IEC Guide

contents

AA. contents B. general - installed power1. methodology 2. rules and statutory regulations2.1 definition of voltage rangestable B1 standard voltages between 100 V and 1000 V (IEC 38-1983) table B2 standard voltages above 1 kV and not exceeding 35 kV (IEC 38-1983) B1 B3 B3 B3 B3 B4 B4 B5 B6 B6 B6 B7 B8 B8 B9 B10 B10 B10 A1

2.2 regulations 2.3 standards 2.4 quality and safety of an electrical installation 2.5 initial testing of an installation 2.6 periodic check-testing of an installationtable B3 frequency of check-tests commonly recommended for an electrical installation

2.7 conformity (with standards and specifications) of equipment used in the installation

3. motor, heating and lighting loads3.1 induction motorstable B4 power and current values for typical induction motors

3.2 direct-current motorstable B6 progressive starters with voltage ramp table B7 progressive starters with current limitation

3.3 resistive-type heating appliances and incandescent lamps (conventional or halogen)

B11 table B8 current demands of resistive heating and incandescent lighting (conventional or halogen) appliances B11 B11 B12 B12 B13 B13 B14 B14 B15 B15 B16 B16 B17 B17 B17 B17 table B10 current demands and power consumption of commonly-dimensioned fluorescent lighting tubes (at 220 V/240 V - 50 Hz) table B11 current demands and power consumption of compact fluorescent lamps (at 220 V/240 V - 50 Hz)

3.4 fluorescent lamps and related equipment

3.5 discharge lampstable B12 current demands of discharge lamps

4. power loading of an installation4.1 installed power (kW) 4.2 installed apparent power (kVA)table B13 estimation of installed apparent power

4.3 estimation of actual maximum kVA demandtable B14 simultaneity factors in an apartment block table B16 factor of simultaneity for distribution boards (IEC 439) table B17 factor of simultaneity according to circuit function

4.4 example of application of factors ku and kstable B18 an example in estimating the maximum predicted loading of an installation (the factor values used are for demonstration purposes only)

contents - A1

contents (continued)

AB. general - installed power (continued)4. power loading of an installation (continued)4.5 diversity factor 4.6 choice of transformer ratingtable B19 IEC-standardized kVA ratings of HV/LV 3-phase distribution transformers and corresponding nominal full-load current values B18 B18 B18 B19

4.7 choice of power-supply sources

C. HV/LV distribution substations1. supply of power at high voltage1.1 power-supply characteristics of high voltage distribution networkstable C1 relating nominal system voltages with corresponding rated system voltages (r.m.s. values) table C2 switchgear rated insulation levels table C3A transformers rated insulation levels in series I (based on current practice other than in the United States of America and some other countries) table C3B transformers rated insulation levels in series II (based on current practice in the United States of America and some other countries) table C4 standard short-circuit current-breaking ratings extracted from table X IEC 56 C1 C1 C2 C3 C3 C4 C4 C11 C13 C15 C15 C17 C17 C22 C25 C26 C27 C31 C31 C34 C34 C36 C37 C38 C38 C41 C42 C44 C44 C46 C48 C49 C49 C49 C52

1.2 different HV service connections 1.3 some operational aspects of HV distribution networks

2. consumers HV substations2.1 procedures for the establishment of a new substation

3. substation protection schemes3.1 protection against electric shocks and overvoltages 3.2 electrical protectiontable C18 power limits of transformers with a maximum primary current not exceeding 45 A table C19 rated current (A) of HV fuses for transformer protection according to IEC 282-1 table C20 3-phase short-circuit currents of typical distribution transformers

3.3 protection against thermal effects 3.4 interlocks and conditioned manuvres

4. the consumer substation with LV metering4.1 general 4.2 choice of panelstable C27 standard short-circuit MVA and current ratings at different levels of nominal voltage

4.3 choice of HV switchgear panel for a transformer circuit 4.4 choice of HV/LV transformertable C31 categories of dielectric fluids table C32 safety measures recommended in electrical installations using dielectric liquids of classes 01, K1, K2 or K3

5. a consumer substation with HV metering5.1 general 5.2 choice of panels 5.3 parallel operation of transformers

6. constitution of HV/LV distribution substations6.1 different types of substation 6.2 indoor substations equipped with metal-enclosed switchgear 6.3 outdoor substationsA2 - contents

A7. appendix 1 : example in coordination of the characteristics of an HV switch-fuse combination protecting an HV/LV transformer7.1 transfert current and take-over current 7.2 types of faults involved in the transfer regionApp C1-1 App C1-2 App C1-3

8. appendix 2 : ground-surface potential gradients due to earth-fault currents 9. appendix 3 : vector diagram of ferro-resonance at 50Hz (or 60 Hz)

App C2-1

App C3-1

D. low-voltage service connections1. low-voltage public distribution networks1.1 low-voltage consumerstable D1 survey of electricity supplies in various countries around the world. table D2 D1 D1 D1 D6 D7 D10 D13 D14

1.2 LV distribution networks 1.3 the consumer-service connection 1.4 quality of supply voltage

2. tariffs and metering

E. power factor improvement and harmonic filtering1. power factor improvement1.1 the nature of reactive energy 1.2 plant and appliances requiring reactive current 1.3 the power factor 1.4 tan 1.5 practical measurement of power factor 1.6 practical values of power factortable E5 example in the calculation of active and reactive power table E7 values of cos and tan for commonly-used plant and equipment E1 E1 E2 E2 E3 E4 E4 E4 E4 E5 E5 E5 E5 E6 E6 E7 E8 E9 E9 E9 E10

2. why improve the power factor?2.1 reduction in the cost of electricity 2.2 technical/economic optimizationtable E8 multiplying factor for cable size as a function of cos

3. how to improve the power factor3.1 theoretical principles 3.2 by using what equipment? 3.3 the choice between a fixed or automatically-regulated bank of capacitors

4. where to install correction capacitors4.1 global compensation 4.2 compensation by sector 4.3 individual compensation

contents - A3


AE. power factor improvement and harmonic filtering (continued)5. how to decide the optimum level of compensation5.1 general method 5.2 simplified methodtable E17 kvar to be installed per kW of load, to improve the power factor of an installation E11 E11 E11 E12 E13 E13 E14 E14 E14 E15 E16

5.3 method based on the avoidance of tariff penalties 5.4 method based on reduction of declared maximum apparent power (kVA)

6. compensation at the terminals of a transformer6.1 compensation to increase the available active power outputtable E20 active-power capability of fully-loaded transformers, when supplying loads at different values of power factor

6.2 compensation of reactive energy absorbed by the transformertable E24 reactive power consumption of distribution transformers with 20 kV primary windings

7. compensation at the terminals of an induction motor E177.1 connection of a capacitor bank and protection settingstable E26 reduction factor for overcurrent protection after compensation E17 E17 E18 E19

7.2 how self-excitation of an induction motor can be avoidedtable E28 maximum kvar of P.F. correction applicable to motor terminals without risk of self-excitation

8. example of an installation before and after power-factor correction 9. the effect of harmonics on the rating of a capacitor bank9.1 problems arising from power-system harmonics 9.2 possible solutions 9.3 choosing the optimum solutiontable E30 choice of solutions for limiting harmonics associated with a LV capacitor bank

E20

E21 E21 E21 E22 E22 E23 E24 E24 E25

9.4 possible effects of power-factor-correction capacitors on the power-supply system

10. implementation of capacitor banks10.1 capacitor elements 10.2 choice of protection, control devices, and connecting cables

11. appendix 1 : elementary harmonic filters 12. appendix 2 : harmonic suppression reactor for a single (power factor correction) capacitor bank

App E3-1

App E4-1

F. distribution within a low-voltage installation1. general1.1 the principal schemes of LV distribution 1.2 the main LV distribution board 1.3 transition from IT to TNF1 F1 F4 F4

A4 - contents

A2. essential services standby supplies2.1 continuity of electric-power supply 2.2 quality of electric-power supplytable F10 assumed levels of transient overvoltage possible at different points of a typical installation table F12 typical levels of impulse withstand voltage of industrial circuit breakers labelled Uimp = 8 kV table F18 compatibility levels for installation materials F5 F5 F6 F8 F8 F13

3. safety and emergency-services installations, and standby power supplies3.1 safety installations 3.2 standby reserve-power supplies 3.3 choice and characteristics of reserve-power suppliestable F21 table showing the choice of reserve-power supply types according to application requirements and acceptable supply-interruption times

F15 F15 F15 F16 F16 F17 F17 F18 F19 F19 F20 F21 F23 F29 F30 F31 F32 F33 F33 F36 F36 F37 F38 F38 F39 F39 F41 F41 F41 F43 F44 F45 F46

3.4 choice and characteristics of different sourcestable F22 table of characteristics of different sources

3.5 local generating sets

4. earthing schemes4.1 earthing connectionstable F25 list of exposed-conductive-parts and extraneous-conductive-parts

4.2 definition of standardized earthing schemes 4.3 earthing schemes characteristics 4.4.1 choice criteria 4.4.2 comparison for each criterion 4.5 choice of earthing method - implementation 4.6 installation and measurements of earth electrodestable F47 resistivity (-m) for different kinds of terrain table F48 mean values of resistivity (-m) for an approximate estimation of an earth-electrode resistance with respect to zero-potential earth

5. distribution boards5.1 types of distribution board 5.2 the technologies of functional distribution boards 5.3 standards 5.4 centralized control

6. distributors6.1 description and choice 6.2 conduits, conductors and cablestable F60 selection of wiring systems table F61 erection of wiring systems table F62 some examples of installation methods table F63 designation code for conduits according to the most recent IEC publications table F64 designation of conductors and cables according to CENELEC code for harmonized cables table F66 commonly used conductors and cables

contents - A5


AF. distribution within a low-voltage installation (continued)7. external influences7.1 classificationtable F67 concise list of important external influences (taken from Appendix A of IEC 364-3) F47 F47 F48 F49

7.2 protection by enclosures: IP code

G. protection against electric shocks1. general1.1 electric shock 1.2 direct and indirect contactG1 G1 G1 G2 G2 G3 G4 G4 G4 G4 G5 G6 G6 G7 G8 G9 G10 G13 G13

