Supply Systems

7.4.1 Deep- Well TIpe Pumps

7.4.1 .l Risers as protective condustors ~-Where a continuous metallic riser pipe is fittedbetween the motor and the well head, noprotection conductor is required between themotor and the protective conductor connecteddirectly to the fixed iiser provided that:

a)

b)

the supply cable is terminated close to thewell head,

the conductivity of the metallic riser (standpipe) and the connections (couplings) shallbe at least equal to the conductivity of theprotective conductor which would otherwisebe necessary, and

cl personnel do not have access down the well.

7.4.1.2 Continued operation after .first earthfbu/t,- Operation may continue after, the first‘earth fault only when all of the followmg condl-tions are met:

a) An IT system is used,b) Personnel do not have access down the well,

andc) Equipotential bonding is provided.

NOTE ~- Electrically initiated explosive devices should not bestored or used in the vicinity of such installations as hazardsmay exist due to fault currents flowing in the ground whensyslems continue to operate following the first earth fault.

7.4.1.3 E q u i p o t e n t i a l bonding - Anequipotential bonding conductor shall be installedbetween the main earth terminals of the supply

229

and the well head(s), where the conductor shall beconnected directly to the fixed riser. Wheretransformers are located at the well head, theirenclosures shall be connected to this bondingconpuctor.

The equipotential bonding conductor shall beso dimensioned that the voltage drop between anytwo points (of resistance value I?) that may becontacted simultaneously shall not exceed 50 V.That .is:

R < -% ohmsKX I ,

where 1, (in amperes) is the rated current of thepower fuses or, in the case of circuit-breakers, 0.2times the releasing current for the instantaneousor short-time delay trip; and K is a multiplyingfactor.

NOTL ~ A value of K;= 2.5 is suggested for the time being.

7.4.1.4 E.uemption from insulation monitoringdevice -- An insulation monitoring device (orearth fault detector) is not necessary.

7.4.1.5 Double line to earth faults - Protectionshall be provided to disconnect the supply in thecase of a double fault (phase-earth-phase).

A device such as one which detects a change inneutral displacement on the occurrence of the firstand second earth faults, may be provided.Disconnection follows the second fault.7.5 Pumps Other Than Deep-Well Types -Under consideration.

7.6 Power Supply Cables - Under consideration.

7.7 Control Circuits and Control Devices ~Under consideration.

7.8 Safety Circuits and Safety Devices - Underconsideration.

SECTION 3E ADDITIONAL GUIDELINESFOR SPECIFIC AREAS

8. ADDITIONAL GUIDELINES FORINSTALLATIONS IN SPECIFIC AREAS

8.0 General

8.0.1 The requirements given in Sections 3A to3D are applicable to the specific areas describedin this Section in so far as the operations areidentical with those described.

8.0.2 Guidance from relevant experts shall betaken in r e spec t of specific areas beforeinstallation work begins.

8.1 Lighting of Aircraft Aprons - The provisionsof relevant Indian Standards shall apply.

8.2 Lighting of Ports ‘and Harbours -Theprovisions of relevant Indian Standards shallapply.

230

8.3 Lighting Installations in Railway MarshallingYards

8.3.1 Classification

8.3.1.1 The classification in respect of yardarea is based on the speed and intensity of trafficboth

a)

b)

C)

vehicular and otherwise.

Multipurpose yard - A marshalling yardwith facilities for receiving, classifying anddespatching vehicles to their several destina-tion. They also deal with traffic originatingat or destined for centres.

A reception Jsard-- A yard in which theloads of incoming trains may stand clear ofrun’ning lines while waiting for their turnto be dealt with.

A class$cation j,ard -- A yard in whichtrains are broken up on the different linesfor the various directions or stations irres-pective of station order, so as to form theminto trains and prepare them for correctmarshalling.

8.3.1.2 The railway yards are also classifiedinto three main categories depending on theirhandling capacity and way of working:

a)

b)

c)

d)

e)

Gra\lit\* _\,art/ A yard where natural gra-dient -is available. It is utilized for classi-fication and sorting of loads. Shunting isdone without engine.

Hump .llard ~~ Hump yard created by raisingtrack levels in specified crest of 2.to 2.5 mheight. Hump yards are those where shun-ting necks have shape of a camel hump.These yards are mechanized where wagonlevel crosses 2 500 wagons per day. Nor-mally one hump handles I 000 to I 500wagons per day. The number of humps canbe increased depending on the work-load.

Flat .l,ard---- Yards with flat shunting neckare called flat yard. It,dzals from 300 to 700wagons per day. It is mostly suitable formetre gauge.

A sorting jlard This is a yard in whichwagons are separated in station order andreformed into trains in special order tomeet the requirements of the section aheador any other special transportation require-ments.

A departure ,13arci This is a yard in whichloads are kept waiting for departure.

8.3.1.3 Each yard can be of any one of thethree formations based on method of construc-tion:

a) Baloon or classification type,

b) Ladder type, and

c) Grid type.

NO~F Yards with grid type formatIon are reception-cwu-despatch yards.


8.3.1.4 For the purpose of illumination, mostimportant locations are ‘king points’ and ‘queenpoints’ and order of priority for lighting isdetermined accordingly.

N OTE I King points are the first pair of points that thewagon meets after passing over the hump summit and thesedivide the hump yard into two portions.

NOTE 2- Queen points are the second pair of points thewagon meets on either of the two diverging lines taking offfrom the king points and these divide the classification linesinto four sub-portion. These are two in each hump yard.

8.3.2 Different segments (functions) of yardsare:

a)

b)

c)

d)

e)

classification yard ~-- zone wise,

sorting yard - station wise,

reception yard.

despatch yard, and

through goods yard.

8.3.3 Design

8.3.3.1 For the purpose of designing thelighting system, the recommended height of toweris 30 m.

8.3.3.2 Selection qf equipments

a)

b)

Light sources - The following sources oflight a’re recommended for the purpose ofyard lighting.

i) High pressure mercury vapour lamps.

ii) High pressure sodium vapour lamps.

Each luminaire may be provided with2 lamps of 400 W or I lamps of I 000 W.

L u m i n a i r e s - Nood lighting types ofluminaires are recommended for yardlighting installation.


8.3.3.3 Levels of illumination would dependon the type of marshalling yard. The levels givenbelow are recommendatory.

Type MinimumSpecial Location

Maximum Like Shunting Neck.King Points. efc

Importantyard 1.2 lux 5 lux IO lux

Small yards 0.5 lux 1.2 lux 5 lux

8.3.4 Power Installation Requirements

8.3.4.0 The source of .electric supply shall belocated at a suitable place nearest to the yard.

8.3.4.1 The power supply to the towers shallbe through underground armoured cables.

Minimum size of cable shall be IO to 16mm? 4core.

8.3.4.2 Means shall be provided to controlsupply to group of towers with controlgearlocated in feeding substation/switching sub-stat ion.

8.3.4.3 The cables shall be preferably termi-nated on column junction boxes by looping joints,rather than ‘T’ joint.

8.3.4.4 The junction boxes shall be p.rovidedwith suitable sized contactors with independentfuses for each phase. The contactors shall becontrolled by electrically operated switch moun-ted for external manual local operation.

Laying of cables in yard, along the track andacross the tracks should be done in accordancewith IS : 1255l983*

*Code of practice for installation and maintenance of paperinsulated power cabies (up to and including 33 kV).

PART 6 ELECTRICAL INSTALLATIONS INAGRICULTURAL PREMISES

O . F O R E W O R D

0.1 This Part of the Code is primarily intended for covering the specificrequirements of electrical installations in agricultural premises which includepremises where livestock are present and farm produce are handled or stored. Withthe increase in sophistication in organizing the farm output of the country, and theuse of electricity for certain essential purposes, it has been felt necessary to coverthe requirements of such installation as a part of the Code.

0.2 Installations in agricultural premises are different from those covered in otherSections of the Code in that the external influences on the electrical services arequite different from those encountered elsewhere. Even though the overall powerrequirements for such installations would be small, the presense of livestock andother extraneous factors necessitate laying down specific requirements.

03 In the preparation of this draft, assistance has been derived from IEC Pub 364-7-705 ‘Electrical installations in buildings, Part 7 Requirements for specialinstallations or location, Section 705, Agricultural and Horticultural premises,issued by the International Electrotechnical Commission.

1. SCOPE 4. GENERAL CHARACTERISTICS OF

1.1 This Part of the Code covers requirements forthe fixed electrical installations in agriculturalpremises excluding .dwellings or similar locationssituated in these premises.

I.2 This part applies to premises where livestockare present.

AGRICULTURAL PREMISES

4.0 General guidelines on the assessment ofgeneral characteristics of buildings are given inPart I /Set 8. For the purpose of installationscovered by this Part the conditions given belowapply.4.1 Environment - The following conditions

NOTE - Examples of such premises are stables, cow houses,sheepfolds, stalls. hen-houses. piggeries, etc.

generally apply:

2. TERMINOLOGYEnvironmen/

(1)

Presence of water

Characrerisrics(2)

Remarks(3)

2.1 For the purposes of this Part, the definitionsgiven in Part 1 /Set 2 of the Code shall apply.

Possibility ofsplashes fromany direction.

3. CLASSIFICATION

3.1 Installations in agricultural premises shall bebroadly classified into:

a) farm houses, and

Possibility of je:sof water fromany direction

Locations whereequipment may besubjected tosplashed water,for e.g. externallighting fittings

Locations wherehose-water isused regularly

b) livestock houses.Presence of for-eign solid bodies

Presence of dustin significantquantity

Applies to barns.stdres and stalls

3.1.1 Farm Houses - Farm houses arepremises where livestock are not normally presentand are those utilized solely for the purposes ofhandling or storing farm inputs and produce.

3.1.2 Livestock Houses - Livestock houses arepremises where livestock are present for longperiods of time during the day (such as in a dairyfarm) with or without associated farm units.

3.1.2.1 Livestock houses are further classifieddepending on the type of climatic conditions:

a) Plain areas with moderate rainfall,

b) Arid areas and high altitude areas, and

c) Heavy rainfall areas and high rainfallhumidity areas.

Presence of corro-sive or pollutingsubstances

a) Intermittent oraccidental sub-jection to cor-rosive or pollu-ting subs-tances

b) Continuouslysubjected to

Applies to locationsin which livestockare present or ferti-lizers or plantprotective productsare stored orhandled

Presence of floraand/or mouldgrowth

Presence of fauna.

Harmful hazardpresent

Harmful hazardpresent

Insects. birds andsmall animals

Electromagneticinfluences

Harmful presence ofinduced currents

4.2 Utitrzation - The following conditions apply:

3.1.2.2 Livestock houses can also be classifieddepending on the type animal or bird housed. For

Ulilization(1)

Electrical resis-tance of humanbody

Characteristics(2)

Low resistancedue to wetconditions

Remarks(3)

example:

Animal1 Bird Housing

Poultry housing

Sheep folds (sheep andgoats)

I4ggeries

Horse stables oequine houses

Cattle housing

Sub-Classificarion

Layer House

i

Stationery

Brooder House Portable

-

-

-

Cattle sheds for average farmer(3 milch animals with theircalves and pair of bullotks)

Cattle sheds for rural milkproducer (average of about20 animals)

Organized milk produces(130 animals)

Large dairy farm(about 500 animals)


Persons are fre-quently in touchwith extraneousconductive partsor stand on con-ducting surfaces

Conditions of Low density occu- Special precautionsevacuation dur- pation difficult to be taken whereing emergency conditions of animals are present

evacuation

High density occu-pation easy con-ditions ofevacuation

Nature of pro- Flammable mate- Barnscessed or stored rial includingmaterials dust

Building design * Propagation of fireis facilitated andrisks due to struc-tural movement ofstructures whichare weak



5.1 information shall be exchanged among thepeople concerned on the electrical needs of thepremises before installation work begins. Eachinstallation may have to cater to the servicesrequii-ed in the subunits of the premises whichdepend on the type of agricultural premises asenumerated in 3.

5.1.1 In sheepfolds, the following sub-units arepresent:

a) Sheds such as flock shed. ram or buck shed,sick shed, etc.

b) Sheering and store room, ati

c) Shepherd house.

5.1.2 In cattle housing, the following sub-unitsare present:

a) Sheds for animals.

b) Milk recording and testing room,

c) Utensils room.

d) Ration room.

e) Stores. and

0 Office.

5.1.3 In meat houses and abbattoirs, thefollowing subunits are firesent:

a) Animal sheds before slaughter,

b) Slaughter shed,

cl Flaying, dressing and washing,

d) Byproducts handhng,

e) Inspection,

f-l Laboratory, and

&a Office.

5.2 Wiring Systems5.2.1 Main switchgear shall not be installed:

a) within reach of livestock, or

b) in any position where access to it may beimpeded by livestock.

5.2.2 Where an installation serves more thanone building, it shall be possible to isolate andcontrol the buildings individually.

5.2.3 Means of access to all live parts of*switchgear and other fixed l ive parts wheredifferent nominal voltages exist shall be markedto indicate the voltages present.

5.2.4 Cables

5.2.4.1 All cables shall be placed out of reachof livestock and clear of all vehicular movement.

5.2.4.2 Where additional protection againstmechanical damage to cables is required. it, shall,

wherever possible. be provided by the use of non-metallic materials.

5.2.4.3 Where long runs of cable must b cplaced along the sides of buildings, they shallwherever possible be placed on the outside of thebuildings, and as high as practicable.

5.2.4.4 Where conductors or cables are carriedoverhead supported by buildings or by poles. Theminimum height above ground shall be 6 m.

5.2.4.5 Cable couplers shall not be used inagricultural premises.

5.3 Selection and Erection of Equipment -Equipment shall be so selected that they suit theenvironmental conditions of use and shall beinstalled in such a way that their normalfunctioning is not affected by the externalinfluences enumerated in 4.

5.3.1 It is recommended to protect final sub-circuits, by residual current devices, the ratedoperating residual current not exceeding 30 mAand as low ai practicable but avoiding nuisancetripping.

5.4 System Protection5.4.1 Protection Against Electric Shock - For

the application of protective measure by safetyextra-low voltage in locations in which hvestockare present or situated outside, protection againstdirect contact shall be provided by:

a) barriers or enclosures affording at least thedegree or protection IP 2X, or

b) insulation capable of withstanding a test VOI-tage of 500 V for one minute.

For achieving protect ion by automaticdisconnection of supply, the conventional voltagelimit in locations in which livestock are present orsituated’outside is (I,_ = 25 V. These ,conditionsare also applicable to locations directly connectedthrough extraneous conductive parts to thelocations where livestocks are present.

Where electrical equipment is installed inlivestock building, supplementary equipotentialbonding shall connect all exposed conductiveparts which can be touched by livestock and theprotective conductor of the installation.

NOTE -~ A metallic grill connected to the protectiveconductor laid in the floor is recommended (see Fig. I).

5.3.2 Protection Against Fire - Heaters usedin the rearing and tending of livestock shall besecured or hung on a safe mounting so that anadequate spacing from both animals (risk ofburns) and combustible materials (fire hazard) isassured. Due consideration shall be given to theevacuation of aliimals in case of emergency. Dueconsiderations shall also be given to locationspresenting fire-risks.

5.3.3 Isolation and Slz,irrhjng -- For fire safetypurposes, a residual current protective device shallbe installed having a rated residual operatingcurrent of OSA. Devices for emergency electrical

PART 6 ELECTRICAL INSTALLATIONS IN AGRICULTURAL PREMISES 237

::3.4.5.

7:8.

-

Earth, conductorSheet metal and foil partitionsWater pipeManure removal devicePotential equali7ation, forexample. structural steel matTethering device

9.IO.Il.12.13.14.15.


Milking apparatusSteel structureProtective earth conductor (PE)Earth electrodeBusbar for equipotential bonding*Earth electrode for lightning protectionEarth electrode for electric fences

Automatic watering deviceFeeding apparatus

‘Equlpotential bonding can also be achieved, without thebusbar. through direct interconnection of conductive parta.

FIG. I EX A M P L E OF EQIIIPOTENTIAI. BO N D I N G ON AG R I C U L T U R A L P R E M I S E S

switching including emergency stopping shall notbe installed within reach of livestock or in anyposition where access to them may be impeded bylivestock, account being taken of the conditionlikely, to arise in the event of panic by livesfock.

6. SERVICES IN AGRICULTURALPERMISES

6.0 Farm houses and iivestock’houses do not ingeneral require sophisticated electrical services,but in the case of the latter lack of properventilation or lighting loads to insanitation anddiscomfort to the livestock thereby leading toretarded growth, high mortality or poor fertility.The houses are required to be maintained’reasonably cool in summer and warm in winter,with a regular supply of fresh air and light. Theguidelines given in 6.1 to 6.3 shall be adhered to.

6.2 Abattoir - In meat houses and abattoirs, inhalls where meat or carcasses are hung, atemperature of not greater that1 iS”C would berequired and air-conditioning may be required. Inunrefrigerated work rooms, ample artificial lightand ventilation shall be provided by electricalmeans. The overall intensity in every abattoirshall not be less than 200 lux throughout theslaughter hall and workroom and at places wheremeat inspection is carried out. the illuminationshall be at least 500 lux.

6.1 Poultry Housing - A minimum of 14 hours 6.3 Farm Cattle Housing - In large dairy farms,day length shall be provided to the birds and roof-lights shall be provided to give 50-200 lux ofartificial lighting shall be provided for the-same.For the purposes, IW (GLS) or SW (fluorescent)

artificial lighting. The lamps shall be hung at/ aheight not less than 2 m above floor level.

per bird or I W per 28-38 cm are consideredadequate. The light sources shall be hung at aheight not less than 1.8 m above floor. Forpoultry sheds of 6 m width and below, one row ofbulbs in the centre shall be adequate. For sheds oflarger width two rows df lamps properlyinterspaced may be desirable.


