Transformer Magnetizing Inrush Current Identification Based On Wavelet Analysis

One of the key problems in power transformer current differential protection is how to distinguish reliably between inrush and internal fault currents. So the wavelet analysis method developed in recent years is applied to inrush identification in this paper. The generating mechanism and characteristics of inrush currents is analyzed. The advantage and disadvantage of the traditional principle for transformer current differential protection is examined. The toolbox of Power System Block set in Matlab is used to establish simulation model for inrush and fault currents, and the waveforms for inrush and fault currents are obtained. On these bases, the wavelet method is used to extract the main feature of discontinuities in inrush currents. The result show that the wavelet analysis method can make reliable inrush identification.