The Sichuan-Chongqing UHV AC project is presently the UHV AC project with the highest altitude in the world

and it faces the triple challenges of high altitude

heavy ice coating and high seismic intensity for the first time. The application 1 100 kV GIS composite bushing of low altitude UHV substations to the high-altitude areas will face such difficulties as insufficient external insulation and higher seismic vulnerability. In order to solve these problems

the key technology for the development of 1 100 kV GIS composite bushing at high altitude of 4 000 m is studied in this paper

the correction methods for the outer insulation voltage and dry arc distance of the high-altitude bushing are proposed

and the rationality of the field strength of the key parts of the inner and outer insulation of the bushing as well as the optimization of the electric field on the surface of the shed are analyzed. Moreover

the internal and external insulation as well as the seismic performance reliability of the product are verified by various testing means

which effectively support the construction of Sichuan-Chongqing UHV AC project.