24V DC Fail

24V DC Fail

EMERGENCY INSTRUCTIONS

Identification of the Emergency

• 1. Boiler trips on loss of 24V DC Supply protection. Turbine trips on boiler trip protection followed by generator.
• 2. All controls operating on DDC becomes inoperative

Response in Handling the Emergency
Action Responsibility Remarks

• 1 Confirm tripping of turbine. In local governing rack the trip oil pressure should be ‘0’ otherwise trip turbine from emergency trip lever in governing rack. Trip TD BFPs from local governing rack UCE & TG Engineer
• 2 Confirm tripping of generator i.e. opening of GCB. If GCB has not opened, open 952 and 852 breakers from switchyard UCE 
• 3 Confirm starting of AOP (local) on turbine trip, otherwise start EOP from local for both main and TDBFP turbines. UCE & TG Operator 
• 4 Confirm running of ACSOP(local) if no seal oil pump is running immediately start DCSOP from local UCE & TG Operator 
• 5 Confirm AC scanner fan is in service(local),else start DC scanner fan from starter panel in LT switch gear room in TG floor Boiler Engr & Operator 
• 6 As controls are in operative do the following operations 
• A Stop FD fan, ID fan and BCW pumps (from local push buttons or switch gear). Close boiler stop valves Boiler Engr & Operator 
• B Stop MD BFP (from local push buttons or switch gear), if it was in service as D/A and drum levels cannot be monitored. TG Engr. & Operator 
• C Depressurise MS, CRH and HRH lines, Kill vacuum. Open atmospheric drains of MS,CRH and HRH lines TG Engr & Operator 
• D Stop CEPs and isolate make up to hot well since hot well level indication is not there TG Engr & Operator 
• E At 540 rpm turbine speed start DC JOP from local, and at 210 rpm open turning gear valve manually UCE,TG Engr. & Operator 
• F Continue to run DMCW pumps. Monitor and maintain DMCW tank level from local Boiler Engr & Operator

HP bypass valve starts opening : Emergency

Emergency Handling by Opn Gr-II:Unit in CMC

Unit Status before 

Unit Load : 350 MW 
Coal Flow : 260 TPH
Mills I/S : BDEFG 
Oil Guns I/S : Nil

INCIDENT:

• 12:59:00 HP bypass valve BP-2 started opening & got opened up to 98% & at 12:59:31 BP-1 also started opening & opened up to 98%.

ACTION TAKEN:

• Machine came in CMC- pressure control mode (earlier in CMC-load control mode) due to pressure deviation and load came down to 174MW. Machine taken in TF mode pressure control after reducing throttle pressure
• HP bypass OSU pump buttons in vertical panel acknowledged, OSU pump-2 took start, but still the valves stayed in open condition.
• AB elevation oil gun taken in service and feeder F unloaded to min followed by oil support at CD elevation for flame stability.
• MDBFP kept in service and TDBFP- A hand tripped to maintain drum level.
• Further as Drum Level was still increasing TDBFP-B also hand tripped due to which runback acted and tripped mill G.
• MDBFP suction flow maintaining high and drum level also increasing rapidly so drum level control taken in manual.
• Air flow master taken in manual and total air flow increased from 950 to 1050 tph
• HP bypass BP-1 and BP-2 closed from local and unit stabilized. Drum level kept in auto at 280MW with MDBFP and one TDBFP in auto.

