Abstract: “Power transformer transients, which are originated from non-linear operating characteristics, may cause failure of a power system. In this study, a special resonance phenomenon where overvoltages observed due to switching capacitances of the line is investigated. This situation is detected while high voltage side of the transformer is open circuit (no-load) and the low voltage side is connected to a transmission line through nonlinear switch (or breaker). This special resonance is caused by the interaction of leakage inductance of the transformer windings and the switching capacitance. A test setup containing 220V/34.5kV transformer is employed for realization of simulation results obtained by SPICE analysis. In order to simulate switching capacitance, a capacitance of 5.54μF is connected to low voltage side. The recorded and simulated test results show good correspondence. Observed overvoltages are analysed by continuous wavelet transform (CWT) and fast Fourier transform (FFT) techniq”

Keywords: switching capacity, power transformer, overvoltage, continuous wavelet transform, resonance