Arc Elongation Research Articles

Study on the influence of transverse magnetic field on the arc and reignition characteristics of HVDC relays

It is of great significance to clarify the influence of transverse magnetic field (TMF) on arc control in high-voltage direct current (HVDC) relays. In this paper, the influence of TMF in a wide range of 0–140 mT on the arc characteristics of HVDC relays is studied, the experimental observations of arc reignition are carried out and the effect of arc reignition on contact erosion, the criterion of arc reignition and the mechanism of TMF enhancement on arc reignition are further analyzed. The results show that the TMF enhancement is beneficial for shortening the arc voltage stagnation duration and accelerating the speed of arc elongation, arc dispersion and dispersed arc motion, thereby improving the arc extinguishing performance. However, higher TMF leads to more severe and earlier arc reignition, as also shown in the experimental observations. The arc reignition further causes a sudden drop in arc voltage, prolonged arc duration and uneven contact erosion. To evaluate the occurrence of arc reignition caused by TMF enhancement, a simplified breakdown criterion is proposed through the defined characteristic variable C¯(t) . Based on this, the mechanism by which the TMF enhancement more easily causes arc reignition is explained, that is the higher TMF leads to an earlier and faster increase in C¯(t) and slightly reduces the breakdown threshold C¯∗(t5,D) . Further, measures to suppress the arc reignition are proposed.

Comparative study of ARC elongation of flat and inclined splitter plates in ARC chamber of moulded case circuit breaker

Comparative study of ARC elongation of flat and inclined splitter plates in ARC chamber of moulded case circuit breaker

Transient Arc Characteristic of a Commutation Switch Utilizing High Velocity Contact Separation

Commutation circuits are commonly used for low on state resistance and high current interruption capability if this can not be achieved by a single device or single current switching path. In case of fault detection, a very fast commutation of the current from the low-impedance main current path into the parallel high-current interrupting path is necessary. For single usage applications a low-cost approach is the utilization of a pyrotechnical switch in the low-impedance path. Compared to other electromechanical switches, those switches provide very high velocity of contact separation and thus a fast arc voltage rise with short commutation times. Here, measurements of the contact movement of a pyrotechnical switch were carried out using optical high speed imaging and an arc elongation up to 100ms−1 was calculated. From this, transient arc characteristics were measured in a simplified commutation network during the period until current zero in the low-impedance main current path.

Physical properties of the swept arc channel in the context of lightning strikes to aircraft

During an in-flight lightning strike, the relative motion between the arc channel and the aircraft causes a sweeping of the attachment point on the aircraft skin. To predict the behaviour of the arc channel and therefore the potential locations for further restrikes, this study aims at investigating the phenomenon with an innovative method for producing sweeping arcs based on a stationary arc and an electromagnetic launcher propelling aeronautical samples. This article focuses on characterisation of the arc channel, aiming at establishing the evolution of its physical properties during swept-stroke for various experimental conditions. Firstly, the experimental coupling of the lightning generator with the electromagnetic launcher and with a wind tunnel is described with a discussion on the representativeness of the experiment. Then, high-speed cameras and voltage and current probes are used to measure the electrical and geometrical behaviour of the electric arc channel during a swept-stroke. The shape, the length, the voltage and the power evolution of the arc channel are evaluated for different input parameters such as speed, polarity, arc current and sample length. Furthermore, the influence of these parameters on the temperature of the arc channel is studied, resorting to an optical emission spectroscopy technique. The results are presented and discussed with the objective of providing a physical insight into arc elongation phenomenology during a swept-stroke.

