Method and device for evaluating anti-short-circuit capability of transformer cushion block

Abstract

The invention is suitable for the technical field of transformers, and provides a transformer cushion block anti-short-circuit capability evaluation method and device. The transformer comprises a plurality of windings and a plurality of cushion blocks, each cushion block is arranged between the adjacent windings, and the method comprises the following steps: aiming at each cushion block, aiming at each short circuit impact after primary short circuit impact of the transformer, obtaining a mechanical parameter corresponding to the short circuit impact according to an initial parameter of the cushion block, the actual compression stress of the cushion block after the short-circuit impact and the allowable stress of the cushion block after the short-circuit impact are obtained, and then the anti-short-circuit capability of the cushion block after the short-circuit impact is obtained based on the ratio of the allowable stress of the cushion block after the short-circuit impact to the actual compression stress. According to the invention, the anti-short-circuit capability of the cushion block after multiple times of short-circuit impact can be accurately obtained, so that the transformer can be maintained in time subsequently based on the anti-short-circuit capability of the cushion block.

Description

Technical Field

[0001] The present application relates to the technical field of transformers, and particularly relates to a method and device for evaluating the short-circuit resistance ability of transformer pads. Background Art

[0002] A transformer is one of the important core devices in the power system. When a transformer is subjected to a short-circuit impact, a high-magnitude short-circuit current flows through the windings of the transformer, and the huge electromagnetic force generated will cause the windings to deform, which is one of the important reasons for transformer damage. Therefore, it is very important to evaluate the short-circuit withstand ability of transformers. It is known that a transformer consists of multiple windings and multiple pads axially, and the pads are arranged between adjacent windings to support the windings and play an important role in the process of the windings resisting deformation. Therefore, the short-circuit resistance ability of the pads can be used to characterize the short-circuit withstand ability of the transformer.

[0003] Currently, the evaluation of the short-circuit resistance ability of pads depends on the relevant data of the pads when the transformer is put into operation. However, the above-mentioned relevant data can only reflect the short-circuit resistance ability of the pads of a newly put into operation transformer, which belongs to "static evaluation". During multiple multi-path impacts, the short-term changing high-magnitude electromagnetic force will cause the mechanical properties of the pads to decline, and the relevant data of the pads will change. Therefore, after multiple short-circuit impacts, using the relevant data of the pads when the transformer is put into operation cannot accurately evaluate the short-circuit resistance ability of the pads, cannot effectively reflect the short-circuit resistance ability of the pads, and thus cannot perform timely maintenance on the transformer based on the accurate and effective short-circuit resistance ability of the pads subsequently, resulting in transformer damage. Summary of the Invention

[0004] In view of this, the embodiments of the present application provide a method and device for evaluating the short-circuit resistance ability of transformer pads to solve the technical problem that the short-circuit resistance ability of pads cannot be accurately evaluated in the related art.

[0005] In a first aspect, the embodiments of the present application provide a method for evaluating the short-circuit resistance ability of transformer pads. The transformer includes multiple windings and multiple pads, and each pad is arranged between adjacent windings. The method includes: for each pad,

[0006] obtain the initial first mechanical parameter and the initial second mechanical parameter of the pad, and obtain the initial compressive stress of the pad after the first short-circuit impact according to the initial first mechanical parameter and the initial second mechanical parameter;

[0007] For each short - circuit impact after the initial short - circuit impact, based on the initial first mechanical parameter, the initial second mechanical parameter, and the initial compressive stress, obtain the first mechanical parameter and the second mechanical parameter after this short - circuit impact; based on the first mechanical parameter and the second mechanical parameter, determine the actual compressive stress of the spacer block after this short - circuit impact, and according to the actual compressive stress and the first formula, determine the allowable stress of the spacer block after this short - circuit impact; the first formula takes the actual compressive stress as the independent variable and the allowable stress as the dependent variable; according to the ratio of the allowable stress to the actual compressive stress, determine the short - circuit resistance ability of the spacer block after this short - circuit impact.

[0008] In one possible implementation, the method further includes:

[0009] Conduct cyclic load tests with different test compressive stresses and different numbers of cycles on each of the same test paperboards;

[0010] For each test paperboard, after the corresponding cyclic load test, conduct a compression test on this test paperboard until it breaks, and obtain the test allowable stress of this test paperboard;

[0011] Based on the corresponding test compressive stresses, numbers of cycles, and test allowable stresses of all test paperboards, fit to obtain a first test formula; wherein, during the fitting process, the test compressive stress and the number of cycles are used as independent variables, and the test allowable stress is used as the dependent variable; the first test formula includes the value of the first fitting coefficient;

[0012] According to the structure of the first test formula and the value of the first fitting coefficient, take the actual compressive stress as the independent variable and the allowable stress as the dependent variable to obtain the first formula.

[0013] In one possible implementation, for each short - circuit impact after the initial short - circuit impact, the step of obtaining the first mechanical parameter and the second mechanical parameter after this short - circuit impact based on the initial first mechanical parameter, the initial second mechanical parameter, and the initial compressive stress includes:

[0014] According to the initial first mechanical parameter, the initial second mechanical parameter, the initial compressive stress, and the second formula, obtain the first mechanical parameter and the second mechanical parameter after this short - circuit impact;

[0015] Wherein, the second formula takes the initial compressive stress as the independent variable and the first mechanical parameter and the second mechanical parameter as the dependent variables.

[0016] In one possible implementation, the method further includes:

[0017] For each test paperboard, measure the test first mechanical parameter and the test second mechanical parameter during the corresponding cyclic load test;

[0018] Construct a second test formula with the test compression stress and the number of cycles as independent variables, and the first test mechanical parameter and the second test mechanical parameter as dependent variables; the second test formula includes the second fitting coefficient to be solved.

