## Plasma Physics and Technology Journal Volume 4 (2017)

### Number 3

Advanced Nonequilibrium Modelling of DC Tungsten-Inert Gas Arcs

Baeva M., Uhrlandt D.

Leibniz Institute for Plasma Science and Technology, Felix-Hausdorff-Strasse 2, 17489 Greifswald, Germany

The paper is concerned with the state-of-the-art nonequilibrium modelling of a DC tungsten-inert gas arc plasma. The advanced description involves the two-way interaction between the plasma and the electrodes. Results in atmospheric pressure argon demonstrating important features of the arc plasma are presented and discussed. First results in the presence of metal vapour released from the molten anode are presented. Outlook for further developments in nonequilibrium arc modelling are discussed.

Keywords: nonequilibrium, arc plasma, magnetohydrodynamic model, diffusion, plasma-electrode interaction.

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Modelling and Simulation of SF6 High-Voltage Circuit-Breakers - an Overview on Basics and Application of CFD Arc Simulation Tools

Reichert F.1, Petchanka A.1, Freton P.2, Gonzalez J. J.2

1Siemens AG, Nonnendammallee 104, 13629 Berlin, Germany
2University Paul Sabatier, LAPLACE, 118 route de Narbonne, CNRS-UPS, 31062 Toulouse, France

The paper gives an overview on the basics of CFD arc simulation tools with respect to the simulation of the fluid mechanical processes in the interrupter unit of SF6 high-voltage circuit-breakers at no-load and short-circuit switching-off processes. On the example of SF6 self-blast circuit-breakers the complete process from the analysis of the switching-off process to the creation of a modular simulation model consisting of several sub models is illustrated. Details to the modelling in the particular sub modules and to the implementation are given. The capability of a CFD arc simulation tool based on the program package ANSYS/FLUENT is demonstrated on the basis of selected simulation results. Furthermore case examples for the application of the presented CFD arc simulation tool in the development process of high-voltage circuit-breakers are given.

Keywords: high-voltage circuit-breaker, CFD arc simulation tool, modelling, application.

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Non-equilibrium Studies in Switching Arc Plasmas in Japan

Tanaka Y.1, Tomita K.2, Inada Y.3, Kumada A.4, Hidaka K.4, Fujino T.7,Suzuki K.5, Shinkai T.6

1Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan
2Kushu University, Kasuga, Fukuoka 816-8580, Japan
3Saitama University, 542 Shimo-Okubo, Sakura, Saitama 338-8570 Japan
4The University of Tokyo,7-3-1 Hongo, Bunkyo, Tokyo 113-8654, Japan
5University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
6Tokyo Denki University, 5 Senju Aasahi, Adachi, Tokyo 120-8551, Japan
7Tokyo University of Technology, 1404-1 Katakura, Hachioji, Tokyo 192-0982, Japan

This paper briefly introduce research work examples of non-equilibrium studies in switching arcs. In understanding arc behavior, one often assumes local thermodynamic equilibrium (LTE) condition in the arc plasma. However, actual arc plasmas are not completely and not always in LTE state because of strong temperature change temporally and spatially, and high electric field application etc. Recently, we have a collaboration work in numerical simulations and experimental approaches for decaying arcs without LTE assumption. First, our numerical model is presented for decaying arcs without chemical equilibrium assumption. Secondly, two experimental methods are introduced for measuring electron density in decaying arcs without LTE assumption: Laser Thomson Scattering method and the Schack-Hartmann method. Finally, comparison results is shown between the LTE simulation, the chemically non-equilibrium simulation, and the above experimental measurements.

Keywords: local thermodynamic equilibrium, chemically non-equilibrium, thermally non-equilibrium, electron density measurement.

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Mechanisms Responsible for Arc Cooling in Different Gases in Turbulent Nozzle Flow

Guo Y.1, Zhang H.1, Yao Y.1, Zhang Q.2, Yan J. D.2

1Pinggao Group Co. Ltd., Pingdingshan City, Henan, China, 467001
2Department of Electrical Engineering and Electronics, the University of Liverpool, Liverpool L69 3GJ, the U.K.

A high voltage gas blast circuit breaker relies on the high speed gas flow in a nozzle to remove the energy due to Ohmic heating at high current and to provide strong arc cooling during the current zero period to interrupt a fault current. The physical mechanisms that are responsible for the hugely different arc cooling capabilities of two gases (SF6 and air) are studied in the present work and important gas material properties controlling the cooling strength identified.

Keywords: SF6 replacement, SF6 alternative gases, switching arc.

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Synthetic Testing of Load Current Interruption in Medium Voltage Load Break Switches

Bendig M.1, Ksoll M.1, Kalter A.2, Schaak M.2, Ermeler K.3, Schnettler A.1

1Institute for High Voltage Technology, RWTH Aachen University, Schinkelstr. 2, 52056 Aachen, Germany
2Siemens AG, Energy Management Division, Carl-Benz-Str. 22, 60386 Frankfurt am Main, Germany
3Siemens AG, Energy Management Division, Nonnendammallee 104, 13629 Berlin, Germany

To conduct the mainly active load current test duty according to IEC 62271-103, a directly powered test circuit and therefore a medium voltage connection or a power generator is needed. A newly developed synthetic test circuit allows to replicate the current as well as the full transient recovery voltage (TRV) and the power frequent recovery voltage (RV) of the direct test circuit up to its crest value. It is dimensioned for voltage classes up to 52 kV and can be adapted to test currents between 630 A and 1250 A. The test circuit allows a detailed investigation of load break switches without costly high power sources and loads. Many parameters, like current and voltage steepness at current zero, as well as different parameters defining the TRV steepness can be varied individually.

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Development of an Experimental Approach for Determining the Arc Quenching Capability of Different Gases

Ksoll M.1, Bendig M.1, Nikolic P. G.2, Schnettler A.1

1Institute for High Voltage Technology, RWTH Aachen University, Schinkelstr. 2, 52056 Aachen, Germany
2Siemens AG, Corporate Technology, G\"unther-Scharowsky-Str. 1, 91058 Erlangen, Germany

After being in the focus of sciences' and industry's research and development activities for many years, the investigation of possible SF6 (sulfur hexafluoride) gas-alternatives has been even more intensified after the revision of the European regulation on fluorinated gases in 2014. This contribution focuses on the scientific assessment of the technical performance of several SF6 gas-alternatives - gases and gas mixtures - currently under discussion. Therefore, a reference experimental setup, that allows the determination of the arc quenching capability of different gases as well as the axial resistance distribution of the switching arc around current zero crossing, is developed. Additionally, first experimental results for the thermal interruption capability and the arc resistance distribution of SF6 and possible SF6 gas-alternatives are shown.

Keywords: arc quenching capability, SF6 gas-alternatives, arc resistance distribution.

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Emission Spectroscopy During High-Current Anode Modes in Vacuum Arc

Khakpour A., Methling R., Franke St., Gortschakow S., Uhrlandt D.

Leibniz-Institut for Plasma Science and Technology, Felix-Hausdorff-Str. 2, 17489 Greifswald, Germany

A vacuum interrupter reaches its interruption limit once high-current anode phenomena occur. High-current anode modes lead to an increase of the anode surface temperature and an increased generation of metal vapor, which may result in a weakening of the dielectric recovery strength after current zero.
In this work, different discharge modes in a vacuum arc for AC 50 Hz including diffuse, footpoint, anode spot type 1 and type 2, and anode plume are investigated. Electrodes made of CuCr7525 with diameter of 10 mm are used. The final gap length is about 20 mm. Time and space resolved optical emission spectroscopy is used to examine the temporal and spatial distribution of atomic and ionic copper lines. The distribution of atomic and ionic lines parallel and perpendicular to the anode surface is investigated. Radiator density is also determined for CuI, CuII, and CuIII near the anode surface.

Keywords: vacuum arc, high-current anode phenomena, emission spectroscopy.

