Cheng Zixia

Investigation on composite insulators in contaminated areas

The usage of composite insulators in various contaminated areas is increasing prominently in recent years. Most of composite insulators are operating in heavy or medium pollution environment in China. As the exposure time in the field prolonging, the change of hydrophobicity and the build-up of pollution layer directly affect pollution performance of the composite insulators. This paper is based on the work of investigation on the pollution performance and aging of nearly 40 composite insulators operated in Jiamusi city, the north east area of China. These composite insulators were removed from 110 kV lines, and they are all made of HTV silicone rubber and mostly are in service for nine years. Four aspects of hydrophobicity of these insulators are studied after the measurement of pollution status.

Study of water droplet discharge by electric field computation and high-speed video

In this paper, model of composite insulators were designed to study distortion, movement of the water droplets when discharging occurs on the shed surface of composite insulators applied with uniformity electric field. The distortion and movements of single and multiple water droplets on the surface of insulator in ac and dc electric fields were studied. The results show that the water droplets gradually increase in length in the action of electric field, and the distortion considerably increases with the increase of the electric fields. From these results, the effect of water droplets on flashover voltage is analyzed.

Four-parameter method for hydrophobicity judgement and mechanism of hydrophobicity transfer property

It is well known that the excellent pollution performance of silicone rubber (SR) insulators originates from its hydrophobicity and hydrophobicity transfer properties. With the sustainable growth of composite insulator usage in China, a convenient method should be given to judge the hydrophobicity properties and to help the utilities choose proper products. In this paper, a four-parameter method used in the evaluation of hydrophobicity status was introduced. The four parameters are hydrophobicity on clean surface, hydrophobicity loss property, hydrophobicity recovery property and hydrophobicity transfer property named H/sub c,/ H/sub l,/ H/sub r/ and H/sub t,/ respectively. Relative values of the four parameters, which were based on the research work of hydrophobicity, were also given. This method has already been used in some parts of China for its easy operation and effectiveness regarded. In addition, the mechanism of hydrophobicity transfer property was further investigated and the difference of the results between contact angle and hydrophobicity classification was also discussed in detail.