DABS Commercialization Part-2 for Generation ...aeic.af/assets/presentation_files/51bc5079d4f93c01... · DABS Commercialization Part-2 for Generation & Transmission Standard Operating

DABS Commercialization Part-2 for

Generation & Transmission

Standard Operating Procedures (SOPs) for Grid Substation

PREPARED FOR:

DA AFGHANISTAN BRESHNA SHERKAT (DABS)

PREPARED BY:

PHOENIX IT SOLUTION PVT LTD. July 15, 2015

Standard Operating Procedures for Grid Substations

Page No. 2

TABLE OF CONTENTS

1.0 STANDARD OPERATING PROCEDURE FOR GRID SUBSTATION ..................................... 6

1.1 INTRODUCTION ..................................................................................................................... 6

1.2 PRESENT MAINTENANCE PRACTICE .................................................................................. 7

1.3 PROPOSED IMPROVEMENT MAINTENANCE PRACTICE: .................................................. 8

1.4 JOB PLANNING: ..................................................................................................................... 8

1.5 SOP FOR GRID SUBSTATION: .............................................................................................. 9

1.6 SOP FOR POWER TRANSFORMER: ..................................................................................... 9

1.7 KEY MAINTENANCE POINTS FOR POWER TRANSFORMERS......................................... 13

1.8 TROUBLE SHOOTING: ........................................................................................................ 13

1.9 RELATED RELAY FUNCTIONS: .......................................................................................... 14

1.10 TESTING OF TRANSFORMER: .......................................................................................... 15

2.0 SOP FOR HV /MV ISOLATORS & EARTH SWITCHES: ...................................................... 20

2.1 KEY POINTS ON MAINTENANCE: ....................................................................................... 20

2.2 TESTING OF ISOLATORS & EARTH SWITCHES: .............................................................. 20

3.0 SOP FOR CIRCUIT BREAKERS: ......................................................................................... 22

3.1 KEY POINTS ON MAINTENANCE OF CIRCUIT BREAKERS: ............................................. 23

3.2 TROUBLE SHOOTING ON CIRCUIT BREAKERS: .............................................................. 24

3.3 TESTING OF CIRCUIT BREAKERS ..................................................................................... 25

A) RATED OPERATING SEQUENCE (DUTY CYCLE) ............................................................... 25

B) TOTAL BREAK TIME FOR HIGHEST SYSTEM VOLTAGE .................................................. 25

4.0 SOP ON LIGHTENING ARRESTORS ................................................................................... 26

4.1 KEY POINTS ON MAINTENANCE & TROUBLE SHOOTING: ............................................. 26

4.2 TESTING OF SURGE ARRESTORS: ................................................................................... 26

5.0 SOP ON INSULATORS ......................................................................................................... 28

6.0 SOP FOR VOLT-VAR CONTROL (VVC): ............................................................................. 29

6.1 OPERATIONAL ASPECTS OF OLTC: ................................................................................. 29

6.2 VAR DISPATCH .................................................................................................................... 29

6.3 VOLTAGE CONTROL ........................................................................................................... 31

6.4 MAINTENANCE POINTS: ..................................................................................................... 32

6.5 TROUBLE SHOOTING-OLTC ............................................................................................... 32

6.6 KEY POINTS ON MAINTENANCE OF CAPACITOR BANKS .............................................. 33

6.7 TROUBLE SHOOTING ON CAPACITOR BANKS ................................................................ 33


Page No. 3

7.0 SOP FOR INSTRUMENT TRANSFORMERS ........................................................................ 34

7.1 MAINTENANCE ASPECTS: .................................................................................................. 34

7.2 CAPACITOR VOLTAGE TRANSFORMERS (CVTS) ............................................................ 35

7.3 TESTING OF CURRENT TRANSFORMERS ........................................................................ 36

7.4 TESTING OF POTENTIAL TRANSFORMERS & CVTS ........................................................ 36

8.0SOP FOR PROTECTION SYSTEM ........................................................................................ 38

8.1 KEY POINTS ON MAINTENANCE ........................................................................................ 39

8.2 TROUBLE SHOOTING FOR NUMERICAL RELAYS (IED) ................................................... 40

8.3 TESTING OF RELAYS .......................................................................................................... 40

9.0 SOP FOR SCADA SYSTEMS ............................................................................................... 42

9.1 KEY MAINTENANCE POINTS AND CHECK LISTS OF STATION AUXILIARIES ............... 44

10.0 FIRE FIGHTING EXTINGUISHERS: .................................................................................... 47

11.0 SOP ON DAILY CHECKS FOR SUBSTATION OPERATORS: .......................................... 49

11.1 SYSTEM HEALTH MONITORING: ...................................................................................... 49

11.2. RECORDING & REPORTING: ........................................................................................... 50

11.3 EFFECTIVE LOAD MANAGEMENT & RELIABILITY IMPROVEMENTS: .......................... 51

12.0 ANNEXURE -1 ..................................................................................................................... 52

13.0 ANNEXURE -2 ..................................................................................................................... 54

13.1 OPERATIONAL SAFETY .................................................................................................... 54

13.1.1 OPERATIONAL SAFETY IN SWITCHING FUNCTIONS: ................................................. 55

13.1.2 DISCONNECTION PROCEDURE: ................................................................................... 55

13.1.3 RECONNECTION PROCEDURE: .................................................................................... 55

13.1.4 RE-ARRANGEMENT OF SYSTEM: .............................................................................. 56

13.1.5 LOAD TRANSFER: ........................................................................................................ 56

13.1.6 ISOLATION OF EQUIPMENT: ......................................................................................... 56

13.1.7 TESTING TO PROVE DE-ENERGIZED: .......................................................................... 57

13.1.8 EARTHING OF EQUIPMENT TO BE WORKED ON: ....................................................... 57

13.1.9 SETTING OUT THE WORK AREA: ................................................................................. 57

13.2 THE PERMIT TO TEST PROCESS (PTT) ........................................................................... 57

13.3 PERMIT TO WORK PROCESS (PTW) ................................................................................ 58

13.3.1 PROCESS OF ISSUING THE PTW .................................................................................. 59

13.3.2 BRIEFING PROCESS ...................................................................................................... 60

13.3.3 TRANSFERRING OF PERMIT TO WORK: ...................................................................... 60

13.3.4 CANCELLATION OF PERMIT TO WORK: ...................................................................... 61

13.4 RESTORATION & RE CONNECTION PROCESS .............................................................. 61

13.4.1 RECONNECTION OF EQUIPMENT ................................................................................. 62


Page No. 4

14.0 ANNEXURE -3 ..................................................................................................................... 63

15.0 ANNEXURE--4 .................................................................................................................. 109

16.0 ANNEXURE -5 ................................................................................................................... 117

17.0 ANNEXURE –6 ................................................................................................................. 134

ACCEPTED STANDARDS AND PERMISSIBLE LIMITS .......................................................... 134


Page No. 5

Acronyms & Abbreviations

People working in Sub-Station environments and performing Sub-Station switching

often abbreviate technical terminology or use acronyms and abbreviations as follows:

Acronyms

Abbreviations

ACB Air Circuit Breaker

AM Asset Management system

ARC Auto Re-Closer

CMMS Computerized Maintenance Management System

CT Current Transformer

CVT Capacitive Voltage transformer

DT Distribution Transformer

DT Danger Tag

ESW Earth Switch

GCB Gas Circuit Breaker

HV High Voltage

LA Lightning Arrestor

LV Low Voltage

N/C Normally Close

N/O Normally Open

O/H Over Head

OCB Oil Circuit Breaker

OLTC On Load Tap changer

PTR Power Transformer

SCADA Supervisory control and data Acquisition

UG Under Ground

VT Voltage Transformer


Page No. 6

STANDARD OPERATING PROCEDURE FOR GRID

SUBSTATION

1.1 INTRODUCTION

Systematic Operation and Maintenance of the system has become most important for

ensuring least possible down time, extension of the service life of the lines &

equipment, reduction of life cycle costs, safety, reduction of interruptions and the

ultimate customer delight.

Substations in the DABS T&D Network mainly consist of Power Transformers,

Switching & Control Gears, Protection Equipment, Telemetry & HV&MV SCADA

systems and Auxiliaries etc. Adopting well-defined Standard Operating Procedures

(SOPs) in the Switching Operations and the detailed checklists play an important role

in safe and un-interrupted operations, both in the standalone and interconnected Grid

System of the DABS. These SOPs shall be displayed in each Substation. Equipment

wise SOPs are broadly structured as follows:

Operational Aspects.

Key points of maintenance.

Emergency maintenance & trouble shooting.

Testing aspects of all equipment.

Detailed equipment wise check lists.

An exclusive SOP for Substation Operators.

Standard Formats on testing of equipment.

A view of 110 KV switchyard of 110/15 KV G/S –Kabul East

Summary of the main equipment of the HV/MV Substation and the network details

updated on yearly basis shall be recorded in the History register in all substations in

the format given in Annexure-1.

In addition, the Grid Map & Single Line Diagram depicting the Incoming source lines,

all the major equipment in the Substation and the Outgoing MV feeders shall be

displayed in all Substations. Following Transmission and Distribution Zones exist in


Page No. 7

DABS which are responsible for the maintenance and upkeep of T&D system in their

respective jurisdictions:

Sl. No. Transmission Zones Distribution Zones

1 Kabul Kabul

2 Mazar-e Sharif (Balkh) Balkh

3 Herat Herat

4 Jalalabad (Nangarhar) Nangarahar

5 Kandahar Kandahar

6 Kunduz Kunduz

7 Baghlan Paktia

8 Parwan Parwan

9 Ghazni

1.2 PRESENT MAINTENANCE PRACTICE

NLCC at Tarakhil

Office of Dy. C.O.O.

HV Maintenance

Dept.

Mechanical

Maint. (MV&LV)

Relay & Communication

Dept. (HV&LV)

Site visit

Substation Mgr.

(Work Order)

Break Down Maintenance

Requests

Preventive

Maintenance Plan

Material receipt Material indent to

purchase Dept.

Work execution

Work order

closure


Page No. 8

Through interactions with maintenance officers of DABS, it is inferred that, as of now

except for minor maintenance calls, provincial Executive officers predominantly

depend on the visit of officers / staff from DABS headquarters for most of the

maintenance activities. They depend on HV maintenance Dept., Mechanical Dept. of

MV & LV lines, Relay & Communication Dept., transformer Testing and repairs etc.

based on the nature of fault or trouble they report to the Dy. C.O.O. office which then

decides on the deputation of the concerned officers to the sites.

As per the feedback report on a field visit, it is learnt that the Sub Station Manager

gets approval for materials indented or manpower requested as needed and then take

up the maintenance /fault rectification work .This process involves considerable

delays and takes few days or a week at times. Hence the following to- be process with

some decentralization is proposed for effective maintenance management and quick

restoration:

1.3 PROPOSED IMPROVEMENT MAINTENANCE PRACTICES A decentralized approach in work management system, wherein the Maintenance

Crews are equipped with the Standard Operating Procedure and system Checklists

and certain delegation of powers for arranging local procurements of minor materials,

as required in emergencies, is recommended. Following measures are proposed in

this regard:

Rationalize the material requirements for each of the key activities under preventive maintenance.

Analyze the historical consumption trends with respect to usual Utility norms and field conditions and arrive at the annual requirements at a reasonable scale.

Analyze the existing Transmission & Distribution Network of DABS and recommend the area-wise System Improvements possible with indicative benefits.

Addressing customer complaints having bearing on maintenance and or calling for preventive steps shall also be addressed through CRM-CMMS integration.

CMMS generated Forms for each checks and MIS Reports on outage times, reliability indices and maintenance costs etc.

1.4 JOB PLANNING Following steps and guidelines should be considered for planning routine

maintenance jobs. The emergency maintenance jobs (such as trouble shooting,

repairing, etc.) are non-scheduled, however, the procedure/steps followed in planning

a scheduled work and the experience gained thereof is equally applicable in handling

emergencies. Special attention should be given to the safety requirements.

Follow the approved work program.


Page No. 9

Arrange maintenance procedures.

Arrange equipment manual and drawings.

Arrange previous maintenance records.

Arrange required spare parts.

Arrange T & P and test equipment needed.

Estimate and arrange to meet the expenditure involved.

Estimate the number of manhours and the length of .time required to complete the job.

Arrange to get co-ordination of the other work groups ( such as Grid maintenance, P&I, T/L, etc.) if needed.

Arrange shut down of the equipment to be worked on, if needed (refer procedure for PTW).

Inspect job site to look for :

o Hazards.

o What equipment are to be de-energized to get safe working clearances?

o Isolation points & grounding facilities.

o What types of aerial devices (i.e. scaffold, bucket truck, ladders, cranes, etc.

required?

o Is there enough room/space for aerial devices and the ground condition to

permit them to be fix/move.

o Condition of approach roads.

o Other information of job site which are necessary for execution of the job.

o Conduct a tailboard conference or meeting with the crew members so that

each member of the crew may know and understand his job and

responsibility.

The List of Acceptable Standards and permissible Limits on testing of the equipment is attached at Annexure – 6.

1.5 SOPS FOR GRID SUBSTATION The standard operating procedure for Grid substation consist the subset of SOPs of

the main Equipment, Auxiliary equipment and the supporting systems as follows:

1.6 SOP FOR POWER TRANSFORMER Electrical Power Transformer is a static device which transforms electrical energy from

one circuit to another without any direct electrical connection and with the help of

mutual induction between two windings. DABS network has 220/110 KV/ 35- 20-15-

10-6 KV power transformers.

http://www.electrical4u.com/electrical-power-transformer-definition-and-types-of-transformer/

http://www.electrical4u.com/what-is-inductor-and-inductance-theory-of-inductor/#Mutual-Inductance


Page No. 10

Power transformer is designed for maximum efficiency at 100% load. As per the load

demand, Transformers are run in parallel.

Before paralleling two or more transformers, the four principal characteristics of those

transformers should match as given below:

a) Same voltage ratios. b) Same % impedances & X/R ratios. c) Same Polarity. d) Same Vector Group.

Typically, transformers should not be operated in parallel when the following

conditions exist:

When the division of load is such that, with the total load current is equal to the combined kVA rating of the transformers, one of the transformers is overloaded.

When the no-load circulating currents in any transformer exceed 10% of the full load rating.

When the combination of the circulating currents and full load current exceeds the full load rating of either transformer.

If two transformers of same output are operating in parallel, the % impedance must

be identical, if Transformers are to share equally.

If % impedance is not identical, suppose T/F 'A' is having 4% impedance and T/F 'B'

is having 2% impedance, then load sharing will be,

Load A = L x (Z1 / Z1+Z2) where L is total combined output.

Load B = L x (Z2 / Z1+Z2) and Z is percentage impedance.

In the above situation, the Transformer A will share only 1/3rd load & B transformer

will share 2/3rd load. Hence, while operating transformers in parallel, the output of

the smallest transformer should not be less than 1/3rd of the output of largest one.


Page No. 11

The different Vector Groups of the Power Transformers with respective Phase

displacements are as follows:

Vector Group Phase displacement of secondary w.r.t. Primary

Group I----with clock hours 0,4, 8 Group I - (0 o'clock, 0¦) - delta/delta, star/star

Group II----with clock hours 6,10, 2

Group II - (6 o'clock, 180¦) - delta/delta, star/star

Group III----with clock hours 1,5 Group III - (1 o'clock, -30¦) - star/delta, delta/star

Group IV----with clock hours 7,11

Group IV - (11 o'clock, +30¦) - star/delta, delta/star

(Minus indicates LV lagging HV and plus indicates LV leading HV)

Vector Group Dyn5 is represented as follows.

Usually group 1 and 2 are interoperable but group 3 and 4 also can be made inter operable for parallel operation through certain reconfiguration of connections.

Vector groups 1 and 2 can only be paralleled with transformers of their own group. However, the transformers of groups 3 and 4 can be paralleled by reversing the phase sequence of one of them. For example, a transformer with Yd1 1 connection (group 4) can be paralleled with that having Dy1 connection (group 3) by reversing the phase sequence of both primary and secondary terminals of the Dy1 transformer.

The predominant vector group in DABS Power transformers is observed as three winding transformer of vector group Ynyn0+d11 i.e. having a delta connected tertiary winding.

When a power transformer or auto transformer is “Y” connected, both on high voltage and low voltage, triple frequency component (3rd harmonic) of the magnetizing current is suppressed and a corresponding voltage is induced in both windings.


Page No. 12

This voltage is usually negligible in three-phase core-type transformers, but in single-phase units it can be dangerous. To allow triple frequency current to flow and thus eliminate this over-voltage, a third or tertiary winding is usually provided. This winding must be connected in delta, whether or not it is to be used as a source of power.

Operational Safety Aspects: Guide lines on Operational Safety including Permit to

Work (PTW) and Permit to Test (PTT) given in Annexure – 2 should be followed.

Sl. No.

Working Condition

Action for Safety

1 Exterior check Be careful not to approach live parts.

2 Electrical test and remedial work

(1) De-energize the transformer by circuit breakers and line switches. (2) Ground the line terminals of the transformer. (3) Attach caution tags not to operate switches for circuit breakers and line switches. (4) De-energize the control cabinets for coolers and tap changer by AC and DC switches. (5) Attach caution tags on switch boxes.

3 When internal inspection is to be made

Same as above except the following additional items: (1) Replace nitrogen gas completely with dry fresh air, if it was filled in the transformer. (2) Make sure there is 18% or more oxygen to sustain life in a transformer tank. (3) Make sure your pockets are empty. (4) Take off wrist watch and any other accessories on your body. (5) List up name and quantity of all tools to be brought into a transformer tank. (6) Spread out clean cloth on coil groups when repairing. (7) Protect lamps with guards not to break them in a tank. (8) Be careful not to drop any tool and foreign material into the transformer. Secure all tools with hand lines. Any metallic item dropped into a transformer must be removed to prevent serious trouble in future.

4 After inspection work

1) Make sure all foreign materials are clear before closing manhole and energizing. (2) Check the quantity of all tools brought out from a tank. (3) Remove the grounding wires on the line terminals of the transformer.


Page No. 13

1.7 KEY MAINTENANCE POINTS FOR POWER TRANSFORMERS As per IEC standard, maintenance is the combination of all technical and administrative actions including supervision, intended to retain an item in, or restore it to a state in which it can perform healthy operation. The regular and periodic checks shall include the following:

Monitoring the Load current in Amps.

Transformer Oil and winding Temperatures.

Maintaining the proper Voltage profile by suitable Tap position on OLTC.

Check for Oil Levels and attend to Oil Leakages, if any.

Ensuring healthy operation of Relays.

Check for any un-usual noise and vibration etc.

1.8 TROUBLE SHOOTING The most common causes of Failures in Power Transformers are as follows:

Lighting Surges.

Line Surges/External Short Circuit.

Poor Workmanship-Manufacturer.

Moisture & Deterioration of Insulation.

Overloading.

Inadequate maintenance.

Loose connections.

Poor Earthing System.

Relay Related functions are as follows:

It is recommended to adhere to any other points in addition to those specified in the user manual of the equipment(s). Following are the generic trouble shooting tips:

Sl. No.

Relay Function Cause and action

1 Dial type thermometer

The dial type thermometer indicates the maximum oil temperature at the top and gives alarm when oil temperature gets to the alarm setting (80°C for example).

Overloading

Insufficient efficiency of cooler units due to dust and other foreign materials accumulated on the finned area or due to a heavy scale in the water-cooling coils.

Mal operation of thermometer or thermal relay due to their own defects.

If indication of thermometer is not correct, check oil level in the sensor pocket and adjust to correct oil level.

2 Thermal relay for oil temperature or winding temperature

The thermal relay detects and indicates maximum Temperature of oil or winding temperature of a transformer. It also has protective functions to


Page No. 14

give an alarm or tripping signal.

3 Oil flow indicator

The magnetic oil flow indicator, indicates the operating condition of an oil pump. When an oil pump stops, the pointer returns to the stop position and the micro-switch contact closes to give an alarm

Trouble in oil pump motor.

Trouble in wiring connection to oil pump motor.

Radiator valves are shut off.

Inverse of power phase.

Sequence.

4 Oil level gauge-dial type

The dial type oil level gauge indicates the oil level in a conservator of an oil-immersed Transformer. When the oil level comes down to the bottom of a conservator, its pointer indicates zero and gives an alarm.

Shortage of oil.

Abnormally low ambient temperature in winter season.

Oil leakage.

Damage of rubber bag or diaphragm in conservator.

If oil level of OLTC is abnormal, breaking of seal between the OLTC and transformer is suspected.

1.9 RELATED RELAY FUNCTIONS If any protective relay pertaining to Power Transformer operates, investigate the cause of the trouble in accordance with the following, which includes dissolved gas analysis for detailed diagnosis:

Sl. No.

