Internal

Prepared by -E.KARTHIK
Internal OPERATION
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CONTENT
 INTRODUCTION
 WHAT IS GOVERNING SYSTEM
 FUNCTIONS OF DEH
 HYDRALLIC POWER UNIT
 WHY FIRE RESISTANT OIL
 BASIC REQUIREMENT OF GOVERNING SYSTEM
 DEH P&ID
 TURBINE LATCHING MECHANISM(LUBE AND HP OIL)
 MANAGEMENT OF VALVES
 TURBINE TESTING
 ONLINE TEST(NOT SIMULATED)
 SPRAY OIL TEST(FLY RING HEALTHINESS)
 ELECTRICAL OVERSPEED AND ITS PROTECTION
 MSV OPERATION (HP OIL)
 GOVERNOR VALVE OPERATION(OPC OIL )
 INTERLOCK AND PROTECTIONS
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CONTENT
 SWITCHES AND SOV’S FUNCTIONS(LUBE & HP OIL)
 CONDITIONS FOR TURBINE TRIPPINGS
 ANTICIPATED CONDITIONS AND CHECKS
 (for latching & spray oil test)
 HOW MECHANICAL I/P CONVERT TO ELECTRICAL O/P

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INTRODUCTION
•To govern means to control and regulate certain parameters to
achieve expected functional Requirements.

•As a matter of facts the output speed characteristic of steam

turbine is not suitable for electrical generation purpose, therefore
some additional form of control must be Applied to ensure that
dynamic change in consumers demand for electrical power are
followed automatically without large deviation from the nominal
electrical frequency(.i.e.) 50HZ in our country.

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WHAT IS GOVERNING SYSTM

 Turbine governing system is meant for regulation of
turbine speed under no load and varying load condition.
 To regulate the steam control valve position and hence load
generated.
 To control the initial run-up and synchronization of the
machine.
 To assist in matching the power generated to that
demanded by responding to the network frequency
changed.

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 The emergency governing system is the actuating mechanism of

the DEH, which works on instruction reception from the DEH,
latching, valve driving and unit interruption, etc.
 The system can be subdivided into a low pressure emergency
governing system and a high pressure fire-resistant oil system
based on its constituents.
 The high pressure fire-resistant oil system is composed by
hydraulic servo system, high pressure trip system and fire-
resistant oil supply system.

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FUNCTION OF DEH
a)Speed control(Latch to 3000 RPM)
b)Overspeed protection function(OPC OIL )
c)Overspeed trip test(HP SAFETY OIL)
d) Auto Synchronize the unit(NO LOAD TO FULL LOAD)
e)Base Mode Operation(valve mode)
f)Load control
g)The function CCS(SLIDE & FIXED)
h)TFCC(SLIDE & FIXED),BFCC(SLIDE & FIXED)
i)Remote control mode
j)Function of valve management
k)The function of valve test
l)The function of throttle pressure limited
m)Manual/Automatic control mode
n)Automatic limit function
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NAME PLATE DETAILS

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EH FLUID SUPPLY PORTION

HP fluid used in EH system to actuate the valves.
The function of the EH fluid supply portion is to provide high pressure oil
to the governing system.

This system consists of filtering unit, fluid conditioning unit, cooling unit,
pressure regulating unit, etc.

accumulators are given to maintain pressure.

This system is used to condition & supply the EH fluid to
all the servo actuators.

It mainly consists of the oil tank, the main EH oil pump, the high
pressure devices including the regenerative device and the the EH oil
circulating pump, the oil filtering component and the associated oil
pipeline.

Internal
Internal EH OIL TANK OVER VIEW

CONTROL BLOCK

HPT MODULE TDBFP A

MS STOP V/V TDBFP B

GOVERNOR V/V
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HYDRALLIC POWER UNIT

LOACL LEVEL GUAGE

PUMP B DIS PR

EH OIL SYSTM PR

EH OIL CYCLE PUMP PR

EH OIL TANK

EH OIL STANDBY PUMP

EH OIL RUNNING P/P

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EH OIL PUMP B SUCTION MIV
EH OIL PUMP A SUCTION MIV
INTERFACE BETWEEN CONTROL
BLOCK AND TERMINAL BLOCK

