CW PASS ISOLATION PROCEDURE:

CW PASS ISOLATION PROCEDURE:
PRE CONDITION OF THE UNIT: -
1 Unit is running at full load (500MW) with 7 mills in operation.
2 Both TDBFPs are in service and Feed water control in auto.
3 MDBFP # C is available on auto (Rapid start up mode).
4 Unit control is in CMC mode / manual mode.
5 Both PA fans and FD fans are in service.
6Both condenser circulating water passes in service.
7 One condenser vacuum pump in service and other is available in standby.
8 Vacuum is maintaining normal i.e. - 0.90 kg/cm².
9 Both ID fans in service and furnace draft control in auto.
10 All four CW pumps (Two pumps per unit) are in service with both units interconnection valves are in open
condition. Discharge header pressure normal (approx: 1.4 kg/cm²).
ENSURE THE FOLLOWING :
Revise the station DC as per the planned shut down programme.
2 Availability of atomizing steam and HFO at requisite pressure & temp (oil: 100ºC / 17-18 kg/cm², Steam: 200 –
210ºC / 6.5 kg/cm²).
3 Completion of WB/LRSB operation before starting the load reduction.
4 Availability of PAPH / SAPH soot blowers for operation.
5 Availability of second (standby) condenser vacuum pump.
6 Stop corresponding CW pass OLTC after collection of balls before starting CW pass isolation process.
7 Take care of ACW pump suction header pressure very low and discharge header pressure very high protection of
the pumps in both corresponding units (ACW suction and discharge header pressure may vary by 0.2kg/cm²).
8 All CT fans (20 fans per each unit) are in service.
9 Check and record CW pump discharge header pressure (CW discharge header pressure may raise approximately
0.2 Kg/cm² after isolation of one pass).
10 Best communication system between local and control room.
11 Availability of condenser pit sump pumps and sump level is normal.
12 Take care of TDBFP – A / B recirculation valve auto-closing when starting the load reduction.
PROCEDURE FOR CW PASSES ISOLATION: -
1 Start standby vacuum pump and check vacuum.
2 Take the unit control to manual from CMC mode. (Turbine on limit pressure control and Boiler master on manual).
3 Take fuel master to manual and gradually reduce the load to 400MW by slowly unloading and removing 7th running
mill.
4 Take HFO support in one elevation corresponding to any running mill according to the mill combination (At least 3
oil guns in one elevation).
5 Gradually reduce the load to 300MW by slowly unloading and removing 6th running mill. Check airflow according to
the load (1450T/ hr corresponding to 300MW).
6 Reduce MS pressure set point according to the load during the process of load reduction.
7 Check the loading and suction flow of TDBFP A / B. If suction flow is low corresponding to the speed, Then keep
open any one TDBFP- A / B recirculation valve.
8 Preferably kept five consecutive mills in service to ensure stable combustion.
9 Start PAPH – A / B and SAPH – A / B soot blowing. (This is to be done at least twice in a shift as long as oil guns in
service).
10 Isolate the vacuum line manual isolation valve provided corresponding to the CW pass which is to be isolated at
the condenser end (8.5m near LPBP).
11 Switch of the CW pass (which is to be isolated) inlet valve power supply, Then gradually close the inlet valve
manually from local and simultaneously observe the vacuum, CW discharge header pressure. After full closing,
Isolate the actuator power supply.
12 Switch of the CW pass (which is to be isolated) outlet valve power supply, Then gradually close the outlet valve
manually from local and simultaneously observe the vacuum, CW discharge header pressure. After full closing,
Isolate the actuator power supply.
13 Open the corresponding condenser water box vent valves (2nos) for depressurisation.
14 Open the drain valve provided in the corresponding water box for draining after depressurisation.
15 If draining of inlet water duct is started, then check sump level and put sump pumps in auto or start / stop
condenser pit sump pump for dewatering manually.
16 Further tighten inlet and outlet valves if there is any passing.
17 After isolation of CW pass, Gradually increase the load to approximately 350MW with 5 mills operation and
simultaneously monitor condenser vacuum.
18 Close TDBFP – A / B recirculation valve, which was kept opened previously after sufficient loading of both
TDBFPs.
19 Remove oil support after stabilisation of load at approximately 350MW with 5 mills operation.
20 Issue PFW after ensuring complete draining and proper isolation.
PROCEDURE FOR CW PASSES NORMALISATION: -
Revise the station DC as per the planned programme.
2 Ensure the cancellation of PFW and clearance from maintenance (TMD).
3 Ensure the complete box up of the CW pass.
4 Close the drain valve provided at the bottom of the corresponding water box.
5 Open the vent valves provided at the top of the corresponding water box.
6 Crack open the CW pass (which is isolated) inlet valve manually from local and observe the CW discharge header
pressure.
7 Ensure air is coming from the vent line and close it after ensuring complete venting.
8 Gradually full open the CW pass (which is isolated) inlet valve manually from local and observe the CW discharge
header pressure.
9 Gradually open the CW pass (which is isolated) outlet valve from local manually and observe the vacuum and CW
discharge header pressure.
10 Normalise the inlet and outlet valve actuator power supply
11 After full opening of CW pass inlet and outlet valves, Open the corresponding CW pass vacuum line manual
isolation valve at 8.5m near LPBP, which is isolated previously.
12 Take 6th mill into service and gradually increase the load to 450MW.
13 Adjust the MS pressure set point according to the variation of load.
14 Take 7th mill into service and increase the load to full (500MW).
15 Adjust the burner tilt to maintain M S & HRH temperature up to maximum possible (540C).
16 Take care of TDBFP – A /B recirculation control valve auto close protection.
17 Take care of ACW pump suction header pressure very low and discharge header pressure very high protection in
both corresponding units.
18 Put fuel master in auto.
19 Take corresponding CW pass OLTC into service.
20 Stop second vacuum pump and check vacuum.
21 Take unit control in to CMC mode.

