Five-Year Field Investigation of Lightning Effects on Transmission Lines I-Data Summary and Suggestions for Improved Line Performance

A 5-year field investigation of lightning-stroke characteristics and effects on transmission lines was conducted by means of kineklydonographs (KKs) and other instruments. Results disclosed that characteristics differ in several important respects from previous concepts still widely accepted, and therefore warrant a new survey of line design practices leading to suggested methods for improvements. The initial rates of rise of stroke current are much steeper than is generally believed and tend to be uniform, independent of the current crest. This emphasizes the importance of low tower surge impedance, low tower height, multiple ground wires, and counterpoises. Induced voltages also appear to be more significant than previously believed and, hence, may merit preventive measures.