stage alarms

7/31/2019 Stage Alarms

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ALARMS CUASES CONSEQUENCES AND ACTIONS (stage-1)P.KOTESWARA RAO, Dy.Supdt (Operation)

* ARRANGED IN ALPHABETICAL ORDER *

AIR PREHEATER

1. APH A/B STANDSTILL

1.APH A/B main and aux. Motor stopped and air motor failed to start

2.Air motor failure/ solenoid failure3.Compressed air not available

4.Isolating valve of solenoid valve closed condition/ air valve closed.

*1.Rapid fall in air temperature

2.Rapid rise in gas temperature3. Possible deformation of rotor

4.Possible fouling of seals

#1.Try to rotate APH periodically

2.Try to restore electric/ air motor3.Close air / gas damper4.Open interconnection valve

5.Run air motor through bypass of solenoid.6.Stop FD fan

7.If nothing is possible, kill the fire before APH distortion & foul

2. APH A/B AIR/ GAS OUTLET TEMPERATURE HIGH

1.APH air outlet temperature high because of SCAPH passing2.APH bypass open3.Gas outlet temperature high because of poor heat absorption in APH/ choking in passage4.Possible APH fire

5.Improper soot blowing6.APH plugging

3. APH BEARING TEMPERATURE HIGH/ VERY HIGH (60 deg.c/ 65 deg.c)

1.Low oil level2.CW flow low

3.Bearing damage4.Air/ gas leakage on to bearing

4. AIR HEATER MAIN MOTOR TRIP A/B AND AUX. MOTOR RUNNING

1.Selection changed to aux.motor2.Main motor tripped due to overload/single-phase preventer/ supply problem

#Check for the cause.


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5. AIR HEATER -A/B FIRE DETECTION

1.Oil burners improper burning/ oil carry over to APH

2.Improper APH soot blowing/ choking of APH3.Foreign material inside the APH

*APH air and flue gas temperature rise sharply

*At local APH colour peels off and very hot to touch

#1.Close air and gas dampers

2.Stop FD fan3.Flood APH with water4.Continue air heater rotation, at least with air motor till it is possible.

6 APH A/B MAIN AND AUX. MOTOR TRIP

1.Main motor tripped. Aux. Motor started and tripped.2.Aux. motor started and tripped

3.Supply interruption

*1.Hot air temperature drop2.Flue gas temperature rise3.If air motor fails to start, corresponding FD and ID will trip with 30 seconds time delay

#1.See whether air motor started. If not try to start it.2.Look for the reason why main and aux. Motor tripped and try to rectify

7. APH-A/B TEMPERATURE DETECTION COOLING WATER FLOW LOW

1.Due to line choking2.Cooling water line leak.

AUXILIARY PRDS

8. APRDS CV OPERATION MISMATCH1. Erroneous switching of torque monitor2. Motor temperature too high3. Position transmitter failure4. Position transmitter second channel failure

9. APRDS CONTROL/MEASURING SYSTEM TROUBLE.1. Measuring system faulty a) Flow meter Auxiliary steam

b) Pressure TransmitterSpray water

c) Temperature element2. Position Transmitter faulty.

10. APRDS TRIP CLOSE VIA OSU1. Down stream temperature high (300 C)2. Control oil pressure /level too low (80 KSC)


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3. Spray water pressure low (


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1. Suction/discharge valve closed2. Suction/ discharge valve seat fallen3. One or more CW pump tripped4. DOR reverse5. Discharge flange/ line leakage6. NRV not opening(STANDBY PUMP STARTS AT 4.0 KSC, IF SUCTION PRESSURE IS OK >0.8 KSC)

While starting the pump from local give close command in UCB to make the interlock work.17. ARCW PUMP TRIP

1. EPB pressed2. Suction pressure low low3. CW pump trip or pressure switch malfunction4. Electrical protection

a) Overloadb) Single Phase preventerc) Motor burntd) Control circuit faultye) Fuse blownf) Power cable got shorted

18. ARCW PUMP AUTO START FAILURE1. Running pump tripped/ Discharge pressure < 4 KSC and suction pressure


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22.ALL BFPs TRIPPED1. Electrical supply lost.2. Suction pressure loss (Very Low- Not connected)

a) actualb) Transmitter Malfunction

3. Deaerator level low (480 MMWC)4. FRS malfunction High BFP discharge5. Running Pumps tripped. Standby pump not started.

Unit trip# If Unit doesnt trip, trip the unit.

23.BFP DISCHARGE TEMPERATURE HIGH HIGH (236 C)1. Temperature Element faulty2. Churning (Recirculation valve not opening, Manual valve not opening, NRV not opening)

Pump gets damaged# Trip the pump if flow cannot be established.

24. BFP FLOW LOW LOW (50 T/Hr)1. BFP scoop failed.2. NRV not opening / Discharge valve seat fallen.3. Discharge valve got closed inadvertently.

4. Flow transmitter failed.5. BFP got unloaded due to internal pump problem.

6. Suction strainer clogged.7. Air pocket in suction line.

* Drum level comes down.* Load may have to be reduced.

# Find the cause and try to rectify.# Or else immediately start the standby BFP and normalize the feed water flow keeping an

Eye on the Drum level.

25. BFP AUTO START FAILURE

1. One of the permissive may be absent.a) Suction valve open (Bypassed in all the Units).b) Brg. Temp normal (1 KSC).d) Suction pressure normal (>10KSC).

e) Lube Oil CW pressure normal (>2KSC).

f) Recirculation valve open.2. Selection not in LEAD/LAG as the case may be.

3. EPB pressed condition (Not Reset).4. Supply may not be available in that bus.

5. Brkr. not racked in / any other brkr. Problem like selection not in remote / any other relay notgetting reset etc.

* Drum level may drop and Unit may trip.# Load has to be reduced (Runback to 50 % load)

# Look for the causes and attend it.


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26. BFP TRIP1. Lube Oil pressure Low (75alarm, 130 trip).

3. Thrust Brg. temp Hi-Hi (> 90 deg C).4. D/A level Lo-Lo (480mm).

5. Balancing Leak off pressure Hi (25 KSC).6. Axial shift High.

7. Suction to Discharge diff temp High (15 deg C).8. EPB pressed.9. 6.6KV Bus dead.

* Drum level goes down and unit may trip on Drum level lo-lo.# Reduce load to maintain the Drum level.

# Start the standby pump and restore the Drum level.# Find out the cause and rectify it.

27. BFP BRG. VIBRN. HIGH (8mm/sec pk to pk)

1. Misalignment2. Insecure foundation

3. Oil flow/pressure adequate4. Foreign particles in impeller5. Bearing seizure

6. Very less flow through pump

* Verify for reasons#1.Maintain comfortable flow (not too low or too high)

2.Inform conditioning monitoring to check

3. If trend is high side, trip the pump, and accordingly see that second pump has taken start. If not,

Reduce load and maintain drum level.

