A transformer residual magnetism content evaluation method and device, a terminal and a medium

Abstract

The application discloses a transformer residual magnetism content evaluation method and device, a terminal and a medium. The technical scheme provided by the application is based on the correlation between the fitting single-phase current waveform evolution law and the transformer residual magnetism content, a residual magnetism content evaluation formula based on the negative amplitude of the single-phase differential current signal of the transformer core is constructed, three-phase current signals of the transformer are collected during evaluation, the negative amplitude of the single-phase differential current signal, that is, the minimum value of the single-phase differential current signal, is calculated, the transformer core residual magnetism content estimation formula is calculated, the residual magnetism content evaluation result is determined according to the calculation result, and the transformer residual magnetism content estimation accuracy is improved.

Description

Technical Field

[0001] This application relates to the field of power transmission technology, and in particular to a method, apparatus, terminal and medium for assessing the residual magnetism content of a transformer. Background Technology

[0002] When the main transformer of a substation is put into operation, due to the presence of residual magnetism, a large inrush current will be generated at the moment of closing. This can easily lead to the safety hazard of unsuccessful closing of the main transformer, which will directly affect the reliable operation of the power grid. Among them, residual magnetism is one of the main causes of inrush current in transformers. Whether the residual magnetism problem during the switching process of the main transformer of the substation can be accurately controlled is the key to affecting the generation and suppression of inrush current when the transformer is closed under no-load.

[0003] Existing methods for assessing residual magnetism are mostly based on empirical values. For example, the actual magnetic flux data is calculated by collecting electrical data from the transformer, and the actual magnetic flux data is compared with the standard saturation magnetic flux density. Finally, the assessment is made based on the difference between the actual data and the standard data, combined with the personal experience of the assessors. This estimation method is difficult to meet the accuracy requirements of existing residual magnetism assessments when faced with the complex working conditions in actual operation. Summary of the Invention

[0004] This application provides a method, apparatus, terminal, and medium for assessing the residual magnetism content of transformers, which addresses the technical problem of low accuracy in existing residual magnetism content assessment methods.

[0005] To address the aforementioned technical problems, the first aspect of this application provides a method for evaluating the residual magnetism content of a transformer, comprising:

[0006] Obtain the three-phase current signal of the transformer;

[0007] Calculate the differential current signal of a single phase based on the three-phase current signal;

[0008] The minimum differential current is determined from the differential current signal, and the minimum differential current is substituted into a preset residual magnetism content evaluation formula. Based on the evaluation score obtained from the residual magnetism content evaluation formula, and combined with the preset correspondence between the evaluation score and the residual magnetism content level threshold, the first residual magnetism content evaluation result of the transformer is determined. The residual magnetism content evaluation formula is obtained by curve fitting of the minimum differential current samples under multiple different residual magnetism content operating conditions.

[0009] Preferably, the formula for evaluating remanence content is as follows:

[0010] f(x)=a1·exp(b1·x)+a2·exp(b2·x)

[0011] In the formula, a1, a2, b1 and b2 are constants, x is the minimum differential current, and f(x) is the evaluation score.

[0012] Preferably, after determining the first residual magnetism content assessment result of the transformer, the method further includes:

[0013] The differential current signal is decomposed using ICEEMDAN to obtain multiple sets of modal components;

[0014] Calculate the correlation coefficient of each mode component based on the modal components and the differential current signal;

[0015] The direction of remanent magnetization is determined by comparing the minimum differential current in the differential current signal with a preset differential current threshold.

[0016] Based on the comparison results between the remanent magnetization polarity direction and the excitation signal direction, and combined with the correspondence between the comparison results and the modal component screening conditions, the modal component screening conditions are determined, so as to screen out the target modal components according to the modal component screening conditions and the correlation coefficient.

[0017] Calculate the sum of energy entropy values ​​of the target modal components, and determine the second remanent magnetization assessment result of the transformer based on the correspondence between the preset sum of energy entropy values ​​and the remanent magnetization level threshold.

[0018] The final residual magnetism content assessment result of the transformer is obtained by comprehensively evaluating the first and second residual magnetism content assessment results.