Relay Function and Investigation

1 Buchholz relay First stage

The first stage of a Buchholz relay detects the gas formation due to minor troubles in transformer tank. Rubber bag or diaphragm type conservator; Stop operation of the transformer immediately, and carry out gas analysis of accumulated gas and dissolved gas in oil and internal inspection of the transformer because a local heating and/or arc discharge is suspected. Breather type and/or nitrogen gas sealed type conservator; Check if abnormal gas exists or not, by gas analysis of the transformer gas and dissolved gas in oil. As the result, if abnormal gas detected, stop operation of the transformer and carry out internal inspection. The type and location of trouble may be predicted by gas analyses of oil. Note: Nitrogen gas dissolved in oil could supersaturate and accumulate in the relay and actuate the relay when oil-


Page No. 15

temperature drops rapidly on a cold day in case of a gas-sealed transformer.

Second stage The second stage of a Buchholz relay detects rushing oil due to a serious trouble in the transformer tank. If other protective relays, such as over-current relay of differential relay operate at the same time, a serious internal damage is suspected.

2 Sudden oil pressure relay

The sudden oil pressure relay detects the high rate of oil pressure increase in a transformer tank due to the gas generation and oil vapour caused by serious troubles. In case of correct operation, the transformer operation should be stopped.

3 Sudden pressure relay

[In case of nitrogen sealed conservator] The sudden pressure relay detects the high rate of nitrogen pressure increase in a tank due to gas generation and oil vapour caused by serious troubles in the transformer tank.

4 Pressure relief device

The pressure relief device operates when the pressure in the relief vent rises abnormally high enough to reach the pressure of approximately 0.7kg/cm2 caused by serious failure in a transformer. It also operates when the pipe of air breather is choked so as to increase the pressure in the relief vent

5 OLTC protective relay

OLTC protective relay detects some faults in diverter of on-load tap changer. Check the following items: 1.Fault of diverter insert 2.Fault of whole of OLTC Malfunction of OLTC relay due to normal deterioration.

6 Differential relay

The differential relay detects the difference between the input current and the output current of a transformer converted by a current transformer.

7 Over current relay and ground fault relay

These relays detect faults in the electrical system.

Following test helps in fault diagnostics and pin pointing of the faults for faster rectification:

1.10 TESTING OF TRANSFORMERS a) Insulation resistance (I.R.) Test. b) Turns Ratio Test. c) Magnetizing current test. d) Short Circuit Test. e) Winding resistance Test. f) Vector Group Test. g) Magnetic core balance test.


Page No. 16

a) I.R. Test and Insulation Ratios:

I.R Value test is very important and the test set up for measuring HV to Earth, with LV winding grounded after safely isolating the Power transformer, is as shown below:

Insulation resistance of transformer windings: Measure the insulation resistance between a pair of windings, and between each winding and ground with a suitable Megger at a period as specified above. The Megger test should be made to check if the transformer is in suitable condition for operation or application of the dielectric test.

Fan motors and/or oil pump motors (At least once every two years): Measure insulation resistance of fan motors and/or oil pump motors with a 500V Megger. Action: If insulation resistance is less than 2M Ω, check balancing of load currents of three phase and dry out the interior of fan motors.


Page No. 17

b) Moisture content in oil (Every one year): Measure moisture content in oil with Automatic Coulometric Karl-Fischer Titration method and confirm that it is satisfactory to the criteria:

For Transformer Voltage ≦69 kV, Moisture content shall be ≦35 ppm

For Transformer Voltage >69 kV, Moisture content shall be ≦25 ppm

For Transformer Voltage >345 kV, Moisture content shall be ≦20 ppm c) Ratio test: Measure the ratio of a transformer by two voltmeter methods or with a ratio tester. If the transformer has taps, the turn ratio should be measured for all taps as well as for the full winding. The test voltage may be between 100V and 200V at the rated frequency. Action: Compare the test results with those in the test report. If it is difficult to measure because of fluctuation of voltmeter pointer or because of unbalance of a bridge circuit, more detailed investigation should be done. d) Winding resistance Test: Measure the winding resistance by bridge method or by drop-of-potential method. The oil temperature should also be recorded at the same time. Action: If the winding resistance, corrected to a specified temperature, is different from the data obtained previously, more detailed investigation should be done.

e) Excitation current at low voltage: Measure the excitation current at low voltage (100-200 volts) applied on the lower voltage winding with other windings being open-circuited. The voltage wave shape should be sinusoidal. Action: If the measured excitation current is much larger than the original data at installation, more detailed investigation should be done. f) Impedance voltage: Measure the impedance voltage at low current (5-10 amperes) applied on the higher voltage winding with lower voltage winding being short-circuited. Action: If the measured impedance voltage is much different from the original data at installation, more detailed investigation should be done.

g) Tests for Transformer Oil

1) Physio chemical tests: Density, Viscosity, Flash point, pour Point, Neutralization Value and water content test.

2) Electrical Tests: Di-electric strength of oil; Resistivity test, Dielectric

Dissipation Factor (Tan δ) Test, Dissolved Gas Analysis.

3) BDV Values: Standard Values of Transformer Oil are as follows:


Page No. 18

Sl. No. Characteristics Standard Values

1 Breakdown Value

a) > 145 KV 60 KV (min.)

b) 72.5 to 145 KV 50 KV (min.)

c) < 72.5 KV 40 KV (min.)

2 Dissipation Factor at 90°C (Tanδ) 0.05

3 Specific Resistance at 90°C 1 X 10 * 12 (Ω-cm)

4 Water content ppm

a) > 145 KV 15 ppm (max.)

b) 72.5 to 145 KV 20 ppm (max.)

c) < 72.5 KV 25 ppm (max.)

5 Inter Facial Tension 0.03 N/m (min.)

6 Density 0.89 g/cu.cm (min.)

7 Flash Point 140°C (max.)

8 Pour Point - 6°C (max.)

9 Total Acidity Test 0.03 mg KOH/g-

(max.) i) Insulation oil Dielectric strength (Every one year): Measure dielectric strength with an oil tester and confirm it is certainly more than 40 kV/2.5 mm gap with 12.5 mm diameter spheres.

Sl.

No.

Nominal Voltage of

Transformer

Dielectric Strength of

Insulating Oil (KV) 1. 145 KV class and above More than 50

2. 72.5 KV class to less than 145 KV More than 40

3. Less than 72.5 KV class More than 30

ii) Acid Content of Insulating Oil (By neutralization)

Sl.

No

Judgment Acid Content (mg KOH/g)

1. Good Less than 0.2

2. Replace or do filtrations 0.3 ~ 0.5

3. Replace immediately Above 0.5


Page No. 19

iii) Resistivity of Insulating Oil

Sl.

No.

Judgment Resistivity of oil at 90 deg C

(Ohm-mtr)

1. Good More than 0.1 x 10 12

2. Fair 1 x 10 11

to 0.1 x 10 12

3. Poor Less than 0.1 x 10 11

iv) Water Content Test

Sl.

No.

Nominal Voltage of Transformer Water Content (ppm)

1. 145 KV class and above 20 ppm max.

2. Below 145 KV class 40 ppm max.

v) Dielectric Dissipation Factor

Sl.

No.

Nominal Voltage of Transformer At 90

0 C, 40 ~ 60 Hz

1. 145 KV class and above 0.2 max.

2. Below 145 KV class 1.0 max.

The detailed test procedures and the threshold limits are given in the Annexure – 4

and 6. It is also recommended to compare the test results with the manufacturer’s

commissioning report.


Page No. 20

2.0 SOPS FOR HV /MV ISOLATORS & EARTH SWITCHES

Isolators or Disconnect Switches are used to open and close the circuit and they are

operated only on no load condition .Isolators in grid Substations are motorized and

can be operated manually.

Normally horizontal double break, Horizontal centre break, Pantograph, Vertical break

Disconnectors are in use for EHV isolations. HV and MV isolators are as shown

below:

Isolation switches are used in electrical substations to allow isolation of apparatus

such as circuit breakers, transformers, and transmission lines, for maintenance.

2.1 KEY POINTS FOR MAINTENANCE Checking of the male / female contacts for good condition and proper

connections.

Checking proper alignment of male & female contacts & rectify if required.

Cleaning of Insulators.

Lubrication of all moving parts on regular basis by applying petroleum jelly.

Tightness of all earthing connections.

In case of Isolator with Earth switch, check electrical and mechanical interlock i.e. Isolator can be closed only when E/switch is in open condition & vice versa.

As Isolators are operated on No load, hence check the interlock with Circuit Breaker, i.e. Isolators shall be operated when Breaker is in OFF condition.

The motor operating mechanism box, in case of motor operated isolators, should be checked for inside wiring, terminal connectors, etc.

Check the Panel indications i.e. semaphore & bulbs, if provided (Isolator and Earth switch - close and open condition) and rectify, if required.

The detailed check lists with periodicity for inspection and Maintenance are given in

the Annexure – 4, 5, and 6 for ready reference.

2.2 TESTING OF ISOLATORS & EARTH SWITCHES a) Testing for Insulation Resistance: Check IR Value between Phase to Phase & Phase to Earth by 5 KV Megger for HV

Isolators.


Page No. 21

b) Contact Resistance check: Measure contact resistance by suitable micro-ohm meter.

Earth Switches: Earth switches connect the equipment to ground to discharge any

capacitive charge present in the equipment (e.g. Bus bar) to ground under no load

condition, and protects the working personnel from shocks. It is mounted on the Frame

of the Isolator.

Sequence for Opening of Isolator

Open CB on no load or full load

Open the isolator on no load

Close the earth switch

Sequence for Closing of Isolator

Open the earth switch

Close the isolator

Close the CB

It must be ensured that an interlock exists and functions promptly to avoid closure of

CB when Earth switch is closed.


Page No. 22

3.0 SOPS FOR CIRCUIT BREAKERS A circuit breaker is an equipment, which can open or close a circuit under normal as

well as fault condition. The circuit breaker breaks for a fault to avoid damage of other

equipment in the station.

The Circuit breaker is so designed that it can be operated manually (or by remote

control) under normal conditions and automatically under fault condition.

Whenever a fault occurs, trip coil gets energized, the moving contacts are pulled by

some mechanism & therefore the circuit is opened or circuit breaks.

The main parts of Circuit Breaker include Poles with interrupter, support porcelain, arc

quenching medium and control circuit. The OCB, ACB, SF6 C.B and ACB are shown

as below.

Oil Circuit Breakers: HV circuit breaker in which arc is drawn into Oil to dissipate heat and extinguish the Arc. It requires periodic check for Oil quality as the oil may get decomposed due to heat. Contacts are separated inside a steel tank filled with transformer oil used for arc quenching.

Air Blast Circuit Breakers: Air circuit breaker is fitted with a chamber surrounding the contact, called as ‘arc chute'. The arc is driven into it. It utilizes high-pressure compressed air for arc extinction. The arc chute is made from some kind of refractory material. - High temperature plastics reinforced with glass fiber and ceramics .The ACB is suitable for fast and repeated operations. An air compressor and receiver is required to maintain high pressure.

SF6 Circuit Breaker: In case of SF6 Breakers Current interruption in a high-voltage circuit-breaker is obtained by separating two contacts in a medium, such as sulfur

http://www.electrical4u.com/electrical-circuit-breaker-operation-and-types-of-circuit-breaker/

http://en.wikipedia.org/wiki/Circuit_breaker

http://en.wikipedia.org/wiki/Sulfur_hexafluoride


Page No. 23

hexafluoride (SF6), having excellent dielectric and arc-quenching properties. After contact separation, current is carried through an arc and is interrupted when this arc is cooled by a gas blast of sufficient intensity.

Vacuum Circuit Breaker: When the contacts of the breaker are opened in vacuum (10-7 to 10 -5 Torr), an arc is produced between the contacts by the ionization of metal vapors of contacts. The arc is quickly extinguished because the metallic vapors, electrons and ions produced during arc condense quickly.

To ascertain the failure of vacuum bottle, it is necessary to check the contact resistance of each pole or the travel of each pole, as specified by the manufacture.

3.1 KEY POINTS FOR MAINTENANCE OF CIRCUIT BREAKERS Tightness of power connections & control wiring connections.

Cleaning of Insulators.

Lubrication.

Checking of contact resistance, close-open timing, and insulation resistance.

Checking of gas pressure for SF6 circuit breaker (leakages, if any).

Checking of air pressure for pneumatic operated breaker (leakages, if any).

Checking of Controls, Interlocks & Protections like checking of pole discrepancy system i.e. whether all three poles are getting ON – OFF at the same time.

Cleaning of Auxiliary switches by CTC or CRC spray and checking its operation.

General Instructions on maintenance of Switch Yard Equipment

Sl. No

Maintenance point Description of the equipment and action points

1 External cleaning Transformer bushings/ circuit breaker / CT / CVT / isolator

2 Rust protection Steel parts of operating mechanism etc. For rust protection grease C or Tetyl 56 are recommended.

3 Lubrication The bearings of the breaker and operating mechanism of isolator and breaker are to be lubricated with grease G.

4 Cleaning of contact surfaces

Silvered contact surfaces and copper surfaces shall be cleaned, if necessary, with a soft cloth and solvent (trichloroethane).

5 Cleaning of aluminum surfaces

Shall be cleaned with steel brush or emery cloth. After this, a thin layer of Vaseline is applied. This shall be done within 5 minutes after the cleaning.

6 Oil Levels Ensure Oil levels in Transformer / OLTC tanks, conservator tank, OCBs, CTs, PTs etc.

http://en.wikipedia.org/wiki/Sulfur_hexafluoride

http://en.wikipedia.org/wiki/Dielectric


Page No. 24

The detailed Check lists for periodic maintenance are given in Annexure – 3.

3.2 TROUBLE SHOOTING OF CIRCUIT BREAKERS

The common troubles, possible reasons and remedial actions for Circuit Breakers are as follows:

Sl. No.

Trouble Possible causes Remedial Actions

1. Low insulation Resistance (below 2000 Mega-ohms) between... Phase terminal and earthed frame, with breaker closed. Phase terminals of a pole.

Moisture.

Dirty insulation surface internal and/or external.

Poor oil.

Carbon/copper particles sticking to internal surface.

Circulate dry hot air or oil through the breaker pole for 4 to 6 hours.

Dismantle, clean, reassemble Insulation resistance should be above 2000 Mega ohm, for 1.1 kV and above 10,000 mega ohms above 36 kV.

2. Contact resistance between Terminals of Pole too high (above 100 micro-ohms)

Reduced contact pressure.

Loose connections.

Contact surface damaged due to repeated operations.

Insufficient contact wipe.

Oxide film on contact surface.

Dismantle, repair and assemble again.

If necessary, replace the contacts.

3. Unequal contact Wipe and Travel in 3-pole Measured from top surface of interrupter flange and the contact tip by a simple rod with:

Breaker open.

Breaker closed.

Contact erosion due to repeated load operations or short circuit operations.

Unequal length due to wrong adjustments of linkages.

Inspect contact tip.

Replace if badly eroded.

Adjust contact if lengths are unequal in three pole.

4. One of the poles does not close.

Pull rod for contact damaged.

One of the links of that pole broken.

Contact of that pole severely damaged.

Dismantle the pole and repair the defect.

5. Breaker operation too Slow During

Excessive friction in the pole unit.

Identify the cause


Page No. 25

opening(Timing from trip command to contact separation instant too large (60 ms instead of say 40 ms)

Contact grip to high

Trip coil operation sluggish.

Low battery voltage, hence higher trip coil pick-up-time.

Take Remedial action.

6. Breaker does not operate on Electrical command.

Open control circuit.

Spring defective.

Trip circuit open.

Trip latch/coil defective.

Spring not changed.

If breaker operates with manual operation of trip release, the mechanism is O.K.

Check control circuit.

Check closing spring visually.

Identify the cause and take remedial action.

Check supply to spring changing motor.

Check pressure switches, relays, control wiring.

3.3 TESTING OF CIRCUIT BREAKERS a) Rated Operating Sequence (Duty Cycle)

The operating sequence denotes the sequence of Opening and Closing operation which the breaker can perform. The operating mechanism experiences severe mechanical stresses during the auto re-closure duty. The circuit breaker should be able to perform the operating sequence as below.

(i) O-t-CO-T-CO O - Opening Operation C - Closing Operation CO - Closing followed by opening t - 0.3 Sec. for rapid or auto re-closures T - 3 minutes (ii) CO-t - CO where t = 15 sec. for circuit breaker not to be used for auto-enclosure.

b) Total Break Time (As per IEC: 62271-100) for highest system voltage

Highest System Voltage KV Break Time (ms)

72.5 60 to 100 145.0 60 to 100 245.0 Not exceeding 60 420.0 Not exceeding 40 800.0 Not exceeding 40


Page No. 26

4.0 SOPS FOR LIGHTENING ARRESTORS Lightening arrestor is used for protecting the equipment from surge voltages and it protects the insulation on the system from the damaging effect of lightning. It protects the system from Lightening when surge travels along the line and the arrestor diverts the surge to the Earth. It consists of a series of spark gaps and several non-linear resistances like Thyrite, metros IL etc.

Surge Counter Lightening Arrestor

Usually the Arrestor Rating is 80% of Max Line to Line Voltage for Neutral earthing system and 100% in case of un-earthed system.

4.1 KEY POINTS FOR MAINTENANCE & TROUBLE SHOOTING Lightning arrestors can deteriorate over a period of time due to factors such as dust, cracks, moisture ingress, degradation of the zinc oxide elements inside, etc. hence following maintenance points shall be observed for their healthy functioning: 1) Insulator cleaning. 2) Connections tightness. 3) Checking of earthing connections. 4) Reading of leakage current on daily basis to be taken. If current shoots in red

zone, then that particular LA is to be replaced as early as possible. Detailed check lists and the respective Periodicity etc. is given in the Annexure – 3 for ready reference.

4.2 TESTING OF SURGE ARRESTORS 1) IR Testing: Insulation resistance test is to be done between Stack to stack & between each Stack to earth by suitable Megger. It shall be in the order of Mega Ohms with 5 KV Megger and is compared with the previous values and the test values of the manufacturers.


Page No. 27

2) Surge Counter Test: Apply 230V AC supply across the counter & check pointer movement in clockwise direction.

3) Harmonic Test (online test): When the lightning arrestor is in line, a small leakage current flows through it. This current can be analyzed for Harmonics. Online harmonics analyzers for lightning arrestors are available. The leakage current is analyzed for the presence of the 3rd Harmonic which usually indicates a failure in the near future. Arrestor thus identified can be isolated and sent for repair before any catastrophic failure can take place.

4) HI Pot Test: The HI pot test is conducted at about 175% of the rated voltage.


Page No. 28

5.0 SOPS FOR INSULATORS

Back Flashovers generally occur in transmission lines during lightning strikes when

the potential of the tower rises vis-a-vis the conductor. This causes the voltage across

the insulators to increase beyond the limits resulting in a flashover.

The creep age distances for different pollution levels are provided in the following

table:

For determining the creepage distance requirement, the highest line-to-line voltage of

the system forms the basis.

Pollution level Creepage distance (mm/kV)

Light 16

Medium 20

Heavy 25

Very Heavy 31


Page No. 29

6.0 SOPS FOR VOLT-VAR CONTROL (VVC): Volt –VAR control (VVC) comprises On Load Tap Changer (OLTC) and the Capacitor Bank

as Voltage regulating equipment in the Grid substation

6.1 OPERATIONAL ASPECTS OF OLTC The OLTC - tap changer is a connection point selection mechanism of the PTR

winding that allows a variable number of turns to be selected in discrete steps. A

transformer with a variable turn’s ratio is produced, enabling stepped voltage

regulation of the output. The tap selection may be made via an automatic or manual

tap changer mechanism – depicted as follows:

DABS shall keep the voltage at the point of supply to vary from the declared voltage, as per the table below:

Permissible Voltage regulation Limits to be maintained by Utility at HV: +10% and -12.5%

Limits at Medium Voltage (above LV, below 33 KV): +6% and -9%

Limits at Low Voltage 415 Volts level: +10 %

Volt-VAR Control which is important for the Utility. It is not only important for

maintaining the above stated power quality parameters but also for achieving loss

reduction.

6.2 VAR DISPATCH Capacitor banks improve power factor, reduce electrical losses, etc. Since Voltage

drop is dictated mostly by Low Power factor due to predominance of inductive loads

at peak periods, the first step shall be tackling reactive power before increasing the

Transformer Tap. Following is recommended:

Measure Power Factor (Energy Meter) for Commercial & Industrial customers and insist consumers to compensate to bring it up to the level of 0.95 at least or the threshold to be decided by Utility.


Page No. 30

Measure Power Factor and voltage (Energy Meter) at transformer level and ensure PF level of 0.90 at least or the threshold to be decided by Utility.

If the PF of at least 0.9 is not achieved, Utility shall install Switched capacitors at Distribution Transformer level to maintain the PF.

Measure Power Factor and voltage (Energy Meter) at Feeder level and ensure PF of 0.95 at least or the threshold to be decided by Utility by having Switched capacitor bank at Substation (line capacitors may not be required).

