Influence of viscosity and conductivity of water droplets on partial discharge inception voltages of polymeric insulating surfaces

This paper investigates the partial discharge inception voltage of a single water droplet with different conductivities and viscosities on silicon rubber insulator surface under the impact of tangential AC electric field stress. Outdoor polymeric insulators are subjected to different environmental conditions, causing the formation of different types of water droplets like rain water, fog, saline water etc. on the surface. In this contribution, the conductivity and viscosity of the water droplet have been varied independently in a wide range and the partial discharge inception voltage of the insulating surface in the presence of water droplets has been measured. The investigations are carried out at 50 Hz for 20 μl, 60 μl and 100 μl water droplets. It has been observed that conductivity has almost no effect on partial discharge inception voltage, but the increased viscosity of water droplet results in a higher inception voltage for all volumes.