SF6 porcelain column type circuit breaker temperature field modeling simulation method suitable for low temperature environment

Abstract

The application provides a SF6 porcelain column type circuit breaker temperature field modeling simulation method suitable for a low temperature environment, and the method comprises the following steps: establishing a simulation model, modeling and simulating the porcelain column type circuit breaker, and building a geometric model; setting part material properties, setting the material properties of the geometric model components; dividing the geometric model, dividing the geometric model through a mesh division method; setting boundary conditions, the geometric model adopts a laminar flow interface and a solid heat transfer interface, and boundary conditions are set for the laminar flow interface and the solid heat transfer interface; steady-state solving, independently solving the fluid flow of the laminar flow interface and the solid heat transfer of the solid heat transfer interface, and fluid-solid boundary coupling is performed on the solving results. The application focuses on the heat transfer effect between the circuit breaker insulation medium (fluid) and the wall and internal structure (solid), considers the fluid-solid coupling under the actual operation of the circuit breaker, and is higher in model accuracy.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of power system simulation, in particular to a temperature field modeling and simulation method for an SF6 porcelain column type circuit breaker suitable for a low-temperature environment. BACKGROUND

[0002] In a power system, an SF6 circuit breaker serves as an important switching device, and the performance of the circuit breaker directly affects the stability and safety of the system. The insulating medium of the circuit breaker, SF6 gas, is prone to liquefaction in a low-temperature environment, which affects the insulation and arc extinguishing performance of the circuit breaker. Therefore, it is very important to carry out heat conduction analysis on the circuit breaker in operation.

[0003] According to the principle of heat transfer, there are three ways of heat transfer: heat conduction, heat convection and heat radiation. In the actual situation of thermal analysis, these three ways of heat transfer generally do not occur alone, and in many cases, they occur in the form of a combination of two or three basic heat transfer modes. There are corresponding numerical calculation methods for the three heat transfer modes. However, the internal structure of a high-voltage circuit breaker is complex, and the internal heat of the circuit breaker in operation is affected by the mutual coupling of mechanics, heat, fluid and electronics. It is extremely complex to establish the overall dynamics equation of the circuit breaker and to perform numerical solution. Generally, it is difficult to consider all the influencing factors comprehensively, and the complex numerical model cannot converge in the solving process. Through finite element simulation of the circuit breaker, researchers are liberated from complex and repetitive dynamics equations, helping them focus on the understanding and interpretation of the physical process. At present, the general research and development process is to first use a three-dimensional CAD software to design the operating mechanism of the circuit breaker, and then import the designed model into a finite element analysis software for dynamics analysis.

[0004] From the current research results of high-voltage circuit breaker dynamics in China, most of the researches are only on the dynamics simulation optimization of the existing high-voltage circuit breaker operating mechanism, and more attention is paid to the breaking characteristics of the circuit breaker, while the simulation optimization of the multi-physical field model of the overall structure of the circuit breaker is ignored, especially the insulating medium of the circuit breaker. At present, common insulating gases include SF6 gas and its mixed gas, perfluorinated nitrile and perfluorinated ketone gas. Such substances are prone to liquefaction in an external low-temperature environment. The liquefaction of insulating gas will cause the pressure in the gas chamber to decrease, leading to circuit breaker alarm and locking accidents, thereby threatening the safe and reliable operation of the power grid. In actual operation, it is difficult to comprehensively summarize the gas-liquid change of the internal insulating gas of the circuit breaker under different structures, voltage levels, operating conditions, insulating gas filling pressures and mixing ratios, and environmental conditions. Therefore, it is necessary to research the finite element simulation method of the temperature field of the circuit breaker, so as to deeply analyze the internal fluid dynamics and heat transfer characteristics of the circuit breaker, thereby improving the optimized design and reliability of the high-voltage circuit breaker. SUMMARY

[0005] In view of this, the purpose of the present application is to provide a SF6 porcelain column type circuit breaker temperature field modeling simulation method suitable for low temperature environment, focusing on the heat transfer effect between the circuit breaker insulating medium (fluid) and the wall and internal structure (solid), considering the fluid-solid coupling under the actual operation of the circuit breaker, and improving the simulation accuracy.

