Hydrophobic Evaluation Of Polymer Insulator Based On Surface Discharge

The application of polymer insulator has been expanded in the field of power supply and distribution system all over the world. Hydrophobic is a prominent characteristic of outdoor polymeric insulators. However, due to the environmental influence, the chemical changes may take place and cause the loss of hydrophobic, which will endanger the long-term performance of outdoor insulators in service. Thus, the accurate evaluation on the insulator hydrophobicity is required.In this paper, six silicone rubber insulators were aged under AC and DC corona discharge. During the whole experimental process, both the dynamic morphology of water droplet and the induced discharge phenomena on the sample surface were captured by using a high-speed camera.Through analyzing the distribution and the characteristics of discharges, the relationship among the discharge area, the discharge light brightness fractal dimension and the ageing levels of insulator surface was established. With the increase of hydrophobic, the brightness, fractal dimension and the light intensity of discharges become much bigger.This paper studied that hydrophobic decreased gradually with the time lapsed under AC corona discharge conditions. With the decrease of surface hydrophobicity, the brightness and the light intensity of discharges become much stronger and so is the fractal dimension. Under DC corona conditions, the sample surface discharge phenomena have similar laws with this. Further, the trend is more obvious, because the DC corona aging is more serious. This paper focused on the discharge phenomenon of different samples which has different levels of HC. The results showed that with the increase of HC levels, the brightness, fractal dimension and the light intensity of discharges become much bigger .It has been found that with the decrease of surface hydrophobicity, the discharges become much stronger to cause the increasing tendency in the area, the brightness and the light intensity of discharges. Therefore, the method based on light characteristics of surface discharge was proposed for the hydrophobicity evaluation of silicone rubber insulators.