Accelerated Life Testing of Wet Cable Specimens at Frequencies Above 60 Hz

Abstract

The use of underground power distribution cables insulated with extruded layers of solid organic dielectrics has undergone a marked increase in recent years as a result of their impressive record of safety, economy and reliability. Moreover, environmental considerations have added further impetus to the deployment of underground distribution circuits, thereby increasing further the demand for extruded dielectric cables. While it has traditionally been an object of power cable manufacturers and users to increase the expected lifetime and serviceability of extruded dielectric cables, these attempts have now assumed a greater importance because of the expense involved in removing and replacing failed cables. Simultaneously, the constantly increasing power loads have required the construction of more sophisticated, more efficient and increasingly higher voltage cables. More recently, the signficant improvements, which have extended the useful service lives of solid extruded dielectric cables have centered on the use of extruded semiconducting conductor and insulation shields, cross-linked or vulcanized insulations and lower dielectric loss compositions. Many miles of these improved solid dielectric cables are now widely used in direct burial with various methods of installation. Increased experience with solid dielectric cables has brought to light a number of problems that were not anticipated when the change from paper-oil constructions began. Particular difficulties have been encountered with cables installed in wet locations, where they were subject to formation of water trees.