With the continuous upgrading of load capacity of ultra-high voltage transformers

how to improve the oxidation stability of transformer oil during high temperature operation has always attracted the attention of the industry. In order to study the effect of different types of antioxidants on the physical and chemical properties of transformer oil at high temperatures

phenolic antioxidant T501

amine antioxidant T531

and T501+T531 mixture were added to the insulation system composed of naphthenic base oil and ordinary kraft paper. Thermal aging test was carried out at 130 ℃. The test regularly measured the acidity

dielectric loss factor

carbonyl index and furfural content of oil samples

and simultaneously detected the degree of polymerization of insulating paper and EDS analysis. The results show that

the antioxidant T501 had a better anti-oxidation effect in early stage of the transformer oil aging at high temperatures. With the prolongation of aging time

the decomposition of oxidation products would accelerate the deterioration of oil paper. With compound addition of antioxidants T501 and T531

the performance indicators of oil paper were relatively stable

and the heat resistance stability of the transformer oil was enhanced. The test results can provide reference for selection of high temperature resistant antioxidants for transformer oil.