Method and system for analyzing short circuit withstand capability of power transformer considering cumulative damage

Abstract

This invention discloses a method and system for analyzing the short-circuit withstand capability of power transformers considering cumulative damage, relating to the field of smart grid technology. It solves the problems of existing power transformer short-circuit withstand capability analysis methods being unsuitable for operational equipment and inaccurate results due to the analysis process only considering independent influencing factors and specific short-circuit scenarios. The key technical points are: considering all short-circuit conditions, for any given short-circuit condition, analyzing the winding safety factor from multiple dimensions (strength, stiffness, stability, and vibration, etc.), simultaneously considering the damage factor of a wide boundary (operational aging, cumulative impact, thermal effects) to perform a first correction to the multi-dimensional safety factor, and considering the strong mechanical coupling effect between windings to perform a second correction to the multi-dimensional safety factor, ultimately obtaining an accurate comprehensive safety factor for the power transformer's short-circuit withstand capability, thus realizing the assessment of the power transformer's short-circuit withstand capability.

Description

Technical Field

[0001] This invention relates to the field of smart grid technology, and more specifically, to a method and system for analyzing the short-circuit withstand capability of power transformers that takes into account cumulative damage. Background Technology

[0002] In power grid fault statistics, equipment damage and system outages caused by short-circuit faults at the output of power transformers have consistently remained high. The fundamental reason for this is the insufficient short-circuit withstand capacity of the power transformers themselves, and the impact of complex operating conditions on the accuracy of short-circuit withstand capacity analysis.

[0003] Existing methods for analyzing the short-circuit withstand capability of power transformers only specify short-circuit testing and verification calculation methods for newly manufactured power transformers, failing to cover the actual degradation mechanisms of operational equipment. Furthermore, when assessing short-circuit withstand capability, they often only consider independent influencing factors or short-circuit scenarios occurring under only one theoretical condition, resulting in inaccurate short-circuit withstand capability analysis. This directly restricts the power grid's assessment of short-circuit risks of operational equipment and reduces the grid's proactive defense capabilities.

[0004] Therefore, this application provides a method and system for analyzing the short-circuit withstand capability of power transformers that takes into account cumulative damage, thereby solving the above-mentioned problems. Summary of the Invention

[0005] The purpose of this application is to provide a method and system for analyzing the short-circuit withstand capability of power transformers that considers cumulative damage. This addresses the problem that existing methods for analyzing the short-circuit withstand capability of power transformers are not applicable to already operational equipment, and that the analysis process only considers independent influencing factors and specific short-circuit scenarios, leading to inaccurate analysis results. The method and system for analyzing the short-circuit withstand capability of power transformers provided in this application cover a wide range of boundary conditions, including historical aging, cumulative impact damage, and thermal effects. It considers multi-dimensional mechanical strength assessments such as strength, stiffness, stability, and vibration, as well as the mechanical coupling effects between windings, achieving a comprehensive and accurate analysis of the short-circuit withstand capability of power transformers.

[0006] This application first provides a method for analyzing the short-circuit withstand capability of power transformers considering cumulative damage, including: S1, obtaining power transformer parameters under all short-circuit conditions, including: operating parameters, structural parameters, and fault parameters; S2, based on the operating parameters, structural parameters, fault parameters, and the comprehensive safety factor of the power transformer's short-circuit withstand capability after the previous short-circuit impact, obtaining the operating aging damage factor, cumulative impact damage factor, and thermal effect damage factor; S3, performing stress analysis on the power transformer under each short-circuit condition to obtain the stress on each winding of the power transformer; S4, based on the stress on each winding of the power transformer, constructing a functional relationship between structural parameters, fault parameters, cumulative impact damage factor, and multi-dimensional safety factor. At least including: strength safety factor, stiffness safety factor, stability safety factor and vibration safety factor; S5, perform a first correction on the multi-dimensional safety factor based on the operation aging damage factor, cumulative impact damage factor and thermal effect damage factor to obtain the first corrected multi-dimensional safety factor; S6, for multi-winding power transformers, perform coupling decoupling on the force influence of each winding to obtain the mechanical coupling coefficient of each winding, and perform a second correction on the first corrected multi-dimensional safety factor based on the mechanical coupling coefficient of each winding to obtain the comprehensive safety factor of the power transformer's short-circuit withstand capability under the current short-circuit condition; S7, determine whether the iteration stop condition is met. If it is met, the analysis ends; otherwise, repeat steps S2-S6.

[0007] In one possible implementation, S1, obtain the power transformer parameters under all short-circuit conditions, including: operating parameters, structural parameters, and fault parameters; wherein: the operating parameters include at least: the service life and the capacity load during operation; the structural parameters include at least: winding, core, and tank parameters; the fault parameters include at least: three-phase short circuit, two-phase short circuit, and single-phase ground fault under high-level, high-low, medium-low power grids, and combined operation modes.

[0008] In one possible implementation, S2, based on the comprehensive safety factor of the power transformer's short-circuit withstand capability after the previous short-circuit impact, obtains the operating aging damage coefficient, the cumulative impact damage coefficient, and the thermal effect damage coefficient; including: obtaining the operating aging damage coefficient based on the operating parameters and structural parameters; obtaining the cumulative impact damage coefficient based on the comprehensive safety factor of the power transformer's short-circuit withstand capability after the previous short-circuit impact, structural parameters, fault parameters, and the thermal effect damage coefficient based on the structural parameters and fault parameters.

[0009] In one possible implementation, S2, based on the comprehensive safety factor of the power transformer's short-circuit withstand capability after the previous short-circuit impact, obtains the operating aging damage coefficient, cumulative impact damage coefficient, and thermal effect damage coefficient; including: performing simulation tests on the power transformer based on the comprehensive safety factor of the power transformer's short-circuit withstand capability after the previous short-circuit impact; generating operating aging curves, mechanical damage curves, and thermal distribution curves based on the simulation test data; and extracting the operating aging damage coefficient, cumulative impact damage coefficient, and thermal effect damage coefficient based on the operating aging curves, mechanical damage curves, and thermal distribution curves.

