Influence of humidity and voltage on characteristic decomposition components under needle-plate discharge model

Abstract

Detecting the decomposition components in air-insulated switchgear is an effective method to evaluate the discharge severity of air-insulated switchgear. Experimental and theoretical studies are conducted to investigate the types of decomposition components and generation mechanism under the partial and disruptive discharge conditions. The discharge experiments use a needle–plate discharge tank, and the effect of relative humidity (50, 70 and 90%) and voltage (6, 6.5, 7 and 7.5 kV) are studied in detail. Considering the partial discharge process, the concentrations of CO and NO2 increase with the applied voltage and partial discharge time. The CO concentration increases with the increase of humidity, while NO2 concentration shows the reverse change trend. During the disruptive discharge process, the decomposition component NO increases with humidity. The dissipation of these decomposition components is also investigated using experiment. The small part of CO dissipation is from the adsorption with H2O molecules and onto the surface of discharge tank. The reaction between NO and O free radical, O2 and O3 consumes the concentration of NO and produces NO2. And the reaction between NO2 and H2O consumes most of the generated NO2 in the discharge tank. In the theoretical research, the reaction energy of CO, NO and NO2 generation is computed to analyze the generation and dissipation mechanism of decomposition components using Materials Studio.