P.G. Halaris and I. Tsitsoglou (Greece)
Electrical Insulation, Partial Discharges, High-Voltage Measurements, Dissipation Factor
This work investigates the phenomena of dissipation factor change at the model solid-liquid insulators during their dielectric aging. For this purpose specimens of pertinax insulator 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 dissipation factor 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 dissipation factor 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 dissipation factor is increased due to the impact ionization which takes place during the dielectric aging stages of the insulating model.
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