A new principle of fault line selection in non-solidly earthed network based on direction traveling wave

Using the traveling wave technology, this paper analyzes the transient state process of non-solidly earthed network in detail when single phase earth fault occurring, and discovered the follow conclusions: in the fault line, forward voltage traveling wave and the backward voltage traveling wave are arrived simultaneously, but in the healthy lines, the arrival time of the backward voltage traveling wave lagged behind that of the forward voltage traveling wave certain amount; the initial polarity of forward voltage traveling wave in the fault line and the health line is extremely opposite. According to those two characteristics, this paper proposed a new algorithm of fault line selection based on the ratio of the forward and backward traveling wave energy and the forward voltage traveling wave polarity, which won´t be affected by fault initial phase angle and transition resistance. The effectiveness of the algorithm has been verified by the ATP simulation results.