Document: NUREG-0800
Document ID: 72cf12c3-a823-4385-bbf4-92e2b543a906
Document Type: srp
Title: AC POWER SYSTEMS (ONSITE)
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070498.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8.3.1
CFR Part: 
CFR Title: 

Content:
ower system is reviewed to determine that the required redundancy of safety-related components and systems is provided. This includes an examination of the ac power system configuration, including the power supplies, power supply feeders, switchgear arrangement, loads supplied from each bus, and power connections to the instrumentation and control devices of the power system. 2. Conformance with the Single Failure Criterion In establishing the adequacy of this system to meet the single failure criterion, both electrical and physical separation of redundant power sources and associated distribution systems are examined to assess the independence between redundant portions of the system. This will include a review of interconnections between redundant buses, buses and loads, and buses and power supplies; physical arrangement of redundant switchgear and power supplies; criteria and bases governing the installation of electrical cables for redundant power systems; and proposed sharing of the ac power system between units at the same site. 3. Onsite and Offsite Power System Independence In evaluating the independence of the onsite power system with respect to the offsite power system, the scope of review extends to the station distribution load centers which are powered from the unit auxiliary transformers and the startup transformers (considered for the purposes of this SRP section as the offsite or preferred power sources). It includes the supply breakers connecting the "low" side of these transformers to the distribution buses. This evaluation includes a review of the electrical protective relaying circuits and power supplies to ensure that, in the event of a loss of offsite power, the independence of the onsite power system is established through prompt opening of isolation-feeder breakers. 4. Standby Power Supplies 5 Design information and analyses demonstrating the suitability of the diesel generators as standby power supplies are reviewed to ensure that the diesel