Investigation of supraharmonics' influence on partial discharge activity using an internal cavity sample

Abstract

This research paper investigated the influence of lower-order supraharmonics on partial discharge activity in an insulation system sample with a predefined spherical cavity defect. The supraharmonics were represented by repetitive sinusoidal oscillations, whose shape, amplitude, and natural frequency were based on typical trends measured or modeled in medium- to high-voltage electric subgrids containing power converters. The combination of a fundamental 50-Hz waveform and a one-per-period oscillation was applied to the test sample, and the occurring partial discharge activity was measured. Throughout the experiment, the oscillation's position and natural frequency were gradually changed. Afterward, partial discharge activity under identical conditions was simulated using an analytical model, and the phenomena observed during the experiment were explained by it. Changes accounting for the presence of supraharmonic oscillations were introduced to the model. Ultimately, conclusions about the significance of the changes in the partial discharge activity were drawn. Among those were predictions of increased aging rate, earlier inception of partial discharge activity, and suggestions for future works.