NTPC Ramagundam Station Blackout and Action Plan


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NTPC Ramagundam Station Blackout and Action Plan

  1. 1. NTPC - Ramagundam Station Blackout & Action Plan M. Murali Mohan, Sr. Engineer
  2. 2. Outline of the presentation • Definitions. • Grid Incidents and disturbances. • Probable causes of Blackout. • Stage –I Units – Action plan. • Stage –II Units – Action plan. • Restoration of power supply. • Do’s & Don’ts during black start restoration. • Major – List of power outages.
  3. 3. Transient fault: It is a momentary (a few seconds) loss of power typically caused by a temporary fault on a power line. Power is automatically restored once the fault is cleared. Brownout or Sag: It is a drop in voltage in an electrical power supply. The term brownout comes from the dimming experienced by lighting when the voltage sags. Definitions
  4. 4. Category GI-1 - Tripping of one or more power system elements of the grid like a generator, transmission line, transformer, shunt reactor, series capacitor and Static VAR Compensator (SVC), which requires re-scheduling of generation or load, without total loss of supply at a sub- station or loss of integrity of the grid at 220 KV. Category GI-2 - Tripping of one, or more power system elements of the grid like a generator, transmission line, transformer, shunt reactor, series capacitor and Static VAR Compensator (SVC), which requires re-scheduling of generation or load, without total loss of supply at a sub- station or loss of integrity of the grid at 400 KV and above. Categorization of Grid Incidents (GI)
  5. 5. "Grid Disturbance" is tripping of one or more power system elements of the grid like a generator, transmission line, transformer, shunt reactor, series capacitor and static VAR Compensator (SVC), resulting in total failure of supply at a sub- station or loss of integrity of the grid, at the level of transmission system at 220 KV and above. The power system in different regions is being interconnected and very often an incident initiated in one region can lead to a disturbance in other region also. Grid Disturbance
  6. 6. Category GD-1:- When less than 10% of the, antecedent generation or load in a regional grid is lost. Category GD-2:- When 10% to less than 20% of the antecedent generation or load in a regional grid is lost. Category GD-3:- When 20% to less than 30% of the antecedent generation or load in a regional grid is lost. Category GD-4:- When 30% to less than 40% of the antecedent generation or load in a regional grid is lost. Category GD-5:- When 40% or more of the antecedent generation or load in a regional grid is lost. Categorization of Grid Disturbance (GD)
  7. 7. A blackout refers to the total loss of power to an area and is the most severe form of power outage that can occur. Blackouts which result from or result in power stations tripping are particularly difficult to recover from quickly. Outages may last from a few minutes to a few weeks depending on the nature of the blackout and the configuration of the electrical network. Blackout
  8. 8. Probable Causes of Blackout • Persistent Fault Condition. • Malfunctioning of Protection System. • Violation of Grid Discipline. • Un planned outage Program. • Inadequate Training & Manual Error.
  10. 10. Unit status immediately after black out • Boiler, Turbine and Generator in tripped condition. • Failure of all HT and LT supply. • All equipment in tripped condition. • Loss of normal lighting and DC lighting is available. • 220 V DC supply is available. • Drum level very low.
  11. 11. Equipment at risk All bearings of Turbine and Generator Needs proper Lubrication. Generator Needs Seal oil at the ends of casing. Air-pre Heaters Basket needs cooling. LP turbine diaphragm Entry of steam into the condenser to be restricted. Flame Scanners Needs sufficient cooling. Turbine Rotor needs uniform cooling.
  12. 12. Action Plan - Starting of DC equipment DC Lube oil pump: Ensure that DC lube oil pump has started on auto and check lube oil pressure at Turbine front pedestal and Amps in UCB. In case DC lube oil pump does not take start on auto the following actions have to be ensured. Start DC lube oil pump (EOP) from LOCAL. If still, DC lube oil pump does not start, TGOP has to be started on resumption of supply from DG set. If there is delay in starting of DG set or resumption of station supply, then kill the vacuum by opening the Vacuum breaker valve manually. Generally vacuum is killed at speed below 2000 rpm. After resumption of supply, if DC lube oil pump (EOP) is still running, change over to Auxiliary oil pump (AOP) when normal supply is restored or to TGOP when EMCC supply is restored.
