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

Abstract

Many recent works have shown that C4F7N and C5F10O have a great potential to replace SF6 as a greenhouse gas. One of the biggest problems for their application is that condensed species (i.e., graphite) may be produced during gas discharges. However, all the previous works are performed under the assumption of local thermodynamic equilibrium (LTE). Therefore, this study investigates the departure of thermodynamic equilibrium and the corresponding effects on the graphite production in the plasmas of C4F7N, C5F10O, and their mixtures with CO2, N2, and O2, based on the two‐temperature (2T) non‐LTE plasma compositions calculated by the Gibbs free energy minimization. The results show that neglecting the nonequilibrium effect can lead to a very inaccurate description of graphite condensation in the above plasmas.

Eco-friendly gas insulating medium for next-generation SF6-free equipment

“…Some previous works reveal that the thermal interruption performance of a gas can be evaluated by the temperature dependence of the product of specific heat and mass density (i.e., ρC p ) [137,148] . C 4 F 8 -CO 2 arc shows higher peaks of ρC p at high temperatures and lower peaks at low temperatures than SF 6 [138] . C 5 F 10 O arc presents a similar characteristic [143] .…”

“…The composition of an arc also plays an essential role in the calculation of arc plasma properties, such as thermodynamic properties and transport coefficients [136] . The computational results indicate that many eco-friendly gases, such as CF 3 I [137] , C 4 F 8 [138] , C 4 F 7 N [139−141] , and C 5 F 10 O [139, 142−144] , cannot recombine into itself after dissociation in arc plasmas. Most composition calculations assume that arc plasmas are at local thermodynamic equilibrium (LTE) and all species are gaseous.…”

“…Since eco-friendly gases are large molecules that have rich products in arc plasmas, many complex chemical reactions have to be considered in the calculation of thermal conductivity. These reactions especially the dissociation and ionization reactions lead to peaks of thermal conductivity [138,140,143,144] . The arc cooling rate strongly depends on the peaks of thermal conductivity, particularly on the peak at the highest temperature.…”

Partial discharge induced decomposition and by-products generation properties of HFO-1234ze(E)/CO2: a new eco-friendly gas insulating medium

“…Normally, the generation of solid by-products will cause dielectric strength deterioration, operational reliability and service life decreases of GIE, which is common in fluorocarbon eco-friendly gases [34][35][36]. As reported by Liu et al, there exists a relatively large voltage drop between the first and second DC breakdown voltage of HFO-1234ze(E)/N 2 gas mixture owing to the generation of solid by-products that increased the surface roughness of electrode under quasiuniform electric field [26].…”

Theoretical study of the decomposition mechanism of a novel eco-friendly insulation medium HFO-1336mzz(E) considering the effect of trace humidity

“…Also, keeping global warming under 2 • C was set as a key target in the Paris Agreement under the United Nations Framework Convention on Climate Change (UNFCCC) of 2016 [2]. Therefore, many researchers have devoted themselves to the research of searching for eco-friendly gases to replace SF 6 that used in the gas-insulated equipment in recent years [3][4][5][6].…”