Circuit breaker arc calculation method based on co-simulation

Abstract

A combined simulation method for calculating arcs in a circuit breaker includes: building a circuit simulation model, using Matlab / Simulink as a simulation platform to build a power system model, calculating the current data passing through the switch, and providing external current excitation for arc simulation; building a mechanism simulation model to simulate the mechanical movement of the circuit breaker, the mechanical movement including the movement trajectory and force of the contacts; building a hydraulic rod contact motion model of the circuit breaker using Adams or AMESim software to simulate the dynamic behavior of the contacts during the breaking process; the hydraulic rod contact motion model is adjusted in real time based on the initial state and external force to obtain the contact force, velocity, and displacement at any time after the circuit breaker is triggered; building an arc simulation model to calculate the arc parameters during the breaking process, building an arc extinguishing chamber model using ANSYS Fluent, and simulating the arc parameters at each moment by combining current excitation with the contact force, velocity, and displacement.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit breaker simulation, and in particular to a circuit breaker arc calculation method for combined simulation. Background Art

[0002] In modern power systems, circuit breakers, as crucial protective devices, play a critical role in preventing electrical failures and ensuring safe system operation. The circuit breaker's opening and closing process involves the coupling of multiple physical fields, including electricity, magnetism, heat, force, and gas. The arc is the most critical factor, determining both the circuit breaker's breaking and arc extinguishing performance. Therefore, the formation and extinction of the arc directly impact circuit safety. Therefore, accurately calculating arc parameters, especially arc resistance, is crucial for optimizing circuit breaker design and improving its reliability.

[0003] Currently, circuit breaker arc parameters are typically estimated through experimental measurements or empirical formulas, lacking real-time calculation and feedback mechanisms. This approach is not only inefficient but also difficult to guarantee accuracy under complex operating conditions. With the advancement of computer simulation technology, simulation-based methods have gradually become an important means of studying circuit breaker arc characteristics.

[0004] Existing simulation tools such as Adams and Amesim are widely used for mechanism dynamics analysis and can effectively simulate the movement of circuit breaker contacts and their impact on the arc. However, these tools are limited in the real-time calculation and feedback of arc parameters, making it impossible to form a complete closed-loop control system. Meanwhile, ANSYS Fluent has powerful simulation capabilities in fluid dynamics and heat conduction, and can provide thermal and current characteristics during arcing processes, but its real-time coupling with mechanism motion still needs further optimization. Matlab / Simulink provides powerful circuit analysis capabilities, but when it comes to the linkage simulation between arc parameters and circuit dynamics, existing methods often lack efficient communication mechanisms, resulting in data transmission delays and information inconsistencies.

[0005] In summary, the current circuit breaker arc simulation method has problems such as insufficient real-time performance, poor computational coupling, and low simulation accuracy.

[0006] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the Invention

[0007] The present invention provides a co-simulation circuit breaker arc calculation method, which can systematically simulate the entire process of high-voltage switch opening and closing to improve the calculation accuracy and real-time performance of the arc, thereby enhancing the performance evaluation capability and design optimization level of the circuit breaker.

[0008] A co-simulation circuit breaker arc calculation method includes:

[0009] Build a circuit simulation model, using Matlab / Simulink as the simulation platform to build a power system model, calculate the current data through the switch and provide external current excitation for arc simulation;

[0010] Build a mechanical simulation model that simulates the mechanical movement of the circuit breaker. The mechanical movement includes the movement trajectory and force of the contacts. Use Adams or AMESim software to build a hydraulic rod contact motion model of the circuit breaker to simulate the dynamic behavior of the contacts during the breaking process. The hydraulic rod contact motion model is adjusted in real time based on the initial state and external force to obtain the contact force, velocity, and displacement at any time after the circuit breaker is triggered.

[0011] An arc simulation model is built to calculate the arc parameters during the breaking process. An arc extinguishing chamber model is built using ANSYS Fluent. The arc parameters at each moment are simulated in conjunction with the current excitation and contact force, velocity, and displacement. The arc resistance data and the reaction force of the gas on the contact required by the circuit model are calculated. The arc resistance data is fed back to the circuit model. The circuit simulation model generates current data based on the arc resistance data, and the reaction force is transmitted to the mechanism simulation model to participate in the calculation of the contact force, velocity, and displacement.

[0012] In the described combined simulation circuit breaker arc calculation method, the initial state includes spring potential energy, the external force includes the reaction force of the gas output by the arc simulation model on the contact, and the arc parameters include temperature and pressure.

[0013] In the described combined simulation method for calculating a circuit breaker arc, the circuit simulation model includes a DC power supply V, a time-varying resistor R when the high-voltage switch is disconnected, an ammeter A connected in series with the switch, and an internal system. The initial value of the time-varying resistor R should be zero. After the simulation starts and the switch is actuated, the value of the time-varying resistor R is obtained in real time from the arc simulation results.