[0010] In one possible implementation, S3, the stress analysis of the power transformer under each short-circuit condition is performed to obtain the stress on each winding of the power transformer; including: loading the winding current and current duration of the power transformer under each short-circuit condition; analyzing the stress on each winding based on the winding current and current duration; and judging the correctness of the stress on each winding in the simulation calculation based on the leakage flux distribution and short-circuit impedance.

[0011] In one possible implementation, S5, the multidimensional safety factor is first corrected based on the operating aging damage coefficient, the cumulative impact damage coefficient, and the thermal effect damage coefficient to obtain the first corrected multidimensional safety factor; including: performing multiplication or division operations on the multidimensional safety factor based on the operating aging damage coefficient, the cumulative impact damage coefficient, and the thermal effect damage coefficient to obtain the first corrected multidimensional safety factor.

[0012] In one possible implementation, S6, for a multi-winding power transformer, the stress influence of each winding is coupled and decoupled to obtain the mechanical coupling coefficient of each winding. Based on the mechanical coupling coefficient of each winding, a second correction is made to the first corrected multi-dimensional safety factor to obtain the comprehensive safety factor of the power transformer's short-circuit withstand capability under the current short-circuit condition. This includes: coupling and decoupling the stress of each winding of the power transformer to obtain the radial mechanical coupling coefficient and axial mechanical coupling coefficient of each winding, and taking the larger value as the mechanical coupling coefficient of the winding; based on the radial mechanical coupling coefficient and axial mechanical coupling coefficient of each winding, the radial mechanical coupling correction value and axial mechanical coupling correction value of each winding are calculated, and the larger value is taken as the mechanical coupling correction value of the winding; for each winding of the power transformer, based on the mechanical coupling correction value of the winding, a second correction is made to the first corrected multi-dimensional safety factor of the winding, and the smallest safety factor is taken from the second corrected multi-dimensional safety factor as the comprehensive safety factor of the winding's short-circuit withstand capability under the current short-circuit condition.

[0013] In one possible implementation, S6, for a multi-winding power transformer, the stress influence of each winding is coupled and decoupled to obtain the mechanical coupling coefficient of each winding. Based on the mechanical coupling coefficient of each winding, the first modified multi-dimensional safety factor is modified a second time to obtain the comprehensive safety factor of the power transformer's short-circuit withstand capability under the current short-circuit condition. The implementation also includes: setting a safety factor threshold, comparing the comprehensive safety factor of the winding's short-circuit withstand capability under the current short-circuit condition with the safety factor threshold, and judging the risk of winding damage.

[0014] In one possible implementation, S7, determine whether the iteration stop condition is met. If it is met, the analysis ends; otherwise, repeat steps S2-S6. The iteration stop condition is: the winding of the power transformer is damaged; or, the comprehensive safety factor calculation of the short-circuit withstand capacity of the power transformer for all short-circuit faults is completed.

[0015] This application also provides a power transformer short-circuit withstand capability analysis system considering cumulative damage, including: a parameter acquisition module for acquiring power transformer parameters under all short-circuit conditions, including: operating parameters, structural parameters, and fault parameters; an iterative loop module, including: a damage coefficient determination module, a short-circuit condition stress analysis module, a multi-dimensional safety factor determination module, a first correction module for the multi-dimensional safety factor, and a second correction module for the multi-dimensional safety factor; and an iterative judgment module for determining whether the iteration stop condition is met. If it is met, the analysis ends; otherwise, it jumps to the iterative loop module.

[0016] The iterative loop module includes: a damage coefficient determination module, used to obtain the aging damage coefficient, cumulative impact damage coefficient, and thermal effect damage coefficient based on the comprehensive safety factor of the power transformer's short-circuit withstand capability after the previous short-circuit impact, considering operating parameters, structural parameters, fault parameters, and the previous short-circuit impact; a short-circuit condition stress analysis module, used to perform stress analysis on the power transformer under each short-circuit condition, obtaining the stress on each winding of the power transformer; and a multi-dimensional safety factor determination module, used to construct a functional relationship between structural parameters, fault parameters, cumulative impact damage coefficient, and multi-dimensional safety factor based on the stress on each winding of the power transformer. The multi-dimensional safety factor includes at least: strength safety. The system includes safety factors such as coefficients, stiffness safety factor, stability safety factor, and vibration safety factor; a first correction module for the multi-dimensional safety factor, which is used to make a first correction to the multi-dimensional safety factor based on the operating aging damage factor, cumulative impact damage factor, and thermal effect damage factor, to obtain the first corrected multi-dimensional safety factor; and a second correction module for the multi-dimensional safety factor, which is used to couple and decouple the stress influence of each winding for a multi-winding power transformer to obtain the mechanical coupling coefficient of each winding, and to make a second correction to the first corrected multi-dimensional safety factor based on the mechanical coupling coefficient of each winding, to obtain the comprehensive safety factor of the power transformer's short-circuit withstand capability under the current short-circuit condition.

