Space charge effect on the impulse breakdown of low density polyethylene

Chen, G (2003) Space charge effect on the impulse breakdown of low density polyethylene. The 2nd International Conference on Insulation Condition Monitoring of Electrical Plant, , Chongqing, China. 27 - 30 Oct 2003. pp. 133-136 .

Abstract

Polymeric materials employed in the power transmission system may be subjected to transient voltages resulting from lighting strokes or switching surges. The rise time of these transient voltages varies in a large range from a fraction of microsecond to several hundred microseconds. The breakdown often occurs during the transient overvoltage. In the present report the breakdown stress of low density polyethylene subjected to impulse with different rise times has been measured. Single impulse was employed in order to reduce space charge ageing effect. It has been found that the breakdown stress increases with the rise time initially and becomes stable when the rise time reaches to 350?s. However, DC breakdown strength is slightly lower than the stable value obtained from the impulse. The results indicate that the space charge plays a very important role in the breakdown. The presence of space charge has been confirmed by the direct measurements of the space charge in the bulk using the pulsed electroacoustic method.

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