A method and system for calculating no-load vibration noise distribution of a transformer

Abstract

The application provides a method for calculating no-load vibration noise distribution of a transformer, comprising the following steps: constructing a three-dimensional geometric model of the transformer; performing mesh division in the three-dimensional geometric model to obtain a structure mesh and an acoustic mesh; after simulating no-load operation conditions of the transformer, performing transient electromagnetic simulation on the structure mesh of the core to obtain transient displacement distribution of the core; performing Fourier transform on the transient displacement distribution to obtain frequency domain distribution, and extracting displacement data of a predetermined frequency band as boundary conditions of transformer vibration to obtain displacement data of the transformer; taking the displacement data of the transformer as boundary conditions of acoustic analysis to obtain noise distribution of an air domain in a frequency domain including a perfect matched layer; determining sound sensor measuring points, and calculating sound pressure levels of each sound sensor measuring point according to the obtained noise distribution in the frequency domain, and further calculating a total sound pressure level of the transformer. By implementing the application, electromagnetic, structure and acoustic field are coupled and analyzed, so that the calculation result is more accurate.

Description

Technical Field

[0001] This invention relates to the field of transformer noise distribution detection technology, and in particular to a method and system for calculating the no-load vibration noise distribution of a transformer. Background Technology

[0002] Transformers are the primary source of vibration and noise in substations, and excessive vibration and noise can impact both the transformer itself and the surrounding environment. Previously, noise reduction was mainly achieved by enclosing the transformer in a soundproof enclosure. Recently, due to fire safety requirements, the roof of the soundproof enclosure has needed to be removed, resulting in a significant increase in substation noise, which no longer meets environmental impact assessment requirements. Therefore, it is necessary to calculate the no-load vibration and noise of transformers to provide a theoretical basis for vibration reduction and noise control.

[0003] Currently, there are various methods for calculating the distribution of transformer no-load vibration noise, including: (1) measuring the vibration acceleration of some points on the transformer surface and the noise pressure level of some points in the surrounding environment using vibration sensors and noise sensors; (2) analyzing and calculating the root causes of transformer core vibration noise and winding vibration noise. This method considers the magnetostriction of the core and the Lorentz force of the winding, establishes a three-dimensional electromagnetic-structural coupling numerical model of the transformer, and further analyzes the sound field distribution generated by the vibration of the core and winding through finite element calculation of the magnetic field and displacement of the transformer core and winding. This model considers the finite element analysis of the electromagnetic vibration of the transformer by the magnetostriction of the core and the Lorentz force of the winding; (3) establishing a transformer tank sound field model based on large-scale finite element acoustic calculation software, and using the measured normal vibration acceleration of the transformer tank surface to predict the radiated noise sound field of the transformer tank. This method uses the normal acceleration of the tank surface vibration measured in the experiment as the boundary condition for sound field calculation, and then calculates the sound field distribution around the transformer based on acoustic calculation software.

[0004] However, all of the above calculation methods have shortcomings. The shortcomings are as follows: In the first method, a lot of manpower and resources are required, live operation is required, the risk factor is high, and only vibration noise at some points can be measured. If the transformer is indoors, due to the refraction and reflection of noise, the measured noise is not equal to the noise generated by the transformer itself, which is not conducive to studying the generation mechanism of transformer vibration noise; In the second method, the sound field analysis of this method adopts empirical formulas, and the calculation results are not ideal; In the third method, due to measurement difficulties and errors, the model is not very accurate.

[0005] Therefore, in order to solve the above problems, there is an urgent need for a new method to calculate the noise distribution of transformers under no-load conditions. This method would couple electromagnetic, structural, and acoustic field analyses to reduce the impact of noise refraction and reflection on the transformer's noise, thus making the calculation results more accurate. Summary of the Invention

[0006] The technical problem to be solved by the embodiments of the present invention is to provide a method and system for calculating the no-load vibration noise distribution of a transformer, which combines electromagnetic, structural and acoustic field analysis to reduce the influence of noise refraction and reflection on the transformer body noise, and makes the calculation results more accurate.

[0007] To address the aforementioned technical problems, embodiments of the present invention provide a method for calculating the no-load vibration noise distribution of a transformer, the method comprising the following steps:

[0008] Based on the structural parameters of the transformer windings, core, tank, clamps, tie rods, foundation, and pads, a three-dimensional geometric model of the transformer is constructed. In the three-dimensional geometric model, the internal cavity of the tank is set as an air domain, and the tank is wrapped with a hollow sphere as a perfectly matched layer to simulate an anechoic chamber.

