Validation of Simulated UHF Electromagnetic Wave Propagation in Power Transformers by Time and Frequency Domain Measurements

Abstract

Ultra-high frequency (UHF) partial discharge (PD) measurement, i.e., detecting electromagnetic (EM) waves in the UHF range radiated from PD, is an attractive method for diagnoses of power transformers and has recently received much attention. However, the EM waves tend to suffer attenuation while propagating within a transformer to UHF sensors, which in some cases results in decreasing detection sensitivity of PD signals. In order to understand the propagation and attenuation characteristics of the EM waves within transformers, simulation technique of the EM wave propagation is essential. Although many previous researches on the EM wave simulation have been published, validations of those simulated results by comparing with the experimental ones are insufficient. In this research, at first, the attenuation characteristics of signal amplitudes, cumulative energies as well as frequency components of the EM waves while propagating through transformer windings were investigated both by time- and frequency-domain measurement. The EM wave propagation was simulated based on time-domain finite integration technique (FIT), then the simulated results were compared with the experimental ones. Consequently, the simulated EM waveforms, their signal attenuation level and S-parameter showed good agreement with the experimental results. Therefore, the validation of this EM wave simulation was successfully confirmed.