A transformer temperature field simulation and prediction method and device based on thermal parameter equivalence and a medium

Abstract

This invention discloses a method, device, and medium for simulating and predicting transformer temperature field based on thermal parameter equivalence, relating to the technical field of temperature field testing. The method includes: constructing a three-dimensional electromagnetic field model of the transformer using the finite element method based on acquired transformer thermal parameters; performing electromagnetic calculations on the three-dimensional electromagnetic field model using acquired rated operating parameters to obtain the transformer's loss results; optimizing the three-dimensional electromagnetic field model of the transformer using the thermal parameter equivalence method based on acquired target transformer thermal property parameters, and constructing a three-dimensional temperature field model of the transformer using the transformer's loss results; and obtaining the steady-state temperature distribution of the transformer under natural cooling conditions using a non-isothermal flow calculation method under laminar flow conditions based on the three-dimensional temperature field model. This invention simplifies winding details and reduces the scale of thermal-fluid coupling solutions, thereby improving computational efficiency while ensuring three-dimensional temperature rise prediction capabilities.

Description

Technical Field

[0001] This invention relates to the field of temperature field testing technology, and belongs to a method, device and medium for simulating and predicting transformer temperature field based on thermal parameter equivalence. Background Technology

[0002] During transformer operation, copper and iron losses are generated in the windings and core under electromagnetic influence, with the majority of these losses being converted into heat energy and causing temperature rise. Research and engineering practice show that the thermal aging of oil-paper insulation follows the "Montessinger's rule": when the temperature is higher than the reference temperature, the insulation aging rate approximately doubles for every 6K increase. Therefore, the ability to accurately and quickly simulate the internal temperature distribution of oil-immersed transformers and effectively sense winding hot spots and temperature rise states is fundamental for transformer condition assessment and life management, and can also support online analysis applications such as digital twins.

[0003] While multiphysics numerical computation (MPC) offers high adaptability in existing methods for hotspot temperature acquisition and temperature rise prediction, it faces technical challenges in engineering applications, including high computational costs and difficulty in rapid evaluation. Firstly, electromagnetic losses exhibit a significant non-uniform spatial distribution. Using only total losses or empirical allocation methods as heat sources makes it difficult to maintain the influence path of loss distribution on temperature rise and hotspot formation, resulting in insufficient specificity and interpretability in temperature rise assessment. Secondly, detailed modeling of complex structures such as windings and performing thermo-fluid coupled solutions to improve accuracy introduces significant geometric scale differences and huge mesh sizes. Furthermore, the coupled solution of solid heat conduction and natural oil convection further increases the computational scale and convergence cost, making it difficult to meet the computational efficiency requirements for rapid engineering applications. The statements in this section merely provide background information related to this invention and do not necessarily constitute prior art. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a transformer temperature field simulation prediction method, device, and medium based on thermal parameter equivalence. By simplifying the complex structure through winding thermal parameter equivalence, it achieves efficient simulation prediction of the steady-state temperature rise of the transformer under natural cooling conditions.

[0005] To achieve the above objectives, the present invention is implemented using the following technical solution.

[0006] In a first aspect, the present invention provides a transformer temperature field simulation and prediction method based on thermal parameter equivalence, comprising:

[0007] Based on the obtained transformer thermal parameters, a three-dimensional electromagnetic field model of the transformer is constructed using the finite element method.

[0008] Based on the three-dimensional electromagnetic field model of the transformer, electromagnetic calculations are performed using the obtained rated operating parameters to obtain the transformer loss results.

[0009] Based on the obtained thermal and structural parameters of the target transformer, a three-dimensional temperature field model of the transformer is constructed.

[0010] Based on the structural parameters of the target transformer, the equivalent thermal conductivity and equivalent specific heat capacity of the transformer winding are calculated using the thermal parameter equivalent method.

[0011] The three-dimensional temperature field model of the transformer is iterated based on the equivalent thermal conductivity, equivalent specific heat capacity and transformer loss results.

[0012] Based on the iterative three-dimensional temperature field model of the transformer, the steady-state temperature distribution of the transformer under natural cooling conditions is obtained by using a non-isothermal flow calculation method under laminar flow conditions.

[0013] Optionally, in the three-dimensional electromagnetic field model of the transformer, a nonlinear magnetization characteristic equation is set for the core region, and an electrical excitation is applied to the winding region to solve the steady-state electromagnetic field, thereby obtaining the magnetic flux density distribution inside the transformer.

[0014] The calculation of the magnetic field distribution inside a transformer is essentially a solution to Maxwell's equations under specific conditions. By setting a nonlinear magnetization characteristic equation in the iron core region, the accuracy of the calculation of the magnetic flux density distribution inside the transformer is ensured.

[0015] Optionally, based on the magnetic flux density distribution inside the transformer, the current density inside the transformer can be calculated using electromagnetic field control equations.

[0016] The transformer loss was calculated based on the current density inside the transformer.

[0017] The heat source of a transformer mainly comes from the core and winding losses. The magnitude of the core loss is closely related to the magnetic flux density distribution inside the core. By calculating the current density based on the magnetic flux density distribution inside the transformer, the heat source loss of the transformer can be accurately calculated.

[0018] Optionally, based on the magnetic flux density distribution inside the transformer, the formula for calculating the current density inside the transformer using the electromagnetic field control equation is as follows:

[0019] (1)

[0020] Where μ is the permeability; A is the vector magnetic potential; J is the current density; σ is the conductivity; and t is time. Represents the curl operator;

[0021] The formula for calculating the transformer loss based on the current density inside the transformer is as follows:

[0022] (2)

[0023] Where V is the volume of the region containing the current density. This represents the transformer's loss results.

[0024] Optionally, based on the structural parameters of the target transformer, the equivalent thermal conductivity and equivalent specific heat capacity of the transformer windings are calculated using the thermal parameter equivalence method, including:

[0025] Based on the structural data of the target transformer, the high-voltage winding and low-voltage winding of the transformer are respectively equivalent to continuous dielectric block conductors with anisotropic thermal conductivity.

[0026] For the continuous dielectric block conductor, the equivalent thermal conductivity of the high-voltage winding and the low-voltage winding of the transformer is calculated through the thermal resistance series mechanism.

[0027] Based on the equivalent thermal conductivity, the heat absorbed by each material in the representative unit at a preset temperature rise is summed, and the equivalent specific heat capacity is obtained by mass-weighted average.

