Method for calculating structural failure of power transformer under high-energy fault and related equipment

Abstract

The invention discloses a power transformer structure failure calculation method under a high-energy fault and related equipment, and belongs to the technical field of power transformer structure failure calculation. Firstly, a power transformer three-dimensional geometric model is built, and the power transformer three-dimensional geometric model comprises a liquid domain model and a solid domain model; performing mesh generation on the liquid domain model and the solid domain model to obtain a mesh liquid domain model and a mesh solid domain model, then calculating a high-energy arc fault oil pressure load based on the mesh liquid domain model, and obtaining the structural strain of the mesh solid domain model based on the high-energy arc fault oil pressure load; according to the method, the state of the power transformer under the impact of the high-energy arc fault is simulated, the failure behavior of the power transformer is obtained based on the structural strain of the grid solid domain model, finally, the failure behavior of the power transformer is evaluated and analyzed, and the accuracy of structural response evaluation of the power transformer under the high-energy arc fault is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of power transformer structure failure calculation, and specifically relates to a power transformer structure failure calculation method under high-energy faults and related equipment. Background Art

[0002] Oil-immersed power transformers are an important part of the power system. As a key hub for modern power generation, transmission, transformation, distribution and consumption, the operating conditions of various types of power transformers are directly related to the safety, reliability and economy of the entire power system. In recent years, there have been many internal high-energy arc faults at home and abroad that have caused large oil-immersed power transformers to spray and explode, causing huge economic losses and social impacts. When a high-energy arc fault occurs inside a large oil-filled device, the insulating oil evaporates and cracks rapidly under the action of the high-energy arc, producing a large amount of hydrocarbon mixed gas such as hydrogen and ethane, and forming rapidly expanding bubbles, resulting in a strong oil pressure load inside the oil tank. The high-pressure impact acts on the oil tank structure, eventually causing the tank to fail and rupture, accompanied by a large amount of insulating oil spraying out. The leaked material is ignited after contacting the outside world, eventually causing a fire.

[0003] With the development of modern computer technology, the simulation technology for the transient evolution of oil pressure surge under internal faults in power transformers has made progress. However, the existing research schemes do not effectively consider the coupling relationship between cavity failure behavior and fault oil pressure load, and the failure mechanism of the oil tank structure under the oil pressure load generated by internal faults remains to be revealed. As a prerequisite for studying transformer fault explosion-proof technology, the industry currently still lacks an accurate and effective numerical calculation method to accurately evaluate the structural response of power transformers under high-energy arc faults. Summary of the invention

[0004] The present invention provides a method for calculating the structural failure of a power transformer under a high-energy fault and related equipment, which solves the problem of inaccurate evaluation of the structural response of the power transformer under a high-energy arc fault.

[0005] To achieve the above object, the present invention provides the following technical solutions: A method for calculating structural failure of a power transformer under high-energy faults, comprising: Building a three-dimensional geometric model of a power transformer, wherein the three-dimensional geometric model of the power transformer includes a liquid domain model and a solid domain model, and meshing the liquid domain model and the solid domain model to obtain a mesh liquid domain model and a mesh solid domain model; Calculate the oil pressure load of high-energy arc fault based on the grid liquid domain model; Obtaining the structural strain of the mesh solid domain model based on the oil pressure load of high-energy arc fault; Obtain failure behavior of power transformers based on structural strains of mesh solid domain models; Evaluate and analyze the failure behavior of power transformers.

[0006] Preferably, the liquid domain model adopts Turbulence models, The transport equation of the turbulence model is:

[0007]

[0008] in, is the fluid mixture density, is the fluid flow rate, is the turbulent kinetic energy, is the energy dissipation rate, is the turbulent Prandtl number, is the molecular viscosity of the fluid, is the correction term, is the turbulent kinetic energy correction term, and is the turbulent viscosity constant, is the symbol of partial derivative, For time, is a vector differential operator.

[0009] Preferably, the steps of calculating the oil pressure load of a high-energy arc fault are specifically as follows: The high-energy arc fault state is simulated, and the bubble dynamics equation of the grid liquid domain model under the arc fault is obtained according to the Navier-Stokes equation. Then the flow field solver of the grid liquid domain model is set, and the high-energy arc fault oil pressure load is solved based on the bubble dynamics equation of the grid liquid domain model under the arc fault.

