Converter transformer bushing is an insulation weak link of the converter transformer

especially

the radial temperature difference generated by the core of the bushing will cause the electric field to be distorted

which is prone to insulation fault during operation. Consequently

we studied the radial electric field distribution of a ±600 kV ultra-high voltage converter transformer bushing under different working conditions

and applied a nonlinear electric conductivity epoxy resin insulation to suppress the radial electric field distortion of the bushing. The research results show that the electric field distribution of the bushing core at the flange is distorted by radial temperature differences with the increasing of the bushing load

and the distortion field strength near the flange is as high as 12 kV/mm under full load. At the same time

the decrease in field strength of the casing core near the guide rod increases the electrical strength of the end SF6 gas by nearly three times

which is highly likely to cause gas discharge. After replacement of non-linear conductive epoxy resin insulation

the electric field distortion of the bushing core at the flange is greatly improved

and the insulation load of SF6 gas and transformer oil at the end of the bushing is also effectively alleviated. The epoxy core loss in non-linear bushing increases during its operation; however

compared with the current heating in the conductor

the loss increase can be ignored. The simulation results prove the feasibility of using nonlinear conductance epoxy resin insulation to suppress the electric field distortion of bushing core and reduce the probability of failure.