Simulation System and Method for Oil-Immersed Transformers Based on Similarity Theory (Scaled-Down Model)

Abstract

This invention discloses a scaled-down model simulation system and method for oil-immersed transformers based on similarity theory, comprising: S1 determining the transformer model and structural parameters required for multiphysics analysis, as well as the similarity ratio of the scaled-down model for simulating physical phenomena; S2 determining the eddy current field control equations adapted to the transformer's electromagnetic field using Maxwell's equations, and deriving the eddy current field similarity criterion based on similarity theory; S3 determining the energy conservation similarity criterion based on the energy conservation equation; S4 determining the momentum conservation similarity criterion based on the momentum conservation equation; S5 determining the convective heat transfer similarity criterion based on convective heat transfer boundary conditions; S6 determining the heat flow compensation principle by integrating various similarity criteria, performing temperature-fluid field simulation, and comparing the simulation results with those of the original structural model and prototype experimental results. This invention is computationally simple, highly accurate, and efficient, and can be well applied to engineering practice.

Description

Technical Field

[0001] This invention belongs to the field of transformer multiphysics simulation technology, and particularly relates to a method for simulating a scaled-down model of an oil-immersed transformer based on similarity theory. Background Technology

[0002] Transformers are among the most critical pieces of equipment in power transmission. They are numerous and complex in structure, and their operational safety directly impacts system reliability. Transformer temperature rise is a significant factor affecting transformer operating conditions, physical conditions, and insulation life. To ensure the safety and efficiency of transformer equipment during operation and to prevent malfunctions, establishing transformer models for multiphysics simulation and experimental verification of operating conditions is of great importance.

[0003] The main methods for conducting simulation tests on oil-immersed transformers include prototype simulation tests and similar model simulation tests. Prototype simulation tests suffer from drawbacks such as high cost, long testing time, and poor controllability, and their implementation is also extremely difficult. Similar model simulation tests, due to their good economic efficiency and practicality, are often used to replace prototype models to indirectly simulate equipment performance and have been widely applied in various fields such as aircraft and shipbuilding. Utilizing similar models to gain a deeper understanding of transformer state evolution, temperature rise patterns, and failure probabilities has significant practical engineering application value. Summary of the Invention

[0004] The purpose of this invention is to provide a simulation system and method for a scaled-down model of an oil-immersed transformer based on similarity theory. This method is highly accurate, efficient, and feasible.

[0005] To achieve this objective, the oil-immersed transformer scaled-down model simulation system designed in this invention includes a transformer scaled-down model building module, an eddy current field similarity model simulation module, an energy conservation similarity model determination module, a momentum conservation similarity model determination module, a convective heat transfer similarity model determination module, and a temperature and fluid field simulation module. The transformer scaled-down model building module is used to determine the transformer's model and structural parameters, as well as the similarity ratio of the scaled-down model for simulating physical phenomena. The eddy current field similarity model simulation module is used to determine the eddy current field control equations adapted to the transformer's electromagnetic field and derive the similarity ratio based on similarity theory. The eddy current field similarity criteria are derived, and eddy current field simulation is performed. The energy conservation similarity model determination module is used to determine the energy conservation similarity criteria. The momentum conservation similarity model determination module is used to determine the momentum conservation similarity criteria. The convective heat transfer similarity model determination module is used to determine the convective heat transfer similarity criteria based on the convective heat transfer boundary conditions. The temperature fluid field simulation module determines the heat flow compensation principle based on the eddy current field similarity criteria, energy conservation similarity criteria, momentum conservation similarity criteria, and convective heat transfer similarity criteria, performs temperature fluid field simulation, and compares the simulation results with the original structural model and the prototype experimental results.

[0006] The convection heat transfer similarity model determination module outputs multiple parameters, including low-pressure heat source, high-pressure heat source, ambient temperature, upper convection heat transfer coefficient, lower convection heat transfer coefficient, and side convection heat transfer coefficient. The low-pressure heat source serves as the loss of the low-pressure winding in the temperature fluid field simulation module, the high-pressure heat source serves as the loss of the high-pressure winding in the temperature fluid field simulation module, the ambient temperature is used to determine the temperature boundary conditions in the temperature fluid field simulation module, and the upper convection heat transfer coefficient, lower convection heat transfer coefficient, and side convection heat transfer coefficient are used as heat transfer boundary conditions in the temperature fluid field simulation module.

