LOT 202.06 EHC Flashcards
- LOT 202.06 EHC*
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What does the turbine actual display meter actually display?
- Speed Control:*
- *Turbine Speed**
- Load Control / Imp In:*
- *% Turbine Load**
- Load Control / Imp Out:*
- *% Cumulative GV Demand**
Located on CP007.
Note:
Indicated value stored in EHC reference controller, not actual turbine RPM or load.
- LOT 202.06 EHC*
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What cools the EHC heat exchangers?
CL-ACW
TCV maintains ECH temp at 125 ˚F ± 5 ˚F
- LOT 202.06 EHC*
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What happens when turbine speed reaches 103%?
Overspeed Protection Controller (OPC):
Two OPC Solenoids Energize (Open)
Drains EHC Fluid from Governor / IVs ONLY
Two OPC solenoids De-Energize (Close) at 1800 RPM (100%)
Governor / IVs Re-Open
Controlled by Aux Governor.
- LOT 202.06 EHC*
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Which steam admission valves have servos?
Throttle Valves
Governor Valves
Linear Variable Differential Transformer (LVDT) is used for VPI and feedback.
Reheat Stop and Intercept valves have no throttling capability.
Note:
All steam admission valves are hydraulically opened / spring closed
- LOT 202.06 EHC*
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As level begins to lower in the EHC Reservoir tank, what is the expected plant response?
Level - Low 2 (11.62”):
Alarm
Secures heaters
- Level - Extreme Low 2 (7.62”):*
- *Prevents Backup pump from starting**
- Does not secure running pump*
- LOT 202.06 EHC*
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How many HP accumulators does the EHC system contain?
8 Total
- HP Turbine Enclosure (4)
- EHC Skid (1)
- SGFPTs (3)
Note:
Charged with N2 (1200 psig - 1300 psig) for system shutdown
- LOT 202.06 EHC*
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What does the turbine governor look at when the turbine is in “Imp In” and “Imp Out.”
- Imp Out:*
- *Cumulative Governor Valve Position**
- Generator MW will change as steam pressure changes*
- (Non-Linear Response)*
Imp In:
1st stage impulse pressure
GV position adjusted to maintain Impulse pressure (Generator MW) constant
(Linear Response)
Note:
Load control consists of 2 modes. “IMP IN” or IMP OUT”.
- LOT 202.06 EHC*
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How many LP accumulators does the EHC system contain?
7 Total
- HP Turbine Enclosure (4)
- SGFPTs (3)
Note:
Pressurized to 24 psig - 30 psig and provides surge volume to displace fluid on turbine trip.
- LOT 202.06 EHC*
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What will auto start the standby EHC pump?
- Auto Start:*
- *Low Pressure (1600 psig)**
- Permissive:*
- *EHC Reservoir Tank Level > Extreme Low 2 (7.62”)**
- Will NOT trip running pump*
Normal: 1900 psig - 2100 psig
- Relief (2350 psig)
Switches located on CP007.
- LOT 202.06 EHC*
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If the turbine were to experience and overspeed event (Mechanical/Electrical), would the SGFPTs trip?
- *No**
- SGFPTs have orifices in supply lines*
Depressurizes the rest of EHC. Will close the Throttle, governor, RSV, and IVs.
- LOT 202.06 EHC*
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How does the EHC reservoir tank maintain low moisture levels in the EHC oil?
Purge Blanket of dry Instrument Air
Vacuum relief in tank set for ± 2 psig.
- LOT 202.06 EHC*
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How does the load drop anticipator work?
Actuated When:
Turbine Load > 30% (Reheat Pressure)
AND
Generator Breaker manually opened
Overspeed Protection Controller:
Two OPC Solenoids Energize (Open)
Drains EHC Fluid from Governor / IVs ONLY
Will remain closed for 8 sec
Resets and repeats as necessary until turbine load < 30% (Reheat Pressure)
- LOT 202.06 EHC*
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When does the EHC system switch to load control?
Generator Output Breaker Closed
Speed control used to startup turbine and bring to 1800 RPM.
- Throttle Valve Control (0 RPM - 1700 RPM)
- Governor Valve Control (1700 RPM - 1800 RPM)
Note:
Load control consists of 2 modes. “IMP IN” or IMP OUT”.
- LOT 202.06 EHC*
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How are the turbine auto-stop trip (AST) solenoids physically arranged?
- *Series / Parallel arrangement**
- Failure of 1 AST neither causes / precludes turbine trip*
Energized Closed / De-energized will trip the turbine
Powered from Non-Class 125 VDC Swbd 1A.
Note:
These 4 AST solenoids are how the electrical turbine trips are accomplished.
