Document: NUREG-0800
Document ID: 853719df-a6ea-408b-8d43-5956155abc38
Document Type: srp
Title: and 8.3.2.
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1007/ML100740246.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8.3.1
CFR Part: 
CFR Title: 

Content:
circuit currents from the generator-source with delayed current zeros. It is also recognized that the magnitudes of these short circuit currents are considerably lower than the magnitudes of the rated short-circuit currents. The capability of the generator circuit breaker to interrupt the delayed current zeros can be ascertained by computations 8.2-36 Revision 5 - May 2010 that consider the effect of the arc voltage on the prospective short-circuit current. The determining arc voltage model is derived from tests with comparable magnitudes of current. If this computation entails too many assumptions on the behavior of the generator circuit breaker during interruption under the most severe conditions, short-circuit tests shall be required. If tests are carried out, it must be recognized that, normally, the required current waveshape cannot be simulated accurately in test stations. Tests shall include a predetermined nonzero current waveform associated with the rated maximum voltage and an inherent circuit transient recovery voltage, and an approximate waveform obtained either by calculation or by measurement at the generator circuit breaker=s particular application. C. The availability of offsite power to the onsite loads for designs utilizing generator circuit breakers should be no less than comparable designs which utilize separate offsite power transformers to supply offsite power to the station loads. In this regard the trip selectivity between the generator circuit breakers and the switchyard high voltage generator circuit breakers should insure against unnecessary tripping of the switchyard generator circuit breakers during abnormal events in order to maintain offsite power to the station loads. D. Load break switches should be designed to perform their intended function during steady-state operation, power system transients, and major faults. Except for item 2.C, the switches should have the same capabilities as defined in guideline 2 for generator circuit