Effect of coil charge duration on combustion variability and flame morphology in a GDI engine working in lean burn conditions

Spark ignition (SI) and subsequent flame front development exert a significant influence on cyclic variability of internal combustion engines (ICEs). The increasing exploitation of lean air-fuel mixtures in SI engines to lower fuel consumption and CO2 emissions is driving the scientific community towards the search for innovative combustion strategies. Moreover, although lean combustion has been widely investigated and an important number of studies is already present in literature, the high cyclic variability typical of this combustion process still represents a major hinder to its exploitation. This study aims to investigate the effects of increasing ignition energy on combustion characteristics of lean mixtures. Tests were performed on an optically accessible gasoline direct injection (GDI) engine that allowed to investigate the correlation between the thermodynamic results and spark arc-flame morphology. Engine speed was fixed at 2000 rpm, a relative air fuel ratio (AFRrel) of about 1.3 was selected and ignition timing was set at 12 crank angle degrees (CAD) bTDC. Coil charge duration was swept from 10 to 40 CAD. Two intake pressure levels were investigated, the first corresponding to wide open throttle under naturally aspirated operating mode, the second with an intake pressure of 1.2 bar, thus corresponding to a boosted operating condition. Two dedicated scripts built using NI Vision were employed for image processing, allowing the evaluation of temporal and spatial evolution of the early stages of combustion. Arc elongation and flame front contour were used as correlation parameters that characterize flame kernel inception and development. The results confirm that, as expected, the increase of the coil charge duration tends to reduce cyclic variability in terms of engine output. The optical investigations revealed that for both examined cases the standard deviation related to the wrinkling effect on flame edge at CA5 decreased as the coil charge duration increased.

Simulation of a single-phase arc grounding fault on a 220-kV cable transmission system

Cable tunnel fires are mainly caused by single-phase arc grounding faults. The massive energy generated by arc can threaten the safety of the densely laid cable tunnels. In this study, a digital arc fault model with a 220-kV cable transmission system was established on Power Systems Computer Aided Design(PSCAD). The arc model was improved because the parameters were acquired from the experimental results. The arc fault can be divided into two stages: a primary arc at the initiation of the fault and a secondary arc after the tripping of the circuit breakers. The primary arc contains few nonlinear components because of the large arc currents. The secondary arc voltages exhibit nonlinear characteristics because of arc elongation. The secondary arc power continues to increase, however, its amplitude is considerably smaller than the primary arc. The lifetime of the primary arc is dependent on the action of the relaying protection system. Further, some limits based on the energy balance theory were introduced to obtain the extinction time of the secondary arc. In addition, the total energy generated by the arc fault in the 220-kV cable transmission system will eventually become 4891 kJ. This digital arc fault model will significantly contribute to future research with respect to the mechanism of cable tunnel fires.

Hydrogen Production from Methane Decomposition Using a Mobile and Elongating Arc Plasma Reactor

Hydrogen and solid carbon were produced through methane decomposition in a plasma reactor with a parallel set of screw type helix and rod-like electrodes. The novel configuration led to the 3-dimensional movement of plasma zone in the axial and angular directions as well as arc elongation. The effect of arc elongation and movement at various angular velocities of high voltage electrode was investigated on the reactor performance in terms of methane conversion, hydrogen yield, and energy yield. In addition, the influence of fluid flow direction was considered. Methane conversion of 47% and hydrogen production rate of 132.7 ml/min with the energy yield of 36.8 g/kWh were achieved at stable operating conditions. The deposition rate of carbon was 35 mg/min which had a graphite-like structure. A reaction pathway is proposed according to reaction path analysis in order to interpret the underlying plasma chemical process.

Lithospheric folding by flexural slip in subduction zones as source for reverse fault intraslab earthquakes

Subduction requires the permanent generation of a bend fold in the subducting slab which mechanics is not well understood. Lithospheric bending of subducting slabs was traditionally considered to be accommodated by orthogonal flexure, generating extensional outer rise earthquakes responsible of the external arc elongation during folding. Here we explore the possibility of lithospheric flexure being accommodated through simple shear deformation parallel to the slab (folding by flexural slip) and evaluate this process as source of earthquakes. The seismicity predicted by flexural slip dominated slab bending explains a significant amount of intermediate earthquakes observed in subduction zones with different degrees of coupling. This mechanism predicts the generation of intraslab thrust earthquakes with fault planes subparallel to the slab top. Being the orientations of the fault planes the same for the interface thrust earthquakes and the flexural-slip intraslab earthquakes, the amount of seismic moment liberated by the interface could be significantly lower than considered before. This proposed seismic source should be taken into account in models and hazard studies of subduction zones. Determining the seismic generating processes in subduction zones and their characteristics is a fundamental issue for the correct assessment of the associated seismic and tsunami risk.

