Impurities in XLPE cables

Impurity analysis by neutron activation was performed on several unaged and field-aged distribution cables differing in origin and manufacturing process (steam and dry curing). The results show principally that impurities found in the insulation can be attributed primarily to unclean semiconductive shields and to the manufacturing process. Aging has less impact. Dry curing leads to higher impurity diffusion in the insulation than steam curing. The inner conductor is also a source of impurities. The chlorine content in the insulation of unaged cables is higher than in aged cables. 4201-EC insulation is an improvement over the 4201 version in the cable context. Contamination of the insulation occurs largely during manufacturing, with temperature being the principal factor. Large variations in impurity contents were found along field-aged cables, with twice as many in the insulation as in the shields. Differences among unaged cables were noted