DESIGN OF RESIDENTIAL UNDERGROUND DISTRIBUTION SYSTEMS IN CANADIAN UTILITIES.

With the growth of residential housing subdivisions following the Second World War, electric utilities perceived a need to place their distribution plant underground for esthetic and operational reasons. In order to reduce the cost of these distribution systems, they adopted new materials and techniques of installation. The new technology gains much from the development of a concentric-neutral conductor with solid polymeric insulation, usually directly buried in the soil; a dead- or load-break connector whereby this conductor can be terminated; and apparatus which can be installed safely above or below grade. The reliability of the system is improved by looping and the provision of alternate sources. Statistics gathered from Canadian utilities show that, despite certain problems encountered in these underground systems, their costs are in the economic range. Further, both the frequency and duration of outages on these underground systems are lower than for comparable overhead systems, as had been hoped in their introductory phase.