CONTROL PHILOSHPHY & MONITORING.ppt

CONTROL PHILOSPHY & MONITORING A PRESNTATION BY S.K.TRIPATHI Dy. MANAGER (E) , CPU

There are two topics in this presentation1. Control Philosophy2. monitoring

Control PhilosophyNormal Start & stop sequenceControls during normal / smooth generation Controls during emergent conditionsTripping and restoration

Check List COOLING WATER FLOOR EL 211.25M Cooling water pump #1 & 2O.L.U working in AUTO/MANUAL Condition of duplex strainer#1 Draft tube pressure Cooling water header pressure Condition of D/T valve pit pump

TURBINE PIT EL 218.70 M Condition of top cover drainage pump Shaft seal water pressure GV shear pin air pressure Oil leakage from TGB Governor servomotor opening& Closing pressure Water pressure /vacuum below top cover & spiral casingHealthiness of PP set motor #1 & 2Pressure in the accumulator & sumpLeakage from idealer valve #1 Healthiness of HS lube pump Healthiness of CGLS Flow meter in the air & Oil cooler Air pressure in breaking system Water leakage from any valve (Give location Healthiness of H.P & LP compressor #1 & 2Condition of UAT breaker. Condition of ESV

Check list MACHINE FLOOR EL 227.70M Hot & Cold air temp. Thrust bearing pad temperature Generator guide bearing (GGB) pad & Oil temperature Turbine guide bearing (TGB) pad & Oiltemperature Cooling water inlet & outlet temperature Governor pressure on EHG cabinet Bridge current in AVR panel Any sparking on slip ring brushes Check any alarm in UCB panel Healthiness of sprinkler in cooling pond

Water level in cooling pond

Check List TRANSFORMER DECK (EL 227.70 M) No of coolers working Healthiness of oil circulation temperature Transformer winding temperature Transformer oil temperature Humming soundAny water leakage from any point Any oil leakage from any point

Check List CONTROL ROOM Regular checking of control desk and control panels Indication of Annunciation panel Healthiness of relay Panels.

HEALTHINESS OF PUMPS ((EL 210.60 M) 90 HP VT Dewatering pump 35 HP submersible pump (Drainage pit)

Check List LT ROOM Battery charger in Float/Boost mode. Healthiness of SST#1 & 2 circuit breaker Healthiness of HALON system

PRESTART CHECK LIST No work permit should be outstanding. Gen.schedule should be approved from NRLDC Oil level in TGB/GGB should be normal. All relevant oil/air/water lines should be charged and cooling water header pressure should be normal. D.C control circuit voltage check relay healthy Gov. Oil pressure and level should be normal Master stop relay reset/Controlled action shutdown relay reset/Emergency shutdown relay reset. Electrical lockout relays reset ESV ckt. should be healthy Top cover pump AC supply should be normal. HS pump AC supply ON. DC supply to all Protection/controlled relay panel should be normal Brake air pressure normal and brakes in released position Guide vanes in closed position with lock disengaged. Penstock & Draft tube gates are open. Air pressure to shaft gland isolating seal released.

PRESTART CHECK LISTPenstock drain valve should be closed. Fire fighting system should be healthy.No alarm/annunciation is present. Transformer oil flow/ oil pressure normal. Generator HV circuit breaker openGenerator Field breaker open. Prestart check indication unit ready to start-ON. For auto start from control room1. Gov. & exciter should be in Auto mode.2. Unit selection in local mode.

Start SequenceGIVE START COMMAND TO THE MACHINEMIV IS OPENED HS PUMP STARTS,MACHINE CREEPSGUIDE VANES OPEN, MACHINE PICKS UP SPEEDMACHINE REACHES 100% SPEEDCLOSE FIELD BREAKER,RAISE THE VOLTAGE TO 11KVFOR MANUAL SYNCHRONIZATION, TURN ON THE SYNCHROSCOPEMATCH THE LINE FREQUENCY AND LINE VOLTAGE WITH THE FREQUENCY AND VOLTAGE OF THE MACHINEWHEN CHECK SYNC. IN LIMIT LIGHT GLOWS,CLOSE THE HVCBINCREASE THE LOAD TO THE DESIRED LEVEL BY OPENING THE GVTURN OFF THE SYNCHROSCOPENOTE THE TIME OF SYNCHRONIZATION