EH OIL PUMP A DIS

TO CONTROL BLOCK

EH OIL PUMP B DIS

TO CONTROL BLOCK
PUMP B SELF REGULATING
LINE TO TANK

PUMP A SELF REGULATING

LINE TO TANK

SELF REGULATING MULTI PISTON PUMP

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EH OIL CONTROL BLOCK

Control block is placed at the bottom of the tank. The
purpose of the control block is to control the fluid pressure. It is
provided with two 5-micron cartridge filter at each discharge
line to filter the EH-supply fluid. Check valve is provided in
each pumps discharge side to avoid back flow of fluid to
standby pump. Two shut-off valves are provided in between the
pump suction & discharge side, this enable the standby stream
to avail maintenance/replacement of strainer
check-valve, pump during online. Relief valve is provided in the
downstream of discharge, this enables to control the discharge
pressure of EH supply. The system discharge pressure can be
adjusted by using pressure control knob present in the control
block. Some portion of the oil will be drained if the pressure of
the EH fluid exceeds the preset value
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EH OIL CONTROL BLOCK

MS STOP VALVE

MS CONTROL VALVE

IP/STOP/CONTROL VALVE

HP TRIP VALVE

TDBFP A OIL

TDBFP B OIL

TDBFP A ISOLATION VALVE

TDBFP B ISOLATION VALVE

Internal EH OI L PUMP COMMON VENT VALVE

Internal
CONTROL BLOCK SIDE VIEW
PUMP B DIS LINE

PUMP B DIS LINE

2CHECK VALVES

PRESSURE ADJUSTING NOB

MAIN CONTROL BLOCK INTERFACE

PRESSURE ADJUSTING NOB

DIS CHARGE 5 MICRONS CATRIDGE FILTERS

CONTROL BLOCK FRONT VIEW

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MAIN TERMINAL BLOCK

PL PLL

24yv 25 YV
TESTING V/V TESTING V/V

INPUT FROM CONTROL BLOCK TO ETS

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High pressure fire-resistant oil system

 The EH (electro-hydraulic) oil supply system is used for driving
the servo actuating mechanism by the supply of the high pressure
fire-resistant oil to adjust openings of each steam valve in response
to electric command signal from a DHE controller.
 The high pressure fire-resistant oil of the unit is chemical synthesis
of tricresyl phosphate (TCP)-TURBO 46 with density more than water,
viscosity little more than the turbine oil under normal temperature,
antiglare temperature in excess of 538 degrees centigrade during an
open-flame test and excellent fire resistance and fluid stability, but little
toxicity.
 Oil supply pressure: 14.2±0.2MPa.

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Why Fire resistant Fluid?

 Mineral Lube Oils used in Hydraulic system situated adjacent to
equip. maintained at high temp. Have always constituted a
considerable fire risk.
 Even at ambient temp. Fires have occassionally resulted due to
leaking of hydraulic fluid on hot surfaces past in power stations.
 So hydraulic oil is replaced by fire resistant fluid.
 FRF is used as a working medium for EH System
❖ Desirable characteristics of FIRE RESISTANT FLUID
➢ Chlorine content < 100 ppm to avoid erosion of system parts.
➢ Water content < 0.1% to avoid hydrolyzing of oil.
➢ Acid value < 0.2 Mg KOH/gram to avoid erosion of system parts.
➢ The cleanliness of oil quality NAS 5 grade or MOOG 2 grade is
needed for system where service pressure is as high as >12 Mpa.
➢ Oil should not burn Or ignite up to 5500C & its thermal stability
should be up to 7500C.
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Accumulator & Polishing filter

 HP accumulator is butyl rubber leather type of accumulator in 3

groups totally with a pre-charged nitrogen pressure of 10Mpa.
 It is used maintain the pressure surge instantaneously
increased in the system and to reduce the system oil pressure
pulsation.
 Polishing filter –Fuller’s Earth filter & cellulose filter- 3.8L/min.
 To maintain the fluid neutralization number & removing water
particle .
 Press increase in filter 0.21 mpa with fluid temp (43-54) need
replace.
 Replace ion exchange resin depends cation or anion in fluid.

