Localization of Partial Discharge Sources in Power Transformers

Abstract:
Partial Discharge (PD) sources located inside the transformer active part typically produce oscillating PD signals at the transformer terminals (bushing tap). Generally, PD signals measured at the bushings of a transformer are responses of the active part of the transformer to the excitation of a PD impulse generated at a specific (unknown) position inside the transformer. On its way from the PD source to the measuring system, the waveform of the original PD impulse is attenuated and shaped. Therefore, PD signals contain information about both, the physical process at the origin of the PD source, and the attenuation and coupling phenomena along the signal propagation path. Based on this background, the evaluation of PD signals in the time- and frequency-domain offers a considerable potential to localize internal PD sources in large power transformers. Advantages and limits of PD signal analysis in the time- and frequency-domain and their application to PD source localization in power transformers are discussed using practical examples.