A new wavelet packet method of single-phase earth fault line selection in distribution network based on the maximum difference comparison

Using wavelet to achieve fault line selection, traditional methods are all in accordance with the principles of the largest energy to determine the characteristic band. However, this square sum operation overlooks the detailed band features, so when the fault characteristics are not obvious, it will cause wrong judgment. For transient quantity mutations are the basis of wavelet fault line selection, a new perspective that ¿the frequency band with the maximum absolute value of adjacent wavelet packet decomposition coefficients difference¿ should be chosen as the line selection frequency band is first proposed in this paper after the wavelet packet decomposition of the complex transient mutational quantity. The paper expounds on the detailed fault line selection steps and practical criterion, and also analyzes the selection of mother wavelet, sampling frequency and scale of the decomposition. Theoretical analysis and simulation results show that the method can accurately select fault line, with high reliability.