Costs and Unreliability Minimization of Transmission System Shield Wires

The purpose of this investigation is to improve the efficiency of the transmission lines by minimizing the current flowing through the shield wires which are utilized along the phase wires to protect them from lightning. The result of this investigation is presented by computation of currents coupled into the shield wires from balanced current flows in parallel three phase circuits and a computation of current flow in the shield wires during short circuit condition when the shield wires become a part of the ground return circuit. A computer package that evaluates the shield wire current for balanced three phase circuits is developed. Results for a specific vertically configured transmission system art presented in this paper.