The dynamic behaviour of wall-stabilized arcs contaminated by Cu and PTFE vapours

Abstract

The transport and thermodynamic properties of gas under contaminated conditions with Cu and PTFE vapours have been determined taking into account the new introduction of molecular particles, produced by chemical interactions between gas and impurities like CuF, , and , making in total 25 species. The main concern of this work is to predict, from the obtained material properties data, the transient behaviour of gas wall-stabilized arcs with these types of contamination that inevitably happen in gas circuit breakers during arc interruption. The results indicate that the electron density and the electrical conductivity increase with Cu vapour contamination, especially below 9000 K, due to the lower ionization potential of Cu atoms, but are almost invariant with PTFE contamination. The thermal conductivity changes only at higher admixture ratios above around 10% for both impurities. Typical increases in due to molecular dissociation have been found at temperatures around 4000 K for Cu vapour and at 3000 - 8000 K for PTFE vapour contamination. The transient behaviours of contaminated gas arcs have been analysed for step-current modulation in the wall-stabilized arcs under the condition of no gas flow. The greater value of arc conductance with Cu vapour contamination broadens the arc current channel, exposing possible disturbance of the current interruption function in gas circuit breakers. PTFE vapour contamination does not affect the arc decay process in wall-stabilized arcs significantly.

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

“…During the OES study of a MCB and a nozzle experiment described in our first paper [9], molecule radiation of C 2 and CuF was recorded under different conditions and to some extent in unexpected ranges of the arc. The molecule CuF is expected when copper vapor from the electrode erosion is mixed with the dissociated PTFE vapor from the nozzle ablation [10]. The results for molecule emission and absorption should be given in this second paper in detail.…”

“…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]). Hence, the study of molecule radiation can help to analyze the interesting ranges of lower temperatures near the nozzle boundaries and in the arc quenching phases.…”

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

“…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].…”

Molecular Dynamic Simulations of the Collision between Copper Ions, SF6 Molecules and a Polyethylene Surface: A Study of Decomposition Products and an Evaluation of the Self‐Diffusion Coefficients

“…[10][11][12] Unfortunately none of the macroscopic models are able to clarify the nature of this boundary layer. [13][14][15] Instead of studying this interaction at the macroscopic scale, we propose a study at the microscopic scale -more precisely, at the atomic level. Indeed, going back to the elementary structure of matter, it should be possible to know precisely how the particles formed during the degradation of the polymer and also to calculate the physical parameters included in macroscopic models.…”

“…The dynamics and the composition of this boundary layer define the thermodynamic properties of the plasma and therefore establish the ablation mechanism 10–12. Unfortunately none of the macroscopic models are able to clarify the nature of this boundary layer 13–15…”