The Impact of Water Trees and Cavities on the Electric Field Distribution in XLPE Power Cables

Many attempts to understand the exact impact of defects in insulating media have been made since the 20th century. However, published papers consider the effect on the electric field due to one kind of defect only and don't mention the impact of having different combinations of defects in the same vicinity in XLPE and this is in fact what happens in practical situations. An important step towards that goal is to observe and understand the effect of defects on the electric field distribution inside such media. In this paper, the impact of different defects on the distribution of the electric field in XLPE power cables is studied and analyzed. The defects entail cavities and water trees (bow tie and vented). The position of the cavities and bow-tie water trees was varied in the insulating medium. Moreover, the effect of having cavities inside and outside vented water trees was also investigated. In addition, the size and relative permittivity of cavities were also examined. The relative permittivity of the cavities and water trees are considered according to standardized values. Both AC and DC high voltage sources were carried out to observe any differences and anomalies in the results obtained. The results acquired from the 2D model in COMSOL Multiphysics would exemplify the effect of these parameters and space charges on the electric field distribution. This would ultimately influence the aging of the insulator.