How Turbine Actuators Work ?

Prepared By- ABHISHEK SINHA | Senior Engineer – Operation

30010175- Group-IV (Guided by Mr.Vineet Garg - Shift Incharge)- ADANI POWER MAHARASHTRA LIMITED 5X660 MW

DEH

• Speed and load of the turbine-generator are controlled by positioning the throttle and governor steam admission valves.

• The DEH controller receives three primary feedbacks from the turbine-generator: speed, megawatts and first stage pressure.

• The DEH uses PI closed loop control during startup and loading to provide accurate speed and load control.

• In the manual mode, an operator can select the valve type he wants to move [Throttle Valve (TV), Governor Valve (GV) or Intercept Valve (IV)],

• The direction [raise or lower] and the rate of valve movement. All these functions are possible from the Optional manual panel.

• 2 Modes of Valve Operation is provided: Single Valve Mode & Sequential Mode.

Turbine & Actuators• We have got 660 MW Shanghai Electric’s Supercritical Turbine at APML.• Its 3 Cylinder Reheat Machine. There are 12 Actuators in our Turbine.

• HPT = 2 Throttle Valves (TV) + 4 Governing Valves (GV).• IPT = 2 Reheat Stop Valves (RSV) + 4 Interceptor Valves (IV).

• Actuators are of 2 Types: 1. Control Type = Governing Valves , Interceptor Valves & Throttle Valve. 2. ON/OFF Type = Only Reheat Stop Valve.

Actuators1.High Pressure Cylinder: Oil to Open Type. Close with Spring Force.

2.Isolation Valve: To isolate Actuators for maintenance.

3.Check Valve: Avoids back-flow of the High Press. Oil to the Low press. Line.

4.Filter: Filters the Oil Entering the Actuators.

5. Servo Valve: I/H Converter. Moog Servo Valve: (-42.80 mA to 37.20 mA).

6. Solenoid Valve: For Full Open & Full Close type Actuators.

7.Dump Valve: For Fast Closing of Actuators. Pressurized by AST/OPC Oil.

8.LVDT: Position Feed back 4-20 mA to DEH.

ETS Control Block• ETS Block on Front Pedestal = 4 AST Solenoids & 2 OPC solenoids.

• AST Solenoid = Auto Stop Trip Solenoid will generate Auto Stop Trip Oil.

• OPC = Over Speed Protection Solenoid will generate Over speed Control Oil.

• 4 AST Solenoids arranged in Series-Parallel.

• OPC Solenoids arranged in Parallel.

• OPC Solenoids Trip will only close the GV & IVs, will not initiate Turbine Trip.

• But AST Solenoid Trip will drain all the AST & OPC Oil & will Trip Turbine closing all the GV, IV, TV & RSV.

ETS• AST Solenoids: Normally Open Type De-Energized to Open Oil Drain Port & Energize to Close the Oil Drain Port.

• OPC Solenoids: Normally Close Type De-Energize to Close Oil Drain Port & Energize to Open the Drain Oil Port.

• AST Solenoids are AC Solenoids i.e. 240 V AC.

• OPC Solenoids are DC Solenoids i.e. 110 V DC.

3 % Over Speed i.e. 3090 RPM• OPC Solenoids will act. i.e. Solenoids energized to drain OPC Oil to close the

GV & IV. Turbine Not Tripped. • Speed Below 3 % Overspeed. The solenoids de-energize to Open GV & IV. 10 % Over Speed i.e. 3300 RPM AST Solenoids will act i.e. Solenoids De-Energized to drain AST Oil & close all

the TV, GV, IV & RSV. Complete Turbine Trip.

Block Diagram of ETS

Trip Oil for TV & RSV = AST Oil. Trip Oil for GV & IV = OPC Oil.

