Method, system and equipment for calculating fatigue life of insulation paper by considering force accumulation effect and medium

Abstract

The invention relates to the technical field of insulation paper fatigue life calculation, and discloses an insulation paper fatigue life calculation method, system and device considering a force accumulation effect, and a medium, and the method comprises the steps: building a three-phase three-winding model based on a power transformer; short-circuit current waveforms are obtained through circuit sampling and serve as excitation to be given to all windings of the three-phase three-winding model; and calculating the distribution of the short-circuit electrodynamic force on the windings of the three-phase three-winding model, and calculating the deformation condition of the windings after being subjected to the short-circuit electrodynamic force to obtain the current fatigue life of the insulation paper. According to the method, the three-phase three-winding model is constructed, the short-circuit current waveform and the distribution of the short-circuit electrodynamic force on the windings are obtained, the fatigue life of the insulation paper is further obtained, thermal aging of the insulation paper is considered, force accumulation damage caused by short-circuit impact is also brought into a calculation model, and the calculation precision is further improved.

Description

Technical Field

[0001] This invention relates to the field of fatigue life calculation technology for insulating paper, and in particular to a method, system, device and medium for calculating the fatigue life of insulating paper that takes into account the force accumulation effect. Background Technology

[0002] Inter-turn short circuit is a common fault in transformer operation. When it occurs, it will generate a large current several times the rated value in the short-circuit ring of the winding, which will increase the temperature of the hot spot, induce secondary damage to the insulation, and eventually cause the copper wire to melt at the connection between the short-circuit ring and the main circuit.

[0003] To prevent power transformers from being damaged by inter-turn short circuits during operation and to improve the stability of the power grid, it is necessary to assess and calculate the lifespan of the insulation paper between the winding turns. Power grid technicians can then decide whether to return the transformer to the factory for insulation repair based on whether the remaining insulation lifespan is below a set threshold, thus improving grid stability. However, current insulation lifespan testing technologies mostly calculate based on thermal cumulative aging, with few methods considering insulation lifespan calculations based on stress cumulative aging under short-circuit impacts. In contrast, insulation paper fatigue life calculations that take into account stress cumulative aging are more comprehensive, have higher calculation accuracy, are applicable in operation, and have greater engineering significance.

[0004] The existing approach to calculating insulation fatigue life involves first recording the short-circuit current waveform generated by the transformer, then using multiphysics software to calculate its hot spot temperature, and finally obtaining the lifespan through thermal aging curves. However, thermal aging curves exhibit a clear saturation trend and are not the ultimate cause of insulation damage. Furthermore, damage caused by winding short-circuit impacts accounts for a significant proportion of insulation damage. Therefore, these factors need to be considered in lifespan calculations to improve calculation accuracy. Summary of the Invention

[0005] In view of the aforementioned existing problems, this invention is proposed. Therefore, this invention provides a method for calculating the fatigue life of insulating paper that takes into account the force accumulation effect, solving the problem of insufficient calculation accuracy in traditional methods for calculating the life of insulating paper.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a method for calculating the fatigue life of insulating paper that takes into account the force accumulation effect, including: constructing a three-phase three-winding model based on a power transformer;

[0008] Based on the three-phase three-winding model, the short-circuit current waveform is obtained by circuit sampling and used as an excitation for each winding of the three-phase three-winding model.

[0009] The distribution of short-circuit electrodynamic force on the windings of the three-phase three-winding model is calculated, and the deformation of the windings after being subjected to short-circuit electrodynamic force is calculated to obtain the current fatigue life of the insulating paper.

[0010] As a preferred embodiment of the method for calculating the fatigue life of insulating paper that takes into account the force accumulation effect described in this invention, the method includes: constructing a three-phase, three-winding model based on a power transformer, which includes:

[0011] The windings of the power transformer are equivalent to a cylinder, and a 3D model of the three-phase three-winding system is performed, including the low-voltage winding, the medium-voltage winding, and the high-voltage winding.

[0012] The transformer has a highly symmetrical structure and forms a spiral short-circuit current to generate a magnetic field.

[0013] As a preferred embodiment of the method for calculating the fatigue life of insulating paper that takes into account the force accumulation effect described in this invention, the method includes obtaining the short-circuit current waveform through circuit sampling:

[0014] Based on the three-phase three-winding model, the leftmost power supply represents the primary input of the power grid, and the rightmost load represents the secondary output. A circuit breaker is set between the primary input and the transformer.

