Method, device and equipment for determining fatigue life of transformer winding, and storage medium

Abstract

The application discloses a method and device for determining the fatigue life of a transformer winding, an equipment and a storage medium. The method comprises the following steps: obtaining the short-circuit electric force borne by the transformer winding under each short-circuit impact in a preset time period; dividing a plurality of continuous stress intervals according to the short-circuit electric force, and counting the frequency of the stress level corresponding to each short-circuit electric force in each stress interval; determining the fatigue life corresponding to the average value of each stress interval according to the stress fatigue life curve of the transformer winding; inputting the fatigue life corresponding to the maximum average value, each average value and the frequency corresponding to each average value into a nonlinear fatigue cumulative damage model to determine the fatigue life of the transformer winding. The method can be used for evaluating the fatigue life of the transformer winding after suffering from multiple short-circuit impacts.

Description

Technical Field

[0001] This application relates to the field of power transformer technology, and more specifically, to a method, apparatus, equipment, and storage medium for determining the fatigue life of transformer windings. Background Technology

[0002] As a crucial piece of equipment in power transmission systems, ensuring the stable operation of power transformers is paramount. In numerous transformer failure cases, short-circuit faults account for a significant proportion. When a short-circuit fault occurs, a current far exceeding normal operating values ​​flows through the transformer windings, subjecting the internal electromagnetic wires and insulation structure to substantial short-circuit electrodynamic impacts. Furthermore, related research indicates that transformer damage is rarely caused by a single or two short-circuit impacts; rather, it involves the cumulative effect of multiple short-circuit impacts. The combined effect of single and multiple short-circuit impacts can induce transformer winding deformation and even lead to transformer failure.

[0003] Currently, the main method for diagnosing transformer winding deformation is frequency response analysis. This method primarily involves detecting the amplitude-frequency response characteristics of each transformer winding and judging the potential winding deformation based on the degree of change in these characteristics. However, this method struggles to detect changes in the material properties of transformer windings caused by the cumulative effect of short-circuit impacts, and therefore cannot be used to assess the fatigue life of transformer windings.

[0004] In fact, existing research has shown that when metallic conductors are subjected to repeated stresses (tensile, thrust, shear, or torsional forces), progressive localized damage occurs. After a certain number of repetitions (the number of repetitions is inversely proportional to the stress intensity), the material's yield strength decreases, leading to fracture. Taking copper wire, most commonly used in power transformers, as an example, annealed copper wire exhibits the characteristics of a cyclically hardening material. Under cyclic loading, this material undergoes two distinct changes. One is damage to the copper wire; when subjected to stresses less than its yield strength (yield limit), microscopic cracks develop. With the accumulation of cyclic loads, the metal fatigue damage gradually accumulates, and these cracks gradually develop and propagate. The second change is strengthening of the copper wire, meaning its internal crystal structure changes, increasing the density of crystal defects. Macroscopically, this manifests as a hardening trend in the copper wire. Under the combined effect of these two changes, permanent cumulative damage occurs in some locations of the copper wire, leading to cracks or sudden fracture in severe cases. Even aluminum wire, used in smaller quantities, exhibits similar problems. Due to differences in metallic properties, aluminum wires have poorer electrical and mechanical properties than copper wires, making them less resistant to short-circuit impacts and more prone to breakage.

[0005] Therefore, determining the fatigue life of transformer windings after multiple short-circuit impacts is a core issue in quantitatively evaluating the cumulative effects of multiple short-circuit impacts on power transformers, and an effective method is urgently needed. Summary of the Invention

[0006] In response to at least one defect or improvement requirement of the prior art, the present invention provides a method, apparatus, device and storage medium for determining the fatigue life of transformer windings, which can evaluate the fatigue life of transformer windings operating under the cumulative effect of short-circuit impact.

[0007] To achieve the above objectives, according to a first aspect of the present invention, a method for determining the fatigue life of a transformer winding is provided, the method comprising:

[0008] Obtain the short-circuit electrodynamic force borne by the transformer winding under each short-circuit impact within a preset time period;

[0009] Based on the short-circuit electrodynamic force, multiple continuous stress intervals are divided, and the frequency of the stress level corresponding to each short-circuit electrodynamic force in each stress interval is counted.

[0010] Based on the stress fatigue life curve of the transformer winding, determine the fatigue life corresponding to the average value of each stress range.

[0011] The fatigue life corresponding to the maximum average value, each average value, and the frequency corresponding to each average value are input into the nonlinear fatigue cumulative damage model to determine the fatigue life of the transformer winding.

[0012] Furthermore, based on the short-circuit electrodynamic force, multiple continuous stress intervals are divided, and the frequency of the stress level corresponding to each short-circuit electrodynamic force in each stress interval is counted. This includes: converting the short-circuit electrodynamic force into a stress level and determining the maximum stress level; dividing the stress level into multiple continuous stress intervals according to the ratio of each stress level to the maximum stress level, and counting the frequency of the stress level in each stress interval.

[0013] Furthermore, the above-mentioned method for determining the fatigue life of transformer windings also includes: inputting the fatigue life corresponding to the maximum average value, each average value, and the frequency corresponding to each average value into a nonlinear fatigue cumulative damage model to determine the single damage and multiple damage accumulation of the transformer winding under short-circuit impact within a preset time period. The single damage and multiple damage accumulation are used to quantitatively evaluate the impact of the short-circuit impact cumulative effect on the transformer under short-circuit impact.

