A method for modeling the temperature field of medium-voltage environmentally friendly gas-insulated switchgear

Abstract

This invention belongs to the field of simulation analysis technology, specifically relating to a method for modeling the temperature field of a medium-voltage environmentally friendly gas-insulated switchgear. The steps include: constructing a three-dimensional geometric model of the switchgear and simplifying it; importing it into COMSOL multiphysics simulation software; performing electromagnetic-thermal bidirectional coupling modeling; adding a "surface-to-surface radiation" physical field; determining the fluid flow state based on the Grashof number and selecting an appropriate fluid dynamics model; setting environmental conditions and calculating the radiative heat exchange power and convective heat transfer coefficient; establishing a mesh generation strategy based on temperature contribution to obtain a preliminary simulation model; performing solution processing and post-processing of the solution results, analyzing hotspot distribution using temperature distribution maps; installing thermocouples in the hotspot areas within the actual switchgear to measure and obtain actual temperature data, and correcting the preliminary simulation model based on the actual temperature data. This invention can accurately predict temperature rise, providing strong protection for the safe operation of equipment.

Description

Technical Field

[0001] This invention belongs to the field of simulation analysis technology, specifically relating to a method for modeling the temperature field of medium-voltage environmentally friendly gas-insulated switchgear. Background Technology

[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 operation. However, with increasing environmental awareness and increasingly stringent environmental regulations, traditional SF6 gas, due to its significant negative impact on the greenhouse effect, is gradually being replaced by environmentally friendly alternative gases such as CO2 and N2.

[0003] While these environmentally friendly alternative gases offer advantages in terms of environmental performance, their thermophysical properties differ significantly from SF6 gas, particularly in thermal conductivity. This characteristic causes heat to easily accumulate inside the switchgear during operation, greatly increasing the risk of equipment overheating. Excessive equipment temperature rise not only accelerates the aging process of insulation materials and shortens their service life but may also trigger electrical faults such as short circuits and discharges, seriously threatening the safety and stability of the power system.

[0004] Currently, while some finite element method-based simulation software, such as COMSOL and ANSYS, exists, capable of simulating temperature rise distribution within gas-insulated switchgear, these methods often struggle to achieve an ideal balance between model accuracy and computational efficiency during the modeling process. Insufficient model accuracy may lead to inaccurate predictions of the internal temperature distribution of the switchgear, failing to detect potential overheating risks in a timely manner; while low computational efficiency increases the time cost of modeling and analysis, hindering the rapid optimization of switchgear design and operation strategies. 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 shortcomings of the prior art, the purpose of this invention is to provide a temperature field modeling method for medium-voltage environmentally friendly gas-insulated switchgear, which can accurately predict the temperature rise, provide strong protection for the safe operation of the equipment, and effectively avoid problems such as insulation material aging and electrical faults caused by excessive temperature rise.

[0006] To achieve the above objectives, this invention provides a method for modeling the temperature field of a medium-voltage environmentally friendly gas-insulated switchgear, comprising the following steps:

[0007] S1. Construct a three-dimensional geometric model of the switchgear using three-dimensional software, retaining the support components and conductor components, and simplifying the three-dimensional geometric model.

[0008] S2. Import the simplified 3D geometric model into COMSOL multiphysics simulation software, set the material of the conductor component, and assign the corresponding electromagnetic and thermal properties to the material.

[0009] S3. Using the electromagnetic-thermal coupling interface in COMSOL, perform electromagnetic-thermal bidirectional coupling modeling, consider resistance loss, and evaluate the heat source.

[0010] S4. Add the "surface-to-surface radiation" physical field to simulate the radiative heat exchange between components of the switchgear and between the components and the environment, and set the surface emissivity;

[0011] S5. Calculate the Grashof number, determine the fluid flow regime based on the Grashof number, and select the appropriate fluid dynamics model according to the determination result for the simulation of convective heat transfer in the switch cabinet.

[0012] S6. Set environmental conditions, including ambient temperature, humidity and atmospheric pressure, and calculate radiative heat exchange power and convective heat transfer coefficient to simulate the heat exchange process between the switch cabinet and the environment.

