Tree growth monitoring by means of digital partial discharge measurements

In this work results relevant to electrical treeing tests performed on several ethylvinylacetate EVA (with different vinylacetate percentage) and on cross linked polyethylene (XLPE) (of two different lots) polymer materials are presented. During the tree growth the partial discharges (PDs) were monitored by means of a digital PD acquisition system and the tree morphologies were optically evidenced by means of video recorder equipment. The PD acquired data, the outcome of the video monitoring and the time-to-breakdown were off-line processed and analysed. In this way, two main results were obtained: the first one, applicable to this kind of laboratory treeing tests, is related to the possibility of predicting the lifetime of the specimens, considering a specific PD measurement derived quantity; the second one demonstrates the possibility to detect the tree morphology considering the phase-number distribution obtained by the digital PD measurement. The presented test procedures are deemed to have a potential for diagnostic applications.