125VDC/120VAC Vital Instrumentation and Control Power System(EPL/EPG)

Question 1

What is the purpose of the 125VDC / 120VAC Vital Instrumentation and Control Power System?

Answer 1

The 125VDC and 120VAC Vital Instrumentation and Control Power System provides a source of reliable and continuous power for SAFETY RELATED control and instrumentation required for the following conditions:

1. Startup, normal operation, and shutdown of each unit.
2. Blackout or Loss of Offsite Power(LOOP)
3. Design Basis Event(DBE)
4. Blackout or LOOP concurrent with DBEs

Question 2

What is the system designator for the 125VDC Vital Instrumentation and Control Power System?

Answer 2

EPL

Question 3

What is the system designator for the 120VAC Vital Instrumentation and Control Power System?

Answer 3

EPG

Question 4

What are the major system components fo the 125VDC Vital Instrumentation and Control Power System?

Answer 4

The 125VDC Vital Instrumentation and Control Power System consists of:
1. Four independent and physically separated channels.
2. Each channel contains:
A. Battery
B. Battery Charger
C. 125VDC Distribution Center
D. 125VDC Panelboard
3. A Spare Battery Charger
4. Distribution Centers EDE/EDF have a backup 125VDC source through auctioneering diodes.

Question 5

What are the designators for the 125VDC Vital Batteries?

Answer 5

1. Channel 1 - EBA
2. Channel 2 - EBB
3. Channel 3 - EBC
4. Channel 4 - EBD

Question 6

What Channels of 125VDC Vital I&C Power makeup Train A and Train B?

Answer 6

1. Train A - Channel 1 and 3

2. Train B - Channel 2 and 4

Question 7

What are the designators for the 125VDC Vital Battery Chargers?

Answer 7

1. Channel 1 - ECA
2. Channel 2 - ECB
3. Channel 3 - ECC
4. Channel 4 - ECD

Question 8

What are the designators for the 125VDC Vital Distribution Centers?

Answer 8

1. Channel 1 - EDA
2. Channel 2 - EDB
3. Channel 3 - EDC
4. Channel 4 - EDD

Question 9

What are the designators for the 125VDC Vital Panelboards?

Answer 9

1. Channel 1 - EPA
2. Channel 2 - EPB
3. Channel 3 - EPC
4. Channel 4 - EPD

Question 10

What is unique about 125VDC Vital Distribution Centers EDE and EDF?

Answer 10

To assure a high availability of power and to protect against loss of DC power due to a fire in the Control Complex, the loads that are required for plant shutdown are located on 125VDC buses supplied with two sources of power through auctioneering diodes.

Question 11

What are the two sources of power to 125VDC Distribution Centers EDE and EDF?

Answer 11

EDE:

1. EDA
2. 125VDC Diesel Control Panel A

EDF:

1. EDD
2. 125VDC Diesel Control Panel B

Question 12

What are the major components of the 120VAC Vital Instrumentation and Control Power System?

Answer 12

The 120VAC Vital Instrumentation and Control Power System consists of:

1. Four independent and physically separated 120VAC Panelboards.
2. Four independent 125VDC - 120VAC Static Inverters
3. Four Manual Bypass Switches
4. Two Swing Static Inverters

Question 13

What are the designators for the 120VAC Static Inverters?

Answer 13

1. Channel A - EIA
2. Channel B - EIB
3. Channel C - EIC
4. Channel D - EID
5. Channel A or C - EIE
6. Channel B or D - EIF

Question 14

What are the designators for the 120VAC Manual Bypass Switches?

Answer 14

1. Channel A - EMA
2. Channel B - EMB
3. Channel C - EMC
4. Channel D - EMD

Question 15

What are the designators for the 120VAC Panelboards?

Answer 15

1. Channel A - ERPA
2. Channel B - ERPB
3. Channel C - ERPC
4. Channel D - ERPD

Question 16

What is the purpose of the 125VDC Vital Battery Chargers?

Answer 16

1. Serve as the normal power supply to the bus.
2. Rectify 600VAC to 125VDC
3. Can carry its own load plus the DC & AC Panelboards of a train related channel.
4. Can charge the associated battery within 8 hours following a 1 hour discharge while supplying it normal loads.

Question 17

Why shouldn’t a charger be connected to a bus without a battery being connected?

Answer 17

The chargers lack sufficient voltage stability to serve as the sole power source to a DC system.

Question 18

How does the 125VDC Battery Charger operate in ‘Float”?

Answer 18

When the “FLOAT” pushbutton is depressed the battery charger operates to maintain battery terminal voltage greater than or equal to 125VDC.

Question 19

What affect on the 125VDC Vital Battery Charger does a High-Voltage Shunt Trip?

Answer 19

A High-Voltage Shunt Trip will trip the AC input breaker for a malfunction that causes a high voltage condition at the charger output.

Question 20

What is the plant response to a 125VDC Vital Battery Charger failure?