STOPPING SEQUENCEINFORM NRLDC AND THE RECEIVING ENDREDUCE THE LOAD SLOWLY TO MINIMUM POSSIBLE VALUETRIP HVCBREDUCE THE FIELD CURRENT TILL THE TERMINAL VOLTAGE IS ALMOST ZEROTRIP FIELD BREAKER, GV CLOSESMACHINE RETARDSENSURE THAT HS LUB PUMP STARTS AT 30% SPEED(AUTO)BREAKS ARE APPLIED JUST AFTER THE HS PUMP STARTSMACHINE COMES TO STANDSTILLHS PUMP STOPSGENERATOR BREAKS RELEASESSHUT OFF COLLONG WATER SUPPLY TO STATOR, GT AND BEARINGSTURN OFF INTER PAD COOLING SYSTEM(IF RUNNING)

STOPPING SEQUENCEENGAGE GV LOCK, IF UNIT SHUT DOWN FOR LONGER PERIODRECORED THE TIME OF OPENING OF HVCB AND STOPPING OF MACHINE

DOSCheck the noise level at turbine and generator floors.Keep an hourly record of RTD & TSD temperatures on the log sheets and any abnormality to be taken due care of and corrective action be taken as required.Check for wobbling of the shaft during operation at the coupling and record. If wobbling is beyond permissible limit, further investigate the matter. Check the shaft vibration at salient points and take corrective action.Keep a close watch on operation of slip ring for any sparking, pitting etc.Check the oil level gauges in oil baths, which are accessible.Check actual flow of water through pipes & water pressure from flow indicator/relay/pressure gauges.Ensure that brakes are applied at the specified speed and with correct air pressure Record of unit stopping time from rated speed to braking speed to rest. Any change in braking time should be investigated.

DONTSDo not operate the machine in forbidden zone.Do not run the machine, if any, abnormal sound is there.Do not ignore any rise in stabilized temperatures. Cause should be investigated and if required, remedial action be taken.Do not run the machine, if water leaks through bearing coolers inside the oil bath.Do not apply brakes at higher speed and higher air pressure than what is specified as it may distort the brake track due to overheating. Do not start the unit until HS Lubrication system is switched on. Do not operate the unit at low speed with HS Lubrication system off, as such operation is likely to damage the TB pads.Do not synchronize the unit when out of the phase, as jerk of the unit is detrimental to its operation.Do not allow the unit to go to runaway speed.

S.No.Operation ParameterNormal ValueMax. Permissible limit/ Alarm Value/Trip Value1.Stator Winding Temperature90 C120 C 2.Rotor Winding Temperature95 C125 C 3.Generation Voltage11 kV11 kV(+/-) 5%4.Generation Current1850 A2362(0.90 Lagging P.F)5.Field Voltage340 V6.Field Current900 A at rated load530 A at no load & rated voltage7.Frequency50.00 Hz.50 Hz(+/-) 3%9.Generator Speed136.4 rpm136.4 rpm (+/-) 3 % (normal)115% speed- Unit tripping135% speed Elect. Overspeed trip150% speed- Mech. Overspeed trip280 rpm- runaway( on-cam)370 rpm runaway (off-cam)10.Power Factor0.9 lagging11.Brake operating air pressure5 kg/cm27 kg/cm2(Max.)12.Brake application speed30% of Syn. speed70 rpm (Max.)

S.No.Operation ParameterNormal ValueMax. Permissible limit/ Alarm Value/Trip Value13.Jacking Oil pressure85 bar14.Cooling water pressure7 kg/cm215.MVAR-Generator4.8 MVAR14 MVAR16.Gen. Air/ Oil circulating cooling water inlet temp.20-35C (depending on weather)17.Gen. Air/ Oil circulating cooling water outlet temp.30-45 C (depending on weather & load)18.Gen. Air/ Oil circulating cooling water inlet pressure5-6kg/cm27 kg/cm2(max.)5 kg/cm2(min.)19.Shaft seal cooling water pressure2-3 kg/cm220.Thyristor convertor bridge current200-250 A21.Runner blade angle ()Depends on load & guide vane opening Range of movement=20.5 22.Governor Oil pressure18-20 kg/cm215 kg/cm2(min. recomended)23.SST Winding Temperature50-60 C 80 C24.SST Oil Temperature50-55 C 70 C

