Electric Field Augmentation on Surfaces of Field Aged Composite Insulators Under Varying Contamination Conditions

The long-term reliability of high-voltage polymeric insulators is critically affected by surfacedegradation processes driven by environmental and electrical stressors. In our prior work, the role of hydrophobicity loss in intensifying surface electric field stress was established using finite element modeling. This study extends that investigation by experimentally assessing the severity and spatial variability of environmental pollution—specifically, soluble and non-soluble deposits—on field-aged 380-kV composite insulators that had been in service for over a decade. Using standardized procedures defined in IEC 60507, the Equivalent Salt Deposit Density (ESDD) and Non-Soluble Deposit Density (NSDD) were measured on individual sheds along the insulator profile to capture localized contamination patterns. Results reveal strong non-uniformity in pollution distribution, with significantly higher contamination levels on lower sheds due to gravitational runoff and environmental exposure asymmetry. Finite Element Method simulations were performed using COMSOL Multiphysics to evaluate the surface electric field distribution on degraded insulators. Material properties and boundary conditions were defined to reflect field-aged conditions and shed-level pollution gradients. The electric field maps showed intensified surface stress in regions with combined effects of hydrophobicity loss and high ESDD/NSDD values, particularly near the lower sheds. Microscopic observations further confirmed contaminant accumulation and physical erosion in these high-risk regions. The findings offer a comprehensive degradation model that integrates field-contamination data with electric field intensification mechanisms. This study provides actionable insights for predictive maintenance, condition assessment, and improved insulation design under polluted service environments.