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Bogatyreva N.1, Bartlova M.1, Aubrecht V.2, Kloc P.2

1Department of Physics, Faculty of Electrical Engineering and Communication, Brno University of Technology, Technicka 3058/10, 616 00 Brno, Czech Republic
2Department of Power Electrical and Electronic Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Technicka 3058/12, 616 00 Brno, Czech Republic

In this paper, attention has been given to the absorption properties of the arc plasma at the different pressure conditions. Calculations of the absorption coefficients for a thermal plasma have been performed as a function of the temperature and the frequency. Methods for prediction of the average absorption coefficients were described and compared in detail.

Keywords: air plasma, radiation transfer, absorption coefficient.

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Diagnostics of Various Phenomena in LV Devices Under Real Switching Conditions

Valenta J., Samohejl M., Fendrych M., Kloc P., Dostal L.

Faculty of Electrical Engineering and Communication, Brno University of Technology, Technicka 12, 616 00 Brno, Czech Republic

The article deals with issues to be tackled when performing experiments with low voltage devices under real switching conditions and subsequently discusses various phenomena in an experimental device. The first part describes optimum setting of diagnostic equipment - mainly for optical diagnostic methods. The second part describes some phenomena encountered during switching process under real switching conditions -- arc roots movement (cathode and anode spots). These phenomena are not only important for experimental study itself but also form necessary input data for numerical models and their validation.

Keywords: electric arc, optical diagnostics, high speed video, arc root movement.

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Modelling of Radiative Transfer in Air Arc Plasma

Bartlova M.1,2, Kloc P.1, Bogatyreva N.2, Aubrecht V.1, Pokorny J.2

1Technische Universität Braunschweig, Institute for High Voltage Technology and Electrical Power Systems, 38106 Braunschweig, Germany
2Department of Physics, FEEC, Brno University of Technology, Technicka 10, 616 00 Brno, Czech Republic

The objective of this work is to compare the accuracy of several approximate models of radiative properties for the prediction of radiative transfer in air arc plasma at the temperatures in the range of 300 - 25 000 K and the pressure of 0.1 MPa. Calculated absorption coefficients are used to generate the parameters of different models. The radiative transfer inside the cylindrically symmetrical air plasma with prescribed temperature profile was studied. The equation of radiative transfer was solved using the P$_1$ and SP$_3$ approximations, calculated radiative source term in the energy equation (net emission) was compared with results obtained by spectral integration.

Keywords: radiative transfer, P1 approximation, SP3 approximation, mean absorption coefficients.

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Experimental Temperature Measurements in Miniature Circuit Breaker

Simek D., Pecek D.

Faculty of Electrical Engineering and Communication, Brno University of Technology, Technicka 3058/10, 616 00 Brno, Czech Republic

Low voltage switching apparatuses efficiency depends on the speed of movement of the switching arc from the contacts to the quenching chamber. The paper is focused on investigation of this movement of an arc. Measurement of radiation spectra of the electric arc burning inside miniature circuit breaker and moving to quenching chamber are presented. Measured radiation spectra contain suitable atomic spectra lines for calculation purposes. The problems connected with the measurements are discussed. The main part of the paper deals with a calculation of temperature of the investigated plasma of the arc. Atomic lines database of National Institute of Standards and Technology was used as a spectral data source for the calculations.

Keywords: switching arc, miniature circuit breaker, atomic emission spectroscopy, temperature measurement.

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Objective Function for Numerical Mean Absorption Bands Optimization

Kloc P., Aubrecht V., Bartlova M.

Centre for Research and Utilization of Renewable Energy, FEEC, Brno University of Technology, Technicka 10, Brno, Czech Republic

Mean absorption coefficients (MACs) offer great potential for fast numerical calculation of radiation heat transfer. They are based on replacing complex absorption coefficient spectrum by a handful of frequency bands with a single, temperature dependent value assigned to each band. Accuracy of radiation transfer calculation thus depends on the accurate interpretation of the mean value inside each frequency band as well as on the proper band distribution. Yet finding optimal band distribution is not an easy task often requiring numerical optimization process. This contribution focuses on the parameters of such optimization process, namely selection of an objective function and its effect on the optimal band distribution. It demonstrates, that improper objective functions can produce physically unreasonable artifacts in the calculation of radiation heat transfer. Optimal formulation of the objective function is proposed in this contribution.

Keywords: mean absorption coefficients, numerical optimization, radiation transfer.

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A Review of Progress Towards Simulation of Arc Quenching in Lightning Protection Devices Based on Multi Chamber Systems

Chusov A.1, Rodikova E.1, Murmann M.2, Nordborg H.2, Fuchs R.2

1Streamer Electric, St Petersburg, 191024, Russia
2Institute for Energy Technology, HSR, Rapperswil, 8640, Switzerland

Two distinct modes of follow current suppression were observed in multi-chamber systems (MCS) under lightning overvoltage: Zero Quenching (ZQ) and Impulse Quenching (IQ). Sufficiently lower erosion of electrodes and evaporation of discharge chamber walls makes the IQ more preferable as a mechanism of arc quenching. Since experimental search for best MCS design is both difficult and expensive numerical modeling is considered as a prospective method for geometry optimization. Several steps were made towards development of efficient arc model. This article highlights most important results of arc quenching simulation and current status of arc model development.

Keywords: lightning protection, multi-chamber system, arc discharge, plasma simulations, design optimization.

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Program Processing Database Data for Calculation of Spectral Lines Width and Shift in Plasma

Pokorny J.

Faculty of Electrical Engineering and Communication, BUT in Brno, Technicka 3058/10, 616 00 Brno, Czech Republic

Electric and magnetic fields cause splitting of energy levels in~an~atom. Transition of electrons among these levels could be seen as broadening and shift of spectral lines. We recognize various types of effects, the most important is Stark effect. We developed a program for calculations of temperature dependence linear coefficients of Stark broadening and shift of spectral lines. Our results were calcutated for temperatures usual for SF6 circuit breaker.

Keywords: spectral line broadening, spectral line shift, Stark effect, Van der Waals effect.

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Modeling of the Interaction between the Switching Arc and Hydraulic Driving Mechanism in Gas-blast Circuit Breakers

Zhang H.1, Cao K.2, Zhang Q.2, Yan J. D.2

1Pinggao Group Co. Ltd., Pingdingshan City, Henan, China, 467001
2Department of Electrical Engineering, University of Liverpool, Brownlow Hill, Liverpool, UK

The presence of an arc in a circuit breaker interrupter creates an opposing force to the driving mechanism by changing of the pressure field. This opposing force alters the dynamics of the driving mechanism, the travel characteristics of the moving contact and therefore the switching process. The severity of the influence depends on the structure of the interrupter, the travel profile and also the current waveform, especially the magnitude of the fault current. A 252 kV puffer circuit breaker was used in the present work to study the key factors that contribute to the uncertainty of the predicted contact travel based on coupled simulation.

Keywords: coupled simulation, driving mechanism, switching arc.

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### Number 2

Optical Investigations on Plasma Temperature Estimation in a Model Spark Gap for Surge Currents

Rungea T.1, Franke St.2, Gortschakow S.2, Kurrat M.1

1Technische Universität Braunschweig, Institute for High Voltage Technology and Electrical Power Systems, 38106 Braunschweig, Germany
2INP Greifswald, Felix-Hausdorff-Str. 2, 17489 Greifswald, Germany

In this experimental investigation optical emission spectroscopy is used to characterize the radiation of the plasma in a spark gap during surge. Different approaches are used, compared and discussed in order to estimate plasma temperatures. The measurements were carried out in a narrow gap arrangement based on spark gap technology. This model is tested using 8/20 μs surge currents according to the IEC 62475 with amplitudes of 5 kA and 11 kA.

Keywords: arc, temperature, plasma, spark gap, surge current, surge protective device.

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Kalanov D.1, Golubovskii Yu. B.1, Uhrlandt D.2, Gortschakow S.2

1Saint Petersburg State University, 7/9 Universitetskaya nab., 199034 St. Petersburg, Russia
2Leibniz Institute for Plasma Science and Technology (INP Greifswald), Felix-Hausdorff-Str. 2, 17489 Greifswald, Germany

The description of radiation transport phenomena in the frames of collisional-radiative models requires the solution of Holstein-Biberman equation. An advanced solutuion method for 3D plasma obejcts is proposed. The method is applicable for various line contours in a wide range of absorption coefficients. Developed approach is based on discretization of the arbitrary plasma volume on a Cartesian voxel grid. Transport of photons between the cells is computed using the ray traversal algorithm by Amanatides. Solution of the particle balance equations with computed in advance radiative transfer matrix is demonstrated for various typical arc shapes, like e.g. free-burning arc and cylindric arc. Results are compared with corresponding calculations using previously developed approaches. As the method is suited for finite geometries and allows for a strict solution of the radiation transport equation, applicability ranges of previous approximations can be specified.

