substation maintenance procedures r1

7/28/2019 Substation Maintenance Procedures R1

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SUBSTATION MAINTENANCE PROCEDURES

33KV VACUUM CIRCUIT BREAKERS

125VDC LEAD ACID BATTERY

POWER TRANSFORMERS

ON - LOAD TAP CHANGERS

STRUCTURES & BUSWORK

POTENTIAL TRANSFORMERS

MV DISCONNECTORS

MV SWITCHGEARS

GROUNDING

FEBRUARY 2009

PREPARED BY: ANSEL GARVEY


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SUBSTATION MAINTENANCE PROCEDURES

TABLE OF CONTENTS

1. INTRODUCTION...............................................................................................................1

1.1 GENERAL ............................................................................................................................11.2 DEFINITIONS ......................................................................................................................11.3 SAFETY................................................................................................................................2

2. SUBSTATION IN-SERVICE INSPECTION...................................................................3

2.1 INTRODUCTION .................................................................................................................32.2 INFORMATION, TOOLS AND MATERIALS...................................................................3

2.3 SAFETY REQUIREMENTS ................................................................................................32.4 DISCONNECT SWITCH INSPECTION .............................................................................42.5 STATION BUS INSPECTION.............................................................................................42.6 33KV VACUUM BREAKER INSPECTION.......................................................................4

2.7 POWER TRANSFORMER INSPECTION ..........................................................................4

2.8 ON-LOAD TAP CHANGER INSPECTION........................................................................52.9 INSTRUMENT TRANSFORMER INSPECTION...............................................................52.10 STRUCTURE INSPECTION................................................................................................52.11 INFRARED INSPECTION...................................................................................................5

3. EQUIPMENT INSPECTION/MINOR MAINTENANCE..............................................7

3.1 INTRODUCTION .................................................................................................................7

3.2 125 VDC LEAD ACID BATTERY AND CHARGER INSPECTION................................73.3 33KV VACUUM CIRCUIT BREAKER..............................................................................8

3.4 POWER TRANSFORMER INSPECTION ..........................................................................103.5 11KV SWITCHGEAR INSPECTION ..................................................................................123.6 33KV SWITCHGEAR INSPECTION ..................................................................................14

4. EQUIPMENT TESTING....................................................................................................17

4.1 SAFETY OF PERSONNEL..................................................................................................174.2 SAFETY HAZARDS............................................................................................................174.3 TRANSFORMER TESTING................................................................................................18

4.4 OIL SAMPLE COLLECTION AND TEST .........................................................................204.5 CIRCUIT BREAKER TESTING..........................................................................................21

5. MAJOR MAINTENANCE.................................................................................................23

5.1 INTRODUCTION .................................................................................................................23

5.2 MAJOR OVERHAULS ON 33KV VACUUM CIRCUIT BREAKERS .............................23

5.3 MAJOR OVERHAULS 125 VDC LEAD ACID BATTERIES & CHARGER...................255.4 MAJOR OVERHAULS ON POWER TRANSFORMERS..................................................285.5 MAJOR OVERHAULS ON ON-LOAD TAP CHANGERS ...............................................315.6 MAJOR OVERHAULS DISCON SWITCHES AND ASSOCIATED EQUIPMENT........345.7 MAJOR OVERHAULS ON INSTRUMENT TRANSFORMERS ......................................365.8 MAJOR OVERHAULS ON 33KV SWITCHGEAR............................................................37

5.9 MAJOR OVERHAULS ON 11KV SWITCHGEAR ...........................................................395.10 SUBSTATION GROUNDING MAINTENANCE...............................................................41


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6. APPENDICES

6.1 INSPECTION SHEETS

6.1.1 33kv Vacuum Circuit Breakers6.1.2 125 VDC Lead Acid Batteries & Charger6.1.3 Power Transformers6.1.4 On-Load Tap Changers6.1.5 Structures & Buswork

6.1.6 Instrument Transformers6.1.7 MV Disconnect Switches6.1.8 MV Switchgear6.1.9 Substation Grounding

6.2 TEST SHEETS

6.3 SAFETY PROCEDURES


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1. INTRODUCTION

1.1 GENERAL

Preventative maintenance is a cycle of planned inspections, tests, minor overhauls and

servicing activities designed to keep equipment in good operating condition and to reveal

the need for reconditioning or major overhaul in time to prevent breakdowns or failure

during operation. This manual contains maintenance standards and procedures for thepreventative maintenance program. The maintenance standards and procedures shall be

used in conjunction with manufacturers manuals.

These Maintenance Procedures identify the Works to be carried out for Maintenance on the

following equipment:

33kV Vacuum Circuit Breakers

125VDC Lead Acid Batteries & Chargers

Power Transformers

On-Load Tap Changers

Structures and bus work

Potential Transformers

Medium Voltage Disconnect Switches

Medium Voltage Switchgears

Grounding

This procedure should be used with the attached inspection sheets and test report forms.Ensure all forms are completely filled out and a local field file is maintained on this

equipment.

1.2 DEFINITIONS

These procedures fall into four categories: Inspections, Minor Overhaul, Major Overhaul

and Test Procedures.

Inspections are comprised of visual checks and test operating of station equipment. Theymay require taking readings and making reports on equipment condition. Usually the workcan be completed with the equipment in service. Inspections identify when further

investigative maintenance is required.

Minor Maintenanceis usually non-invasive and involves assessment of the equipment

condition by a means of inspections, checks, samples and tests etc. Minor maintenance isused to assess the correct functioning of the equipment and to determine further

maintenance requirements. This procedure does not cover all eventualities; the crew is alsoexpected to look for and correct defects, which are not anticipated in this procedure.

Major Maintenance is the replacement and or refurbishment of an equipment major

component or system. Major overhauls are usually performed when a minor overhaul,historical data, modification or system performance deem them necessary. Major overhauls

usually include most of the minor overhaul steps.


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Testing/sampling procedures outline the steps required to indicate equipment condition

through testing of the equipment or equipment insulation i.e. Oil Samples, Thermovision(Infra-red) Capacitance and Power Factor etc. These tests can be performed outside of the

minor or major overhaul procedures. The results of the testing identify when further

maintenance is required.

1.3 SAFETY

It is the responsibility of every employee to avoid unnecessary risks by following safety

rules, approved work procedures and practices. Before undertaking any procedures in thismanual, proper work protection must be established as required by GRENLEC Safety

Policy and Procedures. In addition, safety hazard identification must be an integral part of

everyday work. It is the responsibility of the person in charge of the work and eachcrewmember to constantly be on the lookout for safety hazards and to take definite steps to

eliminate or control the hazards.

Safetyof Personnel

In order to ensure human safety, all personnel involved with the works shall be briefed onall aspects of the work prior to the commencement of any maintenance work or testing, and

the following safety procedures adhered to. Particular emphasis should be placed onpersonnel hazards and the safety precautions associated with these hazards.

Work ProtectionProper work protection shall be established in accordance with the requirements of

GRENLEC Safety Policy and Procedures. Ensure the Controller is notified when a station

inspection is being performed.

SafetyIdentification

A safety identification exercise and safety basics procedure to identify all hazards shall beperformed.


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2. SUBSTATION IN-SERVICE INSPECTION

2.1 INTRODUCTION

2.1.1 This Maintenance Procedure details the work to be carried out during SubstationInspections. The maintenance crew is also expected to identify and correct defects, which

are not anticipated in this procedure.This procedure is performed to:

(i) Assess substation structures, bus work and equipment condition;(ii) Verify the correct functioning of the equipment and determine maintenance

requirements.

2.1.2 The substation inspection should be carried out by trained maintenance personnel and in

accordance with this procedure and the manufacturers instructions.

2.1.3 The Substation Inspection Sheet should be completed during the site inspection.

2.2 INFORMATION, TOOLS AND MATERIALS

2.2.1 Planning

In planning the work, refer to:- Manufacturers instruction books, technical drawings, etc.

- Training lessons

- Previous station inspection reports

- Copy of any special GRENLEC orders or manufacturers technical bulletins

2.2.2 Special Tools and Materials

- Binoculars

- Infrared Camera

2.3 SAFETY REQUIREMENTS

During a station inspection and thermovision testing the electrical equipment will be in-

service and in an energized state. Proper work clearances must be maintained at all times.Operating and testing of equipment must be approved and coordinated by the controllers.

