Transformer anti-short-circuit capability evaluation method based on finite element micro-damage accumulation

Abstract

The invention relates to the technical field of power equipment detection and evaluation, in particular to a transformer anti-short-circuit capability evaluation method based on finite element micro-damage accumulation, which comprises the steps of constructing a transformer full-fault finite element model, simulating and calculating the mechanical strength and safety coefficient of a winding, establishing a micro-damage accumulation model and evaluating the mechanical life. Bidirectional coupling analysis is realized through iterative simulation, and the anti-short-circuit capability of the transformer is dynamically evaluated in real time. According to the method, transformer design parameters, short-circuit impact influences and micro-damage cumulative effects can be comprehensively considered, accurate evaluation and dynamic monitoring of the anti-short-circuit capability in the whole life cycle are achieved, and a scientific basis is provided for operation and maintenance decisions.

Description

Technical Field

[0001] The present invention relates to the technical field of power equipment detection and evaluation, and in particular to a method for evaluating transformer short-circuit resistance based on finite element micro-damage accumulation. Background Art

[0002] As a key component of the power system, the short-circuit resistance of power transformers directly impacts the safe and stable operation of the power grid. However, during actual operation, transformers are inevitably subject to various short-circuit shocks, which can cause irreversible micro-damage to the transformer windings and insulation materials, gradually weakening their short-circuit resistance.

[0003] Existing national and industry standards, such as GB / T 1094.5 and DL / T 2292, primarily address short-circuit testing and verification calculation methods for newly manufactured transformers. These standards fail to fully account for the cumulative damage caused by multiple short-circuit shocks throughout a transformer's lifecycle. Furthermore, due to the diversity and complexity of short-circuit faults, the spatial magnetic fields generated by different fault currents significantly impact transformer stress, further complicating the assessment of cumulative short-circuit damage. Traditional methods lack effective means of assessing changes in the transformer's mechanical state after each short-circuit shock, resulting in an inability to fully assess the transformer's health and remaining mechanical life in real time. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for evaluating the short-circuit resistance of transformers based on finite element micro-damage accumulation, so as to solve the technical problem in the prior art that it is difficult to quantitatively evaluate the cumulative damage of short-circuit impact during the operation of transformers.

[0005] The present invention provides a method for evaluating transformer short-circuit resistance based on finite element micro-damage accumulation, which at least includes: Construct a finite model of transformer full fault; Perform finite element simulation and calculate the mechanical strength of the winding; Establish a micro-damage accumulation calculation model and evaluate the winding mechanical state; Complete full-fault micro-damage iterative simulation; Evaluate the transformer's short-circuit resistance and dynamically display the mechanical life in real time.

[0006] In some embodiments, the finite element model includes transformer windings, core, clamps, and tank boundaries, wherein winding parameters include at least reactance height, total number of turns, inner radius, radial dimension, number and width of struts, and number and width of spacers.

[0007] In some embodiments, the finite element model adopts at least a two-dimensional axisymmetric field finite element model, and uses a parametric modeling approach to take a design parameter set of the transformer as an input variable to achieve modeling and iterative modification.

[0008] In some embodiments, a magnetic field simulation calculation is performed at least by a static field solver to obtain the actual force acting on the winding under a short-circuit fault, and the actual force is converted into a determination value of the mechanical strength characteristic of the winding.

[0009] In some embodiments, the safety factor is also determined S k , the calculation formula is: ; Among them, C k is a collection of short-circuit withstand capability data; A k It is the characteristic quantity of winding mechanical strength, and its data dimensions include at least radial stress, axial falling force, radial bending stress and axial bending stress.

[0010] In some embodiments, establishing a micro-damage accumulation calculation model and evaluating the winding mechanical state at least includes: When the safety factor S k Greater than the threshold of the initial safety factor of micro-damage accumulation S a When the micro damage coefficient is calculated , the calculation formula is: ; in, is the relative value of the safety factor, and its expression is: .

[0011] In some embodiments, the remaining mechanical life is also calculated , whose expression is: .

[0012] In some embodiments, completing the full-fault micro-damage iterative simulation includes: iteratively loading different short-circuit fault currents in sequence, and using the safety factor and micro-damage results calculated previously as boundary conditions and allowable value calculation conditions for the next finite element simulation.

[0013] In some embodiments, the iteration end conditions include: all short-circuit faults are calculated, the internal structure of the transformer is damaged, the safety factor under a certain fault is lower than the safety threshold, or the mechanical life simulation calculation value is lower than a preset control threshold.

