Wavelet technique for noise separation in the neutral current of a power transformer during impulse test

A power transformer is the most important component in an EHV power transmission. During impulse test the neutral current is compared at reduced and full impulse voltages. Any difference in the neutral current is construed as failure of transformer. In this paper, identification and separation of a noise signal from the main neutral current are carried out using wavelet technique. In order to carry out analysis, faults are created in turns of the tapping winding of a 61 MVA, 11/220 kV generator transformer (GT) at different locations. Neutral currents are recorded by applying low voltage impulse through recurrent surge generator (RSG). Contribution of each frequency in time domain signal is calculated by applying Gabor wavelet. The proposed method can be used for isolating the contribution due to any frequency in the waveform.