28. BFP DISCHARGE HAEDER PRESSURE LOW (low-155ksc, low-low-120ksc)1.NRV closure/discharge valve closure

2.Scoop failure3.FRS valve suddenly gets full open.

4.Pump impeller key got sheared off5.Suction strainer choked

*Pump can't pump water to drum where pressure is more#Try to improve the pressure, if not see that other pumps have taken load. See drum level.

29. BFP SUCTION PRESSURE LOW (low-10ksc, low-low-7ksc)

1.D/A level low 1000mm2.Extraction steam N/A (extraction valve closed due to high-high level)

3.Suction valve in closed condition4.Pressure transmitter faulty

*1.BFP trip kept bypassed2.Alarm appeared

#1.See for the cause and rectify


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2.If extraction steams N/A, change auxiliary steam or CRH steam by opening F019 or F055respectively.

Then open F043 keeping an eye on D/A pressure and level.

3. If D/A level is actually low, trip the pump at 468mm if the pump is not tripping in auto.30. BFP MOTOR O/L (high-340amps, high-high-432 amps)

1.Mechanical defect, bending shaft, rotor rubbing against cabins, seizure of any bearing.2.Lub oil pressure /flow low to a bearing coming its seizure.3.Very high flow

#1.Reduce flow2.See for cause and get it rectified.

31. BFP LUB OIL PRESSURE LOW (low-1ksc)

1.MOP/AOP not developing pressure/ major oil leak from lube oil line2.AOP power supply off/made off3.Oil level in the sump very low.

*Pump trips on protection at 0.5ksc

#See for the reason and improve the lube oil pressure.

32. BFP LUB OIL TEMP.BEFORE/AFTER COOLER HIGH (55/95 deg.c)

1.Less/no cooling water flow to coolers (ARCW pump trip)

2.Cooler choking3.Oil level in scoop very low.

*Bearing may seize/damage

#Check for problem and attend.

33. BFP SUCTION TEMP.HIGH (200deg.c)

CRH steam pegging is still continuing after unit in service#Change over to extraction

34. BFP SSUCTION STRAINER CLOGGED (DP-3.5mmwc)

#Start the other pump or else maintain drum level by proper action.

35. BFP MECH.SEAL WATER TEMP. HIGH (80 deg.c)

Seal water tube leakage and feed water entry into seal water/choking of cooler oil/

Choking of magnetic filter#Stop the pump after starting standby pump and change over the load.

36. BFP HYDRAULIC COUPLING LUB OIL PRESSURE LOW (low-0.8ksc, low-low-0.5ksc)

1. W.O.pump problem2. Leakage in cooler3. Leakage in Working Oil line.


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37. BFP BALANCING LEAKAGE PRESSURE HIGH (25ksc)

Balancing disc maloperation*1.Pump trip on pressure

2.Sudden pulling and dropping of load from pump can make pressure very highDue to axial movement of rotor.

38. BFP LUB OIL FILTER CHOKED

If lube oil filter is choked lube oil pressure will drop.#Change over the filter

39. BFP SHAFT DISPLACEMENTHIGH (not in service)

1.Balancing device maloperation2.Thrust pad damage, needs replacement

40. BFP BEARING METAL TEMP.HIGH (75 deg.c)

1.Lub oil pressure/flow low2.Seizure of bearings3.Axial thrust more/-balancing disc not proper

4.Shaft alignment problem*At 90 deg.c of thrust bearing temperature, BFP will trip.

#Check for lube oil flow low, the bearing, stop pump if required.#Balancing gap to be adjusted

41. BFP BEARING VIBRATION HIGH HIGH (high-8mm/sec, high-high-10mm/sec peak to peak)

1.NRV/discharge valve / recirculation valve not opening/operating2.Pump mechanical damage

3.Bearing oil flow low/bearings damaged4.Feed water flow very less in the pump

5.Vibration pickup failure

*Bearing/pump may be damaged

#Verify for the cause and rectify

42. BFP BEARING TEMPERATURE HIGH

1.Lub oil flow/pressure low

2.Coolers ineffective3.CW flow less for cooler

*At 75deg .c alarm will appear*At 90 deg. C will trip with a time delay of 5 seconds

#When alarm appears, check for the same


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#Change cooler if required

43. BFP DISCHARGE PRESSURE LOW (70ksc)

1. Scoop failed

2.Main pump / voith get decoupled.3. One of the impeller got delinked. (Key sheared)

44. BFP HYDRAULIC COUPLING OIL TEMPERATURE HIGH (70/130 deg. C)

1.Cooler ineffective2.CW flow to cooler less

#. Check cooler lineup/CW flow

#Stop the pump and inspect the cooler

45. RUNNING BFP DISCHARGE PRESSURE LOW-LOW (50ksc)

1.Scoop failed2.Main pump / voith get decoupled

3. One of the impeller got delinked. (Key sheared)

CEP

46. CEP TRIP

1. EPB pressed2. Hot well level low low


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2. Mechanical defect i.e., bending of shaft, rotor rubbing against casing3. Bearing seizure

49. CEP AUTO START FAILURE1. One or more permissives not available2. Breaker not racked in or problem in breaker3. DC supply problem4. UCB selection not in auto5. Local selector mode in switchgear mode (not in Remote mode)

50. CEP BEARING TEMPERATURE HIGH1. Bearing oil level low/ contaminated2. Shaft wobbling/bent/eccentricity3. Misalignment(Stop the pump at 90 C bearing temperature)

51. CEP TRIP

1 EPB2 CEP discharge pressure low low (


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CRT

56. CRT LEVEL HIGH (2500MM)1 Maloperation of CRT level C.V2 Maloperation of D/A hi level C.V F571*CRT overflow. DM water wastage

57. CRT LEVEL LOW. (750 MMWC)1. DM Makeup pump tripped2. CRT level CV malfunction3. Drain valve inadvertent opening4. Make up very high due to CBD, PRDS, or Tube leakage. Gland seal water may be lost No make up to condenser.

58. CONTROL AIR PRESSURE LOW (2.5 ksc, operating pressure 5ksc)

1.C.A compressor tripped

2.Leakage in control airline

*Pneumatic valves may fail/ close / open as per normally closed/ open or stall out#Look for FRS valve position, all trip valves, and extraction valvesFail-safe, Stay put-lock up relay. Valves /dampers operation affected with loss of CA.

