Document: NUREG-0800
Document ID: 88ed0d92-9d6e-40b1-b060-6d7334f66eb8
Document Type: srp
Title: Revision 3 - March 2007
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0707/ML070710478.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8
CFR Part: 
CFR Title: 

Content:
he grid and the Class 1E buses or by the starting transients experienced during certain accident events not BTP 8-6-2 Revision 3 - March 2007 originally considered in the sizing of these circuits. See Reference 3 for further background information regarding this event. Regulatory Issue Summary (RIS) 2000-24 summarizes the staff’s concerns about grid reliability challenges that industry deregulation might impose and potential voltage inadequacies of offsite power sources. NUREG-1793 discusses the interfaces of the AP1000 passive plant design with the offsite alternating current power system. This report also presents assumptions on the performance of the offsite power system following loss of offsite power (LOOP) required for supporting Chapter 15 analyses. Information Notice IN 2000-06 informed licensees of possible concerns regarding the voltage adequacy of offsite power sources (i.e., power from the transmission system to nuclear power plants). This notice documents specific examples from plant operating experience. IEEE Std. 741 provides the principal design criteria, design features, and testing requirements for protection of Class 1E power systems and equipment powered from those systems. This standard includes informative sections on degraded voltage protection and protection concerns associated with auxiliary system automatic bus transfer. B. BRANCH TECHNICAL POSITION 1. In addition to the undervoltage scheme provided to detect LOOP at the Class 1E buses, a second level of undervoltage protection with time delay should be provided to protect the Class 1E equipment. This second level of undervoltage protection should satisfy the following criteria: a. The selection of undervoltage and time delay setpoints should be determined from an analysis of the voltage requirements of the Class 1E loads at all onsite system distribution levels. b. Two separate time delays should be selected for the second level of undervoltage protection based on the following