Dadri stage-1 : ST-1, ST-2 Both tripping

 In case of both station transformer tripping following disturbance will be observed

1. Tripping of DM Xmers

a. all CW pumps will keep running without Temp. & vibration protection. Also motorised

operation of discharge v/v will not be available. (CW pump house MCC will trip)

b. A/C & Filter water Pump-1 (out of 3), will not be available for cooling of compressors &

make up of expansion tank.

c. DM make up Pumps for Stage-I & II will not be available.

d. Lightning will not be available in DM Plant.

2. Tripping of Softening Transformers

a. A/C & Filter water Pump-2 (out of3), will not be available for cooling of compressors &

make up of expansion tank.

b. Fore bay Make up for gas plant & Thermal Stage-I will not be available, due to tripping of

softening Streams.

c. Lightning will not be available in Softening Plant.

3. Tripping of both Miscellaneous Xmer

a. Township Supply & 11KV feeders will trip.

b. If R/L & bore well Pumps are in service, then will trip .

4. Station Service Transformers of all the units will trip

a. GT Cooler Supply from SSS will not be available. Additional Supply will be available from

USS. Changeover to be checked.

b. A/C System & Ventilation MCC will trip

c. Additional Air Compressors will trip.

5. Administrative Building Transformers will Trip. Supply will not be available for Administrative

Building.

6. FOPH transformers will trip, leading to tripping of all pumps.

7. Switchyard Service transformer will trip

a. Lightning of Switchyard & Bay Marshalling Box Supply get Interrupted

8. HVDC Supply Transformer will trip.

9. All Back Up Tie to 6.6KV Unit Buses will not available.

10. All AHP/CHP Transformers for Stage-I will trip.

Actions:

Both Station Transformer Tripping Following Disturbance Will Be Observed & Action Plan

1. Tripping of DM Xmers

a. All CW pumps will keep running without Temp. & vibration protection. Also motorised

operation of discharge v/v will not be available. (CW pump house MCC will trip)

Action: before normalisation of supply ensure Bypassing of Temp. & Vib. Protections

b. A/C & Filter water Pump-1 (out of 3), will not be available for cooling of compressors &

make up of expansion tank.

Action: Isolate cooling water supply of all standby compressors.

c. DM make up Pumps for Stage-I & II will not be available.

Action: 1. Aux. prds from Stage-1 units to be closed and charge from stage-2

i. Close DM make up ,if open in any unit to avoid air ingress into the system.

ii. Aux. prds to be charged from Stage-2 & DM makeup to be taken from CST.

d. Lightning will not be available in DM Plant.

Action: Emergency lights to be used.

2. Tripping of Softening Transformers

a. A/C & Filter water Pump-2 (out of3), will not be available for cooling of compressors &

make up of expansion tank.

Action: Isolate cooling water supply of all standby compressors.

b. Fore bay Make up for gas plant & Thermal Stage-I will not be available, due to tripping of

softening Streams.

Action:

(i) Inform gas plant and if possible reduce load

(ii) Close blow down in gas plant if open.

(iii) Stop service water pumps if running.

c. Lightning will not be available in Softening Plant.

Action: Emergency lights to be used.

3. Tripping of both Miscellaneous Xmer

a. Township Supply & 11KV feeders will trip.

Action: Inform to township elect.

b. If R/L & bore well Pumps are in service, then they will trip.

Action: To be informed to offsite mtc.

4. Station Service Transformers of all the units will trip

a. GT Cooler Supply from SSS will not be available. Additional Supply will be available from

USS.

Action: Changeover of GT cooler to be ensured.

b. A/C System & Ventilation MCC will trip

Action: i) To be informed to offsite mtc.

ii) C&I to be informed. (Arrange alternative cooling for panels)

c. Additional Air Compressors will trip.

Action: AHP to be informed.

5. Administrative Building Transformers will Trip. Supply will not be available for Administrative

Building.

Action: Inform to Elect. Erection

6. FOPH transformers will trip, leading to tripping of all pumps.

Action: HFO temp. to be monitored for any rise and steam to heater to isolated if reqd.

7. Switchyard Service transformer will trip

a. Lightning of Switchyard & Bay Marshalling Box Supply get Interrupted

8. HVDC Supply Transformer will trip.

Action: Inform to HVDC control room.

9. All Back Up Tie to 6.6KV Unit Buses will not available.

10. All AHP/CHP Transformers for Stage-I will trip.

Action: Inform to CHP & AHP control room.