ANALYSIS:

• At 12:59 HP bypass valve BP-2 opened up to 98% while demand was 0 followed by opening of BP-1 valve also up to 98% . 
• Load came down to 174 MW from 350 MW and drum level was fluctuating. For controlling the drum level MDBFP taken in service and later both TDBFPs hand tripped one by one.
• It was observed that HP bypass OSU pump-2 took start and run time exceeded alarm came followed by opening of HP bypass valves. HP bypass OSU pump-1 also took start but from MMI close command for BP valves not executing. OSU pump faults acknowledged from vertical panel and OSU pump-2 took start but still valve were full open.. Local checked no oil leakage observed .Both bypass valves closed from local

OBSERVATIONS :

• HP bypass valves did not trip on downstream temperature high.
• OSU pumps operation was normal till 12:56.
• Drum level variation: +ve 138mm & -ve 320mm.
• TDBFP A ESV not getting opened after resetting.
• It is learnt that while doing cleaning by C&I mtc in the HP Bypass area (No PTW/LWC issued) inadvertently BP2 fast opening accumulator valve was opened which was earlier kept closed due to suspected drifting in BP2 valve

SUGGESTION :

• Any PM or Mtc work in HP Bypass valves area should be properly intimated to Operation by taking PTW/LWC.
• HP Bypass valve area being the most vulnerable, any maintenance/operation work should be carried out under proper supervision by respective executives.

NOTE:

• No PTW/LWC was issued from operation related to HP bypass on dtd: 06.09.2016 i.e.; the day 

CHECK LIST FOR AIR INGRESS IN CONDENSER

CHECK LIST FOR AIR INGRESS IN CONDENSER

Sl No	Description	Location	Checked status
1.	Valve gland sealing water pressure (UCB).	UCB
2.	Gland steam pressure & temp	UCB
3.	Vacuum breaker Valve	17 mtr
4.	HPT / IPT / LPT glands	17 mtr
5.	TDBFP-A  gland	17 mtr
6.	TDBFP-B  gland	17 mtr
7.	LPT Diaphragm	17 mtr
8.	TDBFP-A  Diaphragm	17 mtr
9.	TDBFP-B  Diaphragm	17 mtr
10.	LPT Manholes  ( both side )	17 mtr
11.	TDBFP-A  exhaust valve	8.5 mtr
12.	TDBFP-B  exhaust valve	8.5 mtr
13.	LPH-2/3 vents to condenser	8.5 mtr
14.	HPHs vents to condenser	8.5 mtr
15.	LPH-2 shell side vent line valves & flanges	8.5 mtr
16.	LPH-3 shell side vent line valves & flanges	8.5 mtr
17.	Vaccum p/p-1/ 2 suction line manual valve glands at condenser	8.5 mtr
18.	Condenser Man holes (8.5 mtr both sides)	8.5 mtr
19.	LPH-1 Emergency drip to condenser( LCV-0700)	0 mtr
20.	LP Header-2 drip line ( LCR-0757B-HD4-022)	0 mtr
21.	LP Header-3 drip line to condenser	0 mtr
22.	HPH-5A/5B emergency drip to condenser	0 mtr
23.	Drainn valves connected to TFT-1/2	0 mtr
24.	TFT-1/2 header connections	0 mtr
25.	Condenser level transmitters.	0 mtr
26.	Condenser level Switches.	0 mtr
27.	Vaccum pump-1, 2 suction line manual and motorised valve glands and flanges.	0 mtr
28.	Deaerator  to condenser valve glands (Co-I5I)	0 mtr
29.	CEP recirculation lines-A, B, C valve glands.&vents and drains	0 mtr
30.	LPH-1 normal drip top condenser valves.	0 mtr
31.	CEP – A/B/C glands	(- m  mtr)
32.	CEP – A/B/C   suction strainers & vents	(- m  mtr)
33.	CEP – A/B/C suction line drains	(- m  mtr)
34.	Hotwell drain line passing	(- m  mtr)
35.	CEP suction and discharge line flanges	(- m  mtr)
36.
37.

