1E-AC - .5 Flashcards
Switchgear Bus Differential O/C or Bus O/C
- Trips supply breaker and blocks closure of alternate
- Trips and locks out all load/motor feeder breakers
- Initiates breaker failure protection
1E Switchgear Bus Undervoltage transfer actions:
a) If the incoming feeder voltage is <92% for 20 seconds, OR bus voltage decreases to <70% of normal, a degraded bus voltage transfer is initiated.
b) IF bus voltage is < 70%, 27 device trips (regardless of the feeder voltage conditions), the normal breaker will trip and the alternate breaker will close following a .7 second* time delay, provided:
i. AUTO CLOSE BLOCK is not selected.
ii. Associated feeder voltage is ≥ 94%
iii. No lockouts present
iv. Normal supply breaker is open
- The alternate supply breaker will close to supply power to the bus following a time delay of 0.7 seconds. The time delay is to ensure motor breakers are open prior to closure of the alternate breakers. Motor feeders on class 1E USS have time delayed (.25 seconds) undervoltage relays which trip the motor feeder breakers from the bus.
What occurs when 27 device trips?
a) All motor circuit breakers are tripped (.25 sec TD).
b) LOP Sequencer is initiated (.5 sec TD after EDG breaker closure)
c) PSIS block loads start (.5 sec TD)
d) Emergency start of EDG if both normal and alternate infeed voltages are <92%
EDG will start conditions:
- LOP
a) Both incoming feeder voltages ≤92% (20 sec TD) (Degraded Voltage)
b) Both incoming feeder voltages ≤92% AND Bus voltage < 70% (LOP) - LOCA: 1.68 psig or -129.
- Manual initiation of core spray logic.
4160V BRK local emergency takeover
Almost all breakers have local emergency takeover capability.
- Breakers operated from the RSP CANNOT be operated locally from the switchgear rooms
Supply Breakers operated in emergency takeover can be closed IF:
- Associated EDG output breaker is open
- No bus Lockouts
- Associated Station Service Transformer Lockout reset
- EDG breaker failure lockout reset
Infeed BKR numbers for 401-404.
For 401 and 403, 40X08 is the Normal infeed, For 402 and 404, 40X01.
LOCA level 1 and level 2 breaker trips
Generally speaking, a LOCA level 1 will trip your bottom Non-1E breakers and a LOCA level 2 / Hi-Hi Rad signal will trip your upper breakers.
Requirements for the EDG output breaker to close
- EDG Ready to Load:
a) Frequency > 57 Hz (95%)
b) Gen Terminal Voltage > 3950 V (95%) - Switch Gear Permissive:
a) Both Normal and Alt. Feeder Breakers Open
b) Bus Voltage < 70%
c) EDG Lockouts Reset
10A401 Loads
- A SACS Pump
- A Core Spray Pump
- A RHR Pump
- A SSWS Pump
- AK403
- 10B410
- 10B450
10A402 Loads
- B SACS Pump
- B Core Spray Pump
- B RHR Pump
- B SSWS Pump
- BK403
- 10B420
- 10B460
10A403 Loads
- C SACS Pump
- C Core Spray Pump
- C RHR Pump
- C SSWS Pump
- AK400
- 10B430
- 10B470
10A404 Loads
- D SACS Pump
- D Core Spray Pump
- D RHR Pump
- D SSWS Pump
- BK400
- 10B440
- 10B480
LOP vs LOCA signal priority.
LOCA signal will override LOP.
UPS input voltages
a) Normal power – 480VAC
b) Alternate power – 125 VDC (inop if DC unavailable)
c) Backup power- 480VAC