[0006] To achieve the above-mentioned purpose of the application, the present application provides a SF6 porcelain column type circuit breaker temperature field modeling simulation method suitable for low temperature environment, the method comprising:

[0007] Establishing a simulation model, modeling and simulating the porcelain column type circuit breaker, and building a geometric model;

[0008] Setting the material properties of the parts, setting the material properties of the geometric model components;

[0009] Subdividing the geometric model, dividing the geometric model by meshing method;

[0010] Setting the boundary conditions, the geometric model adopts laminar flow interface and solid heat transfer interface, and the boundary conditions of the laminar flow interface and the solid heat transfer interface are set respectively;

[0011] Steady-state solution, the fluid flow of the laminar flow interface and the solid heat transfer of the solid heat transfer interface are solved independently, and the solution results are fluid-solid boundary coupling.

[0012] Further, the geometric model comprises:

[0013] Building a geometric model of the porcelain column type circuit breaker from the outer porcelain sleeve to the internal arc extinguishing chamber insulation pull rod.

[0014] Further, setting the material properties of the geometric model components comprises: upper terminal board, lower terminal board, static contact seat, static arc contact, dynamic contact seat, dynamic arc contact, pull rod, porcelain sleeve, and SF6 filling in the porcelain sleeve.

[0015] Further, SF6 is in liquid or gaseous state, and the state of SF6 in the porcelain sleeve is judged by the Bethe-Briggsman state equation, and the expression of the Bethe-Briggsman state equation is:

[0016]

[0017] Wherein, is the absolute pressure, unit bar, is the absolute temperature, unit K, is the ratio of volume to mass, , , , .

[0018] Further, the geometric model is divided by a mesh division method, specifically including:

[0019] The geometric model is divided into a plurality of triangular meshes according to different parts by a mesh division method, the resolution of the plurality of triangular meshes is distinguished, a resolution threshold is set, and the plurality of triangular meshes are compared with the resolution threshold according to their own resolutions, so as to complete adaptive adjustment of the mesh density.

[0020] Further, the boundary of the laminar flow interface is set, specifically including:

[0021] The inlet boundary condition is set, for steady flow, the expression of the velocity inlet is set as:

[0022]

[0023] wherein, represents a flow velocity vector, is a given constant flow velocity;

[0024] For mass flow, the mass flow of the inlet is set as a constant, the velocity of the fluid is determined by the mass flow and the density of the fluid, and the mass continuity equation is followed, and the expression is:

[0025]

[0026] wherein, is the material density, , are velocity components in x, y, z directions respectively;

[0027] The outlet boundary condition is set, the fluid is set as the gas filling pressure from the outlet pressure of the geometric model;

[0028] The solid boundary condition is set, in the laminar flow interface, the fluid velocity on the solid boundary is zero, so that there is no relative sliding between the solid surface and the fluid, and the no-slip boundary condition is set as:

[0029]

[0030] When the solid surface is not completely fixed, tangential flow occurs between the fluid and the solid, and the slip boundary condition allows the fluid to flow in the tangential direction on the solid surface, and the normal velocity is zero.

[0031] Further, the boundary of the solid heat transfer interface is set, specifically including:

[0032] The solid surface heat flow boundary condition is set, and the heat flux density expression on the solid surface is set as:

[0033] ​

[0034] in, This represents the heat flux density vector, i.e., the area heat flux, with units of . , Temperature of an object, in units of , It represents the unit normal vector on an isotherm or isotherm passing through a point on a solid surface, with the direction from low temperature to high temperature; Thermal conductivity, also known as thermal conductivity, is a measure of the thermal conductivity of an object. The negative sign before the thermal conductivity coefficient indicates that the direction of heat transfer is opposite to the direction of the temperature gradient, that is, heat is transferred from high temperature to low temperature.

[0035] The relationship between thermal conductivity and temperature is:

[0036]

[0037] in, Material 0 Thermal conductivity at time, in units of , Temperature of an object, in units of , It is a constant;

[0038] The boundary conditions for convective heat transfer on solid surfaces are set, and the formula for convective heat transfer on solid surfaces is as follows:

[0039]

[0040] in, It represents the power dissipated per unit volume of fluid medium due to convection. This represents the convective heat dissipation coefficient, in units of... , This represents the area of ​​the cooling surface, in units of... , The surface temperature of a heat-generating object is expressed in units of 1000 ppm. , Represents the temperature of the fluid medium, in units of . ;

[0041] The empirical formula for the convective heat dissipation coefficient is:

[0042] .