[0019] Based on the test compression stress, the number of cycles, the first test mechanical parameter, the second test mechanical parameter of all test paperboards and the second test formula, determine the value of the second fitting coefficient.

[0020] According to the structure of the second test formula and the value of the second fitting coefficient, with the initial compression stress as the independent variable and the first mechanical parameter and the second mechanical parameter as the dependent variables, obtain the second formula.

[0021] In a possible implementation, for each short - circuit impact after the initial short - circuit impact, determining the actual compression stress of the spacer after the short - circuit impact based on the first mechanical parameter and the second mechanical parameter includes:

[0022] Based on the first mechanical parameter and the second mechanical parameter, determine the stiffness of the spacer after the short - circuit impact.

[0023] According to the stiffness, determine the degree of deformation of the spacer after the short - circuit impact.

[0024] According to the first mechanical parameter, the second mechanical parameter and the degree of deformation, obtain the actual compression stress of the spacer after the short - circuit impact.

[0025] In a possible implementation, the first formula is:

[0026]

[0027] In the formula, F Critical values is the allowable stress, σ i is the actual compression stress of the spacer after the i - th short - circuit impact, v = 1, 2,..., n, n is determined according to the number of times of the short - circuit impact, and u and v are the first fitting coefficients.

[0028] In a possible implementation, the second formula is:

[0029]

[0030] In the formula, an is the first mechanical parameter, b n is the second mechanical parameter, a0 is the initial first mechanical parameter, b0 is the initial second mechanical parameter, σ iσi is the actual compressive stress of the spacer after the i-th short-circuit impact, σ1 is the initial compressive stress, and A1, A2, A3, B1, B2, and B3 are the second fitting coefficients.

[0031] In a possible implementation, determining the stiffness of the spacer after the short-circuit impact based on the first mechanical parameter and the second mechanical parameter includes:

[0032] According to the first mechanical parameter, the second mechanical parameter, and the third formula

[0033] Determine the stiffness of the spacer after the short-circuit impact;

[0034] In the formula, k n is the stiffness, k0 is the initial stiffness, a n is the first mechanical parameter, b n is the second mechanical parameter, a0 is the initial first mechanical parameter, b0 is the initial second mechanical parameter, ε is the strain of the spacer under the pressing force after the short-circuit impact, ε0 is the initial strain of the spacer, and n is determined according to the number of times of the short-circuit impact.

[0035] In a second aspect, an embodiment of the present application provides a device for evaluating the short-circuit resistance of a transformer spacer, including:

[0036] An acquisition module, configured to acquire the initial first mechanical parameter and the initial second mechanical parameter of the spacer, and obtain the initial compressive stress of the spacer after the first short-circuit impact according to the initial first mechanical parameter and the initial second mechanical parameter.

[0037] A obtaining module, configured to, for each short-circuit impact after the first short-circuit impact, obtain the first mechanical parameter and the second mechanical parameter of the spacer after the short-circuit impact according to the initial first mechanical parameter, the initial second mechanical parameter, and the initial compressive stress.

[0038] A first determination module, configured to determine the actual compressive stress of the spacer after the short-circuit impact based on the first mechanical parameter and the second mechanical parameter, and determine the allowable stress of the spacer after the short-circuit impact according to the actual compressive stress and the first formula; the first formula takes the actual compressive stress as the independent variable and the allowable stress as the dependent variable.

[0039] A second determination module, configured to determine the short-circuit resistance of the spacer after the short-circuit impact according to the ratio of the allowable stress to the actual compressive stress.

[0040] In a possible implementation, the device further includes a test module;

[0041] The test module is used to perform cyclic load tests with different test compression stresses and different numbers of cycles on each of the same test cardboard sheets;

[0042] For each test cardboard sheet, after the corresponding cyclic load test is completed, a compression test is performed on the test cardboard sheet until the test cardboard sheet is broken, and the allowable test stress of the test cardboard sheet is obtained;

[0043] Based on the corresponding test compression stresses, numbers of cycles, and allowable test stresses of all test cardboard sheets, a first test formula is obtained by fitting; wherein, in the fitting process, the test compression stress and the number of cycles are used as independent variables, and the allowable test stress is used as the dependent variable; the first test formula includes the value of the first fitting coefficient;

[0044] According to the structure of the first test formula and the value of the first fitting coefficient, with the actual compression stress as the independent variable and the allowable stress as the dependent variable, a first formula is obtained.

[0045] It can be understood that the beneficial effects of the second aspect above can be referred to the relevant descriptions in the first aspect above, and will not be elaborated here.

[0046] The method and device for evaluating the short-circuit resistance of transformer pads provided by the embodiments of the present application, when multiple multi-path impacts occur, consider the influence of the short-time varying high-amplitude electrodynamic force on the mechanical properties of the pads, that is, consider the cumulative effect of multiple short-circuit impacts, and consider the influence of the short-time varying high-amplitude electrodynamic force on the mechanical parameters of the pads and the allowable stress of the pads. For each short-circuit impact after the initial short-circuit impact of the transformer, based on the initial parameters of the pad, the mechanical parameters corresponding to the short-circuit impact are obtained, and then the actual compression stress of the pad after the short-circuit impact and the allowable stress of the pad after the short-circuit impact are obtained. After that, based on the ratio of the allowable stress and the actual compression stress of the pad after the short-circuit impact, the short-circuit resistance of the pad after the short-circuit impact is accurately obtained, and subsequently, based on the short-circuit resistance of the pad, the transformer is maintained in a timely manner.

