Loop Plant Modeling: A Simple Model for Studying Feeder Capacity Expansion

As described by N. G. Long 1 (this issue), the feeder portion of the overall loop plant consists of cables, conduit, and various other hardware. It provides communication paths, usually consisting of a pair of copper wires, between the central office and the distribution plant. Additional cables, and perhaps conduit to house those cables, are added to the feeder over time as existing spare is depleted by growth in demand. Optimally sizing such additional cables and conduit is an investment decision problem known as a capacity expansion problem. 2 A sophisticated computer program, called EFRAP,3 has been developed for solving a more general version of the feeder capacity expansion problem than we shall consider here. Our aim in this paper is to develop a manageable "analytic" model of feeder sizing. While we thus ignore some aspects of the problem, such as demand in more than one gauge, which are included in the more sophisticated approach, we can more easily include others, such as the use of temporary pair gain systems (see 807