Transformer transient temperature rise prediction method and device and storage medium

Abstract

The embodiment of the invention discloses a transformer transient temperature rise prediction method and device and a storage medium, and the method comprises the steps: constructing a two-dimensional model, calculating the magnetic flux density distribution conditions of a transformer iron core and a winding under a first preset load rate condition, and further obtaining an iron core loss value and an eddy current loss value of the winding, the method is used as heat source excitation of a temperature-flow field of the transformer, a step type function is adopted for representation and is substituted into a heat flow field coupling calculation model, electromagnetism, fluid mechanics, heat transfer theory and a finite element method are involved, and the problem that transient temperature rise simulation calculation of the dry type transformer under different load rates is difficult to converge can be effectively and accurately solved.

Description

Technical Field

[0001] The present invention relates to the field of electric power technology, and in particular to a method, a device and a storage medium for predicting transient temperature rise of a transformer. Background Art

[0002] Power transformers are the core equipment of the power system and are key equipment for power transmission and voltage conversion. As a type of power transformer, dry-type transformers are increasingly used in distribution networks as their insulation strength and rated capacity continue to improve. In addition, dry-type transformers have the characteristics of superior environmental performance, strong safety and reliability, and high operating efficiency. During operation, power transformers must withstand high internal electric field stress, mechanical stress, and thermal stress. As the scale of the power grid continues to expand, the voltage level and transmission power of power transformers are gradually increasing. The thermal defect problem caused by local overheating is becoming increasingly serious, and the temperature rise characteristics are becoming more complex, making insulation aging failures very likely to occur.

[0003] However, most of the current research results on transformer temperature rise focus on the steady-state temperature characteristics of transformers. There are not many studies on the transient temperature rise of dry-type transformers and their process analysis, which are still under research. In addition, the transient temperature simulation calculation of the three-dimensional transformer model is difficult to converge, so it is urgent to carry out research on the simulation calculation method of the transient temperature rise of dry-type transformer hot spots. In view of the problem that the transient temperature simulation calculation of the three-dimensional transformer model is difficult to converge, it is necessary to carry out further research on the transient temperature rise prediction technology of the transformer. Summary of the invention

[0004] The embodiments of the present invention provide a method, device and storage medium for predicting transient temperature rise of a transformer, so as to solve the problem that the transient temperature simulation calculation of the current three-dimensional transformer model is difficult to converge.

[0005] In one aspect, the present invention provides a method for predicting transient temperature rise of a transformer, comprising:

[0006] Construct a two-dimensional model of the transformer main structure, which includes a high-voltage winding and a low-voltage winding;

[0007] Applying voltage excitation to each phase high-voltage winding according to a first preset load rate, and calculating the magnetic flux density distribution of the transformer core and winding using Maxwell equations based on initial values ​​of various physical quantities of the transformer and material parameters;

[0008] According to the distribution of magnetic flux density, the core loss value of the transformer and the eddy current loss value of the winding are calculated;

[0009] The core loss value and eddy current loss value are used as the heat source excitation of the transformer temperature-flow field, and a step function is used to characterize it and bring it into the thermal-flow field coupling calculation model. The automatic Newton method is used for the nonlinear method of the separation solution module in the transient solver to obtain the transient heat flux temperature distribution of the two-dimensional dry-type transformer. The transient heat flux temperature distribution of the two-dimensional dry-type transformer is displayed based on the two-dimensional model.

[0010] Further, the step of applying voltage excitation to each phase high-voltage winding according to the first preset load rate, and calculating the magnetic flux density distribution of the transformer core and winding using Maxwell equations based on the initial values ​​of each physical quantity and material parameters of the transformer includes:

[0011] Maxwell's equations are used to describe the laws between various physical quantities in the electromagnetic field of the transformer. The Maxwell equations include:

[0012]

[0013]

[0014]

[0015]

[0016] Among them, E is the electric field strength, unit V / m; B is the magnetic induction intensity, unit A / m; H is the magnetic field strength, unit T; D is the current density, unit C / m 2 ; J is the eddy current density, unit A / m 2 ρ e is the charge density, in C / m 3 ;

[0017] Characterizing the constitutive relations of linear media in transformers:

