Surface Conductivity Graded Insulator for DC-GIS—Part II: Surface Charging and Metal Particle Lifting Behaviors

To investigate the effect of surface conductivity gradient design on the electric field regulation of insulators, the surface charging characteristics and metal particle lifting activity of surface conductivity graded insulators were measured under different operating conditions. The platform was designed to replicate the typical conditions of DC-GIS, including DC operating conditions, DC polarity reversal, and AC and DC superposition. The surface charge distribution of various types of insulators and the lifting voltage of metal particles near the insulators were tested. The results indicate that the surface conductivity graded insulator can regulate the surface charge distribution, significantly reduce electric field distortion around the insulator’s grounding shell, and inhibit the lifting behaviour of particles under DC conditions. In addition, the surface-conducting graded insulators demonstrate optimal charge modulation and suppression of metal particle activity under DC polarity reversal and AC-DC superposition conditions, effectively enhancing insulation performance under complex operating conditions. The study may serve as a valuable reference for the optimal design of DC GIS insulators.