In this paper, we present an experimental study in a simpliﬁed arc chamber geometry of Low-Voltage Circuit Breaker (LVCB). The inﬂuence of vent aperture on arc motion and the inﬂuence of splitter plates on arc voltage drop and arc motion are studied. The arc chamber is composed by two parallel arc runners and following the conﬁguration chosen by one or two splitter plates. The experimental setup is completed by a generator (capacitor bench with triggered switch), a high-speed camera and electrical measurements. The arc ignition, arc displacement, arc splitting and arc re-strike have been observed. The results will be described and discussed for diﬀerent experimental conﬁgurations

Benmouffok, M.

Déplaude, G.

Fort, P.

Freton, P.

Gonzalez, J.-J.

Joyeux, P.

Lu, J.

English

CTU Open Journal Systems (Czech Technical University, Prague / České vysoké učení technické v Praze)

doi:10.14311/ppt.2020.1.16Plasma Physics and Technology 7(1):16–20, 2020 © Department of Physics, FEE CTU in Prague, 2020EXPERIMENTAL STUDIES OF ARC MOTION BETWEEN TWOPARALLEL RUNNERS WITH SPLITTER PLATESJ. Lua,∗, J-J Gonzaleza, P. Freton a, M. Benmouffoka, P. Forta,P. Joyeuxb, G. Déplaudeba Laplace, UMR 5213 CNRS-UPS-INP, Université Paul Sabatier 118 rte de Narbonne, bat3R3, 31062 ToulouseCedex, Franceb Hager Electro SAS, 132 Bd d’Europe, 67215 Obernai, France∗ lu@laplace.univ-tlse.frAbstract. In this paper, we present an experimental study in a simplified arc chamber geometry ofLow-Voltage Circuit Breaker (LVCB). The influence of vent aperture on arc motion and the influenceof splitter plates on arc voltage drop and arc motion are studied. The arc chamber is composed bytwo parallel arc runners and following the configuration chosen by one or two splitter plates. Theexperimental setup is completed by a generator (capacitor bench with triggered switch), a high-speedcamera and electrical measurements. The arc ignition, arc displacement, arc splitting and arc re-strikehave been observed. The results will be described and discussed for different experimental configurations.Keywords: LVCB, splitter plate, arc motion, arc voltage.1. IntroductionThe LVCB is an electrical device widely used to pro-tect the power system when a fault current appearsin the circuit. The miniature circuit breaker (MCB)is one of LVCB which provides protection of circuitbelow 1 kV in AC. The electric arc appears during thecontacts opening of MCB and should be extinguishedrapidly. The process includes the displacement of arcbetween the arc runners to the quenching chamberwhich is composed by a series of splitter plates. Thetechnology of arc interruption consists in increase ofthe arc voltage beyond the network voltage to achievethe current interruption. It is well known that thearc voltage increases by arc elongation. But in thecase of MCB, another parameter appears. Due to thevoltage drops of the near-electrode regions of splitterplates, the voltage increases too [1, 2]. This phe-nomenon is mainly responsible for the current inter-ruption. Therefore, the arc motion (due to elongation)and arc voltage (due to voltage drop) are the mostimportant parameters. The vent aperture plays animportant role on the arc motion and splitter plateslead to increase the voltage drop. The study fromShin et al. [3] is devoted to the influence of ventaperture size and repartition on arc motion by arcimaging acquisitions. It is shown that the arc movesfurther and more quickly in case of larger area of ventopening in the quenching chamber. Nevertheless, theconfiguration with more vents helps to increase thearc motion velocity. In previous work, McBride et al.[4] studied arc roots motion from moving contact toarc runners. They developed a flexible test apparatuswith a fast imaging system to investigate the influenceof arc chamber venting on arc motion. The resultsshow that the life time of the arc decreases when thevent area is increased. The arc voltage drop has beenstudied by experimental and theoretical approaches.Lindmayer et al. [5] and Mutzke et al. [1, 6] proposedto consider an additional voltage drop through the re-sistivity in the layer of electrodes to well describe thearc splitting process. The solution is governed by U-Jrelation obtained by experiments. In this relation Uand J represent respectively the voltage and the localvalue of the current density in the neighboring cell ofthe wall (runners and splitter plates). This methodallows presenting a realistic arc root voltage descrip-tion for simulation. Several experiments with onesplitter plate in the arc chamber have been analyzed.They found that about 28-30V are added to the totalvoltage after arc splitting process [1, 5, 6]. Further,Yang et al. [7, 8] studied