Evaluation of Electrical Tree Degradation in Cross-Linked Polyethylene Cable Using Weibull Process of Propagation Time

The main purpose of this paper is to evaluate electrical tree degradation for cross-linked polyethylene (XLPE) cable insulation for three difference models. In order to show the distribution characteristics using phase resolved partial discharge (PD), we acquire data by using a PD detecting system. These acquired data presented four 2D distributions such as phase angle-average discharge distribution, pulse magnitude-pulse number distribution, phase angle-pulse number distribution, and phase angle-maximum discharge derived from the distribution of PD. From the analysis of these distributions, each of the tree models are proved to hold its unique characteristics and the results were then applied as basic specific qualities. In order to evaluate the progresses of an electrical tree, we proposed methods using parameters by means of Weibull distribution to the time of tree propagation. We measured the time of tree propagation for 16 specimens of each artificial tree models from initiation stage, middle stage, and final stage respectively, using these breakdown data, we estimated the shape parameter, scale parameter, and mean time to failure. It is possible to analyze the difference in lifetime between the initial stage, the middle stage, and the final stage, and could be used to predict the lifetime of an XLPE cable from these results.