Effect of Wormhole Defects on Electric Field Distribution under Composite Voltage

The reliability of electrical insulation systems is critical to the continuity of energy transmission and distribution systems. Structural defects that occur in polymer-based insulating materials can affect the distribution of electric fields, leading to partial discharges and subsequently serious failures such as breakdowns. In this study, the effects of wormhole structures with different diameters in cross-linked polyethylene (XLPE) insulators on electric field distribution under alternating current (AC), direct current (DC), and composite voltage (AC+DC) components were numerically investigated using COMSOL Multiphysics software. In the system modeled under a needle-plane electrode configuration, significant increases in both volumetric and surface electric field intensities were observed as the diameter of the wormhole increased. Among all cases, composite voltage conditions resulted in the highest field concentrations, indicating increased electrical stress on the insulation. Additionally, higher field intensities were observed under negative polarity than under positive polarity in all cases. The findings highlight the importance of considering wormhole-type defects in the design of insulating systems and analyzing the electrical stress caused by composite voltage conditions.