This report is primarily concerned with the application of sensitive ground-fault interrupters (gfi's) to ac utilization circuits in U.S. mines. The main concepts examined are shock prevention and methods to reduce nuisance tripping. The research involved a literature search, input from previous Bureau of Mines contracts, and contacts with electrical manufacturers and mining personnel. Several devices that showed promise were tested and the results indicate the existence of gfi's that may be modified to perform adequately on U.S. mining systems. A set of guidelines covering design, construction specifications, and performance tests is included.
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