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Catawba Nuclear Station > Normal Auxiliary Power Distribution System: 6900V, 600V Unit, 600V Shared(EPB) > Flashcards

Normal Auxiliary Power Distribution System: 6900V, 600V Unit, 600V Shared(EPB) Flashcards

1
Q

What is the purpose of the Normal Auxiliary Power Distribution: 6900V, 600V Unit, 600V Shared System?

A

The 6900V and 600V Unit and Shared electrical distribution system provides power for each unit’s auxiliaries normal and shutdown operations as well as abnormal and emergency operations.

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2
Q

What is the system designator for the Normal Auxiliary Power Distribution: 6900V, 600V Unit, 600V Shared System?

A

EPB

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3
Q

What is the general layout of the Normal Auxiliary Power Distribution: 6900V, 600V Unit, 600V Shared System?

A
  1. Each train(A and B train) is connected to the Main Power Distribution System(EPA) through two unit auxiliary transformers 2. The two 22KV/6900KV unit auxiliary transformers are sized to carry all the auxiliaries on one operation unit plus the safety shutdown loads of the other unit, excluding the Auxiliary Electric Boilers and the Cooling Tower loads which are fed from the 22KV/13.8KV auxiliary transformers.
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4
Q

What are the designations of the Unit 1 Auxiliary Transformers?

A

1T1A, 1T1B, 1T2A, and 1T2B

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5
Q

What are the designations of the Unit 2 Auxiliary Transformers?

A

2T1A, 2T1B, 2T2A, and 2T2B

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6
Q

What are the designations of the 6900V Buses?

A

1TA, 1TB, 1TC, and 1TD

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7
Q

What are the loads supplied by the 6900V Buses?

A

The 6900V Buses supply all of the large unit auxiliary loads and the 4160V transformers. They also supply the 600V Shared and Unit Power Systems using 6900V/600V transformers.

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8
Q

How are the 6900V Buses configured?

A
  1. Each 6900V bus is divided into a Short Side Bus and a Long Side Bus. 2. The Short and Long Side Buses each have an incoming supply breaker and the two buses are connected by a tie breaker.
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9
Q

What component integral to the 6900V Buses allows for a higher amperage rating?

A

The incoming breakers are supplied with a fan for cooling to increase the rating of the breaker. The breaker rating increases from 2500amps to 3000amps with the fan running.

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10
Q

What is the normal breaker configuration for the 6900V Buses?

A
  1. The normal breaker configuration for the 6900V buses is both incoming breakers closed with the tie breaker open. 2. The Short Side Bus is normally fed from the train related transformer, while the Long Side Bus is fed from the opposite train transformer(A or B)
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11
Q

What is the memory aid used for transformer supplies to 6900V buses?

A

22 12 12 11 ABBA ABBA

1T2A TA Short

1T2B TA Long

1T1B TB Short

1T2A TB Long

1T1A TC Short

1T2B TC Long

1T1B TD Short

1T1A TD Long

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12
Q

What are the major loads on the 1TA Short Side Bus?

A
  1. 1ATC
  2. 1STXA
  3. 1A NC Pump
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13
Q

What are the major loads on the 1TA Long Side Bus?

A
  1. 1STXG
  2. 1A RC Pump
  3. 1YV-C-1
  4. 1A Hotwell Pump
  5. 1TXS
  6. 1A Condensate Booster Pump
  7. 1TXA
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14
Q

What are the major loads on 1TB Short Side Bus?

A
  1. SATB
  2. 1STXB
  3. 1B NC Pump
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15
Q

What are the major loads on 1TB Long Side Bus?

A
  1. 1YV-C-2
  2. 1B RC Pump
  3. 1B Hotwell Pump
  4. 1B Condensate Booster Pump
  5. B RL Pump
  6. 1TXN
  7. Switchyard Auxiliaries Feeder
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16
Q

What are the major loads on 1TC Short Side Bus?

A
  1. SATA
  2. 1TXC
  3. 1C NC Pump
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17
Q

What are the loads on 1TC Long Side Bus?

A
  1. 1STXC
  2. 1C RC Pump
  3. C RL Pump
  4. 1TXG
  5. RY Pump A
  6. 1C1 Heater Drain Pump
  7. 1-YV-3 Chiller
  8. 1TXE
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18
Q

What are the loads on 1TD Short Side Bus?

A
  1. 1ATD
  2. 1TXD
  3. 1D NC Pump
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19
Q

What are the loads on 1TD Long Side Bus?

A
  1. 1TXF
  2. 1D RC Pump
  3. 1C Condensate Booster Pump
  4. 1C Hotwell Pump
  5. 1C2 Heater Drain Pump
  6. STXS
  7. 1STXD
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20
Q

How many 600V Unit Power System Load Centers are there, and what are their designations?

