The relation between behaviors of water droplet on the polymer surface and third harmonic wave component in salt fog ageing test

In this paper, the experimental results from examining the electrical insulating characteristics and third harmonic components in salt fog aging test for polymer materials are presented. From the aging test results, when polymer hydrophobicity deteriorates with aging time, waterdroplets will make contact in the case of vibration of the waterdroplet under AC applied voltage, deteriorate the resistance on the polymer surface and increase harmonic components of leakage current. Investigations of form change in waterdroplets and change in leakage current in humid conditions thus the rate of the third harmonics were done. Also investigations on polymer hydrophobicity deterioration, contamination of the material surface by salt and the increase of third harmonics with insulation deterioration were conducted. The results showed that, the third harmonics increased with aging time and the rate of the third harmonics to a fundamental wave component also increased. The above-mentioned summary is presumed to be related to the increase in dryband arcing.