arcing phenomenon by con-sidering a non-linear permeability of ferromagneticmaterials. They focus their studies on the influence ofeddy currents and the influence of iron metal vaporscoming from splitter plates erosion. The experimenthas been carried out and the results compared withthe simulation. They show that before arc splitting,the anode arc root moves faster than the cathode one.Once the arc reaches the splitter plates, the cathoderoot moves more quickly than the anode root. In thispaper, we present first the experimental setup and theconfigurations investigated. Then two parameters areexperimentally studied: vent configuration on arc mo-tion and the influence of the number of splitter plateson arc voltage evolution. The results are presentedand discussed before the conclusion.16vol. 7 no. 1/2020 Experimental studies of arc motion2. Experimental setup2.1. ConfigurationsA simplified arc chamber configuration with two par-allel arc runners is used and presented in Figure 1.The chamber allows the presence of zero, one or twosplitter plates located in the upstream area. The arcrunners and the splitter plates are made by steel cov-ered by copper. A copper wire with a diameter of0.1 mm is placed between the two arc runners forarc ignition. Two types of vent condition are used(Figure 2).The copper wire is located 10 mm from thedownstream vent. The distance between the initial po-sition of the copper wire and the splitter plates entryis 30 mm. The position of the copper wire correspondsto the birth place of the conducting channel. The arccan move along 50 mm from its initial position beforereaching the upstream vent which could be totallyor partially open (15 % of the whole surface) (table1). Without upstream vent, the arc could reach 20mm more before leaving the chamber. The distancebetween the two main arc runners is 20 mm. Thethickness of a splitter plate is 1 mm.Figure 1. Arc chamber geometry in 3DFigure 2. Vent conditionsFigure 3 presents a general view of the experimentalsetup. It includes a generator composed by capacitorsand inductances that can produce a current half-waveof frequency 50 Hz, which has a prospective peakvalue up to 13 kA with a maximum voltage chargeof 450V in DC. A high-speed camera (Photron SA5)with a maximal recording speed of 12 000 images/s isused with light filters to limit the images saturation.The images obtained by high-speed camera allow ob-serving the arc motion and the splitting process inthe arc chamber. The observation requires the useof transparent walls in the experimental device. Adifferential voltage probe and a Rogowski coil for theelectrical measurements are also used. The wholesystem (Half-wave of the current, high speed cameraand electrical measurements) is synchronized by anexternal Trigger.2.2. Test configurationsTen configurations have been investigated. The twoparameters studied are the number of splitter platesfrom zero (0 Sp) to two (2 Sp), and the vent configu-ration open (O), close (C) or partially open (PO) forthe upstream or downstream vent aperture. Thesecases are presented in Table 1. Each case is repro-duced three times.The cases 1 and 2 are devoted tothe influence of the number of splitter plates in theconfigurations O-O and C-O. The configurations 0 Spand 1 Sp are related to the study of the influence ofthe vent aperture size. Due to the fact that the arcbehavior observed case 3 and case 4 is similar in theconfigurations 1 Sp and 2 Sp, these last results are notpresented.3. Results and discussionTwo kinds of measurement are performed with the tenconfigurations: electrical measurements (current, volt-age) and images by high speed camera. The resultsare difficult to be analyzed and it’s better to associatethe pictures from the camera with the electrical mea-surements for the interpretation. So a specific toolwas developed with @Matlab software to synchronizeacquisitions. The arc roots positions are determinedby the method of McBride [9]. Depending on thearc emissivity the tool allows determining the arcroots positions and the mean arc column positions.Sometime the high-speed camera frequency is differentwith the electrical measurements and the tool allowsinterpolating to present all the results for the sametime.3.1. Influence of vent conditions on arcmotion Cases without splitter plate (0 Sp):Figure 4 and Figure 5 present respectively the aver-age anode root and cathode root positions versustime for the cases without splitter plate. The cases1, 2, 3 allow showing the influence of the down-stream vent surface. For those cases the upstreamvent is open. The arc motion is only due to loopeffects. The arc moves to the upstream position17J. Lu, J-J Gonzalez, P. Freton et al. Plasma Physics and