Essential Auxiliary Power Distribution System: 4160V Essential, 4160V Blackout, 600V Essential, and 600V Blackout(EPC).

Question 1

What is the purpose of the 4160V Essential Auxiliary Power System?

Answer 1

The 4160V Essential Auxiliary Power System(EPC) provides power to:

1. 4160V Essential Motor Loads
2. 600V Essential Load Centers through 4160V/600V Essential Load Center Transformers.
3. The 4160V Blackout Power System during a loss of normal power, unless the loss of normal power is coupled with a Safety Injection actuation.

Question 2

What is the purpose of the 4160 Blackout Auxiliary Power System?

Answer 2

The 4160V Blackout Auxiliary Power System supplies power to those non-Class 1E loads that are required or may be required following a loss of offsite power.LOOP).

Question 3

Essential power is supplied to Nuclear Safety Related Auxiliary Equipment during what plant conditions?

Answer 3

1. Normal plant operation
2. Hot and Cold Shutdown
3. Refueling
4. Blackout Conditions
5. Safety Injection actuations coupled with a blackout condition.

Question 4

What is the system designator associated with 4160V Essential Auxiliary Power Distribution?

Answer 4

EPC

Question 5

What is the system designator associated with 4160V Blackout Auxiliary Power?

Answer 5

ETB

Question 6

What is the system designator associated with 600V Blackout Auxiliary Power?

Answer 6

ETC

Question 7

What is the system designator associated with 600V Essential Auxiliary Power?

Answer 7

EPE

Question 8

Where is normal power to the 4160V Essential Power System supplied from?

Answer 8

Normal power to the 4160V Essential Power System is supplied from the 6.9KV bus through two 6.9KV/4160V auxiliary transformers per train(1ATC and 1ATD).

Question 9

Where is alternate power to the 4160V Essential Power System supplied from?

Answer 9

Alternate power to the 4160V Essential Power System is supplied from either Unit 1 or Unit 2 6.9KV bus through two 6.9KV/4160V auxiliary transformers(SATA and SATB).

Question 10

What protection is provided to the 4160 V Essential Power Alternate Supply Transformers(SATA and SATB) to prevent closing both feeder breakers?

Answer 10

There is a Kirk-Key interlock such that only one 6.9KV feeder to SATA/SATB can be racked in at a time. This ensure that Unit 1 and Unit 2 6.9KV power systems are not tied together.

Question 11

What type of breaker closing operation is associated with a Kirk-Key Interlock?

Answer 11

Whenever a Kirk-Key Interlock is used to connect a bus the breaker closing operation will be a “Dead Bus Transfer.”

Question 12

What are the designators for the 4160V Essential Power Buses?

Answer 12

1. ETA

2. ETB

Question 13

Where are the breakers for the 4160V Essential Power System controlled from?

Answer 13

All of the breakers are controlled from MC-11 in the Control Room.

Question 14

What is the normal alignment of the feeder breakers for the Alternate Power Transformers(SATA and SATB)?

Answer 14

SATA

1. The Unit 1 Feeder Breaker is normally closed.
2. The Unit 2 Feeder Breaker is normally racked out and open.

SATB

1. The Unit 1 Feeder Breaker is normally racked out and open.
2. The Unit 2 Feeder Breaker is normally closed.

Question 15

What prevents closing both feeder breakers to the Alternate Power Transformers(SATA and SATB)?

Answer 15

A Kirk-Key Interlock prevents closing both feeder breakers at the same time.

Question 16

What is the emergency source of the power to the 4160V Essential Buses?

Answer 16

The Diesel Generators are the emergency source of power to the essential buses. This is the assured source, and would energize the buses automatically if the bus de-energized.

Question 17

What are the loads supplied by the 4160V Essential Buses?

Answer 17

1. KC Pumps A1, A2 (B1, B2)
2. NS Pump A(B)
3. ND Pump A(B)
4. NI Pump A(B)
5. NV Pump A(B)
6. CA Pump A(B)
7. RN Pump A(B)
8. KF Pump A(B)
9. YC Chillers(can be supplied by either unit)
10. Essential 4160V/600V Load Center Transformers

Question 18

What supplies Essential power in the event of an Extended Loss of All AC Power(ELAP)?

Answer 18

Essential Power will be provided to one 4160 Essential Bus using a 4160V Turbine Generator from the National Safer Response Center(NSRC). FLEX

Question 19

What prevents supplying a 4160V Essential Bus from both the normal and alternate power supplies?

Answer 19

A Kirk-Key Interlock, to prevent tying the two sources together.

Question 20

What prevents the 4160V Essential Bus Alternate Supply Transformer(SATA or SATB) from supplying both Unit’s buses?

Answer 20

A Kirk-Key Interlock, to prevent overloading the transformer.

Question 21

What is the configuration of the 4160V/600V Essential Transformers and 600V Essential Load Centers?

Answer 21

The 4160V essential buses each supply three 4160V/600V essential transformers. Two of the transformers normally supply the two 600V essential load centers, and the third is a standby transformer that can supply either 600V essential load center.

Question 22

What type of interlocks are associated with the 600V Essential Load Center feeder breakers?

