An enhanced water tree-retardant crosslinked polyethylene for improved reliability and longevity of distribution power cables

Additive “water tree-retardant” technology for crosslinked polyethylene insulation (TR-XLPE) has served the power distribution market well for over 25 years. The present work considers the opportunity to extend performance beyond TR-XLPE through the use of a supplemental additive to work in conjunction with the established tree-retardant additive technology. “Enhanced tree-retardant crosslinked polyethylene” (EnTR-XLPE) has demonstrated a significant extension in cable life in an accelerated wet-electrical cable test with 15 kV power cable cores subjected to an aging stress of 8kV/mm. The two-fold increase in cable life prompted evaluations of EnTR-XLPE in high-stress cable designs subjected to a 60% higher nominal aging stress (over 12 kV/mm). A qualitative comparison was conducted to determine the extent of water tree growth for cable samples of TR-XLPE and EnTR-XLPE aged under similar conditions. The results suggest that the EnTR-XLPE system reduced the density of small water-trees present and provided better resistance of vented water tree initiation from both the conductor shield and the insulation shield. Cables prepared with EnTR-XLPE also demonstrated stability of dissipation factor over several weeks of electrical aging with a 140°C conductor temperature, which is a requirement in the ICEA-ANSI standards for a continuous operating temperature rating of 105°C.