Non-1E AC - .5

Question 1

What occurs during a Station Service Transformer Lockout?

Answer 1

1. Any breaker supplied from the transformer is tripped and their closing circuit is blocked.
2. The alternate bus power supply breaker is closed and automatic transfer is blocked.
3. Transformer cooling fans and oil pumps stopped.
4. The 13.8 bus section is isolated.

Question 2

What happens to the supply and feeder breakers after Switchgear Bus Differential Overcurrent OR Switchgear Bus Overcurrent occur?

Answer 2

• Trips supply breaker and blocks closure of alternate
• Trips and locks out all load/motor feeder breakers
• Initiates breaker failure protection

Question 3

Switchgear Feeder Undervoltage

Answer 3

• If switchgear feeder voltage lowers to < 90% of normal, the associated feeder breaker is tripped and its Auto Close feature is blocked. (Reset when feeder voltage is ≥ 94%)
• A feeder breaker opening initiates an auto closure permissive signal to the alternate breaker.

Question 4

Switchgear Bus Undervoltage

Answer 4

• If switchgear bus voltage decreases to < 70% of normal for .25 seconds, all load/motor breakers are tripped. (7.2KV Bus)
• If switchgear bus voltage decreases to <70% of normal, all motor circuit breakers will trip and will the logic will permit the alternate breaker closure. (4160V Bus)

Question 5

When does a Switchgear Feeder Fast Transfer* occur?
*A bus section fast transfer will trip its respective feeder breaker and shut the alternate feeder breaker under the following conditions providing there are no existing bus faults.

Answer 5

• Station Service Transformer lockout
• Station power transformer lockout
• Transmission Line Protective relay
• Manual

Question 6

Main Feeder Breaker Trips:

Answer 6

• Associated Transformer Lockout
• Bus diff lockout
• Bus overcurrent
• Feeder Voltage < 90%

Question 7

7.2KV Loads
AX502

Answer 7

Normal Sup Bkr
10A110
VFD A
SCP A
PCP A
AK111

DK111
10K107

Question 8

7.2KV Loads
BX502

Answer 8

Normal Sup Bkr
10A120
VFD B
SCP B
PCP B
BK111
00K107

Question 9

1E Powered Non-1E Loads

Answer 9

1. NSSS Computer
2. Security System
3. PA System
4. Standby Lighting
5. BOP Computer

Question 10

What happens if a BRK trip button is depressed to acknowledge a trip?

Answer 10

13.8 KV and up push buttons do NOT flash on a trip, if a flashing 1E breaker PB is pressed, it will go solid and prevent the diesel from loading to that bus

Question 11

UPS Operation.

Answer 11

After loss of Normal A/C, Alternate D/C is selected, then Backup A/C as a last option.