Streamer characteristic and breakdown in synthetic and natural ester transformer liquids under standard lightning impulse voltage

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    Abstract

    Interests on ester liquids as replacement of mineral oil in large power transformers are growing in recent years. This paper presents experimental studies on streamer and breakdown in synthetic and natural esters. Lightning impulse voltage was chosen when considering the practicality of standard tests of transformer industry. First, streamer length, velocity, shape and mode were analyzed based on optical images obtained by a multi-channel ultra high speed camera. Under the same voltage level, streamer in both natural and synthetic esters propagates faster and further, with more branches, than in mineral oil. Breakdown tests at various gaps from 15 mm to 100 mm were conducted, and it was found that fast streamer led breakdown becomes statistically dominant in a large gap under lightning impulse and ester liquids have lower breakdown voltage than mineral oil due to their low tolerance to fast streamer. Therefore a relationship between the results under lightning impulse and previously published results under step voltage was built up and an empirical formula was obtained to predict the breakdown voltage of esters at very large gaps. © 2011 IEEE.
    Original languageEnglish
    Article number5704520
    Pages (from-to)285-294
    Number of pages9
    JournalIEEE Transactions on Dielectrics and Electrical Insulation
    Volume18
    Issue number1
    DOIs
    Publication statusPublished - Feb 2011

    Keywords

    • breakdown
    • insulating liquids
    • lightning impulse
    • natural ester
    • Power transformer
    • streamer propagation
    • synthetic ester

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