Research on dielectric loss characteristic of 550kV AC resin-impregnated paper oil-SF6 bushing

This paper studied the dielectric loss characteristic of the first 550kV AC RIP oil-SF₆ bushing designed and manufactured by China. A testing platform was established in the 1000kV UHV AC testing base of China, and thermal stability test of the bushing at different temperature were carried out on the platform. The influence rules of temperature and voltage on the dielectric dissipation factor (tanδ) of the bushing was obtained in this paper. Test results demonstrated that the tanδ of the bushing decreases slowly while testing time increasing, and decrease to a steady value at every test temperature (25°C~90°C). When the bushing reaches thermal-stabilization at a certain temperature, its tand varied a little with testing voltages. Similar to the pure epoxy, the tand of the RIP oil-SF₆ bushing decreases first and then increases with the increase of temperature, that is accordance to the dielectric´s physicochemical characteristic in the alternative electric field. The tested bushing shows good insulating characteristic in the testing temperature range, the main insulation material of the bushing has stable and reliable insulating performance. The testing results can provide reference for researching 1100kV AC RIP Oil-SF₆ bushing in China.