Effect of tornado loads on transmission lines

Of all the populated areas in Canada, Southwestern Ontario has experienced the highest tornado incidence and faces the greatest tornado damage. About 1 or 2 tornadoes per 10000 km/sup 2/ can be expected there annually. The probability of a tornado strike at a given point is very small but the probability of a transmission line being crossed by a tornado is significant. The purpose of this paper is to review the literature related to tornadoes in Ontario and to investigate the effect of tornado loads on transmission lines. Based on this investigation a design basis tornado loading for transmission towers is proposed.>