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Exams > 2022 Q47 — EDG Response to Loss of Offsite Power During Surveillance

2022 Q47 — EDG Response to Loss of Offsite Power During Surveillance

⚠️ DRAFT
Q47 — EDG Response to Loss of Offsite Power During Surveillance 062 K3.02 (4.1)
Given:

• Unit 2 is at 100% Power.
• 2A Emergency Diesel Generator (EDG) monthly surveillance test is in progress in accordance with S2.OP-ST.DG-0001, 2A Diesel Generator Surveillance Test.
• The 2A EDG is currently running and paralleled to the grid.
• Subsequently, a Loss of Offsite Power occurs.

Which ONE of the following describes the effect on the 2A EDG?
A. The diesel generator output breaker opens and the diesel remains running; after the bus loads are stripped, the output breaker must be manually closed to allow the load sequencer to sequentially start safeguard loads.
B. The diesel generator output breaker opens and the diesel remains running; after the bus loads are stripped, the output breaker automatically closes and the load sequencer sequentially starts safeguard loads.
C. The diesel generator output breaker remains closed; non safeguards loads are automatically stripped.
D. The diesel generator output breaker remains closed; non safeguards loads must be manually stripped.
▶ Show Answer & Explanation
✓ B. Correct. With the EDG running paralleled to the grid and a loss of offsite power occurs, the SEC will actuate in Mode 2 (blackout), the EDG output breaker will open, the diesel will remain running, then the SEC will open both infeed breakers to the 2A 4KV bus, strip all loads from the 4KV vital bus, then re-close the output breaker, and re-start loads using the SEC load sequencer.
✗ A. The EDG output breaker will automatically reclose when the bus is stripped and infeed breakers are open by the SEC. Plausible because the operator may believe that the output breaker needs to be manually closed when the EDG was paralleled to the grid.
✗ C. Plausible because the operator may believe that since the EDG is in test and running with its output breaker already closed, that the SEC will not open the output breaker and only need to strip the loads off the bus.
✗ D. Plausible because the operator may believe that since the EDG is in test and running with its output breaker already closed, that the SEC will not strip the bus with the EDG in test and manual action will be needed to manually strip and load the safeguard loads.
Ref: NOS05SEC000-08 | LO: NOS05SEC000-08, Obj 4 — Describe in detail each Mode of Safeguards Equipment Control System operation, including setpoints for automatic actuation | Source: Bank — Salem | Cognitive: Fundamental/Memory

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