The results of flashover tests on insulator models with various geometrical configurations under DC field are presented. Dimensional parameters are used to describe the influence of the insulator profile on the flashover performance. The effects of both the surface contamination level and the geometrical shape on the arc propagation characteristics are investigated. It is shown that the flashover voltage of an insulator model under DC field is significantly influenced by the relative width and depth of the insulator underrib. It is also shown that the arc path under DC field is a function of both the geometry and surface contamination distribution. >