Capacitor Bank:

In any power utility, maintaining stable power supply at proper voltage is always a

problem. Due to lot of inductive load, the reactive power flow takes place in the system

which results in lowering of system voltage and increase in Transmission

& Distribution losses. The HT capacitor provides an interim solution in improving the

power system stability, the voltage and power factor. HT capacitor bank also

compensates the losses occurring in the transmission lines. Capacitor unit has one

steel container, two bushings and several capacitor elements enclosed in the unit.

A single HV Capacitor may have a capacitance of 5 KVAr to 200 KVAr. Several

identical units are mounted on Insulator racks and connected in series or parallel

combination to obtain a High Voltage Capacitor Bank.

Before switching on capacitor, bus voltage, system incoming load current and power

factor can be noted. After energizing, check that capacitor draws almost balance

current in all the 3 phases and is near to its rated value. Note the change in bus

voltage, load current and system power factor. Normally after capacitors are

energized, there will be little rise in bus voltage and some reduction in system load

current and improvement in power factor. In case load current increases, instead of

reducing, it shows that capacitors connected are more than required for the load and

in this case the power factor shall be leading.


Page No. 31

Operational Aspects:

Usually Series capacitors are used to improve the Voltage profile and Shunt capacitors to reduce Losses; hence the combination is used for the dual purpose.

Whenever the line capacitor is used, it is placed at a distance of about 1/3rd of the length of the feeder from source.

Protection of Capacitor bank:

1) Fuse is provided for each capacitor in the bank. The fuses shall be external type for 11 KV capacitor bank. The capacitor unit together with external fuse shall be arranged in such a way to avoid bird faults by providing adequate clearance between the body and the line terminal. Capacitor bank of voltage level more than 11 KV is provided with internal fuse type. In case of fault, the faulty element will automatically go out of circuit.

2) Discharge resistors are provided within the capacitor unit to ensure safety after

de-energisation of capacitor (To reduce the residual voltage from crest value of rated voltage to 50 volts or less within 5 minutes). The power loss in these resistors is negligible.

3) Each capacitor bank is protected against lightning by gapless zinc oxide arrester.

4) The capacitor protection equipment include over current, earth leakage and protection to detect unbalance loading due to abnormal conditions.

6.3 VOLTAGE CONTROL Volt control is meant for maintaining optimum voltage, reduce demand and / or help in energy Consumption.

OLTC tap change is meant to increase or decrease incoming HV voltage to compensate the voltage fall at secondary side of the power transformer.

First step is to measure Voltage at metering cubicle of the secondary side of the power transformer.

Approach is to first ensure switching the Capacitor bank in case of voltage fall .If PF is < 0.95 , switch on the capacitor bank available at substation and also at the Distribution

If there is no improvement and the above stated voltage regulation limit is not achieved, Tap increase needs to be initiated.

Once the Voltage comes to normal limit say 15 KV for 15 KV system, the tap shall be brought to normal position. This is taken care by ‘on load tap changers.

Reducing the Tap to be initiated to bring down the voltage.

The holding time for tap change may be decided in consultation with utility, as frequent toggling is undesirable.

Change in voltage per step is given on the name plate of the particular OLTC.


Page No. 32

6.4 MAINTENANCE POINTS Maintenance checklist is given in Annexure – 3.

6.5 TROUBLE SHOOTING OF OLTC

On-load tap changers are the second largest reason for trouble in power transformers after short circuit. The defects in OLTC are of the following type:

o Burning of transition resistance. o Burning and damage of rollers and fixed contacts. o Misalignment of the tap changer assembly. o Error in time sequence operation. o Defect in tap changing driving gear i.e. mis operation of limit switches and step-

by- step contactors etc.

Some of the common problems noticed in the OLTC compartment, selector/debtor switch are:

It appears that proper care for selecting current rating of the OLTC is not exercised by the manufacturer. Factors for efficiency of operation and overloading capability of transformer have to be accounted for to arrive at design current rating. The selected current rating normally should be one step higher than the calculated value.

It would be advisable if purchaser’s technical specifications do not leave this option to the manufacturer and current/voltage ratings are specifically stipulated.

Quality and rating of transition resistors have been one of the main sources of problem in OLTC. Repeated incidences of burning of transition resistors are an area which calls for serious attention from OLTC manufactures.

Open circuiting or burning of transition resistors leading to selector switch spark over and fire in tap switch results into bursting of pressure relief diaphragm in MR type tap changer.

Failure of limit switch to stop operation at extreme position of tap changer have led to severe arching, pressure build-up and bursting of OLTC compartment.

In sealed breathing transformers, defective oil seals and ‘O’ rings have led to transfer of oil under pressure from main tank to diverter switch and leakages through silica gel breather resulting into fall in main tank oil level which is an operational hazard.

Crack in barrier board has also been a cause of failure owing to non-equalization of pressure between main tank and OLTC, while applying vacuum at the time of first erection and drying out.


Page No. 33

6.6 KEY POINTS FOR MAINTENANCE OF CAPACITOR BANKS

Sl. No. Maintenance Checks

1 Checking of leakage of oil

2 Unbalance in capacitors by checking open delta voltage

3 Physical checks, Tightness

4 IR value 5 Leakage current measurement

6 Cleaning of insulators/bushings and tightening of

connections 7 Capacitance measurement of capacitor cells

8 Checking of Protection relays for adopted setting

9 Checking tightness of earth connection and foundation

bolts

Details of the inspections along with work required are given in Annexure – 3.

6.7 TROUBLE SHOOTING OF CAPACITOR BANKS

Sl. No.

Symptom Cause Remedial Action

1 Leakage of Impregnate

Leak in Welded Seam or from Terminal cap

After cleaning and abrading by emery cloth, apply araldite or solder the spot carefully.

2 Overheating of Units

Poor Ventilation

Excessive ambient temperature

Over voltage

Increase space for free air circulation; arrange for forced ventilation; reduce voltage or switch off /adjust OV Relay trip to get 10% of rated voltage of bank.

3 Current below normal

Low voltage

Loose connection

Usual. Tighten carefully.

4 Noise Internal fault Disconnect the noisy, connect balance units.

5

Fuse Blowing

Short circuit in Unit Measure IR value between terminal and case. If reading is Zero, the unit is shorted.

Over current due to Over voltage & Harmonics

Reduce Voltage /eliminate harmonics by adding suitable series reactors.

6 Abnormal bulging

Gas formation due to internal arcing

Replace the unit, refer to the manufacturer.


Page No. 34

7.0 SOPS FOR INSTRUMENT TRANSFORMERS The primary winding of the transformer is connected to the high voltage or high current

circuit, and the meter or relay is connected to the secondary circuit. Standard

secondary current ratings are 5 amperes or 1 ampere, compatible with standard

measuring instruments and 1 Amp CTs of 0.2 class Accuracy are used in Grid

Substation applications.

As per Operational aspects of CTs ,care must be taken that the secondary winding of

a CT is not disconnected from its low-impedance load while current flows in the

primary, as this may produce a dangerously high voltage across the open secondary

(especially in a relaying type CT) and could permanently affect the accuracy of the

transformer.

Potential transformers (PT) (also called voltage transformers (VT)) are a parallel

connected type of instrument transformer. They are designed to present negligible

load to the supply being measured.

7.1 MAINTENANCE ASPECTS

a) Visual Inspection

Current transformers are normally filled with oil and have oil impregnated paper

insulation for both primary and secondary winding. Careful inspection is to be done

for any trace of oil leakages.

If bellows are provided in CTs, the position of bellow indicates either leakage of oil or

expansion due to internal gas generation. Both the conditions are serious for the life

of the CTs and immediate action should be initiated for rectification.

Visual inspection is also to be carried out on the healthiness of terminal connections,

condition of porcelain, development of cracks, chippings, cleanliness of insulator

surface etc.


Page No. 35

b) Maintenance of Gaskets

Marshaling boxes, CT terminal boxes are to be properly sealed to prevent any dust,

rain water and insects. Door gaskets are to be changed periodically to give proper

sealing. All door bolts/ latches are to be properly tightened and never left loose.

c) Secondary Terminals Connections

Stud type terminals are preferred in Marshalling box cable terminals for better grip and

to avoid mal-operation/ non-operation due to improper contacts.

d) Primary Terminals

The thermo-vision scanning indicates proper connection of primary terminal. If

Thermo-vision is not carried out, physical checking of terminal connection is to be

done with proper torque as CT primary carries heavy current, any loose joint may lead

to arcing and welding of terminal connectors.

7.2 CAPACITOR VOLTAGE TRANSFORMERS (CVTS) Visual Inspection

The bellows provided in most of the CVTs are not visible from outside. CTs/ CVTs and CC are also oil filled equipment and oil leak is to be observed. If oil leak is observed in anyone stack, the entire CVT is to be replaced. CVTs are tuned units and replacement of anyone stack is not recommended to avoid phase angle errors.


Page No. 36

Electro-Magnetic Unit Electro-Magnetic Unit (EMU) of CVT houses the secondary transformer, Compensating reactor and Ferro resonance suppression circuit. The color of oil indicated through the gauge glass gives some indication of the healthiness of the internal components. Any abnormal heating may also be observed through Thermo vision scanning. Secondary Voltage Deviation in secondary Voltage of CVT is clear indication of failure of capacitor elements. Necessary action should be taken to replace CVT if secondary voltage in anyone CVT is abnormal (may be +2V and -4V). Continuing the equipment in service beyond this stage may lead to failure/ bursting of CVTs. Other Maintenance

Maintenance of Marshalling box gaskets, tightening of secondary terminal connections and tightening of primary terminal connections, etc., are also to be ensured for healthy operation. It is to be ensured that all extra holes at Marshalling boxes are properly plugged and kept vermin proof. The anti-condensation heater and the thermostat are to be kept in working condition to keep inside of the panel dry.

The details of the inspections with periodicity are given in Annexure – 3.

7.3 TESTING OF CURRENT TRANSFORMERS

Perform resistance measurements through bolted connections with a low-resistance ohmmeter, if applicable.

Perform insulation-resistance test of each current transformer and its secondary wiring with respect to ground at 1000 volts dc for one minute. For units with solid-state components that cannot tolerate the applied voltage, follow manufacturer’s recommendations.

Perform a polarity test of each current transformer.

Perform an excitation test on transformers.

Measure current circuit burdens at transformer terminals.

When applicable, perform insulation-resistance tests on the primary winding with the secondary grounded.

Perform power-factor or dissipation-factor tests. Verify that current transformer secondary circuits are grounded and have only one

grounding point.

7.4 TESTING OF POTENTIAL TRANSFORMERS & CVTS Perform resistance measurements through bolted connections with a low-resistance

ohmmeter.

Perform insulation-resistance tests winding-to-winding and each winding-to-ground. Test voltages shall be applied for one minute for units with solid-state components that cannot tolerate the applied voltage, follow manufacturer’s recommendations.

Perform a polarity test on each transformer.

Perform a turns-ratio test on all tap positions.

Measure voltage circuit burdens at transformer terminals.


Page No. 37

Perform a dielectric withstand test on the primary windings with the secondary windings connected to ground. The test voltage shall be applied for one minute.

Perform power-factor or dissipation-factor tests, in accordance with test equipment manufacturer’s published data.

Verify that voltage transformer secondary circuits are grounded and have only one grounding point.

Test Values for Instrument Transformers

a) I. R. Values:

Transformer Coil Rating Type in

Volts

Minimum DC Test Voltage

Recommended Minimum Insulation Resistance (Mega

Ohms)

Liquid Filled Dry

0 – 600 1000 100 500

601 – 5000 2500 1000 5000

Greater than 5000 5000 5000 25000

The details on testing are mentioned in Annexure – 4.


Page No. 38

8.0 SOPS FOR PROTECTION SYSTEM Relay and switchgear together play an important role in ensuring stable operation of electrical power system under normal as well as faulty or abnormal conditions.

Line protection Relays There is one carrier aided non-switched three zone distance protection scheme and one Directional over current and earth fault relays as back up. Main protection is suitable for single and three phase tripping. IDMT type E/F relay are also to be provided additionally. Bus bar System Bus bar protection is required to be provided for high speed sensitive clearance of bus bar faults by tripping all the circuit breakers connected to faulty bus. The bus bar scheme comprises Hydro bus and Import bus resembling the double bus system, as shown below.

Transformer Protection Generally, following protective and monitoring equipment for transformers of 220 kV and 110 KV class are provided:

Transformer differential protection.

Over fluxing protection.

Restricted earth-fault protection.

Back-up directional O/C + E/F protection on HV side.

Protective Gear consist of ….

1) Relays (2) Current transformers

3) PTs/CVT (4) DC Supply


Page No. 39

Back-up directional O/C + E/F protection on LV side.

Buchholz relay, Winding and Oil Temperature Indicators, Oil Level Indicator, OLTC Oil, Surge Relay and Pressure Relief Device.

Protection for tertiary winding.

Overload alarm.

Circulating current Differential Protection (Inter-turn phase fault).

Local Breaker Back-up Protection

In the event of any circuit breaker failing to trip on receipt of trip command from protection

relays, all circuit breakers connected to the bus section to which the faulty circuit breaker is

connected are required to be tripped with minimum possible delay through LBB protection.

All protections need to be tested periodically for functional operation and record of testing

should be provided in the substation for future records.

8.1 KEY POINTS ON MAINTENANCE


1 Testing of EL with time synchronization unit.

2 Calibration of tariff energy meters.

3 Checking of voltage (in service) for relays.

4 Checking of DC logic circuits for trip and annunciations including timers. Simulation 5 Calibration of panel meters (Indicating / recording instruments along with the transducers).

Distance Protection

Sl. No. Distance Relay Function Checks

1 Reach check for all 4/5 Zones*

2 Times measurement.

3 Power swing blocking check.

4 Switch on the fault (SOTF) check

5 Level detectors of Positive Phase Sequence (PPS).

6 Fuse failure check.

7 Polarization check.

8 Negative Phase Sequence (NPS) detector check.

9 VT fuse failure check.

* Includes Z1, Z2, Z3 and Z3 (reverse) or z 4 z 5 (reverse).

Similarly the Maintenance points and schedules are furnished in detail for definite time over

current, IDMT, Earth fault, over voltage, under voltage, Neutral displacement relays in

Annexure – 3.


Page No. 40

8.2 TROUBLE SHOOTING FOR NUMERICAL RELAYS (IED)

All types of IEDs (Intelligent Electronic Devices) do not require much routine

maintenance after once properly installed, formatted and configured. ABB / SIEMENS /

ALSTOM/SEL make IED / Numerical relays are installed in DABS network.

It is therefore suggested that while commissioning these relays outmost care should be taken so that proper settings and binary inputs/binary outputs are correctly configured. However, following problems may be encountered during operation of these relays for which corrective action to be taken as below:

Problem Corrective Action

Relay in service / Run indication not Glowing.

Check the DC fuse of protection / annunciation at relay. Replace it & Check DC at back panels of relays.

If DC supply of IED is OK and above Problem persists.

Call T&C engineer/service engineer for Replacement of relay.

No display on the relay Call T&C engineer/service engineer for Rectifying fault or replace the relay.

Proper tripping/annunciation indicators not glowing or any mismatch

Call T&C engineer for checking binary Inputs / outputs configurations with Laptop & relay software for making corrections.

Relay malfunctioning or giving false tripping or no tripping.

Call T&C engineer for checking the settings & time grading from the relay front panel and make suitable changes required, if any.

8.3 TESTING OF RELAYS

Testing & Protection

Sl. No. Protection Checks

1 Primary injection test.

2 Protection stability and sensitivity. checks 3 Relay and DC logic check.

(To be done whenever the protection AC circuits are disturbed like addition of new feeder)


Page No. 41

Secondary Injection set

Testing Principles There are two main principles as primary injection and secondary injection. Primary injection: High current is injected to primary side of the CT. Test carried out covers CT, conductors, relay and sometimes circuit breaker as well. The relay unit has to be isolated from the power system. Usually this principle is used at commissioning and also if the secondary of the CT is not accessible. Secondary injection: Relay is disconnected from the CT and the stepped down current is directly injected to relay. Therefore, no need for the primary side of the CT to be disconnected from the rest of the system.

The detailed test procedures prescribed by the manufacturers of the Test Set used, shall

be followed.


Page No. 42

9.0 SOP FOR SCADA SYSTEMS SCADA System: Load monitoring and Load shed Management is carried out by NLCC through a centralized SCADA System. The Grid substations have Remote Terminal Units (RTUs) and associated Power line communication equipment. The station Operators monitors the Loads and enters the Load shed data through SCADA Workstations for the MV feeders and Distribution Transformers which are under SCADA Loop. Power line carrier communication is used for data transmission as well as protection of transmission lines. The output of PLCC goes to coupling capacitor and then to transmission line and travels to another end where it is received through coupling capacitor and inputted to relay and control panel at that end. The carrier energy on the transmission line must be directed toward the remote line terminal and not towards the station bus and it must be isolated from bus impedance variations. This task is performed by the line trap.

SCADA monitor in Grid Substations

http://electrical-engineering-portal.com/how-to-protect-capacitor-banks


Page No. 43

Operator’s Data Entry Screen for Load Shed information


Page No. 44

9.1 KEY MAINTENANCE POINTS AND CHECK LISTS OF STATION AUXILIARIES

a) Line trap / wave trap (Yearly)

Sl. No.

Maintenance Checks

1 Tightness and cleanliness.

2 General inspection/cleaning of tuning unit.

3 Thermovision scanning of joints.

4 Cleaning of post insulators (if provided).

5 Repair of bird guard.

b) PLCC System (Yearly)

Sl. No.

Maintenance Checks

1 Checking of Return Loss.

2 Power supply measurements.

3 Transmitter checks.

4 Receiver checks.

5 Checks for Alarms.

6 Reflex Test.

7 LMU composite/Return loss.

c) Marshaling box and LT panels etc.

The following maintenance aspects are to be taken care of with regard to marshalling boxes and LT distribution panels in the Grid Substation:

Sl. No.

Maintenance Checks

1 Checking of healthiness of gaskets.

2 Checking of space heater and illumination. 3 Checking the tightness of all connections including earthing.

4 Cleaning of marshalling box and junction box.

5 General upkeep and painting.

d) Bus bar Jumpers, connector, clamps and yard lighting


1 Measurement of station earth resistance.

2 Cleaning of insulators.

3 Checking of insulators for cracks.

4 Thermovision scanning of all conductor joints, terminal connectors/clamps.

5 Checking of earthing connection of all structures.

5 Removal of hot spots.

6 De-weeding of switchyard.

7 Repainting, rust removal of all structures, equipment, etc.

8 Checking of switchyard lighting.


Page No. 45

e) LT Switch gears, LT Panels etc.


1 Cleaning of panels, bus bar insulators, etc. 2 Relays testing.

3 Tightness of all electrical connections.

4 Checking of Indicating meters.

5 Check for change-over facility, if provided.

6 Check operation/Indications in Off-load condition of air CB.

7 Check spring charging of air CB.

f) LT Switch Gears


1 Functional checking (Trip,close,etc.) of 33/11 kV CBs.

2 Measurement of operating timings.

3 Cleaning of insulators and tightness of terminal connections of CBs. CTs. PTs, Isolators, etc. 4 Alignment checking of isolators.

g) Station Auxiliary Transformer


1 Testing of oil BDV.

2 IR measurement.

3 Testing/checking of OTI, WTI and Buchholz (if provided).

4 Checking of healthiness of pressure relief diaphragm.

5 Checking healthiness of Buchholz relay.

6 Checking tightness of earthing connections.


Page No. 46

h) Station Batteries, Charger and DC Distribution System


1 Measurement of Specific gravity and voltage of cell.

2 Checking electrolyte level and topping up with DM water, if required. 3 Checking of Emergency DC lighting to control Room.

4 Checking of any earth fault (If E/F relay not provided).

5 Checking of electrical connections of charger panel and DCDB panels for tightness and cleanliness.

6 Checking of electrical connections for batteries and application of petroleum. jelly on cell terminal, if required 7 Checking control cards of charger and measurement of test point voltage. Values 8 Battery impedance testing (Optional).

9 Testing of DC E/F and under voltage relays.

10 IR measurement of charger transformer.

11 Discharge test of battery set.

i) Backup Generator system:

The Operation and maintenance steps are detailed above. The subsystem wise checks are also listed in Annexure – 3 for ready reference. The key maintenance points are given hereunder:

Main Generator


1 Check for air inlet restrictions.

2 Checking for electrical connections for tightness.

3 Stator winding IR measurement.

4 Checking/cleaning of slip ring and its brushes.

5 Testing of protection/control relays and alarms.

Exhaust


1 Check for air leaks and exhaust restrictions.

2 Tight exhaust manifold and turbo charge cap screw.

Detailed Checklist The detailed check lists for the Auxiliaries and supporting systems are given in Annexure – 3. The Checklist for Overhead Crane Hoists are also attached in Annexure – 3.