[0018] D=ε r ε0E

[0019] B=μ m H

[0020] J=σE

[0021] Among them, ε r is the relative dielectric constant of the medium; ε0 is the dielectric constant of vacuum; μ m is the magnetic permeability of the medium, in H / m; σ is the electrical conductivity of the medium, in S / m; for isotropic media, ε r , μ m and σ are scalars. For anisotropic media, ε r , μ m and σ are both vectors;

[0022] Magnetic insulation boundary conditions are set on the outer surface of the transformer oil tank, and the initial vector magnetic potential is set to 0Wb / m. Voltage excitation is applied to the high-voltage windings of each phase based on the first preset load rate. An external circuit is added to the low-voltage windings of each phase using the field-circuit coupling method, and excitation is applied by setting a current source in the external circuit. The magnetic flux density distribution of the transformer core and windings is obtained by simulation.

[0023] Further, the step of calculating the core loss value of the transformer and the eddy current loss value of the winding according to the magnetic flux density distribution includes:

[0024]

[0025]

[0026]

[0027] In the formula, B max is the maximum value of magnetic induction intensity at point x; ω is the eddy current angular frequency; γ is the specific conductivity of the wire material; a is the width of the wire; a is the width of the wire; P Feddy is the radial eddy current loss of the conductor; P Zeddy is the axial eddy current loss of the conductor; P v Average power loss density; f is the excitation frequency; k h is the Steinmetz proportionality constant.

[0028] Furthermore, the core loss value and the eddy current loss value are used as the heat source excitation of the transformer temperature-flow field, and a step-type function is used to characterize and bring it into the thermal-flow field coupling calculation model, wherein the nonlinear method of the separation solution module in the transient solver adopts automatic Newton to obtain the transient heat flow temperature distribution of the two-dimensional dry-type transformer, including:

[0029] The non-isothermal flow process in the air domain of the high-voltage winding and the low-voltage winding follows the laws of conservation of mass, momentum, and energy, and satisfies the constraints of the Navier-Stokes (NS) equations:

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036] Where c is the specific heat capacity, the unit is J / (kg·K); v is the flow velocity, the subscript represents the direction, the unit is m / s; F is the external force on the fluid element, the subscript represents the direction, the unit is N; p is the pressure, the unit is Pa; m is the dynamic viscosity, the unit is N·s / m 2 ; r is density, unit is kg / m 3 ; Se is the ratio of the inertial force to the viscous force caused by the secondary flow, dimensionless;

[0037] Among them, the separation solution module of the transient solver in the solver configuration is improved, the merged variables in the separation step and the nonlinear method in the radiosity are set to automatic Newton, and the transient heat flux temperature distribution of the two-dimensional dry-type transformer is obtained.

[0038] Further, the steps of setting the combined variables in the separation step and the nonlinear method in the radiosity to automatic Newton to obtain the transient heat flux temperature distribution of the two-dimensional dry-type transformer include:

[0039] Calculate the total heat source of the transformer and bring it into the thermal-fluid coupling field for calculation;

[0040] By substituting constant flow parameters into conservation equations, the flow field and temperature distribution are calculated, and the transient heat flux and temperature distribution of the two-dimensional dry-type transformer is obtained.

[0041] Furthermore, after the steps of obtaining the transient heat flow and temperature distribution of the two-dimensional dry-type transformer by substituting the constant flow parameters into the conservation equation and calculating the flow field and temperature distribution, the method includes:

[0042] Determine whether the residual of two adjacent temperature iterations is less than 0.01k;

[0043] If yes, determine whether the second preset load rate exceeds 100%, the second preset load rate being the sum of the first preset load rate and 10%;

[0044] If yes, the prediction is terminated; if no, voltage excitation is applied to each phase high-voltage winding according to the second preset load rate to predict the corresponding transient heat flow temperature distribution.

[0045] Furthermore, after the step of obtaining the transient heat flow temperature distribution of the two-dimensional dry-type transformer, the method further includes:

[0046] The hot spot of the transformer B phase winding was selected as the temperature measurement point for temperature rise test verification, and the temperature rise test fitting curve of the hot spot temperature rise versus load application time was obtained. The error between the fitting curve of the transient heat flow temperature distribution of the two-dimensional dry-type transformer and the temperature rise test fitting curve was compared.

[0047] Furthermore, the step of applying voltage excitation at each phase high voltage winding according to the first preset load rate includes:

[0048] The electromagnetic field simulation calculation method is used to change the magnitude of the current value in the external application circuit in the field-circuit coupling to respectively reflect the magnitude of the first preset load rate, and the first preset load rate is greater than or equal to 40%.

