A method of 20 kV cable line fault location based on sheath grounding current

To solve the problem of fault location in 20 kV medium-voltage distribution network cable line, a method based on sheath grounding current is presented in this paper. When unsymmetrical earth fault occurs, the sheath grounding current contains three ingredients. After analyzing the relationship between induced circulating current flowing in cable sheath and zero-sequence current flowing in the cable core, it is found that the sheath grounding current has characteristics obvious enough to distinguish internal or external fault type. Based on this, sheath grounding current overflowing criterion is proposed which is effective to locate the fault section of cable line. At last, validity of the sheath grounding current overflowing criterion is verified by RTDS simulation results.