Electric field and energy computation on wet insulating surfaces

The paper presents the results of electric field and energy computation on insulating surfaces covered by water in the form ranging from small discrete droplets to large wet patches. The goal of this study was to understand the differences in the flash-over performance of outdoor insulators, in particular nonceramic insulators, under contaminated conditions as a function of surface wettability. The computational algorithm is based on the charge simulation method. A decrease in the maximum electric field at the water droplet tip is obtained as the droplet size increases, however, the electrostatic potential energy increases with the size of the water droplet, which might increase the surface discharge intensity. The role of the coalescence of small water droplets into larger droplets and filaments on the electric field and energy has been investigated. The location of such larger water bodies with respect to the electrodes has been examined. These computations shed some light not only on the role of hydrophobic surfaces but also on the location of hydrophobic surfaces along the insulator on the flashover performance of outdoor insulators. It has been shown that these computations provide quantitative data that compliments information obtained from simpler techniques such as visual observation and surface resistance measurements, for the purpose of assessing the performance of insulators in service.