How governing system of steam turbine is being done?
(pictures insert is not being allowed by wiki. i am sorry)TOPICS OF DISCUSSIONCONCEPT OF GOVERNING SYSTEMFEATURES OF KWU GOVERNING SYSTEMOVERVIEW OF GOVERNING RACKFUNCTIONING OF EHC CIRCUITSFREE GOVERNOR MODE OPERATIONBEST PRACTICES IN GOVERNING SYSTEMEMERGENCIES IN GOVERNING SYSTEMWHAT IS GOVERNING SYSTEM ?n Turbine Governing system is meant for regulation of turbine speed under no load and varying load condition.n It helps in precise control of grid frequency under normal operation and protects the machine as well as grid during emergency situation.KWU GOVERNING SYSTEM-FEATURESn ELECTRO-HYDRAULIC GOVERNING SYSTEM WITH HYDRAULIC BACKUPn OPERATION OF STOP VALVES BY STARTING & LOAD LIMITING DEVICE (HYDRAULIC)n ROLLING, SYNCHRONIZATION & LOAD OPERATION BY HYDRAULIC / ELECTRO- HYDRAULIC SYSTEMn ELECTRO- HYDRAULIC SPEED GOVERNOR WITH HYDRAULIC BACK UPn SAFE SHUTDOWN BY HYDRAULIC / ELECTRO- HYDRAULIC SYSTEMn ELECTRICAL AND HYDRAULIC PROTECTION SYSTEM ALONG WITH TEST FACILITIESFEATURES OF EHCn AUTO ROLLING & SYNCHRONIZATION THROUGH SPEED CONTROLLER UNDER INFLUENCE OF TSEn CONSTANT LOAD OPERATION BY LOAD CONTR. WITH PRESSURE CONTR. AS BACKUPn RUNBACK OPERATION THROUGH PRESSURE CONTR.n EMERGENCY OPERATION THROUGH SPEED CONTR.n AUTO GRID FREQUENCY CONTROL THROUGH EXTERNAL FREQUENCY INFLUENCEn AUTO UNLOADING AT HIGH FREQUENCY THROUGH INTERNAL FREQUENCY INFLUENCEn CONTROL DURING AUTOMATIC TURBINE TESTING,ISOLATED GRID CONDITION & LSR OPERATIONSPEED CONTROLLER CIRCUITL - Raise & Lower command from UCB :nr - Speed Reference :nr limit - Delayed Speed Reference :NLC - No Load Correction (Ensures required Speed controller O/P for Rolling even when Speed reference n r matches n act.)n act - Actual Speed :hr nc - Speed Controller O/P with DROOP of + / - 10.0 V for nr lim ~ n act = 150 RPM ( GAIN = 22LOAD SET POINT GENERATION CIRCUIT1 - SET POINT FOLLOW UP when Automatic Grid Control or CMC In service(Other Raise / Lower commands get blocked)2 -- TSE ENABLING whenA) GCB is closed ANDB) Load controller (L C) not OFF ANDC) Fast calibration signal 6 absent ANDD) I) Load controller (L C) in controlOR ii) Pressure controller with initial pressure in actionOR iii) Turbine follow mode in serviceThis helps to bring manually adjusted gradient and stress effect in service.+/- 10 V gradient => +/- 25 MW / MIN for 200 MW unitsOR +/- 50 MW / MIN for 500 MW units.PRESSURE CONTROLLER CIRCUITEHC TRANSFER CIRCUITFGMO - BACKGROUNDn Unique frequency band of 49.0 Hz to 50.5 Hz, as specified by IEGCn Scheduling & dispatch by RLDCs/SLDCs is based on day ahead demand & availabilityn Frequency control by load-generation balance in every 15 mins time blockn Wide frequency variation during Grid disturbance, Unit outage, change in demand, etc.n No primary response by generators to maintain frequency under such system contingencyn Emergencies caused due to frequency control only through importing /cutting load by system operatornFGMO - GRID CODESn All generating units should have their speed governors in normal operation at all times to enable Grid frequency control by loading / unloadingn Droop characteristic for primary response should be within 3% to 6%n Each unit shall be capable of instantaneously picking up at least 5% extra load for a minimum of 5 mins (up to 105%MCR), during fall in frequencyn No dead bands and/or time delays shall be deliberately introducedn Facilities like load limiters, CMC, etc. shall not be used to suppress the normal governor actionIMPLEMENTATION OF FGMOIn line with clause Clause 1.6 of IEGC and CERC order dated 30-10-99, date of FGMO implementation, as decided by REBs are :-n Western Region - 19-05-03 ( ABT - 01-07-02 )n Southern Region - 01-08-03 ( ABT - 01-01-03 )n Northern Region - 01-10-03 ( ABT - 01-12-02 )n Nor-East Region - 22-12-03 ( ABT - 01-11-03 )n Eastern Region - 02-01-04 ( ABT - 01-04-03 )FGMO CHARACTERISTIC FOR KWU M/CMAJOR ISSUES WITH FGMO IN 2004Ø Wide and frequent variation of freq.