The Moisture Absorption Characteristics and its Influence on AC Breakdown Voltage of Silicone Oil and Mineral Oil

Silicone oil has been applied in the field of transformers with high explosion-proof requirements as a substitute for mineral oil due to its characteristics of high flash point, high fire point and strong self-extinguishing performance. The moisture content in dielectric liquids is a key parameter which could greatly affect their dielectric performance. In this paper, the moisture absorption characteristics and its influence on AC breakdown voltage of silicone oil and mineral oil of similar viscosity are studied. The experimental results indicate that silicone oil exhibits comparable or even higher power frequency breakdown strength than mineral oil under low moisture content conditions. However, the saturated moisture content of silicone oil under identical temperature and humidity conditions can reach 4–5 times that of mineral oil. This study established a quadratic function fitting model to describe the relationship between the AC breakdown voltage of insulating oils and their relative moisture content, revealing similar moisture influence mechanisms on the breakdown voltage of both mineral oil and silicone oil. This study aims to preliminarily investigate the fundamental properties of silicone-based insulating oils, thereby laying the groundwork for their future potential applications in the power industry.