Turbine Governing (Steam Turbines)

TURBINE GOVERNING SYSTEM

PRESENTATION BY M DEENADAYALAN C M NIKHIL B VASANTH KUMAR

TOPICS OF DISCUSSION 

INTRODUCTION

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CONCEPT OF GOVERNING SYSTEM

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FEATURES OF KWU GOVERNING SYSTEM

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GOVERNING SYSTEM DEVICES

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WORKING OF GOVERNING SYSTEM

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HYDRAULIC AND ELECTROHYDRAULIC SYSTEM

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PROTECTIVE DEVICES IN GOVERNING SYSTEM

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QUERIES

WHAT IS GOVERNING SYSTEM ? 

Turbine Governing system is meant for regulation of turbine speed under no load and varying load condition.

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To regulate the steam control valve position and hence load generated.

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To control the initial run up and synchronization of the machine

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To assist in matching the power generated to that demanded by responding to the network frequency changes.

SALENT FEATURES OF 200 MW KWU TURBINE GOVERNING SYSTEM  

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KWU 200 MW turbine is a throttle governed machine. Two governors, electro-hydraulic and hydraulic are incorporated. Both the governors are connected in parallel. Only one governor can be selected at a time through the process of hydraulic minimum selection. The control valve opening depends on secondary oil pressure and there is a definite relationship between the opening of HP control valve and IP control valve. Between 40 to 200MW the turbine load is varied by changing the HP control valve throttling alone.

HYDRAULIC GOVERNOR SALIENT FEATURES  

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Hydraulic governor is having only one control loop called speed controller. Machine speed is measured and indicated as primary oil pressure. Range of speed control is 2800-3210 rpm. Speed regulation range (droop) of HG is 7%. HG acts as a back-up to the EHG. HG can not be isolated mechanically like EHG and HG is considered to be the primary governor of the KWU turbine

ELECTRO-HYDRAULIC GOVERNOR SALIENT FEATURES  

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EHG consists of three control loops for speed, load and pressure. EHG optimizes the turbine life by conservative operation with the aid of TSE. Faster response and precise frequency control. Actual speed of the turbine is measured by using hall probes Range of speed control is wider (0-3210) rpm. Speed regulation (Droop) can be changed from 2.5% to 8% in a step of 0.5% even when the machine runs on load. The usual setting of droop in EHG is 5%. EHG can be mechanically isolated by closing the secondary oil line from the local.

GOVERNING SYSTEM DEVICES 

Remote trip solenoids

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Follow-up piston

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Turbine trip gear

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Hydraulic amplifier

(Main trip valve)

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Electro-hydraulic

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convertor

Starting and load limiting device

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Sequence trimming device

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Speeder gear

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Solenoid for load shedding

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Auxiliary follow-up piston

relay

DIFFERENT OILS USED IN KWU TURBINE 

Control oil (source oil)

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Auxiliary secondary oil

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Auxiliary start-up oil

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secondary oil

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Start-up oil

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Test oil

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Auxiliary trip oil

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Primary oil

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Lube oil

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Jacking oil

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Trip oil

REMOTE TRIP SOLENOIDS

TURBINE TRIP GEAR

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Trip gear is the main protection mechanism of the turbine. It diverts

the control oil coming from the RTS in to TRIP OIL and AUX.TRIP OIL. Aux.trip oil keeps the trip gear spool valve in open condition so that uninterrupted trip oil pressure is ensured. Aux.trip oil is also connected to three hydraulic safety devices namely Over speed , Low

vacuum &Thrust bearing Trip Devices.

STARTING AND LOAD LIMITING DEVICE  

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USED FOR RESETTING THE TURBINE AFTER TRIPPING FOR OPENING THE STOP VALVES AND RELEASING THE CONTROL VALVES FOR OPENING STARTING DEVICE AT 0% POSITION   

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BELLOWS COMPRESSED (CONTROL VALVE CLOSED POSITION) AUX STARTUP OIL RESETS TRIP DEVICES STARTUP OIL RESETS STOP VALVES (ESVs AND Ivs)

PILOT VALVE(STARTING DEVICE) POSITION RAISED  

START-UP OIL AND AUXILIARY START-UP OIL CIRCUITS ARE DRAINED ESVS OPEN AT 42% AND IVS OPEN AT 56% POSITIONS OF THE STARTING DEVICE

SPEEDER GEAR  

ASSEMBLY OF A BELLOW AND A SPRING BELLOW COMPRESSION CONTROLLED BY 

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STARTING DEVICE POSITOIN SPEEDER GEAR POSITION (ALTERS SPRING TENSION) PRIMARY OIL PRESSURE

OPERATED FROM UCB OR LOCAL PRIMARY OIL PRESSURE (SPEED FEEDBACK)

AUXILIARY FOLLOW UP-PISTONS

TEST VALVES 

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HP/IP STOP VALVES RECEIVE TRIP OIL THROUGH THEIR RESPECTIVE TEST VALVES PORT OPENINGS FOR BOTH TRIP OIL AND START-UP OIL USED IN RESETTING OF STOP VALVES AFTER TURBINE TRIP VALVE CAN BE OPERATED WITH HANDWHEEL

WORKING OF GOVERNING SYSTEM CONTROL OIL

SPEEDER GEAR TRIP OIL

AUX START UP OIL TO RESET TRIP V/V

STARTING DEVICE

TRIP VALVE TRIP OIL

AFUP EHC INPUT

CONTROL OIL

TRIP OIL

CONTROL OIL FROM RTS

HYRAULIC CONVERTER

EHC

HP/IP STOP VALVE RESET

AUX TRIP OIL AUX TRIP OIL

LOW VACUUM TRIP DEVICE OVER SPEED DEVICE

FUP

FUP IP SECONDARY OIL

HP SECONDAY OIL

THRUST BEARING DEVICE

SELECTION BETWEEN HYDRAULIC AND ELECTRO HYDRAULIC GOVERNING MINIMUM PRESSURE BETWEEN HP AND IP SECONDARY OIL  TURBINE STARTUP USING EHC WITH HC SYSTEM FOR BACK UP  SECONDARY OIL PRESSURE SET HIGHER THAN THE EHC SYSTEM AND MAINTAINED USING A TRACKING SYSTEM 

ESV OPENING

PROTECTIVE DEVICES IN GOVERNING SYSTEM

TURBINE PROTECTON Two type of protection a)Electrical protection b)Mechanical tripping

Electrical protection(through RTS)  

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Turbine UCB manual trip Stator water conductivity >21 mho/sec Stator water flow 0.6mm)either in left side or right side, one sets of cam comes in contact with the pawl and thereby thrust bearing trip device’s latch will be released. This will cause the opening of the drain port through which auxiliary trip will be drained.

THANK YOU