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6SIX NO OF ACCUMULATORS

BREATHER

EH OIL DRAIN LINES TO TANK

OIL TO COOLER I/L

OIL TO COOLER O/L

Internal EH OIL COOLER A & B

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FILTER O/L TO TANK I/L

CORRUGATED CELLULOSE
FINE FILTER 20 MICRONS

FULLERS EARTH FILTER

5 MICRONS

FROM CYCLE P/P O/L

TO FILTER I/L

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BASIC REQUIRMENT OF GVRNG SYTM

1. Turbine latch,
2. Meeting the combined startup requirement from the high and
low pressure cylinders,
3. Meeting the combined startup requirement from the intermediate
pressure cylinder,
4. With an over-speed limit function,
5. Quickly and reliably interrupting the steam admission from the
steam turbine in need,
6. With an over-speed protection function.
7. Main functions of the system comprise latch and interruption.
8. In view of reliability, three extra interrupting means for this
system is set, including electric, mechanical and manual
interruptions
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P&ID
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TRIP OIL NOT FOR

OSP

OVER SPPED PROTECTION OIL

NOT FOR TRIPPING

DCS LATCH

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AUTO –THERMAL STATE JUDGMENT

It is required to heat the turbine in order to reduce the thermal stress. DEH
Classify the thermal conditions based on inner wall temperature of HP
internal cylinder upper casing at the steam turbine governing stage.

 COLD STATE T ≤ 320 oC

 WARM STATE 320 < T < 420 oC

 HOT STATE 420 < T < 445 oC

 EXTREME HOT T ≥ 445 oC

STATE

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LATCHING-RESET -TUR-PROTECTION

Permits for the LATCHING

 The turbine is tripped
 All valves are full closed

HP Safety oil pressure is generated

 HP safety oil & return oil are controlled by levers of Emergency Trip
Device
 Latch Action shuts the return oil and builds HP safety oil pressure
 ( Indicated from PS1,PS2 and PS3)
 DEH receives LATCH command and solenoid valve ( Rest and Test)
1VY is energized.
 Lub oil enters into the side piston Chamber of Emergency trip device
and shuts off the return oil thru Trip and Isolated Group valve
 At the same time HP trip module solenoid valves 5VY,6VY,7VY and
8VY are energized and builds up HP Trip oil

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TURBINE-LATCH PROCESS
The Reset solenoid valve 1YV of reset and test group valve and limit switches ZS1
and ZS2 of mechanical trip mechanism provided in the system are used for
resetting.
When the reset command is operated from DEH the reset solenoid valve 1YV of
resetting and trip group valve is energized and actuated which leads the lube into
the piston side chamber of emergency trip device.
The piston moves to upper center so that the stay hook of emergency trip device is
reset which reset the mechanical trip valve of trip and isolated valve with the link
lever of the mechanical trip mechanism.
Which seals or stop the turbine drain oil of HP trip line.
The 2 out of 3 pressure switches of the pressure switch assembly will send the
signal to DEH when they detect that the HP protection oil has been formed
De-energizes the reset solenoid valve 1YV and the piston of emergency trip device
will move back to lower center.
DEH senses that normally open contact of limit switch ZS1 indicates the status of
reset power cylinder and ZS2 indicates the status of trip device.
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OVERVIEW

 The emergency governing system is the actuating mechanism of the DEH,

which works on instruction reception from the DEH, latching, valve
driving and unit interruption, etc.
 The system can be subdivided into a low pressure emergency governing
system and a high pressure fire-resistant oil system based on its
constituents.
 The high pressure fire-resistant oil system is composed by hydraulic servo
system, high pressure trip system and fire-resistant oil supply system.

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SYSTEM ARRANGEMENT
Emergency governor

 It is a device for protecting the steam turbine from excessive

speed, namely an emergency governor, an interrupter or an
emergency over-speed governor, and one of the important over-
speed protection devices as well.
 The eccentric ring emergency governor employed in our
plant is assembled on a minor control axle at the head of the
unit’s major axle and rotates with the rotor.

