Study On Hydrophobicity Evaluation Of Composite Insulators And The Influences Of Hydrophobicity On Flashover Characteristics

Composite insulators in power network operation were aged because of the combined effects of the electric field,ultraviolet,the contamination and so on. The aging of composite insulators led to decline of the hydrophobicity, which lowered the flashover voltages of the silicone rubber composite insulator, increased the flashover probability of the silicone rubber composite insulator and reduced the reliability of power system operation. To detect potential accident of the composite insulators in time, avoid incidents of emergency and improve the safety and reliability of transmission line, it is necessary to carry out scientific and effective studies on the detection and performance evaluation with the composite insulators in the power network operation. The methods of the detection and performance evaluation with the composite insulators in the power network operation are immature, and the quantitative relationships between the hydrophobicity and the insulation characteristics haven't known for us. This paper carries out some studies on the new methods of hydrophobicity evaluation of composite insulators and the flashover characteristics of the composite insulators. The work focuses mainly on the following contents:â‘ Theory of dynamic contact angle was analyzed,combining with theoretical analysis of the different hydrophobicity classes of composite insulators, different hydrophobicity composite insulators using the method of dynamic contact angle were measured,and the scanning electron microscope analysis (SEM) of the surface morphology on different hydrophobic compsite insulators, by which the feasibility of hydrophobicity evaluation of composite insulators using the dynamic contact angle was verified, were carried out.â‘¡Based on the methods of hydrophobicity evaluation using the dynamic contact angle, this paper studied the factors affected hydrophobicity of the composite insulators, measured the dynamic contact angle in different climate temperature, in different immersion times and in different pH values, analyzed the influences of climate temperature and humidity on levels hydrophobicity of composite insulators, discussed the characteristics and the reasons of"unidentified flashover", which usally occurred on the composite insulators, studied the influences of the immersion times on the hydrophobicity, analyzed the effects of pH values on the hydrophobicity classes and explored the effects of pH values on the operation of the composite insulators. â‘¢The simplified model of composite insulators in operation was proposed,and up-down method was employed in a large number of contamination flashover tests when the composite insulators had different hydrophobicity levels and contamination levels. Then theories of mathematical statistics were adopted to study the flashover probability on the silicone rubber composite insulators sheet the influences of the receding angle and the salt deposit density on the flashover voltages and the flashover probabilities. Based on the regulations of the specific creepage distances in the standards of different contamination classifaction, divisions of the safe area of the composite insulators on power plants and the substations were accomplished.The above results revealed that the method of dynamic contact angle could objectively evaluate the hydrophobicity. By this method this paper studied the factors affected hydrophobicity of the composite insulators, employed up-down methods to study the flashover charactirasitc on the composite insulator chip, evaluated the reliability of the composite insulators.