Partial Discharge Characteristics of Electrical Tree in XLPE during DC and Voltage Drop

Abstract

To study the electrical tree growth and partial discharge (PD) characteristics of cross-linked polyethylene (XLPE) under the DC electric field, the XLPE insulation was made into needle-plate electrode samples to carry out experiments at 25°C and 50 °C. The results show that the electrical tree grows at 50°C accompanied by PD, and the PD amplitude positively correlates with the tree length. However, under the same voltage condition, the DC electrical tree does not grow at 25°C, and there is only a small amount of PD observed. The elevated temperature not only promotes the growth of the electrical tree but also enhances the amplitude and frequency of PD signals. In addition, when the power is turned off and the applied DC voltage begins to decay to zero, PD with the reversal polarity can be detected in the sample with an electrical tree defect at both 25°C and 50 °C. With the exponential decline of the applied voltage, the PD amplitude increases, as well as the discharge interval, until the applied voltage is close to zero. This may be due to the formation of a reverse electric field at the needle tip during the applied voltage drop, resulting in PD in the electrical tree.