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13 Cards in this Set

  • Front
  • Back

The purpose and/or function of the 250VDC System

Supplies DC electrical power for operation and/or control of the following safety-related (ESS) and non-safety (BOP) loads under normal, abnormal, and accident plant conditions:



1) Channel 1 through 4, control room instrumentation distribution (CRID) static inverters(ESS)



2) Critical control room power(CCRP) static inverter (ESS)



3) Valve control (solenoid/air and motor operated valves for ESS and BOP)



4) Control room emergency lighting (ESS)



5) Breaker control circuits (ESS and BOP)



6) Feed pump turbine lube oil pump (BOP)



7) Main turbine lube oil pump (BOP)



8) Main Generator hydrogen seal oil emergency air oil pump (BOP)

Ground Indication

Light Out = Ground


Light Bright = no ground

250VDC System Design

1)Independence, Redundancy, capacity and testability for ESF and Protection Systems



2) Battery sized for LOOP and SBO events:


-Loop - 3 hours of operation


-SBO - 4 hours of operation



3) The Non-ESS loads are provided power from the BOP battery


-Battery sized for Loop - 2 hours


Plant Battery

-Provide reliable emergency power for critical control room functions



-Supply control power for the 4160 and 600V load control center feeder and load breakers



-BOP Battery supplies:


--Feedpump Turbine Emergency Oil Pump


--Emergency Seal Oil Pumps


--Main Turbine Emergency Oil Pumps



-AB and CD Batteries have enough ampere-hour capacity to supply essential loads during a loss of offsite power, without battery terminal voltage falling below 80% capacity at 77F

Battery Charger Rectifiers

Provide a continuous float charge to the battery while carrying all the normal load requirements of the 250 VDC.



Provide a battery-equalizing charge of up to 280 VDC

Battery Transfer Cabinets

Selects which battery charger will be in service

Distribution Cabinets

Power the various essential and non-essential loads normally serviced by the plant's batteries and regulated low voltage systems.

Battery Crosstie (Transfer Cabinet)

-Cross-connects the AB and CD distribution busses on each unit


-Allows for the transfer of power supply from loads of one train to loads of the other train of the same unit

600 VAC support function to 250 VDC System

Supplies AC power to the battery chargers



During a Loss of Offsite power, the emergency diesel generators supply the busses that power the battery chargers

250 VDC Voltage measurements

1. Battery Voltmeter- indicated bus voltage or positive-to-ground voltage of the station battery bus


2.Charger Voltmeter indicates the battery charger output voltage on negative-to-ground voltage of the station battery bus


3. Emergency Load Voltmeter - Indicates the bus voltage of the opposite battery train when the emergency tie between batteries is closed.


Battery Ammeter- a zero center meter that indicates float current to the battery or discharge current from the battery.


5. Normal Load Ammeter - indicates the total current supplied to the DC loads


6. Emergency Load Ammeter - Indicates the bus voltage of the opposite battery train when the emergency tie between batteries is closed.


Battery Ammeter- a zero center meter that indicates float current to the battery or discharge current from the battery.


7. Charger Voltmeter - Indicates the battery charger output voltage.


8. Charger Ammeter - Indicates battery charger output current, which is an indication of system load.


9. Battery Voltmeter - Indicates battery bus voltage.

DC Ground Indication

1. Ground Detector - Alarms if a ground of 5.4 milliamps occurs on its battery train.



2. Ground Indication Lights - Lights are labeled POS and NEG. Both lights are equal in brightness when no ground is present. When a light indicates a ground, it dims or goes out, and the other light with out the ground brightens.



3.High or Low Voltage Alarm - Alarms when battery terminal voltage deviates from normal.

BOP Battery

Sizes to ensure: 250 VDC during loss of offsite power - 2 hours



BOP battery gets powr from BMC/CMC



BOP Battery - Emerg Seal Oil pump does NOT strip off (prevents H2 explosions)

AB and CD Batteries

250 VDC during Loss of Offsite Power - 3 hours


250 VDC during station Blackout - 4 hours



Batteries have enough amere-hour cpacity to supply essential loads during loss of offsite power, without battery terminal volatge falling below 80% capacity at 77F



U1 CD batteries have more capacity (Like the BOP) due to additional loads - WDS, Drumming, MUP