[0007] The specific implementation method of the eddy current field similarity model simulation module is as follows:

[0008] Based on the three-dimensional model of the transformer, the eddy current field similarity criterion is derived through the eddy current field control equation. The transformer loss under sinusoidal excitation steady-state operating conditions is calculated using the finite element method. The loss is used as a heat source as the excitation of the model based on the subsequent temperature and fluid field similarity theory. Combined with boundary conditions such as environmental factors, the temperature and fluid field of the transformer under various operating conditions is simulated to obtain temperature and fluid field distribution maps.

[0009] The steady-state operating conditions include one or more of rated load, overload, and underload.

[0010] The external environmental parameters required for the transformer convection heat transfer similarity model determination module include one or more of temperature, wind speed, and humidity.

[0011] The specific implementation method of electromagnetic field similarity theory is derived from the eddy current field control equations as follows:

[0012] The governing equations of the eddy current field adapted to the electromagnetic field of the transformer were determined using Maxwell's equations, and the similarity criteria of the eddy current field were derived based on the equation analysis method, namely Γ1=μσlφ / A, Γ2=μσl 2 / t,Γ3=μJ s l 2 / A, where Γ1 represents the ratio of potential gradient to electric field strength, Γ2 represents Faraday's law of electromagnetic induction, and Γ3 represents Maxwell-Ampère's law. Γ1, Γ2, and Γ3 represent the three similarity criteria required for the eddy current field similarity model. μ represents magnetic permeability, σ represents electrical conductivity, l represents structural parameters, φ represents magnetic flux, A represents magnetic vector potential, t represents the time constant corresponding to the power supply frequency, and J s This represents the source current density.

[0013] The specific implementation method of the energy conservation similarity model determination module is as follows: Based on the energy conservation equation, the energy conservation similarity criterion is determined, resulting in Γ4=ρUL / μ f Γ5 is a measure of the ratio of inertial force to viscous force in transformer oil. f c p / k represents the ratio of oil flow diffusion thickness to heat diffusion thickness, where ρ represents transformer oil density, U represents oil flow velocity, L represents structural variables, and μ f c represents dynamic viscosity. p Transformer oil constant pressure heat capacity, k represents the thermal conductivity of transformer oil.

[0014] The specific implementation method of the momentum conservation similarity model determination module is as follows: Based on the momentum conservation equation, determine the momentum conservation similarity criterion to obtain Γ6=βgΔTρ 2 L 3 / μ f 2 , representing the measure of buoyancy and viscous forces in the natural convective heat transfer of transformer oil, where β represents the thermal expansion coefficient of transformer oil, g represents the acceleration due to gravity, ΔT represents the temperature gradient, ρ represents the density of transformer oil, L represents the similarity ratio of the similarity model, and μ f This indicates the thermal conductivity of transformer oil.

[0015] The specific implementation method of the convective heat transfer similarity model determination module is as follows: the convective heat transfer similarity criterion is determined according to the convective heat transfer boundary conditions, and Γ7=hL / k is obtained, which represents the dimensionless temperature gradient on the transformer and the solid heat transfer wall, h represents the convective heat transfer coefficient of the wall, and L represents the structural variable.

[0016] The convective heat transfer criteria in the convective heat transfer similarity model determination module are obtained based on Newton's law of cooling and Fourier's law of heat transfer.

[0017] A scaled-down simulation method for oil-immersed transformers based on similarity theory includes the following steps:

[0018] Step 1: Determine the transformer model and the structural parameters required for multiphysics analysis, as well as the similarity ratio of the scaled-down model for simulating physical phenomena.

[0019] Step 2: Determine the eddy current field control equations that are compatible with the electromagnetic field of the transformer using the Maxwell equations, derive the eddy current field similarity criteria based on similarity theory, and perform eddy current field simulation.

[0020] Step 3: Determine the energy conservation similarity criterion based on the energy conservation equation;

[0021] Step 4: Determine the momentum conservation similarity criterion based on the momentum conservation equation;

[0022] Step 5: Determine the convective heat transfer similarity criterion based on the convective heat transfer boundary conditions;

[0023] Step 6: Determine the heat flow compensation principle by integrating various similarity criteria, perform temperature-fluid field simulation, and compare the simulation results with the original structural model and the prototype experimental results.

