Non Class Control Power (NK)

Question 1

What is ground detection?

Answer 1

Hard ground: <2k ohms
Soft ground:>2kohms; <35k ohms

Question 2

What’re the NKN-U46 & NKN-U45 for ?

Answer 2

Gives power to NAN-S05& NAN-S06

Question 3

How many battery chargers & batteries are there for the NK system ?

Answer 3

E subsystem:TWO battery chargers & battery;125VDC MCC w/ control panel

F subsystem:One batter charger &battery;125VDC MCC w/ control panel

G subsystem: Battery charger & battery ; 125VDC distribution panel

Question 4

Why are the 125VDC systems(NK) ungrounded ?

Answer 4

So one ground fault doesn’t trip the whole system, need multiple faults for it to trip

Question 5

Where are the battery chargers powered from and what do the chargers do ?

Answer 5

Non class 480VAC MCC(NH) & convert 480VAC-> 135VDC

Question 6

What does NKN-U45 & U46 give control power to ?

Answer 6

Gives control power to NAN-S05 & S06

Question 7

What does Float Position mean for a battery charger ?

Answer 7

Supplies 135VDC to NKN-M45&M46 bus to supply DC loads and maintain the batteries charged

Question 8

What does “equalize” operation mean for battery charger ?

Answer 8

Supplies 139.8 VDC to all DC loads and to recharge batteries (after batteries have been discharged)

Question 9

What’re the indication that the battery charger is in service ?

Answer 9

Pilot lamp lights up when 480VAC is going through AC breaker; local DC ammeter and DC voltmeter

Question 10

How do we prevent condensation and possible damage to battery chargers ?

Answer 10

Internal space heaters controlled by thermostats

Question 11

What’re the features of the battery storage assemblies ?

Answer 11

.60 cells of lead calcium type
.sealed and assembled in heat resistant
.shock absorbing
.plastic containers with explosion resistant vent plugs

Question 12

Why must there be constant ventilation to the battery room ?

Answer 12

To prevent explosive environment from hydrogen build up in battery room

Question 13

What happen on a bus under voltage ?

Answer 13

Under voltage relay lights up a white indicator and send alarm to CR

Question 14

What’re the indications for a ground detection ?

Answer 14

Soft ground : white light at control center will be on;(>2kohm &<35kohm)

Hard ground: white light at control center and in CR (<2kohm)

Question 15

How does NK interface with NA?

Answer 15

Provides control power for switchgear and startup transformer indications & control

Question 16

How does NK interface with NB ?

Answer 16

Provides control power to Switchgear & NSF transformer

Question 17

How does NK system interface with NG system ?

Answer 17

Provides control power to load centers

Question 18

How does NK system interface with NH system ?

Answer 18

480VAC MCC gives power to battery chargers

Question 19

How does NK system interface with NN system ?

Answer 19

NK provides control power for ground detector relay circuits on distribution panels

Question 20

How does NK system interface with NQ system ?

Answer 20

NK system provides power to NQ system through inverter for plant computer

Question 21

How does NK system interface with PB system ?

Answer 21

Provides control power for class switchgear isolation relay section and normal chiller

Question 22

What is the battery discharge voltage ?

Answer 22

125DC

Question 23

How does ungrounded operation work for NK system ?

Answer 23

Need simultaneous faults in both the positive and negative bus

Question 24

What is the mechanical interlock for on the two output breakers of the Swing Battery Charger(EF) ?

Answer 24

It’s to prevent closing of both breakers at the same time

Question 25

How should battery chargers be swapped ?

Answer 25

Parallel the new battery charger with the in service battery charger, then remove the in service charger

Question 26

What do panels NKN-D41,42,43 provide power to ?

Answer 26

Controls, instrumentation, and annunciation for all non-class equipment

Question 27

How does NK system interface with MA system ?

Answer 27

Provides power to normal tripping circuit & the back up tripping circuit

Question 28

What does NKN-D19 provide power to ?

Answer 28

Control and annunciation power for cooling tower Load Centers and MCC& annunciation power for control panels