A method and related device for analyzing the impact of HEMP on transformers in the late stage

Abstract

The present invention discloses a method and related device for analyzing the influence of HEMP on transformers in the late stage. The method respectively constructs a transformer core vibration acceleration model caused by the magnetostrictive effect, a transformer sound pressure model, and a transformer heat conduction model. The method comprehensively analyzes the influence of DC bias on the transformer from three aspects of vibration, noise, and temperature rise. The method understands the harm caused by DC bias in the late stage of HEMP to the transformer from multiple angles. The method provides an effective guidance means for analyzing the harm caused by DC bias in the late stage of HEMP to the transformer, and solves the technical problem that the prior art lacks an effective analysis method for the influence of HEMP on transformers in the late stage and is difficult to provide guidance for avoiding the harm caused by DC bias in the late stage of HEMP to the transformer.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a method and related device for analyzing the impact of HEMP on transformers in the late stage. Background Art

[0002] High-altitude electromagnetic pulses (HEMPs) are generated by nuclear explosions at altitudes exceeding 30 km above Earth's surface. The radiation fields generated by HEMPs in near-Earth space can be categorized by their temporal evolution into E1 (early), E2 (mid-term), and E3 (late). E3, also known as magnetohydrodynamic electromagnetic pulses (MHPs), are low-frequency (below 1 Hz) and low-amplitude (approximately tens of volts per kilometer) electromagnetic pulses that cause dramatic fluctuations in the Earth's magnetic field, leading to the formation of an earth surface potential (ESP). This ESP, acting as a voltage source, forms a loop with the Earth through long-distance conductors (rails, transmission lines, oil pipelines, etc.), generating geomagnetically induced currents (GICs). Compared to 50 Hz power-frequency currents, these GICs can be considered quasi-DC currents. These GICs can cause DC bias in transformers in power supply systems, leading to severe magnetic saturation of the transformer core and malfunction, ultimately impacting the safe and stable operation of the system. Therefore, analyzing how the DC bias caused by the late HEMP affects the transformer in order to better solve the damage caused by the DC bias to the transformer is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0003] The present invention provides a method and related device for analyzing the impact of late HEMP on transformers, which are used to solve the technical problem that the existing technology lacks an effective analysis method for the impact of late HEMP on transformers and is difficult to provide guidance for avoiding the damage caused by DC bias magnetic field caused by late HEMP to transformers.

[0004] In view of this, a first aspect of the present invention provides a method for analyzing the impact of HEMP on transformers in the late stage, comprising:

[0005] A transformer core vibration acceleration model caused by magnetostrictive effect is constructed, and the transformer core vibration under DC bias is analyzed to obtain the first analysis result.

[0006] Construct a transformer sound pressure model, analyze the transformer noise under DC bias, and obtain the second analysis result;

[0007] Construct a transformer heat conduction model, analyze the transformer temperature under DC bias, and obtain the third analysis result;

[0008] The first analysis result, the second analysis result and the third analysis result are integrated to obtain an analysis result of the impact of HEMP in the late stage on the transformer.

[0009] Optionally, the transformer core vibration acceleration model is:

[0010]

[0011] in, is the transformer core vibration acceleration, t is time, K is the size of the transformer core before deformation, is the maximum magnetostriction change, is the coercive force, is the maximum value of the transformer excitation voltage, l is the length of the transformer main magnetic circuit coil, R is the transformer equivalent resistance, is the angular frequency, L is the equivalent inductance of the transformer, is the magnetostriction coefficient in saturation state, N is the number of coil turns of the transformer, is the DC bias current.

[0012] Optionally, the transformer sound pressure model is:

[0013]

[0014] in, is the fluid density, q is the dipole source, Q is the monopole source, c is the speed of sound propagation in the fluid, p is the effective value of the transformer noise pressure, is the divergence, is the effective value gradient of transformer noise sound pressure.

[0015] Optionally, the transformer heat conduction model is:

[0016]

[0017] in, is the heat flow rate, T is the transformer temperature, is the temperature gradient along the x-axis, is the temperature gradient along the y-axis, is the temperature gradient along the z-axis, is the thermal conductivity of transformer oil in the x-axis direction, is the thermal conductivity of transformer oil in the y-axis direction, is the thermal conductivity of transformer oil in the z-axis direction, is the transformer oil density, is the specific heat of transformer oil.

