Effect of Surface Roughness of Operating Composite Insulators on the Hydrophobicity characteristic

It is necessary to pretreat insulators before measuring the hydrophobicity of the composite insulators,however,the necessity of such pretreatment is questionable for the operating composite insulators.Therefore,we investigated the surface roughness of the light polluted shed,heavily polluted shed,chalking shed and the impact of surface roughness on hydrophobicity characteristic.Experimental results indicate that pretreatments on HC levels and static contact angles have a remarkable effect,totally different results can be obtained in the HC level test,and the static contact angle changes up to 15.3%.The surface roughness Raand RSM of sheds with different pollution levels change up to 130% and 269% after pretreatment.The composite insulators with high surface roughness degree totally lose the hydrophobicity,of which Raand RSMare 3.242μm and 400μm,respectively.The surface roughness can cause changes in the water drop's status and consequent changes in the static contact angle up to 31% in 10min,leading to difference between the results of the HC levels test and the static contact angle test.Thus the data of surface roughness for the composite insulators were suggested to be added into the hydrophobicity tests.