[0043] Furthermore, the fluid flow at the laminar interface is solved independently, specifically including:

[0044] Set the inlet, outlet and solid surface boundary conditions of the fluid, consider the velocity, pressure and no-slip boundary of the fluid, establish a fluid model, and solve the fluid model to obtain the velocity field and pressure field of the fluid, wherein the fluid model is a natural convection process of the fluid.

[0045] Further, the solid heat transfer of the solid heat transfer interface is independently solved, specifically including:

[0046] S11, a solid heat transfer model is established based on the temperature distribution of the solid part, and the solid heat transfer model is solved, and the velocity field and pressure field of the fluid are taken as the boundary conditions of the solid heat transfer;

[0047] S12, the temperature field of the fluid is transmitted to the solid heat transfer interface, the temperature distribution of the solid is calculated based on the heat transmitted by the fluid, and the temperature distribution heat flux density and temperature boundary condition of the solid are obtained;

[0048] S13, according to the temperature distribution heat flux density, the temperature boundary condition heat flux density and the temperature boundary condition of the solid, a steady-state solution is carried out, and the temperature field of the solid part is calculated.

[0049] Further, the solving result is coupled with the fluid-solid boundary, specifically including:

[0050] The temperature field of the fluid is taken as the input of the solid heat transfer model, and the temperature field and heat flux density of the solid are fed back to the fluid model, and the fluid-solid boundary coupling is carried out.

[0051] Compared with the prior art, the beneficial effects of the present application are:

[0052] The modeling simulation result can provide a basic research model for subsequent development of porcelain column type circuit breaker operation analysis in low temperature environment, and the modeling method can be applied to the simulation model building of similar electrical equipment, and provide a technical route for related research.

[0053] ① The modeling process considers the structure factors that have greater influence on heat transfer in the actual internal mechanism of the circuit breaker, so as to restore the physical model and improve the simulation accuracy.

[0054] ② In the process of setting boundary conditions and simulation calculation, the fluid-structure coupling is fully considered, and the overall simulation structure is constructed from the aspects of fluid simulation and heat transfer simulation, which is more realistic.

[0055] ③ In the steady-state solution of the model, the fluid flow and solid heat transfer are independently solved, after the fluid model is solved, the temperature field of the fluid is taken as the input of the solid heat transfer model, and the temperature field and heat flux density of the solid are fed back to the fluid model, so that the heat exchange between the fluid and the solid can be simulated through the convection heat transfer condition, the results meet the boundary conditions of the fluid and the solid coupling, and finally the simulation result converges. BRIEF DESCRIPTION OF DRAWINGS

[0056] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description only relate to the embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of the provided drawings.

[0057] Figure 1 A flow chart of a temperature field modeling simulation method of an SF6 porcelain column type circuit breaker suitable for a low temperature environment provided by the embodiment of the present application is shown in the figure.

[0058] Figure 2 A schematic diagram of the overall structure of a geometric model of a temperature field modeling simulation method of an SF6 porcelain column type circuit breaker suitable for a low temperature environment provided by the embodiment of the present application is shown in the figure.

[0059] Figure 3 A schematic diagram of a cross-sectional view of a geometric model of a temperature field modeling simulation method of an SF6 porcelain column type circuit breaker suitable for a low temperature environment provided by the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0060] The present application will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application. In addition, it should be noted that, for the convenience of description, only the parts related to the present application are shown in the drawings, but not all the structures.

[0061] Referring to Figure 1 The embodiment provides a temperature field modeling simulation method of an SF6 porcelain column type circuit breaker suitable for a low temperature environment, which comprises the following steps.

[0062] A simulation model is established to model and simulate the porcelain column type circuit breaker and build a geometric model.

[0063] Referring to Figure 2 and Figure 3 The building of the geometric model specifically comprises the following steps.

[0064] The geometric model of the porcelain column type circuit breaker from the external porcelain sleeve to the internal arc extinguishing chamber insulation pull rod is built. In the embodiment, the porcelain column type circuit breaker is modeled and simulated in the soildwork software to build the geometric model from the external porcelain sleeve to the internal arc extinguishing chamber insulation pull rod; and the geometric model entity drawn in the soildwork software is imported into the comsol simulation software.

[0065] The material properties of the parts are set to set the material properties of the geometric model components.

