Study on Controlled Water Tree Degradation in Power Cable

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Water treeing is one of the major degradation mechanisms of power cable with polymeric insulation evolving in the presence of an ac field and of water. Water tree retardant characteristics of polyethylene (PE) were investigated. We were measuring dc leakage currents, observing tree shapes and analyzing aging time dependence of tree numbers and length distribution. It seems to be more different for water trees to redevelop in PE. Here, it is considered that pendent silane plays role of water tree retardant. The condensed silanol groups among PE molecules might act as obstruction to water initiation and growth. From these results, the silanol groups in PE are expected to suppress the water tree degradation. The lengths of water tree decreased with the increase in the amount of HDPE up to 9.1wt%. High crytallinity would suppress the water tree that is believed to grow through amorphous rich region. Water trapping at interface on HDPE cluster would also affect the water tree retardation.