TechnologyFigure 3. Configuration of experimental setupCase 1 Case 2 Case 3 Case 40 Sp O-O C-O PO-O C-PO1Sp O-O C-O PO-O C-PO2Sp O-O C-O — —Table 1. Test configurationsunder the influence of the Lorentz forces. Closingprogressively the downstream vent leads to an in-crease of the arc motion. This difference is probablydue to pressure effects. Decreasing the vent surfaceto 85% (case 3) allows increasing the mean velocityfrom v1=17.6m/s to v3=37.6m/s.These velocities are calculated from the mean po-sitions given in Figure 4 and Figure 5. When thedownstream vent is totally closed the mean arc ve-locity is v2 = 38.4m/s (case 2). In this studiedconfiguration the gas pressure allows increasing bya factor two the mean arc root velocity generatedby the Lorentz forces. Of course in this case theplasma viscosity leads to a clogging effect and thepressure acts to push the arc. This phenomenon ispossible as the upstream event is open and thereis not obstacle to the hydrodynamic flow. On thecontrary when the upstream vent is partially closed(case 4) we can observe a decrease of the mean veloc-ity. In those cases the maximum AC current is I =800A. A comparison between Figure 4 and Figure 5shows that the behavior is similar for the anodicand cathodic arc roots and that the velocities arein the same order of magnitude.Figure 4. Average anode roots positions for differentvent configurations without splitter plate 0 Sp Cases with one splitter plate (1 Sp):The same cases are now considered with the pres-18vol. 7 no. 1/2020 Experimental studies of arc motionFigure 5. Average cathode roots positions for differentvent configurations without splitter plateence of one splitter plate in Figure 6 and Figure 7.The splitter plate is located 30 mm from the wireposition (Figure 1). With the presence of one split-ter plate in the arc chamber, the determinationsof the arc roots positions are less reproducible andso they present higher error bars. Indeed in caseof 1 Sp at the arc commutation beginning multiattachements exist with sometimes a current pathin front of the splitter plates. After the commuta-tion two half arcs exist on each splitter plates faces.These two arcs are not located at the same positionand additional loop effects due to the current pathin the splitter plates appear. All these phenomenonlead to increase the error bars. Similar behavior onarc root velocities observed without splitter plateis found with 1 Sp. Figure 6 and Figure 7 representthe mean arc root positions on the runners in theconfiguration 1 Sp. The splitter plates position isrepresented by an horizontal dashed line.Figure 6. Average anode roots positions for differentvent configurations with one splitter plateFigure 6 shows that the mean anodic arc rootvelocities are lower when one splitter plate is presentin comparison to Figure 4. This behavior is observedfor the four cases. We can observe a real difficultyfor the arc root at the anode to reach the splitterplate in case 1 (O-O). In the same time we observea slope change for the case 3 (PO-O) indicatinga stagnation and a not easy configuration for thearc to overcome the splitter plate. In the two caseswhere the downstream vent is closed, we do notobserve slope change on the curves, indicating thatthe difficulty for the arc to overcome the splitter iscompensated by pressure effects.When we look to the mean cathodic arc root po-sitions, it seems that the arc roots velocities are thesame as in the cases without splitter plate. Except-for the case 1 all the cases seem to be affected by thesplitter presence and arc stagnations are observed.In conclusion it seems that the splitter presencemainly affects the anodic arc root positions leadingto a decrease of the velocities.Figure 7. Average cathode roots positions for differentvent configurations with one splitter plate3.2. Influence of splitter plates on arc voltageIn this section we study the influence of the splitterplate presence on the electrical measurements (inten-sity, arc voltage). Figure 8 presents the total voltagemeasured between the two runners. One peak locatedat time t = 0.33ms is observed, it corresponds to thecopper wire explosion used for the arc ignition. Afterthe wire explosion, in the case without splitter plate,the voltage drop keeps nearly constant with a valuearound 70V. This voltage value corresponds to thesum of the arc column voltage and the values of theanodic and cathodic sheath voltages.Figure 8. Average voltages for case 2 with zero, oneand two splitter platesIn cases of one and two splitters after 1 ms, the volt-age increases. We have seen in Figure 6 and Figure 7that the splitter plate was reached in the time interval19J. Lu, J-J Gonzalez, P. Freton et al. Plasma Physics