[0047] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit this specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0049] Figure 1 It is a schematic diagram of an application scenario provided by an embodiment of the present application;

[0050] Figure 2 is a schematic flow chart of a method for evaluating the short - circuit resistance ability of a transformer spacer provided by an embodiment of the present application;

[0051] Figure 3 is a schematic structural diagram of a device for evaluating the short - circuit resistance ability of a transformer spacer provided by an embodiment of the present application. Detailed implementation manners

[0052] The present application will be described more clearly below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the function of the present application, but do not limit the present application in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made. These all belong to the protection scope of the present application.

[0053] It should be understood that when used in the specification and appended claims of the present application, the term "comprising" indicates the presence of the described features, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or their combinations.

[0054] It should also be understood that the term "and / or" used in the specification and appended claims of the present application refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0055] In the description of the specification and appended claims of the present application, the terms "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0056] The reference to "an embodiment" or "some embodiments" etc. in the specification of the present application means that a specific feature, structure or characteristic described in conjunction with the embodiment is included in one or more embodiments of the present application. Thus, the statements "in an embodiment", "in some embodiments", "in other some embodiments", "in still other embodiments" etc. that appear in different places in this specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "comprising", "including", "having" and their variants all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0057] In addition, the "multiple" mentioned in the embodiments of the present application should be interpreted as two or more.

[0058] Based on the idea of accurately evaluating the short-circuit resistance of the spacer, the inventor's research found that when multiple multi-path impacts occur, the influence of the high-amplitude electrodynamic force with short-term changes on the mechanical properties of the spacer can be considered, that is, the cumulative effect of multiple short-circuit impacts is considered, and the influence of the high-amplitude electrodynamic force with short-term changes on the mechanical parameters of the spacer and the allowable stress of the spacer is considered. For each short-circuit impact after the first short-circuit impact of the transformer, the mechanical parameters corresponding to the short-circuit impact are obtained based on the initial parameters of the spacer, and then the actual compressive stress of the spacer after the short-circuit impact and the allowable stress of the spacer after the short-circuit impact are obtained. Finally, based on the above allowable stress and actual compressive stress, the short-circuit resistance of the spacer after the short-circuit impact is obtained.

[0059] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will be described through specific embodiments with reference to the accompanying drawings.

[0060] First, refer to Figure 1 , Figure 1 which schematically shows the application scenario of the present application. In this application scenario, an electronic device is included.

[0061] Among them, the electronic device obtains the initial first mechanical parameter and the initial second mechanical parameter of the spacer, and based on the initial first mechanical parameter and the initial second mechanical parameter, obtains the initial compressive stress of the spacer after the first short-circuit impact. After that, for each short-circuit impact after the first short-circuit impact, based on the initial first mechanical parameter, the initial second mechanical parameter, and the initial compressive stress, the first mechanical parameter and the second mechanical parameter after the short-circuit impact are obtained, and based on the first mechanical parameter and the second mechanical parameter, the actual compressive stress of the spacer after the short-circuit impact is determined. According to the actual compressive stress and the first formula, the allowable stress of the spacer after the short-circuit impact is determined. Finally, according to the ratio of the allowable stress to the actual compressive stress, the short-circuit resistance of the spacer after the short-circuit impact is determined. Among them, the first formula takes the actual compressive stress as the independent variable and the allowable stress as the dependent variable.

[0062] The above-mentioned electronic device can be a hardware device with data storage, processing, and analysis functions, such as a controller or a computer, etc.

[0063] Next, in combination with Figure 1 , refer to Figure 2 to describe the method for evaluating the short-circuit resistance of a transformer spacer provided according to an exemplary embodiment of the present application.

[0064] Figure 2 is a schematic flowchart of the method for evaluating the short-circuit resistance of a transformer spacer provided in an embodiment of the present application. As Figure 2 shown, the method in the embodiment of the present application may include:

[0065] Step 201: Obtain the initial first mechanical parameter and the initial second mechanical parameter of the spacer. According to the initial first mechanical parameter and the initial second mechanical parameter, obtain the initial compressive stress of the spacer after the first short - circuit impact.

[0066] Exemplarily, the transformer includes a plurality of windings and a plurality of spacers axially. Each spacer is disposed between adjacent windings for supporting the windings. In this embodiment, for each spacer, according to the corresponding initial first mechanical parameter, initial second mechanical parameter and the initial compressive stress formula of the spacer, the initial compressive stress of the spacer after the first short - circuit impact can be obtained.

[0067] It should be noted that, for the convenience of description and understanding, unless otherwise specified, the spacers mentioned in the following embodiments are all for each spacer. Correspondingly, the relevant parameters of the spacer are also the corresponding parameters for each spacer.

[0068] Among them, the initial compressive stress formula is:

[0069]

[0070] In the formula, a0 is the initial first mechanical parameter, b0 is the initial second mechanical parameter, ε0 is the initial strain of the spacer, and Δx 0z is the deformation degree of the z - th spacer after the first short - circuit impact, z = 1, 2,..., Z, Z is determined according to the number of spacers in the transformer, and L0 is the width of the oil duct between adjacent windings.

[0071] Among them, the initial strain of the spacer is calculated according to the winding pressing force.

[0072] a0 + 3b0ε0 2 = P

[0073] In the formula, P is the winding pressing force.

[0074] The deformation degree of the spacer is obtained according to the deformation formula. The deformation formula is:

[0075]

[0076] In the formula, M is the mass matrix of the winding, C is the damping coefficient matrix, K is the stiffness matrix, and x0 are respectively the acceleration matrix, velocity matrix and displacement matrix of the winding, F is the electromagnetic force matrix, g is the gravitational acceleration, and F c is the winding pressing force matrix.