Electric Arc in Low-Voltage Circuit Breakers: Experiments and Simulation

The aim of this paper is to present a further approach for analyzing the air electric arc in low-voltage circuit breakers (LVCBs). In order to achieve that, a new simulation model and experimental tests have been carried out. The simulation model has been designed using ANSYS CFX, a finite-volume method commercial software. This model has been defined as a 3-D geometry, with a high density structured hexahedral mesh, P1 radiation model and hot air characteristics for thermal plasma properties and transport coefficients. The model is applied to simulate the behavior of an LVCB for 50, 100, and 200 A with different numbers of splitter plates in the arc chamber and different locations for the arc ignition. As result, arc elongation and arc voltage increase have been observed when increasing the splitter plates number. Also faster arcs for higher ignition zones and greater expansion and diffusion for higher input currents have been obtained. These simulation results have been verified and validated. The verification process has been accomplished calculating the numerical errors, by means of the grid convergence index and Courant-Friedrichs–Lewis number. Thus, the most accurate mesh densities, time steps, and radiation models have been selected. Finally, the validation process has been achieved performing real experimental tests in the laboratory, proving that the results of the simulation model are close to real scenarios.

CO2 conversion in a gliding arc plasma: 1D cylindrical discharge model

CO2 conversion by a gliding arc plasma is gaining increasing interest, but the underlying mechanisms for an energy-efficient process are still far from understood. Indeed, the chemical complexity of the non-equilibrium plasma poses a challenge for plasma modeling due to the huge computational load. In this paper, a one-dimensional (1D) gliding arc model is developed in a cylindrical frame, with a detailed non-equilibrium CO2 plasma chemistry set, including the CO2 vibrational kinetics up to the dissociation limit. The model solves a set of time-dependent continuity equations based on the chemical reactions, as well as the electron energy balance equation, and it assumes quasi-neutrality in the plasma. The loss of plasma species and heat due to convection by the transverse gas flow is accounted for by using a characteristic frequency of convective cooling, which depends on the gliding arc radius, the relative velocity of the gas flow with respect to the arc and on the arc elongation rate. The calculated values for plasma density and plasma temperature within this work are comparable with experimental data on gliding arc plasma reactors in the literature. Our calculation results indicate that excitation to the vibrational levels promotes efficient dissociation in the gliding arc, and this is consistent with experimental investigations of the gliding arc based CO2 conversion in the literature. Additionally, the dissociation of CO2 through collisions with O atoms has the largest contribution to CO2 splitting under the conditions studied. In addition to the above results, we also demonstrate that lumping the CO2 vibrational states can bring a significant reduction of the computational load. The latter opens up the way for 2D or 3D models with an accurate description of the CO2 vibrational kinetics.

THE DETECTION AND STATISTICS OF GIANT ARCS BEHIND CLASH CLUSTERS

ABSTRACT We developed an algorithm to find and characterize gravitationally lensed galaxies (arcs) to perform a comparison of the observed and simulated arc abundance. Observations are from the Cluster Lensing And Supernova survey with Hubble (CLASH). Simulated CLASH images are created using the MOKA package and also clusters selected from the high-resolution, hydrodynamical simulations, MUSIC, over the same mass and redshift range as the CLASH sample. The algorithm's arc elongation accuracy, completeness, and false positive rate are determined and used to compute an estimate of the true arc abundance. We derive a lensing efficiency of 4 ± 1 arcs (with length ≥6″ and length-to-width ratio ≥7) per cluster for the X-ray-selected CLASH sample, 4 ± 1 arcs per cluster for the MOKA-simulated sample, and 3 ± 1 arcs per cluster for the MUSIC-simulated sample. The observed and simulated arc statistics are in full agreement. We measure the photometric redshifts of all detected arcs and find a median redshift z s = 1.9 with 33% of the detected arcs having z s > 3. We find that the arc abundance does not depend strongly on the source redshift distribution but is sensitive to the mass distribution of the dark matter halos (e.g., the c–M relation). Our results show that consistency between the observed and simulated distributions of lensed arc sizes and axial ratios can be achieved by using cluster-lensing simulations that are carefully matched to the selection criteria used in the observations.