2. protection against direct contact2.1 measures of protection against direct contact 2.2 additional measure of protection against direct contact

3. protection against indirect contact3.1 measure of protection by automatic disconnection of the supplytable G8 maximum safe duration of the assumed values of touch voltage in conditions where UL = 50 V table G9 maximum safe duration of the assumed values of touch voltage in conditions where UL = 25 V

3.2 automatic disconnection for a TT-earthed installationtable G11 maximum operating times of RCCBs (IEC 1008)

3.3 automatic disconnection for a TN-earthed installationtable G13 maximum disconnection times specified for TN earthing schemes (IEC 364-4-41)

3.4 automatic disconnection on a second earth fault in an IT-earthed systemtable G18 maximum disconnection times specified for an IT-earthed installation (IEC 364-4-41)

3.5 measures of protection against direct or indirect contact without circuit disconnection

4. implementation of the TT system4.1 protective measurestable G26 the upper limit of resistance for an installation earthing electrode which must not be exceeded, for given sensitivity levels of RCDs at UL voltage limits of 50 V and 25 V

G13 G14 G15 G18 G18 G18 G20 G20 G20 G21 G21 G22 G22 G23

4.2 types of RCD 4.3 coordination of differential protective devices

5. implementation of the TN system5.1 preliminary conditions 5.2 protection against indirect contacttable G42 correction factor to apply to the lengths given in tables G43 to G46 for TN systems table G43 maximum circuit lengths for different sizes of conductor and instantaneous-tripping-current settings for general-purpose circuit breakers table G44 maximum circuit lengths for different sizes of conductor and rated currents for type B circuit breakers table G45 maximum circuit lengths for different conductor sizes and for rated currents of circuit breakers of type C table G46 maximum circuit lengths for different conductor sizes and for rated currents of circuit breakers of type D or MA Merlin Gerin

5.3 high-sensitivity RCDs 5.4 protection in high fire-risk locations 5.5 when the fault-current-loop impedance is particularly highA6 - contents

A6. implementation of the IT system6.1 preliminary conditionstable G53 essential functions in IT schemes G24 G24 G24 G25 G28 G29 G29 G30 G31 G31 G31 G32 G33 G34 G34

6.2 protection against indirect contacttable G59 correction factors, for IT-earthed systems, to apply to the circuit lengths given in tables G43 to G46

6.3 high-sensitivity RCDs 6.4 in areas of high fire-risk 6.5 when the fault-current-loop impedance is particularly high

7. residual current differential devices (RCDs)7.1 description 7.2 application of RCDstable G70 electromagnetic compatibility withstand-level tests for RCDs table G72 means of reducing the ratio In/lph (max.)

7.3 choice of characteristics of a residual-current circuit breaker (RCCB - IEC 1008)table G74 typical manufacturers coordination table for RCCBs, circuit breakers, and fuses

H. the protection of circuits and the switchgear H1. the protection of circuits1. general1.1 methodology and definitionstable H1-1 logigram for the selection of cable size and protective-device rating for a given circuit H1-1 H1-1 H1-1 H1-3 H1-4 H1-5 H1-5 H1-5 H1-6 H1-8 H1-9

1.2 overcurrent protection principles 1.3 practical values for a protection scheme 1.4 location of protective devicestable H1-7 general rules and exceptions concerning the location of protective devices

1.5 cables in parallel 1.6 worked example of cable calculationstable H1-9 calculations carried out with ECODIAL software (Merlin Gerin) table H1-10 example of short-circuit current evaluation

2. practical method for determining the smallest allowable cross-sectional-area of circuit conductors2.1 generaltable H1-11 logigram for the determination of minimum conductor size for a circuit

H1-10 H1-10 H1-10 H1-10 H1-10 H1-11 H1-11 H1-12 H1-13

2.2 determination of conductor size for unburied circuitstable H1-12 code-letter reference, depending on type of conductor and method of installation table H1-13 factor K1 according to method of circuit installation (for further examples refer to IEC 364-5-52 table 52H) table H1-14 correction factor K2 for a group of conductors in a single layer table H1-15 correction factor K3 for ambient temperature other than 30 C table H1-17 case of an unburied circuit: determination of the minimum cable size (c.s.a.), derived from the code letter; conductor material; insulation material and the fictitious current I'z

contents - A7


AH. the protection of circuits and the switchgear (continued) H1. the protection of circuits (continued)2. practical method for determining the smallest allowable cross-sectional-area of circuit conductors (continued)2.3 determination of conductor size for buried circuitstable H1-19 correction factor K4 related to the method of installation table H1-20 correction factor K5 for the grouping of several circuits in one layer table H1-21 correction factor K6 for the nature of the soil table H1-22 correction factor K7 for soil temperatures different than 20 C table H1-24 case of a buried circuit: minimum c.s.a. in terms of type of conductor; type of insulation; and value of fictitious current I'z (I'z = Iz) K H1-14 H1-14 H1-14 H1-15 H1-15 H1-15

3. determination of voltage drop3.1 maximum voltage-drop limittable H1-26 maximum voltage-drop limits

H1-17 H1-17 H1-17 H1-18 H1-18 H1-18 H1-20 H1-20 H1-20 H1-20 H1-21 H1-21 H1-22 H1-23 H1-23 H1-23

3.2 calculation of voltage drops in steady load conditionstable H1-28 voltage-drop formulae table H1-29 phase-to-phase voltage drop U for a circuit, in volts per ampere per km

4. short-circuit current calculations4.1 short-circuit current at the secondary terminals of a HV/LV distribution transformertable H1-32 typical values of Usc for different kVA ratings of transformers with HV windings i 20 kV table H1-33 Isc at the LV terminals of 3-phase HV/LV transformers supplied from a HV system with a 3-phase fault level of 500 MVA, or 250 MVA

4.2 3-phase short-circuit current (Isc) at any point within a LV installationtable H1-36 the impedance of the HV network referred to the LV side of the HV/LV transformer table H1-37 resistance, reactance and impedance values for typical distribution transformers with HV windings i 20 kV table H1-38 recapitulation table of impedances for different parts of a power-supply system table H1-39 example of short-circuit current calculations for a LV installation supplied at 400 V (nominal) from a 1,000 kVA HV/LV transformer

4.3 Isc at the receiving end of a feeder in terms of the Isc at its sending endtable H1-40 Isc at a point downstream, in terms of a known upstream fault-current value and the length and c.s.a. of the intervening conductors, in a 230/400 V 3-phase system

H1-24 H1-25 H1-26 H1-26

4.4 short-circuit current supplied by an alternator or an inverter

5. particular cases of short-circuit current5.1 calculation of minimum levels of short-circuit currenttable H1-49 maximum circuit lengths in metres for copper conductors (for aluminium, the lengths must be multiplied by 0.62) table H1-50 maximum length of copper-conductored circuits in metres protected by B-type circuit breakers table H1-51 maximum length of copper-conductored circuits in metres protected by C-type circuit breakers table H1-52 maximum length of copper-conductored circuits in metres protected by D-type circuit breakers table H1-53 correction factors to apply to lengths obtained from tables H1-49 to H1-52A8 - contents

H1-28 H1-29 H1-29 H1-29 H1-30

A5.2 verification of the withstand capabilities of cables under short-circuit conditionstable H1-54 value of the constant k2 table H1-55 maximum allowable thermal stress for cables (expressed in amperes2 x seconds x 106) H1-31 H1-31 H1-31 H1-32 H1-32 H1-33 H1-33

6. protective earthing conductors (PE)6.1 connection and choicetable H1-59 choice of protective conductors (PE)

6.2 conductor dimensioningtable H1-60 minimum c.s.a.'s for PE conductors and earthing conductors (to the installation earth electrode) table H1-61 k factor values for LV PE conductors, commonly used in national standards and complying with IEC 724

H1-34 H1-34

H1-35 table H1-63 c.s.a. of PE conductor between the HV/LV transformer and the MGDB, in terms of transformer ratings and fault-clearance times used in France H1-35

6.3 protective conductor between the HV/LV transformer and the main general distribution board (MGDB)

6.4 equipotential conductor 7. the neutral conductor 7.1 dimensioning the neutral conductor 7.2 protection of the neutral conductortable H1-65 table of protection schemes for neutral conductors in different earthing systems

H1-35 H1-36 H1-36 H1-36 H1-37

H2. the switchgear1. the basic functions of LV switchgeartable H2-1 basic functions of LV switchgear H2-1 H2-1 H2-1 H2-1 H2-2 H2-2 H2-4 H2-4 H2-5 H2-5 H2-7 H2-9 H2-11 H2-11 H2-11 H2-11

1.1 electrical protection 1.2 isolationtable H2-2 peak value of impulse voltage according to normal service voltage of test specimen

1.3 switchgear control

2. the switchgear and fusegear2.1 elementary switching devicestable H2-7 utilization categories of LV a.c. switches according to IEC 947-3 table H2-8 factor "n" used for peak-to-rms value (IEC 947-part 1) table H2-13 zones of fusing and non-fusing for LV types gG and gM class fuses (IEC 269-1 and 269-2-1)

2.2 combined switchgear elements

3. choice of switchgear3.1 tabulated functional capabilitiestable H2-19 functions fulfilled by different items of switchgear

3.2 switchgear selection

contents - A9


AH2. the switchgear (continued)4. circuit breakerstable H2-20 functions performed by a circuit breaker/disconnector H2-12 H2-12 H2-12 H2-15 H2-16 H2-17

4.1 standards and descriptions 4.2 fundamental characteristics of a circuit breakertable H2-28 tripping-current ranges of overload and short-circuit protective devices for LV circuit breakers table H2-31 Icu related to power factor (cos ) of fault-current circuit (IEC 947-2)

4.3 other characteristics of a circuit breaker

H2-18 table H2-34 relation between rated breaking capacity Icu and rated making capacity Icm at different power-factor values of short-circuit current, as standardized in IEC 947-2 H2-19

4.4 selection of a circuit breakertable H2-38 examples of tables for the determination of derating/uprating factors to apply to CBs with uncompensated thermal tripping units, according to temperature table H2-40 different tripping units, instantaneous or short-time delayed table H2-43 maximum values of short-circuit current to be interrupted by main and principal circuit breakers (CBM and CBP respectively), for several transformers in parallel

