Effects of Considering A Stroke Angle Distribution on Estimating the Shielding Performance of Overhead Transmission Lines

The shielding analysis method recommended by the IEEE Working Group on Estimating the Lightning Performance of Transmission Lines is based on the Electrogeometric Model and the concept of striking distance. The simplistic assumption of a vertically descending leader is adopted, although a statistical distribution for the stroke angle has been previously proposed in the literature. This paper aimed to investigate the influence of assuming both vertical and non-vertical flashes on the evaluation of the shielding failure flashover rates of overhead transmission lines. The study is based on a modified Electrogeometric Model built in a procedure implemented by the authors in MATLAB, in a comparative perspective with the well-known IEEE Flash program. Parametric studies are performed to determine the sensitivity of the outage rates with respect to the parameters of the transmission line, the striking distance equation and leader angle distribution.