[0019] Preferably, the step of determining the modal component screening conditions based on the comparison results between the remanent magnetization polarity direction and the excitation signal direction, combined with the correspondence between the comparison results and the modal component screening conditions, so as to screen out the target modal components according to the modal component screening conditions and the correlation coefficient, specifically includes:

[0020] Based on the comparison between the remanent magnetization polarity direction and the excitation signal direction, if the remanent magnetization polarity direction is the same as the excitation signal, then based on the first modal component screening condition and the correlation coefficient, the modal component with a correlation coefficient greater than the first correlation coefficient threshold is selected as the target modal component.

[0021] If the remanent magnetization polarity direction is opposite to the excitation signal, then according to the second modal component screening conditions and the correlation coefficient, the modal components with a correlation coefficient greater than the second correlation coefficient threshold are selected as the target modal components.

[0022] Preferably, before determining the remanent magnetization polarity direction based on the comparison result of the minimum differential current in the differential current signal and a preset differential current threshold, the method further includes:

[0023] Obtain samples of three-phase currents without residual magnetism under operating conditions with no residual magnetism.

[0024] Based on the three-phase current samples without residual magnetism, the minimum differential current sample without residual magnetism corresponding to the three-phase current samples without residual magnetism is calculated as the differential current threshold.

[0025] Preferably, the formula for calculating the sum of energy entropy is:

[0026]

[0027]

[0028]

[0029] In the formula, E i Let P be the energy value of the i-th modal component. i SumH represents the proportion of the energy of the i-th modal component in the total energy. EN denoted as the sum of the energy entropy of the target modal components, and m as the number of target modal components.

[0030] The second aspect of this application provides a transformer residual magnetism assessment device, comprising:

[0031] The three-phase current acquisition unit is used to acquire the three-phase current signal of the transformer;

[0032] The differential current calculation unit is used to calculate the differential current signal of a single phase based on the three-phase current signal.

[0033] The first residual magnetism content assessment unit is used to determine the minimum differential current from the differential current signal, and substitute the minimum differential current into a preset residual magnetism content assessment formula. Based on the assessment score obtained from the residual magnetism content assessment formula, and combined with the preset correspondence between the assessment score and the residual magnetism content level threshold, the first residual magnetism content assessment result of the transformer is determined. The residual magnetism content assessment formula is obtained by curve fitting of the minimum differential current samples under multiple different residual magnetism content operating conditions.

[0034] Preferably, it further includes: a second remanence content assessment unit, used for:

[0035] The differential current signal is decomposed using ICEEMDAN to obtain multiple sets of modal components;

[0036] Calculate the correlation coefficient of each mode component based on the modal components and the differential current signal;

[0037] The direction of remanent magnetization is determined by comparing the minimum differential current in the differential current signal with a preset differential current threshold.

[0038] Based on the comparison results between the remanent magnetization polarity direction and the excitation signal direction, and combined with the correspondence between the comparison results and the modal component screening conditions, the modal component screening conditions are determined, so as to screen out the target modal components according to the modal component screening conditions and the correlation coefficient.

[0039] Calculate the sum of energy entropy values ​​of the target modal components, and determine the second remanent magnetization assessment result of the transformer based on the correspondence between the preset sum of energy entropy values ​​and the remanent magnetization level threshold.

[0040] The final residual magnetism content assessment result of the transformer is obtained by comprehensively evaluating the first and second residual magnetism content assessment results.

[0041] A transformer residual magnetism assessment terminal is provided in the third aspect of this application, comprising: a memory and a processor;

[0042] The memory is used to store program code corresponding to the transformer residual magnetism assessment method provided in the first aspect of this application.

[0043] The processor is used to execute the program code.

[0044] The fourth aspect of this application provides a computer-readable storage medium storing program code corresponding to the transformer residual magnetism assessment method provided in the first aspect of this application.

[0045] As can be seen from the above technical solutions, this application has the following advantages:

[0046] The technical solution provided in this application is based on the correlation between fitting the evolution law of single-phase current waveform and the residual magnetism content of transformer. It constructs a residual magnetism content evaluation formula based on the negative amplitude of the single-phase differential current signal of transformer core. During the evaluation, the three-phase current signal of transformer is collected, and the negative amplitude of single-phase differential current signal, i.e. the minimum value of single-phase differential current signal, is calculated. The residual magnetism content of transformer core is estimated by formula, and the residual magnetism content evaluation result is determined based on the calculation result, thereby improving the accuracy of transformer residual magnetism content estimation. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1This is a flowchart illustrating an embodiment of a method for evaluating the residual magnetism content of a transformer provided in this application.