1. HFO trip valve close2. LFO trip valve close

3. Igniter trip valve close4. RH block valve close

5. Seal air discharge damper remain as it is6. Pf valve remain as it is (But due to gravity it may get closed)7.Guns power cylinder remain as it is

8. Igniter power cylinder remain as it is9. HFO PCV remain as it is10.LFO PCV remain as it is

11. Igniter oil PCV remain as it is12. Gas/ air dampers remain as it is

13. Interconnection dampers remain as it is14. FD IGV remain as it is15. ID IGV remain as it is

16.FD discharge damper remain as it is17.ID discharge damper remain as it is

18.SH spray station close19.RH spray station close20.RH spray block valve close

21.CAD/ HAD remain as it is22.Make up control station close

23. LPH/ HPH normal drip control valve close24. LPH/HPH Alternate drip CV open24. BFP recirculation valves open

25.CEP recirculation valves open


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26. Hot well level control valve close27. FC NRVs open (if CRH pressure is OK)28. BDV open

29. FRS remain as it is30. Deaerator High Level CV close

31. Deaerator pressure CV close32. PA IGV remain as it is

33. SH/RH gas bypass dampers remain as it is34. Seal steam diverting valve Open to condenser35. Clinker grinders Close by gravity (If CA is lost during opening)

36. Tampering air damper remain as it is36. HFO short recirculation/ Long recirculation open37. APH gas inlet damper remain as it is

38. Soot Blowing CV Close39. Extraction line drains open

40. Ventilation valve open41. HFO pressurising pump house R/C open42. Deaerator CRH (55) block valve. Close

43. Deaerator over flow Open44. CRT level CV Open

45. Daerator pressure CV remain as it is

# Reduce CBD, APRDS

Fill CRT with bypass valveClose make up to condenser.

Start additional Make Up pump.

59. ANY CW PUMP AUTO TRIP

1.Lub water pressure low2.Pump discharge pressure high/ discharge valve closed3.Overload

#1.Reduce load if vacuum affected

2.Talk to offsite engineer /Unit-1 engineer for CW pump position3.Try to restore back the CW pump, otherwise reduce load so as to maintain vacuum.

DEAERATOR

60. DEAERATOR LEVEL LOW(NORMAL 2600, LOW 1000, LOW LOW 480)1. CEP tripped /low CEP discharge/ CEP faulty operation.2. Drain valve passing or inadvertent opening3. BFP drain passing or inadvertent opening4. D/A level CV malfunction5. DM makeup pump trip6. CEP recirculation opened full in full load condition


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7. Too much drainage from the boiler/ long tube leakage/major feed water line leakage*BFP trips at low low 480 mm

61. DEAERATOR LEVEL HIGH(NORMAL 2600,HIGH 2950,HIGH HIGH 3050)

1. High CEP discharge2. Malfunction of D/A level CV3. Malfunction of Makeup valve4. BFP tripped, Voith failed5. Malfunction of hot well level CV Extraction block valve closes at high high 3050 Possibility of water entry in to turbine increases Heavy hammering in D/A Overflow line opens# Reduce condensate flow to deaerator and direct to CRT

Open drain / overflow if requiredReduce hot well level make up

62. DEAERATOR PRESSURE HIGH(NORMAL 11-12 KSC, HIGH 16 KSC)

D/A minimum pressure control valve maloperationAux/CRH steam pressure high

*Safety valve lifts

# Reduce D/A pressureClose F019/F055 valves

63. DAS TROUBLE

Any one processor halted.1. Loss of supply2. Card problem

DOSING

64. HP DOZING SYSTEM TROUBLE

1. Dosing tank level low2. Preparation tank level low3. Dosing pump motor tripped

a. Motor overloadb. Single phase preventerc. Motor got burnt

4. Discharge pressure low.

65. LPDOSING PUMP DISCHARGE PRESSURE LOW (5ksc)

1.Shear pin broken2.Suction filter choked

3.Motor not running4.D/A pressure low


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5. Dosing tank level low6. Preparation tank level low7. Dosing pump motor tripped


8. Discharge pressure low.

66. HPDOSING PUMP DISCHARGE PRESSURE LOW (160 ksc)

1. Motor not running2. Discharge valve closed3. Pump stroke minimum4. Stroke shear pin got sheared.

66. HP DOZING SYSTEM TANKS LEVEL TROUBLE

1.Preparation tank level low2.Dozing tank level high/ low

67. LPDOSING SYSTEM TROUBLE

1) Pump motor tripped etc2) Dosing tank level low3) Preparation tank level low4) Dosing pump motor tripped


5) Discharge pressure low.

68. LPDOSING SYSTEM TANKS LEVEL TROUBLE

1.Metering tank level low

2.Preparation tank level low

#Make up the tank levels

69. UNIT DC SYSTEM E/ F

*E/ F in DC system

a. Earthling in field devicesb. Earthling in DC equipment

i. Solenoids


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ii. Motorsiii. Chargers

c. Earthling in Busd. Earthling in Cable

# Observe DC voltage Faulty pick up of relays may be there.

ESP

70. PARTICLE EMISSION RATE HIGH

1.ESP field failure/ performance poor2.ESP auxiliary failure (rapping)3.Less retentivity/ reactivity of coal

4.Poor combustion/high ash level in hoppers5.Very high air flow /charge ratio is not proper

71. ESP TROUBLE

1.Power supply failure in one or more passes2.Flushing fan failure in one or more passes

3.ESP failure due to failure in controls/ transformers/ rectifiers etc4.Shorting/ snapping of electrodes/ dislocation of electrodes etc5.ESP fields tripped on low voltage

72. ESP RAPPING MECHANISM TROUBLE

1.Emitter/collector rapping motor failed due to overload or single-phase preventor.

2.Supply problem1 ration of D/A Hi level C.V571*CEP trips on lo lo

LPBP if in service gets trip closed# If it is not possible to restart CEP (Try keeping an eye on D/A level), trip the unit

73. ESP RECTIFORMER (415 V to 80 KV Transformation, then rectification through diodes) TROUBLE

One of the rectiformer failuresOil le81. FD FAN BEARING VIBRATION TROUBLE (high-8mm/sec, high-high -10mm/sec, peak to

peak)

1.Fan impeller or IGV damaged

2.Oil level low/ nil in bearing3.No CW flow to bearings, so bearing got damaged

4.Mis alignment

*Bearing may get damaged and seized

#1.Check for the cause and rectify it

2.If vibrations are in rising trend and maintaining high value, trip the fan


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74. EXHAUST HOOD TEMPERATURE HIGH

1.A thermostatic alarm switch, located in the turbine exhaust hood, closes its contacts when theTemperature of the steam from the last stage turbine wheel exceeds 80 deg.c and is wired to an alarm

#Apply spray water. Excessive use of spray may cause unnecessary erosion of the long last stageBuckets.

*Clearances may be affectedLPT last stage blades*During start up and low load operation, when the turbine stages remove only little energy from the

Steam, the exhaust steam energy at a temperature that is too high for the last stages and the exhaustHood

75. EXTRACTION AIR RELAY DUMP VALVE

When the turbine trips, the dump valve spring is actuated to cut off the air supply to the NRVs. The

Existing air in the NRV cylinder is discharged to atmosphere and this results in NRV being force closed.This is to provide adequate over speed protection by closing of NRVs in extraction linesAlso whenever extraction relay dump valve is actuated, the air signal it provides to the blow-down

Tank will be interrupted and exhausted, thereby opening the blow down valve.

