In a Low-Resistance Ground System (LRGS), it is difficult to detect a high-impedance ground fault (HIGF) using conventional over-current protections because of its low fault current. In this paper, a novel HIGF detection method based on phase current increment ratio is proposed. Using the method of symmetrical components and current branching coefficient, the characteristics of three-phase current increments are analyzed. It is found that the current increment of faulty phase is much larger than that of healthy phases, while the current increments of three phase is approximately the same in the healthy line. According to the above difference, using the phase current before and after the fault happening, the proposed method calculates the phase current increment ratio of line to discriminate the faulty line from the healthy line. The validity of the proposed method is verified by the simulations using PSCAD/EMTDC. The simulation result indicates the proposed method has high performance during HIGF, and the criterion is only slightly affected by fault resistance.

Distribution network,Phase current increment ratio,Symmetrical components method,High-impedance ground fault,Low-resistance ground system