A simulation method for the arc during the contact closure process of a switching device under inrush current.

Abstract

This application provides a simulation method for the arc during the contact closure process of a switchgear under impulse current, belonging to the field of arc simulation modeling technology. The simulation modeling method for the arc during the contact closure process of a switchgear under impulse current includes the following steps: selecting the spatial dimension based on the geometric characteristics of the arc to be studied, and establishing a geometric model using COMSOL software; sequentially adding dimensional parameters and substituting them into the geometric model, and setting the required materials for the geometric model; adding physical field interfaces to the simulation model; setting the specific parameters and boundary conditions of each physical field interface, and adding multi-physics coupling; adding transient studies to the meshed geometric model, configuring a transient solver, calculating the results, and analyzing the variation laws of arc temperature, arc voltage and current curves, and the arc's erosion area on the contact. This method can effectively reduce experimental costs, reduce resource consumption, optimize the design of switchgear products, and improve service life.

Description

Technical Field

[0001] This invention relates to a simulation method for simulating the arc during the contact closure process of switching devices under impulse current conditions. More particularly, it relates to simulating the behavior of arc plasma by applying a current source waveform to simulate the impulse current and by introducing a motion function to simulate the contact closure process. Background Technology

[0002] Currently, switching devices are widely used in industrial automation, energy systems, transportation, household appliances, and communication equipment. Their main functions are to control the on / off state of circuits, protect equipment from overloads, short circuits, and other faults, and provide power isolation and fault protection in emergencies. Contacts, as key components of switching devices, play a role in isolating, connecting, and disconnecting circuits. During the contact opening or closing process, voltage may break down the air, forming an electric arc, causing the contact surface material to melt and leading to contact failure. Especially in new energy vehicles, due to the presence of capacitive loads in the circuit, a large inrush current is generated when the contacts close. The resulting closing arc can lead to contact welding and adhesion failure, which has become a major type of failure. Therefore, studying the contact closing arc under inrush current is of great significance.

[0003] CN202310454688.X discloses a magnetohydrodynamic simulation modeling method suitable for the arc initiation process of a switching electric arc. The method includes establishing a circuit structure and geometric model in the simulation software, defining the solution domain of the electrodes and the arc plasma, adding material properties and physical property parameter constraints, completing multi-frame simulation through mesh generation and transient study steps, obtaining the initial value of the arc temperature, improving the simulation accuracy, and solving the problem of the circuit not being able to conduct at low temperatures.

[0004] CN202110421377.4 discloses a simulation analysis method for electric arc plasma in the metallurgical industry, which specifically includes establishing a two-dimensional axisymmetric space and an electric arc geometric model, setting material properties and multi-physics parameters, meshing and solving the geometric model, generating electric arc temperature and current density distribution maps, and simulating the influence of current on electric arc characteristics.

[0005] CN202210577197.X proposes a method for obtaining the magnetohydrodynamics and circuit model of a switching device and performs field-circuit coupling simulation. This method considers the changes in the fluid motion state inside the electric arc to determine the influence of DC current on the internal air pressure and temperature of the device during the switching process.

[0006] CN202410359696.0 discloses a circuit breaker arc simulation method. It describes the behavior of plasma in a magnetic field by establishing an arc magnetohydrodynamic model and couples multiple physical fields such as electricity, magnetism, and heat with the model to accurately describe the circuit breaker breaking process. By solving the model, the dynamic characteristics of the arc can be obtained to optimize the circuit breaker design.

[0007] Inrush current is usually caused by instantaneous changes in energy in a circuit, such as capacitor charging or short circuit faults. This current peak may cause the contacts of switching devices to burn or weld, increase the energy of the electric arc, and thus increase the failure rate of the switching devices.

[0008] Current research focuses on the electric arc generated during the contact breaking process of switching devices under DC or AC conditions. However, due to the characteristics of high amplitude and short duration of inrush current, the electric arc phenomenon during the contact closing process is more severe, thus requiring in-depth research and analysis.

[0009] In practical applications of switching devices, the causes of inrush current in circuits are complex and varied, potentially involving transient energy changes, alterations in load characteristics, and short-circuit faults, making it difficult to determine its specific waveform characteristics. Furthermore, inrush currents typically have a high peak value and an extremely short duration, usually only a few milliseconds to tens of milliseconds, followed by rapid decay. This characteristic leads to a more severe arcing phenomenon during contact closure compared to the breaking process. Summary of the Invention

[0010] To overcome the above deficiencies, this application establishes a simulation model for simulating the arc during the contact closure process of switching appliances under impulse current, aiming to simulate the arc behavior during the contact closure process under impulse current conditions.