H2-20 H2-21 H2-23 H2-25 H2-27 H2-28 H2-29 H2-32

4.5 coordination between circuit breakerstable H2-45 example of cascading possibilities on a 230/400 V or 240/415 V 3-phase installation table H2-49 summary of methods and components used in order to achieve discriminative tripping

4.6 discrimination HV/LV in a consumer's substation

J. particular supply sources and loads1. protection of circuits supplied by an alternator1.1 an alternator on short-circuit 1.2 protection of essential services circuits supplied in emergencies from an alternator 1.3 choice of tripping units 1.4 methods of approximate calculationtable J1-7 procedure for the calculation of 3-phase short-circuit current table J1-8 procedure for the calculation of 1-phase to neutral short-circuit current J1 J1 J4 J5 J6 J6 J7 J9

1.5 the protection of standby and mobile a.c. generating sets

2. inverters and UPS (Uninterruptible Power Supply units)2.1 what is an inverter? 2.2 types of UPS system

J10 J10

J10 table J2-4 examples of different possibilities and applications of inverters, in decontamination of supplies and in UPS schemes J11 J11 J12 J14 J15 J17

2.3 standards 2.4 choice of a UPS system 2.5 UPS systems and their environment 2.6 putting into service and technology of UPS systems 2.7 earthing schemes

A10 - contents

A2.8 choice of main-supply and circuit cables, and cables for the battery connectiontable J2-21 voltage drop in % of 324 V d.c. for a copper-cored cable table J2-22 currents and c.s.a. of copper-cored cables feeding the rectifier, and supplying the load for UPS system Maxipac (cable lengths < 100 m) table J2-23 currents and c.s.a. of copper-cored cables feeding the rectifier, and supplying the load for UPS system EPS 2000 (cable lengths < 100 m). Battery cable data are also included table J2-24 input, output and battery currents for UPS system EPS 5000 (Merlin Gerin) J20 J21 J21 J21 J22 J23 J24 J25 J25 J25 J26 J26 J26 J26 J27 J27 J28 J29 J29 J30 J30 J31 J31

2.9 choice of protection schemes 2.10 complementary equipments

3. protection of LV/LV transformers3.1 transformer-energizing in-rush current 3.2 protection for the supply circuit of a LV/LV transformer 3.3 typical electrical characteristics of LV/LV 50 Hz transformerstable J3-5 typical electrical characteristics of LV/LV 50 Hz transformers

3.4 protection of transformers with characteristics as tabled in J3-5 above, using Merlin Gerin circuit breakerstable J3-6 protection of 3-phase LV/LV transformers with 400 V primary windings table J3-7 protection of 3-phase LV/LV transformers with 230 V primary windings table J3-8 protection of 1-phase LV/LV transformers with 400 V primary windings table J3-9 protection of 1-phase LV/LV transformers with 230 V primary windings

4. lighting circuits4.1 service continuity 4.2 lamps and accessories (luminaires)table J4-1 analysis of disturbances in fluorescent-lighting circuits

4.3 the circuit and its protection 4.4 determination of the rated current of the circuit breakertable J4-2 protective circuit breaker ratings for incandescent lamps and resistive-type heating circuits table J4-3 maximum limit of rated current per outgoing lighting circuit, for high-pressure discharge lamps table J4-4 current ratings of circuit breakers related to the number of fluorescent luminaires to be protected

J31 J32 J32 J33 J33 J34 J35 J36 J36 J37 J38 J38 J39 J41

4.5 choice of control-switching devicestable J4-5 types of remote control

4.6 protection of ELV lighting circuits 4.7 supply sources for emergency lighting

5. asynchronous motors5.1 protective and control functions requiredtable J5-2 commonly-used types of LV motor-supply circuits

5.2 standards 5.3 basic protection schemes: circuit breaker / contactor / thermal relaytable J5-4 utilization categories for contactors (IEC 947-4)

5.4 preventive or limitative protection

contents - A11


AJ. particular supply sources and loads (continued)5. asynchronous motors (continued)5.5 maximum rating of motors installed for consumers supplied at LVtable J5-12 maximum permitted values of starting current for direct-on-line LV motors (230/400 V) table J5-13 maximum permitted power ratings for LV direct-on-line-starting motors J43 J43 J43 J43 J44 J44 J45 J45 J45 J46 J46 J47

5.6 reactive-energy compensation (power-factor correction)

6. protection of direct-current installations6.1 short-circuit currents 6.2 characteristics of faults due to insulation failure, and of protective switchgeartable J6-4 characteristics of protective switchgear according to type of d.c. system earthing

6.3 choice of protective devicetable J6-5 choice of d.c. circuit breakers manufactured by Merlin Gerin

6.4 examples 6.5 protection of persons

7. Appendix : Short-circuit characteristics of an alternator

App J1-1

L. domestic and similar premises and special locations1. domestic and similar premises1.1 general 1.2 distribution-board components 1.3 protection of persons 1.4 circuitstable L1-9 recommended minimum number of lighting and power points in domestic premises table L1-11 c.s.a. of conductors and current rating of the protective devices in domestic installations (the c.s.a. of aluminium conductors are shown in brackets) L1 L1 L2 L4 L6 L6

L7 L8 L8 L10 L10

2. bathrooms and showers2.1 classification of zones 2.2 equipotential bonding 2.3 requirements prescribed for each zone

3. recommendations applicable to special installations and locations

L11

A12 - contents

1. methodology

Bthe study of an electrical installation by means of this guide requires the reading of the entire text in the order in which the chapters are presented.

listing of power demandsThe study of a proposed electrical installation necessitates an adequate understanding of all governing rules and regulations. A knowledge of the operating modes of power-consuming appliances, i.e. "loads" (steady-state demand, starting conditions, non-simultaneous operation, etc.) together with the location and magnitude of each load shown on a building plan, allow a listing of power demands to be compiled. The list will include the total power of the loads installed as well as an estimation of the actual loads to be supplied, as deduced from the operating modes. From these data the power required from the supply source and (where appropriate) the number of sources necessary for an adequate supply to the installation, are readily obtained. Local information regarding tariff structures is also required to permit the best choice of connection arrangement to the power-supply network, e.g. at high voltage or low voltage. corresponding chapter B - general - installed power

service connectionThis connection can be made at: c High Voltage: a consumer-type substation will then have to be studied, built and equipped. This substation may be an outdoor or indoor installation conforming to relevant standards and regulations (the low-voltage section may be studied separately if necessary). Metering at high-voltage or low-voltage is possible in this case c Low Voltage: the installation will be connected to the local power network and will (necessarily) be metered according to LV tariffs. C - HV/LV distribution substations

D - low-voltage service connections

reactive energyThe compensation of reactive energy within electrical installations normally concerns only power factor improvement, and is carried out locally, globally or as a combination of both methods. E - power factor improvement

LV distributionThe whole of the installation distribution network is studied as a complete system. The number and characteristics of standby emergency-supply sources are defined. Earth-bonding connections and neutralearthing arrangements are chosen according to local regulations, constraints related to the power-supply, and to the nature of the installation loads. The hardware components of distribution, together with distribution boards and cableways, are determined from building plans and from the location and grouping of loads. The kinds of location, and activities practised in them, can affect their level of resistance to external influences. F - distribution within a low-voltage installation

protection against electric shockThe system of earthing (TT, IT or TN) having been previously determined, it remains, in order to achieve protection of persons against the hazards of direct and indirect contact, to choose an appropriate scheme of protection. G - protection against electric shock

general - installed power - B1

1. methodology (continued)

Bcircuits and switchgearEach circuit is then studied in detail. From the rated currents of the loads; the level of short-circuit current; and the type of protective device, the cross-sectional area of circuit conductors can be determined, taking into account the nature of the cableways and their influence on the current rating of conductors. Before adopting the conductor size indicated above, the following requirements must be satisfied: c the voltage drop complies with the relevant standard, c motor starting is satisfactory, c protection against electric shock is assured. The short-circuit current Isc is then determined, and the Isc thermal and electrodynamic withstand capability of the circuit is checked. These calculations may indicate that a different conductor size than that originally chosen is necessary. The performance required by the switchgear will determine its type and characteristics. The use of cascading techniques and the discriminative operation of fuses and tripping of circuit breakers are examined.

H1 - the protection of circuits

H2 - the switchgear

particular supply sources and loadsParticular items of plant and equipment are studied: c specific sources such as alternators or inverters, c specific loads with special characteristics, such as induction motors, lighting circuits or LV/LV transformers, or c specific systems, such as direct-current networks. J - particular supply sources and loads

domestic and similar premises and special locationsCertain premises and locations are subject to particularly strict regulations: the most common example being domestic dwellings. L - domestic and similar premises and special locations

Ecodial 2.2 softwareEcodial 2.2 software* provides a complete conception and design package for LV installations, in accordance with IEC standards and recommendations. The following features are included: c construction of one-line diagrams, c calculation of short-circuit currents, c calculation of voltage drops, c optimization of cable sizes, c required ratings of switchgear and fusegear, c discrimination of protective devices, c recommendations for cascading schemes, c verification of the protection of persons, c comprehensive print-out of the foregoing calculated design data.* Ecodial 2.2 is a Merlin Gerin product and is available in French and English versions.

B2 - general - installed power

2. rules and statutory regulations

BLow-voltage installations are governed by a number of regulatory and advisory texts, which may be classified as follows: c statutory regulations (decrees, factory acts, etc.), c codes of practice, regulations issued by professional institutions, job specifications, c national and international standards for installations, c national and international standards for products.

2.1 definition of voltage rangesIEC voltage standards and recommendationsthree phase, four wire or three wire systems nominal voltage (V) 230/400(1) 277/480(2) 400/690(1) 1000 single phase, three wire systems nominal voltage (V) 120/240 -

table B1: standard voltages between 100 V and 1000 V (IEC 38-1983).1) The nominal voltage of existing 220/380 V and 240/415 V systems shall evolve towards the recommended value of 230/400 V. The transition period should be as short as possible, and should not exceed 20 years after the issue of this IEC publication. During this period, as a first step, the electricity supply authorities of countries having 220/380 V systems should bring the voltage within the range 230/400 V +6% -10% and those of countries having 240/415 V systems should bring the voltage within the range 230/400 V +10% -6%. At the end of this transition period the tolerance of 230/400 V 10% should have been achieved; after this the reduction of this range will be considered. All the above considerations apply also to the present 380/660 V value with respect to the recommended value 400/690 V. 2) Not to be utilized together with 230/400 V or 400/690 V.