Internal
 Internal Low pressure emergency governing system
TO HP SAFETY OIL and High pressure trip system
(AST HDR) AND OSP
To actuator Low pressure emergency governing system
High pressure
trip model Travel limit switch reset testing
valve block
1YV
manual trip Spring
mechanism 2YV

Stay hook
5YV 6YV

Emergency
4YV governor

Electromagnetic
trip device Emergency
7YV 8YV 3YV governor device
Trip isolation
valve group

Air trip valve High pressure

fire-resistant oil
RERE High pressure fire-
RETURN OIL TO resistant returned oil
High pressure fire-
TANK resistant safety oil
Internal Return oil tank
 Internal

EH OIL O/L 2YV SPRAY(LUBE) SOLENOID 3YV LINK LEVER

4YV EH
OIL
SOINOID

HP SAFETY OIL
3YV ELECTRICAL OSP
I/L TO 4YV
TRIP SOLINOID
HP SAFETY OIL (OR)
1YV LATCH(RESET)
(AST HDR)
LUBE OIL SOLINOID

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LATCH PROCESS

1YV LATCH
OIL CYLINDER

LUBE OIL ENTERS DURING LATCH

( LP SAFETY OIL)

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PL<1.2MPA
MOP DIS PR SWITCH

LUBEOIL FROM MOP SUCTION

TO 1 YV I/L

1
LUBE OIL YV O/L TO
LATCH CYLINDER MOP SUCTION

PL<=0.07MPA

MOP SUCTION LOCAL PR

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BRG NO 1 LUB OIL SUPPLY LINE

TAPPING FOR SPRAY OIL 2YV

MOP

MOP SUCTION
MOP DIS

MOP SUCTION PR
TAPPING
LATCH OIL TO 1 YV TAPPING
POINT

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MOP DIS LOCAL PR GAUGE & PR

TMITR TAPPING

BRNG NO 1 LUBE OIL I/L HDR

MOP DIS LINE TO BOOSTER

TUR I/L

LUBE OIL
(PL ,PLL,PLLL) SWITCH

PL<=0.115 TOP STARTS

PLL<=0.09
PLLL<=0.07 EOP STARTS

TUR TRIPS
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MECHANICAL OVER
STAY HOOK SPEED TRIPPING

(LATCH LEVER ) DURING LATCH

IT WILL MOVES INSIDE

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TURBINE TESTING
 Friction Check Test
 Mechanical Over-Speed Test (Spray Oil Test)
 Electrical Over-speed Test (3yv energized)
 HPT Test (Trip Solenoid Block Valve)

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FRICTION CHECK
 FRIC CHECK (Friction Check)
 (It is done for first start-up of Turbine / Overhaul of Turbine.)
 Press FRIC CHECK at 200 r/min.
 All CVs & CRVs will close to “0” Position & Turbine rpm will
reduce.
 When SPEED ≤ 100 rpm, FRIC CHECK button should be
pressed again & note down the time from 200 rpm to 100
rpm.
 NOTE: (The time should be in range specified by the
manufacturer. Approx it will be 12 to 15 sec.)

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FRICTION TEST

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OIL SPRAY TEST

PERMISSIVES
➢ HP DIFF EXPANSION< 4mm
➢ SPEED 2985<N<3015 RPM
➢ OSP TEST NO PERMIT
➢ TRIP VALVE RESET POSITION(ZS2) NOT ACT
➢ OIL EJECT TEST SERVICE BUTTON ON
➢ LOCKOUT VALVE IN TEST POSITION (ZS4) NOT ACT
➢ LOCKOUT VALVE TEST POSITION NORMAL(ZS5) IN ACT POSITION

During the test, 4YV stays energized for 60s while ZS4 sends signal to energize
2YV , oil is sprayed into emergency tripper, fly ring strikes out, and ZS2 sends signal
meaning

A SUCCESSFUL TEST!

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LATCH
DRAIN
SPRAY TEST
HP TRIP OIL
0.1 MPa

LUB OIL
1.96 MPa

1YV 2YV
ZS1

2/3 PS

ZS

3YV

4YV

P:
P: 0.0
14.0MPa
MPa
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SPRAY OIL TEST

FLY BALL
(ECCENTRIC RING)

2YV ENERGIES OIL

(ONLY DURING SPRAY
OIL TEST)

LOCAL TURBINE TRIP

LINK LEVER STAY HOOK
(MECHANICAL OSP TRIP DEVICE)

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 Due to the fact that the emergency governor is important to the steam
turbine, routine tests are necessary in order to ensure its speed and
reliability in a crucial condition.
 In general, the tests include a speed raising test and an oil ejection test.