[0014] Furthermore, the short-circuit electrodynamic force includes at least one of axial electrodynamic force and radial electrodynamic force.

[0015] Furthermore, the short-circuit electrodynamic force includes axial electrodynamic force and radial electrodynamic force, which together form a load cycle. The method for determining the fatigue life of the transformer winding further includes: determining the first fatigue life of the transformer winding corresponding to the axial electrodynamic force when the short-circuit electrodynamic force is axial electrodynamic force; determining the second fatigue life of the transformer winding corresponding to the radial electrodynamic force when the short-circuit electrodynamic force is radial electrodynamic force; and determining the target fatigue life of the transformer winding based on the first fatigue life and the second fatigue life.

[0016] Furthermore, multiple continuous stress intervals are divided based on the short-circuit electrodynamic force, and the frequency of the stress level corresponding to each short-circuit electrodynamic force in each stress interval is counted. This includes: dividing multiple continuous stress intervals based on the short-circuit electrodynamic force; correcting the current stress interval if the average value of the current stress interval is not the average value of the upper and lower limits of the stress interval; and counting the frequency of the stress level corresponding to each short-circuit electrodynamic force in each corrected stress interval.

[0017] Furthermore, the short-circuit impact cumulative effect includes the short-circuit impact force cumulative effect and the short-circuit impact heat cumulative effect.

[0018] According to a second aspect of the present invention, a device for determining the fatigue life of a transformer winding is also provided, comprising:

[0019] The acquisition module is configured to acquire the short-circuit electrodynamic force borne by the transformer winding under each short-circuit impact within a preset time period;

[0020] The statistics module is configured to divide the stress into multiple continuous stress intervals based on the short-circuit electrodynamic force, and to count the frequency of the stress level corresponding to each short-circuit electrodynamic force in each stress interval.

[0021] The module is configured to determine the fatigue life corresponding to the average value of each stress range based on the stress fatigue life curve of the transformer winding.

[0022] The determination module is also configured to input the fatigue life corresponding to the maximum average value, each average value, and the frequency corresponding to each average value into the nonlinear fatigue cumulative damage model to determine the fatigue life of the transformer winding.

[0023] Furthermore, the statistics module is also configured to convert short-circuit electrodynamic forces into stress levels, determine the maximum stress level, divide the stress levels into multiple continuous stress intervals according to the ratio of each stress level to the maximum stress level, and count the frequency of stress levels in each stress interval.

[0024] Furthermore, the fatigue life determination device for transformer windings also includes a damage determination module, which is configured to input the fatigue life corresponding to the maximum average value, each average value, and the frequency corresponding to each average value into a nonlinear fatigue cumulative damage model to determine the single damage and multiple damage accumulation of the transformer winding under short-circuit impact within a preset time period. The single damage and multiple damage accumulation are used to quantitatively evaluate the impact of the short-circuit impact cumulative effect on the transformer under short-circuit impact.

[0025] Furthermore, the short-circuit electrodynamic force includes at least one of axial electrodynamic force and radial electrodynamic force.

[0026] Furthermore, the short-circuit electric force includes axial electric force and radial electric force, which together form a load cycle. The transformer winding fatigue life determination device further includes a target fatigue life determination module, which is configured to determine the first fatigue life of the transformer winding corresponding to the axial electric force when the short-circuit electric force is an axial electric force; determine the second fatigue life of the transformer winding corresponding to the radial electric force when the short-circuit electric force is a radial electric force; and determine the target fatigue life of the transformer winding based on the first fatigue life and the second fatigue life.

[0027] Furthermore, the statistics module is also configured to divide multiple continuous stress intervals based on short-circuit electrodynamic forces; correct the current stress interval if the average value of the current stress interval is not the average value of the upper and lower limits of the stress interval; and count the frequency of the stress level corresponding to each short-circuit electrodynamic force in each corrected stress interval.

[0028] Furthermore, the short-circuit impact cumulative effect includes the short-circuit impact force cumulative effect and the short-circuit impact heat cumulative effect.

[0029] According to a third aspect of the present invention, a device for determining the fatigue life of a transformer winding is also provided, comprising at least one processing unit and at least one storage unit, wherein the storage unit stores a computer program that, when executed by the processing unit, causes the processing unit to perform the steps of any of the methods described above.

[0030] According to a fourth aspect of the invention, a storage medium is also provided, which stores a computer program executable by a transformer winding fatigue life determination device, which, when run on the transformer winding fatigue life determination device, causes the transformer winding fatigue life determination device to perform the steps of any of the methods described above.