[0018] Optionally, the transformer heat conduction model further includes temperature boundary conditions, heat flow boundary conditions and convection boundary conditions;

[0019] The temperature boundary conditions are:

[0020]

[0021] in, is the boundary condition of the object, is the known wall temperature;

[0022] The heat flow boundary conditions are:

[0023]

[0024] in, is the known heat flux density, - is the direction in which heat flows to reduce temperature, is the thermal conductivity of the transformer, is the temperature gradient along the direction of heat flow toward decreasing temperature;

[0025] The convection boundary conditions are:

[0026]

[0027] Among them, - is the direction of heat flow towards lower temperature, is the thermal conductivity of the transformer, is the temperature gradient in the direction of heat flow to lower temperature, h is the convective heat transfer coefficient, is the temperature of the fluid medium in contact with the object.

[0028] A second aspect of the present invention provides an analysis device for the impact of HEMP on transformers in the late stage, comprising:

[0029] A vibration analysis module is used to construct a transformer core vibration acceleration model caused by magnetostrictive effect, analyze the transformer core vibration under DC bias, and obtain a first analysis result;

[0030] A noise analysis module is used to construct a transformer sound pressure model, analyze the transformer noise under DC bias, and obtain a second analysis result;

[0031] The temperature analysis module is used to build a transformer heat conduction model, analyze the transformer temperature under DC bias, and obtain the third analysis result;

[0032] An output module is used to integrate the first analysis result, the second analysis result and the third analysis result to obtain an analysis result of the impact of HEMP in the late stage on the transformer.

[0033] Optionally, the transformer core vibration acceleration model is:

[0034]

[0035] in, is the transformer core vibration acceleration, t is time, K is the size of the transformer core before deformation, is the maximum magnetostriction change, is the coercive force, is the maximum value of the transformer excitation voltage, l is the length of the transformer main magnetic circuit coil, R is the transformer equivalent resistance, is the angular frequency, L is the equivalent inductance of the transformer, is the magnetostriction coefficient in saturation state, N is the number of coil turns of the transformer, is the DC bias current;

[0036] The transformer sound pressure model is:

[0037]

[0038] in, is the fluid density, q is the dipole source, Q is the monopole source, c is the speed of sound propagation in the fluid, p is the effective value of the transformer noise pressure, is the divergence, is the effective value gradient of transformer noise sound pressure;

[0039] The transformer heat conduction model is:

[0040]

[0041] in, is the heat flow rate, T is the transformer temperature, is the temperature gradient along the x-axis, is the temperature gradient along the y-axis, is the temperature gradient along the z-axis, is the thermal conductivity of transformer oil in the x-axis direction, is the thermal conductivity of transformer oil in the y-axis direction, is the thermal conductivity of transformer oil in the z-axis direction, is the transformer oil density, is the specific heat of transformer oil.

[0042] Optionally, the transformer heat conduction model further includes temperature boundary conditions, heat flow boundary conditions and convection boundary conditions;

[0043] The temperature boundary conditions are:

[0044]

[0045] in, is the boundary condition of the object, is the known wall temperature;

[0046] The heat flow boundary conditions are:

[0047]

[0048] in, is the known heat flux density, - is the direction in which heat flows to reduce temperature, is the thermal conductivity of the transformer, is the temperature gradient along the direction of heat flow toward decreasing temperature;

[0049] The convection boundary conditions are:

[0050]

[0051] Among them, - is the direction of heat flow towards lower temperature, is the thermal conductivity of the transformer, is the temperature gradient in the direction of heat flow to lower temperature, h is the convective heat transfer coefficient, is the temperature of the fluid medium in contact with the object.

[0052] A third aspect of the present invention provides a device for analyzing the effects of HEMP on transformers in the late stage, the device comprising a processor and a memory.

[0053] The memory is used to store program code and transmit the program code to the processor;

[0054] The processor is configured to execute the method for analyzing the impact of HEMP in the late stage on the transformer according to any one of the first aspects of the present invention, according to the instructions in the program code.

[0055] A fourth aspect of the present invention provides a computer-readable storage medium for storing program code, wherein the program code is used to execute the method for analyzing the late impact of HEMP on a transformer as described in any one of the first aspects of the present invention.