7.1 Before commissioning the installation shall betested and inspected as given in Part l/See IO ofthe Code.

8. MISCELLANEOUS P.ROVlSlONS

8.1 For large scale livestock keeping, such as in adairy farm, it shall be essential to provide:

a) a warning device for indicating failure of aircirculation system; and

b) for continuity of supply, a fast acting.emer-gency supply system is recommended.

8.2 Electric Fences -- Where electric fences are in*the vicinity of overhead l ines, appropriatedistances shall be observed to take account ofinduction currents, falling lines, etc.

Any earth electrode connected to the earthterminal of an electric lfence controller shall beseparate from the earthing system of any othercircuit and shall be situated outside the resistancearea of any electrode used for protective earthing.

8.3 Circuits of wirings which are onlyoccasionally used, for example, during threshingtime, shall be fitted with a separate switch markedaccordingly.

PART 6 ELECTRICAL INSTAI.I.ATIONS IN ACRICI:I:Fl’RAI. PREMISES 239

TiONAL E L E C T R I C A L C O D EP A R T 7

PART 7 ELECTRICAL INSTALLATIONS INHAZARDOUS AREAS

O . F O R E W O R D

0.1 Hazardous atmosphere is the atmosphere where any flammable gas or vapourin a concentration capable of ignition occurs. Any area, where during normaloperations a hazardous atmosphere is likely to occur in sufficient quantity toconstitute a hazard had to be treated in a special manner from the point of thedesign of electrical installation.

0.2 Many liquids, gases and vapours which in industry are generated, processed,handled and stored are combustible. When ignited these may burn readily and withconsiderable explosive force when mixed with air in the appropriate proportions.With regard to electrical installations, essential ignition sources include arcs, sparksor hot surfaces produced either in normal operation or under specified faultc o n d i t i o n s .

0.3 This Part of the Code is intended to provide guidelines for electricalinstallations and equipment in locations where a hazardous atmosphere is likely tobe present with a view to maximizing electrical safety. The scope of this Parttherefore includes installations in hazardous areas such as petroleum refineries andpetrochemical and chemical industries. The requirements laid down herein are inaddition to those specified in Part 4 of the Code. Some examples of industriallocations which require application of the guidelines in this Part are given inAppendix D.

0.4 It is recognized that when electrical equipment is to be installed in or near ahazardous area. it is frequently possible. by taking care in the layout of theinstallation, to locate much of the equipment in less hazardous or nonhazardousareas and thus reduce the amount of spcciai equipment required.

NOTE -- Hazardous areas can be limited in extant by constructlon measures. that is, walls or dams.Ventilation or application of protective gas will reduce the probability of the presence of explosive gasatmosphere so that areas of greater hazard can be transformed to areas of lesser hazard or to non-hazardous areas.

0.5 This Part includes generalized statements and recommendations on matters onwhich there are diverse opinions. It is, therefore, important that sound engineeringjudgement should be exercised while applying these guidelines.

0.6 While preparing this Part, several standards for electrical equipment forexplosive atmospheres have been referred to. These standards are listed inAppendix A. Some of these standards deal with particular construction techniques,others with aspects of standardization which are relevant to more than onetechniques.

0.7 As distinct from the hazardous areas in buildi& on the surface, environmentalconditions in mines demand special consideration. This Part of the Code does notinclude provisions for installations in underground mines.

1. SCOPE

1.1 This Part of the Code covers recom-mendations for clcctrical installations in chemicalindustries, petroleum refineries and other similarareas where halard\ of explosion due to gases andvapours exist, and in which flammable gases andvolatile liquids arc processed. stored, loaded,unloaded or otherwise handled.

1.2 In addition to the recommendations given inthis Part. the electrical installations in hazardousareas shall complv. with the requirements forindustrial installatcon in nonhazardous areas laiddown in Part 4 of the Code.

1.3 This Part does not apply to installations inhazardous areas having ignitable dusts and fibres.This Part also doe:, not apply to the areas inunderground mines.

1.4 In any plant installation irrespective of sizethere may be numerous sources of ignition apartfrom those associated with electrical apparatus.Precautions may be necessary to ensure safety butguidance on this aspect is outside the scope of thisPart.

2. TERMINOLOGY

2.0 For the purpose of this Part, the followingdefinitions shall apply, in addition tb those givenin Part .I of the Code.

2.1 Flammable Material - A flammable materialis a gas, vapour, liquid and:or mist which canreact continuously with atmospheric oxygen andwhich may therefore, sustain fire or explosionwhen such reaction is initiated by a suitable spark,flame or hot surface.

2.2 Flammable Gas-Air Mixture A mixture offlammable gas. vapour or mist with air, unde’ratmospheric conditions. in which after ignition,combustion spreads throughout the unconsumedmixture.

2.3 Hazard -~ The presence, or the risk ofpresence. of. a flammable gas-air mixture.

2.4 Hazardous (Flammable) Atmosphere - Anatmosphere containing any flammable gas orvapour in a concentration capable of ignition.

2.5 Hazardous Area ~ An area where duringnormal operations. a halardous atmosphere islikely to occur.

2.6 Exvalues or the concentration of a flammable gas orP

losive (Flammable) Limits ~- The extreme

vapour in air under atmospheric conditions.which can be ignited by an electrical arc or spark.These limits are called the ‘lower explosive limit’(LEL) and the ‘upper explosive limit’ (UEL).

2.7 Flammability Range -~ The range of gas orvapour mixtures with air between the flammablel imi t s over which the gas mix tures a recontinuously explosive. (i

2.3l~~mmable Gas or Vapour - Ga: or vapour. w h e n mlxed with a i r In c e r t a i n

proportions. will form an ha/ardou~ atmosphere.

2.9 Flammable I>iquid A liquid capable ofproducing ;I flnmmable \apour. gas or mist underan!’ foreseeable operating conditions.

2.10 Flammable Mist Droplets of flammableliquid. dispersed in air. so as to form a ha;rardousatmosphere.

2.1 I Liquefied flammable Gas Flammable gaswhich. under normal ambient pressures andtempet-atures. is in gaseous state but which ishandled in a liquid state under the appliedconditions of pressure and ‘or temperature.

2.12 Flash Point The temperature at which theliquid gives 50 much vapour that this vapour.when mixed with air. forms an ignitable mixtureand gives a momentary flash on application of asmall pilot flame under specified conditions oftest.

2.13 Boiling Point The ternpcrature of a liquidboiling at an ambient pressure ot lOI.. kPa.

2 . 1 4 I g n i t i o n T e m p e r a t u r e ~~~ T-he l o w e s ttemperature at which ignition occurs in a mixtureof explosive gas and air when the m e t h o dspecified in IS : 7X20-1975* is followed.

2.15 Source of Release A source of release is apoint or location from which a gas, vapour, mistor liquid may be released into the atmosphere sothat a hasardous atmosphere could be formed.

2.16 Restricted Release ~~ A release (normal orabnormal) of flammable gas or \‘apour which canbe diluted below the lower flammable limit.

2.17 Unrestricted Release ~ A release (normal orabnormal) of flammable gas or vapour whichcannot be diluted below the lower flammablelimit.

2.18 Adequate Ventilation -- Adequateventilation IS that which IS sufficient to preventaccumulations of significant quantities of gas-airmixtures in concentration over one-fourth of thelower flammable limit.

A adequately ventilated area could be naturallyventilated or artificially ventilated.

2.19 Re’lative Density of Gas or Vapour -- Thedensity of a gas or a vapour related to the densityof air at the same prcssurc and the sametemperature.

2.20 Nonhazardous (Safe) Area - An area nopart of which has within either a haT.ardous areaor a remotely hazardous area.

2.2 1 Electrical Apparatus for Hazardous AreasElectrical apparatus which will not ignite rhe

*Methods of test for Ignition tempcraturc\.

NATIONAL ELECTRICAL CODE244

surrounding flammable atmosphere in which it isused.

2.22 Ignition Capable Apparatus - Apparatuswhich in normal operation produce sparks, hotsurfaces. or a flame which can ignite a specificflammable mixture.

2.23 Safety Measures- Measures taken toensure that electrical apparatus cannot cause anexplosion.

2.24 Type of Protection - Specific measuresapplied to electrical apparatus to prevent ignitionof a surrounding flammable atmosphere by suchapparatus.

2.25 Maximum Surface Temperature -Thehighest temperature attained under practicalconditions of operation within the rating of theapparatus (and recognized overloads, if any,associated therewith) by any part of any surface(internal or external) the exposure of which to aflammable atmosphere may involve a risk.

2.26 Flame Arrester -~ A device for releasing gasfrom an enclosure in such a way that in case of aninternal explosion there is no appreciable increasein internal pressure and the released gas will notignite the surrounding flammable atmosphere.

2.27 Inert Gas - A gas which cannot be ignitedwhen mixed, with a flammable gas or vapour inany concentration.3. STATUTORY REGULATIONS

3.1 In following the recommendations of thisPart, the various statutes and regulations in forcein the country, applicable to the installation anduse of electrical apparatus in hazardous areasshall be kept in view.

3.2 Attention is invited to the fact that themanufacture and use of equipment in hazardousareas is controlled by the statutory authoritieslisted below for the area of their jurisdiction:

4

b)

c)

The Directorate General of Mines Safety,Dhanbad (Bihar);

The Chief Controllerate of Explosives,Department of Explosives. Nagpur (Maha-rashtra); and

The Directorate General Factory AdviceServices and Labour Institute, Bombay(M aharashtra).

3.3 Testing - Equipment to be installed in hazar-dous area have to be certified by a recognizedtesting authority. Facilities for testing .in thisregard are available at Central Mining ResearchStation (CMRS). Dhanbad. Bihar.

3.4 Marking of equipment shall confdrm toIS : 824l-l976*.

4. FUNDAMENTAL CONCEPTS

4.1 Flammable gases and vapours may cause a

*Method of marking for identifying electrical equipment forexplosive atmospheres.

f’ire or explosion when the following three basicconditions are satisfied:

a) Presence of sufficient quantity of a flam-mable gas or vapour,

b) Mixing of flammable gas or vapour with airor oxygen in the proportions required toproduce an explosive or ignitable mixture,and

c) Occurrence of ignition.

In applying this principle to any potentialhazard the quantity of the substance that might beliberated. its physical characteristics and thenatural tendency of vapours to disperse in thea tmosphere sha l l be recognized. Flammablesubstances, the potential release of which shall beconsidered in area classification of electricalinstallations (see 5) include the followings:

a) Nonliquefiable gases,

b) Liquefied petroleum gas, and

c) Vapour or flammable gas.

4 . 2 I t i s r e c o m m e n d e d t h a t p l a n t s a n dinstallations in which flammable materials arehandled or stored be so designed that the degreeand extent of hazardous areas are kept to aminimum. Similarly consideration should begiven to design and operation of processequipment to ensure that even when it isoperating abnormally, the amount of flammablematerial released to the atmosphere is minimizedin order to reduce the extent of the area madehaz.ardous.

Once a plant has been classliied, it is importantthat no modification to equipment or operatingprocedures are made without discussion withthose responsible for the area classification.Unauthorized action may invalidate the areaclassification.

It is necessary to ensure that process equipmentwhich has been subjected to maintenance shall becarefully checked during and after re-assembly toensure that safety aspect or integrity of theoriginal design has been maintained before it isreturned to service.

4.3 Where it is necessary to use electricalapparatus in an environment in which there maybe a flammable atmosphere and it is not possibleto:

a) eliminate l ike l ihood of a f lammableatmosphere occuring around the source ofignition, or

b) eliminate the source of ignition.

Then .measures should aim at reducing thelikelihood of occurrence of either or both of theabove factors SO that the likelihood of coincidenceis SO small as to be negligible.

4.4 In most practical situations where flammablematerials are used it is difficult to ensure that a

PART 7 ELECTRICAL INSTALLATIONS IN HAZARDOUS AREAS 245

nazardous atmosphere will never occur. It mayalso be difficult to ensure that the electricalapparatus will never give rise to a source ofignition. Reliance is therefore placed on usingelectrical apparatus which has an extremely lowlikelihood of creating a source of ignition insituations where a flammable atmosphere has ahigh likelihood of occurring. Conversely wherethe likelihood of a flammable atmosphere isreduced, electrical apparatus which has anincreased likelihood of becoming a source ofignition may .be used.

5. CLASSIFICATION OFHAZARDOUS AREAS

5.0 General5.0.1 The objective of the hazardous area

classification is to ensure an adequately safe levelof operation of electrical apparatus in flammableatmospheres using the fundamental conceptsoutlined in 4.

The basis for hazardous area classificationrecognises the differing degrees of probabilitywith which flammable atmospheres (explosiveconcentrations of combustible gas or vapour) mayarise in installations in terms of both thefrequency of occurrence and the probableduration of existence on each occasion.5.1 Area Classification - The area classificationis given in Table I.

5.2 Extent of Hazardous Area

5.2.1 Properties qf Flammable Materials

5.2.1.0 A complete knowledge of the physicalproperties of the flammable*materials involved isessential for classifying a hazardous area.Properties< of primary interest from an ignitionstandpoint are:

a) relative density,b) flammable limits,c) flash point,d) volatility,e) ignition temperature, and

f) ignition energy.

Some of these characteristics have a directinfluence on the degree and extent of hazardousareas while the others affect the design ofelectrical equipment.

5.2.1.1 Relative dertsirt* - Where a substantialvolume of gas or vapour is released into theatmosphere from. a localised source, a relativedensity less than one, that is, lighter-than-air. forthe combustible indicates the gas or vapour willrise in a comparatively still atmosphere. A vapourdensity greater than one, that is, heavier-than-air,

246

ZONES(1)

Zone 0

Zone I

Zone 2

TABLE I AREA CLASSIFICATIONDESCRIPTION REMARKS

(2) (3)

An area in which This classification is appli-a flammable cable only where the harardatmosphere is will exist continuously. In thepresent continu- petroleum industry such aously. or is condition is rarely encounter-present for long ed except in confined spaces.periods such as the vapour space of

closed process vessels. storagetanks or closed containers. InZone 0. any arc or sparkwould almost certainly lead tofire or explosion. Any electri-cal apparatus must afford adegree of protection as nearas practicable to absolute. Itis recommended to avoidinstalling electrical equip-ment in Zone 0 areas to theextent possible.

An area in which In Zone I, the hazard is likelya flammable to occur at any time re-atmosphere is quiring fullest practicablelikely to be pre- application of measuressent periodicallyor occasionallyduring normaloperation

An area in which Zone 2 is applicable to areasa flammable where hazard is unlikely and.atmospnere IS may be caused only by thelikely to occur in Hrghly improbable and simul-normal operation taneous occurrence of an arcand* if it does or spark together with aoccur it will exist hazardous atmosphere arisingfor a short time out of failure of conditionsonly of control. It presupposes

that any abnormal occurrenceis rapidly dispersed so thatpossible contact with electri-cal apparatus is of minimumduratton

Norc: I - Earlier. classified areas were called divisions.

NOTE 2 -- This area classification deals only with risks dueto combustible gases and vapours and combustible mists. Itdoes not deal with dusts since these material can be quiescantfor long periods of time until they are disturbed intosuspension by a suitable mechanism (ser also 1.3).

NOTE 3 - By implication, an area not classified as Zone 0.Zone I or Zone 2. is deemed non-hazardous or safe and nospecial precautions are necessary.

indicates the gas or vapour will tend to sink, andmay thereby ‘spread some distance horizontallyand at a low level. The latter effects will increasewith compounds of greater relative vapourdensity.

NOTE - In process industries. the boundary betweencompounds which may be considered lighter-than-air is set ata relative vapour density of 0.75. This limit is chosen so as toprovide a factor of safety for these compounds whose densitiesare close to that of air. and where movement may not,therefore. be predicted without a detailed assessment.

5.2.1.2 Flammable limits - The lower the‘lower flammable limit’ the larger may be theextent of the hazardous area.


5.2.1.3 F l a s h point - A flammableatmosphere cannot exist if the flash point issignificantly above the relevant maximumtemperature of the flammable liquid. The lowerthe flash point. tk larger may.be the extent of thehazardous area.

5.2.1.4 Volatility - Boiling point can be usedfor comparing the volatility of flammable liquids.The rhore volatile a liquid and the lower its flashpoint, the more closely it approximates aflammable gas.

5.2.1.5 Ignition temperature ar;ld ignitionenergy - Ignition temperature and ignitionenergy of a flammable gas or vapour are takeninto account in the design of electrical apparatusfor hazardous areas so that these dd not presentan ignition risk.

5.2.2 Factors A,[fecting Extent of Hazard

5.2.2.0 In addition to the properties oftlammable materials involved, following factorsneed to be considered for determining the degreeand extent of hazardous areas while applying theguidelines given in IS : 5572 (Part I)-l978*

5.2.2.1 Risk points - Normal operation is thesituation in which all plant equipment is operatingwithin its design parameters. Minor releases offlaimable material may be part of normaloperation’ but leakage which entail repair or shutdown are not part of normal operation.

Some examples of persistent risk points are asfollows:

a)

b)c)

4

Interior of pressure vessels and pipes contain-ing gas-air mixtures;Free space above liquid level in tanks;Free space immediately above open dipping,baths, etc; andThi immediate vicinity of vapour exhaustsand liquid outlets where these are designedto discharge as part of normal plantfunction..

Examples of occasional risk points are theimmediate vicinity of mechanical glands, sealsrelying on wetting by the fluid being pumped andother localized spillage points and of vapourexhausts and liquid outlets designed to dischargeonly on plant malfunction.