  13. 13. Seal oil pump: Ensure that DC Seal Oil Pump had started on auto. In case DCSOP does not take start on auto the following actions have to be ensured. Start DCSOP from LOCAL. If still DCSOP does not take start, confirm the running of Turbine EOP. If Turbine DC LOP is running, then oil pressure of 1.75 ksc will be obtained in the oil header. So, taking the seal oil to H2 DP as 0.35 ksc, H2 pressure at 1.4 ksc can be maintained in the generator. Mean while, problem in DC seal oil pump system has to be found. If still DC seal oil pump does not start, AC seal oil pump has to be started from control room after resumption of supply. On availability of AC supply, changeover DC seal oil pump to AC seal oil pump, if DC seal oil pump is still running. Imp Note: In case of DCSOP or ACSOP does not start, then running of turbine lube oil pump (either EOP or TGOP) to be checked. If either of EOP and TGOP doesn't start, then H2 purging by CO2 should be started.
  14. 14. Ensure that DG set had started on auto. If not, it has to be started by Push Button provided in CSSAEP of UCB-1. Even then if DG set does not started on auto, then it has to be started locally from DG set room. Starting DG set locally, a Yellow lamp indication will be available on generator desk indicating that DG set had started. While starting DG set if cranking is observed, start the DG set again and again. After 3 starts DG set will pick up. If it does not take start try another DG set by following the same procedure. Close incoming breaker to charge EMCC from DGMCC after ensuring its tie breaker from LT bus-A is OFF. If the breaker does not close from control panel, it should be closed from EMCC located at zero meter elevation. Charging ‘EMCC’ Bus
  15. 15. After charging EMCC ensure that TGOP is in service (Stop DC EOP after rotor is put on Turning Gear). Unit DCDB Main charger is in service. APH A & B Aux drives are in service. Scanner Air fan is in service. Keep MOT Vapor Extraction fan-B in service.
  16. 16. If LT supply is restored, then all electrically operated valves should be closed from control room. Ensure that diesel fire fighting pump is in service. Start APH motor on availability of supply from DG set. Otherwise try Air motor. If air motor is not running, open the by-pass manual valve of solenoid valve. If resumption of supply from DG set is delayed then position of APH rotor is to be changed by rotating by hand frequently till supply is resumed from DG set or station supply. At 500 rpm speed of Turbine, start Turning Gear motor and engage barring gear when turbine comes to rest. In case DG set does not start and power supply is not restored from Station transformer, then hand turning of turbine is required for uniform cooling of rotor. The rotor should be rotated by handle intermittently till supply is restored. Start the scanner air fan after resumption of supply and open its discharge damper manually.
  17. 17. In order to restrict the entry of Steam into the condenser, the following activities are to be carried out Close Boiler stop valves manually. Close all drains to condenser. Close all Extractions. Close Main Ejector steam valves and break the vacuum by opening Vacuum breaker at 2000 rpm of turbine speed. Close Seal steam header valve from MS line and also ensure Aux. Steam supply to seals is isolated when vacuum drops below 100 mm Hg. ESV, CRV and CV closing to be ensured from control room. NRVs of extraction block valve to be closed. CRH and HRH drains to be closed manually.
  18. 18. Emergency Equipment location Equipment MCC Fuse rating 1. Turning Gear Motor EMCC-3.4 63 A 2. TGOP EMCC-4.4 63 A 3. APH Aux drive-A EMCC-5.4 32 A 4. APH Aux drive-B EMCC-6.4 32 A 5. Vapor Extraction Fan EMCC-3.3 32 A 6. Scanner Air Fan EMCC-2.4 32 A 7. Unit DCDB Main Charger EMCC-4.2 160 A 8. DC Seal Oil Pump 220 V DCDB 60 A 9. EOP Starter panel-1 ---
  19. 19. Unit status after blackout Boiler, Turbine and Generator in tripped condition. All HT and LT supplies failed. All equipments in tripped condition. 220V DC supply is available (self or tied from other units). Loss of normal lighting supply. Drum level very low.
  20. 20. Action plan – Starting of DC Equipments Ensure the starting of the following equipments, in auto or manual. DC lighting. Main Turbine DC LOP. DC seal oil pump. TDBFP-A DCLOP. TDBFP–B DCLOP. DC seal Water pump. DC scanner fan. DC JOP, when the Turbine speed comes below 510 rpm.
  21. 21. Action plan – other emergency activities Start Air Pre heater Air motors if Air is available. If not, Air pre heaters have to be rotated manually with the help of RM. Open Emergency cooling Water to CC pumps. Retract ALCS sector plates to normal if they are in advanced condition. Ensure starting of DG set, in auto or manual. After starting DG set and attaining voltage, charge EMCC by closing incomer DG. (Tie to other units should be in open condition for closing this incomer) If DG set is not starting, charge EMCC by closing the tie with other unit, where DG set has started. (Unit - 5 & 6 case). Ensure that TVDC and BVDC are charged from EMCC.
