The influence of the temperature of insulation oil on the results of measurements of the acoustic emission signals generated by partial discharges

The subject matter of this paper refers to the improvement of the acoustic emission method (AE) used for evaluation of partial discharges (PDs) generated in paper-oil insulation systems of power appliances. The paper presents the measurement and analysis results of the AE signals generated by partial discharges of the surface type (SPDs). The AE signals were measured on the surface of a transformer tub using a broad-band contact transducer, and then they were subject to a time-frequency analysis. The measurements were taken while heating transformer oil in the range from 30 to 85 degrees C with gradation of every 5 degrees C. For time runs, amplitude and energy density spectra the descriptor values that characterize them were calculated and then their comparative analysis was carried out to determine the influence of the insulation oil temperature changes on the measurement results of the AE signals generated by PDs.