Grading ring parameters optimization for 220 kV metal-oxide arrester using 3D-FEM method and bat algorithm

Aging of metal oxide surge arresters is mainly affected by the high electric stress near the high voltage electrode. It has been observed that the distribution of voltage and electric field along an arrester is non-uniform. In this paper, the effect of grading ring geometrical parameters is investigated in order to achieve a more uniform electric field and voltage distribution. A 3D finite element method was employed based on COMSOL MULTIPHYSICS software to calculate these latter. The optimal design of grading ring is achieved by minimizing the electric field along the active column of varistors using a reduced number of simulations based on the Taguchi design and a bat algorithm. Initially, simulation results for a single grading ring were analysed. By using an optimal design of the single ring, the electric field is reduced by 42% in the top of the 220 kV metal oxide surge arrester and the voltage distribution can be improved. It was proposed to install an additional ring at the top of the metal oxide surge arrester. Simulation results shows that using of an optimal design of grading rings, the distribution of voltage and electric field along the surge arrester can be made as uniform as possible.