Construction method of miniature circuit breaker breaking performance evaluation system comprehensively considering mechanical and arc characteristics

Abstract

The invention relates to a construction method of a miniature circuit breaker breaking performance evaluation system comprehensively considering mechanical and arc characteristics, and the method comprises the following steps: S1, constructing a rigid-flexible coupled miniature circuit breaker short circuit breaking process simulation model, employing a Newton-Euler equation and a modal superposition method to respectively establish a rigid body model and a flexible body model, rigid-flexible coupling is realized through interface conditions, so that more accurate mechanical characteristics can be obtained; s2, constructing a miniature circuit breaker arc extinguishing process simulation model considering the three-dimensional characteristics of the metal gate sheet, and performing modeling on the three-dimensional characteristics of the metal gate sheet by the model to excavate the action mechanism of the three-dimensional characteristics of the metal gate sheet in the arc extinguishing process so as to obtain the three-dimensional arc characteristics of the miniature circuit breaker; and S3, adopting a K-means clustering method and an analytic hierarchy process to carry out screening and weighting on the multi-dimensional indexes of the circuit breaker, and establishing a miniature circuit breaker breaking performance evaluation system. According to the evaluation embodiment constructed by the method, the breaking performance of the miniature circuit breaker can be evaluated more accurately and effectively.

Description

Technical Field

[0001] The present invention relates to the field of miniature circuit breakers, and in particular to a method for constructing a miniature circuit breaker breaking performance evaluation system that comprehensively considers mechanical and arc characteristics. Background Art

[0002] As a key protection device in low-voltage power distribution networks, miniature circuit breakers are widely used in industrial, commercial and residential fields, and undertake the important responsibility of overload protection and short-circuit protection of electrical lines and electrical equipment. With the continuous growth of power demand and the diversification of electrical equipment, the performance requirements for miniature circuit breakers are also increasing, especially their breaking performance has become the focus of attention.

[0003] In order to more accurately evaluate the breaking performance of small circuit breakers, we often use computer simulation technology to simulate the working performance of circuit breakers under different working conditions. With the continuous improvement of computer performance, simulation software based on finite element method (FEM) and finite volume method (FVM) has developed rapidly. The friendly UI interface and low calculation conditions have gradually introduced simulation software into the design of auxiliary small circuit breakers.

[0004] However, the existing evaluation system often focuses more on the arc characteristics of the circuit breaker, such as the breaking current and the length of the arc breaking time, while ignoring the mechanical characteristics of the circuit breaker, which may lead to the inability to comprehensively evaluate the breaking performance of the circuit breaker. Therefore, it is of great significance to establish a breaking performance evaluation system for small circuit breakers that comprehensively considers mechanical characteristics and arc characteristics to ensure the safe, stable and efficient operation of the power system. Summary of the invention

[0005] The object of the present invention is to provide a method for constructing a breaking performance evaluation system for a miniature circuit breaker that comprehensively considers mechanical and arc characteristics. The evaluation system constructed by this method can more accurately and effectively evaluate the breaking performance of a miniature circuit breaker.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: a method for constructing a breaking performance evaluation system for a miniature circuit breaker that comprehensively considers mechanical and arc characteristics, comprising the following steps:

[0007] S1. Construct a simulation model of the short-circuit breaking process of a small circuit breaker with rigid-flexible coupling. The model uses the Newton-Euler equation and the modal superposition method to establish a rigid body model and a flexible body model respectively, and then realizes rigid-flexible coupling through interface conditions to obtain more accurate mechanical characteristics;

[0008] S2. Construct a simulation model of arc extinguishing process of a small circuit breaker considering the three-dimensional characteristics of the metal grid. The model models the three-dimensional characteristics of the metal grid to explore the mechanism of the three-dimensional characteristics of the metal grid in the arc extinguishing process and obtain the three-dimensional arc characteristics of the small circuit breaker.

[0009] S3. K-means clustering method and hierarchical analysis method are used to screen and weight the multi-dimensional indicators of circuit breakers, and a small circuit breaker breaking performance evaluation system is established.

