Model Of Electric Arc Research Articles

Electrical Arc Model Based on Physical Parameters and Power Calculation

This paper presents an electrical arc model based on physical parameters of the arc including temperature, enthalpy, pressure, and also arc geometry. In this model, different mass flows and power losses are considered. The different powers including radiative and turbulent power as well as power gain and loss carried by axial and radial mass flows are calculated and simulated as a function of physical parameters. Moreover, the different arc diameter expressions and their influence on power losses are examined by arc experiments with high-speed imaging and arc dynamic behavior analysis. This model can provide the dynamic behavior of the arc easier in contrast to more complex physical models. The comparison with conventional arc models, such as Schwamaker, Habedank, Kema, and Schwarz, illustrates that the new arc model can better reproduce electrical measurements.

Numerical Study of the Impact of Filters Located in the Exhaust Duct of a Low-Voltage Circuit Breaker

Low-voltage circuit breakers under critical situations such as a severe short circuit develop a strong electric arc leading to brutal manifestations such as envelope rupture or fire. Apparatus are strictly designed to avoid damages like personal injury and material destruction. To limit the external manifestations of the electric arc, an efficient way consists of inserting a porous filter in the gas exhaust duct, composed of metallic cloth arranged in a Reps structure. Experimental tests have demonstrated the efficiency of this technique. We propose to complete the experimental study by carrying out the numerical simulations about the filter impact on the hot gas flow. A 2-D model based on the gas flow in porous media is considered, taking into account the porosity variation while the electric arc model derives from the experimental data and a thermal radiation model. A sophisticated finite-volume method based on a well-balanced scheme developed for nonconservative system is used to correctly approximate the solution when dealing with porosity variation.

Quadratic polynomial form of electric arc furnace equation

Purpose – Electric arc furnaces are very often modeled using combined models which cover separately deterministic and stochastic phenomena taking place in the furnace. The deterministic part is expressed by nonlinear differential equations. A closed form of the solution to one of the most popular nonlinear differential equations used for the AC electric arc modeling does not exist for some values of the parameters. The purpose of this paper is to convert electric arc furnace equation for these parameters to the quadratic polynomial form which significantly simplifies solution. Design/methodology/approach – The solution has been obtained in the time domain by a sequence of transformations of the original nonlinear equation which lead to a system of quadratic equations, for which a periodic solution can be found easily using harmonic balance method (HBM). Findings – Quadratic polynomial form of electric arc furnace nonlinear equation in the case for which the solution to the nonlinear differential equation describing electric arc cannot be obtained in a closed form. Research limitations/implications – The complete model of the arc requires extension of the deterministic solution obtained for the quadratic polynomial form using stochastic or chaotic component. Practical implications – The obtained results simplify determination of the arc voltage or radius time waveforms if a closed form solution does not exist. The arc model can be used to evaluate the impact of arc furnaces on power quality during the planning stage of new plants. The proposed approach facilitates calculation of the arc characteristic. Originality/value – In order to avoid problems occurring when a large number of harmonics is required or the system contains strong nonlinearities, a transformation of the original equation has been proposed. Nonlinearities present in the equation have been transformed into purely quadratic polynomial terms. It facilitates application of the classical HBM and allows to follow periodic solutions of the arc equation when its parameters are varied. It also enables better understanding of the phenomenon described by the equation and makes easier the extension of the arc model in order to cover the time-varying character of the arc waveforms.

A simulation model of electric arc

Aspects of construction of a Simulink model of electric arc are discussed. The model allows different problems to be solved that are connected both with investigations of processes occurring in the arc and in its power-supply sources and with tests in static and dynamic regimes, as well as with practical implementation of similar devices. The operating principle of the model is described.

Unsteady three-dimensional model of electric arc. Part 2. Verification

Numerical computations of the electric arc in the external magnetic field have been done for testing the unsteady three-dimensional mathematical model. The arc of a conical and helical shape has been implemented numerically. A satisfactory agreement of the computational results with experimental data points overall to the correctness of the mathematical model and of the computational algorithm.

Unsteady three-dimensional model of electric arc. Part 1. Mathematical model and testing results

A non-stationary three-dimensional mathematical model of the electric arc of constant current in the approximation of a partial local thermodynamic equilibrium of plasma is presented. For the purpose of testing the model and computer code a computation of the isothermal laminar viscous fluid flow past a circular cylinder (the testing of the dynamic part of the system of equations) and a computation of the axisymmetric electric arc with a reduced anode attachment have been done. A fair agreement of numerical results with experimental data points overall to the correctness of the mathematical model and the numerical solution technique.

Modelling of electric arc furnace off-gas removal system

A mathematical model of an electric arc furnace off-gas removal system, aimed at improving the energy efficiency of the smelting process, was created and verified by methods of physical modelling and numerical simulations. For an industrial-scale furnace, equipped with annular distributing off-gas suction system, the possibility to reduce fugitive emissions by 40%, air inflow by 24%, total emissions by 13% and the melting dust removal by 33% was shown. The obtained data will allow, according to estimations, specific energy consumption to reduce by at least 16–20 kW h t−1 and increase the environmental performance of the furnace.

