S-transform based feature for the identification of power quality disturbances

The increased use of power electronics based equipment, nonlinear loads and the changing power system regulations has made power quality (PQ) an important issue. The changed load condition has increased the proliferation of non-stationary PQ disturbances such as; voltage sag, swell, momentary interruptions, transients, along with the stationary harmonics. The conventionally used Fourier transform is found unsuitable for the analysis of non-stationary PQ disturbances. In this paper, a new feature vector based on the time-frequency distribution technique; S-transform is proposed for the analysis of PQ disturbances. The new feature vector is based on the variance. Simulated signals of different short duration PQ disturbances with different possible variations are used to validate the proposed feature vector. Various simultaneously occurring disturbances are also considered for the validation. Further, the average, maximum and minimum values of this feature vector are calculated to show the effectiveness of the proposed feature for the identification of simulated PQ disturbances.