Rapid calculation method for temperature rise of transformer coil

Abstract

The invention provides a rapid calculation method for the temperature rise of a transformer coil, and relates to the technical field of high-voltage power transmission and distribution. Comprising the following steps: determining electromagnetic design parameters and structural design parameters of the liquid-immersed transformer; according to the structural design parameters, performing two-dimensional equivalent processing on the liquid-immersed transformer to construct a corresponding numerical calculation model; calculating loss distribution at the preset temperature according to the numerical calculation model; calculating the corresponding heat source density according to the loss distribution; calculating temperature distribution of the coil according to the heat source density and a fluid-solid coupling method; establishing a thermal circuit model of the flowing-out transformer body oil temperature and the flowing-in transformer body oil temperature of the liquid-immersed transformer; solving the thermal circuit model to obtain the oil temperature of the input coil; adjusting the temperature distribution of the coil according to the input oil temperature of the coil to obtain the adjusted temperature distribution of the coil; and coil temperature extraction is carried out according to the coil temperature distribution, and the extracted temperature is obtained and convergence judgment is carried out. The problems that a numerical calculation method is high in calculation duration and low in precision are solved.

Description

Technical Field

[0001] The invention relates to the technical field of high voltage power transmission and distribution, and in particular to a method for quickly calculating the temperature rise of a transformer coil. Background Art

[0002] Against the backdrop of the rapid development of artificial intelligence technology, electricity, as the core power source of critical infrastructure, has put forward higher requirements for the operational reliability of power equipment. As the core equipment of the high-voltage transmission and distribution system, the intelligent thermal management of liquid-immersed transformers has become an important topic for the modernization and upgrading of power grids. With the breakthrough growth of the capacity of a single device (reaching 1000MVA), the local overheating effect caused by winding loss has shown an intensifying trend, among which the hot spot temperature rise problem in the coil area is particularly prominent, which puts forward new requirements for the accuracy of thermal field simulation of the equipment.

[0003] The thermodynamic properties of liquid-immersed transformers are strongly correlated with their safe service life. For every 6K increase in winding temperature, the aging rate of equipment insulation will double. Therefore, the accuracy of thermal design directly affects the life cycle cost of the equipment. However, the existing transformer thermal field simulation technology faces two challenges: 1. The unique structure of the closed self-circulating system (no forced convection boundary, significant thermal buoyancy drive characteristics) limits the applicability of traditional heat transfer models; 2. The thermal field heterogeneity caused by personalized design parameters (oil channel height 3-5mm, different oil guide plate structures) makes the prediction error of the empirical formula generally exceed 20%.

[0004] The current mainstream numerical simulation technology is based on the principle of multi-physics field coupling, and constructs a three-dimensional thermal flow field model by simultaneously solving the Navier-Stokes equation, the continuity equation, and the energy conservation equation. The theoretical advantages of this method are: 1) It can analyze the temperature / flow velocity distribution at millimeter-level spatial resolution; 2) It supports the visual reconstruction of multi-media coupled heat transfer processes.

[0005] However, there are significant bottlenecks in practical applications: 1. Low steady-state convergence efficiency: A single operating condition simulation requires 5-8 hours of iterative calculation. If the temperature-conductivity nonlinear coupling effect is considered, full parameter convergence requires 15-30 hours; 2. Error accumulation effect: The closed system of the liquid-immersed transformer lacks clear boundary conditions, resulting in residual oscillations and a numerical diffusion error of about 0.3% per thousand iterations; 3. Excessive consumption of hardware resources: A typical example requires 128GB of memory and continuous calls to multi-core parallel computing resources.

[0006] The above technical defects have seriously restricted the research and development of new environmentally friendly cooling medium (natural ester oil, silicone oil, etc.) transformers and ultra-high voltage (≥800kV) equipment. Therefore, it is urgent to develop a fast thermal field calculation method with engineering practical value to achieve a step-by-step improvement in simulation efficiency while ensuring calculation accuracy. Summary of the invention

[0007] In order to overcome the deficiencies of the prior art, an object of the present invention is to provide a method for quickly calculating the temperature rise of a transformer coil.