S.No.Operation ParameterNormal ValueMax. Permissible limit/ Alarm Value/Trip Value25.UAT Winding Temperature50-60 C 80 C26.UAT Oil Temperature50-55 C 70 C27.220/132 kV Auto transformer- Winding Temperature50-60 C 80 C28.220/132 kV Auto transformer- Oil Temperature50-55 C 70 C29.Line Current(CB-Ganj-I/II)140 A/Line280 A30.Line Active Power (CB-Ganj-I/II)48 MW96 MW31.Line Reactive Power (CB-Ganj-I/II)5 MVAR/Line40 MVAR32.Line Voltage (CB-Ganj-I/II)220 kV245 kV(Max)/200kV(Min)33.Line Current(Nepal feeder)28 A98 A34.Line Active Power (Nepal feeder)0-20 MW50 MW35.Line Reactive Power (Nepal feeder)2.5 MVAR9.5 MVAR36.Line Voltage (Nepal feeder)132 kV145 kV(Max.)/120 kV(Min)

S.No.Operation ParameterNormal ValueMax. Permissible limit/ Alarm Value/Trip Value37.Water level (Barrage)246.7 m38.Water Level (Forebay)246.0 m-246.2 m246.4 m(Bye-pass)39.Water level ( TRC)221-223 mdepends on generation(No. of units running)40.Discharge( Sharda River)Upto 150000 cusecs (flood)41.Discharge (Head Regulator)20000 (max.) cusecdepends on load42.Silt in ppm100-1000 ppm-Summer/Winter1000-3500 ppm-Rainy Season5000 ppm max.

43.H.P Pressure Receiver40-42 kg/cm244 kg/cm244.L.P Pressure Receiver6-7 kg/cm245.L.P Station Receiver6-7 kg/cm246.Water pressure in spiral casing2-3 kg/cm24.7 kg/cm2(max.)47.Water pressure / vacuum below top cover-1 to +1 kg/cm248.Shaft gland water pressure2-3 kg/cm2

S.No.Operation ParameterNormal ValueMax. Permissible limit/ Alarm Value/Trip Value49.220 V DCDB Load Voltage220 V220 V+- 10% 50.220 V DCDB Load Current25 A40 A51.220 V DCDB Battery Voltage220 V220 V+- 10% 52.220 V DCDB Battery Current25 A40 A53.Max . guide vane opening ()Depends on loadUpto 46.2 & guide vane servomotor movement =660 mm54.Working air pressure of isolating seal3.0- 5.0 kg/cm26.0 kg/cm2(Max.)55. Max. Runner blade openingDepends on loadFrom 8.2 to +13.0 degrees .Servomotor movement = 105 mm.

Electrical S/D & Lock-out Circuits1Gen field fail Protection with U/V2Reverse power Protection3Gen. spilt phase diff.Protection4Generator stator main E/F protection5Generator Transformer Overall Diff. protection6Generator-Transformer HV REF Protn7Generator-Transformer HV Un.EF protn /Gen over flux protn.8Gen Transformer Buchh, no oil flow & no water flow protn9Emergency shutdown10Gen Transformer on fire/Gen on fire11Gen. Diff protn12Excitation TR O/C Protn.Trip Stage1/StageII13UAT Buchh. Trip Aux14UAT O/C protn15UAT REF protn.16Gen.link line Diff. protn17Generator E/F protn18LBB protn19Voltage balance scheme

Non-Electrical S/D & Lock out Tripping Circuits1Turbine guide bearing Temp.very high2Gen. Guide bearing Temp. very high3Gen thrust guide bearing Temp. very high4Gen air cooler inlet air temp.very high5Gen Tr. wdg Temp. very high6Gen Tr .oil temp very high7Governor oil press. Unit oil press Very low8Unit over speed Elect/Mech.speed9Governor failure10Controlled action shutdown

Elect.Non-Lock out Trip1Gen. Backup Imp protn.2Gen over voltage protn.3Gen. ve Ph sequence protn4Gen.loss of field protn.5No load Tripping protn6Excitation TR O/C instantaneous7Bus bar protn. Contact.

Condition Monitoring in Hydroelectric power stationCondition monitoring existed from eonsMan monitors own temperatureIn motors & generator you monitor whether sound and temperature , vibration etc are OKNew thing is we are able to monitor certain parameters online & real time which were not feasible earlier which was done offlineBenefit in term of reduced outage and increased utilization of useful lifeIn past simple hand held , portable devices used. Now more advanced computerized , IT Tool based Monitoring having historical data logging , trending & diagnostic features are available.

