Ion-Implanted Epoxy With Graded Surface Conductivity: An Approach to Improve Surface Flashover Voltage

The electric field distribution along the insulator surface plays a significant role in improving surface flashover characteristics of the insulation in an HVdc power system. Functionally graded material with conductivity distribution ( $\sigma $ -FGM) is a promising approach that enables the electric field to be more uniform, which leads to hinder the surface flashover. This article proposes a novel method for graded conductivity materials using surface modification via argon (Ar $^{+}$ ) ion implantation. Epoxy samples with homogeneous and graded surface conductivity are prepared considering different ion implantations to verify the effectiveness of the proposed $\sigma $ -FGM method. Flashover tests of the virgin, homogeneously ion-implanted, and graded ion-implanted samples are conducted in air and vacuum at negative dc voltage. Moreover, finite-element method (FEM)-based simulations are carried out using COMSOL Multiphysics software to analyze the electric field relaxation before and after modification. The experimental findings indicate that the flashover characteristics of homogenously implanted samples are improved with the rise in implanted layer conductivity. In particular, the flashover voltage of samples with graded conductivity layers is improved by 27.71% in air and 28.90% in vacuum compared to the virgin samples. The experimental findings and theoretical analysis prove that ion-implantation-based graded conductivity material is a promising solution for the insulation of HVdc applications.