Common parametrizations of electron transport, collision cross section, and dielectric strength data for binary gas mixtures

Abstract

Previously used parametrizations of dielectric strengths (electrical breakdown data) for gas mixtures in terms of electron collision and transport parameters are reviewed. A new method of fitting experimental data on dielectric strengths for binary electronegative gas mixtures is proposed based upon the principal assumption that the electron kinetic energy distributions in the gas are Maxwellian. The method provides physical insight into such behavior as pressure-dependent or pressure-independent synergisms, and is useful in checking the consistency between dielectric strength data and available information on electron transport and ionization, attachment, and momentum transfer collision cross sections. The method is applied here to the mixtures SF6/N2, CCl2F2/N2, and SF6/CCl2F2.

Partial discharges and breakdown in C3F8

“…This method has shown sufficient agreement between estimated and published curves for SF 6 and CF 4 . Further, Wieland approximation [41] for calculating the critical field strength shows no difference to the linear interpolation of the critical field strengths for the mixtures of C 3 F 8 with C 2 F 6 and C 2 F 6 with CF 4 . For C 3 F 8 -CF 4 mixtures, the deviation from the the linear interpolation is 3 % at its maximum and never exeeds the critical field strength of C 3 F 8 .…”

Research for electric energy systems -- an annual report

“…In the present case, the required contribution from reaction (19) For the scheme given in Table 1, it was found that reaction (33) is the dominant S0F 4 formation mechanism with reaction (25) [43] to analyze dielectric strength data for binary gas mixtures with the purpose of determining the consistency of these data with relevant information about swarm and electron-collision cross sections for the individual gas constituents.…”

“…Since details of the model have been described elsewhere [43], only an outline of the main assumptions is given here; namely: 1) the intrinsic dielectric strength of an electronegative gas mixture, i.e., the critical electric field-to-gas density ratio (E/N) c ra , is defined by the criterion a m **^m * where a m and rj m are respectively the electron-impact ionization and attachment coefficients for the mixture; 2) the electron energy-distribution functions for the mixture are Maxwellian; 3) the mean electron energy in a binary gas mixture £ m is given by a weighted sum of the mean energies of the component gases A and B,…”

Research for electric energy systems - an annual report

“…£ i ( 20 ) where B^, b^, and a^are adjustable parameters, the values for which can be found in [28]. The momentum transfer cross section data for SF^and were obtained from Phelps, et al .…”

“…[28] . The discussion given here is restricted to a brief description of the "pressure-independent" model and its application to the analysis of data for the gas mixtures SF^/N^, SF^ which can be readily solved numerically to find the x and 0^d ependencies of T..…”