Corona Ring Improvement to Surface Electric Field Stress Mitigation of 400 kV Composite Insulator

Abstract

This paper aims to enhance the performance of a 400 kV composite insulator by minimizing electric field stress along its surface using COMSOL Multiphysics. The study employs optimization techniques for the corona ring, initially targeting key parameters such as the ring tube radius, corona ring radius, and corona ring height. Recently used optimization algorithms for engineering applications, namely Constrained Optimization by Linear Approximation (COBYLA), Coordinate Search (CS), and Nelder-Mead (NM), are utilized to determine the most effective one for the optimization purpose. The results indicate that the three algorithms converge around similar values, with COBYLA exhibiting a lower iteration number. Furthermore, our research confirms that increasing the corona tube radius results in a reduction of electric field when considering the other optimized parameters; however, this leads to an increase in the corona ring weight.To resolve this concern, we conduct a re-optimization of the ring shape by targeting eight specific points that form a polynomial interface replacing the original ring. The obtained results demonstrate that the re-optimized shape effectively reduces surface electric field, although it leads to an increase in the ring weight. Nonetheless, this approach aids in identifying critical regions of surface deformation that interact with the electric field. In light of this, we explore an alternative approach that involves replacing the new shape with multiple corona rings positioned in the most deformed regions and then optimizing their positions. This approach helps to achieve better results of surface electric field and overall weight, under clean and polluted surfaces.