[0015] Set the opening and closing times of the circuit breaker, and cause a three-phase ground short circuit to obtain the short-circuit current waveform;

[0016] The short-circuit current waveform is discretized, sampled, and exported, and then added to two sections of the corresponding short-circuit winding, with the excitation directions of the two sections being opposite, to form a loop;

[0017] The advantages of this preferred scheme are that sampling the short-circuit current waveform preserves the transient characteristics of the current, which can ensure the accuracy of the electromagnetic force time-domain analysis; applying the current excitation in the opposite direction to the cross sections at both ends of the winding can equivalently simulate the closed loop path of the real short-circuit current, thus avoiding distortion of the magnetic field calculation.

[0018] As a preferred embodiment of the method for calculating the fatigue life of insulating paper that takes into account the cumulative force effect described in this invention, the method for causing a three-phase ground fault includes setting a ground fault between the secondary output and the transformer, wherein the short circuit includes a single-phase ground fault, a two-phase ground fault, a three-phase ground fault, and an inter-turn short circuit.

[0019] As a preferred embodiment of the method for calculating the fatigue life of insulating paper that takes into account the force accumulation effect described in this invention, the calculation of the distribution of short-circuit electrodynamic force on the windings of the three-phase three-winding model includes:

[0020] Based on the three-phase three-winding model after setting the excitation, select the solution type and set a domain around the model to determine the solution space range;

[0021] The three-phase three-winding model is meshed, a new solution command is created, the solution step size and solution time length are set, and the distribution of short-circuit electrodynamic force of electromagnetic field on the winding is calculated.

[0022] The advantage of this preferred solution is that it provides high-precision input for subsequent structural deformation analysis and can avoid errors caused by the assumption of uniform force.

[0023] As a preferred embodiment of the method for calculating the fatigue life of insulating paper that takes into account the cumulative force effect described in this invention, the calculation of the deformation of the winding after being subjected to short-circuit electrodynamic force includes:

[0024] The calculation results of the distribution of the short-circuit electrodynamic force on the winding are used as the electrodynamic force input for the surface density.

[0025] In the simulation of the three-phase three-winding model, both the upper and lower pressure plates are in normal working condition, and fixed constraints are added to the upper and lower ports of the upper and lower pressure plates.

[0026] The mesh is generated according to the preset mesh parameters, a new solution command is created, the step size is set, the electrodynamic input of the surface density is added and applied, and the strain on the surface of the insulating paper of the winding is calculated.

[0027] The advantage of this preferred solution is that by simulating the pressure plate and electrodynamic loading, the strain distribution on the surface of the insulating paper can be directly output, thus identifying fatigue risk areas.

[0028] As a preferred embodiment of the method for calculating the fatigue life of insulating paper that takes into account the cumulative force effect described in this invention, the current fatigue life of the insulating paper is obtained by:

[0029] After the insulation paper on the winding surface reaches the thermal aging saturation state, the stress-strain curve and SN fatigue fracture curve of this type of insulation paper are obtained at the corresponding thermal aging saturation polymerization degree.

[0030] The strain waveform data of the insulating paper is processed, and the peak data is selected;

[0031] The magnitude of the stress wave peak is obtained by combining the strain wave peak with the stress-strain curve of the insulating paper. Based on the magnitude of the stress wave peak and the number of times it is applied, combined with the SN insulation fatigue curve, the current remaining insulation life of the insulating paper is obtained.

[0032] Secondly, the present invention provides a fatigue life calculation system for insulating paper that takes into account the force accumulation effect, comprising:

[0033] The model building module is used to build a three-phase, three-winding model based on a power transformer.

[0034] The acquisition module is used to obtain the short-circuit current waveform through circuit sampling based on the three-phase three-winding model, and to apply it as an excitation to each winding of the three-phase three-winding model.

[0035] The calculation module is used to calculate the distribution of short-circuit electrodynamic force on the windings of the three-phase three-winding model, and to calculate the deformation of the windings after being subjected to short-circuit electrodynamic force, so as to obtain the current fatigue life of the insulating paper.

[0036] Thirdly, the present invention provides a computer device, comprising:

[0037] Memory and processor;

[0038] The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the computer-executable instructions are executed by the processor, they implement the steps of the method for calculating the fatigue life of insulating paper that takes into account the force accumulation effect.

