Advancements in underground cable material and design specifications of the largest rural electric co-ops

This paper discusses the technical advancements in medium voltage (15-35kV) underground residential distribution (URD) power cable material and design specifications for the largest rural electric co-ops. The data was obtained from responses furnished by fifty-seven of the largest electric cooperatives, selected on the number of underground miles installed. Special attention was given to their specification preferences for solid or filled conductors, insulation and conductor shield compounds, extrusion and curing methods, metallic shield type and jacket type and material. Utilities also provided key information on the number of cable miles installed each year, the voltage class, the insulation type and thickness specified, the percentage of cable direct buried versus installed in duct, and the cable tests and reports required. A number of utilities also furnished data on the percentage of cable used for replacement of failed cables and the cable vintage being replaced. The results provide meaningful information that enables all rural electric co-ops to compare their medium voltage underground cable specifications and practices with the largest utilities in their industry.