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Calculation Of Pressure Rise And Energy Of Hot Gases Due To High Energy Arcing Faults In The Metal-clad Switchgear

Iwata M.1, Miyagi T.1, Goda Y.1, Shirai K.2

1Central Research Institute of Electric Power Industry (CRIEPI), Electric Power Engineering Research Laboratory, 2-6-1 Nagasaka, Yokosuka-shi, Kanagawa-ken 240-0196, Japan
2Central Research Institute of Electric Power Industry (CRIEPI), Nuclear Fuel Cycle Backend Research Center, 1646 Abiko, Abiko-shi, Chiba-ken 270-1194, Japan

This paper presents the 3-D CFD calculation results of the pressure rise due to the High Energy Arcing Faults (HEAFs) in the metal-clad switchgears. The calculations were performed considering the came-off of the roof panel that was observed in the arc tests. The calculated pressure development approximately agreed with the measured one. Furthermore, the energy of hot gases exhausted from the broken roof panel was calculated to investigate the thermal effect of hot gases.

Keywords: internal arc, pressure rise, energy of hot gases.

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Experimental Stand for Investigations of Insulator Degradation and Electrode Erosion in High-current Breaker

Budin A. V.1, Pinchuk M. E.1,2, Leontev V. V.1, Leks A. G.1, Kurakina N. K.1,1, Kiselev A. A.1, Simakova J. V.2,3, Frolov V. Ya.2

1Institute for Electrophysics and Electric Power of Russian Academy of Sciences, Dvortsovaya nab., 18, St.-Petersburg, 191186, Russia
2Peter the Great Saint-Petersburg Polytechnic University, Polytechnicheskaya 29, St.-Petersburg 195251, Russia
3NE Open Joint Stock Company, Partizanskaya , 21, St.-Petersburg, 195248, Russia

An experimental stand for studies of electric arc, electrode erosion and insulator degradation processes in high-current circuit breakers and some preliminary experimental data is described. The setup includes a discharge chamber, a capacitive energy storage with capacitance of 0.11 F, voltage up to 10 kV, and all necessary diagnostic techniques. The stand is designed for modeling current pulse with amplitude of 3–150 kA and duration of the first half period of 1.0–3.0 ms during the process of disconnecting the ring and the pin contacts. The arc is cooled by transverse gas blowing at pressure in the chamber of 0.5–3MPa. Acquired experimental data can be used for verification of the modelling results of the heat transfer processes in the discharge chamber. At the stand, advanced composite materials based on carbon and iron-copper pseudoalloy are studied.

Keywords: high-current high-pressure gas discharge, electrode erosion, insulator degradation, highvoltage test techniques, high-current circuit breaker, high-voltage engineering.

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Analysis of Arc Processes in Multi-chamber Arrester for Lightning Protection at High-voltage Overhead Power Lines

Murashov Iu. V.1, Frolov V. Ya.1 Uhrlandt D.2, Gortschakow S.2, Ivanov D. V.1, Sivaev A. D.3

1Peter the Great St.Petersburg Polytechnic University, Polytechnicheskaya, 29, 195251, Saint-Petersburg, Russia
2Leibniz Institute for Plasma Science and Technology, Felix-Hausdorff-Str. 2, 17489 Greifswald, Germany
3Streamer Electric Company, Nevsky Prospect, 147, 191024, Saint-Petersburg, Russia

Nowadays multi-chamber arresters are widely distributed as devices of lightning protection of overhead power lines. A mathematical modelling of processes in the discharge chamber of multichamber arrester is necessary to carry out in order to improve its breaking capacity. A three-dimensional mathematical transient model of thermal, gas-dynamic and electromagnetic processes taking place in the discharge chamber of multi-chamber arrester is presented in the article. Basic assumptions, model equations, a computational domain and the boundary conditions are described. Plasma turbulence is taken into account. The results of the calculation i.e. distributions of plasma temperature and overpressure in the discharge chamber at different time points are shown. The analysis of the results was carried out. It is shown that the presence of cavities in the electrodes design promotes electric arc extinction in the discharge chamber of multi-chamber arrester.

Keywords: lightning protection, electric arc extinction, arrester.

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Quantifying Uncertainties in Mean Absorption Coefficients for a Wall-Stabilized Electric Arc

Fuchs R., Nordborg H.

Institute for Energy Technology, HSR University of Applied Sciences Rapperswil, Oberseestrasse 10, 8640 Rapperswil, Switzerland

The quality of arc simulations depends significantly on radiation modeling. Uncertainties due to physical parameters and modeling errors should be systematically quantified. We solve the energy balance equation for a wall-stabilized arc using the P1 model, i.e. without a prescribed temperature profile. We derive the linearized equation and assess the arc voltage sensitivity. This method allows us to optimize the definition of mean absorption coefficients consistently and at low computational costs.

Keywords: sensitivity, mean absorption coefficient, P1 model, optimization, arc simulation.

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Synthesis of Nanosilver in Plasma-Liquid Microdischarge System

Chernyak V.1, Hamazin D.1, Kolomiiets O.1, Prysiazhna O.1, Goriachkoa A.1, Trohimchuk A.2, Legenchuk O.2, Lendiel V.1, Fedirchyk I.1

1Faculty of Radio Physics, Electronics and Computer Systems, Taras Shevchenko National University of Kyiv, 64/13 Volodymyrska Street, 01601, Kyiv, Ukraine
2F. D. Ovcharenko Institute of Biocolloidal Chemistry NAS Ukraine, 42 Acad. Vernadskoho Blvd., 03142, Kyiv, Ukraine

This paper presents the results of investigation of the plasma-liquid system with the secondary discharge supported by atmospheric pressure microdischarge in the vortex Ar flow. The plasma treated fluids were aqueous solutions of AgNO3. The microplasma discharge was powered by a DC supply. The plasma channel behaviour was characterized by photo/video recording, also plasma was studied using emission spectroscopy technique. The working liquid and firm products created after the treatment were studied also.

Keywords: microdischarge, secondary discharge, Ag nanoparticles, plasma-liquid system.

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Post-arc Current Measurement in Mechanical Circuit Breakers for Hvdc Applications

Schultz T.

High Voltage Laboratory, ETH Zurich, Physikstrasse 3, 8092, Zurich, Switzerland

Post-arc currents contain valuable information on the breaker’s performance. In this paper, the dimensioning procedure for a measurement system for such currents, based on a diode clamped shunt resistor is presented. Based on synthetic low and high power tests, the performance of a mock-up is evaluated. Finally, the post-arc current of a model gas circuit breaker, designed for use in DC applications, is measured.

Keywords: post-arc current, mechanical circuit breaker, small current measurement system.

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Nonequlibrium Plasma Chemistry for Concept of Sustainable Development

Chernyak V., Nedybaliuk O., Tsymbaliuk O., Fedirchyk I., Chunikhina K., Martysh E., Iukhymenko V., Veremii Iu., Prysiazhnevych I., Prysiazhna O., Prysiazhnyi V.

Faculty of Radio Physics, Electronics and Computer Systems, Taras Shevchenko National University of Kyiv, 64/13 Volodymyrska Street, 01601, Kyiv, Ukraine

This work is devoted to the exploration of the compatibility of the hybrid plasma-catalytic conversion of liquid hydrocarbons into syngas with the concept of sustainable development. The results of experimental investigations indicate the high efficiency of plasma-catalytic conversion of ethanol to syngas and the small amount of waste (a few percent of feedstock weight). The results of the simulation of the kinetics using ZDPlasKin code for thermochemical and hybrid plasma-catalytic conversion.

Keywords: sustainable development, non-equilibrium plasma chemistry, rotating gliding discharge, conversion.

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Influence of Ablation on Differential Arc Resistance

Bort L. S. J., Freiermuth V., Franck C. M.