[0066] The setting of the material properties of the components of the geometric model includes: upper terminal board, lower terminal board, static contact seat, static arc contact, movable contact seat, movable arc contact, pull rod, porcelain sleeve, and SF6 filling in the porcelain sleeve. In this embodiment, the materials of the upper terminal board, lower terminal board, static contact seat, static arc contact, movable contact seat, movable arc contact, and pull rod are selected as alumina in the comsol simulation software, and the material of the porcelain sleeve is selected as alumina ceramics in the comsol simulation software. SF6 is selected to fill in the porcelain sleeve, and a custom material is created in the material database of the comsol.

[0067] SF6 is in a liquid or gaseous state, and the state of SF6 in the porcelain sleeve is determined by the bette-bridgman state equation, and the bette-bridgman state equation is expressed as:

[0068]

[0069] wherein, is the absolute pressure, in bar, is the absolute temperature, in K, is the ratio of volume to mass, , , , .

[0070] In this embodiment, under the condition of low temperature and certain pressure, the state of SF6 may be gaseous or liquid, so the “phase change material” is selected under the boundary condition of “fluid” domain, the interval of gaseous-liquid state transition is a constant ΔT, the latent heat of liquefaction is a constant ΔL, and the state and phase transition temperature of SF6 are determined by the bette-bridgman state equation.

[0071] The geometric model is divided by the mesh division method.

[0072] The geometric model is divided by the mesh division method, which specifically includes:

[0073] The geometric model is divided into a plurality of triangular meshes by the mesh division method, the resolution of the plurality of triangular meshes is distinguished, and a resolution threshold is set, so that the plurality of triangular meshes are compared with the resolution threshold according to their own resolutions, to complete the adaptive adjustment of the mesh density.

[0074] In this embodiment, the mesh is divided by the division method flexibly according to the specific requirements of the geometric model, the size of the mesh is set according to the requirements of the analysis problem, the position of the focus analysis is finely divided according to the set threshold, and the position of the analysis with little influence is roughly divided according to the set threshold. The higher the degree of mesh division, the closer the simulation result to the actual situation, so that satisfactory result data is obtained.

[0075] In the comsol simulation software, the geometric model is divided into triangular grid according to different parts by automatic meshing method, the resolution threshold is set, that is, the grid generation parameters are adjusted, more detailed grid is used, especially in the complex geometric area, the adaptive meshing function is used to automatically identify the set resolution threshold, so that the grid is more dense in the area where higher resolution is needed. In this embodiment, due to the complex structure of the circuit breaker arc extinguishing chamber, SF6 in the circuit breaker arc extinguishing chamber contact surface is complex, so that the automatic meshing of this part of the grid will affect the calculation accuracy. Therefore, considering the influence of heat transfer between SF6 and contact material in the circuit breaker, the grid parameters are adjusted here to improve the grid density in this area, so as to ensure that the grid has enough resolution in the key area. At the same time, due to the large number of grids, the calculation time is increased, which affects the work efficiency. Under the premise of ensuring the simulation accuracy, the grid density of the upper connection plate, the lower connection plate and the position of the pull rod is adjusted, and the number of grids is reduced, so as to reduce the calculation amount during simulation running.

[0076] The boundary conditions are set, the geometric model adopts laminar flow interface and solid heat transfer interface, and the boundary conditions of laminar flow interface and solid heat transfer interface are set respectively.

[0077] In this embodiment, the correct setting of boundary conditions is the key to ensure the accuracy of simulation results. The simulation model includes corrugated pipe, moving contact and other geometric components, and adopts two-layer laminar flow interface (Laminar Flow Interface) and solid heat transfer interface (Heat Transfer in Solids Interface) for steady-state solution. The geometric model involves fluid domain (SF6 gas) and solid domain (pull rod, moving contact, etc.), and the heat transfer is realized through fluid-solid coupling between the two.

[0078] The boundary of laminar flow interface is set, which specifically includes:

[0079] The inlet boundary condition is set. For steady flow, the expression of velocity inlet is set as:

[0080]

[0081] wherein, represents the flow velocity vector, is a given constant flow velocity, =10m / s;

[0082] Velocity inlet: this boundary condition is used to specify the velocity distribution of fluid flowing into the geometric model, which is usually set as a constant value or an expression (such as a function of velocity component).

[0083] Mass Flow Inlet: for mass flow, the mass flow of the inlet is set as a constant, the velocity of the fluid is determined by the mass flow and the density of the fluid, and the mass continuity equation is followed, and the expression is:

[0084]

[0085] wherein, is the material density, , are the velocity components in x, y, z directions respectively.