[0031] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0032] By acquiring the short-circuit electrodynamic forces borne by the transformer winding under various short-circuit impacts within a preset time period, and dividing the stress into multiple continuous stress intervals based on these short-circuit electrodynamic forces, the average value of each stress interval is obtained. The average value of each stress interval is a constant amplitude load. Thus, under the condition that the stress level corresponding to each short-circuit electrodynamic force is a variable amplitude load, by dividing the stress level corresponding to each short-circuit electrodynamic force on the transformer winding within a preset time period into multiple continuous stress intervals, the variable amplitude load is equivalent to multiple constant amplitude loads. Furthermore, by statistically analyzing the frequency of the stress level corresponding to each short-circuit electrodynamic force in each stress interval, and based on the stress fatigue life curve of the transformer winding, the fatigue life corresponding to the average value of each stress interval is determined. The fatigue life corresponding to the maximum average value, each average value, and the frequency corresponding to each average value are input into a nonlinear fatigue cumulative damage model to obtain the fatigue life of the transformer winding. This achieves the purpose of determining the fatigue life of the transformer winding operating under single and multiple short-circuit impacts, and provides important reference data for further quantitatively evaluating the cumulative effect of power transformers subjected to multiple short-circuit impacts. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 A flowchart illustrating a method for determining the fatigue life of a transformer winding, provided in an embodiment of this application;

[0035] Figure 2 This is a schematic diagram of the SN curves of various copper materials provided in the embodiments of this application;

[0036] Figure 3 Frequency distribution diagram of the stress range corresponding to the axial electrodynamic force provided in the embodiments of this application;

[0037] Figure 4 Frequency distribution diagram of the stress range corresponding to radial electrodynamic force provided for embodiments of this application;

[0038] Figure 5 This is a schematic diagram of a device for determining the fatigue life of a transformer winding, provided in an embodiment of this application.

[0039] Figure 6 This is a schematic diagram of a device for determining the fatigue life of a transformer winding, provided in an embodiment of this application. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0041] The terms "first," "second," "third," "fourth," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0042] like Figure 1 As shown, a method for determining the fatigue life of a transformer winding is provided. This method can be executed by a terminal, which can be, but is not limited to, various personal computers, laptops, smartphones, tablets, IoT devices, and portable wearable devices. Taking the application of this method to a terminal as an example, the method includes the following steps:

[0043] Step 101: Obtain the short-circuit electrodynamic force borne by the transformer winding under each short-circuit impact within a preset time period.

[0044] Transformer damage is usually not caused by one or two short-circuit electrodynamic impacts, but rather by repeated short-circuit impacts. This leads to a gradual deterioration of certain performance parameters in the transformer's internal windings and insulation, eventually causing permanent damage as the transformer cannot withstand further impacts. Therefore, when assessing the fatigue life of transformer windings, the cumulative effect of short-circuit electrodynamic impacts, i.e., the short-circuit impact cumulative effect, needs to be considered.

[0045] The short-circuit impact cumulative effect is a phenomenon that occurs when the frequency of short-circuit impacts on a transformer increases, the short-circuit electrodynamic force on the transformer windings increases, the radial and axial mechanical properties of the transformer windings decrease, the transformer windings' ability to resist short-circuit impacts weakens, until the transformer windings can no longer withstand short-circuit impacts or are even completely damaged.

[0046] The short-circuit impact cumulative effect includes the short-circuit impact force cumulative effect and the short-circuit impact heat cumulative effect. In terms of force cumulative effect, when a material is subjected to repeated stress, progressive local damage occurs. After a certain number of repetitions (the number of repetitions is inversely proportional to the stress intensity), the yield strength of the material decreases and fracture occurs. In terms of heat cumulative effect, its harm to conductor performance is mainly reflected in: (1) the change in the yield strength of the conductor after multiple impacts, causing the winding to be unable to withstand a certain short-circuit impact. For self-adhesive conductors, high temperature will also affect the strength of the adhesive, further reducing the strength of the conductor; (2) high temperature causes thermal expansion of the conductor.

[0047] Electrodynamic force refers to the interaction force between the metal conductors when current flows through the transformer windings. When a transformer experiences a sudden short circuit, the enormous short-circuit current creates a strong leakage magnetic field in the windings. Under the interaction of the short-circuit current and the leakage magnetic field, the transformer windings will experience a short-circuit electrodynamic force much larger than the rated current. Under normal operating conditions, the electrodynamic force generated by the transformer windings is relatively small; however, in the event of a short circuit, the current flowing through the transformer windings will be far greater than the current under normal operating conditions, resulting in a very large electrodynamic force. Furthermore, after repeated impacts of the short-circuit electrodynamic force on the transformer windings—that is, under the cumulative effect of the short-circuit impact—it can cause deformation of the transformer windings and even damage the transformer.

[0048] The short-circuit electrodynamic forces experienced by transformer windings under various short-circuit impacts include at least one of axial and radial electrodynamic forces. The axial electrodynamic force is generated by the combined action of radial leakage flux and the short-circuit impact current. During rated operation, the axial electrodynamic force causes the ends of the transformer windings to compress towards the middle, reducing the axial height of the windings. The axial electrodynamic force is greatest at the ends of the windings and least, approximately zero, at the middle position along the axial direction. When a transformer is subjected to a short-circuit impact, the axial electrodynamic force causes axial stretching of the low-voltage windings, increasing their axial height; and axial compression of the high-voltage windings, decreasing their axial height. This further increases the height difference between the low-voltage and high-voltage windings, increasing the force on the pressure plates and yoke, and in severe cases, potentially damaging these structures and affecting the normal operation of the transformer.

[0049] Radial electrodynamic forces are generated by the combined effects of axial leakage flux and short-circuit impact current. Since the current directions of the inner and outer windings of the transformer are opposite, the radial electrodynamic forces borne by the inner and outer windings are compressive stress and tensile stress, respectively. Tensile stress acts on the outer winding, causing it to expand outward, while compressive stress acts on the inner winding, causing it to compress inward.