[0049] Figure 2 This is a schematic diagram illustrating the influence of different residual magnetism contents on the negative amplitude of the phase A differential current signal, as provided in this application.

[0050] Figure 3 This is a flowchart illustrating another embodiment of a transformer residual magnetism assessment method provided in this application.

[0051] Figure 4 A flowchart illustrating the secondary residual magnetism level estimation process in a transformer residual magnetism content assessment method provided in this application.

[0052] Figure 5 This is a schematic diagram of one embodiment of a transformer residual magnetism assessment device provided in this application.

[0053] Figure 6 This is a schematic diagram of the structure of an embodiment of a transformer residual magnetism assessment terminal provided in this application. Detailed Implementation

[0054] This application provides a method, apparatus, terminal, and medium for assessing the residual magnetism content of transformers, which addresses the technical problem of low accuracy in existing residual magnetism content assessment methods.

[0055] To make the inventive objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0056] First, a detailed description of an embodiment of a transformer residual magnetism assessment method provided in this application is as follows:

[0057] Please see Figure 1 This embodiment provides a method for evaluating the residual magnetism content of a transformer, including:

[0058] Step 101: Obtain the three-phase current signal of the transformer;

[0059] It should be noted that, firstly, for transformer equipment that requires evaluation of residual magnetism, the three-phase current signal of the transformer should be collected, preferably the three-phase transformer current signal under unbiased magnetization conditions.

[0060] Step 102: Calculate the differential current signal of a single phase based on the three-phase current signal;

[0061] It should be noted that, based on the three-phase current signals acquired in step 101, most existing three-phase transformers are three-phase transformers that adopt the "star-angle" phase conversion method, and the transformers employ a longitudinal differential protection strategy. The differential current signals of each phase are obtained by subtracting the currents of two phases. For example, the differential current signal of phase A is: i da =i a -i b The differential current signal of any one phase can be used for subsequent evaluation, and the differential current signal of phase A is generally preferred.

[0062] Step 103: Determine the minimum differential current from the differential current signal, and substitute the minimum differential current into the preset residual magnetism content evaluation formula. Based on the evaluation score obtained from the residual magnetism content evaluation formula, and combined with the preset correspondence between the evaluation score and the residual magnetism content level threshold, determine the first residual magnetism content evaluation result of the transformer.

[0063] The formula for evaluating remanent magnetization is obtained by curve fitting of the minimum differential current samples under multiple operating conditions with different remanent magnetization contents.

[0064] It should be noted that after step 102, based on the selected single-phase differential current signal, the minimum value of the signal, i.e., the minimum differential current, is determined according to its waveform. This minimum differential current is then substituted into a preset residual magnetism content evaluation formula to obtain an evaluation score. In this embodiment, the residual magnetism content evaluation formula is obtained by curve fitting of minimum differential current samples from multiple operating conditions with different residual magnetism contents. It is assumed that each set of minimum differential current samples is obtained based on the single-phase differential current signal of phase A. Through comparative analysis of phase A current signals under various residual magnetism content conditions, it can be seen that the influence of different residual magnetism content conditions on the negative amplitude of the phase A differential current signal is as follows: Figure 2 As shown, Figure 2 As shown, when the excitation signal remains constant, if the excitation signal is in the same direction as the remanence content, the negative amplitude decreases as the remanence content increases, meaning the minimum value within the signal region increases. Conversely, if the excitation signal is in the opposite direction to the remanence content, the negative amplitude increases as the remanence content increases, meaning the minimum value within the signal region decreases. Therefore, after collecting the minimum values ​​of each differential current signal and performing curve fitting, the remanence content evaluation formula is obtained as follows:

[0065] f(x)=a1·exp(b1·x)+a2·exp(b2·x)

[0066] Where a1, a2, b1, and b2 are preset constant coefficients, x is the minimum differential current, and f(x) is the evaluation score. A confidence interval of 95% is used, and the reference values ​​for each coefficient are as follows:

[0067] a1=-15.04; b1=0.004506; a2=16.09; b2=0.04643.