[0009] In the three-dimensional geometric model, the windings, core, and tank of the transformer are all meshed to obtain a structural mesh, and the air domain, including the perfect matching layer, is meshed to obtain an acoustic mesh.

[0010] In the three-dimensional geometric model after mesh generation, the structural parameters of the transformer are set and excitation and constraint conditions are applied to simulate the no-load operation conditions of the transformer. Then, transient electromagnetic simulation is performed on the structural mesh of the core to obtain the transient magnetic field distribution and transient displacement distribution of the core.

[0011] Fourier transform is performed on the transient displacement distribution of the core to obtain the frequency domain distribution of the core displacement. Based on multiple predetermined frequency bands, the displacement data of each predetermined frequency band is extracted from the frequency domain distribution of the core displacement and used as the boundary condition for transformer vibration analysis. The displacement data of the transformer in each predetermined frequency band is simulated.

[0012] The displacement data of the transformer in each predetermined frequency band were used as boundary conditions for acoustic analysis, and the frequency domain noise distribution of the air domain, including the perfectly matched layer, in each predetermined frequency band was simulated.

[0013] The sound sensor measurement points are determined, and the sound pressure level of each sound sensor measurement point in each predetermined frequency band is calculated based on the frequency domain noise distribution obtained in each predetermined frequency band. Furthermore, the total sound pressure level of the transformer is calculated based on the sound pressure level of each sound sensor measurement point in each predetermined frequency band.

[0014] The internal air domain of the fuel tank is divided into free tetrahedral meshes with a maximum cell size of 50 mm; the external space of the fuel tank to the perfect matching layer is divided into free tetrahedral meshes with a maximum cell size of (567 / n) mm, where n = 1, 2, 3, 4; and the perfect matching layer is divided into swept meshes.

[0015] The structural parameters of the transformer include the core being made of silicon steel sheets with a conductivity of 1 S / m, a relative permittivity of 1, and a relative permeability of 10000; the windings being made of copper with a conductivity of 6e7 S / m, a relative permittivity of 1, and a relative permeability of 1; and the number of turns of the windings.

[0016] The excitation and constraint conditions are as follows: a sinusoidal voltage of 8163V with a phase difference of 120 degrees is applied to the three-phase high-voltage windings, and the low-voltage windings are connected to a large resistor of 1000kΩ.

[0017] The predetermined frequency bands include 100Hz, 200Hz, 300Hz and 400Hz.

[0018] The parameters required for transient electromagnetic simulation of the core's structural mesh include a start time of 0ms, a step size of 0.1ms, and an end time of 500ms.

[0019] The parameters required for the transformer vibration analysis include the material properties of the windings, core, clamps, tie rods, foundation, pads, and air zone; among which,

[0020] The material properties of the core include that it is made of silicon steel sheets, has a Young's modulus of 200e9Pa, a density of 7800kg / m3, and a Poisson's ratio of 0.3.

[0021] The material properties of the winding include copper as the material, Young's modulus of 110e9Pa, density of 8960kg / m3, and Poisson's ratio of 0.35.

[0022] The materials of the clamp, the tie rod, the foot, and the pad all include iron as the material, Young's modulus of 200e9Pa, density of 7850kg / m3, and Poisson's ratio of 0.3.

[0023] The material properties of the air domain include air as the material, a density of 1.29 kg / m³, and a sound speed of 340 m / s.

[0024] This invention also provides a system for calculating the no-load vibration noise distribution of a transformer, the system comprising:

[0025] The three-dimensional geometric model construction unit is used to construct a three-dimensional geometric model of the transformer based on the structural parameters of the transformer windings, core, tank, clamps, tie rods, foundations and pads; wherein, the internal cavity of the tank in the three-dimensional geometric model is set as an air domain, and the outside of the tank is wrapped with a hollow sphere and set as a perfect matching layer to simulate the anechoic chamber.

[0026] The mesh generation unit is used to mesh the windings, core, and tank of the transformer in the three-dimensional geometric model to obtain a structural mesh, and to mesh the air domain, including the perfect matching layer, to obtain an acoustic mesh.

