Experimental and numerical study on Following Streamer mechanism for SF6 breakdown induced by floating linear metal particles

TL;DR

This work investigates how floating linear metal particles trigger SF6 breakdown via the Following Streamer mechanism. It combines an experimental platform with sub-millimeter particles and negative microsecond voltage pulses with 2D axisymmetric fluid simulations to assess streamer morphologies. The results confirm double-end inception and the formation of following streamers, but reveal 3D effects—off-axis initiation and multiple following streamers—not captured by the 2D model, highlighting its limitations. An extended conceptual model that integrates 2D axisymmetric and 3D Cartesian perspectives is proposed to better describe SF6 breakdown in the presence of floating metal particles.

Abstract

A recently proposed Following Streamer mechanism (Feng et al. 2025 Phys. Rev. Applied 23 064039) seeks to explain how floating metal particles induce SF6 streamer breakdown in the combined gap. This mechanism is derived from a 2D axisymmetric fluid model, which has limitations in describing multiple streamer events in real-world 3D scenarios. To validate the Following Streamer mechanism, we experimentally investigate the discharge morphology of SF6 streamers induced by a floating linear metal particle under negative pulsed voltage. The results are then compared with those from 2D axisymmetric fluid simulations. The comparison reveals both consistencies and discrepancies. Regarding consistencies, experimentally observed features-such as streamer inception at both ends of the metal particle and the formation of subsequent following streamers-support the general idea of the Following Streamer mechanism. Regarding discrepancies, the experiments show a larger number of following streamers and off-axis propagation paths, which cannot be described in the 2D simulation. For scientific rigor, an extended physical model was proposed to improve the description of the Following Streamer mechanism.

Figures (7)

• Figure 1: Floating control apparatus and key mechanical details involved
• Figure 2: Comparison of the impact of the silicone pad on the Laplacian field (a, b) and on plasma dynamics (c, d).
• Figure 3: (a) Schematic diagram of the experimental system. (b) Circuit diagram of the microsecond pulsed high-voltage source.
• Figure 4: Microsecond pulsed high-voltage waveform. Notably, the waveform is plotted with inverted polarity for improved readability.
• Figure 5: (a) Measured voltage and current waveforms. (b) Enlarged view of voltage and current waveforms at breakdown moment, along with the ICCD gate temporal window. (c) Diffuse discharge photograph captured at breakdown moment. Notably, all waveforms are plotted with inverted polarity for improved readability. Panels (a) and (b) are obtained from two separate discharge events with similar breakdown voltage.