Effect Mechanism of Ambient Temperature and Humidity on Polyimide Partial Discharge Under High Frequency Electrical Stress

The high frequency power transformer faces some problems such as partial discharge and premature insulation failure due to the effect of electrothermal coupling stress. In order to study the coupling effect of ambient temperature and humidity on the characteristics of polyimide partial discharge, this paper studied the characteristics of polyimide partial discharge at four temperature points of 75–150 ℃ and three humidity points of 40–80%. The initial partial discharge voltage, the maximum and average discharge amplitude and characteristic parameters were counted to observe the surface morphology. The test results show that temperature is proportional to the maximum discharge amplitude, humidity is proportional to the maximum discharge amplitude when the temperature is less than 100 ℃, and the maximum discharge amplitude increases first and then decreases when the temperature is greater than 100 ℃. For the average discharge amplitude and the number of discharge per unit time, with the increase of temperature, the first increase and then decrease, the temperature is less than 100 ℃ and the humidity is less than 60%, the temperature is more than 100 ℃ and the humidity is more than 60%, and the temperature is more dominant.