[0027] The core displacement distribution simulation unit is used to set various structural parameters of the transformer and apply excitation and constraint conditions in the three-dimensional geometric model after meshing, so as to simulate the transformer's no-load operation conditions and then perform transient electromagnetic simulation on the core's structural mesh to obtain the transient magnetic field distribution and transient displacement distribution of the core.

[0028] The transformer displacement distribution simulation unit is used to perform Fourier transform on the transient displacement distribution of the iron core to obtain the frequency domain distribution of the iron core displacement. Based on multiple predetermined frequency bands, the displacement data of each predetermined frequency band in the frequency domain distribution of the iron core displacement is extracted as the boundary condition for transformer vibration analysis, and the displacement data of the transformer in each predetermined frequency band is simulated.

[0029] The noise distribution simulation unit is used to simulate the frequency domain noise distribution of the air domain, including the perfectly matched layer, in each predetermined frequency band by taking the displacement data of the transformer obtained in each predetermined frequency band as the boundary condition for acoustic analysis.

[0030] The transformer total sound pressure level calculation unit is used to determine the sound sensor measurement points, and calculate the sound pressure level of each sound sensor measurement point in each predetermined frequency band based on the obtained frequency domain noise distribution in each predetermined frequency band. Furthermore, based on the sound pressure level of each sound sensor measurement point in each predetermined frequency band, the total sound pressure level of the transformer is calculated.

[0031] The predetermined frequency bands include 100Hz, 200Hz, 300Hz and 400Hz.

[0032] Implementing the embodiments of the present invention has the following beneficial effects:

[0033] 1. This invention performs coupled analysis of electromagnetic, structural, and acoustic fields, enabling accurate data transmission;

[0034] 2. This invention utilizes a perfectly matched layer to reduce the impact of refraction and reflection on the transformer body noise, enabling convenient and accurate calculation of the transformer's no-load noise in a free sound field.

[0035] 3. This invention can be used for vibration and noise analysis of transformer cores, and can also provide methods and ideas for vibration and noise analysis of reactor cores, and provide analysis for vibration reduction and noise reduction of transformers and reactors. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0037] Figure 1 A flowchart of a method for calculating the no-load vibration noise distribution of a transformer is provided in an embodiment of the present invention;

[0038] Figure 2 This is a mesh generation result diagram in a method for calculating the no-load vibration noise distribution of a transformer provided in an embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram of a system for calculating the no-load vibration noise distribution of a transformer, provided as an embodiment of the present invention. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0041] like Figure 1 As shown in the figure, a method for calculating the no-load vibration noise distribution of a transformer is provided in an embodiment of the present invention. The method includes the following steps:

[0042] Step S1: Based on the structural parameters of the transformer windings, core, tank, clamps, tie rods, foundation, and pads, construct a three-dimensional geometric model of the transformer; wherein, the internal cavity of the tank in the three-dimensional geometric model is set as an air domain, and the outside of the tank is wrapped with a hollow sphere and set as a perfect matching layer to simulate the anechoic chamber.

[0043] Step S2: In the three-dimensional geometric model, the windings, core and tank of the transformer are meshed to obtain a structural mesh, and the air domain, including the perfect matching layer, is meshed to obtain an acoustic mesh.

[0044] Step S3: In the three-dimensional geometric model after mesh generation, set the structural parameters of the transformer and apply excitation and constraint conditions to simulate the no-load operation conditions of the transformer. Then, perform transient electromagnetic simulation on the structural mesh of the core to obtain the transient magnetic field distribution and transient displacement distribution of the core.

[0045] Step S4: Perform Fourier transform on the transient displacement distribution of the core to obtain the frequency domain distribution of the core displacement. Based on multiple predetermined frequency bands, extract the displacement data of each predetermined frequency band in the frequency domain distribution of the core displacement as the boundary condition for transformer vibration analysis, and simulate the displacement data of the transformer in each predetermined frequency band.

[0046] Step S5: Use the displacement data of the transformer in each predetermined frequency band as the boundary conditions for acoustic analysis, and simulate the frequency domain noise distribution of the air domain, including the perfectly matched layer, in each predetermined frequency band.

[0047] Step S6: Determine the sound sensor measurement points, and calculate the sound pressure level of each sound sensor measurement point in each predetermined frequency band based on the obtained frequency domain noise distribution. Furthermore, calculate the total sound pressure level of the transformer based on the sound pressure level of each sound sensor measurement point in each predetermined frequency band.