[0010] Preferably, the step of obtaining the structural strain of the grid solid domain model based on the high-energy arc fault oil pressure load is specifically as follows: The high-energy arc fault oil pressure load is loaded into the mesh solid domain model, and then the material properties, load boundary conditions, solution time and calculation step of the mesh solid domain model are set to ensure the convergence of the calculation results. Then, the material constitutive relationship of the mesh solid domain model is added. Based on the material constitutive relationship, load boundary conditions, solution time and calculation step of the mesh solid domain model, the Johnson-Cook constitutive model is used to describe the structural strain of the mesh solid domain model.

[0011] Preferably, the Johnson-Cook constitutive model is:

[0012] in, , , , and All of them are experimental experience parameters. is the Cauchy stress tensor in the solid domain, is the equivalent plastic strain, is the equivalent strain rate, is the relative strain rate, is the relative temperature, The calculation formula is:

[0013] in, is the reference temperature, is the melting temperature of the material, For temperature.

[0014] Preferably, the step of obtaining the failure behavior of the power transformer based on the structural strain of the grid solid domain model is specifically: The structural strain of the grid solid domain model is used to describe the explicit dynamic equations of the failure motion process of the power transformer structure. The solver, solution step and solution time of the grid solid domain model are configured, and the failure behavior of the power transformer is calculated based on the explicit dynamic equations of the failure motion process of the power transformer structure.

[0015] Preferably, the explicit dynamic equation of the power transformer structural failure motion process is:

[0016] in, is the Cauchy stress tensor in the solid domain, where i and j represent the two directions of the stress tensor, is the material density, is the volume force per unit mass, is the displacement acceleration component.

[0017] A system for calculating structural failure of a power transformer under high-energy faults, comprising: Model building module: used to build a three-dimensional geometric model of the power transformer, the three-dimensional geometric model of the power transformer includes a liquid domain model and a solid domain model, and mesh the liquid domain model and the solid domain model to obtain a mesh liquid domain model and a mesh solid domain model; Calculation module: used to calculate the oil pressure load of high-energy arc fault based on the grid liquid domain model; Configuration module: used to obtain the structural strain of the mesh solid domain model based on the oil pressure load of high-energy arc fault; Failure behavior acquisition module: used to obtain the failure behavior of power transformers based on the structural strain of the grid solid domain model; Evaluation and analysis module: used to evaluate and analyze the failure behavior of power transformers.

[0018] A computer device comprises a memory, a processor and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of a method for calculating structural failure of a power transformer under high-energy faults are implemented.

[0019] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a method for calculating structural failure of a power transformer under a high-energy fault.

[0020] Compared with the prior art, the present invention has the following beneficial effects: the present invention provides a method for calculating the structural failure of a power transformer under a high-energy fault, firstly, a three-dimensional geometric model of the power transformer is constructed, the three-dimensional geometric model of the power transformer includes a liquid domain model and a solid domain model, the liquid domain model and the solid domain model are meshed to obtain a mesh liquid domain model and a mesh solid domain model, then based on the mesh liquid domain model, the high-energy arc fault oil pressure load is calculated, the structural strain of the mesh solid domain model is obtained based on the high-energy arc fault oil pressure load, the state of the power transformer under the impact of the high-energy arc fault is simulated, the failure behavior of the power transformer is obtained based on the structural strain of the mesh solid domain model, finally, the failure behavior of the power transformer is evaluated and analyzed, and the accuracy of the structural response evaluation of the power transformer under the high-energy arc fault is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a finite element mesh model diagram of an oil-immersed transformer according to an embodiment of the present invention.

[0022] Figure 2 The present invention is a flowchart of a method for calculating structural failure of a power transformer under high-energy faults according to an embodiment of the present invention.

[0023] Figure 3 1 is a cloud diagram of the oil pressure distribution inside the oil tank at different times after a fault occurs in an embodiment of the present invention, where a is when t=5ms, b is when t=10ms, c is when t=20ms, and d is when t=52ms.

[0024] Figure 4 1 is a cloud diagram of the strain distribution of the oil tank structure at different times after a fault occurs according to an embodiment of the present invention, wherein a is when t=5ms, b is when t=10ms, c is when t=20ms, and d is when t=52ms.

[0025] Figure 5 4 is a weld strain-time curve diagram of an embodiment of the present invention.

[0026] Figure 6The present invention is a block diagram of a system for calculating structural failure of a power transformer under high-energy faults according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings 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. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. 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.

