Download - Asset Maintenance Guidelines for Transmission Division

Document Title Document type:

ASSET MAINTENANCE GUIDELINES FOR TRANSMISSION DIVISION

GUIDELINE

Date of Initial Approval: Sept 2008 (TTC)

Document No:

TNBT/TAMD/09/02/29/06

Revision No: 1.0 of 87

Prepared by:

ASSET MANAGEMENT DEPARTMENT

TRANSMISSION DIVISION TENAGA NASIONAL BERHAD

Revision Number

Description of change record

By [name]

[designation] [date]

Verifier [name]


Approver [name]


Endorsement [name]


@ Copyright TNB Transmission Division

No part of this document may be reproduced or transmitted in any form whatsoever by any means, including, without limitation, electronic, photocopying, recording or otherwise, without the prior written consent of TNB Transmission Division. No information embodied in documents which is not in the public domain shall be communicated in any manner whatsoever to any party without the prior written consent of TNB Transmission Division.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


INTRODUCTION .............................................................................................................. 6 1 Background ................................................................................................................. 6 2 Objectives ................................................................................................................... 6 3 Scope ........................................................................................................................... 7 4 Maintenance Type ....................................................................................................... 7 5 Methodology ............................................................................................................... 8 6 Implementation and Data Monitoring ......................................................................... 9 7 Maintenance Performance .......................................................................................... 9 8 Effective Date ............................................................................................................. 9 9 Acknowledgement .................................................................................................... 10 10 References ............................................................................................................. 10 A. MAINTENANCE GUIDELINES FOR SUBSTATIONS AND SUBSTATION PRIMARY EQUIPMENT ................................................................................................ 11 1 Scope ......................................................................................................................... 11 2 General Information .................................................................................................. 12 3 Inspection and Maintenance Plan ............................................................................. 14

3.1 Entire Plant........................................................................................................ 14 3.2 Building............................................................................................................. 15 3.3 Switchyard ........................................................................................................ 17 3.4 High Voltage (HV) Outdoor Circuit Breaker ................................................... 18 3.5 Medium Voltage (MV) circuit breaker ............................................................. 21 3.6 Power Transformers .......................................................................................... 23 3.7 Earthing Transformer ........................................................................................ 26 3.8 Transformer Cable Tails ................................................................................... 28 3.9 Current Transformer ......................................................................................... 29 3.10 Voltage Transformers/Capacitive Voltage Transformer .................................. 31 3.11 Disconnectors/Earth Switches .......................................................................... 32 3.12 Surge Arresters .................................................................................................. 34 3.13 Compensation Equipment ................................................................................. 35 3.14 Substation Earth Grid and Overhead Earth Wire .............................................. 37 3.15 Neutral Earthing Resistors ................................................................................ 37 3.16 Busbar/Busbar clamps/Dropper ........................................................................ 38 3.17 SF6 Gas-Insulated Switchgears (GIS) ............................................................... 39

B. MAINTENANCE GUIDELINES FOR OVERHEAD TRANSMISSION LINES ..... 41 1 Scope ......................................................................................................................... 41 2 General Information .................................................................................................. 41 3 Critical and Non-Critical Lines ................................................................................. 41 4 Line Inspection and Maintenance ............................................................................. 42

4.1 Line Inspection.................................................................................................. 42 4.2 Line Maintenance .............................................................................................. 42

5 Inspection Tasks and Maintenance Plan ................................................................... 43 5.1 Ground Patrol .................................................................................................... 43 5.2 Aircraft Warning Light Maintenance - ............................................................. 44 5.3 Tower Top Inspection ....................................................................................... 44



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


5.4 Aerial Inspection ............................................................................................... 45 5.5 Thermographic Scanning .................................................................................. 45 5.6 Rentice Clearing................................................................................................ 45 5.7 Ground Access Point Maintenance ................................................................... 45 5.8 Tower Footing Resistance Measurement .......................................................... 45 5.9 Lowest Conductor Height Measurement .......................................................... 46

C. MAINTENANCE GUIDELINES FOR TRANSMISSION UNDERGROUND AND SUBMARINE CABLES ................................................................................................... 47 1 Scope ......................................................................................................................... 47 2 General Information .................................................................................................. 47 3 Inspection and Maintenance Plan ............................................................................. 47

3.1 Cable route patrol .............................................................................................. 48 3.2 Offshore patrol for submarine cable ................................................................. 48 3.3 Oil containment and alarm system inspection for oil-filled cable .................... 48 3.4 Operation test for oil containment alarm system for oil-filled cable ................ 48 3.5 Thermographic scanning ................................................................................... 48 3.6 Cable accessories and supporting structures inspection ................................... 48 3.7 Underground cable manholes and tunnel inspection ........................................ 49 3.8 Sheath insulation test for XLPE Cable ............................................................. 49 3.9 Insulation resistance test ................................................................................... 49 3.10 Link box internal inspection ............................................................................. 49 3.11 Cable PD detection for XLPE cable ................................................................. 49 3.12 Cable outdoor sealing end inspection ............................................................... 49

D. MAINTENANCE GUIDELINES FOR PROTECTION SYSTEM ............................ 51 1 Scope ......................................................................................................................... 51 2 General Information .................................................................................................. 51 3 Maintenance Plan ...................................................................................................... 52

3.1 Distance Relays ................................................................................................. 53 3.2 Current Differential and Current Comparison Relays ...................................... 54 3.3 Pilot Wire Protection Relays ............................................................................. 55 3.4 Auto Re-close Relays ........................................................................................ 56 3.5 Synchro-check Relays ....................................................................................... 56 3.6 Over-current and Earth Fault Relays ................................................................ 57 3.7 Trip Circuit Supervision Relay ......................................................................... 57 3.8 Transformer Differential Relays ....................................................................... 58 3.9 Restricted Earth Fault Relays ............................................................................ 59 3.10 Standby Earth Fault Relays ............................................................................... 60 3.11 Stub Protection .................................................................................................. 61 3.12 High Impedance Busbar Differential Relays .................................................... 62 3.13 Low Impedance Busbar Protection Scheme (Centralized and De-centralized) 62 3.14 Circuit Breaker Failure Relays .......................................................................... 63 3.15 Thermal Overload Relays ................................................................................. 64 3.16 Under/Over Frequency and Under/Over Voltage (For Protection Function Only) 64



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.17 Pole Discrepancy Relays................................................................................... 65 3.18 Automatic Voltage Regulator (AVR) ............................................................... 66 3.19 Unbalanced Protection ...................................................................................... 66 3.20 Transformer Guards .......................................................................................... 67 3.21 Local Instrument meters ................................................................................... 67 3.22 Switch-sync (Point of Wave) relays ................................................................. 68 3.23 Reverse Power, Negative Phase Sequence, Over Excitation, Loss Excitation and Under Impedance Relays ....................................................................................... 68 3.24 Regular Inspection ............................................................................................ 68 3.25 Other Maintenance ............................................................................................ 68

4 Types of Relays Used in TNB Transmission Protection Scheme ............................. 69 4.1 Feeder Bay Protection ....................................................................................... 69 4.2 Power Transformer/ Generator Transformer/ Reactor Bay Protection ............. 70 4.3 Capacitor Bank Protection ................................................................................ 71 4.4 Bus Coupler, Bus Section and Busbar Protection ............................................. 71 4.5 Generator Protection ......................................................................................... 72

E. MAINTENANCE GUIDELINES FOR STATIC VAR COMPENSATOR (SVC) EQUIPMENT ................................................................................................................... 73 1 Scope ......................................................................................................................... 73 2 General Information .................................................................................................. 73 3 Inspection and Maintenance Plan ............................................................................. 73

3.1 Thyristor related equipment .............................................................................. 74 3.2 Control and Protection for SVC equipment ...................................................... 75 3.3 SVC Primary Equipment .................................................................................. 76 3.4 Auxiliary Equipment ......................................................................................... 76

F. MAINTENANCE GUIDELINES FOR HIGH VOLTAGE DIRECT CURRENT (HVDC) EQUIPMENT ................................................................................................... 77 1 Scope ......................................................................................................................... 77 2 General Information .................................................................................................. 77 3 Inspection and Maintenance Plan ............................................................................. 77

3.1 Converter Equipment ........................................................................................ 77 3.2 DC Primary Equipment..................................................................................... 78 3.3 AC Primary Equipment..................................................................................... 80 3.4 HVDC Control and Protection .......................................................................... 81 3.5 General services and auxiliary equipment ........................................................ 81

G. MAINTENANCE GUIDELINES FOR SUBSTATION CONTROL SYSTEM (SCS)........................................................................................................................................... 82 1 Scope ......................................................................................................................... 82 2 General Information .................................................................................................. 82 3 Objectives ................................................................................................................. 83 4 Maintenance Plan ...................................................................................................... 84

4.1 Preventive Maintenance .................................................................................... 84 5 Documentation .......................................................................................................... 84



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


H. MAINTENANCE GUIDELINES FOR REMOTE TERMINAL UNIT (RTUS) ....... 85 1 Scope ......................................................................................................................... 85 2 General Information .................................................................................................. 85

2.1 Failure Modes ................................................................................................... 86 3 Objectives ................................................................................................................. 86 4 Maintenance Plan ...................................................................................................... 86

4.1 Failure Mode, Effect and Criticality Analysis (FMECA) ................................. 86 4.2 Preventive Maintenance .................................................................................... 87

5 Documentation .......................................................................................................... 87



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


INTRODUCTION

1 Background Transmission network assets are developed, operated and maintained to provide transportation of bulk power from generators to distributors. In TNB Transmission, these assets that consist of various equipment and plants are grouped as follows:

• Substations • Overhead Lines • Underground Cables • Secondary Systems (protection relays and telecontrol equipment)

Equipment currently in operation in the Transmission grid system consists of various type and make. Majority of the equipment used are of overseas manufacturer. The age of the equipment installed range from newly commissioned to 40 years. In managing these assets, it is prudent for TNB to balance the cost and the risk involved in maintaining the assets. In line with industries practices in managing the asset and with the increasing expectation for maintenance to deliver improved performance, Transmission Division has prepared a Transmission Asset Maintenance Guidelines.

2 Objectives The objectives of Transmission Asset Maintenance Guidelines are as follow:

• Provide a standard maintenance level requirement and practices in TNB’s Transmission Division.

• Optimise the maintenance cost and performance (reliability and availability) of transmission network assets.

• Assist Asset Maintenance Department to plan, implement and monitor the prescribed inspection and maintenance strategies.

• Ensure maintenance practices comply with statutory requirements • Ensure equipment health, personnel and public safety, and security of supply • Assist departments in achieving Transmission Division’s business plans and

targets. The effective implementation of this guideline is supported by the following documentations:



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


• Engineering guidelines prepared by Engineering Department

(Provide recommendations on actions to be taken after observing results during inspection and maintenance task)

• Work Instructions prepared by Asset Maintenance Department (Provide procedure and checklist to carry out inspection and maintenance)

3 Scope The scope of this guideline covers all assets in substations, lines, cables, SVC, HVDC and secondary systems. Assets in Telecommunication System which are under TNB’s ICT Division are covered in a separate document. Equipment in operation consists of a large population with variety of manufacturers which can be difficult to maintain as the maintenance procedures may be different from one to another. Thus the Maintenance Guidelines is intended to serve majority of the equipment installed in TNB transmission system. Nevertheless, specific recommendations or instructions from the manufacturer need to be adhered to where required.

4 Maintenance Type Figure 1 shows the category of maintenance currently practiced in TNB Transmission Division. Similar structure is also used in the computerized maintenance management system (CMMS) also known as ERMS-PM.

Figure 1 – Category of Maintenance Preventive maintenance is carried out at predetermined intervals or corresponding to prescribed criteria as determined by OEM or TNB. Preventive maintenance is intended to reduce the probability of failure or the performance degradation of an item.

Maintenance

Preventive Maintenance

Corrective Maintenance

Routine/ Scheduled

Maintenance

Condition Based Maintenance

Emergency /Breakdown Maintenance

Deferred Maintenance



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


Routine/Scheduled maintenance is carried out at a fixed interval (time, operations) e.g. OLTC oil replacement after 4 years or 100,000 operations whichever comes first. Condition based maintenance is initiated as a result of knowledge of the condition of an item from monitoring e.g. visual inspection, thermovision and diagnostic tests Corrective maintenance is carried out after a failure or unacceptable condition has occurred and intended to restore an item to a state in which it can perform its required function. Emergency/Breakdown maintenance is carried out immediately to prevent danger to personnel, equipment, or system performance e.g. equipment requires repair under tripping situation. Deferred maintenance is maintenance work that may be programmed for later action e.g. defect found during inspection and the repair is plan in the next available outage. The maintenance tasks and interval stated in this document are primarily for preventive maintenance works.