[0011] The electrical contact test is designed based on common failure types of switch contacts in practical applications. Under normal operating conditions, contacts can reliably open and close. However, when a capacitive load is present in the circuit or a short-circuit fault occurs, a massive inrush current flows through the contacts at the moment of connection. The resulting arc can cause severe welding or even adhesion failure of the contacts, making reliable disconnection impossible. The electrical contact test verifies that switch contacts often experience adhesion failure after a single inrush current. Furthermore, during the contact connection process, the distance between the moving and stationary contacts decreases from its maximum opening to zero, experiencing the peak of the inrush current. The arc generated at this time is the most intense, causing the most severe contact erosion. Therefore, studying the single arc generated during the movement of the moving contact from its maximum opening to the stationary contact is of great significance.

[0012] This application provides a simulation modeling method for the arc during the contact closure process of a switching device under inrush current, characterized by the following steps:

[0013] Step 1: Select the spatial dimension based on the geometric characteristics of the arc to be studied. The spatial dimension includes two-dimensional, two-dimensional axisymmetric, and three-dimensional dimensions. Use COMSOL software to build a geometric model and model it according to the actual contact shape. The model includes the moving contact, the stationary contact, and the air domain.

[0014] Step 2: Add dimensional parameters to the geometric model in sequence. The dimensional parameters include the width and height of the moving contact and the stationary contact. Set the range of the air domain according to actual needs to achieve accurate modeling of different contact structures.

[0015] Step 3: Set the materials required for the model. Add materials from the material library and manually define the applicable domain of the materials to adapt to flexible simulation applications of different contact materials. The specific material type can be selected according to the actual contact material.

[0016] Step 4: Add physical field interfaces to the simulation model, including current interface, laminar flow interface, circuit interface, fluid heat transfer interface, magnetic field interface, and dynamic mesh interface. You can also add other physical field interfaces yourself for simulation research and analysis.

[0017] Step 5: Set the specific parameters and boundary conditions for each physical field interface, and add multi-physics coupling; simulate the discharge process of arc plasma under impact current by setting the coupling relationship between the multi-physics interfaces.

[0018] The circuit interface simulates inrush current by adding a current source. The current source waveform function is based on actual inrush current electrical contact experimental data. First, the capacitor is charged to a specified initial voltage. Then, the switching device is placed in the capacitor discharge circuit. The peak value of the inrush current is controlled by adjusting the value of the external resistor. In the experiment, the current value is collected in real time using an oscilloscope. These measured data are then imported into the circuit interface of the COMSOL software through an interpolation function. The specific parameters of the experiment can be set by the user.

[0019] The moving mesh interface achieves the contact closing process by defining the velocity function of the moving contact. Its velocity change can be defined by a piecewise function, causing the moving contact and its connected area to move towards the stationary contact. The stationary contact area is set as a fixed mesh, and all other areas are set as free deformation domains to ensure that the mesh can deform smoothly with the displacement of the moving contact. Finally, the contact closing process is achieved by changing the velocity function of the moving contact. The specific velocity function can be set by the user.

[0020] Step 6: Add transient analysis to the geometric model after mesh analysis, configure the transient solver, calculate the results and analyze the changes in arc temperature, arc voltage and current curves, and arc erosion area of ​​the contact under different impact currents. The corresponding simulation calculation and analysis can be performed according to actual needs.

[0021] In a preferred embodiment of the present invention, step two includes:

[0022] Based on the size range of bridge contacts in switching electrical appliances, the stationary contact width is set to 2mm-10mm and the height to 2mm-5mm; the moving contact width is set to 2mm-10mm and the height to 1mm-5mm; the remaining area is a gas domain, the width of which is greater than the contact width and the height of which is equal to the sum of the heights of the moving and stationary contacts.

[0023] Applicable contact types include, but are not limited to, wedge-shaped contacts, sliding contacts, and knife-shaped contacts, all of which can be simulated and modeled.

[0024] In a preferred embodiment of the present invention, step three includes:

[0025] The phase transition parameters of the contact material from solid to liquid, including melting point and latent heat coefficient, need to be defined according to the physical field interface type added by the user. The appropriate material can be selected according to the actual situation.

[0026] When adding model materials, the solid and liquid physical properties of the contact material need to be added accordingly.

[0027] In a preferred embodiment of the present invention, step five includes:

[0028] In COMSOL software, the initial temperature of the moving and stationary contacts is set to room temperature of 293.15K. To ensure arc ignition, the initial arc temperature in the central region of the air domain is assumed to be (6000-10000)K.

[0029] In the circuit interface, global current conservation is first set up, with the anode connected to the current source and the cathode grounded to form a complete loop. Different current source waveform functions are manually added to simulate inrush current to meet various experimental requirements. Based on actual measurement data from inrush current electrical contact experiments of switching devices, the current values ​​at various moments in the experiment are first measured using an oscilloscope, and the corresponding time and current data are recorded. This data is then imported into the definition function section of the COMSOL software, and interpolation functions are added. Furthermore, the current function can be customized according to actual needs, including but not limited to any waveform such as sine wave, triangle wave, rectangular wave, and stepped wave. Each waveform form can simulate different types of inrush current. For example, a sine wave is used for periodically changing scenarios, a rectangular wave is suitable for instantaneous impacts, and a stepped wave is used for segmented changing scenarios, meeting the simulation requirements of inrush current in different experimental scenarios.