[0024] The structural parameters in step 1 include the number and spacing of winding discs, the length and width of oil passages, and the position of the oil baffle; the similarity ratio of the scaled-down model is determined according to engineering test requirements or to control manufacturing costs.

[0025] The specific implementation method of step 2 is as follows: Based on the three-dimensional model of the transformer, the eddy current field similarity criterion is derived through the eddy current field control equation, and the transformer loss under sinusoidal excitation steady-state operating conditions is calculated using the finite element method; the loss is used as a heat source as the excitation of the model based on the subsequent temperature and fluid field similarity theory, and combined with boundary conditions such as environmental factors, temperature and fluid field simulation is performed on the transformer under various operating conditions to obtain temperature field and fluid field distribution maps.

[0026] The steady-state operating conditions include one or more of rated load, overload, and underload.

[0027] The external environmental parameters required for the transformer convection heat transfer similarity model determination module include one or more of temperature, wind speed, and humidity;

[0028] The specific implementation method of electromagnetic field similarity theory is derived from the eddy current field control equations as follows:

[0029] The governing equations of the eddy current field adapted to the electromagnetic field of the transformer were determined using Maxwell's equations, and the similarity criteria of the eddy current field were derived based on the equation analysis method, namely Γ1=μσlφ / A, Γ2=μσl 2 / t,Γ3=μJ s l 2 / A, where Γ1 represents the ratio of potential gradient to electric field strength, Γ2 represents Faraday's law of electromagnetic induction, Γ3 represents Maxwell-Ampère's law, μ represents magnetic permeability, σ represents electrical conductivity, l represents structural parameters, φ represents magnetic flux, A represents magnetic vector potential, t represents the time constant corresponding to the power supply frequency, and J s Indicates the source current density;

[0030] Based on the eddy current field similarity criterion, when the electromagnetic field of the scaled-down model is similar to that of the original model, the power supply frequency similarity ratio should be a multiple of the square of the reciprocal of the structural similarity ratio.

[0031] The specific implementation method of step 3 is as follows: Based on the energy conservation equation, determine the energy conservation similarity criterion to obtain Γ4=ρUL / μ f Γ5 is a measure of the ratio of inertial force to viscous force in transformer oil. f c p / k represents the ratio of oil flow diffusion thickness to heat diffusion thickness, where ρ represents transformer oil density, U represents oil flow velocity, L represents structural variables, and μ f c represents dynamic viscosity. p Transformer oil constant pressure heat capacity, k represents the thermal conductivity of transformer oil;

[0032] The specific implementation method of step 4 is as follows: Based on the momentum conservation equation, determine the momentum conservation similarity criterion, and obtain Γ6=βgΔTρ 2 L 3 / μ f 2 , representing the measure of buoyancy and viscous forces in the natural convective heat transfer of transformer oil, where β represents the thermal expansion coefficient of transformer oil, g represents the acceleration due to gravity, ΔT represents the temperature gradient, ρ represents the density of transformer oil, L represents the similarity ratio of the similarity model, and μ f Indicates the thermal conductivity of transformer oil;

[0033] Step 5 outputs multiple values ​​from the following: low-pressure heat source, high-pressure heat source, ambient temperature, upper convection heat transfer coefficient, lower convection heat transfer coefficient, and side convection heat transfer coefficient. The convection heat transfer criterion in step 5 is obtained based on Newton's law of cooling and Fourier's law of heat transfer.

[0034] The beneficial effects of this invention are as follows:

[0035] (1) Based on the equation analysis method and dimensional analysis method, a multi-physics simulation method for a scaled-down transformer model is obtained. This method guides the implementation of electromagnetic field and temperature fluid field experiments of the scaled-down model, which can greatly save the time cost of prototype transformer experiments and can be well applied to engineering practice.

[0036] (2) The calculation is simple, accurate, efficient and feasible. Attached Figure Description

[0037] Figure 1 This is a system structure diagram of the present invention;

[0038] Figure 2 This is a flowchart of the method of the present invention;

[0039] Figure 3 This is a schematic diagram of a 3D model of a transformer;

[0040] Figure 4 This is a simulation diagram of the eddy current field under the original structural parameters of the transformer;

[0041] Figure 5 This is a schematic diagram of the eddy current field simulation of a model that is one-tenth similar to the original structural parameters of the transformer, based on the electromagnetic field similarity criterion.

