OPERATION MANUAL

OF EHT SUB-STATIONS

APTRANSCO,WARANGAL ZONE

INDEX

Page No.

1 GENERAL INSTRUCTIONS TO SHIFT STAFF 1 – 4

2 INSPECTION OF SWITCH YARD & CONTROL ROOM 5 – 7

3 PROCEDURE FOR ISSUING OF LINE CLEAR 8 –10

GENERAL INSTRUCTIONS:

1. All operating staff at the sub-station should arrive 15mts, Before scheduled

time of taking over, go round the sub-station yard for observing any

abnormalities.

2. Correct the time by the Sub-station watch every day at 06:00 Hrs and

18:00 Hrs by contacting nearest EHT Sub-station.

3. Each operator on duty (AE/ADE in the case of EHT, S.S) should go

through all operators carried out the occurrences recorded in the log Book

ever since he had handed over last and get acquainted with the operating

conditions at the moment of his taking over duty.

4. The operator should be fully conversant with all equipment available at the

sub-station and their operating mechanisms and control circuitry.

5. No operation is so urgent and no emergency is go great that it cannot be

tackled safely.

6. While issuing and taking return of the clears, ensure that the person

receiving the line clear and returning the line clear is the same. Exchange

codes for strict identity.

7. The operator on duty should be conversant with the usual loadings on all

equipment at all hours during the working days, holidays along with

seasonal variations.

8. The type of switchgear and other equipment along with feeding

arrangements at the neighbouring sub-stations should also be studied.

9. A complete layout of the sub-station and its position with interconnections

in the system as a whole should be displayed in the control room and this

should be on the finger tips of every operator.

10. The most important telephone numbers to be contacted during

emergencies, especially in darkness; should be by-hearted.

11. Never allow to be confussed even in the most trying circumstances and the

best praise you can earn is that “He is steady Operator”.

12. Keep Fire fighting equipment handy and never very close to the equipment

to be protected.

13. Switch off yard lighting during evening peak hours for about 10Mts

everyday and go round the yard for observing red-hot jumpers, loose

contacts etc.

14. Ensure that there is no D.C. leakage once in every shift.

15. The following checks are to be made during every shift:

a) Healthy trips for all circuit breakers in service. (This check to be

repeated after every operation along with springs charged indication)

b) Compressed air pressures, gas pressures, hydraulic fluid pressures

and levels, whenever applicable.

c) D.C. battery voltage without charger (by switching off AC to

Charger). Specific gravity and voltage of pilot cells (numbers to be

changed once in a month).

d) D.C. Earth leakage.

e) Oil levels in transformers and bushings and MOCBs.

f) Conditions of silicagel in breathers for transformers and breaker

limbs.

g) Operation of cooler fans, pumps etc., if they are not already running.

h) Three phase balanced loads on every Transformer and feeder (to be

repeated after each re-charge).

i) Test check of oil annunciation lamps.

j) All telephones to be in working order.

k) Emergency lighting gets ‘switched on’ whenever there is power

failure.

16. Whenever a ‘Close’ or ‘Trip’ impulse is given do not hold it in the position

and ensure that it returns to ‘neutral’ position quickly.

17. No unauthorized person should be allowed to enter the Control Room or

Switch yard.

18. The yard lighting should be bright and with no dark spots in the yard.

19. Cable trenches should not have any of their cover removed. Operating

personnel may fall into the trenches during emergencies making things

worse.

20. Never keep your Telephone engaged for more the 3Mts continuously.

Others may be requiring to contact you. Be brief in your conversations.

21. Never disturb fellow operators at neighbouring sub-stations during

emergencies. Provide all help you can when requested.

22. Note that all Air break switches are meant only for no load operations.

Never operate them when they are carrying load.

23. Any set of operations instructions cannot cover all contingencies.

Situations may arise which do not find a place in the operations

instructions. A good and steady operator has to quickly grasp what has

happened; keep cool; and restore normalcy without confusing himself and

others around him. It shall be the responsibility of the operator on duty to

take appropriate action depending on the situation.

24. As there are numerous annunciations and alarms, and should first receive

or ‘accept’ them and analyze the ‘reasons for’ and ‘consequences thereof’

carefully and quickly and take remedial action.

25. Safety of equipment and men is most important and take precedence over

reducing interruption to power supply.

26. A complaints book is to be maintained in the control room which is to be

used only by operator/AE/ADE on duty. All abnormalities and points

requiring the attention of the maintenance engineers should be recorded

with dated signatures. The AE (M) has to record the action taken by him

and affix dated initials.

27. No operating person can leave the work spot till a reliever takes charge and

signs in the register with date and timings in token of having taken over

charge.

28. A set of these operating instructions should be available at the control room

in the custody of the operator/AE/ADE on shift duty and passed on to the

next operator.

29. No umbrellas and sticks should be allowed to be taken inside the switch

yard.

30. All the points mentioned in the ‘APSEB safety Code’ should be followed

scrupulously.

31. Calculate the daily sub-station energy losses.

VISUALINSPECTIONS:

1) Control Room

2) Switch yard

CONTROL ROOM:

1) Ensure the healthy trips of all Control & Relay Panels (33, 132, 220 KV &

400 KV).

2) Check the annunciation on all panels.