5 Methodology The guidelines review and formulation was carried out based on manufacturers recommendation, statutory requirement and TNB’s operation and maintenance experience. Using the available information, RCM 2 processes were adopted in formulating the maintenance guidelines. Probable root causes of failures were identified and the respective mitigating actions were identified to prevent and minimise re-occurrence of failures. Several RCM 2 workshops were held and members from the various units and departments in the division were represented. The departments involved were:

• Asset Management Department • Asset Maintenance Department • Asset Development Department • Engineering Department

Following the workshops, an inspection and maintenance plan outlining maintenance tasks to be performed and their frequencies were then established. In general, the inspection and maintenance plan for the assets are categorized based on two broad categories:

• Non – intrusive Inspection: Inspection tasks where no outage of substation equipment is required.

• Intrusive Inspection/Maintenance/Overhaul: Inspection/Maintenance/Overhaul where the equipment is required to be de-energized and therefore plant/equipment outage is compulsory.

The maintenance interval or frequencies are categorized into calendar time, operational number and as required. Calendar time used is months and years. The time interval is



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


normally determined by the statutory requirement, type of equipment and probability of failure (P-F) interval of the equipment to be maintained. For operational number, it is determined by the manufacturer’s recommendation e.g. number of OLTC operation. As for the as required maintenance interval, no specific interval has been defined. The decision on the maintenance interval will be based on the operating environment of the asset, operating duty of the asset, condition of the asset, performance of the asset, age of the asset, criticality of the asset and event related e.g. condition assessment of the asset. The Head of Department (HOD) may be required to carry out a RCM analysis on the asset to be maintained.

6 Implementation and Data Monitoring After commissioning and prior to the equipment warranty expires, end-of-warranty inspection and tests are carried out to determine the equipment condition. This is to ensure equipment is acceptable for further operation in the network. Details of the end-of-warranty test are covered in the Site Acceptance Test document. Once the end-of-warranty test has been carried out successfully, the maintenance plan for the equipment is finalised. The maintenance interval outlined in this guideline is determined based on available data at the point of the analysis. The guideline shall be reviewed in the future when more data is collected and where reliability and efficiency indices could be determined. Hence it is important that all observations during inspections, repair and replacement work are properly recorded and documented by the Asset Maintenance Department in the Plant Maintenance Module of the Enterprise Resource Management System (ERMS).

7 Maintenance Performance In ensuring that the objectives of maintenance are achieved, the maintenance performance shall be monitored in terms of productivity, reliability and availability. These performance indicators shall be specified in the respective Department’s KPI. The KPIs shall be set and recorded such that the KPIs are suitable for performance trending and performance benchmarking with other utilities.

8 Effective Date This document is effective from 30th September 2008 and it supersedes any previous document before this. However, this document will be reviewed and updated from time to time when they are any changes to be made.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


9 Acknowledgement We wish to express our sincere gratitude and appreciation to the Asset Maintenance Department, Engineering Department, Asset Development Department and Strategic Development and Management Department and others who have contributed directly or indirectly to make it possible for the Asset Management Department to formulate this guideline.

10 References [1] TNB Transmission Operation & Maintenance, Network Performance and

Business Development Department, April 2002. [2] Transmission Asset Maintenance Policy, Rev.1.1, Asset Strategy Unit,

December 2004 [3] Internal Technical & Management audit reports, Asset Management

Department. [4] Internal Audit Reports, Group Internal Audit Division. [5] SGM and GM Instructions, Strategic Development and Management

Department. [6] Centralised Tripping Information System, Asset Management Department. [7] Various equipment O&M manuals from manufacturers.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


A. MAINTENANCE GUIDELINES FOR SUBSTATIONS AND SUBSTATION PRIMARY

EQUIPMENT

1 Scope This section provides guidelines for maintenance of all transmission substations in TNB Transmission system. There are two types of transmission substation designs used in TNBT:

• Conventional or Air-Insulated Substations (AIS) – This design consists of air-insulated equipment installed in outdoor switchyards. There is a control building within the same substation compound which houses protective relays, control panels, communication equipment and low voltage switchgears.

• Gas-Insulated Substations (GIS) – This design utilizes SF6 gas-insulated equipment. In TNBT, the GIS switchgears can be located inside a building or outdoor.

The maintenance guidelines determine the tasks to be done at the substation site (civil and M & E works) as well as primary equipment within the substation and the frequencies of these tasks. The primary equipment covered in this document includes equipment in substations energized at 11kV, 22kV, 33kV, 66kV, 132kV, 275kV and 500kV as follows:

i. Circuit breakers ii. Power transformers

iii. Earthing transformers iv. Transformer cable tails v. Instrument Transformers

vi. Disconnectors/earthing switches vii. Surge arresters

viii. Reactor/capacitor banks ix. Earth grid and earth mast x. Neutral Earthing Resistor

xi. Busbar/clamps/droppers

The Maintenance Guidelines document is to be supported by Substation Maintenance Engineering Guidelines documents. The Substation Maintenance Engineering Guidelines provide guidance as to what actions those need to be taken when the tasks in the Maintenance Guidelines are implemented.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


2 General Information Primary equipment in the TNB Transmission system consists of a large population with a variety of manufacturers and designs. In general, there are more than 20 manufacturers for each type of equipment. Failure modes of the primary equipment vary from one to another. Typical root causes of failure as captured form the Centralised Tripping Information System (CTIS) and RCM analysis include:

• Circuit Breakers i. Loose parts in assembly

ii. Degradation of insulation medium (vacuum, oil, SF6) iii. Worn out seals (pneumatic, gas, hydraulic) iv. Fatigue operating rods, cranks,levers and linkages v. Poor lubrication of linkages

• Power transformers

i. Outgoing feeder cable faults ii. Animal encroachment

iii. Transformer cable tail and termination failures iv. Vermin and moisture ingress into accessories v. Earthing transformer failures

vi. Poor workmanship vii. Poor maintenance

viii. Protection scheme failures

• GIS i. Leaking SF6

ii. Flashover of the SF6 compartment iii. Leaking hydraulic and pneumatic circuit breaker operating

mechanisms

• Earthing transformers i. Poor workmanship

ii. Animal encroachment iii. Poor maintenance iv. Vermin and moisture ingress into accessories

• Transformer cable tails

i. Poor cable quality & aging problems ii. Poor workmanship on joints/terminations

• Instrument Transformers (capacitive voltage transformers (CVT), electromagnetic

voltage transformers (VT) and current transformers (CT))



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


Major causes of insulation degradation of instrument transformer are as follow:

i. Contaminant ingress to the insulation ii. Natural ageing due to service condition or age

iii. Transient surges

• Disconnectors/Earthing Switches i. Misalignment of the blade

ii. Vermin intrusion due to improper/degrading seals at cable lugs iii. Faulty motor

• Surge Arresters

Major causes of degradation of surge arresters are as follow: i. Wrong application class of surge arrester

ii. Moisture ingress to the insulation iii. Degradation of housing – applicable to polymeric housing arresters

• Capacitor and Reactor Banks

i. Encroachment of animals/birds at exposed terminal ii. Short circuit of fuse of capacitor can

iii. Leaking of oil from capacitor unit iv. Degradation of paint for reactor (dry type)

• Earth grids/Earth Masts

i. Earth Shield wire: Rubbing at crossing due to loose connection to gantry and conductor sag

ii. Fatigue fittings of earth shield wire iii. Corrosion of earth termination iv. Theft of earthing tape

• Neutral Earthing Resistors Liquid type:

i. Evaporation/leaking of electrolyte ii. Crystallization of electrolyte over years

Dry Type:

i. Loose/corroded connection ii. Failure of resistor elements

• Busbar/clamps and connectors/droppers



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


i. Loose/corroded connection

ii. Tilting of busbar/broken clamp due to sinking foundation iii. Exposed LV busbar iv. Encroachment of foreign objects

3 Inspection and Maintenance Plan After commissioning and prior to the equipment warranty expires, end-of-warranty inspection and tests are carried out to determine the equipment condition as to ensure equipment is acceptable for further operation in the network. Details of the end-of-warranty test are covered in the Site Acceptance Test document. Once the end-of-warranty test has been carried out successfully, the maintenance plan for the equipment is finalized. Inspection and maintenance of substation and substation primary equipment are carried out on a planned routine basis or when situation warrants. The maintenance shall be adequate to provide the acceptable degree of confidence when operating the substation. The maintenance type and maintenance frequency required by plant or equipment are determined based on the manufacturers’ recommendations in the Operation and Maintenance Manual, utilities best practices and RCM analysis carried out by TNB Transmission. This section describes the inspection and maintenance tasks required and the maintenance plan for the substation equipment.

3.1 Entire Plant

3.1.1 Vegetation This includes grass cutting and weeding for existing landscaping if any

3.1.2 Fencing inspection To ensure both fencing and access gate are in good condition

3.1.3 Drainage inspection To ensure all drains are not clogged

3.1.4 Lighting inspection Perimeter lighting, switchyard lighting and building lighting shall be inspected



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.1.5 Pest control

3.1.6 Roadway inspection Table 3.1 Maintenance plan for entire plant No. Details Intrusive/

Non-intrusive

Interval

3.1.1 Vegetation N Monthly 3.1.2 Fencing inspection N Monthly 3.1.3 Drainage inspection N Monthly 3.1.4 Lighting inspection N 2 Months 3.1.5 Pest control N 3 Months 3.1.6 Roadway inspection N 2 Months

3.2 Building

3.2.1 General inspection This includes check on doors, windows, ceiling, walls, flooring, roller shutters are in good condition

3.2.2 Air condition system inspection

3.2.3 Fire equipment inspection i. For portable fire extinguisher equipment: renew BOMBA certification

as per statutory requirements ii. For the CO2 system:

- Check zone operations for smoke and heat detectors - Check wiring for continuity - Activate alarm at control box for correct zone operations - Check high-pressure fire hose to ensure it is intact - Simulate fire within zones (without CO2 discharge)



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.2.4 Water leakage inspection

3.2.5 Telephone system inspection

3.2.6 Lift/hoists/cranes servicing

3.2.7 Compressor system servicing Table 3.2 Maintenance plan for building No. Details Intrusive/

Non-intrusive

Interval

3.2.1 General inspection N 2 Months 3.2.2 Air condition system inspection N 2 Months 3.2.3 Fire equipment inspection N 2 Months 3.2.4 Water leakage inspection N 2 Months 3.2.5 Telephone system inspection N 2 Months 3.2.6 Lift/hoists/cranes servicing N Yearly 3.2.7 Compressor system/ Standby generator servicing N Yearly



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.3 Switchyard

3.3.1 Foundation inspection Check foundation for deterioration of base concrete and steel structure for white rust of all equipment

3.3.2 Thermo graphic scanning Check all equipment, clamps, connections, bushings and cable terminations for hot spot.

3.3.3 Earthing connection inspection Check earthing connections to all the equipment.

Table 3.3 Maintenance plan for switchyard No. Details Intrusive/

Non-intrusive

Interval

3.3.1 Foundation inspection N 2 Months 3.3.2 Thermographic scanning N 6 Months 3.3.3 Earthing connection inspection N 2 Months



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.4 High Voltage (HV) Outdoor Circuit Breaker

HV Outdoor circuit breaker in TNB’s Grid network uses SF6 or minimum oil as the interrupting medium with the former constitutes majority of the circuit breakers. Three types of circuit breaker operating mechanism are in used mainly spring operation followed by hydraulic operation and pneumatic operation. The maintenance activities for the HV circuit breakers are as follows:-

3.4.1 Visual inspection i. Inspect insulators for crack, burn mark and chipping

ii. Check motor, compressor (for pneumatic breakers), pump (hydraulic breakers) for unusual noise

iii. Inspect for oil leak/air leak of the operating mechanism iv. Inspect control circuit and operating mechanism cubicles for the

following:- - heaters operation - clean vents - seals and latch

3.4.2 Trip counter reading

3.4.3 Motor run hour reading This applies to pneumatic and hydraulic operating mechanism

3.4.4 Water purging from the air reservoir/vessel This applies to pneumatic operated mechanism without auto-water-purge facility

3.4.5 Operating mechanism check i. Check pump/motor/compressor operation

ii. Lubrication of linkages where necessary. iii. For spring type operating mechanism:

- Check dashpot for sign of oil leaks - Check spring guides/limit indicator are in place

iv. For hydraulic type operating mechanism: - Inspect accumulator pre-charge pressure and replace worn out

seals if necessary - Inspect accumulator for corrosion and repaint if required. - Check hydraulic pump operation, measuring the time taken to

pressurize the accumulator to required level.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


- Inspect operation of hydraulic oil pressure gauge for hydraulic

mechanism and alarm functions.