[0017] Compared with the prior art, this application has the following beneficial effects: This application comprehensively considers the operating parameters, structural parameters and fault parameters of the circuit transformer, takes into account the effects of aging, cumulative impact and thermal effects as well as the strong mechanical coupling between windings, and proposes a full-condition, wide-boundary, multi-dimensional and strongly coupled power transformer short-circuit withstand capability analysis method. The method has strong engineering guidance value and applicability. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0019] Figure 1 A flowchart of a method for analyzing the short-circuit withstand capability of a power transformer considering cumulative damage, provided for an embodiment of this application;

[0020] Figure 2 An algorithm diagram of the short-circuit withstand capability analysis method for power transformers considering cumulative damage provided in the embodiments of this application;

[0021] Figure 3 A framework diagram of the short-circuit withstand capability analysis method for power transformers considering cumulative damage, provided in the embodiments of this application;

[0022] Figure 4 A structural diagram of a power transformer short-circuit withstand capability analysis system considering cumulative damage, provided in an embodiment of this application. Detailed Implementation

[0023] In the following, the terms “comprising” or “may include” as used in the various embodiments of this application indicate the presence of the claimed function, operation, or element, and do not limit the addition of one or more functions, operations, or elements. Furthermore, as used in the various embodiments of this application, the terms “comprising,” “having,” and their cognates are intended only to indicate a specific feature, number, step, operation, element, component, or combination of the foregoing, and should not be construed as primarily excluding the presence of one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing, or the possibility of adding one or more combinations of the foregoing.

[0024] The terminology used in the various embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the various embodiments of this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of this application pertain. The terms (such as those defined in a generally used dictionary) are to be interpreted as having the same meaning as in the context of the relevant technical field and are not to be interpreted as having an idealized or overly formal meaning, unless clearly defined in the various embodiments of this application.

[0025] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this application are only for explaining this application and are not intended to limit this application.

[0026] Please see Figure 1 As shown, Figure 1 The flowchart illustrates a method for analyzing the short-circuit withstand capability of a power transformer considering cumulative damage, as provided in this application embodiment. The method includes: S1, obtaining power transformer parameters under all short-circuit conditions, including operating parameters, structural parameters, and fault parameters; S2, obtaining an operating aging damage coefficient, a cumulative impact damage coefficient, and a thermal effect damage coefficient based on the comprehensive safety factor of the power transformer's short-circuit withstand capability after the previous short-circuit impact, based on the operating parameters, structural parameters, fault parameters, and the comprehensive safety factor of the power transformer's short-circuit withstand capability after the previous short-circuit impact; S3, performing a stress analysis on the power transformer under each short-circuit condition to obtain the stress on each winding of the power transformer; S4, constructing a functional relationship between the structural parameters, fault parameters, cumulative impact damage coefficient, and multi-dimensional safety factor based on the stress on each winding of the power transformer. The safety factor includes at least: strength safety factor, stiffness safety factor, stability safety factor, and vibration safety factor; S5, perform a first correction on the multi-dimensional safety factor based on the operating aging damage factor, cumulative impact damage factor, and thermal effect damage factor to obtain the first-corrected multi-dimensional safety factor; S6, for multi-winding power transformers, decouple and deconstruct the force influence of each winding to obtain the mechanical coupling coefficient of each winding, and perform a second correction on the first-corrected multi-dimensional safety factor based on the mechanical coupling coefficient of each winding to obtain the comprehensive safety factor of the power transformer's short-circuit withstand capability under the current short-circuit condition; S7, determine whether the iteration stop condition is met. If it is met, the analysis ends; otherwise, repeat steps S2-S6.

[0027] Specifically, the short-circuit withstand capability of a power transformer in operation is constrained by a variety of factors, including: after experiencing a short-circuit impact, the mechanical characteristics of the power transformer will undergo multi-dimensional time-varying degradation, including the attenuation of material strength and support stiffness; its insulation material will undergo accelerated thermal aging under the action of short-time thermal effects, resulting in irreversible weakening of the material's mechanical properties and weakening of insulation support; the nonlinear force amplification effect caused by strong electro-magnetic and mechanical coupling between its windings and the path dependence of mechanical coupling between windings make the windings more prone to local stress concentration and deformation under short-circuit impact; the above factors together constrain the short-circuit withstand capability of the equipment.

[0028] Therefore, the short-circuit withstand capability analysis method for power transformers provided in this application obtains the power transformer parameters under all short-circuit conditions: operating parameters, structural parameters, and fault parameters. Based on the power transformer parameters, the stress condition under any short-circuit fault is calculated, and a multi-dimensional mechanical strength analysis, including strength, stiffness, stability, and vibration, is performed on the stress condition to obtain safety factors for strength, stiffness, stability, and vibration. At the same time, the first correction is made to the multi-dimensional safety factors considering aging damage, cumulative impact damage, and thermal effect damage, and the second correction is made to the multi-dimensional safety factors considering the strong coupling effect between windings. Finally, a comprehensive safety factor for the short-circuit withstand capability of the power transformer is obtained, which is used to evaluate the short-circuit withstand capability of the power transformer.

[0029] Please see Figure 2 As shown, Figure 2 Algorithm diagram of the short-circuit withstand capability analysis method for power transformers considering cumulative damage provided in the embodiments of this application. Step S1: Obtain power transformer parameters under all short-circuit conditions: operating parameter P to Structural parameter P ts and fault parameter P tf Step S2 is based on the running parameter P to Structural parameter P ts Fault parameter P tf Based on the comprehensive safety factor γ of the power transformer's short-circuit withstand capability after the previous short-circuit impact, the operating aging damage coefficient η1, cumulative impact damage coefficient η2, and thermal effect damage coefficient η3 are obtained; step S3 analyzes the stress on each winding of the power transformer under each short-circuit condition; step S4 constructs the structural parameter P based on the stress on each winding of the power transformer. ts Fault parameter P tf Cumulative impact damage coefficient η2 and multidimensional safety factor K S (At least including: strength safety factor K) S1 Stiffness safety factor K S2 Stability safety factor K S3 and vibration safety factor K S4The functional relationship of ); Step S5 is based on the operating aging damage coefficient η1, the cumulative impact damage coefficient η2, and the thermal effect damage coefficient η3 to determine the multi-dimensional safety factor K. S Perform the first correction to obtain the multi-dimensional security coefficient K after the first correction. Sa Step S6, for multi-winding power transformers, decouples the stress effects on each winding to obtain the mechanical coupling coefficient of each winding (taking three windings as an example, the mechanical coupling coefficient ζ of the internal winding). inn ζ, the mechanical coupling coefficient of the middle winding mid External winding mechanical coupling coefficient ζ out Based on the mechanical coupling coefficients of each winding, the first modified multi-dimensional safety factor K is... Sa Perform a second correction to obtain the comprehensive safety factor γ of the power transformer's short-circuit withstand capability under the current short-circuit condition; in step S7, determine whether the iteration stop condition is met. If it is met, the analysis ends; otherwise, repeat steps S2-S6.