[0039] Fourthly, the present invention provides a computer-readable storage medium storing computer-executable instructions that, when executed by a processor, implement the steps of the method for calculating the fatigue life of insulating paper taking into account the force accumulation effect.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention obtains the short-circuit current waveform and the distribution of short-circuit electrodynamic force on the winding by constructing a three-phase three-winding model, thereby obtaining the fatigue life of the insulating paper. While considering the thermal aging of the insulating paper, it also incorporates the force accumulation damage caused by short-circuit impact into the calculation model, further improving the calculation accuracy. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a schematic diagram of the overall process of the method for calculating the fatigue life of insulating paper that takes into account the force accumulation effect according to an embodiment of the present invention.

[0043] Figure 2 A simplified model diagram of a three-phase, three-winding power transformer for calculating the fatigue life of insulating paper considering the force accumulation effect, as described in an embodiment of the present invention.

[0044] Figure 3 This is a Simulink circuit design diagram of a simulated short-circuit condition for the method of calculating the fatigue life of insulating paper that takes into account the force accumulation effect, as described in an embodiment of the present invention.

[0045] Figure 4 This is a diagram showing the short-circuit electrodynamic calculation results of the insulation paper fatigue life calculation method considering the force accumulation effect according to an embodiment of the present invention.

[0046] Figure 5 This is a schematic diagram of the strain magnitude on the winding surface in the method for calculating the fatigue life of insulating paper that takes into account the force accumulation effect, according to an embodiment of the present invention.

[0047] Figure 6 This is a schematic diagram of the SN insulation fatigue curve, which is a calculation example of the method for calculating the fatigue life of insulating paper that takes into account the force accumulation effect according to an embodiment of the present invention. Detailed Implementation

[0048] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0049] Reference Figures 1-3 As an embodiment of the present invention, a method for calculating the fatigue life of insulating paper that takes into account the force accumulation effect is provided, such as... Figure 1 As shown, it includes:

[0050] S101, a three-phase three-winding model based on a power transformer;

[0051] S102, based on a three-phase three-winding model, obtains the short-circuit current waveform through circuit sampling and uses it as an excitation for each winding of the three-phase three-winding model;

[0052] S103 calculates the distribution of short-circuit electrodynamic force on the windings of the three-phase three-winding model, and calculates the deformation of the windings after being subjected to short-circuit electrodynamic force, thus obtaining the current fatigue life of the insulating paper.

[0053] In a preferred embodiment, constructing a three-phase, three-winding model based on a power transformer includes:

[0054] The windings of the power transformer are equivalent to a cylinder, and a 3D model of the three-phase three-winding system is performed, including the low-voltage winding, the medium-voltage winding, and the high-voltage winding.

[0055] The transformer has a highly symmetrical structure and forms a spiral short-circuit current to generate a magnetic field.

[0056] In this embodiment, the windings of the power transformer are represented as a cylinder, and a three-phase, three-winding 3D model is performed. This simulation model is chosen considering the high symmetry of the overall transformer structure and balancing simulation efficiency and accuracy. Given that the transformer support bars and pads used in actual engineering are symmetrical and each turn of the coil is closely adjacent, the windings are simplified to a cylinder to shorten simulation time. Figure 2 As shown, the brown part is a core made of 30Q130 silicon carbon steel laminated and pressed together; the blue part is the low-voltage winding; the yellow part is the medium-voltage winding; and the red part is the high-voltage winding. All windings are made of copper. Two cross-sections are added to each winding. Figure 2 The two vertical lines on the surface are shown in the diagram. These two cross sections are used to apply two excitation sources of equal magnitude and opposite direction, thereby forming a spiral short-circuit current to generate a magnetic field.

[0057] It should be noted that the three-phase three-winding model can accurately reflect the spatial layout and electromagnetic coupling relationship of the low-voltage, medium-voltage, and high-voltage windings in an actual transformer, avoiding magnetic field distribution errors caused by single-phase or simplified models; it provides a structural basis for subsequent simulation of various complex ground faults, ensuring the comprehensiveness of electromagnetic force calculation; and it simplifies modeling and calculation through structural symmetry, significantly reducing computational resource consumption.

[0058] In an alternative implementation, the three-phase, three-winding model can also be constructed by directly coupling the electromagnetic-structure field using finite element software (such as COMSOL), modeling the actual helical structure, and simplifying the calculation through parametric scanning symmetry.