76. FIELD BKR NOT AVAILABLEClosing coil supply failed

Tripping coil supply failed.

77. TRIP FOR BOTH FANS NOT AVAILABLE.

When generator is in service with excitation ON failure of both fans for more than 15 second willgenerate class-A trip through Excitation system fault-A in GRP.

FD FAN

78. FD FAN MOTOR BEARING TEMPERATURE HIGH (high-70deg.c, high-high-75deg.c)

1.Oil level in the bearing low/ contaminated2.Spurious alarm

*Bearing may get damaged and seized#Reduce load on the fan, check oil level and quality. Get it topped up and restore load

79. FD FAN MOTOR OVERLOAD

1.Too high airflow2.Impeller fouling with foreign material

3.Bearing seizure


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*FD fan may trip

Reduce FD load immediately and see that alarm gets reseta. vel lowb. Oil / winding temperature highc. Buchholtz operatedd. Diodes failed (result in high oil/wdg temperature)

*Field gets off#1.Call ESP operator & confirm from which pass and which field it is coming

2.Inform E/M to restore the field

80. FD FAN TRIP

1.EPB pressed

2.Corresponding ID fan tripped (when both FDs in service)3.If both Ids tripped4.Corresponding APH tripped, 30 minutes time delay

5.Electrical problem (O/L, E/F etc)6.Supply dead

*1.Air flow comes down2.Combustion disturbance

3.Disturbance in furnace draft4.Disturbance in drum level

#1.Trip one top mill (preferably D or E, top mill)2. Stabilise furnace

3. Take oil guns preferably in lower mills

4.Check for closing of air and gas dampers of corresponding APH and closing of FD fan dischargeDamper

5.Stabilise drum level6.Reduce load in generator

7.Load running FD fan to maximum as possible and regulate fuel as per requirement8.Maintain steam pressure and temperature

9.Watch turbine differential expansions if steam temperature comes down10.If tripped due to electrical protection, inform E/M11.Check for the cause and try to restore.

81. MILL FEEDER TRIPPED

1.Motor control trouble a. Motor speed less than 60 rpm

b. Overload for 30 secondsc. Input phase lossd. Gross motor speed deviation >200 rpm

e. Momentary power loss > 200 seconds

f. No coal from bunker


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g. No coal deliveryh. Discharge chute plugged

*1.Load comes down2.Mill trips on emptying 3 to 4 minutes time delay (


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1.Wet slurry coal2.Foreign material at chute

*Feeder trips/ mill outlet temperature shoots up

#Stop the milling system and take standby mill in service

87. MILL FEEDER TROUBLE

1.Overweight/ underweight2.Clean out conveyor stopped

#1.If it is due to under weight raise speed and for over weight reduce speed

2.If clean out conveyor stopped, shear pin might have got sheared off. Ask R/M to attend it

88. GRAVIMETRIC FEEDER TEMPERATURE HIGH

Fire inside the feeder

*Belt and C&I cabinet may get damaged#1.Trip the feeder and stop the milling system2.Close bunker gate

3.Close isolating damper4.Open the firewater into the feeder

5.Get the front door opened through R/M6.Inspect whether fire is extinguished or not/ remove the coal and clean the feeder

89. FUEL/ AIR FLOW DIFFERENCE HIGH, VERY HIGH

There is a set curve for different coal flow in ACS for FD vane in auto with oxygen as trimming(Convection factor). If the deviation from the set curve (value) is high/ high high this alarm appears#Check for sudden rise/ drop in coal flows and air flow and restore the deviation to minimum

90. FLUE GAS PERCENT OXYGEN HIGH/LOWLOW

1.Air flow less2.Coal flow more

3.Airflow reduction may be due to FD blade-pitch control problem/ damper vane closing4.Rise in airflow due to CMC5.Feeder overweight

*1.Incomplete combustion

2.High bottom ash/ fly ash, unburnt carbon %

HIGH

1.High excess air due to sudden vane opening2.Coal flow less


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*High exhaust losses cause and flame instability#Adjust air and coal flow so that oxygen is maintained

91. MAXIMUM/ MINIMUM FIELD INTERVENTION

Max. Filed current above 1326 Amps may damage the rotor winding. So over excitation limiterintervenes whenever the machine loading (MW& MVAR) is beyond its capability and brings down the

excitation, thereby keeping the machine within its thermal capability. But this limiter intervenes after a certaindelay so as to permit temporary over excitation. Limiters do not impair the control behavior of the AVR as overexcited condition can exist in the event of a load raise or because of short time faults in the power supply

networks.The AVR reacts to a distant fault and applies ceiling excitation (to the tune of twice full load excitation.

limited to a few seconds), thereby increasing the synchronizing torque of the machine and prevents it form-

loosing synchronism. How ever if the fault persists and not been cleared by a set time, delayed rotor currentlimiter comes into operation preventing the Generator and excitation system from damage.

This limiter intervention level also get affected by the position of a switch in UCB Generator panel whicdecides the capability limits for the generator depending up on generator casing hydrogen pressure.

Min. Field current below 129 Amps may result in Overheating in stator end winding.

During under excitation rotor field is very weak and it normally happens when the machine is operatingin leading MVAR region i.e., when the system is lightly loaded. Under this condition of reactive powerabsorption the rotor end windings are thermally stressed.

HEATERS

92. HP HEATER (5 /6) LEVEL HIGH/ LOW (HIGH-500, HIGH-HIGH-860, LOW- 200)

1.Failure of drip control valve operation

2.Inadequate extraction pressure3.Tube failure

*At High-High level extraction block valve will close and heater gets bypassed#1.Take the control into manual and try to maintain level2.If not possible, bypass the heater and take it out of service

93. LP Heater 2/3 LEVEL LOW/ HIGH/ VERY HIGH (87/ 196/ 296)

1.Drip CV malfunctioning

2.Tube leakage3.Extraction pressure low

*At very high-level heater extraction block valve gets closed and heater gets bypassed

94. LPHeater-1 LEVEL LOW/ HIGH / VERY HIGH (187/ 296/ 55)Maintain with the alternate bypass valve.


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HYDROGEN

95. COLD H2 TEMPERATURE HIGH CE/ OCE

1.Cooler got choked

2.Cooler clarified water flow reduced/ low

96. GENERATOR H2 SUPPLY PRESSURE LOW/ HIGH (HIGH-2.2ksc, LOW-0.22ksc)After the regulator pressure in filling rack high/ lowRegulator not working.

H2 Cylinder got emptied.

