Flashover influence of fog rate on the characteristics of polluted silicone-rubber insulators

This paper presents an experimental investigation on flashover performance of silicone rubber (SiR) outdoor insulators. The AC flashover-voltage (FOV) of selected insulator designs is measured adopting the clean fog test and a high voltage ramp test. A conventional insulator design with a plain surface has been tested and compared with insulators having a textured surface. The FOV dependency on the pollution severity level is quantified. The influence of SiR profiles and wetting rate on the mean FOV are also investigated. For different ranges of wetting and pollution severity conditions, the results showed that the textured insulator designs exhibit an increased flashover performance compared with conventional non-textured insulators. Textured insulators can offer an increased FOV performance up to 16% compared with the average FOV of the conventional insulator. Under lower fog rate, the FOV level for both insulator types does not gradually increase with the testing time but is characterised by a U-trend. For moderate and high fog rates, a stable increase in FOV is observed. The result gives an indication that the average FOV is substantially affected by the higher fog rate for both insulator profiles. Furthermore, a greater improvement was gained on the mean FOV under textured design.