5.2.2.2 Temperature ef process liquid - Theextent of a .hazardous area may increase withincreasing temperature of process liquid providedthe temperature is above the flash point. It shouldbe noted the liquid or vapour temperature afterthe release may be increased or decreased by theambient temperature or other factors (forexample. a hot surface).

*Classification for hazardous areas (other than mines) forelectrical installations: Part I Areas having flammable gasesand va pours (/irsr rr16ion).

N OTE - Some liquids (such. as certain halogenatcdhydrocarbons) do not possess a flash point although they arecapable of producing a flammable atmosphere: in these cases,the equilibrium liquid temperature corresponding to saturatedconcentration at lower flammable limit should be comparedwith the relevant maximum liquid temperature.

5.2.2.3 Concentrat ion of vapour - Forflammable liquids, the concentration of thereleased vapour is related to the vapour pressureat the relevant maximum liquid temperature. Thelower the initial boiling point the greater thevapour pressure for a given liquid temperatureand hence the greater concentration of vapour atthe release source resulting in greater extent ofhazardous area.

5.2.2.4 Rate sf release- The extent ofhazardous area may increase with increasing rateof release of flammabie materiai.

5.2.2.5 Release velocity -- Due to an improved‘dilution for release of flammable gases, vapoursand/or mists in the air, the extent of hazardousarea may decrease if, with constant release rate,the release velocity increases above that whichcauses turbulent flow.

NOTE - Elevated or depressed sources of release will alterthe areas of potential hazard.

5.2.2.6 Air current - Air currents maysubstantially alter the ‘outline of the limits ofpotential hazard. A very mild breeze may serve toextend the area in those directions to whichvapours might normally be carried. However, astronger breeze may so accelerate, the dispersionof vapours that the extent of potentiallyhazardous area would be greatly reduced.

. 5.2.2.7 Ventilation - With an increased rateof ventilation, the extent of hazardous area maybe reduced. The extent may also be reduced by animproved arrangement of the ventilation system.

5.2.2.8 Obstacles - Obstacles (for example,dykes, walls) may impede the ventilation and thusmay enlarge the extent. On the other hand, theymay limit the mo?ement of a cloud of anexplosive gas atmosphere and thus may reducethe extent.

5.2.2.9 For vapours released at or nearground level, the areas where potentiallyhazardous concentrations are most likely to befound are below ground, thoSe at ground are nextmost likely, and as the height above groundincrease, the potential hazard decreases.

NOTE - For lighter-than-air gases. the opposite is true. therebeing little or no potential hazard at and below ground andgreater potential hazard above ground.

5.2.3 Internal Hazards

5.2.3.0 In cases where electrical apparatus,like those used for measurement and control ofprocess variable, are connected directly to gas or aliquid process equipment, this may introduceadditional source of internal and/or externalrelease and consequently influence the externalarea classification.


5.2.3.1 The hazards created inside theelectrical apparatus by an internal release offlammable gas or vapour may be compared to theexternal area classification as follows:

a )

b)

c)

Where pressurization with inert gas is appli-cd. the internal releases cannot create aflammable gas atmosphere, because nooxygen is present.

Where dilution with air is applied in caseof a restricted normal release the internalhazards are comparable to those in a safearea. This applies also when the abnormalrelease (when occurring) would be restricted.When, however, the abnormal release wouldbe unrestricted, the internal hazards arecomparable to the external hazards inZone 2.

In all other types of protection, the internalhazards are comparable to the externalhazards in Zone 2. provided that there is nonormal release and that an abnormal releasewould be very infrequent and of a relativelyshort duration. When there is a normalrelease, the internal hazards are comparableto the hazards in Zone 0 and the abnormalrelcasc is not relevant.

5.2.3.2 When apparatus in which the internalhazards arc comparable to Zone 2 is installed in asafe area’ or in Zone 2. the internal hazardsdetermine the actual hazard condition. but whenthe same apparatus is installed in Zone I or Zone0 the external hazards determine the actualhazard condition. When an apparatus in vvhichthe internal hazards arc comparable to Zone I isinsta!led in a Zone 0 hazardous area, the areaclassification would determine the actual hazard.

5 . 2 . 4 E.rtrn[ o.1’ Zonrs of Ha:ard

5.2.4.1 ‘The treatment of hazardous area, fromthe point of view of determining the extent ofhazardous zones (and their classification) aroundthe source of halard differ in the following broadsituations:

a) Open-air situations (freely ventilated processarea):

i) Source of hazard located near groundlevel. and

ii) Source of hazard above ground level,

b) Enclosed premises and surrounding area(process area with restricted ventilation),

c) Storage tanks:

i) Floating roof. and

ii) Fixed roof tank with vent.

5.2.4.2 Detailed guidelines. on the above situa-tions can be had from IS : 5572 (Part I)-1978*.

*<‘L\sification of hazardous areas (other than mines) forclcctrii‘al installations: Part I Areas having flammable gasesa n d vapours (/ir.rr rc~~Y.tion).

248

6. SPECIFIC GUIDELINES FORELECTRICAL INSTALLATIONSIN HAZARDOUS AREAS

6.1 General

6.1.1 Mechanical Slrength All apparatusshall be installed with due regard to the possibilityof external mechanical damage. Where adequateprotection cannot be ensured. for example. by,location, reference should be made to the impactt e s t r equ i rements accord ing to IS : 82b9-1976* for the apparatus before deciding on anyadditional measures such as the provision ofguards for transparent parts.

6.1.2 Earthing and Bonding

6.1.2.1 Earthing shall be in accordance withPart I /Set I2 of the Code. The connectionbetween metal part to be grounded and thegrounding conductor shall be made securemech.anically and electrically by using adequatemetallic fitting. The earthing conductors shall besufficiently strong and thick, and the portions ofconductor which are likely to be corroded ordamaged shall be well protected. Groundingconductors which shall not reach a hazardouslyhigh temperature due to the anticipated maximumearthfault current flowing, shall be used.

6.1.2.2 Protection against lightning shall beprovided in accordance with Part I /Set 15 of theCode. Specific guidelines for installations inhazardous locations are given in Appendix E.Interconnection system with other buried metalscrviccs and/or earth terminations for equipmentgrounding for the purpose of equalizing thepotential distribution in the ground shouldpreferably be made below ground.

6.1.2.3 Portable and transportable apparatusshall be grounded with one of the cores of flexiblecable for power supply. The earth continuityconductor and the metallic screen whereverprovided for the flexible cable should be bondedto the appropriate metal-work of the apparatusand to earthing pin of the plug.

6.1.2.4 Efficient bonding should be installedwhere protection against stray currents orelectrostatic charges is necessary.

6.1.2.5 Earthing and bonding qf pipelines andpipe-racks ~ Unless adequately connected toearth elsewhere. all utility and process pipelinesshould be bonded to a common conductor bymeans of earth bars or pipe clamps and connectedto the earthing system at a point where thepipelines enter or leave the hazardous area exceptwhere conflicting with the requirements ofcathodic protection. In addition, it isrecommended that steel pipe racks in the processunits and off-site areas should be earthed at every25 m.

*Specification for electrical equipment with type ofprotection ‘n’.


6.1.3 Automcrli” Ekclricai Proreclion

6.1.3.1 It is essential that the severity andduration of faults internal or external to theelectrical apparatus be limited by external meansto values that can bc sustained by the apparatuswithout disruptive effect.

6 .1 .3 .2 Al l c i r cu i t s and appara tus inhazardous areas shall be provided with means toensure disconnection quickly in the event ofexcessive overloads, overcurrent, internal short-circuit or earth-fault conditions. In case ofdistribution systems with isolated neutral, anautomatic earth-fault alarming device may bec o n s i d e r e d a d e q u a t e , i n a d d i t i o n t o ’overload/overcurrent and short-circuit protection.

6.1.33 Protection and control apparatus shallbe normally located in a non-hazardous area.Where its installation in a potentially hazardousarea cannot be avoided, such apparatus shou.ld beprovided with the appropriate type of protection.

6.1.3.4 Apart from sen-powered apparatusand handlamps, earth-leakage protection or earthmonitoring, or both should be included in theprotection of the portable and transportableapparatus. Protection *of the circulating-currenttype which automatically cuts off the supply inthe event of the earth continuity conductorbecoming disconnected, may, with advantage, beadopted as’ the earth-monitoring device.

6.1.4 Isolarion

6.1.4 .1 All electrical circuits should beprovided with an effective means of completecircuit isolation, including the neutral. Suchmeans of isolation should be provided for eachi t em of e lec t r i ca l appara tus and /or eachsubcircuit.

6.1.4.2 The means of isolation, when locatedin a hazardous area, shall be a switch whichbreaks all poles, including the neutral, and whichis provided with an appropriate type of protectionagainst explosive hazards. This applies equallv tosingle ptiase subcircuits. When the means ofisolation is located in a non-hazardous area, theswitch shall break all poles, the neutral beingisolated by a removable link. The means ofisolation shall be capable of being locked in the‘OFF’ position.

6.1.4.3 When the means of isolation is notimmediately adjacent to the associated ap’paratus,effective provision should be made to prevent therestoration of supply to the apparatus while ther i sk o f exposure o f l ine conduc tors to aflammable gas-air mixture continues.

6.1.5 Operation and Maintenance

6.1.5.1 None of the protection techniques forelectrical equipment for hazardous atmospheresare effective unless the apparatus is operatedwithin the limits indicated by its nameplatemarking and is properly maintained according tothe recommendations of appropriate IndianStandards.

6.1.5.2 Care shall be taken when inspectingequipment in hazardous areas; circuits shall bemade dead before removing covers. Flexiblecables are a potential source of hazard, theyshould be frequently inspected, together with theportable apparatus. Equ ipment shou ld beexamined for mechanical faults, cracked glasses,deterioration of cement, slackened conduit jointsand corrosion. Electrical tests should be carriedout at fixed. intervals.

6.2 Wiring Installation

6.2.0 General- Types of wiring and systemswhich may be used for installation in hazardousareas are:

a) cables drawn into screwed, solid drawn orseamless conduits, and

b) cables which are otherwise suitably pro-tected against mechanical damage.

Requirements tor the installation of generalpower systems’may not apply to the installationof apparatus and systems with type of protection‘i’ (intrinsic safety). For intrinsically safe circuits,there is normally no need to have specialenclosures for the conductors. However, someprotection will have to be afforded to suchconductors primarily to prevent contact betweenconductors of intrinsically safe circuits and thoseof any other system, to avoid the possibility ofarcing occurring at the point of contact orinvasion of the intrinsically safe circuits bycurrent arising from contact or electrostatic orelectromagnetic induction. In addition, thec o n d u c t o r s s h o u l d b e p r o t e c t e d a g a i n s tmechanical damage (see 6.2.1.5).

The diameter of each strand of the conductorshall be not less than 0.300 mm of copper orequivalent size of conductor in the case ofaluminium conductors as specified in relevantIndian Standard.

For (b) the following types of cables may beused in principle:

1)2)

3)

4)

5)

Lead-sheathed and armoured cable,

Plastics or rubber-sheathed steel screenprotected or armoured cable, with sheathoverall,

Cables enclosed in a seamless aluminiumsheath with or without armour, with anouter protective sheath,

Mineral insulated metal sheathed cable, and

Braided screen-protected flexible cables.

Unarmoured l ead-covered cab le i s no tacceptable. The sheath of a metal-sheathed cableshould not be used as the neutral conductor.

6.2.1 Factors Ajfecling Choice of WiringSvsrem

6.2.1.1 Screwed steel conduit systems aresatisfactory.for many situations but should not be


u~i bhcrc vibration might cause fracture orloosening of joints and where excessive stress maybe imposed as a result of its rigidity or wherecorrosion or excessive internal condensation ofmoisture is likely to occm.

6.2.1.2 Lead-sheathed and armoured cablesarc suitable for underground installation. Steel-Hire armour is: preferred for underground use.

6.2.1.3 PVC-insulated and armoured cable.complying with IS : 15S4 (Part I)-l976* with ancxt ruded plastic outer sheath may be used l.orabove ground or underground installation. Lead-sheathed cable should be usal Hhcrc spillagesmay affect the intcgriti of the cable and or 3110~migration of the liqujd through rhc cable.

6 .2 .1 .4 Fo r telecc,mmunication c i r cu i t s .plastic-insulated and armoured tclcphonc cablesmay be used.

6.2.1.5 In Zone 0 areas only intrinsically hal’ccircuits shall be installed and its uhe shall be keptto an unavoidable minimum. Wiring\ of circuitswhich have been approved as intrlnsically safemay follow’ the requirements of generaI electricalwiring except that the following requirement\shall

a)

b)

c)

d)

e)

-be obserced:

The conditions of use laid down on the testcertificate issued by the approving authorit)shall be observed.

The wiring shall be so madc.as to avoid con-tact with other circuits,

l-he w i r i n g s h a l l b e \o made as to avoidelectromagnetic or clcctro5tatic i nduc t i onfrom other cil-cuit(s),

The wir ing \hiill be adequateI! p ro tec tedagainst mechanicai damage. and

Aluminium :trmouI-ed or sheathed cableshall not be used in Zone 0 areas.

6.2.2.1 Correctly designed terminations comp-lete with armour clamp\ shall be prokidcd forarmoured cable\. l-he a rmour i ng shou ld becarried into the clamps to pro\idc mechanicalsupport to the cable and to ensure electr icalcontinuity. Where such cable is Icad covcrcd andarmoured. the Iced sh(;ith should bc plumbed orm e c h a n i c a l l y g r i p p e d a n d waled and thearmouring should be carried O\CI the lcad joint.

6.2.2.2 Where circuit:, traverse 3 hazardousarea in passing front one non-ha/ardou.s area toanother, the uiring in the hazardous arca shouldc o m p l y w i t h the rc‘quirt’mcntc of thih htandald.

6.2.2.3 Where practicable. contact. eitherd e l i b e r a t e o r accidental, \houId bs a v o i d e dbetween apparatus, conduit or cable\, and an)

e q u i p m e n t o r pipework used fo r ca r ry ingcombustible gases, vapours or liquids.

6.2.2.4 Where, owing to particularcircumstances, contact between componentsreferred to in 6.2.2.3 is unavoidable. thearmouring, conduit or sheathing of the cableshould’ be bonded to the equipment or pipeworkin such a manner and at such intervals as toensure that under the worst fault conditions. thepassage of any current will not give rise toincendive sparking or bring about a tedperaturerise approaching the ignition temperature of thecombustible gas. vapour or liquid which may bepresent. Alternatively, in the case of cable theinsulation of the sheath may be sufficient toprevent danger.

6.2.2.5 ‘.Vhere cables or conduit pass througha f loor. wall. partition or ceiling. the holepro\,ided for them should be made good withcement or similar incombustible material to thefull thickness of the floor. wall, partition orceding, 50 that no space remains around the cablethrough which combustible gas liquid or vapourmight spread. Alternatively cable glands may beused for this purpose.

6.2.2.6 Where trunking. duets, pipes ortrenches’ are used to accommodate cables,precautions should be taken to prevent thepassage of combustible gases, vapours or liquidsfrom one ar-ca to another, and to prevent thecollection of combustible gases. vapours or liquidsin trenches. Such precautions may involve thesealing of trunking, ducts and pipes, and theadequate ventilation or sand filling of trenches.

6.2.2.7 Where an overhead supply line is usedfor either power or telecommunication circuits,. itshould be terminated outside the hazardous areaand be fitted at or near the terminal pole with aneffective surge-protection apparatus. The cableused to connect the o\,erhead line with theinstallation in the hazardous area should complywith the recommendations for wiring systems inha/ardous areas. Conduit should not be used if itis likelv to be subjected to vibration. The casing,armouiing or sheathing and armouring should beelectrically continuous and the end adjacent to thepoint of connection with the overhead line shouldbe bonded to the earth electrode of the overheadline. In addition. the casing or sheathing shouldbe independently earthed as near as possible tothe .junction of the cable with the installation andbonded to the earthing lead of any lightningprotective system associated with the hazardousarea. If convenient, a common electrode may beused for this independent earth and for thelightning-protective system of the installation.

Where the overhead line supplying a buildingfo rm ing :I hazardous area is supported by thebuilding, a n d the connect ing cable to theinstallation consequently is short. the earthelectrodes for the surge-protection apparatus onthe overhead line may be used for earthing thecable sheath or taxing and for any lightning

250 NATIONAL El.E<l RIC‘At. c-ODE

protective system associated with the hazardousarea.

6.2.2.8 The wiring entry to the apparatus,direct or indirect, should maintain the type ofprotection used.

6.2.2.9 Unused cable entries in electricalapparatus should be closed with plugs suitable forthe type of protection used.

6.2.2.10 Where cable terminals are used inapparatus and accessories with the type ofprotection ‘e’ or ‘n’they shall be fixed in positionso as to ensure maintenance of the creepage andclearance distances as specified in IS : 638l-1972*and IS : 8289-1976t.

6.2.3 Laying qf Conduits

6.23.1 Conduits shall be solid-drawn orseamless, screwed and galvanized.

Conduit, having an exiernal diameter of morethan 25 mm, should be fitted with a stopper boxat each point of connection with apparatus orfittings, unless a self-contained’ assembly,independent of external connections, has beencertified.

6.2.3.2 Elbows of the solid type may be usedfor the immediate connection of conduit toapparatus.

6.2.3.3 The lengths of the screwed part of anyconduit should be in accordance with therequirements of IS : 2148-1968:.

6.2.3.4 Where, in a run of conduit. it isnecessary to employ a joint other than a screwedcoupler, certified unions approved for flame-proofpurposes should be used. The use of runningcouplings is not recommended but where it isimpracticable to avoid their use, factorymadeassemblies should be used and the runningcoupling should be secured by locknuts.

