Simulation evaluation method and verification device for contact ablation of high-voltage SF6 circuit breaker

Abstract

The application discloses a kind of high-pressure SF6 circuit breaker contact ablation simulation evaluation method and verification device, the method comprises: establishing arc-extinguishing chamber three-dimensional geometric model and calculation domain model;By multi-physical field coupling solution, the surface evaporation mass flux of high-pressure SF6 circuit breaker contact ablation is obtained, and the evaporation material and the two-way coupling of flow field are formed;Driving electrode boundary node displacement occurs, and the updated electrode geometric appearance is obtained, and the contact ablation quantitative evaluation index is calculated.The application is based on the quantitative evaluation of plasma arc caused by plasma caused by turbulent flow excitation under the condition of contact deterioration, and provides method support for the electrical life evaluation and structure optimization of high-voltage switchgear.

Description

Technical Field

[0001] This invention belongs to the field of high-voltage electrical equipment condition assessment and arc simulation technology, and relates to a simulation assessment method and verification device for contact erosion of high-voltage SF6 circuit breakers. Background Technology

[0002] High-voltage (10 kV to 252 kV) SF6 circuit breakers are widely used in power transmission and transformation projects due to their excellent insulation and arc-extinguishing performance. When interrupting short-circuit current, the energy deposition at the root of the high-temperature arc between the contacts causes the metal material to melt and evaporate. The cumulative effect leads to a reduction in contact mass and length, further affecting breaking capacity and electrical life. Therefore, accurately assessing the contact erosion state is crucial for the operation and maintenance of high-voltage switchgear.

[0003] Existing methods for assessing SF6 circuit breaker contact erosion fall into two categories: experimental measurement and numerical simulation. Experimental measurement yields accurate results but is costly, time-consuming, and fails to reveal the dynamic evolution of multiphysics fields. Numerical simulation, on the other hand, often employs classical models such as Cassie and Gauss, simplifying the arc as a static surface heat source, thus only obtaining localized pitting erosion morphology. However, in reality, after multiple interruptions, the contact surface often exhibits uniform erosion, significantly differing from the simulation. The underlying physical reason lies in the fact that classical models fail to consider the lateral transport and redistribution of arc energy by strong turbulence within the arc-extinguishing chamber, neglecting the influence of metal vapor on electromagnetism. hot The reverse coupling of the flow field makes it difficult to reproduce the cumulative ablation effect of multiple interruptions under real-world conditions. These limitations make it difficult for existing simulation methods to accurately predict the degree of degradation of circuit breaker contacts under real-world operating conditions, thus restricting the refined assessment of the electrical life of high-voltage circuit breakers. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a simulation evaluation method and verification device for contact erosion in high-voltage SF6 circuit breakers. Based on a multiphase flow plasma model (Maxwell's equations for electromagnetic fields, MHD equations for magnetohydrodynamics, and VOF phase transition transport equations), the method quantitatively evaluates the contact degradation caused by plasma arcing under turbulent excitation, providing methodological support for electrical life assessment and structural optimization of high-voltage switchgear.

[0005] The present invention adopts the following technical solution.

[0006] A simulation evaluation method for contact erosion of high-voltage SF6 circuit breakers includes: S1: Establish a three-dimensional geometric model of the arc-extinguishing chamber of the high-voltage SF6 circuit breaker and perform mesh generation to obtain a three-dimensional computational domain mesh model; apply initial conditions and boundary conditions to the three-dimensional computational domain mesh model to obtain a computational domain model with initial conditions and boundary conditions; S2: Based on the computational domain model and combined with the thermal balance relationship of the electrode surface, the surface evaporation mass flux of the high-voltage SF6 circuit breaker contact ablation is obtained by coupling the solution of the electromagnetic field Maxwell equations, the magnetohydrodynamic MHD equations considering mass source terms and vector momentum source terms, the standard k-ε turbulence model and the VOF phase change transport equations. The surface evaporation mass flux is then fed back to the MHD equations in the form of mass source terms and vector momentum source terms, forming a two-way coupling between the evaporating material and the flow field. S3: The retreat velocity of each grid node is obtained based on the surface evaporation mass flux to drive the electrode boundary nodes to move, thereby obtaining the updated electrode geometry and then calculating the quantitative evaluation index of contact ablation of the high voltage SF6 circuit breaker. S4: Determine whether the preset total arcing time or the interruption completion condition has been met. If not, proceed to the next time step, use the updated electrode geometry as the new geometric boundary of the computational domain model, and return to S2. If the conditions have been met, output the quantitative evaluation index.

[0007] Preferably, the process of establishing a three-dimensional geometric model of the arc-extinguishing chamber of the high-voltage SF6 circuit breaker and performing mesh generation to obtain a three-dimensional computational domain mesh model includes: A three-dimensional geometric model was established based on the measured dimensions of the arc-extinguishing chamber unit of the high-voltage SF6 circuit breaker. The three-dimensional geometric model was then meshed, with local densification implemented on the surfaces of the moving arc contact and the stationary arc contact. A time step was set to obtain a three-dimensional computational domain mesh model.

[0008] Preferably, S2 specifically includes: Based on the computational domain model and the velocity and temperature fields at the current moment, the electromagnetic field distribution in the computational domain at the current moment is solved using the Maxwell equations of electromagnetic fields to obtain the vectors of current density, electric field strength and magnetic induction intensity. Based on the current density, electric field strength, and magnetic induction intensity vector, the magnetohydrodynamic (MHD) equations considering mass source terms and vector momentum source terms are solved to obtain the velocity field and temperature field of the gas, and the velocity field and temperature field are fed back to the Maxwell equations. Based on the velocity field, the VOF phase change transport equation is solved to obtain the volume fraction of each phase, the mixed phase density, and the mixed phase viscosity μ. Based on the mixed phase density and the velocity field, the standard k-ε turbulence model is solved to obtain the turbulent viscosity μ. t ; Utilizing the turbulent viscosity μ t The viscous stress tensor τ in the MHD equations is updated with the mixed phase viscosity μ. Based on the temperature field and the liquid phase fraction in each phase volume fraction, the latent heat loss Q is calculated according to the thermal equilibrium relationship of the electrode surface. melt Latent heat loss due to evaporation Qvap Surface evaporation mass flux; Based on the surface evaporation mass flux, the mass source term and vector momentum source term are obtained; these terms are fed back to the MHD equations, and the Q is... melt Q vap The solution process of the MHD equations is introduced as an additional source term.

[0009] Preferably, the MHD equations include the magnetohydrodynamic mass conservation equation, momentum conservation equation, and energy conservation equation, which are as follows:

[0010]

[0011]

[0012] In the formula, r Indicates the density of the mixed phase; t For time; Indicates the quality source term; p This refers to the pressure of the gas. t For the viscous stress tensor of the gas; This represents the additional vector momentum source term introduced by copper vapor; e Represents the total internal energy per unit mass; T For temperature; l Thermal conductivity; S φ Represents the viscous dissipation source term; For magnetic induction intensity, current density, electric field intensity, and velocity vector; It is a spatial differential operator.

[0013] Preferably, the VOF phase transition transport equation is:

[0014]

[0015] In the formula, The volume fraction of phase q; This refers to the mass exchange term between different phases. Let q be the phase density; Let be the dynamic viscosity of phase q; ρ is the velocity vector; μ is the mixed phase density; ρ is the mixed phase viscosity. It is a spatial differential operator.

[0016] Preferably, the turbulent viscosity μ is used t The formula for updating the viscous stress tensor τ in the MHD equations based on the mixed-phase viscosity μ is:

[0017] In the formula, the subscript T is the transpose variable, I represents the unit tensor, and v is the velocity; It is a spatial differential operator.

[0018] Preferably, the latent heat loss Q is... melt Latent heat loss due to evaporation Q vap The specific formula for surface evaporation mass flux is as follows:

[0019]

[0020]

[0021] In the formula, r Indicates the density of the mixed phase; The liquid phase fraction; L m The latent heat of fusion of the alloy; For the evaporation region, it is a position function. points within , be on point to the molten surface shortest distance No more than the thickness of the near-surface evaporation layer When, the position function takes the value 1, when Exceed When the position function is zero, the position function is zero. For surface evaporation mass flux; L v The latent heat of vaporization of the alloy; A As a pre-factor; E α It is the activation energy for evaporation; R It is the gas constant; T For temperature.

