Measuring particle charges in high electric fields of gas insulation systems using tracking velocimetry

The electric charges of particles are a decisive factor influencing their behavior in electric fields, particularly in high-voltage gas insulation systems. The performance of the latter can be significantly undermined by charged particles, which potentially cause equipment failure in the energy transmission system. This study presents a novel in-situ charge measurement approach using particle tracking velocimetry based on high-speed imaging. For the first time, charge polarities, magnitudes, and distributions are quantified in high electric fields of gas insulations. Characterizing metallic and dielectric particles covering a broad property spectrum allows for identifying decisive charge accumulation parameters. The results show that some particle materials exhibit no detectable charge, while others dynamically acquire broad charge distributions. Among the most influential parameters are the particle material density, the adhesive force between the particles and electrodes, and the applied electric field strength. Particle properties such as the electrical conductivity and relative permittivity appear negligible indicating the surface conductivity to be decisive. The observed minimum charge magnitudes align well with theoretical force-based expectations. Maximum charges, however, are not predictable using such approaches resulting in significant underestimations. Additionally, it is shown that the charge depends on the direction of the particle motion in the electric field. These findings validate the suitability and necessity of the developed measurement approach, highlight statistical charge variability, and inform our understanding of how metallic and dielectric particle dynamics influence the performance of gas insulation systems.