Influence of non-ceramic insulators' shed inclination on their long-term behaviour in cyclic rain and fog conditions

The paper presents the results of comparative tests of model composite insulators with housings made of HTV silicon rubber and sheds inclined at different angles (0 degrees, 10 degrees, 30 degrees). The main aim of the tests was to acquire experimental data for an assessment of the effect of the shed inclintion angle on the ageing degradation of composite insulators under high voltage in rain and fog conditions. The insulators were exposed to AC (50 Hz) voltage and water precipitation in a rain chamber and in a fog chamber. The tests showed clear differences in ageing times between insulators, leading to increased leakage current and surface electric discharges. It was found that the insulators with a large shed inclination angle (30 degrees) have a higher ageing resistance, particularly in rain conditions.