Binoculars should be used for detailed inspection of live equipment. Infrared Camera

should be used to check for and record hot joints.

All personnel involved shall be briefed on all aspects of the work prior to the start of anymaintenance or testing activity. Particular emphasis should be placed on personnel hazards

and the safety precautions associated with these hazards. Proper working clearances must

be maintained at all times.

Make yourself aware of close-by live apparatus while conducting the inspection.


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2.4 DISCONNECT SWITCH INSPECTION

2.4.1 Visually check that the switches are in their required operating position - either fully closed

with blades in proper position or fully open with proper clearances.

2.4.2 Check if the insulators are chipped or cracked. Check for signs of flashover, excessive dirt,

foreign material, copper splash. Check cementing and fasteners.

2.4.3 Check linkages, operating handles for damage and correct positioning.

2.4.4 Visually check the motor mechanism for deterioration, corrosion or damage.

2.4.5 Check the anti-condensation heater in Motor Control Panel

.

2.5 STATION BUS INSPECTION

2.5.1 Check bus support insulators for chips, cracks, flashover burns, excessive dirt, foreignmaterial, copper splash, copper wash, correct cementing and fasteners.

2.5.2 Check bus connections for damage, deterioration or signs of heating.

2.6 33KV VACUUM BREAKER INSPECTION

2.6.1 Perform a general inspection in the operating mechanism/control cabinet and around the

breaker checking for deterioration, corrosion or damage.

2.6.2 Check the anti-condensation heater.

2.7 POWER TRANSFORMER INSPECTION

2.7.1 Check oil levels in tank and tap changer conservators.

2.7.2 Check the pressure gauge reading on sealed tank transformers. The gauge should indicate a

positive pressure with the unit in service.

2.7.3 If the transformer is equipped with a silica gel breather check the color of the silica gel.Blue indicates dry and pink indicates wet.

2.7.4 Check valves, gaskets, welds, and fittings for any sign of oil leakage or damage.

2.7.5 Perform a general inspection in the control cabinet and inspect the transformer fordeterioration, corrosion or damage.

2.7.6 Operate the fans to ensure correct operation. Check that the radiators are free from debristhat could restrict the flow of air.

2.7.7 Check anti condensation heaters

2.7.8 Check temperature readings (oil and winding temperature gauges)


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2.8 ON LOAD TAP CHANGER INSPECTION

2.8.1 Perform a general inspection in the operating mechanism/control cabinet checking fordeterioration, corrosion or damage.

2.8.2 Operate the tap changer raise and lower one tap. Check for irregular operation, noises, etc.

NOTE: Notify controlling authority before operating tap changer.

2.8.3 Check the anti-condensation heater (if applicable).

2.9 INSTRUMENT TRANSFORMER INSPECTION.

2.9.1 Check valves, gaskets, and fittings for any sign of oil leakage or damage.

2.9.2 Perform a general inspection around the instrument transformer checking for deterioration,

corrosion or damage.

2.10 STRUCTURE INSPECTION

2.10.1 Check all foundations and structures for cracking, shifting or deterioration.

2.10.2 Check all equipment ground connections are secure.

2.11 INFRARED INSPECTION

2.11.1 Scope of Program

The objectives of the thermovision testing program are:

1. Detect overheated components in station equipment.2. Monitor equipment showing signs of deterioration.

3. Examine new installations for improper or faulty connections.

4. Examine the condition of equipment which has been repaired.

2.11.2 Test Conditions

2.11.2.1 To obtain the most reliable results, it is recommended to arrange station loading so that the

equipment being surveyed will be carrying as large a current as possible, for one hour prior

to the test. It is recommended that the loading be at least 25% of the equipment rating.

2.11.2.2 Prior to making application for equipment outages and switching required to create the

necessary increased loading on components, a switching schedule and test plan should beestablished for each station.

2.11.2.3 Testing should be carried out with the understanding that equipment may be returned tonormal operating position, without notifying the test crew.


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2.11.3 Evaluation of Test Results (Current Carrying Components)

The thermovision operator will carry out a preliminary evaluation of the test results. Items

found to be outside the normal limits of temperature rise outlined in the operators manualshall be reported to the substation group.

The thermovision operator will assign priority for further action, as shown below:

A Emergency, arrange repair immediatelyB Repair in the immediate future

C Repair in near future possibly with next planned outageD Repair in regular maintenance, retest at next thermovision inspection

2.11.4 Evaluation of Test Results (Non Current Carrying Components)

2.11.4.1 Disconnect Switches (Motor Operated)

Scan the motorized mechanism electrical components for signs of overheated terminalstrips, connections, relays, contactors and defective heaters. Compare results with other

similar mechanisms.

2.11.4.2 Circuit Breakers

Scan the operating mechanism/control cabinets electrical components for signs of

overheated terminal strips, connections, relays, contactors and defective heaters. Compare

results with other similar breaker mechanisms.

Scan the tanks and interrupter poles of circuit breakers and check for hot spots or varianceswhen compared to other similarly loaded circuit breakers.

2.11.4.3 Transformers and Tap Changers

Scan the operating mechanism/control cabinets electrical components for signs of

overheated terminal strips, connections, relays, contactors and defective heaters. Compareresults with other similar transformer mechanisms.

Scan the radiator looking for restrictions in the oil flow that may cause variances whencompared to other parts of the cooling system or similar transformers.

Scan the tap changer compartment looking for variances when compared to other similarlytap changers. Compare the tap changer temperature to the main tank. The tap changer is

normally a few degrees cooler than the main tank.

2.11.4.4 Instrument Transformers

Scan the tanks of instrument transformers looking for variances when compared to similar

instrument transformers.

2.11.4.5 Surge Arrestors (Lightning Arrestors)

Scan the porcelains of surge arrestors and check for variances when compared to similar

surge arrestors.


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3. EQUIPMENT INSPECTION/MINOR MAINTENANCE

3.1 INTRODUCTION

3.1.1 Minor maintenance is performed to assess the overall equipment condition, the correct

functioning of the equipment and to determine requirements for major maintenance.

3.1.2 Maintenance of equipment should be carried out by trained maintenance personnel and in

accordance with this procedure and specific manufacturers instructions.

3.1.3 All appropriate forms should be filled out and a file maintained on the equipment.

3.1.4 All personnel involved shall be briefed on all aspects of the work prior to the start of any

maintenance or testing activity. Particular emphasis should be placed on personnel hazardsand the safety precautions associated with these hazards. Proper working clearances must

be maintained at all times.

3.1.5 In planning the work, refer to:

- Manufacturers instruction books, technical drawings, etc.

- Training lessons- Substation Inspection Reports

- Previous overhaul and trouble reports- Copy of any special GRENLEC orders or manufacturers technical bulletins

3.1.6 Make yourself aware of close-by live apparatus while conducting the inspection.

3.2 125VDC BATTERY & CHARGER INSPECTION

3.2.1 SPECIAL TOOLS AND MATERIALS

- Hydrometer, Voltmeter and Ammeter- Distilled Water

- Face Shield

- Apron

- Gloves (chemical resistant)

3.2.2 SPECIAL SAFETY HAZARDS

Batteries contain sulfuric acid. Do not allow battery fluid to come in contact with eyes or

skin. If contact occurs, flush the affected area immediately with water. Batteries generatehydrogen gas, which is flammable and explosive. To reduce the possibility of explosion,

never expose the battery to open flame or sparks. Do not smoke near the battery. Tools

should be insulated to avoid the chance of sparks. Batteries contain stored energy and mayexplode if inadvertently shorted.


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3.2.3 INSPECTION

3.2.3.1 Check to ensure that the battery room temperature is between 20 and 25C.

3.2.3.2 Record DC voltage reading on the charger voltmeter and note any variation from normal

range of values.

3.2.3.3 Record the charger ammeter reading. The normal current drain on the battery should be

marked on the meter. Note if the reading is outside the normal range.

3.2.3.4 Check the battery terminals for corrosion or discoloration.

3.2.3.5 Check forleaks. There should be no visible signs of electrolyte on the battery jars, the jar

covers or in the trays.

3.2.3.6 Measure and record the corrected specific gravity (S.G.) of the electrolyte in the pilot celland determine if an equalize charge is required. The pilot cell is one which is used as a

convenient means to indicate the condition and state of charge of the whole battery. The

pilot cell is the one of poorest quality, lowest specific gravity reading and lowest voltage.

