WHAT IS GOVERNING SYSTEM ROLE OF GOVERNING SYSTEM METHODS OF GOVERNING TYPE OF GOVERNING SYSTEMS CHARACTERISTICS OF GOVERNING

SYSTEM HIGH PRESSURE GOVERNING SYSTEM LOW PRESSURE BYPASS SYSTEM

IT IS A GROUP OF DEVICES PROVIDED IN STEAM TURBINE SYSTEM WHICH WORK IN COHERENCE TO MAINTAIN THE SPEED OF T-G SET CONSTANT.

THIS CAN ALSO BE DEFINED AS :

IT IS A GROUP OF DEVICES WHICH INITIATE THE CORRECTIVE ACTION TO RECTIFY THE DEVIATION OCURRED DUE TO VARIATION IN SET RELATION BETWEEN INPUT AND OUTPUT.

-MAINTAIN THE TURBINE SPEED REASONABLY CONSTANT AT ALL LOADS IN ORDER TO MAINTAIN THE GRID FREQUENCY WHEN TURBINE IS CONNECTED TO GRID . - PROVIDE VERY FAST CONTROLLING ACTION.

-SUCCESSFULLY LIFT AND CLOSE THE CONTROL VALVES ON WHICH VERY LARGE STATIC AND DYNAMIC FORCES ACT.

-PROVIDE A LINEAR RELATIONSHIP BETWEEN VALVE LIFT V/S LOAD.-TO BE VERY SENSITIVE TO SPEED CHANGES OF THE ORDER OF 0.06% OF RATED SPEED (ie 1.8 rpm).-TO BE FREE FROM HUNTING AND NOT TO HAVE INDUCED OSCILATIONS. (FOR ENSURING GOOD STABILITY A FEEDBACK SIGNAL IS PROVIDED AT EVERY STAGE OF SIGNAL AMPLIFICATION).

CLASSIFICATION OF GOVERNING METHODS IS DONE W.R.T. MODE OF REGULATION OF STEAM MASS FLOW TO THE TURBINE CORRESPONDING TO SPEED CHANGE.

- NOZZLE CONTROLLED GOVERNING- THROTTLE CONTROLLED GOVERNING

VALVE 1 VALVE 2

VALVE 4VALVE 3

VALVE 1 VALVE 2

MECHANICAL

HYDRO-MECHANICAL

HYDRAULIC

ELECTRO-HYDRAULIC

HIGH PRESSURE GOVERNING

MECHANICAL

HERE THE SPEED TRANSMITTER IS MECHANICAL CENTRIFUGAL TYPE SPEED GOVERNOR WHICH ACTUATES CONTROL VALVES THROUGH MEHANICAL LINKAGES.

PURE MECHANICAL GOVERNING SYSTEM ARE NOT USED FOR UTILITY TURBINES NOW A DAYS.

HYDRO-MECHANICAL

IN HYDRO MECHANICAL GOVERNING SYSTEM SPEED TRANSMITTER IS MECHANICAL CENTRIFUGAL TYPE SPEED GOVERNOR. IT IS CONNECTED TO A HYDRAULIC SYSTEM EITHER HYDRAULICALLY OR MECHANICALLY.IN THE HYDRAULIC SYSTEM, THE SIGNAL IS AMPLIFIED SO THAT CONTROL VALVES SERVOMOTORS CAN BE ACTUATED.

HYDRAULIC IN HYDRAULIC GOVERNING SYSTEM SPEED

TRANSMITTER IS CENTRIFUGAL PUMP WHOSE DISCH. PR. IS PROPORTIONAL TO SQUARE OF SPEED. THE PR. OIL IS SENT TO HYDRAULIC GOVERNOR WHICH GENERATES A HYD. SIGNAL PROPORTIONAL TO VALVE OPENING /CLOSURE REQUIRED.

THE HYD. SIGNAL IS SUITABLY AMPLIFIED THROUGH A HYD. AMPLIFIER BEFORE APPLYING IT TO CONTROL VALVES SERVOMOTORS.

HYD. AMPLIFIERwith F.U.Piston

HPCV SERVOMOTOR IPCV SERVOMOTOR

HPCV IPCV

HYD. SPEED GOVERNOR

HYD. SPEED TRANSMITTER

HYD. PRESS.

