Investigations of Water Effects on Degradation of Crosslinked Polyethylene Insulated Conductors

As a result of these investigations it was observed that under certain conditions the degradation of crosslinked polyethylene (XLP) cable due to moisture was accelerated by a continuously applied ac stress as compared to dc or the absence of voltage. Further, the course of the involved activity was believed to take place in three stages. The first was the appearance of tree like channels which were filled with water, second their subsequent growth, and third their ultimate bridge between the inner and outer cable electrodes. Conventional insulation resistance measurements failed to reveal or explain these stages.