Ø Perpetual oscillations in critical parameters due to Boiler response timeØ M/C subjected to cyclic loading and fatigue stressesØ Frequent HP/LP Bypass valve operationØ Continuous manual interventionsØ Self-defeating feature(Unloading when freq. improving towards 50 Hz)Ø Conflict with ABT(Offsetting freq. correction)TRANSIENTS IN GOVERNING SYSTEMn FAILURE OF POWER PACKS OF CONTROLLER RACKS IN EHC PANELn POWER SUPPLY FAILURE IN ATRS PANELn SIGNAL ACQUISITION PROBLEMn FAILURE IN TURBINE SYSTEMn ELECTRICAL SYSTEM FAILUREn COMPONENT FAILURE IN GOVERNING RACKn OPERATIONAL EMERGENCY1 CONTROL RACK SUPPLY FAILUREn M/C is on EHC. Power supply fails in Load control/Pressure control / transfer circuit rack. Starting device becomes off automatically due to EHC fault.Observation: EHC output is minimum/zero and load minimum/ zero with EHC fault alarm. Machine on bar with ESV & IV open (Turbine not tripped).Action: Confirm HP/LP bypass opening, isolate EHC from governing rack and parallely adjust starting device position from UCB. Reduce boiler firing to restrict rise in boiler pressure.2) SUPPLY FAILURE IN ATRS PANEL(ATRS=Automatic Turbine Rolling & Synchronisation)n M/C is on EHC. Power supply fails in CCA panels only.Observation: All indication lamps in ATRS consoles will go off. EHC output and Load will become zero due loss of GCB close feedback. All ATRS drives will become inoperative.Action: Confirm HP/LP bypass opening , isolate EHC. Reduce boiler firing. Adjust starting device position from local. Normalize power supply in CCA panels at the earliest.3) SIGNAL ACQUISITION PROBLEMn Loss of speed signal occurs due to Hall Probe / card failure.Observation: Speed indication will become zero. M/C will be loaded through speed controller. Subsequently Pressure controller will come in service. AOP & JOP will take auto start & Barring Gear valve Will open on auto.Action: Isolate EHC and adjust Starting device position. If pressure oil pressure is normal, make SLC of AOP, JOP and Barring Gear vlv OFF and stop AOP, JOP and close Barring Gear vlv.4)FAILURE IN TURBINE SYSTEMn Loss of speed signal occurs due to breakage of MOP shaft.Observation: Speed indication and pressure oil pressure will come down. M/C will be loaded through speed controller and Pressure controller will come in service. Subsequently, AOP & JOP will take auto start &Barring Gear valve. will open on auto.Action: Safe shutdown of M/C is to be ensured.5) ELECTRICAL SYSTEM FAILUREn M/C is on EHC with Tracking on. Starting device becomes inoperative due to Electrical module trouble/motor failure/overload.Observation: During increase in boiler firing, Boiler pressure will increase due to load restriction by Starting device. EHC output will go to 100%.Action: Switch off the electrical module of Starting device and increase Starting device position from local so that EHC can take control.6) FAILURE IN GOVRRNING RACKn EHC Plunger coil failuren EHC Pilot valve bearing failureObservation: EHC starts huntingAction: Isolate EHC and take Hydraulic mode in service. Replace the failed omponent. Governing characteristic checking should be done before EHC is put in servicen Speeder Gear spring tension gets altered.Observation: M/C may get unloaded at frequency lower than recommended value.Action: Speeder Gear spring tension may be adjusted to increase the start of unloading.Testing for proper setting should be checked during suitable opportunity.LOGICSA SPEED CONTROLLER LOGICS1 Command for slow rate at nr > 2850 RPM to facilitate easy synchronisation2 TSE Influence ON, when min of all the upper stress margins comes into picture to control gradient of nr lim and hence, acceleration of Rolling speed. Upper stress margin = 30 deg C => 10.0 V => 600 RPM ~ (Acceleration < 108 RPM ~ causes dn / dt tripping)B LOAD SET POINT GENERATION LOGICS1 Stopping of nr lim whena) GCB open ANDb) n act is < nr lim by approx. 