[0068] Finally, after obtaining the remanent magnetization content assessment score, based on the actual existing engineering, the levels are divided into mild (±(0pu~0.2pu), moderate (±(0.21pu~0.50pu), and severe (±(0.51pu~0.80pu)) according to the weight of each remanent magnetization content.

[0069] Based on the above embodiments, the transformer residual magnetism assessment method provided in this application may further include the following:

[0070] Furthermore, such as Figure 3 As shown, after determining the first residual magnetism content assessment result of the transformer in step 103 of this embodiment, the following may also be included:

[0071] Step 104: Perform ICEEMDAN decomposition on the differential current signal to obtain multiple sets of modal components;

[0072] Step 105: Calculate the correlation coefficient of each modal component based on the modal components and the differential current signal;

[0073] Step 106: Determine the direction of remanent magnetization polarity based on the comparison result between the minimum differential current in the differential current signal and the preset differential current threshold.

[0074] Step 107: Based on the comparison results between the remanent magnetization polarity direction and the excitation signal direction, and combined with the correspondence between the comparison results and the modal component screening conditions, determine the modal component screening conditions, so as to screen out the target modal components according to the modal component screening conditions and the correlation coefficient.

[0075] Step 108: Calculate the sum of energy entropy values ​​of the target modal components, and determine the second remanent magnetization assessment result of the transformer based on the correspondence between the preset sum of energy entropy values ​​and the remanent magnetization level threshold.

[0076] Step 109: Based on the first and second residual magnetism content assessment results, a comprehensive assessment is conducted to obtain the final residual magnetism content assessment result of the transformer.

[0077] It should be noted that steps 104 to 108 provided in this embodiment are the process for evaluating the secondary residual magnetism content of the transformer provided in this embodiment:

[0078] First, based on the single-phase differential current signal obtained in step 102, ICEEMDAN decomposition is performed. Taking the differential current signal of phase A as an example, ICEEMDAN decomposition is performed on the differential current signal of phase A to obtain multiple sets of modal components. The specific process can be referred to the following example:

[0079] (1) Add preset Gaussian white noise to the differential current signal of phase A. (Preset signal + white noise)

[0080]

[0081] In the above formula, x is the differential current signal of phase A; ω (n) α1 represents the i-th group of Gaussian white noise used for auxiliary decomposition; α1 is the expected signal-to-noise ratio of the signal during the first decomposition; E1(·) is the first-order mode component of the phase A differential current signal after EMD decomposition.

[0082] (2) Calculate the residual r1 of the first decomposition.

[0083]

[0084] In the formula, M(·) is the local mean operator of the signal, and I is the number of white noise groups.

[0085] (3) Calculate the first-order modal component IMF1 of the original signal:

[0086] IMF1 = x - r1

[0087] (4) Construct the i-th (i≥2) group of signals with added Gaussian white noise.

[0088]

[0089] In the formula, α i E represents the expected signal-to-noise ratio of the signal at the i-th decomposition. i () represents the i-th modal component of the phase A differential current signal after EMD decomposition.

[0090] (5) Calculate the i-th residual r i .

[0091]

[0092] (6) Calculate the i-th modal component.

[0093] IMF i =r i-1 -r i

[0094] (7) Iteration termination condition.

[0095]

[0096] In the formula, σ is the standard deviation between adjacent components. During the iterative calculation of the algorithm, if the condition is not met, let i = i + 1, return to step (4) to calculate the next value of i, until the iteration termination condition is met. That is, when σ < 0.2, the iteration terminates.

[0097] Then, the correlation coefficients of each modal component obtained from ICEEMDAN are calculated:

[0098] Because the modal decomposition number of ICEEMDAN is adaptive, the correlation coefficients of each modal component obtained in step 1 need to be calculated before calculating and evaluating the energy entropy value. The correlation coefficient β of each modal component is... i The formula is as follows:

[0099]

[0100] In the above formula: x i For the i-th modal component, y is the mean value of the i-th modal component; y is the differential current signal of phase A. This is the average value of the differential current signal of phase A.

[0101] Next, the direction of remanent magnetization is determined by comparing the minimum differential current in the differential current signal with the preset differential current threshold.