6.2.3.5tight andlocknuts.

All screwed joints should be pulled upshould, in addition, be provided with

6.2.3.6 Surface-mounted conduit should besupported by spacing saddles.

6.23.7 Elbows or tees, other than those of theinspection type, should not be used except for theimmediate connection of conduit to apparatus,and all inspection fittings should be of thefiameproof type,

6.2.3.8 All joints in an assembly of conduitshould be painted aftet assembly with moisture-resisting paint to inhibit ,the development of rust.

NOTE -- It is important to ensure efficient earthing andbonding in a flameproof installation. In view of the operating

*Specification for construction and testing of electricalapparatus with ty e of protection ‘e’.

+Specification, for electrical equipment with type ofprotection ‘n’.

:Specification for flameproof enclosures of electricalapparatus (/irsf revision).

conditions associated. with the use of flameproof apparatus.attention is drawn to the necessity of ensuring that theresistance of all joints. including those in or hetwanflameproof enclosures and conduit. or cable sheaths andarmour. is such as to prevent a dangerous rise of temperatureor voltage from the passage of fault current. and that the totalresistance of the earth-fault current path. measured from anypoint in the installation. is such as to ensure reliable operationof the protection devices in all seasons.

6.2.3.9 Where a run of conduit, irrespective ofsize, passes from a hazardous area to a non-hazardous area. a stopper or sealing box orappropriate sealing device shall be inserted on theside remote from the hazardous area. There shallbe no union, coupling, box or fitting in theconduit between the sealing fittings and point atwhich the conduit leaves the hazardous locations.

6.2.3.10 Seals shall be provided within 450mm where conduit run is terminated on theapparatus.

6.2.3.11 Metal conduit containing no unions.couplings. boxes or fittings that passes through ahazardous location with no fittings less than 300mm beyond each boundary may not be sealed ifthe termination points of the unbroken conduitare in non-hazardous locations.

6.2.3.12 For canned pumps. processconnections for instruments, etc. that dependupon a single seal diaphram or tube to preventprocess fluids from entering the electrical conduitsystem, an additional approved seal or barriershall be provided with an adequate drain betweenthe seals in such a manner that leaks would beobvious.

6.2.3.13 Where there is a probability that anyvapour or moisture in the air may he condensedinto liquid within the conduit runs, boxes orsealing fittings, proper means shall be provided toprevent accumulation of or to permit drainage ofsuch liquid periodically.

6.2.4 Laving qf Cables

6.2.4.1 Cable systems include cables laidabove ground or cables laid underground directlyburied, in concrete trenches, or in cable ducts.The types of the cable for use in hazardous areasshall be as specified in this Section.

6.2.4.2 Cable runs should. where practicable,be uninterrupted, that is. continuous andtherefore, free from intermediate joints. Wherediscontinuities cannot be avoided, either duringinstallation or subsequently, the apparatus usedfor, interconnection should be provided with thetype of protection appropriate to the zone.

6.2,4.3 All cables shall be provided withadequate mechanical protection. Cables shall beadequately supported throughout their length,care being taken to avoid excessive pressure whenclamp supports are used. Horizontal cables maybe carried on supports, cable trays or throughprotective troughs or tubes. Rising cab!es shouldbe clipped, cleated or otherwise attached tosuitable supports which provide adequatemechanical protection.

PART 7 ELECTRICAL INSTALLATIONS TN HAZARDOLIS AREAS 251

6.2.4.4 Where paper-insulated armouredcables are used, and particularly where suchcables ma)’ be exposed to high temperature.preference should be given to non-draining cables.In the case of other types of paper-insulatedarmoured cables, vertical runs should be avoided.

6.2.4.5 The passage of cables f rom ahiTardous area to a non-hazardous area should. ifncccssary, be provided with adequate means toprevent the transmission of flammable materialinto the non-hazardous area co:isidcration shouldalso bc given to the treatment of cables againstfire transmission.

6.2.4.6 Where trunking. ducts. pipes ortrenches arc used to accommodate cables,precautions should bc taken to ’ - precent thepassage of combustible gases. Lapours or liquidsfrom one area to another. and to prc\ent thecollection of combustible ga\es. Lapours or liquidsin trenches. Such precautions may involve thescaling of trunking. ducts and popes and theadequate ventilation or \and fil l ing of trenches.

6.2.4.7 Cables capable of tr-ansmitting gases orvapours through the core shall be sealed in thehazardous location in such a manner as to preventpassage of gases or vapours into a non-hazardouslocation.

6.2.4.8’ Correctly designed terminationscomplete with armour clamps shall be providedfor armourcd cables, the armouring should becarried into the clamps to provide mechanicaisupport to the cable and to ensure electricalcontinuity. Where such cables are load coveredand armoured. the lead sheath should be plumbedor mechanical ly gripped and sealed and thearmouring should be carried over the lead joint.

6.2.4.9 Cable glands. where used, shall beflameproof type for flameproof enclosure anddouble-compre\sion type for enclosure havingtype of protection other than flameproof.

6.2.4.10 Cable fittings for mineral insulatedcables shall be suitable for use with the appropriateapparatus to which they are to be attached.Fittings should bc arranged for scaling the cableinsulat ion and be pro\,idcd wi th means forensuring adequate earth continuity.

6 . 2 . 4 . 1 1 W h c r c elcctrol!,tic corros ion ofcopper sheath of mineral ,insulated cable mayresult from contact with walls or other surfaces towhich the cable is attached. it should be kept clearof such surface or covered with a protectivesheath.

6.2.4.12 Where there is r isk of mineral-insulated cables being exposed to excessivevol tages such as induc t i ve surges. surgesuppression devices should be fitted. Where surgesupprccsion devices are installed in hazardousareas. thq shou ld be su i tab ly explosion-protcctcd.

6.2.4.13 Aluminium sheathed cables, unlesssheathed with a protective covering. should not be

252

instal led in contact with Lvalls o r f l o o r ,Congideration should be giLen to the avoidance offrictignal contact N ith such cables.

b 6.2.5 Pl1r,q.c ntItJ So1~Xrl.v

6.2.5.1 Plugs and sockets for installation inZone 2 areas shall bc flameproof type. Those shallbe of interlocked switch t)pc.

6.2.5.2 Plugs and sockets shall be of the typethat provides for connections to the earthingconductor of the tlexible cables. I he contacts ofgrounding conductor shall be mechanically andelectrically of at least the same quality as the maincontacts and when the plug i:, inserted it shallmake connection before or at the same time as themain contact arc made.

6.2.6.1 Flexible cable of the types specifiedbelow may be used for connection between a fixedsource of supply and the portable transportableapparatus through flatieproof plugs and sockets:

a)

b)

cl

d)

Ordinaq tough rubber sheathed t lcxiblecables,

Ordinaq t o u g h pol!chloroprcnc shcathcdflexible cables.

Heavy tough rubber sheathed flexiblecables, and

Plastic insulated cables equivalent to ordi- .nary tough rubber sheathed tlcxible cables.

Use of screened cables are also permitted.

6.2.6.2 An effective cable clamping device sodesigned as not to damage the insulation of theflexible cable, should be provided at the points ofentry of the flexible cable to the apparatus andplug. In addition, means should be provided toprevent sharp bending of the cable at both pointsof entry.

6 . 2 . 7 Protet,tive M e a s u r e s ,f~om Datlgcrol:sSpark ing

6.2.7.1 Dangers jirom li\?e parts --- In order toavoid the formation of sparks liable to ignite theexplosive gas atmosphere, any contact with barelive parts other than intrinsically safe parts shallbe prevented.

Where th i s requ i remen t i s no t me t byconstruction other precautions shall be taken. Incertain cases a warning label may be sufficient.

6.2.7.2 Datlgers Jwm e.vposed and e.rtrancousc~nndwri~~e purrs It is impracticable to cover allpossible systems in this case but the basicprinciples on which safety depends are thelimitation of earth currents (magni tude andpotentials on equalizing conductors).


Guidance on permissible power systems is givenbelow:

a) If a Dower svstem with an earthed neutral isused: the tipi TN-S system with separateneutral (N) and protective conductor (PE)throughout the system is preferred.

The neutral and the protective conductorshall not be connected together, or com-bined in a single conductor, in a hazardousarea.

b)

cl

4

A power system of type TN-C (havingcombined neutral and protective functionsin a single conductor throughout the system)is not allowed in hazardous areas.If a type IT power system (separate earthsfor power system and exposed conductiveparts) is used in Zone I, it shall be protectedwith a residual current device even if it is asafety extra-low voltage circuit (below 50 V).

The type TT power system is not per-mitted in Zone 0.For an IT power system (neutral isolatedfrom earth or earthed through impedance),an insulation monitoring device should beused to indicate the First earth fault. How-ever equipment in Zone 0 shall be discon-nected instantaneously in case of the firstearth fault, either by the monitoring deviceor by a residual current operated device.For all power system installed in Zone 0irrespective of the voltages due attentionshould be paid to the limitation of earthfault currents in magnitude and duration.Instantaneous earth fault protection shallbe installed.

NoTt -~ It may also be necessary to provide instantaneousearth, fault protection devices for certain applications inZone I.

6.2.7.3 Potential equalization - To avoiddangerous sparking between metallic parts ofstructures, potential equaiization is alwaysrequired for installations in Zone 0 and Zone Iareas and may be necessary for installations inZone 2 areas. Therefore, all exposed andextraneous conductive parts shall be connected tothe main or supplementary equipotential bondingsystem.

The bonding system may include normalprotective conductors, conduits,, metal cablesheaths, steel wire armouring and metallic parts ofstructures but shall not include neutralconductors. The conductance between metallicparts of structures ‘shall correspond to a crosssection of at least IO mm’ of copper.

Enclosures need not be separately connected tothe equipotential bonding system if they aresecured to and are in metallic contact withstructural parts or piping which are connected tothe equipotential bonding system. For additionalinformation, se@ relevant Indian Standards.

However there are certain pieces of tiqui’pment,for example some intrinsically safe apparatus,which are not intended to be connected to theequipotential bonding system.

NATE-Potential equalization between vehicles and fixedinstallations may require special metins. for example. wheninsulated flanges in connecting pipelines are used.

6.2.7.4 Cathodically protected metallicparts -- Cathodically protected metallic partslocated in hazardous areas are live extraneousconductive parts which shall be consideredpotentially dangerous (especially if equipped withthe impressed current m&hod) despite their lownegative potential. No cathodic protection shallbe provided for metallic parts in Zone 0 unlessthey are specially designed for this application.

6.2.7.5 Electromagnetic radiation - Accountshould be taken of the effects due to strongelectromagnetic radiation.

6.3 Selection of Equipment

6.3.1 General

6.3.1.1 The selection of electrical apparatusfor explosive gas atmospheres is based on thegeneral principle that the likelihood of thesimultaneous presence of a hazardous atmosphereand a source of ignition is reduced. to anacceptable low level.

6.3.1.2 When the electrical apparatus does nothave an internal release of flammable material,the classification of the hazardous areasurrounding the electrical equipment decide theselection of an adequate type of protection.

6.3.1.3 When the electrical apparatus has aninternal release of flammable material, the actualhazard is a combination of the external andinternal hazards and both must be taken intoaccount when selecting an adequate type oprotection.,

6.3.1.4 The selected appartus will normallyhave a recognized type of protection and shouldalso be selected for the appropriate temperatureclass and the appropriate apparatus groupapplicable. Where gases of different degrees ofhazard exist in the same area, the type ofprotection appropriate for the highest degree ofhazards shall be applicable.

6.3.1.5 The selected electrical apparatus shallbe adequat@ly protected against corrosive andsolvent agencies, and against water ingress andthermal and mechanical stresses as determined bythe environmental conditions. These constructionrequirements should ensure that the protectionagainst explosion is not reduced when theapparatus is used in the specified conditions ofservice.

6.3.1.6 Particular consideration shall be givento the location of apparatus which incorporatesaluminium or light alloys in the construction of its


enclosure. These have been outlined in IS : 5571-1979* reference to which should be made (see a/so5.1 of IS : 2148-1981-q.

6.3.1.7 As electrical apparatus for flammablegas atmospheres require special safetymaintenance after they are installed, the selectionof electrical apparatus shall be made with fullconsiderations to the facility and frequency ofinspection and maintenance, preparation forspares and repairing materials and the extent ofallowable interruption of power supply duringmaintenance work.

6.3.1.8 It is advisable that the selection ofelectrical apparatus be made after ful lconsiderations hake been given not only to theinitial cost of installation but also to the expectedlife and expenses for operation and maintenanceof the apparatus.

6.3.1.9 Unless otherwise specified for aparticular equipment, the guidance provided inTable 2 shall be followed in the selection ofequipment for hazardous rlreas. However, anyequipment which in the opinion of the authorizedinspector affords a degree of safety not less thanthat afforded by the equipment specified may beaccepted as an alternative.

6.3.1.10 The necessity for equipment withflameproof. enclosures or other enclosures maysometimes be eliminated by the adoption ofspecial design. such as pressurized equipment.

6 .3 .2 Selec.tion P,otdrrrt~

6.3.2.1 In order that electrical apparatus maybe selected for use in hazardous area. thefollowing information is necessary:

a)

b)

c)

The classification of the area, that is--thelone (see 6.2.1.1).

The ignition temperature of the gas orvapour involved. or the lowest values ofignition temperature if more than one com-bustible material is present.

This will permit determination of the,temperature classification required for theapparatus. or the upper-limit temperaturefor any unprotected surface according toIS : 8239-1976 (WC 6.3.2.3).

The characteristics of the gas or vapourinvolved in relation to (see 6.3.2.3).

I) Ignition current or minimum ignitionenergy in the case of installations ofintrinsically safe apparatus. or

2) Safe gap data in the case of installationsfor flameproof enclosures_

Apparatus certified to the constructional anddesign requirements for a particular group mayalso be used with compounds of lesser risk and

*Guide for selection of electrical equipment of halardousareas

tSpecilication for flameproof enclosures for electricalapparatus.

which would be allocated therefore to J. lessergroup. sub.ject again to consideration oftemperature classification and chemicalcompatibility.

Similarly electrical apparatus which is designedso that it may be used with certain fammablematerials in a particular lone ma!’ be used withflammable materials in /one of lesser risk Hithoutrestriction provided it is determined that theflammable materials likeI!, to b e p r e s e n t arecompatible with the following characteristics ofthe apparatus:

a ) The apparatus grouping (where this isapplicable).

b) l’hc temperature classification. and

c) Chemical compatibility.

6.3.2.2 Sc~kcrion of’ t.~pc of protection -..- Theselection d t)‘pc of protection of the equipmentfor different lone of hazardous areas shall bemade an accordance with Tables 2. 3 and 4 asapplicable.

6.3.2,3 Temperature classes -- Besides thedanger 6f explosion caused by an electric spark orarc, there is also a danger of ignition at a hotsurface exposed to a flammable atmosphere. Themaximum surface temperature of any unprotectedsurface of electrical equipment should not exceedthe ignition temperature of the gas or vapour.

Flammable gases and vapours fall into fairlywell-defined groups when classified with referenceto their ignition temperature. To simplify themanufacture of apparatus, therefore, the per-mitted maximum surface temperature have beenclassified in’ IS : 8239-1976* a!, follows:

NOTE I --A‘ reference ambient temperature of 40°C isnormally assumed when apparatus is designed to operatewithin one of the temperature classes indicated above. Forspecial applications. the maximum surface temperture may bebased on a reference ambient temperature other than 40°C isused. the value will be clearly marked on the apparatus.

No’rE 2 It should.be noted that for apparatus with type ofprotection ‘d’ flameproof enclosure. the surface to beconsidered is the external surface. For apparatus with othertypes of explosion protection, internal surfaces are equallyimportant if the explosive gas air mixture has access to them

6.3.2.4 Apparafus groups - For the purposeof flameproof enclosures and intrinsic safety,gases and vapours have been classified accordingto the groups or subgroups of apparatus requiredfor use in the part icular gas or vapour

*Classification of maximum surface temperatures of electri-cal equipment for use in explosive atmospheres.


TABLE 2 TYPES OF PROTECTION FOR DIFFERENT HAZARDOUS AREAS

((‘lousrs 6.3.1 9 und 6.3.2.2)

Zi)xE TYPF OF PROTCCTION DESCRIPTION(1) (2) (3)

Zone 0 No electrical equipment should be allowed; lnrrrnsic Sq/er_v (Ex-i) (see IS : 5780-1980*)when this is not practicable. intrinsically safe A circuit or part of a circuit is intrinsically safeelectrical apparatus catagories ia and ih and when any spark or thermal effect producedassociated circuits should be employed Type normally (that is. by breaking or closing theof protection ‘i’. circuit) or accidentally (for example by short-

circuit or earth fault) is incapable. under pres-cribed test conditions, of causing ignition ofa prescribed gas or vapour.

An intrinsically safe apparatus is one in which allelectrical circuits are intrinpically safe. It isplaced in one of the following categories:

a) CU/CKWI, (Ex-i,)

Apparatus in this category is incapable ofcausing ignition in normal operation, or with asmgle fault, or with any combination of twofaults applied with a specified safety factor forcurrent and ior, voltage.

Zone I

Apparatus in this category is incapable ofcausing Ignition in normal operation. or withany single fault applied, with a specified safetyfactor for current and/or voltage.

a) Type of protection adequate for Zone 0.Flammproq/ Enclosure (Ex-d)

b) Flameproof equipment--Type ofprotection ‘d’

c) Pressurized enclosure-Type ofprotection ‘p’

An enclosure for electrical apparatus that willwithstand when the covers or other accL%!, doorsare properly secured, an internal explosion of theflammable gas or vapour which may enter it orwhich may originate inslde the enclosure. withoutsuffering damage and without communicating theinternal flammation to the external flammable gas

%r vapour for which it is designed, through anyjoints or structural openings in the enclosure(WC IS : 2148-1981,).

