AC flashover voltage and assessment of surface degradations of various polymeric materials in clean and salt fogs

This paper is devoted to the assessment of the resistance to tracking and the severity of surface degradation occurring after performing flashover (FOV) tests on insulator model in polluted environments and on various polymeric materials widely used for medium voltage cables accessories (insulators, terminations and anchoring clamps). The tested materials cover thermoplastics (namely polyamide 6 (PA6/50) and polycarbonate (PC/40)), two cycloaliphatic epoxy resins (namely CEP and hydrophobic CEP (HCEP)) and one EPDM based materials noted as EPDM. FOV experiments have been carried out on polymeric specimens in clean (light) and salt (heavy) fog. A new characterization method based on the electro-geometrical parameters (FOV versus leakage distance) for each polymer is used. It appears that the resistance to tracking resulting from FOV arcs may be assessed via the slope of FOV curves versus the leakage distance and can be used as an indicator of surface degradation in clean or salt fog. The higher the slope value, the stronger the polymeric surface is against tracking and erosion.