[0056] From the above technical solutions, it can be seen that the analysis method of the impact of HEMP on transformers in the late stage provided by the present invention has the following advantages:

[0057] The present invention provides a method for analyzing the influence of late HEMP on transformers, respectively constructing a transformer core vibration acceleration model caused by the magnetostrictive effect, a transformer sound pressure model, and a transformer heat conduction model, comprehensively analyzing the influence of DC bias on the transformer from three aspects: vibration, noise, and temperature rise, and understanding the harm caused by DC bias in the late HEMP period to the transformer from multiple angles. This provides an effective guidance method for analyzing the harm caused by DC bias in the late HEMP period to the transformer, and solves the technical problem that the prior art lacks an effective analysis method for the influence of late HEMP on transformers and is difficult to provide guidance for avoiding the harm caused by DC bias in the late HEMP period to the transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying any creative work.

[0059] Figure 1 A flow chart of a method for analyzing the impact of HEMP on transformers in the late stage provided in an embodiment of the present invention;

[0060] Figure 2 A force and mass flow diagram of a unit small volume element provided in an embodiment of the present invention;

[0061] Figure 3 Schematic diagram of the structure of a device for analyzing the impact of HEMP on transformers in the late stage provided in an embodiment of the present invention;

[0062] Figure 4 This is a schematic structural diagram of a device for detecting the impact of HEMP on transformers in the late stage, provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0063] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of 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 making creative efforts shall fall within the scope of protection of the present invention.

[0064] For easier understanding, see Figure 1 The present invention provides an embodiment of a method for analyzing the impact of HEMP on transformers in the late stage, comprising:

[0065] Step 101: construct a transformer core vibration acceleration model caused by magnetostrictive effect, analyze the transformer core vibration under DC bias, and obtain a first analysis result.

[0066] It should be noted that during normal operation, the total current flowing into the transformer is greater than the generated excitation current. However, when DC bias occurs, the opposite is true. This shows that DC bias has a more significant impact on the vibration of the transformer core. The vibration characteristics can be used to study the impact of late HEMP on the transformer.

[0067] Vibration on the transformer's shell surface is primarily caused by the magnetostrictive effect of the core material (typically silicon steel sheets) and electromagnetic forces. Therefore, the core's vibration acceleration can be calculated to represent the core's displacement. With the continuous optimization and upgrading of core silicon steel sheet stacking methods (such as the use of stepped joints), the gaps between core silicon steel sheets are becoming smaller and smaller, significantly reducing magnetic flux leakage. Therefore, the vibration of the power transformer core caused by electromagnetic forces can be ignored.

[0068] Apply power frequency voltage to the transformer :

[0069]

[0070] in, is the maximum value of the transformer excitation voltage, is the angular frequency, , , t is the time.

[0071] Assume that in the transformer equivalent circuit, the impedance is , R is the transformer equivalent resistance, L is the transformer equivalent inductance, and the AC current is , the DC bias current is , then under normal circumstances the AC current can be expressed as:

[0072]

[0073] Through Fourier transform and then inverse transform, we can get:

[0074]

[0075] The DC bias state of the transformer is simulated by assuming that the current in the transformer winding is a superposition of AC and DC quantities. At this time, the current i in the transformer winding can be expressed as:

[0076]

[0077] When the transformer is running at no load, the current i in the transformer winding is:

[0078]

[0079] According to the full current law, we have:

[0080]

[0081] Where N is the number of turns of the transformer coil and H is the magnetic field strength.

[0082] Therefore, the magnetic field strength H can be expressed as:

[0083]

[0084] according to 、 as well as , we can get:

[0085]

[0086] Where A is the cross-sectional area, is the main magnetic flux, B is the magnetic flux density, l is the length of the transformer main magnetic circuit coil, is the transformer core permeability.

[0087] It can be seen that the main magnetic flux of the iron core is composed of AC and DC magnetic fluxes, the front part is the DC component, and the rear part is the AC component.

[0088] The tiny deformation of the core silicon steel sheet due to the magnetostrictive effect meets the following conditions:

[0089]

[0090] Among them, K is the size of the transformer core before deformation, is the maximum magnetostriction change, is the coercive force, is the magnetostriction in saturation state.

[0091] Magnetostriction of core silicon steel sheet It can be expressed as:

[0092]

[0093] Substitute the expression of magnetic field intensity H into the magnetostriction of the core silicon steel sheet The formula is:

[0094]

[0095] Taking the second-order derivative of the maximum magnetostrictive change, the core vibration acceleration caused by the magnetostrictive effect can be obtained as:

[0096]

[0097] in, is the transformer core vibration acceleration.

[0098] It can be seen from the above transformer core vibration acceleration that when no DC current flows in, the transformer core vibration acceleration only includes the first term in the expression, and when DC current flows in, it includes the entire expression.

