Lightning Investigation on Transmission Lines---V

Continuing an investigation of lightning effects on power transmission lines, a recent study confirms previously reached conclusions as to the effectiveness of overhead and buried ground wires. Also, direct stroke surge currents of from 2,000 to 100,000 amperes in tower structures were measured with the surge crest ammeter, and total stroke currents up to 220,000 amperes were indicated. Values for the rate of build-up of direct stroke currents and values of potentials in the tower were obtained. Negative polarity clouds were found to be the source of almost all direct strokes.