[0048] The specific process is as follows: In step S1, the structural parameters (including specific dimensions) of the transformer windings, core, tank, clamps, tie rods, foundations, and pads are collected, and a three-dimensional geometric model of the transformer is established using finite element simulation software. During the construction of the three-dimensional geometric model, the high-voltage winding and low-voltage winding are respectively equated to cylinders; the lamination structure of the core is ignored, and the core is established as a single unit; based on the actual dimensions of the transformer, structures such as transformer clamps, tie rods, foundations, and pads are established; the tank is established as a cuboid, with the remaining parts treated as an air domain; a hollow sphere is built outside the tank as a perfect matching layer to simulate an anechoic chamber.

[0049] In one example, the structural parameters of transformer model SCB14-800 / 10 are shown in Table 1 below:

[0050] Table 1

[0051]

[0052]

[0053] It should be noted that, in order to reduce the amount of computation, only a 1 / 2 transformer model was constructed based on the symmetry of the transformer.

[0054] In step S2, the finite element method is used to generate structural and acoustic meshes for the three-dimensional geometric model, resulting in structural mesh models and acoustic mesh models. Specifically, the internal air domain of the fuel tank uses free tetrahedral meshing with a maximum element size of 50 mm; the area between the external fuel tank and the perfect matching layer uses free tetrahedral meshing with a maximum element size of (567 / n) mm, where n = 1, 2, 3, 4; and the perfect matching layer uses swept meshing. In one example, the specific meshing results are as follows... Figure 2 As shown.

[0055] In step S3, firstly, the structural parameters of the transformer are set and excitation and constraint conditions are applied to simulate the no-load operation conditions of the transformer. At this time, the structural parameters of the transformer include the core material being silicon steel sheet, with a conductivity of 1 S / m, a relative permittivity of 1, and a relative permeability of 10000; the winding material being copper, with a conductivity of 6e7 S / m, a relative permittivity of 1, and a relative permeability of 1; and the number of turns of the winding. The excitation and constraint conditions are applied by applying a sinusoidal voltage of 8163V with a phase difference of 120 degrees to the three-phase high-voltage windings, and connecting a 1000kΩ large resistor to the low-voltage windings to simulate no-load operation.

[0056] Secondly, a magnetostrictive multiphysics approach is used to simulate the vibration source of the core, and finite element analysis software is employed to perform coil geometry analysis on the transformer windings. Transient electromagnetic simulation of the core structure mesh is then performed to obtain the transient magnetic field and displacement distributions of the core structure. The parameters required for the transient electromagnetic simulation of the core structure mesh include a start time of 0 ms, a step size of 0.1 ms, and an end time of 500 ms. The magnetic field and displacement distributions of the core are calculated at each time step.

[0057] In step S4, firstly, the initial oscillation part of the obtained core displacement distribution is removed, the start time is set to 400ms, the end time is set to 500ms, and the maximum output frequency is set to 1000Hz. The steady-state result is then subjected to discrete Fourier transform to obtain the frequency domain distribution of the core displacement.

[0058] Secondly, using the frequency distribution of the core displacement obtained above as input, the start time, end time, and maximum output frequency are set. Since the transformer vibration frequency is mainly distributed in the 100Hz, 200Hz, 300Hz, and 400Hz frequency bands, 100Hz, 200Hz, 300Hz, and 400Hz are set as predetermined frequency bands to obtain the amplitude and phase of the core displacement in the 100Hz, 200Hz, 300Hz, and 400Hz frequency bands.

[0059] Finally, in the finite element simulation software, the parameters required for transformer vibration analysis were set, including the material properties of the windings, core, clamps, tie rods, foundations, pads, and air. The core's material properties included silicon steel sheet, Young's modulus of 200e9 Pa, density of 7800 kg / m³, and Poisson's ratio of 0.3. The windings' material properties included copper, Young's modulus of 110e9 Pa, density of 8960 kg / m³, and Poisson's ratio of 0.35. The clamps, tie rods, foundations, and pads' material properties all included iron, Young's modulus of 200e9 Pa, density of 7850 kg / m³, and Poisson's ratio of 0.3. The air's material properties included air, density of 1.29 kg / m³, and sound velocity of 340 m / s.

