Circuit breaker arc calculation method based on joint simulation

Abstract

According to the circuit breaker arc calculation method based on joint simulation, a circuit simulation model is built, a power system model is built with Matlab / Simulink as a simulation platform, current data passing through a switch are calculated, and external current excitation is provided for arc simulation; a mechanism simulation model for simulating mechanical motion of the circuit breaker is built, the mechanical motion comprises a motion track and acting force of a contact, a hydraulic rod contact motion model of the circuit breaker is built through Adams or AMESim software so as to simulate dynamic behaviors of the contact in the on-off process, the hydraulic rod contact motion model is adjusted in real time based on an initial state and external stress, and the dynamic behaviors of the contact in the on-off process are simulated. Obtaining the stress, speed and displacement of the contact at any time after the circuit breaker is triggered; an arc simulation model for calculating arc parameters in the on-off process is built, an arc extinguish chamber model is built through ANSYS Fluent, and the arc parameters at each moment are simulated in cooperation with current excitation and contact stress, speed and displacement.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit breaker simulation, and particularly to a method for calculating the arc of a circuit breaker in co-simulation. Background Art

[0002] In modern power systems, circuit breakers, as important protection devices, play a crucial role in preventing electrical faults and ensuring the safe operation of the system. The opening process of a circuit breaker involves the coupled action of multiple physical fields such as electricity, magnetism, heat, force, and gas. Among them, the arc is the most critical factor, which determines the opening performance and arc extinguishing performance of the circuit breaker. Therefore, it can be said that the formation and extinction of the arc directly affect the safety of the circuit. Therefore, accurately calculating arc parameters, especially arc resistance, is of great significance for optimizing the design of circuit breakers and improving their reliability.

[0003] Currently, the arc parameters of circuit breakers usually rely on experimental measurements or empirical formulas for estimation, lacking real-time calculation and feedback mechanisms. This method is not only inefficient but also difficult to ensure accuracy under complex working conditions. With the development of computer simulation technology, simulation-based methods have gradually become an important means for studying the arc characteristics of circuit breakers.

[0004] Existing simulation tools such as Adams and Amesim are widely used in mechanism dynamics analysis and can effectively simulate the movement of circuit breaker contacts and their influence on the arc. However, these tools have limitations in the real-time calculation and feedback of arc parameters and cannot form a complete closed-loop control system. At the same time, ANSYS Fluent has powerful simulation capabilities in fluid dynamics and heat conduction and can provide the thermal and current characteristics during the arc process, but its real-time coupling with mechanism movement still needs to be further optimized. Matlab / Simulink provides powerful circuit analysis functions, but in the co-simulation between arc parameters and circuit dynamics, existing methods often lack an efficient communication mechanism, resulting in data transfer delays and information inconsistencies.

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

[0006] The above information disclosed in the background art section is only used to enhance the understanding of the background of the present invention and may therefore include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0007] The present invention provides a method for calculating the arc of a circuit breaker in co-simulation, which can systematically simulate the whole process of the opening of a high-voltage switch to improve the calculation accuracy and real-time performance of the arc, and further enhance the performance evaluation ability and design optimization level of the circuit breaker.

[0008] A calculation method for circuit breaker arc by combined simulation includes:

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

[0010] Build a mechanism simulation model to simulate the mechanical movement of the circuit breaker. The mechanical movement includes the movement trajectory and acting force of the contact. Build a hydraulic rod contact movement model of the circuit breaker through Adams or AMESim software to simulate the dynamic behavior of the contact during the opening process. The hydraulic rod contact movement model is adjusted in real time based on the initial state and external forces to obtain the contact force, speed and displacement at any time after the circuit breaker is triggered.

[0011] Build an arc simulation model to calculate the arc parameters during the opening process. Build an arc extinguishing chamber model through ANSYS Fluent, and cooperate with the current excitation and contact force, speed and displacement to simulate the arc parameters at each moment, and calculate the arc resistance data required by the circuit model and the reaction force of the gas on the contact. The arc resistance data is fed back to the circuit model, and the circuit simulation model generates current data based on the arc resistance data. The reaction force is transmitted to the mechanism simulation model to participate in the calculation of the contact force, speed and displacement.