High Voltage Laboratory, Eidgenössische Technische Hochschule, Zürich, Switzerland

The influence of ablation on the du/di behavior of an arc in a model gas circuit breaker was examined. Specifically the transition from a state without ablation in the nozzle towards states with ablation was of interest, since prior work indicated that for high currents the voltage becomes constant or du/di gets even positive if ablation is present. Measurements with different blow pressures and rectangular DC currents of varying amplitude were compared, using PMMA-nozzles and dry air as blowing gas. Ablation was measured by weighing the nozzle, scanning the cross section, and using a coordinate measuring machine. The results agreed well, and confirmed that higher pressure shifts the du/di curve towards more favorable values.

Keywords: axially blown arc, ablation, passive oscillation, MRTS, HVDC CB.

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Polymeric Ablation Induced by Free Burning Arcs in Air

Bator M., Bianchetti R., Suetterlin P.

ABB Corporate Research Center Switzerland, Segelhofstrasse 1K, 5405 Baden-Daettwil, Switzerland

We investigate the influence of switching arcs on different polymers and their interaction. We describe a set of experiments on a simplified model geometry typical for low voltage switchgear. In a broad range of experimental conditions and parameters such as arc current, polymeric material or contact material, the voltage, the mass loss and the corresponding pressure build-up are examined. From this raw data, we deduce the arc influence on the ablation process as well as the feedback on some arc plasma properties.

Keywords: free burning arcs, low voltage switchgear, plasma properties, polymeric ablation, thermoplastics.

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Investigation of an Ablation-dominated Arc in a Model Chamber by Optical Emission Spectroscopy

Methling R.1, Khakpour A.1, Wetzeler S.2, Uhrlandt D.1

1Leibniz-Institute for Plasma Science and Technology (INP), Felix-Hausdorff-Str. 2, 17489 Greifswald, Germany
2Institute for High Voltage Technology, RWTH Aachen University, Schinkelstrasse 2, 52056 Aachen, Germany

A switching arc in a model chamber is investigated by means of optical emission spectroscopy. Ignition wire is applied to initiate an arc of several kiloampere between tungsten−copper electrodes. Radiation emitted by the arc plasma is absorbed by a surrounding PTFE nozzle, leading to an ablation– dominated discharge. Video spectroscopy is carried out using an imaging spectrometer combined with a high–speed video camera. Carbon ion and fluorine atom line emission from the heating channel as well as copper, oxygen and nitrogen from ignition wire and ambient air are analyzed with focus on the low–current phases at the beginning of discharge and near current zero. Additionally, electrical parameters and total pressure are recorded while the general behavior of the discharge is observed by another video camera. Considering rotational symmetry of the arc the corresponding radial emission coefficients are determined. Finally, radial temperature profiles are calculated.

Keywords: circuit breaker, mathematical model, electrical switch, short circuit.

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Analysis of Last Development Results for High Voltage Circuit-breakers Using New G3 Gas

Robin-Jouan P.1, Bousoltane K.1, Kieffel Y.1, Trepanier J. Y.2, Camarero R.2, Arabi S. 2, Pernaudat G.2

1General Electric Grid Solutions, France
2Ecole Polytechnique de Montréal, Quebec

Among many alternative gases proposed to replace SF6 as insulating gas, g3 (green gas for grid), fluoronitril based component officially introduced at CIGRE 2014, can be now used for insulation projects and new environmental friendly circuit breakers. This gas mixture g3, presents a reduction of the global warming potential by 98% compared to SF6 gas and shows quite good dielectric withstand capability. Many new investigations about thermal and chemical behavior have been done and are precised in this paper. Last switching test campaigns will be presented for 145 kV applications. Simulation tools should be updated to be applicable to these projects. Developments and comparisons with last test results will be analyzed

Keywords: SF6 alternative gases, CO2, Circuit Breaker, g3.

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Analysis of Electromagnetic Processes Inside the Arc Interrupting System of a High-current Circuit Breaker

Murashov I.1, Frolov V.1, Ivanov D.1, Kvashnin A.2

1Department "Electrical Power Engineering and Equipment", Peter the Great Saint-Petersburg Polytechnic University, 29 Polytechnicheskaya, 195251 Saint-Petersburg, Russia
2NE Open Joint Stock Company, 21 Partizanskaya, 195248 Saint-Petersburg, Russia

Description of electromagnetic processes inside an arc interrupting system of high-current circuit breaker is presented in article. Non-stationary mathematical model of the circuit-breaker operation (short-circuit currents mode) is developed. The main regularities of the displacement of the electric arc inside an arc chute are established. The influence of the movable contact position on the conditions for the displacement of the electric arc is presented. Also, the influence of the arc chute material on the motion and interrupting of an electric arc (alternating and direct currents) is established.

Keywords: ablation, switching arc, spectroscopy.

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Investigating of the Recovery Behaviour of a Small Switching Gap after Current Interuption

Bosche D., Alija M., Hilbert M., Kurrat M.

Institute for High Voltage Technology and Electrical Power Systems - elenia, TU Braunschweig, Schleinitzstrasse 23, 38106 Braunschweig, Germany

The recovery behaviour of switching arcs in a small gap was investigated experimentally. Therefore a simple mechanical model switch without an arcing chamber was designed. For the investigation the current carring contacts are separated. After various arcing times, the current is interrupted by an electronic switch. At a fixed contact distance, the switching gap was tested with variable voltages to investigate the dielectric strength. Based on these results the recovery behaviour was studied using the Weibull distribution function.

Keywords: plasma temperature, switching gap, arc, current zero, reignition, Weibull distribution.

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Application Of Rf (13.56 MHz) Arc Discharge For Plasma Chemical Conversion Of Volatile Fluorides

Kornev R. A.1, Sennikov P. G..1, Nazarov V. V..2

1G.G. Devyatykh Institute of Chemistry of High-Purity Substances of RAS, Nizhny Novgorod, Russia
2Institute of Applied Physics RAS, Nizhny Novgorod, Russia

The report discusses the use of a new type of plasma source of hydrogen plasma based on a RF (13.56 MHz) arc discharge of atmospheric pressure between two electrodes. This discharge was used for hydrogen reduction of the tetrafluorides of silicon, boron and molybdenum. As a result of the studies, the main regularities of the hydrogen reduction process were established and the main synthesized products were determined. Samples of carbides of silicon, boron and molybdenum were prepared.

Keywords: RF arc discharge, boron fluoride, silicon fluoride, molybdenum fluoride.

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Rotating Constricted Switching Arcs Burning in Gas and in Vacuum

Baron D.1, Ettingshausen S.1, Koletzko M.3, Lawall A.b, Rettenmaier T.3, Wenzel N.3

1Siemens AG, Energy Management, Medium Voltage & Systems, Frankfurt am Main, Germany
2Siemens AG, Energy Management, Medium Voltage & Systems, Berlin, Germany
3Siemens AG, Corporate Technology, Erlangen, Germany

The method of controlling high-current switching arcs by transverse magnetic fields (TMF) forcing the constricted arc to rotate in a contact system is being applied successfully to improve the breaking capability of vacuum interrupters and gas circuit breakers. We describe the behavior of magnetically driven switching arcs in vacuum and in gas environment. We report on experiments using high-velocity videography, magnetic probes, and spectroscopy; they deliver the velocity, the temperature and the voltage of an arc. We present models and simulations of the moving constricted arc burning in metal vapor and in air. And we describe a particular switching application of TMF arc control and explain a scaling law of the contact size with the current interruption capability.

Keywords: constricted arc, vacuum arc, gas arc.

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An Efficient Implementation of the Finite-volume Method For the Solution of Radiation Transport in Circuit Breakers

Mazaheri A.1, Trepaniera J. Y.1, Camarero R.1, Robin-Jouan P.2

1École Polytechnique de Montreal, 2900 boul. Edouard-Montpetit, Campus de l'Universite de Montreal, 2500 chemin de Polytechnique, Montreal (Quebec), H3T 1J4, Canada
2GE Grid-Solutions, Villeurbanne, France

In this paper, we propose to revisit the method to solve the radiation transport equation in circuit breakers to reduce the computation time. It is based on an explicit approach using a space marching algorithm. The method can further be accelerated using a Cartesian grid and using the axisymmetric assumption. Comparisons performed in terms of accuracy and efficiency between the P1 model, the implicit finite-volume discrete ordinate method and the space-marching finite-volume discrete ordinate method show that the explicit approach is more that an order of magnitude faster than the implicit approach, for the same accuracy.

