Abstract
The fast development of gas insulated switchgear (GIS) equipment using pressursied SF6 as an insulant, and the recognition that insulation failures are often encountered in practical systems due to electrode surface imperfections, presence of free particles and sharp edges, there is a great concern to substitute SF6 for promising candidates gas. In this regard, nonuniform field breakdown data of SF6/gas mixtures are of considerable interest as they provide valuable information on the fundamental physical processes.