Non-Class Electrical

Question 1

What is the capacity of one secondary winding on a Startup Transformer?

Answer 1

1 half of the non-class loads from one unit, 1 train of class loads from the same unit, and 1 train of class loads from a different unit.

Question 2

What does the “breaker and a half” scheme in the switch yard prevent?

Answer 2

A single fault from having a large impact

Question 3

What happens in Unit 1 on a Double Sequence event that doesn’t happen in the other units?

Answer 3

BOTH WRF breakers open

Question 4

What is a Double Sequence Event?

Answer 4

A combination of a LOCA and degraded grid voltage at the same time. As SI loads sequence on, along with the FBT, class bus voltage will drop to the LOP set point which will load shed the class bus. The DG will start and load and the sequencer will run a second time. This effects the time to get a HPSI pump to inject water into the core.

Question 5

What is done to prevent Double Sequencing if switchyard voltage gets too low?

Answer 5

• Disable FBT

- place a DG on the bus

Question 6

If the multiplexer is lost for the switch yard, how does that effect the Control Room?

Answer 6

Breaker indication is lost on NAN-S05 and NAN-S06. Control is still available via the breaker switches.

Question 7

From where do MCCs get their control power for the magnetic starters?

Answer 7

They supply their own from power downstream of the circuit breaker.

Question 8

What is control power for NAN-S05?

Answer 8

Normal: NKN-M45
Alternate: NKN -M46

Question 9

What is control power for NAN-S06?

Answer 9

Normal: NKN-M46
Alternate: NKN-M45

Question 10

What is control power for the Reactor Coolant Pumps?

Answer 10

NKN-D44

Question 11

What is control power for NAN-S01/S02/S03/S04 and NBN-S01/S02?

Answer 11

NKN-D41 and NKN-D42

Question 12

From where are the breakers for NAN-S05 and NAN-S06 controlled?

Answer 12

Breakers for all three units are controlled from Unit 1

Question 13

What happens to the SI pumps on an Inadvertent CSAS?

Answer 13

They are anti-pumped when stopped.

Question 14

What are the requirements for FBT for NAN-S01/S02?

Answer 14

• Generator Trip
• early b contact
• sync check relay energized
• normal V/Hz on NAN-S03/S04
• no 86 on NAN-S03/S04
• BUS XFR SWITCH in AUTO

Question 15

What are the requirements for FBT on NBN-S01/S02?

Answer 15

• Transformer Fault
• associated bus supply breaker open
• Man/Auto transfer switch on B01 in AUTO
• sync check relay energized
• no 86 on the bus

Question 16

If cross connecting NBN-S01 and NBN-S02, what would happen if the TIE Key Switch (NBN-SS-S01C) was in the wrong position or passed too far through OFF?

Answer 16

When returned to NORMAL during the swapping process, the supply breaker for the supplying bus would open and NBN-S01 and NBN-S02 would be de-energized.

Question 17

What is the purpose of the Kirk Key Interlock?

Answer 17

Prevents damage to the disconnect switch.

Question 18

What should a Unit do if the LAST UNIT ONLINE alarm is received?

Answer 18

This means there is an issue with off-site power and the Unit should take action to prevent a Double Sequence event.

Question 19

What would happen if the UAT tripped while at 100% power?

Answer 19

• the generator would trip
• which would cause the turbine to trip simultaneously
• FBT on NAN-S01 and NAN-S02
• RPCB

Question 20

What kind of cooling do the Normal Service Transformers have?

Answer 20

4 fans that turn on at 70C hot spot temp. Oil cooled and naturally circulated.

Question 21

What kind of cooling do the ESF Transformers have?

Answer 21

4 fans that start at 70C hot spot temp. oil cooled and naturally circulated.

Question 22

If a short occurs on a Non-Class 4160V pump with no control power to the NB bus, what would happen?

Answer 22

The feeder breaker to the NB bus would open.

Question 23

What does the red light mean on a NA or NB breaker?

Answer 23

That the breaker is closed and there is continuity through the trip coil.