Abridgment of rationalization of station insulating structures with respect to insulation of the transmission line

The purpose of this paper is to present a logical basis for the insulation of transmission lines and substations using as a basis the characteristics of traveling waves produced by lightning discharges. The method presented was formulated from the data obtained from the cathode ray oscillograms of actual line surges and upon the laboratory work in which the impulse flashover characteristics of insulating structures was determined. The breakdown volt — time characteristics of various forms of insulation are presented. Using these curves of various forms of gaps in the known characteristics of traveling waves, insulation of the transmission line at various distances from the gap is determined so that flashover will be unlikely to occur at these points. A similar method of analysis is made upon substations and lines protected by lightning arresters, but with the known characteristics of lightning arresters, the insulation on the line up to points 1000 to 5000 ft. away can be apportioned so that the lightning arrester will take the discharge, preventing the flashover of insulation. The system set forth in the paper enables the transmission engineer to design the line and substation in an economical manner and obtain adequate protection for all points desired.