[0008] To achieve the above object, the present invention provides the following solutions:

[0009] A fast calculation method for transformer coil temperature rise, comprising:

[0010] Determine the electromagnetic design parameters and structural design parameters of liquid immersed transformers;

[0011] According to the structural design parameters, a two-dimensional equivalent processing is performed on the liquid-immersed transformer to construct a corresponding numerical calculation model;

[0012] Calculating the loss distribution at a preset temperature according to the numerical calculation model;

[0013] Calculating the corresponding heat source density according to the loss distribution;

[0014] Calculating the temperature distribution of the coil according to the heat source density and the fluid-solid coupling method;

[0015] Establishing a thermal circuit model of the oil temperature outflowing from the liquid-immersed transformer and the oil temperature inflowing into the transformer;

[0016] Solving the thermal circuit model to obtain the input coil oil temperature;

[0017] Adjusting the loss density distribution of the coil according to the input coil oil temperature, and repeatedly calculating to obtain a corrected coil temperature distribution;

[0018] The coil temperature is extracted according to the coil temperature distribution, the extracted temperature is obtained and a convergence judgment is performed to obtain a judgment result. If the judgment result is that the convergence condition is met, the current coil temperature distribution is determined as the final temperature distribution. If the judgment result does not meet the convergence condition, the parameters in the thermal circuit model are adjusted until the judgment result meets the convergence condition.

[0019] Preferably, calculating the loss distribution at a preset temperature according to the numerical calculation model includes:

[0020] Constructing a magnetic field simulation model according to the electromagnetic design parameters and the material properties in the numerical calculation model and the input excitation thereof;

[0021] Determine the corresponding Maxwell equations according to the magnetic field simulation model;

[0022] Determining the corresponding constitutive equations for electromagnetic calculations according to the Maxwell equations;

[0023] The loss distribution at the preset temperature is obtained according to the constitutive equation of the electromagnetic calculation.

[0024] Preferably, the expression of the Maxwell equations is: ; ; ; ; Among them, D is the electric displacement vector, J is the current density vector, B is the magnetic induction intensity vector, E is the electric field intensity vector, H is the magnetic field intensity vector, ρ is the charge density, and t is the time.

[0025] Preferably, the constitutive equation is expressed as: ; ; ; Among them, ε represents the dielectric constant of the medium, μ is the magnetic permeability of the medium, Indicates the conductivity of the medium.

[0026] Preferably, the expression of the thermal circuit model is: ; Among them, C is the heat capacity of the transformer; R is the equivalent thermal resistance of the transformer to air heat dissipation; is the iron loss in the core; is the stray loss in the metal structure; is the transformer oil temperature entering the transformer body; It is the temperature of transformer oil flowing out of the transformer body.

[0027] Preferably, the calculation expression of the transformer thermal capacity is: ; Among them, M tank is the weight of the fuel tank; Cp tank is the specific heat capacity of the oil tank; M core is the weight of the core; Cp core is the specific heat capacity of the iron core; M Cu is the weight of the coil; Cp Cu is the specific heat capacity of the coil; M oil is the weight of transformer oil; Cp oil is the specific heat capacity of transformer oil; M insulation is the weight of the insulating material; Cp insulation is the specific heat capacity of the insulating material.

[0028] Preferably, the calculation expression of the equivalent thermal resistance of the transformer to air heat dissipation is: ; in, is the vertical wall convection heat dissipation coefficient, is the vertical wall area of ​​the transformer tank and radiator, is the horizontal wall convection heat dissipation coefficient, is the horizontal wall area of ​​the transformer tank and radiator, h is the convection heat transfer coefficient, and s is the heat transfer area.

