A method for rapid calculation of transformer hot spot temperature rise

Abstract

A rapid calculation method for transformer hotspot temperature rise is disclosed. The method involves collecting characteristic physical quantities of the transformer, establishing a relationship between the transformer hotspot temperature rise and these characteristic physical quantities, and then dimensionlessly converting this relationship to obtain a dimensionless expression. A finite element simulation model is established for the transformer requiring hotspot temperature rise prediction. Computational fluid dynamics is used to calculate the hotspot temperature of the finite element simulation model under different winding losses and inlet flow velocities, obtaining sample values ​​of the fitting function f. Dimensionless numbers A, B, and C are calculated based on these sample values, and a nonlinear fitting is performed on function f to obtain its expression. Based on the expression of function f obtained through nonlinear fitting, a relationship is established between the transformer hotspot temperature rise and winding losses and inlet flow velocity. When the transformer load changes, the current loss and inlet flow velocity values ​​are input, and the hotspot temperature rise under the transformer's load condition is quickly calculated using function f.

Description

Technical Field

[0001] This invention relates to the field of transformer plate heat sink technology, and in particular to a method for rapid calculation of transformer hot spot temperature rise. Background Technology

[0002] Transformers are crucial equipment for power transmission in power systems, and their safe and reliable operation affects the security and stability of the entire power grid. Currently, liquid-immersed transformers are commonly used in power systems. The lifespan of their oil-paper impregnated insulation system is affected by the degree of heating and temperature under different loads, and the lifespan of the oil-paper insulation system directly impacts the overall service life of the transformer. Determining the hot spot temperature of the oil-paper insulation system is key to calculating transformer lifespan. However, current methods for calculating transformer temperature distribution have drawbacks such as long calculation times and the inability to calculate hot spot temperature rise in real time. Therefore, to better calculate the real-time hot spot temperature rise of transformers and facilitate power grid asset management, a rapid calculation method for transformer hot spot temperature rise is needed.

[0003] The information disclosed in the background section is only intended to enhance the understanding of the background of the present invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for rapid calculation of hot spot temperature rise in transformers, which can perform real-time calculation of hot spot temperature rise in transformers.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention discloses a method for rapid calculation of transformer hot spot temperature rise, including:

[0007] Step 1: Collect characteristic physical quantities of the transformer, including the inlet flow velocity of the insulating liquid, the dynamic viscosity of the insulating liquid, the density of the insulating liquid, the specific heat capacity of the insulating liquid, the thermal conductivity of the insulating liquid, and the current total loss of the transformer. Based on the characteristic physical quantities of the transformer, establish the relationship between the transformer hot spot temperature rise and the characteristic physical quantities:

[0008]

[0009] Wherein, ΔT is the hot spot temperature rise, which is the difference between the transformer hot spot temperature and the ambient temperature or the inlet temperature of the insulating liquid. The hot spot temperature refers to the hottest temperature of the transformer winding section. ρ is the inlet flow rate of the insulating liquid, μ is the dynamic viscosity of the insulating liquid, ρ is the density of the insulating liquid, and C is the inlet flow rate of the insulating liquid. p P is the specific heat capacity of the insulating liquid, k is the thermal conductivity of the insulating liquid, and the subscript θ represents the value at ambient temperature or the inlet temperature of the insulating liquid; loss This is the current total loss of the transformer;

[0010] Step 2: Dimensionlessize the relation to obtain the dimensionless expression:

[0011]

[0012] If we define the variables in the above equation as dimensionless numbers A, B, and C, the equation can be rewritten as follows:

[0013] A = f(B, C);

[0014] Step 3: Establish a finite element simulation model for the transformer requiring hot spot temperature rise prediction. Use computational fluid dynamics to calculate the hot spot temperature of the finite element simulation model under different winding losses and inlet flow velocities, and obtain sample values ​​for fitting the function f:

[0015] Step 4: Based on the results of the finite element simulation in Step 3, calculate the dimensionless numbers A, B, and C, and perform nonlinear fitting on the function f to obtain the expression of the function f.

[0016] Step 5: Based on the expression of function f obtained by nonlinear fitting, establish the relationship between the hot spot temperature rise of the transformer and the winding loss and inlet flow velocity. When the transformer load changes, input the current loss and inlet flow velocity values, and quickly calculate the hot spot temperature rise of the transformer under load conditions through function f.

