Extending the Service Life of 15KV Polyethylene URD Cable Using Silicone Liquid

In the late 1960´s and early 1970´s many electric utilities installed URD HMWPE and XLPE cable throughout their service territories. Within ten years, many utilities began to experience decreased service reliability and a major cause of the increased interruptions was failure of the URD cable. As early as the late 1970´s, Orange and Rockland Utilities became interested in rehabilitating URD cable since there appeared to be an extensive economic advantage over direct replacement of the failing URD cable. Early in the 1980´s, Orange and Rockland Utilities, in cooperation with the Empire State Electric Energy Research Corp., Inc. (ESEERCO), demonstrated the restoration of URD cables which contained electrochemical trees in the cable insulation of sufficient severity to cause extensive service failures. The ESEERCO project essentially removed the moisture in the cable by pushing nitrogen gas through the cable interstices until it was dried, and then impregnated the same cable with liquid acetophenone in order to restore the dielectric strength of the cable. While this method worked well, and to date no failures of the treated cable have occurred, the liquid had limitations since it changed its liquid state at lower temperatures. In addition, perpetual maintenance of the treated cable was required. Thus, a substrate liquid was pursued. Orange and Rockland Utilities sought an improved liquid to rehabilitate failing HMWPE and XLPE cables and Dow Corning Corp. developed a specific silicone fluid.