Comparative Study of Electric-thermal-mechanical of ±800kV U-type and Horizontal wall bushing

The U-type bushing adopts a modular structure, which consists of the indoor bushing, outdoor bushing and the gas-insulated metal-enclosed switchgear (GIS) bus. Its electrical, thermal and mechanical characteristics, as well as structural requirements are different from the conventional horizontal wall bushing. Taking the commonly used ±800kV/5000A bushing as an example, a design case is presented, which is compared with a horizontal bushing applied in real HVDC project. The distribution of electric-thermal-mechanical stress in key positions of the two types of bushing under various testing conditions is obtained by 3d finite element simulation. Based on the simulation results, the electric-thermal-mechanical properties of the two kinds of bushing are compared, which illustrated the distinctive characteristics of the U-type busing. Comparison shows that the U-type busing is slightly better in the electrical and thermal performance, and significantly better in mechanical stability than the horizontal one.