Electronic Devices Mengda Li, Yubo Duan, Yan Wang, Lingyu Zhang 5 1 2016 http://www.dline.info/ed/fulltext/v5n1/edv5n1_2.pdf This paper use the methods of S transformation to test the starting time, the end of the time, frequency and amplitude characteristics of common transient power quality signal disturbance. Through error analysis and simulation show that this method can accurately determine the disturbance occurred time and duration, and the identification and determination of disturbance can be simple and intuitive. It has the practical value and realistic significance to power quality signal interference analysis.