[0028] The equivalent thermal conductivity includes axial equivalent thermal conductivity, radial equivalent thermal conductivity, and winding direction equivalent thermal conductivity.

[0029] Alternatively, the formula for calculating the axial equivalent thermal conductivity is:

[0030] (3)

[0031] Where ka is the axial equivalent thermal conductivity, da1 is the total thickness of the axial copper conductor, da2 is the total thickness of the axial insulating varnish, and da is the total axial thickness.

[0032] The formula for calculating radial equivalent thermal conductivity is:

[0033] (4)

[0034] Wherein, dr1 is the total thickness of the radial conductor layer of the transformer winding; dr2 is the total thickness of the insulating varnish of the radial conductor layer of the transformer winding; dr3 is the total thickness of the radial oil-impregnated insulating paper of the transformer; k1 is the thermal conductivity of the copper conductor of the transformer winding; k2 is the thermal conductivity of the insulating varnish of the conductor layer of the transformer winding; k3 is the thermal conductivity of the oil-impregnated insulating paper of the transformer; and Kr is the radial equivalent thermal conductivity.

[0035] The equivalent thermal conductivity in the winding direction is 401 W / m / Kelvin, which is the thermal conductivity of the copper wire in the winding.

[0036] By using different equivalent thermal conductivity calculation formulas for axial, radial, and winding directions, the accuracy of the equivalent thermal conductivity calculation results is improved.

[0037] Optionally, the formula for calculating the equivalent specific heat capacity is:

[0038] (5)

[0039] in, Let i represent the specific heat capacity of the i-th material within the unit. To absorb total heat, For the temperature of material change, Let the mass of the i-th material be... For equivalent specific heat capacity, This represents the total mass of the winding.

[0040] Optionally, the three-dimensional temperature field model of the transformer is iterated based on the equivalent thermal conductivity, equivalent specific heat capacity, and transformer loss results, including:

[0041] For the three-dimensional temperature field model of the transformer, the mesh is generated by scanning mapping and fusion free meshing to obtain multiple transformer regions;

[0042] Based on the equivalent thermal conductivity and equivalent specific heat capacity, the transformer region of the winding part in the three-dimensional temperature field model is set, and the transformer loss result is used as a heat source input to the three-dimensional temperature field model of the transformer for iteration.

[0043] Secondly, the present invention provides a transformer temperature field simulation and prediction device based on thermal parameter equivalence, comprising:

[0044] The loss calculation module is used to perform electromagnetic calculations under rated operating conditions using the three-dimensional electromagnetic field model of the transformer to obtain the distribution characteristics of core loss and winding loss as the loss result.

[0045] The temperature field model equivalent construction module is used to construct and iterate the three-dimensional temperature field model of the transformer.

[0046] The solver module is used to obtain the steady-state temperature distribution of the transformer under natural cooling conditions by non-isothermal flow calculation under laminar flow conditions based on the iterated three-dimensional temperature field model of the transformer.

[0047] Thirdly, the present invention provides a computer-readable storage medium for storing computer instructions, which, when executed by a processor, perform the steps in the transformer temperature field simulation and prediction method based on thermal parameter equivalence as described in any one of the first aspects.

[0048] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0049] This invention obtains transformer loss results through finite element electromagnetic calculations and uses them as heat sources input into the transformer's three-dimensional temperature field model. This allows the temperature rise calculation to accurately reflect the influence of spatial distribution differences in losses on temperature distribution and the location of heat source points, improving the accuracy of locating local areas with excessively high temperature rises and their corresponding loss sources. By integrating the equivalent thermal parameter method into the transformer's three-dimensional temperature field model to calculate the transformer's equivalent thermal conductivity and equivalent specific heat capacity, the three-dimensional temperature field model of the transformer is simplified, significantly reducing the geometric and mesh complexity of the temperature field model and reducing the scale of the heat-fluid coupling solution. This improves computational efficiency while maintaining the three-dimensional temperature rise prediction capability. By combining non-isothermal flow calculations under laminar flow conditions, high-precision prediction of transformer temperature field changes is ensured. This invention achieves efficient simulation prediction of steady-state temperature rise of transformers under natural cooling conditions.

[0050] This invention calculates transformer losses using a three-dimensional electromagnetic field model of the transformer. The transformer losses are then used as a heat source and input into a three-dimensional temperature field model of the transformer that is iteratively updated using the thermal equivalence method. The three-dimensional temperature field model of the transformer is then accurately solved using a non-isothermal flow calculation method under laminar flow conditions, which improves the accuracy of the simulation results. This invention achieves high-precision simulation of the transformer temperature field, and improves the simulation prediction rate of the temperature field while ensuring the accuracy of the temperature field prediction.

[0051] This invention obtains the steady-state temperature distribution under natural cooling conditions through non-isothermal flow calculations under laminar flow conditions. This makes the invention feasible and engineering-applicable even in scenarios where electromagnetic loss is difficult to obtain and the cost of fully coupled thermal flow field calculations is high. It provides reusable simulation test data for transformer thermal design and temperature rise assessment under operating conditions. Attached Figure Description

[0052] Figure 1 This is a flowchart of the simulation prediction method of the present invention;

[0053] Figure 2 This is a magnetic flux density distribution diagram of the core of a three-dimensional electromagnetic field model of a transformer, a simulation example of the present invention.

[0054] Figure 3 This is a schematic diagram of the winding leakage magnetic field distribution in the three-dimensional electromagnetic field model of the simulation example of the present invention;

[0055] Figure 4 This is a diagram showing the composition of total losses under different load rates in the transformer model of the simulation example of this invention, calculated electromagnetically.

[0056] Figure 5 This is an equivalent schematic diagram of the winding of the present invention;

[0057] Figure 6 This is a diagram showing the overall mesh generation effect of the three-dimensional electromagnetic field model of the transformer of the present invention;

[0058] Figure 7 This is a simulation example of the transformer temperature distribution effect diagram of the present invention. Detailed Implementation

[0059] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations thereof. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0060] The term "and / or" simply describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. Additionally, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0061] Example 1

[0062] This embodiment introduces a transformer temperature field simulation and prediction method based on thermal parameter equivalence, such as... Figure 1 As shown, it specifically includes:

[0063] Based on the obtained thermal parameters of the transformer, a three-dimensional electromagnetic field model of the transformer is constructed using the finite element method; the three-dimensional electromagnetic field model of the transformer constructed using the finite element method can be used for electromagnetic calculations.

