Class 120 VAC Instrument Power (PN)

Question 1

What is the purpose of the PN system?

Answer 1

provide power to RPS, ESFAS, vital instrumentation in CR and RSP

Question 2

Where do the PN inverters receive power from?

Answer 2

PK

Question 3

Is the PN Static transfer switch power seeking?

Answer 3

yes

will transfer to emergency source

WILL NOT TRANSFER BACK automatically

Question 4

What is the alternate source of power for PN?

Answer 4

PH through a voltage regulator

Question 5

Is PN grounded or ungrounded?

Answer 5

ungrounded

reduce possibilities of system degradation due to a ground. Ungrounded systems require a ground to develop on both the line and neutral buses before losing all or part of the system operability

Question 6

What happens if you lose one channel of PN?

Loss of 2 channels?

Answer 6

If power is lost to a single train, components will fail to a safe condition. This failure will not jeopardize reactor safety

If power is lost to two or more trains of PN, a reactor trip and complete ESF initiation for all outputs (i.e. CIAS, CSAS, SIAS, etc) for A and B trains.

Question 7

What is the maximum number of PN busses that should be on the voltage regulator?

Why?

Answer 7

1

Voltage regulator is powered from off-site power
if we had two or more on the voltage regulator and had a LOOP, we would lose two PN busses. full ESFAS actuation on both trains

Question 8

What would bring in this alarm?

Answer 8

This annunciator indicates either a loss or possibly
impending loss of a distribution panel

 Inverter low and high voltage, DC low and high
voltage, fuse blown, breaker tripped, out of sync or
other inverter troubles such as fan failures.
 Distribution panel problems include undervoltage,
ground or standby supply NOT available.

other channel alarms behave similarly