Studies about the electrical treeing growth based on the evolution of the PD patterns

The present work is based on electrical treeing test performed on several EVA and on XLPE polymer materials. The output of PD digital measurements, the outcome (images) of video monitoring and the times-to-breakdown were recorded, off-line processed and analysed. Two main results were obtained. The existence of a linear relation between a specific quantity derived from the PD data and the times-to-breakdown was proven and allows to implement lifetime predictions (applicable to laboratory treeing tests on EVA polymers). In parallel, a different processing of the PD data patterns allowed to link the shape of phase-number PD histograms to the tree shape during treeing growth. While the first obtained results offer a possibility to shorten the testing times (and the relevant costs), the second ones demonstrate that the different shapes of an electrical tree can be detected also in opaque materials, as non visual means can be used. The tested procedures are deemed to have a potential for diagnostic applications.