Insulation Assembly Effects on Performance of Medium-Voltage Cable Terminations

Abstract

Cable terminations are critical components in medium-voltage (MV) cable systems, where localized electric field enhancement may lead to insulation degradation, partial discharge activity, and premature failure. Sources of the enhanced fields may appear due to improper assembling of the terminations, especially on field conditions. This study investigates electric field distributions in a MV cable termination affected by various types of imperfections using three-dimensional finite element simulations performed in COMSOL Multiphysics. A reference termination model was established to identify critical stress regions and evaluate the influence of termination geometry on the electric field distribution. The effects of semiconductive screen edge geometry, dimensions of stress grading components, air-filled defects, and moisture contamination were systematically investigated. Several defect configurations, including air bubbles, air cushions, and moisture layers at different locations, were analyzed and compared. The results show that the highest electric field concentration occurs near the semiconductive screen cut-back region. A smoother semiconductive screen transition significantly reduced the maximum electric field, whereas moderate reductions in stress grading component length had negligible influence on the field distribution. Among the investigated defects, localized air bubbles and moisture contamination located near the screen cut-back region produced the highest electric field enhancement and therefore the highest risk of electrical overstress and partial discharge initiation. The findings improve the understanding of defectinduced electric field enhancement in cable terminations and provide guidance for improved design, installation, and reliability assessment of medium-voltage cable accessories.