Medium-voltage environment-friendly gas insulation switch cabinet temperature field modeling method

Abstract

The invention belongs to the technical field of simulation analysis, and particularly relates to a medium-voltage environment-friendly gas insulation switch cabinet temperature field modeling method, which comprises the following steps: constructing a three-dimensional geometric model of a switch cabinet and carrying out simplification processing; the COMSOL multi-physics field simulation software is imported; electromagnetic-thermal bidirectional coupling modeling is carried out; adding a surface-to-surface radiation physical field; determining a fluid flow state based on a Glassu number, and selecting a corresponding fluid dynamic model; environment conditions are set, and radiant heat exchange power and a convective heat exchange coefficient are calculated; establishing a grid division strategy based on temperature contribution to obtain a simulation model of preliminary modeling; solving and post-processing a solving result, and analyzing hot spot distribution by using a temperature distribution diagram; a thermocouple is installed in a hot spot area in an actual switch cabinet, actual temperature data are obtained through measurement, and the simulation model subjected to preliminary modeling is corrected according to the actual temperature data. The temperature rise condition can be accurately predicted, and a powerful guarantee is provided for safe operation of equipment.

Description

Technical Field

[0001] The invention belongs to the technical field of simulation analysis, and in particular relates to a temperature field modeling method for a medium-voltage environmentally friendly gas-insulated switchgear. Background Art

[0002] In the continuous evolution of modern power systems, gas-insulated switchgear has been widely used in medium-voltage power distribution systems due to its unique advantages such as small footprint, high operational reliability and maintenance-free. However, with the increasing awareness of environmental protection and the gradual tightening of environmental protection regulations, traditional SF 6 Gases are gradually being replaced by other gases such as CO because of their significant negative impact on the greenhouse effect. 2 、N 2 and other environmentally friendly alternative gases.

[0003] Although these environmentally friendly alternative gases have advantages in environmental performance, their thermophysical properties are similar to those of SF 6 Compared with gas, there are significant differences, especially in terms of thermal conductivity. This characteristic causes heat to easily accumulate in the switch cabinet during operation, which greatly increases the risk of equipment temperature rise. Excessive equipment temperature rise will not only accelerate the aging process of insulation materials and shorten their service life, but may also cause electrical faults such as short circuits and discharges, seriously threatening the safety and stability of the power system.

[0004] At present, although there are some simulation software based on the finite element method, such as COMSOL, ANSYS, etc., which can simulate the temperature rise distribution inside the gas-insulated switchgear. However, in the modeling process, these methods often find it difficult to achieve an ideal balance between model accuracy and computational efficiency. Insufficient model accuracy may lead to inaccurate predictions of the temperature distribution inside the switchgear, and failure to detect potential overheating risks in a timely manner; while low computational efficiency will increase the time cost of modeling and analysis, which is not conducive to the rapid optimization of the design and operation strategy of the switchgear. Therefore, there is an urgent need for a modeling method that can more accurately and efficiently simulate the temperature field of medium-voltage environmentally friendly gas-insulated switchgear. Summary of the invention

[0005] In view of the above deficiencies in the prior art, the purpose of the present invention is to provide a temperature field modeling method for a medium-voltage environmentally friendly gas-insulated switchgear, which can accurately predict temperature rise, provide strong guarantees for the safe operation of the equipment, and effectively avoid problems such as aging of insulation materials and electrical failures caused by excessive temperature rise.

[0006] To achieve the above objectives, the present invention provides a method for modeling a temperature field of a medium voltage environmentally friendly gas insulated switchgear, comprising the following steps: S1. Use 3D software to construct a 3D geometric model of the switch cabinet, retain the support components and conductor components, and simplify the 3D geometric model; S2. Import the simplified three-dimensional geometric model into COMSOL multi-physics simulation software, set the material of the conductor component, and assign corresponding electromagnetic properties and thermal physical parameters to the material; S3. Use the electromagnetic-thermal coupling interface in COMSOL to perform electromagnetic-thermal bidirectional coupling modeling, consider resistance loss, and evaluate the heat source; S4. Add the "surface-to-surface radiation" physics field to simulate the radiation heat exchange between components of the switch cabinet and between components and the environment, and set the surface emissivity; S5. Calculate the Grashof number, determine the fluid flow state based on the Grashof number, and select a corresponding fluid dynamics model according to the determination result for simulating convective heat transfer in the switch cabinet; S6. Set environmental conditions, including ambient temperature, humidity and atmospheric pressure, and calculate radiation heat exchange power and convection heat transfer coefficient to simulate the heat exchange process between the switch cabinet and the environment; S7. Establish a grid division strategy based on temperature contribution, perform fine grid division on the hot spot area, and perform coarsening on other areas to obtain a preliminary modeling simulation model; S8. Select the "Frequency Domain-Steady State" solver and set the solver parameters; S9, post-processing the solution result to obtain a temperature distribution map, using the temperature distribution map to analyze the hot spot distribution, and deriving the temperature value of the hot spot area for comparison with the actual temperature data; S10. According to the hot spot distribution obtained by simulation, thermocouples are installed in the hot spot areas in the actual switch cabinet to measure and obtain actual temperature data. The simulation model of the preliminary modeling is corrected according to the actual temperature data to complete the final modeling of the switch cabinet temperature field.