[0017] In the method described, the transformer is a liquid-immersed transformer.

[0018] In the method described, the dimensionless number A is determined based on the hot spot temperature rise calculated by finite element simulation. The dimensionless numbers B and C correspond to different initial conditions. When fitting the function f, they satisfy statistical laws. The closer R-squared is to 1, the better the fitting effect.

[0019] In the method described, when performing nonlinear fitting, the dimensionless numbers A, B, and C are scaled down by an order of magnitude to make the three dimensionless numbers close to the same order of magnitude to ensure the accuracy of the fitting.

[0020] This invention also discloses a device for rapidly calculating the temperature rise of a transformer hot spot, comprising:

[0021] The data acquisition unit is used to collect the characteristic physical quantities of the transformer, including the inlet flow velocity of the insulating liquid, the dynamic viscosity of the insulating liquid, the density of the insulating liquid, the specific heat capacity of the insulating liquid, the thermal conductivity of the insulating liquid, and the current total loss of the transformer. Based on the characteristic physical quantities of the transformer, the relationship between the temperature rise of the transformer hot spots and the characteristic physical quantities is established.

[0022]

[0023] Wherein, ΔT is the hot spot temperature rise, which is the difference between the transformer hot spot temperature and the ambient temperature or the inlet temperature of the insulating liquid. The hot spot temperature refers to the hottest temperature of the transformer winding section. ρ is the inlet flow rate of the insulating liquid, μ is the dynamic viscosity of the insulating liquid, ρ is the density of the insulating liquid, and C is the inlet flow rate of the insulating liquid. p P is the specific heat capacity of the insulating liquid, k is the thermal conductivity of the insulating liquid, and the subscript θ represents the value at ambient temperature or the inlet temperature of the insulating liquid; loss This is the current total loss of the transformer;

[0024] Dimensionless unit, used to dimensionless the relation to obtain a dimensionless expression:

[0025]

[0026] If we define the variables in the above equation as dimensionless numbers A, B, and C, the equation can be rewritten as follows:

[0027] A = f(B, C);

[0028] The sample value acquisition unit is used to establish a finite element simulation model of the transformer for which hot spot temperature rise prediction is required. It uses computational fluid dynamics to calculate the hot spot temperature of the finite element simulation model under different winding losses and inlet flow velocities, obtaining sample values ​​for fitting the function f.

[0029] The fitting unit is used to calculate dimensionless numbers A, B, and C based on the results of finite element simulation, and to perform nonlinear fitting on function f to obtain the expression of function f.

[0030] The fast solver unit is used to obtain the expression of function f based on nonlinear fitting, and to establish the relationship between the hot spot temperature rise of the transformer and the winding loss and inlet flow velocity. When the transformer load changes, the current loss and inlet flow velocity values ​​are input, and the hot spot temperature rise of the transformer under the load condition is quickly calculated by function f.

[0031] In the device described, the transformer is a liquid-immersed transformer.

[0032] In the device, the dimensionless number A is determined based on the hot spot temperature rise calculated by finite element simulation. The dimensionless numbers B and C correspond to different initial conditions. When fitting the function f, they satisfy statistical laws. The closer R-squared is to 1, the better the fitting effect.

[0033] In the aforementioned device, when performing nonlinear fitting, the dimensionless numbers A, B, and C are scaled down by an order of magnitude to ensure that the three dimensionless numbers are at similar orders of magnitude, thereby guaranteeing the accuracy of the fitting.

[0034] Beneficial effects

[0035] Existing technologies for calculating transformer temperature using finite element analysis are time-consuming and lack real-time calculation methods. This invention utilizes dimensional analysis to solve for the physical relationship between hot spot temperature rise, winding losses, and inlet flow velocity, rather than directly solving the physical relationship by fitting mathematical expressions. By accumulating a large number of reliable samples through finite element simulation, a highly correlated function is obtained, establishing a direct link between hot spot temperature rise, winding losses, and inlet flow velocity. This invention enables rapid calculation of hot spot temperature rise in transformers and can be applied to real-time monitoring of transformer temperature status.

[0036] The above description is merely an overview of the technical solution of the present invention. In order to make the technical means of the present invention clearer and more understandable, so that those skilled in the art can implement it according to the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more obvious and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0038] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0039] In the attached diagram:

[0040] Figure 1 This is a two-dimensional axisymmetric structural diagram of the transformer winding portion, which is part of a method for rapidly calculating the temperature rise of transformer hot spots provided in an embodiment of this disclosure.

