Non-Class Electrical Flashcards
What is the capacity of one secondary winding on a Startup Transformer?
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.
What does the “breaker and a half” scheme in the switch yard prevent?
A single fault from having a large impact
What happens in Unit 1 on a Double Sequence event that doesn’t happen in the other units?
BOTH WRF breakers open
What is a Double Sequence Event?
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.
What is done to prevent Double Sequencing if switchyard voltage gets too low?
- Disable FBT
- place a DG on the bus
If the multiplexer is lost for the switch yard, how does that effect the Control Room?
Breaker indication is lost on NAN-S05 and NAN-S06. Control is still available via the breaker switches.
From where do MCCs get their control power for the magnetic starters?
They supply their own from power downstream of the circuit breaker.
What is control power for NAN-S05?
Normal: NKN-M45
Alternate: NKN -M46
What is control power for NAN-S06?
Normal: NKN-M46
Alternate: NKN-M45
What is control power for the Reactor Coolant Pumps?
NKN-D44
What is control power for NAN-S01/S02/S03/S04 and NBN-S01/S02?
NKN-D41 and NKN-D42
From where are the breakers for NAN-S05 and NAN-S06 controlled?
Breakers for all three units are controlled from Unit 1
What happens to the SI pumps on an Inadvertent CSAS?
They are anti-pumped when stopped.
What are the requirements for FBT for NAN-S01/S02?
- 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
What are the requirements for FBT on NBN-S01/S02?
- Transformer Fault
- associated bus supply breaker open
- Man/Auto transfer switch on B01 in AUTO
- sync check relay energized
- no 86 on the bus
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?
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.
What is the purpose of the Kirk Key Interlock?
Prevents damage to the disconnect switch.
What should a Unit do if the LAST UNIT ONLINE alarm is received?
This means there is an issue with off-site power and the Unit should take action to prevent a Double Sequence event.
What would happen if the UAT tripped while at 100% power?
- the generator would trip
- which would cause the turbine to trip simultaneously
- FBT on NAN-S01 and NAN-S02
- RPCB
What kind of cooling do the Normal Service Transformers have?
4 fans that turn on at 70C hot spot temp. Oil cooled and naturally circulated.
What kind of cooling do the ESF Transformers have?
4 fans that start at 70C hot spot temp. oil cooled and naturally circulated.
If a short occurs on a Non-Class 4160V pump with no control power to the NB bus, what would happen?
The feeder breaker to the NB bus would open.
What does the red light mean on a NA or NB breaker?
That the breaker is closed and there is continuity through the trip coil.