[0007] As a preferred embodiment of the present invention, in the S1, the three-dimensional software uses SolidWorks, and the simplification processing is specifically as follows: for the three-dimensional geometric model of the switch cabinet, the support components and conductor components are retained, the support components include a cabinet body and a gas box, and the conductor components include a screen top busbar, a three-position switch, a vacuum circuit breaker conductive part, and a lower busbar; the non-conductive parts, bushings, three-position operating mechanisms, circuit breaker operating mechanisms, screws, nuts and fixings in the sealed poles are removed, and at the same time, the small round holes and rounded corners in the retained components are removed, the support components are simplified into a flat plate form, and the secondary equipment in the instrument room of the switch cabinet is removed to complete the simplification of the support components and the internal layout of the cabinet.

[0008] As a preferred embodiment of the present invention, in S2, the electromagnetic properties include the electrical conductivity and dielectric constant of the conductor, the thermal physical parameters include thermal conductivity, specific heat capacity, density, and thermal expansion coefficient, and the material settings are specifically as follows: the material of the top busbar and the lower busbar is set to copper; the three-position switch is set to copper; the conductive part of the vacuum circuit breaker is set to copper alloy, and the support assembly is set to stainless steel; When setting electromagnetic properties, consider the nonlinear relationship between the conductivity of the conductor and the temperature, and follow the formula: ; Where, T represents temperature; is the initial temperature; It represents the conductivity of the conductor at temperature T; is the initial temperature The conductivity under is the temperature coefficient of resistance of the conductor material.

[0009] As a preferred embodiment of the present invention, in S3, when calculating the resistance loss, the resistance of the conductor itself and the contact resistance between the components are calculated by comprehensively considering the influence of the conductor material properties, the contact surface state, the connection method, and the change of the conductor conductivity with temperature, and the heat source is calculated according to the following formula: ; Where P is the power generated by resistance loss; I is the current; is the connection mode coefficient; is the contact surface state coefficient; is the resistance temperature coefficient of the conductor material; t is the actual temperature; is the reference temperature; The conductor is at a reference temperature The self-resistance under is the contact resistance under ideal contact conditions.

[0010] As a preferred embodiment of the present invention, for a clean, flat, non-oxidized contact surface, The value is 1; for contact surfaces with dirt, roughness or oxidation, >1; for welding connection, The value is 0.8-1; for bolt connections, Greater than 1.

[0011] As a preferred solution of the present invention, in S5, the flow state of the fluid is determined based on the Grashof number Gr. When Gr>10 9 When Gr≤10 9 The laminar flow model is used.

[0012] As a preferred embodiment of the present invention, in S6, the radiation heat exchange power is calculated by an empirical formula. , expressed as: ; In the formula, is the Stewart-Boltzmann constant; A is the radiating surface area; is the surface emissivity; and are the temperatures of the heat source and the cold source; is the surface roughness correction factor; is the surface roughness parameter; L is the characteristic length; m is the index of the effect of surface roughness on thermal radiation; The convective heat transfer coefficient h is calculated using the empirical formula, expressed as: ; Where Nu is the Nusselt number; k is the thermal conductivity of the gas; is the temperature gradient correction factor; and are the maximum and minimum temperatures, respectively; is the average temperature; n is the influence index of temperature gradient on heat transfer.