[0030] Please see Figure 3 As shown, Figure 3 This is a framework diagram of the short-circuit withstand capability analysis method for power transformers considering cumulative damage, provided in the embodiments of this application. The improvement of this application lies in proposing a comprehensive, wide-boundary, multi-dimensional, and strongly coupled short-circuit withstand capability analysis method for power transformers. Considering all short-circuit operating conditions, for any given short-circuit condition, the safety factor of the windings is analyzed from multiple dimensions (strength, stiffness, stability, and vibration, etc.). Simultaneously, a first correction is made to the multi-dimensional safety factor by considering the wide-boundary damage factor (operating aging, cumulative impact, thermal effects), and a second correction is made by considering the strong mechanical coupling between windings. Finally, an accurate comprehensive safety factor for the short-circuit withstand capability of the power transformer is obtained, realizing the assessment of the short-circuit withstand capability of the power transformer.

[0031] It should be noted that the core of this application is to perform stress calculations under any short-circuit condition, assess winding safety from multiple dimensions, and consider the effects of aging, cumulative impact, thermal damage, and strong coupling between windings to comprehensively analyze the short-circuit withstand capacity of the power transformer windings. The specific calculation methods for each parameter in this application include, but are not limited to, standard specifications, principle calculations, finite element simulations, and academic achievements. Different calculation methods will only affect the accuracy of the analysis results and do not constitute a limitation on the scope of protection of this application.

[0032] Step S1 is to obtain the power transformer parameters under all short-circuit conditions, including: operating parameter P to Structural parameter P ts and fault parameter P tf In one possible implementation, step S1 includes: running parameter P toAt least include: service life and capacity load during operation; structural parameter P ts At least including: winding, core, and tank parameters; fault parameter P tf It includes at least three-phase short circuit, two-phase short circuit, and single-phase ground faults in high-voltage, high-low voltage, medium-low voltage, and combined operation modes of power grids.

[0033] Specifically, the fault parameter P of the power transformer tf This includes all short-circuit conditions that may occur during the operation of power transformers, including but not limited to three-phase short circuits, two-phase short circuits, and single-phase ground faults under high-medium, high-low, medium-low, and combined operation modes. The operating parameter P of the power transformer... to This includes the service life and capacity load during operation; the structural parameters P of the power transformer. ts Including but not limited to windings, core, and oil tank; operating parameter P to Structural parameter P ts and fault parameter P tf Used for analysis in subsequent steps.

[0034] It is understandable that this application considers all possible short-circuit conditions that may occur during the operation of power transformers. Compared with considering a specific short-circuit condition, the short-circuit withstand capability analysis of power transformers in this application has a more comprehensive scope.

[0035] Step S2 is based on the running parameter P to Structural parameter P ts Fault parameter P tf The combined safety factor γ of the power transformer's short-circuit withstand capability after the previous short-circuit impact is used to obtain the aging damage coefficient η1, the cumulative impact damage coefficient η2, and the thermal effect damage coefficient η3.

[0036] In one possible implementation, step S2 includes: based on operating parameter P to and structural parameter P ts The operational aging damage coefficient η1 is obtained; based on structural parameter P ts Fault parameter P tf The cumulative impact damage coefficient η2 is obtained by combining the comprehensive safety factor γ of the power transformer's short-circuit withstand capability after the previous short-circuit impact; based on the structural parameter P ts and fault parameter P tf The thermal effect damage coefficient η3 is obtained.

[0037] In another possible implementation, step S2 includes: based on the operating parameter P to Structural parameter P ts Fault parameter P tfThe power transformer is simulated and tested based on the comprehensive safety factor γ of the short-circuit withstand capability after the previous short-circuit impact. Based on the simulation test data, an operating aging curve, a mechanical damage curve, and a thermal distribution curve are generated. Based on the operating aging curve, mechanical damage curve, and thermal distribution curve, the operating aging damage coefficient η1, the cumulative impact damage coefficient η2, and the thermal effect damage coefficient η3 are extracted.

[0038] Specifically, relatively accurate damage coefficients η1, η2, and η3 can be extracted from experimental test data using simulation-generated operating aging, mechanical damage, and thermal distribution curves. Alternatively, these loss coefficients can be extracted using industry research findings within the scope of existing technology.

[0039] The aging damage coefficient η1 and the operating parameters P of the power transformer to and structural parameter P ts Related:

[0040] η1=φ(P ts ,P to (1)

[0041] In the formula, φ is the functional relationship of the aging damage coefficient η1, indicating that the aging damage coefficient η1 is related to the operating parameter P. to Structural parameter P ts Relevant, η1≥1.0.

[0042] The cumulative impact damage coefficient η2 is calculated as follows: assuming η2 = 1.0 for the first short-circuit condition, subsequent calculations should consider the influence of the previous short-circuit impact. Its calculation expression is:

[0043] η2=Π(P ts ,P tf ,γ n-1 (2)

[0044] In the formula, Π is the functional relationship of the cumulative impact damage coefficient η2, η2≥1.0, which is related to the structural parameter P. ts Fault parameter P tf It is related to the comprehensive safety factor γ of the power transformer's short-circuit withstand capability after the previous short-circuit impact. For the first impact, γ is taken as 1.0.

