Simulation Study on Electric Field and Charge Form of GIL Tri-Post Insulator Under the Influence of Electro-Thermal Coupling Field

The goal of this paper is to augment the insulation performance of tri-post insulators and evaluate their safety during operation. To achieve this goal, a multi-physics coupling simulation model incorporating electrical, thermal, and fluid dynamics aspects was established for tri-post insulators. Simulation calculations were conducted to analyze electric surface charge coupled with field strength, this facilitates an in-depth examination of the dynamics of the surface charge during the discharge and the evolution of the electric field along the surface in the context of electro-thermal coupling effects. Notably, the surface of the insulator's three columns, whose tangential electric field strength is mainly concentrated in the lower region of the support legs, reaching a maximum value of 2.47 kV/mm. Additionally, the electric field strength at the contact point where metal inserts are embedded in the epoxy, the electric field strength can elevate to a significant 4.48 kV/mm. The base of the support legs of DC tri-post insulators, especially at the interface with metal inserts, represents a vulnerable point prone to electric field distortion, which can easily lead to localized discharge and subsequent defect degradation, forming brittle fractures. Therefore, in the process of optimizing the design, careful consideration is necessary for scrutinizing the electric fields on the surfaces of the support legs and the embedded metal components when subjected to thermal gradients. The findings of this study serve as a foundation for subsequent fault analysis and optimization process designs for tri-post insulators.