[0014] In the described co-simulation circuit breaker arc calculation method, a variety of hydraulic components and fluid structures in the HCD library of AMESim are used to simulate the hydraulic rod contact motion model, which includes a hydraulic control system model, an operating mechanism transmission dynamics simulation model, and an arc extinguishing unit finite volume fluid simulation model. The arc extinguishing unit finite volume fluid simulation model serves as an input arc simulation model that provides gas reaction force to the operating mechanism transmission dynamics simulation model, and the operating mechanism transmission dynamics simulation model provides the motion state of the contact.

[0015] In the described co-simulation circuit breaker arc calculation method, the hydraulic control system model includes an accumulator, a control valve, and a working cylinder. During the circuit breaker opening and closing process, the control valve is used to realize the circuit breaker in the open and open states. The accumulator provides power for the system. The piston of the working cylinder is connected to the hydraulic push rod of the operating mechanism to drive the operating mechanism to move. The reaction force of the piston rod of the working cylinder is obtained through the UDP communication module, and the speed and displacement of the hydraulic push rod are fed back to the working cylinder.

[0016] In the described combined simulation method for calculating the arc of a circuit breaker, the actuator transmission dynamics simulation model includes a double-acting circuit breaker, which includes a hydraulic push rod, a connecting rod, and a moving contact.

[0017] In the described joint simulation circuit breaker arc calculation method, a geometric model of the arc extinguishing chamber is created using CAD software, and then meshing is performed and imported into the mesh, and the net radiation coefficient NEC is used to evaluate the radiation loss.

[0018] Qrad=4πε(rad,temp,press),

[0019] ε(rad, temp, press) is the NEC coefficient, which is a numerical table of radius, temperature, and pressure. Qrad represents the radiation energy released from a unit sphere or unit area per unit time. Here, rad is the arc radius; temp is the arc temperature; and press is the pressure of the arc gas.

[0020] The k-ε turbulence model provided by Fluent is used to set up the Laval laminar flow model simulation of the nozzle arc in the circuit breaker. In Fluent, the momentum source term is customized using the user-defined function UDF, and the source term is written using the DEFINE_SOURCE macro. By calling the current density and magnetic induction intensity in the DEFINE_SOURCE macro and calculating their difference as the return value, the Lorentz force momentum source term of the area to be defined is obtained; the ohmic heat and Joule heat are marked by the user-defined variable UDM. The calculation equation for Joule heat is: Q = σE 2 , the electric field in the simulation is calculated by the potential module in Fluent, and the potential value of each grid in each area is extracted by the C_PHI_1(c,tc) macro.

[0021] In the described co-simulation circuit breaker arc calculation method, Fluent calculates the potential in the unit grid in real time. By setting a comparison program in the calculation, the potential of the units in all arc areas is compared to find the maximum potential difference in the arc area, and this maximum voltage value is approximately regarded as the arc voltage value.

[0022] In the described joint simulation circuit breaker arc calculation method, the arc is divided horizontally according to the grid, the arc radius is set according to the 5000K temperature line, the arc resistance is calculated for each grid layer, and finally the resistances are added in series to calculate the total arc resistance:

[0023]

[0024]

[0025] Where: G i is the conductivity of each grid column / S; G is the total conductivity / S; σ is the conductivity S / m; A is the cross-sectional area / m 2 ; l is length / m; R is resistance / Ω.

[0026] In the described joint simulation circuit breaker arc calculation method, an autonomously programmed router is established as a client, and its service objects are the mechanism simulation model, the circuit simulation model and the arc simulation model. Its function is to transmit data, and then the piston rod reaction force, the moving contact speed and displacement, the arc resistance and the circuit current are selected as the communication content of the UDP communication module, and a counter is used to determine whether to send data. There is a counter with an initial value of 0 inside the router. Whenever the router receives information about calculated data from the mechanism simulation model, the circuit simulation model and the arc simulation model, the data is first intercepted and the counter is increased by 1. At the same time, the sending end of this information is commanded to enter a waiting state. When the identifier is 3, it means that all calculations in this time step have been completed. The router will enter the transmission stage, transmit the data required by each port to the corresponding address respectively, and reset the counter to zero. Subsequently, the three simulation models read this data and continue the next iterative operation.

[0027] Compared with the prior art, the present invention has the following advantages: it adopts AMESim, Fluent and Matlab / Simulink joint simulation, considers mechanical dynamics, fluid dynamics and electrical characteristics, provides a more comprehensive and more practical system analysis, and considers the situation in a comprehensive and comprehensive manner. Since it is difficult for Matlab / Simulink's M language and Fluent's C language to establish a data interface with each other, in order to improve the efficiency of the overall simulation iteration, a self-programmed executable file is used to act as a data transfer path for each software, playing the role of a data router, rather than directly using the software to transfer data to each other. The self-programmed router ensures the synchronization of the three-party simulation models, and also ensures that the speed of the three-party interaction is faster. The net radiation coefficient model is used in the arc simulation model, fully considering the influence of reabsorption and turbulence, and at the same time, the source terms of the energy conservation equation and the momentum conservation equation are corrected, making the arc simulation more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are intended only to illustrate preferred embodiments and are not to be construed as limiting the present invention. It should be understood that the drawings described below are merely examples of the present invention, and that those skilled in the art will be able to derive other drawings from these drawings without inventive effort. Throughout the drawings, identical reference numerals are used to denote identical components.

