PROJECT TITLE:

Electrical treeing behavior at high temperature in XLPE cable insulation samples

ABSTRACT:

This paper reports on investigations aiming to perceive the behavior of electrical trees formed in XLPE cable insulation at elevated temperatures. Samples cut from a real high voltage cable equipped with an embedded electrode system and composed of a needle separated by 2 mm from counter electrode were used. The temperature was varied between 50 and ninety °C and the vary of voltage changed between 9 and eighteen kV. The electrical treeing method was followed by means that of microscopic observation from the instant of initiation till the leading branches connected the counter electrode and partial discharge (PD) activity was monitored simultaneously. The shape and fractal dimension of the resulting trees were analyzed. It was found that temperature and voltage level had pronounced effect on the process of electrical tree formation. At lower voltages totally different sort of trees might be shaped, whereas at higher voltages branch trees dominated. Increase of test temperature reduced the time for tree initiation, whereas the tree growth time was less affected, aside from rock bottom voltage level at that the slowest tree development was observed at the highest take a look at temperature. It's postulated that the impeding result of elevated temperature on tree growth is due to a modification of tree channel sidewall conductivity, whereas the observed reduction of tree initiation time with the rise of temperature and voltage level is attributed to lowering of the threshold energy for damage at higher temperature with increasing of the injection current at higher voltage level.