Breakdown at Multiple Protrusions in SF6 and CO2

Abstract

The electric breakdown at single and multiple protrusions in SF6 and CO2 is investigated at 0.4 and 0.6 MPa, respectively. Additionally, the breakdown fields at rough surfaces of two different areas were determined. From the measurements, breakdown probability distributions for single protrusions were determined and fitted by Weibull distributions. This allowed the determination of statistical enlargement laws for the 50% breakdown probability fields E50. Such enlargement laws describe, for example, the scaling of breakdown field with electrode area or number of protrusions. The predictions were compared to the experimental data, and both agreement and discrepancies were observed depending on polarity and number of protrusions and gas. Discharge predictions including first electron, streamer inception and crossing, as well as leader propagation, gave further insight to this. It was found that predictions from enlargement laws based on statistical processes may not describe the measured breakdown fields well and that relevant physical breakdown criteria must also be considered.

Simulation of pre-breakdown discharges in high-pressure air: II. Effect of surface protrusions

“…Since different protrusions come into play under different conditions, the presence of several microprotrusions acting in close proximity is unlikely. (Note that this reasoning does not apply to arrays of identical protrusions, nevertheless it is interesting to mention in this connection the recent experiments [41], which showed little effect of the number of protrusions in the array for the case of SF 6 but a more appreciable effect for the case CO 2 ; figures 7, 8 and 12, 13 of [41], respectively. This is an interesting point that may need to be revisited in the future.)…”