[0029] In the attached figure:

[0030] Figure 1 This is a logic diagram of a circuit breaker arc calculation method for joint simulation provided by an embodiment of the present disclosure;

[0031] Figure 2 This is a schematic diagram of a circuit simulation model of a circuit breaker arc calculation method for a joint simulation provided by an embodiment of the present disclosure;

[0032] Figure 3 This is a schematic diagram of the arc resistance calculation principle of a circuit breaker arc calculation method for joint simulation provided by an embodiment of the present disclosure;

[0033] Figure 4 This is a schematic diagram of a source zone injection method for a circuit breaker arc calculation method provided by a joint simulation according to an embodiment of the present disclosure. Figure 4 (a) is a schematic diagram of the electric field distribution obtained by the source region injection method. Figure 4 (b) is a schematic diagram of the current density obtained by the source region injection method;

[0034] Figure 5 This is a schematic diagram of a hydraulic operating mechanism constructed using AMESim for a co-simulated circuit breaker arc calculation method provided by one embodiment of the present disclosure;

[0035] Figure 6 This is a schematic diagram of an arc extinguishing chamber-operating mechanism coupling of a circuit breaker arc calculation method for joint simulation provided by one embodiment of the present disclosure;

[0036] Figure 7 This is a schematic diagram of the operating mechanism structure of a circuit breaker arc calculation method for combined simulation provided by an embodiment of the present disclosure;

[0037] Figure 8 This is a schematic diagram of three-party interaction via a router in a joint simulation circuit breaker arc calculation method provided by an embodiment of the present disclosure;

[0038] Figure 9This is a schematic diagram of verifying a routing method for a circuit breaker arc calculation method of a joint simulation provided by an embodiment of the present disclosure.

[0039] The present invention will be further explained below with reference to the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0040] Specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0041] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the invention. The scope of protection of the present invention shall be as defined in the attached claims.

[0042] To facilitate understanding of the embodiments of the present invention, further explanation will be given below using specific embodiments as examples in conjunction with the accompanying drawings, and the accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0043] like Figures 1 to 9 As shown in FIG, the circuit breaker arc calculation method of the joint simulation includes the following steps:

[0044] Build a circuit simulation model, using Matlab / Simulink as the simulation platform to build a power system model, calculate the current data through the switch and provide external current excitation for arc simulation;

[0045] Build a mechanical simulation model that simulates the mechanical movement of the circuit breaker. The mechanical movement includes the movement trajectory and force of the contacts. Use Adams or AMESim software to build a hydraulic rod contact motion model of the circuit breaker to simulate the dynamic behavior of the contacts during the breaking process. The hydraulic rod contact motion model is adjusted in real time based on the initial state and external force to obtain the contact force, velocity, and displacement at any time after the circuit breaker is triggered.

[0046] An arc simulation model is built to calculate the arc parameters during the breaking process. An arc extinguishing chamber model is built using ANSYS Fluent. The arc parameters at each moment are simulated in conjunction with the current excitation and contact force, velocity, and displacement. The arc resistance data and the reaction force of the gas on the contact required by the circuit model are calculated. The arc resistance data is fed back to the circuit model. The circuit simulation model generates current data based on the arc resistance data, and the reaction force is transmitted to the mechanism simulation model to participate in the calculation of the contact force, velocity, and displacement.

[0047] In a preferred embodiment of the combined simulation circuit breaker arc calculation method, the initial state includes spring potential energy, the external force includes the reaction force of the gas output by the arc simulation model on the contact, and the arc parameters include temperature and pressure.

[0048] In a preferred embodiment of the described combined simulation circuit breaker arc calculation method, the circuit simulation model includes a DC power supply V, a time-varying resistor R when the high-voltage switch is disconnected, an ammeter A in series with the switch, and an internal system. The initial value of the time-varying resistor R should be zero. After the simulation starts and the switch is actuated, the value of the time-varying resistor R is obtained in real time from the arc simulation results. The internal system is a black box. Users can replace the internal system with a specific circuit as needed. The switch itself has an arc resistance when it is disconnected; the switch and the ammeter are connected in series; the relationship between the switch and the power supply is also uncertain, and there can be one or more power supplies. In short, the entire circuit is set up by the user, the ammeter is connected in series with the switch, and attention is paid to the current in the branch where the switch is located.

[0049] In a preferred embodiment of the described combined simulation circuit breaker arc calculation method, a variety of hydraulic components and fluid structures in the HCD library of AMESim are used to simulate the hydraulic rod contact motion model, which includes a hydraulic control system model, an operating mechanism transmission dynamics simulation model, and an arc extinguishing unit finite volume fluid simulation model, wherein the arc extinguishing unit finite volume fluid simulation model serves as an input arc simulation model that provides gas reaction force to the operating mechanism transmission dynamics simulation model, and the operating mechanism transmission dynamics simulation model provides the motion state of the contact.