[0022] Preferably, based on surface evaporation mass flux , obtain quality source item and vector momentum source term The specific formula is as follows:

[0023]

[0024] In the formula, The normal vector of the contact boundary element. For nodes in x , y , zThe unit basis vector in the direction; For the evaporation region, it is a position function. One point of responsibility , be on point to the molten surface shortest distance No more than the thickness of the near-surface evaporation layer When, the position function takes the value 1, when Exceed When the position function is zero, the position function takes the value 0.

[0025] Preferably, the formula for calculating the retreat velocity of each grid node based on the surface evaporation mass flux is as follows:

[0026] In the formula, The retreat velocity vector of the node; For boundary elements in x , y , z The unit basis vector in the direction; The density of the metal vapor; This represents the surface evaporation mass flux.

[0027] Preferably, the quantitative evaluation index is used to compare with a preset standard to determine the contact state; the quantitative evaluation index includes contact length loss, contact evaporation mass loss, ablation morphology and arc voltage; wherein, the ablation morphology is the updated electrode geometry.

[0028] A verification device applied to the simulation evaluation method, comprising: An arc-extinguishing chamber unit, wherein the arc-extinguishing chamber unit is provided axially with a piston, a moving arc contact, a moving main contact, a nozzle, a stationary arc contact, a shield, a stationary contact base, and a moving contact base; The circuit breaker unit is the external load-bearing structure of the arc-extinguishing chamber unit, used to construct the actual short-circuit breaking condition; The nozzle structure unit includes a nozzle body and a plurality of gas openings evenly distributed in the circumferential direction on the inner wall of the nozzle body, which are used to adjust the turbulence parameters in the arc-extinguishing chamber unit. The test measurement and diagnosis unit is used to acquire multi-dimensional measured data of the arc-extinguishing chamber unit under actual short-circuit breaking conditions during the arc-extinguishing chamber unit's breaking test, and to use this data as a benchmark for quantitative evaluation indicators to verify the accuracy of the simulation evaluation method.

[0029] Preferably, the number of gas openings, the opening angle, and the opening cross-sectional area are adjustable structural parameters. The larger the number of openings, the opening angle, and the gas opening cross-sectional area, the greater the gas flow rate entering the arc region from the throat of the nozzle body, and the greater the turbulent kinetic energy and turbulent dissipation rate; conversely, the turbulent kinetic energy and turbulent dissipation rate decrease accordingly.

[0030] A terminal includes a processor and a storage medium; the storage medium is used to store instructions; the processor is used to perform operations according to the instructions to execute the steps of the method.

[0031] A computer-readable storage medium having a computer program stored thereon that, when executed by a processor, implements the steps of the method.

[0032] Compared with the prior art, the beneficial effects of the present invention include at least the following: This invention proposes a three-dimensional simulation model of multiphase flow plasma inside circuit breakers (including the Maxwell equations for electromagnetic fields, the MHD equations for magnetohydrodynamics, and the VOF phase transition transport equations) to achieve coupled simulation of the arc erosion mechanism of circuit breaker contacts under turbulent excitation and multiphysics fields. It can reproduce the uniform ablation morphology of contacts caused by air blowing under the actual arc-extinguishing chamber structure. It can achieve high-precision prediction of contact evaporation mass, length loss, and ablation morphology under multiple interruptions, with prediction errors of no more than ±5% for evaporation mass and length loss, which is a significant improvement over the traditional Gaussian arc model.

[0033] The magnetohydrodynamic (MHD) equations of this invention introduce a mass source term and an additional vector momentum source term introduced by copper vapor, which are used to characterize the mass transport of metal vapor and its additional momentum effect on the electrode surface, respectively. This can more comprehensively describe the plasma-related physical processes. At the same time, the mass source term and the vector momentum source term are precisely limited to the near-surface evaporation layer of the electrode by the position function, avoiding excessive dispersion of the evaporation effect in the computational domain. This can effectively improve the prediction accuracy of contact evaporation mass loss and near-wall flow field parameters.

[0034] Unlike traditional models that only consider a single evaporation mass flux or empirical evaporation parameters, this invention incorporates liquid phase fraction, latent heat of fusion, latent heat of vaporization, and near-wall evaporation region location parameters into the calculation of latent heat of fusion loss and latent heat of vaporization loss. This confines the evaporation process to the actual near-surface region heated by the electric arc and reflects the energy consumption during the material's transition from melting to vaporization. This approach improves the model's accuracy in describing localized evaporation and phase change heat transfer processes on the electrode surface.

[0035] Unlike traditional methods that treat surface evaporation merely as a mass loss or boundary source term, this invention further transforms the evaporation mass flux into the degradation rate of the electrode boundary nodes. This degradation rate is then used to influence the boundary cells... x , y ,z The unit basis vector in the direction drives the dynamic mesh deformation, thereby achieving coupled calculation between surface evaporation, boundary node displacement, and electrode geometry update. This process can dynamically describe the geometric evolution process of the electrode surface caused by evaporation and ablation under electric arc, improving the accuracy of electrode morphology changes and near-wall flow field calculations.

[0036] This invention develops a verification device that complements the geometric modeling and solution algorithm of the simulation evaluation method. It supports the synchronous quantitative evaluation of multiple indicators of contact ablation at 252kV / 40kA under power frequency. By adjusting the nozzle structure to change the turbulence parameters, and combining multi-physics field coupled simulation to output contact ablation and arc electrical quantitative indicators, the macroscopic influence of turbulence on contact ablation can be quantified. This provides data support and experimental basis for arc-extinguishing chamber structure optimization, electrical life assessment, and the determination of contact replacement threshold.

[0037] This invention replaces some high-cost destructive tests with simulation, which can significantly reduce operation and maintenance and R&D costs. Attached Figure Description

[0038] Figure 1 This is a flowchart of the simulation evaluation method for contact erosion of high-voltage SF6 circuit breakers according to the present invention.

[0039] Figure 2 This is a schematic diagram of the multiphysics coupling solution algorithm framework.

[0040] Figure 3 This is a schematic diagram of the deformation of the electrode mesh driven by evaporation mass loss.

[0041] Figure 4 This is a schematic diagram of the dynamic mesh update logic for the liquid phase erosion and gas phase erosion stages.

[0042] Figure 5 This is a schematic diagram of the arc-extinguishing chamber unit structure and the computational mesh generation.

[0043] Figure 6 This is a schematic diagram of the overall unit structure of the circuit breaker.

[0044] Figure 7 This is a schematic diagram of the nozzle structure unit.

[0045] Figure 8 The overall workflow diagram for simulation verification of the evaluation device.

[0046] Figure 9 Image showing the surface element mesh generation result of the arc-extinguishing chamber: Figure 9 (a) is a diagram showing the mesh generation results of the remaining elements on the surface of the arc-extinguishing chamber. Figure 9 (b) is a diagram showing the surface element meshing result of the static arc contact. Figure 9 (c) is a diagram showing the mesh generation result of the surface element of the moving arc contact.

[0047] Figure 10 For the motion characteristic curves of the moving contact and the cylinder piston: Figure 10 (a) is the stroke of the moving contact and the cylinder piston. Time curve, Figure 10 (b) is the speed of the moving contact and the cylinder piston. Time curve graph.

[0048] Figure 11 Here is a diagram of the arc temperature field during the arcing process: Figure 11 (a) is a diagram showing the arc temperature distribution inside the arc extinguishing chamber. Figure 11 (b) is a diagram showing the surface temperature evolution of the static arc contact.

[0049] Figure 12 The diagram shows the evolution of multiphase flow during the arcing process and its impact on the temperature field: Figure 12 (a) is a diagram of the multiphase flow process inside the arc-extinguishing chamber. Figure 12 (b) is a temperature field distribution diagram inside the arc extinguishing chamber.

[0050] Figure 13 A comparison chart of simulation and experimental results for evaporation mass and length loss: Figure 13 (a) is a comparison chart of simulated and experimental values ​​of evaporation mass. Figure 13 (b) is a comparison chart of simulated and experimental values ​​of length loss.

[0051] Figure 14 This is a comparison between the measured arc voltage and the simulated arc voltage.

