The efect of tighter conductor tensions on transmission line costs

Abstract

Conductor stringing tension plays an important part in overhead transmission line capital cost. This paper will demonstrate to what degree the weight of the supporting structures, the steel corealuminum ratio, and the selection of the optimum conductivity are influenced by loose or tight conductor stringing. It also will show the savings which could be effected if tighter conductor tensions were employed. The cost estimates and comparisons contained in the body of this paper sustain the hypothesis that tighter conductor stringing can result in substantial savings in overhead transmission line first cost. Annual cost of energy losses can be reduced by substituting lighter cored ACSR cables at tighter tensions for loosely strung larger cored cables of smaller conductivity at no increase in first cost. The treatment of the broken wire load is the greatest single obstacle in cost reduction with increased conductor tension. The influence which the treatment of the longitudinal load has upon tower weights points up that consideration of conductor tension becomes an even more important cost factor as the broken wire loads are relaxed. It cannot be emphasized too firmly that tighter conductor tensions will require a judicious selection of vibration protection hardware at suspension and strain points or fatigue breaks in the cable elements may well ensure. Forty years or more ago the effects of wind induced aeolian vibration were first recognized, yet we still live in the age of low tensions.