Thermodynamic Properties at High Temperatures and Particles Present After Arc Extinction in CO2-CF3I Mixture

Yokomizu, Yasunobu; Ochiai, Ryusuke; Matsumura, Toshiro

doi:10.1541/ieejpes.129.1187

Cited by 4 publications

(10 citation statements)

References 6 publications

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“…The quantity n tm is the molar number density [mol/m 3 ] in the hightemperature SF 6 and is expressed as n tm = n tot /N AVO in terms of the total number density n tot and the Avogadro constant N AVO (6.02×10 23 mol −1 ). Use of the equilibrium composition shown in Fig.…”

Section: Molar Heat Capacitymentioning

confidence: 99%

“…Use of the equilibrium composition shown in Fig. 1(a) allows us to evaluate C Vm for the high-temperature SF 6 with ρ = 29.7 kg/m 3 .…”

Section: Molar Heat Capacitymentioning

confidence: 99%

“…where E d SF 6 is the dissociation energy of SF 6 . In addition to the Guldberg-Waage equations and the Saha equations, applications of various laws enabled us to form the following simultaneous equations expressed in terms of the number density n i : (i) the charge neutrality equation; (ii) Dalton's law of partial pressures; (iii) an equation defining the composition of S and F. Solving the aforementioned simultaneous equations for a specified total pressure P allowed us to derive n j under the constant-pressure state.…”

Section: Calculation Procedures the Formulamentioning

confidence: 99%

“…Circuit breakers in electricity systems utilize SF 6 , air, or CO 2 as the arc-quenching gas. Concerning these gaseous media, their high-temperature properties, such as an equilibrium composition and thermo-physical properties, have been evaluated to provide the fundamental characteristics of the gas aspect at high temperature [1][2][3][4][5][6][7][8]. By way of example, the obtained composition reveals the predominant particle species present at high number densities in the high-temperature gas.…”

Section: Introductionmentioning

confidence: 99%

“…The first objective is to determine the equilibrium composition of the high-temperature SF 6 present at constant volume. For this objective, numerical solutions are carried out to determine the equilibrium composition in the range 300-30 000 K. This solution is achieved on the basis of the minimization of the Helmholtz free energy of the high-temperature SF 6 .…”

Section: Introductionmentioning

confidence: 99%

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Particle composition and heat capacity of high‐temperature SF₆ present at constant volume: Discussion on formula expressing relationship between constant‐pressure and constant‐volume heat capacities

Yokomizu

Kobayashi

Matsumura

2015

IEEJ Transactions Elec Engng

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Until now, the high‐temperature properties of SF6 have been derived as a function of T for a given constant pressure P. This was based on the adoption of T and P as gas state parameters. In contrast, this paper adopts T and the gas volume V as the gas state parameters and then evaluates the particle composition and gas pressure for high‐temperature SF6 present at a constant volume state. This evaluation is achieved by the minimization of Helmholtz free energy of the high‐temperature SF6. A further derivation for the SF6 gas at constant volume is performed to reveal the temperature dependence of the molar heat capacity CVm [J/(mol·K)] and the specific heat CVg [J/(kg·K)]. Use of the obtained CVm enabled us to discuss whether the formula CPm−CVm=Rm holds true for the high‐temperature SF6 or not, where CPm and Rm are the molar heat capacity at constant pressure and the universal gas constant, respectively. Similar discussion is also performed on the formula indicating the relation between CPg and CVg, where CPg is the specific heat at constant pressure. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

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Section: Molar Heat Capacitymentioning

confidence: 99%

“…Use of the equilibrium composition shown in Fig. 1(a) allows us to evaluate C Vm for the high-temperature SF 6 with ρ = 29.7 kg/m 3 .…”

Section: Molar Heat Capacitymentioning

confidence: 99%

Section: Calculation Procedures the Formulamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Particle composition and heat capacity of high‐temperature SF₆ present at constant volume: Discussion on formula expressing relationship between constant‐pressure and constant‐volume heat capacities

Yokomizu

Kobayashi

Matsumura

2015

IEEJ Transactions Elec Engng

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Electrical and thermal conductivities of high-temperature CO₂–CF₃I mixture and transient conductance of residual arc during its extinction process

Yokomizu¹,

Ochiai²,

Matsumura³

2009

J. Phys. D: Appl. Phys.

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Fundamental properties of CO2 mixed with CF3I were investigated in terms of (i) electrical and thermal conductivities at temperatures up to 30 000 K, (ii) a decay process of an arc conductance around a current zero under a free transient-recovery-voltage condition and (iii) an arc extinguishing capability in a thermal re-ignition region. The electrical conductivity at temperatures below 10 000 K proved to increase gradually with the admixture amount of CF3I. The thermal conductivity, in particular around 7000 K, was found to have marked dependence on the CF3I concentration. The result for the decay process of the residual-arc conductance under the free transient-recovery-voltage situation showed that the arc conductance attenuated more rapidly for CO2 mixed with CF3I at concentrations above 0.9 than for pure CO2. The mixture gas having the same concentrations was also revealed to cause the arc to be extinguished under a higher transient-recovery voltage than pure CO2.