[0052] The attached diagram is labeled as follows: 1-piston, 2-moving arc contact, 3-moving main contact, 4-nozzle, 5-stationary arc contact, 6-shielding cover, 7-stationary contact base, 8-moving contact base, 9-velocity inlet, 10-velocity outlet, 11-multiphase flow plasma zone, 12-closing effect, 13-opening effect, 14-upper insulating platform, 15-gas damper, 16-inlet terminal, 17-stationary main contact, 18-outlet terminal, 19-lower insulating platform, 20-air outlet, 21-air inlet. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0054] Embodiment 1 of this invention provides a simulation evaluation method for the contact erosion of high-voltage SF6 circuit breakers. Addressing the difficulty in accurately quantifying and evaluating the erosion state / deterioration degree of high-voltage SF6 circuit breaker contacts, this method employs high-precision simulation of contact deterioration under turbulent excitation. It reproduces the uniform erosion morphology of the contacts caused by air blowing under a realistic arc-extinguishing chamber structure, achieving a high-precision quantitative evaluation of contact evaporation mass, length loss, and erosion morphology. This allows for a comprehensive evaluation of turbulence intensity, arc-extinguishing effect, and electrode erosion degree, providing a basis for the balanced and optimized design of nozzle structure and arc-extinguishing chamber parameters. Furthermore, simulations under multiple breaking conditions can yield the contact parameter loss limit values, providing a quantitative basis for determining contact replacement thresholds. Figure 1 As shown, the method includes: S1: Establish a three-dimensional geometric model of the arc-extinguishing chamber of the high-voltage SF6 circuit breaker and perform mesh generation to obtain a three-dimensional computational domain mesh model; apply initial conditions and boundary conditions to the three-dimensional computational domain mesh model to obtain a computational domain model with initial conditions and boundary conditions; More preferably, a three-dimensional geometric model is established based on the measured dimensions of the arc-extinguishing chamber unit of the high-voltage SF6 circuit breaker, and the three-dimensional geometric model is meshed. Local densification is implemented on the surface of the moving arc contact 2 and the surface of the stationary arc contact 5. A time step is set to obtain a three-dimensional computational domain mesh model.

[0055] The initial conditions include initial ambient pressure, initial ambient temperature, initial velocity of the moving contact and initial velocity of cylinder piston 1, inlet turbulence intensity and turbulence dissipation rate; The boundary conditions include: the outer wall of the arc extinguishing chamber is set as an insulated wall and adopts a non-slip condition; the non-contact wall is set as an electrically insulated wall; the outlet of nozzle 4 is set as an open boundary and the outlet temperature and pressure are constant values ​​with no backflow; an AC potential is applied to the stationary arc contact 5; and the moving arc contact 2 is grounded.

[0056] S2: Based on the aforementioned computational domain model and combined with the thermal equilibrium relationship of the electrode surface, the surface evaporation mass flux of the high-voltage SF6 circuit breaker contact ablation is obtained by coupled solving the Maxwell equations for the electromagnetic field, the MHD equations for magnetohydrodynamics considering mass source terms and vector momentum source terms, the standard k-ε turbulence model, and the VOF phase transition transport equation. The surface evaporation mass flux The mass source term and the vector momentum source term are fed back to the MHD equations, forming a two-way coupling between the evaporating material and the flow field; This application establishes a multiphysics coupled solution method based on magnetohydrodynamics (MHD) dynamics, turbulence, and phase transition to describe the interactions between arc plasma, electromagnetic field, turbulent air blowing process, and electrode phase transition process during the arc extinguishing process of a circuit breaker. This method can integrate the magnetohydrodynamic equations, Maxwell's electromagnetic equations, and... k - e The turbulence equation and the phase change transport equation based on the VOF method are solved in a coupled manner, and the coupled computational framework is as follows: Figure 2 As shown.

[0057] Preferably, the coupling calculation process includes: Based on the computational domain model and the velocity and temperature fields at the current moment, the electromagnetic field distribution in the computational domain at the current moment is solved using the Maxwell equations of electromagnetic fields to obtain the vectors of current density, electric field strength and magnetic induction intensity. Based on the current density, electric field strength, and magnetic induction intensity vector, the magnetohydrodynamic (MHD) equations considering mass source terms and vector momentum source terms are solved to obtain the velocity field and temperature field of the gas, and the velocity field and temperature field are fed back to the Maxwell equations. Solving the VOF phase transition transport equation based on the velocity field yields the volume fraction a of each phase. q Mixed phase density and mixed phase viscosity μ; Based on the mixed phase density and the velocity field, the standard k-ε turbulence model is solved to obtain the turbulent viscosity μ. t ; Using the turbulent viscosity μ t The viscous stress tensor τ in the MHD equations is updated with the mixed phase viscosity μ. Based on the temperature field and the volume fraction of each phase a q The liquid phase fraction a l Based on the thermal equilibrium relationship of the electrode surface, the latent heat loss Q is calculated. melt Latent heat loss due to evaporation Q vap Surface evaporation mass flux ; According to the surface evaporation mass flux This yields the mass source term and the vector momentum source term; The mass source term and vector momentum source term are fed back into the MHD equations, and the Q... melt Q vap The solution process of the MHD equations is introduced as an additional source term, namely Q. melt Q vap The superposition is applied to the right side of the energy conservation equation, and the MHD equations are solved again based on the superimposed equations.

[0058] Specifically, considering the mass exchange, momentum exchange, and energy exchange that occur during the electrode phase transition, the following mass conservation equation, momentum conservation equation, and energy conservation equation based on the Stokes equation are established: (1) (2) (3) In the formula, r This represents the density of the mixed phase, in kg / m³. 3 ; t For time, s; v The velocity vector is in m / s. S m This represents the mass source item in kg / (m³). 3 ·s); p Let Pa be the pressure of the gas. t Let be the viscous stress tensor of the gas, in Pa; J Current density, A / m 2 ; B Let T be the magnetic flux density. e The total internal energy per unit mass is expressed in J / kg. E Electric field strength is expressed in V / m. T Temperature, K; l The thermal conductivity is W / (m·K); S φ Represents the viscous dissipation source term, W / m 3 This is used to characterize the conversion of mechanical energy into internal energy caused by fluid viscosity, and its expression is:

[0059] In the formula, t For viscous stress tensor, · v For the velocity gradient tensor, ":" indicates the double dot product.

[0060] For the viscous stress tensor of the gas t The laminar dynamic viscosity of pure SF6 gas was calculated at the initial time of the simulation (before arc initiation); at each subsequent time step, the turbulent viscosity μ was obtained using the standard k-ε turbulence model. t The viscosity μ of the mixed phase calculated by the VOF equation is updated.

[0061] The updated formula is:

[0062] In the formula, the subscript T represents the transpose variable, and I represents the unit tensor. m t ν is the turbulent viscosity. μ is the mixed-phase viscosity, and v is the velocity.

[0063] The source term was designed and introduced separately in this invention. S m , S Cu and S φThese are used to characterize mass transport, additional momentum effects, and viscous dissipation effects, respectively. This approach differs from the conventional modeling of the source term in traditional MHD methods, and can more comprehensively describe plasma-related physical processes.

[0064] In this application, the momentum conservation equation is... J × B Used to characterize the Lorentz force generated by the interaction between current density and magnetic induction; in the energy conservation equation J · E Used to characterize the energy input of the electromagnetic field to the fluid region. J, E, and B are first calculated from the Maxwell equations and then substituted into the MHD equations, thus introducing the effect of the electromagnetic field on the flow field and temperature field into the MHD solution process.

[0065] Alternatively, the electromagnetic field can be described by the following Maxwell equations: (4) In the formula, m 0 represents magnetic permeability, H / m; s The conductivity is expressed as temperature-dependent, in S / m. For magnetic induction intensity, current density, electric field intensity, and velocity vector; It is a spatial differential operator.

[0066] It should be noted that current density J With electric field strength E Related to, and related to the velocity field v and magnetic induction intensity B Therefore, when an electric arc plasma moves in a magnetic field, the change in the velocity field affects the current distribution, and the change in the current distribution is further fed back to the momentum equation through the Lorentz force. Thus, the bidirectional coupling mechanism between the electromagnetic field and the flow field can be determined.