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

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

[0014] In the calculation method for circuit breaker arc by combined simulation, use a variety of hydraulic components and fluid structures in the HCD library of AMESim to simulate the hydraulic rod contact movement model, which includes a hydraulic control system model, a dynamics simulation model of the operating mechanism transmission, and a finite volume fluid simulation model of the arc extinguishing unit. Among them, the finite volume fluid simulation model of the arc extinguishing unit is used as an input arc simulation model to provide the gas reaction force for the dynamics simulation model of the operating mechanism transmission, and the dynamics simulation model of the operating mechanism transmission provides the movement state of the contact.

[0015] In the described circuit breaker arc calculation method for co-simulation, the hydraulic control system model includes an accumulator, a control valve, and a working cylinder. During the opening process of the circuit breaker, the circuit breaker is made to be in the open and tripped 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, 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.

[0016] In the described circuit breaker arc calculation method for co-simulation, the kinetic simulation model of the operating mechanism includes a double-acting circuit breaker, and the double-acting circuit breaker includes a hydraulic push rod, a connecting rod, and a moving contact.

[0017] In the described circuit breaker arc calculation method for co-simulation, the geometric model of the arc extinguishing chamber is created using CAD software, and then meshing is carried out and the mesh is imported. The net emissivity coefficient NEC is used to evaluate the radiation loss.

[0018] Qrad = 4πε(rad, temp, press),

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

[0020] The Laval laminar flow model simulation of the nozzle arc in the circuit breaker is set using the built-in k-ε turbulence model in Fluent. In Fluent, the momentum source term is customarily edited 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 cross product result as the return value, the Lorentz force momentum source term of the region to be defined is obtained; the ohmic heat and Joule heat are marked using the user-defined variable UDM. The calculation equation for Joule heat is: Q = σE 2 , and the electric field in the simulation is calculated using the built-in potential module in Fluent. The electric potential value of each grid in each region is extracted by the C_PHI_1(c, tc) macro.

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

[0022] In the described circuit breaker arc calculation method of co-simulation, the arc is transversely divided according to the grid, the arc radius is set according to the 5000K temperature line, the arc resistance of each layer of grid is calculated, and finally the total arc resistance is calculated by adding the resistances in series:

[0023]

[0024]

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

[0026] In the described circuit breaker arc calculation method of co-simulation, an independently programmed router is established as the client, whose service objects are the mechanism simulation model, the circuit simulation model and the arc simulation model, and its function is data transfer. 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 initialized to 0 inside the router. Whenever the router receives the information of the calculated data from the mechanism simulation model, the circuit simulation model and the arc simulation model, it first intercepts the data and increments the counter by 1. At the same time, it commands the sending end that sent 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 respectively, and reset the counter to zero. Subsequently, the three simulation models read these data and continue the next iterative operation.

[0027] Compared with the prior art, the present invention has the following advantages: AMESim, Fluent and Matlab / Simulink are used for co-simulation, considering mechanical dynamics, fluid dynamics and electrical characteristics, providing a more comprehensive and practical system analysis, and the considered situations are comprehensive and all-round. Since it is difficult to establish a data interface between the M language of Matlab / Simulink and the C language of Fluent, in order to improve the efficiency of the overall simulation iteration, an independently programmed executable file is used as the data transfer path between the software, acting as a data router, rather than directly transferring data between the software. The independently programmed router ensures the synchronization of the three-party simulation models and also ensures a relatively fast speed of three-party interaction. In the arc simulation model, the net radiation coefficient model is adopted, fully considering the influence of reabsorption and turbulence, and at the same time correcting the source terms of the energy conservation equation and the momentum conservation equation, making the arc simulation more accurate. Brief Description of the Drawings

[0028] Through reading the detailed descriptions in the following preferred specific embodiments, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The accompanying drawings in the specification are only for the purpose of showing the preferred embodiments and are not considered as a limitation of the present invention. Obviously, the following described drawings are only some embodiments of the present invention, and for those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings. Moreover, throughout the drawings, the same reference numerals are used to represent the same components.

