Some Aspects of the Relationship between Water Treeing, Morphology, and Microstructure of Pplymers

Water treeing is one of the main causes of premature breakdown of the polymeric insulation of HV power cables. The work reported in this paper is the combined effort of three different laboratories to investigate water treeing behavior of several polymers by complementary techniques. These include determination of water tree growth kinetics by continuous optical monitoring, fatigue environmental stress cracking, tensile drawing behavior, and transmission electron microscopy. Two kinds of sample geometry have been used for the water electrodes so as to enlarge signi- ficance of results and experiments have been conducted at 20°C and 65°C. The structural and mechanical evidence presented shows that water tree growth can be modified by several mechanisms and points out the considerable influence of polymer morphology on the propagation of water trees.