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Flashcards in Main Turbine Control and Supervisory Deck (45)

What are the power supplies to P-19A/B, EHC Pumps?

P-19A, EHC Pump

  • MCC-3

P-19B, EHC Pump

  • MCC-4


When will the Standby EHC Pump autostart? When will it not?

Autostarts at 1750 psig

Blocked if EHC Tank less than or equal to 7 5/8 inch from bottom of tank.

  • RESET on back of C04 (386 LFT) after level is restored

Running pump will NOT trip on Low-Low Level Lockout.


What cools EHC fluid and what happens if you loose cooling?

Non-critical service water.

High fluid temperature) can result in erratic turbine valve operation.

Normal: 110 - 130 °F (125 - 130°F preferred)


What is the Main Stop Valves motive force?

Main Stop Valves

Hydraulically opened, spring closed flapper type valves.

Installed in main steam line upstream of governor valves


What and how do the Governor Valves operate?

Each valve actuator is controlled by a servo-valve (MOOG)

  • Output flow varies with the positioning signal from DEH control.
  • Admits EH fluid to the hydraulic cylinder to open the GV and releases EH fluid from the hydraulic cylinder to allow the GV to close.

LVDT (Linear Variable Differential Transformer)

  • Transducer generates a voltage proportional to actual valve position.
  • This voltage signal feeds back to the DEH system for control purposes.

Heavy springs for quick cl


What is the Reheat Stop Valves modus of operation?

  • Hydraulically opened, spring closed.
  • Butterfly design; (similar to main stop valve actuator).
  • An additional safety device to prevent over speeding the turbine if intercept valve fails to close when overspeed trip protection operates.
  • Located in each reheat crossover steam line on top of MSR


What is modus of operation for Reheat Intercept Valves?

  • Four hydraulically opened, spring closed valves
  • Limits flow of steam from MSRs to LP turbines after a load rejection
  • Butterfly design


What is the Interface Valve (AUTO STOP)?

Interface Valve (AUTO STOP)

Held closed by Auto Stop Oil Pressure

  • Supplied by Main Lube Oil Pump (~ 110 psig)

@ 45 psig, valve spring overcomes oil pressure holding valve closed, valve opens

Dumps EHC fluid back to reservoir on a turbine trip causing all Main Stop, Governor, Reheat Stop, and Intercept Valves to close


What are the Interface Valve Turbine Trips (Balance Beam) trips?

  • Low vacuum (18-21 " Hg)

  • Lube oil low pressure (5-7 psig)

  • Over speed (110%)

  • Manual trip lever (front pedestal)

  • Solenoid Trips (20/AST)


What are the Solenoid Trips (20/AST)?

Solenoid Trips (20/AST) - On Balance Beam - Trips Auto Stop Interface Valve

  • MSIVs not fully open
  • Reactor trip (clutch relays coils)
  • Generator trip (386 P, B or C)
  • No load trip (< 8 psid for > 60 sec. across HP turbine)
  • Manual push button on C-01
  • DEH initiated trips (loss of control power to the Manual Cabinet)


What are the 20ET Trips?

20 ET Trips bypass the Interface Valve and directly dumps EHC

  • Auto Stop oil pressure @ 45 psig
    • Initiated by 2 out of 3 logic actuation between 63-1/AST, 63-2/AST, and 63-3/AST, Auto Stop Tripped Pressure Switches
  • Either MSIV is not fully open
  • ATWS actuation
  • Turbine shaft position (thrust bearing trip) >0.040" (40 mils)


What are the 20-1/AG and 20‑2/AG relays?

20-1/AG and 20‑2/AG

NOT a turbine trip

  • Overspeed protection (103%) by closing the governor and intercept valves
  • Governor and intercept valves re-open when overspeed condition clears


What is the Air Pilot Valve?

Air Pilot Valve

Turbine latched with EHC pumps operating (i.e., interface valve and 20/ET closed) routes control air to BTVs, bleeder trip valves and stop valve bypass valves

  • Allows BTVs to be latched and stop valve bypass valves to open

Turbine trip - the spring forces the piston closed routing the control air to atmosphere

  • Allows stop valve bypass valves to close, unlatches BTVs, allowing them to close on reverse flow


What are the Turbine Valve Operating Modes?

Turbine Valve Operating Modes

The only mode used at Palisades

"Single" means all 4 GVs get the same flow demand signal and open equally at the same time.


