Travel Time of Transmission Towers

In prediction of HV and EHV lightning outage rates, the tower surge response consists of two parameters, the tower impedance and the tower travel time. Of the two, tower travel time has a larger effect on the predictions. A new model for tower travel time is developed based on the relationship between tower capacitance and tower surface area. Effects of tower crossarms and other features are modelled correctly by the new theory. When the new model is used, improved lightning outage rate prediction accuracy is obtained for 500kV single circuit lines.