Influence of copper particles on frequency domain spectroscopy characteristics of mineral oil

Abstract

The dielectric properties of transformer oil are greatly threatened by particles especially the metallic particles. In order to obtain the influence of metallic particles on frequency domain spectroscopy (FDS) of mineral oil, we chose copper particles to contaminate the mineral oil artificially. The dielectric properties such as relative permittivity, dielectric loss tangent and volume resistivity of contaminated mineral oil versus frequency with various copper volumetric concentrations were measured by dielectric spectrometer. Measurement results show that the relative permittivity, dielectric loss tangent and volume resistivity of contaminated mineral oil all reduce with increasing frequencies from 10−2 Hz to 106 Hz. Moreover, the relative permittivity and dielectric loss tangent increase with increasing copper volumetric concentration, and the volume resistivity decreases with the increase of copper volumetric concentration. The difference is more obvious at low frequencies than those at high frequencies. These results are then discussed with polarization and classical conduction theories.