[0013] As a preferred solution of the present invention, in S7, the grid division strategy based on temperature contribution is to determine the division range of the hot spot area and other areas according to the pre-analysis or empirical judgment of the temperature field of the switch cabinet, specifically: The hot spots include the busbar overlap on the top of the screen, the busbar overlap on the bottom, the contact surface of the three-position switch, and the contact of the vacuum circuit breaker. When dividing the mesh, the mesh generation rules are followed, including orthogonality, smoothness, and reasonable size transition.

[0014] As a preferred solution of the present invention, in the above S8, the frequency in the frequency domain is 50 Hz, and suitable solvers are selected for different physical fields: the frequency domain solver is used for current calculation; the steady-state solver is used for heat conduction, radiation and convection heat transfer calculation.

[0015] As a preferred embodiment of the present invention, in the above S10, the thermocouples are installed at the top busbar lap joint, the bottom busbar lap joint, and the three-position switch contact surface, and the data acquisition frequency and accuracy are set; When the simulation model after preliminary modeling is corrected according to the actual temperature data, the following temperature correction formula is used: ; Where q is the correction factor; C is a constant used to adjust the correction amplitude; is the actual temperature measured by the thermocouple; is the simulated temperature corresponding to the measurement position of the thermocouple; Based on q, the temperature-related parameters are adjusted. The temperature-related parameters include the resistance value in the resistance loss calculation and the convection heat transfer coefficient. The adjustment method is: Adjusted parameter = original parameter × q; By continuously comparing the actual temperature and the simulated temperature, calculating the correction factor, and adjusting the model parameters, the simulation model is gradually brought closer to the actual situation, so that the final simulation model can accurately predict the temperature field distribution of the switch cabinet under different working conditions.

[0016] The algorithm involved in the present invention can be executed by an electronic device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and the above algorithm calculation is implemented by executing the software by the processor.

[0017] The beneficial effects of the present invention are: The present invention uses SolidWorks and COMSOL multi-physics field simulation software to accurately model and deeply analyze the complex electrothermal effects inside the switch cabinet, focusing on accurate simulation and optimization of the temperature rise at hot spots, thereby achieving accurate prediction of the temperature field of the switch cabinet and providing strong support for the safe and stable operation of the equipment.

[0018] Through the electromagnetic-thermal-fluid multi-physics field coupling model, the present invention can accurately simulate the temperature distribution inside the medium-voltage environmentally friendly gas insulated switchgear, especially in key areas such as busbar joints, three-station contact surfaces and circuit breaker contacts. It can accurately predict the temperature rise, provide strong guarantees for the safe operation of the equipment, and effectively avoid problems such as insulation material aging and electrical failures caused by excessive temperature rise.

[0019] The present invention significantly reduces the complexity of the model and the amount of calculation by reasonably simplifying the internal structure of the switch cabinet, removing components that have little impact on heat generation and heat dissipation, simplifying the design of tiny structures in conductor components, and adopting a meshing strategy based on temperature contribution. This significantly improves the efficiency of simulation calculations, shortens the time cycle for modeling and analysis, and is conducive to quickly optimizing the design and operation strategy of the switch cabinet.

[0020] The present invention uses thermocouples to obtain actual temperature data and compares and corrects it with the simulation results in real time, so that the model can continuously adapt to changes in actual working conditions, effectively making up for the deviation between the model calculation and the actual situation, and ensuring the high accuracy and reliability of the model. This makes the model more accurate and practical in predicting the temperature field distribution of the switch cabinet, evaluating the operating status of the equipment, and guiding fault diagnosis. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the process of the present invention; Figure 2 is a schematic diagram of the main structure of a simplified switch cabinet in an embodiment of the present invention; Figure 3 It is a schematic diagram of the left view of the simplified switch cabinet in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The embodiments of the present invention are further described below in conjunction with the accompanying drawings: like Figure 1 As shown, a method for modeling a temperature field of a medium voltage environmentally friendly gas insulated switchgear includes the following steps: S1. Use 3D software to construct a 3D geometric model of the switch cabinet, retain the support components and conductor components, and simplify the 3D geometric model; S2. Import the simplified three-dimensional geometric model into COMSOL multi-physics simulation software, set the material of the conductor component, and assign corresponding electromagnetic properties and thermal physical parameters to the material; S3. Use the electromagnetic-thermal coupling interface in COMSOL to perform electromagnetic-thermal bidirectional coupling modeling, consider resistance loss, and evaluate the heat source; S4. Add the "surface-to-surface radiation" physics field to simulate the radiation heat exchange between components of the switch cabinet and between components and the environment, and set the surface emissivity; S5. Calculate the Grashof number, determine the fluid flow state based on the Grashof number, and select a corresponding fluid dynamics model according to the determination result for simulating convective heat transfer in the switch cabinet; S6. Set environmental conditions, including ambient temperature, humidity and atmospheric pressure (measured according to the actual use environment or set standard values), and calculate the radiation heat exchange power and convection heat transfer coefficient to simulate the heat exchange process between the switch cabinet and the environment; S7. Establish a grid division strategy based on temperature contribution, perform fine grid division on the hot spot area, and perform coarsening on other areas to obtain a preliminary modeling simulation model; S8. Select the "Frequency Domain-Steady State" solver and set the solver parameters; S9, post-processing the solution result to obtain a temperature distribution map, using the temperature distribution map to analyze the hot spot distribution, and deriving the temperature value of the hot spot area for comparison with the actual temperature data; S10. According to the hot spot distribution obtained by simulation, thermocouples are installed in the hot spot areas in the actual switch cabinet to measure and obtain actual temperature data. The simulation model of the preliminary modeling is corrected according to the actual temperature data to complete the final modeling of the switch cabinet temperature field.

