Breakdown Characteristics of Water Tree Defects Under 0.1Hz Cosine Square Wave Voltage

The cosine square wave voltage of 0.1Hz is widely used in the power cable withstand voltage test due to the small test capacity requirement. Water tree is an important factor leading to cable insulation failure. Its growth is sensitive to voltage frequency. The higher the voltage frequency, the faster the growth. Whether the water tree defect in the cable can be found in the withstand voltage test under the cosine square wave voltage of 0.1Hz has not been reported at present. Therefore, based on the models and methods recommended by CIGRE, under the action of 10kHz high-frequency high-voltage power supply, XLPE flake defect models with different water tree lengths were prepared. The water tree length proportion for about 30% of the XLPE tablet thickness, 60 % And 90%. Under the effect of 3U0 equivalent field strength, the breakdown characteristics of water trees under the effect of 0.1Hz cosine square wave voltage were measured, including breakdown voltage, breakdown time, and channel topography characteristics. The research results show that the 3U0 equivalent field strength 0.1Hz cosine square wave voltage withstand voltage test can find of 90% water tree length proportion insulation defects, but has no obvious effect on 30% and 60% water tree length proportion defects.