[0010] Furthermore, step S1 specifically includes the following steps:

[0011] A1. Establish a 3D geometric model of a miniature circuit breaker and determine the material properties of each component;

[0012] A2. Add corresponding constraints according to the topological relationship between the various components of the miniature circuit breaker;

[0013] A3. Use the Newton-Euler equation to establish a rigid body model and link the changes in kinetic energy and potential energy with external forces. The specific formula is as follows:

[0014] F=ma (1)

[0015] τ=Iα+ω×Iω (2)

[0016] Where F is force, m is mass, a is acceleration, τ is torque, I is inertia tensor, α is angular acceleration, and ω is angular velocity;

[0017] A4. Use the modal superposition method to establish a flexible body model. The specific formula is as follows:

[0018]

[0019] Where u(x,t) is the displacement of the flexible body, φ i (x) i-th mode shape, q i (t) is the corresponding modal coordinate;

[0020] A5. Realize rigid-flexible coupling through interface conditions, that is, the displacement of the end of the rigid body matches the displacement of the flexible body at the connection point;

[0021] A6. Calculate the short-circuit current. When a single-phase short-circuit fault occurs in the circuit breaker, the short-circuit current consists of two parts: a sinusoidal periodic current component and a non-periodic component. The specific formula is as follows:

[0022]

[0023] Among them, I m is the amplitude of the short-circuit current periodic component, ψ is the short-circuit instantaneous voltage phase angle, is the power factor angle, r is the line resistance, L is the line inductance, and τ is the electromagnetic time constant;

[0024] A7. Use electromagnetic simulation software to build an electromagnetic system model of a small circuit breaker to obtain the magnitude of electromagnetic attraction under different currents and core spacings, thereby forming a two-dimensional interpolation curve of electromagnetic attraction changing with current and core spacing, and interpolating the short-circuit current and core spacing to calculate the real-time electromagnetic attraction;

[0025] A8. Use multi-body dynamics simulation software to solve the established model.

[0026] Furthermore, step S2 specifically includes the following steps:

[0027] B1. Establish a three-dimensional geometric model of the metal grid, which includes the three-dimensional size, spacing, arrangement, grooves, and surface texture or layer of the metal grid;

[0028] B2. Import the metal grid 3D geometric model into the MHD simulation software and perform meshing;

[0029] B3. The magnetohydrodynamic model is used to model the multi-physical fields in the arc extinguishing process. The multi-physical field relationship in the magnetohydrodynamic model relies on multiple sets of control equations, among which the Navier-Stokes equations and the energy conservation equations express fluid dynamics, and the Maxwell equations express the electromagnetic field. The specific mathematical model is as follows:

[0030] I. Mass conservation equation:

[0031]

[0032] Where: ρ is the gas density; t is the time; u is the velocity vector in the fluid;

[0033] II. Momentum conservation equation:

[0034]

[0035] F=J×B (8)

[0036] Where: p is the fluid micro-element pressure; μ is the dynamic viscosity of the fluid; I is the unit matrix; F is the Lorentz force; J is the conduction current density; B is the magnetic induction intensity;

[0037] III. Energy conservation equation:

[0038]

[0039] Where: H is enthalpy; λ is thermal conductivity; C p is the specific heat capacity at constant pressure; T is the temperature value; S H is the plasma heat source; Srad is the overall thermal radiation; S p is the electron enthalpy transfer; K B is the Boltzmann constant;

[0040] IV. Gas state equation:

[0041] p=ρRT (12)

[0042] V. Maxwell equations of electromagnetic field:

[0043]

[0044] Where σ is the conductivity; is the electric potential; A is the vector magnetic potential; E is the electric field strength;

[0045] B4. Set the boundary conditions of the metal grid surface;

[0046] B5. Set the initial position, shape, temperature and current density parameters of the arc;

[0047] B6. Use MHD simulation software to simulate and solve the established model.