[0023] In S1, SolidWorks is used as the 3D software. The simplification process is as follows: for the 3D geometric model of the switch cabinet, the support components and conductor components are retained. The support components include the cabinet body and the gas box. The conductor components include the screen top busbar, the three-position switch, the conductive part of the vacuum circuit breaker, and the lower busbar; the non-conductive parts, bushings, three-position operating mechanisms, circuit breaker operating mechanisms, screws, nuts and fixings in the sealed poles are removed. At the same time, the small round holes and fillets in the retained components are removed, the support components are simplified into a flat plate form, and the secondary equipment in the instrument room of the switch cabinet is removed to complete the simplification of the support components and the internal layout of the cabinet. This simplification method only retains the main heat sources and key structures. The simplified switch cabinet structure is as follows: Figure 2 and Figure 3 shown.

[0024] Components such as screws and nuts play a relatively small role in the overall electrothermal performance of the switchgear, but their presence increases model complexity and reduces computational efficiency. By removing them, the computational speed can be effectively improved without significantly affecting the accuracy of the model. Structures such as conductor components are key parts of current transmission and conversion in the switchgear, and are also the main areas of heat generation and accumulation. Retaining them ensures that the model accurately reflects the temperature rise characteristics of the main circuit, laying a solid foundation for subsequent precise analysis.

[0025] In actual conductor components, small circular holes, rounded corners and other tiny structural details exist to a certain extent, but they have little effect on the overall ohmic loss, but will greatly increase the complexity of the model calculation. The support components are further simplified into a flat plate form, and the secondary equipment in the instrument room is ignored to reduce the complexity of the simulation model. After simplifying these designs, the model can focus more on the key electrothermal effects and improve the calculation efficiency without significantly affecting the accuracy of the model.

[0026] In S2, electromagnetic properties include the electrical conductivity and dielectric constant of the conductor, and thermophysical parameters include thermal conductivity, specific heat capacity, density, and thermal expansion coefficient. The values ​​of these parameters are based on the characteristic data of the materials used in actual applications, and they are highly consistent and accurate throughout the simulation process. Thermal conductivity determines the ability of a material to conduct heat, and specific heat capacity affects the rate at which a material absorbs and releases heat. Accurately setting these parameters can ensure that the simulation model is consistent with the actual situation when simulating the heat conduction and heat exchange process, and improve the reliability of the simulation results.

[0027] The material settings are as follows: the material of the top busbar and the lower busbar is copper; the three-position switch is copper; the conductive part of the vacuum circuit breaker is copper alloy, and the supporting component is stainless steel; When setting electromagnetic properties, consider the nonlinear relationship between the conductivity of the conductor and the temperature, and follow the formula: ; Where, T represents temperature; is the initial temperature; It represents the conductivity of the conductor at temperature T; is the initial temperature The conductivity under is the temperature coefficient of resistance of the conductor material.

[0028] Set according to conductor material and experimental determination , conductivity is one of the key factors affecting the temperature rise of conductors, and its nonlinear relationship with temperature is crucial in the simulation process. Through this formula, the model can dynamically adjust the conductivity calculation according to temperature changes, thereby more accurately simulating the resistance changes and power loss of conductors under different temperature conditions, and truly reflecting the electrothermal performance under actual working conditions.

