Comparative Performance of Uniform and Surface Functionally Graded BaTiO3-Sputtered Composite Insulators With and Without Defects

Abstract

Surface functional grading of gas-insulated switchgear (GIS) insulators using ${\text{BaTiO}}_3$ coatings has shown potential for improving electric field distribution under defect-free conditions; however, their performance on hybrid composite substrates and under realistic internal defect conditions remains insufficiently investigated. This study addresses these gaps through finite element analysis using COMSOL Multiphysics, chosen for its capability to model spatially varying dielectric properties and complex defect geometries under AC excitation. Representative GIS insulation defects; including gap voids (G-type), conductor protrusions (N-type) and free metallic particles (P-type) were modelled along with defect-free conditions. Five simultaneous performance metrics were evaluated: normalised electric field, tangential electric field, current density, leakage current and dielectric loss. Simulation results indicate that d-SFGM configurations consistently outperform d-uniform configurations across all evaluated metrics, with G-type defects yielding the largest field reductions (up to 44%–49%) and P-type defects exhibiting the highest instability. The hybrid epoxy/CF/SiC substrate demonstrated lower values across all evaluated performance metrics compared with epoxy/Al₂$O_3$. These findings provide simulation-based guidance for selecting coating configurations in GIS insulator design and may contribute to improving the reliability of compact urban substations.