Partial discharge properties of electrical trees in XLPE

Cross-linked polyethylene is widely used as the insulation of power cables due to its superior insulation and mechanical properties. Electrical trees is one of the main reasons for the breakdown of cable insulation. In order to explore the growth process and partial discharge characteristics of electrical trees in cross-linked polyethylene, cuboid samples taken from a commercial cable and a needle-plane electrodes were used to develop electrical trees. In this paper, a real-time observation system was designed to record the growth picture of electrical trees and a partial discharge measurement system was used to obtain the partial discharge patterns during treeing. The experimental results show that the structure of electrical tree varied in stages. There are four stages during the growth of electrical trees, namely, initiation stage, slow growth stage, rapid growth stage and sustained growth stage. The outline of PD distribution patterns is bimodal shape. During treeing, the numbers of PDs in the two cycle are almost equal.