[0064] Based on the three-dimensional electromagnetic field model of the transformer, electromagnetic calculations are performed using the obtained rated operating parameters to obtain the transformer loss results. The rated operating parameters include: setting the rated voltage, rated frequency, and load according to the transformer nameplate parameters, applying the corresponding electrical excitation according to the connection group number, and introducing the standard nonlinear magnetization curve into the core material.

[0065] The transformer loss results include core loss and winding loss. The three-dimensional distribution results of core loss and winding loss are obtained through finite element electromagnetic calculation.

[0066] Based on the obtained thermal and structural parameters of the target transformer, a three-dimensional temperature field model of the transformer is constructed.

[0067] Based on the structural parameters of the target transformer, the equivalent thermal conductivity and equivalent specific heat capacity of the transformer winding are calculated using the thermal parameter equivalent method.

[0068] By using the equivalent thermal conductivity and equivalent specific heat capacity of the winding as heat sources input into the three-dimensional temperature field model of the transformer, the winding structure in the temperature field is simplified, and the efficiency of solving the three-dimensional temperature field model of the transformer is improved.

[0069] The transformer loss results are input into the three-dimensional temperature field model of the transformer for iteration, which ensures that the distribution differences of loss space and the influence on the location of heat source points are accurately reflected when performing transformer temperature rise simulation calculations.

[0070] Based on the iterative three-dimensional temperature field model of the transformer, the steady-state temperature distribution of the transformer under natural cooling conditions is obtained through a non-isothermal flow calculation method under laminar flow conditions. Obtaining the steady-state temperature distribution under natural cooling conditions through non-isothermal flow calculation under laminar flow conditions ensures the feasibility and engineering applicability of this method even in scenarios where electromagnetic loss is difficult to obtain and the cost of fully coupled thermal flow field calculations is high. This provides reusable simulation test data for transformer thermal design and temperature rise assessment during operation.

[0071] This embodiment accurately calculates the heat sources of the transformer temperature field, iteratively updates the three-dimensional temperature field model of the transformer, and uses a non-isothermal flow calculation method under laminar flow conditions to solve the three-dimensional temperature field model with high precision. This achieves high-precision simulation and prediction of the transformer temperature field with equivalent thermal parameters. This embodiment remains feasible and engineering-applicable even in scenarios where "electromagnetic loss is difficult to obtain and the cost of fully coupled thermal flow field calculation is high." It can provide reusable simulation test basis for transformer thermal design and temperature rise assessment during operation. Using the calculated transformer loss results as the heat source input of the transformer temperature field allows the temperature rise calculation to directly reflect the impact of differences in spatial loss distribution on temperature distribution and hot spot location, better adapting to the three-dimensional temperature field model of the transformer after iterative thermal parameter equivalence. Compared with only using total loss or empirical allocation methods, it is easier to locate local areas with high temperature rise and their corresponding loss sources.

[0072] Example 2

[0073] Based on the same inventive concept as Embodiment 1, this embodiment introduces a transformer temperature field simulation and prediction method based on thermal parameter equivalence, specifically including:

[0074] Based on the acquired transformer thermal parameters, a three-dimensional electromagnetic field model of the transformer is constructed using the finite element method. In this model, a nonlinear magnetization characteristic equation is set for the core region, and electrical excitation is applied to the winding region to solve for the steady-state electromagnetic field, thus obtaining the internal magnetic flux density distribution of the transformer. Solving for the internal magnetic field distribution of the transformer essentially involves solving Maxwell's equations under specific conditions. The accuracy of the solution for the internal magnetic flux density distribution is ensured by using the nonlinear magnetization characteristic equation set for the core region.

[0075] Based on the magnetic flux density distribution inside the transformer, the current density inside the transformer is calculated using the electromagnetic field control equation.

[0076] (1)

[0077] Where μ is the permeability; A is the vector magnetic potential; J is the current density; σ is the conductivity; and t is time. Represents the curl operator;

[0078] The formula for calculating the transformer loss based on the current density inside the transformer is as follows:

[0079] (2)

[0080] Where V is the volume of the region containing the current density. This represents the transformer's loss results.

[0081] The transformer loss is calculated based on the current density inside the transformer. The loss structure of the core is closely related to the magnetic flux density distribution inside the core. The transformer heat source loss is calculated by calculating the current density based on the magnetic flux density distribution inside the transformer, thus achieving accurate calculation of the transformer heat source.

[0082] Based on the obtained thermal and structural parameters of the target transformer, a three-dimensional temperature field model of the transformer is constructed.

[0083] Based on the structural parameters of the target transformer, the equivalent thermal conductivity and equivalent specific heat capacity of the transformer are calculated using the thermal parameter equivalence method, including:

[0084] Based on the structural data of the target transformer, the high-voltage winding and low-voltage winding of the transformer are respectively equivalent to continuous dielectric block conductors with anisotropic thermal conductivity.

[0085] For the continuous dielectric block conductor, the equivalent thermal conductivity of the high-voltage winding and the low-voltage winding of the transformer is calculated through the thermal resistance series mechanism.

[0086] Based on the equivalent thermal conductivity, the heat absorbed by each material in the representative unit at a preset temperature rise is summed, and the equivalent specific heat capacity is obtained by mass-weighted average.

[0087] The equivalent thermal conductivity includes axial equivalent thermal conductivity, radial equivalent thermal conductivity, and winding direction equivalent thermal conductivity, wherein the formula for calculating the axial equivalent thermal conductivity is:

[0088] (3)

[0089] Where ka is the axial equivalent thermal conductivity, da1 is the total thickness of the axial copper conductor, da2 is the total thickness of the axial insulating varnish, and da is the total axial thickness.

[0090] The formula for calculating radial equivalent thermal conductivity is:

[0091] (4)

[0092] Wherein, dr1 is the total thickness of the radial conductor layer of the transformer winding; dr2 is the total thickness of the insulating varnish of the radial conductor layer of the transformer winding; dr3 is the total thickness of the radial oil-impregnated insulating paper of the transformer; k1 is the thermal conductivity of the copper conductor of the transformer winding; k2 is the thermal conductivity of the insulating varnish of the conductor layer of the transformer winding; k3 is the thermal conductivity of the oil-impregnated insulating paper of the transformer; and Kr is the radial equivalent thermal conductivity.

