Polymeric insulators for MV cable to overhead line connection

When underground cables are connected to overhead lines a number of basic functions must be fulfilled by the terminating device: electrical continuity from insulated cable conductors to (generally) uninsulated bare lines; sealing of the cable end against ingress of contaminants and environmental degradation; provision of insulating surfaces between live conductors and earthed parts of the cable or line support structures, that will remain stable throughout the life of the installation; and mechanical fixing of the component parts of the cable so as to provide support and prevent mechanical vibration from the line from passing into the cable. There is now a wide choice of terminating methods to accomplish these functions, but all are crucially dependant on effective outdoor insulation for a long and trouble free service life. The author examines some of the alternatives with particular reference to the use of polymers to supersede traditional outdoor insulation materials