Power transformer protection using S-transform with complex window and pattern recognition approach

A new approach for power transformer protection using S-transform with complex window to distinguish between inrush current and internal fault is presented. The S-transform with complex window is used to extract patterns of transient current samples during inrush and faults. S-transform is a very powerful tool for non-stationary signal analysis giving the information of transient currents both in time and in frequency domains. The spectral energy is calculated for inrush and internal faults and an energy index is found out to distinguish between inrush magnetising current and internal faults. The simulation results and the results obtained using real-time data from a transformer in the laboratory environment indicate the robustness of the proposed technique