[0093] The equivalent thermal conductivity in the winding direction is 401 W / m / Kelvin, which is the thermal conductivity of the copper wire in the winding.

[0094] The formula for calculating equivalent specific heat capacity is:

[0095] (5)

[0096] in, Let i represent the specific heat capacity of the i-th material within the unit. To absorb total heat, For the temperature of material change, Let the mass of the i-th material be... For equivalent specific heat capacity, This represents the total mass of the winding.

[0097] For the three-dimensional temperature field model of the transformer, the mesh is generated by scanning mapping and fusion free meshing to obtain multiple transformer regions;

[0098] Based on the equivalent thermal conductivity and equivalent specific heat capacity, the transformer region of the winding section in the three-dimensional temperature field model is set, and the transformer loss results are used as a heat source input to the three-dimensional temperature field model of the transformer for iteration. Based on the iterated three-dimensional temperature field model of the transformer, the steady-state temperature distribution of the transformer under natural cooling conditions is obtained by using a non-isothermal flow calculation method under laminar flow conditions.

[0099] Example 3

[0100] In one or more of the technical solutions disclosed in the embodiments, such as Figures 1 to 7 As shown, a specific implementation method for transformer temperature field simulation prediction based on thermal parameter equivalence includes the following steps:

[0101] Step 1: Establish a three-dimensional electromagnetic field model of a three-phase transformer based on the finite element method, perform electromagnetic calculations under rated operating conditions, and obtain the distribution characteristics of core loss and winding loss as the loss results.

[0102] Step 2: The three-dimensional electromagnetic field model of the three-phase transformer is constructed. The winding is equivalent to a continuous medium block heat conductor. The complex winding structure is simplified by using the equivalent thermal parameters of the winding. The loss results obtained from the electromagnetic calculation are used as the heat source input to obtain the three-dimensional temperature field model of the transformer.

[0103] Step 3: Based on the obtained three-dimensional temperature field model of the transformer, the steady-state temperature distribution of the transformer under natural cooling conditions is obtained through non-isothermal flow calculation under laminar flow conditions.

[0104] The temperature rise of a three-phase transformer is essentially determined by the energy chain of "electromagnetic loss → heat source → heat transfer / convection dissipation". This implementation first constructs a three-dimensional electromagnetic field model consistent with the actual structure. To balance engineering calculation efficiency and the traceability of the impact of loss distribution, the complex winding structure is equivalently treated in the thermal simulation stage: the winding is regarded as a continuous medium block heat conductor, and "winding equivalent thermal parameters" are assigned to this block heat conductor. Then, the volume loss density field obtained from electromagnetic calculation is mapped to a heat source term, that is, a volume heat source is set for the core and the winding respectively, and together with the oil tank, transformer oil, oil channels / gap and other fluid regions, a three-dimensional temperature field model is formed. Finally, in order to obtain the steady-state temperature distribution under natural cooling conditions, non-isothermal flow calculation under laminar flow conditions is used to solve the natural convection inside the oil-immersed transformer to obtain the steady-state temperature distribution under natural cooling conditions.

[0105] In the above scheme, the three-dimensional distribution results of core loss and winding loss are obtained through finite element electromagnetic calculation and used as the heat source input to the temperature field model. This allows the temperature rise calculation to directly reflect the impact of the spatial distribution difference of loss on the temperature distribution and hot spot location. Compared with only using total loss or empirical allocation methods, it is easier to locate local areas with high temperature rise and their corresponding loss sources. At the same time, the complex winding structure is equivalent to a continuous medium block heat conductor and equivalent thermal parameters of the winding are introduced to simplify the winding details. This can significantly reduce the geometric and mesh complexity of the temperature field model and reduce the scale of heat flow coupling solution, thereby improving computational efficiency while ensuring the three-dimensional temperature rise prediction capability. Furthermore, the steady-state temperature distribution under natural cooling conditions is obtained based on non-isothermal flow calculation under laminar flow conditions. This makes the method feasible and engineering applicable even in scenarios where "electromagnetic loss is difficult to obtain and the cost of fully coupled heat flow field calculation is high". It can provide reusable simulation test basis for transformer thermal design and temperature rise assessment under operating conditions.

[0106] This embodiment uses a three-phase oil-immersed distribution transformer as an example, and its main electrical parameters are shown in Table 1. The core components of the transformer are the core and windings. The core is composed of stacked cold-rolled silicon steel sheets, and its layered structure is simplified to a single solid in the model. The windings are divided into high-voltage and low-voltage windings, which are concentrically wound on the core column. The oil tank is filled with transformer oil, which immerses the core and windings, serving the functions of insulation and heat dissipation.

[0107] Table 1. Main electrical parameters of oil-immersed distribution transformers;

[0108] Main projects Parameter value Rated capacity 200kVA Rated voltage (10 / √3) / (0.4 / √3)kV Rated frequency 50Hz Cooling method ONAN Linkage group label Dyn11

[0109] First, electromagnetic field loss calculation and analysis are performed.

[0110] During transformer operation, the main heat sources are the core and winding losses. The core loss is closely related to the magnetic flux density distribution within the core; therefore, it is necessary to first calculate the internal magnetic field distribution of the transformer. Essentially, this involves solving Maxwell's equations under specific conditions. Combining Maxwell's equations and the principle of magnetic flux continuity, the electromagnetic field control equations can be derived. The calculation formula is as follows:

[0111] ;

[0112] In the formula: μ is the permeability; A is the vector magnetic potential; J is the current density; σ is the conductivity; t is time; The curl operator (curl) represents taking the curl of a vector field.

[0113] Furthermore, based on the obtained current density, the loss / heating power is calculated, thus obtaining the transformer heat source loss. The calculation formula is:

[0114]

[0115] In the formula: V is the volume of the region where the current density is located.

[0116] The spatial distribution of the magnetic field can be calculated using the above formula, and the distribution of the current density J in the conductor can be further obtained; the field results can be converted into heating power.