[0014] In some embodiments, evaluating the transformer's short-circuit resistance and dynamically displaying the mechanical life in real time includes: evaluating the short-circuit resistance of each transformer winding in real time, and dynamically displaying the impact number and state characteristic quantity in the form of a chart.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention combines finite element simulation technology with a micro-damage accumulation calculation model to achieve real-time dynamic evaluation of the transformer's short-circuit resistance throughout its entire life cycle. This method comprehensively considers the transformer's design parameters, maximum ability to withstand short-circuit shocks, safety factor under each short-circuit shock, and micro-damage accumulation effects to ensure the comprehensiveness of the evaluation results.

[0016] The present invention accurately calculates the impact of each short-circuit shock on the mechanical state of the transformer winding through finite element simulation, ensuring the scientificity and reliability of the evaluation results; at the same time, it can dynamically display the changes in the mechanical life of the transformer winding, providing an important reference for operation and maintenance decisions.

[0017] The present invention is applicable to transformers with different structures and various short-circuit working conditions, and has strong engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 A schematic diagram of a simplified process flow of the transformer short-circuit resistance evaluation method based on finite element micro-damage accumulation provided by the present invention; Figure 2 A schematic diagram of a detailed flow chart of the short-circuit resistance evaluation method provided by the present invention; Figure 3 A schematic diagram of the micro-damage assessment algorithm provided by the present invention; Figure 4 A schematic diagram of the relationship between the micro-damage curve and the remaining life provided by the present invention; Figure 5 This is an example diagram of the transformer status display provided by the present invention.

[0020] The reference numerals are explained as follows: P t : transformer parameter dataset; I m : Fault impulse current; η k : micro-damage coefficient; A k : Winding mechanical strength characteristic; C k : short circuit withstand capability data set; S k : safety factor; S a : threshold value of safety factor for micro-damage accumulation;β k : relative value of safety factor; τ k : Remaining life; P tk : the set of transformer parameters in the kth iteration; Λ: the functional relationship of the actual value; Φ: the functional relationship for calculating the tolerance capability; ξ: the functional relationship for calculating the reference value of the safety factor after considering the accumulated micro-damage; f: the micro-damage coefficient update function. DETAILED DESCRIPTION

[0021] The following is a combination of the embodiments of the present invention Figure 1 -Attached Figure 5 The technical solutions in the embodiments of the present invention are clearly and completely described together. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0022] The present invention provides a method for evaluating the short-circuit resistance of transformers based on finite element micro-damage accumulation. The core of the method lies in realizing real-time dynamic evaluation of the short-circuit resistance of transformers throughout their entire life cycle by combining finite element simulation technology with a micro-damage accumulation calculation model.

[0023] Figure 1 A brief flow chart of the transformer short-circuit capability evaluation method based on finite element micro-damage accumulation provided by the present invention is shown, and the specific implementation of each step is described as follows.

[0024] The foundation of the entire evaluation method is a finite element model of the transformer under all operating conditions. At this stage, an electromagnetic structural field model, encompassing the winding core, clamps, and tank boundary, must be established based on the transformer's actual structural parameters. Key winding parameters include characteristic values ​​such as reactance height, total number of turns, inner radius, radial dimension, number and width of stays, and number and width of spacers. These parameters not only define the winding geometry but also reflect its material properties. Core parameters primarily include structural distribution characteristics and material properties, while clamps and tank boundaries must consider geometric, mechanical, and magnetic field constraints.

[0025] In the modeling process, a two-dimensional axisymmetric field or a three-dimensional field finite element model can be used. In this embodiment, a two-dimensional axisymmetric field is preferred to improve the simulation calculation efficiency while ensuring accuracy. At the same time, in order to meet the rapid response requirements of engineering research, this embodiment uses a parametric modeling method to integrate the design parameters of the transformer into the model. P t As input variables, rapid modeling and iterative modification can be achieved. The model should have the ability to flexibly adjust geometric dimensions and material properties to facilitate the iterative calculation of the subsequent micro-damage accumulation effect. In the initial calculation, k=1 is taken, and the micro-damage coefficient It is 1.15-1.5, preferably 1.15.

[0026] Finite element simulation and calculation of the winding's mechanical strength are performed based on the established finite element model. First, the model must be assigned materials and meshed, and boundary conditions such as the short-circuit fault current and duration of each winding must be applied. Magnetic field simulation calculations can be performed using either a static field, time domain, or transient field solver to determine the actual forces acting on the winding.

