Stator Cooling Water (CE) Flashcards
What is the purpose of Stator Cooling?
cools:
main generator stator windings
terminal bushings
connection rings
Isophase bus cooling cools:
isolated phase buses that connect the generator output to the main transformers
collector housing unit cools the main generator collector housing
In regard to the CE system, what do we lose the ability to do on a loss of NKN-D41?
cant trip the turbine
turbine trip relays
What happens in the CE system on a loss of Instrument Air?
TV-33 fails to the full flow position to send water through the heat exchangers
Where are the Stator cooling water pumps powered from?
NGN-L15/L14
How can you tell if a stator cooling water pump auto started?
green flagged HS, Red AND Amber lights illuminated
When will the standby stator cooling water pump auto start?
what are the setpoints?
Lo and Lo-Lo discharge pressure
Lo – 581 gpm
Lo-Lo – 549 gpm
How is the auto start test performed for the standby stator cooling water pump?
pushbutton in the control room or locally
What trips the stator cooling water pump?
electrical fault (standby pump will autostart)
generator differential (no autostart of stdby pump)
stator ground (no autostart of stdby pump)
Unit differential lockout (no autostart of stdby pump)
What signals would cause a turbine trip after a time delay?
what is the trip logic?
How long is the time delay?
Low inlet water pressure - 549 gpm
high outlet temperature - 85*C
connection ring low flow - 85 gpm
stator inlet low flow - 549 gpm
generator bushing low flow - 64 gpm
2/3 logic
70 seconds
When one of the Stator cooling water heat exchangers is removed from service, what does generator load have to drop to?
~80% rated output
Why is the CE deionizer installed on a bypass line?
why is conductivity a big deal in the generator?
continuous deionization of ~10% of coolant flow
direct contact with conductors. High conductivity could cause damage due to flashover (arcing/sparking)
FCV-12, Stator Cooling Water Flow Control Valve regulates flow to what part of the generator?
Associated trip logic and setpoint?
terminal bushings
2/3 - 64 gpm
What is the purpose of the Stator Leak Monitoring System?
How does it work?
monitors hydrogen leakage from stator bars (increases indicate leaks are getting worse)
samples the gas stream through the stator cooling water tank vent
What is the maximum amperage the generator can output without forced cooling?
If cooling is lost, how long do we have to reduce loading?
23,000 amps
30 minutes
How many Isophase bus cooling fans are normally in service?
What is the flow path of air?
both (100% capacity each)
both fans supply to the ‘B’ phase bus duct, return through the ‘A’ and ‘C’
What does this GREEN alarm mean?
Turbine trip circuit is energized
if condition not corrected in 70 seconds, turbine will trip