AST-1

AST-4

AST-2

AST-3

OPC-1

OPC-2

Pressurized Drain

Normally OpenDe-Energized Oil Drain Port Open

N.C

N.C

N.O N.O

N.O N.O

Normally CloseDe-Energized Oil Drain Port Close

AST-1

AST-4

AST-2

AST-3

OPC-1

OPC-2

EH Oil Supply Header

Pressurized Drain

N.C N.O N.O

N.C N.O N.O

AST-1

AST-4

AST-2

AST-3

OPC-1

OPC-2

OPC Trip Oil Header Pressurized.To all GV & IV Dump Valves.

EH Oil Supply Header

Pressurized Drain

N.O N.O

N.O N.O

N.C

N.C

AST-1

AST-4

AST-2

AST-3

OPC-1

OPC-2

AST Trip Oil Header Pressurized.TO all TV & RSV Dump Valves.

EH Oil Supply Header

Pressurized Drain

N.O N.O

N.O N.O N.C

N.C

OPC Trip Oil Header Pressurized.To all GV & IV Dump Valves.

Pressurized Drain to EH Oil Tank

EH Oil Supply

Trip Oil from AST/OPC to Dump Valve

>

Loss of Trip Oil from AST/OPC to Dump Valve

>

Valve OpensValve Close

Solenoid Energized : Valve OpensSolenoid De-Energized : Valve Closes

EH Oil Supply

Pressurized Drain to EH Oil Tank

RSV Actuator : Full Open – Full Close Type

Trip Oil from AST to Dump Valve

Supply = 15 MPa

Drain = 0 Mpa

Output to Actuators = 0 MPa

Moog Servo Valve

Pressurized Drain to EH Oil Tank

EH Oil Supply

Trip Oil from OPC to Dump Valve

Spool Position-1DEH Command = 0%.

>

Valve Full CLose

GV & IV

I/H Converter

Supply = 15 MPa

Output to Actuators = 3.75 MPa

Drain = 11.25 Mpa

EH Oil Supply

Pressurized Drain to EH Oil Tank

Spool Position-2DEH Command = 25%.

Trip Oil from OPC to Dump Valve

>

Valve 25 % Open

Spool Position-3DEH Command = 50%. Output to Actuators = 7.5 MPa

Drain = 7.5 Mpa

Pressurized Drain to EH Oil Tank

EH Oil Supply

Supply = 15 MPa

Trip Oil from OPC to Dump Valve

>

Valve 50 % Open

Spool Position-4DEH Command = 75%. Output to Actuators = 11.25 MPa

Drain = 3.25 Mpa

Pressurized Drain to EH Oil Tank

EH Oil Supply

Supply = 15 MPa

Trip Oil from OPC to Dump Valve

>

Valve 75 % Open

Spool Position-5DEH Command = 100%. Output to Actuators = 15 MPa

Supply = 15 MPa Drain = 0 Mpa

Pressurized Drain to EH Oil Tank

EH Oil Supply

Trip Oil from OPC to Dump Valve

>

Valve 100 % Open

LVDT (Linear Variable Differential Transformer)

THROTTLE VALVE ACTUATOR

GOVERNOR VALVE ACTUATOR

REHEAT STOP VALVE ACTUATOR

INTERCEPTER VALVE ACTUATOR

Interface Diaphragm Valve

• Air pilot valve is an interface between extraction non-return valves and EH fluid system.

• Air source is compressed by extraction non-return valve, which is controlled by air pilot valve.

• Air pilot valve should be opened by OPC fluid pressure and closed by spring force.

• During the operation, air pilot valve is going to be opened by OPC fluid pressure, and compressed air source can be sent to the extraction non-return valves through air pilot valve.

• Solenoid valve on the extraction non-return valves should be controlled by DCS.

• When OPC fluid pressure is released (overspeed), air pilot valve will be closed by spring force, cutting off compressed air source when vent to atmosphere is opened.

Air Pilot Valve

Thank You !Any Questions ?

Special Thanks to Mr.Vineet Garg & Team of Group-IV for their Sheer Guidance & Support !!

Prepared by – Abhishek Sinha | Sr. Engineer - Operation