[0030] Set the gas pressure at the laminar flow interface, and set the pressure range of the arc-extinguishing medium, i.e., the air domain, to 1.5-5 standard atmospheres. Manually define fluid properties, such as fluid discretization settings, constitutive relations, and other important parameters, and set the magnitude and direction of the Lorentz force, define the expression for the Lorentz force, and simulate the effect of electromagnetic force on the fluid;

[0031] By configuring the dynamic mesh interface, a velocity function is manually added to simulate the characteristics of arc plasma during the closing (i.e., connection) process of a switchgear's contacts after being subjected to an inrush current. The dynamic mesh interface sets the stationary contact region as a fixed mesh and the moving contact and its related regions as a free deformation domain, ensuring that the mesh can smoothly deform with the displacement of the moving contact and avoiding mesh distortion and solver convergence issues. The velocity change of the moving contact can be defined using a piecewise function to ensure its smooth movement during the closing process. The velocity function can be flexibly adjusted according to the actual motion trajectory, accurately reflecting the contact's motion behavior under different conditions.

[0032] In a preferred embodiment of the present invention, step five includes:

[0033] In the magnetic field section, the initial value of the magnetic loss is set to 0, that is, the model boundary is magnetically insulated. Then, the out-of-plane vector potential is set and a transverse magnetic field is applied. The magnetic field strength is manually defined as 1mT-10mT, which is used in the expression of the Lorentz force of the laminar flow module.

[0034] By coupling multiple physics fields, including Lorentz force, equilibrium discharge heat source, Lorentz force, and non-isothermal flow, and manually adding initial values ​​and boundary conditions, the simulation accuracy can be improved.

[0035] In a preferred embodiment of the present invention, step six includes:

[0036] Mesh generation, including triangular and quadrilateral meshes, needs to be manually adjusted. The convergence of the calculation results can be improved by changing the mesh fineness. The finer the mesh distribution, the better the convergence, but at the same time, the amount of computation is also greater. The calculation situation should be comprehensively considered, and the amount of computation should be reduced as much as possible while ensuring convergence, so as to optimize the simulation efficiency.

[0037] The advantages of this invention are:

[0038] 1. This invention uses the method of setting the current source waveform to simulate the impact current. It can be set based on the actual current waveform obtained from the experiment, so that the simulation results are more consistent with the actual working conditions and the simulation accuracy is significantly improved.

[0039] 2. The present invention performs arc simulation modeling during the contact closure process. By setting the moving contact speed function to control the movement speed and direction of the moving contact, the generation, development and extinction of the arc during the contact closure process can be accurately simulated, thereby reflecting the influence of the inrush current on the contact and helping to optimize the design of switching appliances.

[0040] 3. This invention has been verified multiple times. The current source waveforms that can be used include, but are not limited to, any waveform such as sine wave, triangular wave, rectangular wave, and stepped wave. It has successfully solved the problem that it is difficult to apply the inrush current to the simulation model. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0042] Figure 1 This is a two-dimensional contact geometry model of Example 1;

[0043] Figure 2 This is the current source waveform function of Example 1;

[0044] Figure 3 The moving contact velocity function of Example 1;

[0045] Figure 4 The arc temperature and contact temperature change curves are shown in Example 1.

[0046] Figure 5 Arc erosion area curve for Example 1

[0047] Figure 6 This is the two-dimensional contact geometry model of Example 2;

[0048] Figure 7 This is the current source waveform function for Example 2;

[0049] Figure 8 The moving contact velocity function of Example 2;

[0050] Figure 9 The arc temperature and contact temperature change curves are shown in Example 2.

[0051] Figure 10 This is the arc erosion area curve for Example 2. Detailed Implementation

[0052] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0053] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0054] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0055] Example 1: Peak inrush current 1000A;

[0056] Please see Figure 1-Figure 5 This invention provides a simulation method for the arc during the contact closure process of a switchgear under impact current. Based on the geometric characteristics of the arc under study, a corresponding spatial dimension is selected to construct a geometric model identical to the actual switchgear contact. The spatial dimension can be two-dimensional, two-dimensional axisymmetric, or three-dimensional, etc. A two-dimensional spatial dimension is initially chosen to improve computational efficiency. The geometric model is established and its dimensions are set. The geometric model includes a moving contact, a stationary contact, and a gas domain. Actual measured values ​​of the switchgear contacts are substituted: the stationary contact is set to a width of 2mm and a height of 2mm; the moving contact is set to a width of 2mm and a height of 1mm; the remaining area is the gas domain, the range of which is set according to actual needs. This allows for accurate modeling of different contact structures. Applicable contact types include, but are not limited to, wedge-shaped contacts, sliding contacts, and knife-shaped contacts, all of which can be simulated. The initial opening distance is set to 2mm. The geometric model is imported into COMSOL software, and relevant parameters such as contact dimensions are set. The anode and cathode domains in the geometric model are defined to ensure model integrity and accuracy.

