Space Charge in Solid Dielectrics (Keynote Lecture).
In, 14th International Symposium on High Voltage Engineering, Beijing, China,
25 - 29 Aug 2005.
Tsinghua University Press, .
The importance of space charge in solid dielectrics has been recognized for a long time. Over the years many attempts have been made to observe its dynamics in solid dielectrics. Significant development in measurement techniques has emerged two decades ago. In this paper several popular non-destructive techniques are briefly reviewed, followed by description of some advanced space charge measurement facilities housed in our laboratory. The selected results obtained over the years will be presented. It has been found that the interfaces play important role in space charge formation in addition to the bulk materials. Electrical ageing of polymeric materials under dc condition has been extensively studied and the technique has been extended to XLPE power cables. Recent work on ac ageing of polymeric materials has clearly indicated that ageing under high ac electric field results in the formation of space charge and these charges are very stable, indicating the formation of deep traps due to ac ageing. The impurities in the materials have significant influence on space charge formation and dynamics while the morphological feature of the material however has less effect on space charge. Simulation based on a bipolar charge model shows a good agreement with experimental results.
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