Thermal Aging Behavior and Deterioration Mechanism of Copper–Silver Contacts and Insulating Oil Under Sulfur Corrosion

Sulfur corrosion and aging of transformer insulating oils have an important impact on the reliable operation of power equipment. In this paper, the aging behavior of insulating oil containing dibenzyl disulfide (DBDS) at different temperatures (90 °C, 115 °C, 140 °C) is investigated. It focuses on the analysis of the law of sulfide deposition on the surface of copper and silver contacts and its effect on the performance of insulating oil. The results show that temperature has a significant effect on the sulfur corrosion reaction. It has been observed that as the temperature rises, the deposition rate of copper sulfide and silver sulfide is found to increase. However, when the aging process reaches a certain threshold, the deposition trend of sulfide tends to reach a state of saturation. Furthermore, it has been observed that the acid value and moisture content of the insulating oil increases significantly with the addition of DBDS. The dielectric loss factor of the DBDS-containing oil samples increases, while the breakdown voltage decreases. This phenomenon can be attributed to the shedding of sulfur corrosion products and the consequent increase in moisture content. Subsequent analysis indicates that, in practical applications, effective regulation of oil temperature and optimization of the oil filtration system can effectively mitigate the effects of sulfur corrosion and aging, thereby extending the operational lifespan of the insulating oil and the transformer.