[0050] For example, the terminal obtains the short-circuit electrodynamic forces experienced by the transformer winding under single and multiple consecutive short-circuit impacts within a preset time period.

[0051] Step 102: Divide the stress range into multiple continuous stress ranges based on the short-circuit electrodynamic force, and count the frequency of the stress level corresponding to each short-circuit electrodynamic force in each stress range.

[0052] The stress range indicates the range of stress level variation. The stress level is the short-circuit electrodynamic force per unit area of ​​the transformer winding, also known as the load.

[0053] Because the short-circuit electrodynamic force experienced by the transformer winding under each short-circuit impact varies within a preset time period, the stress level under a single short-circuit impact is variable. Therefore, the load acting on the transformer winding under a single short-circuit impact is a variable-amplitude load, which can be represented by a continuous curve over a certain time period (e.g., a single short-circuit impact time of 0.8 seconds). To calculate the fatigue life of the transformer winding, the obtained variable-amplitude load needs to be equivalent to a constant-amplitude load.

[0054] In one embodiment, step 102, which involves dividing the short-circuit electrodynamic force into multiple continuous stress intervals and counting the frequency of the stress level corresponding to each short-circuit electrodynamic force in each stress interval, includes: converting the short-circuit electrodynamic force into stress levels and determining the maximum stress level; dividing the stress level into multiple continuous stress intervals according to the ratio of each stress level to the maximum stress level and determining the frequency of the stress level in each stress interval.

[0055] The maximum stress level is the stress level corresponding to the maximum short-circuit electrodynamic force.

[0056] For example, the terminal converts the acquired short-circuit electrodynamic forces into stress levels, obtains the stress levels corresponding to each short-circuit electrodynamic force, and determines the maximum stress level and the ratio of each stress level to the maximum stress level. The ratios are arranged in ascending order, and a preset number of target ratios are determined from these ratios. The preset number is determined based on statistical requirements, and this embodiment does not limit this. The preset number of target ratios increases sequentially, and the target ratio is the average of the ratios of any consecutive target number of stress levels to the maximum stress level among all determined stress levels. The target number is the ratio of the total number to the preset number.

[0057] For example, the short-circuit electrodynamic forces obtained within a preset time period are converted into stress levels, resulting in stress levels of 1 MPa, 2 MPa, 2 MPa, 3 MPa, 4 MPa, 4 MPa, 5 MPa, 6 MPa, 6 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, 11 MPa, 17 MPa, 18 MPa, 24 MPa, 28 MPa, and 30 MPa. The ratios of each stress level to the maximum stress level of 30 MPa are 0.03, 0.06, 0.06, 0.1, 0.13, 0.13, 0.17, 0.2, 0.2, 0.2, 0.23, 0.27, 0.3, 0.33, 0.37, 0.57, 0.6, 0.8, and 0.9, respectively. 3.1, meaning the total number of stress levels is 20. With a preset number of 4, the target number is 5. The target ratio is the average of the ratios of every 5 stress levels to the maximum stress level among the 20 stress levels arranged in ascending order. Specifically, the average values ​​of 0.03, 0.06, 0.06, 0.1, and 0.13 are calculated to obtain the first target ratio of 0.076. The average values ​​of 0.13, 0.17, 0.2, 0.2, and 0.2 are calculated to obtain the second target ratio of 0.18. The average values ​​of 0.23, 0.27, 0.3, 0.33, and 0.37 are calculated to obtain the third target ratio of 0.3. The average values ​​of 0.57, 0.6, 0.8, 0.93, and 1 are calculated to obtain the fourth target ratio of 0.78.

[0058] For each target ratio, the terminal uses the current target ratio as the upper limit of a stress interval and the previous target ratio as the lower limit of that stress interval, resulting in multiple consecutive stress intervals. The current target ratio is any one of these target ratios. For example, with target ratios of 0.076, 0.18, 0.3, and 0.78, five stress intervals are obtained: 0-0.076, 0.076-0.18, 0.18-0.3, 0.3-0.78, and 0.78-1. After dividing the stress into multiple consecutive intervals, the terminal statistically analyzes the frequency of each stress level occurring within each interval, thus obtaining the frequency of the stress level within each interval.

[0059] Step 103: Determine the fatigue life corresponding to the average value of each stress range based on the stress fatigue life curve of the transformer winding.

[0060] Fatigue life is the number of load cycles required for a material or structure to accumulate fatigue damage until it fails completely. Fatigue life is determined by both the mechanical properties of the material or structure itself and the level of the applied load.

[0061] The stress-fatigue life curve (also known as the SN curve) describes the relationship between the stress S acting on a material and the fatigue life N. The stress-fatigue life curve of a material is generally obtained experimentally and is closely related to the material's properties. The higher the material's ultimate tensile strength and the lower the applied load level, the longer the fatigue life; conversely, the lower the ultimate tensile strength and the lower the applied load level, the shorter the fatigue life. Figure 2 As shown, Figure 2 This provides SN curves for various copper materials, including annealed copper, annealed brass, rolled copper, and rolled brass.

