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 VALVE AUXILIARY TRIP OIL-FOR PROTECTION

DEVICES SECONDARY OIL-FOR CONTROL VALVE AUXILIARY SECONDARY OIL-HYDRAULIC

GOVERNING. PRIMARY OIL –FOR SENSING SPEED START UP OIL –FOR RESETTING THE STOP

VALVE AND FOR RELEASING THE CONTROL VALVE

FUNCTION

AUXILIARY 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 SYSTEM

DURING 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 VALVES

WHENEVER 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 VALVES

MAIN 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 DEVICE

USED 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 PRESSURE

WHILE 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 PISTON

THE 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

OIL

AUXILIARY 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

PISTON

AUXILIARY SECONDARY

OIL

OVERSPEED TRIP DEVICE

CONSISTS 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 IT

HYDRAULICALLY DRIVEN EMERGENCY SHUT OFF VALVE

TO 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 OIL

SPEEDER GEAR(HYDRAULIC SPEED GOVERNOR)

TO OPERATE THE CONTROL VALVES TO GIVE THE APPROPRIATE TURBINE SPEED THROUGHOUT FOR THE PARTICULAR LOAD CONDITION

AUTOMATIC TURBINE TESTER

HEALTHINESS OF FOLLOWING COMPONENTS IS CHECKED ONLINE (WITHOUT TRIPPING OF TURBINE)

PROTECTION DEVICES - FUNCTIONING OF REMOTE TRIP SOLENOID- FUNCTIONING OF OVERSPEED TRIP FLYBOLTS- FUNCTIONING OF HYDRUALIC LOW VACUUM TRIP- FUNCTIONING OF THRUST BEARING TRIP

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

SCHEDULE 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 CONVERTER

LINK BETWEEN THE ELECTRICAL AND THE HYDRAULIC PART OF THE TURBINE CONTROL SYSTEM

CONVERTS THE SIGNAL FROM THE ELECTRICAL CONTROLLER INTO HYDRAULIC SIGNAL AND AMPLIFIES THEM BEFORE TRANSMITTING THEM TO THE ACTUATING DEVICES.