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SPRAY & LATCH OIL TAPPINGS

BRG NO 1 LUB OIL SUPPLY LINE

TAPPING FOR SPRAY OIL 2YV

MOP

MOP SUCTION
MOP DIS

MOP SUCTION PR LATCH OIL TO 1 YV TAPPING

TAPPING POINT

PL<=0.07MPA

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ZS1

4YV DRAIN OIL

RETURN TO TANK

4YV
ZS4

HP SAFETY OIL I/LTO 4YV

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EH OIL O/L 2YV SPRAY(LUBE) SOLENOID 3YV LINK LEVER

4YV EH
OIL
SOINOID

HP SAFETY OIL
3YV ELECTRICAL OSP
I/L TO 4YV
TRIP SOLINOID
HP SAFETY OIL (OR)
1YV LATCH(RESET)
(AST HDR)
LUBE OIL SOLINOID

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13M FRONT BEARING

1YV 2YV

3YV

LOCAL MANUAL TRIP LEVER

4YY

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HP TRIP MODULE DCS

6.9m

13M FRONT BEARING 0M

TO 4 YV TRIP VALVE DRAIN TO EH OIL TANK

6.9M

0M
EH OIL SUPPLY
FROM CONTROL
BLOCK
=>7.8 <=3.7

6.9M TO STOP & CV

TO AST HDR /OSP HDR
Internal
PS1,PS2,PS3 <=3.7
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HP TRIP SOV’S TEST

 Hp trip solenoid valves 5, 6, 7 & 8 YV are tested for their
healthiness.
 The test group is 5YV and 7YV or 6 YV and 8YV.
 With the energization of 5YV & 7YV oil drains to Show PS4
Pressure High signal.
 With the energization of 6YV & 8YV oil drains to Show PS5
Pressure Low signal.
 The orifices in the drain lines prevent entire draining of oil
during above test.
 In No condition any two solenoid of different groups tested
together.
 HP TRIP MODULE CONCEPT IS SAME FOR TDBFP A &
B.
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EH- HPT TRIP MODULE LATCH & TRIP POSITION

PR SWITCHES SWITCHES

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HP TRIP BLOCK

OPC CONTROL OIL

AST/HP SAFETY
OIL

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HPT-TRIP MODULE

HP SAFETY OIL TO 4YV

4YV DRAIN OIL

RETURN TO TANK

DRAIN OIL TO TANK

EH OIL SUPPLY TO HPT I/L

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HP SAFETY OIL TO 4YV PS1 PS2 PS3

DRAIN OIL TO TANK

5 YV 6 YV

7 YV 8YV

PS4 PS5
EH OIL SUPPLY

TRIP OIL(MSV1,2) AND OPC OILCV(1,2,3,4)& IP

Internal
 OPERATING PRINCIPLE
Internal

LATCHING:-
HP safety oil is created and HP oil enters the lower chamber of Stop valve

FAST VALVING::-
During normal operation, servo motor controls thru loading pressure, return oil pressure
and safety oil pressure
SHUT DOWN:-
 HP safety oil pressure is unloaded, release valve is opened under effect of oil pressure.
 Lower chamber is connected to upper chamber of cylinder thru release valve
 Part of oil passes to upper chamber and rest returns thru return oil line
 Valve closes under the effect of spring force

AUXILIARY MEASURE FOR FAST VALVING OF ACTUATOR:-

1. Safety oil draining leads release valve operation and connects lower chamber to upper
chamber and drains oil
2. Servo valve opens the oil outlet drain outlet connected to lower piston
3. Isolating valve closes to stop loading oil admission.
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OPERATION OF MSV1
The stop valve for HP/IP will open by the HP fire resistant oil when the
dump valve is closed.
The dump valve will close when trip oil is under pressure.
The trip oil is under pressure when the trip solenoid valve is in de-
energized position and HP Trip oil header is under pressure.
The oil will enter the bottom of piston through isolating valve and orifice.
Thus Stop valve opens slowly against spring force.
In case of trip the trip solenoid valve is energized and HP trip oil header
is de-pressurized and thus dump valve opens to connect bottom and top
ports to drain the oil .
The valve quickly closes due to spring force.

