Sensitive Ground-Fault Protection For Coal Mines - Objective

Improve the safety of mine workers by developing a sensitive ground-fault relay system capable of detecting and isolating low level ground faults and thereby minimize the danger of electrocution. Approach Inadvertent, direct contact with energized conductors in underground coal mines is a major cause of electrocutions. Although relay systems designed to protect workers against such fatal accidents do exist in some industries, there are no effective ground-fault-sensing relay systems that address the special problems presented by power systems designed for U.S. mines. The Bureau of Mines conducted research to design and construct a sensitive ground-fault relay for use with low-voltage, alternating current (ac) mine electrical systems. Such a relay, sensing current leakage or faults in an electrical system, would send a trip signal to a circuit interrupting device which would then shut down power.