[0029] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0030] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0031] like Figure 2 As shown, the present invention provides a method for calculating the structural failure of a power transformer under a high-energy fault based on explicit dynamics, comprising the following steps: (1) constructing a three-dimensional geometric model of a power transformer, wherein the three-dimensional geometric model of the power transformer includes a liquid domain model and a solid domain model, and meshing the liquid domain model and the solid domain model to obtain a mesh liquid domain model and a mesh solid domain model; (2) Calculate the oil pressure load of high-energy arc fault based on the grid liquid domain model; (3) Obtaining the structural strain of the grid solid domain model based on the oil pressure load of the high-energy arc fault; (4) Obtaining the structural strain of the grid solid domain model based on the oil pressure load of the high-energy arc fault; (5) Evaluate and analyze the failure behavior of power transformers.

[0032] Furthermore, the step (1) specifically includes: constructing a liquid domain model and a solid domain model of a three-dimensional geometric model of a power transformer based on Spaceclaim software; Furthermore, the Octree Method function is selected by Meshing software to build a three-dimensional geometric model of the power transformer, and the liquid domain model and the solid domain model are meshed to obtain a mesh liquid domain model and a mesh solid domain model. The mesh solid domain model is divided into 359612 mesh units and 124323 nodes, as shown in Figure 1 shown.

[0033] Furthermore, the step (2) is specifically as follows: The mesh liquid domain model is adopted Turbulence Model (Re-Normalization Group model, renormalization group Turbulence model) indicates that its transport equation is: (1) (2) in, is the fluid mixture density, is the fluid flow rate, is the turbulent kinetic energy, is the energy dissipation rate, is the turbulent Prandtl number, is the molecular viscosity of the fluid, is the turbulent kinetic energy correction term, is the correction term, and is the turbulent viscosity constant, is the symbol of partial derivative, For time, is a vector differential operator.

[0034] The specific expression is: (3) in, is the vortex size, S is the strain rate tensor, is the relative vortex scale, with a value of 4.38, is the model constant, with a value of 0.012. is the turbulent viscosity constant, is the fluid mixture density, is the energy dissipation rate, is the turbulent kinetic energy.

[0035] Furthermore, to simulate the high-energy arc fault state, the oil pressure load of the high-energy arc fault is obtained by the bubble dynamics equation of the grid liquid domain model under the arc fault, and the bubble dynamics equation of the grid liquid domain model under the arc fault is obtained according to the Navier-Stokes equation. The calculation formula of the Navier-Stokes equation is: (4) in, is the fluid velocity vector, is the fluid pressure, is the radial distance, is the fluid density, is the fluid dynamic viscosity, is the symbol of partial derivative, For time.

[0036] Consider the following relationship at the gas-liquid interface: (5) in, is the gas-liquid interface pressure, is the fluid viscosity term, μ is the fluid viscosity, is the surface tension term, is the specific heat ratio, and are the bubble volume and internal energy, is the turbulent Prandtl number of insulating oil, is the bubble radius, is the radial velocity of the bubble surface.

[0037] Based on the first law of thermodynamics, the bubble dynamics equation is obtained as: (6) in, Inject energy into high energy arcs, To dissipate energy, is the arc energy conversion coefficient, is the bubble radius, is the radial velocity of the bubble surface, is the radial acceleration of the bubble surface, is the fluid domain pressure, is the radial distance, is the specific heat ratio, Bubble internal energy, is the fluid density.

[0038] Furthermore, the flow field solver of the grid liquid domain model is set as a transient solver to solve the oil pressure load of the high-energy arc fault.

[0039] Furthermore, the step (3) is specifically as follows: Import the mesh solid domain model into structural mechanics software; The oil pressure load calculated in step (2) is loaded onto the mesh solid domain model, specifically onto the inner wall of the oil tank of the mesh solid domain model.

[0040] Set the material properties, load boundary conditions, solution time and calculation step size of the mesh solid domain model to ensure the convergence of the calculation results; Furthermore, the material constitutive relation of the mesh solid domain model is added, and the Johnson-Cook constitutive model is used to describe the structural strain of the mesh solid domain model. The Johnson-Cook constitutive model is: (7) in, , , , and All of them are experimental experience parameters. is the Cauchy stress tensor in the solid domain, is the equivalent plastic strain, is the equivalent strain rate, is the relative strain rate, is the relative temperature, The calculation formula is: (8) in, is the reference temperature, is the melting temperature of the material, For temperature.