3.4.6 Gauges/interlock system check i. Check operation of all gauges to ensure proper alarms are triggered

and interlocks operated (where applicable)

3.4.7 Diagnostic tests i. Contact resistance measurement

ii. Circuit breaker timing test iii. Dew point test and purity test for SF6 gas iv. Pre-insertion closing resistor/grading capacitance measurement (where

applicable). The above tests are carried out periodically or when required, in order to determine the overall condition of the circuit breaker.

3.4.8 Additional diagnostic tests i. Contact travel and speed measurement

ii. Circuit breaker vibration analysis iii. Insulation test for tripping and closing circuit (from local control

cubicle onwards) iv. SF6 contamination test

Additional diagnostic tests may only be performed upon directives by HOD when situation warrants such as investigative measures when abnormalities are detected during periodic diagnostic tests.

3.4.9 Seals/O-rings replacement i. Replace seals/o-rings, hydraulic filter and hydraulic oil for hydraulic

operated mechanism. This specifically applies to Koncar and Alsthom hydraulic operated circuit breakers

ii. Replace seals/o-rings for pneumatic operated mechanism. This specifically applies to BBC pneumatic operated circuit breakers

3.4.10 Insulating oil replacement (applicable for minimum oil circuit breakers) i. Replace insulating oil

ii. Inspect blast nozzle for pitting marks and misalignment iii. Inspect arcing contacts iv. Replace o-rings



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.4.11 Circuit breaker operation

Circuit breaker is required to be operated by opening/closing operation of the circuit breaker. This is to ensure that circuit breaker operates reliably when intended thus reducing the possibility of CB slow-moving operation due to long inactivity of circuit breaker.

Table 3.4 Maintenance plan for HV (outdoor) circuit breaker No. Details Intrusive/

Non-intrusive

Interval

3.4.1 Visual inspection N 2 months 3.4.2 Trip counter reading N 2 months 3.4.3 Motor run hour reading N 2 months 3.4.4 Water purging from air reservoir N 2 months 3.4.5 Operating mechanism check I 4 Years/

2 Years for Capacitor and Reactor Bank

3.4.6 Gauges/interlock system check I 4 Years 3.4.7 Diagnostic tests I 4 Years/

2 Years for Capacitor and Reactor Bank

3.4.8 Additional diagnostic tests I As required 3.4.9 Seals/o-ring replacement for hydraulic/pneumatic

operating mechanism I 8 Years

3.4.10 Insulating oil replacement for minimum oil circuit breaker

I 4 Years or after 3 faults whichever

come first 3.4.11 Circuit breaker operation

I Once in 2 Years



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.5 Medium Voltage (MV) circuit breaker MV circuit breakers in TNB’s Grid network are metal-clad and use vacuum or minimum oil as the interrupting medium with the former constitute majority of the circuit breakers. The MV circuit breaker uses spring operation for the operating mechanism. The maintenance activities for the MV circuit breakers are as follows:-

3.5.1 Visual inspection i. Check all doors are properly closed

ii. Ensure switchgear door is locked with non-standard lock

3.5.2 Trip counter reading

3.5.3 Trip circuit healthy check

3.5.4 Airborne ultrasound test

3.5.5 Routine inspection i. Inspect the spout and shutter

ii. Check discoloration of tulip contacts/busbar due to heat or improper contact

iii. Clean vacuum bottle (applicable to vacuum circuit breaker) iv. Inspect railing alignment for blockage v. Check operating mechanism for signs of overheating

3.5.6 Lubrication i. Grease contact fingers

ii. Lubricate linkages and operating mechanism as recommended by manufacturer

iii. Check trip hook for LV switchgear.

3.5.7 Interlock system check i. Inspect for both electrical and mechanical interlock



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.5.8 Diagnostic tests

i. Contact resistance measurement ii. Vacuum insulation test (for vacuum circuit breakers)

iii. Circuit breaker timing test

The above tests are carried out periodically or when required, in order to determine the overall condition of the circuit breaker.

3.5.9 Trip coil waveform measurement

3.5.10 Insulating oil replacement for oil circuit breakers

3.5.11 Circuit breaker operation Circuit breaker is required to be operated by opening/closing operation of the circuit breaker. This is to ensure that circuit breaker operates reliably when intended thus reducing the possibility of CB slow-moving operation due to long inactivity of circuit breaker.

Table 3.5 Maintenance plan for MV circuit breaker No. Details Intrusive/

Non-intrusive

Interval

3.5.1 Visual inspection N 2 Months 3.5.2 Trip counter reading N 2 Months 3.5.3 Trip circuit healthy check N 2 Months 3.5.4 Airborne ultrasound test N 3 Months 3.5.5 Routine inspection I 4 Years 3.5.6 Lubrication I 4 Years 3.5.7 Interlock system check I 4 Years 3.5.8 Diagnostic test I 4 Years 3.5.9 Trip coil waveform measurement I As required 3.5.10 Insulating oil replacement for oil circuit breakers I 4 Years or after 5

faults whichever comes first

3.5.11 Circuit breaker operation I 2 Years or in line with TNBD

outages whichever comes

first



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.6 Power Transformers

Power transformers installed in TNB’s Grid network are of oil insulating type. Power transformer has four main components i.e. on-load tap changer (OLTC), bushings, windings and insulating oil. Routine maintenance for power transformers are carried out on either time or operational basis. The maintenance activities for the power transformers are as follows:-

3.6.1 Visual inspection i. Winding and oil temperature checks

ii. Oil level indicator and oil leak checks iii. Gaskets, coolers, pumps, fans, motors operations checks iv. Checks for oil leak at cable boxes and cables v. Paint/protective coating and corrosion checks

vi. Bushing: check for broken/damaged sheds vii. Checks for leaking valves

viii. Checks for name plate visibility/readable ix. Silica gel & container glass inspection x. Local control cubicle panel door seals inspection

xi. Light, heater and thermostat setting in local control panel inspection xii. Foundation plinth and cable bracket inspection

xiii. Check for Hydran alarm (if applicable)

3.6.2 OLTC position and operation counter reading

3.6.3 Oil tests i. Analysis of dissolved gasses in oil (DGA)

ii. Moisture/water content in oil iii. Neutralization index (acidity) of oil iv. Dielectric breakdown of oil

3.6.4 Routine inspection and operational checks i. Clean bushing/insulators

ii. Check of terminal blocks, oil level gauges, cable termination box and other accessories for being fully sealed/moisture proof.

iii. Simulation test on micro-switch for PRD and Buchholz relay iv. Buchholz relay check (for flag/alarm operation and fascia indication)



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


v. Test of emergency stop button for OLTC

vi. Test of fan switching element for on/off at right temperature vii. Test of running oil/winding temperature alarm for functionality

viii. Test of MCB and alarm circuitry ix. Test of OLTC timer alarm x. Test of OLTC out of step alarm

xi. Inspection of V-belt of OLTC motor for looseness xii. Test operation of pump motor contactor

xiii. Valve position check

3.6.5 OLTC operational check Running through of all tap positions is to be done on transformers during routine inspection and operational checks (3.6.4) to ensure that the changing of taps from the lowest to the highest is smooth thus preventing accumulation of coke at the tap contacts. For transformer where the tap position is fixed, OLTC operational check is to be done every 2 years.

3.6.6 OLTC minor maintenance i. Oil replacement and inspection of all transition resistors, braided wire and

contacts (Frequency is based on manufacturer’s recommendations) ii. Check condition of OLTC position and operation counters

3.6.7 OLTC parts replacement i. Braided wire and contact parts replacement (Frequency is based on

manufacturer’s recommendations)

3.6.8 Diagnostic tests i. Power factor test on transformer winding and bushing

ii. Insulation resistance test with polarisation index iii. Transformer winding resistance test iv. Oil power factor test

The above tests are carried out periodically or when required, in order to determine the overall condition of the power transformer.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.6.9 Additional diagnostic tests i. Transformer ratio test

ii. Polarity and vector group test iii. Core excitation iv. Frequency Response Analysis

Additional diagnostic tests may only be performed upon directives by HOD when situation warrants or when abnormalities are detected e.g. after a tripping event.

Table 3.6 Maintenance plan for power transformer No. Details Intrusive/

Non-intrusive

Interval

3.6.1 Visual inspection N 2 Months 3.6.2 OLTC position and operating counter reading N 2 Months 3.6.3 Oil sampling N Yearly 3.6.4 Routine inspection and operational checks I 4 Years 3.6.5 OLTC operational check I 4 Years or 2

Years for tap changer at fixed

position. 3.6.6 OLTC minor maintenance I OEM’s

recommendation 3.6.7 OLTC parts replacement I OEM’s

recommendation 3.6.8 Diagnostic tests I 4 Years 3.6.9 Additional diagnostic tests I As required



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.7 Earthing Transformer

3.7.1 Visual inspection i. External connection checks

ii. Check of terminal blocks, oil level gauges, HV termination and other accessories for being fully sealed/moisture proof

iii. Oil level indicator and oil leak checks iv. Checks for oil leak at cable boxes and cables v. Paint/protective coating and corrosion checks

vi. Transformer/cable guards inspection (for open bushing terminations) vii. Checks for leaking valves and valve positions

viii. Checks for name plate visibility/readable ix. Silica gel & container glass inspection x. Inspection of protective housing for Buchholz relay

xi. Check conservator filling cap for tightness (for MTM transformers)

3.7.2 Oil sampling i. Analysis of dissolved gasses in oil (DGA)


3.7.3 Routine inspection and operational checks

i. Check cable termination condition at cable boxes. ii. Rectify moisture condensation in cable boxes.

iii. Simulation test on micro-switch for PRD (if installed) and Buchholz relay iv. Buchholz relay check (for flag/alarm operation and fascia indication) v. Test of MCB and alarm circuitry

vi. Valve position check

3.7.4 Diagnostic tests i. Power factor test on winding and bushings

ii. Insulation resistance test with polarization index The above tests are carried out periodically or when required, in order to determine the overall condition of the earthing transformer.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.7.5 Additional diagnostic tests i. Transformer ratio test

ii. Polarity and vector group test iii. Core excitation test iv. Winding resistance test

Additional diagnostic tests may only be performed upon directives by HOD when situation warrants or when abnormalities are detected e.g. after a tripping event.

Table 3.7 Maintenance plan for earthing transformer No. Details Intrusive/

Non-intrusive

Interval

3.7.1 Visual inspection N 2 Months 3.7.2 Oil sampling N Yearly 3.7.3 Routine inspection and operational checks I 4 Years 3.7.4 Diagnostic tests I 4 Years 3.7.5 Additional diagnostic tests I As required



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.8 Transformer Cable Tails This covers power cable connections between transformers, earthing transformers, switchgears and neutral earthing resistor inside the substation.

3.8.1 Visual inspection i. Check for leaks at transformer cable box

ii. Check termination oil leak/ discoloured iii. Cable sheath earth connection iv. If applicable inspect the SVL – cracks / tightness v. If applicable check the cable sealing ends.

3.8.2 Cable accessories inspection i. Inspect earthing connections at terminations

ii. Inspect cable support structure at transformer terminations iii. Inspect general condition of cable trenches iv. Inspect general condition of cable markers (if installed along cable route

in the substation)

3.8.3 Insulation resistance measurement with polarization index

3.8.4 Cable sheath insulation test

3.8.5 On-line partial discharge measurement This is a diagnostic test and may only be performed upon directives by HOD when situation warrants or on selected cables.

Table 3.8 Maintenance plan for transformer cable tails No. Details Intrusive/

Non-intrusive

Interval

3.8.1 Visual inspection N 2 Months 3.8.2 Cable accessories inspection N Yearly 3.8.3 Insulation resistance measurement I As required 3.8.4 Cable sheath insulation test I 4 Years 3.8.5 On-line partial discharge measurement N As required



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.9 Current Transformer

Majority of current transformers installed in TNB’s Grid network are hermetically sealed. This type of current transformer requires minimal maintenance. Based on the manufacturers’ recommendations in the Operation and Maintenance Manual, utilities best practices and RCM analysis carried out by TNB Transmission, the maintenance type and frequency required by the current transformer are determined. The maintenance activities for the current transformers are as follows:-

3.9.1 Visual inspection i. Inspect oil level

ii. Check for oil leakage iii. Check for insulator chipping, damage and its cleanliness iv. Check nameplate to ensure it is readable. v. Check cable gland for the tightness & it is vermin proof

3.9.2 Routine inspection i. Secondary terminal box for corrosion and tightness of connection

ii. Primary terminal for tight connection iii. DLA tap for proper grounding iv. Check condition of bellow.