3) Check the healthiness of distance and Backup relays (except mechanical

relays).

4) Inspect the cable trenches in the control room.

5) Check the healthiness of communication system.

6) Check the torch light.

7) Bus-Bar protection.

Status of Bus-Bar protection: In service / Out of service

D.C. SYSTEM:

1) Record the pilot cell voltages and specific gravity of battery bank I & II.

2) Record the DC output voltage and load current once in a shift.

3) Visual inspection of battery banks for Electrolyte level and charger.

4) Test the D.C. lamp provided in the control room.

5) Ensure the status of parallel operation of two battery banks if provided.

6) Checking of healthiness of 3Ф AC supply of charger.

7) Checking the DC earth leakage.

8) Checking of DC Distribution.

SWITCH YARK:

1 CIRCUIT BREAKERS:

1) Drain the condensate from all receiver tanks of circuit breakers.

2) Check the important feeder breakers for auto starting of compressors.

3) Check the Oil level in compressors.

4) Observe the red hot on all clamps connected to circuit breakers.

5) Checkup the SF6 gas pressure.

2 POWER TRANSFORMERS:

1) Check the Oil levels in conservator and OLTC tank.

2) Check the condition of silicagel and oil level in breather.

3) Record the Oil level and winding and Oil temperatures.

4) Examine the Oil leakage from Main tank/Bushing/Cooling system etc.

5) Checking for unusual sounds and vibrations from transformer cooling

system.

6) Physical check for over heating if any and terminal connections and

checking for unusual internal noise.

7) Check the three phase balanced load in each phase of Power Transformers.

3 LIGHTING ARRESTORS:

1) Visual inspection of all LA’s in the switchyard daily.

2) Record the surge counter reading daily.

3) Leakage current reading and analysis once in shift.

4 ISOLATORS:

1) Visual inspection of all isolators.

2) Observe sparks if any from male/female contacts.

5 CURRENT TRANSFORMERS & POTENTIAL TRANSFORMER:

1) Visual check of all current and voltage transformers for unusual noise and

dis coloration of terminals.

2) Observe any oil leakage daily.

3) Chattering sounds if any from CVT’s.

6 EARTH PITS:

1) Watering of earth pits.

7 CAPACITOR BANKS:

1) Visual inspection of capacitor cells / RVT for oil leakages.

8 RED-HOT SPOT:

Thoroughly inspect the switchyard during dawn and dask by switch off

yard lighting for red hot spot at clamps, jumpers, bushings etc.

9 MULSIFIER SYSTEM FOR 400KV SS:

Check the mulsifer system and conduct trial on fire fighting engines.

10 DIESEL GENERATOR SET:

Conduct trial run on Diesel generator set if available.

ISSUE OF LINE CLEAR:

Note: All operator are to be carried out only after obtaining concurrence of load

dispatch center Hyderabad for 132 KV, 220 KV & 400 KV (100MVA & 31.5

MVA) Power Transformers.

1 33 KV FEEDERS:

1) Identify the line Clear requisitioned person and purpose.

2) Ascertain the necessity of Line Clear.

3) Hand Trip feeder breaker.

4) Open line isolator.

5) Open bus isolator.

6) Obtain NBFC from SS where back feeding is possible.

7) Earth the line by placing discharge rods.

8) Issue L.C. instructing receiving party to obtain NBFC from SS where back

feeding is possible and also the earth on either side of the work sort before

proceeding with the work.

2 FEEDER BREAKERS:

1) Hand Trip feeder breaker.

2) Open line isolator.

3) Open bus Isolator.

4) Earth the feeder breaker by placing discharging rods.

3 POWER TRANSFORMERS:

1) Hand Trip HV & LV Circuit breakers.

2) Open particular HV & LV AB Switches.

3) Discharge the Power Transformers.

4) Issue L.C.

4 CAPACITOR BANK:

1) Hand Trip controlling circuit breaker.

2) Do not discharge till 15 minutes after tripping capacitors as they retain

charge for some time even when supply is disconnected.

3) Discharge “after 15 minutes”

4) Issue line clear.

132 KV, 220 KV & 400 KV FEEDERS:

1) Identify the line clear requisitioned person and purpose.

2) Ascertain the necessity of line clear.

3) Arrange alternate supply if available to above 132 KV Sub-Station with the

permission of load dispatch centre.

4) Fill in the LC requisition from by L.C. required person.

5) Contact Asst. Divisional Engineer/Maintenance, Divisional

Engineer/TL&SS & Superintending Engineer/TL&SS regarding the line

clear on particular bay (Line/PTR).

6) Contact load dispatch centre for line clear approval / permission.

7) After obtaining load dispatch permission:

a) Hand trip the Circuit Breaker.

b) Contact over phone to hand trip remote end Sub-station feeder breaker.

c) Observe the CVT voltage indication and the indication lamps turned off

on Control and Relay Panels.

d) Ensure the Circuit Breaker opened.

e) Open this line isolator.

f) Open the Bus isolator.

g) Confirm the remote end Sub-station line isolator opened.

h) Obtain No Back Feeding Certificate from remote end Sub-station with

code.

g) Issue line clear.

h) Record the events in the log book.