A faulty feeder selection method for SLG faults based on active injection approach in non-effectively grounded DC distribution networks

•An improved active injection method is proposed to inject a detection signal to strengthen the fault characteristics with a lesser negative impact on the system during the injection process.•A ZPI algorithm is proposed to calculate the feeder length, and the faulty feeder is selected based on the polarity of the calculated length.•The waveform, frequency, amplitude, and duration of the detection signal are analyzed based on the requirements of the faulty feeder selection method and system constraints.•Simulations verify the feasibility of the proposed method under conditions of up to 5000 Ω transient resistance and 20 dB noise. Identifying single-line-to-ground faults in non-effectively grounded DC distribution networks is challenging because the fault current is fleeting in the transient stage and negligible in the fault steady stage. First, an active signal injection method is proposed to inject signals into the DC network after the fault occurs. And the fault characteristics of the zero-mode fault circuit including the injected signal are analyzed. Second, a zero-mode parameter identification algorithm is proposed to calculate the length of each feeder based on the injected signal in the fault steady stage. It is found that the calculated length of the healthy feeder corresponds to its actual length, but the calculated result of the faulty feeder is the opposite of the total length of all healthy feeders. Finally, a faulty feeder selection method based on the polarity of the calculated length is proposed. The simulation results shown that the method can select faulty feeders under conditions of up to 5000 Ω transient resistance and 20 dB noise.