[0059] In a preferred embodiment, obtaining the short-circuit current waveform through circuit sampling includes:

[0060] Based on the three-phase three-winding model, the power source on the far left represents the primary input of the power grid, and a set of loads on the far right represents the secondary output. A circuit breaker is set between the primary input and the transformer.

[0061] Set the opening and closing times of the circuit breaker, and cause a three-phase ground short circuit to obtain the short-circuit current waveform;

[0062] The short-circuit current waveform is discretized, sampled, and exported. It is then added to two sections of the corresponding short-circuit winding, with the excitation directions of the two sections being opposite, thus forming a loop.

[0063] In a preferred embodiment, causing a three-phase ground fault includes: setting a ground fault between the secondary output and the transformer, the fault including a single-phase ground fault, a two-phase ground fault, a three-phase ground fault, and an inter-turn fault.

[0064] In this embodiment, a simulation model of a three-winding transformer in step-up operation can be built using Simulink. Corresponding circuit breaker opening and closing times are added, which are set according to the actual application scenario. A three-phase ground fault occurs at a selected time (which can be any set time). The short-circuit current waveform for testing is obtained. This waveform is sampled using Simulink to obtain an Excel file containing discrete values ​​of time and current magnitude. This file is converted to a tabbed worksheet format, imported, and named SC. Excitation SCs are added to the two cross-sections of the corresponding short-circuit winding, ensuring that the excitation directions of the two cross-sections are opposite to form a loop. Figure 3 As shown, in this circuit design, a three-phase, three-winding transformer is selected as the core. Figure 3 The option to ignore the medium-voltage winding was selected, so there are only two windings. A power supply is set on the far left to represent the primary input of the power grid, and a set of loads is set on the far right to represent the secondary output. A circuit breaker is set between the primary input and the transformer to simulate the automatic opening and reclosing of the transformer by the protection device after a short circuit. A short circuit is set between the secondary output and the transformer to simulate four short circuit conditions: single-phase ground fault, two-phase ground fault, three-phase ground fault, and inter-turn short circuit. Running this circuit, the short-circuit current waveform is read through the Scope unit, and the discretized sampling is exported using Subtract to obtain the short-circuit current waveform for testing.

[0065] In one alternative implementation, in actual engineering applications, the actual recorded transformer short-circuit current waveform is used as the short-circuit current excitation.

[0066] It should be noted that directly sampling the short-circuit current waveform and preserving the transient characteristics of the current can ensure the accuracy of the electromagnetic force time-domain analysis; applying the current excitation in the opposite direction to the cross-sections at both ends of the winding can equivalently simulate the closed loop path of the real short-circuit current, thus avoiding distortion of the magnetic field calculation; and by setting the opening and closing time of the circuit breaker, the influence of different short-circuit moments on the current waveform can be flexibly simulated.

[0067] In one alternative implementation, the short-circuit current waveform can also be obtained by decomposing the short-circuit current into harmonic components through Fourier transform, calculating the electromagnetic force in the frequency domain, then inversely transforming it back to the time domain, and then simulating the short-circuit state with a variable impedance, thereby achieving different short-circuit types by adjusting the impedance value.

[0068] In a preferred embodiment, calculating the distribution of short-circuit electrodynamic force on the windings of a three-phase, three-winding model includes:

[0069] Based on the three-phase three-winding model after setting the excitation, select the solution type and set a domain around the model to determine the solution space range;

[0070] The three-phase, three-winding model is meshed, a new solver command is created, the solver step size and solver time length are set, and the distribution of short-circuit electrodynamic force of electromagnetic field on the winding is calculated.

[0071] In this embodiment, after importing the model, the excitation is set according to the previous step, the corresponding solution type is selected, and a domain is set around the model to determine the solution space range. The model is then meshed using Maxwell's automatic meshing function. Specifically, a new solution command (Analysis) is created, with a step size of 0.01s and a total solution time of 0.6s, for a total of 600 time steps. Based on the set step size, the calculated results are output as the electrodynamic input for the surface density.

[0072] It should be noted that by directly outputting the electrodynamic distribution (area density) on the winding surface through electromagnetic simulation, a high-precision input can be provided for subsequent structural deformation analysis, thus avoiding errors caused by the assumption of uniform force. By controlling the calculation accuracy through meshing, and refining the mesh in high-stress areas such as the winding surface, a balance can be struck between calculation efficiency and result resolution.

