PROJECT TITLE :

Water ingress in high-voltage cross-linked polyethylene (XLPE) cable terminations

ABSTRACT :

In Norway, there are 6000 to 7000 oil-filled high-voltage cable terminations within the transmission network, most of which are made following the old style shown in Figure 1. Though the quantity of reported failures of medium-voltage cross-linked polyethylene (XLPE) cables and cable accessories is low, during the last few decades some severe explosive failures with potential for personnel injury have been reported [1]. Examination of a number of the failed cable terminations showed that the most doubtless cause was the presence of water within the housing. Water will enter the housing through defective O-rings or through an air ventilation screw on the prime cover of the termination housing. As half of their regular maintenance programs, some Norwegian utilities live the water content of the filling oil. Liquid water was found in some installations, and in one case, the strain cone was found to be covered in ice when the porcelain housing was removed [two] (Figure two). Similar breakdowns have been reported in alternative European countries [three], [4]. The main purpose of the work described in this text was to analyze the effect of water ingress in oil-crammed high-voltage cable terminations, in specific the associated breakdown mechanisms. The work was performed using full-size and model cable terminations.