[0062] The average value of a stress interval is the average of the upper and lower limits of the stress interval. The average value of a stress interval represents the equal-amplitude load at each stress level within that interval. Thus, by dividing the stress levels corresponding to the short-circuit electrodynamic forces acting on the transformer windings within a preset time period into multiple continuous stress intervals, the variable amplitude load is effectively equivalent to multiple equal-amplitude loads.

[0063] For example, when the transformer winding is made of copper wire, the terminal calculates the average value of each stress range and queries the stress fatigue life curve corresponding to the copper wire to obtain the fatigue life corresponding to the average value of each stress range.

[0064] Step 104: Input the fatigue life corresponding to the maximum average value, each average value, and the frequency corresponding to each average value into the nonlinear fatigue cumulative damage model to determine the fatigue life of the transformer winding.

[0065] Nonlinear fatigue cumulative damage model is one type of fatigue cumulative damage theory. Fatigue damage accumulation is the process by which the mechanical properties of structural materials or structures change or deteriorate under repeated cyclic loading.

[0066] In this embodiment, the nonlinear fatigue cumulative damage model adopts the Corten-Dolan model, which summarizes the initiation and development of fatigue cracks into three stages: work hardening occurs in a localized area; micro-voids or micro-cracks form in a localized area; submicroscopic voids or cracks further expand and combine to form macroscopic cracks, which then lead to fracture. This model considers the interaction between loads and stress below the fatigue limit. The fatigue damage nuclei it proposes do not disappear after generation but only increase under subsequent loads, effectively reflecting the law of fatigue damage accumulation. Furthermore, it is widely used in engineering, is simple and reliable, and has high accuracy, making it suitable for analyzing the changes in the mechanical properties of metal conductor materials in power transformer windings after being subjected to the cumulative effects of multiple short-circuit impacts.

[0067] In the Corten-Dolan model, the formula for calculating the fatigue life of a material is:

[0068]

[0069] In the above formula (1), n ​​is the total number of stress intervals, i is any stress interval, d is the material constant, and σ i It is the average value of any stress interval i, σ l It is the maximum average value among the average values ​​of n stress intervals, N l It is the maximum average value σ l The corresponding fatigue life, N is the fatigue life of the material operating under the cumulative effect of short-circuit impact within a preset time period, y i It is the proportion of the frequency of occurrence in any stress interval i to the total frequency (the sum of the frequencies of occurrence of each stress level in n stress intervals).

[0070] For example, the terminal determines the maximum average value among the average values ​​of each stress range, and determines the fatigue life corresponding to the maximum average value by querying the stress fatigue life curve of the transformer winding. When the material constant of the transformer winding is a preset value and the total number of stress ranges is a set number, the fatigue life corresponding to the maximum average value, the average value of each stress range, and the frequency corresponding to the average value of each stress range are input into the above fatigue life calculation formula (1) to obtain the fatigue life of the transformer winding.

[0071] The above method obtains the short-circuit electrodynamic forces borne by the transformer winding under various short-circuit impacts within a preset time period. Based on these short-circuit electrodynamic forces, multiple continuous stress intervals are divided, and the average value of each stress interval is obtained. The average value of each stress interval is a constant amplitude load. Thus, when the stress level corresponding to each short-circuit electrodynamic force is a variable amplitude load, by dividing the stress level corresponding to each short-circuit electrodynamic force on the transformer winding within a preset time period into multiple continuous stress intervals, the variable amplitude load is equivalent to multiple constant amplitude loads. Furthermore, by statistically analyzing the frequency of the stress level corresponding to each short-circuit electrodynamic force in each stress interval, and based on the stress fatigue life curve of the transformer winding, the fatigue life corresponding to the average value of each stress interval is determined. The fatigue life corresponding to the maximum average value, each average value, and the frequency corresponding to each average value are input into a nonlinear fatigue cumulative damage model to obtain the fatigue life of the transformer winding. This achieves the purpose of evaluating the fatigue life of the transformer winding operating under the cumulative effect of short-circuit impacts.

[0072] In one embodiment, the method for determining the fatigue life of a transformer winding further includes: inputting the fatigue life corresponding to the maximum average value, each average value, and the frequency corresponding to each average value into a nonlinear fatigue cumulative damage model to determine the single damage and multiple damage accumulation of the transformer winding under short-circuit impact within a preset time period. The single damage and multiple damage accumulation are used to quantitatively evaluate the impact of the short-circuit impact cumulative effect on the transformer under short-circuit impact.

[0073] Among these, the closer the cumulative damage is to 1, the more severe the damage. When the cumulative damage reaches 1, irreversible damage occurs to the transformer windings. The number of amplitude load impacts corresponds to the number of short-circuit impacts experienced by the power transformer.

[0074] In the Corten-Dolan model, the formulas for calculating single damage and cumulative damage within a certain stress range during the damage process are as follows:

[0075]

[0076]

[0077] In formulas (2) and (3) above, n is the total number of stress intervals, j is any stress interval, d is a material constant, and y j It is the proportion of the frequency of occurrence in any stress interval j to the total frequency (the sum of the frequencies of occurrence of each stress level in n stress intervals), where n j σ is the frequency of occurrence in any stress interval j. j It is the average value of any stress interval j, σ l It is the average value of the maximum stress range prior to the short-circuit electrodynamic force experienced in this event, N. l It is the average value σ of the maximum stress range. l The corresponding fatigue life, D j It is the cumulative damage from multiple stress intervals j during the damage process, D j1 It is a single damage event occurring within any stress range j during the damage process.