[0042] Among them, 1-Transformer scaled-down model building module, 2-Eeddy current field similarity model simulation module, 3-Energy conservation similarity model determination module, 4-Momentum conservation similarity model determination module, 5-Convection heat transfer similarity model determination module, and 6-Temperature fluid field simulation module. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0044] A scaled-down model simulation system for oil-immersed transformers based on similarity theory, such as Figure 1 As shown, it includes a transformer scaled-down model building module 1, an eddy current field similarity model simulation module 2, an energy conservation similarity model determination module 3, a momentum conservation similarity model determination module 4, a convective heat transfer similarity model determination module 5, and a temperature fluid field simulation module 6.

[0045] The transformer scaled-down model building module 1 is used to determine the transformer model and the structural parameters required for multiphysics analysis, as well as the similarity ratio of the scaled-down model for simulating physical phenomena. The structural parameters include the number and spacing of winding discs, the length and width of oil channels, and the position of the oil baffle. The similarity ratio of the scaled-down model is determined according to the needs of engineering tests or to control manufacturing costs.

[0046] The eddy current field similarity model simulation module 2 is used to determine the eddy current field control equations that are compatible with the electromagnetic field of the transformer through the Maxwell equations, derive the eddy current field similarity criteria based on similarity theory, and perform eddy current field simulation.

[0047] The energy conservation similarity model determination module 3 is used to determine the energy conservation similarity criterion based on the energy conservation equation;

[0048] The momentum conservation similarity model determination module 4 is used to determine the momentum conservation similarity criterion based on the momentum conservation equation.

[0049] The convective heat transfer similarity model determination module 5 is used to determine the convective heat transfer similarity criterion based on the convective heat transfer boundary conditions.

[0050] The temperature-fluid field simulation module 6 determines the heat flow compensation principle based on the eddy current field similarity criterion, energy conservation similarity criterion, momentum conservation similarity criterion and convective heat transfer similarity criterion, performs temperature-fluid field simulation, and compares the simulation results with the original structural model and the prototype experimental results.

[0051] In the above technical solution, the convection heat transfer similarity model determination module 5 outputs multiple parameters, including low-pressure heat source, high-pressure heat source, ambient temperature, upper convection heat transfer coefficient, lower convection heat transfer coefficient, and side convection heat transfer coefficient. The low-pressure heat source serves as the loss of the low-pressure winding in the temperature fluid field simulation module 6, the high-pressure heat source serves as the loss of the high-pressure winding in the temperature fluid field simulation module 6, the ambient temperature is used to determine the temperature boundary conditions in the temperature fluid field simulation module 6, and the upper convection heat transfer coefficient, lower convection heat transfer coefficient, and side convection heat transfer coefficient are used as the heat transfer boundary conditions in the temperature fluid field simulation module 6.

[0052] The components of a transformer's 3D model include the core, windings, structural parts, and oil channels, such as... Figure 3 As shown.

[0053] In the above technical solution, the specific implementation method of the eddy current field similarity model simulation module 2 is as follows:

[0054] Based on the three-dimensional model of the transformer, the eddy current field similarity criterion is derived through the eddy current field control equation. The transformer loss under sinusoidal excitation steady-state operating conditions is calculated using the finite element method. The loss is used as a heat source as the excitation of the model based on the subsequent temperature and fluid field similarity theory. Combined with boundary conditions such as environmental factors, the temperature and fluid field of the transformer under various operating conditions is simulated to obtain temperature and fluid field distribution maps.

[0055] The steady-state operating conditions include one or more of rated load, overload, and underload.

[0056] The external environmental parameters required for the transformer convection heat transfer similarity model determination module include one or more of temperature, wind speed, and humidity.

[0057] In the above technical solution, the specific implementation method of deriving the electromagnetic field similarity theory through the eddy current field control equation is as follows:

[0058] The governing equations of the eddy current field adapted to the electromagnetic field of the transformer were determined using Maxwell's equations, and the similarity criteria of the eddy current field were derived based on the equation analysis method, namely Γ1=μσlφ / A, Γ2=μσl 2 / t,Γ3=μJ s l 2 / A, where Γ1 represents the ratio of potential gradient to electric field strength, Γ2 represents Faraday's law of electromagnetic induction, and Γ3 represents Maxwell-Ampère's law. Γ1, Γ2, and Γ3 represent the three similarity criteria required for the eddy current field similarity model. μ represents magnetic permeability, σ represents electrical conductivity, l represents structural parameters, φ represents magnetic flux, A represents magnetic vector potential, t represents the time constant corresponding to the power supply frequency, and J s Indicates the source current density;

