Water treeing retardant materials for cable insulators

In order to improve the resistance to water treeing (WT) of standard crosslinked polyethylene (XLPE) insulations used in medium voltage power cables, a number of materials were selected and studied that represent different water tree growth prevention strategies. Two laboratory procedures were adopted that assess the water tree resistance performance of the materials through different criteria: (1) a C.N.R.S. developed test that utilizes a performance criterion based on the water tree growth kinetics and opacity coefficient of the treed regions; (2) a Pirelli developed test that utilizes performance criterion which is based on the AC breakdown strength of aged samples. Both tests are shown to be complementary in their prediction of the performance of the selected water tree resistant materials. In addition, a range of additives to the polymeric insulation were selected to control the XLPE and water interactions, which resulted in the identification of a specific additive that greatly increased the water tree resistance performance of the insulation.