[0078] For example, the terminal determines the maximum average value among the average values ​​of each stress range, and determines the fatigue life corresponding to the maximum average value by querying the stress fatigue life curve of the transformer winding. When the material constant of the transformer winding is a preset value and the total number of stress ranges is a set number, the fatigue life corresponding to the maximum average value, the average value of each stress range, and the frequency corresponding to the average value of each stress range are input into the above-mentioned damage accumulation calculation formula (2) to obtain the single damage of the transformer winding under a single short circuit impact within a preset time period; and input the above-mentioned single damage calculation formula (3) to obtain the multiple damage accumulation of the transformer winding under multiple short circuit impacts within a preset time period.

[0079] In this implementation, based on the calculation formulas for single damage and cumulative damage of materials within a certain stress range during the damage process in the Corten-Dolan model, the single damage and cumulative damage of the transformer winding under short-circuit impact within a preset time period are calculated. By calculating the single damage and cumulative damage of the transformer winding under short-circuit impact within the preset time period, the cumulative effect of the transformer after a series of short-circuit impacts can be effectively evaluated. This ensures that the probability of short-circuit faults caused by transformer winding deformation can be effectively prevented and controlled during the cumulative damage process of the transformer, and timely maintenance and replacement of the transformer can be carried out.

[0080] In one embodiment, the short-circuit electrodynamic force includes axial electrodynamic force and radial electrodynamic force, which together form a load cycle. The method for determining the fatigue life of the transformer winding further includes: determining a first fatigue life of the transformer winding corresponding to the axial electrodynamic force when the short-circuit electrodynamic force is an axial electrodynamic force; determining a second fatigue life of the transformer winding corresponding to the radial electrodynamic force when the short-circuit electrodynamic force is a radial electrodynamic force; and determining a target fatigue life of the transformer winding based on the first fatigue life and the second fatigue life.

[0081] The first fatigue life is the fatigue life of the transformer winding determined based on the axial electrodynamic force, the second fatigue life is the fatigue life of the transformer winding determined based on the radial electrodynamic force, and the target fatigue life is used to evaluate the cumulative effect of the transformer after a series of short-circuit impacts, and is the smaller of the first fatigue life and the second fatigue life.

[0082] For example, when the short-circuit electromotive force is axial electromotive force, the terminal converts the acquired axial electromotive force into axial stress level, determines the maximum axial stress level as 16.8 MPa, and the ratio of each axial stress level to the maximum axial stress level. The ratios are arranged in ascending order, and eight target ratios are determined: 0.125, 0.275, 0.425, 0.575, 0.725, 0.850, 0.950, and 1.00 times. The axial stress level is divided into eight continuous stress intervals based on the target ratios, with upper limits of 0.125, 0.275, 0.425, 0.575, 0.725, 0.850, 0.950, and 1.00 times, respectively. The frequency of axial stress levels within each stress interval is counted, resulting in the correspondence between stress intervals and frequencies shown in Table 1.

[0083] Table 1

[0084] Stress range / MPA Frequency 0-2.1 166 2.1-4.6 148 4.6-7.14 102 7.14-9.66 48 9.66-12.18 18 12.18-14.28 10 14.28-15.96 6 15.96-16.80 2

[0085] Since the SN curve is used for life prediction based on average stress, if the average value of the stress range is not the average of the upper and lower limits of the stress range, the stress range in Table 1 above needs to be corrected.

[0086] In one embodiment, multiple consecutive stress intervals are divided based on short-circuit electrodynamic forces, and the frequency of occurrence of the stress level corresponding to each short-circuit electrodynamic force in each stress interval is counted. This includes: dividing multiple consecutive stress intervals based on short-circuit electrodynamic forces; correcting the current stress interval if the average value of the current stress interval is not the average value of the upper and lower limits of the stress interval; and counting the frequency of occurrence of the stress level corresponding to each short-circuit electrodynamic force in each corrected stress interval.

[0087] In this embodiment, the Gerber diagram method is used to calculate the average stress level, and the calculation formula is as follows:

[0088]

[0089] In the above formula (4), σ a σ b σ in σ ae These represent the load amplitude, tensile stiffness, average load, and equivalent load amplitude, respectively.

[0090] Based on the revised Table 1, we obtain the following: Figure 3 The frequency distribution diagram for the stress range is shown.

[0091] Then, the corresponding SN curve of the transformer winding was queried, and the material parameter d was set to 5.8. The ratio statistics table shown in Table 2 was obtained. The data in Table 2 includes the proportion of the i-th stress level y. i and y i (σ i / σ l ) d Substituting the data and related data from the statistical table into the fatigue life calculation formula (1) above, we obtain the first fatigue life N1 of the transformer winding.