[0013] S7. Establish a mesh generation strategy based on temperature contribution, perform fine mesh generation on hot spots, and coarse mesh generation on other areas to obtain a preliminary simulation model.

[0014] S8. Select the "Frequency Domain-Steady State" solver and set the solver parameters;

[0015] S9. Post-process the solution results to obtain a temperature distribution map. Use the temperature distribution map to analyze the hot spot distribution and derive the temperature values ​​of the hot spot areas for comparison with actual temperature data.

[0016] S10. Based on the hot spot distribution obtained from the simulation, thermocouples are installed in the hot spot areas of the actual switchgear to measure and obtain actual temperature data. The simulation model is then corrected based on the actual temperature data to complete the final modeling of the temperature field of the switchgear.

[0017] As a preferred embodiment of the present invention, in S1, the three-dimensional software used is SolidWorks. The simplification process specifically involves retaining the support components and conductor components for the three-dimensional geometric model of the switchgear. The support components include the cabinet and the gas box, and the conductor components include the 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 fasteners in the solid-sealed poles are removed. At the same time, the small round holes and rounded corners in the retained components are removed, simplifying the support components to a flat plate form. The secondary equipment in the instrument room of the switchgear is also removed, thus completing the simplification process of the internal layout of the support components and the cabinet.

[0018] As a preferred embodiment of the present invention, in S2, the electromagnetic properties include the conductivity and dielectric constant of the conductor, the thermal properties include thermal conductivity, specific heat capacity, density, and coefficient of thermal expansion, and the material settings are as follows: the material of the top busbar and the bottom busbar is copper; the three-position switch is copper; the conductive part of the vacuum circuit breaker is copper alloy, and the supporting components are stainless steel.

[0019] When setting electromagnetic properties, the nonlinear relationship between conductor conductivity and temperature should be considered, following the formula:

[0020] ;

[0021] In the formula, T represents temperature; The initial temperature; This represents the conductivity of a conductor at temperature T. Initial temperature The conductivity at that point; is the temperature coefficient of resistance of the conductor material.

[0022] As a preferred embodiment of the present invention, in S3, when calculating the resistance loss, the calculation of the resistance of the conductor itself and the contact resistance between components takes into account the influence of conductor material characteristics, contact surface condition, connection method, and the change of conductor conductivity with temperature, and calculates the heat source according to the following formula:

[0023] ;

[0024] In the formula, P is the power generated by resistive loss; I is the current; For connection mode coefficients; This refers to the contact surface condition coefficient; t is the temperature coefficient of resistance of the conductor material; t is the actual temperature. For reference temperature; For the conductor at the reference temperature Its own resistance; This represents the contact resistance under ideal contact conditions.

[0025] As a preferred embodiment of the present invention, for clean, flat, and oxidation-free contact surfaces, The value is 1; for contact surfaces that are dirty, rough, or oxidized, >1; For welded connections, The value ranges from 0.8 to 1; for bolted connections, Greater than 1.

[0026] In a preferred embodiment of the present invention, in S5, the fluid flow regime is determined based on the Grashof number Gr. When Gr > 10 9 When Gr≤10, a turbulence model is used; when Gr≤109 At that time, a laminar flow model was adopted.

[0027] As a preferred embodiment of the present invention, in step S6, the radiative heat exchange power is calculated using an empirical formula. , is represented as:

[0028] ;

[0029] In the formula, is the Stuart-Boltzmann constant; A is the radiation surface area; Surface emissivity; and The temperatures of the heat source and the cold source; This is the surface roughness correction factor; is the surface roughness parameter; L is the characteristic length; m is the exponent of the effect of surface roughness on thermal radiation;

[0030] The convective heat transfer coefficient h is calculated using an empirical formula and expressed as:

[0031] ;

[0032] In the formula, Nu is the Nusselt number; k is the thermal conductivity of the gas; This is the temperature gradient correction factor; and These are the maximum and minimum temperatures, respectively. denoted as the average temperature; n is the exponent of the effect of the temperature gradient on heat transfer.

