Experimental Study on Corona Onset Characteristics of Small Curvature Electrode Under Combined AC–DC Voltages

An investigation into the corona onset characteristics of small curvature electrode with rough surface under combined ac–dc voltages was presented. The experimental platform under combined voltages with different electrode fillet radius and electrode spacing was built. The corona inception voltage of the small curvature electrode was obtained by collecting the corona pulse signal and changes in the number of ultraviolet photons. Based on the finite element algorithm, the corona onset electric field strength under combined ac–dc voltages was calculated. Results showed that the corona inception voltage increased with the increase of electrode fillet radius and electrode spacing. The corona inception voltage of positive dc–ac was higher than that of negative dc–ac. The linear superposition of ac and dc voltages when corona occurred was regarded as combined corona inception voltage. It increased first and then decreased slightly with the increase of ac voltage. The combined corona electric field strength on the electrode surface generally decreased with the increase of ac voltage. The research of this article can provide useful references for the maintenance of electrode surface and insulation optimization of converter valve.