Role of number of consecutive voltage zero-crossings in propagation of water trees in polyethylene

Daisaku Kaneko, Tomoya Maeda, Toshihide Ito, Yoshimichi Ohki, Takeshi Konishi, Yoshinobu Nakamichi, Minoru Okashita

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    Effects of superposition of a low-frequency (0.1 to 50 Hz) voltage and a high-frequency 2 kHz voltage on the growth of water trees in polyethylene are examined. It has become clear that both the number of total voltage zero-crossings during the whole voltage application period and the number of consecutive voltage zero-crossings in the instant of the polarity reversal of the low-frequency voltage play important roles in the length and shape of water trees. Namely, the water tree length becomes longer as the number of total zero-crossings increases. Furthermore, among the voltages with the same number of total zero-crossings, the length becomes even longer with a prolonged shape in the direction of electric field as the number of consecutive zero-crossings increases. Effects of superposition of a high-frequency voltage onto a dc voltage are also examined. In this case, the dc voltage seems not to have any influence to the tree growth. By assuming the presence of space charge around the water-tree tip, the effective zero-crossings become only sensitive to the high-frequency component. Therefore, this result also indicates that the number of voltage reversals at the tree tip plays a crucial role in the growth of water trees.

    Original languageEnglish
    Pages (from-to)708-714
    Number of pages7
    JournalIEEE Transactions on Dielectrics and Electrical Insulation
    Issue number4
    Publication statusPublished - 2004 Aug



    • Low density polyethylene
    • Polymeric insulation
    • Power cable
    • Tree length
    • Water tree

    ASJC Scopus subject areas

    • Electrical and Electronic Engineering

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