[0117] For the fluid temperature field analysis of a transformer, the convective heat transfer process for a transformer with natural oil circulation cooling can be described by the following expression:

[0118]

[0119]

[0120]

[0121] In the formula: f is the external force on a unit volume of fluid; ρ is the fluid density; ν is the fluid velocity vector; p is the fluid pressure; η is the fluid dynamic viscosity; e is the fluid internal energy; T is the fluid temperature; cp is the fluid specific heat capacity; k is the fluid thermal conductivity; Φ is the fluid heat source; Sh is the portion of the fluid mechanical energy converted into heat energy under the action of viscous force.

[0122] The fluid temperature field equation provides a theoretical framework for subsequent coupled temperature field and flow field calculations, and describes the convective heat transfer process under natural oil circulation.

[0123] In step 1, a three-dimensional electromagnetic field model of the three-phase transformer is established based on the finite element method. The spatial distribution of core loss and winding loss under rated operating conditions is calculated as the loss result, including the following steps:

[0124] Step 11: Electromagnetic field modeling and solution: Establish a three-dimensional electromagnetic field model containing the core and windings based on the finite element method; set nonlinear magnetization characteristics in the core of the constructed three-dimensional electromagnetic field model, and apply electrical excitation to the windings to solve the steady-state electromagnetic field and obtain the magnetic flux density distribution inside the transformer.

[0125] The simulation yielded the following magnetic flux density distribution in the transformer core: Figure 2 and Figure 3 As shown; Figure 2 The left side shows the magnetic field distribution of the transformer core in a three-dimensional electromagnetic field model; the right side shows the magnetic field distribution of the transformer casing in a constructed three-dimensional electromagnetic field model. Figure 3 The left side shows the leakage magnetic flux distribution of the high-voltage winding, and the right side shows the leakage magnetic flux distribution of the low-voltage winding.

[0126] Step 12, Loss Calculation: Set different load rates, calculate the spatial distribution of core loss and winding loss based on steady-state electromagnetic field, and generate the volume loss density data of the corresponding region, i.e. loss results;

[0127] Based on the electromagnetic field calculation results in step 11, the core loss and winding loss are further calculated. Core loss mainly consists of hysteresis loss and eddy current loss, and its distribution is closely related to the local magnetic flux density level. Winding loss is generated by resistive loss and is affected by current distribution and structural form. The transformer losses under different load rates obtained from the simulation are shown in Table 2. The component proportions of total loss under different load rates are shown in... Figure 4 As shown;

[0128] Table 2 Transformer losses under different load rates;

[0129] load rate Core loss / W Winding loss / W Core eddy current loss / W Core hysteresis loss / W Total loss / W 50% 230.36 663.47 104.77 125.59 893.83 70% 229.33 1284.5 104.23 125.10 1513.83 100% 227.82 2578.1 103.43 124.39 2805.92 120% 226.81 3668.3 102.90 123.91 3895.11 150% 225.32 5647.0 102.12 123.20 5872.32 170% 224.36 7159.9 101.61 122.75 7384.26 200% 222.89 9767.4 100.84 122.05 9990.29

[0130] As can be seen from the winding structure of the distribution transformer, the detailed modeling of the winding conductors and oil-impregnated insulating paper is very complex, and the mesh generation is difficult. In this paper, the equivalent thermal conductivity of the winding is used to simplify the complex winding structure in the temperature field modeling.

[0131] In step 2, the constructed three-dimensional electromagnetic field model of the three-phase transformer is simplified by using equivalent thermal parameters of the windings to represent the complex winding structure, as follows:

[0132] Step 21: Treat the transformer winding as a continuous medium with equivalent anisotropic thermal conductivity, i.e., as a block conductor, to obtain the equivalent winding structure; in order to reflect its overall heat transfer capacity.

[0133] This approach ignores the microstructural details inside the winding to some extent, but it can effectively reduce the complexity of the model and meet the needs of engineering calculations.

[0134] This embodiment considers the winding portion as equivalent, that is, the winding conductor, the enameled layer on the surface of the winding conductor, and the insulating oil paper for interlayer insulation are considered as a whole. Considering the accuracy of the simulation, it is necessary to perform parameter equivalence on the winding materials. A simplified schematic diagram of the transformer winding structure is shown below. Figure 5 As shown.

[0135] Step 22: For the equivalent winding structure, analyze the anisotropic thermal conductivity of the winding and calculate the equivalent thermal conductivity in all directions, including the equivalent thermal conductivity in the axial, radial and winding directions.

[0136] Equivalent thermal conductivity is used to reflect the directional differences in the overall heat transfer capacity of the winding;

[0137] Furthermore, the calculation process for the radial equivalent thermal conductivity is as follows:

[0138] Step 221: For the winding, calculate the thermal resistance of each material in the winding, including the thermal resistance of the copper conductor, the thermal resistance of the insulating varnish, and the thermal resistance of the insulating paper.

[0139] Under unit area conditions, the relationship between the thermal resistance Rth of a material and the thickness and thermal conductivity of the material is as follows:

[0140]

[0141] Where d represents the thickness of the material in the direction of heat conduction, in meters (m); k represents the thermal conductivity or thermal conductivity coefficient of the material, characterizing the material's thermal conductivity, in W / (m·K).

[0142] Step 222: Connect the thermal resistance of the copper conductor, the thermal resistance of the conductor insulating varnish, and the thermal resistance of the oil-impregnated insulating paper in series according to the radial thermal resistance to obtain the radial equivalent thermal resistance, and convert it into the radial equivalent thermal conductivity in combination with the total radial thickness.

[0143] Oil-impregnated insulating paper is wrapped around the winding conductor layer. The overall equivalent thermal resistance Rthr of the transformer winding in the radial direction is:

[0144]

[0145] In the formula: Rthr is the radial equivalent thermal resistance of the winding; Rthr1 is the thermal resistance of the copper conductor of the wire; Rthr2 is the thermal resistance of the insulating varnish of the wire; Rthr3 is the thermal resistance of the insulating oil paper.

[0146] The overall radial thickness dr of the winding is:

[0147]

[0148] Wherein, dr1 is the total thickness of the metal conductor in the radial conductor layer of the transformer winding; dr2 is the total thickness of the insulating varnish in the radial conductor layer of the transformer winding; and dr3 is the total thickness of the oil-impregnated insulating paper in the radial conductor layer of the transformer.

[0149] The radial thermal conductivity Kr of the high-voltage winding as a whole can be obtained from the above formula. The calculation formula is as follows:

[0150]

[0151] In the formula: k1 is the thermal conductivity of the copper conductor of the transformer winding; k2 is the thermal conductivity of the insulating varnish of the conductor layer of the transformer winding; k3 is the thermal conductivity of the oil-impregnated insulating paper of the transformer.

