PARAMETERS AFFECTING ECONOMIC SELECTION OF CABLE SIZES

The evaluation of cable costs considers the present worth of funds req uired for a new cable installation. Two components make up this cost, first the initial investment cost, and second, the cost of losses over the life of the cable. Generally for a given voltage class, the capit al investment component increases as the conductor size increases. Con versely, the losses decrease as conductor size increases. Selection of cable size is currently based on ampacity considerations; that is, a cable with a minimum acceptable cross-sectional area is usually select ed without consideration of the cost of the losses that will occur dur ing the life of the cable. Since the cost of losses over the lifetime of the cable may be quite substantial, selection of a larger conductor size than required for ampacity consideration will often result in sm aller value of losses and, hence, may lead to a lower overall cost. A number of examples which demonstrate sensitivity of the conductor cros s-section and overall cost to variations in key parameters of the mode l are presented in the paper.