What are the indicated control parameters on the DEH Screen?

DEH Screen


  • 100% load = 869 MW
  • Units are % of turbine load (in Load Control), or RPM (in Speed Control).
  • Moving Setpoint (calculated value) based on the valve curves.  Indicates where turbine load (or RPM) "should" be


  • The actual % of turbine load (or RPM value). 


  • Indicates values that have been manually entered by the NCO, (RPM, turbine load)


  • Indicates value of the flow demand signal being sent to the valve program


What is the Valve Management Program?

Valve Management Program

Software program that defines the valve curves and determines how DEH will control the governor valves.

If perfect, ACTUAL and REFERENCE on DEH screen would match.

Facters impacting match:

  • Plugging S/G
  • SJAE Efficiency
  • Cooling Tower Repair
  • Cooling Tower Basin Levels
  • Anything impacting plant efficiency


What are the DEH Power Supplies?

Two trains of power from LCC-14

  • Panel L-81, Panel L-83

Each computer has a Primary and a Secondary power source (except DPU 2)

  • If primary fails, immediate switchover to secondary (power seeking)

A battery installed in each DPU senses when power is about to transfer

  • Ensures data and memory will not be lost during the transfer


What is the DEH UPS?


Provides a "clean" (i.e., rectified, inverted) source of power to the DPUs

Provides up to 40 minutes of backup power from battery

  • ARP-2 Attachment 1 allows 20 minutes to lower power to 15%

Automatically swaps to BATTERY mode if A/C falls out of specification or fails

Automatically goes on BYPASS for the following conditions:

  • High load current
  • UPS internal high temperature
  • UPS output voltage out of spec.

Remains in BYPASS after 3 failed attempts to go back to NORMAL within 10 minutes


What happens on a loss of power to DEH?

Turbine trip if:

  • Both MANUAL panel power supplies fail (24 volts DC)

What is the Operator Auto Mode?

Operator Auto Mode

Speed Control (for rolling up the turbine)

  • Raises speed demand (reference) to bring shaft speed to its rated value at a controlled selectable rate: 1 RPM/min to 201 RPM/min
  • Operator Auto will NOT allow selection of a RPM value in a critical range of turbine speed

Load Control

  • Not functional when DEH is in MANUAL mode
  • Automatically selected when a generator breaker is CLOSED
  • Allows raising or lowering load at 0.1% to 2000%/hr (normal and emergency rates)


How are the DEH Controls proceduraly operated?

SOP-8 (Main Turbine and Generating Systems) states, the DEH Controls should normally be operated as follows:

  • OPERATOR AUTO at all times
  • No Feedback Loops in service with turbine load greater than 25% as read on the DEH screen
  • Valve Limiter should be positioned just above the valve control signal during steady state operation.


Why do we not run with feedback loops in service?

With Feedback Loops in service, any upset in the system will be fed back into the control loops, and the GVs will be automatically positioned accordingly.

  • Could result is exceeding power limits

DO NOT want anything affecting reactivity other than a direct licensed operator action


What is the function of the limiter and what do you need to do with it?

Stops GV openning beyond a limited setpoint. 

  • Note that the Limiter does not actually limit valve position; it limits flow demand signal (electronically limits)

Failure to raise limiter will prevent Governor Valves from opening, and will cause DEH System to go to HOLD.

Limiter should be positioned just above the valve control signal during steady state operation


What indications are on C-01?

C-01 Indications

  • Governor Valve Position – 0 to 100%


What controls are on C-01?

EHC Pumps (P-19A/B)

Operators Console (DEH)


What indications are on C-11?

C-11 Indications

TUR-0520 TURB/GEN/MSR Condition Monitor

  • Yokagawa Digital Recorder


  • Yokagawa Digital Recorder


What happens on loss of 24 volt dc supply in MANUAL CABINET?

Loss of One

  • System is on backup

Loss of Two

  • Valve Monitor light ON
  • Turbine TRIP because you lose valve control
  • Power Supply Monitor light ON
  • DEH transfers to MANUAL mode


What happens on loss of two 13 volt dc supplies in the OPC Cabinet?

Power Supply Monitor light ON

Everything goes dead on DEH Manual Panel

Lose I/O interface


What happens if two 13 volt dc supplies are lost in the OAC Cabinet?