[0050] In a preferred embodiment of the described combined simulation circuit breaker arc calculation method, the hydraulic control system model includes an accumulator, a control valve, and a working cylinder. During the circuit breaker opening and closing process, the circuit breaker is placed in the open and open states through the control valve. The accumulator provides power for the system. The piston of the working cylinder is connected to the hydraulic push rod of the operating mechanism to drive the operating mechanism to move. The reaction force of the piston rod of the working cylinder is obtained through the UDP communication module, and the speed and displacement of the hydraulic push rod are fed back to the working cylinder.

[0051] In a preferred embodiment of the described combined simulation method for calculating circuit breaker arcs, the actuator transmission dynamics simulation model includes a double-acting circuit breaker, which includes a hydraulic push rod, a connecting rod, and a moving contact. One to three connecting rods are arranged side by side in a group, forming 10 connecting pairs. Connecting rod 1 connects to the hydraulic push rod, connecting rod 2 connects to the moving contact, and connecting rod 3 is bound by a fixed rod. Under the pull of the hydraulic push rod, connecting rods 1 to 3 drive the movement to complete the opening and breaking process of the motion mechanism. In one embodiment, the motion mechanism of the double-acting circuit breaker consists of a hydraulic push rod, a connecting rod, and a moving contact. The hydraulic push rod serves as the power source of the system, providing the necessary power to drive the movement of the entire mechanism. One end of connecting rod 1 is connected to the hydraulic push rod, and the other end is connected to connecting rod 2 via a connecting pair, responsible for transmitting the power of the hydraulic push rod to connecting rod 2. Connecting rod 2 is connected to connecting rod 1 at one end and to the moving contact at the other end, directly driving the movement of the moving contact to achieve the opening and breaking process of the switch. Connecting rod 3 is bounded by a fixed rod, supporting the movement of the other connecting rods and ensuring the stability of the entire system. Connecting rod 3 is designed to form a specific angle with connecting rod 2, thereby facilitating efficient power transmission. The moving contact is a key component of the circuit breaker, responsible for connecting or disconnecting with the stationary contact, ultimately switching the circuit on and off. The fixed rod provides support for connecting rod 3, ensuring that it does not deform or shift during movement.

[0052] In a preferred embodiment of the circuit breaker arc calculation method of the joint simulation, a geometric model of the arc extinguishing chamber is created using CAD software, and then meshing is performed and imported into the mesh, and the net radiation coefficient NEC is used to evaluate the radiation loss.

[0053] Qrad=4πε(rad,temp,press),

[0054] ε(rad, temp, press)——NEC coefficient, which is a numerical table of radius, temperature, and pressure. Qrad is used as the radiation coefficient, which represents the radiation energy released from a unit sphere or unit area per unit time; among them, rad is the radius of the arc; temp is the arc temperature; press is the pressure of the arc gas; the k-ε turbulence model provided by Fluent is used to set the Laval laminar flow model simulation of the nozzle arc in the circuit breaker. In Fluent, the momentum source term is customized using the user-defined function UDF, and the source term is written using the DEFINE_SOURCE macro. By calling the current density and magnetic induction intensity in the DEFINE_SOURCE macro and calculating their difference product as the return value, the Lorentz force momentum source term of the area to be defined is obtained; the ohmic heat and Joule heat are marked by the user-defined variable UDM, and the calculation equation for Joule heat is: Q=σE 2, the electric field in the simulation is calculated by the potential module in Fluent, and the potential value of each grid in each area is extracted by the C_PHI_1(c,tc) macro.

[0055] In a preferred embodiment of the described combined simulation circuit breaker arc calculation method, Fluent calculates the electric potential in the unit grid in real time, compares the electric potentials of the units in all arc areas by setting a comparison program in the calculation, finds the maximum potential difference in the arc area, and approximates this maximum voltage value as the arc voltage value.

[0056] In a preferred embodiment of the circuit breaker arc calculation method of the joint simulation, the arc is divided horizontally according to the grid, the arc radius is set according to the 5000K temperature line, the arc resistance is calculated for each layer of the grid, and finally the resistances are added in series to calculate the total arc resistance:

[0057]

[0058] Where: G i is the conductivity of each grid column / S; G is the total conductivity / S; σ is the conductivity S / m; A is the cross-sectional area / m 2 ; l is length / m; R is resistance / Ω.

