Ground Fault and Overcurrent Protection Criteria for Coal Mine AC Distribution Systems

摘要

Ground fault and overcurrent protection criteria for coal mine ac distribution systems were examined by authorization of the Bureau of Mines. The report begins with a literature review that discusses relaying topics including instrument transformers, ground fault pickup methods, static relaying, and comparison of relaying techniques. A chapter on ground fault relaying provides recommendations for maximum and minimum pickup levels as a function of maximum ground current and power system line-to-ground capacitance. Research in the area of phase overcurrent protection has resulted in a complete set of procedural recommendations for the selection and setting of overcurrent relays and current transformers, molded-case circuit breakers, and distribution system fuses in coal mine power systems. The final chapter discusses relay system maintenance and introduces a unique test set that is used to test the performance of relaying systems in coal mines.