[0077] Among them, M = diag(m T , m1, m2... m Z , m B )

[0078]

[0079] In the formula, m T and m B are the equivalent masses of the end plates of the transformer winding. Here, the ends include the top and the bottom. c T and c B are the equivalent viscous dampings of the spacers at the ends of the transformer winding. k T and k B are the stiffnesses of the spacers at the ends of the transformer winding. The stiffnesses mentioned in this embodiment are all equivalent stiffnesses. c C is the equivalent viscous damping from the top plate to the bottom plate. k C is the stiffness from the top plate to the bottom plate. c s is the equivalent viscous damping from the bottom plate to the ground including support structures such as the bottom feet and the bottom of the oil tank. k s is the stiffness from the bottom plate to the ground including support structures such as the bottom feet and the bottom of the oil tank. m1 to m Z are the masses of the equivalent mass blocks of each coil turn. c1 to c Z are the equivalent viscous dampings of the spacers between adjacent windings. k1 to k Z are the stiffnesses of the spacers between adjacent windings. After the first short - circuit impact, k1 to k Z are the stiffnesses of the 1st to the z - th spacers after the first short - circuit impact.

[0080] Thus, by solving the above deformation formula, the displacement difference between two adjacent windings can be obtained, that is, the deformation degree of the spacers between adjacent windings can be obtained, and the deformation degree Δx of the z - th spacer after the first short - circuit impact can be obtained. 0z After that, according to the deformation formula, the initial compressive stress of each spacer in the transformer after the transformer suffers the first short - circuit impact can be obtained.

[0081] In this embodiment, considering the cumulative effect of multiple short - circuit impacts, a compression cardboard test can be carried out to simulate the short - circuit impacts suffered by the transformer in practice, so as to obtain a first formula that can characterize the allowable stress after multiple short - circuit impacts, and the relationship between the mechanical parameters after multiple short - circuit impacts, the number of short - circuit impacts and the initial compressive stress, and a second formula that can characterize the actual compressive stress after multiple short - circuit impacts.

[0082] In some embodiments, cyclic load tests with different test compression stresses and different numbers of cycles can also be performed on each of the same test cardboard sheets. For each test cardboard sheet, after the corresponding cyclic load test is completed, a compression test is performed on the test cardboard sheet until the test cardboard sheet breaks, and the allowable stress of the test cardboard sheet is obtained. Then, based on the corresponding test compression stresses, numbers of cycles, and allowable stresses of all the test cardboard sheets, a first test formula is obtained by fitting. According to the structure of the first test formula and the value of the first fitting coefficient, with the actual compression stress as the independent variable and the allowable stress as the dependent variable, a first formula is obtained.

[0083] Among them, in the fitting process, the test compression stress and the number of cycles are used as independent variables, and the test allowable stress is used as the dependent variable; the first test formula includes the value of the first fitting coefficient.

[0084] Since the short-circuit impact test is too costly, in this embodiment, a compressed cardboard test is used to replace the short-circuit impact test to determine the first formula, the second formula, and the relationship between the mechanical parameters and the number of short-circuit impacts and the initial compression stress.

[0085] Exemplarily, in the compressed cardboard test, first, a plurality of identical test cardboard sheets are obtained to ensure the consistency of the test objects. For example, the above-mentioned plurality of test cardboard sheets are all insulating cardboard sheets of 30 cm * 30 cm * 1 mm, and they are all compressed at 5 MPa and 100 °C for 48 h.

[0086] After that, the test cardboard sheets are subjected to cyclic load tests on a material testing machine. The conditions of the cyclic load test corresponding to each test cardboard sheet are different. The conditions of the cyclic load test include the test compression stress and the number of cycles. For example, the test compression stress can be 10%, 30%, 50%, and 70% of the initial allowable stress, and the number of cycles can be 20, 40, 60, 80, and 100 times. Here, the initial allowable stress can be the initial allowable stress before the spacer block is subjected to a short-circuit impact. That is, the test compression stress and the number of cycles can be combined to obtain 20 conditions for the cyclic load test. Based on the above 20 conditions for the cyclic load test, cyclic load tests are respectively performed on 20 test cardboard sheets.

[0087] For each test cardboard sheet after the test, a compression test is performed at a strain rate of 1 mm / min until the test cardboard sheet breaks, and the allowable stress of the test cardboard sheet is obtained. Thus, for each test cardboard sheet after the test, the corresponding data are the test compression stress, the number of cycles, and the allowable stress. Therefore, based on the corresponding test compression stresses, numbers of cycles, and allowable stresses of all the test cardboard sheets, a first test formula is obtained by fitting. Then, based on the structure of the first test formula and the value of the first fitting coefficient, with the actual compression stress as the independent variable and the allowable stress as the dependent variable, a first formula is obtained.

[0088] The first formula is as follows:

[0089]

[0090] In the formula, F Critical values is the allowable stress, and σ i is the actual compressive stress of the spacer after the i-th short-circuit impact, where v = 1, 2,..., n, and n is determined according to the number of times of this short-circuit impact. u and v are the first fitting coefficients.

[0091] It should be noted that the first test formula is similar to the first formula. By replacing the sum of the test compressive stresses at the number of cycles in the first test formula with the sum of the actual compressive stresses of the spacer after the 1st to nth short-circuit impacts, the first formula is obtained.

[0092] It should be noted that for the cyclic load test with a condition of 10% of the initial allowable stress and the number of cycles being 20, the sum of the test compressive stresses at the number of cycles in the first test formula is the sum of 20 10% of the initial allowable stresses. Also, in this embodiment, the 1st short-circuit impact is the initial short-circuit impact.

