Decomposition and gas production characteristics of vegetable insulating oil under thermal stress

Vegetable insulating oil, with advantages such as high safety and environmental friendliness, is a good substitute for traditional mineral oil. However, thermal failure is one of the important factors affecting the safe operation of oil-immersed electrical equipment. This study focuses on soybean vegetable oil as the research subject and establishes a simulation model for soybean insulating oil to investigate the influence of thermal stress at different temperatures ranging from 1000K to 2000K on system decomposition and gas generation characteristics. The results indicate that, under elevated temperatures, the decomposition of soybean vegetable insulating oil predominantly occurs through decarboxylation reactions, leading to the generation of CO2 and hydrocarbon radicals. The hydrocarbon radicals further decompose and react with other species, resulting in the formation of characteristic gases. It was observed that CO2 and C2H4 serve as stable thermal decomposition by-products. Increasing temperatures significantly enhance the generation rates of various characteristic products and broaden the variety of such products. For instance, H-2 and CH4 are characteristic gases produced at different temperature ranges. Studying the decomposition and gas generation characteristics of vegetable insulating oil under thermal stress holds crucial significance for transformer design and operation.