[0073] In one alternative implementation, the distribution of short-circuit electrodynamic force on the winding can also be calculated by training a surrogate model (such as a neural network) through machine learning, with the electromagnetic force distribution directly output from the input current parameters; for simple winding structures, the distribution of electrodynamic force can be directly calculated analytically using the Biot-Savart law and the Lorentz force formula.

[0074] In a preferred embodiment, calculating the deformation of the winding after being subjected to a short-circuit electrodynamic force includes:

[0075] The calculation results of the distribution of short-circuit electrodynamic force on the winding are used as the electrodynamic force input for the surface density.

[0076] In the simulation of a three-phase three-winding model, both the upper and lower pressure plates are in normal working condition, and fixed constraints are added to the upper and lower ports of the upper and lower pressure plates.

[0077] The mesh is generated according to the preset mesh parameters. A new solver command is created, the step size is set, the electrodynamic input of the surface density is added and applied, and the strain on the surface of the winding insulation paper is calculated.

[0078] In this embodiment, for the winding to be solved, the case where both the upper and lower pressure plates are working normally is simulated. Fixed constraints are added to its upper and lower ports, and the mesh is divided by selecting the preset mesh parameters, that is, the mesh size is 0.05mm and the mesh type is tetrahedral. A new solve command is created, the step size is set to 0.01s, and there are a total of 600 steps. The surface force input, that is, the short-circuit electrodynamic force distribution, is added, and it is loaded, and the strain on the surface of the insulating paper is calculated.

[0079] Since the winding is in close contact with the insulating paper, its normal strain is continuous. Therefore, the modeling can be done without involving the insulating paper. Instead, the strain on the winding surface can be calculated directly using the transient structural field (which considers damping, velocity, and acceleration during the calculation).

[0080] It should be noted that by using fixed constraints (simulated pressure plate) and electrodynamic loading, the strain distribution on the surface of the insulating paper can be directly output, thus identifying fatigue risk areas.

[0081] In one alternative implementation, the deformation of the winding after being subjected to short-circuit electrodynamic forces can be simplified by reducing the distributed electromagnetic force to concentrated forces at key nodes (such as the middle and ends of the winding), and the deformation can be quickly calculated using beam elements; or, based on historical simulation or experimental data, an electromagnetic force-strain mapping relationship can be established (such as a response surface model) and the strain can be directly output.

[0082] In a preferred embodiment, obtaining the current fatigue life of the insulating paper includes:

[0083] After the insulation paper on the winding surface reaches the thermal aging saturation state, the stress-strain curve and SN fatigue fracture curve of this type of insulation paper are obtained at the corresponding thermal aging saturation polymerization degree.

[0084] The strain waveform data of the insulating paper is processed, and the peak data is selected;

[0085] The magnitude of the stress wave peak is obtained by combining the strain wave peak with the stress-strain curve of the insulating paper. Based on the magnitude of the stress wave peak and the number of times it is applied, combined with the SN insulation fatigue curve, the current remaining insulation life of the insulating paper is obtained.

[0086] In this embodiment, it is first assumed that the insulating paper on the winding surface has reached thermal aging saturation. The stress-strain curve and SN fatigue fracture curve of this type of insulating paper are obtained at the corresponding thermal aging saturation polymerization degree. The strain waveform data of the insulating paper is processed, and only the peak data is selected. The magnitude of the stress wave peak is obtained by combining the strain wave peak value with the stress-strain curve of the insulating paper. Based on the stress wave peak value and the number of stress applications, combined with the SN insulation fatigue curve, the current remaining insulation life of the insulating paper is obtained.

[0087] It should be noted that this step combines the stress-strain curve and SN curve after thermal aging to reflect the degradation of the mechanical properties of the insulating paper after long-term operation, thereby improving the reliability of life prediction; only strain peak data is extracted to simplify the calculation without losing accuracy; the cumulative effect of multiple short-circuit impacts is quantified by the stress-cycle number (SN) relationship, which can clearly define the critical threshold of the remaining life.

[0088] This invention constructs a three-phase, three-winding model to obtain the short-circuit current waveform and the distribution of short-circuit electrodynamic force on the windings, thereby obtaining the fatigue life of the insulating paper. While considering the thermal aging of the insulating paper, it also incorporates the force accumulation damage caused by short-circuit impact into the calculation model, further improving the calculation accuracy.