[0059] Based on the eddy current field similarity criterion, when the electromagnetic field of the scaled-down model is similar to that of the original model, the power supply frequency similarity ratio should be a multiple of the square of the reciprocal of the structural similarity ratio. Eddy current field simulation is then performed based on the eddy current field similarity criterion. Figure 5 The structural parameters shown are Figure 4 1 / 10, Figure 4 , Figure 5 The high-voltage and low-voltage winding currents are the same. Figure 5 The power supply frequency of the scaled-down model is Figure 4 The magnetic vector potential is 1 / 10 of the original model, the magnetic induction intensity is 10 times that of the original model, and the current density in the winding is 10 times that of the original model, which verifies the correctness of the electromagnetic field similarity model.

[0060] In the above technical solution, the specific implementation method of the energy conservation similarity model determination module 3 is as follows:

[0061] Based on the energy conservation equation, the energy conservation similarity criterion is determined, resulting in Γ4=ρUL / μ f Γ5 is a measure of the ratio of inertial force to viscous force in transformer oil. f c p / k represents the ratio of oil flow diffusion thickness to heat diffusion thickness, where ρ represents transformer oil density, U represents oil flow velocity, L represents structural variables, and μ f c represents dynamic viscosity. p Transformer oil constant pressure heat capacity, k represents the thermal conductivity of transformer oil.

[0062] In the above technical solution, the specific implementation method of the momentum conservation similarity model determination module 4 is as follows:

[0063] Based on the momentum conservation equation, the momentum conservation similarity criterion is determined, resulting in Γ6=βgΔTρ 2 L 3 / μ f 2 , representing the measure of buoyancy and viscous forces in the natural convective heat transfer of transformer oil, where β represents the thermal expansion coefficient of transformer oil, g represents the acceleration due to gravity, ΔT represents the temperature gradient, ρ represents the density of transformer oil, L represents the similarity ratio of the similarity model, and μ f This indicates the thermal conductivity of transformer oil.

[0064] In the above technical solution, the specific implementation method of the convective heat transfer similarity model determination module 5 is as follows:

[0065] Based on the convective heat transfer boundary conditions, the convective heat transfer similarity criterion is determined, resulting in Γ7=hL / k, which represents the dimensionless temperature gradient between the transformer and the solid heat exchange wall, where h represents the convective heat transfer coefficient of the wall and L represents the structural variable.

[0066] In the above technical solution, the convective heat transfer criterion in the convective heat transfer similarity model determination module 5 is obtained based on Newton's law of cooling and Fourier's law of heat transfer.

[0067] A scaled-down simulation method for oil-immersed transformers based on similarity theory, such as... Figure 2 As shown, it includes the following steps:

[0068] Step 1: Determine the transformer model and the structural parameters required for multiphysics analysis, as well as the similarity ratio of the scaled-down model for simulating physical phenomena.

[0069] Step 2: Determine the eddy current field control equations that are compatible with the electromagnetic field of the transformer using the Maxwell equations, derive the eddy current field similarity criteria based on similarity theory, and perform eddy current field simulation.

[0070] Step 3: Determine the energy conservation similarity criterion based on the energy conservation equation;

[0071] Step 4: Determine the momentum conservation similarity criterion based on the momentum conservation equation;

[0072] Step 5: Determine the convective heat transfer similarity criterion based on the convective heat transfer boundary conditions;

[0073] Step 6: Determine the heat flow compensation principle by integrating various similarity criteria, perform temperature-fluid field simulation, and compare the simulation results with the original structural model and the prototype experimental results.

[0074] In the above technical solution, the structural parameters in step 1 include the number and spacing of winding discs, the length and width of oil passages, and the position of the oil baffle; the similarity ratio of the scaled-down model is determined according to the needs of engineering testing or to control manufacturing costs.

[0075] The specific implementation method of step 2 is as follows: Based on the three-dimensional model of the transformer, the eddy current field similarity criterion is derived through the eddy current field control equation, and the transformer loss under sinusoidal excitation steady-state operating conditions is calculated using the finite element method; the loss is used as a heat source as the excitation of the model based on the subsequent temperature and fluid field similarity theory, and combined with boundary conditions such as environmental factors, temperature and fluid field simulation is performed on the transformer under various operating conditions to obtain temperature field and fluid field distribution maps.