[0029] Since the stainless steel shell of the switch cabinet is anti-magnetic, the eddy current loss can be ignored under normal working conditions; at the same time, the influence of dielectric loss on the overall thermal energy is relatively small. Therefore, in this modeling method, after comprehensive consideration, it is determined to use resistance loss as the main heat source of the switch cabinet.

[0030] In S3, when calculating the resistance loss, the resistance of the conductor itself and the contact resistance between components are calculated by comprehensively considering the influence of the conductor material characteristics, contact surface state, connection method, and the change of conductor conductivity with temperature, and the heat source is calculated according to the following formula: ; Where P is the power generated by resistance loss; I is the current; is the connection mode coefficient; is the contact surface state coefficient; is the resistance temperature coefficient of the conductor material; t is the actual temperature; is the reference temperature; The conductor is at a reference temperature The self-resistance under is the contact resistance under ideal contact conditions.

[0031] For clean, flat, non-oxidized contact surfaces, The value is 1; for contact surfaces with dirt, roughness or oxidation, >1; For welding connection, the connection is relatively tight and the current transmission is good. The value is 0.8-1; for bolt connections, it is easy to have insufficient tightening. Greater than 1.

[0032] In S5, the fluid flow state is determined based on the Grashof number Gr, and an appropriate fluid model is selected based on the determination result, thereby optimizing the simulation accuracy of the convection heat transfer inside the switch cabinet.9 When Gr≤10 9 The laminar flow model is used.

[0033] The Grashof number reflects the strength of natural convection. Based on its calculation results, it can be determined whether the flow state of the fluid is laminar or turbulent, thereby providing a basis for selecting an appropriate fluid dynamics model.

[0034] In S6, the radiation heat exchange power is calculated by the empirical formula , expressed as: ; In the formula, is the Stewart-Boltzmann constant; A is the radiating surface area; is the surface emissivity; and are the temperatures of the heat source and the cold source; is the surface roughness correction factor (usually 0-0.1); is the surface roughness parameter (usually 0.1-10μm); L is the characteristic length; m is the index of the effect of surface roughness on thermal radiation (usually 0.1-1); The convective heat transfer coefficient h is calculated using the empirical formula, expressed as: ; Where Nu is the Nusselt number; k is the thermal conductivity of the gas; is the temperature gradient correction factor (related to fluid type and flow state); and are the maximum and minimum temperatures, respectively; is the average temperature; n is the influence index of temperature gradient on heat transfer (obtained by fitting experimental data).

[0035] Among them, parameters such as Nu, k, and L are accurately determined based on actual environmental conditions and switchgear structural characteristics to ensure the accuracy of convective heat transfer simulation. For example, ambient temperature, wind speed, and the shape and size of the switchgear housing will affect the values ​​of these parameters, thereby affecting the calculation results of the convective heat transfer coefficient.

[0036] In S7, the grid division strategy based on temperature contribution is to determine the division range of hot spots and other areas according to the pre-analysis or empirical judgment of the switch cabinet temperature field, so as to optimize the balance between simulation accuracy and calculation efficiency. Specifically: The hot spots include the busbar overlap on the top of the screen, the busbar overlap on the bottom, the contact surface of the three-position switch, and the contact of the vacuum circuit breaker. When dividing the mesh, the mesh generation rules are followed, including orthogonality, smoothness, and reasonable size transition, to ensure the mesh quality and calculation stability.

[0037] During the simulation process, the focus was on hot spots such as the busbar overlap in the gas chamber, the contact surface of the three-position switch, and the circuit breaker contacts. Due to the special structure and working mode, these parts are prone to increased contact resistance in actual operation, which leads to current concentration, high temperature rise, and the formation of hot spots. For example, factors such as the overlap quality, contact area, and surface roughness of the busbar overlap will affect the size of the contact resistance; during the switching process of the three-position switch, the change in the state of the contact surface will cause resistance fluctuations; when the circuit breaker contacts are opened and closed, the instantaneous arc and current shock will cause the contact temperature to rise sharply. By accurately simulating the temperature rise in these hot spots, potential overheating risks can be discovered in advance, providing important guarantees for the safe operation of the equipment.