[0089] The above is an illustrative scheme of a method for calculating the fatigue life of insulating paper considering the force accumulation effect according to this embodiment. It should be noted that the technical solution of this insulation paper fatigue life calculation system considering the force accumulation effect belongs to the same concept as the technical solution of the insulation paper fatigue life calculation method considering the force accumulation effect described above. Details not described in detail in the technical solution of the insulation paper fatigue life calculation system considering the force accumulation effect in this embodiment can be found in the description of the technical solution of the insulation paper fatigue life calculation method considering the force accumulation effect described above.

[0090] Example 2

[0091] This embodiment provides a fatigue life calculation system for insulating paper that takes into account the force accumulation effect, including:

[0092] The model building module is used to build a three-phase, three-winding model based on a power transformer.

[0093] The acquisition module is used to obtain the short-circuit current waveform through circuit sampling based on the three-phase three-winding model, and to use it as an excitation for each winding of the three-phase three-winding model.

[0094] The calculation module is used to calculate the distribution of short-circuit electrodynamic force on the windings of the three-phase three-winding model, and to calculate the deformation of the windings after being subjected to short-circuit electrodynamic force, so as to obtain the current fatigue life of the insulating paper.

[0095] This embodiment also provides a computer device applicable to the calculation of the fatigue life of insulating paper taking into account the force accumulation effect, including:

[0096] The system includes a memory and a processor. The memory stores computer-executable instructions, and the processor executes these instructions to implement the method for calculating the fatigue life of insulating paper that takes into account the force accumulation effect, as proposed in the above embodiments.

[0097] This embodiment also provides a storage medium storing a computer program that, when executed by a processor, implements the method for calculating the fatigue life of insulating paper that takes into account the force accumulation effect, as proposed in the above embodiments.

[0098] The storage medium proposed in this embodiment and the method for calculating the fatigue life of insulating paper that takes into account the force accumulation effect proposed in the above embodiments belong to the same inventive concept. Technical details not described in detail in this embodiment can be found in the above embodiments, and this embodiment has the same beneficial effects as the above embodiments.

[0099] Based on the above description of the implementation methods, those skilled in the art can clearly understand that the present invention can be implemented using software and necessary general-purpose hardware, and of course, it can also be implemented using hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk, or optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of the various embodiments of the present invention.

[0100] Example 3

[0101] Reference Figures 4-6 As an embodiment of the present invention, a method for calculating cumulative climbing height is provided. To verify its beneficial effects, it is scientifically demonstrated through economic benefit calculations and simulation experiments.

[0102] In this embodiment, software such as Solidworks can be used for modeling and simulation. A relatively representative transformer is selected as the simulation case, with a capacity of 40000KVA, a voltage ratio of 110KV / 35KV / 10KV, and a total of 102 coils.

[0103] Assuming a three-phase, three-winding power transformer is connected to a high-voltage power source and carries a load at medium and low voltage levels, the calculation results are as follows: Figure 4 The diagram shows the electrodynamic force distribution, where the left winding represents the electrodynamic force on the medium- and low-voltage windings, and the right winding represents the electrodynamic force on the high-voltage windings. Figure 4 It is evident that the electrodynamic forces acting on the two types of windings are in completely opposite directions; the low-voltage and medium-voltage windings experience inward contraction, while the high-voltage windings experience outward expansion; the strain distribution is as follows: Figure 5 As shown, the peak value is mainly concentrated at stress concentration points such as component contact points and sharp corners, with a maximum strain value of 0.33%. Assuming the elastic modulus of the insulating paper is 3 GPa, the stress is 10 MPa.

[0104] For this transformer, different cyclic stresses were applied after thermal aging saturation to record insulation damage data. The data was then processed and interpolated to obtain a fitting curve for SN insulation fatigue, as shown below. Figure 6 As shown, for a short-circuit impact of 10 MPa, if 40% is taken as the remaining life margin, the insulating paper will have a risk of inter-turn short circuit after about 30 impacts.

[0105] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for calculating the fatigue life of insulating paper considering the cumulative force effect, characterized in that, include: A three-phase, three-winding model based on a power transformer was constructed. Based on the three-phase three-winding model, the short-circuit current waveform is obtained by circuit sampling and used as an excitation for each winding of the three-phase three-winding model. The distribution of short-circuit electrodynamic force on the windings of the three-phase three-winding model is calculated, and the deformation of the windings after being subjected to short-circuit electrodynamic force is calculated to obtain the current fatigue life of the insulating paper.

