Study on low current arcs on surfaces of dielectric materials

External polymer insulators are widely used for their superior performance. One mechanism that can lead to serious damage to a polymer insulator is low current stable arcing on its surface. This paper describes experimental research towards quantifying the probability of formation of low current, stable arcs between two droplets on the surfaces of dielectric materials with different hydrophobicity, especially on silicone rubber based materials. Video and still cameras are used during the discharge process. The results show it is difficult to form a stable arc on the top surface of silicone rubber based materials because the two water droplets join together rapidly after power energization, thereby extinguishing the arc. On the underside of a horizontal plate, it is relatively easy to form stable arcs. It can be observed that the stability of a low current arc mainly depends upon the hydrophobicity of the material. Various factors that influence the characteristics of the arc, such as current and salinity of water are investigated. Theoretical analysis is also presented.