[0086] Outlet boundary condition setting, the outlet pressure of the fluid from the geometric model is set as the gas charging pressure;

[0087] In this embodiment, the outlet pressure value is set as a constant according to the gas charging pressure, which is generally (0.3~0.7) MPa, and when SF6 is considered as a liquid state not controlled by temperature in the simulation process, the outlet pressure value is set as 3.76 MPa.

[0088] Solid boundary condition setting, no-slip boundary condition: in the laminar flow interface, the fluid velocity on the solid boundary is zero, so there is no relative sliding between the solid surface and the fluid, and the no-slip boundary condition is set as:

[0089]

[0090] This means that the fluid has a velocity of zero when it contacts the solid surface.

[0091] Slip wall boundary condition: when the solid surface is not completely fixed, tangential flow will occur between the fluid and the solid, and the slip wall boundary condition allows the fluid to flow along the tangential direction on the solid surface, and the normal velocity is zero.

[0092] Solid heat transfer interface is used to simulate the heat conduction process, in which the distribution of temperature and heat flux is the key, and the boundary conditions include fixed temperature, fixed heat flow and convective heat exchange, etc.

[0093] The boundary of the solid heat transfer interface is set, which specifically includes:

[0094] Solid surface heat flow boundary condition setting, the heat flux density expression on the solid surface is set as:

[0095]

[0096] wherein, represents the heat flux vector, that is, the area heat flow, and the unit is , ​Temperature of an object, in units of , It represents the unit normal vector on an isotherm or isotherm passing through a point on a solid surface, with the direction from low temperature to high temperature; Thermal conductivity, also known as thermal conductivity, is a measure of the thermal conductivity of an object. The negative sign before the thermal conductivity coefficient indicates that the direction of heat transfer is opposite to the direction of the temperature gradient, that is, heat is transferred from high temperature to low temperature.

[0097] The relationship between thermal conductivity and temperature is:

[0098]

[0099] in, Material 0 Thermal conductivity at time, in units of , Temperature of an object, in units of , It is a constant.

[0100] In some simulation scenarios, a constant temperature can be set to a known, constant value for the temperature of the solid surface. The expression is:

[0101]

[0102] in, The solid surface temperature The set constant temperature.

[0103] The boundary conditions for convective heat transfer on solid surfaces are set, and the formula for convective heat transfer on solid surfaces is as follows:

[0104]

[0105] in, It represents the power dissipated per unit volume of fluid medium due to convection. This represents the convective heat dissipation coefficient, in units of... , This represents the area of ​​the cooling surface, in units of... , The surface temperature of a heat-generating object is expressed in units of 1000 ppm. , Represents the temperature of the fluid medium, in units of . ;

[0106] The empirical formula for the convective heat dissipation coefficient is:

[0107] .

[0108] In this embodiment, when performing the finite element simulation of the temperature field, the boundary condition setting of the laminar flow interface and the solid heat transfer interface is crucial to ensure the accuracy of the geometric model. The laminar flow interface describes the motion state of the fluid by setting the flow conditions of the inlet, outlet and solid surface. The solid heat transfer interface describes the heat transfer in the solid and between the solid and the fluid by setting the temperature, heat flux and convective heat transfer. Correct selection and setting of each boundary condition can improve the reliability of the simulation results.

[0109] The steady-state solution is independently solved for the fluid flow of the laminar flow interface and the solid heat transfer of the solid heat transfer interface, and the fluid-solid boundary coupling is performed on the solution results.

[0110] In this embodiment, the steady-state solution refers to solving the stable solution of fluid flow, heat transfer or other physical phenomena under the condition that time does not change. For a complex model containing multiple physical fields, especially for the coupling problem of fluid flow and solid heat transfer, a step-by-step solving method is usually used, that is, different physical interfaces are independently solved, and then the solution results are coupled and analyzed.

[0111] The fluid flow of the laminar flow interface is independently solved, specifically including:

[0112] The inlet, outlet and solid surface boundary conditions of the fluid are set, the velocity, pressure and no-slip boundary of the fluid are considered, the fluid model is established, and the fluid model is solved to obtain the velocity field and pressure field of the fluid. The fluid model is the natural convection process of the fluid.

[0113] In this embodiment, the main solution is to solve the flow state of the fluid in the circuit breaker cavity. The inlet, outlet and solid surface boundary conditions of the fluid are set, mainly considering the velocity, pressure and no-slip boundary, etc. The steady-state solution means that the long-term stable state of the fluid flow is simulated and calculated, and the time variation is ignored. The fluid model is solved to obtain the velocity field and pressure field.

