AOP-9 Loss of D Bus

Question 1

What is assumed about the buses supplied by D bus in AOP-9?

Answer 1

That they are fault free.

Question 2

What are the entry conditions for AOP-9, Loss of Delta Bus?

Answer 2

1. EK-0515, “2400V BUS 1C AND/OR 1D HI/LO VOLTAGE/ UNDERVOLTAGE” (< 2375V, 18 sec time delay)
2. EK-0522, “BUS FAIL TO TRANSFER”
3. EK-0521, “2400V STANDBY POWER NOT AVAILABLE”
4. EK-0510, “2400V BUS 1D BKR 152-202 TRIP” (if closed)
5. EK-0504, “2400V BUS 1D BKR 152-203 TRIP” (if closed)
6. EK-0532, “BUS 1C OR 1D OVERCURRENT LOCKOUT”

Question 3

As NCOT, what do you report/recognize on loss of D bus?

Answer 3

Look Left - Right train loop injection valves will be dark.

Look Up - Are the following Alarms in?

• 0521 - 2400V Standby Power Not Available
• 0532- Overcurrent Lockout

Look Right -

• Is D Bus energized?
• Did EDG 1-2 Start

REPORT

• I have 2400V Standby Power Not Available Alarm in.
• Delta bus is de-energized
• 1-2 EDG Did/Did Not Start
• Overcurrent Alarm is/is NOT in.

Question 4

What are the Auto Actions for AOP-9, Loss of Delta Bus?

Answer 4

1-2 EDG Starts

Question 5

What Auto Starts and EDG?

Answer 5

Two Levels of Undervotage Protection

Inverse Time 77%

• 3 out of 3
• At 77% rated voltage or less, trips incoming breaker, initiates load shed and starts EDG

Degraded Voltage

• 3 out of 3
• 93% or less of rated voltage for 0.65 seconds starts the EDG.
• After an additional 6 seconds, trips incoming breaker and initiates load shed.

Question 6

What are the trip criteria of AOP-9, Loss of D Bus?

Answer 6

Only Equipment Trip Crietera for EDG.

JW Temp > 195F

Lube Oil Temp >200F

Question 7

Why do you have to trip the EDG locally?

Answer 7

The control room switches do not have a pull to lock feature. Just taking the switches off would result in the EDg starting again.

Question 8

Why do you check if Y-01 energized?

Answer 8

Y-01 is normally aligned to MCC-1 but swaps to MMC-2.

Question 9

Why is Service Water address in AOP-9, Loss of D Bus?

Answer 9

You loose two service water pumps.

Could result in less than 42 psi pressure.

Close Hi Caps

Verify Exciter Air being cooled.

Question 10

What do you do if EDG output breaker, 152-202, is tripped.

Answer 10

Verify EDG operations per SOP-22.

Trip usisng overspeed lever.