Ionisation and attachment in binary mixtures of SF 6 -N 2 and CCl 2 F 2 -N 2

Xiao

J. Shanghai Jiaotong Univ. (Sci.)

et al. 2008

In c-C4F8 and c-C4F8/CO2 mixtures, the swarm parameters including ionization coefficient, attachment coefficient and effective ionization coefficient were obtained at the ratio of the electric field strength to the gas density between 150-550 Td by the steady-state Townsend (SST) method. Static breakdown voltages at each ratio were also measured at the SST condition. The limiting field strengths were obtained by two methods: computing the density-normalized effective ionization coefficient as a function of the overall density-reduced electric field strength; and measuring static breakdown voltages as a function of the product of gas density and electrode separation. Good agreement was obtained by these two methods, which ensures the correctness of the former method. The limiting field strengths of c-C4F8 and c-C4F8/CO2 mixtures were compared with those of pure SF6, SF6/CO2 mixtures and pure c-C4F8. It is found that buffer gas CO2 does not reduce the limiting field strengths of c-C4F8 greatly, the limiting field strengths of c-C4F8/CO2 mixtures are higher than those of SF6/CO2 mixtures or even pure SF6, and so c-C4F8/CO2 mixtures are suggested to be possible substitutes for SF6.

Section: Test Of the Designed Apparatussupporting

confidence: 56%

“…Therefore, the secondary coefficient is not considered here. Then the equation for the growth of ionization currents in a uniform electric field with steady-state potential is deduced as [9,10] …”

Section: Theory Foundationmentioning

confidence: 99%

Measurement of swarm parameters of c-C4F8/CO2 and its insulation characteristics analysis

Xiao

J. Shanghai Jiaotong Univ. (Sci.)

et al. 2008

1984 IEEE International Conference on Eletrical Insulation

“…Solid lines show present calculations. Figure 5 shows the latter's reported values, which are in very good agreement with our calculations (solid lines), whereas the values by Siddagangappa et al [39] deviate significantly.…”

Section: Ionizaton (A) and Attachment ( N ) Coefficients Of Cclzfzsupporting

confidence: 90%

Insulating properties of mixtures of nitrogen with electronegative gases

Novák

Fréchette

1984

Calculations of the transport coefficients of insulating electronegative gases and their mixtures were performed under the conditions of the Townsend steadystate experiment.The Boltzmann equation was used for evaluation of the unknown collision cross sections by fitting calculated ionization coefficients, drift velocities and diffusion coefficients to experimental data.A stainless-steel vacuum chamber (lO-s torr), provided with a pair of Rogowski-profile electrodes, was set up and used to carry out a series of measurements. The ionization and attachment coefficients were evaluated from the steady-state prebreakdown currents. Results for SF6 are presented in this paper.

Journal of Physical and Chemical Reference Data

“…66͔͒. With the exception of the data of Siddagangappa et al 71 and Harrison and Geballe, 68 there is reasonable agreement among the measurements. The solid line in Fig.…”

Section: Coefficient /Nmentioning

confidence: 59%

“…[63][64][65][66][67][68][69]71,72 Figure 18 shows these measurements which were made at temperatures ranging from 293 K to 298 K. The quoted uncertainties vary from Ϯ5% to Ϯ15% ͓Ϯ5% ͑Ref. 64͒, Ϯ15% ͑Ref.…”

Section: Coefficient /Nmentioning

confidence: 99%

Electron Interactions with CCl2F2

Christophorou

Olthoff

Wang

1997

In this article, available information on the cross sections and rate coefficients for collisional interactions of dichlorodifluoromethane ͑CCl 2 F 2 ) with electrons is critically evaluated and synthesized. This gas has many industrial uses and is of atmospheric and environmental interest. The CCl 2 F 2 molecule fragments rather extensively under electron impact, principally via dissociative ionization and dissociative attachment; the latter process is temperature dependent. Information is presented and discussed on: ͑1͒ electron scattering processes ͓cross sections for total electron scattering, momentum transfer, differential elastic electron scattering, integral elastic electron scattering, and inelastic electron scattering for rotational and vibrational ͑direct and indirect͒ excitation͔; ͑2͒ electron impact ionization ͑cross sections for total, partial, and double ionization and coefficients for electron impact ionization͒; ͑3͒ electron attachment ͑electron attachment cross sections and rate constants and their energy and temperature dependencies, electron attachment coefficients, dissociative attachment fragment anions, and negative ion states͒; ͑4͒ optical emission under electron impact, and ͑5͒ electron transport coefficients ͑electron drift velocity and ratio of transverse electron diffusion coefficient to electron mobility͒. Based upon the assessment of published experimental data, recommended values of various cross sections and rate coefficients are generated in graphical and tabular form. Areas where additional data are needed are identified, such as the measurement of the cross sections for momentum transfer and electron impact dissociation of CCl 2 F 2 into neutral species.