[0114] The solid heat transfer of the solid heat transfer interface is independently solved, specifically including:

[0115] S11, a solid heat transfer model is established based on the temperature distribution of the solid part, and the solid heat transfer model is solved, and the velocity field and pressure field of the fluid are taken as the boundary conditions of the solid heat transfer.

[0116] S12, the temperature field of the fluid is transmitted to the solid heat transfer interface, and the temperature distribution of the solid is calculated based on the heat transferred by the fluid to obtain the temperature distribution heat flux and temperature boundary condition of the solid.

[0117] S13, steady-state solving according to the temperature distribution heat flux density of the solid, the temperature boundary condition heat flux density and the temperature boundary condition, calculating the temperature field of the solid part.

[0118] In this embodiment, the temperature distribution of the solid part (such as the moving contact, the pipe wall, etc.) is solved, the heat exchange boundary condition between the solid surface and the fluid is set, and the heat flux density, the convective heat transfer, etc. are considered. Through step-by-step solving, the fluid flow problem is solved first to obtain the velocity field and pressure field of the fluid, and then these results are used as the boundary conditions of the solid heat transfer to solve the heat transfer problem. In solving, the temperature field will be transmitted to the solid heat transfer interface as a result of fluid flow, and the temperature distribution of the solid will be calculated based on the heat transmitted by the fluid. The solid heat transfer model will be steady-state solved according to the heat flux density and the temperature boundary condition, and the temperature field of the solid part will be calculated.

[0119] The solving results are coupled between the fluid-solid boundary, specifically including:

[0120] The temperature field of the fluid is taken as the input of the solid heat transfer model, and the temperature field and heat flux density of the solid are fed back to the fluid model for fluid-solid boundary coupling.

[0121] In this embodiment, the coupling between the fluid and the solid is usually realized through heat exchange (convective heat transfer) or heat flux density transmission. After the fluid model is solved, the temperature field of the fluid will be taken as the input of the solid heat transfer model, and the temperature field and heat flux density of the solid will be fed back to the fluid model, so that the heat exchange between the fluid and the solid can be simulated through the convective heat transfer condition. The fluid flow problem is solved independently first to obtain the steady-state velocity field and pressure field, and then the results of the fluid model are taken as the boundary conditions for steady-state solving of the solid heat transfer, and finally the steady-state solution of the fluid flow and the solid temperature field is obtained. The key of the steady-state solving is to ensure the correct transmission of the boundary conditions between the fluid flow and the solid heat transfer, and to ensure the correctness of the solving of each interface. The step-by-step solving can help us analyze the influence of each physical process step by step, and finally obtain a comprehensive steady-state solution.

[0122] The above only describes the preferred embodiments of the present application and does not limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for modeling and simulating the temperature field of SF6 porcelain column circuit breakers adapted to low-temperature environments, characterized in that, The method includes: Establish a simulation model to model and simulate the porcelain column circuit breaker, and build a geometric model; Set the material properties of the parts; set the material properties of the geometric model components. The geometric model is partitioned by dividing the geometric model using a mesh generation method; Set boundary conditions. The geometric model adopts a laminar flow interface and a solid heat transfer interface. Set boundary conditions for the laminar flow interface and the solid heat transfer interface respectively. Steady-state solution: The fluid flow at the laminar interface and the solid heat transfer at the solid heat transfer interface are solved independently, and the solution results are coupled to the fluid-solid boundary. The fluid flow at the laminar interface is solved independently, specifically including: The fluid inlet, outlet, and solid surface boundary conditions are set. Considering the fluid velocity, pressure, and no-slip boundary, a fluid model is established and solved to obtain the fluid velocity field and pressure field. The fluid model represents the natural convection process of the fluid. Solving for solid heat transfer at solid heat transfer interfaces independently includes: S11. Establish a solid heat transfer model based on the temperature distribution of the solid part, and solve the solid heat transfer model, taking the velocity field and pressure field of the fluid as the boundary conditions for solid heat transfer. S12. The temperature field of the fluid is transferred to the solid heat transfer interface. The temperature distribution of the solid is calculated based on the heat transferred by the fluid to obtain the temperature distribution heat flux density and temperature boundary conditions of the solid. S13. Based on the temperature distribution, heat flux density, and temperature boundary conditions of the solid, perform steady-state solutions to calculate the temperature field of the solid portion.

