What is SOFA?

 ### SOFA in Power Plants

In the context of power plants—particularly coal-fired thermal power plants—**SOFA** stands for **Separated Overfire Air** (also sometimes written as Separated Over Fire Air). This is a combustion technology used in boiler systems to reduce nitrogen oxide (NOx) emissions, which are harmful pollutants formed during high-temperature fuel combustion.

Stopping one PA Fan

1 Reduce the load to 300 MW & then remove from CMC
2 Keep 4 consecutive Mills in service. If required , take oil guns in service

Check List (Light-Up)

Unit:

Date:

Switchyard Breaker arrangement: Rihand

Stage-I

GT#1  à 1-52  Main (GCB to Bus Bar-1) à 2-52 (Tie-GCB to bus Bar-2) à 3-52(IBT-1 i/c)

GT#2 à 7-52Main (GCB to Bus Bar-2) à 8-52((Tie-GCB to bus Bar-1)

Bus bar-1 à 4-52 (H1) à 5-52(Tie H1-S2) à 6-52(S2) à Bus Bar-2

Bus bar-2 à 10-52 (S1) à 11-52(Tie S1-H2) à 12-52(H2) à Bus Bar-1

Bus-1  ß13-52(Bus-coupler-1) à Bus-3

Bus-2  ß14-52(Bus-coupler-2) à Bus-4

IBT Outage

Consequences on Stage-2 ( Station Transformer Tripped)

Ø  132 KV Switchyard dead results in tripping of -Station Transformers, Construction Transformer, Misc Transformer

Ø  All colony power( Lighting,Water supply) will get interrupted

Ø  Power Supply to DM Plant, HFO Pump house, PTCW Pump house, Offsite Board, ADPH,

Ø  Following Board will get dead:

§  OBA,OBB,OBC,OBD (11 KV station Board)

§  OCA,OCB (3.3 KV Station aux Board), ADPH MCC, CHP Transformers

§  DMPT, CWST, WTPT,BTST,ODA,ODB(Station Service), ODC(FW Pump House),ODD ( Offsite ): 3.3 KV

§  OQA,OQB(St. Serv),3SA,4SA(Air Washer MCC),3TA,4TA(Unit Ventilation MCC),OTA(HVAC ) : 415 V

§  OSA(SW MCC), OTB(Serv Bldg Ventilation MCC), FOPH : 415 V

Emergency Instructions:220 V DC Failure

220 V DC Failure

Unit condition

Ø  DCDB section-1 & 2 under voltage alarm in LVS-5

Ø  All HT/LT Breakers Indication Becomes Bad

Ø  Boiler will Trip on MFT ( after 2 Sec)

Ø  Turbine will Trip on MFT

Ø  Generator will not Trip as GCB Protection will not act

Ø  Generator will run as Synchronous Motor

3.3 KV bus charging

3.3 KV bus charging from bus coupler/ Normal Incomer

A:    Bus charging from bus coupler: - (Only done from Electrical control panel at UCB)

1. Select 3.3 KV bus coupler breaker
2. Select I/C-A or I/C-B in trip selection (Select the incomer that we want to trip).
3. Put Key (Synch selection) in position “1 - check “.
4. Switch ON synchroscope by putting switch in position “2”.
5. If IN PHASE lamp (green LED) glows. Go to step-6. If OUT OF PHASE (RED LED) Glows
check for voltage/frequency difference & inform to EMD.
6. Close Circuit breaker (control switch position “2”). Bus coupler breaker will close &
incomer (which selected in trip selection) will trip.
7. Change over completed, Switch OFF synchroscope & put key in “0 – OFF” position.
8. Deselect bus coupler .
9. Reset all by pressing Control reset.

B: Bus charging from normal incomer :- (Only done from Electrical control panel at UCB)

1. Select 3.3kv Incomer breaker ( incomer-1/ incomer-2)
2. Select Bus coupler in trip selection.
3. Put Key (synch selection) in position “1 - check “.
4. Switch ON synchroscope by putting switch in position “2”.
5. If IN PHASE lamp (green LED) glows. Go to step-6. If OUT OF PHASE (RED LED) Glows
check for voltage/frequency difference & informed to EMD.
6. Close Circuit breaker (control switch position “2”). Incomer will close & Bus coupler
breaker will trip.
7. Change over completed, Switch OFF synchroscope & put key in “0 – OFF” position.
8. Deselect incomer breaker ( incomer-1/incomer-2).

9. Reset all by pressing Control reset.