On the formal correctness of the reaction kinetics model and its solution in HV circuit breakers after current zero

336

214

Electrical arcs and, more generally thermal plasmas, are widely used in many applications and the understanding or the improvement of the corresponding processes or systems, often requires precise modelling of the plasma. We present, here, a double approach to thermal plasma modelling, which combines the scientific procedure with an engineering point of view. First, we present the fundamental properties of thermal plasmas that are required in the models, followed by the basic equations and structures of the models. The third part is devoted to test cases, and its objectives are the study of some basic phenomena to show their influence on arc behaviour in simple configurations, and the validation of the models: we point out the roles of radiation, thermal conductivity and electrical conductivity for a stationary or transient wall-stabilized arc and we validate a three-dimensional model for a free-burning arc.Sections 4–6 deal with several industrial configurations and the model is useful in each case for studying important phenomena or processes in greater detail. For transferred arcs, such as those used in metallurgy, the energy transfer from the arc to the anode, and the presence of metallic vapour and pumping gas are essential. For a non-transferred plasma torch used for plasma spraying, we illustrate the relevance of a three-dimensional model and we present the interaction of the plasma with powders. Problems related to high- and low-voltage circuit-breakers are then presented, and various typical mechanisms are modelled. Finally, several non-equilibrium models useful for quasi-thermal conditions are presented in detail, showing how they take into account the chemical kinetics and two-temperature plasmas occurring under particular conditions, such as decaying arcs or inductively coupled plasmas.

Section: Chemical Kinetics Model Alonementioning

confidence: 99%

Thermal plasma modelling

Gleizes¹,

Gonzalez²,

Freton³

2005

336

214

“…Strictly speaking, the above methods can only be used on the assumption of local thermodynamic equilibrium. But if we consider the problems associated with modelling the kinetics of chemical reactions [31,32], these methods are for the time indispensable in the modelling of phenomena in lowtemperature plasma.…”

Section: Discussionmentioning

confidence: 99%

Composition and thermodynamic properties of thermal plasma up to 50 kK

Coufal¹

2007

Self Cite

The initial relations and the description of a method for calculating the composition and thermodynamic properties of a closed gaseous system in thermodynamic equilibrium at constant pressure and temperature are given. The essence of the method consists in the minimization of the Gibbs energy of a system in ideal state. The calculation algorithm is implemented by the Tmdgas program in the C++ language. This program is part of the database system TheCoufal, available to interested parties at http://www.feec.vutbr.cz/~coufal/. The method described was used to calculate the thermodynamic properties of a system of products of the dissociation and ionization of H2O. The results have been tabulated for pressures of 1, 5 and 20 bar at temperatures ranging from ambient temperature to 50 kK.

“…This work is a direct follow-up to [1]. Before reading this paper, it is advisable to become acquainted with [1].…”

Section: Introductionmentioning

confidence: 92%

“…In [1], Coufal and Sezemský formulated five conditions that the model of chemical reaction kinetics and its solution for a gaseous closed system S must fulfil for the solution to be considered formally correct. This work is a direct follow-up to [1]. Before reading this paper, it is advisable to become acquainted with [1].…”

Section: Introductionmentioning

confidence: 99%

Comparison of some models of reaction kinetics in HV circuit breakers with SF₆after current zero

Bartlova¹,

Coufal²

2002

Self Cite

In this paper, the solutions of three models of reaction kinetics in HV circuit breakers with SF6 after current zero are presented and compared. One model has been proposed by Bartlová, the co-author of this paper, the other two models under comparison have been taken over from the literature. In all the three models a constant pressure p(t) = 4 atm and the same dependence of temperature on time T(t) are assumed. For the description of the relation between equilibrium and kinetic composition in a system, the concept of asymptotic composition is introduced. A comparison of the composition and enthalpy of the products of SF6 dissociation and ionization for the given pressure and T(t) is made. General conclusions have been derived from the comparison.