Recently, the world's first 220kV hybrid insulating oil transformer, jointly developed by China Electrical Equipment, State Grid Chongqing Electric Power Research Institute and Chongqing University, was successfully put into operation at the 220kV Tianjia Substation in Bishan District, Chongqing. This milestone marks a major breakthrough in the application of hybrid insulating oil technology in the 220kV voltage level, promoting the transformation and upgrading of power equipment towards green and low-carbon development.

Different from traditional transformers that rely on pure mineral oil as the insulating medium, the hybrid insulating oil combines the stability of mineral oil and the oxidation resistance of vegetable oil, achieving comprehensive breakthroughs in key performance indicators such as breakdown voltage, flash point, acid value and heat dissipation. Experimental data shows that the thermal aging rate of insulating paper in the hybrid oil is greatly reduced, and its service life is 1.91 times that of mineral oil, which effectively improves the reliability of the equipment and extends its service life in operation[6].