Nitrogen Oxide Formation in the Electric Arc Furnace—Measurement and Modeling

In this article, the results of pilot electric arc furnace (EAF) trials and model calculations regarding the formation of NOx in an electric arc furnace are presented. The results of these investigations confirm that the conditions within the electric arc furnace are favorable for the formation of NOx. During pilot furnace trials, a notable influence of the electric parameters on the NOx formation could not be established. The importance of the influence of the furnace atmosphere, especially the O2 and CO content, could be ascertained clearly. Thermodynamic equilibrium calculations concerning the furnace atmosphere were conducted during the course of the investigations. The results clearly show that the chemical reaction kinetics have a considerable influence on the NOx concentrations measured in the off-gas of electric arc furnaces. Therefore, in addition to the equilibrium calculations, a reactor network model of the EAF was developed subsequently. Using this model, it was possible to reproduce phenomena such as the NOx peak at arc ignition as well as to calculate NOx concentrations, which match measurement data within an order of magnitude.

Asymptotic methods for calculating electric arc model parameters

A new method for calculating the parameters of electric arc models for power circuit breaker is developed. The methodology consists in the optimization of the theoretical arc voltage curve, as a function of a set of parameters, with respect to experimental data. Since the solution of the equation for the electric arc model cannot be obtained in general form, then, the theoretical arc voltage is an asymptotic solution obtained for one or several time-ranges. A case of the irregular behavior of the electric arc is analyzed. The developed methods are applied to obtain an improved arc model for a SF6 power circuit breaker previously published in the literature. The new model has a compact form and exhibits a good correlation between the measured and calculated voltage curves.

Modeling of electrode system for three-phase electric arc furnace

To simulate the process of electrode operation, a dynamic model describing the electrode system of three-phase electric arc furnace was developed. This new model can be divided into three submodels in terms of the practical situation. They are the power supply system model the electric arc model and the hydraulic actuator system model. According to the basic circuit theory, the power supply system model where the high voltage transmission circuit and mutual inductances were considered, was set up. The electric arc model, which was novel for the electrode control, served as the electrical load and was connected to the power supply system model. The hydraulic actuator system model consists of the proportional valve part that is modeled to capture the dead-zone nonlinear characteristics and the hydraulic cylinder part where the impact of the load force is taken into account. By comparing simulation data and actual data, the results show that the electrode system model is proved to be accurate.

Radiation of electric arc burning in argon

Using real experimentally obtained integral values, the paper deals with modelling of electric arc stabilised by flowing gas. Attention is focused namely on approximate estimation of radiation coefficient of argon. A designed model of electric arc burning in argon of atmospheric pressure inside arc heater’s anode channel is described. The model makes it possible to compute axial and/or radial dependencies of some quantities of interest (temperature, velocity, electric field intensity, arc radius, etc.), and subsequently to judge energy exchange between the arc and its surroundings. Sets of model’s input data, including arc voltage, arc current, argon flow-rate, and flow-rates and temperatures of water cooling individual parts of the arc heater, have been measured during numerous experiments. In a studied case with relatively high argon flow-rate, radiation has been found to be prevailing mechanism of energy transfer from arc to anode channel walls. Based on this finding, techniques have been designed for simple approximate estimation of radiation coefficient of argon in a limited extent of temperatures. As an example, they have been tested on a particular set of measured and computed data. Argon radiation coefficient estimated in this way has been compared with the results of theoretical computations carried out by other authors. Considering simplifications used and differences between a real situation and an ideal theoretical model, agreement of the results is within satisfactory limits.

Movement Simulation of Three-Phase Short-Circuit Arcs on Distribution Lines Based on the Coupling of Magnetic Field and Motion

Three-phase short-circuit arcs often cause the breakage of covered conductors on distribution lines, and their movement processes have become an important problem in power-distribution systems. This paper presents the studies on the movement simulation of the three-phase short-circuit arcs. Based on the latest electric arc model and the coupling of magnetic field and motion, this paper develops the procedure to simulate the movement processes of the arcs. Simulation results show that the arcs have different movement directions and behaviors, which are in agreement with the experimental phenomena. This paper is very helpful to design an effective device that prevents the arcs from causing the breakage of the conductor and the damage of the insulator.

Stability of reduced electric arc models

AbstractAn energy equation coupled to the eddy‐current Maxwell equations with nonlinear material coefficients gives a reduced electric arc model with interesting existence and stability behaviour. Applications are arcs in industrial plasma flows. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

SIMULATION RESULTS REGARDING ELECTRODES POSITION CONTROLLING ON ELECTRIC ARC FURNACE

The electric arc furnaces are a very large power load, determining the negative effects on the power quality (harmonics currents, unbalanced load, and reactive power). For a maximum efficiency of the power consumption it is necessary to use an automat system of electrodes position control, in order to obtain a high value of power factor. In this paper are present the simulation results of the electrodes position control on an UHP Electric Arc Furnace in an industrial plants. For simulation it was use an electric arc model, depending on the nonlinearity of the electric arc. The modelling approach adopted in the paper is graphical, as opposed to mathematical models embedded in code using a high-level computer language. The well-developed graphic facilities available in an industry standard power system package, namely PSCAD-EMTDC, are used to conduct all aspects of model implementation and to carry out extensive simulation studies.