[0067] In this application, the standard is adopted. k - e Turbulence model describes turbulent kinetic energy k With turbulent dissipation rate e The transport process, solving for the strong turbulent air blowing condition existing in the arc-extinguishing chamber of the circuit breaker, is expressed as: (5) (6) In the formula, r Indicates the density of the mixed phase; k For turbulent kinetic energy, m 2 / s 2 ; m 1 represents the dynamic viscosity of SF6 gas phase, kg / (m·s); mt The viscosity is turbulent, kg / (m·s); s k for k The turbulent Prandtl number is 1.0, dimensionless; P k For turbulence generation, kg / (m·s) 3 ); e m is the turbulent dissipation rate. 2 / s 3 ; s ε for e The turbulent Prandtl number is 1.3, which is dimensionless. C 1ε , C 2ε These are model constants, 1.44 and 1.92 respectively, and are dimensionless. It is a velocity vector; It is a spatial differential operator.

[0068] Furthermore, the coexistence of solid, liquid, and gas phases caused by electrode phase transitions is constrained by the VOF model, and is represented by different phases. q volume fraction α q As variables in the solution, the transport process between different phases satisfies the following formula: (7) In the formula, S αq For mass exchange between different phases, kg / (m 3 ·s); r q for q Phase density, kg / m 3 .

[0069] Correspondingly, the mixed phase density and mixed phase viscosity can be obtained by weighting the volume fractions of each phase: (8) In the formula, q represents the volume fraction of phase q, in kg / (m·s), where q ranges from 1 to 3, corresponding to the dynamic viscosity of the SF6 gas phase, molten metal liquid phase, and metal vapor phase, respectively.

[0070] Optionally, if multiple phases exist simultaneously within a certain computational unit, the equivalent physical property parameters of that computational unit can be determined based on the volume fraction of each phase. In this way, the evolution of the electrode solid phase, molten liquid phase, and metal vapor phase can be described simultaneously within the same computational domain.

[0071] It should be noted that the MHD equations are used to describe the coupling relationship between the electromagnetic field and the flow field.k - e The turbulence model is used to describe the air-blown turbulence process, the VOF model is used to track the evolution of the phase interface, and the phase change source term is used to realize the mass, momentum, and energy exchange between the electrode material evaporation and melting processes and the fluid region. This enables bidirectional coupled calculations of multiple physics fields during arc ablation.

[0072] In this application, the phase transition state and ablation morphology of the electrode surface are determined by the thermal equilibrium relationship established on the electrode surface. Specifically, the net heat flow on the electrode surface... Q net It can be represented as: (9) In the formula, Q j It is a Joule heat source; Q rad For radiation loss; Q vap This is due to latent heat loss through vaporization; Q melt This is the loss of latent heat of fusion.

[0073] Among them, Joule heat source Q j Determined by the ohmic heat generated when current is injected into the electrode, it can be expressed as: (10) In the formula, f Let V be the electric potential.

[0074] It should be noted that the more concentrated the current density on the electrode surface, the greater the corresponding potential gradient, and the stronger the Joule heat source obtained by equation (10). Therefore, this Joule heat source can be used to characterize the heat input characteristics of the local current concentration area of ​​the contact.

[0075] Optional, radiation loss Q rad The net emissivity method can be used for calculation. If the temperature... T ≥ 4,000K, then Q rad The value is 4π e N , e N Net emissivity, W / m 3 If temperature T <4,000K, then Q rad Set to 0, where 4,000K is a common threshold setting standard for the conversion of copper vapor from a gaseous state to a plasma state; e N It can be determined using a linear approximation of temperature T. At T = 4000K, e N The value is approximately 10 W / (cm3•sr); when T is higher than 4000 K, e N It increases approximately linearly with increasing temperature, with a slope of about 0.03. This setting allows for the introduction of radiative energy loss in the high-temperature arc region and reduces ineffective radiation calculations in the low-temperature region.

[0076] Furthermore, latent heat of fusion Q melt This can be treated using the enthalpy-porous medium method, which can be expressed as: (11) In the formula, The liquid phase fraction as a function of time t; L m The latent heat of fusion of the alloy is 2.05 × 10⁻⁶. 5 J / kg.

[0077] Furthermore, latent heat of vaporization Q vap It can be represented as: (12) In the formula, L v The latent heat of vaporization of the alloy is 4.6 × 10⁻⁶. 6 J / kg; For the evaporation region, it is a position function. One point of responsibility , be on point to the molten surface shortest distance No more than the thickness of the near-surface evaporation layer When, the position function takes the value 1, when Exceed When the position function is 0, the position function is 0; in this embodiment The value is set to 0.1 mm; this position function is used to characterize the 0.1 mm near-wall evaporation region on the surface of the stationary contact. The characteristic scale of the inner boundary unit can confine the evaporation source term within the near-surface thin layer where evaporation actually occurs under arc heating, thereby improving the physical rationality and computational accuracy of the evaporation region description; this position function in The value is 1 within the distance range and 0 in the rest of the computational domain; The surface evaporation mass flux is expressed in kg / (m²). 3 ·s) represents the equivalent mass source term after the evaporation flux is converted to the volume of the computational unit.

[0078] It should be noted that, βThis is used to define the area of ​​effect for the latent heat of vaporization. If the calculation location is located 0.1 mm from the surface of the static arc contact 5, then... β Set the value to 1; if the calculation location is in another region, then... β Set it to 0. This method ensures that the latent heat loss of vaporization only affects the near-surface region where electrode evaporation actually occurs, improving the accuracy of the application location of the phase change heat source term.

[0079] In this application, the evaporation kinetic model is established according to Arrhenius's law. The generation process of metal vapor in the electrode material can be represented as follows: (13) In the formula, A As a pre-factor, kg / (m 3 ·s); E α The activation energy for evaporation is J / mol. R is the gas constant, 8.314 J / (mol·K). Where A and E α Empirical parameters related to the electrode material system can be determined based on the electrode material composition, copper-tungsten alloy doping ratio, surface oxide film state, and experimental calibration results. Preferably, for copper-tungsten alloy contact materials, the value of A ranges from 500 to 1000 kg / (m²). 3 ·s), E α Possible value: 2.5 × 10 5 -3.5×10 5 J / mol, or determined by fitting experimental data of evaporation kinetics of the same or similar material systems.

[0080] It should be noted that, as shown in equation (13), the evaporation mass flux The rate of metal vapor generation increases exponentially with increasing temperature. Therefore, when the local temperature at the root of the arc or the surface of the contact rises rapidly, the rate of metal vapor generation increases significantly.

[0081] Unlike traditional models that only consider a single evaporation mass flux or empirical evaporation parameters, this invention incorporates liquid phase fraction, latent heat of fusion, latent heat of vaporization, and near-wall evaporation region location parameters into the calculation of latent heat of fusion loss and latent heat of vaporization loss. This confines the evaporation process to the actual near-surface region heated by the electric arc and reflects the energy consumption during the material's transition from melting to vaporization. This approach improves the model's accuracy in describing localized evaporation and phase change heat transfer processes on the electrode surface.

[0082] In this application, the electrode phase transition process is bidirectionally coupled with multiphysics fields, and the metal vapor generated by electrode evaporation is fed back to the MHD conservation equation in the form of source terms.

[0083] Specifically, by introducing the evaporation mass flux as a source term into the mass conservation equation (1), it can be expressed as: (14) Furthermore, when metal vapor is ejected from the electrode surface, it exerts a reverse effect on the electrode surface. To describe this effect, the vector momentum source term corresponding to the evaporation process is represented in this application as: (15) In the formula, The normal vector of the contact boundary element. For nodes in x , y , z The unit basis vector in the direction.

[0084] Specifically, Used to indicate the local normal direction of contact boundary elements. Used to indicate the component of the node in the spatial coordinate direction. Together, they determine the direction of local material retreat caused by evaporation.

[0085] It should be noted that if a certain region of the electrode surface meets the evaporation conditions, the mass of metal vapor generated in that region will be determined by... S m Feedback is given to the flow field; simultaneously, the momentum generated by the steam injection is transmitted through... S Cu The feedback is sent to the electrode surface. Through this method, the mass generated by the metal vapor can be kept consistent with the mass lost from the electrode material, and the momentum of the ejected metal vapor and the direction of electrode retreat can satisfy the momentum conservation relationship.