[0049] In order to solve the problem that the transient temperature simulation calculation of the current three-dimensional model of the transformer is difficult to converge, the purpose of the present invention is to provide a method for predicting the transient temperature rise of the transformer, including: constructing a two-dimensional model of the transformer main structure, the two-dimensional model includes a high-voltage winding and a low-voltage winding; applying voltage excitation at each phase high-voltage winding according to a first preset load rate, and calculating the magnetic flux density distribution of the transformer core and windings using the Maxwell equations based on the initial values ​​of various physical quantities of the transformer and material parameters; according to the magnetic flux density distribution, calculating the core loss value of the transformer and the eddy current loss value of the winding; using the core loss value and the eddy current loss value as the heat source excitation of the transformer temperature-flow field, using a step-type function to characterize and bring it into the thermal flow field coupling calculation model, wherein the nonlinear method of the separation solution module in the transient solver adopts automatic Newton to obtain the transient heat flow temperature distribution of the two-dimensional dry-type transformer.

[0050] Compared with the prior art, the present invention has the following advantages:

[0051] By constructing a two-dimensional model and calculating the magnetic flux density distribution of the transformer core and winding under the first preset load rate condition, the core loss value and the eddy current loss value of the winding are further obtained, which are then used as the heat source excitation of the transformer temperature-flow field. A step function is used to characterize it and bring it into the thermal-flow field coupling calculation model, which involves electromagnetism, fluid mechanics, heat transfer, and finite element method. It can effectively and accurately solve the problem of convergence difficulty in the simulation calculation of transient temperature rise of dry-type transformers under different load rates, and can also be used to pave the way for further development of the dynamic temperature rise evolution law of dry-type transformer windings.

[0052] On the other hand, the present invention provides a transformer transient temperature rise prediction device, comprising:

[0053] A construction module is used to construct a two-dimensional model of the transformer main structure, wherein the two-dimensional model includes a high-voltage winding and a low-voltage winding;

[0054] A first calculation module is used to apply voltage excitation to each phase high-voltage winding according to a first preset load rate, and calculate the magnetic flux density distribution of the transformer core and winding using Maxwell equations based on the initial values ​​of various physical quantities of the transformer and material parameters;

[0055] The second calculation module is used to calculate the core loss value of the transformer and the eddy current loss value of the winding according to the magnetic flux density distribution;

[0056] The third calculation module is used to use the core loss value and eddy current loss value as the heat source excitation of the transformer temperature-flow field, and adopts a step function to characterize and bring it into the thermal-flow field coupling calculation model. The nonlinear method of the separation solution module in the transient solver adopts automatic Newton to obtain the transient heat flow temperature distribution of the two-dimensional dry-type transformer.

[0057] In yet another aspect, the present invention provides a computer-readable storage medium storing a computer program, which can implement the above method when executed by a processor. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0059] Figure 1 The present invention is a flowchart of a method for predicting transient temperature rise of a transformer according to an embodiment of the present invention.

[0060] Figure 2 This is a three-dimensional geometric model structure and a two-dimensional geometric model structure of a transformer according to an embodiment of the present invention.

[0061] Figure 3 It is the magnetic field distribution of the transformer core-winding structure and the transformer magnetic field distribution cross section at the rated load rate of the embodiment of the present invention.

[0062] Figure 4 It is a schematic diagram showing that the core heat source excitation and the winding heat source excitation of an embodiment of the present invention are characterized by a step function (the left figure is the core heat source excitation, and the right figure is the winding heat source excitation).

[0063] Figure 5 It is the distribution cloud diagram result of the simulation calculation of the transient temperature rise of the hot spot of the two-dimensional dry-type transformer under the rated load rate of the embodiment of the present invention (the upper left picture is 1h, the upper right picture is 2h, the lower left picture is 4h, and the lower right picture is 8h).

[0064] Figure 6 It is the distribution cloud diagram result of the simulation calculation of the transient temperature rise of the hot spot of the two-dimensional dry-type transformer under the load rate of 40% of the embodiment of the present invention (the upper left picture is 1h, the upper right picture is 2h, the lower left picture is 4h, and the lower right picture is 8h).

[0065] Figure 7 and Figure 8 It is a comparison between the simulation fitting curve and the test fitting curve at 40% load rate and 100% load rate of the embodiment of the present invention.

