Detection of high-impedance fault in distribution network based on time-frequency entropy of wavelet transform

Due to the characteristics of small, nonlinear, random, and unstable current, the high impedance faults (HIF) are not always effectively cleared by conventional over current relays. A new simple and effective algorithm of HIF detection in distribution network based on the wavelet time-frequency entropy is presented in this article. On the basis of analysis, the time-frequency distribution characteristics in the concerned frequency band of HIFs by wavelet transform. The feature sequence developed by the wavelet time-frequency entropy at the time sequence is employed to detect HIF at substation. This criterion is calculated from the sum of wavelet time-frequency entropy at the time sequence every half cycle. If the value of the criterion is more than the threshold during four cycles, the HIF event can be identified. The developed detection method has been tested with real-world recorded signals from different HIF medium and PSCAD/EMTDC-generated signals. The result shows that the proposed method is robust to transients generated during normal events such as capacitor bank switching, load switching, and harmonic load. It has good performance for antinoise ability by noise reduction coefficient improved appropriately. And the proposed method has better reliability than the traditional third-harmonic-based method. (c) 2020 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.