Interpretation of Pulsed Electroacoustic Signals in Oil-Impregnated Materials by Viscoelastic Analysis

Viscoelastic modeling was utilized to analyze the space charge waveforms obtained for papers and pressboards impregnated with natural ester oil. During the study, the signal exhibited attenuation, a phenomenon that was successfully reproduced through modeling. The model parameters used were consistent with samples with various thicknesses and the existing literature. Furthermore, a stronger attenuation was observed when a 6.5 kg-weight electrode was used. A certain amount of oil was squeezed out from the measuring point, resulting in the lightening of the sample color. It is suggested that the diffusive mechanical response plays a significant role in the observed strong attenuation. The viscoelastic analysis in the Cole-Cole model also showed that the signal suffered several mechanical relaxations.