[0029] In the drawings:

[0030] Figure 1 is a logical schematic diagram of a circuit breaker arc calculation method for co-simulation provided by an embodiment of the present disclosure;

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

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

[0033] Figure 4 is a schematic diagram of the source area injection method of a circuit breaker arc calculation method for co-simulation provided by an embodiment of the present disclosure, Figure 4 where (a) is a schematic diagram of the electric field distribution obtained by the source area injection method, Figure 4 and (b) is a schematic diagram of the current density obtained by the source area injection method;

[0034] Figure 5 is a schematic diagram of a hydraulic operating mechanism built by AMESim of a circuit breaker arc calculation method for co-simulation provided by an embodiment of the present disclosure;

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

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

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

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

[0039] The present invention will be further explained below in conjunction with the accompanying drawings and embodiments. Specific embodiments

[0040] The 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 drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, 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 in the description of the specification and claims, certain terms are used to refer to specific components. Those skilled in the art should understand that technicians may use different terms to refer to the same component. The specification and claims do not use the difference in terms as a way to distinguish components, but use the difference in the functions of components as the criterion for distinction. As used throughout the specification and claims, the terms "comprising" or "including" are open-ended terms and should be interpreted as "including but not limited to". The subsequent description of the specification is the preferred embodiment for implementing the present invention, but the description is for the purpose of the general principle of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be defined by the appended claims.

[0042] For the convenience of understanding the embodiments of the present invention, the following will further explain with specific embodiments as examples in conjunction with the accompanying drawings, and each accompanying drawing does not constitute a limitation to the embodiments of the present invention.

[0043] As Figures 1 to 9 shown, the circuit breaker arc calculation method for co-simulation includes the following steps:

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

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

[0046] Build an arc simulation model for calculating arc parameters during the opening process. Build an arc extinguishing chamber model through ANSYS Fluent, and simulate the arc parameters at each moment in cooperation with the current excitation, contact force, speed, and displacement, and calculate the arc resistance data required by the circuit model and the reaction force of the gas on the contact. The arc resistance data is fed back to the circuit model, and the circuit simulation model generates current data based on the arc resistance data. The reaction force is transmitted to the mechanism simulation model to participate in the calculation of the contact force, speed, and displacement.

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

[0048] In the preferred implementation of the combined simulation circuit breaker arc calculation method described above, the circuit simulation model includes a DC power supply V, a time-varying resistance R during the opening of the high-voltage switch, an ammeter A in series with the switch, and an internal system. The initial value of the time-varying resistance R should be zero. After the simulation starts and the switch operates, the value of the time-varying resistance R is obtained in real time from the results of the arc simulation. The internal system is a black box. The user can replace this part of the internal system with a specific circuit according to needs. The switch itself has an arc resistance when opening; the switch and the ammeter are 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 himself, the ammeter and the switch are in series, and the current in the branch where the switch is located is concerned.

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

[0050] In the preferred implementation of the combined simulation circuit breaker arc calculation method described above, the hydraulic control system model includes an accumulator, a control valve, and a working cylinder. During the opening process of the circuit breaker, the circuit breaker is in the open and trip 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 push 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 the preferred embodiment of the described method for calculating the arc of a circuit breaker through co-simulation, the kinetic simulation model of the operating mechanism includes a double-acting circuit breaker, which consists of a hydraulic push rod, a connecting rod, and a moving contact. One to three connecting rods are arranged in a group to form 10 connecting pairs. Connecting rod 1 is connected to the hydraulic push rod, connecting rod 2 is connected to the moving contact, and connecting rod 3 is tied by a fixed rod. Under the pull of the hydraulic push rod, through connecting rods 1 to 3, the movement of the moving mechanism will be driven to complete the opening and breaking process. In one embodiment, the movement 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 through 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. At the same time, connecting rod 3 is tied by a fixed rod, used to support the movement of other connecting rods to ensure the stability of the entire system. The design of connecting rod 3 enables it to form a certain angle with connecting rod 2, thereby helping to effectively transmit power. The moving contact is a key component of the circuit breaker, responsible for making contact with or disconnecting from the static contact, ultimately realizing the switching operation of the circuit. The fixed rod provides support for connecting rod 3 to ensure that it will not deform or displace during the movement process.

[0052] In the preferred embodiment of the described method for calculating the arc of a circuit breaker through co-simulation, use CAD software to create the geometric model of the arc extinguishing chamber, then perform mesh division and import the mesh, and use the net radiation coefficient NEC to evaluate the radiation loss.