[0059] In a preferred embodiment of the described joint simulation circuit breaker arc calculation method, an autonomously programmed router is established as a client, and its service objects are the mechanism simulation model, the circuit simulation model and the arc simulation model. Its function is to transmit data, and then the piston rod reaction force, the moving contact speed and displacement, the arc resistance and the circuit current are selected as the communication content of the UDP communication module, and a counter is used to determine whether to send data. There is a counter with an initial value of 0 inside the router. Whenever the router receives information about the calculated data from the mechanism simulation model, the circuit simulation model and the arc simulation model, it first intercepts the data and increases the counter by 1, and at the same time commands the sending end of this information to enter a waiting state. When the identifier is 3, it means that all calculations in this time step have been completed, and the router will enter the transmission stage, transmit the data required by each port to the corresponding address respectively, and reset the counter to zero. Subsequently, the three simulation models read these data and continue with the next iterative operation.

[0060] In one embodiment, an electromagnetic reaction model based on ANSYS Electromagnetics is introduced as a fourth-party model for interaction to expand the function of joint simulation.

[0061] In one embodiment, data transmission is achieved using a self-programmed routing. The simulation is divided into three models: a circuit simulation model, an arc simulation model, and a mechanism simulation model. The circuit simulation model uses Matlab / Simulink as the simulation platform to build a power system model, calculate the current through the switch, and provide external current excitation for the arc simulation. The arc resistance, a missing circuit parameter, is obtained from the output of the arc simulation. After the calculation is completed, the current data is transmitted to the arc simulation model. The arc simulation model is responsible for calculating arc parameters during the breaking process, primarily the arc resistance. This part uses ANSYS Fluent to build an arc extinguishing chamber model. Combined with the initial current excitation output by the circuit model and the hydraulic force output by the mechanism simulation model, it can simulate arc parameters such as temperature and pressure at each moment and calculate the arc resistance data and gas reaction force on the contacts required by the circuit model. After the calculation is completed, the arc resistance is fed back to the circuit model, which in turn influences the circuit model's calculation of the system current. The gas reaction force data is transmitted to the mechanism simulation model to consider subsequent motion states. The mechanism simulation model simulates the mechanical motion of the circuit breaker, including the movement trajectory and force of the contacts. This section uses Adams or AMESim software to build a hydraulic rod-contact motion model, accurately describing the dynamic behavior of the contacts during the opening and closing process through mechanical motion simulation. The model adjusts in real time based on its initial state, such as spring potential energy, and external forces, such as the gas reaction force output by the arc simulation model, simulating the force, velocity, and displacement of the contacts at any time after the circuit breaker is triggered. The real-time position, velocity, and force of the contacts are transmitted to the arc simulation model for arc calculations.

[0062] In this patent, the circuit simulation model is required to be built using Matlab / Simulink. Figure 2 Taking a DC-powered power system as an example, this paper demonstrates how the circuit simulation model works. V represents the DC power supply; the resistor R represents the time-varying resistance when the high-voltage switch is open, and its initial value should be zero. After the simulation starts and the switch operates, the arc resistance value should be obtained in real time from the arc simulation results. Figure 2In the simulation, the system uses a black box as a replacement, which can be modeled according to needs. The necessary parameters in the model, such as the power supply type and power supply voltage value, can be modeled or specified according to the actual simulation situation. The ammeter in series with the switch will provide the value of the current I passing through the switch at each moment, and output it to the Matlab workspace through the Simulink output window. This window can also be replaced by the oscilloscope Scope module or Display module. Arc simulation is the link between circuit simulation and mechanism simulation and plays a core role. Arc simulation not only involves the effects of electricity and magnetism, but also the large amount of light, heat, fluid and mechanical movement generated, which makes arc simulation very difficult. For this reason, we chose the relatively mature finite element simulation tool ANSYS Fluent as the arc simulation platform in the joint simulation to meet some source terms and calculation terms that need to be customized by the user. The following example of 2D arc simulation of SF6 circuit breaker will illustrate some other important points to note when setting up the simulation process in Fluent in addition to the basic settings:

[0063] Use CAD software (such as SolidWorks or ANSYS Design Modeler) to create the arc extinguishing chamber geometry, then mesh and import the mesh. Because Fluent doesn't contain the relevant physical properties of SF6 gas, before simulation, use Fluent's real-gas-model to import the compiled SF6 gas file. This includes a discrete data table of the relevant physical properties, with pressure and temperature as array variables. Interpolation procedures must also be designed between the discrete points (bilinear interpolation can be used).

[0064] When an arc is present, a large amount of energy is often transferred internally through radiation, a process known as reabsorption. Due to an incomplete database, it is not possible to use a semi-empirical model that relies on gas properties to account for the energy conservation equation. Of the remaining models, we chose the less computationally intensive and more practical net radiation model, using the net radiation coefficient (NEC) to evaluate radiation losses. The key is to obtain a table showing how the NEC varies with radius, temperature, and pressure. This is done using the following formula:

[0065] Qrad=4πε(rad,temp,press)

[0066] ε(rad,temp,press)——NEC coefficient, which is a numerical table of radius, temperature and pressure.

