Extending the service life of 15 kV polyethylene URD cable using silicone liquid

The authors describe methods and materials used to extend the useful life of extruded polyethylene insulated cables rated at 15 kV that have developed electrochemical trees in the insulation of sufficient severity to cause service failures. Earlier rehabilitation methods treated extruded dielectric cables with both gases and insulating liquids. This new method fills the cable and impregnates the insulation with a silicone liquid. This liquid, which is reactive, significantly improves the voltage breakdown strength of the cables, which had been reduced by electrochemical trees, and extends the useful service life of the cable. A review of the criteria used to develop the silicone liquid for this application and the methodology used to inject it into the cable are presented. An assessment of the costs for this life extension indicates a significantly lower cost than conventional cable replacement with little disturbance to the service and property of the customer