Numerical simulations of micro-discharge induced by surface defects on insulation pull rod

Abstract Insulation pull rods used in gas-insulated metal-enclosed switchgear (GIS) are prone to contamination with metallic particles during both production and operation, leading to issues such as electric field distortions, surface partial discharges, and flashovers. The present study proposes a research framework for investigating the evolution of micro-discharges induced by metallic particle defects on the surface of insulation pull rods. Firstly, a plasma chemical reaction model based on hydrodynamics was employed to simulate the corona discharge of a pin plate to derive the rule governing changes in particle yield at the pin tip with field strength. Subsequently, this rule of change was applied to the defect-induced discharge model of the insulation pull rod, which was based on the electrostatic and dilute matter transfer module, to explore the defect-induced discharge mechanism of metallic particles. The results indicate that at lower electric field strengths, discharge is primarily driven by the migration and diffusion of charged particles. However, at a critical field strength, charged particles are generated at triple junctions and initially migrate primarily due to electron mobility, followed by significant movement of positive and negative ions. Additionally, increased field strength, larger defect sizes, and proximity to the electrode enhance the local electric field, thereby increasing particle production rates and discharge intensity, while taller defects impede the movement of positive ions. The findings of the study offer substantiation for the transition from micro-discharge to breakdown discharge, a theoretical rationale for the defect-induced discharges on insulation pull rods, and a theoretical framework for the enhancement of insulation pull rod quality.