[0041] Figure 2 This is a simulation result of a finite element model of transformer hotspot temperature rise, which is provided by an embodiment of the present disclosure for a method for rapid calculation of transformer hotspot temperature rise.

[0042] Figure 3 This is a comparison chart of the calculation results using a prediction function and finite element simulation for a method for rapid calculation of transformer hot spot temperature rise according to an embodiment of this disclosure;

[0043] Figure 4 This is a flowchart illustrating a method for rapidly calculating the temperature rise of a transformer hotspot, provided in one embodiment of this disclosure.

[0044] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Therefore, the following applies to the appendix Figures 1 to 4 The detailed description of the embodiments of the present invention provided herein is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0047] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0048] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0049] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0050] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0051] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0052] To enable those skilled in the art to better understand the technical solution of the present invention, the following will be described in conjunction with the appendix. Figures 1 to 4 The present invention will be described in further detail below, and the accompanying drawings are not intended to limit the embodiments of the present invention.

[0053] In one embodiment, such as Figure 4 As shown, this disclosure provides a method for rapid calculation of transformer hot spot temperature rise, including the following steps:

[0054] Step 1: Collect characteristic physical quantities of the transformer, including the inlet flow velocity of the insulating liquid, the dynamic viscosity of the insulating liquid, the density of the insulating liquid, the specific heat capacity of the insulating liquid, the thermal conductivity of the insulating liquid, and the current total loss of the transformer. Based on the characteristic physical quantities of the transformer, establish the relationship between the transformer hot spot temperature rise and the characteristic physical quantities:

[0055]

[0056] Wherein, ΔT is the hot spot temperature rise, which is the difference between the transformer hot spot temperature and the ambient temperature or the inlet temperature of the insulating liquid. The hot spot temperature refers to the hottest temperature of the transformer winding section. ρ is the inlet flow rate of the insulating liquid, μ is the dynamic viscosity of the insulating liquid, ρ is the density of the insulating liquid, and C is the inlet flow rate of the insulating liquid. p P is the specific heat capacity of the insulating liquid, k is the thermal conductivity of the insulating liquid, and the subscript θ represents the value at ambient temperature or the inlet temperature of the insulating liquid; loss This is the current total loss of the transformer;

[0057] Step 2: Dimensionlessize the relation to obtain the dimensionless expression:

[0058]

[0059] If we define the variables in the above equation as dimensionless numbers A, B, and C, the equation can be rewritten as follows:

[0060] A = f(B, C),

[0061] The expression for function f is obtained, that is, the relationship between hot spot temperature rise, winding loss and inlet flow velocity is established;

[0062] Step 3: Establish a finite element simulation model for the transformer requiring hotspot temperature rise prediction. Use computational fluid dynamics (CFD) to calculate the hotspot temperature of the finite element simulation model under different winding losses and inlet flow velocities, obtaining sample values ​​for the fitted function f. CFD is a built-in method in finite element simulation software. When using the software for calculation, initial values ​​and boundary conditions are set, and the hotspot temperature rise under these conditions is calculated. The specific steps can be summarized as: model establishment - parameter setting - mesh generation - solver setting - calculation results. Using CFD to calculate the hotspot temperature of the finite element simulation model under different winding losses and inlet flow velocities yields the samples needed for the fitted function f. The dimensionless number A, ΔT, is calculated based on the hotspot temperature. Each result obtained through finite element simulation corresponds to a set of dimensionless numbers ABC. Since the hotspot temperature rise ΔT cannot be measured, function f solves the problem of quickly calculating the hotspot temperature rise ΔT from the input measured values.

[0063] Step 4: Based on the results of the finite element simulation in Step 3, calculate the dimensionless numbers A, B, and C, and perform nonlinear fitting on the function f to obtain the expression of the function f.

[0064] Step 5: Based on the expression of function f obtained by nonlinear fitting, establish the relationship between the hot spot temperature rise of the transformer and the winding loss and inlet flow velocity. When the transformer load changes, input the current loss and inlet flow velocity values, and quickly calculate the hot spot temperature rise of the transformer under load conditions through function f.

