Main Turbine Control and Supervisory Flashcards
(45 cards)
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
REFERENCE
- 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
ACTUAL
- The actual % of turbine load (or RPM value).
SETTER
- Indicates values that have been manually entered by the NCO, (RPM, turbine load)
CONTROL
- 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?
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%