A
  1. There are 8 total 600V Unit Power System Load Centers.
  2. The designations are:

1LXA

1LXB

1LXC

1LXD

1LXE

1LXF

1LXG

1LXN

**The designators are similar for unit 2**

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21
Q

Where are the controls for the 6900V Transformer Feeder Breakers that supply the 600V Unit Power Centers?

A

The controls for the 6900V feeder breakers are located in the 6900V Switchgear Room.

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22
Q

What is unique about 600V Unit Power Load Centers 1(2)LXC and 1(2)LXD, and what is their special designation?

A
  1. Load centers 1(2)LXC and 1(2)LXD have two power supplies while the other load centers only have one.
  2. 1(2)LXC and 1(2)LXD are motor dedicated load centers.
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23
Q

Where is alternate power to 1(2)LXC and 1(2)LXD supplied from, and what is the interlock associated with these power supplies?

A
  1. The alternate power supply to 1(2)LXC and 1(2)LXD is 1(2)TXS, which is powered from 1(2)TA
  2. The alternate supply breakers are interlocked to prevent both from closing at the same time.
24
Q

What is the configuration of the 600V Unit Power Motor Control Centers?

A

The 600V Motor Control Centers, powered by the 600V Load Centers, are double ended meaning they are supplied by two load centers.

25
Q

Which 600V Unit Power Motor Control Centers have a different design?

A

The YV system motor control centers have only one power supply.

26
Q

What is the normal position of the 600V Motor Control Center breakers?

A
  1. All motor control center breakers are normally in the ON position(closed).
  2. Spare breakers are left in the OFF position(open).
  3. Some breakers are left in the OFF position by procedure. These breakers will have an information label affixed to the breaker face stating why the breaker is normally OFF.
27
Q

How many 600V Shared Power System Load Centers are there, and what are their designations?

A
  1. The 6900V buses feed four 600V Shared Load Centers per unit through 6900V/600V transformers.
  2. The 600V Shared Load Centers are:

1(2)SLXA

1(2)SLXB

1(2)SLXC

1(2)SLXD

28
Q

Where are the controls for the 6900V Transformer Feeder Breakers that supply the 600V Shared Power Load Centers?

A

The controls for the breakers feeding the Shared Transformers are on the same panel in the 6900V Switchgear Room as the Unit Power Transfomer feeders.

29
Q

What is the configuration of the 600V Shared Power Motor Control Centers?

A

The Shared 600V MCCs are double ended just like the Unit Power 600V MCCs.

30
Q

What is unique about 600V Shared Power Load Center 1(2)SLXC, and what is their special designation?

A
  1. Load centers 1(2)SLXC has two power supplies while the other load centers only have one.
  2. 1(2)SLXC is a motor dedicated load center.
31
Q

Where is alternate power to 1(2)SLXC supplied from, and what is the interlock associated with this power supply?

A
  1. The alternate power supply for 1(2)SLXC is 1STXS which is powered from ITD.
  2. The alternate power supply breakers are interlocked.
  3. The transfer to the alternate power supply for 2SLXC is a dead-bus transfer since you would be tying the two units.
32
Q

What is unique about 600V Shared Load Center 1SLXG, and where is it located?

A
  1. A ninth 600V Shared Load Center is 1SLXG fed through 1STXG from 1TA. 1SLXG has an alternate power supply from Standby Shutdown Facility(SSF) Diesel Generator.
  2. 1SLXG is located in the SSF Room, and supplies power for the Standby Shutdown Facility.
33
Q

What is the allowed voltage deviation for the 600V transformers, and under what circumstancs?

A
  1. During normal operations the 600V transformers are allowed a 10% deviation in voltage(660V).
  2. Under the following circumstances 680V is permitted:

A. One of both units offline

B. High Switchyard Voltages

C. The transformer is unloaded

34
Q

When are high voltages on the 600V transformers reportable, and to who?

A

Any voltages over 660V are to be reported to the Transmission Department.

35
Q

What is the concern with high voltages on the 600V transformers?

A

High voltages may cause deterioration of motor and transformer winding insulation which would lead to electrical shorts.

36
Q

What is a “Hot” Bus Transfer?

A

A “hot” bus transfer is a make-before-break transfer, meaning the alternate supply breaker closes before the normal supply breaker is open. In this case power supplies must be synchronized.

37
Q

What is a “Dead” Bus Transfer?

A

A “dead” bus transfer refers to transfer that is break-before-make, meaning the normal supply breaker is open before the alternate supply breaker is closed. This is done to prevent tying two power sources that may be out of synchronization.

38
Q

What is the purpose of the Sync Check Relay(25)?

A

The synch check relay allows fast transfer of 6900V breakers.

39
Q

What is the purpose of the Lockout Relay(86)?