Pressure Vs Sat Temp

Pressure (Kg/cm2)	Sat. temp	Pressure (Kg/cm2)	Sat. temp	Pressure (Kg/cm2)	Sat. temp	Pressure (Kg/cm2)	Sat. temp	Pressure (Kg/cm2)	Sat. temp	Pressure (Kg/cm2)	Sat. temp
1.0	99.09	5.00	151.11	14.0	197.36	56	269.84	124	325.65	190	359.82
1.1	101.76	5.20	152.59	15.50	198.91	58	272.1	125	326.26	192	360.69
1.2	104.25	5.40	154.02	16.00	200.43	60	274.29	126	326.88	194	361.55
1.3	106.56	5.50	154.71	16.50	201.91	62	276.43	128	328.1	195	361.98
1.4	103.74	5.60	155.41	17.00	203.35	64	278.51	130	329.3	196	362.4
1.5	110.79	5.80	156.76	17.50	204.76	65	279.54	132	330.48	198	363.25
1.6	112.73	6.00	158.08	18.00	206.14	66	280.55	134	331.65	200	364.08
1.7	114.57	6.20	159.36	18.50	207.49	68	282.54	135	332.23	205	366.14
1.8	116.33	6.40	160.61	19.00	208.81	70	284.48	136	332.81	210	368.16
1.9	118.01	6.50	161.21	19.50	210.11	72	286.39	138	333.96	215	370.13
2.0	119.62	6.60	161.82	20.00	211.38	74	288.25	140	335.09	220	372.1
2.1	121.16	6.80	163.01	21.00	213.85	75	289.17	142	336.21	225.65	374.15
2.2	122.65	7.00	164.17	22.00	216.23	76	290.08	144	337.31
2.3	124.08	7.20	165.31	23.00	218.53	78	291.86	145	337.85
2.4	125.46	7.40	166.42	24.00	220.75	80	293.62	146	338.4
2.5	126.79	7.50	166.96	25.00	222.90	82	295.34	148	339.49
2.6	128.08	7.60	167.51	26.00	224.99	84	297.03	150	340.56
2.7	129.14	7.80	168.57	27.00	227.01	85	297.86	152	341.61
2.8	130.55	8.00	169.61	28.00	228.98	86	298.69	154	342.66
2.9	131.73	8.20	170.63	29.00	230.89	88	300.32	155	343.18
3.0	132.88	8.40	171.63	30.00	232.76	90	301.92	156	343.7
3.1	134.00	8.50	172.12	31.00	234.57	92	303.49	158	344.72
3.2	135.08	8.60	172.61	32.00	236.35	94	305.04	160	345.74
3.3	136.14	8.80	173.58	33.00	238.08	95	305.8	162	346.74
3.4	137.18	9.00	174.53	34.00	239.77	96	306.56	164	347.74
3.5	138.19	9.20	175.46	35.00	241.42	98	308.06	165	348.23
3.6	139.18	9.4	176.4	36.00	243.04	100	309.53	166	348.72
3.7	140.15	9.5	176.8	37.00	244.62	102	310.98	168	349.7
3.8	141.09	9.6	177.3	38.00	246.17	104	312.41	170	350.66
3.9	142.02	9.8	178.2	39.00	247.69	105	313.12	172	351.62
4.0	142.92	10.0	179.04	40.00	249.18	106	313.82	174	352.56
4.1	143.81	10.5	181.16	42.00	252.07	108	315.21	175	353.03
4.2	144.68	11.0	183.2	44.00	254.87	110	316.38	176	353.5
4.30	145.54	11.5	185.17	45.00	256.23	112	317.93	178	354.43
4.40	146.38	12.0	187.08	46.0	257.6	114	319.26	180	355.35
