Flashover voltage of silicone insulating surface covered by water droplets under AC voltage

•In the approach the number of water droplets rows and the distance between them are varied.•The performance of the samples decreases with the presence of water droplets.•The system withstand voltage increases when the row of droplets on the electrode axis is removed.•A limiting rows number from which the flashover voltage is minimal and constant was found. Discharges caused by water droplets on the surface of polymeric insulators can affect the long-term reliability of the component by lowering the surface hydrophobicity boosting surface discharges. The main objective of this work is to quantify the effect of different types of water drops arrangements, their position and dry bands width on the flashover voltage of the silicone insulating surface with non-uniform electric field systems. The tests were done on a rectangular sample under AC voltage. Water droplets with different conductivities and volumes were placed on the silicone rubber surface with a micropipette. A rod-rod electrode system is used. The findings of this work indicate that the performance of the samples decreases with the presence of water drops on their surfaces. Further, these experimental findings show that there is a limiting number of rows from which the flashover voltage of the insulation is minimal and constant. This minimum is a function of the distance between two successive rows. Finally, it is concluded that the system withstand voltage increases when the row of droplets on the electrode axis is removed.