Space charge and steady state current in LDPE samples containing a permittivity/conductivity gradient

Joachim Holbøll, K. R. Bambery, R. J. Fleming

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    Abstract

    Electromagnetic theory predicts that a dielectric sample in which a steady DC current of density ε is flowing, and in which the ratio of permittivity ε to conductivity σ varies with position, will acquire a space charge density j·grad(ε/σ). A simple and convenient way to generate an ε/σ gradient in a homogeneous sample is to establish a temperature gradient across it. The resulting spatial variation in ε is usually small in polymeric insulators, but the variation in σ can be appreciable. Laser induced pressure pulse (LIPP) measurements were made on 1.5 mm thick plaques of ultra pure LDPE equipped with vacuum-evaporated aluminium electrodes. Temperature differences up to 27°C were maintained across the samples, which were subjected to DC fields up to 20 kV/mm. Current density was measured as a function of temperature and field. Negligible thermally generated space charge was observed. The charge carrier mobility in the bulk of the samples was estimated to be of order 10-8 cm2 V-1 s-1.
    Original languageEnglish
    Title of host publicationConference on Electrical Insulation and Dielectric Phenomena
    Place of PublicationVictoria, Canada
    PublisherIEEE
    Publication date2000
    ISBN (Print)0-7803-6413-9
    DOIs
    Publication statusPublished - 2000
    Event69th Annual Conference on Electrical Insulation and Dielectric Phenomena - Victoria, Canada
    Duration: 15 Oct 200018 Oct 2000
    http://ieeexplore.ieee.org/xpl/mostRecentIssue.jsp?punumber=7083

    Conference

    Conference69th Annual Conference on Electrical Insulation and Dielectric Phenomena
    CountryCanada
    CityVictoria
    Period15/10/200018/10/2000
    Internet address

    Bibliographical note

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    Cite this

    Holbøll, J., Bambery, K. R., & Fleming, R. J. (2000). Space charge and steady state current in LDPE samples containing a permittivity/conductivity gradient. In Conference on Electrical Insulation and Dielectric Phenomena IEEE. https://doi.org/10.1109/CEIDP.2000.885305