A new algorithm for the identification of high impedance faults in distribution systems utilizing S transform

Using the superior specifications of S-transform (ST) a new algorithm is presented for the high impedance fault (HIF) detection in distribution systems. Here, ST is applied to one cycle of the current signal and all time and frequency information of the signal are extracted. Then, four numerical indices named as total harmonic distortion (THD), even harmonic energy (EHE), variation coefficient (VC) and phase deviation (PD) are calculated from the ST output. According to the values of the four indices and some predefined thresholds, HIF is discriminated from the normal situation and other events of the distribution system. Performance of the proposed algorithm is evaluated by the test signals simulated by PSCAD/EMTDC software and experimental test signals extracted from a real distribution network. Here, the total algorithm implementation time is 21 ms. With the presence of 30 dB gaussian white noise, the HIF identification accuracy is cleared to be 98.48 %.