Dielectric Characteristics of the ±1100kV UHVDC Wall Bushing with SF6 Gas Insulation

The ±1100kV UHVDC wall bushing is the important power equipment in the ±1100kV DC power transmission project of China. However, the reported literature rarely mention its design method and the optimization of its insulation structure. In this paper, the “U” type structure including the metal-shielded core have been adopted in the design of the wall bushing. Moreover, the actual operating environment and the rated parameters of the ±1100kV UHVDC wall bushing have been analyzed. Then, the finite element method (FEM) analysis has been applied in the three-dimensional electric stress simulation of the UHVDC wall bushing. The E-field simulation results indicate that with the metal-shielded core, the potential and electric field distribution can be much more uniform along the composite insulator of the bushing. Therefore, the compact design of the wall bushing can be obtained by this designing scheme. On the other hand, with the type of the metal-shielded core, the high E-field strength areas are mainly concentrated on the metal shield and the outer grading ring of wall bushing. The relationship between the flash-over voltage and the insulation distance has been also discussed. This paper can provide the theoretical guidelines for design, manufacture and operation of the UHVDC wall bushing.