Evaluation on Depth Profile of Surface Degradation of Polymeric Insulators by Microscopic Observation of the Cross Section

Development of evaluation methods and clarification of the degradation mechanisms of silicone rubbers used for the housing material is important to increase the long-term reliability of polymeric insulators. In this research, we investigated the depth profile of surface degradation of polymeric insulators used at an actual 66 kV transmission line for more 10 years. Changes in the ratio of elemental compositions and chemical structures of silicone rubbers were evaluated by microscopic observations of the cross sections using Scanning Electron Microscopy - Energy Dispersive X-ray Spectroscopy (SEM-EDX) and Infrared (IR) imaging analysis. As the results, increase of the ratio of Al/Si compositions of the silicone rubbers within approximate 100 μm deep from the surface was observed by SEM-EDX. Also, some changes in the chemical structures, supposedly oxidation of the silicone materials in the same area were defined by IR imaging analysis.