[0093] In some embodiments, for each test cardboard, in the corresponding cyclic load test, the test first mechanical parameter and the test second mechanical parameter are measured, and a second test formula is constructed with the test compressive stress and the number of cycles as independent variables and the test first mechanical parameter and the test second mechanical parameter as dependent variables. Among them, the second test formula includes the second fitting coefficients to be solved. Then, based on the corresponding test compressive stresses, the number of cycles, the test first mechanical parameter, the test second mechanical parameter, and the second test formula of all test cardboards, the values of the second fitting coefficients are determined. According to the structure of the second test formula and the values of the second fitting coefficients, with the initial compressive stress as the independent variable and the first mechanical parameter and the second mechanical parameter as the dependent variables, the second formula is obtained.

[0094] So far, for each test cardboard after the test, the corresponding data includes the test compressive stress, the number of cycles, the test first mechanical parameter, and the test second mechanical parameter. Thus, substituting the corresponding test compressive stresses, the number of cycles, the test first mechanical parameter, and the test second mechanical parameter of all test cardboards into the second test formula, the values of the second fitting coefficients can be obtained. Then, based on the structure of the second test formula and the values of the second fitting coefficients, with the initial compressive stress as the independent variable and the first mechanical parameter and the second mechanical parameter as the dependent variables, the second formula is obtained.

[0095] The second formula is as follows:

[0096]

[0097] In the formula, an is the first mechanical parameter, and b n is the second mechanical parameter, that is, the first mechanical parameter and the second mechanical parameter after the nth short-circuit impact (i.e., this short-circuit impact), a0 is the initial first mechanical parameter, b0 is the initial second mechanical parameter, and σ i is the actual compressive stress of the spacer after the ith short-circuit impact, σ1 is the initial compressive stress, and A1, A2, A3, B1, B2, and B3 are the second fitting coefficients.

[0098] It should be noted that the second test formula is similar to the second formula. By replacing the sum of the test compressive stresses at the number of cycles in the second test formula with the sum of the actual compressive stresses of the spacer after the 1st to the (n - 1)th short-circuit impacts, the second formula is obtained. The part of obtaining the second formula can refer to the part of obtaining the first formula described above, which will not be elaborated here.

[0099] In this way, for each short-circuit impact after the first short-circuit impact, the first mechanical parameter and the second mechanical parameter obtained in the second formula are not only related to the initial compressive stress, but also related to the actual compressive stress of the spacer after each short-circuit impact before this short-circuit impact, fully considering the cumulative effect of multiple short-circuit impacts. Therefore, the actual compressive stress of the spacer after this short-circuit impact can be accurately obtained subsequently.

[0100] It should be noted that the "actual compressive stress of the spacer after each short-circuit impact before this short-circuit impact" mentioned above can all be calculated by using the method for evaluating the short-circuit resistance of the transformer spacer provided in this embodiment. That is, after obtaining the initial compressive stress and the second formula, for the second short-circuit impact, the actual compressive stress of the spacer after the second short-circuit impact can be obtained according to the initial compressive stress, the second formula, and the compressive stress formula. By analogy, the actual compressive stress of the spacer after the third short-circuit impact can be obtained according to the initial compressive stress, the actual compressive stress of the spacer after the second short-circuit impact, the second formula, and the compressive stress formula. Among them, the compressive stress formula can refer to the subsequent embodiments, which will not be elaborated here.

[0101] Step 202: For each short-circuit impact after the first short-circuit impact, obtain the first mechanical parameter and the second mechanical parameter after this short-circuit impact according to the initial first mechanical parameter, the initial second mechanical parameter, and the initial compressive stress.

[0102] In some embodiments, to obtain the first mechanical parameter and the second mechanical parameter after this short-circuit impact, the first mechanical parameter and the second mechanical parameter after this short-circuit impact can be obtained according to the initial first mechanical parameter, the initial second mechanical parameter, the initial compressive stress, and the second formula. Among them, the second formula takes the initial compressive stress as the independent variable and the first mechanical parameter and the second mechanical parameter as the dependent variables.

[0103] As described above, after this short - circuit impact, based on the initial first mechanical parameter, the initial second mechanical parameter, the initial compressive stress, and the actual compressive stress of the spacer after each short - circuit impact before this short - circuit impact and the second formula, the first mechanical parameter and the second mechanical parameter after this short - circuit impact are obtained. In this way, this embodiment fully considers the cumulative effect of multiple short - circuit impacts and the influence of high - amplitude electrodynamic force with short - term changes on the mechanical parameters of the spacer, rather than still using the initial first mechanical parameter and the initial second mechanical parameter in subsequent solutions. Therefore, the actual compressive stress of the spacer after this short - circuit impact can be accurately obtained subsequently.

[0104] Step 203: Based on the first mechanical parameter and the second mechanical parameter, determine the actual compressive stress of the spacer after this short - circuit impact, and according to the actual compressive stress and the first formula, determine the allowable stress of the spacer after this short - circuit impact.

[0105] Among them, as described above, the first formula takes the actual compressive stress as the independent variable and the allowable stress as the dependent variable.

[0106] In some embodiments, for each short - circuit impact after the first short - circuit impact, to determine the actual compressive stress of the spacer after this short - circuit impact, the stiffness of the spacer after this short - circuit impact can be determined based on the first mechanical parameter and the second mechanical parameter, the degree of deformation of the spacer after this short - circuit impact can be determined according to the stiffness, and then, based on the first mechanical parameter, the second mechanical parameter, and the degree of deformation, the actual compressive stress of the spacer after this short - circuit impact can be obtained.

[0107] Exemplarily, according to the first mechanical parameter, the second mechanical parameter, and the third formula

[0108] Determine the stiffness of the spacer after this short - circuit impact.