[0045] Thermal damage coefficient η3 and structural parameter P of power transformer ts and fault parameter P tf Related:

[0046] η3=f(P ts ,P tf (3)

[0047] In the formula, f is the functional relationship of the thermal effect damage coefficient η3, which is related to the structural parameter P.ts and fault parameter P tf Relevant, η3≥1.0.

[0048] Step S3 involves performing a stress analysis on the power transformer under each short-circuit condition to obtain the stress on each winding of the power transformer. In one possible implementation, step S3 includes: loading the winding current and current duration of the power transformer under each short-circuit condition; analyzing the stress on each winding based on the winding current and current duration; and determining the correctness of the stress on each winding in the simulation calculation based on the leakage flux distribution and short-circuit impedance.

[0049] Specifically, one short-circuit condition is selected from all short-circuit conditions in step S1 for stress calculation. The calculation methods include, but are not limited to, principle formulas, finite element simulations, and research results. Different calculation methods will only affect the accuracy of the evaluation and should all fall within the scope of protection of this application. Preferably, after completing material assignment, mesh generation, and loading and boundary settings through finite element simulation, the stress on each winding is accurately calculated; the correctness of the simulation calculation is judged by the leakage flux distribution and short-circuit impedance obtained from the simulation calculation. Alternatively, the winding stress can be calculated based on theoretical calculations and industry research results.

[0050] Step S4 is based on the forces acting on each winding of the power transformer to construct the structural parameters P. ts Fault parameter P tf Cumulative impact damage coefficient η2 and multidimensional safety factor K S Functional relation, multidimensional security factor K S At least including: strength safety factor K S1 Stiffness safety factor K S2 Stability safety factor K S3 and vibration safety factor K S4 Specifically, the safety of the winding is assessed from multiple dimensions to obtain a multi-dimensional safety coefficient K. S Including winding strength K S1 Stiffness K S2 Stability K S3 and vibration K S4 Equal dimensions, its multi-dimensional security factor K S The cumulative impact damage coefficient η2 and the structural parameters P of the power transformer ts Fault parameter P tf Influence:

[0051] K S =β(P ts ,P tf ,η2) (4)

[0052] In the formula, β is the multi-dimensional security factor K. S The functional relationship. For example, the strength safety factor K.S1 =β1(P ts ,P tf ,η2), β1 is the strength safety factor K S1 The functional relation.

[0053] Understandably, for each short-circuit impact, this application analyzes the short-circuit withstand capability of the power transformer from multiple dimensions, judging the short-circuit withstand capability of the power transformer from multiple dimensions such as strength, stiffness, stability and vibration, thereby improving the accuracy of short-circuit withstand capability analysis.

[0054] Step S5 is based on the operating aging damage coefficient η1, the cumulative impact damage coefficient η2, and the thermal effect damage coefficient η3 to determine the multi-dimensional safety factor K. S Perform the first correction to obtain the multi-dimensional security coefficient K after the first correction. Sa In one possible implementation, step S5 includes: adjusting the multi-dimensional safety factor K based on the operating aging damage coefficient η1, the cumulative impact damage coefficient η2, and the thermal effect damage coefficient η3. S Perform multiplication or division operations to obtain the first corrected multidimensional security factor K. Sa .

[0055] Specifically, based on the damage coefficients η1, η2, and η3 obtained in step S2 as the wide-area boundary influence, the multi-dimensional safety factor K is... S Perform the first correction. The corrected multi-dimensional safety factor K. Sa for:

[0056] K sa =δ(K) s ,η1,η2,η3)(5)

[0057] In the formula, δ is the multi-dimensional safety factor K. Sa Based on the functional relations, a method for correcting the multi-dimensional security factor under the influence of wide-area boundaries was established. Taking the division correction as an example, the corrected multi-dimensional security factor K can be obtained. Sa for:

[0058]

[0059] It should be noted that, in addition to division, subtraction or other algorithms can also be used for correction, and this application does not restrict the correction formula.

[0060] According to industry research practices, the safety factors of each winding in the above-mentioned multiple dimensions are calculated separately according to the radial and axial directions for subsequent analysis.

[0061] Understandably, unlike newly manufactured power transformers, the operating conditions of power transformers already in operation are more complex. After multiple short-circuit impacts, the equipment may suffer mechanical damage, aging due to operation, and thermal aging of insulation materials, affecting its short-circuit withstand capability. Therefore, this application comprehensively considers multiple influencing factors such as operational aging, cumulative impacts, and thermal effects during operation, and corrects the multi-dimensional safety factor. The corrected safety factor more accurately reflects the short-circuit withstand capability of the power transformer windings.

[0062] Step S6 involves decoupling the stress effects on each winding of a multi-winding power transformer to obtain the mechanical coupling coefficients of each winding. Based on these mechanical coupling coefficients, the first corrected multi-dimensional safety factor K is then calculated. Sa A second correction is performed to obtain the comprehensive safety factor γ of the power transformer's short-circuit withstand capability under the current short-circuit condition. In one possible implementation, step S6 includes: decoupling the forces on each winding of the power transformer to obtain the radial mechanical coupling coefficient and axial mechanical coupling coefficient of each winding, and taking the larger value as the mechanical coupling coefficient of the winding; based on the radial mechanical coupling coefficient and axial mechanical coupling coefficient of each winding, calculating the radial mechanical coupling correction value and axial mechanical coupling correction value of each winding, and taking the larger value as the mechanical coupling correction value of the winding; for each winding of the power transformer, applying the first correction to the multi-dimensional safety factor K of the winding based on the mechanical coupling correction value of the winding. Sa A second correction is made, and the smallest safety factor among the multi-dimensional safety factors after the second correction is taken as the comprehensive safety factor of the winding short-circuit withstand capability for the current short-circuit condition.