[0066] Fig. 9 It is a schematic diagram of a transformer transient temperature rise prediction device according to another embodiment of the present invention. DETAILED DESCRIPTION

[0067] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0068] See also Figure 1 A method for predicting transient temperature rise of a transformer according to an embodiment of the present invention comprises the following steps:

[0069] Step 11, constructing a two-dimensional model of the transformer main structure, the two-dimensional model including a high-voltage winding and a low-voltage winding.

[0070] Dry-type transformers have the advantages of simple structure, fire resistance and maintenance-free, and have become the most mainstream choice for power supply and distribution design in buildings. Among dry-type transformers, epoxy resin cast transformers have simple manufacturing processes, large inventory and high popularity compared to open-type transformers. The insulation heat resistance grades of epoxy resin cast transformers are F and H. Although H-grade transformers have high heat resistance and compact structure, they are expensive and are constrained by the insulation heat resistance grades of other equipment in the distribution room. They cannot take advantage of their high heat resistance. Currently, F-grade dry-type transformers are still the mainstream. Therefore, this embodiment carries out corresponding simulation work around a dry-type transformer with a model of SCB13-800 / 10.

[0071] In the actual transformer model, the CAD software can be used to draw and manually divide the original model to construct a three-dimensional model and a two-dimensional model, which are used as the basis for analyzing the transient temperature distribution of the dry-type transformer. In order to reduce the amount of calculation without affecting the simulation accuracy, the dry-type transformer is simplified and processed as follows:

[0072] a. Ignore the transformer lifting rings, high-voltage connecting rods, struts and other device structures and consider the main structural components of the transformer, such as the core, clamps, windings, etc.

[0073] b. Ignore edges and delete holes on the original model to make the model more of an overall structure, which is convenient for meshing.

[0074] c. Construct high and low voltage winding coils respectively. As one implementation method, the high voltage winding is a multi-layer segmented cylindrical coil wound with flat copper wire, and the low voltage winding is a foil coil wound with axially continuous copper foil. Figure 2 , Figure 2This is a three-dimensional geometric model structure and a two-dimensional geometric model structure of a transformer according to an embodiment of the present invention.

[0075] Step 12: applying voltage excitation to each phase high voltage winding according to the first preset load rate, and calculating the magnetic flux density distribution of the transformer core and winding using Maxwell's equations based on the initial values ​​of each physical quantity and material parameters of the transformer.

[0076] The essence of multi-physics field simulation is to use numerical calculation methods such as finite element method, finite volume method and finite difference method to solve the partial differential equations that describe the rules of physical quantity transfer, so as to obtain the evolution law of physical quantities in time and the distribution law in space.

[0077] The magnetic insulation boundary condition is set on the outer surface of the transformer tank, and the initial vector magnetic potential is set to 0Wb / m. In this case, voltage excitation is applied to the high-voltage winding of each phase, and an external circuit is added to the low-voltage winding of each phase using the field-circuit coupling method, and excitation is applied by setting a current source in the external circuit. The magnetic flux density distribution of the transformer core and winding is obtained by simulation.

[0078] As one of the implementation modes, the step of applying voltage excitation at each phase high-voltage winding according to a first preset load rate includes: using an electromagnetic field simulation calculation method to reflect the size of the first preset load rate by changing the size of the current value in the external application circuit in the field-circuit coupling, and the first preset load rate is greater than or equal to 40%.

[0079] In the embodiment of the present invention, the size of the preset load rate is mainly reflected by the size of the load current. Using the above-mentioned electromagnetic field simulation calculation method, by changing the size of the current value in the external application circuit in the field-circuit coupling, 40%, 50%, 60%, 70%, 80%, 90%, and 100% load rates are respectively reflected, and finally the simulation calculation results of the electromagnetic field of the transformer under each load rate are obtained.