[0048] Furthermore, step S3 specifically includes the following steps:

[0049] C1. Determine the initial indicators of the evaluation system, including the mechanical characteristics and arc characteristics of the miniature circuit breaker; among them, the mechanical characteristics include the opening and closing time, opening and closing speed, mechanism closing force and fatigue life; the arc characteristics include arc duration, arc voltage, arc current, arc energy and electromotive repulsion;

[0050] C2. Use K-means clustering method to perform cluster analysis on the initial indicators of the evaluation system and select the final breaking performance evaluation indicators;

[0051] C3. Use the analytic hierarchy process to allocate indicator weights. The calculation method is as follows:

[0052] I. Compare the importance of each indicator pairwise. For n indicators, construct a judgment matrix A. rp ;

[0053]

[0054] Among them, a rp It represents the ratio of the importance of the rth indicator to the importance of the pth indicator. 1 means that the two indicators are equally important. rp is a positive reciprocal matrix;

[0055] II. Check the consistency of the judgment matrix;

[0056] If and only if the maximum eigenvalue λ of the judgment matrix max =n, the n-order positive reciprocal matrix is ​​a consistent matrix; when the matrix is ​​not consistent, it satisfies λ max >n, the greater the difference between the maximum eigenvalue and n, the more inconsistent the matrix; the consistency index CI and consistency ratio CR are calculated as follows:

[0057]

[0058]

[0059] Among them, RI is the average random consistency index; if CR < 0.1, the consistency of the judgment matrix is ​​acceptable; otherwise, the judgment matrix is ​​changed until the consistency check is satisfied;

[0060] III. Calculate the weight by arithmetic mean method;

[0061]

[0062] C4. The breaking performance evaluation index obtained by the K-means clustering method is combined with the weight calculated by formula (17) to perform weighted calculation to obtain the breaking performance of the small circuit breaker.

[0063] Compared with the prior art, the present invention has the following beneficial effects: the present invention provides a method for constructing a breaking performance evaluation system for a small circuit breaker that comprehensively considers mechanical and arc characteristics. The method constructs a simulation model of a short-circuit breaking process of a small circuit breaker based on rigid-flexible coupling. The model performs rigid-flexible coupling processing on flexible components and rigid components through interface conditions to ensure that the interaction between them can be accurately simulated during the simulation process. The use of this model can obtain more accurate mechanical characteristics during the short-circuit breaking process. At the same time, a simulation model of the arc extinguishing process of a small circuit breaker that considers the three-dimensional characteristics of a metal grid is constructed. Through this model, the influence of the three-dimensional characteristics of a metal grid on the arc extinguishing process can be deeply studied, including the processes of arc segmentation, cooling and extinguishing, so as to obtain the three-dimensional arc characteristics of the small circuit breaker. On this basis, a breaking performance evaluation system for a small circuit breaker that comprehensively considers mechanical characteristics and arc characteristics is established. The system uses K-means clustering method and hierarchical analysis method to screen and weight the multi-dimensional indicators of the circuit breaker, and finally obtains the breaking performance of the circuit breaker. This multi-dimensional consideration system can more accurately and effectively evaluate the breaking performance of circuit breakers and provide a scientific basis for the design and selection of circuit breakers. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 is a flow chart of a method implementation of an embodiment of the present invention;

[0065] Figure 2It is a multi-physical field coupling relationship diagram of the arc model in an embodiment of the present invention. DETAILED DESCRIPTION

[0066] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0067] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0068] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0069] like Figure 1 As shown, this embodiment provides a method for constructing a breaking performance evaluation system for a miniature circuit breaker that comprehensively considers mechanical and arc characteristics, including the following steps:

[0070] S1. Construct a simulation model of the short-circuit breaking process of a small circuit breaker with rigid-flexible coupling. The model uses the Newton-Euler equation and the modal superposition method to establish a rigid body model and a flexible body model respectively, and then realizes rigid-flexible coupling through interface conditions to obtain more accurate mechanical characteristics;

[0071] S2. Construct a simulation model of arc extinguishing process of a small circuit breaker considering the three-dimensional characteristics of the metal grid. By accurately modeling the three-dimensional characteristics of the metal grid, the model can deeply study and explore the mechanism of the three-dimensional characteristics of the metal grid in the arc extinguishing process, and obtain the three-dimensional arc characteristics of the small circuit breaker;

[0072] S3. K-means clustering method and hierarchical analysis method are used to screen and weight the multi-dimensional indicators of circuit breakers, and a small circuit breaker breaking performance evaluation system is established.

