TURBINE GOVERNING SYSTEM-AN OVERVIEW

AN OVERVIEW OF GOVERNING SYSTEM TURBINE GOVERNING SYSTEM-AN OVERVIEW THROTTLE CONTROLLED GOVERNING. THE GOVERNING SYSTEM HAS GOT FOLLOWING ADVANTAGES: 1)AVOIDS OVERSPEEDING OF TURBINE DURING LOAD THROW OFFS. 2)ADJUSTMENT OF DROOP IN FINE STEP,EVEN DURING ON-LOAD OPERATION. 3) FOR SMOOTH RUNNING OF THE STEAM TURBINE AT VARYING LOADS. OIL FROM MOT BEING USED AS THE SOURCE OF GOVERNING OIL 220MW STEAM TURBINE HOWEVER FRF FLUID BEING USED AS THE GOVN. OIL IN 500 MW STEAM TURBINE

TRIP OIL AUXILIARY TRIP OIL SECONDARY OIL AUXILIARY SECONDARY OIL START-UP OIL AUXILIARY- START UP OIL PRIMARY OIL CONTROL OIL

FUNCTIONS TRIP OIL FOR STOP VALVEAUXILIARY TRIP OIL-FOR PROTECTION DEVICESSECONDARY OIL-FOR CONTROL VALVEAUXILIARY SECONDARY OIL-HYDRAULIC GOVERNING.PRIMARY OIL FOR SENSING SPEEDSTART UP OIL FOR RESETTING THE STOP VALVE AND FOR RELEASING THE CONTROL VALVEFUNCTIONAUXILIARY START UP OIL FOR RESETTING PROTECTION DEVICES

ELEMENTS OF GOVERNING SYSTEM THE MAIN ELEMENTS OF GOVERNING SYSTEM: 1) REMOTE TRIP SOLENOIDS(RTS) 2) MAIN TRIP VALVE(TURBINE TRIP GEAR) 3) STARTING AND LOAD LIMITING DEVICE 4) SPEEDER GEAR(HYDRAULIC GOVERNOR) 5) AUX. FOLLOW-UP PISTON VALVES 6) FOLLOW- UP PISTON VALVES 7) ELECTRO-HYDRAULIC CONVERTER 8) SOLENOIDS FOR LOAD SHEDDING RELAY 9) TEST VALVE 10) OIL SHUT OFF VALVE 11) HYDRAULIC PROTECTION DEVICES

REMOTE TRIP SOLENOID(RTS)REMOTE TRIP SOLENOID OPERATED VALVES ARE TWO IN NUMBER AND FORM A PART OF TURBINE PROTECTION SYSTEMDURING NORMAL OPERATION OF TURBINE ,SOLENOIDS REMAIN DE-ENERGISED.IN THIS CONDITION THE CONTROL OIL FROM THE RACK IS FREE TO PASS THROUGH THEM TO THE MAIN TRIP VALVESWHENEVER ANY ELECTRICAL TRIP COMMAND IS INITIATED OR TURBINE IS TRIPPED MANUALLY FROM LOCAL OR UCB, THE SOLENOID VALVES GET ENERGISED.

IN THIS CONDITION THE DOWNSTREAM OIL SUPPLY AFTER THE RTS GETS CONNECTED TO THE DRAIN

MAIN TRIP VALVESMAIN TRIP VALVES (TWO IN NUMBER) ARE THE MAIN TRIP GEAR OF THE TURBINE PROTECTION CIRCUIT.ALL TURBINE TRIPPING TAKE PLACE THROUGH THESE VALVES.THE CONTROL OIL FROM REMOTE TRIP SOLENOIDS FLOWS INTO TRIP OIL AND AUXILIARY TRIP OIL.TRIP OIL IS SUPPLIED TO STOP VALVES AUXILIARY SECONDARY OIL CIRCUIT AND SECONDARY OIL CIRCUIT.

THE AUXILIARY TRIP OIL FLOWS IN A CLOSED LOOP FORMED BY MAIN TRIP VALVES AND TURBINE HYDRAULIC PROTECTIVE DEVICES. I.E. OVERSPEED TRIP DEVICE,LOW VACUUM TRIP DEVICE,AND THRUST BEARING TRIP DEVICE.

WHENEVER CONTROL OIL PRESSURE DROPS OR ANY OF THE HYDRAULIC PROTECTIVE DEVICES ARE ACTUATED,THE MAIN TRIP VALVES ARE TRIPPED,THE TRIP OIL IS DRAINED RAPIDLY THROUGH THE MAIN VALVES,CLOSING TURBINE STOP AND CONTROL VALVES.