Similarities and differences between gliding glow and gliding arc discharges

In this work we have analyzed the properties of a gliding dc discharge in argon at atmospheric pressure. Despite the usual designation of these discharges as ‘gliding arc discharges’, it was found previously that they operate in two different regimes—glow and arc. Here we analyze the differences in both regimes by means of two dimensional fluid modeling. In order to address different aspects of the discharge operation, we use two models—Cartesian and axisymmetric in a cylindrical coordinate system. The obtained results show that the two types of discharges produce a similar plasma column for a similar discharge current. However, the different mechanisms of plasma channel attachment to the cathode could produce certain differences in the plasma parameters (i.e. arc elongation), and this can affect gas treatments applications.

Unsteady state analysis of free-burning arcs in a 3-Phase AC plasma torch: comparison between parallel and coplanar electrode configurations

An MHD model with parallel electrode configuration was developed to determine the influence of the electrode configuration on 3-Phase arc discharge behavior. The results obtained with this model were compared to previous results obtained with coplanar graphite electrode configuration. Results show a different arc behavior in both cases. In a parallel electrode configuration, the arcs are not confined within the inter-electrode gap as in coplanar electrode configuration. These results were compared to the arc behavior observed with a high-speed video-camera in a nitrogen atmosphere with a high correlation. The influence of frequency and current was also investigated. By adjusting the electrode configuration, the arc elongation and the dissipated power could be controlled. According to the application, such as plasma-assisted combustion, plasma gasification, plasma spray or for different plasma gases, the electrode configuration could play a key role to improve the discharge or operation. This study gives us a better understanding of 3-Phase AC arc plasma discharge.

Calculating local geomembrane indentation strains from measured radial and vertical displacements

An experimental technique to measure the radial and vertical components of displacement from local gravel indentations in a geomembrane is presented. Results from short-term physical experiments are reported where vertical displacement was imposed by one of three machined steel probes (round, cone, and flat) to a 1.5-mm-thick high-density polyethylene geomembrane. The experiments were intended to simulate the idealised response with nominal 50 mm coarse gravel above the geomembrane under controlled experimental conditions. Measurements of vertical and radial displacements were used to quantify the influence of probe shape on maximum strain in a geomembrane when calculated with large strain–displacement theory. For both the round and cone probes, the maximum strain in the geomembrane was located directly beneath the centre of the probe, while the maximum strain with the flat probe was near the edge of the probe. Strains calculated using large strain–displacement theory are then compared with thin shell theory and the arc elongation method. Thin shell theory and the arc elongation method were both found to calculate incorrect strain distributions and also provide magnitudes that can significantly underestimate the maximum strain in a geomembrane.

Simulation of Low-Voltage Arc Plasma During Contact Opening Progress

This paper focuses on the simulation of the low-voltage arc with an opening contact. A controllable experiment setup with a rotating contact is designed to investigate the arc behaviour. Supported by the experiment, the phenomena of arc elongation and commutation in the case of rotating contact are simulated with the dynamic grid technique introduced. Under the given condition of the external magnetic field and the contact rotating velocity, the stagnation and rapid jump of two arc roots are observed by the calculated and experimental arc root displacement. The voltage of arc column can be divided into four phases and its sharp rising progress comes from the increase of the displacement difference between two arc roots in x direction.

The Adequacy Analysis for Installation of High Speed Grounding Switches on the Korean 765kV Single Transmission Line

This paper analyzes arc phenomena including the secondary arc's elongation in the Korean 765kV single transmission line (79km) between Sin-Ansung S/S and Sin-Gapyeong S/S, which will be installed in Korea in June 2006. In particular, both frequency independent and frequency dependent line models are compared to make our final decisions. As well, the significant simulation results are investigated by the EMTP program. As a result, there is no need of HSGS in the Korean 765kV single transmission line from both a practical and an economical point of view.