[0057] Among them, the moving contact and the stationary contact are initially in the separated position, the moving contact moves from the maximum opening position to the stationary contact, and the initial distance between the two contacts is set to the maximum opening distance between the moving and stationary contacts;

[0058] Manually add the required material and physical property parameters to the geometric model. Select and add solid and liquid physical property parameters of copper-based and silver-based materials according to the actual contact materials of the switchgear, including density, electrical conductivity, constant pressure heat capacity, etc., as well as the arc extinguishing medium with hydrogen as the main component, including physical properties such as density, thermal conductivity, dynamic viscosity, etc. When adding model materials, it is necessary to add the corresponding solid and liquid properties of the contact materials.

[0059] Add various physics modules, including AC / DC, heat transfer, fluid flow, etc.

[0060] Add physical field interfaces to the model, including current interface (EC), laminar flow interface (SPF), circuit interface (CIR), fluid heat transfer interface (HT), magnetic field interface (MF), and dynamic mesh interface (ALE), etc. You can also add other physical field interfaces yourself for simulation research and analysis.

[0061] Set the specific parameters and boundary conditions of each physics interface, and set the coupling relationship between multiple physics interfaces to simulate the discharge process of arc plasma under impact current.

[0062] In the circuit interface (CIR), the inrush current is simulated by adding a current source. The source type is set to a generalized source, and the current source is connected to the anode in the geometric model, while the cathode is grounded. The waveform of the current source is based on actual measurement data from the inrush current experiment of the switching device. First, the current value at each moment in the experiment is measured using an oscilloscope, and the corresponding data of time and current are recorded. Then, this data is imported into the definition function section of the COMSOL software, an interpolation function is added, and it is ensured that the interpolation function has a valid value throughout the total calculation time. The name and parameters of the interpolation function are defined. Finally, the current of the generalized source is set to this interpolation function through the circuit interface (CIR). That is, the waveform of the current source in the simulation model is input according to the experimentally measured current data, completing the current source setup. The specific parameters of the experiment can be set by the user.

[0063] In the moving mesh interface (ale), firstly, a mesh smoothing type is selected to ensure smoothness during mesh deformation. The stationary contact is set to a fixed mesh, and the x and y displacements of the stationary contact and its connected regions are specified to be 0, ensuring that the position of the stationary contact remains unchanged. All other regions except the stationary contact are set as free deformation domains, allowing the meshes in these regions to deform freely according to the movement of the moving contact. The velocity functions in the x and y directions of the moving contact mesh and its connected regions are specified as piecewise functions to ensure that the movement of the moving contact is smooth and without abrupt changes. By setting the velocity function to control the direction and magnitude of the moving contact's movement, the opening distance between the moving and stationary contacts is reduced, simulating the contact closing process. The specific velocity function can be set by the user.

[0064] In the circuit interface (CIR), global current conservation is first set up, with the anode connected to the current source and the cathode grounded to form a complete loop. Different current source waveform functions are manually added to simulate inrush current to meet various experimental requirements. Based on actual measurement data from inrush current electrical contact experiments of switching devices, the current values ​​at various moments in the experiment are first measured using an oscilloscope, and the corresponding time and current data are recorded. This data is then imported into the definition function section of the COMSOL software, and interpolation functions are added. Furthermore, the current function can be customized according to actual needs, including but not limited to any waveform such as sine wave, triangle wave, rectangular wave, and stepped wave. Each waveform form can simulate different types of inrush current. For example, a sine wave is used for periodically changing scenarios, a rectangular wave is suitable for instantaneous impacts, and a stepped wave is used for segmented changing scenarios, meeting the simulation requirements of inrush current in different experimental scenarios.

[0065] By configuring the dynamic mesh interface (ale), a velocity function is manually added to simulate the characteristics of arc plasma during the closing (closing) process of a switchgear contact after being subjected to an inrush current. The dynamic mesh interface (ale) sets the stationary contact region as a fixed mesh and the moving contact and its related regions as a free deformation domain, ensuring that the mesh can smoothly deform with the displacement of the moving contact and avoiding mesh distortion and solver convergence issues. The velocity change of the moving contact can be defined using a piecewise function to ensure that it maintains stable motion during the closing process. The velocity function can be flexibly adjusted according to the actual motion trajectory to accurately reflect the motion behavior of the contact under different conditions.