[0033] As a preferred embodiment of the present invention, in S7, the grid division strategy based on temperature contribution is to determine the division range of hot spot areas and other areas based on the pre-analysis or empirical judgment of the temperature field of the switchgear, specifically as follows:

[0034] Hotspot areas include the top busbar overlap, the bottom busbar overlap, the contact surface of the three-position switch, and the vacuum circuit breaker contacts; when performing mesh generation, the mesh generation rules should be followed, including orthogonality, smoothness, and reasonable size transition.

[0035] As a preferred embodiment of the present invention, in S8, the frequency in the frequency domain is 50Hz, and a suitable solver is selected for different physical fields: a frequency domain solver is selected for current calculation; a steady-state solver is selected for heat conduction, radiation and convection heat transfer calculation.

[0036] As a preferred embodiment of the present invention, in S10, the thermocouple is installed at the top busbar overlap, the bottom busbar overlap, and the contact surface of the three-position switch, and the data acquisition frequency and accuracy are set.

[0037] When correcting the simulation model after initial modeling based on actual temperature data, the following temperature correction formula is used:

[0038] ;

[0039] In the formula, q is the correction factor; C is a constant used to adjust the magnitude of the correction. The actual temperature measured by the thermocouple; This represents the simulated temperature corresponding to the measurement position of the thermocouple;

[0040] Based on q, temperature-related parameters are adjusted. These parameters include the resistance value in the resistance loss calculation and the convective heat transfer coefficient. The adjustment method is as follows:

[0041] Adjusted parameter = original parameter × q;

[0042] By continuously comparing actual and simulated temperatures, calculating correction factors, and adjusting model parameters, the simulation model gradually approaches the actual situation, enabling the final simulation model to accurately predict the temperature field distribution of the switchgear under different operating conditions.

[0043] The algorithm involved in this invention can be executed by an electronic device, which includes a memory, a processor, and a computer program stored in the memory and capable of running on the processor. The processor executes the software to implement the above-mentioned algorithm calculation.

[0044] The beneficial effects of this invention are:

[0045] This invention utilizes SolidWorks and COMSOL multiphysics simulation software to accurately model and deeply analyze the complex electrothermal effects inside the switchgear, focusing on precise simulation and optimization of temperature rise at hot spots. This enables accurate prediction of the switchgear temperature field, providing strong support for the safe and stable operation of the equipment.

[0046] This invention uses an electromagnetic-thermal-fluid multiphysics coupling model to accurately simulate the temperature distribution inside a medium-voltage environmentally friendly gas-insulated switchgear. Especially in key areas such as busbar joints, three-position contact surfaces, and circuit breaker contacts, it can accurately predict temperature rise, providing strong protection for the safe operation of the equipment and effectively avoiding problems such as insulation material aging and electrical faults caused by excessive temperature rise.

[0047] This invention significantly reduces model complexity and computational load by rationally simplifying the internal structure of the switchgear, removing components with minimal impact on heat generation and dissipation, simplifying the design of minute structures in conductor assemblies, and adopting a mesh generation strategy based on temperature contribution. This significantly improves the efficiency of simulation calculations and shortens the modeling and analysis time cycle, which is beneficial for rapidly optimizing the design and operation strategies of the switchgear.

[0048] This invention utilizes thermocouples to acquire actual temperature data and compares and corrects it with simulation results in real time. This allows the model to continuously adapt to changes in actual operating conditions, effectively compensating for discrepancies between model calculations and reality, and ensuring the model's high accuracy and reliability. This makes the model more accurate and practical in predicting switchgear temperature field distribution, assessing equipment operating status, and guiding fault diagnosis. Attached Figure Description

[0049] Figure 1 This is a flowchart illustrating the principle of this invention;

[0050] Figure 2 This is a simplified front view of the switchgear in an embodiment of the present invention.

[0051] Figure 3 This is a simplified left-side view of the switch cabinet in an embodiment of the present invention. Detailed Implementation

[0052] The embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0053] like Figure 1 As shown, a method for modeling the temperature field of a medium-voltage environmentally friendly gas-insulated switchgear includes the following steps:

[0054] S1. Construct a three-dimensional geometric model of the switchgear using three-dimensional software, retaining the support components and conductor components, and simplifying the three-dimensional geometric model.

[0055] S2. Import the simplified 3D geometric model into COMSOL multiphysics simulation software, set the material of the conductor component, and assign the corresponding electromagnetic and thermal properties to the material.

