Comparative Studies of Partial Discharge Using Acoustic Emission Method and Optical Spectroscopy

This paper concerns improvement of evaluation methods of partial discharge (PD), which may occur in the power transformer insulation systems. This particular study regards the next stage of research works, which aim to determine the energy share of particular physical phenomena accompanying generation of PD. The performed works were connected to comparative analysis of PDs, which were measured with the acoustic emission (AE) method and with optical spectroscopy. The applied measurement setup was specially designed for generation of surface partial discharges (SPDs) in transformer oil as insulation medium. In the introduction section elements of the experimental setup, i.e. the spark gap for modeling of SPDs and the transformer tank model filled with insulation oil will be characterized. Further the measurement equipment and the metrological parameters for both applied PDs registration methods will be described in detail. In the following sections the achieved results will be presented and discussed. In particular spectra of optical signals registered in the range from 200 to 1100 nm and frequency spectra of AE signals registered in the range from 0 to 500 kHz will be presented. In order to determine the effect of voltage value, which was used for generation of SPD, on the registered optical and AE signals, the results will be presented for three relative values: 0.6, 0.7 and 0.8 times the value of breakdown voltage of the applied test system. In addition, results of time-frequency analysis of EA signals, in the form of two dimensional spectrograms calculated using the short time Fourier transform will be presented. In the following section the achieved results of performed comparative analysis will be presented and discussed.