Non-Uniform Field Breakdown and Surface Flashover in Liquid Nitrogen Gaps for HTS Applications

Liquid nitrogen (LN₂) is used as a coolant and electrical insulation in many High Temperature Superconducting (HTS) applications. Hence a good understanding of the breakdown characteristics of this medium under a variety of practical electrode geometries and conditions is needed for design of high voltage equipment. While there is considerable literature on breakdown of LN₂ gaps for uniform (plane-plane) or quasi-uniform electric fields (sphere-plane), there is much less data available for highly non-uniform field gaps and for surface flashover along insulators. In this paper we present results on sphere-plane and cylindrical rod-plane gaps in LN₂ as a function of sphere and rod diameters and radius of the rod edge at 1 bar pressure. In addition the surface flashover voltages of Fiber-Reinforced Plastic (FRP) in LN₂ with these electrode arrangements will also be reported