Tower Surge Impedance

Experimental and theoretical methods for determining the surge impedance of towers are presented. It is demonstrated that the values so obtained adequately describe the response of the tower when a transmission line is struck by lightning. A right cone representation for conventional double-circuit steel towers is proposed, and a theoretical analysis using field theory yields the surge impedance as Z= 60 ln (2/S) where S is the sine of the half-angle of the cone.