[0099] In summary, when DC bias occurs in the transformer, the core vibration acceleration spectrum includes both even and odd multiples of the power supply voltage frequency (industrial frequency 50Hz).

[0100] Step 102: construct a transformer sound pressure model, analyze the transformer noise under DC bias, and obtain a second analysis result.

[0101] It should be noted that transformer noise primarily comes from two sources: the transformer's own noise, which consists of the core, windings, and oil tank; and the noise of the transformer's cooling system, caused by the transformer's cooling fan and submersible oil pump. Water-cooled transformer noise can be disregarded because it is very quiet.

[0102] Transformer body noise is generated by body vibration. Since transformer cooling systems are difficult to model and analyze, their noise can be ignored here. The magnetostrictive vibration of the core is the most significant contributor to transformer body noise. This magnetostrictive vibration can be transmitted from the core's feet into the transformer box (solid path) or through the insulating oil into the transformer box (liquid path). The vibration energy transferred from these two paths causes the transformer box walls to vibrate, generating noise. In the air path, transformer body noise is transmitted in the form of sound waves.

[0103] In acoustic theory, the vibration of objects is the source of sound, frequency can describe the pitch of sound, and sound pressure, sound intensity, and sound power can describe the strength of sound. The propagation of sound waves is essentially the propagation of energy, and the transmission of sound waves will cause changes in the energy of surrounding air particles. The atmospheric pressure change caused by air is defined as the effective value of the transformer noise sound pressure. In continuous media, sound pressure can be used to characterize the pressure and operating state of any point in the sound field. Sound pressure can be used to describe the strength of sound. Under normal circumstances, the magnitude of sound pressure varies with the noise, so the magnitude of sound pressure can be used as a physical quantity of noise, and its unit is Pa ( ). 20 Indicates the reference sound pressure. 20 It is the pain valve sound pressure.

[0104] Since the sound pressure of the pain valve is much different from the reference sound pressure, the concept of sound pressure level is introduced to express the level of noise. The unit of sound pressure level is decibel (dB). For the study of transformer noise, the sound pressure level is The expression is:

[0105]

[0106] Where p is the effective value of transformer noise pressure, is the reference sound pressure.

[0107] Unit mass impulse velocity potential The effective value p of the transformer noise pressure has the following wave equation:

[0108]

[0109] in, is the transformer oil density, in units of .

[0110] Unit mass impulse velocity potential The speed of sound propagation c in the medium satisfies:

[0111]

[0112] in, is the Laplace operator, and we define .

[0113] For high-voltage transformers, the sound pressure is transmitted outward from the core and winding as solid vibration through the transformer oil, which can be expressed as:

[0114]

[0115] in, is the sound pressure, and n is the particle area.

[0116] The displacement of a solid particle is represented by d, and the normal velocity of the solid particle is It can be expressed as:

[0117]

[0118] The fluid particle velocity for:

[0119]

[0120] in, is the gradient operator, and we define .

[0121] The unit mass impulse velocity potential is obtained by solving the wave equation , the particle velocity can be obtained through simple differential operation And the effective value of transformer noise sound pressure p.

[0122] like Figure 2 As shown in the figure, take any volume element in the medium and consider the motion characteristics of the element under the action of sound waves. It can be known that the effective value p of the transformer noise pressure is related to the particle vibration velocity The relationship is:

[0123]

[0124] in, is the particle vibration velocity Component along the x-axis.

[0125] Integrating the previous formula, we can get:

[0126]

[0127] Depend on , is the density increment, which means that the fluid density can be decomposed into the sum of the average density of the fluid and the density increment, where:

[0128]

[0129] The first term on the right side of the above formula is the local velocity, and the second term on the right side is the migration velocity. Substitute into the above formula.

[0130] After neglecting higher-order traces, the one-dimensional motion equation of an ideal gas is linear, namely:

[0131]

[0132] In the acoustic field, the mass increment caused by the density change of the volume element is equal to the mass difference of the fluid flowing into the unit, such as Figure 2 As shown in the force and mass flow diagram of a small unit volume element, the mass flowing in on the left is equal to the mass flowing out on the right. According to the law of conservation of mass, the one-dimensional continuity equation in an ideal fluid is:

[0133]

[0134] According to the basic assumptions of acoustics, sound waves propagate adiabatically. Based on the relationship between sound pressure and density, the relationship between the effective value p of transformer noise pressure and space-time variation can be obtained as follows:

[0135]

[0136] For three-dimensional space, we can use the equation One-dimensional generalization to three-dimensional wave equation:

[0137]

[0138] For transformer acoustic field calculation, the transformer core (the main source of noise) can be regarded as a combination of a monopole and a dipole. In this case, the domain governing equation for the acoustic field calculation is:

[0139]

[0140] Among them, q is a dipole source, Q is a monopole source, c is the speed of sound propagation in the fluid, is the divergence, is the effective value gradient of transformer noise sound pressure.