[0056] S3. Using the electromagnetic-thermal coupling interface in COMSOL, perform electromagnetic-thermal bidirectional coupling modeling, consider resistance loss, and evaluate the heat source.

[0057] S4. Add the "surface-to-surface radiation" physical field to simulate the radiative heat exchange between components of the switchgear and between the components and the environment, and set the surface emissivity;

[0058] S5. Calculate the Grashof number, determine the fluid flow regime based on the Grashof number, and select the appropriate fluid dynamics model according to the determination result for the simulation of convective heat transfer in the switch cabinet.

[0059] S6. Set environmental conditions, including ambient temperature, humidity and atmospheric pressure (measured or set according to the actual use environment), and calculate the radiative heat exchange power and convective heat transfer coefficient to simulate the heat exchange process between the switch cabinet and the environment.

[0060] S7. Establish a mesh generation strategy based on temperature contribution, perform fine mesh generation on hot spots, and coarse mesh generation on other areas to obtain a preliminary simulation model.

[0061] S8. Select the "Frequency Domain-Steady State" solver and set the solver parameters;

[0062] S9. Post-process the solution results to obtain a temperature distribution map. Use the temperature distribution map to analyze the hot spot distribution and derive the temperature values ​​of the hot spot areas for comparison with actual temperature data.

[0063] S10. Based on the hot spot distribution obtained from the simulation, thermocouples are installed in the hot spot areas of the actual switchgear to measure and obtain actual temperature data. The simulation model is then corrected based on the actual temperature data to complete the final modeling of the temperature field of the switchgear.

[0064] In S1, SolidWorks is used as the 3D software. The simplification process specifically involves retaining the support components and conductor components in the 3D geometric model of the switchgear. The support components include the cabinet and gas box, while the conductor components include the top busbar, three-position switch, conductive parts of the vacuum circuit breaker, and the lower busbar. Non-conductive parts, bushings, three-position operating mechanisms, circuit breaker operating mechanisms, screws, nuts, and fasteners in the solid-sealed poles are removed. Simultaneously, small holes and rounded corners in the retained components are removed, simplifying the support components to a flat plate form. Secondary equipment in the switchgear's instrument room is also removed, completing the simplification of the support components and the internal layout of the cabinet. This simplification method retains only the main heat sources and key structures. The simplified switchgear structure is as follows: Figure 2 and Figure 3 As shown.

[0065] Components such as screws and nuts play a relatively minor role in the overall electrothermal performance of the switchgear, but their presence increases model complexity and reduces computational efficiency. Removing them can effectively improve computational speed without significantly affecting model accuracy. Conductor components and other structures 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 accurate analysis.

[0066] In actual conductor assemblies, minute structural details such as small holes and rounded corners exist to some extent, but their impact on overall ohmic losses is negligible; however, they significantly increase the computational complexity of the model. Further simplification of the support components into a flat plate and omission of secondary equipment within the instrumentation chamber reduces the complexity of the simulation model. These design simplifications allow the model to focus more on key electrothermal effects, improving computational efficiency without significantly impacting model accuracy.

[0067] In S2, electromagnetic properties include the conductor's conductivity and dielectric constant, while thermophysical parameters include thermal conductivity, specific heat capacity, density, and coefficient of thermal expansion. These parameters are all based on the characteristic data of the materials used in actual applications and maintain a high degree of consistency and accuracy throughout the simulation. Thermal conductivity determines a material's ability to conduct heat, while specific heat capacity affects the rate at which a material absorbs and releases heat. Accurately setting these parameters ensures that the simulation model matches actual conditions when simulating heat conduction and heat exchange processes, improving the reliability of the simulation results.

[0068] The specific material settings are as follows: the top busbar and bottom busbar of the screen are made of copper; the three-position switch is made of copper; the conductive parts of the vacuum circuit breaker are made of copper alloy, and the supporting components are made of stainless steel.

[0069] When setting electromagnetic properties, the nonlinear relationship between conductor conductivity and temperature should be considered, following the formula:

[0070] ;

[0071] In the formula, T represents temperature; The initial temperature; This represents the conductivity of a conductor at temperature T. Initial temperature The conductivity at that point; is the temperature coefficient of resistance of the conductor material.