[0080] Specifically, step 12 may also have the following implementation modes:

[0081] Maxwell's equations are used to describe the laws between various physical quantities in the electromagnetic field of the transformer. The Maxwell equations include:

[0082]

[0083]

[0084]

[0085]

[0086] Among them, E is the electric field strength, unit V / m; B is the magnetic induction intensity, unit A / m; H is the magnetic field strength, unit T; D is the current density, unit C / m 2 ; J is the eddy current density, unit A / m 2 ρ e is the charge density, in C / m 3 ;

[0087] Characterizing the constitutive relations of linear media in transformers:

[0088] D=ε r ε0E

[0089] B=μ m H

[0090] J=σE

[0091] Among them, ε r is the relative dielectric constant of the medium; ε0 is the dielectric constant of vacuum; μ m is the magnetic permeability of the medium, in H / m; σ is the electrical conductivity of the medium, in S / m; for isotropic media, ε r , μ m and σ are scalars. For anisotropic media, ε r , μ m and σ are both vectors;

[0092] Magnetic insulation boundary conditions are set on the outer surface of the transformer oil tank, and the initial vector magnetic potential is set to 0Wb / m. Voltage excitation is applied to the high-voltage windings of each phase based on the first preset load rate. An external circuit is added to the low-voltage windings of each phase using the field-circuit coupling method, and excitation is applied by setting a current source in the external circuit. The magnetic flux density distribution of the transformer core and windings is obtained by simulation.

[0093] See also Figure 3 , Figure 3 It is the magnetic field distribution of the transformer core-winding structure and the transformer magnetic field distribution cross section at the rated load rate of the embodiment of the present invention.

[0094] Step 13, according to the magnetic flux density distribution, calculate the core loss value of the transformer and the eddy current loss value of the winding.

[0095] Specifically, step 13 may also have the following implementation modes:

[0096]

[0097]

[0098]

[0099] In the formula, B maxis the maximum value of magnetic induction intensity at point x; ω is the eddy current angular frequency; γ is the specific conductivity of the wire material; a is the width of the wire; a is the width of the wire; P Feddy is the radial eddy current loss of the conductor; P Zeddy is the axial eddy current loss of the conductor; P v Average power loss density; f is the excitation frequency; k h is the Steinmetz proportionality constant.

[0100] Step 14, using the core loss value and eddy current loss value as the heat source excitation of the transformer temperature-flow field, using a step function to characterize and bring it into the thermal-flow field coupling calculation model, wherein the automatic Newton is used for the nonlinear method of the separation solution module in the transient solver to obtain the two-dimensional dry-type transformer transient heat flux temperature distribution, and the two-dimensional dry-type transformer transient heat flux temperature distribution is displayed based on the two-dimensional model.

[0101] When studying the natural convection model inside a dry-type transformer, steady-state analysis is usually considered. However, in view of the three-dimensional dry-type transformer, when considering natural convection, too many grids need to be divided, and the calculation of the flow field is not easy to converge when considering steady-state analysis. Therefore, a simulation calculation of the transient temperature rise process of the two-dimensional dry-type transformer is performed. The transformer iron loss value and winding loss obtained by the simulation in the above steps are used as the heat source excitation of the transformer temperature-flow field, and the heat source excitation is processed in the form of a step function.

[0102] Specifically, step 14 may also have the following implementation modes:

[0103] The non-isothermal flow process in the air domain of the high-voltage winding and the low-voltage winding follows the laws of conservation of mass, momentum, and energy, and satisfies the constraints of the Navier-Stokes (NS) equations:

[0104]

[0105]

[0106]

[0107]

[0108]

[0109]

[0110] Where c is the specific heat capacity, the unit is J / (kg·K); v is the flow velocity, the subscript represents the direction, the unit is m / s; F is the external force on the fluid element, the subscript represents the direction, the unit is N; p is the pressure, the unit is Pa; m is the dynamic viscosity, the unit is N·s / m 2; r is density, unit is kg / m 3 ; Se is the ratio of the inertial force to the viscous force caused by the secondary flow, dimensionless;

[0111] Among them, the separation solution module of the transient solver in the solver configuration is improved, the merged variables in the separation step and the nonlinear method in the radiosity are set to automatic Newton, and the transient heat flux temperature distribution of the two-dimensional dry-type transformer is obtained.

[0112] As one implementation method, the step of setting the combined variables in the separation step and the nonlinear method in the radiosity to automatic Newton to obtain the transient heat flux temperature distribution of the two-dimensional dry-type transformer includes:

[0113] Step 141, calculate the total heat source of the transformer and bring it into the thermal-fluid coupling field for calculation.

[0114] Step 142, by substituting the constant flow parameters into the conservation equation, the flow field and temperature distribution are calculated to obtain the transient heat flow temperature distribution of the two-dimensional dry-type transformer.

[0115] Step 143, determine whether the residuals of two adjacent temperature iterations are less than 0.01K.