Movement simulation of long electric arc along the surface of insulator string in free air

This paper presents the study of a long electric arc in free air due to lightning stroke on the parallel gap lightning protection device (PGLPD) on high-voltage overhead transmission lines. Based on the latest electric arc model, the analysis method of the magnetic field generated by the current flowing through the PGLPD, electric arc, transmission lines, steel tower, and ground wires is developed, and the movement process of the long arc along the surface of the insulator strings is simulated. The simulation results are in agreement with the experimental results. The study is very helpful for the optimal design and suitable assemblage of the PGLPD.

Coupling of an electrical arc model with FEM for vacuum interrupter designs

We present a model of a rotating arc by coupling a finite element method (FEM) and an arc model. A FEM is used to calculate magnetic field between electrodes taking into account the real current distribution in the contacts and in the arc; moreover, ferromagnetic effects and induced currents can be taken into account. A phenomenological arc model is used to predict the arc voltage, which depends on the local magnetic field and the arc length. This arc voltage is updated as the arc displaces itself across the contact surface. The information about arc voltage and local circuit equations is sufficient to find the velocity of the moving arc; hence this model seems more effective than models using Lorentz-forces to describe arc movement which need a priori knowledge about viscosity. This presented method seems to be a promising tool to describe the behavior of rotating arcs in vacuum circuit breakers.

Mathematical modeling of a direct current electric arc: Part II. Dimensionless representation of a direct current arc

A mathematical model presented in Part I of this work is used to describe fluid-flow, heat-transfer, and electromagnetic phenomena in the arc region of a direct current electric arc furnace (DC EAF). From the analysis of the system, the effects of the arc current and the arc length on the arc characteristics and arc bath interactions can be represented analytically in a rather generalized way, based on the finding that the arc shape is unique (defined with the location of the 10,000 K isotherm) when plotted in the appropriate dimensionless form. This dimensionless arc expansion (only restricted to arcs burned between graphite electrodes in air and outside the region where the arc jet impinges on the bath surface) gives the possibility to derive a unique arc description regardless of the values of the arc current and arc length. Dimensionless correlations representing the relationships among important arc characteristics and arc-bath interactions are derived in this work. These expressions may be used to estimate process variables without the need to run complex numerical calculation.

Mathematical modeling of a direct current electric arc: Part I. Analysis of the characteristics of a direct current arc

A mathematical model is used to describe fluid-flow, heat-transfer, and electromagnetic phenomena in the arc region of a direct current electric arc furnace (DC EAF). Based on those model results, a detailed physical analysis of the arc was performed, where the numerical computations help to explain the arc structure, its behavior, and the highly coupled relationship among their main physical variables. This analysis leads to the conclusion that the arc behaves in such a way that all the arc characteristics are controlled by the expansion of the arc, which is the main feature used to physically describe the arc behavior. The arc expansion is evident from the arc shape, which is defined as the region where conduction of electricity takes place. The arc shape is clearly seen in several contour fields presented in this work, such as the current density, the magnetic flux density, the electric conductivity, the electric potential, and the temperature fields. The results of this article focus on process analysis, to provide insight into the inter-relationship among the arc variables, and to establish physical grounds to subsequently explore dimensionless analytical representations to describe the arc behavior.

RADIATION IN WATER-VORTEX STABILIZED ELECTRIC ARC -COMPARISON AMONG DIFFERENT MODELS

The present paper deals with numerical modelling of electric arc stabilized by water vortex. Two-dimensional axisymmetric model includes the arc discharge area between the cathode and the outlet nozzle of the water plasma torch. Thermal, electrical and fluid-dynamic characteristics as well as power losses of such arc has been studied for the range of currents 150-600 A and three different radiation models (net emission coefficient, net emission approach with reabsorption, partial characteristics). It was proved that the amount of energy losses transferred radially from the arc by conduction and radiation range between 70 and 35 % of the input power. Temperature and velocity fields within the discharge are close to each other for the partial characteristics model and for the net emission model with zero reabsorption of radiation. Calculations carried out by the partial characteristics method showed that reabsorption of radiation in arc fringes reaches about 26 % for the studied range of currents.

Calculation of laminar flows of plasma in the channel of a plasmatron with the self-adjusting length of the electric arc

A simplified method is suggested for the calculation of the parameters of laminar flows of plasma in the channel of a plasmatron. A new analytical solution of the Elenbaas–Heller equation is derived, which generalizes the channel model of electric arc to the case when the volume radiation makes a significant contribution to the electric arc energy balance. Numerical calculations are performed in order to determine the electric field intensity, the longitudinal pressure gradient, and the heat transfer to the electric arc channel wall depending on the working parameters of the plasmatron in a laminar flow of gas in a stabilized section. In determining the arc length, it is assumed that the electric arc is shifted downstream of the flow and, at the same time, performs random walks over the channel cross section. The walks occur under the effect of vortexes whose characteristic size is of the order of the arc diameter.