[0092] Table 2

[0093] The proportion of stress level 1 is y1 0.332 <![CDATA[y1(σ1 / σ l ) d ]]> 3..45E-8 The proportion of stress level 2 is y2 0.296 <![CDATA[y2(σ2 / σ l ) d ]]> 2..57E-5 The third stress level accounts for y3 0.204 <![CDATA[y3(σ3 / σ l ) d ]]> 4..60E-4 The fourth stress level accounts for y4 0.096 <![CDATA[y4(σ4 / σ l ) d ]]> 1..72E-3 The fifth stress level accounts for y5 0.036 <![CDATA[y5(σ5 / σ l ) d ]]> 9E-3 The proportion of stress level 6 is y6 0.020 <![CDATA[y6(σ6 / σ l ) d ]]> 5E-3 The 7th stress level accounts for y7 0.012 <![CDATA[y7(σ7 / σ l ) d ]]> 6..5E-3 Stress level 8 accounts for y8 0.004 <![CDATA[y8(σ8 / σ l ) d ]]> 3..45E-3 Summation 1 Summation 0..026

[0094] In one embodiment, when the short-circuit electromotive force is radial electromotive force, the terminal converts the acquired radial electromotive force into radial stress level, determines the maximum radial stress level as 28.60 MPa, and the ratio of each radial stress level to the maximum radial stress level. The ratios are arranged in ascending order, and eight target ratios are determined: 0.125, 0.275, 0.425, 0.575, 0.725, 0.850, 0.950, and 1.00 times. The radial stress level is divided into eight consecutive stress intervals based on the target ratios, with upper limits of 0.125, 0.275, 0.425, 0.575, 0.725, 0.850, 0.950, and 1.00 times, respectively. The frequency of radial stress levels within each stress interval is counted, resulting in the correspondence between stress intervals and frequencies shown in Table 3. Figure 4 The frequency distribution diagram for the stress range is shown.

[0095] Table 3

[0096]

[0097]

[0098] Similarly, by querying the corresponding SN curve of the transformer winding and setting the material parameter d to 5.8, the ratio statistics table shown in Table 4 is obtained. The data in Table 4 includes the proportion of the i-th stress level y. i and y i (σ i / σ l ) d Substituting the data and related data from the statistical table into the fatigue life calculation formula (1) above, we obtain the second fatigue life N2 of the transformer winding.

[0099] Table 4

[0100] The proportion of stress level 1 is y1 0.316 <![CDATA[y1(σ1 / σ l ) d ]]> 3..30E-8 The proportion of stress level 2 is y2 0.272 <![CDATA[y2(σ2 / σ l ) d ]]> 2..40E-5 The third stress level accounts for y3 0.232 <![CDATA[y3(σ3 / σ l ) d ]]> 5..23E-4 The fourth stress level accounts for y4 0.116 <![CDATA[y4(σ4 / σ l ) d ]]> 2..08E-3 The fifth stress level accounts for y5 0.032 <![CDATA[y5(σ5 / σ l ) d ]]> 2..64E-3 The proportion of stress level 6 is y6 0.020 <![CDATA[y6(σ6 / σ l ) d ]]> 4..97E-3 The 7th stress level accounts for y7 0.008 <![CDATA[y7(σ7 / σ l ) d ]]> 4..34E-3 Stress level 8 accounts for y8 0.004 <![CDATA[y8(σ8 / σ l ) d ]]> 3..46E-3 Summation 1 Summation 0..018

[0101] like Figure 5 As shown, this application also provides a fatigue life determination device 500 for transformer windings, comprising: an acquisition module 501 configured to acquire the short-circuit electrodynamic forces borne by the transformer windings under various short-circuit impacts within a preset time period; a statistics module 502 configured to divide multiple continuous stress intervals based on the short-circuit electrodynamic forces and count the frequency of the stress level corresponding to each short-circuit electrodynamic force in each stress interval; a determination module 503 configured to determine the fatigue life corresponding to the average value of each stress interval based on the stress fatigue life curve of the transformer windings; and the determination module 503 further configured to input the fatigue life corresponding to the maximum average value, each average value, and the frequency corresponding to each average value into a nonlinear fatigue cumulative damage model to determine the fatigue life of the transformer windings.

[0102] This application also provides a device for determining the fatigue life of transformer windings. This device can be a computer device, and its internal structure diagram can be as shown in the figure. Figure 6 As shown, the computer device includes a processor, memory, input / output interface, communication interface, display unit, and input device. The processor, memory, and input / output interface are connected via a system bus, and the communication interface, display unit, and input device are also connected to the system bus via the input / output interface. The processor provides computing and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage medium. The input / output interface is used for exchanging information between the processor and external devices. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, mobile cellular networks, NFC (Near Field Communication), or other technologies. When the computer program is executed by the processor, it implements a method for determining the fatigue life of transformer windings. The display unit of the computer device is used to form a visually visible image. It can be a display screen, a projection device, or a virtual reality imaging device. The display screen can be an LCD screen or an e-ink screen. The input device of the computer device can be a touch layer covering the display screen, or buttons, trackballs, or touchpads set on the casing of the computer device, or external keyboards, touchpads, or mice, etc.

[0103] Those skilled in the art will understand that Figure 6The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0104] In one embodiment, a device for determining the fatigue life of a transformer winding is provided, comprising at least one processing unit and at least one storage unit, wherein the storage unit stores a computer program that, when executed by the processing unit, causes the processing unit to perform the steps of any of the methods described above.

[0105] This application also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method. The computer-readable storage medium may include, but is not limited to, any type of disk, including floppy disks, optical disks, DVDs, CD-ROMs, microdrives, as well as magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, DRAMs, VRAMs, flash memory devices, magnetic cards or optical cards, nanosystems (including molecular memory ICs), or any type of medium or device suitable for storing instructions and / or data.

