Steam Turbine Governor Regulate STEAM FLOW into TURBINE such that at the desired SPEED the OUTPUT TORQUE of the Turbine is exactly equal the LOAD Torque of the Generator (If torque is not equal the result is a change in speed – Newton’s Law) In the event of sudden LOAD TORQUE loss, Quickly reduce STEAM FLOW to maintain desired SPEED below Emergency trip Speed (excessive TURBINE OUTPUT TORQUE results in rapid speed increase) In the event of a complete failure of speed control, emergency over speed governor shall limit speed less than 120%
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Steam Turbine GovernorSteam Turbine Governor
Regulate STEAM FLOW into TURBINE such that at the desired SPEED the OUTPUT TORQUE of the Turbine is exactly equal the LOAD Torque of the Generator
(If torque is not equal the result is a change in speed – Newton’s Law)
In the event of sudden LOAD TORQUE loss, Quickly reduce STEAM FLOW to maintain desired SPEED below Emergency trip Speed(excessive TURBINE OUTPUT TORQUE results in rapid speed increase)
In the event of a complete failure of speed control, emergency over speed governor shall limit speed less than 120%
Steam Turbine Controls Steam Turbine Controls
Provide a means to prewarm
Provide a means to accelerate to speed and synchronize
Provide a means to control flow for MW generation
Provide a means to protect the equipment from adverse operating conditions
Provide a means to test components to ensure operability
Turbine Control HydraulicsTurbine Control Hydraulics
Hydraulic Power UnitProvide high pressure fluid to control the turbine valves
FAS (power for actuator positioning)ETS (logic for tripping)
Lube Oil SystemProvide front standard trip logic
Servo ValvesSolenoid Valves
ActuatorsSteam valvesFront standard
Servo ValveServo Valve
Null
Servo ValveServo Valve
Opening
Servo ValveServo Valve
Closing
Servo ValveServo Valve
Failed Jet
Spring Can & Control PacSpring Can & Control Pac
Single Acting Servo ControlledSingle Acting Servo ControlledFAS supplied and ETS tripped FASV de energizedDisk Dump spring seatedShut off isolatedBiased ServoValve TRIPPED
Single Acting Servo ControlledSingle Acting Servo ControlledFAS supplied and ETS reset FASV de energizedDisk Dump seatedShut off resetNull Servo
Single Acting Servo ControlledSingle Acting Servo ControlledFAS supplied and ETS reset FASV de energizedDisk Dump seatedShut off resetPositive ServoValve Opening
Single Acting Servo ControlledSingle Acting Servo ControlledFAS supplied and ETS reset FASV de energizedDisk Dump seatedShut off resetNull ServoValve position
Single Acting Servo ControlledSingle Acting Servo ControlledFAS supplied and ETS reset FASV de energized Disk Dump seatedShut off resetNegative ServoValve Closing
Single Acting Servo ControlledSingle Acting Servo ControlledFAS supplied and ETS reset FASV energizedDisk Dump dumpedShut off isolatedBiased ServoValve FAST CLOSED
Single Acting Solenoid ControlledSingle Acting Solenoid ControlledFAS supplied and ETS reset FASV de energizedDisk Dump seatedShut off resetDe Energized SolenoidValve OpeningOrifice controls rate
Single Acting Solenoid ControlledSingle Acting Solenoid ControlledFAS supplied and ETS reset FASV de energizedDisk Dump seatedShut off resetEnergized SolenoidValve ClosingOrifice controls rate
BLOCKBLOCK
Main Stop ValvesMain Stop Valves
Primary Purpose: To shut off steam flow in an emergency.
Secondary Purpose: • Steam Chest Warming• Rotor Warming
MSV
Main Control ValvesMain Control Valves
Purpose: To regulate steam flow to the HP turbine.
• Control turbine speed (Speed Governor) or,• Control generator load (Load Control) or,• Control Reactor pressure (Pressure Governor)
1st axiom of Turbine Controls-One valve can control only one variable at one time
CV
CV Balance ChamberCV Balance Chamber
MSV & CVMSV & CV
Reheat (Intermediate) Stop ValvesReheat (Intermediate) Stop Valves
Purpose: To shut off steam flow to IP (LP) turbine in an emergency.
ISV
Intercept ValvesIntercept Valves
Primary Purpose: To regulate steam flow to the IP (LP) turbine in an overspeed where the control valves have been closed and speed continues to increase. Also, to blow down reheater and/or steam piping prior to opening of control valves.
IV
CIV
ByPass Valves
Purpose: Regulate reactor steam flow to the condenser, when steam flow is not needed by the turbine
BPV use a simple double acting actuator (no ETS supply)
1) can be manualy opened during intial criticallity2) regulated by Pressure Control over range of 150 to 1050 psig
ByPass Valves
Speed ControlSpeed Control
Measure turbine speed and provide Speed error to Load Control
INPUTSTurbine speedSpeed hold selectionAcceleration selection
OUTPUTSpeed Error to Load ControlSpeed related Logic
First Line of Over Speed ProtectionFirst Line of Over Speed Protection
Control speed below over speed trip setting
Load ControlLoad Control
Using operator desired set points and measured turbine conditions, provided a valve demand signal to Flow Control
InputsSpeed errorLoad referenceOperating condition (i.e. warming, rolling, or online)BWR- Pressure error
OutputEsubL’s
Flow ControlFlow Control
INPUTSEL
Valve Position
OUTPUTServo Current
Each valve has its own Flow Control LoopMSV#2 (master)CV 1, 2, 3 & 4IV 1, 2 (master)BPV 1 - 10
Flow ControlAdmission Modes
Flow ControlAdmission Modes
Flow Control2 Admission Mode
Flow Control2 Admission Mode
Incremental RegulationIncremental Regulation
Protection (trips)Protection (trips)
VitalLoss of Life
Redundant tripping and testable
ImportantLoss of Capital
2 out of 3 logic for increased availabilityOperational
Increased maintenancePre alarm
Second Line of Over Speed ProtectionSecond Line of Over Speed Protection
If First failsLimit Peak Speed Below 120%