Underground cable specification advances and installation practices of the largest investor-owned utilities

A 2003 study examined the 15- to 35-kV underground residential distribution (URD) power cable specifications and installation practices of 60 large investor-owned utilities (IOUs). A distinctive 10-year trend was established in insulation material preferences. The design and material specifications of the most widely used underground cable instructions were found to be 15- or 25-kV voltage class, solid or filled strand conductor, TRXLPE or EPR insulation of 175 or 260 mil thickness, concentric copper neutral wires, and an encapsulating LLDPE jacket. One-half of all URD cables were installed in duct, and the other half were directly buried. Of all new cable, 13% was used for replacement of old failing cable. More than one-half of the 60 utilities studied tried cable rejuvination for extending cable life. Seventy percent of those attempting rejuvination expressed satisfaction with the results.