[0066] Add transient studies to the meshed geometric model, configure a transient solver, calculate and analyze the results, including the arc temperature, arc voltage and current curves, and the variation of the arc erosion area on the contact under different impact currents. The simulation calculation and analysis can be performed according to actual needs.

[0067] This study delves into the arcing phenomenon during contact closure by configuring a transient solver. Because the arc is compressed and the computational mesh undergoes free deformation during closure, the computation becomes more complex, necessitating appropriate adjustments to the linear solver and its errors. By carefully setting the motion speed and path of the moving contact, convergence issues with the solver during contact closure are prevented. Furthermore, for the transient simulation of the arc during closure, mesh generation and time step configuration need optimization to ensure the stability of the transient solver under complex multiphysics coupling and avoid computational errors during simulation.

[0068] The solid-fluid heat transfer module first selects temperature discretization as a linear unit with temperature T as the dependent variable. Then, the initial values ​​of both the moving and stationary contacts are set to 293.15K (i.e., room temperature 20℃). The initial value of 8000K is set at the center of the gas domain to ensure that the electric arc can be successfully ignited. Finally, the phase change parameters of the contact material are set according to the material properties, such as the melting point and latent heat coefficient when the solid melts into the liquid state.

[0069] In the laminar flow module, the gas pressure is set, fluid properties are defined, the arc-extinguishing medium (mainly hydrogen) is selected as the laminar gas domain, and it is set as incompressible flow. The fluid discretization is set to P1+P1 (both velocity and pressure are linear elements), the constitutive relation is set to Newtonian fluid, the pressure is set to static pressure, the backflow suppression option is enabled, the boundary uses element constraints, the pressure value is set to 2.5 atm (i.e., 2.5 standard atmospheres), the boundary conditions for the moving and stationary contacts are set to slip, and at the same time, the formula for volume force, i.e., Lorentz force, is added to simulate the effect of electromagnetic force on the fluid.

[0070] The magnetic field is set with the initial magnetic vector potential set to 0. The magnetic field is an out-of-plane vector potential (perpendicular to the two-dimensional plane). The background field is solved in the whole field. The magnetic vector potential is discretized into linear elements that satisfy Ampere's law. The transverse magnetic field strength is set to 6 mT.

[0071] For the current and external circuit settings, the potential is first discretized into linear units, satisfying the law of current conservation across the entire domain. A current source is connected above the stationary contact (anode), and grounded below the moving contact (cathode). A current source waveform function is manually added to ensure the peak inrush current of the external circuit reaches 1000A.

[0072] The specific process for obtaining the current source waveform function is as follows: Through an impulse current electrical contact experiment, the capacitor is first charged to a specified initial voltage. Then, the switching device is placed in the capacitor discharge circuit. The peak value of the impulse current is adjusted by changing the external resistance. The current value is acquired in real time using an oscilloscope to obtain the waveform of the current changing over time. Finally, the waveform is imported into the circuit interface (cir) in the COMSOL software using an interpolation function.

[0073] For the dynamic mesh setup, first set the geometry function to 1, select the Laplace method for mesh smoothing, and define the closing speed function of the moving contact. Set its action speed to 0.3 m / s and action time to 2.5 ms. The moving contact and its connected area move along the y-axis towards the stationary contact, and the velocity change of the moving contact is defined by a piecewise function. In this embodiment, the moving contact moves at a constant speed of 0.3 m / s to achieve the closing process of the moving and stationary contacts. In the dynamic mesh interface (ale), the stationary contact area is set as a fixed mesh, and all other areas are set as free deformation to ensure that the mesh deforms smoothly with the displacement of the moving contact and avoids mesh distortion.

[0074] Multiphysics coupling simulation involves the interaction of multiple physical fields, including Lorentz force, equilibrium discharge heat source, and non-isothermal flow. The mutual coupling between each physical field is manually added and set, allowing these coupling phenomena to be fully simulated during arc compression. By manually adding initial values ​​and boundary conditions through multiphysics coupling, including Lorentz force, equilibrium discharge heat source, and non-isothermal flow, the simulation accuracy is improved.

[0075] Mesh generation begins with selecting a user-controlled network and calibrating it as fluid dynamics, suitable for fluid and thermodynamic calculations. A finer mesh distribution leads to better convergence, but also increases computational complexity. Therefore, it's crucial to consider the overall computational requirements and minimize computation while ensuring convergence. A combination of triangular and quadrilateral meshes is used to mesh the model. The mesh fineness is manually adjusted, with localized mesh refinement in critical areas such as the arc region and contact edges to improve accuracy. In other regions, the mesh density is appropriately reduced to decrease computation. The goal is to ensure the mesh is distortion-free, meets the convergence requirements of the calculation results, and optimize computational resources and time.