HYD. SIGNAL(ERROR)

HP SECONDARY OIL IP SECONDARY OIL

MECHANICAL COUPLING MECHANICAL COUPLING

ELECTRO-HYDRAULIC

IN ELECTRO-HYDRAULIC GOVERNING SYSTEM, SPEED TRANSMITTER IS ELECTRICAL SPEED MEASURING DEVICE WHICH SENDS AN ELECTRICAL SIGNAL TO ELECTRONIC CONTROLLER. AN ELECTROHYDRAULIC CONVERTER CONNECTS THE CONTROLLER TO A HYDRAULIC SYSTEM. THE HYD. SIGNAL IS AMPLIFIED SO THAT CONTROL VALVES SERVOMOTORS CAN BE ACTUATED.

THE ELECTRO-HYDRAULIC GOVERNING OFFERS MULTIPLE ADVANTAGES OVER OTHER THREE TYPES OF GOVERNING SYSTEMS AND IS VERY POPULAR FOR UNIT RATINGS LARGER THAN 200 MW.

EHCwith F.U.Piston

HPCV SERVOMOTOR IPCV SERVOMOTOR

HPCV IPCV

ELEC. SPEED TRANSMITTER

HP SEC. OIL IP SEC OIL

MECHANICAL COUPLING MECHANICAL COUPLING

ELECTRONIC CONTROLLER

ELECTRICAL SIGNAL

ELECTRICAL SIGNAL

(ERROR)

STEADY STATE SPEED REGULATION (ALSO CALLED PROPORTIONAL BAND, SPEED DROOP ETC.) IS DEFINED AS THE RATIO OF % SPEED DROOP FROM NO LOAD TO FULL LOAD TO THE NOMINAL SPEED.

IN THE STEAM TURBINES EQUIPPED WITH ELECTRO- HYDRAULIC GOVERNING SYSTEM, THE SPEED REGULATION CAN BE ADJUSTED BETWEEN 2.5 TO 8% IN VERY FINE STEPS.

IN THE EVENT OF FULL LOAD REJECTION, SPEED OF THE T-G SET SHOOTS UP TEMPORARILY BEFORE SETTLING DOWN TO STEADY STATE VALUE.

THIS TEMPORARY SPEED INCREASE IS CALLED TRANSIENT SPEED RISE AND IS EXPRESSED AS PERCENTAGE OF RATED SPEED.

VALUE OF TRANSIENT SPEED RISE IS RESTRICTED TO 8% OF RATED SPEED.

DUE TO INHERENT INERTIA OF THE COMPONENTS OF GOVERNING ELEMENTS AND FRICTION PRESENT IN GOVERING SYSTEM, CERTAIN MOTION OF GOVERNING SYSTEM IS LOST BEFORE CORRECTIVE SIGNAL CAN ACTUATE CONTROL VALVES.THE LOST MOTION IS CALLED DEAD BAND OF THE SYSTEM AND IS EXPRESSED AS PERCENTAGE OF THE RATED SPEED.

THE ORDER OF DEAD BAND IN SIEMENS TURBINES IS 0.06%.

CHARACTERISTIC LOW PR.GOV.HIGH PR.

GOV.OPERATING PR. 8/32 BAR 160 BAR

SIZE OF ACTUATOR BULKYSMALL &

COMPACT

COMMAND TOACTUATOR

HYDRAULIC ELECTRONIC

NO. OF PIPE CONN. INACTUATOR

6 2

GOV. & PROTECTIONELEMENTS

HYDRAULIC ELECTRONIC

CF PIPING LAYOUT 

VOLUMUNOUS &CONGESTED

SIMPLE & COMPACT

 

TURBINE VALVES

BYPASS VALVES

* HYDRAULIC POWER SUPPLY UNIT* ELECTO-HYDRAULIC ACTUATORS* TURBINE CONTROLLER (EHTC)* TURBINE PROTECTION SYSTEMS

HYDRAULIC POWER SUPPLY UNIT

SUPPLIES OIL TO THE ACTUATORS OPERATING MEDIUM - MINERAL OIL OR FRF 2X100% HIGH PRESSURE PUMPS HYDRAULIC ACCUMULATORS TWO RECIRCULATION PUMPS TO SUPPLY OIL TO

