Underground cable technical trends for the largest rural electric co-ops

This paper discusses the technical trends, purchasing requirements, and installation practices for medium-voltage (15-35 kV) underground residential distribution (URD) insulated power cables specified by rural electric co-ops. The data was obtained from survey replies by 50 of the largest electric cooperatives, selected on their number of underground miles installed. These utilities furnished key information about their specification preferences for URD power cables including the following: filled/solid conductors, insulation and conductor shield compounds, extrusion and curing methods, copper neutral type, jacket type and material, and cable acceptance tests. Utilities also provided information on the number of cable miles purchased each year, the voltage class and insulation thickness specified and the percentage of cable direct buried versus installed in duct. The results provide meaningful information that enables all rural electric co-ops to determine whether or not their own URD cable specifications are keeping pace with the industry.