[0073] (1) Constructing a simulation model of the short-circuit breaking process of a small circuit breaker with rigid-flexible coupling

[0074] In the multi-rigid body model, all parts are assumed to be rigid bodies, that is, they do not deform under external forces. However, in actual situations, especially when there are weak structural parts in the tripping system, deformation may occur during the force process. In order to make the simulation results closer to the actual situation, this method constructs a rigid-flexible coupled miniature circuit breaker short-circuit breaking process simulation model. The specific steps are as follows:

[0075] A1. Establish a three-dimensional geometric model of the miniature circuit breaker and determine the material properties of each component.

[0076] A2. According to the topological relationship between the various components of the miniature circuit breaker, add corresponding constraints, including fixed constraints, rotation constraints, direct motion constraints, plane constraints, etc.

[0077] A3. Use Newton-Euler equations to establish the dynamic model of the system. These equations relate the changes in kinetic energy and potential energy of the system to external forces. The specific formulas are as follows:

[0078] F=ma (1)

[0079] τ=Iα+ω×Iω (2)

[0080] Where F is the force, m is the mass, a is the acceleration, τ is the moment, I is the inertia tensor, α is the angular acceleration, and ω is the angular velocity.

[0081] A4. Use the modal superposition method to establish a flexible body model. The specific formula is as follows:

[0082]

[0083] Where u(x,t) is the displacement of the flexible body, φ i (x) i-th mode shape, q i (t) is the corresponding modal coordinate.

[0084] A5. Rigid-flexible coupling is achieved through interface conditions, that is, the end displacement of the rigid body should match the displacement of the flexible body at the connection point.

[0085] A6. Calculate the short-circuit current. When a single-phase short-circuit fault occurs in the circuit breaker, the short-circuit current consists of a sinusoidal periodic current component and a non-periodic component. The key parameters are the expected current peak, power factor angle, and short-circuit voltage phase angle. The specific formula is as follows:

[0086]

[0087] Among them, I m is the amplitude of the short-circuit current periodic component, ψ is the short-circuit instantaneous voltage phase angle, is the power factor angle, r is the line resistance, L is the line inductance, and τ is the electromagnetic time constant.

[0088] A7. Use electromagnetic simulation software to build an electromagnetic system model of a small circuit breaker to obtain the magnitude of the electromagnetic attraction under different currents and core spacings, thereby forming a two-dimensional interpolation curve of the electromagnetic attraction changing with current and core spacing. Interpolate the short-circuit current and core spacing in the interpolation table to calculate the real-time electromagnetic attraction.

[0089] A8. Use multi-body dynamics simulation software to solve the established model.

[0090] The model can accurately simulate the stress distribution and changes of weak components during the stress process, so as to better evaluate the strength and fatigue life of the components and obtain the mechanical properties during the short-circuit breaking process.

[0091] (2) Constructing a simulation model of arc extinguishing process of a small circuit breaker considering the three-dimensional characteristics of metal grids

[0092] The current simulation of arc extinguishing process of metal grid mostly adopts two-dimensional model, which can only simulate the movement of arc in plane, and cannot fully capture the complex behavior of arc in three-dimensional space, nor can it reflect the influence of three-dimensional characteristics of metal grid on arc extinguishing process. In order to obtain three-dimensional arc characteristics, this method constructs a simulation model of arc extinguishing process of small circuit breaker considering three-dimensional characteristics of metal grid based on magnetohydrodynamics (MHD). The specific steps are as follows:

[0093] B1. Establish a three-dimensional geometric model of the metal grid, which includes the three-dimensional size, spacing, arrangement, grooves, and surface texture or layer of the metal grid.

[0094] B2. Import the 3D geometric model of the metal grid into the MHD simulation software and perform detailed meshing. The density and shape of the grid should be optimized according to the physical processes that may occur in the arc (such as heat conduction, electromagnetic field changes, fluid flow, etc.). In the vicinity of the grid and in areas where the arc may pass, a denser grid should be used to improve the accuracy of the simulation.