3.2.3.7 Measure and record the voltage of the pilot cell and determine if an equalize charge is

required. The pilot cell is the one used to estimate the condition and state of charge of thewhole battery.

3.2.3.8 Check the electrolyte level. Add distilled water if the level is below the lower limit.

3.2.3.9 Equalize Battery (periodic application of a controlled overvoltage cycle to battery)

3.3 CIRCUIT BREAKER INSPECTION

3.3.1 SPECIAL TOOLS AND MATERIALS- Multi Meter

- Clip on Ammeter

- Foam Spray- Recommended lubricants

3.3.2 SAFETY OF PERSONNEL

Isolate the equipment

Carry out a visual check to ensure the equipment is isolated

Where visual check is not possible carry out checks with an approved voltage indicatorto ensure the equipment is fully isolated.

Ground the equipment

Ensure the circuit breaker and its mechanisms are disconnected from all power, bothhigh voltage and control voltage before it is inspected.

Mark off the work area with signs and easily visible tape.


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The circuit breaker is composed of many mechanical devices, which may be underspring loading regardless of the operating position. Ensure all spring operating systems

are fully discharged before working on any mechanism.

3.3.3 SAFETY HAZARDS

Some points in the control cabinet may be live. If work is required on a live circuit arrange

for isolation at the source end of the circuit.

This circuit breaker is composed of many mechanical devices, which may be under springloading regardless of the operating position. Ensure that all spring operating systems for

both closing and opening are fully discharged if work is required in the mechanism.

Safety Note: Be aware of near-by live parts before commencing work on the circuit

breaker.

3.3.4 INSPECTION

3.3.4.1 Verify the operation of the breaker operation counter. Record the counter reading before

and after the inspection.

3.3.4.2 Check the bushing for chips, cracks, flashover burns, copper splash, copper wash, correct

cementing and fasteners. Clean the bushings if they are contaminated with dirt, dust or

other pollutants.

3.3.4.3 Check circuit breaker housing, structures, covers, fittings etc. for any sign of rusting,

corrosion or damage to painted surface.

3.3.4.4 Check control and operator mechanism compartments:

a. Look for loose, broken, corroded wire/ terminals, loose contactor parts, burnt coils and

contacts. Check fuses, connections, contactors. Check for any sign of contact burningand deterioration in insulation of control wire or coils.

b. Check for sign of corrosion, moisture, external contamination or damage. Check all

cable entrances are properly sealed against rodent. Inspect seals for any sign of external

contamination or aging.

c. Check the operation of anti-condensation heaters.

3.3.4.5 Inspect the contacts of the auxiliary switches. Check for loose connections and erosion,

burning or chattering of contacts. Check also the auxiliary switch linkage alignment forwear & lubrication. Clean or adjust, if required.

3.3.4.6 Check the condition of the contacts on all the relays.

3.3.4.7 Check the condition of the following items: Mechanism bearings, Linkages, springs and

shafts. Check springs for defects, cracks and tightness of fittings.


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3.3.4.8 Operating mechanism

Inspect operating mechanism. Check lubrication. Check for smooth operation during

manual operation. Clean and lubricate the operating mechanism/ linkage as permanufacturers instructions. Note the condition of the parts. Use recommended lubricant

only.

3.3.4.9 Verify the operation of position indicator (open/close) to ensure it is indicating correctly.

3.3.4.10 Check the charging spring indicator in both the charged and discharged position.

3.3.4.11 Record Contact wear

3.4 POWER TRANSFORMER INSPECTION

Minor overhaul on the transformer shall be conducted with the transformerenergized and in service.


This procedure should be used with the attached inspection report form. Ensure all forms

are completely filled out. A copy of the completed inspection form should be sent to theDistribution Department.

Tools and Materials- Volt / Ohm Meter

- Foam Spray

- Recommended Lubricants

Oil Sample & Test- Approved, Clean, Oil Sample Jars and Syringes

- Labels, GRENLEC and Laboratory Forms and Shipping Information- Clean PVC Hoses, Fittings and Wipers

- Bucket and Waste Oil Container


The maintenance of transformers should be carried out by trained maintenance personnel

and in accordance with this procedure and specific manufacturers instructions.

Some points in the control cabinet may be live even with all the control switches open. Ifwork is required on a live circuit arrange for isolation at the source end of the circuit.

Safety Note: Make yourself aware of close-by live apparatus before starting to work

on the transformer.


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3.4.3 TRANSFORMER INSPECTION (IN-SERVICE)

3.4.3.1 Listen for any abnormal sounds that may indicate loose windings, blocking or othermechanical problems.

3.4.3.2 Check the oil level in the main tank on transformers equipped with conservator tanks. The

gauge should show a normal level, adjusted for temperature.

3.4.3.3 Check the pressure gauge reading on sealed (no conservator) type transformers. The gaugeshould indicate a positive pressure.

3.4.3.4 Check the bushing condition. Look for broken, chipped or cracked bushings, flashover

burns, copper splash, copper wash, correct cementing and fasteners. Clean the bushings if

they are contaminated with dirt, dust or other pollutants.

3.4.3.5 Check pressure relief vent for signs of damage or oil leakage. Check for signs of relief ventdiaphragm operation, cracked diaphragm and visible evidence of oil around relief area.

3.4.3.6 For transformers equipped with a silica gel breather check the color of the silica gel. Check

to ensure the breather vent is not plugged with debris or insects.

3.4.3.7 Check valves, gaskets and fittings for any sign of oil leakage or damage.

3.4.3.8 Check panels, structures, covers, valves, fittings for signs corrosion or damage.

3.4.3.9 Check the control cabinet for broken or corroded wire/terminals, loose contactor parts,burnt coils and contacts. Check fuses, connections. Check conductors and coils for

deterioration in insulation.

3.4.3.10 Inspect the control cabinet for signs of corrosion, moisture, external damage or

contamination. Ensure cable entrances are properly sealed against rodents. Inspect sealsfor signs of external contamination or aging. Check the door.

3.4.3.11 Check the operation of anti-condensation heaters.

3.4.3.12 Check and record the maximum and existing oil and winding temperatures. Check thetemperature gauges for correct functioning - upper drag hand limit is not excessive, drag

hands indicate reasonable temperature range. Reset.

3.4.3.13 Operate the fans. Check that all fans are operating properly and turning in the correct

direction, there is no audible indication of bearing trouble, fan guards are fixed in place and

there is no damage to blades and wiring is in good condition.

3.4.3.14 Check the radiators. Remove any bird nests, bird excrement, or other foreign debris thatwill restrict the flow of air or cause corrosion or damage to the units.

3.4.3.15 Take an oil sample from the tank. Perform a dielectric test. Results of the Dielectric test

should be used to assess the transformer condition. Record and compare the results with

previous tests and ANSI recommended values.

3.4.3.16 Check Buchholz Relay for flammable gas.

3.4.3.17 Check pressure relief device for normal condition.


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3.4.4 ON-LOAD TAP CHANGER IN-SERVICE INSPECTION

3.4.4.1 Operate the Tap changer (raise/lower)

a) Check the tap changer operation counter is operating properly.

b) Check the tap position indicator is operating correctly

c) Check for irregular operation, noises, etc.

d) Record final reading

3.4.4.2 Check the gear lubricant levels and refill if necessary, using manufacturers recommendedlubricant.

3.4.4.3 Check linkages for correct operation. Lubricate drive gears according to manufacturer

recommendations

3.4.4.4 Check the mechanical and electrical limits by operating the tap changer through its

complete range of taps and attempt to overdrive (mechanically and electrically) at both endsof the tap range.

NOTE: The limits must be checked manually first.

3.4.4.5 Test the Buchholz relays. Check for flammable gases.

3.4.4.6 Take an oil sample from the tap changer. Perform a dielectric test. Results of the Dielectric

test should be used to assess the tap changer condition. Record and compare the results with

previous tests, and ANSI recommended values.

3.4.5.7 Check pressure relief device for normal condition.

3.5 11KV SWITCHGEAR INSPECTION


- Clip on Ammeter - Foam Spray

- Recommended lubricants

- Vacuum Cleaner


De-energize the equipment

Carry out a visual check to ensure the equipment is isolated; where visual check is notpossible carry out checks with an approved voltage indicator to ensure the equipment is

fully isolated.


Ensure the circuit breaker and its mechanisms are disconnected from all power, both

high voltage and control voltage before it is inspected.