[0041] Furthermore, the step (4) is specifically as follows: describing the explicit dynamic equation of the power transformer structure failure motion process based on the structural strain of the grid solid domain model, and calculating the power transformer failure behavior based on the explicit dynamic equation of the power transformer structure failure motion process; Furthermore, the explicit dynamic equation describing the failure motion process of the power transformer structure is as follows: (9) in, is the Cauchy stress tensor in the solid domain, where the subscript i and j represent the two directions of the stress tensor, is the material density, is the volume force per unit mass, is the displacement acceleration component.

[0042] Configure the solver, solution step size, and solution time for a meshed solid domain model to compute the failure behavior of a power transformer.

[0043] Furthermore, the step (5) is specifically as follows: Based on the post-processing tools provided by the ANSYS Workbench simulation platform, the distribution and evolution of key parameters such as stress, strain, and displacement are observed to determine the weak points of the power transformer tank structure under high-energy arc faults.

[0044] Figure 3 The internal oil pressure distribution cloud diagram of a large oil-immersed power transformer under a high-energy arc fault is shown. It can be seen that 52 ms after the fault occurs, the oil pressure inside the tank rises sharply, and the local pressure peak can reach 2.5 MPa. Figure 4 The strain distribution cloud diagram of the power transformer oil tank structure is given, revealing the destructive effect of oil pressure shock on the transformer oil tank structure. The strain distribution gradually expands over time, and the maximum strain value appears at the bottom weld, which is also the location where tearing damage occurs first. Figure 5 The variation of strain at the weld with time is shown in detail. After the fault occurs, the strain increases rapidly and reaches a limit strain value of nearly 10% at 20 ms. Then, the strain value tends to stabilize. These simulation results show that the weld at the bottom of the oil tank is the weak link of the oil tank structure under the internal high-energy arc fault. The oil tank structure breaks along the stress concentration direction within tens of milliseconds, eventually leading to the overall tearing failure of the wall. Through the comprehensive analysis of pressure, stress and strain, this study effectively reveals the failure mechanism of power transformers under high-energy arc faults, providing technical support for subsequent explosion-proof design improvements.

[0045] like Figure 6 As shown, another embodiment of the present invention provides a system for calculating structural failure of a power transformer under a high-energy fault, comprising: Model building module: used to build a three-dimensional geometric model of the power transformer, the three-dimensional geometric model of the power transformer includes a liquid domain model and a solid domain model, and mesh the liquid domain model and the solid domain model to obtain a mesh liquid domain model and a mesh solid domain model; Calculation module: used to calculate the oil pressure load of high-energy arc fault based on the grid liquid domain model; Configuration module: used to obtain the structural strain of the mesh solid domain model based on the oil pressure load of high-energy arc fault; Failure behavior acquisition module: used to obtain the failure behavior of power transformers based on the structural strain of the grid solid domain model; Evaluation and analysis module: used to evaluate and analyze the failure behavior of power transformers.

[0046] A terminal device is provided in one embodiment of the present invention. The terminal device of this embodiment includes: a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps in the above-mentioned method embodiments are implemented. Alternatively, when the processor executes the computer program, the functions of the modules / units in the above-mentioned device embodiments are implemented.

[0047] The computer program may be divided into one or more modules / units, and the one or more modules / units are stored in the memory and executed by the processor to accomplish the present invention.

[0048] The terminal device may be a computing device such as a desktop computer, a notebook, a PDA, a cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0049] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

[0050] The memory may be used to store the computer programs and / or modules, and the processor implements various functions of the terminal device by running or executing the computer programs and / or modules stored in the memory and calling the data stored in the memory.

[0051] If the module / unit integrated in the terminal device is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, the steps of the above-mentioned various method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electric carrier signal, telecommunication signal and software distribution medium. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electric carrier signals and telecommunication signals.

[0052] Although the embodiments of the present invention are described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments and application fields, and the above-mentioned specific embodiments are only illustrative and instructive, rather than restrictive. Under the guidance of the specification, a person skilled in the art can also make many forms without departing from the scope of protection of the claims of the present invention, all of which belong to the scope of protection of the present invention.

