A Tree Growth Inhibiting Insulation for Power Cable

This paper describes a power cable insulation with a tree growth inhibiting additive that is nowommer commercially available for use by the electric utilities. The new insulating resin inhibits the growth of both electrical and water trees. A major cause of insulation failure is the progressive ive degradation process called treeing. There is general agreement that electrical and water trees cause insulation degradation leading to cable failure. This paper deals with a thermoplastic polyethylene insulating resin for use in power cable systems. Dodecanol is added to polyethylene to inhibit the growth of both electrical and water trees. The differences between electrical and water trees are reviewed. Test methods for evaluating insulating compositions for resistance to electrical and water tree growth are presented using small laboratory samples in accelerated tests. Data obtained in special model cables show the extent of migration of the dodecanol in accelerated tests. Test results on full sized commercial cables are discussed.