Optimal design of coal-mine power systems

A modern underground coal mine is a maze of electrically oper-ated equipment. In a majority of underground applications, electric-ity is the sole source of power for coal mining and haulage andtransporting personnel into and out of the mine. Electric motorspower continuous miners, shuttle cars, belt conveyors, locomotives,roof bo1ters, dewatering pumps, and ventilation fans, etc •• Occupyingsuch a vital role, it is imperative that the electrical service to~derground coal mining equipment be safe, highly reliable andmeet the highest operating standards.Unfortunately, such a widespread use of electricity in under-ground coal mines is not without its share of problems. A survey-conducted by the United States Department of Interior’s MineEnforcement and Safety Administration (now MSHA) pointed out thatsirty-six percent of all mine fires and twenty-one percent of allmethane ignitions investigated through 1972 were due to electricalarcs, short-circuits and overloads. In 1974, the number of e1ectro-cutions ranked next to roof falls in causing mine deaths - 23electrocutions compared to 102 deaths caused by underground mineroof falls. Besides the fatalities, the number of serious injuriesin coal mines caused by electrical sources is considerable.An analysis of the accidents related to electrical sourcesreveals the following three maj or causes: