This report summarizes research into the root causes of failures in mine power systems that impact safety and reliability. Abnormally low fault currents owing to arcing faults, self-excited systems, and fallen trolley wires are examined and quantified. The reliability of components that are critical for safety is studied, as well as reliability of components that are crucial to the mining process. Failure rates are found through in situ tests, accelerated life tests, studies of mine maintenance, and fault-tree analysis. Reliability data are used to predict fatalities and lost-time accidents through computer-aided fault-tree analysis. Analytical support tasks reported include the determination of trailing-cable ampacities under cyclic loading and the measurement of connected ground beds.