Research on Ultra-Wideband Pulse Current Method for DC Partial Discharge Measurement

Abstract

The conventional pulse current method is commonly used in AC or DC withstand voltage tests with partial discharge (PD) monitoring. Because of its relatively narrow measurement bandwidth, this method tends to ignore critical information in PD waveforms, making it difficult to eliminate pulse-type interference under DC voltage conditions, where phase information is absent. To enhance interference rejection and achieve effective separation of multiple PD sources under DC voltage, an ultra-wideband pulse current method was proposed. A detection impedance was developed to extend the upper limit of the measurement bandwidth to 50 MHz to retain PD waveform information. PD waveforms measured from three defect models using both the conventional pulse current method and the ultra-wideband method were analysed in both time and frequency domains. The criterion function was employed to evaluate the difficulty level of classification of the PD waveforms obtained by the two measurement methods, and the results were validated using equivalent time–frequency (T–F) spectra. Field interference waveforms were introduced, and the density-based spatial clustering of applications with noise (DBSCAN) clustering method was applied for unsupervised clustering of the PD waveforms and interference waveforms. The results demonstrate that the ultra-wideband method can effectively separate multiple PD sources and eliminate interference sources under DC voltage conditions.