[0109] In the formula, k n is the stiffness, k0 is the initial stiffness, a n is the first mechanical parameter, b n is the second mechanical parameter, a0 is the initial first mechanical parameter, b0 is the initial second mechanical parameter, ε is the strain of the spacer after this short - circuit impact under the pressing force, ε0 is the initial strain of the spacer, and n is determined according to the number of this short - circuit impact

[0110] Among them, the strain of the spacer after this short - circuit impact under the pressing force is calculated according to the winding pressing force.

[0111] a n + 3b n ε 2 =P

[0112] In the formula, P is the winding pressing force.

[0113] In this way, according to the third formula, the stiffness of each spacer after this short-circuit impact can be obtained, and the stiffness matrix K after this short-circuit impact can be formed. That is, in the stiffness matrix K after this short-circuit impact, k1 to k Z are the stiffnesses of the 1st to zth spacers after this short-circuit impact. Then, substitute the stiffness matrix K after this short-circuit impact into the deformation formula in the foregoing embodiment to obtain the deformation degree of each spacer after this short-circuit impact.

[0114] After that, for each spacer after this short-circuit impact, according to the corresponding first mechanical parameter, second mechanical parameter, and deformation degree of the spacer, as well as the actual compression stress formula, the actual compression stress of the spacer after this short-circuit impact is obtained.

[0115] The actual compression stress formula is:

[0116]

[0117] Similar to the initial compression stress, in the actual compression stress formula, σ z is the actual compression stress of the zth spacer after this short-circuit impact, a0 is the initial first mechanical parameter, b0 is the initial second mechanical parameter, ε0 is the initial strain of the spacer, and Δx z is the deformation degree of the zth spacer after this short-circuit impact, z = 1, 2,..., Z, Z is determined according to the number of spacers in the transformer, and L0 is the width of the oil duct between adjacent windings.

[0118] In this way, this embodiment fully considers the cumulative effect of multiple multi-channel impacts and can accurately obtain the actual compression stress of the spacer after this short-circuit impact.

[0119] Step 204: Determine the short-circuit resistance ability of the spacer after this short-circuit impact according to the ratio of the allowable stress to the actual compression stress.

[0120] Exemplarily, for each spacer after this short-circuit impact, take the ratio of the corresponding allowable stress to the actual compression stress of the spacer as the safety factor. If the safety factor of the spacer is greater than or equal to the preset threshold, it indicates that the short-circuit resistance ability of the spacer is good. If the safety factors of all spacers in the transformer are greater than or equal to the preset threshold, it indicates that the short-circuit withstand ability of the transformer is good and the transformer can continue to be used.

[0121] If the safety factor of the spacer is less than the preset threshold, it indicates that the short-circuit resistance ability of the spacer is not good. If there is at least one spacer in the transformer whose safety factor is less than the preset threshold, it indicates that the short-circuit withstand ability of the transformer is not good and the transformer should be maintained or replaced in time.

[0122] The method for evaluating the short-circuit resistance of transformer pads provided by the embodiments of the present application considers the influence of high-amplitude electrodynamic forces with short-term changes on the mechanical properties of the pads during multiple multi-channel impacts, that is, considers the cumulative effect of multiple short-circuit impacts, and considers the influence of high-amplitude electrodynamic forces with short-term changes on the mechanical parameters of the pads and the allowable stress of the pads. For each short-circuit impact after the first short-circuit impact of the transformer, the mechanical parameters corresponding to the short-circuit impact are obtained according to the initial parameters of the pad, and then the actual compressive stress of the pad after the short-circuit impact and the allowable stress of the pad after the short-circuit impact are obtained. After that, based on the ratio of the allowable stress and the actual compressive stress of the pad after the short-circuit impact, the short-circuit resistance of the pad after the short-circuit impact is accurately obtained. Subsequently, based on the short-circuit resistance of the pad, the transformer is maintained in a timely manner.

[0123] It should be understood that the magnitudes of the sequence numbers of the steps in the above embodiments do not mean the order of execution. The order of execution of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0124] Figure 3 It is a schematic structural diagram of a device for evaluating the short-circuit resistance of transformer pads provided by an embodiment of the present application. As Figure 3 shown, the device for evaluating the short-circuit resistance of transformer pads provided by this embodiment may include: an acquisition module 301, a obtaining module 302, a first determination module 303, and a second determination module 304.

[0125] Among them, the acquisition module 301 is configured to acquire the initial first mechanical parameter and the initial second mechanical parameter of the pad, and obtain the initial compressive stress of the pad after the first short-circuit impact according to the initial first mechanical parameter and the initial second mechanical parameter.

[0126] The obtaining module 302 is configured to, for each short-circuit impact after the first short-circuit impact, obtain the first mechanical parameter and the second mechanical parameter of the pad after the short-circuit impact according to the initial first mechanical parameter, the initial second mechanical parameter, and the initial compressive stress.

[0127] The first determination module 303 is configured to determine the actual compressive stress of the pad after the short-circuit impact based on the first mechanical parameter and the second mechanical parameter, and determine the allowable stress of the pad after the short-circuit impact according to the actual compressive stress and a first formula; the first formula takes the actual compressive stress as the independent variable and the allowable stress as the dependent variable.

[0128] The second determination module 304 is configured to determine the short-circuit resistance of the pad after the short-circuit impact according to the ratio of the allowable stress and the actual compressive stress.