[0076] Configure the solver and select transient study, suitable for time-dependent transient analysis. Set the total simulation computation time to 15ms and the time step to 0.01ms to capture the rapidly changing physical processes during arc discharge. To ensure the accuracy and stability of the calculation results, set reasonable convergence criteria, including relative and absolute tolerances. Select backward difference formula as the time stepping method and limit the maximum and minimum time steps to prevent computational instability due to excessively large time steps or excessively long computation times due to excessively small time steps. For algebraic variables, set consistent initialization using backward Euler method. Adjust memory allocation and parallel computing options appropriately according to model complexity and computational resources to improve computational efficiency.

[0077] Example 2: Peak inrush current 3000A;

[0078] Please see Figures 6-10This invention provides a simulation method for the arc during the contact closure process of a switchgear under impact current. Based on the geometric characteristics of the arc under study, a corresponding spatial dimension is selected to construct a geometric model identical to the actual switchgear contact. First, a two-dimensional spatial dimension is chosen to improve computational efficiency. The geometric model is established and its dimensions are set. The geometric model includes a moving contact, a stationary contact, and a gas domain. Actual measured values ​​of the switchgear contacts are substituted: the stationary contact is set to a width of 2mm and a height of 2mm; the moving contact is set to a width of 2mm and a height of 1mm; the remaining area is the gas domain, the range of which is set according to actual needs, enabling accurate modeling of different contact structures. The initial opening distance is set to 2mm. The geometric model is imported into COMSOL software, and relevant parameters such as contact dimensions are set. The anode and cathode domains in the geometric model are defined to ensure model integrity and accuracy.

[0079] Among them, the moving contact and the stationary contact are initially in the separated position, the moving contact moves from the open position to the stationary contact, and the initial distance between the two contacts is set to the maximum opening distance between the moving and stationary contacts;

[0080] Manually add the required material and physical property parameters to the geometric model. Select and add solid and liquid physical property parameters of copper-based and silver-based materials according to the actual contact materials of the switchgear, including density, electrical conductivity, constant pressure heat capacity, etc., as well as the arc extinguishing medium with hydrogen as the main component, including physical properties such as density, thermal conductivity, dynamic viscosity, etc. When adding model materials, it is necessary to add the corresponding solid and liquid properties of the contact materials.

[0081] Add various physics modules, including AC / DC, heat transfer, fluid flow, etc.

[0082] Add physical field interfaces to the model, including current interface (EC), laminar flow interface (SPF), circuit interface (CIR), fluid heat transfer interface (HT), magnetic field interface (MF), and dynamic mesh interface (ALE), etc. You can also add other physical field interfaces yourself for simulation research and analysis.

[0083] Set the specific parameters and boundary conditions of each physics interface, and set the coupling relationship between multiple physics interfaces to simulate the discharge process of arc plasma under impact current.

[0084] In the circuit interface (CIR), the inrush current is simulated by adding a current source. The source type is set to a generalized source, and the current source is connected to the anode in the geometric model, while the cathode is grounded. The waveform of the current source is based on actual measurement data from the inrush current experiment of the switching device. First, the current value at each moment in the experiment is measured using an oscilloscope, and the corresponding data of time and current are recorded. Then, this data is imported into the definition function section of the COMSOL software, an interpolation function is added, and it is ensured that the interpolation function has a valid value throughout the total calculation time. The name and parameters of the interpolation function are defined. Finally, the current of the generalized source is set to this interpolation function through the circuit interface (CIR). That is, the waveform of the current source in the geometric model is input according to the experimentally measured current data, completing the current source setup. The specific experimental parameters can be set by the user.

[0085] In the moving mesh interface (ale), firstly, a mesh smoothing type is selected to ensure smoothness during mesh deformation. The stationary contact is set to a fixed mesh, and the x and y displacements of the stationary contact and its connected regions are specified to be 0, ensuring that the position of the stationary contact remains unchanged. All other regions except the stationary contact are set as free deformation domains, allowing the meshes in these regions to deform freely according to the movement of the moving contact. The velocity functions in the x and y directions of the moving contact mesh and its connected regions are specified as piecewise functions to ensure that the movement of the moving contact is smooth and without abrupt changes. By setting the velocity function to control the direction and magnitude of the moving contact's movement, the opening distance between the moving and stationary contacts is reduced, simulating the contact closing process. The specific velocity function can be set by the user.

[0086] In the circuit interface (CIR), the global current conservation is first set, with the anode connected to the current source and the cathode grounded to form a complete loop. Different current source waveform functions are manually added to simulate the inrush current to meet various experimental requirements. Based on actual measurement data from the switching device in the inrush current electrical contact experiment, the current value at each moment of the experiment is first measured using an oscilloscope, and the corresponding time and current data are recorded. Then, this data is imported into the definition function section of the COMSOL software, and interpolation functions are added.

