Analytical approach towards handling DC Failure emergency of 110 MW Units at NTPC Tanda

1. DC FAILURE
4X110 MW NTPC TANDA
RAVI PAL SINGH
OPERATIONS MAIN PLANT GROUP-C

2. LAYOUT
•ELECTRICAL SYSTEMS
•DVR SUPPLY CIRCUITS
•C&I SYSTEMS
•BOILER TRIP
•TURBINE TRIP
•ACTIONS TO BE TAKEN
•HEALTHINESS OF DC SYSTEM

3. ELECTRICAL
SYSTEMS

4. LT SW GR MCC
• LOSS OF 220V DC FOLLOWING WILL RETAIN
THEIR POSITIONS AND BECOME
INOPERATIVE:
– INCOMER BREAKER
– TIE BREAKER
– BUS COUPLER
• HENCE THESE BREAKER NEED TO BE
CLOSED/OPENED MANUALLY FROM PANEL
• CONTROL/PROTECTION OF DRIVES PANEL
BY 230 V AC/110 V AC. HENCE IN CASE OF
220 V DC FAILIURE THESE WILL BE NORMAL.

5. HT SW GR MCC
• LOSS OF 220 V DC FOLLOWING
WILL RETAIN THEIR POSITIONS
AND BECOME INOPERATIVE:
– INCOMER BREAKER
– TIE BREAKER
– BUS COUPLER
– DRIVE MODULE BREAKERS

6. GRP: GENERATOR RELAY
PANEL
• LOSS OF 220 V DC:
– MAIN TRIPPING RELAYS WILL
CONTINUE TO REMAIN IN THEIR
POSITIONS.
– NO PROTECTIONS AND TRIPPING
OF GENERATOR WILL OPERATE.
– ALARM SYSTEM OF UNIT#3 ONLY
(GENERATOR PANELS) WILL BE
LOST.(UNIT#1, 2 AND 4 ALARM
PANEL IS THROUGH 24 V DC).

7. DVR SUPPLY CIRCUITS
AC/DC
CONVERTOR
220 V DC
SELECTORS
DVR
220 V DC
3 ɸ AC

8. DVR SUPPLY CIRCUITS CONTD...
AC/DC
CONVERTOR
220 V DC
SELECTORS
DVR
220 V DC
3 ɸ AC

9. DVR: DIGITAL VOLTAGE
REGULATOR
• LOSS OF 220 V DC WILL CAUSE
NO AFFECT ON PROTECTION
AND OPERATION CONTROL OF
DVR.

10. C&I
SYSTEMS

11. BOILER TRIP
FSSS MFT
ALL PULVERISERS TRIP
ALL FEEDERS TRIP
ALL HAGs CLOSE
HOTV CLOSE
ALL HONVs CLOSE
ALL PA FANS TRIP
TURBINE STOP VALVES CLOSE
24 V DC

12. TURBINE TRIP
TIP
(220 V DC)
SKODA SYSTEM
(24 V DC)
TTR 1 TTR 2
220 V DC
230 V AC
TTS 1
TTS 2
TTS 3
24 V DC CONVERTOR AND MAX
SELECTOR
MFT
GENERATOR
BREAKER OPEN
TURBINE STOP
VALVES CLOSE
TTR 1/2 (220 V DC) :ENERGISE TO TRIP
TTS 2/3 (24 V DC) :DE ENERGISE TO TRIP

13. TURBINE TRIP CONT...
• TIP TURBINE PROTECTIONS:
– CONDENSOR VACUUM VERY LOW
– LUBE OIL PRESSURE VERY LOW
– HRH TEMPERATURE VERY LOW
– AXIAL SHIFT VERY HIGH
– MAIN OIL PRESS VERY LOW
– MOP DISCHARGE PRESSURE VERY LOW
– HP AND MP CASING DIFF TEMP VERY HIGH
– GENERATOR TRIP TO TURBINE TRIP
– BOILER TRIP TO TURBINE TRIP
• SKODA SYSTEM TURBINE PROTECTIONS:
– OVERSPEED
– TRIP OIL LOSS