[0141] The sound pressure level distribution of transformer noise can be obtained through multi-physics field coupling calculation.

[0142] Step 103: construct a transformer heat conduction model, analyze the transformer temperature under DC bias, and obtain a third analysis result.

[0143] It should be noted that DC bias magnetization increases eddy current losses in the transformer housing, leading to higher temperatures. Using indirect coupling, the eddy current loss unit results from the magnetic field analysis are used as the excitation for the thermal field analysis unit, allowing for steady-state thermal analysis.

[0144] Transformer temperature rise refers to the temperature difference between a transformer component and the cooling medium. For safe and reliable transformer operation, the temperature rise must not exceed a certain limit. The normal temperature rise limits for oil-immersed transformers at rated capacity are: an average temperature rise of 60K for the top oil relative to the surrounding air, and an average temperature rise of 65K for the windings relative to the surrounding air. Temperature rise limits are not specified for the core, electrical wiring external to the windings, or structural components in the mailbox. However, the temperature rise must still be limited, typically below 80K, to prevent excessive oil aging or thermal damage to adjacent components.

[0145] The temperature rise of the transformer will accelerate the aging of the transformer insulation, thereby shortening the transformer life. The life of the insulation material determines the service life of the transformer. The increase in the temperature rise of the transformer windings, core pressure plate and other components increases the operating temperature of the insulation material in contact with them, speeding up the oxidation process, leading to faster aging of the transformer insulation, reducing the mechanical and electrical strength of the insulation material, and thus shortening the service life of the transformer.

[0146] There are three basic types of heat transfer in transformers: heat conduction, heat convection and heat radiation.

[0147] Heat conduction follows Fourier's law:

[0148]

[0149] in, is the known heat flux density in units of , “-” means that heat flows in the direction of decreasing temperature, is the thermal conductivity of the transformer, in units of , is the temperature gradient in the direction of decreasing temperature along the heat flow.

[0150] Thermal convection refers to the exchange of heat between a solid surface and the fluid in contact with it due to a temperature difference. Thermal convection is divided into forced convection and natural convection. Convection is generally applied as a surface boundary condition and can be described using Newton's cooling equation as follows:

[0151]

[0152] in, is the surface heat transfer coefficient, in units of , is the temperature of the solid surface, is the temperature of the surrounding fluid.

[0153] In the case of air cooling, for smooth surfaces, we have: , for non-smooth surfaces, we have: , where v is the average velocity of the circulating oil. When the average temperature of the cooling surface and the inlet air is 50 degrees, v is The above formula is applicable to the following. The above formula cannot be applied to the heat calculation with air cooling, because only a part of the air blown out by the fan falls on the cooling pipe, and the air speed is different at different positions of the cooling pipe.

[0154] The convection heat transfer coefficient between transformer oil and box is:

[0155]

[0156] in, is the transformer oil density, in units of , is the specific heat of transformer oil, in units of , v is the average velocity of the circulating oil, generally , H is the temperature reached by the cooling oil as it continues to rise along the heat dissipation surface.

[0157] Thermal radiation is the conversion of electromagnetic energy absorbed by an object into heat by another object. The amount of heat radiated per unit time increases with the object's temperature. While convection and conduction require a heat transfer medium, thermal radiation does not, and is most efficient in a vacuum. Thermal analysis involving thermal radiation is highly nonlinear.

[0158] In engineering, radiation between two or more objects is often considered. Each object in the system radiates and absorbs heat simultaneously. The net heat transfer between them can be expressed as follows:

[0159]

[0160] in, is the heat flow rate, is the absorption rate, is the Sronpen-Boltzmann constant, is the area of ​​radiating surface 1, is the shape coefficient from radiating surface 1 to radiating surface 2, is the thermodynamic temperature of the radiation surface 1, is the thermodynamic temperature of the radiation surface 2.

[0161] In general three-dimensional problems, the temperature field of an object changes with coordinate position and time, that is, According to the principle of thermal equilibrium, the heat stored in any microelement in an object during any time dt is equal to the sum of the heat transferred to the microelement and the heat generated by the heat source in the microelement. The stored heat is The difference between the heat transferred out and into the microelement along the x-axis at the same time is:

[0162]

[0163] in, is the heat flux in the x direction.