[0102] The magnitude of the reverse amplitude when there is no remanent magnetization can be used as a threshold to determine the direction of remanence, as shown in the following formula:

[0103]

[0104] In the above formula, I i I represents the differential current signal of phase A obtained under different remanence contents. PE The differential current signal of phase A is obtained under conditions of no residual magnetism.

[0105] like Figure 4 As shown, based on the complexity of the current signal waveform and energy distribution characteristics in both forward and reverse directions, a method is proposed to use the sum of modal energy entropy (SumHEN) with the correlation coefficient as the primary judgment condition, as the criterion for remanence level estimation, to perform secondary remanence level estimation, as follows:

[0106] When the excitation signal is in the same direction as the remanence, the current signal includes both positive and negative pole regions. The energy entropy sum is calculated using modal components with a correlation coefficient > 0.15, i.e.:

[0107] When 0.7 <SumH EN When <1, the remanence content is judged to be slight; when 1 <SumH EN When the remanence is less than 1.1, it is judged to be moderate; when it is 1.1... <SumHEN At that time, the residual magnetism content was determined to be severe.

[0108] When the excitation signal is opposite to the direction of remanence, the current signal range is basically in the negative pole region. The energy entropy sum is calculated using modal components with a correlation coefficient > 0.5, i.e.:

[0109] When 0.7 <SumH EN When the remanence is 0.5%, it is judged to be slightly high; when it is 0.5%, it is judged to be low. <SumH EN When SumH < 0.7, the remanence content is judged to be moderate; when SumH EN When the remanence is less than 0.5, it is judged to be heavy.

[0110] The formula for calculating the sum of energy entropy is:

[0111]

[0112]

[0113]

[0114] In the formula, E i Let P be the energy value of the i-th modal component. i SumH represents the proportion of the energy of the i-th modal component in the total energy. EN denoted as the sum of the energy entropy of the target modal components, and m as the number of target modal components.

[0115] It should be noted that the threshold values ​​provided in the above embodiments are all exemplary and can be adjusted according to the actual situation in practical applications.

[0116] Finally, based on the first and second remanence content assessment results obtained in steps 103 and 108, a weighted analysis is performed on the two assessment results to obtain the final assessment result.

[0117] The formula is as follows:

[0118] Remanence content assessment grade = First remanence content assessment grade * 0.75 + Second remanence content assessment grade * 0.25.

[0119] Based on the remanence content levels defined in steps 101 to 108, after the second remanence content assessment, the median of the remanence content range for the corresponding level is taken as the final remanence content assessment value. For example, a light remanence content is taken as 0.1 pu, a moderate remanence content as 0.35 pu, and a severe remanence content as 0.65 pu. After the value is determined, a weighted analysis is performed on the results of the first and second remanence content assessments.

[0120] If, under a certain operating condition, the minimum current of phase A is -1.1369A, which is greater than the XPE value of -1.6321A, then the polarity is positive and in the same direction. Substituting this into (II), we can obtain the first residual magnetism content assessment result as 0.2996 pu. Substituting this into (IV), we can obtain the second residual magnetism content assessment result as mild. Therefore, we take 0.10 pu. The final residual magnetism content level is 0.2996*0.75+0.10*0.25=0.2497 pu, which is within the range of [0.21-0.50]. Therefore, we take the final residual magnetism content level as moderate.

[0121] The solution provided in this embodiment is based on the waveform evolution characteristics of current signals under multiple remanent magnetization conditions. It proposes a criterion for judging the direction of remanent magnetization in transformer cores based on the waveform evolution law and an empirical formula for estimating the remanent magnetization content of transformer cores, which improves the accuracy of transformer remanent magnetization content estimation. At the same time, it also uses the ICEEMDAN algorithm to extract time-domain features and uses the correlation coefficient to select the energy entropy as the sum quantity to parametrically represent the current signal and remanent magnetization content as a secondary remanent magnetization content level estimation, which further improves the accuracy of transformer remanent magnetization content estimation.

[0122] The above content is a detailed description of an embodiment of a transformer residual magnetism content assessment method provided in this application. The following is a detailed description of an embodiment of a transformer residual magnetism content assessment device, terminal, and computer-readable storage medium provided in this application.

