Characterization of Ion Transport Properties in Synthetic Ester Oil by Polarization Current and Dielectric Spectroscopy

The accurate estimation of the charge carrier mobility in synthetic ester oil-based insulation systems is required for the reliable prediction of the electric field induced by dc voltages. Some discordance is observed in the literature, therefore, this quantity is investigated by two alternative methods. First, the mobility is estimated in a material sample by measuring the polarization current and the ion time-of- ight during a voltage polarity reversal test. Next, the mobility is derived from the frequency-dependent loss tangent measured by dielectric spectroscopy. The values obtained by the two methods are consistent, in the range of ≈ 2-4·10^-10 [m2/Vs] at 303 K