50 Hz and 60 Hz systems series I highest voltage nominal system for equipment (kV) voltage (kV) 3.6(1) 3.3(1) 3((1) 7.2(1) 6.6(1) 6(1) 12 11 10 (17.5) (15) 24 22 20 36(3) 33(3) 40.5(3) 35(3)

60 Hz systems series II (North American practice) highest voltage nominal system for equipment (kV) voltage (kV) 4.40(1) 4.16(1) 13.2(2) 12.47(2) 13.97(2) 13.2(2) 14.52(1) 13.8(1) 26.4(2) 24.94(2) 36.5(2) 34.5(2) -

table B2: standard voltages above 1 kV and not exceeding 35 kV (IEC 38-1983).* These systems are generally three-wire systems unless otherwise indicated. The values indicated are voltages between phases. The values indicated in parentheses should be considered as non-preferred values. It is recommended that these values should not be used for new systems to be constructed in future. 1) These values should not be used for public distribution systems. 2) These systems are generally four-wire systems. 3) The unification of these values is under consideration.


2. rules and statutory regulations (continued)

B2.2 regulationsIn most countries, electrical installations shall comply with more than one set of regulations, issued by National Authorities or by recognised private bodies. It is essential to take into account these local constraints before starting the design.

2.3 standardsThis Guide is based on relevant IEC standards, in particular IEC 364. IEC 364 has been established by medical and engineering experts of all countries in the world comparing their experience at an international level. Currently, the safety principles of IEC 364 and 479-1 are the fundamentals of most electrical standards in the world. IEC - 38 IEC - 56 IEC - 76-2 IEC - 76-3 IEC - 129 IEC - 146 IEC - 146-4 Standard voltages High-voltage alternating-current circuit breakers Power transformer - Part 2: Temperature rise Power transformer - Part 3: Insulation levels and dielectric tests Alternating current disconnectors and earthing switches General requirements and line commutated converters General requirements and line commutated converters - Part 4: Method of specifying the performance and test requirements of uninterruptible power systems IEC - 265-1 High-voltage switches - Part 1: High-voltage switches for rated voltages above 1 kV and less than 52 kV IEC - 269-1 Low-voltage fuses - Part 1: General requirements IEC - 269-3 Low-voltage fuses - Part 3: Supplementary requirements for fuses for use by unskilled persons (fuses mainly for household and similar applications) IEC - 282-1 High-voltage fuses - Part 1: Current limiting fuses IEC - 287 Calculation of the continuous current rating of cables (100% load factor) IEC - 298 AC metal-enclosed switchgear and controlgear for rated voltages above 1kV and up to and including 52 kV IEC - 364 Electrical installations of buildings IEC - 364-3 Electrical installations of buildings - Part 3: Assessment of general characteristics IEC - 364-4-41 Electrical installations of buildings - Part 4: Protection of safety - Section 41: Protection against electrical shock IEC - 364-4-42 Electrical installations of buildings - Part 4: Protection of safety - Section 42: Protection against thermal effects IEC - 364-4-43 Electrical installations of buildings - Part 4: Protection of safety - Section 43: Protection against overcurrent IEC - 364-4-47 Electrical installations of buildings - Part 4: Application of protective measures for safety - Section 47: Measures of protection against electrical shock IEC - 364-5-51 Electrical installations of buildings - Part 5: Selection and erection of electrical equipment - Section 51: Common rules IEC - 364-5-52 Electrical installations of buildings - Part 5: Selection and erection of electrical equipment - Section 52: Wiring systems IEC - 364-5-53 Electrical installations of buildings - Part 5: Selection and erection of electrical equipment - Section 53: Switchgear and controlgear IEC - 364-6 Electrical installations of buildings - Part 6: Verification IEC - 364-7-701 Electrical installations of buildings - Part 7: Requirements for special installations or locations - Section 701: Electrical installations in bathrooms IEC - 364-7-706 Electrical installations of buildings - Part 7: Requirements for special installations or locations - Section 706: Restrictive conductive locations IEC - 364-7-710 Electrical installations of buildings - Part 7: Requirements for special installations or locations - Section 710: Installation in exhibitions, shows, stands and funfairs IEC - 420 High-voltage alternating current switch-fuse combinations IEC - 439-1 Low-voltage switchgear and controlgear assemblies - Part 1: Types-tested and partially type-tested assemblies IEC - 439-2 Low-voltage switchgear and controlgear assemblies - Part 2: Particular requirements for busbar trunking systems (busways) IEC - 439-3 Low-voltage switchgear and controlgear assemblies - Part 3: Particular requirements for low-voltage switchgear and controlgear assemblies intended to be installed in places where unskilled persons have access for their use Distribution boards IEC - 446 Identification of conductors by colours or numerals IEC - 479-1 Effects of current on human beings and livestock - Part 1: General aspects IEC - 479-2 Effects of current on human beings and livestock - Part 2: Special aspects IEC - 529 Degrees of protection provided by enclosures (IP code) IEC - 644 Specification for high-voltage fuse-links for motor circuit applications


BIEC - 664 IEC - 694 IEC - 724 IEC - 742 IEC - 755 IEC - 787 IEC - 831-1 Insulation coordination for equipment within low-voltage systems Common clauses for high-voltage switchgear and controlgear standards Guide to the short-circuit temperature limits of electrical cables with a rated voltage not exceeding 0.6/1.0 kV Isolation transformer and safety isolation transformer. Requirements General requirements for residual current operated protective devices Application guide for selection for fuse-links of high-voltage fuses for transformer circuit application Shunt power capacitors of the self-healing type for a.c. systems having a rated voltage up to and including 660 V. - Part 1: General - Performance, testing and rating - Safety requirements - Guide for installation and operation

2.4 quality and safety of an electrical installationOnly by c the initial checking of the conformity of the electrical installation, c the verification of the conformity of electrical equipment, c and periodic checking can the permanent safety of persons and security of supply to equipment be achieved.


2. rules and statutory regulations (continued)

B2.5 initial testing of an installationBefore a power-supply authority will connect an installation to its supply network, strict pre-commissioning electrical tests and visual inspections by the authority, or by its appointed agent, must be satisfied. These tests are made according to local (governmental and/or institutional) regulations, which may differ slightly from one country to another. The principles of all such regulations however, are common, and are based on the observance of rigorous safety rules in the design and realization of the installation. IEC 364 and related standards included in this guide are based on an international consensus for such tests, intended to cover all the safety measures and approved installation practices normally required for domestic, commercial and (the majority of) industrial buildings. Many industries however have additional regulations related to a particular product (petroleum, coal, natural gas, etc.). Such additional requirements are beyond the scope of this guide. The pre-commissioning electrical tests and visual-inspection checks for installations in buildings include, typically, all of the following: c insulation tests of all cable and wiring conductors of the fixed installation, between phases and between phases and earth, c continuity and conductivity tests of protective, equipotential and earth-bonding conductors, c resistance tests of earthing electrodes with respect to remote earth, c allowable number of socket-outlets per circuit check, c cross-sectional-area check of all conductors for adequacy at the short-circuit levels prevailing, taking account of the associated protective devices, materials and installation conditions (in air, conduit, etc.), c verification that all exposed- and extraneous metallic parts are properly earthed (where appropriate), c check of clearance distances in bathrooms, etc. These tests and checks are basic (but not exhaustive) to the majority of installations, while numerous other tests and rules are included in the regulations to cover particular cases, for example: TN-, TT- or IT-earthed installations, installations based on class 2 insulation, SELV circuits, and special locations, etc. The aim of this guide is to draw attention to the particular features of different types of installation, and to indicate the essential rules to be observed in order to achieve a satisfactory level of quality, which will ensure safe and trouble-free performance. The methods recommended in this guide, modified if necessary to comply with any possible variation imposed by a local supply authority, are intended to satisfy all precommissioning test and inspection requirements.

2.6 periodic check-testing of an installationIn many countries, all industrial and commercial-building installations, together with installations in buildings used for public gatherings, must be re-tested periodically by authorized agents. Table B3 shows the frequency of testing commonly prescribed according to the kind of installation concerned. installations which require the protection of employees c locations at which a risk of degradation, annually fire or explosion exists c temporary installations at worksites c locations at which HV installations exist c restrictive conducting locations where mobile equipment is used other cases every 3 years according to the type of establishment and its capacity for receiving the public, the re-testing period will vary from one to three years according to local regulations

installations in buildings used for public gatherings, where protection against the risks of fire and panic are required residential

table B3: frequency of check-tests commonly recommended for an electrical installation.


B2.7 conformity (with standards and specifications) of equipment used in the installationconformity of equipment with the relevant standards can be attested in several ways.

attestation of conformityThe conformity of equipment with the relevant standards can be attested: c by an official conformity mark granted by the standards organization concerned, or c by a certificate of conformity issued by a laboratory, or c by a declaration of conformity from the manufacturer.

declaration of conformityIn cases where the equipment in question is to be used by qualified or experienced persons, the declaration of conformity provided by the manufacturer (included in the technical documentation) together with a conformity mark on the equipment concerned, are generally recognized as a valid attestation. Where the competence of the manufacturer is in doubt, a certificate of conformity can be obtained from an independent accredited laboratory.

the standards define several methods of quality assurance which correspond to different situations rather than to different levels of quality.

mark of conformityConformity marks are inscribed on appliances and equipment which are generally used by technically inexperienced persons (for example, domestic appliances) and for whom the standards have been established which permit the attribution, by the standardization authority, of a mark of conformity (commonly referred to as a conformity mark).

certification of Quality AssuranceA laboratory for testing samples cannot certify the conformity of an entire production run: these tests are called type tests. In some tests for conformity to standards, the samples are destroyed (tests on fuses, for example). Only the manufacturer can certify that the fabricated products have, in fact, the characteristics stated. Quality assurance certification is intended to complete the initial declaration or certification of conformity. As proof that all the necessary measures have been taken for assuring the quality of production, the manufacturer obtains certification of the quality control system which monitors the fabrication of the product concerned. These certificates are issued by organizations specializing in quality control, and are based on the international standard ISO 9000, the equivalent European standard being EN 29000. These standards define three model systems of quality assurance control corresponding to different situations rather than to different levels of quality: c model 3 defines assurance of quality by inspection and checking of final products, c model 2 includes, in addition to checking of the final product, verification of the manufacturing process. This method applies, for example, to the manufacture of fuses where performance characteristics cannot be checked without destroying the fuse, c model 1 corresponds to model 2, but with the additional requirement that the quality of the design process must be rigorously scrutinized; for example, where it is not intended to fabricate and test a prototype (case of a custom-built product made to specification).general - installed power - B7

3. motor, heating and lighting loads

Ban examination of the actual apparent-power demands of different loads: a necessary preliminary step in the design of a LV installation.The examination of actual values of apparent-power required by each load enables the establishment of: c a declared power demand which determines the contract for the supply of energy, c the rating of the HV/LV transformer, where applicable (allowing for expected increases in load), c levels of load current at each distribution board.

