Electric field calculation of dry DC bushing under complicated voltage

The converter transformer bushing is one of the key devices in high voltage direct current (HVDC) system, which has a complex insulation system. To comprehensively evaluate the insulation properties of ±600 kV dry DC bushing, a finite element model is built and the electric field distributions under complex voltage are calculated. Results show that: the electric field concentrates more in the epoxy resin under AC voltage while concentrates more in the SF₆ gas under DC voltage. Space charge will accumulate in the DC field, which can lead a tremendous change of electric field under the polarity reversal voltage. During the polarity reversal process, the maximum values of electric field in different materials appear depend on their material properties. Electric field calculation can provide advice to the insulation design of DC dry bushing.