[0029] The present invention discloses the following technical effects:

[0030] The present invention provides a method for quickly calculating the temperature rise of a transformer coil, comprising: determining electromagnetic design parameters and structural design parameters of a liquid-immersed transformer; performing two-dimensional equivalent processing on the liquid-immersed transformer according to the structural design parameters to construct a corresponding numerical calculation model; calculating the loss distribution at a preset temperature according to the numerical calculation model; calculating the corresponding heat source density according to the loss distribution; calculating the temperature distribution of the coil according to the heat source density and a fluid-solid coupling method; establishing a thermal circuit model of the oil temperature flowing out of the liquid-immersed transformer and the oil temperature flowing into the liquid-immersed transformer; solving the thermal circuit model to obtain the input coil oil temperature; adjusting the loss density distribution of the coil according to the input coil oil temperature, and repeatedly calculating to obtain a corrected coil temperature distribution; extracting the coil temperature according to the coil temperature distribution, obtaining the extracted temperature and performing convergence judgment to obtain a judgment result, if the judgment result is that the convergence condition is met, then determining the current coil temperature distribution as the final temperature distribution, if the judgment result does not meet the convergence condition, then adjusting the parameters in the thermal circuit model until the judgment result meets the convergence condition. The present invention is the first to directly associate the temperature of the transformer oil flowing out of the coil with the temperature of the oil flowing into the coil based on the thermal circuit model. The transformer oil circulation process outside the coil is converted from the traditional numerical simulation to the thermal circuit mathematical model, simplifying the process of the hot oil flowing out of the coil exchanging heat with the air through the oil tank wall and the radiator wall. The closed self-circulating cooling system is simplified to a fluid calculation domain containing the inflow boundary and the outflow boundary, realizing the efficient and accurate calculation of the temperature rise of the liquid-immersed transformer coil and the accurate positioning of the hot spot temperature rise position, which makes up for many problems of the traditional liquid-immersed transformer temperature rise calculation. It can solve the temperature distribution calculation in the transformer coil under various operating conditions, and has the advantages of wide application range, high reliability, short calculation time, and less computer resources occupied. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0032] Figure 1 A flow chart of a method for quickly calculating the temperature rise of a transformer coil provided by an embodiment of the present invention;

[0033] Figure 2 A technical roadmap provided for embodiments of the present invention;

[0034] Figure 3 A detailed schematic diagram of a method for quickly calculating the temperature rise of a transformer coil provided by an embodiment of the present invention;

[0035] Figure 4 A schematic diagram of a heat path model of heat dissipation from transformer oil outside a coil to air provided in an embodiment of the present invention;

[0036] Figure 5 A schematic diagram of the transformer assembly provided by an embodiment of the present invention;

[0037] Figure 6 A front view of a transformer body provided by an embodiment of the present invention;

[0038] Figure 7 A schematic diagram of a coil area temperature rise calculation model provided in an embodiment of the present invention;

[0039] Figure 8 A schematic diagram of a BH curve of a silicon steel sheet provided in an embodiment of the present invention;

[0040] Fig. 9 A schematic diagram of coil loss density distribution at temperature T1 provided by an embodiment of the present invention;

[0041] Fig.10 The temperature distribution cloud diagram calculated by the present application provided by the embodiment of the present invention;

[0042] Fig.11 A partial enlarged view of the temperature distribution cloud map calculated by the present application provided in the embodiment of the present invention;

[0043] Fig.12 A temperature distribution cloud diagram calculated by the prior art provided in an embodiment of the present invention.

[0044] Description of reference numerals:

[0045] 1- Transformer oil storage cabinet; 2- Radiator; 3- High-voltage bushing; 4- Low-voltage bushing; 5- Neutral point bushing; 6- Transformer box cover; 7- Transformer oil tank; 8- Coil group; 9- Upper clamp; 10- Lower clamp; 11- Insulating paper tube; 12- Oil inlet; 13- Oil outlet. DETAILED DESCRIPTION

[0046] 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 only 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.

[0047] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] like Figure 1 As shown, the present invention provides a method for quickly calculating the temperature rise of a transformer coil, comprising:

[0049] Step 100: Determine electromagnetic design parameters and structural design parameters of the liquid immersed transformer;

[0050] Step 200: According to the structural design parameters, two-dimensional equivalent processing is performed on the liquid immersed transformer to construct a corresponding numerical calculation model;

[0051] Step 300: Calculate the loss distribution at a preset temperature according to the numerical calculation model;

[0052] Step 400: Calculate the corresponding heat source density according to the loss distribution; the loss density distribution is the heat source density distribution;

[0053] Step 500: Calculating the temperature distribution of the coil according to the heat source density and the fluid-solid coupling method;