  22. 22. Prevent entry of steam into the condenser. LP Turbine diaphragm will rupture if steam entry into the condenser is not prevented as CW pumps and vacuum pumps are not in service. For this: Close boiler stop valves. Take SLC drains into manual and close all MAL drains. Close CRH steam block valves to TDBFP. Close all TDBFP steam line drains (extraction steam, aux steam, and CRH steam line drains). Close D/A overflow line manual isolate valves. Close CRH steam to deaerator control valve. Ensure that vacuum breaker has opened. Open HRH ERV’S for depressurizing Reheater. After closing boiler stop valves, open atmospheric drains of MS, HRH & CRH lines.
  23. 23. START OF EMERGENCY AC EQUIPMENTS Start AOP-2 and stop DCEOP of main Turbine. Ensure the opening of main Turbine turning gear valve either on interlock or in manual when the Turbine speed becomes less than 210 rpm. Start JOP 2 and stop DCJOP of main Turbine. Normalize seal oil system by starting Air Side SOP-1 and H2 SOP. Stop DCSOP. If no SOP is in service, H2 has to be purged out with CO2. Put TDBFPS on tuning gear after starting AOP and JOP. Stop TDBFP DCEOP’S. Action plan – other emergency activities
  24. 24. Stop DC seal Water pump. Start AC scanner fan and stop DC scanner fan. Start Secondary and primary air preheater auxiliary motor, if they are free to rotate (take clearance from Local. Ensure the normalization of Emergency lighting and switch off DC lighting wherever not required. Ensure that 220V DC and +24/-24V battery chargers are feeding normally. Ensure that passenger lift supply is restored.
  25. 25. Restoration of Station Power
  26. 26. Southern Region – Geography ANDHRA PRADESH TAMIL NADU KARNATAKA KERALA POPULATION :- 27 CRORES (21.8% OF INDIA) AREA :- 651 (‘000 SQ KM) (19.3% OF INDIA) INSTALLED CAPACITY:- 50,164 MW (28.89%) SEA COAST :- AROUND 4000 KM
  29. 29. Andhra Pradesh Andhrapradesh has been divided into three subsystems. • SUB SYSTEM–1: Comprises of major thermal stations viz. VTPS, Lanco, RYTPS, SEPL & MEPL and the important load centers like Hyderabad, Vijayawada, Kurnool, Machilipatnam & Nellore along with Black Start facilities at Srisailem & N’Sagar, Jurala (if Water Available) Hydro stations. • SUB SYSTEM–2: Comprises of Ramagundam Thermal power station, Kakatiya and the important load centers like Ramagundam loads & Western Region with No Black Start facilities in the Sub system. • SUB SYSTEM–3: Comprises of major thermal stations viz. KTPS, Simhadri, & Gas Stations viz Jegrupadu, VGTS, Spectrum, Gowthami, Konaseema, GMR Vemagiri, Jegrupadu Extn and BSES and the important load centers like Vizag, Kakinada along with Black Start facilities at U’Sileru, L’Sileru Hydro stations. • Synchronisation of Sub Systems: Once the individual subsystems are built to a stable level, the systems are synchronized with each other. The synchronization of subsystems will be done at the generating stations, preferably.
  30. 30. Subsystem-1 Subsystem-3 Subsystem-2 Startup of AP System Start up of this system is from the N’SAGAR(1*110+7*100), SRISAILAM RB (7*110) AND SRISAILAM LB (150*6) Objective:- Start up of VTPS (6*210), Muddanur(4*210) and lanco. Extend to Hyderabad City and Traction RSTPS Startup would be availed from WR with Bhadrawathi on A/C Bypass mode. Units would be started up and loads would be cut in to gradually build up the island. Synch with rest of AP after stabilisation Startup of this subsystem is through Lower Sileru (4*115), Upper SIleru(4*60) Objective- Startup supply to Simhadri, KTS and Gas units.
  31. 31. Important connections of AP System WITH OTHER REGIONS With Western Region: HVDC Back to Back Station at Chandrapur (Bhadrawathi) with A/C by-pass arrangement and 400kV Chandrapur – Ramagundam – D/C. With Eastern Region: HVDC Back to Back Station at Gajuwaka with A/C by-pass arrangement and 400kV Jeypore – Gajuwaka – D/C. 220kV Barasur – Lower Sileru and 220kV Balimela – Upper Sileru. Lines are not in use.