[0038] In order to improve the simulation efficiency, a meshing strategy based on temperature contribution is adopted. In potential hot spots, such as busbar joints and circuit breaker contacts, the temperature changes dramatically, which have an important impact on the safety of equipment operation. Therefore, fine meshing is adopted. Fine meshing can more accurately capture the subtle changes in the temperature field in these areas, for example, it can accurately describe the changes in the temperature gradient in the hot spots, thereby improving the accuracy of the simulation. In other areas that are not very sensitive to temperature changes, such as some areas of the switch cabinet shell, coarse meshing is adopted because their temperature changes are relatively mild and have limited impact on the overall temperature field. Coarse meshing can greatly reduce the amount of calculation and improve the calculation efficiency without significantly affecting the calculation accuracy. In the meshing process, a combination of rectangular coordinate system and tetrahedral mesh is adopted to reasonably allocate the mesh density according to the geometric shape and temperature distribution characteristics of the model. At the same time, certain mesh generation rules are followed, such as the orthogonality, smoothness and reasonable size transition of the mesh, to ensure the mesh quality and calculation stability. Through this optimization strategy, while ensuring the simulation accuracy of key areas, the efficiency of the entire simulation process is effectively improved, making the modeling method more practical and feasible.

[0039] In S8, the frequency in the frequency domain is 50 Hz, and the appropriate solver is selected for different physical fields: the frequency domain solver is used for current calculation; the steady-state solver is used for heat conduction, radiation and convection heat transfer calculations.

[0040] To further improve the accuracy of the model, thermocouples are used to obtain actual temperature data at key locations in the environmentally friendly gas-insulated switchgear. As a high-precision temperature measurement sensor, thermocouples have the advantages of fast response speed, high measurement accuracy, and good stability. When installing thermocouples, carefully select their installation locations so that they can accurately reflect key temperature changes inside the switchgear, such as the core position of the hot spot area, the connection where the temperature changes frequently, etc. Set the appropriate data acquisition frequency (determined according to the temperature change rate and model correction requirements, such as collecting once per second or several times per minute, etc.) and accuracy (determined according to the accuracy of the thermocouple sensor and the model requirements, such as accurate to 0.1°C or 0.5°C, etc.).

[0041] In S10, the thermocouples are installed at the top busbar lap joint, the bottom busbar lap joint, and the contact surface of the three-position switch, and the data acquisition frequency and accuracy are set; When the simulation model after preliminary modeling is corrected according to the actual temperature data, the following temperature correction formula is used: ; Wherein, q is the correction factor; C is a constant (a constant determined based on experience, and in this embodiment, the value is 0.5), which is used to adjust the correction amplitude; is the actual temperature measured by the thermocouple; is the simulated temperature corresponding to the measurement position of the thermocouple; Based on q, the temperature-dependent parameters are adjusted, including the contact resistance value in the resistance loss calculation. , the convection heat transfer coefficient h, the adjustment method is: Adjusted parameter = original parameter × q; By continuously comparing the actual temperature and the simulated temperature, calculating the correction factor, and adjusting the model parameters, the simulation model is gradually approached to the actual situation (the model calculation results and the measured temperature data have a high degree of consistency), so that the final simulation model can accurately predict the temperature field distribution of the switch cabinet under different working conditions.

[0042] In addition, the Internet of Things technology can be combined to collect the actual temperature data in the switch cabinet in real time, and transmit the data to the cloud through wireless communication technology. The computing resources of the cloud can be used to correct the simulation model in real time to ensure the high accuracy of the model.

[0043] In order to improve the accuracy and adaptability of the simulation model, the parameter adjustment method can be further improved by introducing a nonlinear adjustment function, which not only considers the difference between the actual temperature and the simulated temperature, but also introduces the influence of temperature gradient and environmental conditions to adjust the parameters more comprehensively. Let the original parameter be A, the adjusted parameter be B, and the ambient temperature be , then the adjustment method is: ; In the formula, a is the linear adjustment coefficient; b is the quadratic adjustment coefficient; and c is the cubic adjustment coefficient. By introducing quadratic and cubic terms, the complex nonlinear relationship between the actual temperature and the simulated temperature can be captured more accurately, improving the adaptability and accuracy of the model; by normalizing to the ambient temperature, the relativity and robustness of the adjustment can be ensured, so that the model can maintain high accuracy under different environmental conditions; by adjusting the coefficients a, b, and c, it can flexibly adapt to different equipment and working conditions, improving the versatility and applicability of the model; the coefficients a, b, and c are determined by experimental data or historical data, and the coefficients a, b, and c are automatically adjusted according to the difference between the actual temperature and the simulated temperature by the least squares method.

