Application of Spill Gaps and Selection of Insulation Levels

This paper presents, from the viewpoint of the engineer who plans and operates electric power systems, the application logic or theory and the performance results with various forms of spill gaps, for the protection of circuits and equipment from lightning, and the selection of insulation levels co-ordinated with this type of protection. The performance results are largely confined to transmission voltages, although the same general principles and logic apply over the entire transmission and distribution operating voltage range.