[0063] Specifically, for multi-winding power transformers, there are strong mechanical coupling relationships between the windings, and their influence mechanisms differ. Therefore, it is necessary to correct the mechanical coupling effects between the windings. Taking a three-winding power transformer as an example, the stress effects are coupled and decoupled according to the radial and axial directions, and the multi-dimensional safety factor is corrected to obtain the final short-circuit withstand capacity. The specific method is as follows:

[0064] For ease of description, let the subscripts for the inner, intermediate, and outer windings, from the core outwards, be inn, mid, and out, respectively. Therefore, let the radial mechanical coupling coefficients of each winding be ζ. innr ζ midr and ζ outr The axial mechanical coupling coefficients are respectively ζ innz ζ midz and ζ outz The larger value is taken as the mechanical coupling coefficient ζ of the winding. inn ζ mid and ζ out .

[0065] Based on the winding stress characteristics and support relationship, and ignoring minor influencing factors, the mechanical coupling relationship between windings is summarized in Table 1:

[0066] Table 1. Mechanical Coupling Relationships Between Windings

[0067]

[0068]

[0069] In the table, "√" indicates relevant and "--" indicates irrelevant. Based on the relationships in the table above, the radial mechanical coupling correction value K, which takes into account the mutual coupling effect between windings, can be directly calculated. innr K midr K outr And axial mechanical coupling correction value K innz K midz K outz The larger value is taken as the mechanical coupling correction value K of the winding. inn K mid K out Taking the middle winding as an example:

[0070] K midr =ζ innr ·ζ midz (7)

[0071] K midz =ζ midr ·ζ innz ·ζ outz (8)

[0072] Take the larger value as the mechanical coupling correction value K for the middle winding. mid =max[K midr ,K midz ].

[0073] In this embodiment, the above six mechanical coupling coefficients (ζ) innr ζ midr ζ outr ζ innz ζ midz and ζ outz All coefficients are not less than 1.0.

[0074] Based on the mechanical coupling coefficient (ζ) of each winding inn ζ mid ζ out The first revised multidimensional safety factor K sa After correcting for the mechanical coupling effects between windings (i.e., the second correction), a comprehensive safety factor for the short-circuit withstand capability of the power transformer is obtained, which is used to comprehensively evaluate the short-circuit withstand capability of the power transformer.

[0075] γ=Λ(ζ inn ,ζ mid ,ζ out ,K sa (9)

[0076] In the formula, Λ represents the functional relationship between the comprehensive safety factor γ of the short-circuit withstand capability of the power transformer and the mechanical coupling effect between the windings. In the multi-dimensional (strength, stiffness, stability and vibration) safety factor calculation results obtained by formula (9), the minimum value is extracted as the comprehensive safety factor of the short-circuit withstand capability of this power transformer.

[0077] Taking the middle winding as an example, substituting equations (7) and (8) into equation (9) and performing a second correction using division, the comprehensive safety factor for the short-circuit withstand capability of the middle winding can be calculated as follows:

[0078]

[0079] In the formula, γ mid K represents the comprehensive safety factor of the short-circuit withstand capability of the middle winding. mid K represents the mechanical coupling correction value of the middle winding. sa-mid This represents the minimum value of the multi-dimensional (strength, stiffness, stability, and vibration) safety factor of the middle winding.

[0080] Understandably, this application, based on the correction of the multi-dimensional safety factor by considering multiple influencing factors such as aging, cumulative impact, and thermal effects, further considers the influence of mechanical coupling between windings to correct the multi-dimensional safety factor. The final comprehensive safety factor for short-circuit withstand capability takes into account the influence of aging, cumulative impact, thermal effects, and mechanical coupling between windings, thus achieving a more accurate analysis of short-circuit withstand capability.

[0081] In one possible implementation, step S6 further includes: setting a safety factor threshold K. cr The winding short-circuit withstand capability under the current short-circuit condition is combined with the safety factor and the safety factor threshold K. cr Compare and assess the risk of damage to the windings.

[0082] Specifically, through a pre-set safety factor threshold K cr As a criterion, if the comprehensive safety factor γ of the winding short-circuit withstand capability obtained from subsequent calculations is lower than the safety factor threshold K... cr This indicates that there is a risk of damage to the windings.

[0083] Step S7 determines whether the iteration stopping condition is met. If it is met, the analysis ends; otherwise, steps S2-S6 are executed repeatedly. In one possible implementation, the iteration stopping condition is: the winding of the power transformer is damaged; or, the comprehensive safety factor calculation of the power transformer's short-circuit withstand capability for all short-circuit conditions is completed.

[0084] Specifically, the analysis of the short-circuit withstand capability of a power transformer ends when one of the following conditions occurs: (1) the comprehensive safety factor calculation of the short-circuit withstand capability of the power transformer under all short-circuit conditions is completed; (2) the windings of the power transformer are damaged after the short-circuit impact. It should be noted that when the windings of the power transformer are damaged, it is meaningless to analyze its short-circuit withstand capability, and the analysis process is terminated at this time.

[0085] Furthermore, this application can also develop a visualization software platform to display the parameters and results of the power transformer short-circuit withstand capability analysis process in the form of data, charts, etc., and store them in the form of reports; at the same time, based on the calculated comprehensive safety factor of the winding short-circuit withstand capability, it can assist in determining the health status of the power transformer and realize display and monitoring.

[0086] Understandably, this application comprehensively considers the operating parameters, structural parameters, and fault parameters of the circuit transformer, taking into account the effects of aging, cumulative impact, thermal effects, and strong mechanical coupling between windings. It proposes a method for analyzing the short-circuit withstand capacity of power transformers under all operating conditions, with wide boundaries and multi-dimensional strong coupling. The method has strong engineering guidance value and applicability.