[0054] Step 600: Establishing a thermal circuit model of the oil temperature outflowing from the liquid-immersed transformer and the oil temperature inflowing into the transformer;

[0055] Step 700: Solve the thermal circuit model to obtain the input coil oil temperature;

[0056] Step 800: adjusting the loss density distribution of the coil according to the input coil oil temperature, and repeatedly calculating to obtain a corrected coil temperature distribution;

[0057] Step 900: Extract the coil temperature according to the coil temperature distribution, obtain the extracted temperature and perform convergence judgment to obtain a judgment result. If the judgment result is that the convergence condition is met, the current coil temperature distribution is determined as the final temperature distribution. If the judgment result does not meet the convergence condition, the parameters in the thermal circuit model are adjusted until the judgment result meets the convergence condition.

[0058] The temperature of the calculation node on the coil structure is extracted, and the difference between the temperature calculation of the coil node obtained in the previous calculation is calculated, and then the difference of all the calculation nodes is averaged. If this average value is less than 0.1, it means convergence.

[0059] If it has not converged, enter a loop until it converges.

[0060] Specifically, from the physical process of the heat balance of the liquid-immersed transformer, the heat generated by the transformer coil, core and other metal structural parts is transferred to the surface of the structural parts as a heat source; this heat causes a temperature difference between the high-temperature solid surface and the low-temperature fluid, resulting in convective heat transfer, and the heat is transferred to the transformer oil with a lower temperature in the nearby area, causing the temperature of the transformer oil to gradually rise; when the oil temperature rises, the density of the transformer oil decreases, generating thermal buoyancy, and the oil with a higher temperature flows upward under the action of thermal buoyancy, and after encountering the wall of the oil tank and radiator with a lower temperature, it transfers part of the heat to the oil tank wall and radiator. After the temperature of the transformer oil decreases, the density increases, and it flows downward under the action of gravity, flows to the bottom of the oil tank, and forms a complete oil flow cycle inside the transformer. The oil flow cycle not only makes the temperature of each part of the transformer more uniform, but also increases the overall temperature of the transformer oil tank; the temperature of the oil tank wall and the radiator gradually increases under the action of convection, and finally dissipates the heat to the surrounding environment.

[0061] Combined with the actual structure of the transformer, the coil is the hottest area in the transformer, and the oil channel in the coil is complex and difficult to simplify. However, the oil flow process outside the coil is relatively simple and the temperature is low. The oil flow heat dissipation process outside the coil can be simplified by using a thermal circuit model. The technical route is as follows: Figure 2 As shown. The hot oil in the coil flows out from the gap above the body, and the hot oil temperature is θ out After flowing out of the coil, θ out As the reference temperature, consider the iron loss q in the core Fe and stray losses in metal structures q St Establish a mathematical model of the heat path of the transformer to the air to obtain the transformer oil temperature θ after the temperature is reduced in The temperature is iteratively calculated as the inlet temperature entering the device body until the coil temperature reaches the convergence standard.

[0062] Further, such as Figure 3As shown, the calculation of the loss distribution at a preset temperature according to the numerical calculation model includes:

[0063] Constructing a magnetic field simulation model according to the electromagnetic design parameters and the material properties in the numerical calculation model and the input excitation thereof;

[0064] Determine the corresponding Maxwell equations according to the magnetic field simulation model;

[0065] Determining the corresponding constitutive equations for electromagnetic calculations according to the Maxwell equations;

[0066] The loss distribution at the preset temperature is obtained according to the constitutive equation of the electromagnetic calculation.

[0067] Furthermore, the expression of the Maxwell equations is: ; ; ; ; Among them, D is the electric displacement vector, J is the current density vector, B is the magnetic induction intensity vector, E is the electric field intensity vector, H is the magnetic field intensity vector, and ρ is the charge density.

[0068] Furthermore, the constitutive equation is expressed as: ; ; ; Among them, ε represents the dielectric constant of the medium, μ is the magnetic permeability of the medium, Indicates the conductivity of the medium.

