Formulas for conductor size according to cost of resistance loss

IN DESIGNING an electric-power line the choice of conductor depends on several factors such as mechanical strength, corona loss, reactance, and resistance. In the early years of electric-power transmission and distribution, a size of conductor was chosen which was considered the best in view of all the requirements. At present so many different types of line conductors are available that each feature can be provided for almost independently. Thus, a core of steel or bronze may be specified to provide the required mechanical strength; a hollow conductor may be chosen to avoid corona and to reduce the reactance; and the resistance, that is the current density, may be chosen according to the cost of resistance loss or according to temperature rise.