[0087] By configuring the dynamic mesh interface (ale), a velocity function is manually added to simulate the characteristics of arc plasma during the closing (closing) process of a switchgear contact after being subjected to an inrush current. The dynamic mesh interface (ale) sets the stationary contact region as a fixed mesh and the moving contact and its related regions as a free deformation domain, ensuring that the mesh can smoothly deform with the displacement of the moving contact and avoiding mesh distortion and solver convergence issues. The velocity change of the moving contact can be defined using a piecewise function to ensure that it maintains stable motion during the closing process. The velocity function can be flexibly adjusted according to the actual motion trajectory to accurately reflect the motion behavior of the contact under different conditions.

[0088] Add transient studies to the meshed geometric model, configure a transient solver, calculate and analyze the results, including the arc temperature, arc voltage and current curves, and the variation of the arc erosion area on the contact under different impact currents. The simulation calculation and analysis can be performed according to actual needs.

[0089] This study delves into the arcing phenomenon during contact closure by configuring a transient solver. Because the arc is compressed and the computational mesh undergoes free deformation during closure, the computation becomes more complex, necessitating appropriate adjustments to the linear solver and its errors. By carefully setting the motion speed and path of the moving contact, convergence issues with the solver during contact closure are prevented. Furthermore, for the transient simulation of the arc during closure, mesh generation and time step configuration need optimization to ensure the stability of the transient solver under complex multiphysics coupling and avoid computational errors during simulation.

[0090] The solid-fluid heat transfer module first selects temperature discretization as a linear unit with temperature T as the dependent variable. Then, the initial values ​​of both the moving and stationary contacts are set to 293.15K (i.e., room temperature 20℃). The initial value of 8000K is set at the center of the gas domain to ensure that the electric arc can be successfully ignited. Finally, the phase change parameters of the contact material are set according to the material properties, such as the melting point and latent heat coefficient when the solid melts into the liquid state.

[0091] In the laminar flow module, the gas pressure is set, fluid properties are defined, the arc-extinguishing medium (mainly hydrogen) is selected as the laminar gas domain, and it is set as incompressible flow. The fluid discretization is set to P1+P1 (both velocity and pressure are linear elements), the constitutive relation is set to Newtonian fluid, the pressure is set to static pressure, the backflow suppression option is enabled, the boundary uses element constraints, the pressure value is set to 2.5 atm (i.e., 2.5 standard atmospheres), the boundary conditions for the moving and stationary contacts are set to slip, and at the same time, the formula for volume force, i.e., Lorentz force, is added to simulate the effect of electromagnetic force on the fluid.

[0092] The magnetic field is set with the initial magnetic vector potential set to 0. The magnetic field is an out-of-plane vector potential (perpendicular to the two-dimensional plane). The background field is solved in the whole field. The magnetic vector potential is discretized into linear elements that satisfy Ampere's law. The transverse magnetic field strength is set to 6 mT.

[0093] For the current and external circuit settings, the potential is first discretized into linear units, satisfying the law of conservation of current throughout the entire domain. A current source is connected above the stationary contact (anode), and grounded below the moving contact (cathode). A current source waveform function is manually added so that the peak inrush current of the external circuit reaches 3000A.

[0094] The specific process for obtaining the current source waveform function is as follows: Through an impulse current electrical contact experiment, the capacitor is first charged to a specified initial voltage. Then, the switching device is placed in the capacitor discharge circuit. The peak value of the impulse current is adjusted by changing the external resistance. The current value is acquired in real time using an oscilloscope to obtain the waveform of the current changing over time. Finally, the waveform is imported into the circuit interface (cir) in the COMSOL software using an interpolation function.

[0095] For the dynamic mesh setup, first set the geometry function to 1, select the Laplace method for mesh smoothing, and define the closing speed function of the moving contact. Set its action speed to 0.6 m / s and action time to 3 ms. The moving contact and its connected area move along the y-axis towards the stationary contact, and the velocity change of the moving contact is defined by a piecewise function. In this embodiment, the moving contact moves at a constant speed of 0.6 m / s to achieve the closing process of the moving and stationary contacts. In the dynamic mesh interface (ale), the stationary contact area is set as a fixed mesh, and all other areas are set as free deformation to ensure that the mesh deforms smoothly with the displacement of the moving contact and avoids mesh distortion.

[0096] Multiphysics coupling simulation involves the interaction of multiple physical fields, including Lorentz force, equilibrium discharge heat source, and non-isothermal flow. The mutual coupling between each physical field is manually added and set, allowing these coupling phenomena to be fully simulated during arc compression. By manually adding initial values ​​and boundary conditions through multiphysics coupling, including Lorentz force, equilibrium discharge heat source, and non-isothermal flow, the simulation accuracy is improved.

