Simultaneous Electrical, UHF, Current and Optical PD Measurements on Floating Potential under DC Stress

In this contribution, the partial discharge behavior of two types of floating electrodes under DC stress in air at atmospheric pressure are investigated. Either a hexagonal-shaped nut or a sphere are positioned at a distance of 0.4 mm to the high voltage electrode. The influence of the geometry of the floating electrodes as well as the level and polarity of the applied DC voltage on the partial discharge activity are investigated. Several PD measurement techniques are used simultaneously, namely electrical measurement, ultra-high frequency (UHF) and both high frequency current transformer (HFCT) and shunt measurements. The obtained data is post-processed and visualized with Pulse Sequence Analysis (PSA) diagrams in order to provide characteristic patterns of the investigated defect. In addition, a corona camera detecting the light emissions generated by the discharges provide a further understanding of the defect mechanisms.