Application of flashover characteristics of air gaps to insulation co-ordination

Experimental data are presented on the flashover characteristics of rod-rod and rod-plane air gaps for unidirectional impulse voltages having different front durations. The data are used to examine a problem in the co-ordination of insulation, where it is required to protect a clearance approximating to a rod-plane configuration by a control gap provided by rod-rod electrodes. Comparisons are made with the flashover values for power-frequency voltages derived from published sources.