[0123] Please see Figure 5 The second aspect of this application provides a transformer residual magnetism assessment device, comprising:

[0124] The three-phase current acquisition unit 201 is used to acquire the three-phase current signal of the transformer;

[0125] The differential current calculation unit 202 is used to calculate the differential current signal of a single phase based on the three-phase current signal.

[0126] The first residual magnetism content assessment unit 203 is used to determine the minimum differential current from the differential current signal and substitute the minimum differential current into the preset residual magnetism content assessment formula. Based on the assessment score obtained from the residual magnetism content assessment formula, and combined with the preset correspondence between the assessment score and the residual magnetism content level threshold, the first residual magnetism content assessment result of the transformer is determined. The residual magnetism content assessment formula is obtained by curve fitting of the minimum differential current samples of multiple different residual magnetism content operating conditions.

[0127] Furthermore, it also includes: a second remanence content assessment unit 204, used for:

[0128] The differential current signal is decomposed using ICEEMDAN to obtain multiple sets of modal components;

[0129] Calculate the correlation coefficient of each modal component based on the modal components and the differential current signal;

[0130] The direction of remanent magnetization polarity is determined by comparing the minimum differential current in the differential current signal with the preset differential current threshold.

[0131] Based on the comparison results between the remanent magnetization polarity direction and the excitation signal direction, and combined with the correspondence between the comparison results and the modal component screening conditions, the modal component screening conditions are determined, so as to screen out the target modal components according to the modal component screening conditions and the correlation coefficient.

[0132] Calculate the sum of energy entropy values ​​of the target modal components, and determine the second remanent magnetization assessment result of the transformer based on the correspondence between the preset sum of energy entropy values ​​and the remanent magnetization level threshold.

[0133] The final evaluation result of the transformer's residual magnetism content is obtained by comprehensively evaluating the results of the first and second residual magnetism content assessments.

[0134] like Figure 6 As shown, the third aspect of this application provides a transformer residual magnetism content assessment terminal. The terminal type includes, but is not limited to, personal computers, industrial computers, servers and embedded intelligent devices. The terminal mainly consists of a memory 33 and a processor 31, which can be connected via a communication bus 34.

[0135] The memory 33 is used to store program code corresponding to the transformer residual magnetism assessment method provided in the first aspect of this application.

[0136] Processor 31 is used to execute program code.

[0137] The fourth aspect of this application provides a computer-readable storage medium storing program code corresponding to the transformer residual magnetism assessment method provided in the first aspect of this application.

[0138] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the terminals, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0139] In the several embodiments provided in this application, it should be understood that the disclosed terminals, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection between devices or units through some interfaces, and may be electrical, mechanical, or other forms.

[0140] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0141] It should be understood that in this application, "at least one (item)" means one or more, and "more than" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0142] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0143] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0144] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0145] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for evaluating the residual magnetism content of a transformer, characterized in that, include: Obtain the three-phase current signal of the transformer; Calculate the differential current signal of a single phase based on the three-phase current signal; The minimum differential current is determined from the differential current signal, and the minimum differential current is substituted into a preset residual magnetism content evaluation formula. Based on the evaluation score obtained from the residual magnetism content evaluation formula, and combined with the preset correspondence between the evaluation score and the residual magnetism content level threshold, the first residual magnetism content evaluation result of the transformer is determined. The residual magnetism content evaluation formula is obtained by curve fitting of the minimum differential current samples under multiple different residual magnetism content operating conditions.

2. The method for evaluating the residual magnetism content of a transformer according to claim 1, characterized in that, The formula for evaluating remanence content is as follows: f(x)=a1·exp(b1·x)+a2·exp(b2·x) In the formula, a1, a2, b1 and b2 are constants, x is the minimum differential current, and f(x) is the evaluation score.

3. The method for evaluating the residual magnetism content of a transformer according to claim 1, characterized in that, After determining the first residual magnetism assessment result of the transformer, the following is also included: The differential current signal is decomposed using ICEEMDAN to obtain multiple sets of modal components; Calculate the correlation coefficient of each mode component based on the modal components and the differential current signal; The direction of remanent magnetization is determined by comparing the minimum differential current in the differential current signal with a preset differential current threshold. Based on the comparison results between the remanent magnetization polarity direction and the excitation signal direction, and combined with the correspondence between the comparison results and the modal component screening conditions, the modal component screening conditions are determined, so as to screen out the target modal components according to the modal component screening conditions and the correlation coefficient. Calculate the sum of energy entropy values ​​of the target modal components, and determine the second remanent magnetization assessment result of the transformer based on the correspondence between the preset sum of energy entropy values ​​and the remanent magnetization level threshold. The final residual magnetism content assessment result of the transformer is obtained by comprehensively evaluating the first and second residual magnetism content assessment results.