Keywords: radiation, circuit-breaker, finite-volume method, space-marching.

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Development of Current Limiting Device for Short and Autonomous Networks

Vostrov K., Frolov V., Safonov E.

Department of Electrical Power Engineering and Equipment, Peter the Great Saint-Petersburg Polytechnic University, Polytechnicheskaya 29, 195251 St. Petersburg, Russia

In this paper, the problem of tripping of high values of short-circuit currents in mediumvoltage networks will be considered. Disconnection of short-circuit currents which can reach 100–300 kA in short networks is difficult task for modern switching equipment due to the impossibility of damping the electric arc generated by such currents, and due to strong thermal and electrodynamic effects on elements of the switching device. Solution based on active current limiting reactor will be presented.

Keywords: current limiting, short circuit, arcless commutation, arc extinction.

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Vacuum Arc Ion Flux From Vacuum Interrupter Contact Gap

Kurrat M.

Technische Universitaet Braunschweig, Institute for High Voltage Technology and Electrical Power Systems Schleinitzstrasse 23, 38106 Braunschweig, Germany

Dielectric properties of vacuum interrupters are influenced by metal vapour deposition on the inner ceramic surfaces. Therefore these surfaces are partly protected by shield electrodes. The metal vapour originates from the vacuum arc in the contact gap during switching off process. Metal layer thickness on ceramics after switching operations were measured by Gramberg and the negative effect on dielectric performance was demonstrated. In this paper we address the principle transport process of metal vapour in vacuum interrupters. Duning and Beilis performed ion flux measurements from vacuum arcs. We regard experiments with 5 kA effective arc current. There seems to be experimental evidence that the final particle transport onto the ceramic surface within a shield gap can be explained by particle tracing. The measured deposited layer thickness is taken as quantity to validate vapour densities and transport processes in vacuum interrupters.

Keywords: vacuum interrupter, vacuum arc, ion flux, metal vapour, layer deposition, particle tracing.

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Determination of Cr Density in the Active Phase of a High-current Vacuum Arcs

Gortschakow S.1,Khakpour A.1, Popov S.2, Franke St.1, Methling R.1, Uhrlandt D.1

1Leibniz Institute for Plasma Science and Technology e.V. (INP Greifswald), Felix-Hausdorff-Str. 2, 17489 Greifswald, Germany
2Institute of High Current Electronics, Siberian Branch of the Russian Academy of Sciences, Tomsk 634055, Russia

Melting and evaporation of the anode surface strongly influence the interruption capability of vacuum circuit breakers, because they lead to injection of atomic vapour into the inter-electrode gap. Determination of the vapour density and its dynamics with respect to different anode phenomena is therefore of great importance. Results of Cr density measurements in a high-current vacuum arc by using broadband absorption spectroscopy are presented. The vapour density of atomic Cr is determined after the formation of anode spots as well as close to the current zero. Cr I resonance lines at 425.43nm have been used for the analysis. An AC current pulse with maximum value of 7 kA and a frequency of 100 Hz is applied to a vacuum arc between two cylindrical butt electrodes made of CuCr7525 with a diameter of 10 mm. The high-current anode modes are observed by means of high-speed camera imaging. The temporal evolution of the Cr ground state density is presented and discussed.

Keywords: vacuum arc, anode spot, absorption spectroscopy.

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Interruption of Weakly Cooled Arcs in Air and Airplus

Ranjan N., Carstensen J., Scheel S.

ABB Switzerland Ltd, Corporate Research, Segelhofstrasse 1, 5405 Baden-Dattwil, Switzerland

Switching of low current arcs in free burning or weakly cooled conditions is mainly determined by the thermal properties of the gas. Products with such switching conditions are widely found in secondary distribution medium voltage (MV) gas insulated switchgears (GIS). In this study, we compare the current interruption capability of synthetic air and AirPlusTM, i.e. a mixture of synthetic air with C5F10O fluoroketone (C5-FK). We focus on thermal interruption performance of the gases. AirPlus mixture corresponds to -25&‌deg;C condensation temperature of C5-FK. An arc is drawn between the contacts and cooled by blowing cold gas from a tank. Blowing pressure required for current interruption is compared. Within the measurement accuracy, the current interruption performance of both gases is similar. Chemical analysis of the AirPlus mixture after 69 shots was performed using Gas Chromatography Mass Spectroscopy (GCMS) and it shows very little decrease in the concentration of C5-FK.

Keywords: weakly cooled arcs, load break switches, C5-FK, thermal interruption.

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Modeling of Perfluorocarbons Decomposition in Nitrogen Thermal Plasma

Chau S. W.1, Chen S. H. 2

1Department of Engineering Science and Ocean Engineering, National Taiwan University, 1, Sec. 4, Roosevelt Rd., 10617 Taipei, Taiwan, ROC
2Physics Division, Institute of Nuclear Energy Research, 1000 Wenhua Rd., Longtan, 32546 Taoyuan, Taiwan, ROC

This paper develops an axisymmetric flow model to predict the flow field inside a directcurrent plasma torch reactor, where the magneto-hydrodynamic equations, including the continuity, momentum, energy and current continuity equations as well as turbulence transport equations are solved with a finite volume discretization in a segregated manner. The thermodynamic and transport coefficients of thermal plasma are obtained from the condition of local thermal equilibrium, whereas a kinetics model is employed to consider the production and destruction of species due to the chemical reactions in a decomposition process. Species transport phenomena arising in the decomposition process are described by the transport equations for different species. The perfluorocarbons decomposition characteristics in a well-type, non-transferred nitrogen torch reactor are analyzed by the proposed numerical model to disclose the influence of working parameters on the decomposition efficiency.

Keywords: perfluorocarbons decomposition, nitrogen, thermal plasma, direct-current, plasma torch.

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Contact and Nozzle Wear from 100 Interruptions for a Puffer-Type Air Load Break Switch

Stoa-Aanensen N., Jonsson E., Runde M.

SINTEF Energy Research, 7465, Trondheim, Norway

One type test requirement for medium voltage load break switches is to interrupt 100 consecutive "mainly active loads". A puffer-type switch with axial-blown arc has been tested according to the 630 A/24 kV ratings. The nozzle and contact wear were measured regularly to investigate design requirements and the impact from nozzle wear on gas flow. The contact wear is only moderate, while the nozzle wear causes a decrease in pressure build-up, which in turn may influence the interruption performance.

Keywords: load break switch, switchgear, medium voltage, electric arc, puffer switch, nozzle wear

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Investigation of Pulse Glow Discharge Excitation Modes in N2 in a Hollow Cylindrical Combined Cathode

Bordusau S. Madveika S., Bozhko A., Tsikhan O.

Belarusian State University of Informatics and Radioelectronics, P.Brovki 6, 220013 Minsk, Belarus

Electric discharge excitation modes and N2 pressure range for a stable formation and maintaining of pulse glow discharge plasma in a hollow combined cathode have been investigated. It has been found that both of these parameters are influenced by the constructive peculiarities of the cathode. It has been established experimentally that the value of N2 breakdown voltage for the studied construction of the cathode within the range of 50-250 Pa does not exceed -700 V.