[0129] Optionally, the short-circuit resistance evaluation device for transformer pads further includes a test module; the test module is configured to perform cyclic load tests with different test compressive stresses and different numbers of cycles on each of the same test cardboard sheets;

[0130] For each test cardboard sheet, after the corresponding cyclic load test is completed, a compression test is performed on the test cardboard sheet until the test cardboard sheet breaks, and the allowable stress of the test cardboard sheet is obtained;

[0131] Based on the test compressive stresses, numbers of cycles, and allowable stresses of all the test cardboard sheets, a first test formula is obtained by fitting; wherein, in the fitting process, the test compressive stress and the number of cycles are used as independent variables, and the allowable stress is used as the dependent variable; the first test formula includes the value of the first fitting coefficient;

[0132] According to the structure of the first test formula and the value of the first fitting coefficient, with the actual compressive stress as the independent variable and the allowable stress as the dependent variable, a first formula is obtained.

[0133] Optionally, the obtaining module 302 is further configured to:

[0134] According to the initial first mechanical parameter, the initial second mechanical parameter, the initial compressive stress, and the second formula, the first mechanical parameter and the second mechanical parameter after this short-circuit impact are obtained;

[0135] Wherein, the second formula uses the initial compressive stress as the independent variable and the first mechanical parameter and the second mechanical parameter as the dependent variables.

[0136] Optionally, the obtaining module 302 is further configured to:

[0137] For each test cardboard sheet, during the corresponding cyclic load test, the test first mechanical parameter and the test second mechanical parameter are measured;

[0138] A second test formula is constructed with the test compressive stress and the number of cycles as independent variables and the test first mechanical parameter and the test second mechanical parameter as dependent variables; the second test formula includes the second fitting coefficient to be solved;

[0139] Based on the test compressive stresses, numbers of cycles, test first mechanical parameters, test second mechanical parameters of all the test cardboard sheets, and the second test formula, the value of the second fitting coefficient is determined;

[0140] According to the structure of the second test formula and the value of the second fitting coefficient, with the initial compressive stress as the independent variable and the first mechanical parameter and the second mechanical parameter as the dependent variables, a second formula is obtained.

[0141] Optionally, the first determining module 303 is further configured to:

[0142] Based on the first mechanical parameter and the second mechanical parameter, determine the stiffness of the spacer after this short-circuit impact;

[0143] According to the stiffness, determine the degree of deformation of the spacer after this short-circuit impact;

[0144] According to the first mechanical parameter, the second mechanical parameter and the degree of deformation, obtain the actual compressive stress of the spacer after this short-circuit impact.

[0145] Optionally, the first determination module 303 is further configured to:

[0146] According to the first mechanical parameter, the second mechanical parameter and the third formula

[0147] Determine the stiffness of the spacer after this short-circuit impact;

[0148] In the formula, k n is the stiffness, k0 is the initial stiffness, a n is the first mechanical parameter, b n is the second mechanical parameter, a0 is the initial first mechanical parameter, b0 is the initial second mechanical parameter, ε is the strain of the spacer under the pressing force after this short-circuit impact, ε0 is the initial strain of the spacer, and n is determined according to the number of times of this short-circuit impact.

[0149] It should be noted that for the information interaction, execution process, etc. between the above-mentioned devices / units, since they are based on the same concept as the method embodiments of the present application, for their specific functions and the technical effects brought, reference can be specifically made to the method embodiment part, and details are not described here again.

[0150] In the above embodiments, the descriptions of each embodiment have their own emphases. For the parts not detailed or recorded in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0151] Those of ordinary skill in the art can realize that, combined with the templates, units and algorithm steps of the examples described in the embodiments disclosed in this article, they can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0152] If the above-mentioned module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such understanding, to implement all or part of the processes in the above-mentioned embodiment methods of the present invention, it can also be completed by instructing relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, the steps of the above-mentioned various method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in the form of source code, object code, executable file or some intermediate form, etc. The computer-readable medium can include: any entity or device that can carry the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory, random access memory, electrical carrier signal, telecommunication signal, and software distribution medium, etc.

[0153] The above-mentioned embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A method for evaluating the short-circuit resistance of a transformer pad, characterized in that: The transformer comprises a plurality of windings and a plurality of spacers, each spacer being arranged between adjacent windings. The method comprises: for each spacer, Acquire an initial first mechanical parameter and an initial second mechanical parameter of the cushion block, and obtain an initial compressive stress of the cushion block after an initial short-circuit impact according to the initial first mechanical parameter and the initial second mechanical parameter; For each short-circuit impact after the initial short-circuit impact, the first mechanical parameter and the second mechanical parameter after the short-circuit impact are obtained according to the initial first mechanical parameter, the initial second mechanical parameter and the initial compressive stress; based on the first mechanical parameter and the second mechanical parameter, the actual compressive stress of the cushion block after the short-circuit impact is determined, and according to the actual compressive stress and the first formula, the allowable stress of the cushion block after the short-circuit impact is determined; the first formula takes the actual compressive stress as the independent variable and the allowable stress as the dependent variable; according to the ratio of the allowable stress to the actual compressive stress, the short-circuit resistance of the cushion block after the short-circuit impact is determined.

2. The method for evaluating the short-circuit resistance of transformer spacers according to claim 1, characterized in that: The method further comprises: The same test paperboards are subjected to cyclic load tests with different test compression stresses and different cycle times; For each test paperboard, after the corresponding cyclic load test is completed, a compression test is performed on the test paperboard until the test paperboard is broken, and the test allowable stress of the test paperboard is obtained; Based on the test compressive stress, the number of cycles and the test allowable stress corresponding to all the test paperboards, a first test formula is obtained by fitting; wherein, in the fitting process, the test compressive stress and the number of cycles are used as independent variables, and the test allowable stress is used as a dependent variable; the first test formula includes the value of the first fitting coefficient; According to the structure of the first test formula and the value of the first fitting coefficient, the first formula is obtained by taking the actual compressive stress as the independent variable and the allowable stress as the dependent variable.