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are fully discharged before performing an inspection or maintenance.

De-energize control power to the circuit breaker by removal of the fuse holder or byopening the molded case circuit breaker.

Perform the spring discharge test before removing or inserting the circuit breaker. See

Instruction Manual for procedure.

Ensure circuit breaker door is closed before racking. See Instruction Manual for racking

procedures.







breaker.

3.5.4 INSPECTION

3.5.4.1 A general visual inspection of the switchgear and a check on accessories shall be conducted

every year.

A more detailed inspection shall be carried out every five (5) years.

3.5.4.2 Inspect general condition of the switchgear installation. Check housing, structures, covers,fittings etc. for any sign of rusting, corrosion or damage to painted surface.

3.5.4.3 Check the bushing for chips, cracks, flashover burns, copper splash, copper wash, correctcementing and fasteners. Clean the bushings if they are contaminated with dirt, dust or

other pollutants.



3.5.4.5 Inspect switchgear interior for accumulation of dust, dirt or foreign matter.

3.5.4.6 Clean panels and check connections

3.5.4.7 Check control and circuit breaker compartments:

a. Look for loose, broken, corroded wire/ terminals, loose contactor parts, burnt coils,contacts and terminal blocks. Check fuses, connections, contactors. Check for any signof contact burning and deterioration in insulation of control wire or coils.

b. Check for sign of corrosion, moisture, external contamination or damage. Check allcable entrances are properly sealed against rodent. Inspect seals for any sign of external



d. Examine indicating lamps and replace as required


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3.5.4.8 Inspect the contacts of the auxiliary switches. Check for loose connections and erosion,burning or chattering of contacts. Check also the auxiliary switch linkage alignment for

wear & lubrication. Clean or adjust, if required.


3.5.4.10 Check the condition of the following items: Mechanism bearings, Linkages, springs andshafts. Check springs for defects, cracks and tightness of fittings.


Inspect operating mechanism. Check lubrication. Check for smooth operation duringmanual operation. Clean and lubricate the operating mechanism/ linkage as per

manufacturers instructions. Note the condition of the parts. Use recommended lubricant

only.



3.5.4.14 Record Contact-wear while checking spring

3.5.4.15 Check for proper condition of instrument transformers. Replace burned out fuses. Check

primary and secondary connections.

3.5.4.16 Insert the draw-out section into the panel

3.5.4.17 Check out all the necessary functions and interlocking

3.5.4.18 Replace reassemble, re-insulate, return all items to proper operating conditions and remove

grounds prior to energizing.

3.6 33KV SWITCHGEAR INSPECTION


- Clip on Ammeter


- Vacuum Cleaner


De-energize the equipment

Carry out a visual check to ensure the equipment is isolated; where visual check is notpossible carry out checks with an approved voltage indicator to ensure the equipment is

fully isolated.


Ensure the circuit breaker and its mechanisms are disconnected from all power, bothhigh voltage and control voltage before it is inspected.


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are fully discharged before performing an inspection or maintenance.

De-energize control power to the circuit breaker by removal of the fuse holder or byopening the molded case circuit breaker.

Perform the spring discharge test before removing or inserting the circuit breaker. See

Instruction Manual for procedure.

Ensure circuit breaker door is closed before racking. See Instruction Manual for racking

procedures.







breaker.

3.6.4 INSPECTION

3.6.4.1 A general visual inspection of the switchgear and a check on accessories shall be conducted

every year.

A more detailed inspection shall be carried out every five (5) years.

3.6.4.2 Inspect general condition of the switchgear installation. Check housing, structures, covers,fittings etc. for any sign of rusting, corrosion or damage to painted surface.

3.6.4.3 Check the bushing for chips, cracks, flashover burns, copper splash, copper wash, correctcementing and fasteners. Clean the bushings if they are contaminated with dirt, dust or

other pollutants.



3.6.4.5 Inspect switchgear interior for accumulation of dust, dirt or foreign matter.

3.6.4.6 Clean panels and check connections

3.6.4.7 Check control and circuit breaker compartments:

a. Look for loose, broken, corroded wire/ terminals, loose contactor parts, burnt coils,contacts and terminal blocks. Check fuses, connections, contactors. Check for any signof contact burning and deterioration in insulation of control wire or coils.

b. Check for sign of corrosion, moisture, external contamination or damage. Check allcable entrances are properly sealed against rodent. Inspect seals for any sign of external



d. Examine indicating lamps and replace as required


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3.6.4.8 Inspect the contacts of the auxiliary switches. Check for loose connections and erosion,burning or chattering of contacts. Check also the auxiliary switch linkage alignment for



3.6.4.10 Check the condition of the following items: Mechanism bearings, Linkages, springs andshafts. Check springs for defects, cracks and tightness of fittings.


Inspect operating mechanism. Check lubrication. Check for smooth operation duringmanual operation. Clean and lubricate the operating mechanism/ linkage as per

manufacturers instructions. Note the condition of the parts. Use recommended lubricant

only.



3.6.4.14 Record Contact-wear while checking spring

3.6.4.15 Check for proper condition of instrument transformers. Replace burned out fuses. Check

primary and secondary connections.

3.6.4.16 Insert the draw-out section into the panel

3.6.4.17 Check out all the necessary functions and interlocking

3.6.4.18 Replace reassemble, re-insulate, return all items to proper operating conditions and remove

grounds prior to energizing.


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4. EQUIPMENT TESTING

4.1 INTRODUCTION

4.1.1 Equipment testing is performed to assess the overall equipment condition and to determine

requirements for major maintenance.

4.1.2 Testing of equipment should be carried out by trained maintenance personnel and in

accordance with this procedure and specific manufacturers instructions.

4.1.3 All appropriate forms should be filled out and a file maintained on the equipment.

4.1.4 All personnel involved shall be briefed on all aspects of the work prior to the start of anytesting activity. Particular emphasis should be placed on personnel hazards and the safety

precautions associated with these hazards. Proper working clearances must be maintained at

all times.

4.1.5 In planning the work, refer to:- Manufacturers instruction books, technical drawings, etc.

- Training lessons

- Relevant IEEE Standards- Copy of any special GRENLEC orders or manufacturers technical bulletins

4.2 SAFETY OF PERSONNEL

Prior to performing any test of power apparatus, there should be a meeting of all people

who will be involved or affected by the test. The test procedure should be discussed sothere is a clear understanding of all aspects of the work to be performed. Consideration of

safety in electrical testing applies not only to personnel but also to the test equipment and

equipment under test. Particular emphasis should be placed on personnel hazards and the

safety precautions associated with these hazards.

4.3 SAFETY HAZARDS

Insulation tests in the field present a hazard to personnel unless suitable precautions aretaken.

Equipment to be tested shall be disconnected from the power system. A visual check ofthe disconnection should be carried out. When this is not possible, check with a voltageindicator.

Grounds are then applied. Personnel shall be instructed to treat all ungroundedapparatus as energized.

Ground Connection

Use of working grounds should comply with established company guidelines.

Warning Signs and Barriers

The test area may be marked off with signs and easily visible tape.


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4.4 TRANSFORMER TESTING






Ensure the transformer and its controls are disconnected from all power, both highvoltage and control voltage before it is inspected.




for isolation at the source end of the circuit.Be aware of near-by live parts before commencing work on the transformer.

Under no conditions shall tests be performed on a transformer under vacuum because

under these conditions the dielectric strength of the system is significantly reduced.

4.4.3 TEMPERATURE INDICATOR TEST

Test the alarm points, cooling operation and correct indication of the temperature indicators

by removing the temperature sensor bulb from the transformer and putting it in a oil heater

and slowly raise and lower the temperature.

4.4.4 MEGGER TEST

Perform a MEGGER test on the windings and core. Test HV to LV, HV and LV to ground

and the core to ground (if core is accessible). If a core ground resistor is installed check itsvalue. Record the results

4.4.5 WINDING RESISTANCE TEST

Objective - Check for abnormalities, due to loose connections, broken strandsand high contact resistance in tap changers.

Interpretation of results is usually based on a comparison of measurements made separately

on each phase in the case of a wye-connected winding or between pairs of terminals on adelta-connected winding. Comparison may also be made with original data measured in the

factory. Variations of up to 5 % for any of the above comparisons is satisfactory.

