The Impulse Strength of Naturally Aged XLPE Cables Containing Water Trees

The results of impulse-voltage tests on 15 kV crosslinked polyethylene (XLPE) cables with a taped conductor strand shield which have been in service for eight years are reported. The tests were performed with the insulation dry and also containing visible water trees at conductor temperatures of 25° and 90°C. The impulse strength is significantly lower at the higher temperature and with visible water trees.