Electric field distribution in power cable insulation affected by various defects

Electrostatic numerical models of cable insulation affected by cavities/impurities and water trees are proposed in this study. The individual influence of cavities and the simultaneous effects of cavities and vented water trees, and of solid impurities and bow-tie water trees are analyzed. The values and spatial distribution of relative permittivity and space charge in the subdomains of the 3D computational domain are set by scaling experimental results found in literature. The models are implemented in the finite element method based on the software package COMSOL Multiphysics. The results show the influence on the electric field distribution of the cavity position inside the insulation, both in the absence and in the presence of water trees, as well as of a bow-tie water tree grown in the insulation from a dielectric impurity. The role of the cavity diameter and of the permittivity of the impurity is also discussed.