[0069] Specifically, the detailed process of heat source calculation steps is as follows:

[0070] A1: Establish a magnetic field simulation model based on the electromagnetic design parameters of the transformer;

[0071] A2: Input material properties. The coil material is electrical copper, the core material is silicon steel sheet, and its magnetic permeability follows the BH curve. The material of other metal structural parts is structural steel, and its magnetic permeability also follows the BH curve.

[0072] A3: Input excitation. This transformer is an on-load tap-changing transformer. The heat source during the temperature rise test is the loss generated when the voltage is at the minimum tap. Therefore, the input excitation is the current at the minimum tap. At this time, there is a loss density distribution in the low-voltage coil, high-voltage coil and voltage regulating coil.

[0073] A4: Magnetic field finite element analysis follows Maxwell's equations.

[0074] Furthermore, the temperature field calculation uses the convection heat dissipation calculation model and the heat conduction model. The overall temperature inside the liquid-immersed transformer is low, and the effect of thermal radiation on heat dissipation can be ignored. The calculation follows the continuity equation; Navier-Stokes equation; and energy conservation equation.

[0075] ; ; ; In the formula, is the fluid density, is the fluid velocity, is the fluid viscosity, is the volume force, For internal energy, for heat;

[0076] In the initial state, that is, when the number of calculation iterations is 1, the inlet temperature is estimated according to the capacity and loss design value of the transformer, and the inlet flow rate is calculated according to the mass of the transformer oil calculated outflow, to ensure the conservation of the transformer oil mass in the calculation domain; starting from the second iteration calculation, the inlet temperature is θ obtained by the previous iteration calculation in。

[0077] Further, such as Figure 4 As shown, the expression of the thermal circuit model is: ; Among them, C is the heat capacity of the transformer; R is the equivalent thermal resistance of the transformer to air heat dissipation.

[0078] Furthermore, the calculation expression of the transformer thermal capacity is: ; Among them, M tank is the weight of the fuel tank; Cp tank is the specific heat capacity of the oil tank; M core is the weight of the core; Cp core is the specific heat capacity of the iron core; M Cu is the weight of the coil; Cp Cu is the specific heat capacity of the coil; M oil is the weight of transformer oil; Cp oil is the specific heat capacity of transformer oil; M insulation is the weight of the insulating material; Cp insulation is the specific heat capacity of the insulating material.

[0079] Furthermore, the calculation expression of the equivalent thermal resistance of the transformer to air heat dissipation is: ; in, is the vertical wall convection heat dissipation coefficient, is the vertical wall area of ​​the transformer tank and radiator, is the horizontal wall convection heat dissipation coefficient, is the horizontal wall area of ​​the transformer tank and radiator.

[0080] More specifically, a liquid-immersed transformer is used as an example, the model is SFZ-175000 / 138, the transformer is a double-winding liquid-immersed transformer with a voltage regulating coil, the cooling medium is mineral oil, and radiators are arranged on both sides of the oil tank. Figure 5 This is the general assembly diagram of the transformer, transformer oil storage cabinet 1; radiator 2; high-voltage bushing 3; low-voltage bushing 4; neutral point bushing 5; transformer cover 6; transformer oil tank 7. After the transformer starts to operate, the main heat source in the transformer is heat exchanged with the transformer oil. The transformer oil starts to circulate in the oil tank and exchanges heat with the air through the transformer cover, oil tank and radiator.

[0081] The internal structure of the transformer, that is, the main view of the transformer body, is as follows Figure 6 As shown, the coil of the transformer is a multi-layer cylindrical structure. The coil of the transformer is round, and the high-voltage, low-voltage and voltage regulating windings are pancake windings wound with copper wires. In order to improve the overload bearing capacity, the turn insulation paper uses thermally modified paper with a higher heat resistance level. The iron core is stacked with silicon steel sheets and adopts a three-phase five-column type. Because the iron core is stacked together in sheets, the upper clamp 9 and the lower clamp 10 are used to tighten the iron core by pulling the screw.

[0082] The specific parameters of the prototype are shown in Table 1.