45 RPM.This restricts hr nc up to around 30 % during Rolling to avoid wide v/v opening.2 Stopping speed set point control when,a) n act > 2850 RPM ANDb) nr raised ( I.e, nr > nr lim) ANDc) I) TSE ON and faulted in GCB open conditionOR ii) Stop command from SGC in SGC ON condition.3 Tracking in synchronized condition ifa) Frequency within limit (adjustable, say 48.5 to 51.5 Hz.) ANDb) Load controller O/P , hr PC > hr nc ANDc) I) Load controller (L C) in controlOR ii)Pressure controller in action4 Set Point Follow Up (Fast Calibration) duringa) Tracking condition 5 ( nr = n act + 21 RPM ) ORb) Turbine Trip ( nr = n act - 120 RPM ). Simultaneously nr lim immediately equals to nrCondition (a) ensures certain speed controller O/P during emergency to keep machine in rolled condition along with some load.Condition (b) ensures negative speed controller O/P during Trip condition.LOAD CONTROLLER (L C) IN CONTROL CONDITIONS -a) Speed OR Pressure Controller not in action ANDb) Isolated Grid condition absent ANDc) Both Load Controller OFF and Schedule OFF absent (I.e, L C ON)LOAD CONTROLLER SCHEDULE OFF - L C can be made OFF if Speed controller is in action and hrnc > hr PC. Otherwise, with OFF command OFF lamp blinks - called Schedule OFFC .LOAD SET POINT GENERATION LOGICS1TSE ON AND NOT FAULTEDThis helps to keep stress effect for gradient control in service.2-- LOAD GRADIENT ONThis helps to keep manual gradient control in service3-- STOP POWER SET POINT CONTROL whena) TSE ON and Faulted ORb) Stop command from SGC ORc) Pr raised when Pressure controller is in action with CMC ON OR Limit pressure mode selected OR Boiler follow mode selectedIn above conditions Pr lim stops, I.e,Set point can not be increased.4-- FAST CALIBRATION whena) Pressure controller is in action ORb) Follow above (h v0) condition presentUnder this condition MW error (ep) is selected and Pr lim immediately equals to Actual load (P act) without any gradient .5 -- FREQUENCY INFLUENCE ONThis is made ON from ATRS panel to put EXTERNAL FREQUENCY EFFECT in service forloading / unloading w.r.t. 50 Hz ( with 2.5 % to 8 % Frequency Droop)6 TSE TEST RELEASE : TSE TEST (For checking healthiness of TSE Margins) can be done whena) TSE Influence is OFF ORb) Both Pr, Pr lim and hr, hr lim are balanced, I.e, Speed and Power set point controls are not in action.D .LOAD CONTROLLER LOGICSFOLLOW ABOVE ( h v0 ) --a) GCB closed and load < 10 % (station load) ORb) GCB open ORc) Load controller OFFAbsence of these conditions help Load controller output to track above Pressure controller output when Pressure controller is in service.FOLLOW LOW ( h vu ) - GCB CLOSED AND Speed controller in action.This helps Load controller output to track below Speed controller output.8 -- Either a) Initial pressure mode selected ORb) Turbine follow mode in action ORc) CMC Runback activeThis ensures Load controller output above pressure controller output9 -- Load controller OFFThis defeats transmission of Load Controller output to Transfer circuit.R & L - Raise & Lower command from UCB :nr - Speed Reference :nr limit - Delayed Speed Reference :NLC - No Load Correction (Ensures required Speed controller O/P for Rolling even when Speed reference n r matches n act.)n act - Actual Speed :hr nc - Speed Controller O/P with DROOP of + / - 10.0 V for nr lim ~ n act = 150 RPM ( GAIN = 22LOAD SET POINT GENERATION CIRCUIT1 - SET POINT FOLLOW UP when Automatic Grid Control or CMC In service(Other Raise / Lower commands get blocked)2 -- TSE ENABLING whenA) GCB is closed ANDB) Load controller (L C) not OFF ANDC) Fast calibration signal 6 absent ANDD) I) Load controller (L C) in controlOR ii) Pressure controller with initial pressure in actionOR iii) Turbine follow mode in serviceThis helps to bring manually adjusted gradient and stress effect in service.