Stator Water Cooling

Question 1

What is the power supply for the Stator Water Cooling pumps?

Answer 1

Remember, need 2 As and 2 Bs, so

Unit 2 - 2A 2B
Unit 1 - 1AA 1BB

Stator Cooling Pump 2A - 600 “A” (2R23-S001)
Stator Cooling Pump 2B - 600 “B” (2R23-S002)
Stator Cooling Pump 1A - 600 “AA” (1R23-S011)
Stator Cooling Pump 1B - 600 “BB” (1R23-S012)

Question 2

When does the standby stator water cooling pump start?

Answer 2

110 psig discharge pressure

100 psig backup switch

Question 3

What happens to the stator water cooling temperature control valve on a loss of air?

Answer 3

On a loss of air, valve fails open to direct all flow thru the Stator Coolers.

Question 4

How does the stator water cooling pressure control valve work? What happens on a loss of air to the valve?

Answer 4

Pressure Control Valve (2N43-F095/1N43-F140)
Maintains stator cooling water pressure at inlet to Generator at ~ 3 psig < H2 pressure in the generator casing

Loss of Air – Fails Full Open (would rather have higher pressure than a loss of cooling & subsequent shutdown)

Question 5

On a loss of stator water cooling, what happens to the main generator?

Answer 5

Must start >6466 amps for protections circuits to be engaged

Generator Runback (to < 25.6% (6466) load) – 2 of 3 logic

Initiation Signals

• Low Inlet Pressure – 35 psig (25.6 psig)
• High Stator Outlet Temperature - 81°C
• Low System Flow – 405 gpm

If generator amps > 6466 and initiation signal present
Load must be < 20,232 amps within 2 minutes AND
Load must be < 6466 amps within 3.5 minutes OR ELSE TURBINE TRIP