LOSS EVALUATION FOR UNDERGROUND TRANSMISSION AND DISTRIBUTION CABLE SYSTEMS

The calculation of losses has always been important to the cable system designer, since losses, and the thermal resistances through which the losses flow, are the basis for determining required conductor size. The cost of supplying those losses—in terms of demand and energy charges—has recently increased in concern because of generally higher charge rates for losses and because of growing sophistication by users in evaluating alternative systems. This paper is intended to discuss the sources of losses, the effects of losses on cable sizing, effects of load growth rates and load shapes on losses, and the economic evaluation of losses. The paper also addresses a slightly different type of losses: the energy costs for operating circulating and cooling equipment for forced-cooledcable systems. The purpose of this paper is to provide unified, consistent methods for the cable engineer and system planner to evaluate the magnitude of losses on a cable system and the costs of those losses. The paper has been prepared by the Cost of Losses Task Group of the IEEE Insulated Conductors Committee. © 1990 IEEE