Monitoring the condition of insulator shed materials in overhead distribution networks

Methods of sampling and analyzing the surface material of sheds of composite insulators are reviewed. It is shown that scanning electron microscopy gives useful information from slivers cut from the insulator surfaces, and emission Fourier transform infrared (FTIR) spectroscopy enables derivation of indicators of material oxidation to be developed from surface swabbing with solvents. FTIR absorption spectroscopy and diffuse reflectance FTIR spectroscopy give indicators of surface chalking for ethylene propylene diene monomer (EPDM) insulators. X-ray photoelectron spectroscopy is used to determine surface layer elemental composition and concentration of oxidized bonds. The techniques are applied to field aged 275 kV EPDM and silicone rubber insulators and tentative correlations developed between surface condition and leakage current. Cluster analysis of results from sampling of a large population of EPDM insulators shows that the surface analysis methods facilitate grouping by location and manufacturer