+/- 10 V gradient => +/- 25 MW / MIN for 200 MW unitsOR +/- 50 MW / MIN for 500 MW units.PRESSURE CONTROLLER CIRCUITEHC TRANSFER CIRCUITFGMO - BACKGROUNDn Unique frequency band of 49.0 Hz to 50.5 Hz, as specified by IEGCn Scheduling & dispatch by RLDCs/SLDCs is based on day ahead demand & availabilityn Frequency control by load-generation balance in every 15 mins time blockn Wide frequency variation during Grid disturbance, Unit outage, change in demand, etc.n No primary response by generators to maintain frequency under such system contingencyn Emergencies caused due to frequency control only through importing /cutting load by system operatornFGMO - GRID CODESn All generating units should have their speed governors in normal operation at all times to enable Grid frequency control by loading / unloadingn Droop characteristic for primary response should be within 3% to 6%n Each unit shall be capable of instantaneously picking up at least 5% extra load for a minimum of 5 mins (up to 105%MCR), during fall in frequencyn No dead bands and/or time delays shall be deliberately introducedn Facilities like load limiters, CMC, etc. shall not be used to suppress the normal governor actionIMPLEMENTATION OF FGMOIn line with clause Clause 1.6 of IEGC and CERC order dated 30-10-99, date of FGMO implementation, as decided by REBs are :-n Western Region - 19-05-03 ( ABT - 01-07-02 )n Southern Region - 01-08-03 ( ABT - 01-01-03 )n Northern Region - 01-10-03 ( ABT - 01-12-02 )n Nor-East Region - 22-12-03 ( ABT - 01-11-03 )n Eastern Region - 02-01-04 ( ABT - 01-04-03 )FGMO CHARACTERISTIC FOR KWU M/CMAJOR ISSUES WITH FGMO IN 2004Ø Wide and frequent variation of freq.Ø Perpetual oscillations in critical parameters due to Boiler response timeØ M/C subjected to cyclic loading and fatigue stressesØ Frequent HP/LP Bypass valve operationØ Continuous manual interventionsØ Self-defeating feature(Unloading when freq. improving towards 50 Hz)Ø Conflict with ABT(Offsetting freq. correction)TRANSIENTS IN GOVERNING SYSTEMn FAILURE OF POWER PACKS OF CONTROLLER RACKS IN EHC PANELn POWER SUPPLY FAILURE IN ATRS PANELn SIGNAL ACQUISITION PROBLEMn FAILURE IN TURBINE SYSTEMn ELECTRICAL SYSTEM FAILUREn COMPONENT FAILURE IN GOVERNING RACKn OPERATIONAL EMERGENCY1 CONTROL RACK SUPPLY FAILUREn M/C is on EHC. Power supply fails in Load control/Pressure control / transfer circuit rack. Starting device becomes off automatically due to EHC fault.Observation: EHC output is minimum/zero and load minimum/ zero with EHC fault alarm. Machine on bar with ESV & IV open (Turbine not tripped).Action: Confirm HP/LP bypass opening, isolate EHC from governing rack and parallely adjust starting device position from UCB. Reduce boiler firing to restrict rise in boiler pressure.2) SUPPLY FAILURE IN ATRS PANEL(ATRS=Automatic Turbine Rolling & Synchronisation)n M/C is on EHC. Power supply fails in CCA panels only.Observation: All indication lamps in ATRS consoles will go off. EHC output and Load will become zero due loss of GCB close feedback. All ATRS drives will become inoperative.Action: Confirm HP/LP bypass opening , isolate EHC. Reduce boiler firing. Adjust starting device position from local. Normalize power supply in CCA panels at the earliest.3) SIGNAL ACQUISITION PROBLEMn Loss of speed signal occurs due to Hall Probe / card failure.Observation: Speed indication will become zero. M/C will be loaded through speed controller. Subsequently Pressure controller will come in service. AOP & JOP will take auto start & Barring Gear valve Will open on auto.Action: Isolate EHC and adjust Starting device position. If pressure oil pressure is normal, make SLC of AOP, JOP and Barring Gear vlv OFF and stop AOP, JOP and close Barring Gear vlv.4)FAILURE IN TURBINE SYSTEMn Loss of speed signal occurs due to breakage of MOP shaft.Observation: Speed indication and pressure oil pressure will come down. M/C will be loaded through speed controller and Pressure controller will come in service. Subsequently, AOP & JOP will take auto start &Barring Gear valve. will open on auto.Action: Safe shutdown of M/C is to be ensured.5) ELECTRICAL SYSTEM FAILUREn M/C is on EHC with Tracking on. Starting device becomes inoperative due to Electrical module trouble/motor failure/overload.Observation: During increase in boiler firing, Boiler pressure will increase due to load restriction by Starting device. EHC output will go to 100%.Action: Switch off the electrical module of Starting device and increase Starting device position from local so