Experimental Research on Deterioration Effect of Transition Metals on Natural Ester

Natural ester insulating oil has the advantages of excellent electrical properties, a high ignition point, and is renewable and degradable. Transition metal materials such as iron and copper used in transformer cores and windings can accelerate the deterioration of natural ester insulating oils. In this paper, natural ester (based on soybean oil) is used for the accelerated aging test at 100°C. The physicochemical and electrical properties of the natural ester after aging are tested. The results show that both iron and copper accelerate the degradation of natural ester, leading to a decrease in their physicochemical and electrical properties. Compared with iron, copper has stronger catalytic properties, which makes the degradation of insulating oil more severe. Metal ions have stronger oxidizing properties compared to metals. The degradation of natural ester with metal ions is much higher than that with metal. Especially copper ions lead to a drastic degradation of the physicochemical and electrical properties of insulating oil. The above research provides theoretical and technical support for revealing the mechanism of the degradation effect of transition metals on natural esters in transformers.