[0087] Please see Figure 4 As shown, Figure 4 A structural diagram of a power transformer short-circuit withstand capability analysis system considering cumulative damage, provided in an embodiment of this application. The system is used to perform, for example... Figure 1 The method shown includes a system comprising: a parameter acquisition module for acquiring power transformer parameters under all short-circuit conditions, including: operating parameter P. to Structural parameter P ts and fault parameter P tf The iterative loop module includes: a damage coefficient determination module, a short-circuit stress analysis module, a multi-dimensional safety factor determination module, a first correction module for the multi-dimensional safety factor, and a second correction module for the multi-dimensional safety factor; and an iterative judgment module, which is used to determine whether the iteration stop condition is met. If it is met, the analysis ends; otherwise, it jumps to the iterative loop module.

[0088] Among them, the iterative loop module includes: a damage coefficient determination module, used to determine the damage coefficient based on the running parameter P. to Structural parameter P ts Fault parameter P tfThe comprehensive safety factor γ of the power transformer's short-circuit withstand capability after the previous short-circuit impact is used to obtain the operating aging damage factor η1, the cumulative impact damage factor η2, and the thermal effect damage factor η3. The short-circuit condition stress analysis module is used to perform stress analysis on the power transformer under each short-circuit condition to obtain the stress on each winding of the power transformer. The multi-dimensional safety factor determination module is used to construct the structural parameter P based on the stress on each winding of the power transformer. ts Fault parameter P tf Cumulative impact damage coefficient η2 and multidimensional safety factor K S Functional relation, multidimensional security factor K S At least including: strength safety factor K S1 Stiffness safety factor K S2 Stability safety factor K S3 and vibration safety factor K S4 The first correction module for the multi-dimensional safety factor is used to adjust the multi-dimensional safety factor K based on the operating aging damage factor η1, the cumulative impact damage factor η2, and the thermal effect damage factor η3. S Perform the first correction to obtain the multi-dimensional security coefficient K after the first correction. Sa The second correction module for the multi-dimensional safety factor is used to decouple and decouple the stress effects on each winding of a multi-winding power transformer to obtain the mechanical coupling coefficient of each winding. Based on the mechanical coupling coefficient of each winding, the first correction module is applied to the multi-dimensional safety factor K. Sa A second correction is made to obtain the comprehensive safety factor γ of the power transformer's short-circuit withstand capability under the current short-circuit condition.

[0089] It is understood that the power transformer short-circuit withstand capability analysis system considering cumulative damage provided in this application is used to achieve, for example... Figure 1 The methods shown correspond one-to-one with the methods and have corresponding technical effects, so they will not be elaborated further.

[0090] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., 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 analyzing the short-circuit withstand capability of power transformers considering cumulative damage, characterized in that, include: S1. Obtain all power transformer parameters under short-circuit conditions, including: operating parameters, structural parameters, and fault parameters; S2. Based on the operating parameters, structural parameters, fault parameters, and the comprehensive safety factor of the power transformer's short-circuit withstand capability after the previous short-circuit impact, the operating aging damage coefficient, cumulative impact damage coefficient, and thermal effect damage coefficient are obtained. S3. Perform stress analysis on the power transformer under each short-circuit condition to obtain the stress on each winding of the power transformer. S4. Based on the forces on each winding of the power transformer, construct a functional relationship between structural parameters, fault parameters, cumulative impact damage coefficient and multi-dimensional safety factor. The multi-dimensional safety factor includes at least: strength safety factor, stiffness safety factor, stability safety factor and vibration safety factor. S5. Based on the operational aging damage coefficient, cumulative impact damage coefficient and thermal effect damage coefficient, the multi-dimensional safety factor is first corrected to obtain the first corrected multi-dimensional safety factor. S6. For a multi-winding power transformer, the stress influence of each winding is coupled and decoupled to obtain the mechanical coupling coefficient of each winding. Based on the mechanical coupling coefficient of each winding, the first modified multi-dimensional safety factor is modified a second time to obtain the comprehensive safety factor of the power transformer's short-circuit withstand capability under the current short-circuit condition. S7. Determine if the iteration stopping condition is met. If it is met, end the analysis; otherwise, repeat steps S2-S6.

2. The method for analyzing the short-circuit withstand capability of power transformers considering cumulative damage according to claim 1, characterized in that, S1. Obtain all power transformer parameters under short-circuit conditions, including: operating parameters, structural parameters, and fault parameters; including: The operating parameters include at least: the number of years of operation and the capacity load during operation; The structural parameters include at least the parameters of the winding, core, and oil tank. The fault parameters include at least three-phase short circuit, two-phase short circuit, and single-phase ground faults under high-medium, high-low, medium-low power grids, and combined operation modes.

3. The method for analyzing the short-circuit withstand capability of power transformers considering cumulative damage according to claim 1, characterized in that, S2. Based on the aforementioned operating parameters, structural parameters, fault parameters, and the comprehensive safety factor of the power transformer's short-circuit withstand capability after the previous short-circuit impact, the aging damage coefficient, cumulative impact damage coefficient, and thermal effect damage coefficient are obtained; including: Based on the aforementioned operating parameters and structural parameters, the operating aging damage coefficient is obtained; Based on the structural parameters, fault parameters, and the comprehensive safety factor of the power transformer's short-circuit withstand capability after the previous short-circuit impact, the cumulative impact damage coefficient is obtained. Based on the structural parameters and fault parameters, the thermal effect damage coefficient is obtained.

4. The method for analyzing the short-circuit withstand capability of power transformers considering cumulative damage according to claim 1, characterized in that, S2. Based on the aforementioned operating parameters, structural parameters, fault parameters, and the comprehensive safety factor of the power transformer's short-circuit withstand capability after the previous short-circuit impact, the aging damage coefficient, cumulative impact damage coefficient, and thermal effect damage coefficient are obtained; including: Based on the aforementioned operating parameters, structural parameters, fault parameters, and the comprehensive safety factor of the power transformer's short-circuit withstand capability after the previous short-circuit impact, a simulation test is conducted on the power transformer. Based on the simulation test data, an operational aging curve, a mechanical damage curve, and a thermal distribution curve are generated. Based on the aforementioned operating aging curve, mechanical damage curve, and thermal distribution curve, the operating aging damage coefficient, cumulative impact damage coefficient, and thermal effect damage coefficient are extracted.