[0086] S3: Based on the surface evaporation mass flux Obtain the retreat velocity v of each grid node node The electrode boundary nodes are driven to displace, and the updated electrode geometry is obtained. Then, the quantitative evaluation index of contact ablation of high voltage SF6 circuit breaker is calculated. In this application, to reflect the changes in electrode geometry caused by arc ablation in real time, a dynamic mesh deformation method is introduced based on VOF phase transition calculations. For example... Figure 3 As shown, this method can update the electrode boundary nodes based on the evaporation mass flux, phase fraction distribution, and jet momentum direction on the electrode surface.

[0087] Specifically, for a grid cell located near the surface of the electrode, if it experiences mass loss due to the evaporation process, the corresponding boundary node can be displaced in the direction opposite to the momentum of the metal vapor ejection. The node velocity can be expressed as: (16) In the formula, vnode The node velocity is in m / s; The retreat velocity vector of the node; For boundary elements in x , y , z The unit basis vector in the direction; The density of the metal vapor is kg / m³. 3 ; This represents the surface evaporation mass flux.

[0088] It should be noted that the node velocity in equation (16) is determined by both the evaporation mass flux and the metal vapor density. If the evaporation mass flux of a certain region is greater, the node retreat velocity corresponding to that region will be greater, thus reflecting the non-uniform ablation characteristics of the electrode surface.

[0089] Unlike traditional methods that treat surface evaporation merely as a mass loss or boundary source term, this invention further considers evaporation mass flux. Degradation rate converted into electrode boundary node Through its boundary element in x , y , z The unit basis vector in the direction drives the dynamic mesh deformation, thereby achieving coupled calculation between surface evaporation, boundary node displacement, and electrode geometry update. This process can dynamically describe the geometric evolution process of the electrode surface caused by evaporation and ablation under electric arc, improving the accuracy of electrode morphology changes and near-wall flow field calculations.

[0090] Optionally, during the liquid phase erosion stage, a damping term can be introduced during mesh deformation to suppress non-physical movement in the solid phase region. If the liquid phase fraction gradually increases and approaches 1, the damping effect gradually decreases, and the mesh nodes begin to retreat in the direction of material loss caused by the phase transition, such as... Figure 4 As shown.

[0091] Optionally, during the vapor phase erosion stage, mesh deformation can be guided according to the momentum direction of the metal vapor jet. This method ensures that the displacement direction of the mesh elements aligns with the direction of evaporation mass loss, avoiding local topographic distortion caused by arbitrary node movement.

[0092] Furthermore, after updating the mesh nodes at each time step, the Laplacian smoothing method can be used to smooth the deformed mesh. If the local mesh quality is lower than a preset quality threshold, a local remeshing operation can be performed on that region to maintain the stability of the computational mesh.

[0093] In this application, based on the above-mentioned multiphase flow plasma arc solution results, evaluation indicators such as contact evaporation mass, contact length loss, ablation morphology, and arc voltage can be obtained. These evaluation indicators can be used to characterize the degree of electrode ablation and its impact on the arc extinguishing capability of the circuit breaker.

[0094] Specifically, contact length loss ΔL It can be obtained by integrating the velocity of the electrode tip surface elements before and after the dynamic mesh update over the arc duration, expressed as: (17) In the formula, This refers to the duration of the electric arc. The retreat velocity vector of the node; The normal vector of the contact boundary element. For nodes in x , y , z The unit basis vector in the direction; t is time; Specifically, contact evaporation mass loss Δm The evaporation mass flux can be obtained by integrating over the electrode surface unit and the arc duration, expressed as: (18) In the formula, S This refers to the electrode surface region where evaporation occurs. For surface evaporation mass flux; Arc voltage can be obtained through path integration, and the calculation formula is as follows:

[0095] In the formula, u arc The arc voltage is Ω. arc For plasma channels, i arc ( t () represents the arc current. denoted as the magnetic current density and electric field intensity vector.

[0096] When the moving and stationary arc contacts 5 are in a state of complete breakdown, the plasma channel forms an effective conductive connection, so the arc current can be taken as the external input current applied to both ends of the electrodes.

[0097] S4: Determine whether the preset total arcing time or the interruption completion condition has been met. If not, proceed to the next time step, use the updated electrode geometry as the new geometric boundary of the computational domain model, and return to S2. If the conditions have been met, output the quantitative evaluation index.

[0098] Furthermore, by simultaneously outputting arc voltage, contact evaporation mass, contact length loss, and ablation morphology, the arc-extinguishing capacity decay process can be evaluated from both electrical performance and material loss perspectives. This approach provides a basis for optimizing the arc-extinguishing chamber nozzle structure, selecting contact materials, and establishing contact replacement thresholds.

[0099] Embodiment 2 of the present invention provides a verification device for the simulation evaluation method described in Embodiment 1, comprising: An arc-extinguishing chamber unit is provided with a piston 1, a moving arc contact 2, a moving main contact 3, a nozzle 4, a stationary arc contact 5, a shield 6, a stationary contact base 7, and a moving contact base 8 arranged sequentially along the axial direction. The circuit breaker unit is the external load-bearing structure of the arc-extinguishing chamber unit, used to construct the actual short-circuit breaking condition; The nozzle structure unit includes a nozzle body and a plurality of gas openings evenly distributed in the circumferential direction on the inner wall of the nozzle body, which are used to adjust the turbulence intensity in the arc-extinguishing chamber unit. The test measurement and diagnosis unit is used to acquire multi-dimensional measured data of the arc-extinguishing chamber unit under actual short-circuit breaking conditions during the arc-extinguishing chamber unit's breaking test, and to use this data as a benchmark for quantitative evaluation indicators to verify the accuracy of the simulation evaluation method.

[0100] It should be noted that the measured data is mainly used to verify the accuracy and reliability of the simulation evaluation method, and is not directly used as the basis for determining the contact state. The purpose of setting up the verification device in this invention is to construct an adjustable test platform corresponding to the actual short-circuit breaking process. By changing the gas intensity at nozzle 4 and the relevant structural parameters of the arc-extinguishing chamber, the airflow (turbulence) intensity and arc development process during the test can be adjusted, so that the verification conditions can be more easily matched with relevant standards, such as IEC 62271-100 or other type test standards.

[0101] The simulation quantitative evaluation index, after calibration with measured data, can be compared with the preset deterioration threshold, serving as a direct basis for determining the contact operating status and whether maintenance or replacement is required, thereby realizing the quantitative evaluation of the electrical life of circuit breaker contacts.

[0102] Specifically, in this application, to support the boundary condition input, parameter calibration, and result verification of the aforementioned simulation evaluation method, a corresponding evaluation device is further designed. This evaluation device takes a 252kV / 40kA self-energized SF6 circuit breaker as its object and includes an arc-extinguishing chamber unit, an overall circuit breaker unit, a nozzle structure unit, and a test measurement and diagnostic unit. The geometric parameters and operating conditions of each unit can be synchronously mapped in the simulation evaluation method in the form of meshes, boundary conditions, and source terms, thereby forming a closed-loop verification device.

[0103] In this application, the arc-extinguishing chamber unit is the core physical entity of the evaluation device, and its internal component composition is completely consistent with the geometric model of the three-dimensional simulation domain, such as... Figure 5 As shown. Specifically, the arc extinguishing chamber is arranged axially in the following order: piston 1, moving arc contact 2, moving main contact 3, nozzle 4, stationary arc contact 5, shielding cover 6, stationary contact base 7, and moving contact base 8.

[0104] Optionally, the piston 1 is rigidly connected to the moving contact base 8 and is driven to move by a spring operating mechanism during the opening action, thereby axially compressing the cylinder located inside the moving contact base 8, so that the pre-stored SF6 gas is blown into the arc area through the nozzle 4.

[0105] Figure 5 The simulation demonstrates the closing effect 12 of the arc-extinguishing chamber closing, the opening effect 13 of the opening, and the multiphase flow plasma region 11 formed between the throat of the nozzle 4 and the static arc contact 5. The simulation calculation domain is set with velocity inlet 9 and velocity outlet 10 to define the SF6 airflow boundary.