[0060] Using the displacement data of the core in the 100Hz, 200Hz, 300Hz, and 400Hz frequency bands as excitation (i.e., the boundary conditions for transformer vibration analysis), frequency domain vibration simulations were performed on the transformer core, windings, clamps, tie rods, foundations, and pads to obtain the displacement distribution of the transformer in the 100Hz, 200Hz, 300Hz, and 400Hz frequency bands.

[0061] In step S5, frequency domain noise analysis is performed on the air domain, including the perfectly matched layer, using finite element simulation software. A perfectly matched layer is set up so that the transformer is in a free sound field. The displacement distribution of the transformer in the 100Hz, 200Hz, 300Hz, and 400Hz frequency bands is extracted as excitation (i.e., acoustic boundary conditions), resulting in the frequency domain noise distribution of the air domain, including the perfectly matched layer, in the 100Hz, 200Hz, 300Hz, and 400Hz frequency bands.

[0062] In step S6, firstly, the sound sensor measurement points are determined. Based on the obtained frequency domain noise distribution in the 100Hz, 200Hz, 300Hz, and 400Hz frequency bands, the noise is then determined using the formula... Calculate the sound pressure level at each sound sensor measurement point. Where, P e P represents the effective value of the sound pressure level to be measured. ref For reference sound pressure, 20 μPa is used in air;

[0063] In one example, the calculated sound pressure levels at various sound sensor measurement points in the 100Hz, 200Hz, 300Hz, and 400Hz frequency bands are shown in Table 2 below.

[0064] Table 2

[0065]

[0066] Secondly, the total sound pressure level of the transformer can be calculated using the following formula:

[0067]

[0068] In the formula, N is the number of sound sensor measurement points, and L... pAi Let be the A-weighted sound pressure level at the i-th sound sensor measurement point.

[0069] In one example, the weighted total sound pressure level of transformer A was 42.1874 dB, which is very small compared to the experimentally measured 43.6240 dB.

[0070] like Figure 3 As shown in the figure, a system for calculating the no-load vibration noise distribution of a transformer is provided in an embodiment of the present invention. The system includes:

[0071] The three-dimensional geometric model construction unit 110 is used to construct a three-dimensional geometric model of the transformer based on the structural parameters of the transformer windings, core, tank, clamps, tie rods, foundation and pads; wherein, the internal cavity of the tank in the three-dimensional geometric model is set as an air domain, and the outside of the tank is wrapped with a hollow sphere and set as a perfect matching layer to simulate the anechoic chamber.

[0072] Mesh generation unit 120 is used to perform mesh generation on the windings, core and tank of the transformer in the three-dimensional geometric model to obtain a structural mesh, and to perform mesh generation on the air domain including the perfect matching layer to obtain an acoustic mesh.

[0073] The core displacement distribution simulation unit 130 is used to set various structural parameters of the transformer and apply excitation and constraint conditions in the three-dimensional geometric model after meshing, so as to simulate the transformer no-load operation conditions and then perform transient electromagnetic simulation on the structural mesh of the core to obtain the transient magnetic field distribution and transient displacement distribution of the core.

[0074] The transformer displacement distribution simulation unit 140 is used to perform Fourier transform on the transient displacement distribution of the iron core to obtain the frequency domain distribution of the iron core displacement. Based on multiple predetermined frequency bands, the displacement data of each predetermined frequency band in the frequency domain distribution of the iron core displacement is extracted as the boundary condition for transformer vibration analysis, and the displacement data of the transformer in each predetermined frequency band is simulated.

[0075] The noise distribution simulation unit 150 is used to simulate the frequency domain noise distribution of the air domain, including the perfectly matched layer, in each predetermined frequency band by taking the displacement data of the transformer obtained in each predetermined frequency band as the boundary condition for acoustic analysis.

[0076] The transformer total sound pressure level calculation unit 160 is used to determine the sound sensor measurement points, and calculate the sound pressure level of each sound sensor measurement point in each predetermined frequency band based on the obtained frequency domain noise distribution in each predetermined frequency band. Furthermore, based on the sound pressure level of each sound sensor measurement point in each predetermined frequency band, the total sound pressure level of the transformer is calculated.

[0077] The predetermined frequency bands include 100Hz, 200Hz, 300Hz and 400Hz.