3.1 induction motorsthe nominal power in kW (Pn) of a motor indicates its rated equivalent mechanical power output. The apparent power in kVA (Pa) supplied to the motor is a function of the output, the motor efficiency and the power factor. Pa = Pn cos

current demandThe full-load current Ia supplied to the motor is given by the following formulae: Pn x 1,000 3-phase motor: Ia = ex U x x cos 1-phase motor: Ia = Pn x 1,000 U x x cos where Ia: current demand (in amps) Pn: nominal power (in kW of active power) U: voltage between phases for 3-phase motors and voltage between the terminals for single-phase motors (in volts). A single-phase motor may be connected phase-to-neutral or phase-to-phase. : per-unit efficiency, i.e. output kW input kW cos : power factor, i.e. kW input kVA input

motor-starting currentStarting current (Id) for 3-phase induction motors, according to motor type, will be: c for direct-on-line starting of squirrel-cage motors: v Id = 4.2 to 9 In for 2-pole motors v Id = 4.2 to 7 In for motors with more than 2 poles (mean value = 6 In), where In = nominal full-load current of the motor, c for wound-rotor motors (with slip-rings), and for D.C. motors: Id depends on the value of starting resistances in the rotor circuits: Id = 1.5 to 3 In (mean value = 2.5 In). c for induction motors controlled by speedchanging variable-frequency devices (for example: Altivar Telemecanique), assume that the control device has the effect of increasing the power (kW) supplied to the circuit motor (i.e. device plus) by 10%.

it is generally advantageous for technical and financial reasons to reduce the current supplied to induction motors. This can be achieved by using capacitors without affecting the power output of the motors.

compensation of reactive-power (kvar) supplied to induction motorsThe application of this principle to the operation of induction motors is generally referred to as "power-factor improvement" or "power-factor correction". As discussed in chapter E, the apparentpower (kVA) supplied to an induction motor can be significantly reduced by the use of shunt-connected capacitors. Reduction of input kVA means a corresponding reduction of input current (since the voltage remains constant). Compensation of reactive-power is particularly advised for motors that operate for long periods at reduced power. As noted above cos = kW input so that a kVA input reduction in kVA input will increase (i.e. improve) the value of cos . The current supplied to the motor, after power-factor correction, is given by: Ia x cos cos ' where cos is the power factor before compensation and cos ' is the power factor after compensation, Ia being the original current.

table of typical valuesTable B4 shows, as a function of the rated nominal power of motors, the current supplied to them at different voltage levels under normal uncompensated conditions, and the same motors under the same conditions, but compensated to operate at a power factor of 0.93 (tan = 0.4). These values are averages and will differ to some extent according to the type of motor and the manufacturer concerned.B8 - general - installed power

Note: the rated voltages of certain loads listed in table B4 are still based on 220/380 V. The international standard is now (since 1983) 230/400 V. To convert the current values indicated for a given motor rating in the 220 V and 380 V columns to the currents taken by 230 V and 400 V motors of the same rating, multiply by a factor of 0.95.

B3.1 induction motors (continued)nominal power Pn kW HP 0.37 0.5 0.55 0.75 0.75 1 1.1 1.5 1.5 2 2.2 3 3 4 3.7 5 4 5.5 5.5 7.5 7.5 10 9 12 10 13.5 11 15 15 20 18.5 25 22 30 25 35 30 40 33 45 37 50 40 54 45 60 51 70 55 75 59 80 63 85 75 100 80 110 90 125 100 136 110 150 129 175 132 180 140 190 147 200 150 205 160 220 180 245 185 250 200 270 220 300 250 340 257 350 280 380 295 400 300 410 315 430 335 450 355 480 375 500 400 545 425 580 445 600 450 610 475 645 500 680 530 720 560 760 600 810 630 855 670 910 710 965 750 1020 800 1090 900 1220 1100 1500 without compensation cos Pa current at different voltages at Pn 1-PH 3-PH 220 V 220 V 380 V 440 V kVA A A A A 0.73 0.79 3.6 1.8 1.03 0.99 0.75 1.1 4.7 2.75 1.6 1.36 0.75 1.4 6 3.5 2 1.68 0.79 1.9 8.5 4.4 2.6 2.37 0.80 2.4 12 6.1 3.5 3.06 0.80 3.5 16 8.7 5 4.42 0.80 4.6 21 11.5 6.6 5.77 0.80 5.6 25 13.5 7.7 7.1 0.80 6.1 26 14.5 8.5 7.9 0.83 7.9 35 20 11.5 10.4 0.83 10.6 47 27 15.5 13.7 0.85 12.3 32 18.5 16.9 0.85 13.7 35 20 17.9 0.86 14.7 39 22 20.1 0.86 19.8 52 30 26.5 0.86 24.2 64 37 32.8 0.86 28.7 75 44 39 0.86 33 85 52 45.3 0.86 39 103 60 51.5 0.86 43 113 68 58 0.86 48 126 72 64 0.86 51 134 79 67 0.86 57 150 85 76 0.86 65 170 98 83 0.86 70 182 105 90 0.87 74 195 112 97 0.87 79 203 117 109 0.87 94 240 138 125 0.87 100 260 147 131 0.87 112 295 170 146 0.87 125 325 188 162 0.87 136 356 205 178 0.87 159 420 242 209 0.87 161 425 245 215 0.87 171 450 260 227 0.87 180 472 273 236 0.87 183 483 280 246 0.87 196 520 300 256 0.87 220 578 333 289 0.87 226 595 342 295 0.88 242 626 370 321 0.88 266 700 408 353 0.88 302 800 460 401 0.88 311 826 475 412 0.88 335 900 510 450 0.88 353 948 546 473 0.88 359 980 565 481 0.88 377 990 584 505 0.88 401 1100 620 518 0.88 425 1150 636 549 0.88 449 1180 670 575 0.88 478 1250 710 611 0.88 508 1330 760 650 0.88 532 1400 790 680 0.88 538 1410 800 690 0.88 568 1490 850 730 0.88 598 1570 900 780 0.88 634 1660 950 825 0.88 670 1760 1000 870 0.88 718 1880 1090 920 0.88 754 1980 1100 965 0.88 801 2100 1200 1020 0.88 849 1260 1075 0.88 897 1350 1160 0.88 957 1450 1250 0.88 1076 1610 1390 0.88 1316 1980 1700 with compensation cos capa- Pa at Pn citor rating kvar kVA 0.93 0.31 0.62 0.93 0.39 0.87 0.93 0.48 1.1 0.93 0.53 1.6 0.93 0.67 2.1 0.93 0.99 3 0.93 1.31 4 0.93 1.59 4.8 0.93 1.74 5.2 0.93 1.80 7 0.93 2.44 9.5 0.93 2.4 11.3 0.93 2.6 12.5 0.93 2.50 13.6 0.93 3.37 18.3 0.93 4.12 22.4 0.93 4.89 26.6 0.93 5.57 30 0.93 6.68 36 0.93 7.25 39 0.93 8.12 44 0.93 8.72 47 0.93 9.71 53 0.93 11.10 60 0.93 11.89 64 0.93 10.98 69 0.93 11.66 74 0.93 13.89 88 0.93 14.92 93 0.93 16.80 105 0.93 18.69 117 0.93 20.24 127 0.93 23.84 149 0.93 24 151 0.93 25.55 160 0.93 26.75 168 0.93 27.26 172 0.93 29.15 183 0.93 32.76 206 0.93 33.79 212 0.93 30.78 229 0.93 33.81 252 0.93 38.44 286 0.93 39.45 294 0.93 42.63 317 0.93 44.80 334 0.93 45.66 339 0.93 47.98 356 0.93 51 379 0.93 54 402 0.93 57.1 424 0.93 60.84 453 0.93 64.60 481 0.93 67.63 504 0.93 68.50 509 0.93 70.40 538 0.93 72.26 566 0.93 80.64 600 0.93 85.12 634 0.93 91.33 679 0.93 95.81 713 0.93 101.88 758 0.93 107.95 804 0.93 114 849 0.93 121.68 905 0.93 136.86 1019 0.93 167.35 1245 current at different voltages 1-PH 3-PH 220 V 220 V 380 V 440 V A A A A 2.8 1.4 0.8 0.77 3.8 2.2 1.3 1.1 4.8 2.8 1.6 1.3 7.2 3.7 2.2 2 10.3 5.2 3 2.6 13.7 7.5 4.3 3.8 18 9.9 5.7 5 22 11.6 6.6 6.1 22 12.5 7.3 6.8 31 17.8 10.3 9.3 42 24 13.8 12.2 29 16.9 15.4 32 18 16.4 36 20 19 48 28 25 59 34 30 69 41 36 79 48 42 95 55 48 104 63 54 117 67 59 124 73 62 139 79 70 157 91 77 168 97 83 182 105 91 190 109 102 225 129 117 243 138 123 276 159 137 304 176 152 333 192 167 393 226 196 398 229 201 421 243 212 442 255 221 452 262 230 486 281 239 541 312 270 557 320 276 592 350 304 662 386 334 757 435 379 782 449 390 852 483 426 897 517 448 927 535 455 937 553 478 1041 587 490 1088 602 519 1117 634 544 1183 672 578 1258 719 615 1325 748 643 1334 757 653 1410 804 691 1486 852 738 1571 899 781 1665 946 823 1779 1031 871 1874 1041 913 1987 1135 965 1192 1017 1277 1098 1372 1183 1523 1315 1874 1609

