Breakdown mechanism of internal cracks in porcelain materials

Abstract Alumina-based porcelain insulators are widely used in power systems and have become one of the most essential insulating materials in the grid. However, the issue of zero-value insulators—those that have lost their insulating function—remains a major challenge, posing serious risks to the safe and stable operation of power systems. The formation of zero-value insulators is closely linked to the presence of internal cracks within the ceramic body. In this study, the influence of internal cracks on the power frequency breakdown voltage of alumina ceramics is investigated. Simulated crack configurations of varying lengths and bending geometries were analyzed to examine their effect on breakdown behavior. The results show that the breakdown voltage decreases progressively with increasing air-gap length within the crack. In contrast, the degree of crack bending has minimal impact on breakdown voltage. Overall, the breakdown voltage is determined primarily by the total air path length, rather than the shape of the crack. These findings provide important insights for understanding failure mechanisms in porcelain insulators and guiding the identification and prevention of zero-value degradation.