Detection of Power Quality Disturbances using Phase Corrected Wavelet Transform

Wavelet transform is very widely used for power quality analysis to detect voltage events. Although wavelet transform is an excellent tool to detect and localize the power quality disturbance events, it fails to classify them. This paper shows that phase correction to wavelet transform improves the performance of wavelet transform in identifying the power quality disturbances such as voltage sag, interruption, swell and harmonics. Phase corrected wavelet transform, commonly referred to as S-transform, has excellent time–frequency resolution characteristics and has the ability to detect the disturbance correctly even under noisy condition. This tool is applied on various voltage disturbances, generated as per IEEE Std. 1159 using MATLAB and the analysis can identify the magnitude and duration of the disturbances. The effectiveness of the S-transform is shown for multiple sag/swell condition in the presence of transients or noise. Wavelet transform is also used for analysis and results are compared with S-transform performance. Simulation results are also shown to identify both the harmonic magnitudes and phase angles using S-transform analysis. Experimental verification has been performed with transmission line model connected to linear and non-linear loads and S-transform is used to detect and classify various voltage disturbances. © 2012, The Institution of Engineers (India).