14. 220 V DC LOST AND 24 V DC
AVAILABLE
• FSSS:
– MFT WILL OPERATE AND FOLLOWING INTERLOCKS WILL
INITIATE:
• ALL PULVERISERS TRIP
• ALL FEEDERS TRIP
• ALL HAGS CLOSE
• HOTV CLOSE
• ALL HONVS CLOSE
• ALL PA FANS TRIP
– TRIP DUE TO LOSS OF 220 V DC ALARM WILL APPEAR.
– HOTV WILL CLOSE (220 V DC DEENERGISE TO CLOSE).
– ALL FEEDERS WILL TRIP.
– HAGS WILL CLOSE.
– HONVS WILL CLOSE.
– BOILER TO TURBINE TRIP WILL INITIATE.
– PULVERISERS WILL NOT TRIP
– PA FANS WILL NOT TRIP

15. 220 V DC LOST AND 24 V DC
AVAILABLE CONT...
• TIP AND SKODA SYSTEM:
– TIP TURBINE PROTECTIONS WILL BECOME
UNAVAILABLE
– SKODA SYSTEM TURBINE PROTECTIONS WILL BE
AVAILABLE
– IN CASE OF TURBINE TRIP BY SKODA SYSTEM
PROTECTIONS TURBINE WILL TRIP BUT TTR WILL NOT
OPERATE AND HENCE GENERATOR TRIP COMMAND
WILL NOT BE INITIATED.
– TIP SYSTEM SUPPLY FAIL ALARM WILL APPEAR
– AC EOP WILL BECOME ON.
– TTR WILL NOT OPERATE AT BOILER TO TURBINE TRIP
TURBINE STOP VALVES WILL NOT CLOSE.
GENERATOR WILL NOT TRIP.

16. 220 V DC AVAILABLE AND 230 V AC
(FOR 24 V DC SKODA SYSTEM) LOST
• FSS:
– MFT AT ALL ELEVATION SCANNER SUPPLY LOSS AND FOLLOWING
INTERLOCKS WILL INITIATE
• ALL PULVERISERS TRIP
• ALL FEEDERS TRIP
• ALL HAGs CLOSE
• HOTV CLOSE
• ALL HONVs CLOSE
• ALL PA FANS TRIP
– ALL ABOVE MENTIONED PROTECTIONS WILL OPERATE.
– BOILER TO TURBIN TRIP WILL INITIATE.
• TIP AND SKODA SYSTEM:
– ALL TIP AND SKODA SYSTEM TURBINE PROTECTIONS WILL BE
AVAILABLE.
– TTR WILL OPERATE AT BOILER TO TURBIN TRIP PROTECTION.
– GENERATOR TRIP COMMAND WILL INITIATE.
– ALL MAX AND OVATION WORKSTATIONS WILL SWITCH OFF (AT 230 V
AC LOSS).
TURBINE STOP VALVES WILL CLOSE.
GENERATOR WILL TRIP.

17. 220 V DC LOST AND
24 V DC LOST
• FSSS:
– HOTV WILL CLOSE AT LOSS OF 220 V DC
– FEEDER MOTORS WILL TRIP.
– HAGS WILL NOT CLOSE.
– HONVS WILL NOT CLOSE. (EXCEPT FOR ELEV GA AND
EF)
– PULVERISERS WILL NOT TRIP
– PA FANS WILL NOT TRIP
– BOILER TO TURBINE TRIP WILL NOT INITIATE.