[0072] Based on conductor materials and experimental measurements Electrical conductivity is one of the key factors affecting the temperature rise of a conductor, and its nonlinear relationship with temperature is crucial in the simulation process. Using this formula, the model can dynamically adjust the conductivity calculation based on temperature changes, thereby more accurately simulating the resistance changes and energy losses of the conductor under different temperature conditions, and truly reflecting the electrothermal performance under actual operating conditions.

[0073] Because the stainless steel casing of the switchgear is antimagnetic, eddy current losses are negligible under normal operating conditions; meanwhile, dielectric losses have a relatively small impact on overall heat energy. Therefore, in this modeling method, after comprehensive consideration, resistive losses are chosen as the main heat source for the switchgear.

[0074] In S3, when calculating resistive losses, the calculation of the conductor's own resistance and the contact resistance between components comprehensively considers the influence of conductor material properties, contact surface condition, connection method, and the change of conductor conductivity with temperature, and calculates the heat source according to the following formula:

[0075] ;

[0076] In the formula, P is the power generated by resistive loss; I is the current; For connection mode coefficients; This refers to the contact surface condition coefficient; t is the temperature coefficient of resistance of the conductor material; t is the actual temperature. For reference temperature; For the conductor at the reference temperature Its own resistance; This represents the contact resistance under ideal contact conditions.

[0077] For clean, smooth, and non-oxidized contact surfaces, The value is 1; for contact surfaces that are dirty, rough, or oxidized, >1; For welded connections, the connection is relatively tight and current transmission is good. The value should be between 0.8 and 1; for bolted connections, insufficient tightening is a common issue. Greater than 1.

[0078] In S5, the fluid flow regime is determined based on the Grashof number Gr, and a suitable fluid model is selected according to the determination result, thereby optimizing the simulation accuracy of convective heat transfer inside the switchgear. When Gr > 10 9 When Gr≤10, a turbulence model is used; when Gr≤10 9 At that time, a laminar flow model was adopted.

[0079] The Grashof number reflects the strength of natural convection. Based on its calculation results, it can be determined whether the fluid flow is laminar or turbulent, thus providing a basis for selecting a suitable fluid dynamics model.

[0080] In S6, the radiative heat exchange power is calculated using empirical formulas. , is represented as:

[0081] ;

[0082] In the formula, is the Stuart-Boltzmann constant; A is the radiation surface area; Surface emissivity; and The temperatures of the heat source and the cold source; This is a surface roughness correction factor (usually with a value of 0-0.1). is the surface roughness parameter (usually taken as 0.1-10 μm); L is the characteristic length; m is the exponent of the effect of surface roughness on thermal radiation (usually taken as 0.1-1).

[0083] The convective heat transfer coefficient h is calculated using an empirical formula and expressed as:

[0084] ;

[0085] In the formula, Nu is the Nusselt number; k is the thermal conductivity of the gas; This is the temperature gradient correction factor (related to fluid type and flow regime). and These are the maximum and minimum temperatures, respectively. is the average temperature; n is the influence index of the temperature gradient on heat transfer (obtained by fitting experimental data).

[0086] The parameters Nu, k, and L are precisely selected based on actual environmental conditions and the structural characteristics of the switchgear to ensure the accuracy of the convective heat transfer simulation. For example, ambient temperature, wind speed, and the shape and size of the switchgear enclosure all affect the values ​​of these parameters, thus affecting the calculated convective heat transfer coefficient.

[0087] In S7, the temperature contribution-based meshing strategy determines the division range of hotspot regions and other regions based on pre-analysis or empirical judgment of the switchgear temperature field, in order to optimize the balance between simulation accuracy and computational efficiency. Specifically:

[0088] Hotspot areas include the top busbar overlap, the bottom busbar overlap, the contact surface of the three-position switch, and the vacuum circuit breaker contacts. When performing mesh generation, the mesh generation rules are followed, including orthogonality, smoothness, and reasonable size transition, to ensure mesh quality and computational stability.