[0053] Qrad = 4πε(rad, temp, press),

[0054] ε(rad, temp, press) - the NEC coefficient, which is a numerical table regarding radius, temperature, and pressure. Qrad is used as the radiation coefficient, representing the radiation energy released per unit time from a unit spherical surface or unit area; where rad is the radius of the arc; temp is the arc temperature; press is the pressure of the arc gas. Use the built-in k-ε turbulence model in Fluent to set up the simulation of the Laval laminar flow model of the nozzle arc in the circuit breaker. In Fluent, use the user-defined function UDF to customize the editing of the momentum source term, write the source term with the DEFINE_SOURCE macro, call the current density and magnetic induction intensity in the DEFINE_SOURCE macro, and calculate their cross product result as the return value to obtain the Lorentz force momentum source term of the region to be defined. Mark the ohmic heat and Joule heat through the user-defined variable UDM. The calculation equation for Joule heat is: Q = σE 2, the electric field in the simulation is calculated through the built-in potential module in Fluent, and the electric potential value of each grid in each region is extracted by the C_PHI_1(c,tc) macro.

[0055] In the preferred embodiment of the circuit breaker arc calculation method for co-simulation, Fluent calculates the electric potential in the unit grid in real time. By setting a comparison program in the calculation, the electric potentials of the units in all arc regions are compared to find the maximum potential difference in the arc region, and this maximum voltage value is approximately regarded as the arc voltage value.

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

[0057]

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

[0059] In the preferred embodiment of the circuit breaker arc calculation method for co-simulation, an independently programmed router is established as the client, whose service objects are the mechanism simulation model, the circuit simulation model and the arc simulation model, and its function is data transfer. 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 initialized to 0 inside the router. Whenever the router receives the information of the calculated data from the mechanism simulation model, the circuit simulation model and the arc simulation model, it first intercepts the data, increments the counter by 1, and at the same time commands the sending end that sent this information to enter the 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 the next iterative calculation.

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

[0061] In one embodiment, autonomous programming routing is utilized to achieve data transmission. The simulation is divided into three partial 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 passing through the switch, and provide an external current excitation for the arc simulation. The missing item of arc resistance in the circuit parameters is obtained from the output of the arc simulation. After the calculation, the end current data will be passed to the arc simulation model. The arc simulation model is responsible for calculating the arc parameters during the opening process, mainly calculating the arc resistance. In this part, an arc extinguishing chamber model is built by ANSYS Fluent. With the initial current excitation output by the circuit model and the hydraulic force output by the mechanism simulation model, it can simulate the arc parameters such as temperature and pressure at each moment, and calculate the arc resistance data required by the circuit model and the reaction force of the gas on the contact. After the calculation, the obtained arc resistance will be fed back to the circuit model, thereby affecting the calculation of the system current by the circuit model; the reaction force data of the gas will be passed to the mechanism simulation model for considering the subsequent motion state. The mechanism simulation model is used to simulate the mechanical motion of the circuit breaker, including the motion trajectory and acting force of the contact. In this part, a hydraulic rod - contact motion model is built by Adams or AMESim software, which can accurately describe the dynamic behavior of the contact during the opening process through the simulation of mechanical actions. The model is adjusted in real time based on its own initial state such as spring potential energy and external forces such as the gas reaction force output by the arc simulation model, and simulates the force, speed, and displacement of the contact at any time after the circuit breaker is triggered. The real-time position, speed, and acting force of the contact will be passed to the arc simulation model for arc calculation.

[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, it shows how the circuit simulation model operates. Among them, V represents the DC power supply; the resistor R represents the time-varying resistance when the high-voltage switch is opened, and its initial value should be zero. After the simulation starts and the switch operates, the value of the arc resistance should be obtained in real time from the results of the arc simulation. Figure 2In this case, the system uses a black box for substitution and can build its own model according to needs. All necessary parameters in the model, such as the power supply form, the value of the power supply voltage, etc., can be modeled or specified by itself according to the actual simulation situation. The ammeter connected 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 output window of Simulink. This window can also be replaced by the oscilloscope Scope module or the Display module. Arc simulation is the link connecting circuit simulation and mechanism simulation and plays a core role. Arc simulation not only involves the interaction of electricity and magnetism, but also the large amount of light, heat, fluid and mechanical motion generated therein makes arc simulation very difficult. Therefore, we choose the relatively mature finite element simulation tool ANSYS Fluent as the arc simulation platform in the co-simulation to meet some source terms and calculation terms that need to be user-defined. The following will take the 2D arc simulation of an SF6 circuit breaker as an example to illustrate some other important precautions for setting up the simulation process in Fluent in addition to the basic settings:

[0063] Use CAD software (such as SolidWorks or ANSYS DesignModeler) to create the geometric model of the arc extinguishing chamber, and then perform mesh generation and import the mesh. Since there are no relevant physical property parameters of SF6 gas in Fluent, before the simulation, it is necessary to use the real-gas-model model in Fluent to import the compiled SF6 gas file. It includes the discrete data table of relevant physical property parameters with pressure and temperature as array variables, and at the same time, the interpolation program between discrete points also needs to be designed (bilinear interpolation can be used).

[0064] When the arc exists, a large amount of energy is often transferred internally in the form of radiation, which is called reabsorption. Due to the imperfect database, it is impossible to use a semi-empirical model that depends on gas physical property parameters to consider the energy conservation equation. Among the remaining models, we choose the net radiation model with less computational effort and more practicality, and use the net emissivity coefficient (NEC) to evaluate the radiation loss. The most crucial thing is to obtain the table of the variation of NEC with radius, temperature, and pressure. The following formula is used:

[0065] Qrad = 4πε(rad,temp,press)

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

[0067] When using the Laval laminar model to simulate the arc in the nozzle of a circuit breaker, there are significant differences between the simulation results and the experimental results, especially in the radial temperature distribution and voltage distribution. This phenomenon indicates that turbulence cannot be ignored in the arc simulation of SF6 circuit breakers. Therefore, we directly use the k-ε turbulence model built into Fluent for setting. Since there is a Lorentz force in the arc, this force will affect the momentum equation. Therefore, it is necessary to customize and edit the momentum source term. In Fluent, this can be achieved using the User-Defined Function (UDF). To this end, the DEFINE_SOURCE macro needs to be used to write 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 intensity in the macro and calculating their cross product result as the return value, the Lorentz force momentum source term for the region to be defined can be obtained. When using the User-Defined Memory (UDM) function, ensure that each UDM is numbered so that it can be verified whether the source term is successfully added in the subsequent results. Similarly, in the energy equation, we need to define radiation and ohmic heat for each grid in order to perform corresponding calculations in different regions. For example, different radiation coefficients need to be defined according to the center, radius, and corresponding temperature and pressure values of the arc. This also needs to be achieved using the DEFINE_SOURCE macro, which works in a similar way to the momentum source term, but the return value needs to be the difference between the ohmic heat and the radiation. During this process, the ohmic heat at each position needs to be checked, and the ohmic heat and joule heat are marked using the User-Defined Memory (UDM). The calculation equation for joule heat is:

[0068] Q = σE 2 , the electric field in the simulation is calculated through the potential module built into Fluent, so the electric potential value of each grid in each region can be extracted by the C_PHI_1(c,tc) macro. If the electric field strength gradient of the corresponding grid in the corresponding region is to be extracted, then C_PHI_1_G(c,tc)[i] can be used, and the corresponding electric field strength value can be obtained through the root mean square value of the amplitudes of each gradient.

[0069] Obtaining the arc voltage during interruption has always been extremely difficult, especially in the case of high voltage and large current. Calculate the arc voltage in real time during interruption, and then calculate the arc resistance: Fluent arc calculation will calculate the electric potential in the unit grid in real time. By setting up a comparison program in the calculation to compare the electric potentials of the cells in all arc regions, it is easy to find the maximum potential difference in the arc region, and this maximum voltage value can be approximately regarded as the arc voltage value. Generally, the arc resistance can only be obtained through actual measurement. This patent gives a simple and effective formula for calculating the arc resistance in arc simulation by accumulating the regional resistances. The arc is divided horizontally according to the grid, the arc radius is set according to the 5000K temperature line, the arc resistance of each layer of grid is calculated, and finally the resistances are connected in series to calculate the total arc resistance:

[0070]

[0071]

[0072] In the formula: G i —— Conductance of each column of 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 a specific region. Therefore, the injection method of the current excitation obtained in the circuit simulation on both sides of the contact must be set by itself. After inspection, injecting in the source area (volume density injection) can obtain relatively reasonable results. Volume density current injection assigns a current value to each unit grid, and its magnitude is the ratio of the current value to the grid volume.