PTessL~ri:ed f?nnc/osure ( Ex-p) [see IS : 7389 (PartI)-197621 An enclosure for electrical apparatus inwhich the entry of flammable gas or vapour isprevented by maintaining the air (or other non-flammable gas) within the enclosure at a pressureabove that of the external atmosphere.

This type of protection has following categories(for choice see Table 3).

a) Pressurization with air and alarm in case of lessof air pressure [Ex-p( I)]

b) Pressurization with air and automatic switchingoff from electric supply in case of loss of airpressure [Ex-p(2)]

c) Pressurization with inert gas and alarm in caseof loss of inert gas pressure [Ex-p(3)]

d) Pressurization with inert gas and automaticswitching off from electric supply in case ofless of inert gas pressure [Ex-p(4)]

e) Dilution with air and alarm in case of loss of airsupply [Ex-p(S)]

f) Dilution with air and automatic switching offfrom electric supply in case of loss of air supply[Ex-P(6)]

*Intrinsically safe electrical apparatus and circuits (firs/ rethion).tspecification for flameproof enclosures of electrical apparatus (.WWJ~I~ rnision).ZSpecification for presburi7ed enclosures of electrical appartus for use in explosive: Part I Pressurized enclosure with no

internal source of flammable gas or vapour (firsr re\*itrt~).

(Conrinued)

PART 7 E:LE(‘TRICAL INSTALLATIONS IN HA%ARDOI:S A R E A S 255

TABLE 2 TYPES OF PROTECTION FOR DIFFERENT tlAZARDD1’S AREAS Ccmrtl

JOV6 TYpt, 01 PROTFL’llOh

(1) (2)

Zone 2

e) Oil immersed apparatus Type ofprotection ‘0’

d) Sand fil led apparatus~-Type ofprotection ‘q’

Surrd-/i/M U/I/XI~&LC\ (Fx-q) (.w IS 7724-I975*) Flectrtcal apparatu\ which ha\ all it\ Ii\cpa r t \ cntircl) e m b e d d e d in a ma\\ of powder>material. in huch a \cay that under the conditionsof WC for- H hich the apparatus ha\ been designed.no arc occur\ Nithin the outer cxplosi\r atmos-phcrc either h! the transmi\+lon o f f l a m e o r h!the overheating of the fail\ of the cnclo\ure.

fJ Such other apparatus as mav he rpeclflcall>cer t i f ied or as:iessed for use in Zone I arear\.rvpe of protectmn 6s’

a) Tlpe of protection applicable for Zone 0or Zone I.

c) Increased safety apparatus type of /~1l~rW\<‘~/ .SCJ/<./\ (t Y-c‘) (WC’ IS h?X 1-1972$)protection ‘e’. (see Note 2) A method ol protcctl~,n in \\hlch IIIC.I\,UIC\

additional to those adop ted in ordinal! !ndu\trlalpractice a r e applltd. \o a\ to gl\c InctcCl\i+securlt! aga~nht the po\\lhlllt! r11 C\CCI\I\Ctemperature5 and the occurrcncc 01 ate\ or \parh\in electrical apparatur uhlch di>ci !~ot p r o d u c earc\ 01 \parks i n norm31 WI\ ~LC

d) Hermetically sea!ed apparatus 1 ypc 01 A m e t h o d oI protection in u htc,h the cquipmellt ]\Iprotection ‘s’ (see Note I) 40 de\lpned and con\tructcd that the cutcrnal

intlammable ga\e\ or Lapour\ cann~>t en te r t hecnclo\ure and hence prc\ent\ ;I \our-ce of ~gnltlonlike an ale or spark from corn~rlg unto c~nl;~cl withthe Inflammable gas or \apour.

Nort I Special protection category IS reserved for those types of protrctlon that cannot be classilied as belongingwholly to any one of the above types. It may be that a combination of several types of protection is incorporated within onepiece of apparatus.

Norr. 2 For outdoor installation. the apparatus with type of protection ‘e’ and ‘n’ should be used with enclosuresproviding at least the following degree of protection:

a) IP 55 where there are uninsulated conducting parts mternally. and

b) IP 44 for insulated parts.

Norb 3 ~~~ Oil-immersed apparatus may bC used only m case its security will’pot be impaired by tilting or vibration of theapparatus.

NOlb 4 For apparatus with type of protection ‘p’ ‘c’. ‘n’ and where applicable. ‘9’ only area classification and ignitiontemperature are required. However. where apparatus ‘is protected by Ex-‘I’ or Ex-‘d in addition to one of these types ofprotection. it is necessary to determine the appropriate apparatu\ grouplr,g according to IS : 5780-1979 ij and IS : 214%19818) respectively.

*Specification for sand-filled protection of electrical equipment for use in explosive atmospheres.tSpccification for oil-immersed eiect.rical apparatus for llse in explos~e gas atmospheres.:Speclflcation for electrical equipment with type of protection ‘n’.@Specification for construction and testing of electrical apparatus with type of protection ‘e’.;iSpeclllcatlon lor intrinsically sale electrical apparatus and circuits.

71 Spccillcatlon for flameproof enclosures of electrical apparatus (ser,ond revision).

256 NAtIONAt ELECT?fICAL CODE

TABLE 3 MINIMI’M ACTIONS IF FAILURE OF PROTECTIVE GAS FOR TYPE OF PROTECTION ‘p’(Clause 6.3.2.1)

AKEA ENCLOSURE DUES NOT C ONTAIN ENCLOSURE CONTAINS IGNITION-Cl \SSIFI<‘ATIO\ IGNITION -CAPABLE APPARATUS CAPABLE APPARATUS

(1) (2) (3)Zone I

Zone 2

Alarm Alarm and switch off

No action required Alarm

TABLE 4 ADEQUATE TYPES OF PROTECTION FOR ELECTRICAL APPARATUS WITH AN INTERNALSOURCE OF RELEASE

(Clause 6.3.2.1)

IISTERNAL RELEASE

i--7-Normal Abnormal

AREACLASSIFICATION

TYPE OF PROTECTION

.’ d e i, i, n NL) P(2) P(3) P(4) P(5) P(6)

NoneRestricted

Unrestricted

NH, Zone-2Zone-l

NH, None-2Zone-l

Restrtcted NH, Zone-2Restricted Zone-i f

Unrestricted NH, Zone-2 IZone-I I

Unrestricted Not relevant NH, Zone-2 1Zone-I I

Not relevant Not relevant Zone-O - J - - - - - - .- -

Legend :N H Non-hazardous area./Y2

Adequate.Adequate. of the internal components of circuits have type of protection adequate for Zone-l.Adequate, if the internal components of circuits are not ignition-capable during normal operation.Not adequate.

atmosphere. The groups of the apparatus are:

Group I ~~ for mining applications(fire damp)

Group II ~- applications in other industries.

Group II - apparatus is sub-divided accordingto the requirements appropriate to the, nature ofthe flammable. atmosphere for which theapparatus is intended. These sub-groups with arepresentative gas and the design parameters areas follows:

Appar- Represenrarive Ma rimum Minimumatus Suh- Gas Eqwimenral lgnirion

&TO”P Safe Gap Currenr Ratio

IIA Propane > 0.9 mm Above 0.8IIB Ethylene Greater than Betbeen 0.45

0.5 mm less and 0.Xthan 0.9 mm

IIC Hydrogen < 0.S mm Below 0.45

Various gases and vapours. for which a parti-cular group of enclosure is suitable are listedin IS : 9570-1980*.

NOTE -. For flameproof enclosures. gases and vapours areclassified according to their maximum experimental safe gap(MESG). For intrinsic safety. gases and vapours are classifiedaccording to the ratio of their minimum igniting currents(MIC) with that of laboratory methane.

*Classification of flammable gases of vapours with airaccording to their maximum experimental safe gaps andminimum igniting currents.

6.3.3 Individual Features o f ElectricalEquipmenf for Hazardous Areas - The essentialfeatures of individual equipment for installationin hazardous areas are indicated in Table 5.

6.4 Miscellaneous Requirements

6.4.1 Exceptional Circumsfances

6.4.1.1 In exceptional circumstances (forexample, research, development or repair-work,and in emergency situations) apparatus may beused which is not specially designed for use inZone I or Zone 2 hazardous areas, provided thatadequate measures have been taken to ensure anadequate level of safety.

6.4.1.2 Apparatus which is intended to beused for short periods only may be of normalindustrial design but only when operating in Zone2. it is either regularly supervised by trainedpersonnel or gas-free conditions are regularlymonitored.

6.4.2 Stark Electricit!! - see IS : 7689-1974*

6.4.3 Pressurized Rooms

6.4.3.1 Where unavoidable, electricalswitchgear and equipment may be located in apressurized room within a hazardous area meetingthe following requirements:

*Guide for control of undesirable static electricity.


TABLE 5 FEATURES OF ELECTRICAL EQUIPMENT

EQUIPMENT ZONE 0(1) (2)

I) Motors No motor shall be usedin this area

ii) Transformersandcapacitors

iii) Lightingfittings

iv) Switchgearandcontrolgear

No transformer orcapacitor shall be usedin this area.

No lighting fittingsshall be used

No switchgear andcontrolgear shall beused. When notpracticable use type 5’protection

(Clause 6.3.3)

ZONE I(3)

a) Motors with typeprotection ‘d’

b), Motors with typeprotection ‘p’

ZONE 2(4)

of

of

a) Motor suitable for Zone I areas.b) Motors with type of protection ?t’

a n d ‘e’

However all normally sparking parts suchas slip-rings and brushes shall beprovided with type of protection ‘d’or ‘p’

Motors provided with a combinationof the above forms of protection.for example, slip-ring motors in whichthe main enclosures and windingsare offype ‘e’ but the normallysparking parts of type ‘d’.protection

a) All power and drstribution Transformers and capacitors suitabletransformers and capacitors for Zone I areas

with type ‘d’ protection

b) For control and. instru-mentation purposes. typeof protection ‘i’

All ltghtrng fittings shall beflameproof. If necessary asuitable guard shall beprovided by means of cablesin screwed steel conduits.Provision against lateraldisplacement necessary

All switches. circuit-breakers.fuses and other equipment,the enclosure together withthe enclosed apparatus shallbe type ‘d’ protection

Transformers and capacitors that aredry type or contatning liquids thatneed not have an)i special enclosureprovided that the following requite-ments are satisfied:

Cable boxes shall be suitable forspecified level of current andfault clearing time

Only off-circuit manually-operatedtapchangers shall be allowed withprovision for locking the operatinghandle in position

Auxiliary devices shall be intrinsi-cally safe or if they have sparkingcontacts, these shall be:

i) type ‘d’ or hermitically sealed.

ii) under adequate head of oil,

iii) of mercury in glass type withadequate mechanical protection,

iv) of enclosed break type

Or, alternatively, auxiliary devicesmay be deleted or installed in a safezone rendered safe by pressurization.

Any other sparking accessories orswitch shall comply with the re-quirements for Zone I area

Where oil-filled transformers areused, necessary precautions againstspread of fire (see 1646-1961)shall be complied with

a) Lighting fittings for Zone Ib) Lighting ftttings with type of

protection ‘e’ or ‘n’

All equipment where arcing may occurunder normal conditions of operationshall be type ‘d’ unless the interruptionof current occurs in a hermeticallysealed chamber, and the equipment isprovided with a general purpose

(Conrimed)

2!% NATIONAL ELECTRICAL CODE

TABLE 5 FEATURES OF ELECTRICAL EQUIPMENT-Contd

EQUIPMENT ZONE 0 ZONE I

(1) (2) (3)

v) Generators No generators shall be Generators with Type ‘d’used in Zone 0 area and ‘p’ protectton

vt) Dieselengines

Unacceptable The use of permanentalyinstalled diesel engines tothe avoided

Where ncccs~~ry, they shallbe protected as giveni n Appendts H

vii) Storagebatteries

Shall not be used. Storage batteries shall not beinstalled in Zone I areasexcept those in portablelamps where the enclosureshousing the bulb. jwitchand battcrv shall beflameprooi type

Z O N E 2(4)

enclosure and also if the currentinterrupting contacts are oil-immersed,enclosed break switches for lighting.etc. with flameproof breaking chamber,mercury in glass switches and enclosedbreak microswitches

Equipment suitable for Zone I areas

Generators with type ‘n’ protection or‘0’ and haying brushless excitationsystem and sparking parts, if providedshall comply with Zone I requirements

The use of permanently installeddiesel engines to be avoided

Equipment suitable for Zone I areas

Storage batteries shall be of type *e’protection (see Appendix C)

a)

b)

cl

d)

e)

h)

The pressurized room shall be situated insuch area within a hazardous location,which is least hazardous and from which theoperators working in the room can easilyevacuate in the event of an accident.

Main structural parts such as wells, pillars,ceiling, floor, doors and the like shall be onnon-combustible materials and shall besufficiently resistant to explosion blasts orother mechanical effects.

Structural materials and construction of theroom shall be such as not-to allow gases orvapours to penetrate easily through them.

More than one doorway shall be provided,and at least one of them shall face the direc-tion of no source of hazard as for as prac-ticable.

The design of the doorway facing the hazar-dous area shall be such that the doors canonly be opened outwards from the interiorand they shall be double doors.

In case it is necessary to provide a windowfacing the hazardous area, the window shallhave enough strength to resist an explosionblast. blowout of gases or other possiblemechanical effects.

The source of air shall be free of hazardousconcentrations of flammable gases andvapours contaminants and any other foreignmatter. It shall be determined from thenature of the process and the physicallayout.

The voiume and pressure of supplying airshall be such that the air pressure in the

.i)

” k)

vicinity of doorways is maintained higherthan the atmospheric pressure outside theroom.

An alarm or other device shall be providedso that any disorder in the pressurizationsystem may’ be assuredly noticed.

Openings to lead uirings or pipings from thehazardous locations into the room shall beso constructed as not to admit explosivegases into the room. by filling tightly thespace around conduits or pipes with cementor similar incombustible materials.

Nort - - Elevated ambient temperatures can bee x p e c t e d i n pressurized room\. Accordingly, tt isadvisable that due account be taken while selectingelectrical equipment for installation In pressurizedrooms.

6.4.3.2 Prior to commissioning apparatusp r o t e c t e d b y pressurization o r c o n t i n u o u sdilution, it shall be verified by competentpersonnel that the installation of the equipmentfulfils the requirements of relevant IndianStandards, either by inspection of the referencedocuments, or by tests if necessary.

The following shall be considered:

a) the protective gas supply is suitable, that is.impurities in the protective gas will notreduce the level of safety such as by attack-ing the enclosure or ducting material orintroducing flammable material into theenclosure.

b) The apparatus design and safety provisionsare such that purging can be completedsatisfactorily.


cl

d)

NOTE -Satisfactory completion of purgin wouldinclude pas&g a volume of protective gas o Bat leastfive times the free internal volume of the protectedenclosure and associated ducting, prior to energizingthe electrical apparatus.

The minimum pressure required is main-tained with the minimum protective gassupply stated by the manufacturer.

The maximum temperature limits stated arenot exceeded.

With regard to installation practices, thefollowing shall be considered:

4

b)

c)

d)

For wiring swtems:

9

ii)

When cable wiring systems are used, thecable entries shall prevent excess leakageof the protective gas and ensure thatsparks or incandescent particles do hotescape from the enclosure.

When conduit’wiring systems a;e used, itis recommended that all conduit entra-nces to an enclosure be sealed to preventexcess leakage of protective gas unlessthe conduit system is being used as aduct for supplying the protective gas.

The point at which the protective gas entersthe supply duct’ or ducts should be situatedin a non-haz.ardous area.

Ducting should, as far as possible, be loca-ted in a non-hazardous area. If ductingp/asses through a hazardous area, it shallbe checked for leaks prior to start-up of theelectrical apparatus to ensure that the re-quirements of 6.3,3.2.1 (a) are met.

Exhaust ducting shall vent to a non-hazard-ous area or otherwise be designed to preventthe emission of sparks 3r hot particles suchas by the use of spark arrestors or baffles.Care should be taken tp ensure that theexhaust does not result in a secondaryhazardous source in an otherwise non-hazardous area

6.4.4 Intrinsicall~l Safk Installations -- Afundamentally different installation philosophyhas to be recognized in tIie installation ofintrinsically safe circuits. In comparison with allother types of installations, where care is taken toconfine electrical energy to the installed system asdesigned so that a hazardous environment cannotbe ignited, the integrity of an intrinsically safecircuit has to be electrically protected from theenvironment in order that the safe energylimitation in the kircuit is not exceeded, evenwhen breaking, shorting or earthing of the circuitoccurs.

As a consequence of this principle the aim ofthe installation rules for intrinsically safe circuitsis to maintain separation from other circuits.

6.4.4.1 Intrinsically safe circuits may beinstalled either:

a) isolated from earth, or

260

b)

cl

connected at one point to the potentialequalization conductor if this exists in thewhole area of the installation of the intrinsi-cally safe circuits, or

connected to earth at one point only ifearthing is required for functional or pro-tective purposes.

The installation method shall be chosen withregard to the functional requirements of thec i rcu i t s accord ing to the manufac tu re r s ’instructions.

If the circuit is isolated from earth, particularattention should be given to any possible dangerdue to static charges.

More than one earth connection is permitted ona ne twork p rov ided tha t the ne twork i sgalvanically separated into circuits each of whichhas only onC earth point.