[0078] Implementing the embodiments of the present invention has the following beneficial effects:

[0079] 1. This invention performs coupled analysis of electromagnetic, structural, and acoustic fields, enabling accurate data transmission;

[0080] 2. This invention utilizes a perfectly matched layer to reduce the impact of refraction and reflection on the transformer body noise, enabling convenient and accurate calculation of the transformer's no-load noise in a free sound field.

[0081] 3. This invention can be used for vibration and noise analysis of transformer cores, and can also provide methods and ideas for vibration and noise analysis of reactor cores, and provide analysis for vibration reduction and noise reduction of transformers and reactors.

[0082] It is worth noting that in the above system embodiments, the various system units included are only divided according to functional logic, but are not limited to the above division, as long as the corresponding functions can be achieved; in addition, the specific names of each functional unit are only for easy differentiation and are not used to limit the scope of protection of the present invention.

[0083] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, such as ROM / RAM, disk, optical disk, etc.

[0084] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for calculating the no-load vibration noise distribution of a transformer, characterized in that, The method includes the following steps: Based on the structural parameters of the transformer windings, core, tank, clamps, tie rods, foundation, and pads, a three-dimensional geometric model of the transformer is constructed. In the three-dimensional geometric model, the internal cavity of the tank is set as an air domain, and the tank is wrapped with a hollow sphere as a perfectly matched layer to simulate an anechoic chamber. In the three-dimensional geometric model, the windings, core, and tank of the transformer are all meshed to obtain a structural mesh, and the air domain, including the perfect matching layer, is meshed to obtain an acoustic mesh. In the three-dimensional geometric model after mesh generation, the structural parameters of the transformer are set and excitation and constraint conditions are applied to simulate the no-load operation conditions of the transformer. Then, transient electromagnetic simulation is performed on the structural mesh of the core to obtain the transient magnetic field distribution and transient displacement distribution of the core. Fourier transform is performed on the transient displacement distribution of the core to obtain the frequency domain distribution of the core displacement. Based on multiple predetermined frequency bands, the displacement data of each predetermined frequency band is extracted from the frequency domain distribution of the core displacement and used as the boundary condition for transformer vibration analysis. The displacement data of the transformer in each predetermined frequency band is simulated. The displacement data of the transformer in each predetermined frequency band were used as boundary conditions for acoustic analysis, and the frequency domain noise distribution of the air domain, including the perfectly matched layer, in each predetermined frequency band was simulated. The sound sensor measurement points are determined, and the sound pressure level of each sound sensor measurement point in each predetermined frequency band is calculated based on the frequency domain noise distribution obtained in each predetermined frequency band. Furthermore, the total sound pressure level of the transformer is calculated based on the sound pressure level of each sound sensor measurement point in each predetermined frequency band. The air space inside the fuel tank is divided into free tetrahedral meshes with a maximum cell size of 50 mm; the area between the outside of the fuel tank and the perfect matching layer is divided into free tetrahedral meshes with a maximum cell size of 567 / n mm, where n = 1, 2, 3, 4; the perfect matching layer is divided into swept meshes. The structural parameters of the transformer include the core being made of silicon steel sheets with a conductivity of 1 S / m, a relative permittivity of 1, and a relative permeability of 10000; the windings being made of copper with a conductivity of 6e7 S / m, a relative permittivity of 1, and a relative permeability of 1; and the number of turns in the windings. The excitation and constraint conditions are as follows: a sinusoidal voltage of 8163V with a phase difference of 120 degrees is applied to the three-phase high-voltage windings, and the low-voltage windings are connected to a large resistor of 1000kΩ. The parameters required for transient electromagnetic simulation of the core's structural mesh include a start time of 0ms, a step size of 0.1ms, and an end time of 500ms. The parameters required for the transformer vibration analysis include the material properties of the windings, core, clamps, tie rods, foundation, pads, and air zone; among them... The material properties of the core include that it is made of silicon steel sheets, has a Young's modulus of 200e9Pa, and a density of 7800 kg / m³. 3 Poisson's ratio is 0.3; The material properties of the winding include that it is made of copper, has a Young's modulus of 110e9Pa, and a density of 8960kg / m³. 3 Poisson's ratio is 0.35; The clamp, the pull rod, the foot, and the pad are all made of iron with a Young's modulus of 200e9Pa and a density of 7850kg / m³. 3 And Poisson's ratio is 0.3; The material properties of the air domain include air as the material, with a density of 1.29 kg / m³. 3 And the speed of sound is 340 m / s.