[0106] It should be noted that the moving arc contact 2 and the stationary arc contact 5 together constitute the arc-ignition main circuit, and the root of the high-temperature arc is formed between the two when the short-circuit current is interrupted; the moving main contact 3 and the corresponding stationary main contact 17 constitute the normal operating current circuit.

[0107] It should be noted that the shielding cover 6 and the stationary contact base 7 are mainly used for voltage equalization and structural support, and have a constraining effect on the electric field distribution and turbulence path.

[0108] It should be noted that the geometric boundaries of the components strictly correspond to the simulation evaluation method.

[0109] Specifically, the stationary arc contact 5 and the moving arc contact 2 are respectively subjected to high voltage potential and grounding conditions, while the remaining wall surfaces are all set as electrically insulating, heat-insulating, and non-slipping wall surfaces. In this way, it can be ensured that the physical boundary of the evaluation device strictly corresponds to the mathematical boundary of the simulation domain.

[0110] In this application, the circuit breaker unit serves as the external load-bearing structure of the evaluation device, used to construct actual short-circuit breaking conditions, such as... Figure 6 As shown. The circuit breaker unit comprises, along the axial direction, the following components in sequence: upper insulating platform 14, gas damper 15, incoming terminal 16, stationary main contact 17, nozzle 4, moving main contact 3, moving contact base 8, outgoing terminal 18, and lower insulating platform 19.

[0111] It should be noted that the incoming terminal 16 is used to receive a 40kA short-circuit current, and the outgoing terminal 18 is grounded via a shunt circuit; the upper insulating platform 14 and the lower insulating platform 19 are used to withstand a 252kV power frequency withstand voltage and isolate the high-voltage circuit from the ground potential.

[0112] It should be noted that the gas damper 15 cooperates with the spring operating mechanism to constrain the movement speed of the moving contact at the opening end, ensuring that the moving contact follows a preset stroke. Velocity-curve motion.

[0113] Optionally, the internal contact stroke and cylinder piston 1 speed of the circuit breaker unit are synchronously acquired by displacement and velocity sensors and input into the initial condition settings of the simulation evaluation method in the form of linear interpolation. In this way, the measured stroke curve of the evaluation device can be used as the dynamic mesh driving input of the simulation evaluation method, ensuring the correspondence between the geometric position of the moving contact and the actual breaking process during the simulation.

[0114] In this application, the nozzle structural unit is a key component that determines the turbulence intensity and arc energy transport pattern within the arc-extinguishing chamber, and its structure is as follows: Figure 7 As shown. The nozzle structure unit includes a nozzle body and a plurality of gas openings evenly distributed in the circumferential direction on the inner wall of the nozzle.

[0115] Specifically, the nozzle body is made of polytetrafluoroethylene (PTFE) material, and its axis coincides with the axis of the stationary arc contact 5. The gas openings are evenly distributed along the circumference of the nozzle body below the throat of the nozzle 4. High-pressure SF6 gas ejected from the cylinder inside the moving contact base 8 forms a radial airflow through the gas openings and is finally discharged from the nozzle 4 outlet to the outside of the stationary arc contact 5. The positions of the air outlet 20 and the air inlet 21 are as follows: Figure 7 As shown.

[0116] Optionally, the number of gas openings, the opening angle, and the opening cross-sectional area can be used as adjustable structural parameters. By changing these structural parameters, the SF6 gas flow rate and gas flow cross-section entering the arc region can be altered, thereby adjusting the turbulence intensity within the arc-extinguishing chamber.

[0117] Specifically, the larger the cross-sectional area of ​​the gas opening, the greater the gas flow rate entering the arc region from the throat of nozzle 4, and the greater the turbulent kinetic energy. k and turbulent dissipation rate e As the cross-sectional area decreases, the turbulent kinetic energy increases; conversely, as the cross-sectional area decreases, the turbulent kinetic energy... k and turbulent dissipation rate e The corresponding decrease.

[0118] It should be noted that the aforementioned turbulent kinetic energy k and turbulent dissipation rate e Changes need to be evaluated through the standard simulation evaluation method. k - e The inlet boundary conditions of the turbulence model are input synchronously.

[0119] It should be noted that the changes in the opening parameters of the nozzle structure unit can be mapped to the MHD-turbulence coupling equations in the form of inlet turbulence intensity and turbulence dissipation rate in the simulation evaluation method, thereby affecting the shear velocity on the electrode surface, the metal vapor transport path and the final ablation morphology.

[0120] Specifically, the structural parameters of the gas opening are changed by altering the inlet gas flow velocity U and the inlet turbulence intensity I, thereby further determining the inlet turbulent kinetic energy k and turbulent dissipation rate. e and with k and e The inlet boundary condition form is introduced into the standard k-ε turbulence model.

[0121] The relationship between the inlet turbulence intensity I and the turbulence kinetic energy k is as follows: k = 3 / 2 × (U × I) 2 U is the average inlet airflow velocity, and I is the inlet turbulence intensity; the turbulence dissipation rate ε can be further determined based on the turbulence length scale l: ε = Cμ 3 / 4 × k 3 / 2 / l Cμ is k - e Model constants l The inlet turbulence length scale.

[0122] Therefore, structural parameters such as the number of gas openings, opening angle, and opening cross-sectional area can be adjusted by changing the inlet velocity U, the inlet turbulence intensity I, and the resulting changes in k, e Impact on standards k Turbulent kinetic energy in the -ε turbulence model k Turbulent dissipation rate e Turbulent viscosity m t and turbulence generation term P k Furthermore, it can further couple and influence multiple variables in the MHD equation, such as v, τ, Sφ, etc.

[0123] The above methods can quantitatively assess the design trade-off between improving arc extinguishing capability and electrode electrical life, providing a quantitative basis for nozzle structure optimization.

[0124] In this application, the test measurement and diagnostic unit is used to acquire multidimensional data of the evaluation device under actual switching conditions, and uses this data as a benchmark for comparison with the results of the simulation evaluation method. The test measurement and diagnostic unit includes: a stroke displacement sensor, a velocity sensor, and a data acquisition system.

[0125] Specifically, the stroke displacement sensor and the speed sensor are used to record the displacement of the moving contact and the speed of the cylinder in real time, and output continuous stroke. Time curve and velocity The data acquisition system measures the instantaneous arc current during arcing; it also collects the instantaneous arc voltage between the moving and stationary arc contacts; and it synchronously records the aforementioned electrical and mechanical quantities according to a preset sampling rate.

[0126] Optionally, after each interruption test, the stationary arc contact 5 is disassembled, cleaned, and weighed.

[0127] Optionally, the difference in contact mass before and after arcing can be measured using a precision balance. Δm The measurement results were used as the actual measured value of evaporation mass loss.

[0128] Optionally, the difference in contact length before and after arcing can be measured using vernier calipers and 3D scanning equipment. ΔL The measurement results were used as the measured values ​​of length loss.

[0129] Optionally, the ablation surface of the contact can be imaged using a microscopic camera as a measured sample of the ablation morphology.

[0130] In this application, the evaporation quality of the contact, the contact length loss, the ablation morphology and the arc voltage are further comprehensively judged according to the preset evaluation criteria.

[0131] Specifically, the preset evaluation criteria can be determined according to the requirements of IEC62271-100 regarding the breaking performance, rated short-circuit breaking capacity, operating sequence and test qualification criteria of high-voltage AC circuit breakers, and the contact replacement threshold can be established by combining the rated voltage level, rated short-circuit breaking current, contact material parameters and manufacturer's allowable ablation margin of the circuit breaker being evaluated.

[0132] It should be noted that the contact replacement threshold includes at least one or more of the following: contact mass loss threshold, contact length loss threshold, ablation depth threshold, ablation area threshold, and arc voltage offset threshold.

[0133] Optionally, if the simulation evaluation method outputs the contact evaporation quality... Δm Contact length loss ΔL If at least one of the ablation morphology parameters or arc voltage changes reaches the corresponding contact replacement threshold, the contact is determined to have reached the deterioration limit, and a contact replacement or maintenance prompt is output.

[0134] Optionally, if the evaporation mass of the contact is less than the mass loss threshold, the length loss of the contact is less than the length loss threshold, the ablation morphology does not show the typical defects specified in standard IEC62271-100, and the arc voltage change is within the preset allowable deviation range, then it is determined that the contact has not met the replacement conditions, and the circuit breaker can continue to operate and enter the status assessment of the next interruption cycle.