Claims

1. A method for calculating the structural failure of a power transformer under high-energy faults, characterized in that: include: Building a three-dimensional geometric model of a power transformer, wherein the three-dimensional geometric model of the power transformer includes a liquid domain model and a solid domain model, and meshing the liquid domain model and the solid domain model to obtain a mesh liquid domain model and a mesh solid domain model; Calculate the oil pressure load of high-energy arc fault based on the grid liquid domain model; Obtaining the structural strain of the mesh solid domain model based on the oil pressure load of high-energy arc fault; Obtain failure behavior of power transformers based on structural strains of mesh solid domain models; Evaluate and analyze the failure behavior of power transformers.

2. The method for calculating the structural failure of a power transformer under a high-energy fault according to claim 1 is characterized in that: The liquid domain model uses Turbulence models, The transport equation of the turbulence model is: in, is the fluid mixture density, is the fluid flow rate, is the turbulent kinetic energy, is the energy dissipation rate, is the turbulent Prandtl number, is the molecular viscosity of the fluid, is the correction term, is the turbulent kinetic energy correction term, and is the turbulent viscosity constant, is the symbol of partial derivative, For time, is a vector differential operator.

3. The method for calculating the structural failure of a power transformer under a high-energy fault according to claim 1 is characterized in that: The specific steps for calculating the oil pressure load of a high-energy arc fault are: The high-energy arc fault state is simulated, and the bubble dynamics equation of the grid liquid domain model under the arc fault is obtained according to the Navier-Stokes equation. Then the flow field solver of the grid liquid domain model is set, and the high-energy arc fault oil pressure load is solved based on the bubble dynamics equation of the grid liquid domain model under the arc fault.

4. The method for calculating the structural failure of a power transformer under a high-energy fault according to claim 1 is characterized in that: The specific steps for obtaining the structural strain of the mesh solid domain model based on the high-energy arc fault oil pressure load are as follows: The high-energy arc fault oil pressure load is loaded into the mesh solid domain model, and then the material properties, load boundary conditions, solution time and calculation step of the mesh solid domain model are set to ensure the convergence of the calculation results. Then, the material constitutive relationship of the mesh solid domain model is added. Based on the material constitutive relationship, load boundary conditions, solution time and calculation step of the mesh solid domain model, the Johnson-Cook constitutive model is used to describe the structural strain of the mesh solid domain model.

5. The method for calculating the structural failure of a power transformer under a high-energy fault according to claim 4 is characterized in that: The Johnson-Cook constitutive model is: in, , , , and All of them are experimental experience parameters. is the Cauchy stress tensor in the solid domain, is the equivalent plastic strain, is the equivalent strain rate, is the relative strain rate, is the relative temperature, The calculation formula is: in, is the reference temperature, is the melting temperature of the material, For temperature.

6. The method for calculating structural failure of a power transformer under high-energy faults according to claim 1 is characterized in that: The steps to obtain the failure behavior of power transformer based on the structural strain of the mesh solid domain model are as follows: The structural strain of the grid solid domain model is used to describe the explicit dynamic equations of the failure motion process of the power transformer structure. The solver, solution step and solution time of the grid solid domain model are configured, and the failure behavior of the power transformer is calculated based on the explicit dynamic equations of the failure motion process of the power transformer structure.

7. A method for calculating structural failure of a power transformer under high-energy faults according to claim 6, characterized in that: The explicit dynamic equation of the power transformer structural failure motion process is: in, is the Cauchy stress tensor in the solid domain, where i and j represent the two directions of the stress tensor, is the material density, is the volume force per unit mass, is the displacement acceleration component.

8. A system for calculating the structural failure of a power transformer under high-energy faults, characterized in that: include: Model building module: used to build a three-dimensional geometric model of the power transformer, the three-dimensional geometric model of the power transformer includes a liquid domain model and a solid domain model, and mesh the liquid domain model and the solid domain model to obtain a mesh liquid domain model and a mesh solid domain model; Calculation module: used to calculate the oil pressure load of high-energy arc fault based on the grid liquid domain model; Configuration module: used to obtain the structural strain of the mesh solid domain model based on the oil pressure load of high-energy arc fault; Failure behavior acquisition module: used to obtain the failure behavior of power transformers based on the structural strain of the grid solid domain model; Evaluation and analysis module: used to evaluate and analyze the failure behavior of power transformers.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method for calculating the structural failure of a power transformer under a high-energy fault as described in any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of a method for calculating structural failure of a power transformer under a high-energy fault as described in any one of claims 1 to 7 are implemented.

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