Effect of insulation distance on surface charge accumulation at the gas-solid interface under DC voltage

This study aims to investigate the effect of insulation distance on the charge accumulation characteristics at the gas-solid interface under DC voltage. Here a plate-shaped epoxy was selected as the sample, and its charging process was provided by a pair of finger-shaped electrodes. With varying the insulation distance between the electrodes, the surface charge distributions were measured under two cases of charging methods. In Case 1 the applied voltage level was constant while in Case 2 the average field strength was unchanged. As a result, for Case 1, hetero-charge accumulation was the main surface charging mode, and the hetero-charge density increased with the insulation distance. This is mainly because the reduced tangential electric field weakens the migrating process of injected homo-charges to the gas-solid interface. As for Case 2, the main surface charging mode presented a polarity reversal, i.e., from hetero-charge to homo-charge accumulation, with increasing the insulation distance. This phenomenon is attributed to the enhancement of HV electrode injection. At last, the experimental results were analyzed through electric field calculation. This study offers a preliminary understanding of the effect of insulation distance on surface charge accumulation under DC voltage.