Resistance measurements are converted to values corresponding to the referencetemperature in the transformer test report by the following formula:

RS = RM * TS + TKTM +TK


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Where:

RS = Resistance at desired temperature Ts

RM = Measured resistance

TS = Desired reference temperature (C)

TM = Temperature at which resistance was measured (C)

TK = 234.5 C (copper))

= 225 C (Aluminum))

Note: The value of Tk may be as high as 230 for Alloyed Aluminum.

4.4.6 POWER FACTOR TEST

This test is carried out to determine deterioration of, contamination of, or physical damage

to the insulation

Test voltages for typical field test sets range from below 100v to as high as 12 kV.

Temperature correction should be made during the measurements.

Interpretation

Power Factor Insulation condition

Less than 0.5% Good

0.5%-1.0% Acceptable

Above 1.0% Questionable

One of the most useful methods of evaluating test results is by comparison to previous test

results on the same equipment.

4.4.7 TRANSFORMER TURNS RATIO TEST (TTR)

The turns ratios should be determined for all taps. The turns ratio tolerance should bewithin 0.5 % of the nameplate specifications for all windings. For three-phase Y connected

windings this tolerance applies to the phase-to-neutral voltage.

Out-of-tolerance ratio measurements may be symptomatic of shorted turns, especially if

there is an associated high excitation current.

Open turns in the excited winding will be indicated by low exciting current and no outputvoltage. Open turns in the output winding will be indicated by normal levels of exciting

current, but no or very low levels of unstable output voltage.

The turn ratio test may also detect high-resistance connection in the lead circuitry or high

contact resistance in tap changer by higher excitation current.


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4.5 OIL SAMPLE COLLECTION AND TEST

4.5.1 SAFETY PRECAUTION

The oil sampling of electrical equipment should be carried out by trained maintenance

personnel and in accordance with this procedure If the transformer is suspected to be

developing internal problems avoid area of transformer explosion vent discharge when

sampling the equipment.Personnel sensitive to Transformer Oil should wear latex gloves to avoid skin contact.

4.5.2 GATHER SAMPLES

Setup

Connect sample hose to bottom sampling valve.

Note: Special tests may call for top oil samples.

Flush

Flush oil through the valve, fittings and hose to clean and dry them and to ensure the

sample is representative of the oil in the equipment, not just in the valve and piping. Usinga clear jar check the oil being flushed for water and debris. When satisfied that samplingcan begin reduce oil flow and maintain the same rate throughout sample collection as

opening and closing the sample valve may release unwanted debris.

Fill Sample Jars and Syringes

Jars: rinse Jar 3 times, put PVC hose to bottom of Jar (to avoid aeration) and fill almost

completely with final sample. Label Jar and place in container to protect it from breakageand sunlight.

Syringes: hold Syringe vertical with its valve at top and rinse Syringe 3 times and

manipulate to expel air bubbles. Fill slightly above full mark with final sample. Tilt Syringe

and inspect for air bubbles. If any bubbles are detected repeat final fill and inspect again.Repeat if necessary until a bubble free sample is obtained. Note that if a bubble appears

later this is a result of the sample cooling and evolving gas: this bubble must not be

expelled. Record syringe serial number and store it in its protective container away fromsunlight.

Complete Sample Information

Fill in all information requested on the sample forms completely and accurately -equipment data, sampling point, oil temperature(s), ambient temperature, humidity, purpose

of sample, date, crew name(s), etc.

Local Dielectric Testing

Ensure that the Oil Tester is set up to perform tests according to the proper ANSI Standard.

Note - Compare results to previous test results to establish if there is a Trend


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4.6 CIRCUIT BREAKER TESTING


Isolate the equipment and carry out a visual check to ensure the equipment is isolated



Ensure the breaker and its controls are disconnected from all power, both high voltage

and control voltage before it is inspected.





Safety Note: Be aware of near-by live parts before commencing work.

4.6.3 MICRO-OHM TEST

Measure and record the micro-ohm readings of each phase with the breaker closed. Testleads should be placed between the power leads on the bushing terminals. Be sure that both

the power leads and test leads are making a good connection with the bushing terminal.

Sources of high micro-ohm readings could be poor connection of test leads, bushing caps,

bushing adapter & interrupter and contact block.

4.6.4 TIME/ TRAVEL TEST

Perform a circuit breaker timing test using an approved circuit breaker timer and compare

the results with the recommended values provided in the manufacturers instruction manual.

The results for the following tests should be recorded.

1. Opening time

2. Open spread (difference between poles)

3. Closing time

4. Close spread (difference between poles)5. Close/trip time

6. Slow operating speed could be an indication of weak opening or closing springs or

binding in the mechanism.7. Investigate any readings, which exceed the maximum values given by the manufacturer.

4.6.5 DC HI-POT TEST

The high pot test should be carried with the following values:

11kV Breakers -

33kV Breakers -

Circuit Breaker Open:

Connect high-voltage lead to pole 1 and ground all other poles. Repeat all other poles.

Circuit Breaker Closed:

Connect high-voltage lead to Pole 1 with either pole of phase 2 and 3 grounded.


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4.6.6 VACUUM BOTTLE TEST

With the circuit breaker open conduct test on each phase. For each phase connect high-

voltage lead to pole 1 with other pole grounded.

4.6.7 LOW DC VOLTAGE TEST

Perform low voltage close and trip test at 80% of the rated control voltage.

4.6.8 SPRING CHARGING SYSTEM CHECK

After normal close operation, measure and record the spring recharging time. Measure and

record the charging motor current.

4.6.9 FUNCTION TESTS

Perform the breaker function tests: seal-in, anti-slam and anti-pump.

5. MAJOR MAINTENANCE

5.1 INTRODUCTION

Major overhauls are an internal or more in depth analysis of the equipment to determine if

replacement or overhaul of parts is required and if required carry out the necessary partreplacement or refurbishment.

Equipment maintenance in the field presents a hazard to personnel unless suitableprecautions are taken.

Equipment to be maintained shall be disconnected from the power system. A visual check

of the disconnection should be carried out. When this is not possible, check with a voltage

indicator.

Grounds are then applied. Personnel shall be instructed to treat all ungroundedapparatus as energized.

5.2 MAJOR OVERHAUL ON 33KV VACUUM CIRCUIT BREAKERS


- Micro-ohm Tester

- Circuit Breaker Timing Tester

- Volt / Ohm Meter

- Clip on Ammeter- Minimum Voltage Tester

- Hi-Pot Tester

- Foam Spray



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The maintenance of vacuum circuit breakers should be carried out by trained maintenance

personnel and in accordance with this procedure and specific manufacturers instructions.


Where visual check is not possible carry out checks with an approved voltage indicator

to ensure the equipment is fully isolated. Ground the equipment

Ensure the circuit breaker and its mechanisms are disconnected from all power, both

high voltage and control voltage before it is overhauled.


The circuit breaker is composed of many mechanical devices, which may be underspring loading regardless of the operating position. Ensure all spring operating systemsare fully discharged before working on any mechanism.

Follow the manufacturers recommendation to protect against radiation hazard whilecarrying out HI POT tests.

5.2.3 CIRCUIT BREAKER MAINTENANCE

5.2.3.1 Check the breaker operation counter is operating. Record the counter readingbefore and after the overhaul.

5.2.3.2 Check the bushing condition. Look for broken, chipped or cracked bushings,flashover burns, copper splash, copper wash, correct cementing and fasteners.Clean the bushings if they are contaminated with dirt, dust or other pollutants.

5.2.3.3 Check operating mechanism/control cabinets, structures, covers, fittings etc. forany sign of rusting, corrosion or damage.

5.2.3.4 Check the general condition of the operating mechanism/control panel. Look forloose, broken, corroded wire/ terminals, loose contactor parts, burnt coils andcontacts. Check fuses, connections, contactors for signs of contact burning, andcontrol wire and coils for sign of deterioration in insulation.

5.2.3.5 Inspect the operating mechanism/control panel for any sign of corrosion, moisture,external contamination or damage. Check all cable entrances are properly sealedagainst rodents and check for signs of external contamination or aging. Check the

door fits properly.


5.2.3.7 Inspect auxiliary switch contact - check for loose connections and erosion, burningor chattering of contacts. Check also the auxiliary switch linkage alignment for wear& lubrication. Clean or adjust as required.



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5.2.3.9 Check the condition of the following items: Mechanism bearings, Rollers, Linkages,springs and shafts for defects, cracks and tightness of fittings.

