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To operate &control Emergency Stop valve, Controlvalve & Extraction NRVs during normal ,start up,shut down & Load changes on the unit.

To prevent the Turbine reaching dangerouscondition.

To protect the turbine by closing ESV &control

valves &extraction NRVs in case of any dangerousoperating condition.

To test & ensure healthiness of protection device.

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Electro - HydraulicGoverning

( EHG)

Mechanical HydraulicGoverning

( MHG)

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Reset MTV &Open ESV

Load Limiter

Hydraulic Converter

Follow up Piston

Develop Sec. OilPressure

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LoadController

Electro - Hydraulic Governing

(EHG)

SpeedController

PressureController

Electro Hydraulic Converter

Follow-up Piston

Develop Sec. OilPressure

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Pre- Emergency DevicesLoad Shedding Relay Trim Device

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Load shedding Relay

For short time interruption of secondary oil

to control valves / extraction NRV relay

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Trim -Device

To limit rise in H.P.exhaust hood

temperature in case of load drop below 20%

coupled with rise in CRH pressure.

To facilitate Turbine operation with OR

without HP-LP bypass.

This is achieved by adjusting relative

opening of IPCV with respect To HPCV

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How does Turbine

Trip take place?

Solenoid Trip

Manual Trip

Overspeed Trip

Thrust Bearing Trip

Vacuum Trip

Aux. Trip fluid pressure drops Throughcorresponding channel

Trip valves are actuated & Trip fluid

pressure drops

Closes all ESV& Closes control valves

through secondary fluid pressure drop

Closes extraction check valve

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Emergency Governing Devices

Solenoid Trip

(Remote trip)Over-

speed

Trip

Local

Manual

Trip

Thrust

Brg. Wear

Trip

Condenser

Vacuum Low

Trip(Mech.)

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Manual (local trip )

Should not be operated while ATT isin

progress as otherwise turbine will trip

electrically through Limit switches.

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Solenoid Trip ( Remote Trip )

UCB Trip push button

Boiler Trip

Turbine Lub Oil pr. LoLo

Low Condenser Vacuum (Elec.) High Primary water Temp.

H.P. turbine casing distortion High

I.P. Front / Rear casing distortion

High

Generator bushing box level High Primary water flow LoLo( stator

winding)

Primary water flow LoLo

(Generator bushing )

Generator Hydrogen gas

Temperature HiHi

Exciter cooling air temperature

HiHi Generator Seal oil Temperature

Hi

Fire protection push button

operation

Generator protection signals

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Automatic Turbine testing

Turbine protection

testing (safety device )

MS / RH ESV & Control

valve testing

Remote solenoid

Thrust bearing

Over speed

Low vacuum

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Over speed trip device testing methods

1) By Automatic Turbine Tester (On Load )

2) By Local manual ( On Load )

3)Tested under actual over speed condition

(Off bar condition )

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Over speed trip device testing manual

1) Isolate Over speed Trip from Turbine trip circuit by

manually depressing KA03.

2) Move Center valve down with hand wheel KA01, allowinginjection oil to reach o/s trip bolts and making them fly

outwards thereby actuating o/s trip mechanism

3) Bring the center valve back to its original position with hand

wheel (KA01)

4) Reset O/S trip mechanism by depressing valve KA02 &

then releasing KA02

5) Release valve KA03 making protection effective again.

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Over speed trip device testing(During ATT )1) O/S Trip device made ineffective in tripping Turbine. (End

step of pre test )

2)Center valve of O/S trip tester moved down ( with elec.Motor )to admit injection oil into O/S bolts and actuating

O/S mechanism and MTV.

3) Center valve moved back to its Original position.

4) MTV & O/S trip mechanism reset and protectionnormalised.

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STEP

1) Closing command given for motor

operated positioner of control valve

2) Test solenoid valve 1 energised

3) Test solenoid valve 2 energised

4) Test solenoid valve 1 De- energised

RESULT

1) Control valve closes

2) Changeover Slide valve moves up

and depressurises the space belowpiston disc of ESV, Thus closing

stop valve

3) Test valve moves down and admit

trip fluid above Top disc of ESV

actuator and forces Top disc to

reach its bottom position

4)C/O Valve moves down and blocks

the drain for bottom disc of ESV.

MS / RH ESV & Control valve testing

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MS / RH ESV & Control valve testing

STEP

5) Test solenoid valve 2 energised.

6) Opening command given for motor

operated positioner of control valve.

RESULT

1) Test valve moves up and allows trip

medium to pressurise underside of

bottom disc & De- pressurise spaceabove top disc of ESV, Thereby

opening stop valve.

6) Control valve opens as per

secondary oil pressure.

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Turbine protection testing

Pre Test Main Test Reset

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Pre Test STEP

1) Both ATT Sol. Valves energised

2) 1st solenoid valve De-energised

3) 2nd solenoid valve de-energised

4) Both ATT sol. Valves energised again

5) C/O valve solenoid valve energised

RESULT

1) Control medium pr. Builds up

upstream of changeover valve

2) Control medium between 1st sol.&

c/o valve is drained

3) Control medium between 1st & 2nd

sol. valve is drained

4)Control medium pr. Builds up

upstream of changeover valve

5)Drains control fluid at the bottom of

C/O V/V to bring it down Thus

change over Trip fluid supply to Att

Sol.

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Resetting STEP

1) Both reset solenoid valves

energised

2)1st Reset solenoid valve De-

energised3) 2nd Reset solenoid valve De-

energised

RESULT

1) Aux. Startup fluid pr. Builds up

and forces the tripped

protection device back to itsnormal position also forces

MTV to reset position

2)Aux. Startup fluid pr. Down

stream of 1st sol.is drained

3)Aux. Startup fluid depre

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Over speed trip device testing (Actual over speed )

1) Bring the Turbine to no load condition

-turbine running at rated speed &GT

breaker open.

2) Depress lever KA07 of speeder gear

thereby increasing secondary oil pressure

and control valve opening to reach O/Slimit. O/S trip mechanism is actuated &trips

the turbine through actuation of MTV.

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Vacuum Trip Device Test -ATT

1)Mechanical vacuum trip device made ineffective in tripping

turbine. (Pre test last step ) *** Electrical vacuum trip

remains effective during test.

2) Test solenoid valve energised and atmospheric pressure

applied on the top of diaphragm thereby achieving the same

effect as it has tripped.

3)Test solenoid valve De- energised & Device gets reset.

4) Main Trip valve reset & original condition restored.

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Thrust bearing wear trip device Testing -ATT

1)Thrust bearing wear trip made ineffective in tripping turbine.

( Pre test Last step)

****Thrust bearing wear trip protection is not availableduring test.

2)Hydraulic Test signal transmitter is energised thereby

admitting test oil and actuating the trip mechanism and

Main Trip Valve

3) Main trip valve & thrust bearing trip mechanism reset and

protection normalised. ( Resetting)