To study seismic performance of the gas insulated transmission line（GIL） in UHV converter station

the incoming GIL of a 550 kV AC filter is taken as the research object in this paper. The factors

such as different types of supports

different types of connection between the three-pillar insulator and the GIL shell

and GIL internal conductor joint slip

were taken into account

so that a fine finite element model of GIL composed of inner conductor

three-pillar insulator

shell and supports was established. Time history response analysis was carried out under the condition of three-direction seismic input to study the seismic response characteristics and the weak position of GIL-support system.The results show that the average acceleration amplification coefficient of the movable support is more than 2. Under the rare earthquake of 8-degree seismic intensity

the displacement of the connection of the GIL inner conductor exceeds the limit of 48 mm and the average stress peak response of the shell exceeds the allowable stress value. The average stress response of conductor in GIL exceeds the allowable stress value under the rare earthquake of 9-degree seismic intensity.The weak positions of GIL are the inner conductor connector and the shell in the vertical corner during earthquake. In the design

the dynamic amplification of the movable support should be focused on

and displacement of the GIL inner conductor joint and the stress response of the shell should be taken into consideration.