3.9.3 Diagnostic tests i. Power factor test

ii. Capacitance measurement

Diagnostic tests may only be performed upon directives by HOD when situation warrants such as oil leak detected during visual and routine inspection.

3.9.4 Oil Tests Diagnostic tests may only be performed upon directives by HOD when situation warrants such as oil leak detected during visual and routine inspection.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


Table 3.9 Maintenance plan for current transformer No. Details Intrusive/

Non-intrusive

Interval

3.9.1 Visual inspection N 2 months 3.9.2 Routine inspection I 4 years 3.9.3 Diagnostic tests I As required 3.9.4 Oil tests I As required



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.10 Voltage Transformers/Capacitive Voltage Transformer Most of voltage transformers installed in TNB’s Grid network are of the capacitive type and hermetically sealed. This type of voltage transformer requires minimal maintenance. Based on the manufacturers’ recommendations in the Operation and Maintenance Manual, utilities best practices and RCM analysis carried out by TNB Transmission, the maintenance type and frequency required by the voltage transformer are determined. The maintenance activities for the voltage transformers are as follows:-

3.10.1 Visual inspection i. Inspect oil level

ii. Check for oil leakage iii. Check for insulator chipping and its cleanliness

3.10.2 Secondary voltage measurement

3.10.3 Routine inspection i. Secondary terminal box for corrosion and tightness of connection

ii. Primary terminal for tight connection iii. Check condition of bellow iv. Check voltage limiting device (where applicable)

3.10.4 Diagnostic test i. Capacitance measurement

Diagnostic tests may only be performed upon directives by HOD when situation warrants such as oil leak detected during visual and routine inspection.

Table 3.10 Maintenance plan for voltage transformer No. Details Intrusive/

Non-intrusive

Interval

3.10.1 Visual inspection N 2 months 3.10.2 Secondary voltage measurement N 2 months 3.10.3 Routine inspection I 4 years 3.10.4 Diagnostic test I As required



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.11 Disconnectors/Earth Switches

3.11.1 Visual inspection i. Inspect insulators for cracks, or burns or pollutants deposits

ii. Check motor drive cabinet for the following: − Heater operation − Miniature circuit breaker (MCB)

iii. Clean ventilation openings iv. Check motor drive cabinet is properly latched and seals are in good

condition v. Check for visible misalignment/over travel/discoloration of primary

contacts vi. Check for leakage of grease at insulator base and motor gear

vii. Check earth tape connections from the disconnectors to the substation earthing system

viii. Check condition of earth mat (if applicable)

3.11.2 Primary contact routine inspection Where possible

i. Check tightness of bolts and nuts ii. Check springs of female contact for rust and its elasticity

iii. Check contact fingers for pitting marks, erosion, corrosion and clean if necessary

iv. Check for alignment of primary contacts and arcing tips v. Check arcing tips for excessive arc damage

vi. Check for simultaneous closing of all blades for 3 phases

3.11.3 Operating mechanism functional check i. Check linkages, rods and levers for smooth operation, ensure all joints

are secured tightly ii. Lubrication of bearings with appropriate approved grease for non

sealed bearings iii. Grease rotating and hinges points iv. Check alignment of auxiliary contacts v. Grease operating mechanism of the auxiliary contacts

vi. Check operation of interlocks vii. Check operation of motor

viii. Check operation of all safety interlocks ix. Operate ON/OFF switch to ensure proper functioning



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


Table 3.11 Maintenance plan for disconnector No. Details Intrusive/

Non-intrusive

Interval

3.11.1 Visual Inspection N 2 months 3.11.2 Primary contact routine inspection I 4 years 3.11.3 Operating mechanism functional check I 4 years Note : Item 3.11.2, 3.11.3 are applicable to busbar disconnector when visual inspection/thermographic scanning detects sign of failure



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.12 Surge Arresters

3.12.1 Visual inspection i. Inspect for cracks, pollutant deposits on insulator housing

ii. Check for operation of pressure relief vent iii. Check earthing connection from surge arresters to the ground iv. Check condition of surge counter and leakage current gauge v. Record reading of surge counter and leakage current gauge

3.12.2 Resistive leakage current measurement

3.12.3 Routine inspection i. Visual inspection as per 3.12.1

ii. Clean insulators Table 3.12 Maintenance plan for surge arresters No. Details Intrusive/

Non-intrusive

Interval

3.12.1 Visual Inspection N 2 months 3.12.2 Resistive leakage current measurement N 6 months 3.12.3 Routine inspection I As per interval of

associated bay/feeder



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.13 Compensation Equipment

3.13.1 Air-core reactors visual inspection i. Inspect support insulators for cracks, or burns or pollutants deposits

ii. Check for paint damage

3.13.2 Oil-filled reactor visual inspection i. Winding and oil temperature checks

ii. Oil level indicator and oil leak checks iii. Gaskets, coolers, pumps, fans, motors operations checks iv. Checks for oil leak at cable boxes and cables v. Paint/protective coating and corrosion checks

vi. Checks for leaking valves and valve positions vii. Checks for name plate visibility/readable

viii. Silica gel & container glass inspection ix. Foundation plinth and cable bracket inspection

3.13.3 Oil-filled reactor operational checks i. Test of fan switching element for on/off at right temperature

ii. Test of running oil/winding temperature alarm for functionality iii. Test of MCB and alarm circuitry

3.13.4 Oil test for oil-filled rector i. Analysis of dissolved gasses in oil (DGA)


3.13.5 Capacitor bank visual inspection i. Check for leakage of oil

ii. Check for fouling, paint damage iii. Check for shrouding of live parts

3.13.6 Capacitance bank capacitance measurement



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.13 Maintenance plan for compensation equipment No. Details Intrusive/

Non-intrusive

Interval

3.13.1 Air-cored reactors visual inspection N 2 months 3.13.2 Oil-filled reactors visual inspection N 2 months 3.13.3 Oil-filled reactors operational checks I 4 years 3.13.4 Oil-filled reactors oil test N Yearly 3.13.5 Capacitor bank visual inspection N 2 months 3.13.6 Capacitor bank capacitance measurement I 2 years



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.14 Substation Earth Grid and Overhead Earth Wire

3.14.1 Visual inspection of overhead earth wire i. Check crossing of earth conductors to ensure conductors are not in

contact ii. Check condition of conductor fittings

3.14.2 Visual inspection of gantry top i. Check lightning rod condition and connection (where applicable)

3.14.3 Measurement for earth grid resistance Table 3.14 Maintenance plan for substation earth grid/earth masts No. Details Intrusive/

Non-intrusive

Interval

3.14.1 Visual inspection of earth mast N 6 months 3.14.2 Visual inspection of gantry top N 6 months 3.14.3 Measurement for earth grid resistance N 8 years

3.15 Neutral Earthing Resistors

3.15.1 Visual inspection i. Inspect electrolyte level (applicable to liquid type)

ii. Check ground connection

3.15.2 NER resistance measurement Table 3.15 Maintenance plan for neutral earthing resistors No. Details Intrusive/

Non-intrusive

Interval

3.15.1 Visual inspection N 2 months 3.15.2 NER resistance measurement I As required (Dry

type) 4 Years (Liquid

Type) Note: Item 3.15.2 is normally carried out during 11/33kV busbar shutdown



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.16 Busbar/Busbar clamps/Dropper

3.16.1 Thermographic scanning Table 3.16 Maintenance plan for busbar/busbar clamps/dropper No. Details Intrusive/

Non-intrusive

Interval

3.16.1 Thermographic scanning N 6 months



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.17 SF6 Gas-Insulated Switchgears (GIS) Most of SF6 GIS installations in TNB’s Grid network are in-door and located at power stations and urban areas. GIS installation requires minimal maintenance. Based on the manufacturers’ recommendations in the Operation and Maintenance Manual, utilities best practices and RCM analysis carried out by TNB Transmission, the maintenance type and frequency required by GIS are determined. The maintenance activities for the GIS are as follows:-

3.17.1 Visual inspection i. Record the SF6 pressure from the density gauge

ii. Check for oil leaks (applicable to hydraulic or hydraulic-spring operated breakers)

iii. Check that all earth switches and disconnectors are locked with non-standard padlocks

iv. Check heater operation of control cubicle to prevent condensation v. Check ‘ON/OFF’ indicator for correct indication

vi. Check earth connections vii. Check for oil leaks at cable termination compartment

3.17.2 Motor run hour reading Record motor run hour for circuit breakers with pneumatic and hydraulic operating mechanisms

3.17.3 Trip counter reading Record circuit breaker counter reading

3.17.4 Routine maintenance i. Conduct circuit breaker timing test (where facility permits)

ii. Check contact resistance of circuit breakers and disconnectors so that they are within tolerance (where facility permits)

iii. Check interlocks of disconnectors for correct operation iv. Greasing and oiling of linkages as recommended by OEM v. Conduct SF6 dew point & SF6 purity measurement (inclusive of busbar

compartment) vi. Check alarm and fascia indication for correct operation

vii. Bleeding of hydraulic oil



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.17.5 Partial discharge measurement

3.17.6 Hydraulic oil and oil filter replacement This applies to hydraulic and hydraulic-spring operated circuit breakers as recommended by OEM.

3.17.7 Complete assessment of GIS Complete assessment to determine overall condition of GIS.

3.17.8 Maintenance of SF6 gas handling device Table 3.17 Maintenance plan for GIS No. Details Intrusive/

Non-intrusive

Interval

3.17.1 Visual inspection N 2 months 3.17.2 Motor run hour reading N 2 months 3.17.3 Trip counter reading N 2 months 3.17.4 Routine Maintenance I 4 years 3.17.5 Partial discharge measurement N 2 years 3.17.6 Hydraulic oil and oil filter replacement I OEM’s

recommendation 3.17.7 Complete assessment of GIS I >16 years or 20

fault clearing whichever comes

first 3.17.8 Maintenance of SF6 gas handling device N As required



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


B. MAINTENANCE GUIDELINES FOR OVERHEAD TRANSMISSION LINES

1 Scope This section outlines the maintenance guidelines for 66kV, 132kV, 275kV and 500kV transmission line network in Transmission Division. The guidelines describe the maintenance works to be carried out and their frequencies.

2 General Information Overhead transmission lines are meant to transmit electricity at high voltages from generating plants/high voltage substations to customers. The transmission line network in the Transmission Division’s system ranges from 66kV to 500kV.The total length of transmission line network that is maintained by Transmission Division constitutes more than 17,000 circuit-km. Based on the analysis of failure modes on lines tripping history, it is concluded that the common causes of tripping are due to the followings:-

i. Lightning ii. Encroachment activities

iii. Danger trees/bamboo shoots iv. Broken cross arms v. Line hardware failures (e.g. broken insulator strings, conductor snaps)

vi. Others (e.g. relay faulty/malfunction, faulty surge arrestor and circuit breaker, etc.)

3 Critical and Non-Critical Lines The inspection frequency is determined by the area category of the lines which are:

a) Critical/Special (C) This category includes transmission lines or sections of lines that fall into at least one of the following conditions:

i. Highly loaded or strategic lines (to be determined by SPOD) ii. Road/railway/river/line crossing

iii. Highly polluted areas a. Agricultural area with high usage of fertilizer or pesticide b. Industrial area e.g. cement plant or steel plant c. Marine area or sea shores.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


b) Non-Critical (NC) This category includes transmission lines in areas other than described in (a) above (e.g. rural, residential etc.)

The respective region(s) shall identify the criticality of lines/sections of lines based on the above criteria. Any lines or sections of lines that do not fall within any of the conditions as described above, but need special maintenance requirements, shall nevertheless be attended to as required (e.g. soil erosion places ).

4 Line Inspection and Maintenance Failure modes have shown that other than lightning, most line tripping could be avoided by ensuring healthy operation practice and carrying out thorough monitoring activities. The controllable failures are addressed by categorizing the transmission lines maintenance program into 2 major categories which are line inspection and line maintenance.

4.1 Line Inspection Line inspection shall be carried out while the line is energized and shall include the following activities:

i. Ground patrol & rentice inspection ii. Aircraft warning light system inspection

iii. Tower Top Inspection (TTI) iv. Aerial inspection v. Thermography scan

vi. Rentice clearing vii. Clearing of ground access point

viii. Measurement of tower footing resistance

4.2 Line Maintenance Generally, maintenance actions are carried out based upon the condition of the line component that is observed during inspection. Line maintenance works shall include repair, replacement and refurbishment/overhaul works. Maintenance works on the line component may be carried out by the following two methods:-

i. Live-line maintenance – maintenance work that is carried out by the Live Line Unit of Asset Maintenance Department of Transmission Division using live-line tools and techniques on all 500kV lines and on technically selected 275kV and 132kV lines (Note: Not all 275kV and 132kV lines are designed



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


for live-line maintenance. Refer to Line Maintenance Engineering Guidelines document for lines that can be maintained live).

ii. Dead-line maintenance – maintenance work that is carried out by the

respective regions of Asset Maintenance Department of Transmission Division on non-critical lines, where line outage is permitted by the System Operation Department of Transmission Division.