ATRS Rolling: 500 MW

CHECKLIST FOR ROLLING THROUGH ATRS (HOT start up)

PRESENT CONDITION:

• M/C on barring
• MS temp :  >480 Deg /Pressure : 90 ksc
• HRH temp : >460 Deg /pressure : 9 ksc
• Lube oil temperature : 55 deg
• CF temperature : > 50 deg
• PW/CG/CF temperature control valves in auto
• Speed controller active

CHECK LIST

• Turbine in Reset condition ( Trip oil pressure : > 8 ksc)
• Starting device:  0% / Speeder gear : 99%
• HP & IP CVs showing : 0%
• Turbine throttle pressure set point 0 ksc
• MAL 11 & MAL 12 in open condition/ all MAL drains manual valve open /SLC drains ON
• Load contol On / Limit pressure mode selected
• MS 109 / MS 110 & HRH 105/106 valves open feedback
• Load refrence (PR) set point to be 70 MW/ PRmax 120 MW
• Trim device to be made off
• Check TSC margins &TSC influence on
• Plunger coil not off
• check X1 &X2 criteria for opening of STOP valves
• Temperature curves X3,X4& X5 for control valve opening and upto 360 rpm
• Reset all relays in the GRP panel
• Lube oil temperature set point to be kept at 45 deg.

PROCEDURE OF STARTING ATRS

• Check all start permissives are coming
• Ensure normal mode is displayed in ATRS mimic

Raising speed upto 360 RPM

• Select A/M from SGC turbine tile
• To start the programme press startup from the tile
• Check for closing of MAL 11 & MAL 12 in STEP 3
• Observe starting device raise command in STEP no 5 and stop valve opening( SD > 42%)
• Observe in STEP -8 that MAL 11 & 12 control goes to auto
• Step no.9 TRACKING DEVICE gets ON followed by opening of IP stop valves ( SD >56%)
• Check that in STEP -11 MAL 11& 12 opens in manual mode
• Check in step no-12 turbine speed set point increasing upto 360 RPM and accordingly the actual speed .
• Hold the programme in step no 12 if required (criteria not satisfied) by pressing A/M from SGC turbine tile.
• Ensure closing of barring valve at 240 rpm otherwise close it manually.Mot level will increase
• Soaking time for Hot start up 180 sec
• Check for closing of MAL 11 & 12 .

RAISING SPEED UPTO 3000 RPM

• Check TSC margin >30
• Check X6 criteria is satisfied (Ensure opening of MAL 11& 12 in manual )
• Check speed margin (600 mw/min)
• Sufficient margin in HP bypass
• Switch on the ATRS programme (Auto) & start
• Speed set point will increase upto 3000 rpm in STEP -16 and actual speed will raise accordingly
• Switch OFF the programme once speed set point reaches 3000 rpm
• Observe JOP stopping at 540 rpm & AOP at 2850 rpm
• Check vibration /Brg temperatures & other TSI parameters
• Change the lube oil filter if required
• LPBP in Auto with pr setpoint around 8 KSC.
• Check for HP (below 95 deg ) / IP casing DT before synch(below 40 deg)

BEFORE SYNCHRONISATION

• Check X7 criteria
• Close the field breaker & made excitation On (one AVR will come in auto)
• After excitation ON observe voltage build up 90% of 21kv (19kv)
• Slowly voltage raise up to 21kv & Adjust the generator terminal voltage

SYNCHRONISATION IN AUTO FROM ELECTRICAL VERTICAL PANNEL

• Select the GCB
• Switch ON the synchroscope
• Select the mode to ATRS by selection key
• Switch on the AUTO synchronizer from the vertical panel
• GCB closes in auto at 12 o clock
• Observe speed setpoint raises by 15 rpm as per logic other wise give one raise pulse to speed set point so that unit comes to block load .
• Unit is synchronised

Immediately after Synchronization

• Increase the Speed reference and maintain the unit load around 50 MW
• After ensuring all parameters are normal increase the load set point to 70 -75 MW by increasing the load reference.
• Change over the Turbine control from Speed to Load by increasing the load reference.
• While changing the control from speed to load always ensure that LP bypass is in auto, No hunting in IP Control valves, and increase the load set point in such a way that the IPCV opening to 100%.
• After IPCVs full open increase the load set point further and slowly close the HP bypass.
• After closing the HP bypass close the LP .
• After unit load more than 150 MW only keep machine in pressure control, if required.
• Charge the LP & HP heaters.