Document: NUREG-0800
Document ID: 61198d64-419c-45ea-aebb-cf34c3b171fe
Document Type: srp
Title: Revision 0 – July 2015
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1505/ML15057A085.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8
CFR Part: 
CFR Title: 

Content:
of a transformer connecting an offsite power circuit to the transmission system. The protection scheme should consider all operating electrical system configurations and loading conditions: a. with a high impedance ground fault condition; and b. without a high impedance ground fault condition; and (ii) Loss of two of the three phases of the offsite power circuit (without ground) on the high voltage side of a transformer connecting an offsite power circuit to the transmission system under all operating electrical system configurations and loading conditions. Notes: i. The staff should ensure that licensees have considered all potential OPCs on the high voltage and low voltage side of transformers and interconnecting onsite auxiliary power circuits. Any connections that are not evaluated should be documented with an adequate justification. If there is a potential for OPCs in the intervening power path, the licensee should have analyses to show that the above open phase conditions are the limiting conditions. ii. For AP 1000 plants, electric power from the transmission network to the onsite electric distribution system is supplied by only one circuit. iii. For the purpose of OPC evaluation, high impedance ground faults are ground faults that produce fault currents below the ground fault relay setting. 2. For operating reactors and new reactors with active design safety features, reviewed under 10 CFR Part 50 and 10 CFR Part 52, “Licenses, Certifications, and Approvals for Nuclear Power Plants,” the following criteria should be satisfied when evaluating OPCs: a. The OPC should be automatically detected and alarmed in the main control room under all operating electrical system configurations and plant loading conditions. The detection circuits should be sensitive enough to identify OPCs under all operating electrical system configurations and plant loading conditions for which the offsite power supplies are required to be operable in accordance with plant technical