[0067] When using the Laval laminar flow model to simulate the arc at the nozzle of a circuit breaker, the simulation results differ significantly from the experimental results, particularly in the radial temperature and voltage distributions. This phenomenon demonstrates that turbulence is crucial in arc simulations of SF6 circuit breakers. Therefore, we directly use the k-ε turbulence model built into Fluent. The Lorentz force in the arc affects the momentum equation, so the momentum source term must be customized. In Fluent, this can be achieved using user-defined functions (UDFs). To do this, use the DEFINE_SOURCE macro to define the source term. This macro requires specifying the region to be defined in the Fluent settings window. By calling the current density and magnetic induction in the macro and calculating their difference as the return value, we can obtain the Lorentz force momentum source term for the region to be defined. When using the user-defined variables (UDM) feature, be sure to number each UDM to verify the successful addition of the source term in subsequent results. Similarly, in the energy equation, we need to define radiation and ohmic heating for each grid cell to perform calculations in different regions. For example, you need to define different emissivity values ​​based on the arc's center, radius, and corresponding temperature and pressure values. This is also done using the DEFINE_SOURCE macro, which works similarly to the momentum source term, but returns the difference between ohmic heating and radiation. During this process, you need to check the ohmic heating at each location and label it as either ohmic or joule heating using user-defined variables (UDMs). The equation for calculating joule heating is:

[0068] Q=σE 2 The electric field in the simulation is calculated using the potential module in Fluent, so the electric potential value of each grid in each region can be extracted using the C_PHI_1(c,tc) macro. To extract the electric field intensity gradient for a specific grid in a specific region, use C_PHI_1_G(c,tc)[i] to obtain the corresponding electric field intensity value by taking the RMS value of the amplitude of each gradient.

[0069] It has always been very difficult to obtain the arc voltage during interruption, especially under high voltage and high current conditions. Real-time calculation of the arc voltage during interruption, and then calculation of the arc resistance: Fluent arc calculation will calculate the potential in the unit grid in real time. By setting a comparison program in the calculation to compare the potentials of the units in all arc areas, it is easy to find the maximum potential difference in the arc area, and this maximum voltage value can be approximately regarded as the arc voltage value. Generally, arc resistance can only be obtained through actual measurement. This patent provides a simple and effective formula for calculating arc resistance in arc simulation by accumulating regional resistances. Divide the arc horizontally according to the grid, set the arc radius according to the 5000K temperature line, calculate the arc resistance for each layer of grid, and finally calculate the total arc resistance by adding the resistors in series:

[0070]

[0071]

[0072] Where: G i ——Conductance of each grid / S; G——Total conductance / S; σ——Conductivity S / m; A——Cross-sectional area / m 2 ; l——length / m; R——resistance / Ω.

[0073] Fluent cannot apply current excitation to specific areas. Therefore, the current excitation obtained in circuit simulation must be injected into the contacts on both sides. Source area injection (volume density injection) has been shown to produce more reasonable results. Volume density current injection assigns a current value to each cell mesh, where the current value is the ratio of the current value to the cell volume.

[0074]

[0075] Where: J V ——Current fluid density / cm -3 ;I——current / A;V cell ——Grid volume / m -3 .

[0076] This method requires the energy source item to be set in the potential in the SOURCE area, in which the DEFINE_SOURCE macro is applied. In current injection, the absolute value of the injected current is used to achieve the zero point crossing and the calculation between different half-waves. In the arc extinguishing chamber, the high temperature and the compression of the gas during closing cause the pressure P inside the gas to increase rapidly. This force acts on the contacts and other moving structures, forming a reaction force that hinders the movement of the contacts. In order to ensure the accuracy of the joint simulation results, this reaction force must be considered and transmitted to the mechanism simulation model. In Fluent, the resultant pressure of the gas on the contact surface and other moving structure surfaces can be obtained. Generally speaking, only the component of the resultant force in the direction of contact movement is taken and transmitted to the mechanism simulation model.

[0077] The mechanism simulation model was built using AMESim. Hydraulic actuation offers numerous advantages, including high power, high efficiency, low losses, low maintenance costs, and strong adaptability. Therefore, its application in circuit breakers offers significant advantages over other actuation methods, such as electric, pneumatic, and mechanical actuation. In this proposal, hydraulic actuation will be selected as the operating mechanism for opening and closing the circuit breaker.

[0078] The hydraulic actuator simulation model can be quickly designed using the model library provided by AMESim. This solution uses a variety of hydraulic components and basic components of fluid structure in the HCD library. According to the actual situation, users can assemble the structure for simulation by themselves, which is very flexible. A designed actuator simulation model is as follows: Figure 5 As shown, the hydraulic operating mechanism system can be simplified as an "accumulator-control valve-working cylinder-oil tank" system. In high-voltage, high-current circuit breakers, due to the short opening and closing times, high flow rates, and infrequent operation, accumulators are generally used for oil supply. This oil supply method uses an oil pump to supply energy to the accumulator during non-operating periods, reaching a certain hydraulic pressure. During operation, the pressure is released to the mechanism for operation.