Page No. 47

10.0 FIRE FIGHTING EXTINGUISHERS

“Fire is a rapid, self-sustaining oxidation process accompanied by the evolution of heat and light of varying intensity”. Fire results from the combination of fuel, heat and oxygen when a substance is heated to a certain critical temperature called the “Ignition Temperature”. The material will ignite & continue to burn as long as there is fuel, the proper temperature and a supply of oxygen (air). Classification of Fires is mentioned below: Class “A” Fires: These are fires involving solid materials (such as wood, cloth, paper, rubber, etc.), normally of an organic nature (compounds of carbon), in which combustion generally occurs with the formation of glowing ambers, where the cooling effect of water is essential for extinguishment of fire. Class “B” Fires: These are fires involving flammable liquids e.g. kerosene, naphtha, LDO, mix oil, gasoline, where blanketing effect (a layer of foam over the surface of burning liquid) is essential for extinguishing such fires. Class “C” Fires: These are fires involving gases e.g. LPG, Methane, Ethylene, Propylene, Hydrogen etc. Fire can be put out either by dry chemical powder or carbon dioxide gas. Here isolation of leaking source is essential.

Class “D” Fires: These are fires involving combustible metals, such as magnesium, titanium, sodium. These fires can be put out with the help of special dry powders. Ordinary DCP or Foam or Water is of no use on such fires.

Electrical Fires: According to latest concept, electrical fires do not constitute a particular class. Any fire involving electrical equipment is a fire of class A or class B. The normal procedure in such fires is to cut off the electrical supply of the equipment and to use an extinguishing media appropriate to the burning material. Water in the form of hose stream should in no case be used in electrical fires unless positive isolation of electric supply has been ensured.

Classification of Fire and Suitability of Portable Fire Extinguishers

Sl. No. Class of Fire Foam Extinguisher

Carbon Dioxide Extinguisher

Dry Chemical Powder

Extinguisher

1 Class A Fire Suitable Not recommended except for small surface fire

Suitable

2 Class B Fire Suitable Suitable Suitable

3 Class C Fire Not Suitable Suitable Suitable

4 Class D Fire Not Suitable Not Suitable Special dry powder

5 Electrical Fire Not Suitable Suitable Suitable


Page No. 48

Caution:

Do not use Foam Fire Extinguisher on fires involving live electrical equipment and metal.

Do not use CO2 Fire Extinguisher on big size fire. It is also not to be used on metal fire. While extinguishing oil fire, precaution against flash back or re-ignition is to be taken.


Page No. 49

11.0 SOPS FOR DAILY CHECKS FOR SUBSTATION OPERATORS

It has been observed that Sub Station Operators are not following the general operating instructions and precautions required to ensure the smooth operation of Substation. Following checks are proposed for ensuring healthy functioning of all Substations and to report to the Substation Manager and other Superiors on observing the abnormalities, if any.

11.1 SYSTEM HEALTH MONITORING

Ensure that UPDATED Single Line Diagram of Substation as well Updated Single

Line Diagram of Grid System is available and displayed at prominent location in

Control Room.

Check and ensure Trip Circuit Healthy light is ON for all Circuit Breakers

Check functioning of anti-condensation heaters

Attention to be paid to items such as broken relay or annunciator glasses and

similar defects. These should be repaired in coordination with Protection Dept. at

the earliest.

Inspect the entire Switch yard for evidence of flashovers, excessive corona, and

evidence of overheating, any hissing /unusual sounds and sparks on the

overhead jumpers, connectors and terminations of the equipment.

Check alignment and condition of Isolators.

Check Oil levels in the OCBs / Transformers / CTs / VTs, Gas pressure in SF6

Breakers & Oil level in the air compressors. If oil/gas leak is observed; oil/gas

level of that equipment must be checked and confirmed as acceptable. If not;

immediately inform Station Manager for attendance.

Transformer Breathers to be checked. If color change indicates significant

moisture absorption arrange for early replacement.

Check functioning of all fans and pumps of Power Transformers.

Confirm that the DC battery volts are correct. This will ensure that protection

equipment will operate correctly.

Check Electrolyte levels in Station Batteries.

Check for functioning of all Pressure and temperature Gauges.

Check and ensure no Air lock in the Air compressor system by draining certain

quantity of Air from the Receiver.

Check and ensure healthiness of the Station Battery Charger. Top up distilled

water in case of non-dry type batteries.

Ensure that all inter cell and battery bank connections are intact to avoid voltage

drop.

Check and ensure functioning of all annunciation panels by pressing the Test

button.

Ensure that all the Relay flags are in re-set condition in case of no fault /fault

rectified & supply restored.


Page No. 50

Check for proper functioning of all feeder Energy Meters.

In case of Energisation of feeder after Load Shedding or after Fault repair or after

Major System Disturbance, monitor loading of feeder very closely.

In case it is observed that load is increasing rapidly; initiate Immediate Load

reduction to prevent major System Disturbance.

Follow the Trip and Restore instructions of NLCC in respect of tripping of MV

feeders, Load shed from Distribution transformers as applicable.

Observe the Station Power Factor and see that the Capacitor Bank is in service

in case the power factor drops below 0.90 and it is switched off when P.F. meter

shows leading side.

At light loads, see that the system voltage does not rise beyond 10% of the rated

voltage and ensure that capacitor Bank is kept off in such a case.

Check and ensure communication equipment is intact and functioning.

Ensure that the SCADA work stations in the Sub Station are well maintained and

no undesired software / programs are loaded in these systems.

Ensure that the Earth pits are well maintained and earthing connections of all

equipment in the switch yard and control rooms are intact.

Ensure proper functioning of lighting / emergency lighting in the yard and control

Rooms

Ensure that the backup DG Set / Emergency lights are in working condition.

Ensure that the Periodic Preventive Maintenance is carried out w.r.t the Check

lists proposed in the Annual Maintenance plan.

11.2 RECORDING & REPORTING

Following events and conditions are to be recorded in the Station Log book and Shift

duty hand over register.

Hourly recording of System Voltages, Amps, Frequency and Power Factor of the

Station.

Hourly Recording of Oil & Winding Temperatures of Power Transformers.

The operation counter reading of all Circuit Breakers must be recorded in the log

book.

Readings are to be taken of oil and winding temperature, the operation counter,

tap changer position and operating range.

Recording of Battery voltages and Charger current.

Record the specific gravity and voltage of a few pilot cells on rotation to cover all

the cells once in each month.

Record Relay indications on all HV and MV feeders after each feeder tripping.

In case of incoming feeder trips, contact and obtain the relay indications from

feeding substation breaker and record the same.

Promptly record Feeder load before trip and Feeder load after restoration in the

Log book.


Page No. 51

In case of needing Tap changing of transformers ,report to the Station Manager

and the Transformer section besides recording in the log book on the existing tap

position and Voltages and the new tap position with voltages achieved.

In case of MV Feeder is overloaded by 10% continuously; arrange to shift load to

other MV Feeder in consultation with Station Manager and NLCC. Also initiate

system improvements measures by promptly informing the Station Manager and

the Expansion Dept.

Ensure that the Fire safety and Fire extinguishing systems are intact.

Promptly report on mal functioning of any interlocks to Protection Dept. and

follow-up on speedy rectification.

Most importantly, the Line clear and Line return procedures are to be strictly

followed to avoid any electrical accidents to the personnel working on the lines &

equipment for any Planned or Unplanned outages.

11.3 EFFECTIVE LOAD MANAGEMENT & RELIABILITY IMPROVEMENTS

In case of Incoming supply restoration after supply failure, never switch ON all

outgoing feeders at the same time. Switch ON the Feeder Breakers one by one

by taking clearance from the NLCC and monitoring Power Transformer Load.

In case of a feeder fault, if the incoming trips along with outgoing, inform

Protection Dept. to review the Relay Settings to achieve appropriate protection

coordination.

Wherever Alternate feeder is used to restore supply to customers fed from a

faulty feeder, ensure that Alternate feeder load is not over loaded.

In case of repetitive Feeder tripping coordinate necessary line patrolling to trace

and rectify the fault as early as possible and keep Station Manager informed.


Page No. 52

12.0 ANNEXURE – 1

EQUIPMENT HISTORY OF THE GRID SUBSTATION

The Summary of the main equipment of the HV/MV Substation and the network details

are as follows:

Description Name of the Line/

Feeder

Voltage Level

Length in Ckt KM

Conductor Size

HV Line -1

HV Line-2

MV Feeder -1

MV Feeder-2

MV Feeder -3

MV Feeder -4

MV feeder -5

MV Feeder-6

Description Capacity in MVA

Make Year of Manufacture

Last date of repair

Power Transformer -1

Power Transformer-2

OLTC -1

OLTC-2

Station Transformer

Reactor -1

Reactor-2

Capacitor Bank -1

Capacitor Bank -2

Switch Gears

Description Voltage level

Type (SF6/MOCB/ACB)


Last date of repair

Circuit Breaker(CB)-1

CB-2

CB-3


Page No. 53

Auxiliary Supplies

Description Capacity in MVA


Last date of repair

Station Transformer

Battery Charger -1

Battery Charger-2

station Battery bank-1

Station Battery Bank-2

Manufacturers Test certificates and Test results at the Time of Commissioning of the

Equipment are to be preserved for comparison of On-site test results and for warranty

claims etc.


Page No. 54

13.0 ANNEXURE – 2

13.1 OPERATIONAL SAFETY

Switching operators must have the knowledge and skill to operate the equipment and must have valid HT Operating License issued by the competent Authority. Incorrect switching operations may cause failure of equipment, electrical arcing, and explosions, all of which have the potential to cause serious injury or endangering of life. Following are the key considerations in terms of safety. The concerned Substation manager ensure adherence of the safety procedures given below and shall have the following Personnel Protection Equipment (PPE) for his personnel:

Protective headwear.

Safety shoes.

High visibility clothing, including long sleeved shirt.

Safety Gloves.

Safety goggles for eye protection.

High voltage test rod.

Proper measuring Instruments and Test Equipment.

Clamp meter for LV installations.

Electrician’s Tool kit including Insulated Plier, Spanners etc.

Earth discharge Rods for discharging residual charge on lines after supply Isolation.

Safety Interlocks between Isolators & CBs, Isolators and Earth switches in MV/HV systems.

First Aid Kit.

The maintenance checks of PPE are detailed in Annexure – 3.


Page No. 55

13.1.1 Operational Safety in switching Functions

Substation switching operations may be required for a number of purposes which include:

Switching on the Incoming Isolators, Operation of Power transformer with on load tap changer, Bus couplers, Capacitor Bank /Reactor, MV feeders etc.

Switching a high voltage feeder in or out of service.

Isolation of other substation equipment including circuit breakers, bus bars, capacitor banks, and singular items of HV apparatus such as isolators, earth switches, surge arrestors, current transformers and voltage transformers for maintenance.

Performing maintenance or replacement of equipment such as transformers & Circuit breakers.

Making temporary or permanent reconfigurations in the substation.

There are two major elements of substation switching: o Disconnection of supply- Open CB o Reconnection of supply o One is essentially the reverse procedure of the other. o If the disconnection has been done to allow work or testing to be performed

on HV equipment, then there is a third intermediary step between disconnection and reconnection.

o In this step, a work area is designated and Permission to Work (PTW) is prepared and issued to the work crew.

13.1.2 Disconnection Procedure

Routine Disconnection for work in Substations comprises the following key steps:

Re-arrangement of the System.

Load transfer (if necessary).

Isolation of apparatus to be worked upon.

Testing to prove de-energized.

Earthing of apparatus to be worked upon.

Setting out the approved colored tapes or barriers for the Work Area.

Issue of Access Authorities for Work or Test.

Procedure on Permit to test and Permit to work.

13.1.3 Reconnection Procedure

Re connection for work in Substations comprises of the following key steps:

Return of Access Authority for Work or Test.

Removal of defined work area.

Removal of earths.

Reconnection of apparatus.


Page No. 56

13.1.4 Re-arrangement of System

Re-arrangement of the System could include any or all of the following items:

Firstly, the transmission lines may need to be switched to close in a line that may be on stand-by to maintain reliability, or take some line(s) out of service to take into account fault levels.

It may also require close consultation / checks with an interconnecting authority to ensure their System, which could cause problems or conversely may be needed in an emergency, if failure within our System required load support to maintain System stability.

13.1.5 Load Transfer

Often equipment which needs to be isolated so that work can be performed on it could result in an interruption of supply. If two transformers operating in parallel, however when one is taken off line the other single transformer is unable to handle the load (is overloaded).

It may be possible to prevent this interruption by transferring the load to another feeder or substation. Load transfer should be carried out wherever possible to promote quality of supply.

13.1.6 Isolation of Equipment

When equipment is to be worked on it must be isolated from all sources of supply.

A Distribution Substation can be energized from the MV side, if MV side has not been isolated and the paralleling MV lines with adjacent substations are closed, it may cause a dangerous situation to exist.

An HV line, which has been isolated by opening the Isolators, can still be energized by the Distribution Substation stepping up the MV as above.

An HV Bus bar, which has been isolated, can be energized by a Voltage Transformer (VT), if the secondary side of the VT was not isolated. (This would not normally occur, as VT secondary are generally dedicated supplies, and so would not normally have back-feeds). However, to comply with the Electrical Safety Rules and standard HV Isolation and Access Procedures, and to cover any possibility, the secondary side of any VT within the area of isolation shall be isolated.

Therefore, it is necessary to isolate the equipment to be worked on from all possible sources that could energize the equipment.


Page No. 57

13.1.7 Testing to Prove De-energized

As proof to ensure that the equipment is completely isolated and de-energized, it is necessary to check with an HV Tester or other approved device that no voltage is present. The procedure is as follows: o Prove that the Tester is operating correctly by testing against a known live

source or approved test source. o The points at which earths are to be attached are tested to prove de-

energized. o The Tester is then checked again against a known live source or approved

test source to prove all indications are correct.

13.1.8 Earthing of Equipment to be Worked On

After proving the isolated apparatus is de-energized, the section to be worked on must be short-circuited and earthed on both sides of the work location. Earthing should preferably be visible from the work location.

HV Earthing procedures require a set of earths between the worksite and all possible sources of supply and at least one set must be in view of worksite.

13.1.9 Setting out the work Area

Once the equipment is isolated and earthed, the Work Area must be set out. Approved colored tapes or barriers are used for issuing of an Access Authority for Work or Access Authority for Test and define the enclosed Work Area.

The tape and/or barriers are set at a height of approximately 1.2m., leaving an opening as an entrance to the Work Area. When creating the Work Area it must exclude live equipment, the only exception being overhead strung conductors that are out of reach.

Warning notices may need to be placed in positions of danger to advice staff of any overhead or adjacent danger or advice of any testing being conducted, which must be done with the entrance closed.

The detailed procedure for Permit to Test (PTT) and Permit to work (PTW) with the related Forms is as detailed below:

13.2 THE PERMIT TO TEST PROCESS (PTT)

A PTT shall be required when a test is to be carried out on HV equipment. The tests include a Megger test, pressure test, primary injection test, phasing test, and other tests.

These Tests cannot be done under a Permit to Work for the reason being that under a permit to work the System Earths cannot be disturbed.

A PTT will allow the Authorized Personnel to use his earths when required, e.g. for discharging a cable, etc.

Ensure that the permit to test Procedures used is an Approved one.


Page No. 58

A PTT transfers responsibility to the authorized Person who shall then be responsible for ensuring correct testing procedures are followed.

The Authorized personnel shall be listed under category F (authorized to receive PTT).The Authorized Person shall: o Ensure members of his work party are competent and in a condition

able to perform the work required of them. o Ensure that adequate precautions (refer test procedures) are taken for

the safety of all employees. o Have all members of his work party sign on the PTT form.

An original PTT form must be completed by the System Controller. A duplicate PTT must be completed and signed on behalf of the System Controller by the authorized Person, the latter taking the PTT number, wordings and all instructions from the System Controller by means of the radio telephone or other means of communication authorized by the Authority.

The duplicate PTT form shall be fully completed and all entries read back to, and agreed to by the System Controller issuing the PTT.

PTT shall be valid only when the PTT number is issued and not before that. A PTT can’t be transferred to another Authorized Person.

13.3 PERMIT TO WORK PROCESS (PTW)

A PTW is required when work is to be carried out on or near MV/ HV equipment

such that it renders it unusable for system purposes.

A PTW is also required for work to be carried out on generating equipment such

that it renders it unusable for system purposes. A PTW can only be issued by

a System Controller to an authorized Person and shall be required before any

work can commence.

A PTW is required by an authorized Person who has personnel under his control

working on the equipment. The equipment cannot be returned to service unless

all associated PTWs have been cancelled.

The following point set out in detail the steps to be followed and considerations

for issuing, transferring and cancelling of PTWs by the System Controller:

o The Permit to work is a Legal document which transfers the responsibilities

of safe working procedures of the network element from System Control

department to an authorized Person:

i. Who will then be responsible for the placing of working earths, safety barriers etc.

ii. To whom the PTW is issued shall be responsible for ensuring that all personnel in the working party: o Are in a state able to perform the work required. o Understand the nature of the work covered by the PTW and sign

on the PTW form before commencing work. iii. When it is not possible to deliver the PTW by hand, a Duplicate PTW

shall be completed and signed on behalf of the Controller by the


Page No. 59

authorized person, the latter taking the PTW number, wording and all instructions from the System Controller by means of the radio telephone.

iv. Radio or wireless communication may be made available for ensuring trouble free communication.

13.3.1 Process of Issuing the PTW

An approved switching program is made available to all Authorized Officers who shall carry out the switching operations in the field and the System Controller at the National Load Control Centre (NLCC). To start, it is important to have an approved switching program:

The Issuing Officer shall be authorized.

The recipient of a PTW shall be authorized who will take charge of the work at the worksite.

It is absolutely necessary that all communications between the System Controller and Recipient of PTW and other Authorized Officers in the field shall be in the locally understandable language.

The above is to ensure that all parties are aware of the state of the power system and switching operation carried out at any time.

The System Controller shall be fully conversant with the scope of work required and the switching to completely isolate and make safe the plant to be accessed.

All instructions issued by the System Controller shall be repeated to ensure it has been correctly understood by the Authorized Person and confirmed correct by the System Controller before executing the instruction.

Tests for complete isolation using the approved Test Process. Once complete isolation is confirmed by the tests, the system earths are installed and the process of placing earths using earth switches or portable earths shall be strictly followed.

Install the system earths (earth switches or portable earths) using the approved earthing process

The original PTW is filled by the System Controller detailing the scope of work, isolating points, areas made safe, system earths locations, names of System Controller and Recipient of PTW etc. of the Permit To Work form.

The duplicate PTW is filled by the Recipient and together with the System Controller shall be jointly responsible to ensure that the contents are the same as the original PTW, word by word.

The process of filling the PTW is read out by the System Controller, repeated by the Recipient and confirmed by the System Controller. PTW is valid once the PTW number is issued and not before that.

The Recipient of PTW shall be required to brief all the workers on site, including those that may come at a later time, pointing out, the scope of work, the visual break opening points and danger areas including exposed live cables, the areas made safe using a single line diagram, and other hazards as outlined in the Briefing Process.


Page No. 60

At the end of briefing process, each worker shall sign in on part B, item 4 of the Duplicate PTW form to confirm that they understood the brief. (Part B Attachment form is available for additional names.)

The PTW holder shall inform the System Controller of the names and sign on time of all workers working under the PTW.

Install working earths using the approved earthing process.

Start the work.

Nothing in the above shall restrict an authorized Person from holding more than one PTW at a time within a generating station complex, provided that workers are engaged under one Permit at a time. Workers shall not sign on more than one permit at a time.

13.3.2 Briefing Process

At this stage the PTW has been issued to the Authorized Recipient and accordingly the responsibility for the safety of all team members including assets are transferred to the PTW holder. The PTW holder shall ensure that safe working practices are observed at the work site using the process below:

Outline to the team the scope of work and identify individual roles.

Point out to the team the isolating points, system earths locations, safe working areas and other hazards including live plant and precautions to take.

Locations of working earths.

If the PTW is in force and the workers knock off for the day, they must sign off the PTW and sign on again the next day before commencing work, using the Part B attachment form.

13.3.3 Transferring of Permit to Work

A PTW shall only be transferred provided the conditions given below are satisfied:

(a) The PTW holder’s supervisor has given the approval for his subordinate’s release to attend to other matters of serious or considerable importance.

(b) The originator of PTW shall be at the work site to explain to the proposed PTW recipient, the conditions of plant and equipment, work progress and status of the system covered by the PTW.

(c) Only when parts (a) and (b) have been successfully carried out shall the originator of PTW inform NLCC of his requirement to transfer his PTW to a new Authorised Person. He shall indicate to the duty System Controller his reasons for the transfer of the PTW and that he has satisfied both requirements in (a) and (b) above.