TechnologiesOffline

Analysis of Lubricating OilAnalysisi of transformer OilTan Delta & Power Factor of transformer bushingsThermography

Online Vibration analysisAir gap between stator & rotorTemperature of bearing , oil & windingInflowEfficiency of Turbine & generatorCavitation in turbineSilt monitoringPartial dischargeGas & moister in transformer oil

Vibration Monitoring & AnalysisMost effective method of detecting faults of various origin , diagnosis & analysis of fault and maintenance planningHydro units are generally vertical shaft & conditions & forces are uniqueVibration behavior is also unique and require specialized vibration monitoring equipmentPotential problems are Unbalance , Misalignment , Looseness , Bearing defects , Resonance , Electrical problems . Some problems specicific to hydro are rough load zone , Shear pin failure , Debris in guide vane / wicket gates , cavitation Radial & axial vibraion of important elements in terms of relative / absolute value is obtained by suitable sensors / probes and transmitted to monitoring , diagnostic , analysis system

For complete assesment vibraion mesurement is correlated with wicket gate opening , air gap , Flux , head , discharge , load etc

Vibration Monitoring & AnalysisMost important consideration is Type of probe / sensor and feature & functionality in monitoring /diagnostic softwareVibration transducer must give reliable & accurate measurement The latest development is capacitive probe which is superior to eddy current type proximity probes because air gap capacitance is immune to magnetic fields , metallurgical properties , electrical run out , shaft current , residual magnetism etc.Vibration behavior of a machine is an excellent indicator of the machine condition through which problems of various electrical / mechanical / hydraulic defects having origin in turbine as well as generator can be monitored and diagnosedIt is considered as most essential condition monitoring tool of generating units

Dissolved gas analysis of Transformer OilDGA is well established tool to asses health & suggest further course by assessing risk involved in operating with suspected faultsDGA only indicates suspected fault not conclusive in nature and further complementary tests are required for validating & pinpointingGases evolve due to normal aging of oil & cellulose as well as due to various faultsActual phenomena of gas generation is very complex and host of factors like type & design of equipment , load pattern , age , type of oil used , application etc affect gas generationThese gases partly dissolve in oil and also find way to free gas spaceRatio of dissolved and free gas depend on solubility of gas in oil in equilibrium conditionSuspected fault is analyzed by monitoring gas in free space and / or dissolved in oilAs name suggest in DGA the emphasis is on extracting & analyzing dissolved gases and pattern of gas generation indicate type & severity of fault

IEC METHOD Table 2 DGA interpretation table

CaseCharacteristic faultC2H2C2H4CH4H2C2H4C2H6PDPartial dischargeNS1D2Discharges of high energy0.6 2.50.1 - 1>2T1Thermal faultT1 butNS 7000C1>4NOTE 1- In some countries the ratio C2H2/C2H6 is used ,rather than the ratio CH4/H2. Also in some countries , slightly different ratio limits are used.Note 2- The above ratios are significant and should be calculated only if at least one of the gases is at a concentration and a rate of gas increase above typical values.( see clause 9NOTE 3 CH4/H2

Typical faults in power transformers

TypeFaultPDPartial DischargesDischarges in gas filled cavities resulting from incomplete impregnation, high humidity in paper , oil super saturation or cavitation and leading to Wax formationD1Discharges of low energySparking or arcing between bad connections of different or floating potential , from schielding rins , toriods , adjacent discs or conductors of winding , broken brazing or closed loops in the core.Discharges between clamping parts, bushing and tank , high voltage and ground within windings or tank wallsTracking in wooden blocks , glue of insulating beam , winding spacers. Breakdown of oil , selector breaking current.D2Discharge of high energyFlashover ,tracking or arcing of high local energy or with power follow through.Short circuits between low voltages and ground , connectors , windings, bushings and tank , copper bus and tank , winding and core , in oil duct , turret. Closed loops between two adjacent conductors around the main magnetic flux insulated bolts of core , metal rings holding core legs.T1Thermal faultsT , 3000COverloading of transformers in emergency situations.Blocked item restricting oil flow in winding.Stray flux in daming beams of yokes.

