Analysis of the Electric Field Distribution within MV Cable Joint in the Presence of Defects in Cable Insulation

Power cables have great importance in power transmission and distribution systems. Joints are the main accessories of the power cables. They are necessary to make connections between lines. The design of a cable joint mostly depends on the cable type, the applied voltage, and the cores. These factors add to the way of how electric field stress is distributed at the cable joint. This paper presents a numerical analysis study to the stress control layering electric field distribution within a cable joint. In this paper, a 2D Finite Element Method (FEM) is used.
A developed program using FEM has been used to simulate the electric field distribution in the joint of a single core cross-linked polyethylene (XLPE) underground medium voltage cable, as well as to investigate the presence of the defects and water droplets in the joint.
Many factors such as the defect size and location, insulation material dielectric constant, insulation thickness, as well as the cavity dimensions, shapes (cylindrical or spherical), and number (one to three either in horizontal or in vertical
formation) have been investigated. Also, the electric field in water droplets having different shapes (spherical, hemispherical, and cylindrical) is presented. The electric field in this region is increasing the electrical discharges at the defect sites. In turn, the breakdown occurs when the magnitude of the electric field is larger than the breakdown strength. The results obtained to assist in the design of cable joint structures, which can increase the reliability of the cable system.