The Method of Time Difference Based on Wavelet Analysis

In this paper, according to the characteristic that wavelet analysis has the ability of detecting signal singularities accurately a time difference method based on wavelet analysis is proposed. Using the suggested method the difference between fault occurrence time and differential-current appearance time can be precisely detected and it can be applied for discriminating the internal fault sand external faults of power transformer consequently in the case of a fault happening outside power transformer the disoperation of differential protection caused by the iron core saturation of current instrument transformer can be avoided. In order to verify the effectiveness of this time difference method the simulation analysis on a system is carried out in PSCAD.