[0083] Table 1 Basic performance parameters of SFZ-175000 / 138 transformer parameter value Voltage ratio(kV) 138 / 69 Capacity ratio (MVA) 175 / 175 Cooling method ONAN Connection Group Dyn1 High voltage winding BIL / AC 650 / 275 Low voltage winding BIL / AC 350 / 140

[0084] Corresponding to the following steps:

[0085] S1: Determine the electromagnetic design parameters and structural design parameters of the liquid immersed transformer;

[0086] S2: Numerical calculation model of two-dimensional axisymmetric processing transformer;

[0087] The coil area temperature rise calculation model is as follows: Figure 7 As shown, the coil group 8 is composed of a low-voltage coil, a high-voltage coil and a voltage regulating coil from the inside to the outside. Each coil has an insulating paper tube 11 on the inside and outside. The thermal conductivity of the paper tube is very low, so that the transformer oil can only enter and exit the coil for heat exchange through the gap at the end of the paper tube. The transformer hot oil flowing out of the oil outlet 13 is cooled and then enters the coil through the oil inlet 12 to realize the transformer oil circulation.

[0088] S3: Calculate the loss distribution at the initial preset temperature T1;

[0089] The detailed process of heat source calculation steps is as follows:

[0090] A1: Establish a magnetic field simulation model based on the electromagnetic design parameters of the transformer;

[0091] The magnetic field model is different from the temperature field model. Only materials with large magnetic permeability, such as the iron core and the coil, need to be considered. Materials with magnetic permeability close to that of air can be ignored. The model is relatively simple.

[0092] A2: Input material properties. The coil material is electrical copper, the core material is silicon steel sheet, and its magnetic permeability follows the BH curve. The material of other metal structural parts is structural steel, and its magnetic permeability also follows the BH curve. For example Figure 8 As shown;

[0093] A3: Input excitation. This transformer is an on-load voltage-regulating transformer. The heat source during the temperature rise test is the loss generated when the voltage is at the minimum tap. Therefore, the input excitation is the current at the minimum tap. At this time, there is a loss density distribution in the low-voltage coil, high-voltage coil and voltage-regulating coil. The most negative current of the low-voltage coil is 2197A, and the most negative current of the high-voltage coil is 445A.

[0094] A4: Magnetic field finite element analysis follows Maxwell's equations.

[0095] S4: Coil loss density distribution calculated by the electromagnetic module is coupled to the fluid-solid coupling calculation module as the heat source density for coil temperature calculation;

[0096] The calculation results of loss density are as follows: Fig. 9 As shown;

[0097] S5: Calculation of coil temperature distribution using fluid-structure interaction;

[0098] The temperature field calculation adopts the convection heat dissipation calculation model and the heat conduction model. The overall temperature inside the liquid-immersed transformer is low, and the effect of thermal radiation on heat dissipation can be ignored. The calculation follows the continuity equation; Navier-Stokes equation; and energy conservation equation.

[0099] In the initial state, that is, when the number of calculation iterations is 1, the inlet temperature is estimated according to the capacity and loss design value of the transformer, and the inlet flow rate is calculated according to the mass of the transformer oil calculated outflow, to ensure the conservation of the transformer oil mass in the calculation domain; starting from the second iteration calculation, the inlet temperature is θ obtained by the previous iteration calculation in ;

[0100] S6: Establish a mathematical equation for the relationship between the oil temperature outflowing from the liquid-immersed transformer and the oil temperature inflowing from the transformer, and derive it into a differential equation form with respect to time;

[0101] S7: Solve the transformer parameters in equation S6;

[0102] S8: Known θ out ,q Fe ,q St , R, C, and then solve the heat path equation to calculate θ in

[0103] S9: extract and count the temperature value T2 on the coil grid unit to determine whether the convergence condition is reached. If not, correct the resistance value and repeat S3-S8 until a converged temperature distribution is obtained.

[0104] After the calculation is completed, the coil area temperature rise distribution calculated by the method of the present invention is as follows: Figure 10-11 shown.

[0105] After the calculation is completed, the coil area temperature rise distribution calculated by the traditional method is as follows Fig.12 shown.

