The long span problem in the analysis of conductor vibration damping

In analysis of vibration damping of overhead spans, expected severity is determined on the basis of the balance of vibration power supplied by the wind through vortex shedding against dissipation by self damping in the conductor and by damping devices. Conventional practice is to approximate the vibration of the span as a series of sine-shaped loops, all of equal amplitude, for purposes of estimating wind input and self damping. However, for long spans requiring efficient damping, most of the loops are not sine shaped, and loop amplitude varies along the span. The effects of these differences are explored by representing the vibration as opposite-moving waves that grow as they travel. Nonlinearity in the wind excitation and self damping functions is taken into account. Results show that so-called long span effects significantly reduce required span-end damping in long spans.