Detection Method of Pole to Ground Fault in Ungrounded LVDC Distribution Grid Using DWT

Recently, concerns have been raised about LVDC distribution grid and DC microgrid. The LVDC distribution grid connected with renewable energy sources adopts an ungrounded system factoring power loss and economical efficiency. However, it is difficult to detect the pole to ground fault because the change of the fault current is very minute when a pole to ground fault happens. In this paper, we propose a detection method of the pole to ground fault in ungrounded LVDC distribution grid using the DWT of measurement current by signal injection method. To demonstrate the effects of the proposed ground fault detection method, the collected signals were analyzed after the LVDC grid modeling process using PSCAD, and then the proposed method was conducted. Simulation results show that the proposed detection method can correctly detect the pole to ground fault without malfunction. In addition, the proposed algorithm accurately estimates the fault resistance.