97. H2 PURITY LOW IN GENERATOR CASING (


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102. HOTWELL LEVEL HIGH

Hi-650 MMWC High High-750 MMWC1. Maloperation of condenser make up valve (F556, F557)2. Maloperation of Hot well level C.V.3. LPBypass opened.4. CEP not delivering properly.

Vacuum drops LPBP gets trip close at High High (730 MMWC)

103 . ISLANDING OPERATION:The station survives with some predetermined load in grid feeder mode (Part-grid), islanding itself fromthe rest of the grid.

HOUSE LOAD: Station survives as a separate entity just feeding its own auxiliaries.

46 Hz 2 sec Time delay TRIP ALL FEEDERS

45 Hz instantaneous

ID FAN

104. ID FAN MOTOR BEARING TEMPERATURE HIGH (high-70 deg.c, high-high-85deg.c)1.Oil level in bearing low

2.Oil contaminated3.Misalignment

*Bearing may get damaged#1.Check for oil level and get it topped up.

2.Check oil if contaminated

105. ID FAN TRIP1.EPB pressed

2.Scoop oil pressure low (0.24ksc with a time delay of 3 minutes)3.Scoop oil temperature high (130deg.c)

4.Both APH tripped5.Electrical protection, O/L, E/F, flashover, etc6.Supply dead

*1.Corresponding FD fan trips

2.Furnace gets pressurized3.Combustion disturbance4.Disturbance to water level in drum

5.FD fan discharge damper, APH inlet/outlet damper closed


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#1. Trip one top mill preferably DE if 5 mills are in service and reduce coal flow2. Stabilize furnace draft

3. Stabilise drum level4. Take oil guns preferably in lower mills

5. Reduce load on generator6. Adjust airflow with running FD fan

7. Observe wind box pressure8. Stabilise combustion and unit load at coal flow at which one FD fan can give enough excess air

2.5%(at least)

9 Check furnace flame condition and can remove oil support10. Check for the cause of ID tripping and try to restore it11 .If it tripped due to electrical cause refer to E/M

106. ID FAN HYDRAULIC COUPLING OILPRESSURE LOW (low-0.3ksc, low-low- 0.24ksc)

1.Working oil pump not discharging properly

2.Filter got choked

*1.Fan will trip if pressure drops to 0.24ksc with 3 minutes time delay2.Hydraulic oil temperature may rise

#Change the filter and check for improvement in pressure

107. ID FAN MOTOR OVERLOAD (appear at 132 amps)1.Bearings seized/ fan reverse rotation2.Impeller fouling / foreign material inside

*ID fan may trip on O/L#1.Reduce ID fan load and check for alarm resetting2.Reduce unit load if required

108. ID FAN HYDRAULIC COUPLING OIL TEMPERATURE HIGH (80 deg.c)

1.Running at lower scoop position for longer time2.Low oil lID FAN BEARING VIBRATION TROUBLE (8/10 mm/sec peak to peak)

1.Inboard/outboard bearing vibration high2.Oil level in the bearing low/ contaminated

3.Bearing damaged4.Impeller fouling5.Signal lost

6.Misalignment7.Oil flow less due to filter choked

*Bearing may get damaged and seized#Reduce load on the fan, check for the cause oil level and quality from local. Get it topped up and

Restore load level3.Low CW flow/pressure


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*ID will trip at 130 deg.c#1.Increase scoop2.Check for oil level and pressure

109. ID FAN HYDRAULIC COUPLING OIL LEVEL LOW

1Oil leakages/ level switch malfunction

*Scoop oil pressure may come down and temperature may rise

#Get the oil topped up

110. ID FAN HYDRAULIC COUPLING COOLING WATER FLOW LOW

1.Water is not available/ clarified pump trip/ cooler choked/ cooler valve closed inadvertently

*Hydraulic oil temperature may rise#Check for the CW availability if not restore

111. ID FAN SCOOP OIL PRESSURE LOW

1.Working oil pump not discharging properly/ failed2.Filter got choked3.Working oil level very low

*1.Fan will trip if pressure drops to 0.28ksc with 3 minutes time delay#Change the filter, oil level, its condition etc and check for improvement in pressure

MILL

112. MILL MOTOR OVERLOAD (32.4 amps trip)

1.Foreign material in the mill2.Too much coal flow3.Mill outlet is blocked

4.Primary air flow drop out5.Ball and race broken

#1.Do not take local run without informing E/M2.Reduce coal feeding to minimum

3.If needed cut out feeder after taking oil support4.Stop the mill and inspect, remove foreign material

113. MILL OUTLET TEMPERATURE HIGH (100 DEG.C)

1.Fire in mill2.Mill is emptied

3.Low coal feeding and high airflow4.HAD full open and CAD not opening


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*1.It is not advisable to run the mill at higher temperature as it may damage the total mill2.Explosion can occur

#1.Reduce the mill outlet temperature by opening cold air and giving more coal feed2.If it is due to fire in mill, dump coal and minimise hot air flow

3.Trip milling system and close isolating damper and PF valves

114. MILL DP LOW/ HIGH (low-250 mmwc, high-750 mmwc)a. LOW1.Low coal feeding

2.Worn out throat gap or air regulating ring due to chute jamming3.Very less recirculation

*1.Chance of coarse coal particles entering the furnace is high2.Fineness may come down/ PF valve closed/ pipe choking

b. HIGH1.High coal feeding

2.Throat gap/ air regulating ring choked/ blocked3.Very high recirculation

*More load on mill

#Take measures to get DP between 400-600 MMWC .If not stop the mill and inform R/M for checks

115. MILL NITROGEN PRESSURE LOW/ VERY LOW (low-26ksc, low-low-18ksc)

1.Leakage in nitrogen system

2.Drop in oil pressure due to leakage

3.Maloperation of loading pump

*At low-low mill trips#1.Immediately charge nitrogen

2.Pump oil in the loading system

116. MILL LUB OIL PRESSURE VERY LOW (low-0.8ksc, low-low-0.5ksc)

1. Pump not discharging properly/ failed2.Filter got choked

3.Gearbox oil level very low

*1.Mill will trip if pressure drops to 0.5ksc with 10 minutes time delay

#1.Change the filter, oil level, its condition etc and check for improvement in pressure

2.If improvement cannot be improved trip the system

117. MILL LUB OIL FLOW VERY LOW


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Comes from flow switch

118. MILL LUB OIL PUMP TRIP

1.Breaker closed in test position2.Actually lube oil pump tripped

a. Motor over loadb. Single phase preventerc. Motor burntd. EPB pressed

*If lube oil pump trips, within 10 seconds mill also will trip

#If lube oil pump tripped and mill did not trip, trip the milling system

119. MFT

1.Furnace pressure high/ low + or - 200mmwc2.Boiler drum level high/ low + or- 250mm (time delay 5 sec)

3.Loss of both ID and FD fans4. Loss of both BFPs5. Loss of both APHs

6. Loss of all flame.7.All fuel loss

8.Airflow 60%, at least one set of

HPLP bypass failed to open

#1.Check for the cause2.Do furnace purging to relight up

120. Aux oil Pump (AOP)IN SERVICE

When lube oil pressure low and MOP discharge low-12.2ksc/sceonds

121. TG Oil Pump (TGOP)IN SERVICE (discharge pressure-8.75ksc)

1. Abnormal stoppage of AOP due to mechanical fault2. Thermal overload in motor

3. Supply problem.

122 . Emergency Oil pump (EOP) IN SERVICE (discharge pressure-1.6ksc)

Abnormal stoppage of TGOP due to mechanical fault, thermal overload in motor

But EOP will not stop in case of thermal overload, but alarms comes

123 . PA FAN BEARING TEMPERATURE HIGH (high-65deg.c, high-high-70 deg.c)1.Lub oil level low/ nil in bearing/ FLOP tripped

2.No CW flow to bearings, so bearing got damaged


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3.Misalignment4. Unbalance.