  32. 32. WITHIN THE REGION A. With Karnataka 400kV S/C Gooty – Hoody 400kV S/C Gooty – Neelamangala 400kV D/C Gooty – Raichur 400kV S/C Mehaboobnagar – Raichur 400kV S/C Kadapa – Kolar 220kV S/C Gooty – Regulapadu -Alipur (Bellary) 220kV S/C Tandur – Sedam B. With Tamil Nadu 400kV S/C Chittoor – Sriperumpudur 400kV D/C Nellore – Alamathy 220kV S/C Sulurpet – Gummidipoondi 220kV S/C Chittoor - Thiruvalam S/C = Single Circuit, D/C = Double Circuit
  33. 33. Important Criteria for deciding Restoration approach in AP System (Region blackout). SURVIVAL of Ramagundam islanding scheme is the most important criteria in deciding restoration approach of AP system during total black out condition. If the Ramagundam islanding scheme successfully survives, then the surviving island has to be synchronized with rest of AP at the earliest possible with increase in hydro generation along with matching loads in other subsystems of AP. Islanding scheme setting is at: 47.6Hz frequency with time delay of 200msec. (Islanding scheme successfully tested on 11.12.2010)
  34. 34. NTPC – Ramagundam Islanding scheme UFR Relay 1 UFR Relay 2 & VAJHM Trip Relays 186A, B,C,D Trip 400kV RDM - NS- 1 & Trip 400kV RDM - WGL “186A” (252, 352, 452 Breakers) Trip 400kV RDM - NS – 2 “186B” (852, 952 Breakers) Trip 400kV RDM – DPL “186C” (3852 & 4052 Breakers) Under frequency Relays : Make : ABB, Model: SPAF VAJHM Tripping Relays : Make : AREVA, Model VAJHM 42 Operating Philosophy: At a frequency of 47.6 Hz with a time delay of 200msec, the UFR relays will Initiate the lockout relays. This results in tripping of the six nos of 400kV lines and forms an island comprising of NTPC-RDM, Hyderabad city and 5 nos of Local ICTs with a connected load of approx. 2000 MW. Trip 400kV RDM - CHP- 1 & 2 “186D” (1A52, 1B52 & 1C52 Breakers)
  35. 35. Incase, the Ramagundam islanding scheme could not survive, then, this subsystem can avail start up power supply from the following sources. 1) From Western Region through HVDC Back to Back station at Bhadrawati (Chandrapur) with A/C bypass arrangement and 400kV Chandrapur- Ramagundam line. 2) From Subsystem - 1 by availing self-starting facility of hydro units at Nagarjuna sagar/ Srisailam.
  36. 36. Sub-Station Synchronizing Facility Thermal Load 1) From Western Region:- Preferred Method N’Sagar Ramagundam 400 kV / 33 kV Tie Transformer at Ramagundam Hyderabad 2) From Sub-system - 1:- SUB-SYSTEM - I Warangal Bhupalapalli Bhupalapalli Ramagundam 400 kV / 33 kV Tie Transformer at Ramagundam WESTERN REGION BHADRAVATHI HVDC BYPASSED Warangal
  37. 37. Ensure that line breakers of 400 kV Ramagundam - Chandrapur lines I and II are opened at Ramagundam & Chandrapur end. Ensure that HVDC system is isolated from both West and South Bus. Ensure that all filter Isolators are opened. Ensure that West Bus 2 is in energized condition. Close A/C bypass link isolators. Close breaker of Ramagundam line I or II in consultation with Ramagundam. This would extend start up power to Ramagundam. In case the bus voltage at Ramagundam is very high, request AP to avail some loads radially to control the voltage. Extend startup supply to Kakatiya via 400kv Ramagundam – Warangal – Bhoopalpally alternately via 220kv Malayalapalli - 220kv Nagaram – 220kv Warrangal - 400kv Warangal. Ramagundam would build up the generation gradually with load through ICTs at Ramagundam. Procedure for taking startup supply to RDM from Western Region through Chandrapur.
  38. 38. Synchronizing of Subsystem – 2 (Ramagundam & Kakatiya) with rest of A.P & Opening of AC By-Pass Link with WR • After the AP system develops into a stable island of about 2500 to 3000MW, A/C inter connection with WR will be opened out only after reducing the flow on the interconnection to a minimum value by adjusting the load generation balance in AP Subsystem. • Load in AP system would be regulated to bring down the flow on 400kV Ramagundam - Chandrapur line as minimum as possible (10 to 20MW) by regulating generation at N’sagar, Srisailam and Chandrapur (WR). • NTPC would then manually open 400 kV Ramagundam- Chandrapur line to separate part SR system from WR system in consultation with SRLDC / Bhadrawati.