[0027] Furthermore, the above force is converted into the winding mechanical strength characteristic quantity A k , and calculate the short-circuit withstand capability data set C by numerical method k Safety factor S k The calculation formula is , where C k and A k The data are multidimensional data sets of winding tolerance and actual force, including radial stress, axial falling force, radial bending stress and axial bending stress, etc. The correctness of the simulation calculation can be judged by the leakage magnetic distribution and short-circuit impedance calculated by simulation. When the computing resources meet the conditions, it is preferred to consider the expression of the influence of micro-damage on the input parameters, that is, , where Φ is the functional relationship of the input parameters. Simulation results can be used to calculate safety factors using national or industry standard judgment methods, or industry research results can be used for more accurate safety factor judgment. This embodiment uses a static field to improve response speed and uses national standards for judgment to enhance the universality of the research.

[0028] The calculation model of micro-damage accumulation and evaluation of the winding mechanical state are one of the core parts of this invention. According to the research data, the initial safety factor threshold of micro-damage accumulation is set as S 0, the end safety factor threshold is S a When the safety factor S k Less than threshold S 0 and greater than the threshold S a When , calculate the micro damage accumulation. S 0 is 1.67~2.5, preferably 2.0; S a Take 1.05~1.35, preferably 1.1; micro damage coefficient The calculation formula is .in, , is the relative value of the safety factor, which indicates the degree of influence of the current short-circuit impact on the mechanical state of the transformer winding.

[0029] Furthermore, the mechanical life loss caused by micro-damage is calculated as the remaining life in the form of a division ratio , whose expression is The micro-damage accumulation calculation model is based on the elastic-plastic nonlinear micro-damage mechanism of transformer winding conductors and insulation materials. Macroscopically, it is manifested as the accumulation of micro-damage caused by windings under different safety factors, resulting in a decrease in their tolerance. Figure 4 A schematic diagram showing the relationship between the micro-damage curve and the remaining life. The horizontal axis is the impact ratio, which is defined as the relative value of the safety factor; the vertical axis is the micro-damage coefficient, which is calculated in the form of a coefficient in the range of (1, ).when Less than (Right now S k > S 0), it is considered that the transformer is not damaged in this impact; when Greater than 1.0 (i.e. S k <S a ), it is judged that the transformer impact exceeds the transformer tolerance level, and the transformer will be damaged and no micro-damage evaluation will be performed.

[0030] Full-fault microdamage iterative simulation enables dynamic updating of the cumulative effects of microdamage. Different short-circuit fault currents are iteratively applied to the established finite element model in multiple steps. The fault parameter table is iteratively calculated for each short-circuit fault according to the time of its occurrence. The safety factor and microdamage results from each calculation serve as the boundary conditions and allowable value calculation criteria for the next finite element simulation. The reduction in allowable values ​​caused by microdamage is an important basis for determining the cumulative effects. When computing resources permit, the geometric model and material properties should be updated to ensure the accuracy of the iterative calculation.

[0031] The basis for the completion of the iterative process includes any of the following situations: (1) after the simulation calculation of all short-circuit transformer fault conditions; (2) the internal structure damage has been measured and verified; (3) the safety factor under a certain fault is lower than the safety threshold or the mechanical life simulation calculation value is lower than the preset control threshold.

[0032] The system evaluates the transformer's short-circuit resistance and dynamically displays its mechanical life in real time, enabling comprehensive monitoring of the transformer winding's mechanical condition. Based on multiple iterative calculations, the system dynamically evaluates the mechanical condition of each transformer winding in real time and displays it in a data chart or other format. Preferably, the chart is used, with the horizontal and vertical axes representing the impact number and characteristic parameters of the condition, such as loss coefficient and remaining life. Furthermore, the evaluation results can be displayed in a software interface or as a report, and the display content can be customized according to user needs. Figure 5This example shows a transformer status display, using short-circuit current damage factor, remaining life, and withstand times as characteristic indicators. This allows operators to intuitively understand the transformer's health and take timely action.

