125 V DC, 120 Volt Preferred AC and Instrument AC Power Flashcards Preview

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Flashcards in 125 V DC, 120 Volt Preferred AC and Instrument AC Power Deck (17)

Explain the design basis of the Station Batteries per the FSAR

Designed to:furnish continuous power to

1. Select normal Plant control and instrumentation circuits
2. ESS control and instrumentation circuits
3. Emergency Plant lighting.


Explain the design basis of the Station Batteries per the DBD

During a loss of normal and standby AC power to furnish power to:

1. All Preferred AC and DC loads until one of the diesel generators has started and AC is restored (4 hours).
2. In the event of a cable spreading room fire, to provide 72 hours of DC power to achieve plant cold shutdown (via D11A/D21A)


Draw the 125V DC and AC Power system showing: 125 VDC Busses No. 1 and No. 2 Battery Chargers 1-4, Battery 1 & 2, DC Distribution Panels D11-1, D11-2, D11A, D21-1, D21-2, D21A, Preferred AC Busses No. 1 (Y-10) through No. 4 (Y-40), Inverters No. 1 through No. 4 (ED-06 through ED-08), Instrument AC Bus, (Y-01), Bypass Regulator, Instrument AC Transformers No. 1 and No. 2, EY-50 Transfer Switch, 125 VDC Shunt Trip and Bus Tie Breaker



Describe the operational design and operating range of Battery Chargers No. 1 through No. 4.

A single charger supplying each DC bus has sufficient capacity to carry bus load as well as charge the battery at a rate of approximately 100 amps/hour
Ambient temperature between 32°F - 104°F
Relative humidity 60 - 100%
Rated at Input of 480V +10% -15%, 3Φ, 60 hz ± 5%
Continuous output of 200 amperes
2 adjustable outputs - for float charge or equalizing charge
Current limited at 200 amps ±5%
Output voltage ripple 30 millivolts maximum.


Describe the operational design and operating range of Battery No. 1 and No. 2


Supply all DC and preferred AC loads for four (4) hours (with load stripping)
Furnish maximum load down to an operating temperature of 70°F without total battery terminal voltage dropping below 105 volts (1.78V/cell)


Lead-Calcium, 125 V DC,
59 Cells,
Battery Capacity 1,739 AH @ 8 Hours


Describe the operational design and operating range of Preferred AC Busses No. 1 (Y-10) through No. 4 (Y-40)

The reliability of the system is the single most important design consideration.

Four separate buses to provide power for the four separate Reactor Protective System channels.

The bypass regulator has the potential of being a limiting factor to the operation of the preferred AC system.

It is an ungrounded system.


What bounds the Preferred AC System load tabulations or analyses for accident conditions (Loss of Coolant Accident with offsite power available).

SBO Calculations


Describe the operational design of Inverters No. 1 through No. 4.

Equipped with ground detectors.

Inverter inefficiency is approximately 13-15 amps.

Each Preferred AC System inverter is rated at 6.0 KVA.

Ambient temperature between 60°F-104°F

Uncontrolled humidity

Seismic Rated,


Describe the operating range of Inverters No. 1 through No. 4.

Continuous power output of 6 KVA single phase at all power factors from 1.0 to 0.7 lagging,

Output voltage of 118 volts ±3%,

Output frequency of 60 hertz ±½%Harmonic content of output wave ≤5% with no single harmonic 3%.

Input voltage , from 100 VDC to 145 VDC with output power within above parameters.

Output characteristics of the inverters limit the output current to 175-200% of its rated value. This provides short circuit protection to the output of the inverter.

They do not shut down automatically when the input voltage drops below the minimum of 105V DC. Rather, the output will begin to decrease as the input voltage decreases


What does it take to recharge a battery within the design basis time?

To recharge the battery within the design basis recharge time, after an emergency discharge cycle, the two chargers would be paralleled on each bus.


Why is the 125V DC system ungrounded?

Equipping the 125V DC systems with the means of detecting insulation faults serve the same purpose as grounding on a grounded system, but without the risk of interruption to supply, which a fault would cause on a grounded system.


On station blackout, how long will the cable spreading area stay below 104F?

Approximately 6 hours.


What are the post accident conditions amp hour loads on left and right channel 125V DC system during?

832 A-H left channel
904 A-H right channel
Based on a four hour profile with no load
shed is used because no load shedding occurs without a "loss of all AC" event.


When is an Inverter Operable?

Inverter Operable

When it supplying the proper voltage and frequency to its Preferred AC Bus.


What must be done when initially powering up Y-30/Y-40?

Initial Powering of Y-30/Y-40

Y-30/40 supply clutch power supplies. First powered up from bypass regulator and then transferred to inverter. 


What are the tech spec category C paramaters for operable battery cells?

Temperature - not Cat C requirement


Electrolyte Level

  • Above top of plates, and not overflowing

Float Voltage

  • ≥ 2.07 V

Specific Gravity

  • Not more than 0.020 below average connected cells


  • Average of all connected cells ≥ 1.195


What battery chargers must be operable?

The Directly Connecte Chargers (ED 15/16) Chargers 1 & 2 are required

ED-17/18, Chargers 3 & 4 are not required and cannot be credited to LCO 3.8.4 - DC Sources Operating.