that EHC can take control.6) FAILURE IN GOVRRNING RACKn EHC Plunger coil failuren EHC Pilot valve bearing failureObservation: EHC starts huntingAction: Isolate EHC and take Hydraulic mode in service. Replace the failed omponent. Governing characteristic checking should be done before EHC is put in servicen Speeder Gear spring tension gets altered.Observation: M/C may get unloaded at frequency lower than recommended value.Action: Speeder Gear spring tension may be adjusted to increase the start of unloading.Testing for proper setting should be checked during suitable opportunity.LOGICSA SPEED CONTROLLER LOGICS1 Command for slow rate at nr > 2850 RPM to facilitate easy synchronisation2 TSE Influence ON, when min of all the upper stress margins comes into picture to control gradient of nr lim and hence, acceleration of Rolling speed. Upper stress margin = 30 deg C => 10.0 V => 600 RPM ~ (Acceleration < 108 RPM ~ causes dn / dt tripping)B LOAD SET POINT GENERATION LOGICS1 Stopping of nr lim whena) GCB open ANDb) n act is < nr lim by approx. 45 RPM.This restricts hr nc up to around 30 % during Rolling to avoid wide v/v opening.2 Stopping speed set point control when,a) n act > 2850 RPM ANDb) nr raised ( I.e, nr > nr lim) ANDc) I) TSE ON and faulted in GCB open conditionOR ii) Stop command from SGC in SGC ON condition.3 Tracking in synchronized condition ifa) Frequency within limit (adjustable, say 48.5 to 51.5 Hz.) ANDb) Load controller O/P , hr PC > hr nc ANDc) I) Load controller (L C) in controlOR ii)Pressure controller in action4 Set Point Follow Up (Fast Calibration) duringa) Tracking condition 5 ( nr = n act + 21 RPM ) ORb) Turbine Trip ( nr = n act - 120 RPM ). Simultaneously nr lim immediately equals to nrCondition (a) ensures certain speed controller O/P during emergency to keep machine in rolled condition along with some load.Condition (b) ensures negative speed controller O/P during Trip condition.LOAD CONTROLLER (L C) IN CONTROL CONDITIONS -a) Speed OR Pressure Controller not in action ANDb) Isolated Grid condition absent ANDc) Both Load Controller OFF and Schedule OFF absent (I.e, L C ON)LOAD CONTROLLER SCHEDULE OFF - L C can be made OFF if Speed controller is in action and hrnc > hr PC. Otherwise, with OFF command OFF lamp blinks - called Schedule OFFC .LOAD SET POINT GENERATION LOGICS1TSE ON AND NOT FAULTEDThis helps to keep stress effect for gradient control in service.2-- LOAD GRADIENT ONThis helps to keep manual gradient control in service3-- STOP POWER SET POINT CONTROL whena) TSE ON and Faulted ORb) Stop command from SGC ORc) Pr raised when Pressure controller is in action with CMC ON OR Limit pressure mode selected OR Boiler follow mode selectedIn above conditions Pr lim stops, I.e,Set point can not be increased.4-- FAST CALIBRATION whena) Pressure controller is in action ORb) Follow above (h v0) condition presentUnder this condition MW error (ep) is selected and Pr lim immediately equals to Actual load (P act) without any gradient .5 -- FREQUENCY INFLUENCE ONThis is made ON from ATRS panel to put EXTERNAL FREQUENCY EFFECT in service forloading / unloading w.r.t. 50 Hz ( with 2.5 % to 8 % Frequency Droop)6 TSE TEST RELEASE : TSE TEST (For checking healthiness of TSE Margins) can be done whena) TSE Influence is OFF ORb) Both Pr, Pr lim and hr, hr lim are balanced, I.e, Speed and Power set point controls are not in action.D .LOAD CONTROLLER LOGICSFOLLOW ABOVE ( h v0 ) --a) GCB closed and load < 10 % (station load) ORb) GCB open ORc) Load controller OFFAbsence of these conditions help Load controller output to track above Pressure controller output when Pressure controller is in service.FOLLOW LOW ( h vu ) - GCB CLOSED AND Speed controller in action.This helps Load controller output to track below Speed controller output.8 -- Either a) Initial pressure mode selected ORb) Turbine follow mode in action ORc) CMC Runback activeThis ensures Load controller output above pressure controller output9 -- Load controller OFFThis defeats transmission of Load Controller output to Transfer circuit.
