Diagnosis of hydrophobic condition of silicone rubber using dielectric measurement and image analysis

Dielectric measurement and image analysis are used to evaluate the hydrophobic condition of silicone rubber surface. Hydrophobicity of silicone rubber surface was studied by using image data analysis of sprayed water droplets on the sample surface. Hydrophobicity class, HC from 1 to 7, is evaluated by the analyzed image data indices. The water droplets on the sample surface are digitized and the image indices such as size and shape factor of the droplets were evaluated. After this evaluation, 3D mapping technique is used to evaluate the HC value. The hydrophobic condition of the sample surface was also determined by measuring dielectric property of silicone rubber using a pair of inter-digital electrodes. The dielectric properties were detected by using unbalanced operation of current comparator type capacitance bridge. The changes in dielectric loss current and the capacitive current by the change in hydrophobic condition were measured for every one cycle of AC applied field. Comparing of these results can define the degradation of hydrophobicity of polymer insulator more accurately.