Keywords: hollow cathode, glow discharge, electric pulses, vacuum

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Recent Trends in Development of High Voltage Circuit Breakers with SF6 Alternative Gases

Seeger M.1, Smeets R.2, Smeets R.2, Yan J.3, Ito H.4, Claessens M.1, Dullni E.5, Falkingham L.6, Franck C. M.7, Gentils F.8, Hartmann W.9, Kieffel Y.10, Jia S.11, Jones G.3, Mantilla J.1, Pawar S.12, Rabie M.7, Robin-Jouan P.10, Schellekens H.8, Spencer J.3, Uchii T.13, Li X.11, Yanabu S.11

1ABB Switzerland Ltd, Corporate Research Center, Segelhofstrasse 1K, CH-5405 Baden-D\"attwil, Switzerland
2DNV GL, Utrechtseweg 310, 6800 ET, Arnhem, Netherlands
3University of Liverpool, Department of Electrical Engineering and Electronics, Liverpool, L69 3GJ, UK
4Mitsubishi Electric Corp., Tokyo Building 2-7-3, Marunouchi, Chiyoda-ku, Tokyo 100-8310, Japan
5ABB AG, Bahnstrasse 39-4, D-40832 Ratingen, Germany
6Vacuum Interrupters Limited, Sir Frank Whittle Business Centre, Great Central Way, Rugby CV21 3XH, UK
7ETH Z\"urich, R\"amistrasse 101, 8092 Z\"urich, Switzerland
8Schneider Electric, 35, rue Joseph Monier, 92500 Rueil-Malmaison, France
9Siemens AG, Corp.Techn., Otto-Hahn-Ring 6, 81739 Munich, Germany
10GE Grid Solutions, 51 Espl. du General de Gaulle, 92900 Puteaux, France
11Xi'an Jiaotong University, 28 Xianning West Road, Beilin, Xi'an, Shaanxi, China
12Crompton Greaves, Dr. Annie Besant Road, Worli, Mumbai -- 40001, India
13Toshiba Corp., Power and Industrial Systems R\&D Center, 8 Shinsugita-cho, Kanagawa 235-8523, Japan

The available knowledge of state-of-the-art of SF6 alternative gases in switching applications was collected and evaluated in an initiative of the Current Zero Club together with CIGRE. The present contribution summarizes the main results of this activity and will also include the latest trends. The main properties and switching performance of new gases are compared to SF6. The most promising new gases are at the moment perfluoroketones and perfluoronitriles. Due to the high boiling point of these gases, in HV applications mixtures with CO2 are used. For MV insulation perfluoroketones are mixed with air, but also other combinations might be possible. The dielectric and switching performance of the mixtures, with mixing ratios that allow sufficiently low operating temperatures, is reported to be only slightly below SF6. Minor design changes or de-rating of switchgear are therefore necessary. Differences between the gas mixtures are mainly in the boiling point and the GWP.

Keywords: SF6 alternative gases, CO2, circuit breaker

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The Influence of Microwave CF4 Plasma Activation on the Characteristics of Reactive Ion Etching of Mono-Si

Bordusau S., Madveika S., Lushakova M., Kovalchuk N.

Belarusian State University of Informatics and Radioelectronics, P.Brovki 6, 220013 Minsk, Belarus

The experiments have shown that microwave preliminary ionization of the plasma-forming gas increases the rate of the reactive ion etching of monocrystalline silicon (mono-Si) by four and more times in comparison with the etching process without it. It is established that the mode of plasma activation (the power of microwave discharge) and the value of plasma-forming gas pressure significantly affect the characteristics of mono-Si surface micro-roughness obtained in the result of etching.mixtures are mainly in the boiling point and the GWP.

Keywords: microwave discharge, activation, etching, roughness, surface

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Investigation of Vacuum Arc Anode Temperatures of Cu-Cr and Pure Cu Contacts

Franke St.1, Methling R.1, Gortschakow S.1, Abplanalp M.2, Sutterlin R.-P.2, Delachaux T.2, Menzel K. O.2

1INP Greifswald, Felix-Hausdorff-Str. 2, 17489 Greifswald, Germany
2ABB Corporate Research, ABB Switzerland, Segelhofstrasse 1K, 5405 Baden-D\"attwil, Switzerland

The present contribution reports on investigations of electrode temperatures for pure Cu electrodes and Cu-Cr electrodes of different diameters exposed to vacuum arcs with sinusoidal currents of 5-15 kA and an axial magnetic field up to 180$nbsp;mT. It is found that surface temperatures of pure Cu electrodes are significantly lower than for Cu-Cr electrodes of the same diameter. This must be explained by different thermal properties of both materials. Reducing the diameter of Cu-Cr electrodes it is found that surface temperatures increase, but moreover it is shown that the enthalpy stored in the electrode bulk material may effect electrode temperatures on timescales much longer than the current pulse width, particularly if there is no effective heat dissipation after current zero. Keywords: vacuum arc, anode temperature, thermography Full text * * * Utilisation of the High Speed Camera for the Pin-hole Discharge Diagnostics Kozakova Z., Krcma F., Drimalkova L., Hlochova L. Faculty of Chemistry, Brno University of Technology, Purkynova 118, 612 00 Brno, Czech Republic The high speed camera was utilised for plasma diagnostics of the DC pin-hole discharge in electrolyte solutions. Two discharge modes were determined. Plasma channels were observed either in the bubble or outside the bubble in the bulk solution, which confirms both thermal and electron theory of the discharge ignition in liquid. In the diaphragm discharge, plasma streamers were better visible on the cathode side of the dielectric barrier because they formed significantly longer channels. Keywords: discharge in liquid, pin-hole discharge, high speed camera, plasma diagnostics Full text * * * Experimental Investigations on Electrical Plasma Conductivity in a Model Spark Gap for Surge Currents Runge T., Kopp T. H., Kurrat M. Technische Universitat Braunschweig, Institute for High Voltage Technology and Electrical Power Systems, 38106 Braunschweig, Germany In this experimental investigation the electrical conductivity of plasma is measured during surge current using potential probes. The measurements were carried out in a narrow gap arrangement based on spark gap technology. In order to investigate the electrical conductivity during surge this model is tested using 8/20%nbsp;$mu;s surge currents according to the IEC 62475. The measured behaviour of the electrical conductivity during surge and the uncertainty of these measurements are discussed.

Keywords: arc, electrical conductivity, plasma, spark gap, surge current, surge protective device

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Plasma Assisted Generation of Micro- and Nanoparticles

Veklich A.1, Lebid A. Lebid1, Tmenova T.1, Boretskij V.1, Cressault Y.2, Valensi F.2, Lopatko K.3, Aftandilyants Y.3

1Taras Shevchenko National University of Kyiv, 64/13, Volodymyrska str., Kyiv, Ukraine
2Universite de Toulouse; UPS, INPT; LAPLACE (Laboratoire Plasma et Conversion d'Energie); 118 route de Narbonne, F-31062 Toulouse Cedex 9, France
3National University of Life and Environmental Sciences of Ukraine, Kiev, Ukraine

In this research, the peculiarities of micro- and nanoparticles generation are considered. Two techniques of micro- and nanoparticles' formation using electric arc and underwater discharge plasma sources are proposed.

