Water treeing retardant XLPE insulation grade with improved electrical endurance

The authors describe the development and testing of a water-tree retardant (WTR) XLPE (cross-linked polyethylene) insulation grade. The major points included are a description of a hypothesis relevant for the growth of water treeing, verification of the efficiency of the material from laboratory to full-scale compound manufacture, showing that it is possible to process the grade on conventional cable production lines, and finally the short- and long-term electrical properties of these cables. All results obtained from the extended processing trials and long-time electrical aging testing under most-severe conditions verify the expectations that the described WTR-XLPE grade exhibits: drastic suppression of the generation of bow-tie trees and vented trees; significant improvement of electrical breakdown strength after wet aging; and excellent extrudability and crosslinking during cable processing. Thus it is affirmed that through use of the investigated WTR insulation grade it would be possible to further extend the life expectancy and reliability of power cables under severe service conditions