18. 220 V DC LOST AND
24 V DC LOST CONTD...
• TIP AND SKODA SYSTEM:
– TIP TURBINE PROTECTIONS WILL BECOME
UNAVAILABLE
– SKODA SYSTEM TURBINE PROTECTIONS WILL BE
AVAILABLE
– TURBINE WILL ONLY TRIP IF ANY SKODA SYSTEM
PROTECTIONS ACTS.
– AC EOP WILL BECOME ON.
– TTR WILL NOT OPERATE
– ALL MAX & OVATION WORKSTATIONS WILL BE RUNNING
BUT NO MONITORING AND CONTROL WILL BE
AVAILABLE.
– TIP SYSTEM SUPPLY FAIL ALARM WILL NOT APPEAR
TURBINE STOP VALVES WILL NOT CLOSE.
GENERATOR WILL NOT TRIP.

19. 220 V DC LOST, 24 V DC LOST AND 230 V AC
LOST (FOR 24 V DC TO SKODA SYSTEM)
• FSSS:
– HOTV WILL CLOSE AT LOSS OF 220 V DC
– FEEDER MOTORS WILL TRIP
– HAGS WILL NOT CLOSE.
– HONVS WILL NOT CLOSE.(EXCEPT FOR ELEV GA AND
EF)
– PULVERISERS WILL NOT TRIP
– PA FANS WILL NOT TRIP
– BOILER TO TURBIN TRIP WILL NOT INITIATE.

20. 220 V DC LOST, 24 V DC LOST AND 230 V AC
LOST (24 V DC TO SKODA SYSTEM) CONTD...
• TIP AND SKODA SYSTEM:
– TTS WILL OPERATE AT LOSS OF 24V DC (BOTH
SUPPLIES).
– AC EOP WILL BECOME ON.
– TTR WILL NOT OPERATE.
– TIP SYSTEM SUPPLY FAIL ALARM WILL NOT APPEAR.
– ALL MAX AND OVATION WORKSTATIONS WILL SWITCH
OFF (AT 230 V AC LOSS).
TURBINE STOP VALVES WILL CLOSE.
GENERATOR WILL NOT TRIP.

21. ELECTROMAGNETIC
RELAY PANEL
• LOSS OF 220 V DC
– NRV WILL REMAIN INOPERATIVE
– TO BE CLOSED BY ISOLATING AIR SUPPLY
MANUALLY.

22. ACTIONS TO BE TAKEN
• IMMEDIATELY INFORM TO HOD (OPERATION), HOD
(EMD) & OTHER EMD PERSONALS ABOUT DC
FAILURE.
• PERFORM THE UNDER MENTIONED ACTIVITIES :
– TRIP TURBINE FROM FRONT PEDASTAL EPB, TO
CLOSE THE STOP VALVES.
– TRIP PULVERISERS AND PA FANS MANUALLY
FROM SW GR PANEL EPB.
– TAKE THIS UNIT ON 220KV TRANSFER BUS.
– TRIP THE BUS COUPLER BREAKER FROM MCB
CONTROL PANEL.
– GENERATOR WILL TRIP.
• IN CASE OF S/Y 220 V DC FAILURE TRIP S/Y
BREAKER BY MANUAL EPB PRESENT NEAR THE
BASE OF Y-PHASE BREAKER IN SWITCH YARD.

23. HEALTHINESS OF DC SYSTEM
OK
DCDB
DC EOP STARTER PANEL
DC EOP EPB
DC EOP CONTROL SUPPLY
OVERLOAD RELAY OF DC EOP

24. HEALTHINESS OF DC SYSTEM
NOT OK
DCDB
DC EOP STARTER PANEL
DC EOP EPB
DC EOP CONTROL SUPPLY
OVERLOAD RELAY OF DC EOP

25. VIJAY VERMA
ALEKH SINHA
ABHISHEK CHAUHAN
ASHOK KUMAR YADAV
ANIL KUMAR SRIVASTAVA
ASHISH TRIPATHI
KAMAL SHANKAR UPADHYAY
VISHNU PRATAP SINGH
PRADEEP ARYA
AWN HAIDER RIZVI
MAYANK JAIN
ANKIT KUMAR
SANJEEV KUMAR SINGH
SHYAM SUNDER RAM
SPECIAL THANKS TO

26. THANK YOU