Reduction effect of cross-linking by-products on dielectric strength in polyethylene under DC stress

Abstract

XLPE(Cross-Linked Polyethylene) power cable is expected to be applied to a long distance power transmission cable in HVDC systems. DC transmission system is effective for the long distance power transmission, and XLPE cable is not necessary to give a periodical maintenance procedure. However, when DC high voltage is applied to XLPE, it is said that on electrical breakdown may occur due to an effect of space charge accumulation. While the relationship between them in LDPE(Low density polyethylene) was revealed, it has not been clear in XLPE yet. In the case of XLPE, not only the space charge behavior, the conduction current seemed to be also important factor to understand the relationship. In this paper, the space charge distribution and an external circuit current measurement were carried out for the materials, which were immersed in the by-products. It was found that the reduction of breakdown strength and a rapid change of the conduction current in the case of LDPE were observed, and them were much obvious in LDPE immersed in cumylalcohol than those observed in LDPE immersed in acetophenone.