ABSTRACT
Following the development of the simplified model of the last step of the lightning stroke by C. F. Wagner, F. S. Young developed the geometric model with the primary and indeed sole purpose of showing that shielding angles should be decreased as tower height increases. Prior to this investigation, shielding angles of about 30° were used with success on all lines for which tower heights were in the range of 80 feet. The impetus for both Wagner’s and Young’s studies was the poor performance, 7.2 flashovers/100 miles-years, of the AG&E – OVEC 345-kV double circuit line, which had a tower height of 150 feet and employed a shielding angle of 33°. Although the geometric model has proven successful in determining the proper shielding angle, the aforementioned methods based on an improved theory of the last step of the lightning stroke has been proposed.
