Simulation and Evolution Analysis of Temperature Field of Electrical Connection Structure for Grid-Side Bushing of Converter Transformer Under Seismic Conditions

The electrical connection structure of the grid-side bushing of a converter transformer is a core current-carrying component in ultra-high voltage direct current (UHVDC) transmission systems. Under seismic conditions, it is prone to overheating and discharge faults, endangering the safe operation of converter stations. To reveal the damage mechanism and temperature evolution law of the electrical connection structure under seismic conditions, this paper establishes a refined finite element model for the structure and conducts seismic response analysis. Combined with the empirical formula of contact resistance and the electrothermal coupling model, the evolution of contact resistance and distribution characteristics of the temperature field of the electrical connection structure under different seismic peak accelerations are analyzed. The results indicate that earthquakes disrupt the stress distribution at the electrical contact interface, causing eccentric load and stress concentration, reducing the effective high-stress current-carrying area. The contact resistance rises rapidly with increasing acceleration, leading to severe degradation of current-carrying performance. The increase in contact resistance results in a manifold increase of Joule heat, and both the maximum and minimum temperatures of the structure increase significantly as acceleration rises. This study clarifies the mechanical–electrothermal coupling response mechanism of the structure, providing theoretical basis and technical support for its seismic design, thermal stability evaluation, operation, maintenance, and overhaul.