[0076] The steady-state operating conditions include one or more of rated load, overload, and underload.

[0077] The external environmental parameters required for the transformer convection heat transfer similarity model determination module include one or more of temperature, wind speed, and humidity;

[0078] The specific implementation method of electromagnetic field similarity theory is derived from the eddy current field control equations as follows:

[0079] The governing equations of the eddy current field adapted to the electromagnetic field of the transformer were determined using Maxwell's equations, and the similarity criteria of the eddy current field were derived based on the equation analysis method, namely Γ1=μσlφ / A, Γ2=μσl 2 / t,Γ3=μJ s l 2 / A, where Γ1 represents the ratio of potential gradient to electric field strength, Γ2 represents Faraday's law of electromagnetic induction, Γ3 represents Maxwell-Ampère's law, μ represents magnetic permeability, σ represents electrical conductivity, l represents structural parameters, φ represents magnetic flux, A represents magnetic vector potential, t represents the time constant corresponding to the power supply frequency, and J s Indicates the source current density;

[0080] Based on the eddy current field similarity criterion, when the electromagnetic field of the scaled-down model is similar to that of the original model, the power supply frequency similarity ratio should be a multiple of the square of the reciprocal of the structural similarity ratio.

[0081] The specific implementation method of step 3 is as follows: Based on the energy conservation equation, determine the energy conservation similarity criterion to obtain Γ4=ρUL / μ f Γ5 is a measure of the ratio of inertial force to viscous force in transformer oil. f c p / k represents the ratio of oil flow diffusion thickness to heat diffusion thickness, where ρ represents transformer oil density, U represents oil flow velocity, L represents structural variables, and μ f c represents dynamic viscosity. pTransformer oil constant pressure heat capacity, k represents the thermal conductivity of transformer oil;

[0082] The specific implementation method of step 4 is as follows: Based on the momentum conservation equation, determine the momentum conservation similarity criterion, and obtain Γ6=βgΔTρ 2 L 3 / μ f 2 , representing the measure of buoyancy and viscous forces in the natural convective heat transfer of transformer oil, where β represents the thermal expansion coefficient of transformer oil, g represents the acceleration due to gravity, ΔT represents the temperature gradient, ρ represents the density of transformer oil, L represents the similarity ratio of the similarity model, and μ f Indicates the thermal conductivity of transformer oil;

[0083] Step 5 outputs multiple values ​​from the following: low-pressure heat source, high-pressure heat source, ambient temperature, upper convection heat transfer coefficient, lower convection heat transfer coefficient, and side convection heat transfer coefficient. The convection heat transfer criterion in step 5 is obtained based on Newton's law of cooling and Fourier's law of heat transfer.

[0084] The contents not described in detail in this specification are prior art known to those skilled in the art. Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0085] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0086] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0087] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the invention, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the invention.

Claims

1. An oil-immersed transformer scaled model simulation system based on similarity theory, characterized in that: The module includes a transformer scaled-down model building module (1), an eddy current field similarity model simulation module (2), an energy conservation similarity model determination module (3), a momentum conservation similarity model determination module (4), a convective heat transfer similarity model determination module (5), and a temperature fluid field simulation module (6). The transformer scaled-down model building module (1) is used to determine the transformer model and structural parameters, as well as the similarity ratio of the scaled-down model for simulating physical phenomena. The eddy current field similarity model simulation module (2) is used to determine the eddy current field control equations that are compatible with the electromagnetic field of the transformer, and to derive the eddy current field similarity criteria based on similarity theory, and to perform eddy current field simulation. The energy conservation similarity model determination module (3) is used to determine the energy conservation similarity criterion; The momentum conservation similarity model determination module (4) is used to determine the momentum conservation similarity criterion; The convective heat transfer similarity model determination module (5) is used to determine the convective heat transfer similarity criterion based on the convective heat transfer boundary conditions; The temperature fluid field simulation module (6) determines the heat flow compensation principle based on the eddy current field similarity criterion, energy conservation similarity criterion, momentum conservation similarity criterion and convective heat transfer similarity criterion, performs temperature fluid field simulation, and compares the simulation results with the original structural model and the prototype experimental results.