[0152] Furthermore, the axial equivalent thermal conductivity of the winding is obtained by: using the axial equivalent thermal resistance formed by the axial thermal resistance of the copper conductor and the axial thermal resistance of the insulating varnish, and combining it with the total axial thickness to convert it into the axial equivalent thermal conductivity.

[0153] The equivalent thermal resistance of the high-voltage winding in the axial direction is shown in the following formula:

[0154]

[0155] In the formula: Rtha is the axial equivalent thermal resistance of the high voltage winding, Rtha1 is the thermal resistance of the copper conductor, and Rtha2 is the thermal resistance of the copper wire insulation varnish.

[0156] Similarly, the equivalent thermal conductivity ka of the transformer winding in the axial direction can be calculated using the following formula:

[0157]

[0158] In the formula: Ka is the axial equivalent thermal conductivity of the high voltage winding, da1 is the total thickness of the axial copper conductor, and da2 is the total thickness of the axial insulating varnish.

[0159] The thermal conductivity of the winding conductor in the winding direction is taken as 401 W / (m∙K) of the thermal conductivity of the copper conductor.

[0160] Based on the transformer material and structural parameters, the equivalent thermal conductivity of the high and low voltage windings in each direction of the transformer is calculated and shown in Table 3.

[0161] Table 3. Calculation results of equivalent thermal conductivity;

[0162]

[0163] Step 23: For the equivalent winding structure, based on the energy conservation of the representative unit (RVE), sum the heat absorbed by each material in the representative unit under the same temperature rise ΔT, and obtain the equivalent specific heat capacity by mass weighted average.

[0164] For a single material, the physical formula for calculating specific heat capacity is:

[0165] ;

[0166] In the formula: m is the mass of the material; Q is the heat absorbed or released when the material's temperature changes by ΔT.

[0167] To solve for the equivalent specific heat capacity of the periodic representative element of the winding, assuming that the total heat absorbed when the temperature of all materials in the representative element rises by ΔT is Qrve, then:

[0168] ;

[0169] In the formula: Qi represents the heat absorbed when the temperature of the i-th material in the unit rises by ΔT; ci represents the specific heat capacity of the i-th material in the unit.

[0170] The formula for calculating equivalent specific heat capacity is:

[0171]

[0172] in, Let i represent the specific heat capacity of the i-th material within the unit. To absorb total heat, For the temperature of material change, Let the mass of the i-th material be... For equivalent specific heat capacity, This represents the total mass of the winding.

[0173] For the specific example transformer in this embodiment, based on the transformer material and structural parameters, the equivalent specific heat capacities of the high-voltage and low-voltage windings of the transformer are calculated to be 388 J / (kg·K) and 393 J / (kg·K), respectively.

[0174] In this step, the multi-material hybrid winding structure is converted into an equivalent specific heat capacity so that the complex winding details can be replaced with equivalent bulk materials in the temperature field simulation.

[0175] In step 2, a block conductor with anisotropic thermal conductivity and equivalent specific heat capacity is used to replace the actual transformer winding structure. The calculated anisotropic thermal conductivity and equivalent specific heat capacity are used as setting parameters. The loss results obtained from electromagnetic calculation are used as the heat source input to establish a three-dimensional temperature field model of the transformer.

[0176] In this embodiment, natural cooling conditions refer to the operating condition where the transformer is not equipped with external power cooling devices such as oil pumps, fans or water cooling, and internal heat exchange is achieved solely by the natural convection circulation formed by the change in transformer oil density caused by the heating of the windings and iron core. The heat is dissipated to the environment through natural convection between the outer surface of the oil tank and the ambient air.

[0177] In step 3, based on the obtained three-dimensional temperature field model of the transformer, a method for obtaining the steady-state temperature distribution of the transformer under natural cooling conditions through non-isothermal flow calculations under laminar flow conditions is used, including the following steps:

[0178] Step 31: The constructed three-dimensional temperature field model of the transformer is meshed using a scan mapping meshing and fusion free meshing method;

[0179] The constructed three-dimensional temperature field model of the transformer includes equivalent windings, core, insulation structure, transformer shell, internal structural components, etc. Specifically, the symmetrical structure of the transformer is partitioned by scanning mapping, and the irregular structure of the transformer is partitioned by free partitioning.

[0180] The symmetrical structure of a transformer includes windings, insulation layers, oil ducts, and other symmetrical structures; the irregular structure of a transformer includes the transformer casing, transformer oil, and internal structural components.

[0181] A concrete example is the breakdown of the overall internal structure and winding structure of a transformer, as shown below. Figure 6 As shown, the number of elements in the overall 3D model of the transformer after partitioning is 1.108 × 10⁶.

[0182] Step 32, Temperature field heat source setting: The core loss and winding loss calculated based on the electromagnetic field in Step 1 are applied as volume heat sources to the core region and winding region, respectively.

[0183] Step 33, Material thermal property input: Set the thermal conductivity parameters of the winding, including the equivalent specific heat capacity of the winding and the anisotropic thermal conductivity of the winding calculated in Step 2;

[0184] Step 34: Describe the flow behavior of the oil field using a laminar flow model, couple the flow and heat transfer processes using a non-isothermal flow method, and solve for the temperature distribution under steady-state conditions based on heat conduction and natural convection. This includes the following steps:

[0185] Physics field interface selection and coupling establishment: In the finite element simulation software, select the "laminar flow" physics field interface and the "solid heat transfer" physics field interface, and establish a two-way coupling relationship between the flow field and the temperature field through the "non-isothermal flow" multi-physics field coupling node; Input parameters include thermophysical properties such as density, dynamic viscosity, specific heat capacity, and thermal conductivity of transformer oil, as well as the equivalent thermal conductivity and specific heat capacity of the winding and core regions; Output variables include fluid velocity field ν, pressure field p, and temperature field T.

[0186] Fluid domain boundary condition settings: Set no-slip wall conditions in the oil domain inside the tank, that is, the fluid velocity is zero at the solid wall; set the direction of gravitational acceleration to simulate natural convection driving conditions; the input is the gravitational acceleration g and its direction vector; the output is the natural circulation velocity distribution inside the oil domain.

