Stator Cooling/Isophase bus cooling Flashcards
What does the stator cooling system do?
Provides cooling for the stator windings, terminal bushings, excitation rectifiers and connection rings.
Where does stator cooling enter and leave the main generator?
At the top of the generator to prevent uncovering the stator bars on a loss of system flow.
What pressure is stator cooling coolant leaving the generator maintained at? Why?
ATM pressure to help remove H2 picked up by the coolant.
Where is the H2 removed from the coolant and where does it go?
It is removed at the storage tank and is vented to the roof
Explain the cooling mechanism for the CE system.
2 series HX cooled by TCW
What is the CE supply temperature maintained at?
Approx. 42 degrees C
Can CE flow be isolated to a cooler? Can TCW?
CE flow can not be isolated. TCW can be. The main generators output will have to be reduced to approx. 80 percent.
What valve maintains pressure of the coolant going to the Main Generator?
PCV-34 at around 22-28 psig
Explain the Stator cooling pumps
2 pumps. 1 normally running and one in standby.
Powered from NGN-L14 and L15
Standby pump starts at CE lo flow 581 GPM.
Both pumps receive another start signal at a lo-lo flow of 549 gpm.
If the standby CE pump autostarts; what indication does the control room see?
Amber light
What are the CE pump trips?
- Gen differential
- Stator Ground
- Unit differential lock
What provides cooling to the isophase and stator cooling coolers?
TCW
What provides makeup to the CE system?
DW
How is conductivity maintained in the CE system?
10 percent of system flow goes thru a deionizer (resin) to remove impurities.
When do we need to change the resin in the deionizer?
delta-P greater than 15 psid
conductivity greater than 0.5 micro uhmo/cm
What does the stator leak monitoring system (SLMS) do for us?
Detects H2 concentration in storage tank
Helps find leaks early which help prevent insulation damage and electrical malfunctions.
What are the CE malfunctions that cause a MT trip?
All CE trips have a 70 second time delay
- Low inlet water pressure (549 gpm)
- High outlet temperature (85 degrees F)
- Stator in flow (549 gpm)
- Connection ring flow (90 gpm)
- Gen. Bushing flow (64 gpm)
- Rectifier flow (54 gpm)
What is the isophase bus temperature limit?
105 degrees C
What is the enclosure temperature limit?
80 degrees C
How many fans are in the Isophase system?
2 100 percent capacity fans powered from L15 and L14
What does the H2 gas detector in the isophase system do?
Alarms in control room on hi or hi hi. Indicative of a Bushing failure.
What do the operators need to do on a Hi H2 alarm in the isophase bus system?
On a Hi alarm the H2 pressure needs to be reduced.
What do the operators need to do on a hi-hi H2 alarm in the isophase bus system?
The generator needs to be removed from service and the bushings repaired.
