Analytical model for surface charge accumulation at the gas–solid interface considering the effect of bulk space charge

Abstract

Electric field distortions caused by charge accumulation at the gas-solid interface have long posed a serious threat to the safe and stable operation of power systems. To further investigate the surface charge accumulation characteristics of dry bushing, this paper established an experimental platform for measuring surface charge on dry bushing. The study determined the patterns of surface charge accumulation under three types of voltage conditions and developed a simulation model for charge accumulation at the gas-solid interface that accounts for the influence of space charge on the core side. The results show that charge accumulation on the surface of the dry bushing is primarily of opposite polarity, with the most severe charge accumulation occurring near the end of the high-voltage shield along the surface. The superposition of harmonic components leads to a further increase in the surface charge density, with an increase of up to 15.6%. The multi-layer capacitive screen structure of dry-type bushing is prone to the accumulation of space charge between the screens and at the edges, primarily in the form of trapped charge carriers. The accumulation of space charge causes conduction on the solid side to become the dominant factor, significantly exacerbating the accumulation of surface charge on the bushing. The intervention of space charge effects caused the maximum charge density on the bushing surface to increase from −0.07 μC m−2 to −0.96 μC m−2. For electrical equipment such as dry-type bushing, which are prone to space charge accumulation, the influence of space charge on the solid side must not be overlooked when studying surface charge characteristics. The findings of this study can provide insights and serve as a reference for research into the charge accumulation characteristics and mechanisms at the gas-solid interface.