[0187] Thermal boundary condition setting: The volumetric power density of core loss and winding loss obtained by electromagnetic calculation is used as a volume heat source and applied to the corresponding regions respectively; natural convection heat transfer boundary conditions are set on the outer wall of the oil tank, and the ambient temperature and heat transfer coefficient are input; the output is the overall temperature rise distribution.

[0188] Solver settings and steady-state solution: A steady-state solver is used for fully coupled solution, and reasonable nonlinear iteration tolerance and convergence criteria are set. The initial values ​​of the temperature field and the zero flow velocity field are used as initial conditions, and iterative calculation is performed until the residual meets the convergence condition. The output results include the steady-state temperature distribution cloud map inside the transformer, the winding axial temperature gradient curve, and the highest hot spot temperature value.

[0189] Post-processing and data extraction: The winding hot spot temperature and its spatial coordinates are obtained through cross-sectional temperature distribution extraction, path integration and maximum value search functions; the temperature difference between the top and bottom of the winding is output to characterize the axial temperature gradient characteristics under natural cooling conditions.

[0190] In the temperature rise test, the total loss applied to the transformer is the sum of no-load loss and load loss. Stray losses on distribution transformers are relatively small. Therefore, under rated load conditions, the core loss and winding loss are treated as volumetric heat sources applied to their respective regions in the calculation. A laminar flow model is used to describe the flow behavior in the oil region, and a non-isothermal flow method is employed to couple the flow and heat transfer processes. The model primarily considers conduction and natural convection heat transfer, solving for the temperature distribution under steady-state conditions to accurately predict temperature changes in the transformer temperature field under natural cooling conditions.

[0191] The example transformer structure in this embodiment uses the equivalent specific heat capacity and anisotropic thermal conductivity of the windings, obtained from thermal equivalence calculations of the winding structure materials, to calculate the transformer's temperature fluid field. Under rated load conditions with an ambient temperature of 25°C, the calculated transformer temperature distribution is as follows: Figure 7 As shown, Figure 7The left side shows the overall temperature distribution of the transformer, while the right side shows the core temperature distribution. Temperature field calculations show that the overall temperature distribution of the transformer is relatively flat, with the high-temperature areas of the windings and core coinciding with the areas of concentrated losses. The winding temperature distribution shows that the winding temperature increases along the axial direction. This is because the oil near the bottom of the winding absorbs heat and flows upwards, resulting in poorer heat dissipation at the top of the winding compared to the bottom. The temperatures of the tank casing and above the core all show a trend of increasing from bottom to top. The hot spot temperature of the middle B-phase winding is slightly higher than that of phases A and C, mainly in the middle sections between phases A and B, and between phases B and C, where the oil channels are narrow and heat dissipation is poor. For the B-phase winding, the hot spot appears at the upper edge of the B-phase high-voltage winding. Because the top of the winding is in direct contact with the transformer oil, it has better heat dissipation conditions compared to the lower part of the winding. Therefore, the hot spot temperature of 67.4℃ appears at 85% height of the low-voltage winding, located in the upper part of the B-phase coil of the low-voltage winding. The temperature rise of the low-voltage winding is greater than that of the high-voltage winding. The temperature field calculation results show that the internal temperature distribution and loss distribution of the transformer are well consistent and can reflect the main temperature rise characteristics. The proposed method, while ensuring computational efficiency, has certain engineering reference value and can provide support for transformer thermal design and operation analysis.

[0192] Because this embodiment employs an equivalent thermal parameter method and a simplified flow model, the calculated temperature field results show a relatively gentle temperature gradient amplitude, but its overall distribution trend can reasonably reflect the impact of loss distribution on the transformer's temperature rise characteristics. This method achieves a balance between computational accuracy and efficiency, and is suitable for rapid temperature rise assessment and scheme comparison analysis during the transformer engineering design phase.

[0193] Example 4

[0194] Based on the same inventive concept as Embodiment 1, this embodiment introduces a transformer temperature field simulation and prediction device based on thermal parameter equivalence, comprising:

[0195] The loss calculation module is used to perform electromagnetic calculations under rated operating conditions using the three-dimensional electromagnetic field model of the transformer to obtain the distribution characteristics of core loss and winding loss as the loss result.

[0196] The temperature field model equivalent construction module is used to construct and iterate the three-dimensional temperature field model of the transformer.

[0197] The solver module is used to obtain the steady-state temperature distribution of the transformer under natural cooling conditions by non-isothermal flow calculation under laminar flow conditions based on the iterated three-dimensional temperature field model of the transformer.

[0198] The specific functions of each module mentioned above are implemented with reference to the relevant content in the method of Embodiment 1. In this embodiment, the transformer loss results are calculated by the three-dimensional electromagnetic field model of the transformer. The transformer loss results are then used as a heat source and input into the three-dimensional temperature field model of the transformer that is iteratively updated using the thermal equivalence method. The three-dimensional temperature field model of the transformer is then accurately solved by the non-isothermal flow calculation method under laminar flow conditions to improve the accuracy of the simulation solution. This achieves high-precision simulation of the transformer temperature field and improves the simulation prediction rate of the temperature field while ensuring the accuracy of the temperature field prediction.

[0199] Example 5

[0200] Based on the same inventive concept as Embodiments 1 and 2, this embodiment introduces a computer storage medium that can be located in a server to store at least one instruction, at least one program, code set, or instruction set for implementing the method embodiments. The at least one instruction, the at least one program, the code set, or the instruction set is loaded and executed by the processor to implement the transformer temperature field simulation and prediction method steps based on thermal parameter equivalence as described in either Method Embodiments 1 and 2.

[0201] Optionally, in embodiments of the present invention, the storage medium may be located at at least one of a plurality of network servers in a computer network. Optionally, in embodiments of the present invention, the storage medium may include, but is not limited to, various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0202] As can be seen from the technical solutions provided in the embodiments of this specification above, this embodiment equates the complex winding structure to a continuous medium block heat conductor and introduces equivalent thermal parameters of the winding, simplifying the details of the winding. This can significantly reduce the geometric and mesh complexity of the temperature field model, reduce the scale of heat flow coupling solution, and thus improve computational efficiency while ensuring the three-dimensional temperature rise prediction capability.

