Multiphysics Simulation Study of ±800kV SF 6 Gas Insulated Wall Bushing with Two Structures

UHVDC wall bushing is one of the key equipments of UHV DC power transmission. The ±800kV SF 6 gas-insulated DC wall bushing has been applied in many China's UHVDC projects. However, ±800kV SF 6 gas-insulated DC wall bushings exposed some problems during operation. In some bushings, flashover discharges occur on the legs of the three-support insulators used to support the conductive rods, and there is evidence of overheating in the butt joint part. Besides, a large amount of aluminum fluoride powder is accumulated on the surface of the conductive rods. In this paper, multiphysics simulation calculations are performed for two typical design structures of ±800kV SF 6 gas insulated wall bushings. The comparison of the electric field strength under four working conditions and stress distribution under the conditions of self weight, wind load, and icing load is given. The results show that the point of maximum electric field strength occurs at the maximum curvature of the shield of the epoxy insulator. The maximum field strength point of the shield cover surface at the flange appears at the R angle. When the structure is changed from three-support to double-support, the maximum field strength of the insulator shield is increased, the maximum surface field strength of the inserts is reduced. The maximum stress of the bushing occurs at the joint between the through-wall cylinder and the hollow composite insulator, and the maximum displacement occurs at the small shield ring at the outdoor end. This paper provides guidance for the structural optimization and operation and maintenance strategies of bushing.