Plasma chemistry modelling of SF₆ replacement gas for high voltage switches

Although it has desirable properties as an arc-quenching medium in high voltage switches, SF₆ has a global warming potential noticeably higher than CO_2. The replacement of SF₆ with a more environmentally friendly gas will be of great benefit to pulsed-power systems. A major candidate is C₄F₇N, commonly known as Novec 4710, which is generally mixed with some percentage of CO₂ as a buffer gas [1]. However, the Novec 4710 and CO₂ mixture in the switch could generate some undesirable long-lived decomposition products after many arcing processes [1]. The modified gas composition could affect the breakdown voltage of the switch as well as contain toxic molecules that can react with the switch materials [2]. A zero-dimensional plasma global model [3] is used to simulate the arc decay process of a Novec 4710/CO₂ switch with the available reaction rate coefficients and cross sections [4]. Using relevant high voltage switch parameters, the model is used to investigate the composition of Novec 4710/CO₂ after one or multiple switches. This information will be critical to determine the feasibility of this replacement gas for use in high voltage switches.

SNL is managed and operated by NTESS under DOE NNSA contract DE‐NA0003525. We thank the support by the Office of Naval Research under grant no. N00014-21-1-2698.

[1] Zhang et al 2020 J. Phys. D: Appl. Phys. 53 173001

[2] Li et al 2020 ACS Omega 5 5911–5920

[3] Lietz et al 2022 Spectrochimica Acta Part B: Atomic Spectroscopy 197 106543

[4] Fu et al 2020 J. Phys. D: Appl. Phys. 53 105202