(d) The System Controller on duty shall in this instant only transfer the PTW without going through the standing procedures for the normal cancellation of a PTW.


Page No. 61

(e) The new PTW recipient shall satisfy and familiarize himself with the requirements in (c) above and communicate this to the System Controller as per the Communication Procedure.

(f) The System Controller on duty shall transfer the PTW only when the above requirements are met.

(g) The System Controller and new PTW recipient shall effect the transfer on the PTW form.

(h) In the event the original holder of PTW is not available to explain to the proposed PTW recipient as outlined in (b), then all persons who have signed on the PTW shall sign off and the Supervisor or Team Leader shall cancel the PTW. A new PTW shall be required under such circumstances to complete the work.

13.3.4 Cancellation of permit to work

The System Controller shall instruct the PTW Holder to complete the

Cancellation section of the Duplicate PTW and then complete the original PTW.

Cancelled Duplicate PTWs shall be immediately forwarded to the Control Centre

from where they were issued.

Upon completion of the work the PTW Holder shall notify the System Controller

that he is ready to cancel the PTW. The System Controller shall confirm the

following:

The PTW number of the duplicate to be cancelled is the same as on the original.

The PTW Holder and work area description on the duplicate PTW to be cancelled is the same as on the original.

All persons signed on to the duplicate PTW have signed off to confirm they are well clear of the work site and now treat the plant as live.

All working earths have been removed.

System earths required by the PTW are to remain closed or attached until after the PTW is cancelled.

Any alterations, etc. made to the network are noted down in the log book and on the single line drawings where appropriate. Once checks are completed, cancel the PTW as per the PTW form.

Once the PTW is cancelled the Authorized Person shall proceed to carry out the reverse switching to normalize the isolated network. A PTW shall only be cancelled by the Authorized person to whom the PTW was issued to.

In the event the PTW holder is not available to cancel the PTW, then all other persons who have signed on the PTW are to sign off and an authorized person can cancel the PTW.

13.4 RESTORATION & RE CONNECTION PROCESS

Once the work is completed and the PTW is returned, the steps involved for restoration are as follows: o Clearing the Work Area.


Page No. 62

o Once the Access Authority for Work or Test has been surrendered the colored tapes or barriers enclosing the work area must immediately be dismantled. This is done before the removal of Operator earths.

o Removal of the barrier provides a visual indication that no further work is to be undertaken.

o Removal of Earths. o After the work area is removed the Switching Operator can proceed with the

restoration section of the D & R. The first stage of reconnection on the Switching Instruction will be the removal of earths.

o The earths should be left on the ground after disconnection from the equipment until all reconnection work is completed and the equipment is back in service. This reduces the out-of service-time of the equipment and is particularly important if the equipment is critical to security of supply.

o When the work is part of a Coordinated Switching Instruction involving work at the remote end of a transmission line as well, the Switching Instruction is written to indicate that restoration can only proceed when Access Authorities are surrendered at all locations involved in the work.

o Work at the remote end of a transmission line will also include earths at both ends. The Coordinated Switching Instruction will permit removal of earths only. Clearance will be given to continue with restoration only when all earths are removed.

13.4.1 RECONNECTION OF EQUIPMENT

The isolation can be restored after the earths have been removed. The

Switching Operator can then proceed with the steps in the Switching

Instruction covering the closing of Isolators, up to the point where the

apparatus is restored, and the Circuit Breaker (CB) is open.

The order of closure of CB’s will depend on the System configuration and will

only be carried out after all other restoration involved at any remote end(s) is

completed. After the closure of CB’s, which could be carried out locally at the

Substation or via SCADA, the earths can be picked up off the ground and

returned to the storage area.


Page No. 63

14.0 ANNEXURE – 3

DETAILED CHECK LISTS FOR SUBSTATION EQUIPMENT

MONTHLY CHECKLIST OF POWER TRANSFORMERS

Name of the Substation: Sl. No / Equipment No:

Sl. No

Items to be checked

Description Action Point Attended Date

1 Oil level in conservator tank

Read magnetic oil level gauge on conservator.

If indicator shows less, identify the cause of leakage; repair accordingly. Arrange for topping up, as required.

2 Oil level in the OLTC

Read the oil level in glass indicator.

If level is above or below the red zone find out the cause and rectify.

3 Oil level in diverter switch

Read magnetic oil level gauge on diverter switch oil conservator compartment on main conservator tank.

If indicator shows less, identify the cause of leakage; repair accordingly. Arrange for topping up, as required.

4 Oil in breather

Check the oil in oil cup of breather.

If color of oil is brown or there is less oil, arrange for topping up in the cup, as required.

5 Oil level in bushing

Check the oil level of MV bushings and oil level in glass indicator.

Check for any visual leakage of oil. If oil is leaking from the transformer, initiate corrective action for stopping the leakage and/or replace bushing, if necessary.

6 Oil leakage Visually observe the oil leakage on all 4 corners of the transformer tank.

If any oil leakage is observed, identify the cause of leakage; repair accordingly. Arrange for topping up, as required.

7 Silica gel color

Inspect the color of silica gel in dehydrating breather of transformers.

If color of silica gel is white or pink, replace the silica gel depending on Manufacturer of Silica Gel.

8 AC Supply Check the visual indication provided on power receptacles near transformer.

If all phase indicators not proper, check fuses & MCB etc. and rectify.

9 Temperature indicator –Oil temperature and winding temperature

Check the indicating type thermometers of OTI & WTI on transformers and on control panel.

Ensure that the readings of these two are within limits (Normally OTI limit is 45° over the ambient and WTI is 10° more than OTI). Initiate appropriate action to limit temperatures within limits by reducing load on transformer/ ensuring proper functioning of all radiator fans etc.


Page No. 64

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Items to be checked


10 Crack & dust on bushings

Visually check that there is no dust on bushings. Also, visually observe any crack on bushings.

If dust deposited, take shut down and clean the bushings. If cracks are observed, replace bushings.

11 Noise and Vibration

Observe abnormal sound from transformers. If sound is more, check the frequency and voltage ratio i.e. V/F if voltage is too high and frequency too low. Observe if sound is from a loose part.

Initiate action to normalize the voltage/frequency. Also tighten the loose parts, if any.

12 Relief vent Check the Relief vent diaphragm to be intact.

Investigate, replace if found broken.

13 OLTC Check and ensure operation with no unusual noise etc.

Should any abnormality is noticed; initiate appropriate action as per Manufacturer’s guidelines.

14 Operations Count

Check OLTC Operations from the counter.

Record the cumulative count.

15 Relays Check whether the Relay flags are in reset condition during normal operation and anti-pumping relays and Pole discrepancy relays are functioning healthy.

In case of issues on Relay protection, interact with Relay protection wing and get the problem resolved. Attempt to repeat reset of relays and operate breakers is not advised.

16 Meters Check and ensure proper functioning of Energy meters, Ammeters and Volt meters etc.

Take action to set right the defects noticed, if any.

17 Operator’s Log Book

Check and review Operator’s Log Book and obtain firsthand information on the events happenings.

Take necessary action on the points of concern.

CAUTION: No work should be carried out on electrical equipment without proper shutdown. Follow Manufacturer’s Manual / Instruction Book.

Name & Designation Signature Date

Substation Manager


Page No. 65

YEARLY CHECKLIST OF POWER TRANSFORMERS

Name of the Substation: Sl. No. / Equipment No:

Sl. No

Items to be checked


1 Connections of HV, MV & LV terminals

Check the tightness of clamps on HV, MV & LV bushing top terminals.

Tighten if loose, after taking shut down and necessary precautions.

2 Neutral and earth connection

Check the tightness of neutral connection of neutral bushing and all earth strips i.e. from neutral of transformer and also from transformer body. The earth resistance of the solidly grounded neutral should be checked from the top of the neutral bushing terminal itself so that any loose or bad connection in the earth circuit is reflected in the form of high earth resistance.

Tighten if loose, duly observing the precautions.

3 Buchholz relay Main

Open the cover of main Bucholtz relay and press the push button provided to observe alarm and tripping.

If alarm and trip does not occur, check circuits of the relay and rectify the defect.

4 Buchholz relay OLTC

-do- -do-

5 Thermometer HV/LV /MV oil

Open the cap of thermometer pockets on the top of transformer tank and see that the oil in the pocket is available.

If no oil or less oil, pour transformer oil in the pocket and replace the cap of thermometer.

6 Dial Glass of Thermo meter

The Glass cover of dial type thermometer mounted on transformer main tank may be checked.

Replace the glass of thermometer, if broken.

7 Contact testing of thermometer

In the dial type thermometer, on one side of the thermometer a knob has been provided for manually operating the thermometer, Operate the thermometer and read the temp. of various settings i.e. alarm, fan, starting, pump start, trip etc. ( Note: Do not forget to reset the maximum Temp indicator).

If the settings are disturbed, reset the temperature. If any contact found defective, replace it.

8 Transformer Oil

Take samples of oil about 1/2 lit. each from (i) bottom of tank (ii)

If average BDV of the samples is less than


Page No. 66

Sl. No

Items to be checked


bottom of radiator bank and (iii) from OLTC after opening the valves provided at these places.

Note: The samples should be taken in a glass flask having air tight cork and two Nos. glass tubes fitted. The oil during sampling should not come in contact with atmosphere. (Detailed procedure can be seen in instruction manual of transformer).

35 KV at 4.0 mm gap of 12.5 mm dia spheres balls, then centrifuge/filter the oil.

9 Oil level (i) The oil level in conservator tank should be checked by reading the indicator of magnetic oil level gauge. The scale has been marked with temperature and the reading must tally to the temperature of oil read by the thermometer. If the oil is less, then check for leakage of oil from transformer.

(ii) Check oil gauge pointer for free movement.

If there is substantial oil loss and leakage, attend the leakage and top up the oil (tested oil). If no leakage is there, then check magnetic oil level gauge & repair/replace it, if found defective.

10 Oil in bushing Record the reading of oil level gauge provided on the top of the bushing (HV/MV/LV)

If needle or level in glass shows no oil in bushing, check the leakage of oil and if there is leakage take action to prevent it.

11 Cracks deposit on bushing

Cracks and dirt deposit on bushing shall be checked thoroughly. Cleaning of dirt deposit on bushings is essential.

Clean the dirt on bushings and check for crack and replace the bushing, if needed.

12 Radiator The dirt & foreign material deposited on the radiator fins & in between the radiator fins shall be checked. Dust and dirt deposits on radiator banks affect the efficiency of the radiator.

Clean the Radiator Surface.

13 Fans and Pumps

The cooling fans and pumps mounted on the radiators banks and below the radiators banks shall be checked for cleanliness & running.

Check IR value motor windings after rainy season.

Clean the fans and pumps, oiling and greasing must be done in fans & pumps. The defective bearings may also be


Page No. 67

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Items to be checked


changed. Replace the defective pumps.

Dry out the windings, if IR values found low.

14 Main tank & pipe connections

Main tank, pipe connections to various accessories such as Radiator, Conservator, Bucholtz relay etc. shall be checked for cleanliness and oil leakage. Gasket joints should be thoroughly checked.

Clean the main tank and repair pipe connections. Replace the defective joint and gaskets to attend oil leakage.

15 OLTC contacts The contacts of diverter switch should be cleaned. This may be done by carrying out operations of the tap changer from 1 to 17 and 17 to 1 when the transformer is under shutdown.

NOTE: During operation of OLTC, keep the transformer OLTC, master/follower/individual switch on individual, and do not forget to take the tap position back to the same of other T/F while energizing the Transformer.

Clean the contacts of OLTC.

16 Cooling system Check the starting of cooling fans and pumps by operating the WTI (Thermometer) and check the starting of fans pumps are running and no abnormal noise is there.

If fans do not start, check and rectify the control circuit. If pumps do not start check and rectify the control circuit. Repair/replace the defective fans and pumps, if any fan/pump gives abnormal sound. Replace the bearings and properly lubricate.

17 OLTC Cubicle & control cubicle

Open the OLTC cubicles power cubicles & control cubicle and check that all these are water tight and have rubber beading. Check the tightness of connection. Check

Replace defective rubber beading, defective wires and switches etc. Tighten all the connections.


Page No. 68

Sl. No

Items to be checked


operation of switches illumination and operation of heater circuits.

Replace the heater if defective.

18 OLTC Record the counter reading of the tap changer which is visible from outside the cubicle. Check the operation of OLTC. Check oil in gear casing. Check limits switch & cleanliness.

Find out number of operations from the last operation or commissioning. If no. is more than 5000, replace the oil. If it has given the service of more than 3 years, centrifuge the oil lubricate the gear, clean the finger areas, provide oil in gear casing if less, repair/replace the limit switch and clean the parts.

19 Fastenings & gasket joints

Thoroughly check the jacketed joints on main tank, pipe connections, radiators, relays etc. for any oil leakage and loose/missing bolts and nuts.

Tighten all loose bolts and nuts & replace the missing bolt, if any.

20 Valves & Stop Cocks

The valves have been provided on pipes connecting the main tank and radiators. Stop cocks have been provided for smaller pipes on main tank; check these for operation and leaks. Also ensure the position of these valves and stop cocks.

Attend the leaks and put the valves in correct position.

21 Insulation resistance

Disconnect the connection of HV, MV & LV terminals and record the IR values with 5 KV Megger. Compare the values with those at the time of commissioning.

If Megger values are poor, find out the cause, and centrifuge the oil. Compare readings with previous values.

22 Moisture content Analysis of Transformer

Take out oil samples from valve provided in bottom of Main tank, radiator bank and OLTC and get it tested for moisture content.

If moisture content exceeds 25 ppm (mg/kg), moisture ingress spots to be checked – (includes gaskets and functioning of breather). Replenish silica gel and replace breather if found


Page No. 69

Sl. No

Items to be checked


defective carry out oil filtration on testing of BDV.

23 Transformer testing

Measurement of magnetizing current at normal tap and extreme tap, DC winding resistance test, IR Value with 2.5 KV Megger for MV and 5 KV Megger for HV

Check with commissioning values and initiate appropriate action for rectification e.g. drying up etc.

24 Gauges Calibration Get all gauges calibrated and replace defective / erroneous gauges.


Name& Designation Signature Date

Substation Manager


Page No. 70

YEARLY CHECKLIST FOR SHUNT REACTOR

Name of the Substation: Sl. No. / Equipment No.:

Sl. No.

Items to be Checked

Description of the Check

Action Point Comment /Observation

1 Main Conservator Tank.

Check for oil leakage. Clean the indicator to have proper visibility of oil level. Ensure no oil leakage.

2 Bushings Check for oil leakage from oil level indicator.

Clean Bushings properly, apply corrosion inhibitor and fix/tight with recommended torque. Take care of oil sealing system to ensure no oil leaks.

3 Cooling Fans. Check whether all fuses are intact and the Units are functional.

If any unit is found defective, bulged out (IR Value shows zero), disconnect the same but the remaining units are to be connected in balanced manner with equal Nos. in all phases.

4 Cooling Oil Circulating Pumps.

Check for any leakage of impregnate from welded seam or terminal cap.

If minor leakage is found, after cleaning and abrading by emery paper, apply araldite or solder the spot carefully.

5 Ground Connections.

Measure neutral current with clip-on-ammeter to ensure healthy connection between body and the earth mess.

Ensure all ground connections (Both Neutral Terminal as well Body Tank) are proper and tight.

6 Silica-gel Breather

Ensure color of Silica Gel is blue and oil in the glass pot clean.

Replace/Recondition Silica-gel should 1/3 volume has turned Pink.

7 Buchholz Relay. Check relay is operative, no damages and points towards conservator tank.

Ensure no oil leaks. Cover packing healthy, neat and clean. Glands at wiring cable entrance is appropriate and tight.

8 Radiator Tubes. Ensure all clamps/supports are in properly secured. Touch and feel degree of hotness of all tubes comparatively similar.

Check the valves to ensure no oil leaks.


Page No. 71

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Items to be Checked



9 Pressure Relief Devices.

Ensure healthiness of micro switch and wiring connections.

Initiate corrective action, as required.



Substation Manager


Page No. 72

YEARLY CHECKLIST FOR HV OUTDOOR BUS BARS


Sl. No.

Items to be Checked



1 Conductor. Inspect for no broken/damaged strands.

Repair as required.

2 Disc Insulators. Check for broken/chipped insulator.

Clean Insulators properly, Replace damaged insulators. Tighten Pins, Clamps, and Cotter-keys properly.

3 Risers/Droppers. Check for no damaged parts and no hot-spots.

Repair/replace as required.

4 Support Structures.

Ensure tightness of all nuts/bolts. Check for tightness of each ground connections

Tighten/repair as required.


Substation Manager


Page No. 73

YEARLY CHECKLIST FOR ISOLATORS

Name of the Sub-Station: Sl. No /Equipment No:

Sl. No.

Items to be checked

Description Action Point Comment /Observation

1 Operational matching

Check for any mismatch in operation of the Isolator blades, sparking etc.

Set right for simultaneous operation, lubricate if required for the smoothness in operating mechanism, tightness of stopper bolts etc.

2 Blades and contacts.

Operate the isolator several times and check that blades are properly aligned to engage contacts.

Clean contact surfaces if corroded. Tighten bolts and nuts as required.

3 Contacts and hinge springs and shunts.

Check pressure spring in contact and hinge.

Replace if contacts are not adequate. Replace flexible shunts, if required.

4 Arcing Horns. Check arcing horns to ensure they are not bent/out of shape.

Clean up if burnt.

5 Manual Operating Rod

Check for proper engagement of emergency operating handle and further its operation is smooth and satisfactory.

Realign if required.

2 Earth switch Check whether any loose contact of earth blade of earthing switch.

Tighten the same and ensure perfect earth continuity. Clean main contacts, earthy blades and spring.

3 Insulators Check for any cracks or damages

Replace the insulators, if required.

4 Jumpers & Clamps

Check for any loose contact

Set right tightness and replace in case of damaged/ worn out condition





Page No. 74

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Items to be checked




Ensure all ground connections are proper and tight.

7 Ground Potential Mat.

Check the connection between Earth Mat & earthing of Mat.

Repair/tighten, as required.

8 Remote operation

Check for remote operation from SCADA if it exists.

In case of any problem with remote operation, initiate appropriate action in coordination with SCADA.


Signature of Substation Manager


Page No. 75

MONTHLY CHECKLIST FOR MINIMUM OIL CIRCUIT BREAKERS

Name of the Substation: Sl. No /Equipment No:

Sl. No.

Items to be checked


1 Poles of the Circuit Breaker

Check Oil level in each pole and ascertain that the oil is not less than the middle mark of the sight glass.

Rectify in case of any leakage and replenish.

2 Oil level Check oil level in the accumulator. Check oil level both at high pressure and low pressure.

Should be above the red mark on the oil level indicator.

3 Pressure gauge Observe the reading of pressure gauge.

It should not be less than 335 atm.

4 Breather Check for the Color of Silica Gel.

If color of silica gel is white or pink, replace the silica gel depending on Manufacturer of Silica Gel.

5 Heaters Open the mechanism Door and check for functioning of the heater.

Replace the Heaters if not working or check for supply connections.

6 Indications Check for trip circuit healthy. Breaker ON & OFF indications are working.

Rectify in case of any defect and ensure normal functioning of these Annunciations.

7 Tripping count Record No of tripping. If fault occurred in one particular phase frequently, carry out shorter trip base overhauling.





Page No. 76

YEARLY CHECKLIST FOR MINIMUM OIL CIRCUIT BREAKERS


Sl. No.

Items to be checked


1 After 500 interruptions at rated current Or as per OEM.

Check dielectric strength of oil.

Minimum permissible value shall be at least 30 KV for one minute at 4 mm gap. Preferable to have 50 KV.

2 Mechanism Check the breaker mechanism

Clean and lubricate the mechanism and Insulators with non-fluffy cloth and Lubricate.

3 Foundation Check the foundation, structure bolts and fixing screws etc. in the mechanism.

Tighten as required.

4 Electrical connections

Check all Auxiliary contacts, connections in Terminal blocks.

Tighten all Electrical connections.

5 Collector Motor

With Accumulator fully charged, check pressure gauge.

Indication of Pressure gauge shall be of 335 atm. Switch ON motor pump for some revolutions till the pressure is stabilized.

6 Tripping Coil Check operation of Trip coil at 50% of rated voltage.

If not operated, then check the coil and remove the defect.

7 Contacts Measure contact resistance. Check for contact burning.

Replace contact fingers, Arcing fingers and moving contact arcing tip if wear exceeded limit .Compare with Initial values and take corrective action –filing or replacement as required.

8 Contacts and Coils

Check timing of Opening & Closing breaker.

Rectify in case of deviation.

9 Opening & Closing Coils

Check up for Pick up Voltage.

Tighten the connections and rectify to get pick up voltage and functioning of coils.

10 Operational checks

Check for complete operations like C, O, C-O, O-C, O-C-O timings, Dynamic contact resistance measurement,

Initiate corrective actions as specified in the Operation manual, in case of deviations.