[0095] B3. Use the magnetohydrodynamic model to model the multi-physics field in the arc extinguishing process. The multi-physics field relationship in the magnetohydrodynamic model relies on multiple sets of control equations, among which the Navier-Stokes equations and energy conservation equations express fluid dynamics, and the Maxwell equations express electromagnetic fields. The multi-physics field coupling relationship of the arc model is as follows: Figure 2 shown.

[0096] The specific mathematical model is as follows:

[0097] I. Mass conservation equation:

[0098]

[0099] Where: ρ is the gas density; t is the time; u is the velocity vector in the fluid.

[0100] II. Momentum conservation equation:

[0101]

[0102] F=J×B (8)

[0103] Where: p is the fluid micro-element pressure; μ is the dynamic viscosity of the fluid; I is the unit matrix; F is the Lorentz force; J is the conduction current density; B is the magnetic induction intensity.

[0104] III. Energy conservation equation:

[0105]

[0106] Where: H is enthalpy; λ is thermal conductivity; C p is the specific heat capacity at constant pressure; T is the temperature value; S H is the plasma heat source; S rad is the overall thermal radiation; S p is the electron enthalpy transfer; K B is the Boltzmann constant.

[0107] IV. Gas state equation:

[0108] p=ρRT (12)

[0109] V. Maxwell equations of electromagnetic field:

[0110]

[0111] Where σ is the conductivity; is the electric potential; A is the vector magnetic potential; E is the electric field strength.

[0112] B4. Set the boundary conditions of the metal grid surface, such as temperature, heat flux density, electromagnetic field boundary conditions, etc. These conditions should be based on experimental data or theoretical calculations.

[0113] B5. Set the initial position, shape, temperature, current density and other parameters of the arc. These parameters will affect the initial behavior of the arc between the grids.

[0114] B6. Use MHD simulation software to simulate and solve the established model.

[0115] Through this simulation model, the impact of different metal grid designs, such as groove shape, size, and arrangement, on the arc extinguishing performance of the circuit breaker can be evaluated, which helps to quickly screen out the optimal grid design solution and improve the arc extinguishing efficiency and reliability of the circuit breaker. The simulation model can also simulate the arc extinguishing process under different working conditions to obtain the three-dimensional arc characteristics of the small circuit breaker.

[0116] (3) Establishment of a breaking performance evaluation system for miniature circuit breakers that comprehensively considers mechanical characteristics and arc characteristics

[0117] The existing breaking performance evaluation system focuses on the arc characteristics of the circuit breaker, such as the breaking current and the length of the arc breaking time, while ignoring the mechanical characteristics of the circuit breaker, which may lead to the inability to comprehensively evaluate the breaking performance of the circuit breaker. The evaluation system proposed in this method not only focuses on the arc characteristics of the circuit breaker, but also deeply considers the influence of mechanical characteristics, such as the opening and closing time, opening and closing speed, closing force, etc. of the mechanism. This multi-dimensional consideration method can more comprehensively reflect the breaking performance of the circuit breaker; the specific steps are as follows:

[0118] C1. Determine the initial indicators of the evaluation system, including the mechanical characteristics and arc characteristics of the small circuit breaker. Among them, the mechanical characteristics include the opening and closing time, opening and closing speed, mechanism closing force and fatigue life, etc.; the arc characteristics include arc duration, arc voltage, arc current, arc energy and electromotive repulsion, etc.

[0119] C2. There are many indicators in the initial evaluation system, and there is correlation between the information. In order to solve the problem of indicator redundancy and screen out evaluation indicators with high information density, a clustering algorithm is introduced to screen the indicators. The K-means clustering method has the advantages of fast speed and high computational efficiency. Therefore, this method uses the K-means clustering method to perform cluster analysis on the initial indicators of the evaluation system and screen out the final segmentation performance evaluation indicators.

