Potentially Damaging Failure Modes of High- and Medium-Voltage Electrical Equipment (NUREG/CR-3122, ORNL/NSIC-213)
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Manuscript Completed: July 1983
Date Published: August 1983
Harry C. Hoy
Nuclear Operations Analysis Center
Oak Ridge National Laboratory
Oak Ridge, Tennessee 37830
Office for Analysis and Evaluation of Operational Data
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001
NRC FIN B-1672
The electrical equipment failures of both nuclear and nonnuclear public utilities were reviewed. Those failures that could pose an additional problem to surrounding and connected equipment were defined. The literature was searched; utilities, repair shops, and large electrical equipment users were contacted or failure information. The data were reviewed in detail, and failure modes were determined. Sample cascade failures are discussed. The failure rate of electrical equipment in utilities is historically quite low. Nuclear plants record too few failures to be statistically valid, but failures that have been recorded show that good design usually restricts the failure to a single piece of equipment. An exception to this, of course, was the December 5, 1981, North Anna Unit 1 failure, where the initial fault in one of the main transformers resulted in damage to the generator, the generator bus, and associated equipment.