[0135] It should be noted that the data acquired by the aforementioned test measurement and diagnostic unit... Δm , ΔL The four types of parameters—arc voltage, ablation morphology, and polarization—correspond one-to-one with the corresponding indicators output by the simulation evaluation method, forming a complete physical and simulation comparison system for the evaluation device. This supports the verification of the effectiveness of the simulation evaluation method under different voltage levels, current amplitudes, and number of interruptions.

[0136] To fully illustrate the feasibility and beneficial effects of the simulation evaluation method and supporting evaluation device proposed in this invention, this embodiment 3 uses a 252kV / 40kA self-energized SF6 circuit breaker as the object and conducts an example analysis in conjunction with the aforementioned evaluation device. This example covers five complete steps: geometric modeling, boundary condition setting, multiphysics coupling solution, evaluation index output, and comparison and verification with experimental results.

[0137] In this embodiment, a three-dimensional computational domain is constructed based on the measured dimensions of the arc-extinguishing chamber unit and the overall circuit breaker unit in the evaluation device. The specific process, according to the technical solution and key points of this application, is as follows: Figure 8 As shown.

[0138] Specifically, the computational domain covers the moving arc contact 2, the nozzle 4, the stationary arc contact 5, the shield 6, and the stationary contact base 7 along the axial direction, and radially covers the outer wall of the arc-extinguishing chamber. The computational domain is approximately 2.2 × 10⁻⁶. 6 The mesh is divided into tetrahedral sections, and local densification is applied to the surfaces of the stationary arc contact 5 and the moving arc contact 2. The densification results are as follows: Figure 9 As shown.

[0139] Optional, the time step can be 5×10. -6 For local regions where the mesh quality is below a preset threshold, the Laplacian smoothing method is used for smoothing after the dynamic mesh update is completed at each time step. If necessary, local remeshing is performed to maintain the mesh stability of long-term transient calculations.

[0140] In this embodiment, the boundary conditions and initial conditions of the simulation evaluation method are obtained by actual measurement and diagnosis in the evaluation device.

[0141] Specifically, in the boundary conditions, all outer walls of the arc extinguisher are set as insulated walls, and all walls are subject to no-slip conditions; all walls except the stationary arc contact 5 and the moving arc contact 2 are set as electrically insulated; the outlet of the nozzle 4 is set as an open boundary, and the outlet temperature and pressure are constant values, for example, the outlet temperature is 293.15 K, the pressure is 0.5 MPa, and there is no backflow; the stationary arc contact 5 is applied with an AC potential of 252kV, 40kA, and 50Hz, and the moving arc contact 2 is grounded.

[0142] Specifically, in the initial conditions, the initial ambient pressure is taken as 0.5 MPa, and the initial ambient temperature is taken as 293.15 K; the initial velocity of the moving contact and the initial velocity of cylinder piston 1 are obtained from the stroke measured by the sensor. The velocity curve is given, and the curve is as follows: Figure 10 As shown; the inlet turbulence intensity is taken as 5%, the turbulence dissipation rate is taken as 10; the break phase angle is taken as -120° to ensure that the simulated arc duration is consistent with the experimentally measured arc duration.

[0143] Optional, material properties (density) r Electrical conductivity s Specific heat at constant pressure C p Dynamic viscosity m and thermal diffusivity The values ​​are provided by a temperature-dependent SF6 plasma database; the effects of PTFE vapor products on plasma electrical and thermal conductivity are corrected using interpolation methods rather than explicit transport solutions. This approach significantly reduces memory consumption and solution time for three-dimensional calculations while preserving the influence of major property changes on MHD field quantities.

[0144] In this embodiment of the application, the multiphysics coupling equations (1)-(6) are solved by simulation evaluation method to obtain the arc temperature field distribution inside the nozzle 4 and the surface temperature distribution of the static arc contact 5 during the arc extinguishing process, such as Figure 11 As shown.

[0145] Furthermore, by coupling the phase change source term to the VOF model, the multiphase flow evolution results can be obtained simultaneously. This multiphase flow consists of molten metal droplets and metal vapor, which are rapidly transported downstream of nozzle 4 under turbulent shear force. Figure 12 As shown.

[0146] It should be noted that the latent heat of fusion and the latent heat of vaporization will participate in the solution of the energy conservation equation as negative feedback source terms, thereby effectively suppressing the problem of overestimation of electrode surface temperature that is common in classical models.

[0147] In this embodiment of the application, the dynamic mesh geometry output by the simulation evaluation method is synchronously imported into the 3D modeling software for measurement.

[0148] Optionally, the contact geometry, surface temperature, and surface velocity can be extracted along five characteristic moments: 1.0ms, 5.0ms, 9.0ms, 13.0ms, and 17.0ms on the surface of the static arc contact 5.

[0149] It should be noted that under turbulent shearing, the peak surface temperature of the stationary arc contact 5 can reach approximately 22,000 K, and the maximum shear velocity along the surface is approximately 125 m / s. Under this condition, metal vapor and microdroplets are rapidly entrained and transported downstream, ultimately forming a uniform ablation morphology on the surface of the stationary arc contact 5, rather than the localized pitting morphology predicted by traditional models.

[0150] Furthermore, through three-dimensional measurement, it was found that after the interruption, the surface length of the static arc contact 5 decreased from 10.0 mm to 9.12 mm, and the overall length decreased from 255.0 mm to 254.12 mm; according to the contact material, namely copper-tungsten alloy CuW80 with a density of 14.60 g / cm³, the contact length decreased. 3 The calculated evaporation mass loss is 3.31g.

[0151] In this embodiment, multiple sets of measured data collected by the experimental measurement and diagnostic unit are used as a benchmark to evaluate the prediction accuracy of the simulation evaluation method proposed in this invention, covering evaporation quality. Δm Length loss ΔL Two indicators.

[0152] Specifically, as shown in Table 1, comparisons were made for eight test conditions with a cumulative interruption count of 1 to 7 at two voltage levels: 252kV / 40kA and 72.5kV / 40kA. The results are as follows: Figure 13 As shown. Specifically, the evaporation quality error range is -3.38% to +3.43%, the length loss error range is -3.56% to +3.52%, and the error of all indicators does not exceed ±5%.

[0153] Table 1

[0154] It should be noted that the simulation results are slightly lower than the experimental measurements under some operating conditions. This is mainly because the actual test involved continuous operation and arc reignition, which caused the initial temperature of the contact to be higher than the ambient temperature, resulting in changes in the thermodynamic state of the material and thus exacerbating the actual ablation.

[0155] Optionally, the line integral of the electric field intensity along the arc path can be used as the simulated arc voltage, and compared with the measured arc voltage obtained by the data acquisition system. The results are as follows: Figure 14 As shown.

[0156] It should be noted that there is a high-frequency oscillation section caused by the recovery voltage of the external circuit before and after the current crosses zero, and this section was not included in the simulation model; except for this brief section, the simulation curve and the measured curve match well throughout the entire arcing time.

[0157] As can be seen from the above examples, the simulation evaluation method and supporting evaluation device proposed in this invention can achieve high-precision quantitative evaluation of contact evaporation quality, length loss, ablation morphology and arc voltage under actual working conditions of 252kV / 40kA. The prediction errors of evaporation quality and length loss are both no more than ±5%, which is a significant improvement over the traditional Gaussian arc model. This provides systematic methodological support and experimental basis for the electrical life evaluation of high-voltage switchgear, the optimization of arc-extinguishing chamber structure and the determination of contact replacement threshold.

[0158] Embodiment 4 of the present invention provides a terminal, including a processor and a storage medium; the storage medium is used to store instructions; the processor is used to perform operations according to the instructions to execute the steps of the method.

[0159] Embodiment 5 of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method.