[0116] Step 144: If yes, determine whether the second preset load rate exceeds 100%, the second preset load rate being the sum of the first preset load rate and 10%.

[0117] Step 145, if yes, then end the prediction; if no, then apply voltage excitation to each phase high voltage winding according to the second preset load rate to predict the corresponding transient heat flux temperature distribution.

[0118] See also Figures 4 to 6 ,in Figure 4 Schematic diagram of the iron core heat source excitation and the winding heat source excitation of the embodiment of the present invention using step-type functions (the left figure is the iron core heat source excitation, and the right figure is the winding heat source excitation), Figure 5 It is the distribution cloud diagram result of the simulation calculation of the transient temperature rise of the hot spot of the two-dimensional dry-type transformer under the rated load rate of the embodiment of the present invention (the upper left figure is 1h, the upper right figure is 2h, the lower left figure is 4h, and the lower right figure is 8h). Figure 6 It is the distribution cloud diagram result of the simulation calculation of the transient temperature rise of the hot spot of the two-dimensional dry-type transformer under the load rate of 40% of the embodiment of the present invention (the upper left picture is 1h, the upper right picture is 2h, the lower left picture is 4h, and the lower right picture is 8h).

[0119] As one implementation manner, after step 14, the following may also be included:

[0120] Step 15, select the hot spot of the transformer B phase winding as the temperature measurement point to perform a temperature rise test verification and obtain the temperature rise test fitting curve of the hot spot temperature rise versus load application time, and compare the error between the fitting curve of the two-dimensional dry-type transformer transient heat flow temperature distribution and the temperature rise test fitting curve.

[0121] As one of the implementation methods, the hot spot of the transformer B phase winding is selected as the temperature measurement point to perform the transformer temperature rise test verification and obtain the fitting curve of the hot spot temperature rise with the load application time. The error comparison analysis of the temperature rise simulation fitting curve and the temperature rise test fitting curve is performed to verify the accuracy and effectiveness of the simulation method. For example, the dynamic temperature rise fitting formula of the transformer B phase winding hot spot at 40% and 100% load rate is as follows:

[0122]

[0123]

[0124] See also Figure 7 and Figure 8 , respectively, are comparisons between the simulation fitting curve and the test fitting curve at 40% load rate and 100% load rate of the embodiment of the present invention.

[0125] The two-dimensional dry-type transformer hot spot transient temperature rise simulation method proposed in the embodiment of the present invention can effectively solve the problem of difficult convergence of transformer transient temperature rise simulation calculation under different load rates, and lay the foundation for further developing the dynamic temperature rise evolution law of dry-type transformer windings.

[0126] The embodiment of the present invention develops a two-dimensional dry-type transformer hot spot transient temperature rise simulation calculation method based on the finite element method with fast calculation speed and high accuracy. The present invention develops a two-dimensional dry-type transformer hot spot transient temperature rise simulation calculation method under different load rates based on the finite element method, involving electromagnetics, fluid mechanics, heat transfer, etc. Specifically, a three-dimensional geometric model of the dry-type transformer is constructed according to its actual size, and the Maxwell equations are solved by setting the initial values ​​of each physical quantity and the material parameters to obtain the magnetic flux density distribution of the transformer core and winding, and then the transformer iron loss and copper loss are obtained; the transformer loss is used as the excitation heat source, and a step function is used to characterize it and bring it into the thermal flow field coupling calculation model, wherein the automatic Newton is used for the nonlinear method of the separation solution module in the transient solver, and finally the two-dimensional dry-type transformer transient heat flow temperature distribution is obtained; according to the simulation method, the heat flow field distribution of the two-dimensional dry-type transformer with a load rate of 40%, 50%, 60%, 70%, 80%, 90%, and 100% is obtained; the B-phase winding hot spot is selected as the temperature measurement point, and the transformer temperature rise test is carried out to verify the accuracy and effectiveness of the simulation method. Based on the above scheme, the two-dimensional dry-type transformer hot spot transient temperature rise simulation method proposed by the present invention can effectively and accurately solve the problem of the difficulty of convergence of the transient temperature rise simulation calculation of the dry-type transformer under different load rates, and lay a foundation for further developing the dynamic temperature rise evolution law of the dry-type transformer winding.