Page No. 77

Sl. No.

Items to be checked


healthiness of auxiliary contacts& coils.

11 Extinguishing chamber

Check the cover disc and arcing blocks.

Replace if worn out.

12 Gaskets Check the condition of Gaskets.

All Gaskets, removed during dismantling of breaker are to be examined and if worn out or damaged replace as required.




Page No. 78

MONTHLY CHECKLIST FOR SF-6 BREAKERS


Sl. No

Items to be checked


1 Gas Pressure Record pressure and Temperature from the Pressure gauge.

It shall be within the limits prescribed in the Operation manual, rectify leakage, if any.

2 Air Pressure Check Air pressure. Maintain the Air pressure as per limits.

Rectify leakage through joints, if any.

3 Porcelain Bushing

Check for any visible cracks, chipping etc.

Clean the Bushing and replace damaged Bushing.

4 Cubicle Check the cubicle for healthy condition.

Clean the cubicle by Vacuum cleaner, if required.

5 Air Receiver Check moisture in the Air reservoir.

Drain the moisture from Air Reservoir, if any.

6 Indications Check for functioning of Trip Circuit Health, Breaker ON & OFF indications.

If not OK, rectify and ensure working of these annunciations.





Page No. 79

YEARLY CHECKLIST FOR SF-6 BREAKER


Sl. No.

Items to be checked


1 Grounding Check the grounding pad for looseness.

Tighten the connections.

2 Breaker Foundation

Check the foundation bolts for looseness.

Tighten, if necessary.

3 Compressor Check the compressor for normal operation. Check the Oil Level

In case of any defect/abnormality, attend to the same and set right as per the Manufacturer’s guidelines. Rectify leakage, if any noticed. Add Oil, if necessary.

4 Leakages Check the joints of pipe line for any leakage.

Rectify the leakages.

5 Mechanism Check rust in mechanical linkage and their looseness.

Necessary cleaning to remove the rust and tighten.

6 Mechanism Lubricate all mechanism. Carry out lubrication of parts, preferably as per instructions in Operations Manual.

7 SF6 Gas in Pole

Check the Gas density through the meter provided in the cubicle.

In case of difference, attend the same to maintain the gas density as per Manufacturer’s guidelines.

8 Control wiring Check the control wiring for looseness and tighten the loose connection, if any

Tighten the connections.

9 Auxiliary Switch Check the contacts of the auxiliary switch.

Smooth filing of the contacts if carbonization noticed.

10 Contact resistance and Timing tests

Measure contact resistance in close position and compare with Firm's Test Results.

Set right if required, preferably as per the instructions in the Operations Manual.

11 Tripping & Closing check

Check the tripping and closing at 50% of DC Voltage.

Set right if required, preferably, as per the instructions in the Operations Manual.

12 Heaters Check Heaters are working properly.

Attend/replace if found defective.

13 External Condition

Visually inspect external conditions including

Tighten as desired.


Page No. 80

Sl. No.

Items to be checked


external screws, bolts etc.





Page No. 81

MONTHLY CHECKLIST FOR AIR CIRCUIT BREAKERS


Sl. No

Item to be checked


1 Indications Check for functioning of Trip Circuit Healthiness, Breaker ON and Off indications by pressing the test switch.

Rectify to restore the functions /replace the indicating lamps if lamp(s) found defective

2 Air Receiver Check for any moisture condensation.

Drain a little Air from the receiver to purge the moisture content.

3 Air pressure Check the pressure gauge and see that the service Air pressure stays between 15 to 16 kg /cm2.

Attend to rectify any Air leakages etc., if pressure is dropping. Also verify running hours counter to ascertain any excess consumption.





Page No. 82

YEARLY CHECKLIST FOR AIR CIRCUIT BREAKERS


Sl. No

Items to be checked


1 Switching Cubicles

Check general condition and for any looseness in connections etc.

Clean the cubicle for dust and tighten the connections.

2 Running Hours Check running hours and assess if there is any air leakage.

Rectify the leakages, if any.

3 Insulators Check for dust deposits and cracks.

Clean insulators and replace the cracked insulators.

4 Mechanism Check mechanism for smooth operations.

Carry out cleaning and lubrication as required.

5 Heaters Check for functioning of the Heaters & Thermostat

Rectify if any heater/thermostat is non-functional.

6 Coils Check tripping and closing of breaker with local and remote switch both as well as tripping at 50% DC volts.

Replace the coil, if required.

7 Air Quality Check whether the Service Air is free from Oil and water.

Clean the Air filters purge moisture /water content from the Air receiver.

8 Non Return Valve

Check whether NRV is working properly.

Rectify /replace in case of valve leakage.

9 Alarm Functions

Check Low pressure alarm for functioning.

Rectify if nonfunctional.

10 Air Receiver Draining and cleaning. Drain-out air of air-receivers, clean inside the tank by opening side covers.

11 Air Filters Check for cleanliness of Air Filters.

Clean the Filters if found dirty.

12 Earthing Check Earthing connections. Tighten the same, if required.

13 Auxiliary Switch

Check the contacts of the auxiliary switch.

Clean the contacts if carbonization noticed

14 Contact resistance and Timing tests

Measure contact resistance in close position and compare with Manufacturer's Test Results.

Set right if required, as per the instructions in the Operations Manual.


Page No. 83

Sl. No

Items to be checked


15 Tripping & Closing check

Check the tripping and closing at 50% of DC Voltage.

Set right if required, as per the instructions in the Operations Manual.





Page No. 84

YEARLY CHECKLIST FOR AIR COMPRESSORS


Sl. No.

Items to be checked


1 Oil Level Check cranks case oil level.

Top up if found less.

2 Air Receivers Check moisture indicator.

Drain Air Receiver a little to purge the water content

3 3 Phase Supply Check whether 3 phase supply is OK.

Set right 3 phase voltage if not in normal limits

4 Operation Check for any unusual noise or overheating of the Motor and Compressor.

Examine and ensure correct 3 phase supply is made available, and system is free from air leakages and lubrication problems.

5 Safety Valves Check for proper operation.

Rectify in case of any mal-operation.

6 Cylinder Heads Open the cylinder heads of all stages to check for any carbon deposit.

Decarbonize air passages and cylinder valve assemblies including valve plates, springs and discharge valve plates.

7 Piston Rings Check any wear out on piston rings.

Replace with new, if piston rings are scratched or worn out.

8 Valves Check pilot valves and all hand valves and joints for any Air leakage.

Examine the valve gaskets etc. and rectify the leakages.

9 Electrical Connections

Check for tightness of all electrical connections.

Tighten all connections in the supply and relay control panel.





Page No. 85

MONTHLY CHECKLIST FOR VACUUM CIRCUIT BREAKERS


Sl. No

Items to be checked


1 Breaker functions-remote operation

Checkup whether VCB trips through push button and check position indicator. Depress Trip Rod & close breaker.

Release Trip Rod depress and close Breaker to see VCB close and Trip.

Rectify if it does not work as per Manufacturer’s instruction Manual.

2 Breaker close Check proper closing of all poles together

If the closure mismatches, open the VCB assembly, tighten the hardware and set right the alignment as per Manufacturer’s instruction Manual.

3 Manual Operation Operate VCB manually by depressing the armature plate of magnet valve and check that the breaker operates freely and that the auxiliary contacts drive mechanism functions correctly.

If any abnormality or air leakage is noticed, record the same and rectify as per Manufacturer’s instruction Manual.

4 Mechanism Check whether the mechanism is operating smoothly.

If not, tighten the nuts and bolts and lubricate the gears and linkages as required.

5 Charge –Discharge Indicators

Check for functioning of Charge- Discharge Indicators.

Set right / replace if indicators are non-functional.

6 Porcelain Housing Inspect the housing and check condition of insulators/bushings.

Clean up as required.

7 Counter Check whether counter is working properly.

Record the cumulative count on the No of VCB Operations. If found counter is not recording correctly, repair or replace as per


Page No. 86

Sl. No

Items to be checked


Manufacturer’s Instruction Manual.





Page No. 87

YEARLY CHECKLIST FOR VACUUM CIRCUIT BREAKERS


Sl. No. Items to be checked


1 Electrical Operation

Operate VCB electrically and check that the VCB drive mechanism functions correctly.

If any abnormality or air leakage is noticed, record the same and rectify.

2 Limit switches Check and ensure Limit switches operation. Also, check the VCB in test position.

Set right the connections /replace the defective limit switch etc.

3 Mechanism Check whether the mechanism is smoothly operating.

If not, tighten the hardware and lubricate the gears and linkages.

4 Other hardware

Check if there are any loose contacts and dirt etc.

Tighten the connections and clean the hardware using Vacuum cleaner after shout down.

5 Disconnects & Auxiliary contacts

Check primary and secondary disconnects and Auxiliary contacts.

Lubricate the disconnects and ensure smooth operation.

6 Porcelain Housing

Inspect housing. Clean up as required.

7 Space Heaters

Check up Space Heaters for working.

In case Heater found to be non-working; replace the Heater or ensure availability of appropriate power supply.

8 Arc Chutes Check the condition of arc shuts.


9 Connections. Check the condition of bolts, nuts, washers, cotter pins and all terminal connections.

Retighten as required. Replace the worn out/defective parts.

10 Control wiring and Relay coordination

Check whether VCB is working on relays activation.

Set right the connections etc. to ensure VCB Trip on Relay activation simulations.

11 Timing and contact resistance measurement

Check contact resistance of fixed and moving contacts and the timing between O-C, C-O, O-C-O cycles of the VCB.

Carry out Timing adjustment/matching corrections as per instructions in Manufacturer’s Manual.



Page No. 88




Page No. 89

YEARLY CHECKLIST FOR INSTRUMENT TRANSFOMRMERS


Sl. No.

Items to be Checked


1 Porcelain insulators

Clean the porcelain for dust etc. and check for any chipping.

Clear the dust and foreign matter from the porcelain surface and replace cracked insulators.

2 Clamps & Jumpers and terminal bushings

Check the clamps and jumpers whether there are loose contacts or any looseness.

Tighten the same and ensure tightness of nut bolts of supporting structure and terminal bushings.

3 Foundation Check the foundation for any crack etc.

Initiate repair as required.

4 Oil Level Check oil level through the sight glass and for any abnormal change in the oil level and check the diaphragm of pressure relief vent.

In case of abnormality, investigate and attend the leaks and replenish. If pressure relief vent found /cracked burst, replace the same once the reason is ascertained.

5 Quality of Oil In case the transformer is not Hermetically sealed then check the dielectric strength of oil and record the result.

It dielectric strength is poor i.e. < 30 KV/min and Tan delta >3%, water content >40 PPM, then recondition /replace the oil.

6 Connections Check the secondary terminal connections of the Transformer and connection in the junction box for tightness.

Tighten the connections duly taking the following precaution: When the current is flowing in the primary, secondary circuit of C.T. should never be open as this may cause overheating of core and breakdown of the insulation due to the high voltage developed across the secondary terminals.

7 Corona ring Check the existence of Corona.

Tighten the connections for loose contact, if any.

8 Nitrogen pressure

Check pressure of Nitrogen. Fill, if necessary.

9 Earthing Check Earthing of earthed end of primary winding of transformers and body Earthing

Tighten and ensure both Earthing connections are intact.


Page No. 90

Sl. No.

Items to be Checked


10 Insulation level

Measure IR value between primary and secondary; primary and Earth.

IR value if falls less than One Meg ohm per KV, repair as per Manufacturer’s Instruction Manual.





Page No. 91

YEARLY CHECKLIST FOR CAPACITOR VOLTAGE TRANSFORMERS (CVT)


Sl. No.

Items to be checked


1 Capacitors. Check for any oil leakages. Ensure no oil leakages.

Clean the oil level indicator clean and visible.

2 Voltage Transformer.

Check for any oil leakage. Ensure no oil leakages.

Clean the oil level indicator clean and visible.

3 Bushings. Check for oil leakage from oil level indicator.

Clean Bushings properly, apply corrosion inhibitor and fix/tight with recommended torque. Take care of oil sealing system to ensure no oil leaks.



Ensure all ground connections (Both Neutral Terminal as well Body Tank) are proper and tight.






Signature of Substation Manager:


Page No. 92

YEARLY CHECKLIST FOR CAPACITOR BANKS


Sl. No.

Items to be Checked

Description of the Check Action Point Attended Date

1 Capacitor Units Check the capacitors for cleanliness, tightness of connections and free circulation of Air around.

Clear the dust and foreign matter, tightness of connections in the Panels and terminals and ensure proper ventilation for the Capacitor cells/units.

2 Earthing Check whether the structural Earthing for capacitors is intact.

Tighten Earthing connections. (Note: Neutral of star connected capacitor banks with residual Voltage transformer should not be earthed.)

3 Fuses Check whether all fuses are intact and the Units are functional.

If any unit is found defective, bulged out (IR Value shows zero), disconnect the same but the remaining units are to be connected in balanced manner with equal Nos. in all phases.

4 Leakages Check for any leakage of impregnate from welded seam or terminal cap.

If minor leakage is found, after cleaning and abrading by emery paper, apply araldite or solder the spot carefully.

CAUTION: No work should be carried out on Live electrical equipment without proper shutdown. Follow Manufacturer’s Manual / Instruction Book.


Substation Manager


Page No. 93

YEARLY CHECKLIST FOR LIGHTNING ARRESTORS


Sl. No.

Items to be checked


1 Surge counter Note and record operation indicator reading and compare with previous reading.

Rectify or replace if it is found defective.

2 Corona Ring Check for any damage/chipping.

Repair as required.

3 Bushings Check for any dust accumulation on the Porcelain and for any looseness in connections and jumpers connected with L.A are of correct length.

Clean the surface and ensure connections are tight and avoid excess strain on the Lightning Arrestor stack by providing adequate length of jumpers.

4 Jumpers and clamps.

Check for proper tightness.

Retighten as required.

3 Support Structures

Check for any shifting of base support, porcelain cracks /damage etc.

Tighten the nuts, bolts and repair.

4 Earthing Check and tighten the line and ground connections. Check ground lead for corrosion or damage below ground line. Check that all leads are short and direct as possible.

Measure earth resistance and strengthen earthing if ER Value is more than one Ohm.

5 Insulation Resistance

Check for I.R value The IR Value when measured with 5 KV Megger. If the value exceeds 1 Meg Ohm per KV, carry out further investigation.



Signature of the Substation Manager


Page No. 94

YEARLY CHECKLIST FOR PROTECIVE RELAYS

Name of the S/S: Feeder: Relay Type: Make:

Sl. No.

Items to be checked


1 Visual Checks Check the Relay compartments after taking the shutdown.

Replace the defective relay coils or contact hardware etc. if any damages are detected and could not be set right.

2 Master Trip Relay

Check and ascertain by simulation.

Get rectified in case of any mal operation or in-operation.

3 History data on Trips

Check from the Log book on which Relays have acted most.

Attend to the Relays /associated circuitry accordingly and set right. Based upon analysis arrange to adopt appropriate Relay settings.

4 Testing & Calibration by Secondary injection

Annual testing of all relays – Over Current, Earth fault, Restricted Earth Fault, Over Voltage, Under Voltage, Differential, Distance Relays as well the Temperature Relays

Carry out various Tests using a reference standard Relay Test kit.


Note: Actions also need to be taken, wherever necessary in addition to above periodicity and also w.r.t respective Manufacturer’s Manuals. The Relay specific Checks are listed below –

Sl. No. Common Tests for Distance and unit Protections

Comment / Observation 1 Trip contacts check 2 Annunciation check 3 Check for carrier send 4 Auxiliary relays healthiness 5 Over voltage relays 6 Local breaker back-up 7 STUB protection check 8 Fault locator initiation check 9 DR. EL initiation check

10 Auto recluse check 11 DC logic


Page No. 95

Sl. No. Common Tests for Distance and unit Protections

Comment / Observation 12 Reactor back up impedance 13 Carrier send for remote trip 14 Auxiliary relays (Buchholz, PRD, etc) 15 Reactor differential protection 16 REF protection 17 DC logic 18 Over fluxing relay 19 Over load 20 Directional over current 21 LBB 22 Auxiliary relays (Buchholz, PRV, etc.) 23 Fuse failure check 24 Transformer differential protection 25 Restricted Earth fault

Sl. No. Bus Bar Protection Comment / Observation

1 Primary injection test

2 Protection stability and sensitivity checks

3 Relay and DC logic check

Sl. No. Differential Relays Comment / Observation

1 Pick up current at the fixed/selected setting

2 Operation of high set element/instantaneous unit at the fixed/selected setting

3 Operation of the relay at the selected restraint bias setting.

4 Checking of 2nd harmonic current restraint feature

5 Operation of alarm and trip contacts.

6 Through current stability checks on the existing load.

Sl. No. Under Voltage Relay Comment / Observation

1 Starting and pick up of the relay as per plug setting

2 Relay operating time as per relay characteristic

3 Operation of alarm and trip contacts

4 Verification of input voltage on relay terminals

Sl. No. Over Voltage Relay Comment / Observation




Page No. 96

3 Operation of high set element / instantaneous unit at voltage setting, if applicable



Sl. No. Neutral Displacement Relay Comment /

Observation



3 Operation of alarm and trip contacts 4 Verification of continuity of input circuit (for

RVT/NCT secondary circuit in case of capacitor banks, under shutdown).

5 Verification of open delta voltage input by by-passing PT secondary supply one phase at a time (in case of 3 nos. single phase PT's).

Sl. No. Over current And Earth Fault Relay Comment / Observation



3 Operation of high set element / instantaneous unit at current setting, if applicable.

4 Operation of alarm and trip contacts 5 Verification of input currents 6 Verification of directional feature, if

applicable.

Sl. No. Under Frequency Relay Comment / Observation

1 Pick up value of the relay at its settings by slowly decreasing the frequency from 50 Hz

2 Drop off value of the relay at its settings by slowly increasing the frequency from pick up value

3 Verification of df / dt feature of the relay, if applicable


Page No. 97

4 Operation of alarm and trip contacts 5 Verification of input voltage on relay

terminals

Sl. No. Over Fluxing Relay Comment / Observation

1 Operating of over flux alarm as per relay setting by varying the voltage and frequency one at a time

2 Operating of over flux trip features as applicable for the following;

IDMT characteristic Instantaneous element

Fixed time setting



Sl. No. Local breaker back up protection,

restricted earth fault (REF) and other instantaneous current operated relays

Comment / Observation

1 Pick up value of the relay at the selected setting

2 Operating time of the relay 3 Operation of alarm and trip contacts 4 Verification of input currents 5 Through current stability checks on the

existing load in case of REF/circulating current differential protection.


Signature of Manager – Relay & Communication Department



Page No. 98

QUARTERLY CHECKLISTS FOR BACKUP D.G SET


Sl. No. Lubricating System Comment

/Observation 1 Check for oil leaks

2 Replacement of oil filter after recommended running hours

Sl. No. Cooling System Comment /Observation 1 Check for radiator air blocking and coolant

level

2 Check for fan hub, drive pulley and water pump

Sl. No. Air Intake System Comment /Observation 1 Check for air leaks

2 Cleaning of air filters

3 Replacement of Air cleaning element

Sl. No. Fuel System Comment /Observation

1 Check for Intactness of Governor Linkages, connections of Fuel transfer pumps & Injection Pumps air leaks

2 Drain the sediments from fuel tank ,change fuel filter and clean fuel tank breather Cleaning of air filters

Sl. No. Electrical Panels Comment /Observation

1 Check for any signs of overheating, burning etc. and take remedial action as required.

2 Ensure tightness of all connections.


Substation Manager


Page No. 99

MONTHLY CHECKLIST FOR SUBSTATION BATTERIES, CHARGERS & DC PANELS

Name of the Substation: SL. No. / Equipment No:

Sl. No.

Items to be checked


1 Pilot cells Check the Voltage of pilot cells to cover all the Cells and the Battery voltage; keeping the float charger in ON position and in FLOAT condition not on BOOST charge.

Examine if each cell voltage is within 2.16 to 2.2 Volts. Top up the Cells with pure distilled water in case of Lead Acid batteries. Record the Pilot cell voltages (use Multi meter).

2 Pilot Cells Measure the Specific gravity of the pilot cells (Lead Acid batteries). (Use Hydrometer).

Attend to Cells having SG lower than 1.140 or higher than 1.200.

3 Battery Bank Check the total battery bank Voltage.

Tighten the cell interconnectors if found loose and record the total Battery Bank voltage.

4 Float Charger Check for Float indication and for any alarms /indications on the Annunciation panel.

Acknowledge and take action to attend to alarm indications and rectify.

5 Equalizing Charge

Check and provide equalizing charge to Batteries @10%of AH capacity.

In case of any cells not improving /picking up, take necessary action to replace these cell(s).

6 General Cleanliness

Ensure Battery sets, Stands and in general Battery Room is properly clean and dry.

No extra material should be kept/stored in battery room.