COOLING CUM FILTRATION / REGENERATION CIRCUIT

FLUID TANK EQUIPPED WITH LEVEL & TEMP MEASURING DEVICES

EMERGENCY SWITCH FOR SHUT DOWN OF SYTEM

AIR COOLERSAIR COOLERS

MANIFOLDMANIFOLD

PUMP MOTORPUMP MOTOR

FLUID TANKFLUID TANK

ENCLOSUREENCLOSURE

DRIP TRAYDRIP TRAY

LEVEL GAUGELEVEL GAUGE

ELECTRO-HYDRAULIC ACTUATORS

• POWER CYLINDER

- DISC SPRINGS, PISTON

• CONTROL MANIFOLD

- FOR SV ACTUATOR- PILOT VALVE, TRIP SOLENOID VALVES, CARTRIDGE VALVES & FILTER

- FOR CV ACTUATOR- SERVO-VALVE, TRIP SOLENOID VALVES,

CARTRIDGE VALVES & FILTER

STOP STOP VALVE VALVE

ACTUATORACTUATOR

CONTROL VALVE CONTROL VALVE ACTUATORACTUATOR

Cushioning

Piston

Actuator housing

Displacementtransducer

Spring packet

Spring housingMain orifice

Cushioning orifice

Coupling

Mounting flange

Optical position indicator

Simplified plant layout due to overall compact size

Due to higher operating hydraulic pressure (160 bar) the actuator sizes are greatly reduced and moreover with the use of electronic devices there is an overall reduction in equipment sizes and space requirement compared to bulky hydraulic equipments and system provided in low pressure hydraulic system.

Control oil piping reduced

Control oil piping from various hydraulic devices to the respective hydraulic servomotors will be greatly reduced with the provision of control blocks (servo/pilot valves) mounted directly on the high pressure actuators in high pressure governing system, which has only 2 connections one supply and the other return line from centralised supply unit device. The Governing racks provided in the low pressure hydraulic system will totally be eliminated with the provision of centralised supply unit.

Faster response due to state of art electronic control and protection system

In conventional hydraulic system hydraulic signal oil is routed through various protection devices thus causing delay in the operation of stop and control valves. In high pressure EHA based system these devices are not required as the protection are realised electronically.

Better interconnection with other system

Being microprocessor based system, interconnection with other system is easier, faster and more reliable.

Ease of operation and maintenance

With reduction in number of hydro-mechanical devices, the operation and maintenance of the EHA based system, which is more electronically governed equipment, will be easy and maintainable.

EACH ACTUATOR HAS 2 TSVs FOR REDUNDANCY

EACH TSV HAS TWO COILS FOR RELIABILITY. WORKS ON ‘DEENERGISE TO TRIP’ PRINCIPLE OVERSPEED PROTECTION IS REALISED

ELECTRICALLY. ON LINE CYCLIC TESTING OF TURBINE VALVES

IS PROVIDED ALL HYD. TRIPS REPLACED WITH ELECTRICAL

TRIPS

CV ACTUATOR

SV ACTUATOR

MANIFOLD

MANIFOLDINLET

LP Bypass system provide a very effective means of controlling reheat –steam flow during

Sudden load rejection Low-load / part load operation Startup

On receiving load rejection signal from electrical system:

Fast closure of HP & IP turbine control valves takes place.

Fast closure of turbine control valves causes an immediate decrease in HP & IP 1st Stage pressure

Subsequently the Pressure increases in reheat steam system

These pressure changes are sensed by LP Bypass controllers

Respective bypass valves are opened (In case LP bypass system fails or the condenser

cannot accept LP bypass steam , Safety Valves open and dump steam to atmosphere)

LP steam-bypass system operate in parallel with the Steam turbine to regulate the reheat steam flow at any load.

Protect Condenser from excessive temperature and pressure that could result from sudden injection of superheated steam

It regulates the reheater pressure to a fixed set value.

If the reheater pressure exceeds this set value, the Controller causes the electro-hydraulic actuator to operate and initiate bypass operation.

a) Condenser vacuum is low ( > 0.6 bar absolute )

b) Spray water pressure is low (< 8.5 / 9.5 bar )

c) Temperature of condenser body is high (> 90° C )