and Technology1 to 1.3 ms. During this lapse of time the voltage in-creases due to the bent of the arc increasing its length,this is why we do not really observe difference betweenthe configurations with one or two splitters. After 1.3ms, the two curves present different evolutions with anhigher voltage in case of two splitters. The differencebetween the two curves is around 30V. Figure 6 andFigure 7 have shown different positions versus timefor the anodic and cathodic arc roots. This indicatesthat the arc length changes with time and that thearc is not perpendicular to the runners. It is so dif-ficult to discuss the additional voltage value in moredetail which is a combination of changes in arc lengthand additional drops due to the splitters presence. InFigure 9 we have represented the current intensityevolution versus time for zero, one and two splitterscorresponding to the case 2 (C-O). In this same figurethe prospective current intensity corresponding to theapplied current without limitation is plotted. Thecurrent limitation occurs close to 1ms and 1.3ms asindicated previously. From the curve of the prospec-tive current, we can note a greater limitation followingthe number of splitter plates.Figure 9. Average current intensity versus time. Case2 with zero one and two splitter plates.4. ConclusionIn this paper the arc behavior in a simple chamber ofLVCB is studied. The experimental setup is presented.The geometrical parameters investigated are relatedto the area of the vents and to the number of splitterplates. The results show that the arc ignition occursat around 0.3 ms. Depending on the vent surfacethe pressure effect is highlighted. Indeed in the open-open (O-O) configuration the arc moves only underthe influence of the Lorentz forces due to loop effects.When the downstream area is closed or partially closedthe arc velocity increases. This can be explained bypressure effects. The mean arc velocity is multipliedby a factor two between the configurations O-O andC-O. Depending on the number of splitter plates, thetotal voltage increases leading to a current limitation.The total voltage is directly correlated to the numberof splitter plates. Due to the changes in arc lengthfollowing the configuration and the fact that the arcvelocities are also not the same, the arc positionsbetween two configurations differ. It is so difficult toestimate deeper the splitter contribution, neverthelessa contribution of around 30V by splitter is estimated.References[1] A. Mutzke, T. Ruther, M. Lindmayer, and M. Kurrat.Arc behavior in low-voltage arc chambers. EuropeanPhysical Journal Applied Physics, 49, 2010.doi:10.1051/epjap/2010001.[2] J. Lu, G. Déplaude, F. Freton, J.-J. Gonzalez, andP. Joyeux. Experimental and simulation studies on thevoltage drop of arc in low-voltage circuit breaker.European Physical Journal Applied Physics, 6(3), 2019.doi:10.14311/ppt.2019.3.256.[3] D. Shin, I. O. Golosnoy, T. G. Bull, and J. W.McBride. Experiment study on the influence of ventaperture size and distrubution on arc motion andinterruption in low-voltage switching devices. 4thInternational Conference on Electric PowerEquipment-Switching Technology (ICEPE-ST), 2017.doi:10.1109/ICEPE-ST.2017.8188830.[4] J. W. McBride, K. Pechrach, and P. M. Weaver. Arcroot commutation from moving contacts in low voltagedevices. IEEE Transactions on Components andPackaging Technologies, 24(3), 2001.doi:10.1109/6144.946475.[5] M. Lindmayer, E. Marzahn, A. Mutzke, T. Ruther,and S. M. The process of arc splitting between metalplates in low voltage arc chutes. IEEE Trans. CPMT,29(2), 2006. doi:10.1109/HOLM.2004.1353090.[6] A. Mutzke, T. Ruther, M. Kurrat, M. Lindmayer, andE. D. Wilkening. Modeling the arc splitting process inlow voltage arc chutes. 53 rd IEEE Holm Conf. onElectrical Contacts Pittsburgh, 2007.doi:10.1109/HOLM.2007.4318213.[7] F. Yang, M. Rong, and Y. Wu. Numerical simulationof the eddy current effects on the arc splitting process.Plasma Science and Technology, 14(11), 2012.doi:10.1109/TPS.2012.2050703.[8] F. Yang, M. Rong, and Y. Wu. Numerical analysis ofarc characteristics of splitting process consideringferromagnetic plate in low-voltage arc chamber. IEEETrans. Plasma Sci., 43(43), 2010.doi:10.1088/0022-3727/43/43/434011.[9] J. W. McBride and P. M. Weaver. A review of arcingphenomena in low voltage current limiting circuitbreakers. IEE Proc. Sci. Meas. and Tech., 1(23), 2001.doi:10.1049/ip-smt:20010185.20

Experimental Studies of Arc Motion Between Two Parallel Runners with Splitter Plates

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Experimental Studies of Arc Motion Between Two Parallel Runners with Splitter Plates

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