5.2.3.10 Clean and lubricate the operating mechanism as per manufacturers instructions.Note the condition of the parts. Use only the recommended lubricant.

5.2.3.11 Check the operation of open/close position indicator/ linkage to ensure it isindicating correctly.

5.2.3.12 Check the charging spring indicator in both the charged and discharged position toensure it is indicating correctly.

5.2.3.13 Check the mechanism measurement specifications as per the manufacturersinstruction manual.

5.2.3.14 Check and record the measurements of the contact wear indicator as per the

manufacturer instruction manual.

5.3 125VDC LEAD ACID BATTERIES AND CHARGER


- Hydrometer

- Voltmeter Ammeter- Distilled Water

- Impedance Tester

- Cleaning Solution (baking soda)

- Durable Wipers- Face Shield

- Apron

- Gloves (chemical resistant)


Batteries contain sulfuric acid. Do not allow the battery fluid to contact eyes or skin. Ifcontact occurs, flush the affected area immediately with water. Batteries generate hydrogen

gas, which is flammable and explosive. To reduce the possibility of explosion, never expose

the battery to open flame or sparks. Do not smoke near the battery. Tools should beinsulated to avoid the chance of sparks. Batteries contain a large amount of stored energy

and may explode if inadvertently shorted during the overhaul.


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5.3.3 CHARGER INSPECTION

5.3.3.1 Calibrate the charger voltmeter for correct float and equalize voltages. The calibrationshould be done using an accurate portable voltmeter.

5.3.3.2 Calibrate the charger ammeter reading. The calibration should be done using an accurate

portable ammeter.

5.3.3.3 Remove dust and contamination from all the components and surfaces in and on thecharger.

5.3.3.4 Check the contacts on timing devices, relays, and switches for signs of burning, heating ordeterioration.

5.3.3.5 Check the calibration of the under-voltage and over-voltage alarms as per manufacturer

instructions.

5.3.4 BATTERY INSPECTION

5.3.4.1 Check to ensure that the battery room temperature is between 20 to 25 Deg. C.

5.3.4.2 Battery cells:

a) Check for signs of deterioration. Check plates for buckling, sulfating or plate growth.Check inter-plate spacers for signs of charring; check bottom of cell for excessive

sedimentation, or active material fallen from plates.

b) Check outside of the batteries for cracked cells or acid attack on inter-cell connections

c) Check for corrosion or discoloration on battery cell terminals on connections

d) Check for leaks. There should be no visible signs of electrolyte on the battery jars, thejar covers or in the trays

e) Clean the outside of the cells to remove any conductive salt deposits or dust deposits.Use a baking soda solution to neutralize the acid. Do not allow any cleaning solution to

enter the cells.

f) Replace defective cell as per instructions outlined in Section 4.3.5.

5.3.4.3 Measure and record the corrected relative density (specific gravity) of the electrolyte in the

pilot cell.

5.3.4.4 Measure and record the voltage of the pilot cell.

5.3.4.5 Measure and record the corrected relative density (specific gravity) of the electrolyte in allthe cells. Measure and record the voltage of all the cells. Choose the new pilot cell (lowest

reading). The pilot cell is one, which is used as a convenient means to indicate the condition

and state of charge of the whole battery. The pilot cell is generally the poorest cell,determined by the specific gravity reading and the cell with the lowest voltage.


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5.3.4.6 Shut off the battery charger and test the ability of the battery to supply typical peak load,

e.g., breaker closing current.

5.3.4.7 With the charger shut off for 90 minutes; test the capacity of the battery to supply a steady

load while maintaining the voltage. Record the results

5.3.4.8 Perform an Impedance test on all the battery cells. Compare with previous test results.Check the percent change of each cell and percent deviation from the average cell.

5.3.4.9 Check the electrolyte level. Add distilled water if required

5.3.4.10 Place batteries on equalize.

5.3.5 BATTERY CELL CHANGE OUT

5.3.5.1 Special Tools and Materials

- Standby battery of same voltage and enough capacity for short term use- Suitably sized temporary cables and connectors for battery connections

- Micro-ohmmeter, insulated tools, cleaning materials and suitable connection corrosioninhibitor for inter-cell/block connectors

5.3.5.2 Special Safety Hazards

The change out of defective batteries should be carried out by trained maintenancepersonnel and in accordance with this procedure and specific manufacturers instructions.

Batteries contain sulfuric acid. Do not allow the battery fluid to contact eyes or skin.

Personal protective equipment must be worn. If contact occurs, flush the affected area

immediately with water.Batteries generatehydrogen gas, which is flammableandexplosive. To reducethepossibilityof explosion, never exposethebattery toopen flameor sparks. Do not smokenear thebattery. Tools should beinsulated to avoid thechanceof sparks or shorts.Personnel should touch a grounded surfaceprior totouching thebattery todrain anystatic charge.

Batteries contain large amounts of stored energy and can cause high energy DC arcs and

cell explosion if shorts are created. Extreme care and thorough job planning must be

employed to avoid these hazards. Rubber gloves and flash goggles should be used whilemaking and breaking the parallel connections.

5.3.5.3 Battery Change-out Procedure

5.3.5.3.1 Ensure that the replacement battery is of the same voltage as the one to be replaced, is in asimilar state of charge and has adequate capacity to meet the minimal needs of the DC

Network during the time of the Works. Check that the battery area is well ventilated in

order to prevent build up of explosive gasses.


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5.3.5.3.2 If required, ground or insulate the replacement battery rack/carrier as required to match the

setup of the battery to be replaced. Check to ensure that the replacement batteries inter-

cell/block connections are secure.

5.3.5.3.3 Securely connect the negative of the replacement battery to the negative of the battery to be

replaced using adequately sized cable. Use two-hole terminal lugs at the load bus better

facilitates replacement battery connections without disturbing the normal connections.

5.3.5.3.4 Connect the positive side cable to the positive of the replacement battery. Check with a DCvoltmeter to ensure minimal voltage between the positive cable and the positive of the

battery to be replaced. A 100W light bulb in a pigtail lamp holder can be temporarily

connected across the two positives to allow the two batteries to equalize their charges andprevent any appreciable spark when the final connection is made-up.

5.3.5.3.5 When it is safe to do so, connect the positive cable to the positive of the battery to be

replaced. This now puts the two batteries in parallel. Disconnect the replaced battery at bothnegative and positive side so as to fully isolate it.

5.3.5.3.6 Proceed with repairs as required on the replaced battery. Note that inter-cell/blockconnections can be checked with a Micro-ohmmeter to determine resistance and any need

to dismantle for cleaning and re-greasing.

5.3.5.3.7 The above procedure may be used to replace a few cells if the work allows this but great

care must be exercised with polarities, number of cells replaced/paralleled, minimal voltage

difference and connection security before the parallel is completed. It is usually safer to

replace the whole battery.

5.3.5.3.8 When the work is completed, the original battery can be returned to service and the

temporary battery can be removed, using the same step-by-step procedure outlined above.

5.4 MAJOR OVERHAULS ON POWER TRANSFORMERS


- Volt / Ohm Meter

- Transformer Test Equipment

- Oil Sample Equipment- Processed transformer oil for top up

- Temperature Control Oil Heater- Thermometer- Foam Spray






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Ensure the transformer and its controls are disconnected from all power, both highvoltage and control voltage before it is inspected.



Some points in the control cabinet may be alive even with all the control switches open. If

work is required on a live circuit, then it may be necessary to arrange for isolation at thesource end of the circuit.

Safety Note: Be aware of near-by live parts before commencing work.

5.4.4 TRANSFORMER INSPECTION

5.4.4.1 Prior to isolating the transformer listen for any abnormal sounds that may indicate loosewindings, blocking or other mechanical problems.

5.4.4.2 Check the oil level in the main tank on transformers equipped with conservator tanks. Thegauge should show a normal level, adjusted for temperature.

5.4.4.3 For transformers equipped with a conservator tank drain the conservator tank to remove

condensation.

5.4.4.4 Check the pressure gauge reading on sealed (no conservator) type transformers. The gauge

should indicate a positive pressure.

5.4.4.5 Check the bushing / porcelain condition. Look for broken, chipped or cracked bushings/

porcelain, flashover burns, copper splash, copper wash, correct cementing and fasteners.

Clean the bushings if they are contaminated with dirt, dust or other pollutants.

