Transmission line tower collapse investigation: A case study

Two adjacent 110kV self support suspension towers failed under broken conductor conditions. The conductor failed due to lightning damage and fatigue contributed to by Aeolian vibration. There were no earth wires on the structures which could prevent lightning damage and subsequent conductor breakage. The earth wires have a structural benefit of preventing a potential tower failure in excessive twisting of the tower top during broken phase conductor loading. This paper presents a methodology for the tower failure investigation using finite element modeling. The loading used under broken conductor conditions and the slenderness of members will be discussed. Recommendations for remedial strategies will be made.