Document: NUREG-0800
Document ID: 98a045ec-37ef-46fc-9eaa-9e695c2d6e53
Document Type: srp
Title: OFFSITE POWER SYSTEM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052350488.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8.2
CFR Part: 
CFR Title: 

Content:
site circuits as described above, but only on a delayed basis. Since this is a new design feature, the staff made the use of generator circuit breakers and load break switches a generic item no. B-53. In the case of McGuire and Catawba, References 1, 2, and 3, an expert consultant was retained to evaluate the generator circuit breaker verification testing program and its results. These guide- lines are formalization of the results of that extensive work. Also guide- lines for the load break switches are incorporated, as these devices have some common functional requirements as generator breakers as described above. The staff has made a determination that only devices which have the capability of interrupting the system maximum available fault current, i.e., circuit breakers will be approved as a means of isolating the unit generators from the offsite power system in order to provide immediate access in accordance with GDC 17. This is necessary because a non fault- current interrupting device, i.e., load break switch, must delay its trip for electrical faults until the switchyard circuit breakers have inter- rupted the current. Following opening of the load break switch, the switchyard circuit breakers must then be reclosed to establish offsite power to the unit. A generator circuit breaker, however, could interrupt the fault current and isolate the unit generator at the same time, main- taining continuous power to the onsite ac power system. B. Specific Guidelines 1. Only devices which have maximum fault current interrupting capability i.e., circuit breakers, can be used to isolate the unit generator from the offsite and onsite ac power systems in order to provide immediate access for the onsite ac power system to the offsite source. Generator load break switches can only be used for isolating the unit generator for the purpose of providing a delayed access offsite source. 2. Generator circuit breakers should be designed to perform their intended function during