The opening process of thermal plasma contacts in a post-arc channel after current zero in a flat-type gas-blast quenching chamber

Abstract

The electrical resistivity of a post-arc channel after current zero was measured along the nozzle axis in a flat-type gas-blast quenching chamber. In the chamber, iron electrodes were intentionally adopted, since Fe spectral lines at wavelengths of 426 and 443 nm have much higher radiation intensities than those of , F or Cu at temperatures below 5000 K. Observation of the two Fe spectral lines permitted determination of temperature T and iron vapour concentration in the post-arc channel up to s after current zero. On the other hand, of gas contaminated with iron vapour was theoretically calculated on the basis of the simplified first Chapman - Enskog approximation. Use of this calculation result made it possible to estimate of the post-arc channel from the measured T and . The estimation result revealed that increased more dramatically at the nozzle throat than at other axial locations, reaching at after current zero. Furthermore, on the basis of the axial distribution of , the concept of `thermal plasma contacts' was developed to interpret behaviour of the post-arc channel.

Ablation-Dominated Arcs in CO² Atmosphere - Part II: Molecule Emission and Absorption

“…[3]). This is because atomic and ionic species dominate in the high temperature regions and generate an intense spectral line radiation which can be well used for the determination of temperatures and species densities [6][7][8]. However, the analysis of low-temperature regions of the arc fringes, of the regions near nozzle walls and of the temporal phase of arc quenching is much more challenging due to low line radiation intensities.…”

“…It is well known from composition calculations of thermal plasmas that the dissociation of filling gases like SF 6 and CO 2 and reactions with the ablation product C 2 F 4 and metal vapor from electrode erosion can produce a number of molecular species in an intermediate temperature range before an almost complete dissociation to atoms occurs at higher temperatures (see e.g. [10]).…”

Ablation-Dominated Arcs in CO2 Atmosphere—Part II: Molecule Emission and Absorption

“…Meanwhile, a sufficiently good knowledge of the arc properties during the high-current phase and in the high-temperature regions (above 6000 K) of the arc has been developed from spectroscopic studies of switching arc experiments and MCBs (see e.g., [3]). This is because atomic and ionic species dominate in the high-temperature regions and generate an intense spectral line radiation which can be well used for the determination of temperature and species densities [6][7][8]. However, the analysis of low-temperature regions of the arc fringes, of the regions near nozzle walls and of the temporal phase of arc quenching is much more challenging due to low line radiation intensities.…”

“…It is well-known from composition calculations of thermal plasmas that the dissociation of filling gases like SF 6 and CO 2 , reactions with the ablation product C 2 F 4 and metal vapor from electrode erosion can produce a number of molecular species in an intermediate temperature range before an almost complete dissociation of atoms occurs at higher temperatures (see e.g., [10]). Mixtures of CO 2 with higher amount of C 2 F 4 are expected to contain considerable amounts of molecules at temperatures above 3000 K, namely CF 4 , CF 3 , CF 2 , C 2 F, C 3 , C 2 , CF, and CO (in order of dissociation with increasing temperatures) [11].…”

Transient Response Simulation of Downstream Thermofluid Field in a Gas Circuit Breaker during Current Interruption

“…Although there are many papers on hot gas behavior at arcing contacts (5), (6) , there are few papers on SF 6 hot gas behavior inside the exhaust tube during current interruption (7), (8) . Furthermore, it is difficult to obtain the real time experimental data of SF 6 hot gas flow inside the exhaust tube just at current zero in the real GCB, since SF 6 thermal arc interruption has transient and complex phenomenon.…”