Simulation Of High-current Vacuum Arc Research Articles

3D modeling and simulation of high-current vacuum arc subjected to real external transverse magnetic field

Vacuum circuit breakers (VCBs) are widely used in power distribution systems. When the VCB in a switchgear interrupts the short circuit current, the U type loop, which consists of a vacuum interrupter, an external busbar and a conductive rod, generates an external transverse magnetic field (ETMF). This field deflects the vacuum arc and affects the interruption performance of the VCB. In this paper, the real magnetic field data of the arc region are obtained by establishing a simulation model of an electrode system, taking into account the real ETMF and real axial magnetic field (AMF). Furthermore, the three dimensional steady magnetohydrodynamic model of the vacuum arc is established by using real magnetic field data as the boundary condition. The vacuum arc characteristics under the combined effect of AMF and the asymmetric transverse magnetic field (TMF) are studied. The simulation results show that the ETMF considerably changes the Bx of the arc column, which demonstrates asymmetry in the positive and negative directions, whereas By demonstrates a weaker asymmetry. Moreover, the asymmetric TMF deflects the distributions of the vacuum arc plasma and increases the partial heat flux density and axial current density. With the increase in the severity of the short circuit, the TMF asymmetry of the arc region is enhanced and the deflection of the vacuum arc plasma is also enhanced.

Hybrid Numerical Simulation of High-Current Vacuum Arc Taking Into Account Secondary Plasma Generation

This paper is devoted to the further development of a numerical model for the simulation of high-current vacuum arcs (HCVA) with cathode attachment in the form of multiple cathode spots. The model allows one to simulate different modes of HCVA and the transition between them. It is shown that the secondary plasma, arising from the anodic sputtering and nonadherence of the incident ions, affects the constriction of the plasma and the transition between the HCVA modes.

Modeling and simulation of high-current vacuum arc considering the micro process of anode vapor

In vacuum arc (VA), when the arc current is very high (usually in the tens of kilo-ampere), the heat flux density injecting into an anode is larger and leads to a higher anode temperature with the increasing of current. The strong anode evaporation drives the evaporated atoms from the anode surface to the arc column. Simultaneously, the anode evaporated atoms impact with the cathode plasma, and then the micro processes as ionization and recombination between anode atoms and plasma will happen. In this paper, the two fluid three-dimensional (3D) magneto-hydro-dynamic (MHD) model of VA considering ionization and recombination processes is built, and the influence of the anode vapor and its micro processes on the arc column is obtained by solving the two fluid MHD equations, which control anode neutral atoms and cathode plasma, respectively. In the model, the ionization of neutral atoms and the recombination of ions are both considered, the mass, momentum and energy exchange caused by the ionization and recombination processes are also considered. Moreover, the influence of ionization and recombination processes on the electromagnetic process of VA is also considered in the model. By numerical simulation, the anode vapor distribution, cathode plasma distribution and VA distribution, such as density, temperature, pressure, etc, are all obtained, and the parameters related to ionization and recombination processes are also obtained. When the anode temperature is high enough, the anode neutral vapor will enter into the arc column, and strong ionization happens at the interface between anode vapor and cathode plasma. Then, the anode vapor will be quickly ionized (usually smaller than a few microseconds) and generate a lot of ions (usually higher than 1021 m−3 orders of magnitude). The anode neutral vapor has the same temperature with the anode surface, which is much lower than the temperature of the arc column, so the anode neutral vapor obviously has a cooling effect on the arc column. Whether anode neutral vapor will enter into the arc column or not, is determined by the balance between anode neutral vapor and cathode plasma.

3-D Simulation of High-Current Vacuum Arcs Under Combined Effect of Actual Magnetic Field and External Transverse Magnetic Field

Based on a steady-state 3-D magnetohydrodynamic (MHD) model, the high-current vacuum arc (HCVA) under combined effect of actual magnetic field (MF) and external transverse MF (ETMF) is simulated. The actual MF is generated by cup-type axial magnetic field contact system commonly used in commercial vacuum circuit breakers. The ETMF may cause the deflection of arc column, which is the main reason of the contact deflected erosion. According to some experimental results, the electron temperature in HCVA is assumed to be uniform and equal to 3 eV. Therefore, the MHD model is simplified by neglecting the electron energy equation to improve the simulation efficiency. With the three conservation equations (mass, momentum, and energy) of ion flow coupling solved, the spatial distributions of some flow parameters can be obtained. The influence of all three components of the MF is inserted by solving the magnetic transport equations sequentially. Proper boundary conditions are set on the cathode and anode side, which separated the cathode spots mixing region and anode sheath region from computation domain, respectively. Under the influence of the ETMF, the deflection of the plasma flow can be predicted, which may be helpful to understand the mechanism of the contact deflected erosion.

