Numerical Simulation of Water Droplet Impingement on Composite Insulator Surface and Analysis of Shed Configuration

Existing composite insulators’ sheds are easily bridged by icicles and their ice flashover performance is not obviously superior to that of glass and porcelain insulators. For the rational design and selection of composite insulators’ shed applied in icing area, the 3-D fluid field mathematical model of composite insulators was established and the water droplet trajectories were calculated in Lagrange framework according to the basic principles of fluid dynamics. Then the water-droplet impingement characteristics were determined. It was found that the collision coefficient(E) increases with increasing of air flow velocity or mean diameter of water droplet and the bottom surface inclination or shed distance, but decreases with increasing of top surface inclination, diameter or diameter ratio of shed, in which the increasing of diameter ratio is the key factor. The influence of shed distance on droplet collision coefficient can be neglected. According to the results, integrated the electrical characteristics of composite insulators, suggestions of the optimized shed structures of composite insulators used in iced area were obtained: top surface inclination is 15° and bottom surface inclination is 0°; diameters of sheds are different, there should be more than three small sheds between adjacent large sheds; the diameter ratio of sheds should be increased; shed distance should be more than 30 mm.