[0106] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

[0107] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0108] In the several embodiments provided in this application, it should be understood that the disclosed apparatus can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some service interface; the indirect coupling or communication connection between devices or units may be electrical or other forms.

[0109] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0110] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0111] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage device (CMD). Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a memory and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned memory includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0112] Those skilled in the art will understand that all or part of the steps in the various 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, which may include: a flash drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, etc.

[0113] The foregoing description is merely an exemplary embodiment of this disclosure and should not be construed as limiting the scope of this disclosure. Any equivalent changes and modifications made in accordance with the teachings of this disclosure shall still fall within the scope of this disclosure. Those skilled in the art will readily conceive of embodiments of this disclosure upon considering the specification and practicing the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not described herein. The specification and embodiments are to be considered exemplary only, and the scope and spirit of this disclosure are defined by the claims.

[0114] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0115] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for determining the fatigue life of a transformer winding, characterized in that, include: Obtain the short-circuit electrodynamic force borne by the transformer winding under each short-circuit impact within a preset time period; Based on the short-circuit electrodynamic force, multiple continuous stress intervals are divided, and the frequency of the stress level corresponding to each short-circuit electrodynamic force in each stress interval is counted. This includes converting the short-circuit electrodynamic force into stress levels and determining the maximum stress level. According to the ratio of each stress level to the maximum stress level, the stress level is divided into multiple continuous stress intervals, and the average value of each stress interval is a constant amplitude load. The frequency of the stress level in each stress interval is counted. Based on the stress fatigue life curve of the transformer winding, determine the fatigue life corresponding to the average value of each stress range. The fatigue life corresponding to the maximum average value, each of the aforementioned average values, and the frequency corresponding to each of the aforementioned average values ​​are input into the nonlinear fatigue cumulative damage model to determine the fatigue life of the transformer winding. The nonlinear fatigue cumulative damage model adopts the Corten-Dolan model.

2. The method as described in claim 1, characterized in that, The method further includes: The fatigue life corresponding to the maximum average value, each of the average values, and the frequency corresponding to each of the average values ​​are input into the nonlinear fatigue cumulative damage model to determine the single damage and multiple damage accumulation of the transformer winding under short-circuit impact within a preset time period. The single damage and multiple damage accumulation are used to quantitatively evaluate the impact of the short-circuit impact cumulative effect on the transformer under short-circuit impact.

3. The method as described in claim 1, characterized in that, The short-circuit electrodynamic force includes at least one of axial electrodynamic force and radial electrodynamic force.

4. The method as described in claim 1, characterized in that, The short-circuit electrodynamic force includes axial electrodynamic force and radial electrodynamic force, the axial electrodynamic force and the radial electrodynamic force forming a load cycle, and the method further includes: When the short-circuit electromotive force is an axial electromotive force, determine the first fatigue life of the transformer winding corresponding to the axial electromotive force. When the short-circuit electromotive force is radial, determine the second fatigue life of the transformer winding corresponding to the radial electromotive force. The target fatigue life of the transformer winding is determined based on the first fatigue life and the second fatigue life.

5. The method as described in claim 4, characterized in that, The step of dividing the stress range into multiple continuous stress intervals based on the short-circuit electrodynamic force and counting the frequency of the stress level corresponding to each short-circuit electrodynamic force in each stress interval also includes: Based on the short-circuit electrodynamics, multiple continuous stress intervals are defined; If the average value of the current stress range is not the average value of the upper and lower limits of the stress range, the current stress range is corrected. The frequency of the stress level corresponding to each short-circuit electrodynamic force in each corrected stress interval is statistically analyzed.

6. The method as described in claim 2, characterized in that, The short-circuit impact cumulative effect includes the short-circuit impact force cumulative effect and the short-circuit impact heat cumulative effect.

7. A device for determining the fatigue life of a transformer winding, characterized in that, include: The acquisition module is configured to acquire the short-circuit electrodynamic force borne by the transformer winding under each short-circuit impact within a preset time period; The statistics module is configured to convert short-circuit electrodynamic forces into stress levels, determine the maximum stress level, divide the stress levels into multiple continuous stress intervals according to the ratio of each stress level to the maximum stress level, with the average value of each stress interval being a constant amplitude load, and count the frequency of stress levels within each stress interval. The module is configured to determine the fatigue life corresponding to the average value of each stress range based on the stress fatigue life curve of the transformer winding. The determining module is further configured to input the fatigue life corresponding to the maximum average value, each of the average values, and the frequency corresponding to each of the average values ​​into a nonlinear fatigue cumulative damage model to determine the fatigue life of the transformer winding. The nonlinear fatigue cumulative damage model adopts the Corten-Dolan model.

8. A device for determining the fatigue life of a transformer winding, characterized in that, It includes at least one processing unit and at least one storage unit, wherein the storage unit stores a computer program that, when executed by the processing unit, causes the processing unit to perform the steps of the method according to any one of claims 1 to 6.

9. A storage medium, characterized in that, It stores a computer program that can be executed by a transformer winding fatigue life determination device, which, when run on the transformer winding fatigue life determination device, causes the transformer winding fatigue life determination device to perform the steps of the method according to any one of claims 1 to 6.

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