Fault Detection and Clearance in DC Distributed Power Systems

This paper treats fault detection in DC distributed power systems, with emphasis on ground faults. The difficulty of detecting ground faults arises from the fact that the AC sources and loads are ungrounded or have heavy impedance to ground, on the converter side, to effectively block zero sequence currents otherwise flowing between the AC systems. A grounding scheme for the DC distribution system together with algorithms for detection of ground faults is presented. The proposed method detects ground faults on both the AC and DC sides and is extended to cover also short circuit faults with a minor work effort, which is also discussed.