Analysis the Impact of Void Defect Position and Size on Medium Voltage PILC Cable

Abstract

Worldwide, most medium-voltage paper-insulated lead-covered cables are operating beyond their intended design life, increasing the likelihood of failure. Irregular electric field distribution over the insulation material causes partial discharge degradation, which reduces the cable’s efficiency. Online partial discharge monitoring is used to evaluate the health condition of medium-voltage underground cables. Online partial discharge behaviour detection is highly sensitive to variations in the electric field distribution within three phase medium-voltage cable insulation. The analysis of partial discharge phenomena in medium-voltage cables is mainly based on electric field analysis. Analysing online partial discharge characteristics requires a deep understanding of partial discharge behaviour in insulation systems. The initiation and propagation of partial discharge activity are subject to the critical electric field across the degradation of voids within the cable insulation. This paper presents a study of the electrostatic consequences of void defects and considers the likelihood of internal partial discharge occurring within these defects based on their position and size in belted medium-voltage cables. The nature of the electric field distribution in the cable is presented through finite element analysis. The electric stress variation across different air-filled void defect sizes at multiple positions within the insulation of 11 kV three-phase paper-insulated lead-covered belted cables under online in-service conditions is analysed. The findings contribute to a better understanding of partial discharge behaviour in three-phase medium-voltage cables, enabling enhanced evaluation of asset condition and effective extension of operational lifespan.