4.50	147.20	12.5	188.92	48.0	260.2	115	319.92	182	356.26
4.60	148.01	13.0	190.71	50.0	262.7	116	320.57	184	357.16
4.70	148.81	13.4	192.45	52.0	265.2	118	321.87	185	357.61
4.80	148.59	13.6	194.13	54	267.53	120	323.15	186	358.06
4.90	150.36	13.8	195.77	55	268.69	122	324.41	188	358.94

24 V DC Fail

24 V DC Fail

Identification of the Emergency:-

(1) Boiler trips on loss of 24V DC. Turbine trips on boiler trip protection followed by generator

(2)All controls operating on DDC becomes inoperative

Actions:

1. Confirm tripping of turbine. In local governing rack the trip oil pressure should be ‘0’ otherwise trip turbine from emergencytrip lever in governing rack. Trip TD BFPs from local governing rack

2.Confirm tripping of generator i.e. opening of GCB. If GCB has not opened, open  from switchyard

3.Confirm starting of AOP (local) on turbine trip, otherwise start EOP from local for both main and TDBFP turbines.

4.Confirm running of ACSOP(local) if no seal oil pump is running immediately start DCSOP from local

5.Confirm AC scanner fan is in service(local),else start DCscanner fan from starter panel in LT switch gear room in TG Floor

As controls are in operative do the following operations

6.Stop FD fan, ID fan and BCW pumps (from local push buttons or switch gear). Close boiler stop valves

7.Stop MD BFP (from local push buttons or switch gear), if it was in service as D/A and drum levels cannot be monitored.

8.Depressurise MS, CRH and HRH lines, Kill vacuum. Open atmospheric drains of MS,CRH and HRH lines

9.Stop CEPs and isolate make up to hot well since hot well level indication is not there

10.At 540 rpm turbine speed start DC JOP from local, and at 210 rpm open turning gear valve manually

11.Continue to run ECW pumps. Monitor and maintain ECW tank level from local

Profit Optimizer

Profit Optimizer

Salient features of this correction are:

1. The new correction works independently of RGMO. RGMO correction is implemented as per grid code and no changes are done to this. It will be visible more during FAST frequency changes. It is possible that frequency very slowly drifts away from 50.00 Hz but RGMO correction is not at all giving significant correction. During such times profit optimisation correction will help in earning UI.