[0044] The acquisition frequency and accuracy of the measurement data should be reasonably set according to the requirements of the model correction. A higher acquisition frequency can obtain more detailed temperature change information, but it will increase the amount of data processing; the appropriate accuracy can ensure the reliability of the measurement data and provide an accurate basis for model correction. Compare and analyze the actual temperature data collected by the thermocouple with the temperature results calculated by the simulation model, and adjust and correct the parameters and boundary conditions of the simulation model based on the difference between the two. For example, if the measured temperature is higher than the simulation temperature, it may be necessary to check whether the resistance loss calculation is accurate, whether the convection heat transfer coefficient setting is reasonable, etc., and adjust the model parameters accordingly. By continuously comparing data and correcting the model, the model can gradually approach the actual situation, thereby improving the accuracy of the model, enabling it to more accurately predict the temperature field distribution of the switch cabinet under different working conditions, and provide a more reliable basis for equipment design optimization, operation monitoring and fault prevention.

Claims

1. A method for modeling the temperature field of a medium voltage environmentally friendly gas insulated switchgear, characterized in that The following steps are involved: S1. Use 3D software to construct a 3D geometric model of the switch cabinet, retain the support components and conductor components, and simplify the 3D geometric model; S2. Import the simplified three-dimensional geometric model into COMSOL multi-physics simulation software, set the material of the conductor component, and assign corresponding electromagnetic properties and thermal physical parameters to the material; S3. Use the electromagnetic-thermal coupling interface in COMSOL to perform electromagnetic-thermal bidirectional coupling modeling, consider resistance loss, and evaluate the heat source; S4. Add the "surface-to-surface radiation" physics field to simulate the radiation heat exchange between components of the switch cabinet and between components and the environment, and set the surface emissivity. S5. Calculate the Grashof number, determine the fluid flow state based on the Grashof number, and select a corresponding fluid dynamics model according to the determination result for simulating convective heat transfer in the switch cabinet; S6. Set environmental conditions, including ambient temperature, humidity and atmospheric pressure, and calculate radiation heat exchange power and convection heat transfer coefficient to simulate the heat exchange process between the switch cabinet and the environment; S7. Establish a grid division strategy based on temperature contribution, perform fine grid division on the hot spot area, and perform coarsening on other areas to obtain a preliminary modeling simulation model; S8. Select the "Frequency Domain-Steady State" solver and set the solver parameters; S9, post-processing the solution result to obtain a temperature distribution map, using the temperature distribution map to analyze the hot spot distribution, and deriving the temperature value of the hot spot area for comparison with the actual temperature data; S10. According to the hot spot distribution obtained by simulation, thermocouples are installed in the hot spot areas in the actual switch cabinet to measure and obtain actual temperature data. The simulation model of the preliminary modeling is corrected according to the actual temperature data to complete the final modeling of the switch cabinet temperature field.

2. A method for modeling a temperature field of a medium voltage environmentally friendly gas insulated switchgear according to claim 1, characterized in that: In the S1 described above, SolidWorks is used as the 3D software, and the simplification process is specifically as follows: for the 3D geometric model of the switch cabinet, the support components and conductor components are retained, the support components include the cabinet body and the gas box, and the conductor components include the screen top busbar, the three-position switch, the conductive part of the vacuum circuit breaker, and the lower busbar; the non-conductive parts, bushings, three-position operating mechanisms, circuit breaker operating mechanisms, screws, nuts and fixings in the sealed poles are removed, and at the same time, the small round holes and rounded corners in the retained components are removed, the support components are simplified into a flat plate form, and the secondary equipment in the instrument room of the switch cabinet is removed to complete the simplification of the support components and the internal layout of the cabinet body.

3. A method for modeling temperature field of medium voltage environmentally friendly gas insulated switchgear according to claim 2, characterized in that: In the S2, the electromagnetic properties include the electrical conductivity and dielectric constant of the conductor, the thermal physical parameters include thermal conductivity, specific heat capacity, density, and thermal expansion coefficient, and the material settings are specifically as follows: the material of the top busbar and the lower busbar is set to copper; the three-position switch is set to copper; the conductive part of the vacuum circuit breaker is set to copper alloy, and the support component is set to stainless steel; When setting electromagnetic properties, consider the nonlinear relationship between the conductivity of the conductor and the temperature, and follow the formula: ； Where, T represents temperature; is the initial temperature; It represents the conductivity of the conductor at temperature T; is the initial temperature The conductivity under is the temperature coefficient of resistance of the conductor material.

