Q49 — 125VDC Battery Discharge Indication
063000A4.03 (3.0)
Given:
• The Unit 2 125 VDC Vital Bus Batteries are aligned to "float charge" mode.
• A Loss of All AC Power event has occurred.
What 125 VDC Battery indications in the control room will indicate that the batteries are discharging? How many hours of operation by design are the batteries sized for after a loss of all AC power?
• The Unit 2 125 VDC Vital Bus Batteries are aligned to "float charge" mode.
• A Loss of All AC Power event has occurred.
What 125 VDC Battery indications in the control room will indicate that the batteries are discharging? How many hours of operation by design are the batteries sized for after a loss of all AC power?
A. Battery voltage indication will rise greater than 0 volts on 2RP9 panel volt meters. 2 Hours.
B. Battery amp indication will rise greater than 0 amps on 2RP9 panel amp meters. 2 Hours.
C. Battery amp indication will rise greater than 0 amps on 2RP9 panel amp meters. 4 Hours.
D. Battery voltage indication will rise greater than 0 volts on 2RP9 panel volt meters. 4 Hours.
▶ Show Answer & Explanation
✓ B. Correct. When the batteries are normally in "float charge" mode, the typical volt meter reading on 2RP9 would be 134 volts and the amp meter is reading zero amps because the battery charger is supplying the loads. On a loss of all AC, the batteries start to discharge, and this is indicated by rising amps on the amp meters on 2RP9. Also, by design, the batteries are sized for 2 hours of operation after a loss of AC power, based upon the required operation of the DC emergency equipment.
✗ A. Incorrect. Plausible because the candidate may believe that when the battery chargers are supplying the loads, the battery volt meters read zero. The second part is correct.
✗ C. Incorrect. The first part is correct. The candidate may believe that the design hours of operation are 4.
✗ D. Incorrect. Plausible because the candidate may believe that when the battery chargers are supplying the loads, the battery volt meters read zero. The candidate may also believe that the design hours of operation are 4.
Ref: NOS05DCELEC-09, DC Electrical Distribution | LO: ELOs 2 & 8 | Source: New | Cognitive: Fundamental
Connections
- Related systems: DC Power
- Related exam: 2020 NRC Written Exam