[0106] The comparison of temperature rise calculation results is shown in Table 2:

[0107] Table 2 Comparison of temperature rise calculation results

[0108] The comparison between calculation time and grid quantity is shown in Table 3:

[0109] Table 3 Comparison of calculation time

[0110] The calculation results of the method of the present invention are basically consistent with those of the traditional method, with a small error, the maximum error is only 4.37%, and the maximum absolute error is 3.2 K. However, the present invention greatly shortens the calculation time, reduces the occupation of computer resources, and greatly improves engineering efficiency.

[0111] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0112] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A fast calculation method for transformer coil temperature rise, characterized in that: include: Determine the electromagnetic design parameters and structural design parameters of liquid immersed transformers; According to the structural design parameters, a two-dimensional equivalent processing is performed on the liquid-immersed transformer to construct a corresponding numerical calculation model; Calculating the loss distribution at a preset temperature according to the numerical calculation model; Calculating the corresponding heat source density according to the loss distribution; Calculating the temperature distribution of the coil according to the heat source density and the fluid-solid coupling method; Establishing a thermal circuit model of the oil temperature outflowing from the liquid-immersed transformer and the oil temperature inflowing into the transformer; Solving the thermal circuit model to obtain the input coil oil temperature; Adjusting the loss density distribution of the coil according to the input coil oil temperature, and repeatedly calculating to obtain a corrected coil temperature distribution; The coil temperature is extracted according to the coil temperature distribution, the extracted temperature is obtained and a convergence judgment is performed to obtain a judgment result. If the judgment result is that the convergence condition is met, the current coil temperature distribution is determined as the final temperature distribution. If the judgment result does not meet the convergence condition, the parameters in the thermal circuit model are adjusted until the judgment result meets the convergence condition.

2. A fast calculation method for transformer coil temperature rise according to claim 1, characterized in that: The calculating the loss distribution at a preset temperature according to the numerical calculation model includes: Constructing a magnetic field simulation model according to the electromagnetic design parameters and the material properties in the numerical calculation model and the input excitation thereof; Determine the corresponding Maxwell equations according to the magnetic field simulation model; Determining the corresponding constitutive equations for electromagnetic calculations according to the Maxwell equations; The loss distribution at the preset temperature is obtained according to the constitutive equation of the electromagnetic calculation.

3. A fast calculation method for transformer coil temperature rise according to claim 2, characterized in that: The expression of the Maxwell equations is: ； ； ； ； Among them, D is the electric displacement vector, J is the current density vector, B is the magnetic induction intensity vector, E is the electric field intensity vector, H is the magnetic field intensity vector, ρ is the charge density, and t is the time.

4. A fast calculation method for transformer coil temperature rise according to claim 3, characterized in that: The expression of the constitutive equation is: ； ； ； Among them, ε represents the dielectric constant of the medium, μ is the magnetic permeability of the medium, Indicates the conductivity of the medium.

5. The method for quickly calculating the temperature rise of a transformer coil according to claim 3, characterized in that: The expression of the thermal circuit model is: ； Among them, C is the heat capacity of the transformer; R is the equivalent thermal resistance of the transformer to air heat dissipation; is the loss in the core; is the stray loss in the metal structure; is the transformer oil temperature entering the transformer body; It is the temperature of transformer oil flowing out of the transformer body.

6. A method for quickly calculating the temperature rise of a transformer coil according to claim 5, characterized in that: The calculation expression of the transformer thermal capacity is: ； Among them, M tank is the weight of the fuel tank; Cp tank is the specific heat capacity of the oil tank; M core is the weight of the core; Cp core is the specific heat capacity of the iron core; M Cu is the weight of the coil; Cp Cu is the specific heat capacity of the coil; M oil is the weight of transformer oil; Cp oil is the specific heat capacity of transformer oil; M insulation is the weight of the insulating material; Cp insulation is the specific heat capacity of the insulating material.

7. A method for quickly calculating the temperature rise of a transformer coil according to claim 6, characterized in that: The calculation expression of the equivalent thermal resistance of the transformer to air heat dissipation is: ； in, is the vertical wall convection heat dissipation coefficient, is the vertical wall area of ​​the transformer tank and radiator, is the horizontal wall convection heat dissipation coefficient, is the horizontal wall area of ​​the transformer tank and radiator, h is the convection heat transfer coefficient, and s is the heat transfer area.

Images