DSP wavelet-based tool for monitoring transformer inrush currents and internal faults

This paper proposes a wavelet-based technique for monitoring nonstationary variations in order to distinguish between transformer inrush currents and transformer internal faults. The proposed technique utilizes a small set of coefficients of the local maxima that represent most of the signal's energy: only one coefficient at each resolution level is utilized to measure the magnitude of the variation in the signal. The data is processed while sliding through a Kaiser window and the technique has been applied in the laboratory as well as with simulated data, producing excellent results.