Electrothermal Simulation and Insulation Condition Evaluation of Converter Transformer Valve Side Bushing

Due to the laborious heat dissipation structure of the bushings, along with the continuously growing capacity of HVDC transmission projects and the corresponding converter transformers, the intertwined thermal-insulation issue has become the bottleneck for the safe and reliable operation of the valve side bushings. In this paper, the physical model of coupled thermal-electric field in the frequency domain is established considering the wideband harmonics generated by the HVDC converter. On this basis, an insulation condition assessment method is proposed. In order to solve the physics coupling model, this paper proposes a corresponding iterative solution process based on COMSOL Multiphysics. Using the above model and method, this paper analyzes the fields distribution of a bushing model and conducts an insulation evaluation. In the process of designing and maintaining the insulating part, more attention should be paid to the distribution of the electric field. Significantly increased areas and locations will be the weak link in insulation, but the temperature will still be a need-ism factor.