[0160] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0161] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0162] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0163] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0164] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A simulation evaluation method for contact erosion of high-voltage SF6 circuit breakers, characterized in that, include: S1: Establish a three-dimensional geometric model of the arc-extinguishing chamber of the high-voltage SF6 circuit breaker and perform mesh generation to obtain a three-dimensional computational domain mesh model; apply initial conditions and boundary conditions to the three-dimensional computational domain mesh model to obtain a computational domain model with initial conditions and boundary conditions; S2: Based on the computational domain model and combined with the thermal balance relationship of the electrode surface, the surface evaporation mass flux of the high-voltage SF6 circuit breaker contact ablation is obtained by coupling the solution of the electromagnetic field Maxwell equations, the magnetohydrodynamic MHD equations considering mass source terms and vector momentum source terms, the standard k-ε turbulence model and the VOF phase change transport equations. The surface evaporation mass flux is then fed back to the MHD equations in the form of mass source terms and vector momentum source terms, forming a two-way coupling between the evaporating material and the flow field. S3: The retreat velocity of each grid node is obtained based on the surface evaporation mass flux to drive the electrode boundary nodes to move, thereby obtaining the updated electrode geometry and then calculating the quantitative evaluation index of contact ablation of the high voltage SF6 circuit breaker. S4: Determine whether the preset total arcing time or the interruption completion condition has been met. If not, proceed to the next time step, use the updated electrode geometry as the new geometric boundary of the computational domain model, and return to S2. If the conditions have been met, output the quantitative evaluation index.

2. The simulation evaluation method for contact erosion of a high-voltage SF6 circuit breaker according to claim 1, characterized in that: The process involves establishing a three-dimensional geometric model of the arc-extinguishing chamber of the high-voltage SF6 circuit breaker and performing mesh generation to obtain a three-dimensional computational domain mesh model, including: A three-dimensional geometric model was established based on the measured dimensions of the arc-extinguishing chamber unit of the high-voltage SF6 circuit breaker. The three-dimensional geometric model was then meshed, with local densification implemented on the surfaces of the moving arc contact and the stationary arc contact. A time step was set to obtain a three-dimensional computational domain mesh model.

3. The simulation evaluation method for contact erosion of a high-voltage SF6 circuit breaker according to claim 1, characterized in that: S2 specifically includes: Based on the computational domain model and the velocity and temperature fields at the current moment, the electromagnetic field distribution in the computational domain at the current moment is solved using the Maxwell equations of electromagnetic fields to obtain the vectors of current density, electric field strength and magnetic induction intensity. Based on the current density, electric field strength, and magnetic induction intensity vector, the magnetohydrodynamic (MHD) equations considering mass source terms and vector momentum source terms are solved to obtain the velocity field and temperature field of the gas, and the velocity field and temperature field are fed back to the Maxwell equations. Based on the velocity field, the VOF phase change transport equation is solved to obtain the volume fraction of each phase, the mixed phase density, and the mixed phase viscosity μ. Based on the mixed phase density and the velocity field, the standard k-ε turbulence model is solved to obtain the turbulent viscosity μ. t ; Utilizing the turbulent viscosity μ t The viscous stress tensor τ in the MHD equations is updated with the mixed phase viscosity μ. Based on the temperature field and the liquid phase fraction in each phase volume fraction, the latent heat loss Q is calculated according to the thermal equilibrium relationship of the electrode surface. melt Latent heat loss due to evaporation Q vap Surface evaporation mass flux; Based on the surface evaporation mass flux, the mass source term and vector momentum source term are obtained; these terms are fed back to the MHD equations, and the Q is... melt Q vap The solution process of the MHD equations is introduced as an additional source term.

4. The simulation evaluation method for contact erosion of a high-voltage SF6 circuit breaker according to claim 3, characterized in that: The MHD equations include the magnetohydrodynamic mass conservation equation, momentum conservation equation, and energy conservation equation, which are as follows: In the formula, ρ Indicates the density of the mixed phase; t For time; Indicates the quality source term; p This refers to the pressure of the gas. τ For the viscous stress tensor of the gas; This represents the additional vector momentum source term introduced by copper vapor; e Represents the total internal energy per unit mass; T For temperature; λ Thermal conductivity; S φ Represents the viscous dissipation source term; For magnetic induction intensity, current density, electric field intensity, and velocity vector; It is a spatial differential operator.

5. The simulation evaluation method for contact erosion of a high-voltage SF6 circuit breaker according to claim 3, characterized in that: The VOF phase transition transport equation is as follows: In the formula, The volume fraction of phase q; This refers to the mass exchange term between different phases. Let q be the phase density; Let be the dynamic viscosity of phase q; ρ is the velocity vector; μ is the mixed phase density; ρ is the mixed phase viscosity. It is a spatial differential operator.

6. The simulation evaluation method for contact erosion of a high-voltage SF6 circuit breaker according to claim 3, characterized in that: Using the turbulent viscosity μ t The formula for updating the viscous stress tensor τ in the MHD equations based on the mixed-phase viscosity μ is: In the formula, the subscript T is the transpose variable, I represents the unit tensor, and v is the velocity; It is a spatial differential operator.

7. The simulation evaluation method for contact erosion of a high-voltage SF6 circuit breaker according to claim 3, characterized in that: The latent heat loss of melting Q melt Latent heat loss due to evaporation Q vap The specific formula for surface evaporation mass flux is as follows: In the formula, ρ Indicates the density of the mixed phase; The liquid phase fraction; L m The latent heat of fusion of the alloy; For the evaporation region, it is a position function. points within , be on point to the molten surface shortest distance No more than the thickness of the near-surface evaporation layer When, the position function takes the value 1, when Exceed When the position function is zero, the position function is zero. For surface evaporation mass flux; L v The latent heat of vaporization of the alloy; A As a pre-factor; E α It is the activation energy for evaporation; R It is the gas constant; T For temperature.

8. The simulation evaluation method for contact erosion of a high-voltage SF6 circuit breaker according to claim 3, characterized in that: Based on surface evaporation mass flux , obtain quality source item and vector momentum source term The specific formula is as follows: In the formula, The normal vector of the contact boundary element. For nodes in x , y , z The unit basis vector in the direction; For the evaporation region, it is a position function. One point of responsibility , be on point to the molten surface shortest distance No more than the thickness of the near-surface evaporation layer When, the position function takes the value 1, when Exceed When the position function is zero, the position function takes the value 0.

9. The simulation evaluation method for contact erosion of a high-voltage SF6 circuit breaker according to claim 1, characterized in that: The formula for calculating the retreat velocity of each grid node based on the surface evaporation mass flux is as follows: In the formula, The retreat velocity vector of the node; For boundary elements in x , y , z The unit basis vector in the direction; The density of the metal vapor; This represents the surface evaporation mass flux.

10. The simulation evaluation method for contact erosion of a high-voltage SF6 circuit breaker according to claim 1, characterized in that: The quantitative evaluation index is used to compare with a preset standard to determine the contact state; the quantitative evaluation index includes contact length loss, contact evaporation mass loss, ablation morphology and arc voltage; wherein, the ablation morphology is the updated electrode geometry.

11. A verification apparatus for use in the simulation evaluation method according to any one of claims 1-10, characterized in that, include: An arc-extinguishing chamber unit, wherein the arc-extinguishing chamber unit is provided axially with a piston, a moving arc contact, a moving main contact, a nozzle, a stationary arc contact, a shield, a stationary contact base, and a moving contact base; The circuit breaker unit is the external load-bearing structure of the arc-extinguishing chamber unit, used to construct the actual short-circuit breaking condition; The nozzle structure unit includes a nozzle body and a plurality of gas openings evenly distributed in the circumferential direction on the inner wall of the nozzle body, which are used to adjust the turbulence parameters in the arc-extinguishing chamber unit. The test measurement and diagnosis unit is used to acquire multi-dimensional measured data of the arc-extinguishing chamber unit under actual short-circuit breaking conditions during the arc-extinguishing chamber unit's breaking test, and to use this data as a benchmark for quantitative evaluation indicators to verify the accuracy of the simulation evaluation method.

12. The apparatus according to claim 11, characterized in that, The number of gas openings, the opening angle, and the opening cross-sectional area are adjustable structural parameters. The larger the number of openings, the opening angle, and the gas opening cross-sectional area, the greater the gas flow rate entering the arc region from the throat of the nozzle body, and the greater the turbulent kinetic energy and turbulent dissipation rate. Conversely, the turbulent kinetic energy and turbulent dissipation rate decrease accordingly.

13. A terminal, comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to perform the steps of the method according to any one of claims 1-10.

14. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the program implements the steps of the method according to any one of claims 1-10.

Images