Stator Cooling Water

Question 1

What are the SCW pump auto starts?

Answer 1

• Low Disch pressure at 130 psi (U1) and 80 psi (U2)
• Low Flow at 845gpm (U2 only)

Question 2

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

Answer 2

Temperature, flow and pressure trips

• 2/3 RTDs at 81°C (U1) 95°C (U2) after 5 second delay
• 2/3 Low Flow at 499 gpm (U1) and 666 gpm (U2)
• 2/3 Low Pressure at 36 psi (U1) and 28 psi (U2)

(Each auto trip will actuate)

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

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 pressure is maintained 3-4 psi less than machine gas pressure

Question 5

Why is the SCW maintained 3-4°C warmer than 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

Maintain less than 100 gpm flow through the deionizer

Question 9

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

Answer 9

Less than 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 U2’s 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 does 1-CRV-640 (SCW Reg Valve) do in U1 only?

Answer 14

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

Question 15

How will a loss of CCRP affect the SCW Sys?

Answer 15

A loss of CCRP blocks the SCW High Temp Turbine Trip

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

Question 16

Which SCW Trips are blocked to allow Unit Backfeed operations?

Answer 16

Low pressure and Low Flow

Question 17

What are the conductivity numbers associated with SCW?

Answer 17

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

Question 18

What is the purpose of the teflon connectors in the SCW System?

Answer 18

Provide electrical insulation between the stator bars and the system piping