5.4.4.6 Check the relief vent and/or the self-resetting pressure relief vent for signs of damage or oil

leakage. Check for signs of past relief vent diaphragm operation; cracked/brokendiaphragm, self resetting pressure relief vent indicator operated, visible evidence of oil

around relief area.

5.4.4.7 If the transformer is equipped with a silica gel breather check the colour of the silica gel.

Blue indicates dry and pink indicates wet. Check to ensure the breather vent is not pluggedwith debris or insects.

5.4.4.8 Check valves, gaskets, packing, and fittings for any sign of oil leakage or damage.

5.4.4.9 Check control cabinet, structures, covers, valves, fittings piping etc. for any sign of rusting,corrosion or damage.


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5.4.4.10 Check the general condition of the control cabinet. Look for loose, broken, corroded wire/

terminals, loose contactor parts, burnt coils and contacts. Check fuses, connections,

contactors, any sign of contact burning, any sign of deterioration in insulation of controlwire or coils.

5.4.4.11 Inspect the control cabinet for any sign of corrosion, moisture, external contamination or

damage. Check all cable entrances are properly sealed against rodents. Inspect weather/rodent seals for any sign of external contamination or aging. Check the door fits properly

and hardware keeps the door secure.


5.4.4.13 Check and record the maximum and existing oil temperature and winding temperature.

Check that the temperature gauge is functioning properly; upper drag hand limit is not

excessive, upper and lower drag hands indicate a reasonable temperature range and reset

properly. In addition record the maximum current.

5.4.4.14 Operate the fans. Check that all fans are operating properly and turning in the correct

direction. No audible indication of mounting/bearing trouble, fan guards are fixed in placeand there is no damage to blades. Wiring is in good condition.

5.4.4.15 Operate the pumps. Check that all pumps are operating properly with no audible indicationof trouble and that the flow indicators are working. Wiring is in good condition.

5.4.4.16 Check the radiators/coolers. Remove any bird nests, bird excrement, or other foreign debris

that will restrict the flow of air or cause corrosion or damage to the units.

5.4.4.17 Take an oil sample from the tank. Perform a dielectric test. Results of the Dielectric test

should be used to assess the transformer condition. Record and compare the results withprevious tests, GRENLEC specifications and the manufacturers specifications. An oil

sample should also be taken from the tap changer if it is not scheduled for maintenance

5.5 MAJOR OVERHAUL ON ON-LOAD TAP CHANGERS


- Volt / Ohm Meter

- Ratiometer- Winding Resistance Tester

- Oil Sample Equipment

- Dielectric Test Set

- Oil Filter/Handling Equipment- New Filtered Oil

- Oil Pails

- Durable Wipers/Cloths (Lint Free)- Filtered transformer oil

- Manufacturer Recommended Tools


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- Lifting Rig (Crane)

- Lifting Equipment (slings & rope-blocks)


5.5.2 SPECIAL SAFETY HAZARDSThe maintenance of under load tap changers should be carried out by trained maintenance


Some points in the control cabinet may be alive even with all the control switches open. Ifwork is required on a live circuit, then it may be necessary to have the Protection

Department arrange for isolation at the source end of the circuit.

The ULTC consists of mechanical components, which will be set in motion to observe theirperformance during the overhaul.

Safety Note: Make yourself aware of close-by live apparatus before starting to work on thetap changer.

5.5.3 TAP CHANGER OVERHAUL

Prior to opening the tap changer ensure all tools and foreign material from workers

pockets etc. are prevented from falling into the tap changer compartment.

5.5.3.1 Check the tap changer operation counter is operating. Record the counter reading beforeand after the overhaul.

5.5.3.2 Operate the tap changer manually one tap position in both directions (raise and lower).Check the operation of mechanism and linkages for any undue mechanical restriction,

binding, irregular operation, noises, etc.

5.5.3.3 Operate the tap changer by raising and lowering it one tap position. Check for irregular

operation, noises, etc. Check the winding resistance on each of these three positions.

Operate the ULTC through the neutral position, stop at the next tap and again check the

winding resistance. This process will check the diverter and reversing switches prior to theoverhaul.

NOTE: Refer to the manufacturer manual to ensure the tap changer is on the recommended

tap position before beginning the overhaul. Do not change the diverter switch position afterit has been disengaged from the drive linkage.

5.5.3.4 Ensure the oil handling equipment is clean, dry and there is a supply of approved insulatingoil. Connect the oil handling equipment and slowly remove the oil from the tap changer.

Open the bleeder valve in the tap changer cover.

5.5.3.5 After the oil is removed, open the cover as per manufacturer recommendation. Flush (using

the tube flush device) the insert with filtered oil, inserting the flushing nozzle down into the

openings in the top casting to flush down the arcing chamber. Disconnect and remove the

insert from the transformer following the manufacturer recommendations. Continue to flush


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as it is being lifted, paying particular attention to the center, interphase drive tube both

inside and out. When the flushing is complete, drain the remaining oil from the tap changer.

5.5.3.6 Remove any remaining carbon from the insert and the housing using clean durable lint free

wipers.

5.5.3.7 Check the support cylinder and internal insulating components. Inspect all insulation forsigns of deterioration including tracking, overheating and cracking.

5.5.3.8 Check the mechanical condition of the shafts, gearboxes and pivot points for signs of wear

or misalignment.

5.5.3.9 Measure the contact thickness of the moving and stationery contacts as per the

manufacturer recommendations. Compare the readings with the recommended

measurements.

5.5.3.10 Inspect the flexible shunts, contacts and joints for signs of fraying, heating or deterioration.

5.5.3.11 Measure the diverter resistors resistance values as per the manufacturer recommendation.Compare the results with the recommended values.

5.5.3.12 Re-install the tap changer insert into the transformer following the manufacturerinstructions.

5.5.3.13 Fill the tap changer compartment with new filtered oil and perform recommended bleeding

procedures.

5.5.3.14 Operate the tap changer manually one tap position in both directions (raise and lower).

Check the operation of mechanism and linkages for any undue mechanical restriction,binding, irregular operation, noises, etc.

5.5.3.15 Perform any other checks recommended by the manufacturer to ensure the tap changer hasbeen assembled and installed correctly.

5.5.3.16 Check the gear lubricant levels and refill if necessary, using manufacturers recommendedlubricant.

5.5.3.17 Check the mechanism / linkages for correct operation. Lubricate drive gears according to

manufacturer recommendations

5.5.3.18 Check that the tap position indicator/linkage operates correctly.

5.5.3.19 Check the mechanical and electrical limits by operating the tap changer through its

complete range of taps and attempt to overdrive (mechanically and electrically) at both ends

of the tap range.

NOTE: The limits must be checked manually first.

5.5.3.20 Test the RS 1000/2000 Bucholtz protective device.


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5.5.3.21 Take an oil sample from the tap changer after it has been refilled. Perform a dielectric test

to ensure the installed oil is of acceptable quality. Compare the results with the

manufacturers and GRENLECs recommended specifications.

5.5.3.22 Perform a ratio test on 5 tap positions - top, bottom, neutral, and both sides of neutral

positions. Record the results.

5.6 MAJOR OVERHAULS ON DISCONNECTS & ASSOCIATED EQUIPMENT


- Micro-ohm Tester

- Volt / Ohm Meter

- Clip on Ammeter- Recommended lubricants

5.6.2 SPECIAL SAFETY HAZARDSSome points in the control cabinet of motor operated disconnect may be live even with all

control switches open. If work is required on a live circuit, it may be necessary to arrangefor isolation at the source end of the circuit.

5.6.3 DISCONNECT SWITCH INSPECTION

5.6.3.1 Manually operate the switch and check: contact alignment, toggles, stops, linkage, undueinsulator movement and general ease of operation

5.6.3.2 Check porcelain for chips or cracks, flashover burns, copper splash, copper wash, correct

cementing and fasteners. Clean the porcelains if they are contaminated.

5.6.3.3 Check contact pressure. Check jaw for correct compression. Observe jaw spread as blade

closes into jaw.

5.6.3.4 Check contacts for burning, erosion or deterioration.

5.6.3.5 Check the wiping contacts for burning, erosion or deterioration.

5.6.3.6 Clean and lubricate the contacts with recommended lubricants.

5.6.3.7 Clean and lubricate the linkages with recommended lubricants.

5.6.3.8 Remove gearbox covers and inspect the gears, linkages, bearings, shafts and pins. Lubricate

if necessary with approved lubricant.