Molybdenum oxide crystals were deposited on side surface of the bottom electrode (anode) of the free-burning discharge between metallic molybdenum electrodes. Friable layer of MoO3, which consists of variously oriented transparent prisms and platelets (up to few hundreds of mu;m in size), was formed by vapor deposition around the electrode. In the second technique, plasma of the underwater electric spark discharges between metal granules was used to obtain stable colloidal solutions with nanoparticles of 20-100 nm sizes. Keywords: molybdenum trioxide, plasma evaporation, underwater spark discharge, colloidal liquids Full text * * * Changing the Surface Properties of ABS Plastic by Plasma Chlupova S., Kelar J, Slavicek P. Department of Physical Electronics, Masaryk University, Kotlarska 2, 602 00 Brno, Czech Republic The research deals with plasma treatment of acrylonitrile butadiene styrene plastic (ABS). The plastic was treated with Diffuse Coplanar Surface Barrier Discharge (DCSBD) and Gliding arc at atmospheric pressure. ABS was chosen because of its low price, wide use in industry. Samples were analyzed with contact angle measurement and the surface energy was determined as well. The results show that only a few seconds of plasma treatment can cause relatively large wettability change. Keywords: plasma, surface treatment, DCSBD discharge, ABS plastic, contact angle, surface energy Full text * * * Properties of Vacuum Arc Influenced by Electrode Diameter and Material in TMF Contact Based on Forced Current Zero Wenlei Huo1, Jianwen Wu1, Yun Deng1, Xinchen Jin1, Liying Zhu2 1School of Automation Science and Electrical, Beihang University, Beijing 100191, China 2Institute of Spacecraft System Engineering CAST, Beijing 100094, China With the increase in electrical equipment in More/All Electric Aircraft, 270V dc power supply systems will be needed. One method for DC interruption is forced current zero (FCZ). Based on FCZ technology with transverse-magnetic-field (TMF) contact, the spiral-type contacts are designed. Experiments with different currents are carried out with contact diameters being 30 mm, 40 mm, and 50 mm, and arcing surface materials Cu-W80 alloy and Cu-Cr50 alloy respectively. It is indicated by the experimental results that breaking capacity of vacuum interrupter and vacuum arc appearance are closely related to the electrode diameter and material. For the same size of electrode diameter, the breaking capacity in Cu-Cr50 is better than that in Cu-W80. With increasing electrode diameter, arc column expansion velocity and diameter increase gradually. Breaking capacity is increasing with larger contact diameter. Keywords: vacuum arc, forced current zero, transverse magnetic field, breaking capacity, electrode diameter and material Full text * * * Calculation of Arc Power Losses in the Simplified Model of Intensively Blasted Electric Arc Senk J., Laznickova I., Jakubova I. Faculty of Electrical Engineering and Communication, Brno University of Technology, Technicka 12, 616 00 Brno, Czech Republic In previous versions of the simplified model of intensively blasted electric arc burning in argon in the arc heater's anode channel, the authors used the constant total power loss coefficient for estimation of arc power losses in all anode channel individual parts. Using this approach, the model with relatively low computational complexity has led to very good agreement between the total computed and experimentally obtained values, but when the computed and measured power losses of individual anode channel segments have been compared, considerable differences have been revealed. In the modified model, theoretically computed net emission coefficient of argon is used in the energy equation to express the arc power losses. This way, satisfactory accordance is achieved between not only the total, but also partial measured and computed values. Exemplary results are given in figures and tables and discussed. Keywords: electric arc, model, experiment, power loss, net emission coefficient Full text * * * Optical Diagnostics of Switching Arcs Near Current-zero: Speckle Imaging and Interferometry Stoller P. C., Carstensen J., Galletti B., Doiron C. B., Sokolov A. ABB Switzerland Ltd., Segelhofstrasse 1K, 5405 Baden-Daettwil, Switzerland Optical diagnostics can be used to obtain spatially resolved measurements of the density, temperature, conductivity, and electron density of circuit breaker arcs embedded in transonic flows; these can be used to validate the results of simulations, the accuracy of which can currently be assessed in only a limited way. We compare speckle imaging and an interferometric approach. Both use a pulsed nanosecond laser. The speckle imaging setup does not require a reference beam, but only yields information about the gradient of the refractive index. Its accuracy is sensitive to the alignment of the optical components. Interferometry directly yields high resolution images of the index of refraction, from which the density can be calculated using the Gladstone-Dale relation. By using two laser beams, interferometry provides spatially resolved information about the electron density. Such measurements are a significant step towards more accurate CFD models. Keywords: circuit breaker, current-zero, interferometry, imaging, density, temperature Full text * * * Numerical Analysis of low voltage Arc Motion Process at Various Frequencies Yin J.1, Li X.1, Wang Q.2 1State Key Laboratory of Electrical Insulation and Power Equipment, Xi'$an Jiaotong University, Xi$'$an, Shaanxi, 710049, China 2School of Sciences, Xi'an University of Technology, Xi'an, Shaanxi, 710048, China A three-dimensional (3D) magneto-hydro-dynamic (MHD) model of air arc plasma is built to investigate the frequency effects on the arc motion process with different number of splitter plates. Based on this model, the arc voltage and current density are obtained. The arc motion time is normalized with the frequency and compared at different numbers of splitter plate. The result shows that the normalized time and the arc voltage peak increase with increases of the number of splitter plate. Keywords: magneto-hydro-dynamic (MHD), eddy current, frequency, motion process Full text * * * Influencing Factors on the Dielectric Breakdown Strength in F-gas Free High-voltage Switchgear Gossmann S.1, Lutz B.2, Nikolic P. G.1 1Siemens AG, Corporate Technology, G\"unther-Scharowsky-Str.1, 91058 Erlangen, Germany 2Siemens AG, Energy Management, Nonnendammallee 104, 13629 Berlin, Germany After being in the focus of sciences' and industry's research and development activities for many years, the investigation of possible SF6 gas-alternatives has been even more intensified after the revision of the European regulation on fluorinated gases in 2014. In this contribution the influencing factors on the dielectric breakdown of clean air are investigated for weak inhomogeneous field and gas pressures up to 10 bar. Modelling approaches and experimental data are compared. Keywords: F-gas free switchgear, dielectric breakdown, clean air, surface roughness Full text * * * Analysis of Radiation Discretization for Modelling a Spark Gap for Surge Currents Sander C.1,2, Schmutz J.-E.1, Kurrat M.2 1PHOENIX CONTACT GmbH \& Co. KG, Flachsmarktstra�e 8, D-32825 Blomberg, Germany 2Institute for High Voltage Technology and Electrical Power Systems, Technical University Braunschweig, Schleinitzstra�e 23, 38106 Braunschweig, Germany In this paper we address a method for spectrally resolved radiation modelling in thermal plasmas encountered in surge protective devices based on spark gaps. Compared to most switching applications, power input and plasma pressure are much higher which leads to an optically thick plasma with line broadening and enhanced wall ablation. In this situation it is possible to capture the full effect of spectrally resolved radiation on plasma dynamics by performing line-by-line calculations with downsampled absorption spectra. We show that it is possible to achieve radiation convergence with 1000 lines. Approaches for a further reduction of calculation times using band-averaged models and$\kappa$-group models are discussed. The κ-group model is based upon a grouping of the absorption coefficients into subgroups with different ranges of κ before averaging. The spectral calculation results are compared to the approximative methods and significant differences for Rosseland means are observed. Keywords: spark gap, radiation, spectral, simulation, arc, surge protective device Full text * * * Experimental Study on Arcing Effects to Contact Materials in 270V dc Zhu Q.C.1, Li Z.B.1, Wei J.1, Liu Z.X.1, Huang J.1, Zhang D.D.1, Hasegawa M.2 1 State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong Univ.of Science and Technology, 430074, Wuhan, China 2Chitose Institute of Science and Technology, 066-8655, Chitose, Hokkaido, Japan As supply DC voltage levels in automobiles, aviation and aerospace are becoming higher, high voltage and large capacity compact DC electromagnetic relays or contactors are becoming more important. In this paper, experiments were conducted at DC 270V/100A in air and nitrogen, respectively, with CuCr40, CuCr45, CuCr50, CuW60, CuW70 and CuW90 as contact materials. Welding resistance (corresponding to electrical contact life), contact erosion and breaking arc durations were measured, and the obtained results were discussed. Keywords: contact materials, DC voltage, arcing duration, welding, erosion, relay Full text * * * Device for Protection Against Transient and Temporary Overvoltage Including Limitation of the Specific Energy Ehrhardt A., Buhler K. B DEHN + SOHNE GmbH + Co.KG., Hans-Dehn-Strass e 1, D-92318 Neumarkt, Germany An arrangement is presented which ensures protection against transient and line frequency overvoltage and limits the load on the consumer to a minimum even in case of transient currents. The arrangement consists of a special arrester in the shunt circuit, a fast switch in the series circuit as well as a control and measuring device. The design, mode of operation and parameters of the components of the arrangement are described based on different loads. The protective effect is discussed. Keywords: overvoltage protection, surge protection, spark gap, semiconductor switch Full text * * * Optimal Band Selection for the Calculation of Planck Mean Absorption Coefficients Gnybida M.1, Rumpler Ch.2, Narayanan V. R. T.1 1Eaton European Innovation Center, Borivojova 2380, 252 63 Roztoky, Czech Republic 2Eaton, 1000 Cherrington Pkwy Moon Township, PA 15108, USA Radiative heat transfer is a major heat loss mechanism in thermal plasmas generated during arc flashes/faults in switchgear applications or during high current interruption in low voltage circuit breakers. A common way to calculate the radiation balance is by means of approximate non-gray radiation models like P1 or discrete ordinates (DOM), where the frequency dependent absorption and emission are described in a number of frequency intervals (bands) using a constant absorption coefficient in each band. Current work is focused on finding the optimal number of bands as well as band interval boundaries that provide a reasonable level of accuracy in comparison to a full spectral solution. An optimization procedure has been applied to different SF6 and copper vapor gas mixtures for an assumed temperature profile. Radiation model results using optimized band averaged absorption coefficients as well as spectral values are provided and discussed for the exemplary temperature profile. Keywords: radiation, thermal plasma, circuit breaker, SF6 Full text * * * Chemical and Electron Interaction Properties of Potential Gaseous Insulation and Arc-quenching Media Lili Zhu, Dongxian Tanand, Su Zhao, Dengming Xiao Department of Electrical Engineering, Shanghai Jiao Tong University, No.1954 Huashan Rd., 200030,Shanghai, People's Republic of China The global warming effects of sulphur hexafluoride (SF6) lead researchers to look for new environmentally-friendly gas media in high-voltage electrical apparatus. The present paper discusses basic chemical and electron interaction properties that brings high insulation strength and good arc interruption capability for a gas. The conclusion shows that gaseous compounds composed of elements in the upright area of periodic table of elements generally have stronger electronegative ability and good electrical properties. And double bond or triple bond in gas molecule can effectively improve the dielectric strength. For gas mixtures, good cooperation of gases will generate synergetic effect, which makes its dielectric strength higher than the weighted average value of each gas. Some aspects in searching for new arc interruption media are also discussed. Keywords: chemical property, electron interaction, insulation, arc interruption Full text * * * Towards an Efficient Arc Simulation Framework Fuchs R., Murmann M., Nordborg H. Institute for Energy Technology, HSR University of Applied Sciences Rapperswil, Oberseestrasse 10, 8640 Rapperswil, Switzerland Arc simulations require a coupled solution of the flow and electromagnetic equations. Despite of industrial interest, there is no established simulation framework available yet. We assess the usability of STAR-CCM+ for low voltage circuit breaker simulations using a test case of a model arc chamber, since this toolkit allows to define and control the simulation in a single environment. In spite of a partially implemented arc root model, the results agree well with reference data of previous publications. Keywords: arc simulation, arc root model, splitter plates, low voltage circuit breakers, computational magnetohydrodynamics Full text * * * Diagnostics of Nitrogen-methane Atmospheric Glow Discharge Used for a Mimic of Prebiotic Atmosphere Mazankova V.1, Torokova L.1, Trunec D.2, Krcma F.1, Matejcik S.3, Mason N. J.4 1Faculty of Chemistry, Brno University of Technology, Purkynova 118, 612 00 Brno, Czech Republic 2Faculty of Science, Masaryk University, Kotlarska 2, 611 37 Brno, Czech Republic 3Faculty of Mathematics, Physics and Informatics, Comenius University, 842 48 Bratislava, Slovakia 4Department of Physical Sciences, Open University, Walton Hall, Milton Keynes MK7 6AA, UK The exploration of planetary atmosphere is being advanced by the exciting results of the Cassin-Huygens mission to Titan. The complex chemistry revealed in such atmospheres leading to the synthesis of bigger molecules is providing new insights into our understanding of how life on Earth developed. This work extends our previous investigation of nitrogen-methane (N2-CH4) atmospheric glow discharge for simulation chemical processes in prebiotic atmospheres. In presented experiments 2 % of water vapor were addet to nitrogen-methane gas mixture. Exhaust products of discharge in this gas mixture were in-situ analysed by Fourier Transform Infra Red spectroscopy (FTIR). The major products identified in spectra were: hydrogen cyanide, acetylene and acetonitrile. Keywords: prebiotic atmosphere, Fourier Transform Infra Red spectroscopy, glow discharge Full text * * * Implosive Thermal Plasma Source for Energy Conversion Sonsky J.1, Tesar V.1, Gruber J.1, Maslani A.2 1Institute of Thermomechanics of The Czech Academy of Sciences, Dolejskova 1402/5, 182 00 Prague, Czech Republic 2Institute of Plasma Physics of The Czech Academy of Sciences, Za Slovankou 1782/3, 182 00 Prague, Czech Republic Laboratory scale thermal plasma source for magnetohydrodynamic or magnetocumulative generator was developed. The thermal plasma is created from combustible stochiometric mixture of hydrogen and oxygen by spherical implosion of convergent detonation wave. Resulting high velocity plasma is observed by capturing emitted light by hi-speed camera to determine plasma velocity and also spectroscopically in order to estimate of plasma temperatures. Construction of the implosion plasma source is discussed. Keywords: implosion, thermal plasma, detonation wave Full text * * * Study of the Insulating and Arc-quenching Performance of CO2 and Its Mixtures: A Brief Review Zhao H.1, Gu W.2, Li X.3 1School of Automation, Northwestern Polytechnical University, Xi$'$an, Shaanxi, 710072, China 2Sieyuan Electric Co., Ltd. Shanghai, 201108, China 3State Key Laboratory of Electrical Insulation and Power Equipment, Xi$'$an Jiaotong University, Shaanxi, 710049, China SF6, which is widely used as an insulating or arc-quenching medium in electrical apparatus, has a strong global warming potential. Recently, CO2 and its mixtures attract great attention as a promising alternative gas. This paper presents our calculation and measurement results on the insulating and arc-quenching capabilities of CO2 and its mixtures, including the discharge parameters, arc characteristics, post-arc breakdown properties, and arc-quenching capabilities. On the basis of our study and other published literatures, a discussion of and perspectives on current research and future research directions are presented as well. Keywords: insulating, arc-quenching, CO2 Full text * * * Investigation on the Influence of Gas Pressure on CO2 Arc Characteristics in High-Voltage Gas Circuit Breakers Guo Z., Li X., Zhang Y., Guo X., Xiong J. State Key Laboratory of Electrical Insulation and Power Equipment, Xi$'$an Jiaotong University, Xi$'\$an 710049, China

