注入探测信号的直流配电网接地故障识别方法

In order to accurately and reliably identify the grounding faults of the DC distribution network and solve the problems of insufficient reliability and sensitivity of the existing methods based on the fault transient information, a grounding fault identification method based on the detection signal injection is proposed. An additional control strategy using MMC to inject the sinusoidal detection signal is first proposed. Furthermore, a selection criterion of the detection signal is determined based on the response speed of MMC, the guideline of DC distribution system and the accuracy of measuring equipment. On this basis, by analyzing the response characteristics of the fault network to the detection signal, it is concluded that the zero-mode impedance of the line viewing from the head of the faulty feeder is inductive, while from the healthy feeder it is capacitive. Therefore, a grounding fault identification method is proposed, which has the ability to identify the permanent fault. The simulation results show that the proposed method can identify the grounding fault occurring at any location of the feeder or the bus under 500Ω high resistance. The overall performance is better than the other existing methods.