5 Inspection Tasks and Maintenance Plan Inspections of Right-of-way (ROW), conductors and towers shall be carried out on a planned routine basis or when situation warrants. This section describes the inspection tasks and the maintenance plan required.

5.1 Ground Patrol • Tower/Line components

i. Check for broken glass insulators or chipped porcelain insulators ii. Check for missing, bending or corrosion bracing

iii. Check for operation of aircraft warning light (This task is best done in the evening e.g. during thermovision inspection)

iv. Check stubs for signs of corrosion or soil erosion near tower legs v. Check for visibility and corrosion danger and phase plates

vi. Check for missing step bolts vii. Check for general condition of pole, tower, cross-arm, conductors,

fittings(including spacers and dampers) and earthwire viii. Check for any dropped or moved spacer or vibration damper

ix. Check for corrosion or soil erosion at stays and stay anchors x. Check for corrosion or damaged anti-climbing devices

xi. Check for corrosion or broken earth tape connection xii. Check air craft warning spheres

• R.O.W./access route activities:

Visual checks on: i. vegetation condition

ii. access roads iii. centre paths iv. construction activities under/near transmission lines v. soil erosion

vi. stubs covered by earth vii. vegetation removal from tower legs

viii. alertness on danger tree outside rentice



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


ix. trees above 6 feet height within R.O.W.

(Note: Transmission lines that traverse urban areas where there are active construction activities should be patrolled at shorter intervals to prevent any encroachment to the transmission lines. In the case of vegetation in R.O.W., certain local authorities require more frequent cutting of vegetation to ensure good aesthetics of the local surrounding. In such cases, compliance to conditions imposed by local authorities is necessary).

5.2 Aircraft Warning Light Maintenance - This task is performed on aircraft warning light equipment where the installation of such equipment is required by DCA. Maintenance is carried out to examine the integrity of the aircraft warning light system which includes, ensuring:-

i. Battery electrolyte is at adequate level ii. Connectivity of cables is intact

iii. High intensity light bulbs are in good operating condition (including reserve bulb)

iv. Cleaning of control box and solar panels etc.

5.3 Tower Top Inspection This task entails climbing the tower while the line remains energized to visually inspect the condition of the top part of line/tower components. It is imperative that the safety clearances as outlined in the Line Maintenance Engineering Guidelines are followed to carry out this task.

i. Check insulator pin for corrosion and/or pollution deposits condition ii. Check for detrimental cracks (for timber cross-arms) or bent/corroded

steel cross-arms iii. Check insulator for cracks iv. Check for connectivity and/or corrosion of earth bond at

earthwire/OPGW cross-arms. Retighten if necessary. v. Check for any displaced or dropped dampers

vi. Check visibility and corrosion of air borne number plate vii. Check stability and signs of corrosion of maintenance platform

viii. Check condition of fittings ix. Check condition Transmission Line Arrester (if applicable)



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


5.4 Aerial Inspection

This task may only be performed as and when required upon directives by Heads of Departments in Transmission Division. Examples of situations requiring aerial inspection are listed below:-

i. Emergency patrols to quickly locate faults after line tripping

ii. Inspection of overall conditions of towers and R.O.W. after floods or monsoon season

iii. Patrols for lines traversing lands which are inaccessible using ground transportation

5.5 Thermographic Scanning i. Thermography scan of transmission lines that includes joints, mid-span

joints and clamps and to check for hotspots which indicate deteriorating/loose connections.

5.6 Rentice Clearing i. Cutting of vegetation within rentice area

5.7 Ground Access Point Maintenance

i. Maintaining ground access points for lines/towers so that access to towers is available at all times, especially when emergency work at the tower location is required.

This task may only be performed as and when required upon directives by Heads of Departments in Transmission Division.

5.8 Tower Footing Resistance Measurement i. Tower footing resistance (TFR) (to measure earth resistance at tower

base) This task may only be performed as and when required upon directives by HOD. Due consideration to be given to towers where the soil resistance may vary due to seasonal changes or changes of soil condition and section of lines that have experienced tripping due to lightning.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


5.9 Lowest Conductor Height Measurement

i. Check for excessive sags of lowest conductor in accordance with Section 3.13.8 of TNB Transmission Electrical Safety Rules (for crossings and highly loaded lines only).

Table B1 Maintenance Plan for Overhead Lines No Details Intrusive/

Non-Intrusive Interval for Critical Lines

Interval for Non-Critical Lines

5.1 Ground Patrol

N <2 Months or As required

2 Months

5.2 Aircraft Warning Light Maintenance

N Yearly Yearly

5.3 Tower Top Inspection

N Yearly 4 Years

5.4 Aerial Inspection

N As required As required

5.5 Thermographic Scanning

N Yearly 4 Years

5.6 Rentice Clearing

N 6 months or As required

6 months

5.7 Ground Access Point Maintenance

N As required As required

5.8 Tower Footing Resistance Measurement

N As required

As required

5.9 Lowest Conductor Height Measurement

N Yearly N/A



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


C. MAINTENANCE GUIDELINES FOR TRANSMISSION UNDERGROUND AND

SUBMARINE CABLES

1 Scope This section outlines the maintenance guidelines for 132kV, 230kV and 275kV underground and submarine transmission cable network in the TNB Transmission Division. The guidelines describe the maintenance works to be carried out and their frequencies.

2 General Information Underground transmission cables are commonly used in urban areas where there is land constraint to build overhead transmission lines. The total circuit length of underground cables that is maintained by TNB constitutes more than 700 km. There are 2 types of transmission cables used in the TNB transmission system. They are:

• Oil-filled cables • XLPE insulated cables

Oil-filled cables are normally used as submarine cables in providing power connection crossing the sea or the straits. Based on the analysis of failure modes on transmission cables tripping history, it is concluded that the common causes of tripping are due to the followings:

• Human intervention • Poor cable and accessories quality • Poor workmanship on joints

3 Inspection and Maintenance Plan Maintenance of transmission cables and cable accessories shall be carried out on a planned, routine basis. The maintenance works are aimed to provide acceptable degree of confidence when operating the cables. This section describes the inspection and maintenance tasks required and the maintenance plan for the transmission cable.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.1 Cable route patrol

Inspection is carried out while the cable is in service and it includes the following activities:

i. Check for missing or damaged cable markers/sign boards ii. Check for excavation/piling activities near/along the cable route and

condition of cable accessories e.g. underground oil pressure tank iii. Check physical condition of cable joint box/cable bridge/link box and

pressure gauge. iv. Check for condition of manhole cover (if applicable)

3.2 Offshore patrol for submarine cable Regional Asset Maintenance office is required to seek cooperation from Jabatan Laut Malaysia or relevant authority in monitoring maritime activities in the non-anchoring zone of the submarine cable and maintenance of the beacon house. Monitoring and maintenance may include the following activities:

i. Check condition of beacon light. ii. Monitor maritime activities in the ‘non-anchoring zone’.

iii. Check overall condition of the beacon house.

3.3 Oil containment and alarm system inspection for oil-filled cable i. Check for any operation of oil pressure alarm system

ii. Check for oil leaks at cable sealing ends iii. Check the condition of earthing connections iv. Record oil pressure from gauge. v. Carry out lamp test at control panel

3.4 Operation test for oil containment alarm system for oil-filled cable

3.5 Thermographic scanning i. Check for hot spots on clamps, connections and overall thermal condition

of outdoor cable sealing ends

3.6 Cable accessories and supporting structures inspection i. Inspection of cable bridge support structure

ii. Inspection of link boxes external condition iii. Inspection of warning signs.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.7 Underground cable manholes and tunnel inspection

i. Check for condition of steel supporting structure ii. Check for cable duct seal

iii. Check for overall concrete structure particularly for cracks and water seepage.

iv. Check cable joint overall condition v. Check for link box condition

vi. General cleaning and painting (when required)

3.8 Sheath insulation test for XLPE Cable

3.9 Insulation resistance test i. Insulation resistance test for all cables

This task may only be performed as and when required upon directives by HOD.

3.10 Link box internal inspection i. Check SVL condition

ii. Check for cable bonding termination condition iii. Check for moisture sealing condition and vermin proofing iv. Check general cleanliness

3.11 Cable PD detection for XLPE cable Cable PD detection is carried out while the cable is in service. This task may only be performed as and when required upon directives by HOD.

3.12 Cable outdoor sealing end inspection i. Check for any leakage on outdoor sealing end oil

ii. Check cleanliness of sealing end iii. Check earthing connections



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


Table C1 Maintenance Plan for Underground cables

No Details Intrusive/ Non-Intrusive

Interval

3.1 Cable route patrol

N 2 Months or as required

3.2 Offshore patrol for submarine cable

N As required

3.3 Oil containment and alarm system inspection

N 2 Months

3.4 Oil containment alarm system operation test

I 4 Years

3.5 Thermographic scanning

N 6 Months

3.6 Cable accessories inspection

N 6 Months

3.7 Underground cable manholes and tunnel inspection

N 4 Years

3.8 Sheath insulation test

I 4 Years

3.9 Insulation resistance test

I As required

3.10 Link Box Internal Inspection I 4 Years

3.11 Cable PD Detection

N As required

3.12 Cable outdoor sealing end inspection

N 2 Months in substation

6 months for terminal tower



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


D. MAINTENANCE GUIDELINES FOR PROTECTION SYSTEM

1 Scope This section outlines the maintenance guideline for all protection and control schemes installed in TNB transmission network. Where applicable, this section shall be applied to Generation and Distribution protection maintenance scope of work and the frequencies shall be decided by the respective owners. The purpose of performing maintenance as stipulated in this Guideline is to ensure that all protective systems component installed in the transmission network are in good working order. It is not intended to resolve design and commissioning related issues and failures

This guideline determines the tasks to be done on the protection relay systems and frequencies of these tasks. Protection relays are devices that detect and response to any abnormalities in the system and initiate appropriate control action(s) such that the power system is affected the least.

The boundary of the protection scope of maintenance is from the terminal blocks (inclusive of terminal blocks) of the marshalling kiosks or/and local control panel (e.g. transformers/GIS) to the secondary equipment panels (e.g. Relay/control panels, RTU interface panels). Marshaling Kiosk is under the ownership of Primary team.

2 General Information

There are four types of relays:

a) electromechanical b) static (analogue) c) digital d) numerical

Protection relays in operation consist of large population with variety of manufacturers that can be difficult to establish common maintenance procedures, as one model is different from another. The maintenance frequency of the protection system (which requires plant outage) will be based on the type of relay used for Main protection. For plants where the Main protection consists of electromechanical relay, the frequency of maintenance (which requires plant outage) will be done in every two years. For plants where the Main protection consists of static and/or digital and/or



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


numerical only, the frequency of maintenance (which requires plant outage) will be done in every four years.

The maintenance guidelines on SCADA, RTU, and SCS equipment will be addressed in separate guidelines.

From Reliability Centered Maintenance (RCM) analysis, three major failure modes for the relays were identified:

� Internal relay faulty – in static, digital, numerical relays, this will result in changing the faulty cards or modules whereas in electromechanical relays, the moving parts may get worn out after being in operation for a number of years.

� Wrong settings – this failure mode can be attributed to staff configuring or keying the wrong settings especially after maintenance work was done. There were also cases were the relay themselves are giving such problems. For instance, the potentiometer for the reach settings for static distance relay may wear out after so many years in operation.

� Other (e.g. Faulty connections) – inputs include CT and VT signals to the relays and outputs include trip and alarm signals. There are many possibilities that contribute to this failure mode where there is no signal coming in or going out of the relays.