[0127] See also Fig. 9 A transformer transient temperature rise prediction device 20 according to another embodiment of the present invention can be used to implement the corresponding steps of the above method embodiment, including:

[0128] A construction module 21 is used to construct a two-dimensional model of the transformer main structure, wherein the two-dimensional model includes a high-voltage winding and a low-voltage winding;

[0129] A first calculation module 22 is used to apply voltage excitation to each phase high-voltage winding according to a first preset load rate, and calculate the magnetic flux density distribution of the transformer core and winding using Maxwell equations based on the initial values ​​of various physical quantities of the transformer and material parameters;

[0130] The second calculation module 23 is used to calculate the core loss value of the transformer and the eddy current loss value of the winding according to the magnetic flux density distribution;

[0131] The third calculation module 24 is used to use the core loss value and the eddy current loss value as the heat source excitation of the transformer temperature-flow field, and adopts a step function to characterize and bring it into the thermal-flow field coupling calculation model, wherein the nonlinear method of the separation solution module in the transient solver adopts automatic Newton to obtain the transient heat flow temperature distribution of the two-dimensional dry-type transformer.

[0132] In yet another aspect, the present invention provides a computer-readable storage medium storing a computer program, which can implement the above method when executed by a processor.

[0133] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in the embodiments of the present invention can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0134] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0135] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for predicting transient temperature rise of a transformer, characterized in that: include: Constructing a two-dimensional model of the transformer main structure, wherein the two-dimensional model includes a high-voltage winding and a low-voltage winding; Applying voltage excitation to the high-voltage winding of each phase according to a first preset load rate, and calculating the magnetic flux density distribution of the transformer core and winding using Maxwell's equations based on the initial values ​​of various physical quantities of the transformer and material parameters; According to the magnetic flux density distribution, the core loss value of the transformer and the eddy current loss value of the winding are calculated; The core loss value and the eddy current loss value are used as the heat source excitation of the transformer temperature-flow field, and are characterized by a step function and brought into the thermal-flow field coupling calculation model, wherein the automatic Newton is used for the nonlinear method of the separation solution module in the transient solver to obtain the two-dimensional dry-type transformer transient heat flux temperature distribution, and the two-dimensional dry-type transformer transient heat flux temperature distribution is displayed based on the two-dimensional model.

2. The method for predicting transient temperature rise of a transformer according to claim 1, characterized in that: The step of applying voltage excitation to the high-voltage winding of each phase according to a first preset load rate, and calculating the magnetic flux density distribution of the transformer core and winding using Maxwell's equations based on the initial values ​​of various physical quantities and material parameters of the transformer, comprises: The Maxwell equations are used to describe the laws between various physical quantities in the electromagnetic field of the transformer, and the Maxwell equations include: Among them, E is the electric field strength, unit V / m; B is the magnetic induction intensity, unit A / m; H is the magnetic field strength, unit T; D is the current density, unit C / m 2 ; J is the eddy current density, unit A / m 2 ρ e is the charge density, in C / m 3 ; Characterizing the constitutive relation of the linear medium in the transformer: D=e r ε0E B=μ m H J=σE Among them, ε r is the relative dielectric constant of the medium; ε0 is the dielectric constant of vacuum; μ m is the magnetic permeability of the medium, in H / m; σ is the electrical conductivity of the medium, in S / m; for isotropic media, ε r , μ m and σ are scalars. For anisotropic media, ε r , μ m and σ are both vectors; Magnetic insulation boundary conditions are set on the outer surface of the transformer oil tank, and the initial vector magnetic potential is set to 0Wb / m. Based on the first preset load rate, voltage excitation is applied to the high-voltage winding of each phase. The field-circuit coupling method is used to add an external circuit to the low-voltage winding of each phase, and excitation is applied by setting a current source in the external circuit. The magnetic flux density distribution of the transformer core and winding is obtained by simulation.

3. The method for predicting transient temperature rise of a transformer according to claim 2, characterized in that: The step of calculating the core loss value of the transformer and the eddy current loss value of the winding according to the magnetic flux density distribution comprises: In the formula, B max is the maximum value of magnetic induction intensity at point x; ω is the eddy current angular frequency; γ is the specific conductivity of the wire material; a is the width of the wire; a is the width of the wire; P Feddy is the radial eddy current loss of the conductor; P zeddy is the axial eddy current loss of the conductor; P v Average power loss density; f is the excitation frequency; k h is the Steinmetz proportionality constant.