6.4.4.2 Where a safety barrier is used, themaximum fault voltage in apparatus connected tothe barrier input terminals shall not exceed thefault voltage rating of the barrier. for example,2 5 0 V. Where a safety barrier requires aconnection to earth, the connecting load to theearthing terminal of the safety barrier should beas short as possible. The cross section of theconnecting load shall t,ake account of the shortcircuit current to be expected, and shall have aminimum value of 1.5 mm2 copper.

Consideration should be given to the need for.earthing of the supply system connected to thebarrier input terminals.

6.4.4.3 In installations with instrinsically=safecircuits, for example, in measuring and controlcabinets, the terminals shall be reliably separatedfiom the tion-intrinsically safe circuits (forexample. by a separating Ijanel, or a gap of atleast 50 mm). The terminals of the intrinsicallysafe circuits shall be marked as such. All terminalsshall satisfy the requirements of relevant lndianStandards.

Where terminals are arranged to provideseparation of circuits by spacing alone, care shallbe taken in the layout of terminals and the wiringmethod used. to prevent contact between circuitsshould a wire become disconnected.

6.4.4.4 Enclosures and wiring of intrinsicallysafe circuits should meet the requirements whichwould be applied to similar types of equipmentwhich are intended to be installed in non-hazardous areas otherwise having the sameenvironmental conditions. If an enc losurecontains both intrinsically safe circuits and non-intrinsically safe cirCuits, the intrinsically safecircuits shall be clearly identified.

In installation containing both intrinsically safeapparat.us and apparatus having another type ofprotection, the intrinsically safe circ_uits shall beclearly marked.

6.e.4.5 Marking may be achieved by labelling


or colour coding of enclosured, terminals andcables. Where a colour is used for this purpose itshall be light blue.

6.4.4.6 Where intrinsically safe circuits may beexposed to disturbing magnetic or electric fields,suitable attention shall be given to transpositionor shielding to ensure that these fields do notadversely affect the intrinsic safety of the circuit.

6 .4 .4 .7 Unless spec i f i ca l ly pe rmi t t ed ,conductor of intrinsically safe circuits andconductors of non-intrinsically safe circuits shallnot be run together in cables, cords, conduits, orbundles. In cable ducts and trays, intrinsically safecables shall be separated from non-intrinsicallysafe cables by a mechanical barrier. Such a barrieris not required if all cables are provided withadditional protective sheathing or sleeves whichprovide equivalent separation, or if the cables aresecurely fastened to ensure that physicalseparation is maintained.

6.4.4.8 A flexible cable may contain morethan one intrinsically safe circuit if the cableinstallation is such as to minimize the risk ofdamage which could cause interconnectionbetween different circuits.

6.4.4.9 The installation of intrinsically safecircuits shall be such that the extreme permittedvalues, such as capacitance, inductance andinducatance to resistance ratio, are not exceeded.The permissible values shall be taken from thecertificate, the nameplate of the apparatus, orfrom the installation instructions.

6.4.4.10 Where intrinsically safe circuits areinterconnected to form a system, due accountshall be taken by calculation or by measurementof the resultant combination of electricalparameters, such as inductance, and capacitance,which may affect the intrinsic safety of the systemas a whole.

NOTE - In addition to electrical sparking due accountshould be taken of thermal effects particularly where non-certified apparatus is used.

6 .4 .4 .11 The fo l lowing equ ipment i sconsidered to be intrinsically safe withoutcertification:

Devices whose electr ical parameters,according to the manufacturer’s specification,do not exceed any of the values 1.2 V, 0. I A.20 J or 25 mW need not be certified or marked.They wi l l be sub jec t , however , to therequirements of relevant lndian Standardspecification, if they are connected to a devicewhich contain a source of energy which couldcause the circuit to exceed these parameters.


7.0 All equipment intended for use in hazardousareas shall be approved by a recognized, testingand certifying authority (see 3.2).

7.1 Installation tests should include insulationresistance and earth continuity resistance and thechecking of fused ratings and other protectiondevices, settings and operation.

7.2 For periodical electrical testing, the followingprecautions shall be followed:

a)

b)

cl

Insulation tests should, in general, be carriedout with certified intrinsically safe insulationtester for use in hazardous areas.

Earth continuity tests, in general, be carriedout with certified intrinsically safe earthtester embodying a hand-driven generatorsuitable for use in hazardous areas.

The rating of fuses and the settings ofprotective devices, where practicable, andthe operation of other protective devicesshould be checked.

A P P E N D I X A(Clause 0.6)

INDIAN STANDARDS FOR ELECTRICAL EQUIPMENT FOR USE INHAZARDOUS ATMOSPHERES

IS : 2148-1968 Flameproof enclosures of electri- IS : 6539-1972 Intrinsically safe magneto-tele-cal apparatus (first revision).

IS : 5571-1979 Guide for selection of electricalequipment of hazardous areas IS : 6789-(fht revision)

1972

IS : 5572 (Part I)-1978 Classification of hazar-dous areas for electrical installa-

1s : 7389- 1974

IS : 5780-1980

IS : 6381-1972

tions: Part I Areas having gasesand vapours wrsr revision)

phones foruse in -hazardousatmospheres

Bolted flameproof cable couplersand adaptors.

Pressurized enclosures of electricalequipment for use in explosiveatmospheres

Intrinsically safe electrical appara-tus and circuits @rst revision)

(Part l)-1976 Part I Pressurized enclosures with nointernal source of flammable gasor vabour (first revision)

Construction and testing of elec-s Y I

trical apparatus with type of pro- IS : 7693-1975 Oil immersed apparatus for use intection ‘e’ explosive gas atmospheres


IS : 7724-1975

IS : 7820-1975

IS : 8239-1976

IS : 8240-1976

Sand-filled protection of electricalequipment for use in explosiveatmospheres

Methods of tests for ignitiontemperatures

Classification of maximum sur-face temperatures of electricalequipment for use in explosiveatmospheres

Guide for electrical equipmentfor explosive atmospheres.

IS : 8241-1976

IS : 8289-1976

IS : 9166-1979

IS : 9570-1980

Methods of marKIng for identify-ing electrical equipment for explo-sive atmospheres

Electrical equipment with type ofprotection ‘n’

Spark test apparatus for intrinsi-cally safe circuits

Classification Jf flammable gasesor vapours with air according totheir maximum experimental safeg a p s a n d m i n i m u m i g n i t i n gcurrents

A P P E N D I X B[Table 5? hem (iv)]

RECOMMENDATIONS FOR THE PROTECTION OFPERMANENT INSTALLATION IN HAZARDOUS AREAS

DIESEL ENGINES FOR

B-O. To ensure a maximum degree of safety in theevent of a permanently installed diesel enginebeing necessary on Zone I or 2, it isrecommended that it should have the followingprotection.

B-l. The, starter shall be either of flameproofelectrical type (usually operated from the mainssupply) or of the following non-electric types:

a) Pneumatic,

b) Hydraulic,

c) Spring recoil,

d) Inertia, or

e) Hand start.

Any other electrical equipment associated withthe engine shall be flameproof. Electricalequipment shall be effectively earthed andbonded.

B-2. Cooling fan blades shall be made from non-metallic materials which do not accumulateelectrostatic charge.

B-3. All belts shall be of antistatic fire-resistanttype.B-4. In order to contain discharge of sparks orflames from the exhaust system, a gas conditionerbox and a flame trap shall be installed.Alternatively, the exhaust should be designed todischarge to a location within a safe area.

B-5. To prevent flashback through inductionsystem, wherever possible, air intakes for enginesshall be located in a safe area. Alternatively, aflame trap should be installed.

B-6. The surface temperature of the engine andexhaust system shall not exceed 250°C whentested under full load conditions. In somesituations cooling of the exhaust manifold andpiping may be necessary, using water jacketing or

262

finned coolers and/or high temperature cut-outsor alarms should be provided.

However, when either the free movement of airis restricted by thermal or accoustic shielding orthe ignition temperature of the surroundingflammable atmosphere is below 200°C, exposedsurface temperature of engine shall not exceedthe minimum ignition temperature of the gasesinvolved.

B-7. To prevent overspeeding of the engine due toinduction of flammable gases or vapours, meansshall be provided to stop the engine. It can beeither:

a) a valve to close the air intake, or

b) a system to inject carbon dioxide intothe air intake.

B-8. Alarms or automatic shutdown devices shallbe provided, activated by excessive watertemperature and low lube oil pressure.B-9. 4 system using an’ alarm or trip device toprotect the engine from excessive vibration shouldbe considered.B-10. An engine having a crankcase volume ofover 0.5 m3 shall be provided with relief devices.Relief valves or breathers on engines shall befitted with flame traps or dischar e

#into the

induction system downstream,of the ame trap, iffitted, and upstream of the shut-off valve, if fitted,as specified B-7. Dipsticks and/or filler capsshould be screwed or effectively secured by oth,ermeans.B-11. Intake and exhaust system design shallmeet the following minimum requirements:

a) The length of the flame path through oracross any joint shall b6 ‘not less than13 mm,

b) Suitable metal-clad or other acceptable

NATIONAL ELECl’RICAL CODE

c)

jointing material shall be interposed between through the wall of any component of theall joint faces to ensure that leakage does system.not occur. B - 1 2 . L)ecompression sys tems should not

Where valve spindles pass through the wallsnormally be provided. However. if they are

of anv component of the induction system.essential, then the decompression parts should be

the d-iametrical clearance shall not exceedprovided with flametraps and ducted away to safearea.

d)

0.13 mm for an axial length of not less th’an25 mm. unless end caps are fitted, and B-13. The fuel injection pump and governor,

where fitted, should be so designed that reverseNo screw. stud or bolt-hole shall pass running of the engine is not possible.

A P P E N D I X C[Table 5, /rem (vii)]

RECOMMENDATIONS FOR STORAGE BATTERIES FOR 1lSE INZONE 2 AREAS

c-o. Storage batteries for use in Zone 2 areas creepage distance shall be correspondinglyshall be of increased safety type. These shall meet increased by I mm per 2 volts.the following requirements.C-l. Celluloid and similar combustibles shall notbe used as constructional materials. ‘,

C-2. Battery containers as well as fittings andinsulating parts outside the enclosed cells shall notconsist of porous materials, for example, wood orother flammable materials and shall be resistantto flame and the action of electrolytes.

C-3. Openings, of calls necessary for the escape ofthe gases given 6ff shtiil ‘be so constructed as toprevent splashing of the electrolyte.‘

C-4. The exterior of the cells shall be soconstructed as to resist impact, and the cell casesshall be firmly fixed.

C-5. The cells shall be so built into the containersthat working loose of connection of the cells withone another is impossible and normally adischarge voltage exceeding 24 volts shall notappear between adjacent rows of cells.

The creepage distance between two poles ofadjacent cells shall not be less than 35 mm. Wherethe discharge voltage exceeds 24 volts, the

Where voltage of batteries is not less than 50volts. either the battery case shall be sub-dividedby partitions or the batteries shall be grouped intocontainers so that in no grouping does a voltageexceeding 50 volts occur. In these cases. thepartitions or the containers shall have, heights atleast half that of the batter) case.

C-6. The battery case shall be so constructed asto ensure sufficient ventilation in order to preventaccumulation of gases given off fro’m the batter).and the free space within the case shall be as smallas possible.

C-7. The metallic cover of the battery case shallbe lined, with materials resistant to electrolyte.

C-8. The cover of the battery case shall havespecial fastenings.

C-9. Exposed live parts of battery contained in acase shall be protected with rubber or equivalentinsulating materials. However, the opening forchecking voltage may be provided.

NoTt Charging of storage batteries shall be conducted innon-hazardous location, while the cover of the hatter:,enclosure is kept open.

A P P E N D I X D(Clause 0.3)

EXAMPLE OF INDUSTRIES AND THEIR WORKING PLACESWHICH REQUIRE CONSIDERATIONS IN REGARD TO

HAZARDOUS LOCATIONS

D-l . Though i t i s d i f f icu l t to de te rminehazardous locations merely according to kind ofindustries or kind of working places, typicalindustries and working places which require

.considerations in regard to hazardous locationsare listed below:

I ) Ammonium sulvhate manufacrurina indus-

2)

3)

try - Places wiere gaseous raw materialsare produced, electrolysis of water is conduc- 4)ted or synthesis of ammonia is carried out.

Elec:ric ,/tirnac,e industr~~ .--- working placeswhere calcium carbide is pulverized and stor-age of it.

Compressed or liyuqfied~flammahle gas indus-try--- Working places where flammable gases

PART I ELECTRICAL INSTALLATIONS IN HAZARDOUS AREAS 263

Soda manufacturing industr>! --- Workingplaces of electrolysis, synthetic hydrochloricacid manufacturing and liquid chlorine hand-ling.

6)

7)

8)

9)

10)

11)

12)

I?)

14)

15)

264

are produced. compressed or filled. Storageof containers filled with flammable gases.Coal tar products industry - Working placeswhere coal tar is fractionally distilled or lightoil extracted from coal is refined or fraction-ally distilled. Places where benzene or theother volatile flammable liquids are filledor stored.

Dyestgffs and their intermediates manu-facturing industry - Working places whereflammable gases or volatile flammable liquidsare handled in large quantity.

Fermentation industry - Working placeswhere volatile flammable liquids are distilledor filled. Storage of volatile flammableliquids.

Acetylene, eth.vlene or methanol deriilativemanefacturing industries - Working placeswhere gaseous raw materials or volatileflammable liquids are produced, refinedreacted, distilled, filled or stored.

Synthetic resin and plastic marwfacturingindustry - Working places where flammablegases or volatile flammable liquids are hand-led in large quantity.

Synthetic ,fihres manufacturing industrlj -Working places where flammable gases .orvolatile flammable liquids are added. reacted,produced, recovered or stored.

Vegetable oil industry, solvent extractionplants - Working places where extraction orrecovery is conducted using volatile flam-mable liquids. Storage of volatile flammableliquids. Hydrogeneration plants..Fatty acids, hardened oil and glvcerine manu-

,facturing industry - Working places wherehydrogen is produced or added. Other work-ing places where flammable gases or volatileflammable liquids are used in large quantity.

Wood dr,l distillation industry - Workingplaces where dry distillation or rectification isconducted. Places where volatile flammableliquids are filled or stored.

Drugs and medicines manefacturing indus-try - Working places where flammable gasesor volatile flammable liquids are handled inlarge quantity. Storage of the gases andliquids.

Paints manufacturing industry - Workingplaces where volatile flammable paints orthinners are produced. Places where volatileflammable raw materials or finished productsare stored.

16)

17)

18)

19)

20)

21)

Insecticides and germicides manufacturingindustry - Working places where flammablegases or volatile flammable liquids are hand-led in large quantity.

Perfumes and cosmetics manefacturing indus-try - Working places where volatile flam-mable liquids are added, prepared, distilled orextracted. Storage of these liquids.

Photographic sensitive materials manujacrur-ing industr,! -- Working places where volatileflammable liquids are added, prepared, appli-ed, recovered or distilled. Storage of theseli.quids.

Oil refining and petrochemical indust,:,, -Worki’ng places where various refining pro-cesses or chemical reactions are conducted.Places ‘where volatile flammable liquids aretransported, filled or stored.

Gum products industry* - Working placeswhere gum arabic is produced or applied.Storage of volatile flammable liquids.

Brecc+ng industrrv - Places where alcohol isdistilled, added or stored.

22) Processed paper or coated cloth manefacturingindustr,! - Working pi&es where volatileflammable liquids are added, applied or re-covered.

23)

24)

25)

26)

27)

Drj?-cleaning industr.1, --- Working p laceswhere washing using flammable liquids andrecovery of the said liquids are conducted.Storage of the said liquids.

Finishing processes -- Working places wherepreparation of volatile flammable paints,locations where paints, lacquers or otherflammable finishers are regularly or frequent-ly applied by spraying, dipping, brushing orby other means, where flammable thinnersare used, and where readily ignitable depositsor residues from such paints, lacquersfinishers may occur.

Printing industr,v - Working places whereprinting is done using inks with addition ofvolatile flammable liquids.

Aircrqft hangars - Location used for storageor servicing of aircraft in which gasoline, jetfuels or other volatile flammable liquid orflammable gases are used.

Petrol birnks and service stations - Locationwhere petrol or other volatile flammableliquids, or liquefied flammable gases aretransferred to the fuel tanks of vehicles.

NATIONAL ELECI’RICAL CODE

A P P E N D I X E(Clause 6. I .2.2)

LIGHTNING PROTECTION OF STRUCTURES WITHEXPLOSIVE OR HIGHLY FLAMMABLE CONTENTS

E-O. The presence of explosives or highlyflammable materials in a structure may increasethe risk to persons or to the structure and th.vicinity in the event of a lightning stroke. For thisreason higher degree of protection is essential forthese structures. Protection of a different deg-eemay be secured in the case of both self-protectingand other structures by installation of varioustypes of protection equipment, such as verticaland horizontal air terminations and other means.The recommendations given in E-l to E-IO shouldbe followed for structures in which explosive orhighly flammable solids, liquids, gases, vapours ordusts are manufactured, stored or used or inwhich highly flammable or explosive gases,vapours or dusts may accumulate.

E-l. PRECAUTIONS

E-1.1. Following precautions should be taken forthe protection of structures and their contentsfrom lightning.

a)

b)

c)

4

4

0

g)

E-2.

‘Storage of flammable liquids and gases inall-metal structures, essentially gas-tight,

Closure or protection of vapour or gasopenings against entrance of flames,

Maintenance of containers in good condi-tion, so far as potential hazards are con-cerned,

Avoidance, so far as possible, of the accu-mulation of flammable air-vapour mixturesabout such structures,

Avoidance of spark gaps between metallicconductors at points where there may be anescape or accumulation of flammablevapours or gases,

Location of structures not inherently self-protecting in positions of iesser exposurewith regard to lightning, and

For structures not inherently self-protecting,the establishment of zones of protectionthrough use of earthed rods, masts, or theequivalent.

