Insulation Breakdown Strength Under AC and DC Stress Using Different Dielectric Materials: An Empirical Synthesis

Abstract

The reliability and efficiency of high-voltage power systems are critically dependent on the performance of insulating materials, which prevent electrical failures by withstanding high voltages. Insulation breakdown occurs when the dielectric strength of a material is exceeded, leading to system faults and reduced operational safety. Despite extensive use of various dielectric materials in transformers, cables, and capacitors, limited empirical data exists on their breakdown behavior under both alternating current (AC) and direct current (DC) stresses, particularly for emerging polymeric and composite insulators. This study aims to empirically determine the breakdown voltages of eight selected dielectric materials under controlled AC and DC conditions, compare their dielectric performance, analyze the influence of stress type on failure mechanisms, and provide practical data for insulation design. Experimental measurements of AC and DC dielectric strengths revealed significant variations among materials. Polyethylene Film exhibited the highest breakdown strength with 500 kV/mm under AC and 600 kV/mm under DC, while Transformer Oil showed 12 kV/mm (AC) and 14 kV/mm (DC). DC stresses consistently resulted in 7–20% higher dielectric strength than AC for all materials. Temperature dependent analysis indicated that breakdown voltages decreased exponentially with increasing temperature, with Transformer Oil dropping from 24 kV at 25°C to 10 kV at 150°C. Safety factor calculations demonstrated that only high-performance insulators such as Polyethylene Film, Epoxy Resin, and Silicon Rubber meet recommended design thresholds under 20 kV operation. Optimal insulation thicknesses were derived using empirical dielectric strengths, revealing that robust materials can reduce insulation requirements by up to 60% compared to conventional oil paper systems. These findings provide quantitative guidance for material selection, insulation coordination, and design policies in high-voltage systems, enabling safer, more efficient, and cost-effective deployment of AC and HVDC networks.