[0089] During the simulation, the focus was on hotspot areas such as busbar overlaps, three-position switch contacts, and circuit breaker contacts within the gas chamber. Due to their unique structure and operating methods, these areas are prone to increased contact resistance during actual operation, leading to current concentration, high temperature rise, and the formation of hotspots. For example, factors such as the overlap quality, contact area, and surface roughness of the busbar overlaps all affect the contact resistance; changes in the contact surface state during three-position switch switching cause resistance fluctuations; and during circuit breaker opening and closing operations, the instantaneous arc and current surge cause a rapid increase in contact temperature. Accurate simulation of the temperature rise in these hotspot areas allows for the early detection of potential overheating risks, providing crucial protection for the safe operation of the equipment.

[0090] To improve simulation efficiency, a meshing strategy based on temperature contribution was adopted. In potential hotspot areas, such as busbar joints and circuit breaker contacts, where drastic temperature changes significantly impact equipment safety, a fine mesh was used. Fine meshes can more accurately capture subtle temperature field changes in these areas, precisely describing temperature gradient variations in hotspot regions, thus improving simulation accuracy. In other less temperature-sensitive areas, such as parts of the switchgear enclosure, where temperature changes are relatively mild and have limited impact on the overall temperature field, a coarse mesh was used. Coarse meshes can significantly reduce computational load and improve efficiency without significantly affecting accuracy. During meshing, a combination of Cartesian coordinates and tetrahedral meshes was used, with mesh density appropriately allocated based on the model's geometry and temperature distribution characteristics. Simultaneously, certain mesh generation rules were followed, such as mesh orthogonality, smoothness, and reasonable size transitions, to ensure mesh quality and computational stability. This optimization strategy effectively improves the efficiency of the entire simulation process while maintaining simulation accuracy in critical areas, making the modeling method more practical and feasible.

[0091] In S8, the frequency in the frequency domain is 50Hz. For different physical fields, a suitable solver is selected: the frequency domain solver is used for current calculation; the steady-state solver is used for heat conduction, radiation and convection heat transfer calculation.

[0092] To further improve model accuracy, thermocouples were used to acquire actual temperature data at key locations within the environmentally friendly gas-insulated switchgear. Thermocouples, as high-precision temperature sensors, offer advantages such as fast response, high measurement accuracy, and good stability. Careful selection of thermocouple installation locations ensured they accurately reflected critical temperature changes within the switchgear, such as the core of hotspot areas and connection points where temperature fluctuations were frequent. Appropriate data acquisition frequencies (determined based on the rate of temperature change and model calibration requirements, such as once per second or several times per minute) and accuracy (determined based on the thermocouple sensor accuracy and model requirements, such as accuracy to 0.1℃ or 0.5℃) were set.

[0093] In S10, the thermocouples are installed at the top busbar overlap, the bottom busbar overlap, and the contact surface of the three-position switch, and the data acquisition frequency and accuracy are set.

[0094] When correcting the simulation model after initial modeling based on actual temperature data, the following temperature correction formula is used:

[0095] ;

[0096] In the formula, q is the correction factor; C is a constant (a constant determined based on experience, and in this embodiment, it is taken as 0.5) used to adjust the correction magnitude; The actual temperature measured by the thermocouple; This represents the simulated temperature corresponding to the measurement position of the thermocouple;

[0097] Based on q, temperature-related parameters are adjusted, including the contact resistance value in the resistance loss calculation. The convective heat transfer coefficient h is adjusted as follows:

[0098] Adjusted parameter = original parameter × q;

[0099] By continuously comparing actual and simulated temperatures, calculating correction factors, and adjusting model parameters, the simulation model gradually approaches the actual situation (the model calculation results and measured temperature data achieve a high degree of consistency), enabling the final simulation model to accurately predict the temperature field distribution of the switchgear under different operating conditions.

[0100] Furthermore, it can be combined with IoT technology to collect real-time temperature data inside the switch cabinet and transmit the data to the cloud via wireless communication technology. The cloud's computing resources can then be used to correct the simulation model in real time, ensuring the model's high accuracy.

