Impact of Cu₂S Activity on Dielectric Properties of Oil-Paper Insulation Under Different Ambient Conditions

This study investigates the impact of Dibenzyl Disulfide (DBDS) on the aging and insulating properties of the pressboard used in transformer systems under varying ambient conditions. While DBDS acts as an antioxidant during the initial stages of aging, its thermal decomposition generates corrosive sulfur compounds that contribute to the chemical degradation of both the oil and pressboard insulation. These sulfur interactions in the transformer lead to the formation of copper sulfide, which subsequently diffuses into the pressboard, altering its thermal and electrical characteristics. Laser-Induced Breakdown Spectroscopy (LIBS) is employed to confirm the presence of elemental copper and sulfur, indicating the copper sulfide diffusion in the pressboard. The study correlates the heat trap density of the pressboard with the effects of DBDS and ambient gases on dielectric parameters. Heat trap density is identified as a critical parameter influencing the material’s electrical behaviour, affecting charge storage and dissipation processes. Additionally, heat dissipation properties of the aged pressboard are evaluated using Laser Flash Analysis (LFA) highlighting differences in thermal behaviour under air and nitrogen aging conditions.