Chemical species produced in arc-quenching gas CO₂/O₂ mixed with C₃H₂F₄, C4-FN or C5-FK: prevention of condensed-phase carbon formation and its formulation

Abstract

Regarding CO 2 /O 2 -based mixture as an arc quenching gas in high-voltage circuit breakers, the predominant component species present in high numbers at temperatures of 300-20 000 K are determined in consideration of addition of CF 3 CFCH 2 (hereinafter written as C 3 H 2 F 4 ) gas to the CO 2 /O 2 -based mixture. In the determination, not only are 87 gaseous species but also condensed-phase carbon (hereinafter written as C(c)) taken into account as component species. The evaluation results reveal that CO 2 , O 2 , CF 4 and HF in gaseous phase behave as the predominant component species at 300-1000 K for lower content additive-gas, whereas the species C(c) is also generated as the predominant component at the same temperature for higher content additive-gas.Subsequently, reactions of chemical elements C, O, F and H to form the above-described chemical species are successfully expressed using CO 2 , O 2 and C 3 H 2 F 4 contents as stoichiometric coefficients. Expressing the reactions furthermore enables us to formulate the prevent condition of the C(c) generation as a function of O 2 content X O2 and C 3 H 2 F 4 content X CHF . Similar formulations are successfully performed for CO 2 /O 2 /C4-FN and CO 2 /O 2 /C5-FK mixtures.

Graphite production in two‐temperature non‐LTE plasmas of C4F7N and C5F10O mixed with CO2, N2, and O2 as eco‐friendly SF6 replacements: A numerical study

“…These three subgraphs also indicate that the condensed species, that is, graphite, exists at low temperatures in the plasmas of C 4 F 7 N, C 5 F 10 O, and their mixtures. Several previous works [ 7,10,11 ] have reported similar results in LTE plasmas, whereas this study first reports the production of graphite in non‐LTE 2T plasmas. This will be discussed in detail in Section 3.…”

“…Recently, C 4 F 7 N (C4‐PFN) and C 5 F 10 O (C5‐PFK) have been considered as potential alternatives to SF 6 and have attracted a lot of attention. [ 1,5–13 ] The dielectric strength of C 4 F 7 N and C 5 F 10 O is approximately two times as much as that of SF 6 , and the GWP of both gases is much lower. [ 2,7 ] Moreover, these two gases have zero ozone‐depleting potential.…”

“…However, one of the biggest problems when applying C 4 F 7 N and C 5 F 10 O in the power industry is that not only gaseous species but also condensed species may be produced upon high‐energy gas discharge, for example, during the arc interruption process in circuit breakers. The previous works by Zhong et al, [ 7 ] Yokomizu et al, [ 10 ] and André‑Maouhoub et al [ 11 ] reveal by computation or experiments (e.g., the current interruption test using a self‐blast circuit breaker conducted by Supergrid Institute [ 11 ] ) that condensed‐phase carbon, that is, graphite, may exist in arc plasmas of C 4 F 7 N, C 5 F 10 O, and their mixtures with CO 2 , N 2 , and O 2 when arc temperatures decrease. Similar phenomena are also observed in arc plasmas of other carbonaceous gas mixtures, such as C 2 F 4 –CO 2 [ 15 ] and CO 2 –CH 4 .…”

Behavior of Eco-Efficient Insulation Mixtures Under Internal-Arc-Like Conditions

“…It is, however, possible to use instead chemical equilibrium considerations to gain some information about the overall reaction enthalpies associated with this chemical process. Such chemical equilibrium models are commonly used in the context of circuit breaker applications [38], and recently have been applied to different C5-FK and C4-FN containing gas mixtures [31], [39], [40].…”

“…The decomposition mechanisms for C5-FK and C4-FN have been addressed theoretically in a number of recent studies [29], [30]; one theoretical study focused specifically on decomposition under electric arc conditions [31]. Prévé et al [32] studied the decomposition of C5-FK and C4-FN experimentally in a model of a medium voltage load break switch, albeit under conditions (energy input to volume ratio) that are far from realistic for such equipment.…”