[0164] Then the net heat input to the infinitesimal body is:

[0165]

[0166] in, is the heat flux density in the y direction, is the heat flux in the z direction.

[0167] According to the law of heat conduction, the heat flux is proportional to the temperature gradient, but in the opposite direction, that is:

[0168]

[0169] in, is the temperature gradient along the x-axis, is the temperature gradient along the y-axis, is the temperature gradient along the z-axis, is the thermal conductivity of transformer oil in the x-axis direction, is the thermal conductivity of transformer oil in the y-axis direction, is the thermal conductivity of transformer oil in the z-axis direction.

[0170] The net heat input to the microelement is:

[0171]

[0172] The heat source density in the microelement is , then the heat supplied by the heat source in time dt is , then the differential equation for heat conduction is:

[0173]

[0174] There are countless solutions that satisfy the above equation. The initial transient temperature distribution must be determined, and the law of heat exchange between the surface of the object and the surrounding medium, that is, the boundary conditions, must also be known.

[0175] In order to make the solution of the heat balance equation at each node unique, temperature boundary conditions, heat flow boundary conditions and convection boundary conditions are attached.

[0176] The temperature boundary conditions are:

[0177]

[0178] or

[0179]

[0180] in, is the boundary condition of the object, is the known wall temperature, is a known function of temperature that varies with position and time.

[0181] The heat flow boundary conditions are:

[0182]

[0183] or

[0184]

[0185] in, is the known heat flux density, - is the direction in which heat flows to reduce temperature, is the thermal conductivity of the transformer, is the temperature gradient in the direction of decreasing temperature along the heat flow, is a known function of heat flux density that varies with position and time.

[0186] The convection boundary conditions are:

[0187]

[0188] or

[0189]

[0190] Among them, - is the direction of heat flow towards lower temperature, is the thermal conductivity of the transformer, is the temperature gradient in the direction of heat flow to lower temperature, h is the convective heat transfer coefficient, is the temperature of the fluid medium in contact with the object, and h can be constants or functions that vary with position and time, is the convective heat transfer coefficient of radiation surface 1, Convective heat transfer coefficient of radiating surface 2.

[0191] Based on the above transformer heat conduction differential equation, temperature boundary conditions, heat flow boundary conditions and convection boundary conditions, the temperature rise of the transformer can be determined.

[0192] HEMP E3 causes dramatic changes in the geomagnetic field, leading to the formation of a ground-induced electromotive force on the surface. This creates a loop with the earth, generating a geomagnetic induced current. This current, relative to the 50Hz power frequency current, can be considered quasi-DC. This creates a DC bias effect, which in turn causes transformer vibration, noise, and temperature rise. Therefore, the present invention comprehensively evaluates and analyzes the impact of HEMP late-stage DC bias on transformers through vibration, noise, and temperature rise, effectively addressing the problem of analyzing the harmful effects of DC bias on transformers.

[0193] Step 104: Integrate the first analysis result, the second analysis result, and the third analysis result to obtain an analysis result of the impact of HEMP on the transformer in the late stage.

[0194] It should be noted that by analyzing transformer core vibration under DC bias using a model of transformer core vibration acceleration caused by the magnetostrictive effect, we can determine the impact of DC bias on transformer core vibration in the late HEMP period. By analyzing transformer noise under DC bias using a transformer sound pressure model, we can determine the impact of DC bias on transformer noise in the late HEMP period. By analyzing transformer temperature rise under DC bias using a transformer heat conduction model, we can determine the impact of DC bias on transformer temperature in the late HEMP period.

[0195] The present invention provides a method for analyzing the influence of late HEMP on transformers, respectively constructing a transformer core vibration acceleration model caused by the magnetostrictive effect, a transformer sound pressure model, and a transformer heat conduction model, comprehensively analyzing the influence of DC bias on the transformer from three aspects: vibration, noise, and temperature rise, and understanding the harm caused by DC bias in the late HEMP period to the transformer from multiple angles. This provides an effective guidance method for analyzing the harm caused by DC bias in the late HEMP period to the transformer, and solves the technical problem that the prior art lacks an effective analysis method for the influence of late HEMP on transformers and is difficult to provide guidance for avoiding the harm caused by DC bias in the late HEMP period to the transformer.