Answer 22

There is a double Kirk-Key arrangement that allows either 600V Essential Load Center to be supplied from the standby transformer:

1. One Kirk-Key Interlock prevents powering either 600V essential load center form two sources at one time.
2. The other Kirk-Key Interlock prevents overloading the standby transformer by allowing it to supply only one load center at a time.

Question 23

What are the designators for the 600V Essential Load Centers?

Answer 23

ETA:

1. 1ELXA
2. 1ELXC

ETB:

1. 1ELXB
2. 1ELXD

Question 24

What is the configuration of the 600V Essential Motor Control Centers?

Answer 24

The 600V essential MCCs are single-ended except for 1EMXG, 1EMXS, and 2EMXH.

Question 25

What type of interlock is associated with the 600V Essential Motor Control Center feeder breakers?

Answer 25

Kirk-Key Interlocks are provided for each of the four double-ended MCCs to prevent closing both feeder breakers at one time.

Question 26

What is the purpose of the 4160V Blackout Bus, and what are the designators?

Answer 26

1. The 4160V Blackout Bus supplies power to non-essential loads necessary to achieve normal shutdown following a blackout, but not required during a LOCA. 2. The 4160V Blackout Buses are: A. 1FTA, 1FTB B. 2FTA, 2FTB

Question 27

What are the two power supplies for the 4160V Blackout Buses?

Answer 27

1. The 4160V Essential Bus Transformer(1(2)ATC or 1(2)ATD) | 2. The 4160V Essential Bus(1(2)ETA or 1(2)ETB)

Question 28

What are the loads supplied by the 4160V Blackout Buses?

Answer 28

1. 4160V/600V Blackout Transformers TXI(TXH) and LXI(LXH) which supply the 600V Blackout Load Centers. 2. Two Main Fire(RY) Pumps

Question 29

What are the designators for the 600V Blackout Load Centers?

Answer 29

The 600V Blackout Load Centers are: 1. Unit 1 A. 1LXI B. 1LXH 2. Unit 2 A. 2LXI B. 2LXH

Question 30

What supplies power to the 600V Blackout Load Centers?

Answer 30

The 600V Blackout Load Centers receive power from: 1. Unit 1 A. 4160V/600V Transformer 1TXI B. 4160V/600V Transformer 1TXH 2. Unit 2 A. 4160V/600V Transformer 2TXI B. 4160V/600V Transformer 2TXH

Question 31

What is the purpose of Power Lockouts?

Answer 31

Power Lockouts ensure power interruption to certain components to prevent movement such as NI Valves.

Question 32

What type of interlock is associated with the feeder breakers to the 4160V Blackout Buses?

Answer 32

The feeder breakers coming from the 4160V Essential Bus and the 4160V Essential Bus normal supply transformer are interlocked: 1. If the feeder breaker from the transformer is closed than the feeder breaker from the bus cannot be closed. 2. If the feeder breaker from the bus is closed, and the feeder breaker from the transformer is closed, the feeder breaker from the bus will trip open. 3. To close the feeder from the transformer, with the bus feeder breaker closed, the Diesel Generator must be running and in sync with the normal source. If the Diesel Generator is shutdown with the bus feeder breaker closed, the normal feeder breaker cannot be closed.

Question 33

What type of interlock is there between the two breakers between the 4160V Essential Bus and the 4160 Blackout Bus?

Answer 33

1. The breaker on the blackout bus must be closed before the breaker on the essential bus can be closed. 2. When the breaker on the blackout bus opens, the breaker on the essential bus will open.

Question 34

What type of transfer is performed on 600V Blackout Motor Control Centers?

Answer 34

A swap of power supplies for the 600V Blackout MCCs is a "dead bus transfer" since the normal and alternate power supplies may be from different sources.

Question 35

How are 4160V breakers manually closed?

Answer 35

There may be a need to manually close 4160V breakers during a Station Blackout due to insufficient voltage on the close coil. This is accomplished by tying a cord to the manual close lever at the breaker cubicle and pulling from a safe distance.

Question 36

When does the 4160V Essential Bus Undervoltage(Blackout Condition) Logic actuate and what type of logic is it?

Answer 36

1. When essential bus voltage is less than 82.9%(3450V) on the 4160V bus the UV logic will actuate the sequencer to start the Diesel Generator. 2. The UV logic is 2 out of 3 channels to actuate.

Question 37

When does the 4160V Essential Bus Degrade Voltage Logic actuate, and what type of logic is it?

Answer 37

1. When essential bus voltage is less than 90%(3766V) the Degraded Voltage Logic timer starts. 2. If the condition is present for 10 minutes the normal and alternate incoming breakers will trip. 3. If power is restored to greater than 90% within the 10 minutes the timer resets and the alarm clears.

Question 38

What affect does a Transformer Fault on ATC or ATD have?

Answer 38

A transformer fault on ATC or ATD will trip, and lock-out, the 6900V feeder breaker and the 4160V output breakers.

Question 39

What affect does a Breaker Failure Lockout on a 4160v Output Breaker have?

Answer 39

The 6900V feeder breaker to the respective transformer will trip. On the shared transformers(SATA and SATB) it trips and locks out both feeder breakers.