The hydrophobicity of silicone rubber insulators subjected to water droplet corona under HVDC potential

When the surface of a silicone rubber insulator gets wet, its hydrophobic surface properties promote the formation of discrete water droplets, These droplets cause a localised intensification of the electric field because of their spherical shape and high permittivity. The introduction of this field intensification causes the electric field to exceed the corona inception gradient and electric discharges occur on the surface of the insulator. Previous research has shown that this corona discharge around water droplets causes a temporary loss of hydrophobicity in the silicone rubber insulator housing. The work presented in this paper followed a structured investigation into the effects of water droplet corona on the hydrophobicity of silicone rubber insulators under HVDC potential. The results obtained show that both positive and negative corona led to temporal loss of hydrophobicity, depending on the size and conductivity of the water droplets.