A three-dimensional model of ±1 100 k V DC converter valve module is established to simulate and opti-mize the electric field distributions on the metal parts and interlayer insulators in the module. Single-valve voltagewithstand simulation tests are conducted on the model in both AC and DC conditions to obtain the electric field distri-butions on the metal parts and the insulators

and to further optimize the insulation of the model. Test results showthat:（1） severe electric field distribution on the heat sink is observed in DC condition;（2） the electric fields on thesurfaces of busbar and pipe fittings are all within the limits in both AC and DC conditions;and（3） the electric fieldson the interlayer insulators and their fittings are far lower that the corresponding limits in both AC and DC conditions.Moreover

the chamfer radius of the heat sink is optimized to make its surface electric field reduce to within the limit.It is revealed that reduction of interlayer spacing can still ensure the electric fields on the interlayer insulators andmetal parts being in safe range.