7 Exhaust Fan Ensure Exhaust Fans are adequate and in working condition.

Repair/Replace as required if fan is not working.

8 Leakage Check the cells for leakage of electrolyte and crack visually.

Replace the cell in case of cracks/leakage.

9 Connection Check the connections for tightness and corrosion.

Old Jelly to be replaced after thorough cleaning.





Page No. 100

YEARLY CHECKLIST FOR SUBSTATION BATTERIES, CHARGERS

AND DC DISTRIBUTION PANELS


Sl. No.

Item to be checked


1 Float cum Boost Charger

Check for the functioning of all alarms in the Annunciation panel by press to test option.

Rectify /replace any defective lamps.

2 Batteries Cleaning and lubrication. Clean the batteries and apply petroleum jelly to battery terminals to avoid oxidation. Ensure proper Electrolyte levels in all cells and record the Specific Gravities/Voltages.

3 Earth Leakage Check for DC Earth leakage. Measure the voltage from the Battery Positive terminal to ground. If it is zero, there is no ground fault on the negative DC bus. Similarly, check for Negative terminal.

If the readings show earth leakage, rectify the same by strengthening the Earthing system.

4 Condition of Insulation

Check the physical condition of cell stand insulators

Replace the damaged insulator.

5 Indication and fuses

Check the battery charger for healthy fuses and indications. Check the operation of DC emergency light.

Carry out the equalizing charging of battery on float charge. Check and adjust the float voltage 2.16 volts per cell at 27 degree C.

6 Condition Check all the connections in the battery charger for tightness.

Tight the loose connections.

7 Condition of battery stands, leads, discs, rubber pads etc.

Check the battery stands for physical condition of rubber pads, leads and discs required for leveling of cells. Check the condition of paint as well.

Repair/ replace as required. Repaint the stands with acid proof black paint if required.



Page No. 101




Page No. 102

MONTHLY CHECKLIST FOR AUXILIARIES & SUPPORTING FACILITIES


Sl. No.

Items to be checked


1 Annunciation panels in marshaling boxes in Control Room

Check all Annunciation panels for functioning of all lamps, hooter alarm etc. by pressing the Test button.

Rectify the defects / replace the failed lamps.

2 Measuring Instruments and Energy meters

Check for any defects or nonfunctional meters

Rectify the defects /replace the faulty meters.

3 Yard Lighting Check for working of Switch yard and control Room Luminaries.

Set right /provide sufficient illumination.

4 Heating / Ventilation

Check for functioning of Heating and ventilation system.

Set right /provide minimum required heating / ventilation.

5 Emergency Lighting

Check whether the Emergency DG set /emergency lights are in service.

Attend to any defects observed immediately.

6 Safety & First Aid / Firefighting equipment

Check whether the Electricians Tool kit, safety Aids, Firefighting equipment and First Aid Kit are intact in Control Room.

Replenish the missing/defective items.

7 Vegetation Check for no growth of vegetation in the switchyard.

Ensure switchyard free of vegetation.

8 Earthing of all equipment

Check for any loose or rusted Earthing connections of all equipment.

Set right earth continuity, as required.

9 Cable Trenches Check all covers are intact. Check Trench is clear of any debris; accumulation of water etc.





Standard Operating Procedures (SOPs) for Grid Substation Page No. 103

YEARLY CHECKLIST FOR PERSONAL PROTECTIVE EQUIPMENTS.


Sl. No.

Items to be checked


1 Personal Protective Ground (Earth Mat)

Check for no physical damage/worn out.

Replace in case of any damage.

2 Personal Protective Ground (Earth Mat)

Carry out DC millivolt drop test.

Replace in case millivolt drop is more than approved.

3 Hot Stick Visual inspection for any cracks/ scratching etc.

Clean the surface. In case any damage observed; replace the Hot Stick.

4 Hot Stick Carry out Hi-pot Test. Note: Apply 150kV for MV Hot Sticks; 300kV for HT Hot Sticks.

Replace if test result is not satisfactory.

5 Gloves, sleeves, leather protectors, blankets,

Visual inspection to check for healthiness.

Replace in case of rips, tears, cuts, thermal damage etc.

6 Gloves Carry out compressed air test.

Replace if found leakages of air.

7 Insulated Gloves.

Carry Out Hi-pot Test for 150kV.


8 Voltage Test Indicators.

Carry Out Hi-pot Test for 150kV.






HALF -YEARLY CHECKLIST FOR FIRE DETECTION & FIRE FIGHTING

ARRANGEMENTS.


Sl. No.

Items to be checked


1 Fire/Smoke Detector.

Check for proper operation.

Rectify/Replace in case of any mal-operation.

2 Water Sprinkler System.

Check the heat sensors, water supply and water storage tanks, piping, and valves/regulators.

Rectify/Replace in case of any defects observed.

3 Firefighting Hydrant pump

Operate by pump start device.

Run for five minutes. Check for smooth operation with slight leakage from shaft seal. (it is a healthy indication)

4 Oil Sump. Check the oil sump below Transformer.

Clean the sump from any accumulation of debris etc. Also drain water from sump, if required.

5 Portable Fire Extinguishers.

Check chemical-foam type, CO2, gas type, etc.

Replace/Refill as required.

6 Electrical Connections.

Check for tightness of all electrical connections.

Tighten all connections.

7 Sand Buckets, Water Buckets.

Check for general condition, damages, leakage etc.

Rectify/replace as required.

8 Partition Wall. Check for general upkeep, cracks etc.

Repair as required.





THREE YEARLY CHECKLISTS FOR STATION EARTHING SYSTEM.


Sl. No.

Items to be checked


1 Earth Mesh Layout.

Check for any abnormality in the route.

Rectify as required.

2 Equipment Ground Connections.

Check for loose connections, corrosion, mechanical damages etc. at each earthing point on each equipment.


3 Fence Ground Connections.



4 Station Building Ground Connections.



5 Overhead Ground Conductor Shield.

A 30° angle from top of the structure should be sufficient to protect the area.

Readjust the angle as required.

6 Overhead Ground Conductor Shield Connections.

Check for proper connections with earth mesh, general condition, fittings, tension or sag

Tighten/readjust as required.

7 Earth Mesh Check for loose connections, corrosion, mechanical damages etc. at each earthing point on each Earth Electrodes.

Repair/Tighten as required.

8 Earth Resistance Test

Megger at each Equipment Ground Connections.

Test Value should be < 2 Ω. If found more; improve the earthing by adding salt etc.

9 Earth Mesh Integrity Test

Test at Each Equipment Ground Connections with 300 A Primary Injection Test Set and/or with Proper Test Set

Compare the test results with commissioning test results and/or previous test results can also be a reference.






THREE YEARLY CHECKLISTS FOR SCADA SYSTEMS


Sl. No.

Items to be checked


1 Indication Lamps Test for proper functioning.

Rectify/Replace as required.

2 Enclosure Physically inspect the enclosure

Rectify/Replace in case of any defects observed.

3 Circuit Functional Tests.

Carry out functional tests* for all inputs and outputs.

Rectify/Replace as required.

4 Communication Testing.

Will be tested along with above functional checks.

Diagnose and rectify as required.

5 Power Supply. Check for healthiness of power supply.


6 Uninterruptible Power Supply (UPS)

Check for healthiness of Unit.



Note: Functional testing requires activation of an initiating device (in the field), monitoring

of the point into the SCADA system for correct operation, and activation of the correct

SCADA output point as anticipated.




YEARLY CHECKLIST FOR OVERHEAD CRANES HOISTS.


Sl. No.

Items to be checked


1 Electric Motor. Inspect and carry out Insulation Test

Clean the motor.

2 Controllers. Carry our inspection to check any abnormality. Test Controllers.

Any control that does not operate properly should be adjusted or repaired as required.

3 Upper-limit Switch.

Check the trip setting of the primary upper limit switches under no load condition by inching the block into the limit (running at low speed).

Adjust the setting as required. NOTE: Hoist operating on rails must have positive safe limit stops.

4 Electromagnetic Braking.

Carry out inspection for any abnormality.

Clean the braking system.

5 Resistor Bank. Test the resistor bank. Clean the resistor bank.

6 Hoist Chain. Check for distortion, wear, stretching, nicks and kinking.

Repair broken hoist chain. Lubricate as required. NOTE: Hoist chain should not contain any splices.

7 Hoist Cable Check for broken strands, kinking etc.

Ensure at least two wraps of cable on drum when hook is in lowest position. Lubricate as required.

7 Hooks. Check for cracks, nicks, gouges and weld spatter. Latch engagement, damaged or malfunctioning latch.

Readjust/Repair as required.

8 Support Structure.

Check for cracks, bends or distortion. Check tightness of bolts, nuts and rivets.

Repair / readjust as required.





15.0 ANNEXURE – 4

Testing of Substation Equipment

A Power Transformer:

1) Insulation Resistance Test:

Between HV & Earth

Between LV & Earth.

Between HV & LV by suitable range of Megger.

2) Voltage Ratio Test:

This test is essential to check the output or the secondary voltage on each tap position. By virtue of this test the problems in the OLTC can be easily detected.

3 Phase, 440 V LT supply is applied to the primary side of the transformer and the output volts at the secondary side for each tap position is measured.

If any break in voltage reading is observed during change of tap position, then there is some problem in that particular tap.

3) Magnetizing Current Test:

When a Power Transformer is charged, it is generally presumed that it is to be charged on NO Load condition because it draws magnetizing current containing high harmonics. Transformer may trip on differential protection if it is not provided harmonic restraint protection.

This current inrush is due to the iron losses of the transformer. This current should be equal in all three phases so that there would not be any spill current in the relay to trip the primary circuit breaker of the transformer. The test is carried out at normal tap position.

Apply 3 Phase L.T. Voltage to primary windings through ammeters (ma) connected in series of windings and keeping secondary winding open.

It would be seen that the current drawn by all the three phases would be same. The current is drawn on account of the magnetizing of the core. (Iron loss) It can also be called as no load current when the transformer is charged with rated primary voltage applied across the primary, keeping secondary open.

4) Short Circuit Current Test:

Short circuit test is carried out to check the healthiness of windings. Apply 3 Phase L.T. voltages to primary windings & secondary windings are shorted through ammeters of suitable range.

If the readings are equal in all three phases, transformer is supposed to be healthy.

The reduced voltage required to be applied across the primary of a transformer to cause rated full load current to flow through this winding when secondary winding is shorted.

In the above case current flowing through secondary is the full load current & is indicative of the copper losses.


5) Magnetic core balance Test:

This test is carried out to check the balancing of the induced voltages in the windings & flux distribution. Transformer is kept on normal tap position and 3 Phase, 440 V LT supply is applied to the primary windings as given below:

Ex: YNyn0 Transformer: - First the voltage is applied between R & N. Voltage will be induced in between YN and BN. Voltages are noted & will be observed that:

Primary: - V RN = V YN + V BN = 2/3 + 1/3; Secondary - V rn = V yn + V bn = 2/3 + 1/3

If the voltage readings on secondary are observed as above, then it can be assumed that the flux distribution is balanced & proper. The procedural steps using 230 VAC are detailed below - o First keep the tap changer of transformer in normal position. o Now disconnect the transformer neutral from ground. o Then apply single phase 230 V AC supply across one of the HV winding

terminals and neutral terminal. o Measure the voltage in two other HV terminals in respect of neutral

terminal. o Repeat the test for each of the three phases. In case of auto transformer,

magnetic balance test of transformer should be repeated for LV winding also.

o The voltage induced in different phases of transformer in respect to neutral terminals given in the table below.

Sl. No.

Description RN YN BN

1 Voltage applied at left side phase

230 V 180 V 50 V

2 Voltage applied at central phase

115 V 230 V 115 V

3 Voltage applied at right side phase

50 V 180 V 230 V

6) Vector Group Test:

A three-digit vector symbol is adopted to designate the vector group. o First letter in capital represents Primary winding connection - D: Delta &

Y: Star o Second letter in small represents Secondary winding connection - d:

Delta and y: Star. o Third digit represents the phase displacement between the primary and

secondary.

This test is carried out to check correctness of windings connections. The Phase angle difference arises out of the internal connections of the windings.

A star / star transformer having the similar vector diagram for primary and secondary side can be connected in two different ways internally.

http://www.electrical4u.com/voltage-or-electric-potential-difference/

http://www.electrical4u.com/voltage-or-electric-potential-difference/


In the first case there is 0° displacement between primary and secondary whereas in the second case there is 180° displacement. In addition to this, a +30 or −30° displacement is possible in a 3 phase transformer when the vector diagram is different i.e. delta/star OR star/delta type.

For parallel operation, secondaries must have same phase angle displacement with respect to their primaries so that there may be no phase difference between the terminals of the secondaries themselves.

The convention employed is to describe it by the hour in a clock in which the HT voltage is represented by the minute hand set to 12 o'clock position, and the LT voltage is represented by the hour hand. Since 12 hours represents 360°of a full circle, each hour represents a 30° phase difference. Thus ‘0’ represents no phase difference, ‘1’ stands for minus 30°, ‘6’ for 180° and ‘11’ for plus 30° displacement as referred to the standard counter clockwise vector rotation.

Ex: YNyn0 Transformer: Keep the transformer on normal tap position. Short R &r of windings. Apply 3 Phase L.V to primary windings. Measure voltages on the secondary side.

1) Following conditions are to be satisfied:

a) V RN = V Nn + V rn

b) V Bb = V Yy

c) Dyn11 Transformer: - Keep the transformer on normal tap position.

d) Short R &r of windings.

B

R

Y

r

y b

n n

b

B

y

Y

N

N

Primary

Secondary Vector Representation

R, r


2) Apply 3 Phase L.T. Voltage to primary windings. Measure voltages on the secondary side. Following conditions are to be satisfied:

a) V Bb < V By

b) V Yb = V Yy

7) Testing of Transformer Oil:

The oil is used as insulation between windings & core and between windings & tank without oil, the paper insulation of the windings could be punctured early which in turn will result in failure of transformer. The oil facilitates cooling of the windings and magnetic circuits. The oil protects windings and core of transformer from the absorption of moisture. The test on oil is divided into two different categories – o Physio chemical Testing o Electrical Tests

7.1 Physio chemical Testing

Density - It indicates the type of transformer oil whether paraffin base or naphtha base.

Kinematics Viscosity - The oil should circulate freely in the equipment to

maximize heat transfer. A low viscosity oil fulfils this need. Viscosity of oil increases because of oxidation taking place at all times. If viscosity increases by 15%, then oil needs replacement.

B

R

Y

r

y b

n n

b

B

y

Y

Primary

Secondary Vector Representation

R, r


Flash Point – Flash point is a minimum temperature at which oil will support instantaneous combustion (flash) but before it burns continuously. Flash point of new oil should be fairly high.

Pour Point - It is the indicator of the ability of oil to flow at cold operating conditions. It is the lowest temperature at which the fluid will flow when cooled under prescribed conditions.

Neutralization Value - This indicates the presence of combined acids i.e. organic & inorganic. The degradation of oil gives rise to acidic compounds and formation of sludge. The acidity is given by its neutralization value, which indicates the total acidity and is evaluated by milligrams of KOH per gram of oil. Acidity content in oil should be low.

Water Contents - It is expressed in parts per million (ppm). Dielectric strength of oil is very high when water content is low.

Inter Facial Tension - It is a measure of the molecular attractive force between

their unlike molecules at the interface. When oil oxidizes, the organic acid thus produced are concentrated at the placing a drop and used oil on water surface, water is spread rapidly over the surface in contrast to a new oil, which may float as a lens on the water. It is considered that IFT gives an indication of degree of slugging of oil as dissolved impurities in the oil tends to diffuse into the water, which lowers the IFT.

7.2 Electrical Tests:

Dielectric Strength - The BDV of oil is its ability to withstand electric stresses without failure.

Resistivity - It is the measure of electrical insulating properties of oil. High

resistivity reflects low content of free flowing particles.

Dielectric Dissipation Factor (Tan δ) o It is a measure to the ratio of the power dissipated in the oil to the product

of effective voltage and current. It is tangent of loss angle & expressed in unit or percent.

o It determines the cleanliness of oil & is related to aging characteristic of the oil.

Dissolved Gas Analysis

o The gases generated under abnormal electrical or thermal stresses are hydrogen (H2), methane (CH4), ethane (C2H6), ethylene (C2H4), acetylene (C2H2), carbon monoxide (CO), carbon dioxide (CO2), nitrogen (N2) and oxygen (02) which get dissolved in oil are known as fault gases.

o The evolution of individual gas concentrations and total dissolved

combustible gas (TDCG) generation over time and the rate of change (based on IEC 60599 and IEEE C 57-104 standards) are the key indicators of a developing problem.


o From these values and based on experience, acceptable limits or threshold levels have been determined as given in table (as per IEC 60599) below:-

Transformer Type

Fault Gases

No OLTC

H2 CH4 C2H6 C2H4 C2H2 CO CO2

60-150 40-110

50-90 60-280 30- '50 540-900

13000

Communicating OLTC

75-150 35-130

50-70 110-250

80-270 400-850

5300-12000

Evaluation of Gases: The temperature at which the fault gas evolves is given in the

table below:

TDGC limits, PP Action

<or = 720 Satisfactory operation, Unless individual gas acceptance values are exceeded

721-1920 Normal ageing/slight decomposition, Trend to be established to see if any evolving incipient fault is present.

1921-4630 Significant decomposition, Immediate action to establish trend to see if fault is progressively becoming worse.

> 4630 Substantial decomposition, Gassing rate and cause of gassing should be identified and appropriate corrective action such as removal from service may be taken.


Faults Associated with Different Gases

Oil Overheating C2H4, C2H6, CH4

Overheated Cellulose Traces of acetylene with smaller quantity of Hydrogen may be evolved. Large quantity of Carbon-Di-Oxide (CO2) and Carbon Monoxide (CO) are evolved from overheated cellulose. Hydrocarbon gases such as Methane and Ethylene will be formed if the fault involved oil impregnated structure.

CO

Partial discharge in Oil (Corona) Ionization of high stressed area where gas/vapor filled voids are present or ‘wet spot’ produces Hydrogen and methane and small quantity of other hydrocarbons like ethane and ethylene. Comparable amounts of carbon mono-oxide and di - oxide may result due to discharges in cellulose.

H2,CH4

Arcing in Oil Large amount of Hydrogen and acetylene are produced with minor quantities of methane and ethylene in case of arcing between the leads, lead to coil and high stressed area. Small amounts of carbon mono-oxide and di-oxide may also be formed, if fault involves cellulose.

C2H2,H2

8. Steps for filtration/Hot Oil circulation:

Connect bottom filter valve of tank to inlet point of filter machine

Connect top filter valve of tank to outlet of vacuum filter machine and start oil circulation. The filter outlet temperature should be limited to 60 ~ 700 C. Continue filtration up to 4 times.

Oil circuit should include a vacuum chamber in which oil drawn from the transformer is sprayed and the moisture and gases are released from the oil are extracted by the vacuum pump.

Oil drawn from transformer is passed through a filter press before being admitted to the vacuum chamber to remove impurities.

A minimum capacity of 6000 liters per hour is recommended for the circulation equipment. Cooler connection at inlet shall be kept closed to minimize loss of temperature during circulation.

Outlet valve shall be kept open to allow expansion of oil inside the cooler. Coolers also shall be included in the hot oil circulation towards the end of the process.

Drain the oil by simultaneously admitting dry air or nitrogen gas from the top. This is to avoid winding insulation coming in contact with moisture.

Apply vacuum of 1.0 torr or better and maintain for 12 Hrs. (1 mm of Hg).

Inject oil under vacuum up to a level of approximately half of the conservator

Repeat vacuum/hot oil circulation cycle till required dryness is obtained.

The oil temperature shall not increase more than 75 0C in any case.


Normally 3 or 4 cycles of hot oil circulation and evacuation will be sufficient to obtain the required dryness for the insulation.

Dryness of insulation is determined by measuring insulation resistance of transformer winding.

Insulation resistance between each pair of windings and also between windings and earth shall be measured by using a 2000 V Megger. Readings shall be comparable with the factory test results.

Direct heating of transformer is not recommended for drying out at site.

Oil samples shall be tested for moisture content, (below

20/15/10 ppm for 145/220/400 KV class respectively). Break down voltage (more than 60 KV at 2.5 mm gap). Resistivity (> 1012 ohm meter) before final oil filling.

Do not measure insulation resistance when the transformer is under vacuum.

9. Testing Norms for Instrument Transformers

Following Voltage norms are applicable for testing of Instrument transformers

Nominal System

Voltage (kV)

BIL (kV) Periodic Dielectric Withstand Test Field test Voltage (kV)

AC DC

0.60 10 3.0 4

1.20 30 7.5 10

2.40 45 11.25 15

5.00 60 14.25 19

8.70 75 19.5 26

15.00 95 25.5 34

15.00 110 25.5 34

25.00 125 30.0 40

25.00 150 37.5 50

34.50 200 52.5 70

46.00 250 71.2 +

69.00 350 105 +

115.00 450 138 +

115.00 550 172 +

138.00 650 206 +

161.00 750 243 +

230.00 900 296 +

230.00 1050 345 +

345.00 1300 431 +

500.00 1675 562 +

500.00 1800 600 +

756.00 2050 690 +


نظريه كارشناسي :

……………………………………………………………………………………………………………………………

.