[0101] To improve the accuracy and adaptability of the simulation model, the parameter adjustment method can be further improved by introducing a nonlinear adjustment function. This function not only considers the difference between the actual temperature and the simulation temperature but also incorporates the effects of temperature gradient and environmental conditions, allowing for a more comprehensive parameter adjustment. Let the original parameter be A, the adjusted parameter be B, and the ambient temperature be... The adjustment method is as follows:

[0102] ;

[0103] 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 actual and simulated temperatures can be captured more accurately, improving the model's adaptability and accuracy. By normalizing to ambient temperature, the relativity and robustness of the adjustment are ensured, enabling the model to maintain high accuracy under different environmental conditions. By adjusting coefficients a, b, and c, the model can flexibly adapt to different equipment and operating conditions, improving its versatility and applicability. Coefficients a, b, and c are determined using experimental or historical data, and the least squares method is used to automatically adjust coefficients a, b, and c based on the difference between actual and simulated temperatures.

[0104] The acquisition frequency and accuracy of measurement data should be set reasonably according to the requirements of model calibration. A higher acquisition frequency can obtain more detailed temperature change information, but it will increase the data processing workload; appropriate accuracy can ensure the reliability of measurement data and provide an accurate basis for model calibration. The actual temperature data acquired by thermocouples is compared and analyzed with the temperature results calculated by the simulation model. Based on the differences between the two, the parameters and boundary conditions of the simulation model are adjusted and corrected. For example, if the measured temperature is higher than the simulated temperature, it may be necessary to check whether the resistance loss calculation is accurate, whether the convective heat transfer coefficient setting is reasonable, etc., and adjust the model parameters accordingly. Through continuous data comparison and model calibration, the model can gradually approach the actual situation, thereby improving the model accuracy and enabling it to more accurately predict the temperature field distribution of the switchgear under different operating conditions, providing a more reliable basis for equipment design optimization, operation monitoring, and fault prevention.

Claims

1. A method for modeling temperature field of a medium voltage environmentally friendly gas insulated switchgear, characterized in that Comprise the following steps: S1, a three-dimensional software is used to construct the three-dimensional geometric model of the switch cabinet, the support assembly and the conductor assembly are retained, and the three-dimensional geometric model is simplified; S2, the three-dimensional geometric model after the simplification is imported into the COMSOL multi-physics field simulation software, the material of the conductor assembly is set, and the corresponding electromagnetic properties and thermal physical parameters are given to the material; S3, the electromagnetic-thermal two-way coupling modeling is carried out by using the electromagnetic-thermal coupling interface in COMSOL, the resistance loss is considered, and the heat source is evaluated; When calculating the resistance loss, the conductor resistance and the contact resistance between the elements are calculated, the influence of the conductor material characteristics, the contact surface state, the connection mode and the change of the conductor conductivity with temperature are considered, and the heat source is calculated according to the following formula: ； where P is the power generated by the resistive losses; I is the current; is the connection mode coefficient; is the contact surface state coefficient; is the resistive temperature coefficient of the conductor material; t is the actual temperature; For reference temperature; For the conductor at the reference temperature Its own resistance; The contact resistance under ideal contact conditions; for clean, flat, non-oxidized contact surfaces, 1 ; for contact surfaces with dirt, roughness or oxidation, > 1 ; for welded connections, 0.8 - 1 ; for bolted connections, > 1 ; S4, the "surface-to-surface radiation" physical field is added, the radiation heat exchange between the components of the switch cabinet and the environment is simulated, and the surface emissivity is set; S5, the Grashof number is calculated, the fluid flow state is determined based on the Grashof number, and the corresponding fluid dynamics model is selected according to the determination result for simulating the convection heat exchange in the switch cabinet; S6, the environmental conditions including the environmental temperature, humidity and atmospheric pressure are set, and the radiation heat exchange power and the convection heat exchange coefficient are calculated for simulating the heat exchange process between the switch cabinet and the environment; S7, a grid division strategy based on temperature contribution is established, fine grid division is performed on the hot spot area, and coarse processing is performed on other areas to obtain a preliminary modeling simulation model; S8, a "frequency domain-steady state" solver is selected, and the solver parameters are set; S9, the solution result is post-processed to obtain a temperature distribution map, the hot spot distribution is analyzed by using the temperature distribution map, the temperature value of the hot spot area is derived, and the actual temperature data is compared; S10, according to the hot spot distribution obtained by simulation, a thermocouple is installed in the hot spot area of the actual switch cabinet to measure and obtain the actual temperature data, the preliminary modeling simulation model is corrected according to the actual temperature data, and the final modeling of the switch cabinet temperature field is completed.