2. The scaled-down model simulation system for oil-immersed transformers based on similarity theory as described in claim 1, characterized in that: The structural parameters in the transformer scale-down model building module (1) include the number and spacing of winding discs, the length and width of oil channels, and the position of the oil baffle. The similarity ratio of the scale-down model is determined according to the needs of engineering tests or to control manufacturing costs. The convection heat transfer similarity model determination module (5) outputs multiple parameters, including low-pressure heat source, high-pressure heat source, ambient temperature, upper convection heat transfer coefficient, lower convection heat transfer coefficient, and side convection heat transfer coefficient.

3. The similarity theory based oil immersed transformer scaled model simulation system of claim 1, wherein: The specific implementation method of the eddy current field similarity model simulation module (2) is as follows: Based on the three-dimensional model of the transformer, the eddy current field similarity criterion is derived through the eddy current field control equation. The loss of the transformer under sinusoidal excitation steady-state operating conditions is calculated using the finite element method. The loss is used as the heat source and as the excitation of the model based on the subsequent temperature and fluid field similarity theory. With environmental factors as boundary conditions, temperature and fluid field simulations of the transformer under various operating conditions are performed to obtain temperature and fluid field distribution maps. The steady-state operating conditions include one or more of rated load, overload, and underload. The external environmental parameters required by the convection heat transfer similarity model determination module include one or more of temperature, wind speed, and humidity.

4. The similarity theory based oil immersed transformer scaled model simulation system of claim 3, wherein: The specific implementation method of electromagnetic field similarity theory is derived from the eddy current field control equations as follows: The eddy current field control equations are determined by Maxwell equations, and the similarity criteria are derived based on the equation analysis method, which are , , where, represents the ratio of the electric potential gradient to the electric field intensity, represents the Faraday's law of electromagnetic induction, represents the Maxwell-Ampere law, represents the magnetic permeability, represents the electric conductivity, represents the structural parameter, represents the magnetic flux, represents the magnetic vector potential, represents the time constant corresponding to the power frequency, represents the source current density; Based on the eddy current field similarity criterion, when the electromagnetic field of the scaled-down model is similar to that of the original model, the power supply frequency similarity ratio should be a multiple of the square of the reciprocal of the structural similarity ratio.

5. The scaled-down model simulation system for oil-immersed transformers based on similarity theory as described in claim 1, characterized in that: The specific implementation method of the energy conservation similarity model determination module (3) is as follows: Based on the energy conservation equation, the energy conservation similarity criterion is determined, and the following is obtained: This is a measure of the ratio of inertial force to viscous force in transformer oil. This is a measure representing the ratio of oil flow diffusion thickness to heat diffusion thickness, where... Indicates the density of transformer oil. Indicates the oil flow velocity. Represents structural variables, Indicates dynamic viscosity. Transformer oil constant pressure heat capacity This indicates the thermal conductivity of transformer oil.

6. The scaled-down model simulation system for oil-immersed transformers based on similarity theory as described in claim 1, characterized in that: The specific implementation method of the momentum conservation similarity model determination module (4) is as follows: Based on the momentum conservation equation, the momentum conservation similarity criterion is determined, and the following is obtained: , represents the measure of buoyancy and viscous force in the natural convection heat transfer of transformer oil, where, This represents the coefficient of thermal expansion of transformer oil. Represents gravitational acceleration. Represents the temperature gradient. Indicates the density of transformer oil. This represents the similarity ratio of similar models. This indicates the thermal conductivity of transformer oil.

7. The scaled-down model simulation system for oil-immersed transformers based on similarity theory as described in claim 1, characterized in that: The specific implementation method of the convection heat transfer similarity model determination module (5) is as follows: Based on the convective heat transfer boundary conditions, the convective heat transfer similarity criterion is determined, and the results are obtained. This represents a measure of the dimensionless temperature gradient between the transformer and the solid heat exchange wall. This represents the convective heat transfer coefficient of the wall surface. Represents a structure variable.

8. The scaled-down model simulation system for oil-immersed transformers based on similarity theory as described in claim 1, characterized in that: The convective heat transfer criteria in the convective heat transfer similarity model determination module (5) are obtained based on Newton's cooling law and Fourier's heat transfer law.

