Detecting Single-Phase-to-Ground Fault Event and Identifying Faulty Feeder in Neutral Ineffectively Grounded Distribution System

In neutral ineffectively grounded distribution systems, a conventional zero-sequence voltage criterion to detect a single-phase-to-ground (SPG) fault event suffers from some drawbacks, and existing fault feeder selection techniques demonstrate low reliability in the field. For improvement, a new protection scheme is proposed in this paper. It is composed of a fault event detection unit and a fault feeder identification unit. Based on data distribution kurtosis of transient zero-sequence current, the former unit is employed to detect whether a SPG fault event has occurred and capture a fault starting moment. According to the behavior of average data distribution skewness, the latter unit is employed to identify which feeder is faulty. Superior to the zero-sequence voltage criterion, the proposed scheme can reliably detect the SPG fault event under a three-phase voltage imbalance condition and intermittent arc grounding fault. Besides, it is also found that the proposed scheme can validly identify a faulty feeder even under high background noises. Case test results indicate that the proposed scheme is able to work well with not only simulation data but also recorded field data, which demonstrates the high value in engineering practice.