3D Numerical simulation of high current vacuum arc in realistic magnetic fields considering anode evaporation

A time-dependent 3D numerical model considering anode evaporation is developed for the high current vacuum arc (VA) under a realistic spatial magnetic field. The simulation work contains steady state 3D numerical simulation of high current VA considering anode evaporation at nine discrete moments of first half wave of 50 Hz AC current, transient numerical simulation of anode activity, and realistic spatial magnetic field calculation of commercial cup-shaped electrodes. In the simulation, contact opening and arc diffusion processes are also considered. Due to the effect of electrode slots, the simulation results of magnetic field and temperature of anode plate exhibit six leaves shape (SLS). During 6–8 ms, the strong evaporation of anode surface seriously influence the parameter distributions of VA. Ions emitted from anode penetrate into arc column and the axial velocity distribution on the anode side exhibits SLS. The ions emitted from anode surface have the same temperature with anode surface, which cool the arc plasma and lead to a relative low temperature area formed. The seriously evaporation of anode leads to the accumulation of ions near the anode, and then the current density is more uniform.

Transient MHD Modeling and Simulation of High-Current Vacuum Arc Under Three Kinds of Interruption Processes

With the increase of interruption frequency of high-current vacuum arc (HCVA), the relaxation time of arc plasma is close to characteristic time of arc current and transient characteristics of vacuum arc plasma become more obvious. In this paper, based on a 2-D transient magneto-hydrodynamic model, HCVA under different interruption processes is simulated and analyzed. The simulation results of power-frequency (50 Hz) current show that transient simulation results are the same as those of the steady-state model, as characteristic time of current is much longer than relaxation time of plasma. For fast current drop stage in dc interruption process, simulation results show that higher frequency makes current drops faster and ion number density larger; besides, residual plasma density between electrodes at current-zero moment is higher, and interruption becomes more difficult. Finally, transient characteristics of high-frequency HCVA is also simulated and analyzed. Simulation results show that change curve of ion number density lagged behind current curve; higher ion number density in the second 1/4 cycle can lead to reignition more easily.

Three-Dimensional Time-Dependent Model and Simulation of High-Current Vacuum Arc in Commercial Axial Magnetic Fields Vacuum Interrupters

With a quasi-steady 3-D MHD model, time-dependent axial magnetic field vacuum arcs (AMFVAs) characteristics in commercial vacuum interrupters for half-wave interruption of power-frequency (50 Hz) current are simulated. In a current time-dependent simulation, the influence of AMF lagged from arc current is considered in the arc model. 3-D spatial distributions of many important plasma parameters and electrical characteristics in AMFVAs can be obtained, such as ion number density, ion temperature, electron temperature, plasma pressure, current densities along different directions ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$x$</tex></formula> , <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$y$</tex></formula> , and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$z$</tex></formula> ), electric fields strength along different directions, and so on. Simulation results show that there exists a significant spiral-shaped rotational phenomena in the AMFVAs and the rotational velocity at the moments (9, 8, 7, and 6 ms) after 5 ms (the current peak value moment) is always larger than that before 5 ms (1, 2, 3, and 4 ms) because of the lagged AMF. This kind of plasma rotational phenomena also can be observed by high-speed arc photographs. In the future, the asymmetric appearance in high-current vacuum arc will be simulated based on a 3-D model.

Numerical Simulation of High-Current Vacuum Arc with Consideration of Anode Vapor

A high-current vacuum arc (HCVA) with the consideration of anode vapor is modeled and simulated. First, from the HCVA column model, the heat flux density to the anode is obtained, which is put into the anode activity model, and the parameter distributions (such as the vapor temperature and velocity) of anode vapor are obtained from the simulation results of the anode activity model. Then, by iterating and calculating the HCVA column model and anode activity model, the interaction between the HCVA column and the anode vapor is simulated and analyzed. In the simulation, the distribution of the axial magnetic field (AMF) generated by the electrode system is calculated by software ANSYS. The simulation results show that the influence of anode vapor on the parameter distributions in the arc column is significant. The simulation results are also compared with the vacuum arc photograph.

