Discriminating Between Magnetizing Inrush Current and Fault Current in Power Transformer Protection using Wavelet Transform

This paper presents the discrimination between magnetic inrush current and fault current for power transformer protection using wavelet transform. The wavelet transform which can simultaneously collect information from transient signals in both frequency and time domain is employed in the analysis of power transformer transient phenomena in several conditions of inrush and internal fault currents. The fault conditions regarding the power transformer were modeled in MATLAB/SIMULINK environment and the discrete waveform transform was applied to decompose the fault signals up to level 5 into several detailed wavelet components. The test results from the simulations showed that the deeper the level of decomposition the better the attainment of obtaining good distinguishing characteristics as levels 1 and 5 of the waveforms presented in this work proved this concept.