2. The method for calculating the no-load vibration noise distribution of a transformer as described in claim 1, characterized in that, The predetermined frequency bands include 100Hz, 200Hz, 300Hz and 400Hz.

3. A system for calculating the no-load vibration noise distribution of a transformer, characterized in that, The system includes: The three-dimensional geometric model construction unit is used to construct a three-dimensional geometric model of the transformer based on the structural parameters of the transformer windings, core, tank, clamps, tie rods, foundations and pads; wherein, the internal cavity of the tank in the three-dimensional geometric model is set as an air domain, and the outside of the tank is wrapped with a hollow sphere and set as a perfect matching layer to simulate the anechoic chamber. The mesh generation unit is used to mesh the windings, core, and tank of the transformer in the three-dimensional geometric model to obtain a structural mesh, and to mesh the air domain, including the perfect matching layer, to obtain an acoustic mesh. The core displacement distribution simulation unit is used to set various structural parameters of the transformer and apply excitation and constraint conditions in the three-dimensional geometric model after meshing, so as to simulate the transformer's no-load operation conditions and then perform transient electromagnetic simulation on the core's structural mesh to obtain the transient magnetic field distribution and transient displacement distribution of the core. The transformer displacement distribution simulation unit is used to perform Fourier transform on the transient displacement distribution of the iron core to obtain the frequency domain distribution of the iron core displacement. Based on multiple predetermined frequency bands, the displacement data of each predetermined frequency band in the frequency domain distribution of the iron core displacement is extracted as the boundary condition for transformer vibration analysis, and the displacement data of the transformer in each predetermined frequency band is simulated. The noise distribution simulation unit is used to simulate the frequency domain noise distribution of the air domain, including the perfectly matched layer, in each predetermined frequency band by taking the displacement data of the transformer obtained in each predetermined frequency band as the boundary condition for acoustic analysis. The transformer total sound pressure level calculation unit is used to determine the sound sensor measurement points, and calculate the sound pressure level of each sound sensor measurement point in each predetermined frequency band based on the obtained frequency domain noise distribution in each predetermined frequency band. Furthermore, based on the sound pressure level of each sound sensor measurement point in each predetermined frequency band, the total sound pressure level of the transformer is calculated. The air space inside the fuel tank is divided into free tetrahedral meshes with a maximum cell size of 50 mm; the area between the outside of the fuel tank and the perfect matching layer is divided into free tetrahedral meshes with a maximum cell size of 567 / n mm, where n = 1, 2, 3, 4; the perfect matching layer is divided into swept meshes. The structural parameters of the transformer include the core being made of silicon steel sheets with a conductivity of 1 S / m, a relative permittivity of 1, and a relative permeability of 10000; the windings being made of copper with a conductivity of 6e7 S / m, a relative permittivity of 1, and a relative permeability of 1; and the number of turns in the windings. The excitation and constraint conditions are as follows: a sinusoidal voltage of 8163V with a phase difference of 120 degrees is applied to the three-phase high-voltage windings, and the low-voltage windings are connected to a large resistor of 1000kΩ. The parameters required for transient electromagnetic simulation of the core's structural mesh include a start time of 0ms, a step size of 0.1ms, and an end time of 500ms. The parameters required for the transformer vibration analysis include the material properties of the windings, core, clamps, tie rods, foundation, pads, and air zone; among them... The material properties of the core include that it is made of silicon steel sheets, has a Young's modulus of 200e9Pa, and a density of 7800 kg / m³. 3 Poisson's ratio is 0.3; The material properties of the winding include that it is made of copper, has a Young's modulus of 110e9Pa, and a density of 8960kg / m³. 3 Poisson's ratio is 0.35; The clamp, the pull rod, the foot, and the pad are all made of iron with a Young's modulus of 200e9Pa and a density of 7850kg / m³. 3 And Poisson's ratio is 0.3; The material properties of the air domain include air as the material, with a density of 1.29 kg / m³. 3 And the speed of sound is 340 m / s.

4. The system for calculating the no-load vibration noise distribution of a transformer as described in claim 3, characterized in that, The predetermined frequency bands include 100Hz, 200Hz, 300Hz and 400Hz.

Images