Abstract: The causes of the direct current system earth faults were discussed, the harm of direct current deuce earth was analyzed, while the working theory, technical parameters and performance index of portable LT-2000A were introduced. On base of the understanding of direct current system, keeping mastering utilization method of the stationary insulation detector equipment and LT-2000A, which is an important way to correctly check and deal with the faults of direct current system.

Key words: direct current system, earth, Breakdown reason, harm, analysis, insulation detector set, LT-2000A portable direct current earth fault earth position finder, search method