% 64 68 72 75 78 79 81 82 82 84 85 86 86 87 88 89 89 89 89 90 90 91 91 91 92 92 92 92 92 92 92 93 93 94 94 94 94 94 94 94 94 94 94 94 95 95 95 95 95 95 95 95 95 95 95 95 95 95 95 95 95 95 95 95 95 95 95

500 V A 0.91 1.21 1.5 2 2.6 3.8 5 5.9 6.5 9 12 13.9 15 18.4 23 28.5 33 39.4 45 50 55 60 65 75 80 85 89 105 112 129 143 156 184 187 200 207 210 220 254 263 281 310 360 365 400 416 420 445 472 500 527 540 574 595 608 645 680 720 760 830 850 910 960 1020 1100 1220 1500

660 V A 0.6 0.9 1.1 1.5 2 2.8 3.8 4.4 4.9 6.6 8.9 10.6 11.5 14 17.3 21.3 25.4 30.3 34.6 39 42 44 49 57 61 66 69 82 86 98 107 118 135 140 145 152 159 170 190 200 215 235 274 280 305 320 325 337 365 370 395 410 445 455 460 485 515 545 575 630 645 690 725 770 830 925 1140

500 V A 0.71 1 1.2 1.7 2.2 3.3 4.3 5.1 5.6 8 10.7 12.7 13.7 17 21 26 31 36 42 46 51 55 60 69 74 80 83 98 105 121 134 146 172 175 187 194 196 206 238 246 266 293 341 345 378 394 397 421 447 473 499 511 543 563 575 610 643 681 719 785 804 861 908 965 1041 1154 1419

660 V A 0.47 0.72 0.88 1.3 1.7 2.4 3.3 3.8 4.2 5.9 7.9 9.7 10.5 13 16 20 23 28 32 36 39 41 45 53 56 62 65 77 80 92 100 110 126 131 136 142 149 159 178 187 203 222 259 265 289 303 306 319 336 350 374 388 420 431 435 459 487 516 544 596 610 653 686 729 785 875 1079

table B4: power and current values for typical induction motors.Reminder: some columns refer to 220 and 380 V motors. The international (IEC 38) standard of 230/400 V has been in force since 1983. The conversion factor for current values for 230 V and 400 V motors is 0.95, as noted on the previous page.


3. motor, heating and lighting loads (continued)

B3.2. direct-current motorsD.C. motors are mainly used for specific applications which require very high torques and/or variable speed control (for example machine tools and crushers, etc.). Power to these motors is provided via speedcontrol converters, fed from 230/400 V 3-phase a.c. sources; for example, Rectivar 4 (Telemecanique). The operating principle of the converter does not allow heavy overloading. The speed controller, the supply line and the protection are therefore based on the duty cycle of the motor (e.g. frequent starting-current peaks) rather than on the steady-state full-load current. For powers i 40 kW, this solution is progressively replaced with a speedchanging variable-frequency device and an asynchronous motor. It is still used for gradual starters and/or retarders.Im

MV power-supply network

In

fig. B5: diagram of a low-power speed controller. motor maximum power 220 V 380 V 415 V kW kW kW 1.5 3 3.3 4 5.5 6 5.5 7.5 8 11 18.5 20 18.5 30 33 22 37 40 55 60 440 V (60 Hz) kW 3.5 6.5 8.5 21.5 35 42 63 motor In A 7 7 12 12 16 16 37 37 60 60 72 72 105 105 GRADIVAR Ith A 10 10 20 20 30 30 60 60 100 100 130 130 200 200 catalogue number weight kg VR2-SA2121 VR2-SA2123 VR2-SA2171 VR2-SA2173 VR2-SA2211 VR2-SA2213 VR2-SA2281 VR2-SA2283 VR2-SA2361 VR2-SA2363 VR2-SA2401 VR2-SA2403 VR2-SA2441 VR2-SA2443 1.95 1.95 3.10 3.10 4.90 4.90 5.30 5.30 5.30 5.30 5.40 5.40 10.00 10.00

table B6: progressive starters with voltage ramp. motor maximum power 220 V 380 V 415 V kW kW kW 4 5.5 6 5.5 7.5 8 11 18.5 20 18.5 30 33 22 37 40 55 60 75 80 132 140 440 V (60 Hz) kW 6.5 8.5 21.5 35 42 63 90 147 motor In A 12 12 16 16 37 37 60 60 72 72 105 105 140 140 245 245 GRADIVAR Ith A 20 20 30 30 60 60 100 100 130 130 200 200 350 350 530 530 catalogue number weight kg VR2-SA3171 VR2-SA3173 VR2-SA3211 VR2-SA3213 VR2-SA3281 VR2-SA3283 VR2-SA3361 VR2-SA3363 VR2-SA3401 VR2-SA3403 VR2-SA3441 VR2-SA3443 VR2-SA3481 VR2-SA3483 VR2-SA3521 VR2-SA3523 3.30 3.30 5.10 5.10 5.50 5.50 5.50 5.50 5.60 5.60 11.00 11.00 45.00 45.00 45.00 45.00

table B7: progressive starters with current limitation.B10 - general - installed power

B3.3. resistive-type heating appliances and incandescent lamps (conventional or halogen)the power consumed by a heating appliance or an incandescent lamp is equal to the nominal power Pn quoted by the manufacturer (i.e. cos = 1). the currents are given by: c 3-phase case: Ia = Pn* ex U c 1-phase case: Ia = Pn* U where U is the voltage between the terminals of the equipment.The power consumed by a heating appliance or an incandescent lamp is equal to the nominal power Pn quoted by the manufacturer (i.e. cos = 1). The currents are given by: c 3-phase case: Ia = Pn* ex U c 1-phase case: Ia = Pn* U where U is the voltage between the terminals of the equipment. nominal power kW 0.1 0.2 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 6 7 8 9 10 For an incandescent lamp, the use of halogen gas allows a more concentrated light source. The light output is superior and the life of the lamp is doubled. Note: at the instant of switching on, the cold filament gives rise to a very brief but intense peak of current. * Ia in amps; U in volts. Pn is in watts. If Pn is in kW, then multiply the equation by 1,000.

current demand 1-phase 1-phase 127 V 230 V 0.79 0.43 1.58 0.87 3.94 2.17 7.9 4.35 11.8 6.52 15.8 8.70 19.7 10.9 23.6 13 27.6 15.2 31.5 17.4 35.4 19.6 39.4 21.7 47.2 26.1 55.1 30.4 63 34.8 71 39.1 79 43.5

3-phase 230 V 0.25 0.50 1.26 2.51 3.77 5.02 6.28 7.53 8.72 10 11.3 12.6 15.1 17.6 20.1 22.6 25.1

3-phase 400 V 0.14 0.29 0.72 1.44 2.17 2.89 3.61 4.33 5.05 5.77 6.5 7.22 8.66 10.1 11.5 13 14.4

table B8: current demands of resistive heating and incandescent lighting (conventional or halogen) appliances.

3.4. fluorescent lamps and related equipmentthe power in watts indicated on the tube of a fluorescent lamp does not include the power dissipated in the ballast. the current is given by: Pballast + Pn Ia = U x cos If no power-loss value is indicated for the ballast, a figure of 25% of Pn may be used.

standard tubular fluorescent lampsThe power Pn (watts) indicated on the tube of a fluorescent lamp does not include the power dissipated in the ballast. The current taken by the complete circuit is given by: Ia = Pballast + Pn U x cos where U = the voltage applied to the lamp, complete with its related equipment. with (unless otherwise indicated): c cos = 0.6 with no power factor (PF) correction* capacitor, c cos = 0.86 with PF correction* (single or twin tubes), c cos = 0.96 for electronic ballast. If no power-loss value is indicated for the ballast, a figure of 25% of Pn may be used. Table B8 gives these values for different arrangements of ballast.* "Power-factor correction" is often referred to as "compensation" in discharge-lighting-tube terminology.


3. motor, heating and lighting loads (continued)

B3.4. fluorescent lamps and related equipment (continued)arrangement of lamps, starters and ballasts single tube with starter tube power (W) (1) 18 36 58 single tube without 20 starter (2) with 40 external starting strip 65 twin tubes with starter 2 x 18 2 x 36 2 x 58 twin tubes without starter 2 x 40 single tube with 32 high frequency ballast 50 cos = 0.96 twin tubes with high2 x 32 frequency ballast 2 x 50 cos = 0.96 power consumed (W) 27 45 69 33 54 81 55 90 138 108 36 56 72 112 current (A) at 220V/240 V PF not PF electronic corrected corrected ballast 0.37 0.19 0.43 0.24 0.67 0.37 0.41 0.21 0.45 0.26 0.80 0.41 0.27 0.46 0.72 0.49 0.16 0.25 0.33 0.50 tube length (cm) 60 120 150 60 120 150 60 120 150 120 120 150 120 150

(1) Power in watts marked on tube. (2) Used exclusively during maintenance operations.

table B10: current demands and power consumption of commonly-dimensioned fluorescent lighting tubes (at 220 V/240 V - 50 Hz).

compact fluorescent tubesCompact fluorescent tubes have the same characteristics of economy and long life as classical tubes. They are commonly used in public places which are permanently illuminated (for example: corridors, hallways, bars, etc.) and can be mounted in situations otherwise illuminated by incandescent lamps. type of lamp lamp power 9 13 18 25 9 11 15 20 5 7 9 11 10 13 18 26 power consumed (W) 9 13 18 25 9 11 15 20 10 11 13 15 15 18 23 31 current at 220/240 V (A) 0.090 0.115 0.160 0.205 0.070 0.090 0.135 0.155 0.185 0.175 0.170 0.155 0.190 0.165 0.220 0.315

globe lamps with integral ballast cos = 0.5 (1) electronic lamps cos = 0.95 (1)

lamps with starter only incorporated (no ballast)

type single "U" form cos 0.35 type double "U" form cos 0.45

(1) Cos is approximately 0.95 (the zero values of V and I are almost in phase) but the power factor is 0.5 due to the impulsive form of the current, the peak of which occurs "late" in each half cycle.

table B11: current demands and power consumption of compact fluorescent lamps (at 220 V/240 V - 50 Hz).


