Influence of design parameters and defects on electric field distributions inside MV cable joints

This paper presents a 2d finite-element analysis for a 33-kV, three-phase, three-core cross-linked polyethylene (XLPE) underground cable (UGC) straight joint of the heat shrink type. The aim of this work is to show how the joint design parameters and different defects affect the electric field distribution, and find optimum material properties to enhance the lifetime of cable joints. This is investigated by calculating the electric field distributions and showing how the optimized selection of joint material properties can reduce the localized high electric field to avoid partial discharge activities. Several design parameters are investigated such as insulation layer's thickness and relative permittivity, and termination angles of ferrule and its insulation. In addition, size and location of different defects such as air voids, water droplets, sharp tips and delamination are examined. The paper concludes important points for proper design of medium-voltage (MV) cable joints to enhance their lifetime and hence increase the reliability of such cable systems.