双极性直-交切换电场下环氧树脂表面电荷输运与闪络特性OA

High-voltage AC gas-insulated switchgear(GIS)plays a crucial role in ensuring the reliable transmission of electrical power,but it also introduces new challenges to the resilience of power systems against ice-related disasters.Compared to traditional segmented DC ice-melting methods,GIS-connected lines ice-melting method is more efficient when dealing with widespread ice accumulation on power grids.However,when transitioning from DC ice-melting to AC power supply restoration,the basin insulators in GIS systems are vulnerable to surface flashover due to the stress of DC-AC switching electric fields.This study combines experimental and simulation approaches to investigate the charge transport mechanism and flashover characteristics of epoxy resin(EP)under DC-AC switching electric fields.The results show that under DC electric fields,charge accumulation occurs at triple junctions,with charge density positively correlated with both voltage and charging time.Upon switching to AC,the electric field strength sharply increases during the half-period of opposite polarity,combined with dissipation of accumulated charges leading to an 80%higher flashover probability.Compared to negative polarity DC,positive polarity DC results in higher charge density(up to 60%)and more significant field distortion,thereby increasing the risk of flashover.Based on simulations of the 252 kV basin insulator,this study suggests that using a negative polarity DC source is preferable during GIS-connected lines ice-melting operations,providing key theoretical support for engineering insulation design.