Lightning Performance -- I Shielding Failures Simplified

A radically simplified method for determining shielding failure and shielding failure outage rates is presented. The method is shown to have excellent correlation with over 120,000 km-yrs of actual line outage rates (1974 CIGRE Survey). For lines of realistic design, total shielding failure rate is found to be a function dependent only on the maximum strike distance, which is governed by line configuration and height. Shielding failure outage rate depends on line configuration and CFO, and depends heavily on the statistical distribution of heights along the line. Methodology is developed to utilize or to approximate such distributions.