STARTING AND LOAD LIMITING DEVICEUSED FOR RESETTING THE TURBINE AFTER TRIPPING,FOR OPENING THE STOP VALVES AND RELEASING THE CONTROL VALVES FOR OPENING.CONSISTS OF A PILOT THAT CAN BE OPERATED EITHER MANUALLY BY HAND WHEEL OR BY MEANS OF REMOTE.AT 0 POSITION OF THE PILOT VALVE ALL THE PROTECTION GET RESET AND THE SPEEDER GEAR BELLOW GETS COMPRESSED ,AVOIDING THE DEVELOPMENT OF SECONDARY OIL PRESSUREWHILE OPENING THE VALVE THE START UP OIL GETS DRAINED ,THUS OPENING THE STOP VALVE ESV OPENS AT AROUND 42%OF THE POSITION OF STARTING DEVICE.

FOLLOW UP PISTONTHE TRIP IS SUPPLIED TO THE FOLLOW UP PISTON VALVES THROUGH ORIFICES AND FLOWS IN THE SECONDARY OIL PIPING TO CONTROL VALVES.THE SECONDARY OIL PRESSURE DEPENDS UPON THE POSITION OF THE SLEEVES OF FOLLOW UP PISTON.TRIP OILFOLLOW UP PISTONSECONDARY OILAUXILIARY FOLLOW UP PISTON TWO AUXILIARY FOLLOW UP PISTON ARE CONNECTED IN PARALLEL AND THE TRIP OIL IS SUPPLIED TO THEM THROUGH ORIFICE. THE AUXILIARY SECONDARY OIL PRESSURE DEPENDS UPON THE POSITION OF THE SLEEVE OF THE AUXILIARY FOLLOW -UP PISTON. TRIP OILAUXILIARY FOLLOW UP PISTONAUXILIARY SECONDARY OILOVERSPEED TRIP DEVICECONSISTS OF TWO STRIKERS ECCENTRICALLY MOUNTED ON THE MAIN TURBINE SHAFT AND RESTING AGAINST THE SPRING FORCE.IN CASE OF OVERSPEEDING OF THE TURBINE I.E 10-11% OVERSPEEDING THE STRIKERS GET OUT OF THE SPRING FORCE AND HIT THE PAWLS.THIS ULTIMATELY GIVES COMMAND FOR CONNECTING THE AUXILIARY TRIP OIL TO DRAIN THEREBY DEPRESSURISING ITHYDRAULICALLY DRIVEN EMERGENCY SHUT OFF VALVETO INTERRUPT THE SUPPLY OF OIL TO ALL CONTROL &PROTECTION DEVICES IMMEDIATELY IN CASE OF FIRE DUE TO LEAKAGE IN CONTROL OIL SYSTEM.OPERATED BY HYDRAULIC OILSPEEDER GEAR(HYDRAULIC SPEED GOVERNOR)TO OPERATE THE CONTROL VALVES TO GIVE THE APPROPRIATE TURBINE SPEED THROUGHOUT FOR THE PARTICULAR LOAD CONDITION

AUTOMATIC TURBINE TESTERHEALTHINESS OF FOLLOWING COMPONENTS IS CHECKED ONLINE (WITHOUT TRIPPING OF TURBINE)

PROTECTION DEVICES FUNCTIONING OF REMOTE TRIP SOLENOIDFUNCTIONING OF OVERSPEED TRIP FLYBOLTSFUNCTIONING OF HYDRUALIC LOW VACUUM TRIPFUNCTIONING OF THRUST BEARING TRIP

TURBINE STOP & CONTROL VALVE - FREE MOVEMENT OF ALL HP / IP STOP VALVES- FREE MOVEMENT OF ALL HP / IP CONTROL VALVESSCHEDULE OF TESTING

ATT FOR PROTECTION DEVICES TWICE IN A WEEK

ATT FOR TURBINE STOP & CONTROL VALVE ONCE IN A MONTH

ATT FOR PROTECTION DEVICES IS CONDUCTED AT FULL LOAD CONDITION WHEREAS FOR TURBINE STOP & CONTROL VALVE IT IS CONDUCTED AT PART LOAD CONDITION.

ELECTROHYDRAULIC CONVERTERLINK BETWEEN THE ELECTRICAL AND THE HYDRAULIC PART OF THE TURBINE CONTROL SYSTEMCONVERTS THE SIGNAL FROM THE ELECTRICAL CONTROLLER INTO HYDRAULIC SIGNAL AND AMPLIFIES THEM BEFORE TRANSMITTING THEM TO THE ACTUATING DEVICES.THANK YOUSheet1

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