  39. 39. AC Bypass Switch
  40. 40. WESTERN REGIONAL GRID HVDC STATION BHADRAWATHI AC BYPASS MODE 500 OR 200 MW UNIT ANDHRA PRADESH / SOUTHERN GRID T O N S R T O W G L 1. Bhadravathi to bypass pole and charge RDM-CHPR one circuit. 2. RDM to avail start up supply for auxiliaries on any bus. STEP 1 LOAD WESTERN REGIONAL GRID HVDC STATION BHADRAWATHI 500 OR 200 MW UNIT ANDHRA PRADESH / SOUTHERN GRID T O H Y D T O N S R T O W G L 1. Normalize ICT and put loads corresponding to generation and import constraints. STEP 2 LOAD T O H Y D AC BYPASS MODE
  41. 41. WESTERN REGIONAL GRID HVDC STATION BHADRAWATHI AC BYPASS MODE 500 OR 200 MW UNIT ANDHRA PRADESH / SOUTHERN GRID T O H Y D T O N S R T O W G L 1. After AP system becomes stable with at least 2500- 3000 MW generation, frequencies of AP and WR system are matched and either Khammam or N'Sagar line is closed. WR and AP are now one system. STEP 3 LOAD WESTERN REGIONAL GRID HVDC STATION BHADRAWATHI 500 OR 200 MW UNIT ANDHRA PRADESH / SOUTHERN GRID T O H Y D T O N S R T O W G L 1. After flow on RDM-CHPR line is brought down to less than 50 MW or so Chandrapur line is opened thus moving RDM to SR side. STEP 4 LOAD SYNCH
  42. 42. During Blackout of Sub system 2 alone The startup power can be extended from the following From KTPS 1st and 2nd stage through 132 kV KTPS – Warangal - Malayalapalli - Ramagundam. From 220kV Nagarjuna Sagar – Chellakurthi – Miryalguda – Khammam – Warangal – Malyalapalli - Ramagundam lines. From KTPS 5th Stage through - 220 kV KTPS- Budidampadu (Khammam 400 kV) - 400 kV Khammam –Ramagundam line From VTPS through - 400 kV Vijayawada-Khammam-Ramagundam From Srisailam, N’sagar Hydro complex through - 220 kV N’sagar – Tallapalli – 400 kV N’sagar-Ramagundam
  43. 43. Mock drill conducted on 20.09.2010 Black out start up mock drill successfully completed (bypassing HVDC Bhadrawathi and extending supply to Southern Region after availing assistance from Western Region). However extending actual power supply to the auxiliaries through Tie Transformer-1 could not be carried out due to prevailing “HIGH VOLTAGE” conditions in the link. “This activity has to be carried out once in a year as per CERC Regulations to ensure the supply”.
  44. 44. RAMAGUNDAM 400KV BUSRAMAGUNDAM 400KV BUS--I DETAILSI DETAILS Colony-1 WTPTr-2 CHPAugTr-1 CWTr-1 Tietosec-F StationTr-1 StationTr-6 SwydserTr-1 Colony-3 Tie Transformer-1 33 KV SECTION-A 400 KV BUS-I G-2 N. SAGAR-I HYD-I AUTO-IICHNDRAPUR-II GT-II GT-IV TIE BREAKER
  45. 45. Readily have the Single Line Diagrams of the Station. Readily have the Black Start Restoration Scheme Diagrams. Readily have the outage details. Communicate the Concerned Station in-charge and Load Despatch Centre immediately. Assign the Responsibilities to the available staff clearly. Follow the instruction of Load Despatch Centre in full. Do not keep all the communication channels busy simultaneously. Do not entertain external enquiries till the restoration complete. Do not indulge in argument during restoration. Do not Panic. Do’s & Don’ts during Black Start Restoration
  46. 46. Largest - List of Power outages USA30 millionsUSA, Canada9-Nov-196507 Indonesia100 millionsIndonesia18-Aug -200502 06 05 04 03 01 S. No. Italy55 millionsItaly, Switzerland, Austria, Slovenia, Croatia 28-Sep-2003 USA55 millionsUSA, Canada14-15-Aug-2003 Brazil87 millionsBrazil, Paraguay10-11-Nov-2009 Southern Brazil 97 millionsBrazil11-March-1999 India670 millionsIndia30-31 Jul-2012 LocationPopulation affected Country affectedDate Courtesy: Wikipedia
  47. 47. Thank you Reference: SRLDC Documents