3 Maintenance Plan

Currently, protection systems in TNB consist of static, numerical, digital and electromechanical relays. For maintenance purposes, the relays/schemes are grouped into the following functional units:

a) Line/Cable/Hybrid Feeder Bay b) Power Transformer/ Generator Transformer/ Reactor Bay c) Capacitor Bank Protection d) Bus Coupler, Bus Section and Busbar Protection e) Generator Protection

The types of relays/schemes used for each of the above functional units are shown in section 4: Types of relay used in TNB Transmission Protection scheme.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


The following are the inspection and maintenance task for all protection relays in the network and the detailed plan including the inspection and maintenance cycle for the various types of relays:

3.1 Distance Relays

(i) Check and confirm power supply unit is healthy (ii) Check CB and Isolator auxiliary contacts to relay (iii) Check Local Alarms & annunciation (Facia & Substation Control System) (iv) Check Tele-protection signals (v) Measurement of CT and VT input to relay (vi) Confirm settings and configuration (vii) Functional Test

• Distance Reach check • Timing test • Power Swing Blocking operation • Switch On To Fault functions • Voltage Transformer Supervision functions • Directional Earth Fault if in used (includes external DEF ) • Stub function if in used (include external Stub relay)

(viii) Confirm the operation of the tripping circuits (ix) Check for lock out operation

Table 3.1 Maintenance plan for Distance Relays No Details

(I/N) Interval

Non-Electromechanical

Electromechanical

1 Check and confirm power supply unit is healthy

N 2 Years 2 Years

2 Check CB and Isolator auxiliary contacts to relay

N 2 Years 2 Years

3 Check local alarms and annunciation I 4 Years 2 Years 4 Check Tele-protection signals I 4 Years 2 Years 5 Measurement of CT and VT inputs to relay N 2 Years 2 Years 6 Confirm settings and configuration I 4 Years 2 Years 7 Functional Test I 4 Years 2 Years 8 Confirm operation of tripping circuit I 4 Years 2 Years 9 Check for lock out operation I 4 Years 2 Years



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.2 Current Differential and Current Comparison Relays

(i) Check and confirm power supply unit is healthy (ii) Check CB and Isolator auxiliary contacts to relay (iii) Check Local Alarms & annunciation (Facia & Substation Control System) (iv) Check Tele-protection signals (v) Measurement of CT (Or VT if used) inputs to relay (vi) Confirm settings and configuration (vii) Functional Test

• Transfer or Inter-trip tripping if available • Backup Distance check if used ( Refer to Distance Relays Tests) • Timing test

(viii) Confirm the operation of the tripping circuits (ix) Check for lock out operation

Table 3.2 Maintenance plan for Current Differential and Current Comparison Relays No Details

(I/N) Interval


Electromechanical


N 2 Years 2 Years


N 2 Years 2 Years

3 Check local alarms and annunciation I 4 Years 2 Years 4 Check Tele-protection signals I 4 Years 2 Years 5 Measurement of CT (or VT if used) inputs

to relay N 2 Years 2 Years

6 Confirm settings and configuration I 4 Years 2 Years 7 Functional Test I 4 Years 2 Years 8 Confirm operation of tripping circuit I 4 Years 2 Years 9 Check for lock out operation I 4 Years 2 Years



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.3 Pilot Wire Protection Relays

(i) Check and confirm power supply unit is healthy (ii) Check Local Alarms & annunciation (Facia & Substation Control System) (iii) Check condition and integrity of pilot wire (iv) Measurement of CT inputs to relay (v) Confirm settings and configuration (vi) Functional Test

• Pilot wire supervision • End to end injection tests • Inter-tripping circuit • Timing test

(vii) Confirm the operation of the tripping circuits (viii) Check for lock out operation

Table 3.3 Maintenance plan for Pilot Wire Protection Relays No Details

(I/N) Interval


Electromechanical


N 2 Years 2 Years

2 Check local alarms and annunciation I 4 Years 2 Years 3 Check condition and integrity of pilot wire I 4 Years 2 Years 4 Measurement of CT inputs to relay N 2 Years 2 Years 5 Confirm settings and configuration I 4 Years 2 Years 6 Functional Test I 4 Years 2 Years 7 Confirm operation of tripping circuit I 4 Years 2 Years 8 Check for lock out operation I 4 Years 2 Years



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.4 Auto Re-close Relays

(i) Check and confirm power supply unit is healthy (ii) Check CB auxiliary and “Sync-check input” contacts to relay (iii) Check Local Alarms & annunciation (Facia & Substation Control System) (iv) Confirm settings and configuration (v) Operational Test with actual breaker (vi) Check for lock out operation

Table 3.4 Maintenance plan for Auto re-close Relays No Details

(I/N) Interval


Electromechanical


N 2 Years 2 Years

2 Check CB auxiliary and “Sync-check input” contacts to relay

N 2 Years 2 Years

3 Check local alarms and annunciation I 4 Years 2 Years 4 Confirm settings and configuration I 4 Years 2 Years 5 Operational test with actual breaker I 4 Years 2 Years 6 Check for lock out operation I 4 Years 2 Years

3.5 Synchro-check Relays

(i) Check and confirm power supply unit is healthy (ii) Check Local Alarms & annunciation (Facia & Substation Control System) (iii) Measurement of VT input to relay (iv) Confirm settings and configuration (v) Functional Test

Table 3.5 Maintenance plan for Synchro-check Relays No Details

(I/N) Interval


Electromechanical


N 2 Years 2 Years

2 Check local alarms and annunciation I 4 Years 2 Years 3 Measurement of VT input to relay I 4 Years 2 Years 4 Confirm settings and configuration I 4 Years 2 Years 5 Functional test I 4 Years 2 Years



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.6 Over-current and Earth Fault Relays

(i) Check and confirm power supply unit is healthy (ii) Check local Alarms & annunciation (Facia & Substation Control System) (iii) Measurement of CT input to relay (iv) Confirm settings and configuration (v) Operational and timing test (vi) Built in Trip circuit supervision test if in used (vii) Confirm the operation of the tripping circuits (viii) Check for lock out operation

Table 3.4 Maintenance plan for Over-current and Earth Fault Relays No Details

(I/N) Interval


Electromechanical


N 2 Years 2 Years

2 Check local alarms and annunciation I 4 Years 2 Years 3 Measurement of CT input to relay N 2 Years 2 Years 4 Confirm settings and configuration I 4 Years 2 Years 5 Operational and timing test I 4 Years 2 Years 6 Built in trip circuit supervision test if in

used I 4 Years 2 Years

7 Confirm the operation of the tripping circuits

I 4 Years 2 Years

8 Check for lock out operation I 4 Years 2 Years

3.7 Trip Circuit Supervision Relay

(i) Check and confirm power supply unit is healthy (ii) Check Local Alarms & annunciation (Facia & Substation Control System) (iii) Operational test for each trip coil

Table 3.7 Maintenance plan for Trip Circuit Supervision Relays No Details

(I/N) Interval


Electromechanical


N 2 Years 2 Years

2 Check local alarms and annunciation I 4 Years 2 Years 3 Operational test for each trip coil I 4 Years 2 Years



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.8 Transformer Differential Relays

(i) Check and confirm power supply unit is healthy (ii) Check Local Alarms & annunciation (Facia & Substation Control System) (iii) Measurement of CT input to relay (iv) Confirm settings and configuration (v) Functional Test

• Operational test • Biased characteristic test • Inrush Blocking • Over-excitation / Over-fluxing if in used • Timing test

(vi) Confirm the operation of the tripping circuits (vii) Check for lock out operation

Table 3.8 Maintenance plan for Transformer Differential Relays No Details

(I/N) Interval


Electromechanical


N 2 Years 2 Years

2 Check local alarms and annunciation I 4 Years 2 Years 3 Measurement of CT input to relay N 2 Years 2 Years 4 Confirm settings and configuration I 4 Years 2 Years 5 Functional test I 4 Years 2 Years 6 Confirm the operation of tripping circuits I 4 Years 2 Years 7 Check for lock out operation I 4 Years 2 Years



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.9 Restricted Earth Fault Relays

(i) Check and confirm power supply unit is healthy (ii) Check Local Alarms & annunciation (Facia & Substation Control System) (iii) Confirm settings and configuration (iv) Operational and Timing Test (v) Confirm the operation of the tripping circuits (vi) Check for lock out operation

Table 3.9 Maintenance plan for Restricted Earth Fault Relays No Details

(I/N) Interval


Electromechanical


N 2 Years 2 Years

2 Check local alarms and annunciation I 4 Years 2 Years 3 Confirm settings and configuration I 4 Years 2 Years 5 Operational and timing test I 4 Years 2 Years 6 Confirm the operation of the tripping

circuits I 4 Years 2 Years




GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.10 Standby Earth Fault Relays

(i) Check and confirm power supply unit is healthy (ii) Check Local Alarms & annunciation (Facia & Substation Control System) (iii) Confirm settings and configuration (iv) Operational and timing test (v) Confirm the operation of the tripping circuits (vi) Check for lock out operation

Table 3.10 Maintenance plan for Standby Earth Fault Relays No Details

(I/N) Interval


Electromechanical


N 2 Years 2 Years

2 Check local alarms and annunciation I 4 Years 2 Years 3 Confirm settings and configuration I 4 Years 2 Years 4 Operational test with actual breaker I 4 Years 2 Years 5 Confirm the operation of the tripping

circuits I 4 years 2 Years




GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.11 Stub Protection (i) Check and confirm power supply unit is healthy (ii) Check line Isolator auxiliary contacts to relay (iii) Check Local Alarms & annunciation (Facia & Substation Control System) (iv) Confirm settings and configuration (v) Functional Test

• Transfer or Inter-trip tripping if available • Timing test

(vi) Confirm the operation of the tripping circuits (vii) Check for lock out operation

Table 3.11 Maintenance plan for Stub Protection Relays No Details

(I/N) Interval


Electromechanical


N 2 Years 2 Years

2 Check line Isolator auxiliary contacts to relay

N 2 Years 2 Years

3 Check local alarms and annunciation I 4 Years 2 Years 4 Confirm settings and configuration I 4 Years 2 Years 5 Functional test I 4 Years 2 Years 6 Confirm the operation of tripping circuits I 4 Years 2 Years 7 Check for lock out operation I 4 Years 2 Years



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.12 High Impedance Busbar Differential Relays

(i) Check and confirm power supply unit is healthy (ii) Check Local Alarms & annunciation (Facia & Substation Control System) (iii) Confirm settings and configuration (iv) Operational and Timing Test for all zones (v) Test on CT Supervision Circuit (vi) Check the condition of the tripping circuits

• Isolator auxiliary contact in tripping circuit for all bays • Transfer trip to remote end if applicable

(vii) Check for lock out operation Table 3.12 Maintenance plan for High Impedance Busbar Differential Relays No Details

(I/N) Interval


Electromechanical


N 2 Years 2 Years

2 Check local alarms and annunciation I 4 Years 2 Years 3 Confirm settings and configuration I 4 Years 2 Years 4 Operational and timing test for all zones I 4 Years 2 Years 5 Test on CT supervision circuit I 4 Years 2 Years 6 Check condition of tripping circuits N 2 Years 2 Years 7 Check for lock out operation I 4 Years 2 Years

3.13 Low Impedance Busbar Protection Scheme (Centralized and De-centralized)

(i) Check and confirm power supply unit is healthy (ii) Check Local Alarms & annunciation (Facia & Substation Control System) (iii) Check CB and Isolator auxiliary contacts to relay (iv) Measurement of CT inputs from all bays (v) Confirm settings and configuration (vi) Check the condition of the tripping circuits (negative check)



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


Table 3.13 Maintenance plan for Low Impedance Busbar Protection Relays No Details

(I/N) Interval


Electromechanical


N 2 Years 2 Years

2 Check local alarms and annunciation I 4 Years 2 Years 3 Check CB and Isolator auxiliary contacts to

relay N 2 Years 2 Years

4 Measurement of CT inputs from all bays N 2 Years 2 Years 5 Confirm settings and configuration I 4 Years 2 Years 6 Check condition of tripping circuits

(negative check) N 2 Years 2 Years

3.14 Circuit Breaker Failure Relays

(i) Check and confirm power supply unit is healthy (ii) Check CB and Isolator auxiliary contacts to relay if wired (iii) Check Local Alarms & annunciation (Facia & Substation Control System) (iv) Measurement of CT input (v) Check protection initiation to breaker failure relay (vi) Confirm settings and configuration (vii) Operational and timing test (viii) Check the condition of the tripping circuits

• Isolator auxiliary contact in tripping circuit • Transfer trip to remote end

(ix) Check for lock out operation Table 3.14 Maintenance plan for Circuit Breaker Failure Relays No Details

(I/N) Interval


Electromechanical


N 2 Years 2 Years


N 2 Years 2 Years

3 Check local alarms and annunciation I 4 Years 2 Years 4 Measurement of CT inputs N 2 Years 2 Years 5 Check protection initiation to breaker

failure relay I 4 Years 2 Years

6 Confirm settings and configuration I 4 Years 2 Years 7 Operational and timing test I 4 Years 2 Years



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.15 Thermal Overload Relays

(i) Check and confirm power supply unit is healthy (ii) Check Local Alarms & annunciation (Facia & Substation Control System) (iii) Measurement of CT input to relay (iv) Confirm settings and configuration (v) Operational and timing test (vi) Confirm the operation of the tripping and/or alarm circuits (vii) Check for lock out operation if used