2. Profit correction overall limits are settable between 10 to 25 MW. Correction droop is settable between 4 to 10% (default 4%). Breakeven frequency is settable (presently 50.00 Hz). Correction will be be subject to all directional blocks/limits as applicable normally in CMC.

3. Profit correction is based on selected frequency, which may be instanteneous, block average or weighted average - selection will be decided dynamically based on breakeven and asking frequencies, as well as block elapsed time. Note: asking frequency is the calculated frequency value which is required to be exactly maintained for blokc remaining time to bring block average to exactly breakeven. weighted average frequency is calculated taking block average frequency for block elapsed time and assuming instantaneous frequency for block remaining time.

4. To determine selection strategy, one block is divided into 5 segments of 3 minutes each.

i) First segment will always be giving correction as per instantaneous frequency.

ii) Second segment will give correction as per inst.freq. if inst.freq. and avg.freq. are on the same side of breakeven, and inst.freq. is more drifted. Inst.freq. can also be selected if it goes to other side of breakeven as compared to avg.freq.

Avg.freq. will be selected if inst.freq. and avg.freq. are on the same side of breakeven, and inst.freq. is between avg.freq. and breakeven.

iii)Third and fourth segments will also give correction as per inst.freq. if inst.freq. and avg.freq. are on the same side of breakeven, and inst.freq. is more drifted. Inst.freq. can also be selected if it goes to other side of breakeven as compared to avg.freq, and beyond asking freq. Avg.freq. will be selected if inst.freq. and avg.freq. are on the same side of breakeven, and inst.freq. is between avg.freq. and breakeven. Weighted avg.freq. will be selected if inst.freq. goes to other side of breakeven as compared to avg.freq, but within asking freq.

v) Fifth segment will behave similar to third and fourth till preset timer (60-120 sec), and then follow instantaneous frequency in order to be ready for next block start.

Correction is under implementation in Stage-II and III, and will be communicated in respective register accordingly. Performance in service may be kept under observation and feedback may be given to C&I.

It is once again brought to notice that the correction will have its desired effect of load change only if ALL mills are in auto, otherwise it will just result in throttle pressure larger variations (and then pressure correction will nullify it leading to little effective load change). Hence it is required that ALL mills be kept in auto for maximum possible duration (except for short periods during mill changeovers) to get maximum benefit out of this scheme.

TURBINE PROTECTION

TURBINE PROTECTION

1)         TG Lub oil pressure very low   (< 1.2 ksc)

2)         Axial  shift  high (+/-1.0mm)

3)         HP  exhaust  temp. high          (> 500 degc)

4)         Condenser  vaccum  low(VSP)

5)         Condenser vaccum  low(FSP)  (> -0.7 ksc)  AND Turbine speed > 240 rpm

6)         HP casing  top/btm DT high  (> 100 degc) AND  Load >100MW

7)         IP casing front top/ btm DT high  (> 45 degc) AND             Load >100MW

8)         IP casing rear top/ btm DT high  (> 45 degc)  AND Load >100MW

9)         MFT                                                    S/W  &  H/W

10)       Generator  electrical protection           S/W  &  H/W

11)       Liquid in Generator Main leads top  (> 90 mm)

12)       Cold gas temp after cooler A&B high  (> 60 degc)

13)       Cold gas temp after cooler C&D high (> 60 degc)

14)       Primary water temp after cooler high (> 71 degc)

15)       Seal oil temp after cooler high   (> 55 degc)

16)       Hot air main exciter temp high  (> 80 degc)

17)       Stator winding flow very low (< 48 tph)

18)       Stator Main bushing  R flow low (< 1.33 tph)

19)       Stator Main bushing  S flow low (< 1.33 tph)

20)       Stator Main bushing  T flow low (< 1.33 tph)