[0196] For easier understanding, see Figure 3 The present invention provides an embodiment of a device for analyzing the effects of HEMP on transformers in the late stage, comprising:

[0197] A vibration analysis module is used to construct a transformer core vibration acceleration model caused by magnetostrictive effect, analyze the transformer core vibration under DC bias, and obtain a first analysis result;

[0198] A noise analysis module is used to construct a transformer sound pressure model, analyze the transformer noise under DC bias, and obtain a second analysis result;

[0199] The temperature analysis module is used to build a transformer heat conduction model, analyze the transformer temperature under DC bias, and obtain the third analysis result;

[0200] The output module is used to integrate the first analysis result, the second analysis result and the third analysis result to obtain the analysis result of the impact of HEMP in the late stage on the transformer.

[0201] In one embodiment, the transformer core vibration acceleration model is:

[0202]

[0203] in, is the transformer core vibration acceleration, t is time, K is the size of the transformer core before deformation, is the maximum magnetostriction change, is the coercive force, is the maximum value of the transformer excitation voltage, l is the length of the transformer main magnetic circuit coil, R is the transformer equivalent resistance, is the angular frequency, L is the equivalent inductance of the transformer, is the magnetostriction coefficient in saturation state, N is the number of coil turns of the transformer, is the DC bias current;

[0204] The transformer sound pressure model is:

[0205]

[0206] in, is the fluid density, q is the dipole source, Q is the monopole source, c is the speed of sound propagation in the fluid, p is the effective value of the transformer noise pressure, is the divergence, is the effective value gradient of transformer noise sound pressure;

[0207] The transformer heat conduction model is:

[0208]

[0209] in, is the heat flow rate, T is the transformer temperature, is the temperature gradient along the x-axis, is the temperature gradient along the y-axis, is the temperature gradient along the z-axis, is the thermal conductivity of transformer oil in the x-axis direction, is the thermal conductivity of transformer oil in the y-axis direction, is the thermal conductivity of transformer oil in the z-axis direction, is the transformer oil density, is the specific heat of transformer oil.

[0210] In one embodiment, the transformer heat conduction model further includes temperature boundary conditions, heat flow boundary conditions, and convection boundary conditions;

[0211] The temperature boundary conditions are:

[0212]

[0213] in, is the boundary condition of the object, is the known wall temperature;

[0214] The heat flow boundary conditions are:

[0215]

[0216] in, is the known heat flux density, - is the direction in which heat flows to reduce temperature, is the thermal conductivity of the transformer, is the temperature gradient along the direction of heat flow toward decreasing temperature;

[0217] The convection boundary conditions are:

[0218]

[0219] Among them, - is the direction of heat flow towards lower temperature, is the thermal conductivity of the transformer, is the temperature gradient in the direction of heat flow to lower temperature, h is the convective heat transfer coefficient, is the temperature of the fluid medium in contact with the object.

[0220] For easier understanding, see Figure 4 The present invention provides an embodiment of a device for analyzing the effects of late HEMP on transformers, the device comprising a processor and a memory:

[0221] The memory is used to store program codes and transmit the program codes to the processor;

[0222] The processor is configured to execute any one of the methods in the embodiments of the method for analyzing the influence of the late stage of HEMP on the transformer according to the instructions in the program code.

[0223] The present invention also provides an embodiment of a computer-readable storage medium, which is used to store program code, and the program code is used to execute any one of the methods for analyzing the late impact of HEMP on the transformer in the embodiments of the present invention.

[0224] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for analyzing the impact of HEMP on transformers in the late stage, characterized in that: include: A transformer core vibration acceleration model caused by magnetostrictive effect is constructed, and the transformer core vibration under DC bias is analyzed to obtain the first analysis result. Construct a transformer sound pressure model, analyze the transformer noise under DC bias, and obtain the second analysis result; Construct a transformer heat conduction model, analyze the transformer temperature under DC bias, and obtain the third analysis result; Integrating the first analysis result, the second analysis result, and the third analysis result to obtain an analysis result of the impact of HEMP on the transformer in the late stage; The transformer core vibration acceleration model is: ； in, is the transformer core vibration acceleration, t is time, K is the size of the transformer core before deformation, is the maximum magnetostriction change, is the coercive force, is the maximum value of the transformer excitation voltage, l is the length of the transformer main magnetic circuit coil, R is the transformer equivalent resistance, is the angular frequency, L is the equivalent inductance of the transformer, is the magnetostriction coefficient in saturation state, N is the number of coil turns of the transformer, is the DC bias current; The transformer sound pressure model is: ； in, is the fluid density, q is the dipole source, Q is the monopole source, c is the speed of sound propagation in the fluid, p is the effective value of the transformer noise pressure, is the divergence, is the effective value gradient of transformer noise sound pressure; The transformer heat conduction model is: ； in, is the heat flow rate, T is the transformer temperature, is the temperature gradient along the x-axis, is the temperature gradient along the y-axis, is the temperature gradient along the z-axis, is the thermal conductivity of transformer oil in the x-axis direction, is the thermal conductivity of transformer oil in the y-axis direction, is the thermal conductivity of transformer oil in the z-axis direction, is the transformer oil density, is the specific heat of transformer oil.