…………………………………………………………………………………………………………………………….

.

TESTED BY : CHEKED BY: DATE

16.0 ANNEXURE – 5

STANDARD FORMATS ON TESTING

DABSدافغانستان برشناشرکت

گروه مهام شرق شركت مهندسي انتقال نيرو و مخابرات شرق

SERVICE AND MAINTENANCE OFFICE

SUBSTATION : TEST SHEET :

POWER

TRANSFORMER

VECTOR GROUP :

SERIAL NO: RATED VOLTAGE:

TEMPERATURE:

RATED POWER:

TEST :

NO LOAD CURRENT TYPE : BAY: ON-LOAD TAP

On-load tap

HV WINDIN

G (V) HV

WINDING

(MA) REMARKS

U-V U-W V-W U V W


R = RAISED,

L = LOWERED,

N = NEUTRAL. نظريه

كارشناسي :

……………………………………………………………………………………………………………………………………………………………………………

……………………………………………………………………………………………………………………………………………………………………………

TESTED BY CHECKED BY DATE


Company Date

Test location Tested by

XFMR Indent Test set No.

XFMR Serial No Air temperature

XFMR MFR Type KVA Oil temperature

High KV SGL Y %RH

Low KV SGL Y Weather

Tertiary KV SGL Y

TEST SHEET: TRANSFORMER EXCITATION CURRENT TESTS

Test No

Load Tap Ch.

Position

Test KV

PHASE A PHASE B PHASE C REMARKS

Terminal

Symbol

Millie- Ampere

s

Terminal

Symbol

Millie- Ampere

s

Terminal

Symbol

Milli- Amper

es

1

2

3

4

5

6

7

8

10




POWER

TRANSFORMER

VECTOR GROUP :

SERIAL NO:

RATED VOLTAGE:

TEMPERATURE:

RATED POWER: TEST :

RATIO OFF - LOAD

TYPE : BAY: ON-LOAD TAP

STANDARD TEST : IEC – 76 / ANSI – C56

Off load tap

Ratio Voltage

Reference ratio

Measuring Ratio A B C

Average

Tolerance<0.5%

Resultant

1

2

3

REMARKS :

TEST BY CHEKED BY: DATE

: نظريه كارشناسي ………………………………….

TEST SET : T . T . R ( A . V . O )


DABSشرکت برشنا دافغانستان


RATIO

RATED VOLTAGE:

TYPE:

SERIAL NUMBER:

BAY/LINE: SHORT CIRCUIT CURRENT:

ore Class Ratio Test VA Remarks

1S1-1S2

1S1-1S3

1S1-1S4

1S1-1S5

2S1-2S2

2S1-2S3

2S1-2S4

2S1-2S5

3S1-3S2

3S1-3S3

3S1-3S4

3S1-3S5

نظريه كارشناسي

REMARKS: ………………………………………………………………………………………………… TESTED BY: CHECKED BY: DATE

μ

Ω


DABS برشناشرکت دافغانستان


POWER TRANSFORMER

VECTOR GROUP :


TEMPERATURE:

RATED POWER:

TEST :

SHORT CIRCUIT CURRENT TYPE : BAY: ON-LOAD TAP

On-

load

tap

HV WINDIN

G

(V) HV WINDIN

G

(A) RATED POWER:

U-V U-W V-W U V W

REMARKS


Remarks …………………………………………………………………………………………………………………………… . TEST BY : CHEKED BY: DATE:




POWER TRANSFORMER

DATE:

VECTOR GROUP :


TEMPE RATURE: Amb : oil :

TEST :

WINDING RESISTANCE

RATED POWER:

TYPE : BAY: OFF-LOAD TAP

Tap Winding Terminal Current Voltage Ohm/T Ohm/PH Ohm/PH

T-75 Resulta

nt

HV

U-N

V-N

W-N

HV

U-N

V-N

W-N

HV

U-V

U-W

V-W

LV

REMARKS: نظريه كارشناسي :

…………………………………………………………………………………………………………………

TEST BY : CHECKED BY: DATE



……………………………………………………………………………………………………………………………..

TEST BY : CHEKED BY: DATE

DABS برشناشرکت دافغانستان*


AUTO TRANSFORMER

DATE:

VECTOR GROUP :


TEMPE RATURE:

Ambi : oil :

TEST :

WINDING RESISTANCE

RATED POWER:

TYPE : BAY: OFF-LOAD TAP

Standard Test : IEC 76 / ANSI C57

TA

P

1U - N 1V - N 1W - N Ohm/PH

T

Ohm/P

H T-75

Resultan

t

I V R I V R I V R

1

2

3

LV

2U - 2V 2U – 2W 2V – 2W

TV

U-V U-W V-W



……………………………………………………………………………………………………………………………..




POWER TRANSFORMER

DATE :

VECTOR GROUP : SERIAL NO:

RATED VOLTAGE:

TEMPE RATURE:

RATED POWER:

TYPE : TEST:

VECTOR GROUP

BAY :

OFF-LOAD TAP

TERMINALS ENERGIZED

INPUT VOLTAGE LINKED TERMINALS DIAGRAM

1U - 1V

1U – 1W

1V – 1W

TERMINALS MEASURING

READING VOLTAGE

2V – 2U

2W – 2U

1V – 2V

1W – 2V

1V – 2W

1W – 2W




POWER TRANSFORMER THREE WINDING

DATE:

VECTOR GROUP:

SERIAL NO:

RATED POWER:


TEST :

I.R .TEST -MEGGER RATED POWER:

TYPE : BAY:

Standard Test

MINUTE 1/4 1/2 3/4 1 2 3 4 5 6 7 8 9 10 PI C.F

HV to Earth

Voltage used

HV to LV

Voltage used

LV to Earth

Voltage used

ACTIVE CORE

U0=500 V

C.F= Correct Factor

TEST SET : BM 21 (AVO) TEST BY : CHEKED BY: DATE


10/1 MINUTES RATE (PI) 60/15 SECONDS RATE (AT) INSULATION CONDITION

LESS THAN 1.0 LESS THAN 1.0 DANGEROUS

1.0 - 1.11 LESS THAN 1.1 POOR

1.1 - 1.25 1.1 – 1.25 DOUBTFULL

1.25 – 2.0 1.4 – 1.6 GOOD

Temperature

(c) 0 5 10

15.6

20 25 30 35 40 45 50 55 60 65 70 75

Correction factor

0.25

0.36

0.52

0.74

1.0 1.40

4.98

2.80

3.95

5.60

7.85

11.2

15.85

22.4

31.75

44.7



……………………………………………………………………………………………………………………………..


GREATER THAN 2.0 OVER 1.6 EXCELLENT


SUBSTATION :

TEST SHEET :

POWER

TRANSFORMER

DATE:

VECTOR GROUP :


TEMPE RATURE:

Ambi: oil : TEST:

MAGNETIC FLUX

RATED POWER:

TYPE : BAY:


TAP

INPUT

VOLTAGE

(V)

NO-LOAD

CURRENT

(mA)

WINDING HV WINDING LV WINDING TV

U / N V / N W / N U / V U / W V / W U / V U / W V / W


برشناشرکت برق دافغانستان DABS


EARTHING

TRANSFORMER

DATE: VECTOR GROUP:

SERIAL NO:

RATED POWER:


TEST :

ELECTRICAL

RATED POWER:

TYPE : BAY:

NO LOAD CURRENT

ON Load tap

HV WINDING (V) HV WINDING (MA) REMARKS

U – V U – W V – W U V W

1

WINDING RESISTANCE

Tap Winding Terminal Current Voltage Ohm/T Ohm/PH OHM/PH

T-75 Resultant

HV

U – V

U – W

V – W

MEGGER

MINUTE 1/4 1/2 3/4 1 2 3 4 5 6 7 8 9 10 PI C.F

HV To Earth

G Ohm

G Ohm

G Ohm

G Ohm

G Ohm

G Ohm

G Ohm

G Ohm

G Ohm

G Ohm

G Ohm

Voltage used


REMARKS:

نظريه كارشناسي :……………………………………………………………………………………………………………………………..


دافغانستان برشناشرکت

DABS


AUXILIARY TRANSFORMER

DATE :

VECTOR GROUP :


TEMPERATURE Amb : Oil :

TEST :

ELECTRICAL TESTS

RATED POWER:

TYPE : BAY:


[[ NO LOAD CURRENT ]]

ON load tap

Winding

HV WINDING (V) HV WINDING (mA) REMARKS

U-V U-W V-W U V W

1 HV

2 HV

3 HV

LV

[[ WINDING RESISTANCE ]]

Tap Winding Terminal Current Voltage Ohm/ T Ohm / PH

Ohm/PH T-75

Resultant

1

HV

2

HV

3

HV

4

LV


REMARKS:

نظريه كارشناسي :……………………………………………………………………………………………………………………………..



REMARKS:

نظريه كارشناسي :…………………………….



FORM NO : T - 9 DATE :

COMPANY : TESTED BY :

TEST LOCATION : TYPE OIL :

EQUIPMENT TEST : WEATHER

SERIAL NO : AIR TEMPERATURE :

HIGH KV SGL Y D OIL TEMPERATURE :

LOW KV SGL Y D % RH

TERTIARY KV SGL Y D TYPE: KVA :

tg delta & capacitance Test for Transformer Oil

STANDARD TEST : ASTM D924 – 82b; TEST SET : BIDDLE DELTA 2000

10 KV Automated Insulation Test Set

Sample

TEST

TEST

MODE

TEST

KV

CAPACITANCE

(PF)

%DISSIPTION

FACTOR

EQUIV 10 KV

EQUIV 2.5 KV

INSULATION

RESULT

MEASURED CORR

FCTR

20 C

%DF

mA

WATTS

1 UST

2 UST

3 UST

4 UST

5 UST

Da Afghanistan Breshna Sherakat دافغانستان برشنا شرکت


Capacitance and Power Factor Tests

TWO-WINDING TRANSFORMERS

COMPANY : DATE :

TEST LOCATION : TESTED BY :

XFMR IDENT : TYPE OIL :

XFMR SERIAL NO : AIR TEMPERATURE :

XFMR MFR TYPE: KVA : OIL TEMPERATURE :

HIGH KV SGL Y D % RH :

HIGH KV BUSH WEATHER :

LOW KV SGL Y D TERTIARY KV SGL Y D

LOW KV BUSH TERTIARY BUSH

Standard Test :

TES

T

NO

INSULATION

TESTED

TEST

MODE TEST

CONNECTIONS (WINDINGS)

TEST

KV

CAPACITA

NCE (PF)

%DISSIPTION

FACTOR

EQUIV 10 KV

EQUIV 2.5 KV

INS

UL

AT

ION

EN

G

GN

D

GA

R

UST MEAS

URED

20 C

%DF

CORR

FCTR

MA

WATTS

1 CHG+CHL

GST

GND

H L

2 CHG GST H L

3 CHL UST H L

4 CHL ---- TEST 1 MINUS TEST2 ----

5 CLG+CHL GST

GND

L H

6 CLG GST L H

7 CHL UST L H

8 CHL ---- TEST 5 MINUS TEST6 ----

9 CHG ---- CHG MINUS HIGH

BUSH

----

10 CLG ---- CLG MINUS LOW

BUSH

----


نظريه كارشناسي:

………………………………………………………………………………………………………………….

ن

BUSHING TESTS

TEST NO BUSHING

NO.SER.N

HI

KV

11 A UST

12 B UST

13 C UST

14 N UST

LO KV

15 A UST

16 B UST

17 C UST

18 N UST

19 OIL TEST UST

G = GOOD , D = DETERIORATED , I = INVESTIGATE , B = BAD(REMOVE OR RECONDITION)

TESTED BY : CHEKED BY DATE

POINT OF MEASURMENT NO

POINT OF MEASURMENT REMARKS

1/3 OF HEIGHT 2/3 OF HEIGHT 1/3 OF HEIGHT 2/3 OF HEIGHT 1 1

2 2 3 3 4 4


G = GOOD, D = DETERIORATED, I = INVESTIGATE, B = BAD (REMOVE OR

RECONDITION)

TESTED BY: CHEKED BY DATE

نظريه كارشناسي:

………………………………………………………………………………………………………………….

ن


LENGTH: TEST SHEET:

POWER TRANSFORMER

SUBSTATION:

WIDTH: SERIAL NO:

HEIGHT: BAY RATED VOLTAGE:

TEST:

SOUND LEVEL METER

TYPE:

RATED POWER:

RATEDCURRENT:

AMBENT, SOUND, LEVEL: (dB)

AMBENT, SOUND, LEVEL: (dB)

OPERATED CONDATION ONAN

OPERATED CONDATION ONAN


17.0 ANNEXURE – 6

ACCEPTED STANDARDS AND PERMISSIBLE LIMITS

Sl. No. Equipment / test data Permissible limits Reference

1. Transformer (A) Transformer oil

a) BDV - At the time of first charging 60 kV (Gap – 2.5 mm) – Minimum IEC-137 - During O&M 50 kV (Gap – 2.5 mm) – Minimum b) Moisture content - At the time of first charging 15 PPM (Max.)

- During O&M 25 PPM (Max.) -do- c) Resistivity at 90 degree C 0.1-1012 Ohm-CM (Min.) -do- d) Acidity 0.2 mg KOH/gm (Max.) e) IFT at 27 degree C 0.018 N/M (Min.) f) Tan delta at 90 degree C 0.20 (Max.) -do- g) Flash point 126 Deg. C (Min.) -do-

B) Tan delta for bushing at 20 Deg.

C 0.007* IEC – 137

C) Capacitance for bushing + 5% variation

D) IR value for winding 1000 M-Ohm By 5.0/10.0 kV Megger E) Tan delta for windings at 20 Deg.

C 0.007* IEEE/C57.12.90.19

80 F) Contact resistance of bushing

terminal

connectors

10 M. Ohm / Connector NGC.UK

Recommendations

G) Turret Neutral CT ratio errors + 39 2. Circuit Breakers A) Dew point of SF6 gas Dew point values as per Annexure – II B) Dew point of operating air -45 Deg. C at ATM. Pressure C) CB Operating timings 400 kV 220 kV

a) Closing time (Max.) 150 MS 200 MS

b) Trip time (Max.) 25 MS 35 MS

c) Close/trip time, Pole

discrepancy

– Phase to Phase (Max.) 3.33 MS 3.33 MS

- Break to break (Max.) of same

phase

2.5 MS 2.5 MS


Sl. No. Equipment / test data Permissible limits Reference

D) PIR time

BHEL make 12-16 MS Manufacturers

Recommendations

CGL make 8-12 MS ABB make 8-12 MS -do-

NGEF make 8-12 MS M&G make 8-12 MS TELK make 8-12 MS

ABB make (HVDC) 8-12 MS E) Tan delta of grading capacitors 0.007 at 20 Deg. C

F) Capacitance of grading

capacitors

Within + 10% / - 5% of the rated value IEC 358 G) Contact resistance of CB 150 M. Ohm H) Contact resistance of CB

terminal

connector

10 M. Ohm per connector NGC, UK

recommendations I) IR value: 1. Phase – earth 1000 M Ohm (Min.) by 5.0 / 10.0 kV

Megger

2. Across open contacts 1000 M Ohm (Min.) by 5.0/10.0 kV

Megger

3. Control cables 50 M Ohm (Min.) by 0.5 kV Megger J) Pressure switch settings

- SF6 gas pressure switches Within + 0.1 Bar of set value - Operating air pr. Switches Within + 0.1 Bar of set value - Operating oil pr. Switches Within + 1.0 Bar of set value

K) BDV of oil used for MoCB - At the time of filling 40 kV at 2.5 mm Gap (Min.) Mfgs.

Recommendation - During O&M 20 kV at 2.5 mm Gap. (Min.) Mfgs.

Recommendation 3. Current Transformers A) IR value

1. Primary – earth 1000 M – Ohm (Min.) by 5.0/10.0 kV

Megger

2. Secondary – earth 50 M – Ohm (Min.) by 0.5 kV Megger

3. Control cables 50 M-Ohm (Min.) by 0.5 kV Megger B) Tan delta value 0.007* at 20 Deg. C

C) Terminal Connector 10 M-Ohm per connector NGC, UK

Recommendations D) CT ratio errors + 3% - Protection cores + 1% - Metering cores -do-


Sl.

No.

Equipment / test data Permissible limits Reference

4. Capacitive Voltage Transformers

A) Tan Delta 0.007* at 20 Deg. C

B) Capacitance Within +10%/-5% of the rated value

IEC – 358

C) Contact resistance of terminal connector

10 M-Ohm per connector NGC, UK Recommendations

D) IR Value

1. Primary – earth 1000 M – Ohm (Min.) by 5.0/10.0 kV Megger

2. Secondary – earth 50 M – Ohm (Min.) by 0.5 kV Megger

3. Control cables 50 M-Ohm (Min.) by 0.5 kV Megger

E) EMU tank oil parameters

a) BDV (Min.) 30 kV (Gap. –2.5 mm) IS – 1866

b) Moisture content (Max.) 35 ppm -do-

c) Resistivity at 90 Deg. C 0.1 – 1012 Ohm. – CM -do-

d) Acidity 0.5 mg kOH /gm (Max.) -do-

e) IFT at 27 Deg. C 0.018 N/M (Min.) -do-

f) Tan delta at 90 Deg. C 1.0 Max. -do-

g) Flash point 125 Deg. C (Min.) -do-

F) CVT voltage ratio errors + 5% protection cores IEEE/C93.1.1990

+ 0.5% metering cores IEC 186

5. Isolators

A) Contact resistance 300 M-Ohm. (Max.)

B) Contact resistance of terminal connector

10 M – Ohm per connector NGC, UK Recommendations

C) IR value

1. Phase – earth 1000 M – Ohm (Min.) by 5.0/10.0 kV Megger

2. Across open contacts 1000 M – Ohm (Min.) by 5.0/10.0 kV Megger

3. Control cables 50 M-Ohm (Min.) by 0.5 kV Megger

6. Surge Arrester

A) Leakage current 500 M-Amp. (Resistive) Hitachi, Japan Recom.

B) IR value 1000 M-Ohm. (Min.)

7. Miscellaneous

A) Station earth resistance 1.0 Ohm (Max.)

B) Thermovision scanning

Temp. upto 15 Deg. C (above ambient)

Normal


Sl.

No.

Equipment / test data Permissible limits Reference

Temp. above 15-50 Deg. C (above

Alert

ambient)

Temp. above 50 Deg. C (above ambient)

To be immediately attended

C) Terminal connectors – Contact resistance

10 M- Ohm per connector HGC, UK Recommendations

D) IR values

1. All electrical motors 50 M- Ohm (Min.) by 0.5 kV Megger

2. Control cables 50 M- Ohm (Min) by 0.5 kV Megger

3. Lt. Transformers 100 M.- Ohm (Min.) by Megger

4. Lt. Switchgears 100 M – Ohm (Min.) by 0.5 kV Megger

8. Batteries

A) Terminal connector resistance

10 M – Ohm + 20% ANSI / IEEE – 450 1987

B) Specific gravity 1200 + 5 GM/L at 27 Deg. C

*Temperature correction factor for measured values of Tan Delta to be applied which given in

Annexure

Temperature Correction Factor for Tan Delta Measurement

Sl. No. Oil temperature Deg. C Correction factor (K) 1 10 0.8 2 15 0.9 3 20 1.0 4 25 1.12 5 30 1.25 6 35 1.40 7 40 1.55 8 45 1.75

9 50 1.95 10 55 2.18 11 60 2.42 12 65 2.70 13 70 3.00

If Tan Delta of bushing/winding/CVT/CT is measured at oil temperature T Deg. C. Then Tan

Delta at 20 Deg. C shall be as given below:

Tan Delta at 20 Deg. C = Tan Delta at Temp T Deg. C / Factor K.


Dew Point Limits for SF6 Gas in EHV Circuit Breakers

Sl. No. Make of CB Dew point at rated

Pr. Deg. C

Correspondin

g dew point at

Atmo. Pr.

Remarks

1. BHEL

-15 -36 At the time of

commissioning

-7 -29 During O&M

-5 -27 Critical

2. M&G

-- -39 At the time of

commissioning

-32 During O&M

3. CGL


commissioning

-10 -31 During O&M

4. ABB


commissioning

-5 -26 During O&M

5. NGEF


commissioning

-7 -29 During O&M

-5 -27 Critical

Note: Dew point of SF6 gas varies with pressure at which measurement is carried out. So it is to

be ensured that if measurement is done at pressure other than atmospheric pressure, it needs

to be converted to the atmospheric pressure.

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