Comparison of water droplet discharge behavior under surface-insulation and gap-insulation conditions

In power grid, a variety of different structures of surface insulation and gap insulation are inevitably exposed to humid or rainy weather. Even with the application of hydrophobic materials in some equipment, the presence of water droplets in the insulation structure cannot be completely avoided. The presence of water droplets will change the distribution of electric field and induce discharges in some distorted parts where are usually located in the interface between water droplets and other materials or on the surface of water droplets. Water droplet discharges are also the preliminary manifestation of more serious discharges in humid climate. Therefore, it is significant to study the discharge behavior of water droplets to evaluate the insulation status and the reliability of insulation design. In this work, the mechanism of water droplet discharge and its performance were experimentally explored under two typical insulation structures, namely, along the surface and in the gap, and a comparative analysis of the two was carried out to investigate the changes in the morphology of the water droplets under the action of the electric field and its effect on the discharge, as well as to obtain the effects of the insulation structure, the volume of the droplets, and the droplet location on the discharge. This study can lay the experimental foundation for constructing the mathematical model of discharge under rainfall conditions.