Table 3.15 Maintenance plan for Thermal Overload Relays No Details

(I/N) Interval


Electromechanical


N 2 Years 2 Years

2 Check local alarms and annunciation I 4 Years 2 Years 3 Measurement of CT input to relay N 2 Years 2 Years 4 Confirm settings and configuration I 4 Years 2 Years 5 Operational and timing test I 4 Years 2 Years 6 Confirm the operation of the tripping

and/or alarm I 4 Years 2 Years

7 Check for lock out operation if used I 4 Years 2 Years

3.16 Under/Over Frequency and Under/Over Voltage (For Protection Function Only)

(i) Check and confirm power supply unit is healthy (ii) Check Local Alarms & annunciation (Facia & Substation Control System) (iii) Measurement of VT input to relay (iv) Confirm settings and configuration (v) Operational and timing test (vi) Confirm the operation of all relevant tripping circuits (vii) Check for lock out operation



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


Table 3.16 Maintenance plan for Under/Over Frequency and Under/Over Voltage Relays No Details

(I/N) Interval


Electromechanical


N 2 Years 2 Years

2 Check local alarms and annunciation I 4 Years 2 Years 3 Measurement of VT input to relay N 2 Years 2 Years 4 Confirm settings and configuration I 4 Years 2 Years 5 Operational and timing test I 4 Years 2 Years 6 Confirm the operation of all the relevant

tripping and/or alarm I 4 Years 2 Years

7 Check for lock out operation if used I 4 Years 2 Years

3.17 Pole Discrepancy Relays

(i) Check and confirm power supply unit is healthy (ii) Check Local Alarms & annunciation (Facia & Substation Control System) (iii) Operational and timing test (iv) Confirm the operation of the tripping circuits (v) Check for lock out operation

Table 3.17 Maintenance plan for Pole Discrepancy Relays No Details

(I/N) Interval


Electromechanical


N 2 Years 2 Years

2 Check local alarms and annunciation I 4 Years 2 Years 3 Operational and timing test I 4 Years 2 Years 4 Confirm the operation of the tripping

and/or alarm I 4 Years 2 Years




GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.18 Automatic Voltage Regulator (AVR)

(i) Check and confirm power supply unit is healthy (ii) Check Local Alarms & annunciation (Facia & Substation Control System) (iii) Measurement of CT and VT input to relay (iv) Operational and timing test

Table 3.18 Maintenance plan for Automatic Voltage Regulator Relays No Details

(I/N) Interval


Electromechanical


N 2 Years 2 Years

2 Check local alarms and annunciation I 4 Years 2 Years 3 Measurement of CT and VT input to relay N 2 Years 2 Years 4 Operational and timing test I 4 Years 2 Years

Note: AVR supervisory test is to be conducted by Tele-control Unit.

3.19 Unbalanced Protection

(i) Check and confirm power supply unit is healthy (ii) Check Local Alarms & annunciation (Facia & Substation Control System) (iii) Measurement of CT input to relay (iv) Confirm settings and configuration (v) Operational and timing test (vi) Functional Test (vii) Confirm the operation of the tripping circuits (viii) Check for lock out operation



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


Table 3.15 Maintenance plan for Unbalanced Protection Relays No Details

(I/N) Interval


Electromechanical


N 2 Years 2 Years

2 Check local alarms and annunciation I 4 Years 2 Years 3 Measurement of CT input to relay N 2 Years 2 Years 4 Confirm settings and configuration I 4 Years 2 Years 5 Operational and timing test I 4 Years 2 Years 6 Functional test 7 Confirm the operation of the tripping

circuits I 4 Years 2 Years


3.20 Transformer Guards (i) Alarms check (ii) Confirm the operation of tripping circuits Note: Maintenance tests for all transformer guards alarm and tripping signals are under Primary unit. The transformer guards shall be jointly tested with the presence of protection personnel.

3.21 Local Instrument meters

(i) Secondary Injection test

Note: Telecontrol section is responsible to ensure the reading registered (output from transducers) at SCS and NLDC are within allowable range. Work to be assisted by Protection.

Table 3.15 Maintenance plan for Instrument Meters No Details

(I/N) Interval


Electromechanical

1 Secondary injection test I 4 Years 2 Years



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.22 Switch-sync (Point of Wave) relays Maintenance of this type of relay will be carried out as and when required.

3.23 Reverse Power, Negative Phase Sequence, Over Excitation, Loss Excitation and Under Impedance Relays Maintenance of these relays will be carried out upon request and complete maintenance task/checklist is to be provided by Power Plant Operator/ Generation Division.

3.24 Regular Inspection

Component/Scheme Frequency Remark Charger 2 months Including 30V DC

system Battery Banks 2 months Including 30V DC

system DC distribution board 2 months - Protection Panels 2 months - Control Panels 2 months - RTCC/AVR 2 months - Marshalling Kiosks 2 months - Disturbance recorder 2 months - Battery Alarm Test 2 months -

3.25 Other Maintenance

Component/Scheme Frequency Remarks Discharge tests on battery banks

4 years 4 years for each bank.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


4 Types of Relays Used in TNB Transmission Protection Scheme

4.1 Feeder Bay Protection

Plant Voltage Level Component/Schemes Relay Maintenance

Plan Line 132 and below Distance Relay 3.1

Current Diff 3.2 OC/EF 3.6 DOC/DEF 3.6 Sync Check 3.5 Auto Re-close 3.4 Breaker Failure 3.14 Measurement Instruments

3.21

Line 500/275 Distance Relay 3.1 Current Diff 3. 2 OC/EF 3.6 DOC/DEF 3.6 Sync Check 3.5 Auto Re-close 3.4 Breaker Failure 3.14 Measurement Instruments

3.21

Pole Discrepancy 3.17 Thermal Overload 3.15 Stub 3.11

Cable 132 and below Pilot Wire Scheme 3.3 Current Diff 3.2 OC/EF 3.6 DOC/DEF 3.6 Breaker Failure 3.14 Measurement Instruments

3.21

Cable 275 Pilot Wire Scheme 3.3 Current Diff 3.2 OC/EF 3.6 DOC/DEF 3.6



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


Breaker Failure 3.14 Measurement Instruments

3.21

Thermal Overload 3.15 Stub 3.11

4.2 Power Transformer/ Generator Transformer/ Reactor Bay Protection

Plant Voltage Level Component/Schemes Relay Maintenance

Plan Transformer/ Reactor

132 and below Transformer Differential 3.8 REF (HV / LV) 3.9 OC/EF (HV/ LV) 3.6 DOC/DEF 3.6 SBEF (where applicable) 3.10 Transformer guards 3.20 RTCC/AVR 3.18 Measurement Instruments

3.21

Transformer/Reactor

500/275 Transformer Differential 3.8 High Impedance Diff 3.8 REF (HV/LV) 3.9 OC/EF (HV/LV) 3.6 DOC/DEF 3.6 SBEF 3.10 Transformer Guards 3.20 Breaker Failure 3.14 RTCC/AVR 3.18 Measurement Instrumentation

3.21



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


4.3 Capacitor Bank Protection

Plant

Voltage Level

Component/Scheme

Relay Maintenance Plan

Cap Bank All Unbalance Current 3.22 Under Current 3.6 Under/Over Voltage 3.16 OC/EF 3.6 Thermal Overload 3.15 Switch Sync 3.23 AVR 3.18

4.4 Bus Coupler, Bus Section and Busbar Protection

Special note: Bus section, Bus coupler and busbar maintenance are to be performed together.

Plant Voltage Level Component/Scheme

Relay Maintenance

Plan

Busbar 500/275/132 High/ Low Impedance 3.12, 3.13 CT supervision (for high impedance relays

3.12, 3.13

Busbar Aux Contact 3.12, 3.13 Bus coupler and Bus section

All Over Current 3.6



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


4.5 Generator Protection

Plant Voltage Level Component/scheme Relay

Maintenance Plan

Generator All Overall Diff 3.8 Reverse Power 3.23 Negative Phase Sequence

3.23

Over Excitation 3.23 Loss of Excitation 3.23 Under Impedance 3.23 Stator Earth Fault 3.6 Rotor Earth Fault 3.6 Thermal Overload 3.15 Under/Over Frequency 3.16 Under/Over Voltage 3.16 Over-current/Earth Fault

3.6

Measurement Instrument

3.21



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


E. MAINTENANCE GUIDELINES FOR STATIC VAR COMPENSATOR (SVC) EQUIPMENT

1 Scope This section outlines the maintenance guidelines for SVC equipment in TNB Transmission Division. The guidelines describe the maintenance works to be carried out on SVC equipment and their frequencies.

2 General Information SVC is used mainly to provide voltage control during daily load cycles, dynamic reactive power reserves in the event of network disturbances such as loss of generation and/or loss of transmission and also for damping of active power oscillations. At present, there are two SVC installations located at KL North substation (KULN) and Yong Peng North substation (YGPN). The major equipment in SVC installation are Circuit breaker, Transformer, Thyristor-switched capacitor (TSC), Thyristor-controlled reactor (TCR), Filter banks and secondary equipment. The maintenance strategy for SVC equipment is based on manufacturer’s recommendation and TNB maintenance experience. In deriving the maintenance guidelines, SVC equipment are divided into four major groups as follows:-

a) Thyristor related equipment b) Control and Protection for SVC Equipment c) SVC Primary Equipment d) Auxiliary equipment

3 Inspection and Maintenance Plan Maintenance of SVC and related equipment shall be carried out on a planned, routine basis. The maintenance works are aimed to provide acceptable degree of confidence when operating the SVC. This section describes the inspection and maintenance tasks required and the maintenance plan for the SVC equipment.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.1 Thyristor related equipment

3.1.1 Thyristor Valves


Interval

i Visual inspection on cleanliness, fibre optics condition, cooling tubes and valve components

NI Monthly

ii Inspection on Trigger pulse amplifier panels and LED statuses

NI Monthly

iii Inspection on By-pass Breaker (where applicable)

NI Monthly

iv Check on power supply circuits and test points at trigger pulse amplifier

I Quarterly

v Check Thyristor valve voltage division (as recommended by the manufacturer)

I Yearly

vi Trigger pulse converter and Thyristor fault monitoring (as recommended by the manufacturer)

I Yearly

3.1.2 Thyristor cooling system


Interval

i Visual inspection on cleanliness, leakage and general condition

NI Monthly

ii Record reading from pressure gauges, level meter, flow meter and conductivity meter.

NI Monthly

iii Note the operational sound and vibration for the motor pump

NI Monthly

iv Check cooling supervision function against actual operation

I Quarterly

v Cleaning of the outdoor air blast coolers

I Quarterly

vi Thyristor cooling system year end maintenance (as recommended by the manufacturer)

I Yearly



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.2 Control and Protection for SVC equipment The control system must provide stable operation under normal as well as contingency conditions whilst the protection system is designed such that all equipment is fully protected and any equipment which is operating in abnormal way is properly removed from service. All SVC protections are properly coordinated between each of the SVC equipment and with the AC system protection (where required).

3.2.1 VarMaster Control Local and Remote panel No Details Intrusive/

Non-Intrusive Interval

i Visual inspection on cleanliness, cubicle lights and heaters.

NI Monthly

ii Confirm correct readings are indicated on the meters and instrumentations.

NI Monthly

iii Check for any alarm operation on the facia.

NI Monthly

iv Check computer operation and LED statuses.

NI Monthly

v VarMaster Hardware check (as recommended by the manufacturer)

I Yearly

vi VarMaster Control Pulse computers functional check (as recommended by the manufacturer)

I Yearly

3.2.2 On-load measurement for protection scheme No Details Intrusive/


i Record the unbalance current for capacitor banks

NI Monthly

ii Record current and voltage for all protection scheme (as recommended by the manufacturer)

NI Yearly



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.2.3 Protection Relays for the SVC Primary Equipment

The maintenance task for the protection relays for the SVC Primary equipment follows the maintenance task for the protection relays as mentioned in Maintenance Guideline for Protection Systems.

3.3 SVC Primary Equipment The SVC Primary equipment consists of transformer, circuit breaker, isolator, current transformer, voltage transformer, capacitor, reactors and switchyard. The maintenance task for the SVC primary equipment follows the maintenance task for equipment as mentioned in Substation Maintenance Guidelines.