[0074]

[0075] In the formula: J V —— Current volume density / c·m -3 ; I —— Current magnitude / A; V cell —— Grid volume / m -3 .

[0076] In this method, the energy source term of the potential must be set in the SOURCE region, where the DEFINE_SOURCE macro is applied. In current injection, the zero-crossing and the calculation between different half-waves are achieved by the absolute value of the injected current. In the arc extinguishing chamber, the high temperature and the compression of the gas during closing cause the internal pressure P of the gas to increase rapidly. This force acts on the contact and other moving structures, forming a reaction force that hinders the movement of the contact. To ensure the accuracy of the co-simulation results, this reaction force must be considered and transmitted to the mechanism simulation model. The resultant force of the gas pressure on the contact surface and other moving structure surfaces can be obtained in Fluent. Generally, only the component of the resultant force in the direction of the contact movement needs to be transmitted to the mechanism simulation model.

[0077] The mechanism simulation model is built using AMESim. Hydraulic drive has many advantages such as large force, high efficiency, low loss, low maintenance cost, and strong adaptability. Therefore, it has significant advantages over electric drive, pneumatic drive, mechanical drive, etc. in application to circuit breakers. In this solution, hydraulic drive will be selected as the operating mechanism for the opening and closing of the circuit breaker.

[0078] The simulation model of the hydraulic operating mechanism can be quickly designed using the built-in model library of AMESim. This solution uses a variety of basic components of hydraulic components and fluid structures in the HCD library. According to the actual situation, users can assemble the structure by themselves for simulation, with high flexibility. A designed simulation model of the operating mechanism is as Figure 5 shown. The hydraulic operating mechanism system can be simplified to a "pressure accumulator - control valve - working cylinder - oil tank" system. In high-voltage and high-current circuit breakers, due to the very short opening and closing time, extremely large flow rate, and infrequent operation, a pressure accumulator is generally used for oil supply. This oil supply method uses an oil pump to provide energy to the pressure accumulator during the non-working period to reach a certain hydraulic value, and releases the pressure to the mechanism for operation during work.

[0079] The entire hydraulic system model includes three parts: the hydraulic control system model, the kinetic simulation model of the operating mechanism transmission, and the finite volume fluid simulation model of the arc extinguishing unit. Among them, the finite volume fluid simulation model of the arc extinguishing unit is the arc simulation model. It provides the input of the gas reaction force for the operating mechanism, and the operating mechanism provides the motion state of the piston (contact) for it. How to model and operate it has been described in the previous chapter. The modeling methods and principles of the first two models will be given below, and users can model by themselves according to actual needs.

[0080] The hydraulic control system of the circuit breaker mainly includes hydraulic components such as accumulators, control valves, and working cylinders. During the opening process of the circuit breaker, the circuit breaker is made to be in the open / closed state through the control valve. The accumulator provides power for the system, and the working cylinder piston is connected to the hydraulic push rod of the operating mechanism to push the operating mechanism to move.