A

The Lockout Relay will actuate for any of the following relays:

  1. Overcurrent
  2. Ground Fault
  3. Breaker Failure
40
Q

What is the purpose of the Breaker Failure Relay?

A
  1. The breaker fails to trip, will give a Zone Lockout if normal incoming breaker doesn’t trip.
  2. A Tie Breaker failure will trip and lockout both incoming breakers.
41
Q

What is the purpose of the Undervoltage Relay?

A
  1. The Undervoltage Relay is set at less than 75% voltage. Incoming breaker trips and blocks other breakers from closing.
  2. This relay automatically resets at greater than 75%.
42
Q

What happens to the Protective Relaying when control power is lost?

A

Loss of control power to the breakers results in a loss of protection from the protective relaying.

43
Q

Where are the incoming and tie breakers for the 6900V Buses?

A

The incoming and tie breakers are controlled from MC-11 in the Control Room by a three position transfer switch.

44
Q

How does placing the Control Switch for the 6900V Buses in AUTO affect breaker operation?

A

Placing the control switch in AUTO allows an automatic closure of the tie breaker if the incoming breaker opens.

45
Q
A
46
Q

How does placing the Control Switch for the 6900V Buses in MAN A & TIE affect breaker operation?

A

Allows opertinng the”A” Incoming and Tie Breaker.

47
Q

How does placing the Control Switch for the 6900V Buses in MAN B & TIE affect breaker operation?

A

Allows operating the “B” Incoming and Tie Breaker.

48
Q

How does an Automatic Transfer from the Incoming Breakers to the Tie Breakers occur, and what is the difference between a “Fast” and “Slow” transfer?

A
  1. A Zone Lockout occurs or a less than 75% UV on the incoming line with no fault on the affected bus.
  2. If the sources are in synchronization a “Fast Transfer” will occur. The incoming breaker opens first but the tie breaker closes so fast, within a few cycles, that the loads are not lost.
  3. If the sources are not in synchronization a “Slow Transfer” will occur. The transfer is delayed to allow voltage to decay to a point that synchronization is not a concern (25% voltage). This will take approximately one second, and a loss of loads on the bus will occur.
49
Q

What is the purpose of the Automatic Fast Transfer Switch, when is it used, and where is it located?

A
  1. The Automatic Fast Transfer Switch will allow defeat of the fast transfer. The purpose of this switch is to prevent equipment damage from surges on fast transfer.
  2. The fast transfer is disabled when the unit is offline.
  3. The switch is located in the 6900V Bus rooms on the control panels with the under voltage transfer relays.
50
Q

What are the Automatic Fast Transfer Switch positions, and how does each position affect operation?

A
  1. Switch Positions:

A. ENABLE

B. DEFEAT

  1. The ENABLE position allows the fast transfer to occur.
  2. The DEFEAT position removes the sync check relays(25) from the circuit and provides for only a slow transfer.
51
Q

How is a 600V Unit Motor Control Center affected by a loss of power from the normal load center?

A

On a loss of power to the normal load center the supply from the alternate load center will auto close to supply the MCC.

52
Q

What will happen if power is lost to 1(2)LXC and 1(2)LXD simultaneously?

A

1(2)LXC will swap to 1(2)TXS transformer supplied by 1(2)TA. 1(2)LXD is time delayed to allow this to occur. The alternate incoming breakers are interlocked to prevent both from closing at the same time.

An auto transfer of power will occur on low voltage on the incoming line. If the sources are in sync the alternate breaker closes and then the normal breaker opens. This is called a “Hot Bus Transfer.”

53
Q

How does an undervoltage condition affect the power supplies to a 600V Shared Motor Control Center?

A

With AUTO selected, for an undervoltage on the normal load center the normal feeder breaker to the MCC will trip. After a time delay the alternate feeder breaker closes.

54
Q

How is a 6900V Bus manual transfer performed?

A
  1. Place the Mode Select Switch in the MAN A(B) & TIE position.
  2. Close the associated tie breaker.
  3. The feeder breaker will automatically open.

**This is a “Hot Bus Transfer”**

55
Q

How is a 600V Unit MCC manual transfer performed?

A
  1. Place both load center feeder breakers to the MCC in the MANUAL position.
  2. Closed the alternate feeder breaker.
  3. The normal feeder breaker will automatically open.

**This is a “Hot Bus Transfer”**

56
Q

How is a 600V Shared MCC manual transfer performed?

A

The manual transfer of power between shared MCCs in normally a “Dead Bus Transfer” since the normal and alternate supplies are from separate units.

  1. Place both load center feeder breakers to the MCC in the MANUAL position.
  2. Open the normal feeder breaker.
  3. Closed the alternate feeder breaker.

**This is a “Dead Bus Transfer”**

Catawba Nuclear Station (72 decks)

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