Comparative evaluation by laboratory aging of 15 and 35 kV extruded dielectric cables

It is pointed out that utility engineers encounter a significant problem in discerning the accuracy of claims of superior cable quality and in identifying cables which will provide reliable performance over their anticipated life. The authors, in two independent investigations of 15 and 35 kV cables, have compared the performance of a number of cables made with different compounds by different manufacturers. It is shown that judging cables by their unaged voltage breakdown characteristics alone can be very misleading; that, in the long run, dry-cured cables aged in moist environments rapidly lose their original dielectric strength advantage; that certain ethylene-propylene rubber formulations degrade as fast as cross-linked polyethylene; that the best overall results during aging are obtained with tree-resistant polyethylene insulated cables; and that from a voltage-breakdown point of view water-tree length is more influential than the number of water trees