CO2 is identified as a promising alternative gas of SF6. The magnetohydrodynamics (MHD) arc model is established for a CO2 circuit breaker. The influence of gas pressure is studied. The simulations are carried out for 0.5 MPa, 0.7 MPa and 0.9 MPa absolute filling pressure, allowing predictions of pressure and temperature distributions. The arc time constant θ and the power loss coefficient Q is extracted. The thermal interruption capability is estimated to grow with increasing filling pressure.

Keywords: CO2, gas pressure, circuit breaker, Mayr equation

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Evolution of the Cathode Spot Distribution in an Axial Magnetic Field Controlled Vacuum Arc at Long Contact Gap

Tezenas du Montcel B.1,2, Chapelle P.1, Jardy A.1, Creusot C.2

1Institut Jean Lamour - UMR 7198 CNRS/Universit'e de Lorraine, Laboratoire d'Excellence DAMAS, CS 50840, 54011 Nancy Cedex, France
2SuperGrid Institute SAS, 130 rue Leon Blum, BP1321, 69611 Villeurbanne, France

The distribution of cathode spots in a CuCr25 vacuum arc controlled by an axial magnetic field and ignited on the lateral surface of the cathode is investigated for long gap distances, from the processing of high-speed video images. The processing method includes also estimating the current carried by a single spot and reconstructing the distribution of the current density at the cathode. Various distributions depending partly on the arc current are described.

Keywords: vacuum arc, axial magnetic field, long gap, cathode spot distribution, experimental study

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Feedbacks in Non-equilibrium Oxidative Plasma Reacting with Polyethylene

Kadnikov D. V., Ovtsyn A. A., Shibaev S. A. Smirnov S. A

Department of technology devices and materials for electronic equipment, Ivanovo State University of Chemistry and Technology, Sheremetevsky Avenue 7, 153000, Ivanovo, Russia

The experimental results on studies of loading effect at the action of a glow DC discharge in oxygen and air on polyethylene film are presented. At the increase in a polymer amount under a treatment the specific rates of etching and CO2, CO, H2O, H2 product formation rates are decreased. The gas temperature is changed slightly. The reduced electric field strength is increased in oxygen plasma and decreased in air plasma.

Keywords: air plasma, oxygen plasma, loading effect, gas temperature, reduced electric field strength, polyethylene

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