DC Electrical Trees in XLPE Induced by Short Circuits

This study aims at understanding electrical treeing in XLPE due to DC short circuits. A wire-plane type test object has been excited by a series of short circuit events after applying DC voltages of different levels and duration. The development of thin filamentary trees and their morphology was correlated with the inception probability. It was observed that the latter as well as the length of the trees increased with the magnitude of the applied voltage and the number of short circuit events. These observations are in good agreement with the hypothesis that the release of stored energy during short circuit causes electromechanical stresses in the materials giving rise to treeing process analogous to mechanical crack formation. It is suggested that the application of an adequate number of short circuits at a suitable voltage level and a sufficient stress duration can be used as a DC treeing test procedure.