Numerical Algorithm for Adaptive Autoreclosure and Protection of Medium-Voltage Overhead Lines

In this paper, a new numerical algorithm for medium-voltage overhead lines, autoreclosure, is described. The subfunction of the autoreclosure scheme that would inhibit the first shot after detecting a solid fault (as compared with an arc fault) is evaluated and presented. It is based on one terminal data processing and it is derived in the time domain. In the algorithm the fault nature (arcing or arcless fault) is estimated using linear least error squares estimation technique. The arc, occurring on the fault point during arcing faults on overhead lines, is included in the problem consideration. In addition, by introducing the prefault load current in the existing model, better algorithm performances and a more reliable adaptive algorithm for autoreclosure are achieved. The algorithm is derived for the case of three-phase symmetrical fault. The results of the algorithm testing through computer simulation are presented. Particularly the algorithm sensitivity to arc elongation effects, supplying network parameters, and processing of the signals in the presence of harmonics are tested and analyzed.

Probabilistic modelling of the high-pressure arc cathode spot displacement dynamic

A probabilistic modelling approach for the study of the cathode spot displacement dynamic in high-pressure arc systems is developed in an attempt to interpret the observed voltage fluctuations. The general framework of the model allows to define simple, probabilistic displacement rules, the so-called cathode spot dynamic rules, for various possible surface states (un-arced metal, arced, contaminated) and to study the resulting dynamic of the cathode spot displacements over one or several arc passages. The displacements of the type-A cathode spot (macro-spot) in a magnetically rotating arc using concentric electrodes made up of either clean or contaminated metal surfaces is considered. Experimental observations for this system revealed a 1/f∼1 signature in the frequency power spectrum (FPS) of the arc voltage for anchoring arc conditions on the cathode (e.g. clean metal surface), while it shows a `white noise' signature for conditions favouring a smooth movement (e.g. oxide-contaminated cathode surface). Through an appropriate choice of the local probabilistic displacement rules, the model is able to correctly represent the dynamic behaviours of the type-A cathode spot, including the FPS for the arc elongation (i.e. voltage) and the arc erosion trace formation. The model illustrates that the cathode spot displacements between re-strikes can be seen as a diffusion process with a diffusion constant which depends on the surface structure. A physical interpretation for the jumping probability associated with the re-strike event is given in terms of the electron emission processes across dielectric contaminants present on the cathode surface.

Numerical algorithm for medium voltage overhead lines protection and adaptive autoreclosure

In this paper a new numerical algorithm for medium voltage overhead line protection and autoreclosure is presented. It is based on one terminal data processing and it is derived in the time domain. In the algorithm, the fault location and fault nature (arcing or arcless fault) are estimated using the linear least error squares estimation technique. An arc occurring on the fault point during arcing faults on overhead lines is included in the consideration of the problem. Additionally, by introducing the pre-fault load current in the existing model, better algorithm performances are achieved. The algorithm is derived for the case of a three-phase symmetrical fault. The computer simulation results of the algorithm testing are presented and, in particular, the algorithm sensitivity to arc elongation effects and processing of the signals in the presence of harmonics is tested and analysed.

A new approach to arc resistance calculation

An important macroscopic arc parameter, describing its complex nature is arc resistance. As known, the fault arc resistance can be calculated by the Warrington formula. The authors investigated the results of Warrington's tests. Warrington derived a relation for the arc voltage by using the measured arc voltage gradient and arc current as input data. By analyzing these measurements and by taking into account the conditions under which they are obtained (inaccurate measurement devices), it is unquestionable that the results are highly empirical and not accurate and general enough. Laboratory testing, provided in the high power test laboratory FGH-Mannheim (Germany), in which long high current arcs are initiated, was the base for the research results presented. In this paper a new approach to arc resistance calculation is given. Two independent approaches delivered the same equation. Both approaches are based on a suitable and a simple arc model assuming the rectangular wave form of the arc voltage, which is in phase with the arc current wave form. The new formula for arc resistance is compared with the Warrington formula. The influences of arc elongation are also investigated.