Enhancing plasma injection in high-pressure SF6 by a PTFE–Al particle-doped capillary

There have been six incidents of ultra-high-voltage transformer explosions in China recently, causing massive economic losses. The ultrafast bypass switch (UFBPS), based on plasma injection to quickly bypass the internal arc and eliminate the risk of converter transformer explosion, is therefore considered a highly promising solution. However, the requirement for reliably triggering the gap switch is extremely high, and it must be dependably triggered even when the working coefficient is close to zero. In this study, a plasma jet enhancement method is proposed by doping aluminum powder into the Polytetrafluoroethylene (PTFE) microcavity to enhance the plasma injection driven by the electrical explosion of metal wires in the capillary. The effects of the addition ratio and particle size of aluminum powder mixed with PTFE are mainly investigated. The research results show that the triggering stability and the conduction speed of the gap switch are improved to varying degrees compared to the pure PTFE microcavity after adding 2%–5% by mass of aluminum powder. The gap conduction characteristics first improve and then degrade with the increase of the Al addition ratio or particle size when the other condition is unchanged. It is observed that the ablation amount of the microcavity is the highest under the Al addition parameter of a mass ratio of 2% or 5% and a particle size of 150 μm, and the conduction performance of the gas gap switch is relatively optimum under such parameters. This study provides useful guidance for enhancing plasma injection to trigger megavolt UFBPSs at very low energy.