Simulation Analysis of Electrical-Thermal-Fluid Coupling Property for Supporting Insulation in SF6 Filled HVDC Apparatus

Supporting insulation in SF
₆
-insulated high voltage direct current (HVDC) apparatus is a complicated issue as it involves the coupling behavior of electric field distribution, heat transfer process, and fluid property of SF
₆
gas. So far, comprehensive work investigating the insulation performance in this multiphysics coupled field has been absent. In this article, the distribution characteristics of state parameters in SF
₆
-insulated ±800-kV dc wall bushing have been simulated and analyzed under various coupled fields. The simulation result shows that, when the fluid behavior of SF
₆
gas is taken into consideration, the temperature and electric field distribution are substantially different from those in previous studies. Particularly, the postinsulator right above the HV conductor suffers from the concentration of high normal electric field, high tangential field, and a relative high temperature near the metal shell side, which greatly threatens the long-term insulation performance of the insulator and increases the risk of flashover. Furthermore, this article has investigated the effect of different supporting structures and material properties on the insulation performance of the bushing, based on which suggestions for insulator layout and material modulation are proposed. This article can serve as a reference for subsequent design and fault analysis on SF
₆
-insulated HV apparatus.