2. The method for analyzing the impact of HEMP on transformers in the late stage according to claim 1, characterized in that: The transformer heat conduction model also includes temperature boundary conditions, heat flow boundary conditions and convection boundary conditions; The temperature boundary conditions are: ； in, is the boundary condition of the object, is the known wall temperature; The heat flow boundary conditions are: ； in, is the known heat flux density, - is the direction in which heat flows to reduce temperature, is the thermal conductivity of the transformer, is the temperature gradient along the direction of heat flow toward decreasing temperature; The convection boundary conditions are: ； Among them, - is the direction of heat flow towards lower temperature, is the thermal conductivity of the transformer, is the temperature gradient in the direction of heat flow to lower temperature, h is the convective heat transfer coefficient, is the temperature of the fluid medium in contact with the object.

3. An analysis device for the impact of HEMP on transformers in the late stage, characterized in that: include: A vibration analysis module is used to construct a transformer core vibration acceleration model caused by magnetostrictive effect, analyze the transformer core vibration under DC bias, and obtain a first analysis result; A noise analysis module is used to construct a transformer sound pressure model, analyze the transformer noise under DC bias, and obtain a second analysis result; The temperature analysis module is used to build a transformer heat conduction model, analyze the transformer temperature under DC bias, and obtain the third analysis result; an output module, configured to integrate the first analysis result, the second analysis result, and the third analysis result to obtain an analysis result of the impact of HEMP on the transformer in the late stage; The transformer core vibration acceleration model is: ； in, is the transformer core vibration acceleration, t is time, K is the size of the transformer core before deformation, is the maximum magnetostriction change, is the coercive force, is the maximum value of the transformer excitation voltage, l is the length of the transformer main magnetic circuit coil, R is the transformer equivalent resistance, is the angular frequency, L is the equivalent inductance of the transformer, is the magnetostriction coefficient in saturation state, N is the number of coil turns of the transformer, is the DC bias current; The transformer sound pressure model is: ； in, is the fluid density, q is the dipole source, Q is the monopole source, c is the speed of sound propagation in the fluid, p is the effective value of the transformer noise pressure, is the divergence, is the effective value gradient of transformer noise sound pressure; The transformer heat conduction model is: ； in, is the heat flow rate, T is the transformer temperature, is the temperature gradient along the x-axis, is the temperature gradient along the y-axis, is the temperature gradient along the z-axis, is the thermal conductivity of transformer oil in the x-axis direction, is the thermal conductivity of transformer oil in the y-axis direction, is the thermal conductivity of transformer oil in the z-axis direction, is the transformer oil density, is the specific heat of transformer oil.

4. The device for analyzing the effects of HEMP on transformers in the late stage according to claim 3, characterized in that: The transformer heat conduction model also includes temperature boundary conditions, heat flow boundary conditions and convection boundary conditions; The temperature boundary conditions are: ； in, is the boundary condition of the object, is the known wall temperature; The heat flow boundary conditions are: ； in, is the known heat flux density, - is the direction in which heat flows to reduce temperature, is the thermal conductivity of the transformer, is the temperature gradient along the direction of heat flow toward decreasing temperature; The convection boundary conditions are: ； Among them, - is the direction of heat flow towards lower temperature, is the thermal conductivity of the transformer, is the temperature gradient in the direction of heat flow to lower temperature, h is the convective heat transfer coefficient, is the temperature of the fluid medium in contact with the object.

5. An analysis device for the effects of HEMP on transformers in the late stage, characterized in that: The device includes a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is configured to execute the method for analyzing the impact of HEMP in the late stage on a transformer according to any one of claims 1 to 2 according to the instructions in the program code.

6. A computer-readable storage medium, characterized in that The computer-readable storage medium is used to store program code, and the program code is used to execute the analysis method of the late HEMP impact on the transformer according to any one of claims 1-2.

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