Experimental investigation of the flashover problem at the XLPE cable terminations under coastal environments

Coastal environments can drastically raise the flashover probability at XLPE (cross-linked polyethylene) cable terminations. The authors report on a field study and experimental investigations of this flashover phenomenon for the 12/2-kV XLPE cables used in Egypt. The influence of sharp-edge shield or smooth shield of termination, the axial longitudinal distance of termination, tape insulation, and the number of tape layers on the termination disruptive corona voltage and flashover voltage have been investigated and analyzed. Important guidelines toward an optimum treatment of cable terminations have been derived from the experiments. In particular, it is noted that the disruptive corona voltage can be taken as the main parameter affecting the design of the cable termination profile. The breakdown voltage per tape layer is not constant; the first four tape layers have higher electric stress. The effect of sharp-edge shield and high radial stress can be improved by lapping four layers of an insulation tape on the first five centimetres of the longitudinal axial distance. The increase of the longitudinal distance improves the effect of wet conditions and this is suitable for outdoor termination at normal humid conditions