04_space_bdxlpe - IEEE Transactions on Dielectrics and...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
IEEE Transactions on Dielectrics and Electrical Insulation Vol. 11, No. 1; February 2004 41 Space Charge Development and Breakdown in XLPE under DC Field Mahmoud Abou-Dakka, Alexander Bulinski and Soli Bamji National Research Council Canada Institute for National Measurement Standards Ottawa, Ontario, K1A 0R6, Canada ABSTRACT The correlation between space charge accumulation and insulation failure has been investigated in four, polyethylene-based materials subjected to a dc field of 50 kV r mm. Two of the materials contained tree-retardant additives and all four mate - rials were aged for extended periods up to 19,000 h. The specimens were removed periodically from the external field and subjected to space charge density measure - ( ) ments under no-voltage conditions using the Thermal Step TS technique. Not a single parameter that would consistently correlate with times to insulation failure could be derived from the space charge measurements. However, the space charge measurements provided valuable insight into a possible link between the dynamics of space charge development and the time of dc aging. In particular, a consistent surge in the amount of accumulated space charge shortly before insulation break - down was observed in practically all samples. Also, a consistent relationship be - tween time to breakdown and the position of the internal space charge density peaks in the sample was observed. Samples that had space charge density peaks further apart consistently survived longer than specimens for which the peaks were closer together. These phenomena, if confirmed, could be used to screen new materials for dc voltage applications. Index Terms — XLPE insulation, dc field, aging, space charge, thermal step technique, insulation diagnostics. 1 INTRODUCTION PACE charge effects have been widely recognized as S one of the major components of the electrical aging processes in polymeric insulation, such as cross-linked Ž . polyethbylene XLPE , not only under dc fields, where w x their influence is prevailing, but also under ac fields 1 3 . Space charge can lead to local energy dissipation and to the lowering of the energy barrier for various thermo- chemical processes, thus facilitating material degradation. Local electric fields created by space charge may lead to electrical tree initiation by locally exceeding the break- down strength of the material. It is believed that dc fields above 40 kV r mm lead to significant local modifications of w x polymer morphology and creation of microcavities 4 . The understanding of the role of space charge in polymer ag- ing has been considerably improved by the recent devel- opment of several techniques to measure space charge w x distribution 5 8 . A large amount of new experimental data clearly indicates that charge injection occurs at sig- Manuscript recei ® ed on 12 No ® ember 2002, in final form 7 April 2003.
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.
  • Spring '11
  • ghjk
  • Electric charge, Fundamental physics concepts, Indian Institute of Technology Kanpur, IEEE Xplore, space charge

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern