Instrument Power 120VAC (PN)

Question 1

What’re the 4 subsystems dedicated to provide power to ?

Answer 1

-Reactor Protection System(RPS)monitors reactor and plant conditions

-Engineered Safety Features Actuation System (LOCA, steam line break,feedwater line break)

Question 2

What is normal flow path for PN system ?

Answer 2

Power comes from PK battery system, goes through inverter 125DC->120VAC,then static switch,& manual bypass switch, PN bus

Question 3

What is alternate power for PN system ?

Answer 3

Class 480VAC MCC,through voltage regulating transformer 480->120, Static Transfer Switch, Manual Bypass Switch in inverter cabinet

Question 4

What is primary power source for PN system ?

Answer 4

Receives power from PK battery system

Question 5

What is housed inside the inverter cabinet ?

Answer 5

Inverter, static switch, and manual bypass switch

Question 6

What is the pre charge push button for on inverter ?

Answer 6

Pre charges the DC input filtering capacitor, so the capacitor isn’t damaged closing the DC breaker ;energize alarm panel

Question 7

Protective relays on PN system ?

Answer 7

DC under voltage (INPUT)
DC over voltage (INPUT)
AC under voltage (OUTPUT)
AC over voltage(OUTPUT)
AC instan.(OUTPUT)

Question 8

Breaker indications on inverter?

Answer 8

Open(green light)
Closed(Red Light)
Pre Charge(orange light) must be lit before closing input breaker

Question 9

What is Third of a kind swing lineup switch used for ?

Answer 9

Allows an alternate flow path to the respective train, and allows for maintnence to be done on the normal inverter cabinet

Question 10

If the alternate supply power through voltage regulators were in use, what will open the contacts for it? what will close it 5 seconds later ?

Answer 10

It will open on a load shed signal during a LOP condition. Contacts will be sequenced on by a BOP ESFAS after 5 seconds DG output breaker closes

Question 11

When will static transfer switch change to alternate power ?

Answer 11

Low DC input voltage
Low AC output voltage
High AC output current

Question 12

What light indication is inverter to load ?

Answer 12

Green light

Question 13

What light indication is bypass source to load ?

Answer 13

Orange light

Question 14

What is used on the PN system to protect system from a fault?

Answer 14

A fuse disconnect after switch, the fuses are fast acting and current limiting to protect system

Question 15

What do the PN system D-panels supply power to?

Answer 15

Each distribution panel supplies one channel RPS & ESFAS, they’re physically separated; If one fails the other three can safely monitor and shutdown reactor

Question 16

What is the indication light for a ground fault on a distribution panel ?

Answer 16

It’s annunciated in control room, has a red light locally,and must be reset cleared and reset locally

Question 17

How does PH interface with PN?

Answer 17

PH supplies alternate power to PN system

Question 18

How does PK interface with PN system ?

Answer 18

PK supplies normal power to PN system

Question 19

How does HJ interface with PN ?

Answer 19

HJ supplies ventilation to ESF DC equipment room that has the PN system in

Question 20

How does PN interface with RPS ?

Answer 20

PN provides power to RPS to monitor reactor and nuclear steam support system

Question 21

What does RPS do?

Answer 21

They initiate protective action shutdown the reactor if monitored parameters are out of range

Question 22

How does PN interface with ESFAS ?

Answer 22

PN provides power to ESFAS to monitor plant parameters

Question 23

How does PN interface with CEDMCS ?

Answer 23

PN supplies power to CEDMCS Auxiliary relay cabinets, which contain:
-Reed Switch Position transmitters to indicate CEA position
-Plant Protection System to initiate shutdown

Question 24

How does PN system interface with SQ system ?

Answer 24

PN provides power to safety related Radiation Monitors

Question 25

What happens if normal ventilation is lost to the ESF DC equipment room ?

Answer 25

Both trains essential ventilation will start up

Question 26

What’re the two ways you can lose essential ventilation ?

Answer 26

The blower goes out or you lose essential chilled water

Question 27

What is a temporary solution to the loss of the blower?

Answer 27

Installing a temporary blower and expandable ducting into DC equipment room

Question 28

How many PN channels need to be lost for plant to trip ?

Answer 28

Need 2 channels for a plant trip ; One lost channel WONT trip plant

Question 29

What’re tech spec for PN system in mode 5&6 ?

Answer 29

Must have ONE train of inverter, TWO channels with one inverter per channel, is required to be operable for LCO requirements

Question 30

How does a Swing Lineup Switch work ?

Answer 30

Manual Break-Before-Make to change the position of all 3 connections to 1 of 3 positions, this is done to always allow the input & output to be on the same train/channel.

Question 31

What’re the 3 connections for Swing Lineup Switch ?

Answer 31

-DC input from normal power supply(PK)
-AC input from alternate supply(MCC) that goes through voltage regulating transformer
-AC output is directed to to the Channel specific Manual Bypass Switch

Question 32

How fast do you need to close the DC input breaker to inverter ?

Answer 32

You need to close it within a minute of charging the filtering capacitor, due to the capacitor having a bleeder resistor discharging to circuit.