DEVELOPMENT OF XLPE CABLE HAVING MOISTURE IMPERVIOUS LAYER.

CV cables are increasingly in use. But their reliability is liable to be affected by external environments such as dielectric degradation caused by water trees. This report sums up the knowledge so far obtained of water tree degradating phenomenon and introduces measures to improve the reliability of CV cables. One of such measures is the development of a watertree cable having a metal layer, viz, a metal-plastic laminate tape, to shut off water because the water tree develops in the presence of water. This cable was satisfactory in water shutoff and other characteristics. In view of the critical importance or grasping the degradation of cables now in operation, the report also discusses the problems involved in the conventional leak current method and dielectric dissipation factor measuring method and relates the results of a study on dc withstand voltage method, a new technique for diagnosing dielectric degradation.