Influence of Frequency and Distance on Acoustic Emission Velocity Propagating in Various Dielectrics

Abstract

The results obtained for the measurements of acoustic emission (AE) signal parameters emitted in three dielectric liquids are presented in this paper. In particular, the velocity of AE wave was calculated based on the time of arrival of the AE signal. A frequency modulated signal was generated by a piezoelectric transducer and measured at various distances by a hydrophone. The changes in velocity values at particular distances and for different frequencies were investigated. The analyses include the determination of the dependency of the velocity values from the distance between the communicating devices. A nonlinear regression model was calculated, and the differences between AE velocities propagating in the considered dielectrics were determined. Similarly, the influence of modulation frequency on the AE velocity was determined using nonlinear regression. Based on the calculation data, it can clearly be stated that the velocity of AE wave depends significantly on the frequency and distance at which it is registered. These two factors may have an important influence on the localization of partial discharges (PD) occurring in these types of dielectric liquids.

Assessment of Partial Discharges in the Air by Application of Corona Camera

“…For detection and measurement purposes involving internal PDs, electrical methods are appropriate, consisting mainly of measuring their apparent charge Q p [9,10]. The acoustic method is also used, based on the measurement of the acoustic signal generated by the PDs [11][12][13][14] and the chromatographic method (DGA) that is applied to identify by-products of insulation failure resulting from the effects of PDs [15][16][17][18]. These methods are mainly used for diagnostics of faults found in the isolation of large power transformers and high voltage cables.…”