21)       Turbine over speed trip (electrical)     (> 3330 rpm)

22)       Turbine over speed trip                       H/W

23)       Oil tank level very low ( 1150 mm from top)

24)       Turbine trip from desk operated

25)       Turbine trip from console operated

26)       Turbine trip from ATRS

27)       Emergency trip from HMI

28)       Fire protection 1 or 2 operated

29)       Generator class B protection

30)       Low Vacuum Trip Device operated

31)       Manual Trip Device operated

1.2)      ALARM LIMITS

1)         TG Lub oil pressure very low (< 4.5ksc)

2)         Axial  shift  high (+/-0.5 mm)

3)         HP  exhaust  temp. high (> 485 degc)

4)         Condenser vaccum  low (FSP)  (> -0.8 ksc)

5)         HP casing  top/btm DT high  (> 90 degc)

6)         IP casing front top/ btm DT high  (> 30 degc)

7)         IP casing rear top/ btm DT high  (> 30 degc)

8)         Cold gas temp after cooler A&B high   (> 55 degc)

9)         Cold gas temp after cooler C&D high   (> 55 degc)

10)       Stator winding flow very low (< 54 tph)

11)       Stator Main bushing  R flow low (< 1.4 tph)

12)       Stator Main bushing  S flow low (< 1.4 tph)

13)       Stator Main bushing  T flow low (< 1.4 tph)

14)       Turbine over speed   (> 3300 rpm)

Generator Air Tightness Test

Generator Air Tightness Test

Period Of Test= 24 Hrs without a Break

Air Pressure Drop (Allowed in 24 Hrs) : <=0.15 ksc

Air Test Pressure = 3.5 ksc

All LLDs Drain Closed.

Ensure Seal Oil system in Operation

Seal Oil DP >1.5 ksc

AS Seal Oil Pr>4.5 ksc, start H2S Seal Oil system

H2 Cooler Isolated

PW in Winding is in filled condition, Winding Isolated. PW also kept Isolated.

PW Tank at Atmospheric Pressure

Ensure availability of  Instrument air and Bleed Out moisture from it by keeping it open till

Connect flexible air hose with the gas plant through the coupling and ensure no air leakage is there

The filling is to be done by opening the valves in the normal H2 filling line where as the valve from H2 rack side will remain closed.

Once the air filling is commenced the test record data sheet

The air valve is to be opened full.

While pressurising the LLD / Seal oil DP / Seal oil parameters are to be recorded as per the enclosed sheet.

The generator casing is to be pressurised with instrument air up to pressure of 3.5 ksc.

The approximate time to attain rated pressure will be around 7- 8 hrs

Record the time when the pressure has reached at 3.5 ksc at the special gauge fixed in the gas rack

Stop the air filling and shut off the valve when the test pressure has been reached (3.5bar) and then disconnect the air hose from the system to avoid further pressurisation of the system.

Once the rated pressure has been attained, the test can be commenced.

Once the test is commenced the test record data sheet is to be filled at hourly basisfor continuous 24 hrs. No break is allowed.

During test ensure the LLD‘s are not getting oil

If a pressure increase was observed in the primary water tank, a leak of the primary water system with in the generator would be expected and must be located and attended

If an air loss higher than 0.15 bar/ 24 hrs, a search for leakages must be made.

Suspected areas should be brushed with Diprol or other foaming solution. The formation of bubbles (foam) indicates a leak.

Attend the leakages and then repeat the test until satisfactory results are obtained.

If a satisfactory tightness is established the generator may be filled with CO2 and subsequently with H2 as per normal operation practice.

After the test is declared complete, the air is to be depressurised and the system is to be normalised

After completion of the test, the electrical purity meter system should be calibrated with pure CO2 and H2

Normalise the primary water coolers and take the primary water system into service.

Normalise the all-4 hydrogen coolers

Then the generator may be filled with CO2 and subsequently with H2 as per normal procedure.