2. The method for modeling and simulating the temperature field of SF6 porcelain column circuit breakers adapted to low-temperature environments according to claim 1, characterized in that, Building a geometric model specifically includes: Construct a geometric model of a porcelain column circuit breaker, from the outer porcelain bushing to the internal arc-extinguishing chamber insulating tie rod.

3. The method for modeling and simulating the temperature field of SF6 porcelain column circuit breakers adapted to low-temperature environments according to claim 1, characterized in that, Setting the material properties of geometric model components includes: upper terminal block, lower terminal block, stationary contact seat, stationary arc contact, moving contact seat, moving arc contact, tie rod, porcelain sleeve, and selecting SF6 filler inside the porcelain sleeve.

4. The method for modeling and simulating the temperature field of SF6 porcelain column circuit breakers adapted to low-temperature environments according to claim 3, characterized in that, SF6 is in either a liquid or gaseous state. The state of SF6 inside the ceramic sleeve is determined using the Betty-Bridgeman equation of state, which is expressed as follows: in, Absolute pressure, unit: bar. Absolute temperature, unit K. It is the ratio of volume to mass. , , , .

5. The method for modeling and simulating the temperature field of SF6 porcelain column circuit breakers adapted to low-temperature environments according to claim 1, characterized in that, The geometric model is divided using a mesh generation method, specifically including: The geometric model is divided into several triangular meshes according to different parts by meshing method. The resolution of several triangular meshes is distinguished and a resolution threshold is set. The several triangular meshes are compared with their own resolution and the resolution threshold to complete the adaptive adjustment of mesh density.

6. The method for modeling and simulating the temperature field of SF6 porcelain column circuit breakers adapted to low-temperature environments according to claim 1, characterized in that, Boundary settings for laminar flow interfaces include: For steady-state flow, the inlet boundary condition setting is as follows: in, Represents the velocity vector. For a given constant flow rate; For mass flow rate, the inlet mass flow rate is set to a constant. The fluid velocity is determined by the mass flow rate and the fluid density, following the mass continuity equation, which is expressed as: in, For material density, , They are respectively Velocity components in the y and z directions; The outlet boundary conditions are set to set the fluid outlet pressure from the geometric model to the gas charging pressure; In a laminar flow interface, when the fluid velocity at the solid boundary is zero, there is no relative slippage between the solid surface and the fluid. Therefore, the no-slip boundary condition is set as follows: When the solid surface is not completely fixed, tangential flow will occur between the fluid and the solid. The slip boundary condition allows the fluid to flow tangentially on the solid surface, in which case the normal velocity is zero.

7. The method for modeling and simulating the temperature field of SF6 porcelain column circuit breakers adapted to low-temperature environments according to claim 1, characterized in that, Boundary settings for solid heat transfer interfaces include: The heat flux boundary condition for a solid surface is set, and the expression for the heat flux density on the solid surface is defined as follows: in, This represents the heat flux density vector, i.e., the area heat flux, with units of . , Temperature of an object, in units of , It represents the unit normal vector on an isotherm or isotherm passing through a point on a solid surface, with the direction from low temperature to high temperature; Thermal conductivity, also known as thermal conductivity, is a measure of the thermal conductivity of an object. The negative sign before the thermal conductivity coefficient indicates that the direction of heat transfer is opposite to the direction of the temperature gradient, that is, heat is transferred from high temperature to low temperature. The relationship between thermal conductivity and temperature is: in, Material 0 Thermal conductivity at time, in units of , Temperature of an object, in units of , It is a constant; The boundary conditions for convective heat transfer on solid surfaces are set, and the formula for convective heat transfer on solid surfaces is as follows: in, It represents the power dissipated per unit volume of fluid medium due to convection. This represents the convective heat dissipation coefficient, in units of... , This represents the area of ​​the cooling surface, in units of... , The surface temperature of a heat-generating object is expressed in units of 1000 ppm. , Represents the temperature of the fluid medium, in units of . ; The empirical formula for the convective heat dissipation coefficient is: 。 8. The method for modeling and simulating the temperature field of SF6 porcelain column circuit breakers adapted to low-temperature environments according to claim 1, characterized in that, The solution results are coupled to the fluid-solid boundary, specifically including: The temperature field of the fluid is used as the input to the solid heat transfer model, and the temperature field and heat flux density of the solid are fed back to the fluid model to perform fluid-solid boundary coupling.

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