# Methodology for quantifying particle charge statistics in electric fields of gas insulations

## TL;DR

This paper introduces a new method to measure and understand how charged particles behave in high-voltage gas insulation systems.

## Contribution

A novel experimental methodology is introduced to quantify particle charge statistics and their motion in high-voltage gas insulation systems.

## Key findings

- Particle diameter is the most influential factor in determining charge magnitude.
- Non-Gaussian charge distributions are observed, attributed to adhesive forces between particles and electrodes.
- Mirror-charge-induced motion patterns are identified as a new term in particle motion equations.

## Abstract

Electrically charged particles in high-voltage gas insulation systems can lead to field distortion, partial discharges, and ultimately, insulation breakdowns. Despite their significance, particle charges have rarely been studied in this context. This work therefore characterizes the electric charges of metallic and dielectric particles with diameters ranging from 1 to 170 \documentclass[12pt]{minimal}
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\begin{document}$$\upmu$$\end{document}m. The charge magnitudes measured at different field strengths using tracking velocimetry range from approximately 1 fC to 10 pC. The particle diameter is observed to be the most influential factor, while intrinsic particle material properties show little effect. Thereby, contact electrification is identified as the underlying charging mechanism. Broad, non-Gaussian charge distributions are observed across all particles, which is attributed to adhesive forces between particles and the electrode surface. The adhesion spanning from 6nN to 780nN is measured using atomic force microscopy and is shown to be dependent on the particle material and its surface topography. However, the maximum measured charge during motion is smaller than that which would be necessary to overcome adhesion at the upper end of the adhesion spectrum. The particle surface field strength limitation due to the breakdown field strength of air explains this. While constant charges compensate for gravity and low adhesion, charge loss during motion from initially high charges is observed. Mirror-charge-induced motion patterns are observed for these high charges, adding a previously not considered term to the motion equation. Overall, the results provide a quantitative description of particle charges, linking adhesion, charge loss, and motion. This establishes a new fundamental experimental methodology to support future assessments of the particle’s influence on high-voltage gas insulation systems.