GENERAL PRINCIPLES OFPROTECTION

E-2.1 For the protection of structures withexplosives or highly flammable contents thegeneral principles are given below. In case ofdoubt, expert advice should be sought.E-2.2 An air termination network should besuspended at an adequate height abqve the area tobe protected. If one horizontal conductor only isused, the protective angle adopted. should notexceed 30”. If two or more parallel’ horizontal

conductors are installed, the protective angle to beapplied may be as much as 45’ within the spacebonded by the conductors. but it should notexceed 30’ outside that space. The height of thehorizontal conductor should be sufficient to avoidall risk of flashover from the protective system tothe structure to be protected. The supports of thenetwork should be adequately earthed.

E-2.3 Where the expense of the method givenin E-2.2 is unjustified, and where no risk isinvolved in discharging the lightning current overthe surfaces of the structure to be protected, anetwork of horizontal conductors with a spacingof 3 m to 7.5 m, according to the risk. should befixed to the roof of the structure.

E-2.4 If the vertical conductor is separate fromthe structure to be protected, the minimumclearance between it and the protected structureshall be not less than 2 m; this clearance should beincreased by I m for every IO m of structureheight above I5 m to prevent sidesflashes. Alsothe minimum clearance between the suspendedhorizontal air termination and the highestprojection on the protected structure shall be 2 m.

E-2.5 A structure which is wholly below groundand which is not connected to any services aboveground may be protected by an air terminationnetwork in accordance with E-2.2 by virtue of thefact that soil has an impulse breakdown strengthw h i c h c a n b e t a k e n i n t o a c c o u n t w h e ndetermining the risk of flashover from theprotective system to the structure to be protected,including its services. Where the depth of buryingis adequate, the air termination network may bereplaced by a network of earthing strips arrangedon the surface in accordance with expert advice.W h e r e t h i s m e t h o d i s a d o p t e d , t h erecommendations for bonding between metal inthe structure, or metal conductors entering thestructure given in E-4, should be ignored.

E-3. TYPES OF LIGHTNING PROTECTIONSYSTEM

E-3.1 These should generally be of the integralmounted system with the horizontal air terminalsrunning along the perimeter of the roof in allcases except for buildings r?ntaining highly

Type of Building .Recommended Tvpe qfProreccrion

Building with explosives Integrally mounted systemdust or flammable vapour with vertical air terminalsrisk 1.5 m high and horizontal air

terminals spaced 3 to 7.5 mfrom each other dependmg onthe type of storage and pro-cesses involved

265

Type of Building Recommended 7jape 01Prorecrion

Explosives storage building Integrally mounted systemand Pxplosives workshops with vertical air terminals

0.3 m high and horizontalair terminals spaced 7.5 .m.

Small explosives storagebuildings

Vertical pole type

Buildings storing more Suspended horizontal airdangerous types of explo- terminations at least 2 msives, for example, nitro- higher than the structure andglycerine (NG) and for with a spacing of 3 minitiatory explosivesmanufacturing

sensitive explosives and very small buildings. Thefollowing types of protection are recommended:E-3.2 Each separate structure protected inaccordance with E-2.3 should be equipped withtwice the number of down conductors recom-mended in Part I /Set 15 of the Code.

E-3.3 The earth terminations of each protectivesystem should be interconnected by a ringconductor. This ring conductor should preferablybe buried to a depth of at least 0.5 m unless otherconsiderations, such as the need for bonding otherobjects to it, testing, or risk of corrosion make itdesirable to leave it exposed in which case itshould be protected against mechanical damage.The resistance value of the earth terminationnetwork should be maintained permanently at IOohms or less. If this value proves to beunobtainable, the methods recommended inIS : 2309-1969* should be adopted, or the ringconductor should be connected to the ringconductors o f one o r m o r e n e i g h b o u r i n gstructures until the above value is obtained

E-4. BONDING

E-4.1 All major members of the metall icstructure, including continuous metalreinforcement and services, should be bondedtogether gnd connected to the lighting protectivesystem. Such connections should be made at leastin two places and should, so far as is possible. beequally spaced round the perimeter of thestructure at intervals not exceeding I5 m.

E-4.2 Major metalwork inside the structureshould be bonded to the lightning protectivesystem.

E-4.3 Electrical conductors entering a structure ofthis category should be metal-cased. This metalcasing should be electrically continuous within thestructure. It should be earthed at the point ofentry outside the structure on the supply side ofthe service and bonded directly to the lightningprotective system.

*Code of practice for the protection of building and allied *Code of practice for the protection of building and alliedstructures against lightning. \tructurer against lightning.

E-4.4 Where the electr ical conductors areconnected to an overhead electric supply line, alength of buried cable with metal sheath orarmouring should be inserted between theoverhead line and the point of entry to thestructure and a surge protective device. forexample, o f t h e t y p e c o n t a i n i n g voltage-dependent resistors. should be provided at thetermination of the overhead line. The earthterminal of this protective device should bebonded direct to the cable sheath or armouring.The sparkover voltage of the lightning protectivedevice should not exceed one-half the bieakdownwithstand voltage of the electrical equipment inthe structure. On account of the low impulsestrength of mineral-insulated metal-sheathedcable, such cables are not recommended for theabove purpose.

E-4.5 Metallic pipes, electrical cable sheaths, steelropes, rails or guides not in continuous electricalcontact with the earth, which enter a structure ofthis kind, should be bonded to the lightningprotective system. They should be about 75 maway and the other a further 75 m away.

E-5. MISCELLANEOUS REQUIREMENTS

E-5.1 For a buried structure or undergroundexcavation to which access is obtained by an aditor shaft, the recommendation in E-4.5 as regardsextra earthing should be followed for the adit orshaft at intervals not exceeding 75 m.

E-5.2 The metal uprights, components and wiresof all fences. and of retaining walls in closeproximity to the structure. should be connected insuch a way as to provide continuous metallicconnection between themselves and the lightningprotective system. Discontinuous metal wirefencing on non-conducting supports or wirecoated with insulating material should not beemployed.

E-5.3 The vents of any tanks conta in ingllammable gas or liquid and exhaust stacks fromprocess plants emitting flammable vapours ordusts should either be constructed of non-conducting material or be filled with flame traps.

E-S.4 Structures of this category should not beequipped with a tall component, such as spire orflagstaff or radio aerials on the structure or withmI5 m of the structure. This clearance applies alsoto the planting of new trees, but structures nearexisting trees should be treated in accordance’withIS : 2X)9-1969*


INDEXExplanatory Note Evcr~ key word III the index is followed by a designation of location in the Code (Indci numhcl) dcrwtcd h!i

the Part number in bold. S&lion Nuniber (if any) in italics and the specific clause number in Roman. I Ire ;thcr~~ ot rhc clxc~w~number Indicates that the uhole Section or Part is relevant to the aspel’t

A

Air-cond:cloningl)c\~gn. General 1, 14C. 5.1(~cnclal ayocct~ 1 . 14CRequlrementb. Electrical 1. 14C. 5.2Speclllc bulldingc

(SW under individual titles)Agt’lcuitural premises

Cables 6. 52.4Classification 6, 3.1Flectric~l installations i n 6Fence\. Flrctric 6. X.2Gcnc~al characteristics. Assessment

of 6. 4Safrt! 6. 5.3Ser\lces 6, 6lesting 6. 7Wlrlng s!stcm 6. 5.2

.Audu)-s! slemsGeneral aspects 1. 14EPoucr supply 1. 14E. 7.2.2Requirements. design I, 14. 7.2resting 1. 14E. 7.3.1W i r i n g 1. /4E, 7.2.1

B

Bathroomsequipment. Selection of 3. 1. A-4.1Electrical mstallation in 3. I, App ASafety in 3. I. A-3Zones, classification of 3. I. A-2.1

Bulldmg. Building servicesAtr-conditlonmg 1. 14C. 5Audio-systems 1. 14E. 7Call-bells I. 14G‘. 9.1Clock5 1 , 14c‘. 10.1Fire-protrction 1. /4F, 8General characteristics. Assessment

for 1. RHeacIng 1. 14c‘. 5Heat Insulation of 1. i. 2.4I iltr and escalators 1. 141). 6l.lphting design I. 14A. 3LLlghting. general 1, 7. 2.3Ventilarlon. dcslgn 1. 148. 4Vrntila~ion. gcncral 1. 7 . 2 .3

c

Call-bell. electricEquipment 1. 14G‘. 9.1General aspects 1. 14GPower supply 1. 14G. 9.2Wiring I. 14G‘. 9 . 3

Celling fan.\Clamps 1. //. 2.8. JCRcgulatorc 1 . II. 2.8.IA

Ceiling roses J. II. 2.1Cbaractcristlcs of buildings. General

Aprlcultural buildings. 6. 4Assessment of 1. CI. 2Domestic dwellmgs 3. /, 4Hotels 3, 5. 4ldcntificatlon of 1. 8. 2.2Industrial buildings 4. 4Institutions 3. 2. 4Medical establishments 3. 4. 4Ot’fice buildings 3, 2, 4Recreational buildings 3, 3. 4Shopping crntres 3, 2. 4Sports buildings 3. 6. 4Temporary outdoor installations 5.2.4

INDEX

ChartsClassification 1. 4. 2.1Guide for preparation I. 3Explanatory 1, 4. 2.1.2Sequence 1. 4. 2.1.2aTime sequence 1. 4, 2.1.2b

ClearanceDefinition 1. 2. 2.4.5Electric lines and buildings 1. 7. 2.2

Clock systemsD e s i g n I. 14G. IO.1General aspects I, 14GLocation I. 14c‘. 10.2Wiring 1. 14G‘. 10.3

ConductorsArrangement of 1. ‘4, 2 6.2Definition I . 2. 2.1.2F i x i n g tu walls I. //. 3.1.7Identification of 1. 4. 2.6.1Marking I. 4. 2.6Passing through walls. lloors 1. II.

3. I .6Protective I. 4. 2.6.1Selection of si7e 1. II. 3.1.4

ConduitFlexible I, II. 4.5.4Recessed I. II. 4.5.2Rigid. non-metallic J. II. 4.5.3Rigid steel I. II. 4.5.1Silea of 1 . 18Surface 1. II. 4.S I

Current. preferred rated 1. 6. 3

D

Defimtions I . .?Accessible part\. Simultanec~u\l> I. 2.

2.4.7Acces\ory I. 2, 2.3.1Apparatus. I. -7. 2.3.2Apparatus. FIxed 5. .{A. 2. IOApparatus. Mobile 5. 3A. 2.13Apparatus. Movable S. 3A. 2.13Apparatus. Portable 5. 3A. 2.1 IArc I. 2. 2.1.9Arm-a reach 1. 2. 2.4 XBarr ie r I. 2. 2.4.10Building 1. 2, 2.4.1Building point 7, 2.13Bus-bar. Interconnecting I. 2. 2.2.26Cables I, 2, 2.3.5Cable, Armoured 1. 2. 2.3.6Cables. Bunched 1. 2. 2.3.5Cable. Flexible 1. 2. 2.3.7Capacitor 1. 2, 2.1.1Circuit I. 2. 2.3.8Circuit-breaker 1. 2. 2.2.18Circuit-breaker. Miniature I. 2. 2.2.23Circuits. Connection of I, 2. 2. I. I2Clearance 1. 2. 2.4.5C lea t I. 2. 2.3.10Conductive part. Exposed 5. 3A. 2.18Conductor I, 2, 2.1.2Conductor, Aerial 1. 2. 2.3.3Conductor. Bare 1. 2, 2.3.1 IConductor, Earth continuity I. 2.

2.3.23Conductor, Earthed I, 2. 2.3.12Conductor, Insulated 1, 2, 2.3.13Conductor, Portable appliances 1, 2.

2.3.15Conductor, Neutral 1. 2. 2.3.32Connector. Bimetallic I. 2. 2.2.26Connector box 1. 2, 2.3.14Consumer I. 2. 2.4.17

Con\umer‘\ terminal 1. _‘. 2.3. I6Contt-c~lgeal 1. 2. 2 .2 . I4Con\e)tnp \! \trm. lransport 5. 3. 2.7C o r d , F!e.xlble 1. 2. 2.3.17C u r r e n t 1. 2. 2.1 5Current. Icahagc. I , .?. 2.4.12Cut-out I. 2. 2.3 IXDead I. -7. 2 3 I9D e m a n d 1. 2. 24 19Diclectrlc 1. 2, 2. I .3Disconnector 1. 2. 2.3.28Distance. Creepage I. 2. 2.4.6Distribution pillar 1. .?. 2.2.25Di\trlbution undertaking J. 7. 2.4.16Earth 1 . -7. 2.3.12Farthahle point 5. 3. 2.191 arthed neutral system. Multiple I. 2.

2.3.21Farth electrode 1. 2. 2.3.24Farth fault 1. 2. 2.1 I3Farthing lead I. 2. 2.3.25Earthing system. Direct 1. 2. 2.3.20Earth leakage current 1, 2. 2.1.14LTlectric circuit 1. 2. 2.1.6Electric current I. 2. 2.1.7Elec t rode 1. 2. 2.1.4Fncloaure 1. _?. 2.4.9Equipment I. 2. 2.2Equipment, Current using 1. 2. 2.2.2Equipment. Electrical I. 2. 2.2.1Equipment. l-axed 1 . -7. 2.2.6tquipment, Hand held. I. 2. 2.2.4IKqu~pment. Portable 1. 2. 2.2.3Fquipmenr. Stationary I. 2. 2.2.5Fxplo\~ve Ilmit\ 7. 2.6&-lame arrester 7. 2.26Flammahiltty lange 7. 2.7Flammable 1. 2, 2 3.27I- lammahle ga‘. l.lquificd 7. 2.1 IFlammable ga\ or vapour 7. 2.8Flammables liquid 7 . 20Flammable material 7. 2. IFlammahlc miht 7. 2 10!-lammahlr mlxturc 7. 2.2Fla\ho\cr 1. 7. Xl. IOt’la\h point 7. 2 I2l-use I. 2. 2.2 I9Fu\e-base I. 2 2 . 2 . 2 9Fuse-hoard I&butron 1. -7, 2.3.21I-use-board. Enclosed distrlbutlon 1. 2.

2 . 2 . 2 0Fuse-carrier 1. 2. 2.2.30Fuse. D-type 1, 2. 2.2.24Fuse-element 1. 2. 2.2.28Fuse-link 1. 2. 2.2.22Fuse-link, Cartridge 1. 2. 2.2.21Fuse-switch 1. 2. 2.2.17Fuse-wire 1. 2. 2.2.28Generator I. 2, 2.2.7Halard 7, 2.3Hazardous area 7, ‘2.5.HazardoIls atmosphere 7. 2.4Haulage truck 5. 3A. 2.14Ignition temperature 7, 2.14Impulse 1, 2, 2.4.4Insulation. Double 1, 2. 2.3.29Insulation fault 1. 2. 2.1.15Lighting arrester 1. 2. 2.2.31Lighting fitting 1, 2, 2.3.26L i v e 1. 2. 2.3..30Load, connected I. 2, 2.4.20Load factor I. 2. 2.4.29Load, Installed 1. 2, 2.4.19Meter rent I. 2, 2.4.22Motor, Electric 1, 2, 2.2.8Motor, Induction 1, 2, 2.2.9

267

Motor generator set. 1. 2. 2.2.10Neutrial I. 2. 2.3.32Non-hazardous area 7. 2.20Obstacle I. 2, 2.4.1 IOccupancy 1. 2. 2.4.2Operating area 5, 3A. 2.2 to 2.4Operations, Electrical 5. 3A. 2.1Overload 1. 2. 2.1.16Point I. 2, 2.3.33Potential difference 1. 2. 2.1.8Power supply. External 5. 34. 2.17Po~;r6 supply. self-contained 5. 34.