[0097] Mesh generation begins with selecting a user-controlled network and calibrating it as fluid dynamics, suitable for fluid and thermodynamic calculations. A finer mesh distribution leads to better convergence, but also increases computational complexity. Therefore, a comprehensive consideration of computational factors is necessary to minimize computational load while ensuring convergence. Thus, a combination of triangular and quadrilateral meshes is used to mesh the model. The mesh fineness is manually adjusted, with localized mesh refinement in critical areas such as the arc region and contact edges to improve computational accuracy. In other regions, the mesh density is appropriately reduced to decrease computational load. Ensuring the mesh is distortion-free and meets the convergence requirements of the calculation results optimizes computational resources and time, thereby improving simulation efficiency.

[0098] Configure the solver and select transient study, suitable for time-dependent transient analysis. Set the total simulation computation time to 15ms and the time step to 0.01ms to capture the rapidly changing physical processes during arc discharge. To ensure the accuracy and stability of the calculation results, set reasonable convergence criteria, including relative and absolute tolerances. Select backward difference formula as the time stepping method and limit the maximum and minimum time steps to prevent computational instability due to excessively large time steps or excessively long computation times due to excessively small time steps. For algebraic variables, set consistent initialization using backward Euler method. Adjust memory allocation and parallel computing options appropriately according to model complexity and computational resources to improve computational efficiency.

[0099] Based on electrical contact experiments of actual switching electrical products under impulse current conditions, a simulation model was established to simulate the arc during the contact closure process of switching electrical products under impulse current. This model can effectively reduce experimental costs, reduce resource consumption, optimize the design of switching electrical products, and improve service life.

[0100] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A simulation modeling method for the electric arc during the contact closure process of a switching device under impulse current, characterized in that, The steps are as follows: Step 1: Select the spatial dimension based on the geometric characteristics of the arc to be studied. The spatial dimension includes two-dimensional, two-dimensional axisymmetric, and three-dimensional dimensions. Use COMSOL software to build a geometric model. The geometric model includes the moving contact, the stationary contact, and the gas domain. Model the model according to the actual contact shape. Step 2: Add the dimensional parameters into the geometric model in sequence. The dimensional parameters include the width and height of the moving contact and the stationary contact. Step 3: Set the materials required for the geometric model, add materials from the material library and manually define the applicable domain of the materials to adapt to flexible simulation applications of different contact materials; Step 4: Add physical field interfaces to the simulation model. The physical field interfaces include current interface, laminar flow interface, circuit interface, fluid heat transfer interface, magnetic field interface, and dynamic mesh interface. Step 5: Set the specific parameters and boundary conditions for each physical field interface, and add multi-physics coupling; the circuit interface simulates the impact current by adding a current source, and the current source waveform function is based on actual impact current electrical contact experimental data; the moving mesh interface realizes the contact closing process by defining the velocity function of the moving contact; Step 6: Add transient analysis to the meshed geometric model, configure the transient solver, calculate the results and analyze the variation of arc temperature, arc voltage and current curves, and arc erosion area on the contact.

2. The simulation modeling method for the arc during the contact closure process of a switching device under impulse current as described in claim 1, characterized in that, Step two includes: Based on the size range of the bridge contact of the switching device, the width is 2mm-10mm and the height is 2mm-5mm; the size range of the moving contact is 2mm-10mm in width and 1mm-5mm in height; the remaining area is a gas domain, the width of which is greater than the width of the contact, and the height of which is equal to the sum of the heights of the moving and stationary contacts.

3. The simulation modeling method for the arc during the contact closure process of a switching device under impulse current as described in claim 1, characterized in that, Step three includes: The phase transition parameters of the contact material from solid to liquid, including melting point and latent heat coefficient, need to be defined according to the type of physical field interface added.

4. The simulation modeling method for the arc during the contact closure process of a switching device under impulse current as described in claim 1, characterized in that, Step five includes: Set the gas pressure at the laminar flow interface, setting the pressure of the arc-extinguishing medium (gas domain) to 1.5-5 standard atmospheres; manually define fluid properties, and set the magnitude and direction of the Lorentz force, defining the expression for the Lorentz force to simulate the effect of electromagnetic force on the fluid.

5. The simulation modeling method for the arc during the contact closure process of a switching device under impulse current as described in claim 1, characterized in that, Step five includes: In the magnetic field section, the initial value of the magnetic displacement is set to 0, that is, the model boundary is magnetically insulated. Then, the out-of-plane vector potential is set and a transverse magnetic field is applied. The magnetic field strength is manually defined as 1mT-10mT, which is used in the expression of the Lorentz force of the laminar flow module.

6. The simulation modeling method for the arc during the contact closure process of a switching device under impulse current as described in claim 1, characterized in that, In step six, the mesh division includes triangular and quadrilateral meshes, which need to be manually adjusted. The convergence of the calculation results is improved by changing the fineness of the mesh. The finer the mesh distribution, the better the convergence, but the greater the computational load.

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