NOTE - THE PRINCIPLE OF OPERATION OF RSVs IS SIMILAR

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MSV 1

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MSV 1 MSV 2

EH DRAINOIL MSV1 EH DRAIN OIL MSV2

1
SAFETY OIL MSV 2
SAFETY OIL MSV

3 MICRON
FILTER

EH PRESSURE OIL MSV1 EH PRESSURE MSV2

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OPERATION OF GOVERNOR VALVE

After the unit is reset and HP trip oil is formed.

The trip solenoid valve in de-energized conditions will give
pressurized oil to the dump valve to keep it closed.
the isolating valve is kept in open position to admit the HP fire resistant
oil to the EH servo valve.
The EH Servo valve based on DEH valve command signal and valve
position feedback signal from LVDT will connect the HP Fire resistant
oil to lower port of the piston or lower port to the drain till the
matching is achieved.
In case of Trip, dump valve opens due to energisation of trip solenoid
or de pressurization of HP trip fluid header. The dump valve
opening leads to control valve quick closing due to spring force.

NOTE - THE PRINCIPLE OF OPERATION OF ALL CVs & CRVs IS SIMILAR

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GOVERNOR VALVE

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CV 3,4,1,2

EH OIL SUPPLY(PR) LINE

EH OIL DRIAN LINE

OPC LINE CV(HP SAFETY)

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OVER SPEED PROTECTION

Over speed Protection :
➢ In case of failure of speed restriction, there is a turbine tripping at
too high rotation speed.
➢ For the purpose of safe operation, there setup several layers of over
speed protection in the system:
✓ DEH electric over speed protection 110 %.

✓ Manual tripping by operator.

✓ By ETS; Emergency trip system.

OIL spray test is conducted for the over speed protection.

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OVER SPEED
Over speed control:
a) Load rejection :
o When the load rejection occurs, the rotation speed rises very
quickly due to mechanical and electrical torque unbalance.
o At this time the over speed limit integrated package and the fast
solenoid valve of all oil servo motors will act quickly to close CVs
meanwhile the target rotation speed is change into 3000 rpm.
o 5 seconds later, all solenoid valves are reset, and the control valves
are restored to be under the control of servo valves, and the over
speed control turns back to normal speed control circuit.
b) 103 % Over speed :
o At this time the over speed limit integrated package and the fast
solenoid valve of all oil servo motors will act quickly to close CVs &
ICVs. When the rotation speed is lower than 103 %, all solenoid
valves are reset, and the control valves are restored to be under the
control of servo valves, and the over speed control turns back to
normal speed control circuit.

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OVER SPEED PROTECTION

A. Mechanical over-speed protection
 Upon the action rotating speed accounts for 110%-111% (3300-
3330r/min) of the rated speed, the protection ring of an emergency
governor will hit a stay hook to trip; the link lever of a mechanical
emergency governor system will drive the emergency governor of the
high pressure governor component into action to cut off the high pressure
safety oil supply and to drain it by opening an oil drainage port. As a
result, each main stop valves and control valves should be fast closed; the
unit steam admission should be cut off quickly as well.

B. DEH and TSI electric over-speed protection

 When the rotating speed of the unit accounts for 111% (3330r/min) of
the rated speed, an electric stop signal is sent to drive an electromagnetic
governor device in a main trip electromagnetic valve (5YV, 6YV) and a
mechanical stop electromagnetic valve (3YV) into action to drain the high
pressure safety oil and to cut off the unit steam admission. Meanwhile, it is
sent to each valve as well to fast close every electromagnetic valve and
steam valves, thereby guaranteeing the safety of the unit.

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INTERLOCKING & PROTECTION

 Mechanical over-speed protection

 Local manual trip
 Remote manual trip
 Electric trip protection

The unit will be tripped by the synchronous actions of 3YV, 5YV and
6YV of the said electromagnetic valve and electromagnet under the
several conditions.