Numerical Simulation of High-Current Vacuum Arcs Under Axial Magnetic Fields With Consideration of Current Density Distribution at Cathode

Based on a 2-D magnetohydrodynamic model, high-current vacuum arcs (HCVAs) under axial magnetic fields (AMFs) with consideration of current density distribution at the cathode are simulated and analyzed. The current density distribution at the cathode used in the simulation is obtained by processing the image of cathode spots from experiments. In order to study the influence of current density distribution at the cathode on vacuum arc characteristics, HCVA is simulated under two kinds of current density distribution at the cathode. Then, for HCVA simulation in a half-sinusoidal period, the current density distribution at the cathode and the AMF delay are both taken into account. The simulation results show that the nonuniform current density at the cathode makes the values of the arc plasma parameters in the interelectrode region larger and their radial distribution more nonuniform than the uniform current density at the cathode. The more uniform current density at the cathode and the stronger AMF at the moments in the second 1/4 cycle make the values of the arc plasma parameters in the central region smaller and their radial distribution broader than those in the first 1/4 cycle. In addition, the simulation results will also be compared with the experimental results.

A Compact Design for High Voltage Direct Current Circuit Breaker

The absence of current-zero points in the direct current (DC) waveform of high voltage DC (HVDC) circuit breakers makes the interruption process more severe than the case of conventional AC networks with sinusoidal currents. In this way, in the current HVDC networks, a parallel precharged capacitor is inserted to inject the reverse current into the interruption chamber of the vacuum circuit breaker and create the artificial current-zero points. In this paper, a novel method for reverse current injection has been proposed. In this method, two separate helical flux compression generators (HFCGs) have been applied to generate the reverse current and an intense axial magnetic field (AMF), respectively. Numerical simulation of high-current vacuum arc (VA) in the presence of very strong AMF has been presented. For this purpose, the magnetohydrodynamic equations describing the behavior of the VA are coupled to a simple circuit analysis and the previously developed multiphysics model of HFCG. The results indicate that the explosively driven current injection set can make current-zero points properly in a typical HVDC network and lead to successful interruption of fault current. This method needs much less volume and cost in comparison to the parallel precharged capacitor sets.

High-current vacuum arc under axial magnetic field: Numerical simulation and comparisons with experiments

Based on a magnetohydrodynamic model, a numerical simulation of high-current vacuum arc (HCVA) is carried out. In this model, the kinetic energy terms and ion viscosity terms in energy conservation equations are considered. Compared with the supersonic constricted vacuum arc, the ion flow in HCVA is in the subsonic status. Therefore, boundary conditions of cathode and anode sides have to be adjusted for HCVA. According to the simulation results of HCVA, we can find that the maximal plasma pressure appears near the cathode side. The characteristics of HCVA are significantly different from those of supersonic vacuum arc. Then, we make the comparisons between simulation results and experimental results (such as electron number density, electron temperature, ion temperature, high speed charge-coupled device photographs, and so on). The simulation results are in agreement with the experimental results. In addition, we also analyze the influence of different arc models on the distribution of current density in the anode side.

Erratum to “Numerical Simulation of High-Current Vacuum Arcs With an External Axial Magnetic Field”

Erratum to “Numerical Simulation of High-Current Vacuum Arcs With an External Axial Magnetic Field”

Numerical simulation of high-current vacuum arcs with an external axial magnetic field

Numerical simulations are presented for physical behavior and heat flux to the anode of high-current diffuse of arcs as found in vacuum interrupters. The magnetohydrodynamic approach is applied. Of importance is the consideration of energy balance. Heat flux densities to the anode are predicted in the right order of magnitude and essential physical details of the high-current vacuum arc are disclosed. Only at low or no axial magnetic field superimposed externally and low-arc currents, the anode-directed flow of plasma of diffuse arcs reveals supersonic conditions. Otherwise, subsonic conditions exist. In supersonic diffuse arcs, the anode-directed plasma flow is decelerated and highest pressures appear in front of the anode. At subsonic conditions the highest pressure prevails in the cathode region and the pressure gradient drives the flow to the anode. The transition from diffuse to diffuse columnar arc seems to occur when the evaporation rate of metal vapor from the contact surfaces approaches the emission rate of plasma from the body of cathode spots. Diffuse columnar arcs have moderate pressure variations from cathode to anode. With rising plasma density, the energy loss from the emission of electromagnetic radiation increases and can no longer be neglected.