The lightning performance of unshielded steel-structure transmission lines

A method is presented for calculating the lightning performance of unshielded steel-structure transmission lines. The method is an adaptation of the Anderson/IEEE method for shielded lines, and it incorporates an algorithm for calculating separate magnitudes and frequency distributions of the strokes to the towers and the strokes to the conductors. The results of applying the method to 230 kV, 500 kV and 765 kV lines are presented, and the effects of voltage class, span and form of striking distance equation are discussed.>