Abstract: Dielectric dissipation factor is a very effective key parameter to judge the insulation condition of electrical equipment and the quality of insulating materials. In order to better guide the development of new transformer oil products and provide more exact fault diagnosis of operating equipment, the influence of hydrocarbon composition of base oil on dielectric dissipation factor of oil-paper composite system was studied at different temperatures. The results showed that the change of the content of saturated hydrocarbon and aromatic hydrocarbon in base oil had no obvious effect on the dielectric dissipation factor of oil immersed paperboard at low temperature, and the higher the content of alkane and aromatic hydrocarbon in base oil was, the greater the dielectric dissipation factor of oil immersed paperboard was. At the same time, the higher the sulfur content in base oil was, the greater the dielectric loss of the oil-paper composite system was, but the effect of sulfur content on dielectric loss at different temperatures was not significant. The ideal base oil for oil-paper composite system transformer oil is naphthenic base oil containing proper amount of aromatic hydrocarbons.

Key words: oil-paper composite system, transformer oil, hydrocarbon composition, dielectric dissipation factor, sulfur content