[0081] Based on the hydraulic principle, models are established for the UDP communication module, working cylinder, accumulator, in-cylinder buffer control, main valve, sub / switching secondary valve, and sub / switching solenoid valve. During the co-simulation process, the UDP communication module can obtain the reaction force of the piston rod of the working cylinder 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 kinetic simulation model of the operating mechanism. The double-acting circuit breaker is upgraded from the single-acting circuit breaker, which is more conducive to improving the time performance of the circuit breaker. Based on the single-acting circuit breaker, the double-acting circuit breaker adds 6 more connecting rods, which connect the static contact and moving contact of the single-acting circuit breaker. Among them, 1 to 3 connecting rods are arranged in a group, forming 10 connecting pairs. Connecting rod 1 is connected to the hydraulic push rod, connecting rod 2 is connected to the moving contact, and connecting rod 3 is tied by a fixed rod. Under the pull of the hydraulic push rod, through connecting rods 1 to 3, the opening and breaking processes of the moving mechanism will be driven to complete. The interaction between the operating mechanism simulation model, the arc simulation model, and the circuit simulation model is a three-way interaction process. To realize the data transmission between the three models, UDP communication modules need to be added to the hydraulic system (operating mechanism) model, the arc simulation model, and the circuit simulation model respectively. First, an independently programmed router is established as the client. Its service objects are the mechanism simulation model, the circuit model, and the arc model, and its function is data transmission. Then, the reaction force of the piston rod, the speed and displacement of the moving contact, 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 inside the router that is initially 0. Whenever the router receives the information of the calculated data from a certain model, it will first intercept the data, increment the counter by 1, and at the same time command the sending end that sent 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 respectively, and reset the counter to zero. Subsequently, the three simulation models read these data and continue the next iterative calculation. This method can effectively transfer the real-time working conditions and ensure the synchronization of the simulation.

[0083] Example: Suppose that after initialization, all three models start running, and the circuit model runs the fastest. At this time, it sends the circuit current data to the router. The router will accept this data, the counter becomes 1, and it commands the circuit model to enter the waiting state. After a period of time, the mechanism simulation model also finishes its calculation and sends the data. The router will also accept this data, set the counter to 2, and command the mechanism simulation model to wait. Until the last arc model also finishes its calculation and the counter reaches 3, the router transfers the speed and displacement at the next moment to the arc model, transfers the gas reaction force at the next moment to the mechanism simulation model, transfers the arc resistance at the next moment to the circuit model, and transfers the circuit current at the next moment to the arc model. Finally, the counter is cleared. The following figure is the verification of the router working process of this method, and the result shows that it can perform three-party interaction.

[0084] Although the embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments and application fields. The above specific embodiments are merely illustrative and guiding, rather than restrictive. Those of ordinary skill in the art can also make many forms under the inspiration of this specification and without departing from the scope protected by the claims of the present invention, and all of these fall within the scope of protection of the present invention.

Claims

1. A circuit breaker arc calculation method for joint simulation, characterized in that: The steps include: Build a circuit simulation model, use Matlab / Simulink as a simulation platform to build a power system model, calculate the current data through the switch and provide external current excitation for arc simulation; Build a mechanism 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 movement model of the circuit breaker to simulate the dynamic behavior of the contacts during the breaking process. The hydraulic rod contact movement model is adjusted in real time based on the initial state and external force to obtain the contact force, speed 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 through ANSYS Fluent. The arc parameters at each moment are simulated in conjunction with the current excitation and the contact force, speed and displacement. The arc resistance data and the reaction force of the gas on the contact required by the circuit model are calculated, and 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, speed and displacement.

2. A circuit breaker arc calculation method for joint simulation according to claim 1, characterized in that: Preferably, 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.

3. A circuit breaker arc calculation method for 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 high-voltage switch is turned off, 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.

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 actuator 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 actuator transmission dynamics simulation model, and the actuator 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 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 push 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 actuator transmission dynamics simulation model includes a double-acting circuit breaker, and the double-acting circuit breaker includes a hydraulic push rod, a connecting rod and a moving contact.

7. A circuit breaker arc calculation method for joint simulation according to claim 1, characterized in that: The geometric model of the arc extinguishing chamber was created using CAD software, and then meshed and imported into the grid. The net radiation coefficient (NEC) was used to evaluate the radiation loss. Qrad=4πε(rad,temp,press), 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; 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 up the Laval laminar model simulation of the nozzle arc in the circuit breaker. In Fluent, the momentum source term is customized by using the user-defined function UDF, and the source term is written by 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 of 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.

8. The circuit breaker arc calculation method of joint simulation according to claim 1, characterized in that: Fluent calculates the electric potential in the unit grid in real time. By setting a comparison program in the calculation, the electric potential of all units in the arc area is compared to find the maximum potential difference in the arc area. This maximum voltage value is approximately regarded as the arc voltage value.

9. A circuit breaker arc calculation method for joint simulation according to claim 1, 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: 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.

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 the 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 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 these data and continue the next iterative operation.

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