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LP PROTECTION

MANUAL / LOCAL TRIP DEVICE:-

 By pulling manual trip mechanism trip oil can be drained Trip and Isolated
solenoid group valve
RESET AND TEST BLOCK VALVE-
 Reset and test valve block 1VY is utilized to inject lub oil into the side piston
chamber of emergency trip device to reset the turbine
 Reset and test block valve 2VY is utilized tp inject lub oil to oil ring guide for
overspeed test.
MECHANICAL TRIP SOLENOID:-
 Provided to trip the unit in emergency, receiving electrical signal.
OIL GUIDE RING-
 Used for injecting oil for triggering over speed device during testing.

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HP PROTECTION
HP TRIP MODULE:-

 4 HP solenoid valves energize for HP safety oil built up and de-energize draining
of safety oil
 System connected with 2 pressure switches and 3 orifices
MANUAL REMOTE STOP:-
 Pressing 2 buttons in control panel, emergency trip valve operates thru solenoid
5VY,6VY,7VY and 8VY and drains HP safety oil.
ELECTRO-HYDRAULIC EMERGENCY TRIP :-
 HP Breaker module utilizes electric signal, when HP breaker module loose power,
ETS activates 3VY and also 5VY,6VY,7VY and 8VY
TURBO SUPERVISORY PROTECTION:-
When any of the ETS condition is satisfied , ETS trip actuates HP trip module, Mech Trip
valve and simultaneous command to Trip solenoid valves of stop and control
valve.

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ANTICIPATED EMERGENCY
Turbine is not latching (resetting)
 Checks – 1YV should energize, when stay hook is reseting
ZS2 should get open
 3 YV should be reset – mechanical latch to be checked
 All HP trip sol. 5,6,7,8 YV should get energize , Hp trip oil
press. Should be checked for > 12 mpa
 All stop valve trip sol. 9,10,17,20 YV should deenergize

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ANY OF MSV OR RSV NOT OPENING

 Physically check the opening if open, check open limit
switch of respective SV .
 If physically not open check the trip sol. Should be in de -
energize condition.
 The supply sol. Should receive signals for de-
energization.

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Control Valves are not Opening

 The trip sol. (12,13,14,15,16,19) YV should be de-
energize.
 OPC press. to be checked on HP trip and OPC module
 Check the supply signals of respective control valves
EHSV.

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MANAGEMENT OF VALVES
Turbine has two admission modes of steam admission:
1. Full Arc Admission (Single valve Governing or Throttle
governing)
2. Partial Arc Admission (Sequential valve governing or Nozzle
governing )
Test of valves
Control functions of load rejection
1. Over Speed Control
2. Over Speed Protection

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1. DEH Speed control

1. Range of speed regulation: 0～3500 r.p.m.
Control precision of speed control loop: ± 0.1％ of rated speed
Overshoot under the maximum speed raising rate: no more than
0.15％ of rated speed
2. The design of automatic speed raising system should be in
conformity with its different speed raising mode
1.IP START UP
2.HIP START UP
3. The speed raising rate during turbine speed up, target speed can be
selected manually or by the DEH system automatically according to
hot states of turbine.
4. The speed control loop should ensure that the critical speed zone
can be automatically and quickly passed.
5. The DEH system should have interfaces to automatic synchronizing
devices, so as to cooperate automatic synchronizing devices to
realize the automatic synchronization of generator.

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2. Load control
1. After synchronization of turbine-generator unit, the DEH system should
realize automatic control of turbine-generator unit from initial load to
full load. And this system will engage in PRIMARY FREQUENCY
MODULATION and SECONDARY FREQUENCY MODULATION
according to requirements of power grid.
 Control precision of power is not less than
± 2MW (on condition that the steam parameter is stable)
Static characteristic speed regulation can be regulated,
its setting range is not less than
3％~ 6％
Near specified power (power changes within the range of ± 1.5％~ ±
12％ of rated power), on condition that the frequency changes within
the range of ± 0.025 Hz ~ ± 0.25 Hz, the setting range of local
regulation should reach 3％~20000％.
II. Setting of target load
The target load of this system can be set by operators, it can
also receive directives come from the DCS system. The
forms of directives are pulse value signals or analog signals.
III. The variable load factor can be set by operators; also the variable load
factor can be restricted by the DEH system according to thermal stress
computing system.
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STEAM TURBINE FOLLOWING WAY

