The study of voltage sag detection by improved S-transform

Nowadays, Short Time Fourier Transform (STFT), Wavelet Transform (WT) and S-transform are applied for signal processing and power quality disturbance detection. But S-transform, Using localizing scalable Gaussian window called generalized S-transform, provides the best time-frequency resolution and is suitable for analysis and detection of power quality disturbance under noisy conditions. According to the operation of scalable window in S-transform, the mother wavelet function is suggested for improved S-transform as a scalable window. It is Important to specify the best mother wavelet function for accurate detection of power quality disturbance. In this paper, simulations have been performed to evaluate the effectiveness of five selective mother wavelet functions for detection of the voltage sag by the improved S-transform.