460/230V AC
Function
Steps down 4160V vital bus power via unit substations to feed motors, MOVs, heaters, and smaller loads throughout the plant. (UFSAR 8.3.1.3)
460V/230V Systems
- Step-down from 4160V vital buses via unit substations
- Feed motors, MOVs, heaters, and smaller loads
- Pressurizer heater buses (EP and GP) backed by EDGs for natural circulation support (UFSAR 8.3.1.3)
JPM — 2022 IP-i
Transfer of 22 Backup Group PZR heaters to 2A 460V Vital Bus (emergency power) per S2.OP-SO.PZR-0010 Section 5.3. Only 3 of 14 heater disconnects remain ON to limit load within emergency bus capacity. Emergency feed breaker: 2AX1AX14X (84 ft. Switchgear Room). Emergency feed disconnect switch: 2AX1AX14X-1, 2EP PZR HTR BUS EMERGENCY FEED (78 ft. Electrical Penetration, JAM key required).
Exam — 2020 Q56
Rod Drive MG Set power supplies: 11 MG set powered from 1E 460V bus; 12 MG set powered from 1G 460V bus. Loss of 1E + 1F 460V buses does NOT cause reactor trip because 12 MG set remains powered on 1G bus.
Exam — 2020 Q54
460V Vital Bus loads: #1 ECAC is powered from the 1C 460V Vital Bus (breaker 1C4D). Do not confuse with Station Air Compressors (SACs) which are powered from 4KV Group Buses. #1 SAC = 1H 4KV Group Bus. The 460V Group Buses (1E, 1H) do NOT feed the ECACs.
Connections
- Related systems: 4KV, Pressurizer & PRT, Pressurizer Level & Press Control, Control Rod Drive
- Related procedures: S2.OP-SO.PZR-0010 — Pressurizer Backup Heaters Power Supply Transfer, OP-AA-109-115 — Equipment Tagging
- Related exam questions: 2020 Q54, 2020 Q56, 2020 Q70
- Related JPMs: 2022 JPM IP-i
- Related exams: 2022 NRC Operating Exam, 2020 NRC Written Exam