**Bearing may get damaged and seized

#1.Check for the cause and rectify it2.If temperature is in rising trend and maintaining high value, trip the fan

124. PA FAN MOTOR OVERLOAD

1.Too high airflow2.Impeller fouling with foreign material

3. Locked rotor due to bearing seizure4.Discharge bellow leaking

5.PF valve not opened6.Inlet vanes are in open condition while starting

*PA fan may trip#1.Reduce. PA air flow immediately and see that alarm get reset

2.While starting see that vanes are closed, PF valves closed, fluid coupling is OK

125. PA FAN BEARING VIBRATION HIGH (high-8mm/sec, high-high-10mm/sec)

1.Lub oil level low/ nil in bearing/ FLOP tripped2.No CW flow to bearings, so bearing got damaged

3.Misalignmen

126. PF BURNER TROUBLE

1.When > two scanners sense no flame2.Air regulator of running mill closed

3.Impeller retracted4.Coal available permissive gone5.Feeder tripped

6.Nitrogen pressure/ lube oil pressure is low7.PF valves open feedback gone for running system

8.Lub oil pump tripped9.PF/ FO logic problem10.CW flow to mill oil cooler low

11. Mill bearing oil temperature high

#Look for the cause and inform C&I

127. RUNBACK IN OPERATION

1.Load is raised above capacity


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2.Capacity lost due to loss of auxiliaries such as mills, ID fan, and FD fan, BFP, CEP etc

128. SCANNER AIR PRESSURE VERY LOW

1.Fan tripped and other fan discharge damper fails to open2. Impeller disengaged from shaft

3.Heavy leakage in line

*1.At 500-mmwc alarms appears

2.At 400 mmwc standby fan comes in auto3.Scanner may sense no flame due to dust problem

#See that all scanners are showing flameClean the scanners, one after another

129. SEAL AIR FAN TRIP/ TROUBLE

1.On starting the fan if discharge damper is not opening with second command, this alarm appears

#At local get the discharge valve opened

2. When one of the seal air fan tripped/ stopped.

130. SEAL AIR HEADER PRESSURE LOW (low-1000mmwc, low-low-900mmwc)

1.Seal air fan tripped/ trouble

2.Line puncture

*Mills seals may not be effectiveIf seal air header pressure cannot be improved, trip one/ two mills and close their seal air valves

2.Start the standby fan and stop the first seal air fan3.Close the seal air valve of standby mills

131. SEAL OIL COOLERS COOLING WATER FLOW LOW

1.Isolating valve in the line closed

2.CW pressure/ flow dropped

132. H2/ SEAL OIL DP LOW ( 0.8kscRotate the magnetic filter.


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134. SEAL OIL DISCHARGE TANK LEVEL HIGHFloat mal-operation.

135. SEAL OIL TANK VACUUM LOW (500mm Hg)

1.Seal oil pressure at turbine end high2. Seal oil pressure at exciter end low

3. Seal oil tank vacuum low

136. MAIN AC SEAL OIL PUMP TRIP

1.Supply problem

2.Motor overload or single-phase preventer

*If DC SOP fails to take start, hydrogen may escape to atmosphere

#1.Start DC SOP locally if it not started

2.If DC SOP fails to take start see whether EOP or TGOP is running3.With EOP/ TGOP in service maintain 1.4 ksc of hydrogen pressure in the generator

4.If no pump is running, purge out the hydrogen with CO2.

137. EMERGENCY DC SEALOIL PUMP RUNNING

1.Started from UCB

2.Took start in auto if so pressure drops to 5.6 ksc

#Look for the cause and start AC SOP after resumption of power or rectification of pump problem

138. AC/ DC SEAL OIL PUMP OVER LOAD

AC SOP trips on overloadDC SOP remains in service even after overload alarms appears. Care should be taken to take out

The cause of overload

139. EMERGENCY DC SEAL OIL PUMP UNHEALTHY

1.DC supply not available2.Not in remote

140. SEAL OIL VACUUM TANK LEVEL HIGH/ LOW (+ OR - 150)Maloperation of float.Seal oil leakage.

141. SEAL OIL PUMP TRIP

1.Supply problem2.Motor overload or single-phase preventer3.All belts got cut

*H2 purity may come down


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142. H2/ SEAL OIL PANEL LOCAL SUPPLY FAILURESupply is from TGMCC-C.Check for the reason and eliminate it.

143. STAND BY FANS IN

Thyrister cooling fans effectiveness is monitored through flow switch (independent for each fan). Theymonitor the airflow and initiates auto changeover through a five seconds timer and initiates an alarm,

"standby fans in". To reset this alarm the fans selector switch (SVE) is to be brought the running fansposition.The fans can fail in any of the following conditions:

1. Motor overload2. Flow switch sensed low flow3. Selected power supply failed4. Control supply failure5. Main supply under voltage if selected to main.

144. SEAL OIL FEEDBACK PRESSURE LOW (5.5)

*DC SOP starts

145. INTERVENTION MINIMUM SEAL OIL DP TURBINE TRIP (DP-0.2)

Seal oil DP low alarm appears at 0.45 KSC.Rotate the magnetic filter which in service.

If feed pressure is OK and this alarm is coming means DPR malopetaion.With the help of E/M change over the DPR.If DPR changing is not helping crack open the DPR bypass valve.

146. SEAL STEAM PRESSURE LOW1. Load is less so leak off is less.2. Seal steam regulator malfunction.3. Unloading valve inadvertent opening.(Gland steam is to seal against steam leakages to atmosphere and from section to section (HP-IP)

Labyrinth type shaft pickings provide a series of throttling that limit steam leakage along theRotating shaft to a minimum as it is throttled from the HP space to LP space. )

147. GLAND (SEAL) STEAM CONDENSER LEVEL HIGH

GSC tube leakage*Vacuum may fall

148. ONE OR MORE IN OPERATIVE STRINGS

With reference to voltage current leads in capacitive circuit and lags in an inductive circuit.So (R-C network) Capacitors are placed in parallel to thyristers to avoid abrupt changes in voltage.And Inductor or choke (L-network) is placed in series with the thyriseters to avoid abrupt changes in the

filed current .The basic purpose is to protect the thyristers.Search coils are placed above the inductor to monitor the thyrister healthiness by sensing current

flow through them.