Pr;ying machinery. Primary 5. 34,

Processing machinery. Secondary 5.3A. 2.9

Protection. Type of 7. 2.24Public dighting installations 5. 1. 2Room height 1, 2. 2.4.3Relay. I. 2. 2.2.13Release. Restricted 7. 2.16Release, Source of 7. 2.15Release. Unrestricted 7, 2. I7Risk Zones, Medical 3. 4, 2.2Rooms. Medical 3. 4. 2.1Safety circuits 5. 3A. 2.29Safety devices 5. 3A. 2.29Service 1, 2, 2.3.34Service line I. 2, 2.4.15Short-circuit I, 2. 2.1.17Socket-outlet and plug 1. 2. 2.3.35Spark 1. 2. 2.1.11Subcircuit. final I. 2, 2.3.9Supply terminals 1, 2, 2.4.14Surge diverter I. 2, 2.2.31Switch 1. 2. 2.2.15Switchboard I. 2. 2.3.36Switch-fuse 1, 2. 2.2.16Switchgear I, 2. 2.2.14Tariff 1. 2. 2.4.23Tariff, domestic 1. 2, 2.4.24Tariff. Heating I. 2. 2.4.27Tariff, Industrial 1. 2. 2.2.25Tariff. Lighting I. 2. 2.4.27Temporary -installations 5, 2. 2.1Transformer 1. 2. 2.2.12Transformer. Auto 1, 2. 2.2.1 IVoltage 1. 2. 2.1.8Voltage, Extra-high 1. 2. 2.3.40Voltage. High 1. 2. 2.3.39Voltage. Low I. 2. 2.3.37Voltage. Medium I, 2. 2.3.38Voltage. Nominal I. 2. 2.4.13Winning, Stacking machinery 5, 3. 2.6Working level 5. 3. 2.5

DiagramBlock 1. 4. 2.l.la)Circuit 1. 4. 2.l.lb)Classification of 1. 4, 2.1Equivalent circuit I. 4. 2.1. Ic)Explanatory I. 4. 2. I.1Guide for preparation I. 4Interconnection I. 4. 2. I .3.2Location I. 4. 2.1.4Rules for I. 4. 2.4Terminal I. 4. 2.1.3.3Unit wiring 1. 4. 2.1.3.1Wiring I. 4. 2.1.3

Domestic dwellingsAir-conditioning 3. 1. 10.2Classification 3. 1, 3.1Conductors. selection of size 3, 1. 5. I .4Distribution boards 3, 1, 6.4Earthing 3. 1. 9Electrical Installations 3, /Fire-safety 3. 1. I I.1General characteristics, Assessment of

3.-i. 4Load. Estimation of 3. 1. 5.1.1Lifts 3. 1. 10.3Light ing 3, 1. IO.1

268

Metering 3. 1. 8Socket-outlets 3, 1. 5.1.3Switchboards. 3. 1. 6.2Switchboards. Types of 3. 1. 6.3Switchgear, location of 3. 1. 6.1Wiring 3. 1. 5.1

E

Earth. EarthingAlphanumeric notation 1. 4. Table IAudio-systems 1. 14. 7.2.3Bus, wire I. 12. 4.0Circuit-breaker, Earth leakage 1. 12,

B-3Continuity conductor 1, 2. 2.3.23Definition 1: 2. 2.3.22Design constderations 1. 12, 2.1Electrode. Depth of burial I. 12. 3.5.3Electrodes. Design data 1. /2. 3.5Electrode. Lighting protection 1. IS,

8.4Electrode. Pipe 1. /2. Fig. IElectrode. Plate I, 12, Fig. 3Electrode resistance 1. I2, 3.5.2Electrodes. Types of I. 12. 3.4Equipment 1. /2. 2.1.2General. common aspects 1. I2Hazardous areas 7, 6.1.2IE rules for 1. 12. 2.0.4Industrial premises 4. 5.6Lift and escalators 1, 140. 6.2.2.9Loop impedance 1. 12, 6. IMetal sheathed wiring system 1, /I.

4.4. IONoiseless 1, 4. Table IObject of 1, 12. 2.0.2Symbol 1. 4. Table ISystem 1. 12. 2.1.1Systems, Types of 1. 8. 2. I.0Temporary outdoor installations 5. 2.

6.2.3Temination. Lighting protection 1. IS.

8.5Testing 1. 10. 3.3.6

Equipment. electricalCompatibility I, 8. 2.3Definition. I. 2, 2.2.1Maintainability I. 8,. 2.4Selection of I. 9 ’Space for I, 7. 2.6

Exhaust Fans I, /I. 2.8.2

F

Fire-safety, Fire protectionDetectors 1. 14. 8.1Equipment, fire-fighting I,. 14, 8.3Specific buildings (see under indivi ual

titles)Wiring, Fire-alarm I. 14.. 8.2

FrequencyLimits 1. 6. 4.2Standard values I. 6. 4

H

Hazardous areaApparatus, Portable 7. 6.2.6Cables. Choice of 7. 6.2.0Cables, Laying of 7. 6.2.4Classification 7. 5. IConduits, Laying of 7. 6.2.3Diesel engines 7. Appendix BEarthing, Bonding 7. 6.1.2Electrical installations in 7Equipment, selection of 7. 6.3Examples of 7. Appendix D.Fundamental concepts 7. 4

Hazards. internal ‘7. 5.2.3Intrinsically. safe 7, 6.4.4Isolation 7. 6.1.4Lightning protection 7. Appendix EOperation and maintenance 7. 6. I.5Plugs and sockets 7, 6.2.5Pressurized room 7. 6.4.3Protection, automatic 7. 6. I .3Sparking. Protection from 7. 6.2.7Static electricity 7. 6.4.2Statutory regulations 7. 3Storage batteries 7, Appendix CTesting 7, 7Wiring in 7, 6.2Wiring, design 7, 6.2.2Wiring system, choice of 7. 6.2.1Zones, extent of 7, 5.2.4

Hospitals (see under Medical Establish-ment)

HotelsAir-conditioning 3. 5. 5.6.2Call-systems 3. 5. 7.1Classification 3. 5, 3.1Clocks 3, 5, 7.3Electrical installation 3, 5Emergency supply 3, 5. 7.4Fire-safety 3. 5, 5.5General characteristics, assessment of3. 5. 4Lifts 3. 5. 5.6.3Lighting 3, 5. 5.6.1Services 3, 5, 5.6Socket-outlets 3. 5, 5.1.5Sub-station 3, 5. 5.4Swimming Pools 3, 5, Appendix ASwitchboards 3. 5. 5.1.4Telephones 3. 5, 7.2Testing 3, 5. 6Wiring 3, 5. 5.1

I

IE RulesCohformity to I. 7. 2.0.1

Industrial buildingsAir-conditioning 4. 8.2Cables. choice of 4. 5.3Circuits. sub- 4, 5.4Classification 4. 3Distribution, main 4. 5.3Distribution, power 4. 5.2Earthing. 4. 5.6Electrical installations in 4Electra-heat installations 4. 9.2Emergency supply 4, 6Equipment. location of 4, 5.1.4fire-safety 4. 7.2General characteristics. assessment of

4. 4Hazardous areas, 7Heating 4. 8.2Lifts 4, 8.3Lighting 4. 8. IPower-factor compensation 4, 9.3Services 4. 8Static electricity, Control of 4. 9.1Substation 4. 5.1Supply 4. 5.0Switchgear, Medium voltage 4. 5.2.3Ventilation 4, 8.2Wiring 4. 5.4Wiring system. Restrictions for 4. B-4Wiring system, Selection of 4. 5.5

Influence. ExternalCodification I, 8, 2.2.2Identification 1. 8. 2.2

Installation, ElectricalAgricultural premises 6Air-port aprons 5, 3E. 8.1Apartments 3. IAsse bly buildings 3. 3

I N D E X

Bathrooms 3. 1. A-lBusiness buildings 3, 2Design I. 7. 3Direct contact. Protection against I, 7.

3.1.1Dockyards 5. 3EDomestic dwellings 3. IEducational buildings 3. 2Erection I, 10. 2Farm houses 6Fault currents, Protection against 1. 7.

3.1.5Fundamental principles 1, 7, IGenerating stations, standby 2Hazardous area 7Hospitals 3, 4Hotels 3, 5Indirect contact, Protection against 1.

7, 3.12Industrial 4Inspection 1, 10, 3.1Institutional buildings 3. 2Livestock houses 6Lodging houses 3, 5Materials 1, 7. 2.0.2Medical establishments 3. 4Mercantile buildings 3. 2Methods of protection I, 7, 3.1.7Mines, open-cast 5. 3Non-industrial 3Office buildings 3, 2Outdoor 5Oy;-;Urrent Protection against 1, 7.

Ov$rltage Protection against 1, 7.

Permanent outdoor 5. 3Ports, Harbours 5. 3E. 8.2Poultry 6Protection for safety 1. 7, 3.1Public lighting 5. IQuarrys 5, 3Railway yards ‘5, 3E. 8.3Recreational buildings 3, 3Residential buildings 3. IRooming houses 3. 5Shopping and commercial centres 3, 2Sports buildings 3. 6Swimming pools 3. 5. A-lTemporary outdoor 5. 2Testing of 1. 10, 3Thermal effects, Protection against 1,

7. 3.1.3Workmanship I. 7, 2.0.3

Item-designation I, 4. 2.3

L

LiftsEarthing 1. 140. 6.2.2.9General aspects 1, 140Requirements, electrical 1, 140, 6.2Specific buildings (see under individual

titles)Wiring 1, 140. 6.2.2

Light ing , LampsElectrical aspects, general 1. f4AFittings 1. /I. 2.3Lamp-holders, 1, /I, 2.5Levels of illuminatian, 1, 14, 3.2.1 ’

Levels of illumination, specific build-ings (see under individual titles)

Outdoor 1, /I, 2.6Specific buildings (see under individual

titles)Wiring for I, /I

LightingConductor, material for I, IS, 7.1Conductor, shape. 1, 15. 7.2Discharge, characteristics. 1, IS. 4Electrical Effects 1. IS, 4.2

INDEX

Mechanical effects I. 1.5. 4.4Protection against I. I5Thermal effects I. IS. 4.3

Lighting protectionGeneral, Common aspects I, 1.5Hazardous areas 7. Appendix EIsolation and bonding I, 15. 9Sub-stations, 2, 16.1System design I. IS. 8Testing of systems 1. 15, I IZones of 1, /5. 6

M

MarkingAlphanumeric, 1, 4Conductors 1, 4. 2.6

MeasurementElectrical units 1, 5, 2.2Systems of 1. 5. 2

Medical establishmentsAir-conditioning 3. 4, 8.2Anti-static floor 3, 4. 7.2Call-systems 3. 4, 12. ICircuit Installation measures 3. 4. 6.1Classification 3, 4, 3.1Clocks 3, 4. 12.3Electrical installation 3, 4Emergency lighting 3, 4. E-lEssential circuits 3. 4, E-2Explosion protection 3, 4, 7.1Fire-protection 3. 4, 6.7General characteristics, AsseJsment of

3. 4. 4Interfe’rence suppression 3. 4. I ILifts 3, 4, 8.3Lighting 3, 4, 8.1Paging system 3, 4, 12.1.2Safety 3, 4. 5Safety supply systems 3. 4, IOServices 3. 4. 8Sub-station 3. 4. 6.5Telephones 3. 4, 12.2Testing 3. 4. 9Wiring 3. 4. 6.2Zones of risk 3, 4. Appendix A

0

Office-buildingsAir-conditioning 3. 2. 5.6.2Call-bell system 3, 2. 7.3Classification 3. 2. 3.1Clocks 3, 2. 7.4Electrical installations 3. 2General characteristics, Assessment of

3. 2. 4Emergency supply 3, 2. 5.3.4Fire-safety 3, 2. 5.5Lighting 3, 2. 5.6.1Lifts 3, 2, 5.6.3Metering 3. 2, 5.4Services 3, 2, 5.6Substation 3, 2, 5.2Switchboards 3. 2. 5.3.5Telephones 3. 2, 7.2Testing 3, 2, 6Wiring 3, 2. 5.1

Outdoor installationsPermanent outdoor 5, 3

Cables 5, 38, 5.1.5Connectors. Cable 5. 38, 5.1.6Direct contact, protection against 5,

3C. 6.1Equipment for 5. JB, 5General characteristics 5. 3A. 4Primary processing machinery 5.3 D.

7.1Pumping, Water supply system 5.

30, 7.4Rotating machines 5. 38. -5. t. I

Requirements 5, 3D. 7Sefetv 5. 3C. 6

:oAd&y processing machinery5. 3D. 7.2

Set1

Static converters 5. _?B, 5. I .3Switching devices 5, 38. 5.1.4Transformers 5. 3. 5.1.2Transport convey or system 5,

3D, 7.3Types 5. 3A. 3.1

Temporary outdoor 5, 2Circuit, main 5, 2, 6.2.1Classification 5, 2, 3Construction sites 5, 2, 6.2.2.6Definition 5, 2, 2. IEarthing 5, 2, 6.2.3General characteristics, Assess-

ment of 5, 2, 4Requirements 5, 2. 5Safety 5, 2, 7Sub-circuit 5, 2, 6.2.2Substation 5, 2, 6.2.2Supply 5, 2, 6.1Testing 5, 2, 8Wiring 5, 2, 6.2.2

PPower factor compensation

Capacitors for 1, 17. 4Capacitor rating I, 17, 5Central 1, 17, 4.6Domestic dwellings 3, I, 13.3Economics of 1. 17, 3.5Group I, 17, 4 .5Guidelines for 1. 17Individual 1. 17. 4.4Industrial .buildings 4. 9.3

Public lighting installationsAerodrome 5, 1. 5.5Aims of 5. I. 4.1Bridges 5. I, Table 7Cables 5. 1. 8.2Car-parks 5, .I. Table 8Classification, Roads 5. 1. 3.2Control 5. 1. 8.4Design 5, 1. 5Docks 5. I, 5.6Equipment. selection of 5. 1. 6Flyovers 5. I. 5.2Junctions 5. 1. 5.3Light sources 5. 1. 6.1Luminaires 5. 1. 6.2Main squares 5. I. Table 8Power installation, Requirements for

5. 1. 8Quality 5, 1. 4.3Railways 5. I. 5.6Roads 5, 1, 5.1Roundabouts 5. 1, 5.4Shopping streets 5, I, Table 8Supply 5. 1. 8.3Vision, Principles of 5. 1. 4.2Waterways 5. 1. 5.6

R

Railway marshalling yardsClassification 5. 3E. 8.3.1Lighting 5. 3E. 8.3.3Power installations 5. 3.K 8.3.4

RecreationalAir-conditioning 3. 3, 5.6.2Audio-visual 3. 3; 7.4Electrical installations 3, 3Emergency supply 3, 3. 711Fire-safety 3. 5.5General characteristics. Assessment of

3. 3. 4Lifts 3. 3, 5.6.3Lighting 3. 3, 5.6.1

269

Services 3. 5.6Substation 3. 3. 5.4Testmg 3. 3. 6Wrring 3. 5.1Short-ctrcuit calculation\ I. /3Socket-outlets. Plugs 1. II. 2.2

sSafety

Electrical work 1, 16Equipment. Devices for I, l6. 4.2Instructions I. 16. 3Permit-to-work, system for I. 16, 2Posters I. 16. 5PJactices I. /6. 4Protection for I. 7. 3.1Working distance for I, 16. 3.2.2Short-circuit calculations 1, I3

Sports BuildingsAir-conditioning 3. 6. 5.5.2Audio-systems 3. 6. 7.1Classification 3, ‘6, 3Clocks 3. 6, 7.4Control-room 3. 6. 7.2Electrical installations 3. 6Fire-safety 3, 6, 5.4General characteristics. Assessment of

3. 6. 4Group switching 3. 6. 5.5.1.5Lifts 3. 6. 5.5.3Light sources 3, 6. 5.5.1.4Lighting 3. 6. 5.5.1Score-board 3, 6. 7.3Services 3, 6. 5.5Substation 3, 6, 5.3Switchboards 3. 6. 5.1.3Testing 3. 6, 6Wiring 3. 6. 5.1

SubstationsBuilding. 2lnspcction of 1 . 10. 3.1.1Auxilltartes 2. I IEquipment, Selection of 2. 6.1High voltage 2, Y1.0~ voltage 2. IOSpecific buildings (see under individual

title)Wiring in 2. 12.1

SupplyCommencement 1, /I, 3.1.1

270

Emergency 2Emergency. Specific buildings (see

under individual titles)Reception and distribution 1. I/. 3.1Voltage. values 1. 5

Swsimmtng PoolsEquipment. selection 01 3. 5. A-4Electrical Installations in 3. 5. App-ASafety 3. 5. A-3Zones. classification 3. 5. A-2.1Wiring 3, 5. A-5

SwitchboardsArrangement o f appara tus 1 , /I.

3.1.2.6Distribution 1, II, j.l.3Identification of 1. /I, 3.1.2.7Locat ion of 1. If, 3.1.2.2Marking of 1, I/. 3.1.2.7Testing 1, IO. 3.3.1Types 1, II, 3.1.2.3Wiring of 1, Il. 3.1.2

SymbolsGraphical, 1, 3, 2Letter 1. 3, 4Subscripts 1. 3, 4.1Tables for, 1, 3. 4.1.1

T

TablesClassification 1. 4. 2.1Explanatory 1, 4, 2.1.2Guide for preparation 1, 4Interconnectiq-,t I. 4 , 2 .5Location 1. 4, 2.1.4Sequence 1, 4, 2.1.2a)Time sequence 1, 4. 2.1.2b)Wiring I, 4. 2.1.3

TransformerInstallations 2Testing 1. 10, 3.3.2

U

UnitsAbsolute I, 5, 2.1Electrical 1, 5. 2System International 1, 5. 2.1

VVentilation

General aspects 1, 146Specific buildings (see under individual

titles)Voltage

Declared. standard value I. 6. 2.1Definition I. 2. 2.1.8Limits. Installation design I. 6. 2.2.2Limits, supplier 1, 6, 2.2.1Single phase system I. 6, 2.1.1‘Three phase system I, 6, 2.1.2

W

Wiring, Wiring installations, WiringsystemsAgricultural premises 6. 5.2Assembly buildings 3, 3, 5. IAudio systems 1, 14, 7.2.1Call-bell 1, 14. 9.4Cleated I, II, 4.1Clocks I. 14. 10.3Conduit 1, /I. 4.5Domestic dwellings 3, I, 5.1Fire-alarm 1, 14. 8.2General, Common aspects 1, /IHazardous area 7, 6.1Hotels 3. 5, 5.iIndustrial 4. 5.4internal methods of 1, II, 4Lifts and escalators I, 14. 6.2.2Medical establishments 3, 4. 5Metal sheathed I, II. 4.4Office building 3, 2. 5.1Pressurized rooms 7, 6.3.3PVC sheethed 1, /I. 4.3Recessed conduit 1, If. 4.5.2Recreational buildings 3, 3, 5.1Restrictions, industrial 4, B-4Rubber-sheathed 1, /I, 4.3Selection. Domestic 3, I, 5.2Selection, Hazardous area 7. 6.2.1Selection, Industrial 4, 5.5. ISports buildings 3, 6, 5.1Substation 2, 12.1Surface Conduit I, I/, 4.5.1Swimming pools 3, 5, A-5Testing 1. 10, 3.3.5Wood casing 1, /I. 4.2

INDEX

SP30

Documents

Transcript of SP30