5.6.3.9 Check that all the connections to the switch are tight with no signs of burning, damage, ordiscoloration indicating heating.

5.6.3.10 Check that there is no undue stress on the insulator stacks

5.6.3.11 Check the switch grounding connections are tight and undamaged.

5.6.3.12 Clean and paint corroded spots on linkages, mechanism or gearbox.

5.6.3.13 Operate the switch manually and electrically where so equipped.


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5.6.3.14 Perform a micro-ohm test on switches that are in highly contaminated or corrosive

environments. The readings on all three phases should be comparable.

Measure and record the micro-ohm readings of each phase with the switch closed. Testleads should be placed between the power leads on the connection terminals. Be sure that

both the power leads and test leads are making a good connection with the connection

terminal.

5.6.4 MOTOR MECHANISM INSPECTION

5.6.4.1 Check the general condition of the operating mechanism. Look for loose, broken, corroded

wire/ terminals, loose contactor parts, burnt coils and contacts. Check fuses, connections,

contactors (for signs of contact burning), insulation of control wire or (coils for signs ofdeterioration).

5.6.4.2 Inspect the operating mechanism box for signs of corrosion, moisture, or damage. Check

cable entrances are properly sealed. Inspect seals for signs of contamination or aging.

Check the door fits properly and the door secure.

5.6.4.3 Check the operation of anti-condensation heaters.5.6.4.4 Inspect the contacts of the auxiliary switches. Check for loose connections and erosion,

burning or chattering of contacts. Check also the auxiliary switch linkage alignment for


5.6.4.5 Clean and lubricate the operating mechanism as per manufacturers instruction. Oil the

bearings in the operating mechanism. Use recommended lubricant.

5.6.4.6 Inspect motor commutator and brushes for wear.

5.6.4.7 Check interlock switches and locking devices for proper operation.

5.6.4.8 Measure and record motor current during open and close operation.

5.6.5 STATION BUS INSPECTION

5.6.5.1 Check the porcelain condition. Look for broken, chipped or cracked porcelain, flashoverburns, copper splash, copper wash, correct cementing and fasteners. Clean the porcelains if

they are contaminated with dirt, dust or other pollutants.

5.6.5.2 Check that all the connections to the bus are tight with no signs of burning, damage, or

discoloration indicating heating. Ensure all locking washers are secure and not damaged.Check welded connections for cracks.

5.6.5.3 Check expansion connections for fraying, binding or damage to shunts.

5.6.5.4 Check that there is no undue stress on insulator stacks.

5.6.6 SURGE ARRESTORS (LIGHTNING ARRESTORS)

5.6.6.1 Check the porcelain for chips or cracks, flashover burns, copper splash, copper wash,

correct cementing and fasteners. Clean porcelains if contaminated.

5.6.6.2 Check that all the line and ground connections to the arrestor are tight with no signs of

burning, damage, or discoloration.


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5.7 MAJOR OVERHAULS ON INSTRUMENT TRANSFRMERS


- Oil Sample Equipment

- Dielectric Test Set

- Durable Wipers/Cloths


The maintenance of Instrument Transformers should be carried out by trained maintenancepersonnel and in accordance with this procedure and specific manufacturers instructions.

Some points in the junction/connection box may be live even with all the control switchesopen. If work is required on a live circuit arrange for isolation at the source end of the

circuit.

Safety Note: Make yourself aware of close-by live apparatus before starting to workon the instrument transformers.

5.7.3 INSTRUMENT TRANSFORMERS INSPECTION

5.7.3.1 Check the bushing / porcelain condition. Look for broken, chipped or cracked bushings/porcelain, flashover burns, copper splash, copper wash, correct cementing and fasteners.

Clean the bushings if they are contaminated.

5.7.3.2 Check valves, gaskets, packing, and fittings for any sign of oil leakage.

5.7.3.3 Check the oil level of the tank, adjusted to the temperature.

5.7.3.4 Check main tank, fittings, etc. for any sign of rusting, corrosion or damage.

5.7.3.5 Check the general condition of the junction/connection box. Look for loose, broken,corroded wire/ terminals. Check fuses and connections for any sign of burning and

insulation of control wire for signs deterioration.

5.7.3.6 Inspect the junction/connection box for any sign of corrosion, moisture, external

contamination or damage. Check all cable entrances are properly sealed against rodents.

Inspect weather/ rodent seals for any sign of external contamination or aging. Check thecover fits properly and hardware keeps the cover secure.


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5.8 MAJOR OVERHAUL ON 33KV SWITCHGEAR


- Micro-ohm Tester


- Volt / Ohm Meter

- Clip on Ammeter

- Minimum Voltage Tester

- Hi-Pot Tester

- Foam Spray



The maintenance of vacuum circuit breakers should be carried out by trained maintenance





Ensure the circuit breaker and its mechanisms are disconnected from all power, bothhigh voltage and control voltage before it is overhauled.



are fully discharged before working on any mechanism. Follow the manufacturers recommendation to protect against radiation hazard while

carrying out HI POT tests.

5.8.3 33KV SWITCHGEAR MAINTENANCE

5.8.3.1 Record the counter reading before and after the overhaul.

5.8.3.2 Check the bushing condition. Clean the bushings if they are contaminated with dirt, dust or

other pollutants.

5.8.3.3 Inspect auxiliary switch contact - tighten loose connections. Check the auxiliary switch

linkage alignment for wear & lubrication. Clean, lubricate or adjust as required.

5.8.3.4 Clean and lubricate the operating mechanism as per manufacturers instructions. Note the

condition of the parts. Use only the recommended lubricant.

5.8.3.5 Check the operation of open/close position indicator/ linkage to ensure it is indicating

correctly.


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5.8.3.6 Check the charging spring indicator in both the charged and discharged position to ensure it

is indicating correctly.

5.8.3.7 Check the mechanism measurement specifications as per the manufacturers instruction

manual.

5.8.3.8 Check and record the measurements of the contact wear indicator as per the manufacturer

instruction manual.

5.9 MAJOR OVERHAUL ON 11KV SWITCHGEAR


- Micro-ohm Tester


- Volt / Ohm Meter

- Clip on Ammeter

- Minimum Voltage Tester

- Hi-Pot Tester

- Foam Spray



The maintenance of vacuum circuit breakers should be carried out by trained maintenancepersonnel and in accordance with this procedure and specific manufacturers instructions.




Ensure the circuit breaker and its mechanisms are disconnected from all power, bothhigh voltage and control voltage before it is overhauled.



are fully discharged before working on any mechanism. Follow the manufacturers recommendation to protect against radiation hazard while

carrying out HI POT tests.


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5.9.3 11KV SWITCHGEAR MAINTENANCE

5.9.3.1 Record the counter reading before and after the overhaul.

5.9.3.2 Check the bushing condition. Clean the bushings if they are contaminated with dirt, dust or

other pollutants.

5.9.3.3 Inspect auxiliary switch contact - tighten loose connections. Check the auxiliary switch

linkage alignment for wear & lubrication. Clean, lubricate or adjust as required.

5.9.3.4 Clean and lubricate the operating mechanism as per manufacturers instructions. Note the

condition of the parts. Use only the recommended lubricant.

5.9.3.5 Check the operation of open/close position indicator/ linkage to ensure it is indicating

correctly.

5.9.3.6 Check the charging spring indicator in both the charged and discharged position to ensure it

is indicating correctly.

5.9.3.7 Check the mechanism measurement specifications as per the manufacturers instruction

manual.

5.9.3.8 Check and record the measurements of the contact wear indicator as per the manufacturer

instruction manual.

5.10 STATION GROUND MAINTENANCE

This procedure should be used with the attached inspection report form plus copies of the

Station Ground Network Drawing. Complete the report form and mark drawings to reflect

the connections, test points used, the test results.


- Ground/Earth Resistance Tester

- Micro-ohmmeter- Bonding Jumpers and Portable Grounds


The maintenance inspection of Station Ground Networks should be carried out by trained

maintenance personnel and in accordance with this procedure.

A system fault may occur during a test. The use of Rubber Gloves is recommended. Proper

work clearances must be maintained at all times.

Jumper ground connections requiring repairs to prevent electrocution if system conditionscreate a current flow while the connection is insecure.

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substation maintenance procedures r1

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