Document: NUREG-0800
Document ID: bc7e4c14-0eaa-4591-a506-23d7893f8a00
Document Type: srp
Title: as establishing acceptable guidance for meeting the requirements of this criterion.
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:
ently, the added capacity resulting from the connection of nonsafety-related loads to the diesel generator under test will cause the tripping of this diesel due to overload or underfrequency . The end result 100 could be the total loss of power to the safety buses. However, this power interruption could be of momentary duration if the remaining redundant diesel generators are commanded automatically to start by undervoltage relay action 8.3.1-19 DRAFT Rev. 3 - April 1996 immediately after total power is lost. The diesel generator under test will be inoperable due to the self-locking feature preventing restarting after an overload or underfrequency trip condition. The reviewer ascertains that the time delay 101 introduced in making power available to the safety buses as a result of this event is within the response time limits assumed in the accident analyses. Included is verification that subsequent failures such as those resulting from improper electrical relaying coordination and self-locking features will not impair the automatic starting of the remaining redundant diesel generators required to meet minimum safety requirements. If the time delay introduced in making power available to the safety buses is not tolerable, it must be demonstrated that either the probability of occurrence of this event is low when compared towith the frequency and duration 102 of testing each diesel, or the design must provide diverse automatic signals, other than undervoltage, to ensure the availability of standby power to the safety buses. As an outcome of reviewing the parallel operation of the offsite and onsite power systems, the use of the standby power supply diesel generator sets to supply power to the electrical system during peak load demand periods was found by the staff to be unacceptable. The basis for this conclusion is that the required frequent interconnections of the offsite and standby power supplies do not minimize the probability of their coincident loss (General