United States Nuclear Regulatory Commission - Protecting People and the Environment

Potentially Damaging Failure Modes of High- and Medium-Voltage Electrical Equipment (NUREG/CR-3122, ORNL/NSIC-213)

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Publication Information

Manuscript Completed: July 1983

Prepared by:
Harry C. Hoy
Nuclear Operations Analysis Center
Oak Ridge National Laboratory
Oak Ridge, Tennessee 37830

Prepared for:
Office for Analysis and Evaluation of Operational Data
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

NRC FIN B-1672

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Abstract

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, ofcourse, was the December 5, 1981, North Anna Unit 1 failure, where theinitial fault in one of the main transformers resulted in damage to the generator, the generator bus, and associated equipment.

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