Quantitative study of electric conduction in mineral oil by time domain and frequency domain measurement

Polarization and depolarization current measurement is a non-destructive testing method to study the dielectric properties of insulating materials. Two types of mineral oils with different aging times have been studied using both time domain and frequency domain methods separately. In this paper, a novel approach to understanding the correlation between the electric conduction in time domain and frequency domain has been proposed. When the charge carriers drift to the electrodes, they may be blocked and accumulated near the electrode. The amount of charge in the vicinity of electrode has been estimated. In the depolarization period, these charge layers will return to the bulk resulting in a depolarization current. In this paper, an analytical solution to the time dependence of the depolarization current has been developed and used to fit the experimental results. The field and temperature dependence of the polarization and depolarization current have been used to study the characteristics of charge carriers in mineral oil. The calculated conductivity has been used to simulate the frequency response in mineral oil and the simulating results have been compared with the experimental data.