Electrical treeing inception and growth in XLPE in presence of harmonics

This work is focused on the study of electrical treeing phenomena in polymeric materials, commonly employed in medium voltage cable insulation, when voltage harmonics are present. Specimens of cross-linked polyethylene (XLPE) have been brought to breakdown by the application of high voltages having a different harmonic content. The inception and the growth of electrical treeing was observed and the duration of each specimen was recorded. The durations were then put in relation with the voltage amplitude and with the partial discharge (PD) activity measured during the tests. In certain cases the output suggested that PD were not the main degradation factor.