B3.5. discharge lampsthe power in watts indicated on the tube of a discharge lamp does not include the power dissipated in the ballast.These lamps depend on the luminous electrical discharge through a gas or vapour of a metallic compound, which is contained in a hermetically-sealed transparent envelope at a pre-determined pressure. These lamps have a long start-up time, during which the current Ia is greater than the nominal current In. Power and current demands are given for different types of lamp in table B12 (typical average values which may differ slightly from one manufacturer to another). The power in watts indicated on the tube of a discharge lamp does not include the power dissipated in the ballast. type of power current In(A) starting lamp demand PF not PF Ia/In period (W) at corrected corrected (W) 230V 400V 230V 400V 230V 400V (mins) high-pressure sodium vapour lamps 50 60 0.76 0.3 1.4 4 to 6 to 1.6 70 80 1 0.45 100 115 1.2 0.65 150 168 1.8 0.85 250 274 3 1.4 400 431 4.4 2.2 1000 1055 10.45 4.9 low-pressure sodium vapour lamps standard lamp 18 26.5 0.14 1.1 7 to 15 to 1.3 35 43.5 0.62 0.24 55 72 0.34 90 112 0.84 0.50 135 159 0.73 180 216 0.98 economy lamps 26 34.5 0.45 0.17 1.1 7 to 15 to 1.3 36 46.5 0.22 66 80.5 0.39 91 105.5 0.49 131 154 0.69 mercury vapour + metal halide (also called metaliodide) 70 80.5 1 0.40 1.7 3 to 5 150 172 1.80 0.88 250 276 2.10 1.35 400 425 3.40 2.15 1000 1046 8.25 5.30 2000 2092 2052 16.50 8.60 10.50 6 mercury vapour + fluorescent substance (fluorescent bulb) 50 57 0.6 0.30 1.7 3 to 6 80 90 0.8 0.45 to 2 125 141 1.15 0.70 250 268 2.15 1.35 400 421 3.25 2.15 700 731 5.4 3.85 1000 1046 8.25 5.30 2000 2140 2080 15 11 6.1 luminous efficiency lumens (per watt) 80 to 120 average utilization life of lamp (h) 9000 - lighting of large halls - outdoor spaces - public lighting

table B12 gives the current taken by a complete unit, including all associated ancillary equipment.

100 to 200 8000 to - lighting of 12000 autoroutes - security lighting, station platform, stockage areas

100 to 200 8000 to - new types 12000 more efficient same utilization 70 to 90 6000 6000 6000 6000 6000 2000 - lighting of very large areas by projectors (for example:sports stadiums, etc)

40 to 60

8000 to - workshops 12000 with very high ceilings (halls, hangars) - outdoor lighting - low light output (1)

(1) replaced by sodium vapour lamps. Note: these lamps are sensitive to voltage dips. They extinguish if the voltage falls to less than 50% of their nominal voltage, and will not re-ignite before cooling for approximately 4 minutes. Note: Sodium vapour low-pressure lamps have a light-output efficiency which is superior to that of all other sources. However, use of these lamps is restricted by the fact that the yellow-orange colour emitted makes colour recognition practically impossible.

table B12: current demands of discharge lamps.


4. power* loading of an installation

BIn order to design an installation, the actual maximum load demand likely to be imposed on the power-supply system must be assessed. To base the design simply on the arithmetic sum of all the loads existing in the installation would be extravagantly uneconomical, and bad engineering practice. The aim of this chapter is to show how all existing and projected loads can be assigned various factors to account for diversity (nonsimultaneous operation of all appliances of a given group) and utilization (e.g. an electric motor is not generally operated at its full-load capability, etc.). The values given are based on experience and on records taken from actual installations. In addition to providing basic installation-design data on individual circuits, the results will provide a global value for the installation, from which the requirements of a supply system (distribution network, HV/LV transformer, or generating set) can be specified.

*power: the word "power" in the title has been used in a general sense, covering active power (kW) apparent power (kVA) and reactive power (kvar). Where the word power is used without further qualification in the rest of the text, it means active power (kW). The magnitude of the load is adequately specified by two quantities, viz: c power, c apparent power. power The ratio = power factor apparent power

4.1 installed power (kW)the installed power is the sum of the nominal powers of all powerconsuming devices in the installation. This is not the power to be actually supplied in practice.Most electrical appliances and equipments are marked to indicate their nominal power rating (Pn). The installed power is the sum of the nominal powers of all power-consuming devices in the installation. This is not the power to be actually supplied in practice. This is the case for electric motors, where the power rating refers to the output power at its driving shaft. The input power consumption will evidently be greater (See 3.1). Fluorescent and discharge lamps associated with stabilizing ballasts, are other cases in which the nominal power indicated on the lamp is less than the power consumed by the lamp and its ballast (See 3.4). Methods of assessing the actual power consumption of motors and lighting appliances are given in Section 3 of this Chapter. The power demand (kW) is necessary to choose the rated power of a generating set or battery, and where the requirements of a prime mover have to be considered. For a power supply from a LV public-supply network, or through a HV/LV transformer, the significant quantity is the apparent power in kVA.


B4.2 installed apparent power (kVA)the installed apparent power is commonly assumed to be the arithmetical sum of the kVA of individual loads. The maximum estimated kVA to be supplied however is not equal to the total installed kVA.The installed apparent power is commonly assumed to be the arithmetical sum of the kVA of individual loads. The maximum estimated kVA to be supplied however is not equal to the total installed kVA. The apparent-power demand of a load (which might be a single appliance) is obtained from its nominal power rating (corrected if necessary, as noted above for motors, etc.) and the application of the following coefficients: output kW = the per-unit efficiency = input kW kW cos = the power factor = kVA The apparent-power kVA demand of the load Pn Pa = x cos From this value, the full-load current Ia (amps)* taken by the load will be: Pa 103 for single phase-to-neutral c Ia = V connected load Pa 103 c Ia = for three-phase balanced load ex U where: V = phase-to-neutral voltage (volts) U = phase-to-phase voltage (volts) It may be noted that, strictly speaking, the total kVA of apparent power is not the arithmetical sum of the calculated kVA ratings of individual loads (unless all loads are at the same power factor). It is common practice however, to make a simple arithmetical summation, the result of which will give a kVA value that exceeds the true value by an acceptable "design margin". * For greater precision, account must be taken of the factor of maximum utilization as explained below in 4-3. When some or all of the load characteristics are not known, the values shown in table B13 may be used to give a very approximate estimate of VA demands (individual loads are generally too small to be expressed in kVA or kW). The estimates for lighting loads are based on floor areas of 500 sq-metres.

fluorescent lighting (corrected to cos = 0.86) type of application estimated (VA/m2) fluorescent tube with industrial reflector (1) roads and highways 7 stockage areas, intermittent work heavy-duty works: fabrication and 14 assembly of very large work pieces day-to-day work: 24 office work fine work: 41 drawing offices high-precision assembly workshops power circuits type of application estimated (VA/m2) pumping station compressed air 3 to 6 ventilation of premises 23 electrical convection heaters: private houses 115 to 146 flats and apartments 90 offices 25 dispatching workshop 50 assembly workshop 70 machine shop 300 painting workshop 350 heat-treatment plant 700

average lighting level (lux = Im/m2) 150 300 500 800

(1) example: 65 W tube (ballast not included), flux 5,100 lumens (lm), luminous efficiency of the tube = 78.5 lm/W.

table B13: estimation of installed apparent power.


4. power* loading of an installation (continued)

B4.3 estimation of actual maximum kVA demandall individual loads are not necessarily operating at full rated nominal power nor necessarily at the same time. Factors ku and ks allow the determination of the maximum power and apparent-power demands actually required to dimension the installation.All individual loads are not necessarily operating at full rated nominal power nor necessarily at the same time. Factors ku and ks allow the determination of the maximum power and apparent-power demands actually required to dimension the installation.

factor of maximum utilization (ku)In normal operating conditions the power consumption of a load is sometimes less than that indicated as its nominal power rating, a fairly common occurrence that justifies the application of an utilization factor (ku) in the estimation of realistic values. This factor must be applied to each individual load, with particular attention to electric motors, which are very rarely operated at full load. In an industrial installation this factor may be estimated on an average at 0.75 for motors. For incandescent-lighting loads, the factor always equals 1. For socket-outlet circuits, the factors depend entirely on the type of appliances being supplied from the sockets concerned.

factor of simultaneity (ks)It is a matter of common experience that the simultaneous operation of all installed loads of a given installation never occurs in practice, i.e. there is always some degree of diversity and this fact is taken into account for estimating purposes by the use of a simultaneity factor (ks). The factor ks is applied to each group of loads (e.g. being supplied from a distribution or sub-distribution board). The determination of these factors is the responsibility of the designer, since it requires a detailed knowledge of the installation and the conditions in which the individual circuits are to be exploited. For this reason, it is not possible to give precise values for general application. Factor of simultaneity for an apartment block Some typical values for this case are given in table B14, and are applicable to domestic consumers supplied at 230/400 V (3-phase 4-wires). In the case of consumers using electrical heat-storage units for space heating, a factor of 0.8 is recommended, regardless of the number of consumers. Example: 5 storeys apartment building with 25 consumers, each having 6 kVA of installed load. The total installed load for the building = 36 + 24 + 30 + 36 + 24 = 150 kVA The apparent-power supply required for the building = 150 x 0.46 = 69 kVA From table B 14, it is possible to determine the magnitude of currents in different sections of the common main feeder supplying all floors. For vertical rising mains fed at ground level, the cross-sectional area of the conductors can evidently be progressively reduced from the lower floors towards the upper floors. These changes of conductor size are conventionally spaced by at least 3-floor intervals. In the example, the current entering the rising main at ground level is 150 x 0.46 x 103 = 100 A 400 x e The current entering the third floor is: (36+24) x 0.63 x 103 = 55 A 400 x e number of downstream consumers 2 to 4 5 to 9 10 to 14 15 to 19 20 to 24 25 to 29 30 to 34 35 to 39 40 to 49 50 and more factor of simultaneity (ks) 1 0.78 0.63 0.53 0.49 0.46 0.44 0.42 0.41 0.40

table B14: simultaneity factors in an apartment block.