[0120] C3. Each indicator in the evaluation system contributes to different degrees to the evaluation results. In order to measure the impact of each indicator on the evaluation results, the analytic hierarchy process (AHP) is used to assign indicator weights. The calculation method is as follows:

[0121] I. Compare the importance of each indicator pairwise. For n indicators, construct a judgment matrix A. rp .

[0122]

[0123] Among them, a rp It represents the ratio of the importance of the rth indicator to the importance of the pth indicator. 1 means that the two indicators are equally important. Obviously, A rp is a positive reciprocal matrix.

[0124] II. Perform consistency check on the judgment matrix.

[0125] If and only if the maximum eigenvalue λ of the judgment matrix max =n, the n-order positive reciprocal matrix is ​​a consistent matrix. When the matrix is ​​not consistent, it must satisfy λ max >n, the greater the difference between the maximum eigenvalue and n, the more inconsistent the matrix is. The consistency index CI and consistency ratio CR are calculated as follows:

[0126]

[0127] Among them, RI is the average random consistency index, which can be determined by looking up the table. If CR < 0.1, the consistency of the judgment matrix is ​​considered acceptable; otherwise, the judgment matrix must be changed until the consistency check is satisfied.

[0128] III. Calculate the weight by arithmetic mean method;

[0129]

[0130] C4. The breaking performance evaluation index obtained by the K-means clustering method is combined with the weight calculated by formula (17) to perform weighted calculation to obtain the breaking performance of the small circuit breaker.

[0131] By comprehensively considering the mechanical and arc characteristics, the evaluation system can more accurately predict the breaking performance of the circuit breaker under different working conditions, providing a scientific basis for the design and selection of circuit breakers.

[0132] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0133] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0134] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1A function specified in one or more boxes.

[0135] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0136] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A method for constructing a breaking performance evaluation system for a miniature circuit breaker that comprehensively considers mechanical and arc characteristics, characterized in that: The following steps are involved: S1. Construct a simulation model of the short-circuit breaking process of a small circuit breaker with rigid-flexible coupling. The model uses the Newton-Euler equation and the modal superposition method to establish a rigid body model and a flexible body model respectively, and then realizes rigid-flexible coupling through interface conditions to obtain more accurate mechanical characteristics; S2. Construct a simulation model of arc extinguishing process of a small circuit breaker considering the three-dimensional characteristics of the metal grid. The model models the three-dimensional characteristics of the metal grid to explore the mechanism of the three-dimensional characteristics of the metal grid in the arc extinguishing process and obtain the three-dimensional arc characteristics of the small circuit breaker. S3. K-means clustering method and hierarchical analysis method are used to screen and weight the multi-dimensional indicators of circuit breakers, and a small circuit breaker breaking performance evaluation system is established.

2. The method for constructing a breaking performance evaluation system for a miniature circuit breaker that comprehensively considers mechanical and arc characteristics according to claim 1, characterized in that: Step S1 specifically includes the following steps: A1. Establish a 3D geometric model of a miniature circuit breaker and determine the material properties of each component; A2. Add corresponding constraints according to the topological relationship between the various components of the miniature circuit breaker; A3. Use the Newton-Euler equation to establish a rigid body model and link the changes in kinetic energy and potential energy with external forces. The specific formula is as follows: F=ma (1) τ=Iα+ω×Iω (2) Where F is force, m is mass, a is acceleration, τ is torque, I is inertia tensor, α is angular acceleration, and ω is angular velocity; A4. Use the modal superposition method to establish a flexible body model. The specific formula is as follows: Where u(x,t) is the displacement of the flexible body, φ i (x) i-th mode shape, q i (t) is the corresponding modal coordinate; A5. Realize rigid-flexible coupling through interface conditions, that is, the displacement of the end of the rigid body matches the displacement of the flexible body at the connection point; A6. Calculate the short-circuit current. When a single-phase short-circuit fault occurs in the circuit breaker, the short-circuit current consists of two parts: a sinusoidal periodic current component and a non-periodic component. The specific formula is as follows: Among them, I m is the amplitude of the short-circuit current periodic component, ψ is the short-circuit instantaneous voltage phase angle, is the power factor angle, r is the line resistance, L is the line inductance, and τ is the electromagnetic time constant; A7. Use electromagnetic simulation software to build an electromagnetic system model of a small circuit breaker to obtain the magnitude of electromagnetic attraction under different currents and core spacings, thereby forming a two-dimensional interpolation curve of electromagnetic attraction changing with current and core spacing, and interpolating the short-circuit current and core spacing to calculate the real-time electromagnetic attraction; A8. Use multi-body dynamics simulation software to solve the established model.