[0203] In summary, this invention improves the accuracy of thermal-fluid coupling solution by modeling the transformer temperature field. On the other hand, it simplifies the winding details by treating the complex winding structure as a continuous medium block heat conductor and introducing equivalent thermal parameters of the winding, which can significantly reduce the geometric and mesh complexity of the temperature field model and reduce the scale of thermal-fluid coupling solution, thereby improving computational efficiency while ensuring the three-dimensional temperature rise prediction capability.

[0204] 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.

[0205] 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.

[0206] 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 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0207] 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.

[0208] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A transformer temperature field simulation prediction method based on thermal parameter equivalence, characterized in that, include: Based on the obtained transformer thermal parameters, a three-dimensional electromagnetic field model of the transformer is constructed using the finite element method. Based on the three-dimensional electromagnetic field model of the transformer, electromagnetic calculations are performed using the obtained rated operating parameters to obtain the transformer loss results. Based on the obtained thermal and structural parameters of the target transformer, a three-dimensional temperature field model of the transformer is constructed. Based on the structural parameters of the target transformer, the equivalent thermal conductivity and equivalent specific heat capacity of the transformer winding are calculated using the thermal parameter equivalent method. The three-dimensional temperature field model of the transformer is iterated based on the equivalent thermal conductivity, equivalent specific heat capacity and transformer loss results. Based on the iterative three-dimensional temperature field model of the transformer, the steady-state temperature distribution of the transformer under natural cooling conditions is obtained by using a non-isothermal flow calculation method under laminar flow conditions.

2. The transformer temperature field simulation and prediction method based on thermal parameter equivalence according to claim 1, characterized in that, In the three-dimensional electromagnetic field model of the transformer, a nonlinear magnetization characteristic equation is set for the core region, and an electrical excitation is applied to the winding region to solve the steady-state electromagnetic field, thereby obtaining the magnetic flux density distribution inside the transformer.

3. The transformer temperature field simulation and prediction method based on thermal parameter equivalence according to claim 2, characterized in that, Based on the magnetic flux density distribution inside the transformer, the current density inside the transformer is calculated using the electromagnetic field control equation. The transformer loss was calculated based on the current density inside the transformer.

4. The transformer temperature field simulation and prediction method based on thermal parameter equivalence according to claim 3, characterized in that, Based on the magnetic flux density distribution inside the transformer, the formula for calculating the current density inside the transformer using the electromagnetic field control equation is as follows: （1） where μ is the magnetic permeability; A is the vector magnetic potential; J is the current density; σ is the electrical conductivity; t is time; denotes the curl operator; The formula for calculating the transformer loss based on the current density inside the transformer is as follows: （2） Where V is the volume of the region containing the current density. This represents the transformer's loss results.

5. The transformer temperature field simulation and prediction method based on thermal parameter equivalence according to claim 1, characterized in that, Based on the structural parameters of the target transformer, the equivalent thermal conductivity and equivalent specific heat capacity of the transformer windings are calculated using the thermal parameter equivalence method, including: Based on the structural data of the target transformer, the high-voltage winding and low-voltage winding of the transformer are respectively equivalent to continuous dielectric block conductors with anisotropic thermal conductivity. For the continuous dielectric block conductor, the equivalent thermal conductivity of the high-voltage winding and the low-voltage winding of the transformer is calculated through the thermal resistance series mechanism. Based on the equivalent thermal conductivity, the heat absorbed by each material in the representative unit at a preset temperature rise is summed, and the equivalent specific heat capacity is obtained by mass-weighted average. The equivalent thermal conductivity includes axial equivalent thermal conductivity, radial equivalent thermal conductivity, and winding direction equivalent thermal conductivity.

6. The transformer temperature field simulation and prediction method based on thermal parameter equivalence according to claim 5, characterized in that, The formula for calculating axial equivalent thermal conductivity is: （3） Where ka is the axial equivalent thermal conductivity, da1 is the total thickness of the axial copper conductor, da2 is the total thickness of the axial insulating varnish, and da is the total axial thickness. The formula for calculating radial equivalent thermal conductivity is: （4） Wherein, dr1 is the total thickness of the radial conductor layer metal conductor of the transformer winding; dr2 is the total thickness of the radial conductor layer insulating varnish of the transformer winding; dr3 is the total thickness of the radial oil-impregnated insulating paper of the transformer; k1 is the thermal conductivity of the copper conductor of the transformer winding; k2 is the thermal conductivity of the insulating varnish of the conductor layer of the transformer winding; k3 is the thermal conductivity of the oil-impregnated insulating paper of the transformer; and Kr is the radial equivalent thermal conductivity. The equivalent thermal conductivity in the winding direction is 401 W / m / Kelvin, which is the thermal conductivity of the copper wire in the winding.

7. The transformer temperature field simulation and prediction method based on thermal parameter equivalence according to claim 5, characterized in that, The formula for calculating the equivalent specific heat capacity is as follows: （5） in, Let i represent the specific heat capacity of the i-th material within the unit. To absorb total heat, For the temperature of material change, Let the mass of the i-th material be... For equivalent specific heat capacity, This represents the total mass of the winding.

8. The transformer temperature field simulation and prediction method based on thermal parameter equivalence according to claim 1, characterized in that, The three-dimensional temperature field model of the transformer is iterated based on the equivalent thermal conductivity, equivalent specific heat capacity, and transformer loss results, including: For the three-dimensional temperature field model of the transformer, the mesh is generated by scanning mapping and fusion free meshing to obtain multiple transformer regions; Based on the equivalent thermal conductivity and equivalent specific heat capacity, the transformer region of the winding part in the three-dimensional temperature field model is set, and the transformer loss result is used as a heat source input to the three-dimensional temperature field model of the transformer for iteration.

9. A transformer temperature field simulation and prediction device based on thermal parameter equivalence, characterized in that, include: The loss calculation module is used to perform electromagnetic calculations under rated operating conditions using the three-dimensional electromagnetic field model of the transformer to obtain the distribution characteristics of core loss and winding loss as the loss result. The temperature field model equivalent construction module is used to construct and iterate the three-dimensional temperature field model of the transformer. The solver module is used to obtain the steady-state temperature distribution of the transformer under natural cooling conditions by non-isothermal flow calculation under laminar flow conditions based on the iterated three-dimensional temperature field model of the transformer.

10. A computer-readable storage medium, characterized in that, Used to store computer instructions, which, when executed by a processor, complete the steps in the transformer temperature field simulation and prediction method based on thermal parameter equivalence as described in any one of claims 1-8.

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