A new theory for torsional stiffness of multi-span bundle overhead transmission lines

A new theory for the torsional stiffness of multi-span bundle overhead power transmission lines is presented. The torsional mechanism is clarified. A simplified torsional stiffness formula is obtained which allows for the complex bundle stiffness to be directly calculated from the basic parameters. Applications in the choices of yoke plates and suspension clamps are detailed. The new theory correlates with experiments to a high degree of accuracy.