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:
lear Regulatory Commission, Washington, DC 20555, Attention: Reproduction and Distribution Services Section, or by fax to (301) 415-2289; or by email to DISTRIBUTION@nrc.gov. Electronic copies of this section are available through the NRC's public Web site at http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr0800/, or in the NRC's Agencywide Documents Access and Management System (ADAMS), at http://www.nrc.gov/reading-rm/adams.html, under Accession # ML070710478. NUREG-0800 U.S. NUCLEAR REGULATORY COMMISSION STANDARD REVIEW PLAN BRANCH TECHNICAL POSITION (BTP) 8-6 ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES REVIEW RESPONSIBILITIES Primary - Organization responsible for electrical engineering Secondary - None A. BACKGROUND Events at the Millstone station have shown that adverse effects on the Class 1E loads can be caused by sustained low grid voltage conditions when the Class 1E buses are connected to offsite power. Loss-of-voltage relays, which generally have a low-voltage pickup setting in the range of .7 per unit voltage or less, will not detect these low-voltage conditions. See Reference 2 for further background information regarding these events. The Millstone events also demonstrated that improper voltage protection logic can itself cause adverse effects on the Class 1E systems and equipment, such as spurious load shedding of Class 1E loads from the standby diesel generators and spurious separation of Class 1E systems from offsite power resulting from normal motor starting transients. An event at the Arkansas Nuclear One station and the subsequent analysis performed disclosed the possibility of degraded voltage conditions existing on the Class 1E buses, even those with normal grid voltages, as a result of deficiencies in equipment between the 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