[0065] In a preferred embodiment of the method, the transformer is a liquid-immersed transformer.

[0066] In a preferred embodiment of the method, the dimensionless number A is determined based on the hot spot temperature rise calculated by finite element simulation. The dimensionless numbers B and C correspond to different initial conditions. When fitting the function f, they satisfy statistical laws, and the closer R-squared is to 1, the better the fitting effect.

[0067] In a preferred embodiment of the method, when performing nonlinear fitting, the dimensionless numbers A, B, and C are scaled down by an order of magnitude so that the three dimensionless numbers are at similar orders of magnitude to ensure the accuracy of the fitting.

[0068] In one embodiment, the method includes,

[0069] Step 1: Provide the relationship between the transformer hotspot temperature rise and characteristic physical quantities:

[0070]

[0071] ΔT is the hot spot temperature rise, which is the difference between the transformer hot spot temperature and the ambient temperature or the inlet temperature of the insulating liquid. The hot spot temperature refers to the hottest temperature of the transformer winding section. ρ is the inlet flow rate of the insulating liquid, μ is the dynamic viscosity of the insulating liquid, ρ is the density of the insulating liquid, and C is the inlet flow rate of the insulating liquid. p P is the specific heat capacity of the insulating liquid, k is the thermal conductivity of the insulating liquid, and the subscript θ represents the value at ambient temperature or the inlet temperature of the insulating liquid; loss This is the current total loss of the transformer.

[0072] Step 2: Dimensionlessize the relation given in Step 1:

[0073] Dimensionlessness involves converting the variables on both sides of the equation into quantities with a unit of 1, i.e., without physical units. The inlet flow velocity is selected from step 1. Specific heat capacity C p Using dynamic viscosity μ and density ρ as representative quantities, a dimensionless expression is obtained:

[0074]

[0075] For ease of expression, the variables in the above formula are defined as dimensionless numbers A, B, and C, respectively, and the formula is rewritten as:

[0076] A = f(B, C)

[0077] By obtaining the expression for function f, the relationship between hot spot temperature rise, winding loss, and inlet flow velocity can be established.

[0078] Step 3: For the transformer requiring hotspot temperature rise prediction, establish its finite element simulation model, and use computational fluid dynamics to calculate the hotspot temperature of the model under different winding losses and inlet flow velocities, obtaining the sample values ​​of the function f from Step 2:

[0079] Finite element simulation and computational fluid dynamics are methods that can accurately obtain the hot spot temperature of transformer windings, but their calculation time is relatively long. To ensure the accuracy of the fitting function, the winding loss and inlet flow velocity should be selected from values ​​within the transformer's operating conditions, and the sample size should be relatively large.

[0080] Step 4: Based on the results of the finite element simulation in Step 3, calculate the dimensionless numbers A, B, and C, and perform nonlinear fitting on the function f to obtain the expression for f.

[0081] The dimensionless number A is determined based on the hotspot temperature rise calculated from finite element simulation, while dimensionless numbers B and C correspond to different initial conditions. When fitting the function f, statistical laws should be followed; the closer R-squared is to 1, the better the fit. In nonlinear fitting, the dimensionless numbers A, B, and C can be scaled down by orders of magnitude to ensure they are on similar orders of magnitude and thus guarantee fitting accuracy.

[0082] Step 5: Based on the function obtained in Step 4, establish the relationship between the hot spot temperature rise of the transformer and the winding loss and inlet flow velocity. When the transformer load changes, only the current loss and inlet flow velocity values ​​need to be input, and the hot spot temperature rise under that operating condition can be quickly calculated using the function.

[0083] In one embodiment, this embodiment takes the hot spot temperature rise of a 110kV / 40MVA power transformer as the calculation object. First, according to step 1, the relationship between the hot spot temperature rise of the transformer and the characteristic physical quantity is established:

[0084]

[0085] Then, perform dimensionless transformation according to step 2, and write it as the following expression:

[0086] A = F(B, C)

[0087] Then, according to the requirements of step 3, a two-dimensional axisymmetric structure of the high-voltage winding of the transformer was established in the finite element simulation software COMSOL Multiphysics 5.6. The total height of the winding is 74 discs, and some of the structures are as follows. Figure 1 As shown, the high-voltage winding has 74 coils, each with a height of 12.4 mm and a width of 90 mm, and is wrapped with 0.475 mm thick cellulose insulating paper. The inner and outer axial oil passages have widths of 9 mm and 9.5 mm, respectively. The horizontal oil passage height is 4 mm, and the inner radius of the winding is 434 mm. Furthermore, the finite element simulation model is constructed as a two-dimensional axisymmetric structure, with the high-voltage winding comprising an array of multiple coils.

