An Investigation into the Growth of Electrical Trees in XLPE Cable Insulation

This paper describes the effects of frequency, voltage, temperature and mechanical stress on the times to breakdown of XLPE cable insulation subjected to highly divergent fields. Temperature and mechanical stress reduce the times to breakdown but tests with increasing voltage and high frequency produced unexpected results which could not be explained by the existing theory of electrical tree growth. Results of partial discharge measurements indicate that space charges are dominant in determining the shape of the tree and the time to breakdown of the insulation.