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Optimal Design of Insulation Structure of Converter Transformer Valve-Side Bushing Based on Electric Field Balance

With the continuous advancement of DC transmission projects around the world, the valve-side bushings of converter transformers working in complex harmonic environments have become nodes with high failure rates because of electric field stress. The main insulating structure in the existing valve-side bushing is formed by stacking structures of equal thickness, in which aluminum foil layers with a uniform electric field are inserted. In practice, such a design is difficult to achieve the overall optimum. Therefore, this paper proposes an optimal selection method for the thickness of the insulating plate of the converter transformer valve-side bushing based on electric field equalization. The method realizes the reasonable selection of thickness according to the radial distribution law of the electric field based on the finite element calculation in the frequency domain. In this paper, the COMSOL Multiphysics software is used to optimize the design of the insulation structure of a valve-side bushing, and the optimization effect is simulated and verified, which fully proves the rationality of the method proposed in this paper.