The influence of extruded semiconducting shields on the contamination of XLPE cables

Nuetron activation is a powerful tool to determine the average concentrations of contaminants in XLPE aged cables. It also allows the determination of radial contaminant profiles in full size cables. Semiconducting shields appear to act as sources of contamination in XLPE cables. The increase of tan δ in thermally aged cables could be due to the presence of ionic impurities; one cannot exclude, however, the possibility of oxidation effects. More work is needed to establish clearly a relation between contamination and treeing.