3. The method for constructing a breaking performance evaluation system for a miniature circuit breaker that comprehensively considers mechanical and arc characteristics according to claim 1, characterized in that: Step S2 specifically includes the following steps: B1. Establish a three-dimensional geometric model of the metal grid, which includes the three-dimensional size, spacing, arrangement, grooves, and surface texture or layer of the metal grid; B2. Import the metal grid 3D geometric model into the MHD simulation software and perform meshing; B3. The magnetohydrodynamic model is used to model the multi-physical fields in the arc extinguishing process. The multi-physical field relationship in the magnetohydrodynamic model relies on multiple sets of control equations, among which the Navier-Stokes equations and the energy conservation equations express fluid dynamics, and the Maxwell equations express the electromagnetic field. The specific mathematical model is as follows: I. Mass conservation equation: Where: ρ is the gas density; t is the time; u is the velocity vector in the fluid; II. Momentum conservation equation: F=J×B (8) Where: p is the fluid micro-element pressure; μ is the dynamic viscosity of the fluid; I is the unit matrix; F is the Lorentz force; J is the conduction current density; B is the magnetic induction intensity; III. Energy conservation equation: Where: H is enthalpy; λ is thermal conductivity; C p is the specific heat capacity at constant pressure; T is the temperature value; S H is the plasma heat source; S rad is the overall thermal radiation; S p is the electron enthalpy transfer; K B is the Boltzmann constant; IV. Gas state equation: p=ρRT (12) V. Maxwell equations of electromagnetic field: Where σ is the conductivity; is the electric potential; A is the vector magnetic potential; E is the electric field strength; B4. Set the boundary conditions of the metal grid surface; B5. Set the initial position, shape, temperature and current density parameters of the arc; B6. Use MHD simulation software to simulate and solve the established model.

4. The method for constructing a breaking performance evaluation system for a miniature circuit breaker that comprehensively considers mechanical and arc characteristics according to claim 1, characterized in that: Step S3 specifically includes the following steps: C1. Determine the initial indicators of the evaluation system, including the mechanical characteristics and arc characteristics of the miniature circuit breaker; among them, the mechanical characteristics include the opening and closing time, opening and closing speed, mechanism closing force and fatigue life; the arc characteristics include arc duration, arc voltage, arc current, arc energy and electromotive repulsion; C2. Use K-means clustering method to perform cluster analysis on the initial indicators of the evaluation system and select the final breaking performance evaluation indicators; C3. Use the analytic hierarchy process to allocate indicator weights. The calculation method is as follows: I. Compare the importance of each indicator pairwise. For n indicators, construct a judgment matrix A. rp ; Among them, a rp It represents the ratio of the importance of the rth indicator to the importance of the pth indicator. 1 means that the two indicators are equally important. rp is a positive reciprocal matrix; II. Check the consistency of the judgment matrix; If and only if the maximum eigenvalue λ of the judgment matrix max =n, the n-order positive reciprocal matrix is ​​a consistent matrix; when the matrix is ​​not consistent, it satisfies λ max >n, the larger the difference between the maximum eigenvalue and n, the more inconsistent the matrix; the consistency index CI and consistency ratio CR are calculated as follows: Among them, RI is the average random consistency index; if CR < 0.1, the consistency of the judgment matrix is ​​acceptable; otherwise, the judgment matrix is ​​changed until the consistency check is satisfied; III. Calculate the weight by arithmetic mean method; C4. The breaking performance evaluation index obtained by the K-means clustering method is combined with the weight calculated by formula (17) to perform weighted calculation to obtain the breaking performance of the small circuit breaker.

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