Answer 20

1. The plant is not affected by a charger failure because the battery will provide backup power to the loads.
2. Control Room alarm will be received.

Question 21

What is the purpose of the 125VDC Vital Batteries?

Answer 21

1. The batteries serve as a backup power supply for the buses.
2. The batteries are normally maintained on “FLOAT”
3. When a battery is removed from service the tie-breakers to the train related bus must be closed.

Question 22

What is the capacity of the 125VDC Vital Batteries?

Answer 22

Each battery is sized to carry Its own vital bus loads and the loads of another battery in an emergency for a 2 hour period.

Question 23

When does “Cell Reversal” occur?

Answer 23

80-85% of normal battery voltage

Question 24

Can “Cell Reversal” be corrected?

Answer 24

NO

Question 25

What is the potential damage of "Cell Reversal"?

Answer 25

1. Damage to remaining cells of the battery bank | 2. Damage to equipment being supplied by the battery

Question 26

What do we do to prevent the possibility of "Cell Reversal"?

Answer 26

1. Minimize drain on the battery: A. Removing non-vital loads from the DC bus B. Placing AC portions of these systems on alternate power sources C. Consulting station management for recommended loads to remove from a DC bus 2. Removing a battery from service when the battery's voltage drops below 105VDC

Question 27

What indicators/controls are located on the Ground Detection Panels?

Answer 27

1. Ground Indication Lights 2. Battery Voltage to Ground Meter 3. Battery Voltage to Ground Volt Meter Selector Switch 4. Battery Under Voltage Relay 5. Undervoltage Relay Test Switch 6. Battery Ground Detector Test Switch

Question 28

What is the local indication of a ground on the Ground Detection Panel?

Answer 28

1. The Ground Indication lights are normally dimly lit. If a ground is in the the grounded leg's light will be brighter. 2. When the Battery Voltage to Ground Volt Meter Mode Selector Switch is taken to the grounded leg's position it will show the magnitude of the ground on the volt meter.

Question 29

Who operates the two test switches on the Ground Detection Panel, and what is the normal position for both?

Answer 29

1. I & E personnel operate the test switches, not Operations.**They will bring in a Control Room alarm** 2. The normal position of both switches is NORM

Question 30

What is the purpose of the Auctioneering Diodes for the 125VDC Vital I&C System?

Answer 30

1. Supply EDE and EDF with power from the source with the highest voltage. 2. Ensures that EDE and EDF have a high availability of power and protect against a loss of DC power due to fire in the Control Complex.

Question 31

What type of interlock is on the 125VDC Vital Standby Charger?

Answer 31

There is a Kirk-Key interlock between: 1. The supply breakers to the standby charger so only one can be closed at a time to prevent tying together two vital AC trains 2. The standby charger output breakers so only one can be closed at a time to prevent tying together two vital DC trains.

Question 32

What is the purpose of the 125VDC - 120VAC Vital Static Inverters?

Answer 32

1. Invert 125VDC to 120VAC for supply to the AC portion of the Vital Instrumentation and Control Power System. 2. Supply 120VAC Vital Power to 120VAC Vital Panelboards through a Manual Bypass Switch.

Question 33

What is the purpose of the 120VAC Vital Static Inverter Synchronizing Circuit?

Answer 33

1. Compares the frequency and phase of inverter output to the alternate supply for the distribution panel if the sync disconnect switch is closed and the alternate AC breaker is closed for the distribution panel. 2. Causes the inverter to turn in sync with the alternate source thereby allowing the 120VAC Panelboard power supply to be swapped without interruption.

Question 34

How can you tell if the Normal and Alternate 120VAC sources for a vital panelboard are synchronized?

Answer 34

The "In Sync" light will be lit

Question 35

What is the precaution associated with restarting a Static Inverter?

Answer 35

A 60 second wait is required to all the capacitors and rectifiers to cool down.

Question 36

What is the precaution associated with pre-charging a Static Inverter?

Answer 36

1. Static Inverters must be "pre-charged" prior to closing the DC input breaker. 2. Once the "Pre-Charge" button is released, the "Battery Input" breaker must be closed immediately to prevent blowing the inverter input fuses.

Question 37

What is the purpose of the Swing Inverters?

Answer 37

1. Enhance system reliability and availability by providing an alternated source of 120VAC Vital Power. 2. Allow for the removal of the normal inverters from service without having to enter a Tech Spec action statement.

Question 38

What is the purpose of the Static Inverter Manual Bypass Switch?

Answer 38

The Manual Bypass Switch provides a means of bypassing the Static Inverter.

Question 39

What are the positions of the Manual Bypass Switch, and what do they accomplish?

Answer 39

1. Inverter to Load - Loads are on the static inverter | 2. Alternate Source to Load - Bypasses the inverter

Question 40

What part of the 120VAC Vital System is not safety related?

Answer 40

The 600V AC power supplied to the regulated portion of the 120VAC Vital System.