Stator Cooling Water

Question 1

What are the SCW pump auto starts?

Answer 1

• Low Disch # at 120#(U1) and 80#(U2)

- Low Flow at 845gpm (U2 only)

Question 2

What are the Main Turbine and Unit Differential trips associated with SCW?

Answer 2

• 2/3 RTDs at 95°C after 5 second delay
• 2/3 Low Flow at 195 gpm (U1) and 666 gpm (U2)
• 2/3 Low Pressure at 13#(U1) and 28# (U2)

(Each auto trip will actuate)

• Main Turbine Trip after 10 seconds
• Unit Differential Trip after 30 seconds.

Manual Actions

• Conductivity at 9.9 mho/cm (reduce load)
• MANUAL TRIP at 18 mho/cm conductivity

Question 3

What cools the SCW coolers?

Answer 3

• TACW

Question 4

How is the SCW maintained to prevent water leaking in the Generator?

Answer 4

• SCW # is maintained 3-4# < machine gas #

Question 5

Why is the SCW maintained 3-4°C > Cold Gas Temp?

Answer 5

• Prevent moisture from forming on the outside of the Stator Water Teflon tubes

Question 6

What is the auto makeup to the SCW system?

Answer 6

• Demin Water

Question 7

What is the purpose of the SCW system?

Answer 7

• Removes heat from the Main Gen stator armature conductors
• Designed for continuous operation and must be in service to allow operation of the Main Generator
• Cools U2 Output Bushings

Question 8

How to you prevent channeling of the SCW Deionizer?

Answer 8

• By maintaining < 100gpm flow through the deionizer

Question 9

What temp must you maintain in the deionizer to prevent resin breakdown?

Answer 9

• < 120°F to prevent breakdown of the resin

Question 10

Why does the SCW system have deionizers?

Answer 10

• To remove conductivity so transfer of electricity thru water is not possible

Question 11

What is the backup source of makeup water to the SCW system?

Answer 11

• Condensate (Manual only) (HWP Discharge)

Question 12

Where is the U1 SCW tank vented to?

Answer 12

• Atmosphere

Question 13

How does U2s SCW Tank differ from U1s SCW Tank?

Answer 13

• Unit 2 SCW tank has H2 cover pressure instead of being vented to atmosphere

Question 14

What are the SCW Pump trips?

Answer 14

• Unit Differential HEA
  (Prevents flooding of generator)
• Overload/Overcurrent

Question 15

What does 1-CRV-640 (SCW Reg Valve) do in U1 only?

Answer 15

• Maintains Main Gen water inlet pressure at about 3# < machine gas pressure
• Mechanical stops prevent flows < 340 gpm (25#) and > 550 gpm.

Question 16

How will a loss of CCRP affect the SCW Sys?

Answer 16

• A loss of CCRP blocks the SCW High Temp Turbine Trip

- When power is restored, the block is removed 15 seconds later.

Question 17

Which SCW Trips are blocked to allow Unit Backfeed operations?

Answer 17

• Low # and Low Flow Trips are blocked to allow Unit Backfeed operations.

Question 18

In U1, how many SCW Coolers are in service?

Answer 18

• Both are normally in service, if only one is available, you have to reduce Generator load to 80%