4. The method for predicting transient temperature rise of a transformer according to claim 3, characterized in that: The step of using the core loss value and the eddy current loss value as the heat source excitation of the transformer temperature-flow field, using a step function to characterize and bring into the thermal-flow field coupling calculation model, wherein the nonlinear method of the separation solution module in the transient solver adopts automatic Newton to obtain the transient heat flow temperature distribution of the two-dimensional dry-type transformer, includes: The non-isothermal flow process of the air domain in the high-voltage winding and the low-voltage winding follows the law of conservation of mass, the law of conservation of momentum and the law of conservation of energy, and satisfies the constraints of the Navier-Stokes (NS) equations: Where c is the specific heat capacity, the unit is J / (kg·K); v is the flow velocity, the subscript represents the direction, the unit is m / s; F is the external force on the fluid element, the subscript represents the direction, the unit is N; p is the pressure, the unit is Pa; m is the dynamic viscosity, the unit is N·s / m 2 ; r is density, unit is kg / m 3 ; Se is the ratio of the inertial force to the viscous force caused by the secondary flow, dimensionless; Among them, the separation solution module of the transient solver in the solver configuration is improved, the merged variables in the separation step and the nonlinear method in the radiosity are set to automatic Newton, and the transient heat flux temperature distribution of the two-dimensional dry-type transformer is obtained.

5. The method for predicting transient temperature rise of a transformer according to claim 4, characterized in that: The step of setting the combined variables in the separation step and the nonlinear method in the radiosity to automatic Newton to obtain the transient heat flux temperature distribution of the two-dimensional dry-type transformer includes: Calculate the total heat source of the transformer and bring it into the thermal-fluid coupling field for calculation; By substituting constant flow parameters into conservation equations, the flow field and temperature distribution are calculated to obtain the transient heat flow temperature distribution of the two-dimensional dry-type transformer.

6. The method for predicting transient temperature rise of a transformer according to claim 5, characterized in that: After the step of substituting the constant flow parameters into the conservation equation, calculating the flow field and temperature distribution, and obtaining the transient heat flow and temperature distribution of the two-dimensional dry-type transformer, the method includes: Determine whether the residual of two adjacent temperature iterations is less than 0.01k; If yes, determining whether a second preset load rate exceeds 100%, the second preset load rate being the sum of the first preset load rate and 10%; If yes, the prediction is terminated; if no, voltage excitation is applied to the high-voltage winding of each phase according to the second preset load rate to predict the corresponding transient heat flux temperature distribution.

7. The method for predicting transient temperature rise of a transformer according to claim 1, characterized in that: After the step of obtaining the transient heat flow temperature distribution of the two-dimensional dry-type transformer, the method further includes: The hot spot of the transformer B phase winding is selected as the temperature measurement point for temperature rise test verification and the temperature rise test fitting curve of the hot spot temperature rise with the load application time is obtained, and the error comparison is performed between the fitting curve of the transient heat flow temperature distribution of the two-dimensional dry-type transformer and the temperature rise test fitting curve.

8. The method for predicting transient temperature rise of a transformer according to claim 1, characterized in that: The step of applying voltage excitation to the high-voltage winding of each phase according to the first preset load rate comprises: The electromagnetic field simulation calculation method is used to change the magnitude of the current value in the external application circuit in the field-circuit coupling to respectively reflect the magnitude of the first preset load rate, and the first preset load rate is greater than or equal to 40%.

9. A transformer transient temperature rise prediction device, characterized in that: include: A construction module, used to construct a two-dimensional model of the transformer main structure, wherein the two-dimensional model includes a high-voltage winding and a low-voltage winding; A first calculation module is used to apply voltage excitation to the high-voltage winding of each phase according to a first preset load rate, and calculate the magnetic flux density distribution of the transformer core and winding using Maxwell equations based on the initial values ​​of various physical quantities of the transformer and material parameters; A second calculation module is used to calculate the core loss value of the transformer and the eddy current loss value of the winding according to the magnetic flux density distribution; The third calculation module is used to use the core loss value and the eddy current loss value as the heat source excitation of the transformer temperature-flow field, characterize it with a step function and bring it into the thermal flow field coupling calculation model, wherein the nonlinear method of the separation solution module in the transient solver adopts automatic Newton to obtain the two-dimensional dry-type transformer transient heat flux temperature distribution, and the two-dimensional dry-type transformer transient heat flux temperature distribution is displayed based on the two-dimensional model.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 8 can be implemented.

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