OAC Cabinet - Operator Auto Controller) Panel C23-03A

  • DEH Transfers to MANUAL
  • Power Supply Monitor light ON



What is Runback?

Ramps down (runsback) the turbine to a preset point at a preset rate.

Runback is a function of the Operator Auto software program, even though the initiate buttons are on the Manual Panel.  Runback is not available when turbine control is in MANUAL

  • HOLD will appear during runback when ACTUAL is different from SETTER
  • This HOLD does NOT mean that the unit load is holding.
  • SETTER remains constant while runback is in progress
  • If MANUAL is selected, it clears the Runback.  You will have to reselect Oper Auto before re-initiating a Runback


What is the OPC Key Switch?

Three Position Keyswitch

  • GV and Intercept Valves CLOSE (if turbine is latched and generator output breakers are open.
  • Allows operation of OPC
  • INHIBITS OPC function (used for testing 110% Mechanical Overspeed Trip

Normal metal temperatures for journal and thrust bearings should not exceed what?

185°F (Alarm at 210°F)

To prevent damage to bearing surfaces


Turbine exhaust temperatures should not exceed what?

217°F for extended operation or 250°F for periods of 15 minutes or more

Prevent overheating later stages of LP Turbine blades


What is risk of relamping Latch light?

The LATCH button on the DEH Panel SHALL NOT be relamped when the turbine is latched due to possible turbine trip.


What are the Required Parameters prior to Synchronization to Grid?

Required Parameters prior to Synchronization to Grid

Reactor Power

  • ≤ 13% (higher of delta T or NI power)


  • ≤ 540°F


  • > 60% (>75% preferable)



What are some changes to parameters on syncing to the grid?

Reactor Power

  • Upon synchronization, the turbine automatically assumes ~20 MW load per DEH design.
  • However, if the TBV output was > 60% as required, this should ensure that reactor power remains relatively stable.


  • Should remain relatively stable if TBV output was as required prior to synchronization

Main Steam Flow

  • Since turbine automatically assumes ~5% load (~20 MW), main steam flow will rise

Main Feed Flow

  • Since main steam flow rises, main feed flow will by design rise also to maintain steam generator levels.

Steam Generator pressure

  • Steam Generator pressure lowers as power rises.


What are the turbine critical speeds and why don't we operate there?

Critical Speeds

  • 700 – 890 rpm
  • 1040 – 1360 rpm
  • 1375 – 1710 rpm

Excessive operation at any of the following critical speeds could cause turbine damage


What should you do if a malfunction occurs during valve testing?

If unexpected or uncontrolled response occurs, Place DEH controls to MANUAL

If necessary to stop Governor valve closing, PRESS P-6, “Hold Valve Test” pushbutton

ISOLATE EH fluid to the selected valve AGITATE valve with a blow hammer; SLOWLY UNISOLATE EH fluid to valve



What are the power limitations for valve testing?

Turbine valve testing may be performed at any point between 10% and 88% reactor power

Ensure the following conditions are met:

  • LOWER turbine load to 85%-88% power
    • Allows other 3 GVs opening margin for closing a GV (maintain same power level)


What and why do we have limits on the cooldown rate for the MSR?

Limits on Reheater outlet temperature during valve testing

Reheater cooldown rate to be less than 250°F/hr

  • Prevents undue thermal stress and possible distortions to LP Turbine stationary parts


What auto starts Turbine Oil Lift Pumps (P-124A/B, P-125A/B)

Switch in AUTO START

Rotar Shaft Speed <600 rpm and lowering


What are the turning gear interlocks?

WHITE indicating light illuminated when interlocks are satisfied for Turning Gear Operation.

  • Bearing Lift Disch Pressure > 600 psig
  • Generator Lift Oil Pressure > 600 psig
  • Turbine Speed < 600 rpm


What auto starts Generator Lift Oil Pump (P-28)?

Generator Lift Oil Pump (P-28) handswitch in AUTO START

  • starts at 600 rpm decreasing


What autostarts Emergency Bearing Oil Pump (P-27)?

Emergency Bearing Oil Pump (P-27) handswitch in AUTO START

starts at 6 psig decreasing


What autostarts HP Seal Oil Backup Pump (P-24)?

HP Seal Oil Backup Pump (P-24) handswitch in autostart

starts at 9 psig decreasing