Time-frequency analysis of step response in medium voltage networks

Measurements of free-burning arc in the power network were recorded at 22 kV busbar voltage transformer. As the measuring transformer distort the record, it was not possible to determine the response by measurements. The experiment was therefore modeled using EMTP -ATP. In addition to the described model of measuring voltage transformer, it has been modeled the network in which the measurement takes place. In order to analyze time-varying oscillatory character of voltage response two kind of time-frequency signal processing method were proposed: those which characterize time behavior of the waveform, and those which give information about frequency components. Obtained representations are based on classical Fourier spectrum and time-frequency representations: Smoothed Pseudo-Wigner-Ville Distribution and the S-transform.