[0079] The entire hydraulic system model consists of three parts: the hydraulic control system model, the actuator transmission dynamics simulation model, and the arc-quenching unit finite volume fluid simulation model. The arc-quenching unit finite volume fluid simulation model, also known as the arc simulation model, provides gas reaction force input to the actuator, which in turn provides the piston (contact) motion state. The previous chapter explained how to model and operate this model. The following sections describe the modeling methods and principles for the first two models. Users can create their own models based on their specific needs.

[0080] The circuit breaker hydraulic control system primarily includes hydraulic components such as the accumulator, control valve, and working cylinder. During the circuit breaker's opening and closing process, the control valve maintains the circuit breaker in the open / closed state. The accumulator provides power to the system, and the working cylinder piston connects to the hydraulic push rod of the operating mechanism, driving the operating mechanism.

[0081] Based on hydraulic principles, the UDP communication module, working cylinder, accumulator, in-cylinder buffer control, main valve, opening / closing secondary valve, and opening / closing solenoid valve were modeled. During the co-simulation process, the UDP communication module can obtain the reaction force of the working cylinder piston rod and feedback the speed and displacement of the hydraulic push rod to the working cylinder.

[0082] This solution uses a double-acting circuit breaker as the actuator transmission dynamics simulation model. The double-acting circuit breaker is an upgrade from the single-acting circuit breaker, which is more conducive to improving the circuit breaker's time performance. Based on the single-acting circuit breaker, the double-acting circuit breaker adds six connecting rods, connecting the static and moving contacts of the single-acting circuit breaker. Connecting rods 1 to 3 are arranged side by side in a group, forming 10 connecting pairs. Connecting rod 1 connects to the hydraulic push rod, connecting rod 2 connects to the moving contact, and connecting rod 3 is bound by a fixed rod. Under the pull of the hydraulic push rod, connecting rods 1 to 3 drive the movement to complete the opening and breaking process of the motion mechanism. The interaction between the actuator simulation model and the arc simulation model, and the circuit simulation model and the arc simulation model, is a three-way interaction. To enable data transmission between the three models, it is necessary to add a UDP communication module to the hydraulic system (actuator) model, the arc simulation model, and the circuit simulation model. First, a self-programmed router was established as a client. Its service objects are the mechanism simulation model, circuit model, and arc model, and its function is to transmit data. The piston rod reaction force, moving contact speed and displacement, arc resistance, and circuit current are then selected as the communication content of the UDP communication module. A counter is used to determine whether to send data. The router contains an internal counter that is initially set to 0. Whenever the router receives calculated data from a model, it first intercepts the data, increments the counter by 1, and simultaneously commands the sender of this information to enter a waiting state. When the identifier is 3, indicating that all calculations for this time step are complete, the router enters the transmission phase, transmitting the data required by each port to the corresponding address and resetting the counter to zero. The three simulation models then read this data and continue the next iterative calculation. This method effectively transmits real-time working conditions and ensures the synchronization of the simulation.

[0083] For example, suppose all three models start running after initialization. The circuit model runs the fastest. It then sends circuit current data to the router. The router accepts this data, sets a counter to 1, and instructs the circuit model to enter a wait state. Some time later, the mechanism simulation model completes its calculations and sends data. The router also accepts this data, sets a counter to 2, and instructs the mechanism simulation model to wait. When the last arc model completes its calculations and the counter reaches 3, the router transmits the next velocity and displacement to the arc model, the next gas reaction force to the mechanism model, the next arc resistance to the circuit model, and the next circuit current to the arc model. Finally, the counters are reset to 0. The figure below demonstrates the router's operational process for this method, demonstrating its ability to support three-way interaction.

[0084] Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments and application fields. The above-mentioned specific embodiments are merely illustrative and instructive, and are not restrictive. A person skilled in the art, guided by this specification and without departing from the scope of protection of the claims of the present invention, may also devise various forms, all of which fall within the scope of protection of the present invention.

Claims

1. A circuit breaker arc calculation method based on joint simulation, characterized in that: The steps include: Build a circuit simulation model, using Matlab / Simulink as the simulation platform to build a power system model, calculate the current data through the circuit breaker and provide external current excitation for arc simulation; Build a mechanical simulation model that simulates the mechanical movement of the circuit breaker. The mechanical movement includes the movement trajectory and force of the contacts. Use Adams or AMESim software to build a hydraulic rod contact motion model of the circuit breaker to simulate the dynamic behavior of the contacts during the breaking process. The hydraulic rod contact motion model is adjusted in real time based on the initial state and external force to obtain the contact force, velocity, and displacement at any time after the circuit breaker is triggered. An arc simulation model is built to calculate the arc parameters during the breaking process. An arc extinguishing chamber model is built using ANSYS Fluent. The arc parameters at each moment are simulated in conjunction with the current excitation and contact force, velocity, and displacement. The arc resistance data and the reaction force of the gas on the contact required by the circuit simulation model are calculated. The arc resistance data is fed back to the circuit simulation model. The circuit simulation model generates current data based on the arc resistance data, and the reaction force is transmitted to the mechanism simulation model to participate in the calculation of the contact force, velocity, and displacement.