3.4 Auxiliary Equipment Auxiliary equipment includes ventilation, air conditioning, fire detection and fighting system, building condition and etc. as appropriate. The maintenance task for these items follows the maintenance task for Building and Entire plant as mentioned in Substation Maintenance Guidelines. Additional maintenance task which is considered important is also to be carried out.

3.4.1 Measurement of room temperature No Details Intrusive/


i Measurement of room temperature for main control room, Var Master conrol room and Thyristor valve room.

NI Weekly



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


F. MAINTENANCE GUIDELINES FOR HIGH VOLTAGE DIRECT CURRENT (HVDC)

EQUIPMENT

1 Scope This section outlines the maintenance guidelines for HVDC equipment in TNB Transmission Division. The guidelines describe the maintenance works to be carried out and their frequencies.

2 General Information HVDC is used mainly for long distance transmission, interconnection of power systems, long submarine cables and to increase efficiency in power control. At present, there is only one HVDC converter station in Gurun and the station provides interconnection of the power networks between Malaysia and Thailand. The maintenance guidelines cover equipment in HVDC convertor station. The maintenance strategy for HVDC equipment is based from manufacturers’ recommendation and TNB maintenance experience. In deriving the maintenance guidelines, HVDC convertor station is divided to five major areas as follows:-

a) Convertor equipment b) DC Primary Equipment c) AC Primary Equipment d) Control, Instrumentation and Protection e) General services and auxiliary equipment

3 Inspection and Maintenance Plan Maintenance of HVDC equipment and related equipment shall be carried out on a planned, routine basis. The maintenance works are aimed to provide acceptable degree of confidence when operating the HVDC equipment. This section describes the inspection and maintenance tasks required and the maintenance plan for the HVDC equipment.

3.1 Converter Equipment This includes equipment required for conversion from AC to DC and vice versa. The convertor equipment is located in the Valve hall. It consist of indoor air



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


insulated suspension type thyristor and direct water cooling system for the component of the valve.

3.1.1 Thyristor Valve


Interval

i Visual inspection N 2 Monthly ii Routine Inspection I Yearly iii Check grading electrode 2% at

random and long rod insulators 10% at random

I 4 Years

3.1.2 Valve cooling system


Interval

i Visual inspection Check conductivity

N 2 Monthly

ii Routine Inspection Check cooling coil for scaling, cleaning of cooling towers

I Yearly

iii Replace resin I 4 Years iv Overhaul cooling pump I 2 Years

3.1.3 Thyristor Valve Electronics


Interval

i Visual inspection and dust cleaning

I Yearly

3.2 DC Primary Equipment DC Primary equipment provides the interfacing between the convertor equipment and the DC overhead lines. The equipment and the maintenance task are described in the following clauses.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.2.1 DC Filter Active Part

DC Filter active parts are used to eliminate higher harmonic and minimize telecommunication interference. The maintenance activities are as follows:-


Interval

i Visual Inspection N 2 Monthly ii Replace backup batteries, clean

pcbs, lubrication and greasing I Yearly

iii Replace fan bearings I After 30000 hrs of operation

iv Check tightness of connections I 5 Years

3.2.2 DC Voltage Divider The maintenance task for DC Voltage divider follows the maintenance task for Capacitive Voltage Transformer as mentioned in Substation Maintenance Guideline.

3.2.3 High Speed Ground Switch High speed ground switch is used for continuous operation during neutral line fault where the switch is closed and the DC current will return to the ground. The maintenance task for High Speed Ground Switch follows the maintenance task for HV Circuit breaker as mentioned in Substation Maintenance Guideline.

3.2.4 DC Filter Circuit Breaker The maintenance task for DC Filter Circuit Breaker follows the maintenance task for HV Circuit breaker as mentioned in Substation Maintenance Guideline.

3.2.5 DC Disconnector, Grounding Switches and Valve Hall Earthing switches The maintenance task for DC Disconnector, grounding switches and valve hall earthing switches follows the maintenance task for Disconnectors as mentioned in Substation Maintenance Guideline.

3.2.6 DC Filter Capacitors, DC Filter Reactors and Smoothing Reactors The DC filters consist of capacitor and reactors and they are used to eliminate the lower harmonic content. The smoothing reactors are used to reduce rate of rise of DC current for DC side fault and it also forms part of high frequency noise filtering. The maintenance task for DC Filter Capacitors, DC Filter Reactors and Smoothing Reactors follows the maintenance task for Compensation Equipment as mentioned in Substation Maintenance Guideline.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.2.7 DC Switchyard

The DC switchyard is similar to AC substation switchyard. The maintenance task for DC switchyard follows the maintenance task for AC Switchyard as mentioned in Substation Maintenance Guideline.

3.3 AC Primary Equipment AC Primary equipment provides the interfacing between the convertor equipment and the AC network or the Transmission grid. The equipment and the maintenance task are described in the following clause.

3.3.1 AC Filter Capacitors, AC Filter Reactors and Capacitor Subbank The AC filters consist of capacitor and reactors and they are used to eliminate the harmonic content. The Capacitor subbank is used for compensation of reactive power absorbed by the converter. The maintenance task for AC Filter Capacitors, AC Filter Reactors and Capacitor subbank follows the maintenance task for Compensation Equipment as mentioned in Substation Maintenance Guideline.

3.3.2 AC Filter Resistors


Interval

i Visual Inspection NI 2 Monthly ii Cleaning , check tightness of

connections I Yearly

3.3.3 Converter Transformer The converter transformer consists of three single-phase, three-winding transformer. The converter transformer is used to stepdown/up the AC voltage to commutation voltage for the converter equipment. The maintenance task for Converter transformer follows the maintenance task for Power Transformer as mentioned in Substation Maintenance Guideline.

3.3.4 AC Current and Voltage Transformers The AC Current and Voltage transformers are used for AC,DC Filters and shunt reactors. The maintenance task for these instrument transformers follows the maintenance task for current transformer and voltage transformer as mentioned in Substation Maintenance Guideline.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


3.3.5 AC Switchyard

The maintenance task for HVDC station’s AC switchyard follows the maintenance task for AC Switchyard as mentioned in Substation Maintenance Guideline.

3.4 HVDC Control and Protection HVDC control system is designed such that to provide the desired power transmission level. The control system must provide stable operation under normal as well as contingency conditions. The protection system is designed such that all equipment is fully protected and any equipment which is operating in abnormal way is properly removed from service. All HVDC protections are properly coordinated between each of the HVDC equipment and with the AC system protection (where required). The monitoring system provides operation information related to HVDC system, HVDC station, auxiliary equipment and station alarms. The maintenance activities for HVDC control and protection are as follows:-


Interval

i DC Protection and Pole Control Function test

Intrusive Yearly

ii Teleprotection Intertrip test

Intrusive Yearly

iii Converter Transformer Protection test

Intrusive Yearly

iv AC Protection relays

Intrusive Yearly

v Circuit breaker trip test

Intrusive Yearly

The maintenance task for secondary DC supply system follows the maintenance task as mentioned in Protection equipment maintenance guidelines.

3.5 General services and auxiliary equipment Auxiliary equipment includes ventilation, air conditioning, fire detection and fighting system, building condition and etc. as appropriate. The maintenance task for these items follows the maintenance task for Building and entire plant as mentioned in Substation maintenance guidelines.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


G. MAINTENANCE GUIDELINES FOR SUBSTATION CONTROL SYSTEM (SCS)

1 Scope The section outlines the maintenance guidelines for substation control system (SCS) installed in TNB Transmission network. The guidelines describe the tasks to be done on the equipment and the frequencies of these tasks.

2 General Information The Substation Control System (SCS) are installed in substations for the collection, processing, storage, retrieving, and distribution of data obtained from substation equipment and other sources. SCS also supports the operation of power system by providing local monitoring and control facilities as well as providing interface to SCADA master station for remote operation. The SCS is designed to be an expandable, technology adaptable, modular hierarchy of segments, elements and subsystems. It is not expected that SCS equipment will require extensive scheduled preventive maintenance. Advancements in technology, with self-supervision features, have eliminated most preventive maintenance requirements. • Operational Availability (OA)

Operational Availability is measured from the issuance of fault reports to the rectification of the problem.

• Mean Down Time (MDT)

Maximum MDT is the maximum time for Maintenance Team to clear/repair/normalized the fault from the issuance of fault report to the rectification of the problem.

• Preventive Maintenance

Preventive maintenance includes all scheduled maintenance action performed to retain SCS in specified condition. Scheduled maintenance includes the periodic inspections, condition monitoring, critical item servicing, software back up and calibration.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


• Corrective Maintenance

Corrective Maintenance includes unscheduled maintenance actions performed as a result of SCS failure to restore the SCS to a specified condition. The tasks include failure identification, isolation of faulty equipment, replacement and retesting.

• Failure Modes

SCS failure could cause a total or partial failure to the Network, Station, and Bay Level control and monitoring function. The SCS is designed such that a single failure shall not affect the operation and functions of both network level and station level. The SCS is designed such that a single failure shall not affect the operation and functions of more than one bay or diameters.

Possible Failure includes:

Subsystem and Functions Failure Mode Human Machine Interface Total Partial Gateway Total Station Level Controller Total Partial Bay Controller Unit Total Partial Internal Communication Network:

Single Bay Total Partial Multiple Bay Impossible Impossible

3 Objectives The primary objective of SCS maintenance is to achieve and sustain the operational availability (OA) and mean down time (MDT) objectives of the SCS at the least life cycle cost. It also describes the general concept and plan for maintaining Substation Control System (SCS) Hardware (HW) and Software (SW) in support of SCS operational objectives. This guideline is applicable for maintenance support of SCS HW and SW until the end of the system life cycle. This guideline also serves to:

i. Document SCS maintenance strategies ii. Optimize maintenance costs

iii. Standardize maintenance activities iv. Help achieve TNBT’s business plans and targets



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


4 Maintenance Plan

4.1 Preventive Maintenance Frequency Task One year interval per substation Back up Application Software

Data (Settings, Events, Log Files) Visual Inspection Cleaning

Maintenance support (i.e. Organization, Spares Parts Provision, etc) will be performed as required to meet SCS operations requirements.

5 Documentation All visual inspection observation, tests performed on all SCS shall be recorded appropriately and kept in regional database for future references and analysis. The data shall be kept both in hard copy and soft copy.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


H. MAINTENANCE GUIDELINES FOR REMOTE TERMINAL UNIT (RTUS)

1 Scope The section outlines the maintenance guidelines for all Remote Terminal Units (RTUs) installed in TNB Transmission network. These guidelines determine the tasks to be done on the equipment and the frequencies of these tasks.

2 General Information The maintenance guidelines cover the Remote Terminal Unit and include the Supervisory Interface Panel and the I/O wiring between the RTU and the Supervisory Interface Panel, as shown in Figure 1 below. These guidelines does not cover plant auxiliary contacts, heavy-duty interposing relays and transducers mounted in control panels, DC system and the communication network equipment.

�



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


2.1 Failure Modes

• Hidden Failure A functional failure that does not manifest itself until function is required.

• Partial Failure A failure that results in reduced performance or functionality of any of the RTU’s primary functions. For example, an RTU is said to have suffered a partial failure when 16 out of its total 128 analog measurements cannot register any readings.

• Complete Failure

Failure which results complete loss of all of the RTU’s primary functions.

3 Objectives The primary objective of RTUs maintenance is to achieve and sustain the operational availability (OA) and mean down time (MDT) of the RTUs at the least life cycle cost. The guidelines also serve to:

i. Document RTU maintenance strategies ii. Optimize maintenance costs

iii. Standardize maintenance activities iv. Improve RTUs operational reliability and availability v. Help achieve TNBT’s business plans and targets

4 Maintenance Plan

4.1 Failure Mode, Effect and Criticality Analysis (FMECA) FMECA study performed on the RTU established that the most appropriate maintenance strategy involves operating the RTU to failure and restoring it back to service as soon as possible. The FMECA also identified the need to perform regular periodic inspections to ensure that the RTU’s operating environment is within specified limits, and to conduct periodic functional checks to resolve any hidden failures before they manifest themselves.



GUIDELINE


Document No:

TNBT/TAMD/09/02/29/06


4.2 Preventive Maintenance Periodic inspections shall be carried out on all RTU sites to:

i. Ensure that RTU’s operating environment is within the specified acceptable limits. The inspection shall check for environmental parameters such as temperature and input supply voltages. This Overall System Check shall be carried out once a year on each RTU.

ii. Confirm RTU functionality. Functional System Check shall be performed once every 4 years and can be performed at the same time as the overall system check.

5 Documentation All visual inspection observation, tests performed on all RTU shall be recorded appropriately and kept in regional database for future references and analysis. The data shall be kept both in hard copy and soft copy.