The Prestrike Theory and Other Effects in the Lightning Stroke

Because of the high lightning outage rates being experienced on high-voltage transmission lines, a re-examination of the physical nature of lightning was made. The investigation led to the following: 1. A theory of the time and space dynamics of burst corona was evolved, and justified within the limits of available data. 2. The burst corona concepts were used to devise a theory of the physical processes involved in the step-by-step advance of the initial leader. 3. The combination of items 1 and 2 led to the conclusion that the head or lower-most portion of the initial leader contains a very large concentration of immediately available energy. 4. The rapid dumping of the leader head charge precedes the return lightning stroke. It is therefore termed a "prestrikerestrike." It results in the delivery of a high-magnitude short-time current pulse into the stricken tower. 5. The prestrike current flowing into the tower creates high-magnitude short-time voltage spikes at the tower top. It is believed that, with certain ranges of transmission-line design constants, the prestrike current determines the outage rate, rather than the return stroke current. Also, that the phenomenon accounts for the heretofore unexplained high outage rates on some transmission lines. 6. A return stroke mechanism is suggested, the details of which indicate that the current crest is reached in 5 to 10 ¿sec. 7. The theories are correlated with Boys camera photographic records. 8.