[0088] The power consumption and inlet flow rate combinations selected for the simulation are shown in Table 1, with a total of 34 samples. The calculated results of the hotspot temperature rise are as follows: Figure 2 As shown.

[0089] Table 1. Simulation values ​​of the finite element model in the example.

[0090] Total loss (W) 13320.2,26640.4,39960.6,53280.8,66601,79921.2,99901.5 Inlet velocity (m / s) 0.016,0.032,0.048,0.064,0.08,0.096,0.12

[0091] Then, according to step 4, the dimensionless number ABC is calculated and the F function is fitted. The structure of the fitted function is shown in Table 2. The R-squared value of the F function is... 2 The value of 0.9994 indicates a good fit.

[0092] Table 2. Expression and coefficient values ​​of the dimensionless function F obtained in the examples.

[0093]

[0094] Finally, based on step 5, five different combinations of loss and inlet velocity were randomly selected. The hotspot temperature rise under different combinations was calculated using prediction functions and finite element simulations, and the results are as follows: Figure 3 As shown, the fitting function can calculate the hot spot temperature rise of the transformer more accurately than finite element simulation, while also greatly reducing the calculation time. After obtaining the prediction function, the hot spot temperature rise of the transformer can be calculated quickly and accurately under any loss and inlet flow velocity conditions.

[0095] In one embodiment, the present invention also discloses a device for rapid calculation of transformer hot spot temperature rise, comprising:

[0096] The data acquisition unit is used to collect the characteristic physical quantities of the transformer, including the inlet flow velocity of the insulating liquid, the dynamic viscosity of the insulating liquid, the density of the insulating liquid, the specific heat capacity of the insulating liquid, the thermal conductivity of the insulating liquid, and the current total loss of the transformer. Based on the characteristic physical quantities of the transformer, the relationship between the temperature rise of the transformer hot spots and the characteristic physical quantities is established.

[0097]

[0098] Wherein, ΔT is the hot spot temperature rise, which is the difference between the transformer hot spot temperature and the ambient temperature or the inlet temperature of the insulating liquid. The hot spot temperature refers to the hottest temperature of the transformer winding section. ρ is the inlet flow rate of the insulating liquid, μ is the dynamic viscosity of the insulating liquid, ρ is the density of the insulating liquid, and C is the inlet flow rate of the insulating liquid. p P is the specific heat capacity of the insulating liquid, k is the thermal conductivity of the insulating liquid, and the subscript θ represents the value at ambient temperature or the inlet temperature of the insulating liquid; loss This is the current total loss of the transformer;

[0099] Dimensionless unit, used to dimensionless the relation to obtain a dimensionless expression:

[0100]

[0101] If we define the variables in the above equation as dimensionless numbers A, B, and C, the equation can be rewritten as follows:

[0102] A = f(B, C);

[0103] The sample value acquisition unit is used to establish a finite element simulation model of the transformer for which hot spot temperature rise prediction is required. It uses computational fluid dynamics to calculate the hot spot temperature of the finite element simulation model under different winding losses and inlet flow velocities, obtaining sample values ​​for fitting the function f.

[0104] The fitting unit is used to calculate dimensionless numbers A, B, and C based on the results of finite element simulation, and to perform nonlinear fitting on function f to obtain the expression of function f.

[0105] The fast solver unit is used to obtain the expression of function f based on nonlinear fitting, and to establish the relationship between the hot spot temperature rise of the transformer and the winding loss and inlet flow velocity. When the transformer load changes, the current loss and inlet flow velocity values ​​are input, and the hot spot temperature rise of the transformer under the load condition is quickly calculated by function f.

[0106] In one embodiment, the transformer is a liquid-immersed transformer.

[0107] In one embodiment, the dimensionless number A is determined based on the hot spot temperature rise calculated by finite element simulation. The dimensionless numbers B and C correspond to different initial conditions. When fitting the function f, they satisfy statistical laws. The closer R-squared is to 1, the better the fitting effect.