2. A circuit breaker arc calculation method for joint simulation according to claim 1, characterized in that: The initial state includes the spring potential energy, the external force includes the reaction force of the gas output by the arc simulation model on the contact, and the arc parameters include temperature and pressure.

3. The circuit breaker arc calculation method of joint simulation according to claim 1, characterized in that: The circuit simulation model includes a DC power supply V, a time-varying resistor R when the circuit breaker is open, an ammeter A connected in series with the circuit breaker, and the internal system. The initial value of the time-varying resistor R should be zero. After the simulation starts and the circuit breaker operates, the value of the time-varying resistor R is obtained in real time from the arc simulation results.

4. The circuit breaker arc calculation method of joint simulation according to claim 1, characterized in that: The hydraulic rod contact motion model is simulated using a variety of hydraulic components and fluid structures in the HCD library of AMESim, which includes a hydraulic control system model, an operating mechanism transmission dynamics simulation model, and an arc extinguishing unit finite volume fluid simulation model. The arc extinguishing unit finite volume fluid simulation model serves as an input arc simulation model that provides gas reaction force to the operating mechanism transmission dynamics simulation model, and the operating mechanism transmission dynamics simulation model provides the motion state of the contact.

5. A circuit breaker arc calculation method for joint simulation according to claim 4, characterized in that: The hydraulic control system model includes an accumulator, a control valve, and a working cylinder. During the circuit breaker opening and closing process, the control valve is used to keep the circuit breaker in the open and open states. The accumulator provides power for the system. The piston of the working cylinder is connected to the hydraulic push rod of the operating mechanism, pushing the operating mechanism to move. The reaction force of the piston rod of the working cylinder is obtained through the UDP communication module, and the speed and displacement of the hydraulic push rod are fed back to the working cylinder.

6. A circuit breaker arc calculation method for joint simulation according to claim 4, characterized in that: The operating mechanism transmission dynamics simulation model includes a double-acting circuit breaker, which includes a hydraulic push rod, a connecting rod and a moving contact.

7. The circuit breaker arc calculation method of joint simulation according to claim 1, characterized in that: Use CAD software to create the geometric model of the arc extinguishing chamber, then mesh it and import it into the grid, and use the net radiation coefficient NEC to evaluate the radiation loss. ， As the NEC coefficient, it is a numerical table of radius, temperature, and pressure; Qrad represents the radiation energy released from a unit sphere or unit area per unit time; where rad is the radius of the arc; temp is the arc temperature; and press is the pressure of the arc gas. The k-ε turbulence model provided by Fluent is used to set up the Laval laminar flow model simulation of the nozzle arc in the circuit breaker. In Fluent, the momentum source term is customized using the user-defined function (UDF). The source term is written using the DEFINE_SOURCE macro. By calling the current density and magnetic induction intensity in the DEFINE_SOURCE macro and calculating their difference as the return value, the Lorentz force momentum source term of the area to be defined is obtained. The user-defined variable (UDM) is used to mark the ohmic heat and Joule heat. The calculation equation for Joule heat is: ， The electric field in the simulation is calculated using the potential module in Fluent. The potential value of each grid in each area is extracted by the C_PHI_1(c,tc) macro.

8. A circuit breaker arc calculation method for joint simulation according to claim 7, characterized in that: Fluent calculates the electric potential in the unit grid in real time. By setting up a comparison program in the calculation to compare the electric potential of all units in the arc area, the maximum potential difference in the arc area is found, and this maximum voltage value is approximately regarded as the arc voltage value.

9. The circuit breaker arc calculation method of joint simulation according to claim 7, characterized in that: Divide the arc horizontally according to the grid, set the arc radius according to the 5000K temperature line, calculate the arc resistance for each layer of grid, and finally calculate the total arc resistance by adding the resistors in series: ， ， ， Where: is the grid conductance per column / S; is the total conductance / S; is the conductivity ; is the cross-sectional area / ; is the length / ; is the total resistance / .

10. The circuit breaker arc calculation method of joint simulation according to claim 1, characterized in that: A self-programmed router is established as the client, and its service objects are the mechanism simulation model, circuit simulation model and arc simulation model. Its function is to transmit data. Then, the piston rod reaction force, moving contact speed and displacement, arc resistance and circuit current are selected as the communication content of the UDP communication module, and the counter is used to determine whether to send data. There is a counter with an initial value of 0 inside the router. Whenever the router receives information about calculated data from the mechanism simulation model, circuit simulation model and arc simulation model, it first intercepts the data and increases the counter by 1. At the same time, it commands the sender of this information to enter the waiting state. When the identifier is 3, it means that all calculations in this time step have been completed. The router will enter the transmission stage, transmit the data required by each port to the corresponding address, and reset the counter to zero. Subsequently, the three simulation models read this data and continue with the next iterative operation.

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