Method of distribution network single-phase ground fault line selection based on relative entropy of discrete orthogonal S-transform energy

The frequency band energy of different lines shows inconsistent distribution when single-phase earth fault occurs in distribution network. To solve this problem this paper proposes a faulty line selection method which combines discrete orthogonal S-transform with the relative entropy of frequency band energy. Firstly, based on half cycle of the transient zero-sequence current of every line after single-phase earth fault occurs, the method calculates the transform coefficients of each frequency band with the method of discrete orthogonal S-transform(DOST) and then calculates the value of transient energy accordingly. Secondly, combine with the great signal recognition ability of relative entropy, the relative entropy of DOST energy in different frequency bands of every line are respectively calculated which compose the integrated relative entropy of DOST energy for each line, then the faulty line is chosen based on the integrated values. Matlab simulation shows that this method is free from the influence of ground resistance, fault time and fault distance, it can realize the accurate fault line selection for single-phase earth fault in wire-cable mixed lines even when intermittent arc fault occurs.