The effects of void presence on the tree growth phenomena

The ethylene vinyl acetate (EVA) compound has been chosen for this study because of its transparency and because it allows on to obtain a low percentage of rejects during the moulding procedure. Therefore this work was focused on the influence of artificial voids at the tip of needle electrodes on the parameters characterizing treeing inception and growth, usually considered when comparing different materials. It is worth noting here that in real insulation, dielectric strength and ageing endurance are features which generally do not directly and always depend on the presence of voids, as the latter generally are dispersed in an unknown way into the bulk or at the interfaces of the insulation. Therefore the presented findings, although interesting for material characterization, cannot be directly used for actual insulation evaluation.