2. The temperature field modeling method for a medium voltage environmentally friendly gas insulated switchgear according to claim 1, characterized in that: In the S1, the three-dimensional software adopts SolidWorks, and the simplification process is as follows: for the three-dimensional geometric model of the switch cabinet, the support assembly and the conductor assembly are retained, the support assembly includes the cabinet body and the gas tank, and the conductor assembly includes the screen top bus, the three-position switch, the conductive part of the vacuum circuit breaker and the lower bus; the non-conductive part in the solid sealed pole, the sleeve, the three-position operating mechanism, the circuit breaker operating mechanism, the screw, the nut and the fixing part are removed, at the same time, the small round holes and the round corners in the retained components are removed, the support assembly is simplified into a flat plate form, and the secondary equipment in the instrument room of the switch cabinet is removed to complete the simplification processing of the support assembly and the internal layout of the cabinet body.

3. The temperature field modeling method of a 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 the dielectric constant of the conductor, and the thermal physical parameters include the thermal conductivity, the specific heat capacity, the density and the thermal expansion coefficient; the material setting is as follows: the materials of the screen top bus and the lower bus are set as copper; the three-position switch is set as copper; the conductive part of the vacuum circuit breaker is set as copper alloy, and the support assembly is set as stainless steel; When setting the electromagnetic properties, the nonlinear relationship between the conductor conductivity and the temperature change is considered, and the formula is followed: ； where T represents temperature; is the initial temperature; represents the conductivity of the conductor at temperature T; is the initial temperature of the conductivity at temperature T; is the temperature coefficient of resistance of the conductor material.

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

5. The temperature field modeling method of a medium voltage environmentally friendly gas insulated switchgear according to claim 1, characterized in that: In the S6, the radiant heat exchange power is calculated by an empirical formula is expressed as: ； wherein is the stuart-boltzmann constant; A is the radiating surface area; is the surface emissivity; and is the temperature 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 the surface roughness on the thermal radiation; The heat transfer coefficient h is calculated by using an empirical formula and is expressed as: ； wherein Nu is the Nusselt number; k is the thermal conductivity of the gas; is a temperature gradient correction factor; and are the maximum and minimum temperatures, respectively; is the average temperature; and n is an index of the effect of the temperature gradient on heat transfer.

6. The temperature field modeling method of a medium voltage environmentally friendly gas insulated switchgear according to claim 2, characterized in that: In the 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 experience judgment of the switch cabinet temperature field, and specifically is: The hot spot area includes the top busbar lap joint, the lower busbar lap joint, the three-position switch contact surface and the vacuum circuit breaker contact; when the grid division is performed, the grid generation rules are followed, including orthogonality, smoothness and size transition rationality.

7. The temperature field modeling method of a medium voltage environmentally friendly gas insulated switchgear according to claim 1, characterized in that: In the S8, the frequency value of the frequency domain is 50 Hz, and an appropriate solver is selected for different physical fields: the frequency domain solver is selected for current calculation; the steady-state solver is selected for heat conduction, radiation and convection heat transfer calculation.

8. The temperature field modeling method of a medium voltage environmentally friendly gas insulated switchgear according to claim 2, characterized in that: In the S10, the installation position of the thermocouple is the top busbar lap joint, the lower 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 a correction factor; C is a constant to adjust the magnitude of the correction; is the actual temperature measured by the thermocouple; is the simulated temperature corresponding to the measurement location of the thermocouple; Based on q, the temperature-related parameters are adjusted, including the resistance value in the resistance loss calculation and the convection heat transfer coefficient, and the adjustment method is: Adjusted parameter = original parameter x q; By continuously comparing the actual temperature and the simulation temperature, the correction factor is calculated, and the model parameters are adjusted, so that the simulation model gradually approaches the actual situation, and the finally modeled simulation model can accurately predict the temperature field distribution of the switch cabinet under different working conditions.

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