Effects of sulfur corrosion on the properties of oil–paper insulation induced by dibenzyl disulfide

As a corrosive sulfur, dibenzyl disulfide (DBDS) is an efficient antioxidant in oil-immersed insulation. This study explored the reaction mechanism of corrosive sulfur with copper through heating experiments stipulated by IEC 62535. Thermal aging experiments were further conducted at 130 °C under nitrogen to investigate the comprehensive effect of the oxidation resistance and corrosivity of DBDS on the properties of oil-paper insulation. Experimental results showed that DBDS can decompose into corrosive benzyl mercaptan at a high temperature. Dibenzyl sulfide cannot corrode copper to form copper sulfide at 150 °C. Furthermore, the oxidation resistance and corrosivity of DBDS depend on the dynamic change in DBDS concentrations. This study suggests that 25 mg/kg should be used as the maximum additive content of DBDS in oil. With this additive content, the oxidation resistance of oil can be improved, and the corrosion damage of insulation winding can be controlled to a certain extent.