4. The method for evaluating the residual magnetism content of a transformer according to claim 3, characterized in that, The step of determining the modal component screening conditions based on the comparison results between the remanent magnetization polarity direction and the excitation signal direction, combined with the correspondence between the comparison results and the modal component screening conditions, and then screening out the target modal components according to the modal component screening conditions and the correlation coefficient, specifically includes: Based on the comparison between the remanent magnetization polarity direction and the excitation signal direction, if the remanent magnetization polarity direction is the same as the excitation signal, then based on the first modal component screening condition and the correlation coefficient, the modal component with a correlation coefficient greater than the first correlation coefficient threshold is selected as the target modal component. If the remanent magnetization polarity direction is opposite to the excitation signal, then according to the second modal component screening conditions and the correlation coefficient, the modal components with a correlation coefficient greater than the second correlation coefficient threshold are selected as the target modal components.

5. The method for evaluating the residual magnetism content of a transformer according to claim 3, characterized in that, Before determining the remanent magnetization polarity direction based on the comparison result between the minimum differential current in the differential current signal and the preset differential current threshold, the method further includes: Obtain samples of three-phase currents without residual magnetism under operating conditions with no residual magnetism. Based on the three-phase current samples without residual magnetism, the minimum differential current sample without residual magnetism corresponding to the three-phase current samples without residual magnetism is calculated as the differential current threshold.

6. The method for evaluating the residual magnetism content of a transformer according to claim 3, characterized in that, The formula for calculating the sum of energy entropies is: In the formula, E i Let P be the energy value of the i-th modal component. i SumH represents the proportion of the energy of the i-th modal component in the total energy. EN denoted as the sum of the energy entropy of the target modal components, and m as the number of target modal components.

7. A device for evaluating the residual magnetism content of a transformer, characterized in that, include: The three-phase current acquisition unit is used to acquire the three-phase current signal of the transformer; The differential current calculation unit is used to calculate the differential current signal of a single phase based on the three-phase current signal. The first residual magnetism content assessment unit is used to determine the minimum differential current from the differential current signal, and substitute the minimum differential current into a preset residual magnetism content assessment formula. Based on the assessment score obtained from the residual magnetism content assessment formula, and combined with the preset correspondence between the assessment score and the residual magnetism content level threshold, the first residual magnetism content assessment result of the transformer is determined. The residual magnetism content assessment formula is obtained by curve fitting of the minimum differential current samples under multiple different residual magnetism content operating conditions.

8. The transformer residual magnetism assessment device according to claim 7, characterized in that, Also includes: The second remanence content assessment unit is used for: The differential current signal is decomposed using ICEEMDAN to obtain multiple sets of modal components; Calculate the correlation coefficient of each mode component based on the modal components and the differential current signal; The direction of remanent magnetization is determined by comparing the minimum differential current in the differential current signal with a preset differential current threshold. Based on the comparison results between the remanent magnetization polarity direction and the excitation signal direction, and combined with the correspondence between the comparison results and the modal component screening conditions, the modal component screening conditions are determined, so as to screen out the target modal components according to the modal component screening conditions and the correlation coefficient. Calculate the sum of energy entropy values ​​of the target modal components, and determine the second remanent magnetization assessment result of the transformer based on the correspondence between the preset sum of energy entropy values ​​and the remanent magnetization level threshold. The final residual magnetism content assessment result of the transformer is obtained by comprehensively evaluating the first and second residual magnetism content assessment results.

9. A terminal for assessing the residual magnetism content of a transformer, characterized in that, include: Memory and processor; The memory is used to store program code corresponding to the transformer residual magnetism assessment method as described in any one of claims 1 to 6; The processor is used to execute the program code.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium contains program code corresponding to the transformer residual magnetism assessment method as described in any one of claims 1 to 6.

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