4th floor

6 consumers 36 kVA

0.78

3rd floor

4 consumers 24 kVA

0.63

2nd floor

5 consumers 30 kVA

0.53

1st floor

6 consumers 36 kVA

0.49

ground floor

4 consumers 24 kVA

0.46

fig. B15: application of the factor of simultaneity (ks) to an apartment block of 5 storeys.


BFactor of simultaneity for distribution boards Table B16 shows hypothetical values of ks for a distribution board supplying a number of circuits for which there is no indication of the manner in which the total load divides between them. If the circuits are mainly for lighting loads, it is prudent to adopt ks values close to unity. number of circuits assemblies entirely tested 2 and 3 4 and 5 6 to 9 10 and more assemblies partially tested in every case choose factor of simultaneity (ks) 0.9 0.8 0.7 0.6 1.0 Factor of simultaneity according to circuit function ks factors which may be used for circuits supplying commonly-occurring loads, are shown in table B17. circuit function lighting heating and air conditioning socket-outlets lifts and catering hoists (2) - for the most powerful motor - for the second most powerful motor - for all other motors factor of simultaneity (ks) 1 1 0.1 to 0.2 (1)

1 0.75 0.60

table B16: factor of simultaneity for distribution boards (IEC 439).

(1) In certain cases, notably in industrial installations, this factor can be higher. (2) The current to take into consideration is equal to the nominal current of the motor, increased by a third of its starting current.

table B17: factor of simultaneity according to circuit function.

4.4 example of application of factors ku and ksan example in the estimation of actual maximum kVA demands at all levels of an installation, from each load position to the point of supply.In this example, the total installed apparent power is 126.6 kVA, which corresponds to an actual (estimated) maximum value at the LV terminals of the HV/LV transformer of 65 kVA only. Note: in order to select cable sizes for the distribution circuits of an installation, the current I (in amps) through a circuit is determined from the equation level 1utilization apparentpower (Pa) kVA utilization factor max. apparentsimultaneity power demand factor max. kVA apparentsimultaneity power demand factor kVA

kVA x 103 Ue where kVA is the actual maximum 3-phase apparent-power value shown on the diagram for the circuit concerned, and U is the phaseto-phase voltage (in volts). I=

level 2apparentsimultaneity power demand factor kVA

level 3apparentpower demand kVA

workshop A

lathe

n1 n2 n3 n4

5 5 5 5 2 2 18 3

0.8 0.8 0,8 0.8 0.8 0.8 1 1 0.8 1 1 1 1 1 1 1 1

4 4 4 4 1.6 1.6 18 3 12 10.6 1 2.5 2.5 15 15 18 2

distribution boxpower circuit

0.75

14.4

pedestaldrill

n1

workshop A distribution board

n2 5 socket10/16 A outlets 30 fluorescent lamps workshop B

0.2 1 1 0.4 1distribution box

3,6 lighting 3circuit power circuit

socketoutlets

0,9

18.9

main general distribution board MGDB

compressor 15 3 socket- 10/16 A 10.6 outlets 1 10 fluorescent lamps ventilation n1 fan n2 oven n1 n2 2,5 2,5 15 15

12 socketoutlets 4,3 lighting circuit

workshop B distribution board

LV/HV

15.6

0.9

65

1

0.9

workshop C

1

35

power circuit

workshop C distribution board

0.9 0.28 1 5 2socketoutlets lighting circuit

37.8

5 socket10/16 A 18 outlets 20 fluorescent 2 lamps

table B18: an example in estimating the maximum predicted loading of an installation (the factor values used are for demonstration purposes only).general - installed power - B17

4. power loading of an installation (continued)

B4.5 diversity factorThe term DIVERSITY FACTOR, as defined in IEC standards, is identical to the factor of simultaneity (ks) used in this guide, as described in 4.3. In some English-speaking countries however (at the time of writing) DIVERSITY FACTOR is the inverse of ks i.e. it is always u 1.

4.6 choice of transformer ratingWhen an installation is to be supplied directly from a HV/LV transformer and the maximum apparent-power loading of the installation has been determined, a suitable rating for the transformer can be decided, taking due account of the following considerations: voltage (at no load) rated power (kVA) 50 100 160 250 315 400 500 630 800 1000 1250 1600 2000 2500 In (A) 400 V 72 144 231 361 455 577 722 909 1155 1443 1804 2309 2887 3608 c the possibility of improving the power factor of the installation (see chapter E), c anticipated extensions to the installation, c installation constraints (temperature...) standard transformer ratings.

420 V 69 137 220 344 433 550 687 866 1100 1375 1718 2199 2749 3437

433 V 67 133 213 333 420 533 667 840 1067 1333 1667 2133 2667 3333

480 V 60 120 192 301 379 481 601 758 962 1203 1504 1925 2406 3007

table B19: IEC-standardized kVA ratings of HV/LV 3-phase distribution transformers and corresponding nominal full-load current values.

The nominal full-load current In on the LV side of a 3-phase transformer is given by: Pa 103 In = where Ue Pa = kVA rating of the transformer U = phase-to-phase voltage at no-load* (in volts) In is in amperes. For a single-phase transformer: 3 In = Pa 10 where V V = voltage between LV terminals at no-load* (in volts).

Simplified equation for 400 V (3-phase load) In = kVA x 1.4 The IEC standard for power transformers is IEC 76. * as given on the transformer-rating nameplate. For table B19 the no-load voltage used is 420 V for the nominal 400 V winding.


B4.7 choice of power-supply sourcesThe study developed in F2 on the importance of maintaining a continuous supply raises the question of the use of standby-power plant. The choice and characteristics of these alternative sources are described in F3-3. For the main source of supply the choice is generally between a connection to the HV or the LV network of the public power-supply authority. In practice, connection to a HV source may be necessary where the load exceeds (or is planned eventually to exceed) a certain level - generally of the order of 250 kVA, or if the quality of service required is greater than that normally available from a LV network. Moreover, if the installation is likely to cause disturbance to neighbouring consumers, when connected to a LV network, the supply authorities may propose a HV service. Supplies at HV can have certain advantages: in fact, a HV consumer: c is not disturbed by other consumers, which could be the case at LV, c is free to choose any type of LV earthing system, c has a wider choice of economic tariffs, c can accept very large increases in load. It should be noted, however, that: c the consumer is the proprietor of the HV/LV substation and, in some countries, he must build and equip it at his own expense. The power authority can, in certain circumstances, participate in the investment, at the level of the HV line for example, c a part of the connection costs can, for instance, often be recovered if a second consumer is connected to the HV line within a certain time following the original consumer's own connection, c the consumer has access only to the LV part of the installation, access to the HV part being reserved to the supply-authority personnel (meter reading, operational manuvres, etc.). However, in certain countries, the HV protective circuit breaker (or fused load-break switch) can be operated by the consumer, c the type and location of the substation are agreed between the consumer and the supply authority.


1. protection of circuits supplied by an alternator

Ja major difficulty encountered when an installation may be supplied from alternative sources (e.g. a HV/LV transformer or a LV generator) is the provision of electrical protection which operates satisfactorily on either source. The crux of the problem is the great difference in the source impedances; that of the generator being much higher than that of the transformer, resulting in a corresponding difference in the magnitudes of fault currents.Most industrial and large commercial electrical installations include certain important loads for which a power supply must be maintained, in the event that the public electricity supply fails: c either, because safety systems are involved (emergency lighting, automatic fire-protection equipment, smoke dispersal fans, alarms and signalization, and so on...) or: c because it concerns priority circuits, suchHV LV

as certain equipment, the stoppage of which would entail a loss of production, or the destruction of a machine tool, etc. One of the current means of maintaining a supply to the so-called essential loads, in the event that other sources fail, is to install a diesel-generator set connected, via a changeover switch, to an emergency-power standby switchboard, from which the essential services are fed (figure J1-1).

G

standby supply change-over switch

non essential loads

essential loads

fig. J1-1: example of circuits supplied from a transformer or from an alternator.

1.1 an alternator on short-circuitthe establishment of short-circuit current (fig. J1-2)Apart from the limited magnitude of fault current from a standby alternator, a further difficulty (from the electrical-protection point of view) is that during the period in which LV circuit breakers are normally intended to operate, the value of short-circuit current changes drastically. For example, on the occurrence of a shortcircuit at the three phase terminals of an alternator, the r.m.s. value of current will immediately rise to a value of 3 In to 5 In*. An interval of 10 ms to 20 ms following the instant of short-circuit is referred to as the sub-transient period, in which the current decreases rapidly from its initial value. The current continues to decrease during the ensuing transient interval which may last for 80 ms to 280 ms depending on the machine type, size, etc. The overall phenomenon is referred to as the a.c. decrement. The current will finally stabilize in aboutr.m.s. subtransient period transient period

0.5 seconds, or more, at a value which depends mainly on the type of excitation system, viz: c manual; c automatic (see figure J1-2). Almost all modern generator sets have automatic voltage regulators, compounded to maintain the terminal voltage sensibly constant, by overcoming the synchronous impedance of the machine as reactive current demand changes. This results in an increase in the level of fault current during the transient period to give a steady fault current in the order of 2.5 In to 4 In* (figure J1-2). In the (rare) case of manual control of the excitation, the synchronous impedance of the machine will reduce the short-circuit current to a value which can be as low as 0.3 In, but is often close to In*.

3 In

alternator with automatic voltage regulator

In 0.3 In instant of fault 10 to 20 ms 0.1 to 0.3 s

alternator with manual excitation control

t

fig. J1-2: establishment of short-circuit current for a three-phase short circuit at the terminals of an alternator.* depending on the characteristics of the particular machine.

particular supply sources and loads - J1

1. protection of circuits supplied by an alternator (continued)

J1.1 an alternator on short-circuit (continued)Figure J1-2 shows the r.m.s. values of current, on the assumption that no d.c. transient components exist. In practice, d.c. components of current are always present to some degree in at least two phases, being maximum when the short-circuit occurs at the alternator terminals. This feature would appear to complicate still further the matter of electrical protection, but, in fact, the d.c. component in each phase simply increases the r.m.s. values a

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