Typical faults in power transformers

TypeFaultT2Thermal fault3000C < t < 7000CDefective contacts between bolted connections ( Particularily between aluminium bus bar) , gliding contacts , contacts with selector switch ( Pyrolitic carbon formation), connection from cable and draw-rod of bushingsCirculating currents between yoke clamps and bolts , clamps and laminations , in ground wiring , defective welds or clamps in magnetic shields.Abraded insulation between adjacent parallel conductors in windingsT3Thermal faultT> 7000CLarge circulatin currents in tank and coreMinor currents in tank walls created by a high uncompensated magnetic field.Shorting links in core steel laminations

Ranges of 90 % typical values observed in power transformers of all types

Typical rate of gas increase for power transformers

Transformer sub typeH2COCO2CH4C2H6C2H4C2H2No OLTC600-150540-9005100-1300040-11050-9060-2803-50Communicating OLTC75-150400-8505300-1200035-13050-70110-25080-270NOTE 1 The values listed in this table were obtained from individual networks. Values on other networks may differ.NOTE 2 Communicating OLTC means that some oil oil and/ or gas communication is possible between the OLTC compartment and the main tank or between the respective conservator. These gases may contaminate the oil in the main tank and affect the normal values in these types of equipment. No OLTC refers to transformers not equipped with an OLTC or equipped with an OLTC not communicating with or leaking to the main tank.NOTE 3- In some countries, typical values as low as 0.5 l/l for C2H2 and 10 l/l for C2H4 have been reported.

HhdrogenMethaneEthaneEthyleneAcetlyneCarbon MonoxideCarbon Di oxide

IEEE Method , Dissolved gas concentrations

StatusH2CH4C2H2C2H4C2H6COCO2TDCGCondition 11001203550653502500720Condition 2101-700121-10036-5051-10066-100351-5702500-4000721-1920Condition 3701-1800401-100051-80101-200101-150571-14004001-100001921-4630Condition 4>1800>1000>80>200>150>1400>10000

Condition 1TDCG below this level indicates the transformer is operationg satisfactorily. Any individual cumbustible gas exceeding specified levels should be prompt additional investigation.

Condition 2TDCG within this range indicate higher than normal cumbustible gas level . Any individual cumbustible gas exceeding specified level should prompt additional investigation.

Condition 3TDCG within this range indicate a high level of decomposition. Any individual cumbustible gas gas exceeding specified levels should prompt additional investigation . Faults are probably present.

Condition 4TDCG within this range indicates excessive decomposition. Continued operation could result in failure of transformer.

Further action should be taken based on table 2

Actions based on TCG ( Total combustible gas in free space)

TCG levelsTCG Rate( %/day)Sampling interval and operating procedures for gas generation ratesSamplingIntervalOperating ProceduresCondition 4>=5>.03DailyConsider removal from serviceAdvise manufacturer.03 - .01Daily.03WeeklyExercise extreme caution.Analyze for individual gases.Plan outage.Advise manufacturer..03 - .01Weekly< .01MonthlyCondition 2< 2 to >=0.5>.03MonthlyExercise caution.Analyze for individual gases.Determine load dependence..03 - .01Monthly

Actions based on TDCG ( Total dissolved cumbustible gas in transformer oil)

TDCG LevelsPPMTDCGRates(ppm/day)Sampling interval and operating procedures for gas generation ratesSamplingIntervalOperating procedureCondition 4>4630>30DailyConsider removal from serviceAdvise manufacturer10 - 30Daily< 10WeeklyExercise extreme caution.Analyse for individual gases.Plan outageAdvise manufacturer.Condition 31921 - 1630>30WeeklyExercise extreme caution.Analyse for individual gases.Plan outageAdvise manufacturer10 30Weekly30MonthlyExercise cautionAnalyse for individual gases.Determine load dependence.10-30Monthly

Doernenburg method for fault interpretation , Based on Ratio of key gases

Ratio R1CH4/H2Ratio R2C2H2/C2H4Ratio R3C2H2/CH4Ratio R4C2H6/C2H2Extracted fromExtracted fromExtracted fromExtracted fromOilGas spaceOilGas spaceOilGas spaceOilGas space1. Thermal decomposition >1.0>1.0

Rogerss method for fault interpretationBased on ratios of key gases

CaseR2C2H2/C2H4R1CH4/H2R5C2H4/C2H6Suggested fault diagnosis00.1