Influence of composite insulator inclination on its properties degradation in rain conditions

Results of ageing tests of composite insulators exposed to AC (50 Hz) high voltage and cyclic water precipitation in a rain chamber were presented. The subject of the investigation were composite insulators destined for 20 kV rated voltage with their housings made of HTV silicon rubber. The insulators were tested in horizontal, vertical and inclined position. During the tests, the leakage currents were recorded and surface hydrophobicity was estimated. Photo and video registration of the behavior of water drops on the tested surfaces were made. The following phenomena were described: non-uniform loss of insulator surface properties, merging of water drops which caused creation of conduction current paths, development of surface electric discharges. Essential influence of insulator operating position on the way of its surface wetting during rainfall and development of ageing process was described.