The influence of square voltage rise time on partial discharge spectra

Literature data regarding the behavior of partial discharge inception voltage (PDIV) under repetitive impulsive voltage waveforms is contradictory. Some authors have found that rise time can lower PDIV, others just the opposite. The picture complicates further when repetitive PDIV (RPDIV) is discussed. In many papers, antenna sensor working in the UHF range were used, but no standardized sensors (and setup geometry) is defined yet. Therefore, if some parameters of the supply waveform could affect partial discharge spectra, that could be one of the possible reasons for the differences reported in literature. In this paper, experiments carried out on crossed pairs subjected to square voltages, aimed at inferring the dependence of rise time on partial discharge pulse spectra, are discussed. The results show that shorter rise times favor the inception of pulses having large magnitude and frequency content. As a consequence, depending on the bandwidth of the sensor-detector chain, PD detection sensitivity can vary with rise time, thus affecting PDIV measurement.