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Predominant reaction products and dielectric breakdown properties of gas mixtures consisting of SF₆ and ablation products of C₂F₄/BN in the temperature range of 300–3000 K

Yokomizu¹,

Terada²,

Kodama³

et al. 2021

J. Phys. D: Appl. Phys.

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For a high voltage SF6 circuit breaker equipped with a boron nitride (BN)-filled polytetrafluoroethylene ((C2F4) n ) nozzle, the predominant reaction products in a high-temperature SF6 mixture with vapor decomposition of C2F4 and BN at temperatures of 300–3000 K are determined based on calculations of equilibrium composition. The calculation is performed by considering the molecular products obtained by chemical reactions with boron atoms (e.g. BN, BS, BC, BF, BF2 and BF3), nitrogen atoms (e.g. N2, N3, CN, NS, NF, NF2 and NF3) and carbon atoms (e.g. CS, CS2, C2F4, CF2, CF3 and CF4). The results obtained for the C2F4–BN molar fraction X C F B N of 20%–80% reveal that BF3, N2 and CF4, the molecules originating from the nozzle material, are produced at high molar fractions over a range of 300–3000 K. Such an evaluation of the gas composition allows the derivation of a reduced collision ionization coefficient α/N and a reduced electron attachment coefficient η/N of the gas, considering various electron impact processes such as BF3 + e → BF2 + F− and CF4 + e → CF3 + F−. The evaluation subsequently enables us to determine a critical reduced electric field strength E c r / N causing ( α − η ) / N = 0 . The results suggest that the decomposed C2F4–BN mixture at X C F B N of 80% causes the reduction of E c r / N to 110 Td in the range of 1000–2000 K at a gas pressure of 1.0 MPa. This strength E c r / N is 20 Td lower than that determined separately for the SF6 gas mixture with only 80% C2F4 vapor decomposition, because of the CF4 molar fraction reduction in the SF6/C2F4–BN mixture.

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Thermodynamic Properties at High Temperatures and Particles Present After Arc Extinction in CO2-CF3I Mixture

Cited by 4 publications

References 6 publications

Particle composition and heat capacity of high‐temperature SF₆ present at constant volume: Discussion on formula expressing relationship between constant‐pressure and constant‐volume heat capacities

Particle composition and heat capacity of high‐temperature SF₆ present at constant volume: Discussion on formula expressing relationship between constant‐pressure and constant‐volume heat capacities

Electrical and thermal conductivities of high-temperature CO₂–CF₃I mixture and transient conductance of residual arc during its extinction process

Predominant reaction products and dielectric breakdown properties of gas mixtures consisting of SF₆ and ablation products of C₂F₄/BN in the temperature range of 300–3000 K

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Thermodynamic Properties at High Temperatures and Particles Present After Arc Extinction in CO2-CF3I Mixture

Cited by 4 publications

References 6 publications

Particle composition and heat capacity of high‐temperature SF6 present at constant volume: Discussion on formula expressing relationship between constant‐pressure and constant‐volume heat capacities

Particle composition and heat capacity of high‐temperature SF6 present at constant volume: Discussion on formula expressing relationship between constant‐pressure and constant‐volume heat capacities

Electrical and thermal conductivities of high-temperature CO2–CF3I mixture and transient conductance of residual arc during its extinction process

Predominant reaction products and dielectric breakdown properties of gas mixtures consisting of SF6 and ablation products of C2F4/BN in the temperature range of 300–3000 K

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Particle composition and heat capacity of high‐temperature SF₆ present at constant volume: Discussion on formula expressing relationship between constant‐pressure and constant‐volume heat capacities

Particle composition and heat capacity of high‐temperature SF₆ present at constant volume: Discussion on formula expressing relationship between constant‐pressure and constant‐volume heat capacities

Electrical and thermal conductivities of high-temperature CO₂–CF₃I mixture and transient conductance of residual arc during its extinction process

Predominant reaction products and dielectric breakdown properties of gas mixtures consisting of SF₆ and ablation products of C₂F₄/BN in the temperature range of 300–3000 K