Characteristics of Direct Lightning Strokes to Phase Conductors of UHV Transmission Lines

Since transmission towers are taller and interphase distances are longer for ultra-high voltage (UHV) transmission lines than for conventional transmission lines, it is important to know the features of direct lightning strokes to phase conductors. With this in mind, the features of direct lightning strokes to UHV transmission lines were observed and 81 datasets were obtained for seven years between 1998 and 2004. Of the 81 datasets, 79 recorded strokes from negative lightning, and the characteristic features of these direct lightning strokes were quantitatively evaluated by Electromagnetic Transients Program analysis of the current amplitude, front duration, and stroke duration. The frequency distribution of lightning strokes to each phase conductor was different from the estimated values obtained from conventional shielding models. Based on the cumulative frequency distribution of the current amplitude observed in this study, a method is proposed for calculating direct lightning stroke current as part of designing lightning protection