3. The method for evaluating the short-circuit resistance of transformer spacers according to claim 2, characterized in that: For each short-circuit impact after the initial short-circuit impact, obtaining the first mechanical parameter and the second mechanical parameter after the short-circuit impact according to the initial first mechanical parameter, the initial second mechanical parameter and the initial compressive stress includes: According to the initial first mechanical parameter, the initial second mechanical parameter, the initial compressive stress and the second formula, obtaining the first mechanical parameter and the second mechanical parameter after the short-circuit impact; The second formula uses the initial compressive stress as an independent variable, and uses the first mechanical parameter and the second mechanical parameter as dependent variables.

4. The method for evaluating the short-circuit resistance of transformer spacers according to claim 3, characterized in that: The method further comprises: For each test paperboard, in the corresponding cyclic load test, the first mechanical parameter and the second mechanical parameter of the test are measured; Constructing a second test formula with the test compressive stress and the number of cycles as independent variables and the test first mechanical parameter and the test second mechanical parameter as dependent variables; the second test formula includes a second fitting coefficient to be solved; Determine the value of the second fitting coefficient based on the test compressive stress, the number of cycles, the test first mechanical parameter, the test second mechanical parameter and the second test formula corresponding to all the test paperboards; According to the structure of the second test formula and the value of the second fitting coefficient, the second formula is obtained by taking the initial compressive stress as the independent variable and the first mechanical parameter and the second mechanical parameter as the dependent variables.

5. The method for evaluating the short-circuit resistance of a transformer spacer according to any one of claims 1 to 4, characterized in that: For each short-circuit impact after the initial short-circuit impact, determining the actual compressive stress of the cushion block after the short-circuit impact based on the first mechanical parameter and the second mechanical parameter includes: Determining the stiffness of the cushion block after the short-circuit impact based on the first mechanical parameter and the second mechanical parameter; Determine the deformation degree of the cushion block after the short circuit impact according to the stiffness; According to the first mechanical parameter, the second mechanical parameter and the deformation degree, the actual compressive stress of the cushion block after the short-circuit impact is obtained.

6. The method for evaluating the short-circuit resistance of a transformer spacer according to any one of claims 1 to 4, characterized in that: The first formula is: In the formula, F Criticalvalues is the allowable stress, σ i is the actual compressive stress of the pad after the i-th short-circuit impact, v=1,2,...,n, n is determined according to the number of short-circuit impacts, and u and v are the first fitting coefficients.

7. The method for evaluating the short-circuit resistance of a transformer spacer according to claim 3 or 4, characterized in that: The second formula is: In the formula, an is the first mechanical parameter, b n is the second mechanical parameter, a0 is the initial first mechanical parameter, b0 is the initial second mechanical parameter, σ i is the actual compressive stress of the pad after the i-th short-circuit impact, σ1 is the initial compressive stress, and A1, A2, A3, B1, B2 and B3 are the second fitting coefficients.

8. The method for evaluating the short-circuit resistance of transformer spacers according to claim 5, characterized in that: The determining, based on the first mechanical parameter and the second mechanical parameter, the stiffness of the cushion block after the short-circuit impact comprises: According to the first mechanical parameter, the second mechanical parameter and the third formula Determine the stiffness of the pad after the short-circuit impact; In the formula, k n is the stiffness, k0 is the initial stiffness, a n is the first mechanical parameter, b n is the second mechanical parameter, a0 is the initial first mechanical parameter, b0 is the initial second mechanical parameter, ε is the strain of the cushion block under the compression force after the short-circuit impact, ε0 is the initial strain of the cushion block, and n is determined according to the number of short-circuit impacts.

9. A transformer spacer short-circuit resistance evaluation device, characterized in that: include: An acquisition module, used to acquire an initial first mechanical parameter and an initial second mechanical parameter of the cushion block, and obtain an initial compressive stress of the cushion block after an initial short-circuit impact according to the initial first mechanical parameter and the initial second mechanical parameter; An obtaining module is used for obtaining, for each short-circuit impact after the first short-circuit impact, the first mechanical parameter and the second mechanical parameter after the short-circuit impact according to the initial first mechanical parameter, the initial second mechanical parameter and the initial compressive stress; A first determination module is used to determine the actual compressive stress of the pad after the short-circuit impact based on the first mechanical parameter and the second mechanical parameter, and determine the allowable stress of the pad after the short-circuit impact according to the actual compressive stress and a first formula; the first formula takes the actual compressive stress as an independent variable and the allowable stress as a dependent variable; The second determination module is used to determine the short-circuit resistance of the cushion block after the short-circuit impact according to the ratio of the allowable stress to the actual compressive stress.

10. The transformer spacer short-circuit resistance evaluation device according to claim 9, characterized in that: The device also includes a test module; The test module is used to perform cyclic load tests with different test compression stresses and different cycle times on the same test paperboards; For each test paperboard, after the corresponding cyclic load test is completed, a compression test is performed on the test paperboard until the test paperboard is broken, and the test allowable stress of the test paperboard is obtained; Based on the test compressive stress, the number of cycles and the test allowable stress corresponding to all the test paperboards, a first test formula is obtained by fitting; wherein, in the fitting process, the test compressive stress and the number of cycles are used as independent variables, and the test allowable stress is used as a dependent variable; the first test formula includes the value of the first fitting coefficient; According to the structure of the first test formula and the value of the first fitting coefficient, the first formula is obtained by taking the actual compressive stress as the independent variable and the allowable stress as the dependent variable.

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