An Experimental Estimation of the Average Mobility Change of Free Electrons during Dielectric Aging at the Model Solid-Liquid Insulators

P.G. Halaris, P.T. Tsarabaris, J.S. Katsanis, and A.D. Polykrati (Greece)

Keywords

521802 Electrical Insulation, Partial Discharges, HighVoltage Measurements, Solid Polymeric Insulators, Electrical Protection.

Abstract

In this paper, an experimental estimation of the average mobility change of free electronic carriers at the model solid-liquid insulators during their dielectric aging. For this purpose specimens of industrial bakelite were electrically stressed by an imposed high AC voltage. The electrode set-up used was metal tip-sample of solid insulator-metal in an environment of transformer oil. Measurements were taken by increasing the imposed voltage in steps of 1 kV until the ultimate breakdown of the insulators. The values of the average mobility of the model was calculated through the measurement of charge which flows through the sample, as a result of partial discharges, the kinetic energy of free electrical carriers and the applied field value. From these measurements the exponential increase of the average mobility change of the model solid-liquid insulator in relation with the value of the imposed electric field was noted. In satisfactory agreement with the theoretical data it seems that the average mobility is increased due to the impact ionization which takes place during the dielectric aging stages of the insulating model.

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