➢ Pressure regulated by steam turbine:

o When the steam turbine control system receive the instruction
of secondary frequency regulation to increase the load set
point, first of all it turns up the fuel control valve.
o With the increase of fuel, the throttle pressure and steam flow
will increase, and as a result the generator power will increase.
o For the purpose of keeping the throttle pressure constant, the
steam turbine control system adopts the steam pressure feed
back system, which can change the control valves opening and
increase the steam flow and finally keep the pressure constant.
➢ Sliding pressure mode :
o When the steam turbine control system receive the instruction
of secondary frequency regulation to increase the load set
point, first of all it turns up the fuel control valve.
o With the increase of fuel, the throttle pressure and steam flow
will increase, and as a result the generator power will increase.
But the steam turbine control system maintains the control
valves in the fully open position.
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CCS :

o This method has Advantages of both the above ways.

o The power instruction of secondary frequency regulation directly acts
on both systems.
o First, it changes the opening of control valves within the range of
allowable pressure variation.
o By using the BOILER’S ACCUMULATION OF ENERGY, it improves the
load response speed ; meanwhile it changes the fuel control valve.
o With the change of boiler output, the throttle pressure is maintained
constant.

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CONDITION FOR TURBINE TRIPPING

1. The speed of turbine is over limiting value; (DEH 3300 RPM i.e. 110 % of rated
speed),Mechanical overspeed Device operation-110 % to 111 %)
2. Vacuum is lower than limiting value offered by manufacturer;
3. Pressure of lube oil falls to below limiting value; (< 0.0792 mpa )
4. Pressure of EH oil falls to below limiting value; (< 7.8 MPA)
5. Axial displacement of rotor is over limiting value;
6. Shaft vibration of turbine reaches dangerous value;
7. Shutdown the machine manually in central control room (double buttons);
8. DEH tripped; Both pumps Stopped or DEH pannel power failure
Temperature of HP Turbine steam exhaust is high .
11. Differential expansion is over limiting value.
12. Boiler MFT
13. Remote manual Emergency shutdown
14. HP turbine Exhaust Temp. High

Other tripping conditions required by turbine manufacturer.

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EH OIL & LUBE OIL SWITCHES

 ZS1- TRIP VALVE RESET POSITION (it will act during latch condition)
 ZS2- MECHANICAL TRIP VALVE RESET POSITION
 ZS3- MECHANISM VALVE RESET
 ZS4- LOCKOUT VALVE IN TEST POSITION(act only during spray oil)
 ZS5- LOCKOUT VALVE NORMAL POSITION(always acted in normal condition)

EH OIL PR SWITCHES

 PS1- TRIP OIL PRESSURE HIGH

 PS2- TRIP OIL PRESSURE HIGH <= 3.9 Mpa.
 PS3- TRIP OIL PRESSURE HIGH
 PS4- HP TRIP SOLENOID TEST PASS >= 7.8 Mpa.
 PS5- HP TRIP SOLENOID TEST PASS <= 3.9 Mpa.
LUBE OIL PR SWITCHES

 PL LUBE OIL SUCTION MOP

 PL LUBE OIL DIS
 PL FOR TOP PICK UP
 PLL FOR EOP PICK UP
 PLLL FOR TURBINE TRIP

Internal
Internal Spray Test CV’s MSV’s Latch EH Tank

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SPEED CONTROL

In power plant the working condition of steam turbine generator unit

depends on the equilibrium relationship between “ The operating
Torque that the steam acted on turbine rotor & the reactionary torque
that the load acted on Generator stator.”
For Constant Speed:
Tm = TE T m : Mechanical Torque
T E : Electrical Torque
But TE is of varying nature due to LOAD Demand & Supply Unbalance.
So the actual speed of turbine varies according to grid.

Control System compares it with rated speed 3000 rpm &

through “FREQUENCY DIFFERENCE AMPLIFICATION” &
“REGULATOR SERVO CONTROL” Controls the opening extent of CVs
& ICVs to form a negative feedback of rotation speed, which will keep
the rotation within a preset range.

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Thank you for your attention any

& suggestion

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