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If no current flows this alarm appears

149. SERVICE AIR PRESSURE LOW (3.5ksc, operating pressure 6 ksc)

1.S.A compressor tripped 2.Heavy leakage in PA airline*APH air motor may not run

150. SOOT BLOWING SYSTEM TROUBLE

1.Motor overload2.Blower gets struck up, fails to retract

3.MOV not closing

#Ask burner floor operator for any problem in soot blower

151. THRUST BEARING WEAR HIGH (axial shift high)

1.Sudden change in load

2.Abrupt change of steam temperature or condenser vacuum3.Sudden isolation of HP heaters4.Sudden closure of force close NRVs

5.Failure of lube oil supply to thrust bearing6.Pick up of load is too quick

7.Wear out of thrust bearing (causing the axial shift)8. Formatting salt in turbine (causing the axial shift)9.Wear out of thrust pad (causing the axial shift)

10.Overloading of turbine

11.Steam flow in reheater is high

*1.Seal rubbing2.Mettalic sound

3.Turbine vibration4.Squealer rings are provided to give an early warning by sound.

5. Squealer rings come into contact before the wheels /collar come into contact

#1.Load must be reduced

2.Steam temperature / vacuum must be improved3.Damaged thrust bearing/ thrust pad have to be replaced

152. TURBINE EMERGENCY TRIP OPERATED/ HYDRAULIC /OVER SPEED

1. Over speed of the turbine will cause the emergency governor to strike the trip finger, which allowsThe trip piston to travel to its dump position, closing off the trip oil supply from the vacuum trip andDumping pressure from the various relay cylinders

2. Manual operation of the master trip handle located on the turbine front standard strikes the trip.

153. TG MOTOR STOPPED/ TG DISENGAGED


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1.Stopped from console2.Tripped on overload

3.Supply lost4.Lub oil pressure switch problem/ lube oil low interlock problem

#1.If the rotor is hot and TG motor stopped, try to do barring by hand, by pulling the BG lever overThe square head of the shaft on the vertical motor at least by 90 deg every 30 minutes.

2.See for the cause and rectify it.*1.Due to top and bottom temperature DT, distortion of rotor (hogging).

2.Inter stage packing clearances may get affected there by reducing the operating efficiency.

154 . UPS INVERTER TROUBLE

1.DC supply voltage low2.DC supply voltage high

3.AC output voltage low4.Input DC supply lost5.Fan failure

6.UPS failure7.Out of synchronism

8.Static switch fuse blown9.Alternate source failure10.Alternate source deviation

11.One inverter is bypassed12.Inverter operation abnormal

*UPS supply interruption/ loss#Bypass the inverter, which has the trouble

See that the other inverter is supplying load

155. UPS CHARGER TROUBLE

1.Charger A/B/C/ AC supply failure2.Charger A/B/C output bus ground

3.Charger A/B/C/ DC volt low4.Charger A/B/C no voltage

*1.UPS inverter supply may be interrupted2.Interruption will trip the unit

3.Under voltage may cause electric supply failure

#Inform C&IThe charger alternate source has to be taken over.

156. UAT OIL LEVEL LOW/ BUCHHOLZ


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Leakage ina. Drainb. Gasket

Hot spotb. Loose boltsc. Internal faults

i. Insulation failurec. Short circuit

i. Core to windingii. Phase to phaseiii. Core to core

Unload the transformer and change loads to other source. Inform E/M.

157. UT OIL LEVEL LOW/ BUCHHOLZ

Leakage in

d. Draine. Gasket

Hot spotd. Loose boltse. Internal faults

i. Insulation failuref. Short circuit



158. UT TEMPERATURE HIGH 90 DEG.C1. Over load2. Core fault (eddy current)-Only oil temperature goes high and winding

temperature does not change.Following causes may cause high temperature problem

Mechanical Devices:a. Buchholtzb. Oil temperature highc. Winding Temperate highd. PRD (Pressure Relief Device)e. SPR (Sudden Pressure Relay)- Based on rate of rise of pressure

Electrical:

a. Over currentb. Over voltagec. Over fluxingd. Earth fault

i. Phase to phaseii. Phase to body


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iii. Core to coreiv. Core to body

159. UAT TEMPERATURE HIGH 100 DEG.C1. Over load

2. Core fault (eddy current)-Only oil temperature go high and windingtemperature does not change.

Following causes may cause high temperature problem

Mechanical Devices:f. Buchholtzg. Oil temperature highh. Winding Temperate highi. PRD (Pressure Relief Device)j. SPR (Sudden Pressure Relay)- Based on rate of rise of pressure

Electrical:e. Over currentf. Over voltageg. Over fluxingh. Earth fault

i. Phase to phaseii. Phase to bodyiii. Core to coreiv. Core to body

160 . BOTH VAPOUR EXTRACTION FANS NOT RUNNING

1.EPB

2.Supply problem3.Motor problem

a. Motor over loadb. Single phase preventerc. Motor got burnt

FUNCTIONS1.Constantly remove air and hydrogen leakage accumulation from oil tank2.Remove vapors, which may be harmful to the lube system

3.Keep vacuum in the tank around 8cm of WC.4.Also prevents oil vapors from oozing out through the oil tank cover and depositing

5.Air trapped in the oil may be pressurized at bearing and tend to blow into the windings where it mayDamage the windings

6.Governor open and bearings rusting may be caused due to moisture. More over rust is an active

Catalyst, which increases the rate of oil oxidation and shorten the useful life of the oil charged

*Above things will be affected

#1.See that one of the fans is started2.Steam parameters must be corrected

3.Lub oil temperature and pressure should be verified and maintained


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4.Proper flow of oil to the bearings should be ensured5.The extraction drains must be kept open6.Differential expansions should be brought within limits

7.Seal steam pressure and temperature should be verified8.If the trend is increasing side, trip the turbine and kill vacuum

One should not wait the speed to come down to 2000 rpm (2/3 speed) for breaking vacuum,To avoid severe duty on last blades of LPT, as in other cases

The most important symptom of crack propagation is the typical increase of vibration ofAmplitude of one or two mills with a sudden temperature drop. As the crack progressed in a

matterOf weeks, the amount of temperature drop required has decreased, and the resulting vibrationAmplitude increased

Generally such vibration contain substantial vibration components at the second and third

Harmonics of running speed, when analyzed through IRD variable frequency filter analyserIn such case stop the unit and notify ANSALDO

161. 6.6KV BUS A/ B INCOMING BREAKER TRIPWhen Unit tripsBus electrical fault

a. Earth faultb. Bus Over currentc. Station Incomer closedd. UT oil/ winding temperature high

162. 6.6/ 415 SWGR AUTO CHANGE OVER

Bus under Voltage. (80% through under voltage relay)If this continues and NO Voltage is sensed then all motor feeders trip. (To avoid motor over current)

*HT/ LT incomer tripped#Look for proper change over and loads on bus remaining live

163. 415 V BMCC/ VDDC TRIPOn electrical fault/ Short circuit/ Sustained over load downstream of the incomer breaker then it trips.

