Stator Cooling

Question 1

How does Stator cooling water enter/leave the main generator and why

Answer 1

• Enters and leaves Generator from above
• ensures Generator stays full is stator cooling lost
• Lines also have vacuum break to prevent siphoning

Question 2

How does Stator cooling water enter/leave the main generator and why

Answer 2

• Enters and leaves Generator from above
• ensures Generator stays full is stator cooling lost
• Lines also have vacuum break to prevent siphoning

Question 3

How is Hydrogen removed from Stator Cooling water

Answer 3

• Cooling leaving generator maintained atm. press.
• Line leaving generator is much larger than supply
• Stator cooling water tank vented to atm.

Question 4

How is Stator cooling water system affected by a loss of NKN-D41

Answer 4

• Tripping power is lost

Question 5

What does Stator Cooling Water cool

Answer 5

• Stator
• Connector Ring
• Terminal bushings

Question 6

What causes a Stator Cooling Water stby pump to start

Answer 6

• Low Disch press. 581 gpm

- LoLo Disch press. 549 gpm

Question 7

What will Cause Stator Cooling Water pump trips

Answer 7

• Electrical Fault
• Generator Differential
• Stator Ground
• Unit Differential Lockout

Question 8

What is the capacity of the Stator Cooling HX’s

Answer 8

• Each HX approx. 80%

- 1 HX lost reduce power to 80%

Question 9

What temperature does Stator Cooling water maintain

Answer 9

42*C leaving the HX’s

Question 10

What is the concern if Stator Cooling Water conductivity is too high

Answer 10

• Flashover within Generator

Question 11

When is Stator Cooling Water Resin changed

Answer 11

• 24 Months
• press drop of 15 psi
• Conductivity > 0.5 micromhos/com

Question 12

What is the purpose of the Stator cooling Water pressure control vlv

Answer 12

• Max press 28 psig
• Min press 22 psig
• Ensures bubbles or gas in stators are purged
• Prevents exceeding value req’d at full load

Question 13

When is SLMS started

Answer 13

• After Main Generator is Synched to the grid

Question 14

What is the Main Generator output limited to without Isophase bus cooling

Answer 14

• 23,000 amps

- Full load can be maintained for 30 minutes

Question 15

What is the Main Generator output limited to without Isophase bus cooling

Answer 15

• 23,000 amps

- Full load can be maintained for 30 minutes

Question 16

What are the Isophase bus temperature limits

Answer 16

Iso Buses - 105C
Enclosures - 80C
- If exceeded lower generator load

Question 17

How is Isophase bus cooling controled

Answer 17

• Manually throttle cooler outlet vlvs (TC)
• Air inlet temp maintained < 130*C
• If cooler removed from svc close inlet vlv

Question 18

What actions are required if H2 is detected in Isophase bus

Answer 18

Hi Alarm - Reduce H2 press in Generator

HiHi Alarm - Remove Generator from svc.

Question 19

What can be done if Isophase bus cooling is lost

Answer 19

• A portable unit can be used instead

Question 20

What Stator Cooling Water conditions will cause a Turbine Trip

Answer 20

Low Inlet water press  - 549 gpm 
Stator Inlet Flow           - 549 gpm
Connecting Ring flow  - 85 gpm
High Outlet Temp         - 85*C
Gen bushing low flow  - 64 gpm 

• 70 Second Time Delay for all
• 2/3 logic for all

Question 21

At what Stator Cooling Water conductivity must an Operator Trip the Generator

Answer 21

> 9.9 micromho/cm