4. A method for modeling a temperature field of a medium voltage environmentally friendly gas insulated switchgear according to claim 1, characterized in that: In the above S3, when calculating the resistance loss, the resistance of the conductor itself and the contact resistance between the components are calculated, and the influence of the conductor material characteristics, the contact surface state, the connection method, and the change of the conductor conductivity with temperature are comprehensively considered, and the heat source is calculated according to the following formula: ； Where P is the power generated by resistance loss; I is the current; is the connection mode coefficient; is the contact surface state coefficient; is the resistance temperature coefficient of the conductor material; t is the actual temperature; is the reference temperature; The conductor is at a reference temperature The self-resistance under is the contact resistance under ideal contact conditions.

5. A method for modeling temperature field of medium voltage environmentally friendly gas insulated switchgear according to claim 4, characterized in that: For clean, flat, non-oxidized contact surfaces, The value is 1; for contact surfaces with dirt, roughness or oxidation, >1; for welding connection, The value is 0.8-1; for bolt connections, Greater than 1.

6. A method for modeling temperature field of medium voltage environmentally friendly gas insulated switchgear according to claim 1, characterized in that: In S5, the flow state of the fluid is determined based on the Grashof number Gr. When Gr>10 9 When Gr≤10 9 The laminar flow model is used.

7. A method for modeling temperature field of medium voltage environmentally friendly gas insulated switchgear according to claim 1, characterized in that: In S6, the radiation heat exchange power is calculated by an empirical formula , expressed as: ； In the formula, is the Stewart-Boltzmann constant; A is the radiating surface area; is the surface emissivity; and are the temperatures of the heat source and the cold source; is the surface roughness correction factor; is the surface roughness parameter; L is the characteristic length; m is the index of the effect of surface roughness on thermal radiation; The convective heat transfer coefficient h is calculated using the empirical formula, expressed as: ； Where Nu is the Nusselt number; k is the thermal conductivity of the gas; is the temperature gradient correction factor; and are the maximum and minimum temperatures, respectively; is the average temperature; n is the influence index of temperature gradient on heat transfer.

8. A method for modeling temperature field of medium voltage environmentally friendly gas insulated switchgear according to claim 2, characterized in that: In the above S7, the grid division strategy based on temperature contribution is to determine the division range of the hot spot area and other areas according to the pre-analysis or empirical judgment of the temperature field of the switch cabinet, specifically: The hot spots include the busbar overlap on the top of the screen, the busbar overlap on the bottom, the contact surface of the three-position switch, and the contact of the vacuum circuit breaker. When dividing the mesh, the mesh generation rules are followed, including orthogonality, smoothness, and reasonable size transition.

9. A method for modeling temperature field of medium voltage environmentally friendly gas insulated switchgear according to claim 1, characterized in that: In the above-mentioned S8, the frequency in the frequency domain is taken as 50 Hz, and suitable solvers are selected for different physical fields: the frequency domain solver is used for current calculation; the steady-state solver is used for heat conduction, radiation and convection heat transfer calculation.

10. A method for modeling temperature field of medium voltage environmentally friendly gas insulated switchgear according to claim 2, characterized in that: In the above-mentioned S10, the installation positions of the thermocouples are the overlap of the busbars on the top of the screen, the overlap of the lower busbars, and the contact surface of the three-position switch, and the data collection frequency and accuracy are set; When the simulation model after preliminary modeling is corrected according to the actual temperature data, the following temperature correction formula is used: ； Where q is the correction factor; C is a constant used to adjust the correction amplitude; is the actual temperature measured by the thermocouple; is the simulated temperature corresponding to the measurement position of the thermocouple; Based on q, the temperature-related parameters are adjusted. The temperature-related parameters include the resistance value in the resistance loss calculation and the convection heat transfer coefficient. The adjustment method is: Adjusted parameter = original parameter × q; By continuously comparing the actual temperature and the simulated temperature, calculating the correction factor, and adjusting the model parameters, the simulation model is gradually brought closer to the actual situation, so that the final simulation model can accurately predict the temperature field distribution of the switch cabinet under different working conditions.

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