[0108] In one embodiment, when performing nonlinear fitting, the dimensionless numbers A, B, and C are scaled down by an order of magnitude to bring the three dimensionless numbers to a similar order of magnitude to ensure the accuracy of the fitting.

[0109] Although embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art can make many other forms based on the guidance of this specification and without departing from the scope of protection of the claims of the present invention, and all of these are within the scope of protection of the present invention.

Claims

1. A method for rapid calculation of transformer hot spot temperature rise, characterized in that, It includes the following steps: Step 1: Collect characteristic physical quantities of the transformer, including the inlet flow velocity of the insulating liquid, the dynamic viscosity of the insulating liquid, the density of the insulating liquid, the specific heat capacity of the insulating liquid, the thermal conductivity of the insulating liquid, and the current total loss of the transformer. Based on the characteristic physical quantities of the transformer, establish the relationship between the temperature rise of the transformer hot spot and the characteristic physical quantities. Step 2: Dimensionlessize the relation to obtain the dimensionless expression A = f(B, C); Step 3: Establish a finite element simulation model for the transformer requiring hot spot temperature rise prediction. Use computational fluid dynamics to calculate the hot spot temperature of the finite element simulation model under different winding losses and inlet flow velocities to obtain sample values ​​for fitting the function f. Step 4: Calculate dimensionless numbers A, B, and C based on the sample values, and perform nonlinear fitting on function f to obtain the expression of function f; Step 5: Based on the expression of function f obtained by nonlinear fitting, establish the relationship between the hot spot temperature rise of the transformer and the winding loss and inlet flow velocity. When the transformer load changes, input the current loss and inlet flow velocity values, and quickly calculate the hot spot temperature rise of the transformer under load conditions through function f.

2. The method according to claim 1, characterized in that, The transformer is a liquid-immersed transformer.

3. The method according to claim 1, characterized in that, The dimensionless number A is determined based on the hot spot temperature rise calculated by finite element simulation. The dimensionless numbers B and C correspond to different initial conditions. When fitting the function f, they satisfy statistical laws. The closer R-squared is to 1, the better the fitting effect.

4. The method according to claim 1, characterized in that, When performing nonlinear fitting, the dimensionless numbers A, B, and C are scaled down by orders of magnitude to bring them to similar orders of magnitude, thus ensuring the accuracy of the fitting.

5. A device for rapidly calculating the temperature rise of a transformer hot spot, characterized in that, It includes: The data acquisition unit is used to acquire the characteristic physical quantities of the transformer, including the inlet flow velocity of the insulating liquid, the dynamic viscosity of the insulating liquid, the density of the insulating liquid, the specific heat capacity of the insulating liquid, the thermal conductivity of the insulating liquid, and the current total loss of the transformer. Based on the characteristic physical quantities of the transformer, the relationship between the temperature rise of the transformer hot spot and the characteristic physical quantities is established. A dimensionless unit is used to dimensionless the relation to obtain a dimensionless expression A = f(B, C); The sample value acquisition unit is used to establish a finite element simulation model of the transformer for which hotspot temperature rise prediction is required. It uses computational fluid dynamics to calculate the hotspot temperature of the finite element simulation model under different winding losses and inlet flow velocities, obtaining sample values ​​for fitting the function f. The fitting unit is used to calculate dimensionless numbers A, B, and C based on the sample values, and to perform nonlinear fitting on the function f to obtain the expression of the function f; The fast solver unit is used to obtain the expression of function f based on nonlinear fitting, and to establish the relationship between the hot spot temperature rise of the transformer and the winding loss and inlet flow velocity. When the transformer load changes, the current loss and inlet flow velocity values ​​are input, and the hot spot temperature rise of the transformer under the load condition is quickly calculated by function f.

6. The apparatus according to claim 5, characterized in that, The transformer is a liquid-immersed transformer.

7. The apparatus according to claim 5, characterized in that, The dimensionless number A is determined based on the hot spot temperature rise calculated by finite element simulation. The dimensionless numbers B and C correspond to different initial conditions. When fitting the function f, they satisfy statistical laws. The closer R-squared is to 1, the better the fitting effect.

8. The apparatus according to claim 5, characterized in that, When performing nonlinear fitting, the dimensionless numbers A, B, and C are scaled down by orders of magnitude to bring them to similar orders of magnitude, thus ensuring the accuracy of the fitting.

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