Motion and Discharge Characteristics of Mixed Submillimeter Metal Particles and Diverse Insulating Impurities Under AC Voltages

Submillimeter metal particles and insulating impurities are introduced during the operation of gas insulated switchgear (GIS), forming mixed particles that pose localized insulation weaknesses and compromise dielectric integrity. This study investigates the motion and discharge behaviors of such mixed particles and evaluates their impact on insulation performance. An experimental platform combining an AC voltage source with a simultaneous motion and partial discharge (PD) detection system is developed. Metal particles are mixed with five representative impurities, including adsorbent powder, closing resistor powder, glass fibers, insulating paint flakes, and rubber granules. Their motion and discharge characteristics are systematically recorded and analyzed. Polarization effects and charge accumulation are considered in interpreting the observed behaviors. The relative threat levels are evaluated using onset voltage, phase-resolved PD (PRPD) patterns, maximum PD amplitude, and PD repetition rate. Results show that mixing with adsorbent powder reduces discharge risk, reflected by a low comprehensive threat score of S = 0.1495. In contrast, other impurities increase the risk to varying degrees: closing resistor powder and insulating paint flakes cause mild effects with scores of 0.4287 and 0.3856, respectively; rubber granules have a moderate impact with S = 0.6415; while glass fibers pose the greatest threat with a score of 1.0. These conclusions provide a theoretical basis for early insulation defect detection in GIS.