The insulation coordination of the UHVDC converter station plays an important role in the security andeconomic of UHVDC system. In this paper

we build the simulation model of the ±1 100 k V UHVDC converter sta-tion based on PSCAD for the arrester configuration scheme of ±1 100 k V converter station. And using the system con-trol parameter for reference

we simulate and analyze the effect of the different layout scheme of the smoothing reac-tor on the highest operating voltage in each key point of the converter valve system and analyze the voltage variationat valve-side on the highest converter transformer when happening grounding fault on the DC line. The results showthat the highest operating voltage of the key position can be reduced by about 33 k V（3%）and the voltage variation ofvalve-side winding can be ruduced by about 60 k V by separating arrangement of split smoothing reactor

the simula-tion data is of reference significance to the overvoltage protection of ±1 100 k V converter station.