9. A method for simulating an oil-immersed transformer using a scaled-down model based on similarity theory, using the system described in claim 1, characterized in that: It includes the following steps: Step 1: Determine the transformer model and the structural parameters required for multiphysics analysis, as well as the similarity ratio of the scaled-down model for simulating physical phenomena. Step 2: Determine the eddy current field control equations that are compatible with the electromagnetic field of the transformer using the Maxwell equations, derive the eddy current field similarity criteria based on similarity theory, and perform eddy current field simulation. Step 3: Determine the energy conservation similarity criterion based on the energy conservation equation; Step 4: Determine the momentum conservation similarity criterion based on the momentum conservation equation; Step 5: Determine the convective heat transfer similarity criterion based on the convective heat transfer boundary conditions; Step 6: Determine the heat flow compensation principle by integrating various similarity theories, conduct temperature-fluid field simulation, and compare the simulation results with the original structural model and the prototype experimental results.

10. The method for simulating a scaled-down model of an oil-immersed transformer based on similarity theory as described in claim 9, characterized in that: The structural parameters in step 1 include the number and spacing of winding discs, the length and width of oil passages, and the position of the oil baffle. The similarity ratio of the scaled-down model is determined according to the needs of engineering testing or to control manufacturing costs.

11. The method for simulating a scaled-down model of an oil-immersed transformer based on similarity theory as described in claim 9, characterized in that: The specific implementation method of step 2 is as follows: Based on the three-dimensional model of the transformer, the eddy current field similarity criterion is derived through the eddy current field control equation. The loss of the transformer under sinusoidal excitation steady-state operating conditions is calculated using the finite element method. The loss is used as the heat source and as the excitation of the model based on the subsequent temperature and fluid field similarity theory. With environmental factors as boundary conditions, temperature and fluid field simulations of the transformer under various operating conditions are performed to obtain temperature and fluid field distribution maps. The steady-state operating conditions include one or more of rated load, overload, and underload. The external environmental parameters required by the convection heat transfer similarity model determination module include one or more of temperature, wind speed, and humidity; The specific implementation method of electromagnetic field similarity theory is derived from the eddy current field control equations as follows: The governing equations of the eddy current field adapted to the electromagnetic field of the transformer were determined using Maxwell's equations, and the similarity criteria of the eddy current field were derived based on the equation analysis method. , , ,in, It represents the ratio of the potential gradient to the electric field strength. This represents Faraday's law of electromagnetic induction. This represents the Maxwell-Ampère law. Indicates permeability, Indicates electrical conductivity. Indicates structural parameters, Indicates magnetic flux. Represents the magnetic vector potential. This represents the time constant corresponding to the power supply frequency. Indicates the source current density; Based on the eddy current field similarity criterion, when the electromagnetic field of the scaled-down model is similar to that of the original model, the power supply frequency similarity ratio should be a multiple of the square of the reciprocal of the structural similarity ratio.

12. The method for simulating a scaled-down model of an oil-immersed transformer based on similarity theory as described in claim 9, characterized in that: The specific implementation method of step 3 is as follows: Based on the energy conservation equation, the energy conservation similarity criterion is determined, and the following is obtained: This is a measure of the ratio of inertial force to viscous force in transformer oil. This is a measure representing the ratio of oil flow diffusion thickness to heat diffusion thickness, where... Indicates the density of transformer oil. Indicates the oil flow velocity. Represents structural variables, Indicates dynamic viscosity. Transformer oil constant pressure heat capacity This indicates the thermal conductivity of the transformer oil.

13. The method for simulating a scaled-down model of an oil-immersed transformer based on similarity theory as described in claim 9, characterized in that: The specific implementation method of step 4 is as follows: Based on the momentum conservation equation, the momentum conservation similarity criterion is determined, and the following is obtained: , represents the measure of buoyancy and viscous force in the natural convection heat transfer of transformer oil, where, This represents the coefficient of thermal expansion of transformer oil. Represents gravitational acceleration. Represents the temperature gradient. Indicates the density of transformer oil. This represents the similarity ratio of similar models. This indicates the thermal conductivity of transformer oil.

14. The method for simulating a scaled-down model of an oil-immersed transformer based on similarity theory as described in claim 9, characterized in that: Step 5 outputs multiple values ​​from the following: low-pressure heat source, high-pressure heat source, ambient temperature, upper convection heat transfer coefficient, lower convection heat transfer coefficient, and side convection heat transfer coefficient. The convection heat transfer criterion in step 5 is based on Newton's law of cooling and Fourier's law of heat transfer.

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