Observe for survival of the other section.

164. UNIT#1 TRIPPED

1.When any unit tripped looks for MVAR changes and acts accordingly2.Also look if PRDS has taken over (come into service)

3.If in UNIT#1, look for 1S1, 1S2, 2S1, 2S2 supply voltages and maintain

165. UT A/B cooler / OLTC trouble.Cooler fan/pump motor Trouble

Supply problem


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OLTC supply 3 phase 415 V failFans supply to Marshal box to tap changer boxOil operated relay

PRD (OLTC Chamber) (Note: UT has no PRD)166. UT A/B fire:

Taken from Deluge valve. (Deluge valve supply from marshalling box.Mulsifire:

a. PBb. Leverc. Bulb sensing

167. 6.6 KV bus A/B hot changeover out of synchronization.Mismatch between Unit and Station buses

a. Frequencyb. Voltagec. Phase sequence

168. UAT Buchholtz/ oil level low

Leakage in

g. Drainh. Gasket

Hot spot

f. Loose boltsg. Internal faults

i. Insulation failurei. Short circuit



169. UAT temperature high.High-100 C Trip-105 C

170. ESP Transformer-A/B buchholtz/Oil level low

Leakage inj. Draink. GasketHot spoth. Loose boltsi. Internal faults

i. Insulation failurel. Short circuit




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171. ESP Transformer-A Temp High

Winding hi-95 C trip-105C

Oil Hi-80 C Trip-90C

1. Over load


Following causes may cause high temperature problemMechanical Devices:

k. Buchholtzl. Oil temperature highm. Winding Temperate highn. PRD (Pressure Relief Device)o. SPR (Sudden Pressure Relay)- Based on rate of rise of pressure

Electrical:

i. Over currentj. Over voltagek. Over fluxingl. Earth fault


172. Unit & Station transformers parallel.

Station breaker did not trip on closing the Unit breaker.Ensure that only one breaker is in service.

173. Unit DC volt AbnormalHigh voltage (250V)

If high voltage is there relays coil may get damaged.

Solenoid valves,Indication lamps

DC motors may failUnder voltage.(185V)

Low voltage cause more current to flow leading to overheating of motor.

At thresh hold voltage chattering of relays may take place leading to variation in processparameters.

174. UnitLighting Transformer Buchholtz/ Oil level lowWdg. Hi-95 trip-105

Oil Hi-80 trip-901. Over load


Following causes may cause high temperature problem

Mechanical Devices:p. Buchholtzq. Oil temperature highr. Winding Temperate high


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s. PRD (Pressure Relief Device)t. SPR (Sudden Pressure Relay)- Based on rate of rise of pressure

Electrical:

m. Over currentn. Over voltageo. Over fluxingp. Earth fault


175. Unit Bus A/B VT trouble.One of the fuses must have failed.

176. Generator TRIP RELAYoperated

OVER VOLTAGE

GT DIFFERENTIALLOW FORWARD POWERPOLE SLIPPING

STATOR EARTHFAULTGENERATIOR DIFFL.

GT PRDGT BUCH HOLTZGT WINDING TEMP

LBB

EXCITATION FAULTY-AOVERHEAD LINE DIFFL.

86 G

TURBINE TRIP RELAY-A

TTR-BMAIN BKR (trip coil#1)MIDDLE BKR (trip coil#2)

GEN FIELD BKRUT-A I/C

UT-B I/CBUS A auto changeoverBUS B auto changeover

TO 386G

TO 486GMIDDLE BKR LBBTO 286G

177. Turbine bearing Vibration High.When the shaft vibration crosses 125 microns this alarm appears.

Possible reasons for high vibration could be1. Oil film distortion2. Oil temperature variation 42 C3. Less seal steam temperature.4. High moisture /mechanical impurities in the oil5. Loose/damaged blades6. Fouling in side the turbine7. High eccentricity.

# Try reducing load and observe the trend. Trip the turbine if the vibrations cross 200 microns. Duringcoasting down if the vibrations cross 280 microns vacuum breaker is to be opened. Boiler to be handtripped and boxed up. When TG comes to rest engage the Turning Gear.


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178. Turbine bearing temperature high.TRIP the turbine IFThrust bearing metal temperature crosses 90 C

ORSleeve bearing metal temperature crosses 95 C.

Vacuum to be killed at


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179. TOTAL POWER FAILURE.

TOTAL POWER FAILURE

Insure starting of EOPnsure Closing of EMCC

Incomer from DG set if DG isRunning.

nsure running of DC SOP.nsure all CVs, Ivs, ESVs closed.

Main, Middle, Field breakers

Tripped.nsure APH aux motor running

nsure DC lighting

TOTAL 220 V DC FAILURES1. All breaker indication lamps

Go dark.

2. Turbine trips through ETD3. If GRP supply is available

Main, Middle, Field breakersTrip. Else Trip them manually

After ensuring all CVs ESVsClosure.

4. Filed breaker is to be opened

from local.5.For 6.6 KV buses ensure stand

by DC supply by changing

over the switch.6.Ensure charging of EMCC at

the earliest and start TGOP.7. If 6.6KV buses are OK with

standby DC source try

normalizing LT buses.8. Ensure running of AOP.

TOTAL POWER FAILURE

II8. 1. Close all Extraction9. Block valves.10. 2. Look for flame if any11. Shown by scanners12. 3. Ensure DC scanner fan13. Running14. 4. Close CBD, SB valve if open.15. 5. Close RH, SH attemporation

Block valves.

6. Reset all ESP fields manually

TOTAL 220 V DC FAILURES1. ID, FD, PA fans and

MILLs will be in service

without any protection.2. On loss of DC, FD fans

Get trip command on lossof ID fan running contact.

But they remain inservice, as there is no DCsupply to the tripping

coil.3. Also On loss of Both ID

fans MFT acts but no mill

or PA fan trips. Allfeeders trip.

4. On resumption of DCThrough standby source to6.6KV buses all Mills,

PA fans, FD fans trip.5. ID fans remain in service.

TOTAL POWER FAILURE

III1. Close main ejector steam

valve and break vacuum

below 2000 rpm or 200-mmHg vacuum.

2. Close seal steam atVacuum below 100mmHg.

TOTAL 220 V DC FAILURE


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stage alarms

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