125VDC

Question 1

State Function of Vital 125DC System

Answer 1

Provide back up power to UPS
Control power
EDG and EPS control power

Question 2

Discuss DC Bus 11C UV protection

Answer 2

When DC link voltage decreases to 125VDC a 13.5 min timer is started (T.S. limit is 15min)
Computer UPS 2A at Bus 11c will trip open if power is not restored

Question 3

Discuss DC Bus 12B UV protection

Answer 3

When DC link voltage inside I-2B decreases to 132 VDC a 15 min timer is started
If AC power is not restored in in 15 min then:
- CB1 opens
- CB2 opens

Question 4

State how to Vital battery chargers may be operated in parallel

Answer 4

Alternate battery supply breaker can be closed

ensure that both chargers are in the same mode (float/equalize)

Question 5

What 125 VDC parameters can be monitored from MCB

Answer 5

Battery current
Bus Voltage
Ground faults

Question 6

State 1 hour T.S. for DC sources - shutdown

Answer 6

3. 8.2.2: With both battery banks and/or chargers inoperable immediately suspend all operation involving core alterations, positive reactivity additions or movement of irradiated fuel. initiate corrective action to reenergize ASAP
4. 8.3.2: suspend Core alts statement as above

Question 7

In 125 VDC SWYD system discuss ABTs

Answer 7

normal supply is US14/26
Emergency is from US53 via normal seeking ABT
-opens in LOP, closes at EPS step LR8