Converter transformer is the core equipment in converter station and its valve-side bushing

which extends horizontally and obliquely from the oil tank

is significantly affected by vertical seismic action. For enhancing the seismic performance of the converter transformer

a three-dimensional seismic isolation system

consisting of a sliding friction pendulum horizontal isolation system

a spring-viscous damper vertical isolation system and an anti-rocking device

is proposed. This isolation bearing is applied to a ±800 kV converter transformer. The seismic responses of the converter transformer before and after the installation of the seismic isolation system are calculated and analyzed through finite element numerical simulation. The results show that the three-dimensional seismic isolation significantly reduces the acceleration responses of the valve-side bushing at horizontal and vertical directions. Compared to horizontal isolation

the stress isolation efficiency at the root of the valve-side bushing of the three-dimensional isolation system is increased by approximately 12%. The displacement responses of the isolation system are mainly concentrated at the bearings

and the displacement of the upper structure

with the busing in particular

is significantly reduced than before isolation. The three-dimensional seismic isolation effectively enhances the seismic performance of the converter transformer and has excellent applicability in regions with high seismic intensity.