2. The method for calculating the fatigue life of insulating paper considering the force accumulation effect as described in claim 1, characterized in that, The construction of a three-phase, three-winding model based on a power transformer includes: The windings of the power transformer are equivalent to a cylinder, and a 3D model of the three-phase three-winding system is performed, including the low-voltage winding, the medium-voltage winding, and the high-voltage winding. The transformer has a highly symmetrical structure and forms a spiral short-circuit current to generate a magnetic field.

3. The method for calculating the fatigue life of insulating paper considering the force accumulation effect as described in claim 2, characterized in that, The short-circuit current waveform obtained through circuit sampling includes: Based on the three-phase three-winding model, the leftmost power supply represents the primary input of the power grid, and the rightmost load represents the secondary output. A circuit breaker is set between the primary input and the transformer. Set the opening and closing times of the circuit breaker, and cause a three-phase ground short circuit to obtain the short-circuit current waveform; The short-circuit current waveform is discretized, sampled, and exported. It is then added to two sections of the corresponding short-circuit winding, with the excitation directions of the two sections being opposite, thus forming a loop.

4. The method for calculating the fatigue life of insulating paper considering the force accumulation effect as described in claim 3, characterized in that, The method of causing a three-phase ground fault includes setting a ground fault between the secondary output and the transformer, wherein the short circuit includes a single-phase ground fault, a two-phase ground fault, a three-phase ground fault, and an inter-turn short circuit.

5. The method for calculating the fatigue life of insulating paper considering the force accumulation effect as described in claim 1, characterized in that, The calculation of the distribution of short-circuit electrodynamic force on the windings of the three-phase three-winding model includes: Based on the three-phase three-winding model after setting the excitation, select the solution type and set a domain around the model to determine the solution space range; The three-phase three-winding model is meshed, a new solver command is created, the solver step size and solver time length are set, and the distribution of short-circuit electrodynamic force of electromagnetic field on the winding is calculated.

6. The method for calculating the fatigue life of insulating paper considering the force accumulation effect as described in claim 5, characterized in that, The calculation of the deformation of the winding after being subjected to short-circuit electrodynamic force includes: The calculation results of the distribution of the short-circuit electrodynamic force on the winding are used as the electrodynamic force input for the surface density. In the simulation of the three-phase three-winding model, both the upper and lower pressure plates are in normal working condition, and fixed constraints are added to the upper and lower ports of the upper and lower pressure plates. The mesh is generated according to the preset mesh parameters, a new solver command is created, the step size is set, the electrodynamic input of the surface density is added and applied, and the strain on the surface of the insulating paper of the winding is calculated.

7. The method for calculating the fatigue life of insulating paper considering the force accumulation effect as described in claim 6, characterized in that, The current fatigue life of the insulating paper includes: After the insulation paper on the winding surface reaches the thermal aging saturation state, the stress-strain curve and SN fatigue fracture curve of this type of insulation paper are obtained at the corresponding thermal aging saturation polymerization degree. The strain waveform data of the insulating paper is processed, and the peak data is selected; The magnitude of the stress wave peak is obtained by combining the strain wave peak with the stress-strain curve of the insulating paper. Based on the magnitude of the stress wave peak and the number of times it is applied, combined with the SN insulation fatigue curve, the current remaining insulation life of the insulating paper is obtained.

8. A fatigue life calculation system for insulating paper considering the force accumulation effect, comprising applying the fatigue life calculation method for insulating paper considering the force accumulation effect as described in any one of claims 1 to 7, characterized in that, include, The model building module is used to build a three-phase, three-winding model based on a power transformer. The acquisition module is used to obtain the short-circuit current waveform through circuit sampling based on the three-phase three-winding model, and to apply it as an excitation to each winding of the three-phase three-winding model. The calculation module is used to calculate the distribution of short-circuit electrodynamic force on the windings of the three-phase three-winding model, and to calculate the deformation of the windings after being subjected to short-circuit electrodynamic force, so as to obtain the current fatigue life of the insulating paper.

9. A computer device, characterized in that, include: Memory and processor; The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the computer-executable instructions are executed by the processor, they implement the steps of the method for calculating the fatigue life of insulating paper taking into account the force accumulation effect as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, It stores computer-executable instructions, which, when executed by a processor, implement the steps of the method for calculating the fatigue life of insulating paper taking into account the force accumulation effect as described in any one of claims 1 to 7.

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