5. The method for analyzing the short-circuit withstand capability of power transformers considering cumulative damage according to claim 1, characterized in that, S3. Perform stress analysis on the power transformer under each short-circuit condition to obtain the stress on each winding of the power transformer; including: Load the power transformer winding current and current duration under each short-circuit condition; Based on the winding current and current duration, analyze the forces acting on each winding; Based on finite element simulation calculations of leakage flux distribution and short-circuit impedance, the correctness of the force on each winding in the simulation calculation is determined.

6. The method for analyzing the short-circuit withstand capability of power transformers considering cumulative damage according to claim 1, characterized in that, S5. Based on the operational aging damage coefficient, cumulative impact damage coefficient, and thermal effect damage coefficient, the multi-dimensional safety factor is first corrected to obtain the first corrected multi-dimensional safety factor; including: The first corrected multidimensional safety factor is obtained by multiplying or dividing the multidimensional safety factor based on the operational aging damage coefficient, cumulative impact damage coefficient, and thermal effect damage coefficient.

7. The method for analyzing the short-circuit withstand capability of power transformers considering cumulative damage according to claim 1, characterized in that, S6. For multi-winding power transformers, the stress influence of each winding is decoupled to obtain the mechanical coupling coefficient of each winding. Based on the mechanical coupling coefficient of each winding, the first modified multi-dimensional safety factor is modified a second time to obtain the comprehensive safety factor of the power transformer's short-circuit withstand capability under the current short-circuit condition; including: The forces on each winding of the power transformer are coupled and decoupled to obtain the radial mechanical coupling coefficient and axial mechanical coupling coefficient of each winding. The larger value is taken as the mechanical coupling coefficient of the winding. Based on the radial mechanical coupling coefficient and axial mechanical coupling coefficient of each winding, calculate the radial mechanical coupling correction value and axial mechanical coupling correction value of each winding, and take the larger value as the mechanical coupling correction value of the winding. For each winding of the power transformer, the first corrected multi-dimensional safety factor of the winding is corrected based on the mechanical coupling correction value of the winding. The minimum safety factor is taken from the second corrected multi-dimensional safety factor as the comprehensive safety factor of the winding short-circuit withstand capability under the current short-circuit condition.

8. The method for analyzing the short-circuit withstand capability of power transformers considering cumulative damage according to claim 7, characterized in that, S6. For multi-winding power transformers, the stress influence of each winding is decoupled to obtain the mechanical coupling coefficient of each winding. Based on the mechanical coupling coefficient of each winding, the first modified multi-dimensional safety factor is modified a second time to obtain the comprehensive safety factor of the power transformer's short-circuit withstand capability under the current short-circuit condition; This also includes: A safety factor threshold is set, and the comprehensive safety factor of the winding's short-circuit withstand capability under the current short-circuit condition is compared with the safety factor threshold to determine the risk of winding damage.

9. The method for analyzing the short-circuit withstand capability of power transformers considering cumulative damage according to claim 1, characterized in that, S7. Determine whether the iteration stopping condition is met. If it is met, end the analysis; otherwise, repeat steps S2-S6. The iteration stopping condition is: The windings of the power transformer are damaged; or, Calculate the comprehensive safety factor of the short-circuit withstand capability of power transformers for all short-circuit faults.

10. A power transformer short-circuit withstand capability analysis system considering cumulative damage, characterized in that, A system for performing the short-circuit withstand capability analysis method for power transformers considering cumulative damage as described in any one of claims 1 to 9, comprising: The parameter acquisition module is used to acquire power transformer parameters under all short-circuit conditions, including: operating parameters, structural parameters, and fault parameters; The iterative loop module includes: a damage coefficient determination module, a short-circuit stress analysis module, a multi-dimensional safety factor determination module, a first correction module for the multi-dimensional safety factor, and a second correction module for the multi-dimensional safety factor. The iteration judgment module is used to determine whether the iteration stopping condition is met. If it is met, the analysis ends; otherwise, it jumps to the iteration loop module. In the iterative loop module: The damage coefficient determination module is used to obtain the aging damage coefficient, cumulative impact damage coefficient, and thermal effect damage coefficient based on the comprehensive safety factor of the power transformer's short-circuit withstand capability after the previous short-circuit impact, including the operating parameters, structural parameters, fault parameters, and the short-circuit withstand capability after the previous short-circuit impact. The short-circuit stress analysis module is used to perform stress analysis on the power transformer under each short-circuit condition to obtain the stress on each winding of the power transformer. The multi-dimensional safety factor determination module is used to construct a functional relationship between structural parameters, fault parameters, cumulative impact damage coefficient and multi-dimensional safety factor based on the force on each winding of the power transformer. The multi-dimensional safety factor includes at least: strength safety factor, stiffness safety factor, stability safety factor and vibration safety factor. The first correction module for the multi-dimensional safety factor is used to make a first correction to the multi-dimensional safety factor based on the operating aging damage factor, the cumulative impact damage factor and the thermal effect damage factor, so as to obtain the first corrected multi-dimensional safety factor. The second correction module for the multi-dimensional safety factor is used to decouple and decouple the stress influence of each winding for a multi-winding power transformer to obtain the mechanical coupling coefficient of each winding. Based on the mechanical coupling coefficient of each winding, the first correction of the multi-dimensional safety factor is corrected to obtain the comprehensive safety factor of the power transformer's short-circuit withstand capability under the current short-circuit condition.

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