[0033] In summary, the present invention realizes the real-time dynamic evaluation of the short-circuit resistance of the transformer throughout its life cycle by combining finite element simulation technology with a micro-damage accumulation calculation model. In the specific implementation process, from the construction of the full-fault finite element model of the transformer to the precise calculation of the mechanical strength of the winding, to the dynamic update of the micro-damage accumulation effect, and the final real-time dynamic evaluation of the short-circuit resistance, each link is analyzed and optimized in detail. The above method can not only quantitatively evaluate the impact of the cumulative damage of short-circuit impact during the operation of the transformer, but also provide an important reference basis for operation and maintenance decisions. Among them, the attached Figure 1 To the attached Figure 5 The complete technical support framework provided for this invention ensures the scientificity and reliability of this method in practical applications.

[0034] The above description describes the basic principles, main features and advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, from all points of view, the embodiments should be regarded as illustrative and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes that fall within the meaning and range of equivalents of the claims be included in the present invention. Any reference signs in the claims should not be construed as limiting the claim to which they relate.

[0035] Furthermore, it should be understood that although this specification describes the embodiments, not every embodiment includes only one independent technical solution. This description is provided for clarity only. Those skilled in the art should consider this specification as a whole. The technical solutions in the various embodiments may also be appropriately combined to form other embodiments that are understandable to those skilled in the art.

Claims

1. A method for evaluating transformer short-circuit resistance based on finite element micro-damage accumulation, characterized in that: At least: Construct a finite model of transformer full fault; Perform finite element simulation and calculate the mechanical strength of the winding; Establish a micro-damage accumulation calculation model and evaluate the winding mechanical state; Complete full-fault micro-damage iterative simulation; Evaluate the transformer's short-circuit resistance and dynamically display the mechanical life in real time.

2. The method for evaluating transformer short-circuit resistance based on finite element micro-damage accumulation according to claim 1, characterized in that: The finite element model includes transformer windings, cores, clamps and tank boundaries, wherein winding parameters include at least reactance height, total number of turns, inner radius, radial dimensions, number and width of stays, and number and width of spacers.

3. The method for evaluating transformer short-circuit resistance based on finite element micro-damage accumulation according to claim 2, characterized in that: The finite element model uses a parametric modeling approach, with the transformer's design parameter set serving as input variables to achieve modeling and iterative modification.

4. The method for evaluating transformer short-circuit resistance based on finite element micro-damage accumulation according to claim 1, characterized in that: At least complete the magnetic field simulation through the solver to obtain the actual force acting on the winding under the short-circuit fault, and convert it into the judgment value of the mechanical strength characteristic of the winding.

5. The method for evaluating transformer short-circuit resistance based on finite element micro-damage accumulation according to claim 4, characterized in that: Also includes determining the safety factor S k , the calculation formula is: ; Among them, C k is a collection of short-circuit withstand capability data; A k It is the characteristic quantity of winding mechanical strength, and its data dimensions include at least radial stress, axial falling force, radial bending stress and axial bending stress.

6. The method for evaluating transformer short-circuit resistance based on finite element micro-damage accumulation according to claim 5, characterized in that: The establishment of the micro-damage accumulation calculation model and evaluation of the winding mechanical state at least includes: When the safety factor S k Greater than the threshold of the initial safety factor of micro-damage accumulation S a When the micro damage coefficient is calculated , the calculation formula is: ； in, is the relative value of the safety factor, and its expression is: .

7. The method for evaluating transformer short-circuit resistance based on finite element micro-damage accumulation according to claim 6, characterized in that: Also includes calculation of remaining mechanical life , the expression is: 。 8. The method for evaluating transformer short-circuit resistance based on finite element micro-damage accumulation according to claim 1, characterized in that: The method of completing the full-fault micro-damage iterative simulation includes: sequentially and iteratively loading different short-circuit fault currents, and using the safety factor and micro-damage result calculated previously as boundary conditions and allowable value calculation conditions for the next finite element simulation.

9. The method for evaluating transformer short-circuit resistance based on finite element micro-damage accumulation according to claim 8, characterized in that: The conditions for ending the iteration include: all short-circuit faults are calculated, the internal structure of the transformer is damaged, the safety factor under a certain fault is lower than the safety threshold, or the mechanical life simulation calculation value is lower than the preset control threshold.

10. The method for evaluating transformer short-circuit resistance based on finite element micro-damage accumulation according to claim 1, characterized in that: The method of evaluating the transformer's short-circuit resistance and dynamically displaying the mechanical life in real time includes: evaluating the short-circuit resistance of each transformer winding in real time, and dynamically displaying the impact number and state characteristic quantity in the form of a chart.

Images