Analysis of Ultrasonic Signal Characteristics of Generator Stator Wire Bar Discharge Based on Wideband Ultrasonic Sensor

The stator bars of large generators are of vital importance to the generator sets in power system，and their insulation performance is related to the stability and safety of the generator and power grid. Insulation corrosion and breakdown accidents caused by corona discharge occur frequently. Since most previous studies focus on the installation of sensors on the casing of the generator set，and the mainstream resonant sensors have limitations in detecting ultrasonic signals of different frequencies and cannot accurately reflect its time-frequency domain characteristics. For this purpose，a wideband ultrasonic sensor is used in this paper to detect the ultrasonic signals of stator wire bar discharge，thereby obtaining the characteristics of different types of signals and providing a basis for the future online monitoring and diagnosis of wire bar discharge based on ultrasonic signals. First，the optimal placement position of the sensor is determined through electric field simulation. Then，a partial discharge test is designed to verify the feasibility of the wideband sensor. Finally，the characteristics of the ultrasonic signal in the time-frequency domain and phase are analyzed. The results show that the wideband sensor has a significant effect on detecting ultrasonic signals of different frequencies，and the feature analysis results can be used for identification of defect types.