A Distributed High-Impedance Fault Detection and Protection Scheme in DC Microgrids

This paper proposes a high-impedance fault (HIF) detection and protection scheme for DC microgrids. HIFs occur when a (live) conductor makes contact with a surface which restricts the flow of fault current to a level that cannot be reliably sensed/detected by the conventional relays. HIF detection is an important concern for the electric power grid since it may cause public safety hazards. In this paper, a distributed HIF detection and localization scheme is proposed which considers the inherent HIF arc-characteristics of very low fault current amplitude, nonlinearity, buildup, shoulder, intermittence, and high-frequency content. The proposed scheme effectively identifies the faulty section, and provides forward and reverse fault discrimination capability. To verify the effectiveness of the proposed method, different sets of test cases and experiments are analyzed and presented. In the test cases, the forward/reverse faults and the noise-induced signals are considered and evaluated. Furthermore, detection and localization of both ideal and non-ideal HIFs are evaluated on the test system. The non-ideal HIFs are modeled based on the experimental test waveforms of HIFs. Also, the functionality of the proposed scheme is verified under normal condition with operational changes in a DC microgrid.