A transformer winding strength detection method and system based on short-circuit test

Abstract

The present invention discloses a transformer winding strength detection method based on a short-circuit test, comprising the following steps: S1: According to a transformer parameter table, the winding coil parameters are determined, and accordingly the transformer single coil size, the size of the support bar and the size of the pad are obtained; S2: According to the single coil size obtained in step S1, the support bar and the pad are ignored, and the winding compression height is evenly distributed to each oil channel, a two-dimensional coil-by-coil model is constructed, a single short-circuit impact current excitation is applied to the two-dimensional coil-by-coil model, and the displacement deformation distribution of each coil is obtained by coupling the electromagnetic-structural field calculation. The boundary constraint effect of the support bar and the pad is considered in the three-dimensional single coil model, which can more accurately simulate the stress condition of the winding under the short-circuit impact. This simulation analysis considering the boundary constraint can more realistically reflect the deformation and stress distribution of the winding under the short-circuit impact, and provide more reliable data support for evaluating the winding strength.

Description

Technical Field

[0001] The invention belongs to the technical field of safe operation and accidents of power transformers in power systems, and in particular relates to a transformer winding strength detection method and system based on a short-circuit test. Background Art

[0002] As a key equipment in the power transmission and transformation link, the safe and reliable operation of power transformers is the top priority of power grid maintenance. If the transformer's short-circuit resistance is insufficient, the huge short-circuit electromagnetic force will cause the winding to "swell" or "fall" when a short-circuit fault occurs, which may evolve into a more serious internal transformer hidden danger, causing a huge impact on the continuous and stable power supply of the power grid in the entire region.

[0003] The radial deformation displacement caused by short-circuit force on the winding cannot be ignored. Among the existing detection methods, there are some that use the short-circuit impedance method or frequency response method to roughly determine the degree of winding deformation, but it is impossible to determine the coil number and relatively accurate position where the larger deformation displacement occurs; there are also some that use finite element software to calculate the short-circuit electromotive force and displacement law of the winding, but there is a lack of strong verification by short-circuit prototype tests, resulting in a large difference between the displacement deformation distribution obtained by simulation and the actual short-circuit test results; currently, the technology of capturing coil displacement with the help of grating sensors has been initially applied, but the workload of post-processing data is still huge. Summary of the invention

[0004] The purpose of the present invention is to address the problems existing in the prior art and to provide a transformer winding strength detection method and system based on a short-circuit test, so as to solve the problem that the transformer winding coil unit is deformed and loses stability due to a huge short-circuit electromotive force generated by a sharp increase in the leakage magnetic field and the short-circuit current, thereby endangering the safe operation of the transformer. The existing simulation method for predicting the winding strength according to the calculation results of the finite element model has too much calculation amount and does not converge.

[0005] To achieve the above object, on the one hand, the present invention provides a transformer winding strength detection method based on a short-circuit test, comprising the following steps:

[0006] S1: According to the transformer parameter table, the winding coil parameters are determined, including the compression rate, reactance height, single coil size and oil channel gap of the low voltage inner winding, the high voltage winding and the low voltage outer winding, and the transformer single coil size, the support bar size and the spacer block size are obtained accordingly;

[0007] S2: Based on the single coil size obtained in step S1, ignoring the stays and pads, the winding compression height is evenly distributed to each oil channel, a two-dimensional coil-by-coil model is constructed, a single short-circuit impulse current excitation is applied to the two-dimensional coil-by-coil model, and the displacement deformation distribution of each coil is obtained by coupling electromagnetic-structural field calculation;

[0008] S3: According to the winding coil parameters in step S1, hollow cylinders with different inner and outer diameters are respectively established as low-voltage inner windings, high-voltage windings and low-voltage outer windings to participate in electromagnetic calculations, material parameters and constraints are set, and a three-dimensional winding model of the transformer is constructed. Multiple short-circuit impulse current excitations are applied to the three-dimensional winding model of the transformer. After each short-circuit impulse current excitation, the deformation result is saved as the initial geometric model for the next impulse, and the short-circuit electromagnetic force body density distribution under the repeated short-circuit impulse current excitations is obtained, and the short-circuit impedance and the relative impedance change rate after each short-circuit impulse current excitation are calculated;

[0009] S4: According to the winding coil parameters obtained in step S1 and the displacement deformation distribution obtained in step S2, the coil with the largest deformation is selected to construct a three-dimensional single coil model, the short-circuit electromagnetic force body density distribution obtained in step S3 is applied to the three-dimensional single coil model, and the deformation change rate after each calculation is saved as the initial geometric model for the next time;

[0010] S5: Select a brand new power transformer to conduct a short-circuit test, apply a short-circuit current that is consistent with the short-circuit impulse current excitation in step S2 and step S3, measure the short-circuit impedance and calculate the relative impedance change rate;

[0011] S6: Compare the short-circuit impedance, relative impedance change rate and maximum cumulative deformation change rate calculated by the three-dimensional single-wire cake model in step S3 and step S5. If the short-circuit impedance and relative impedance change rate obtained in step S3 and step S5 are both above the target values ​​in a short-circuit impact, and the maximum cumulative deformation change rate of the three-dimensional single-wire cake model is above the limit value, it is judged that the winding strength is insufficient.

[0012] This method combines finite element simulation and short-circuit test to comprehensively and accurately evaluate the strength of transformer windings. Through gradually in-depth simulation analysis (from two-dimensional to three-dimensional, and then to the single-wire pancake model), the deformation of the winding under the impact of short circuit can be accurately captured, providing a reliable basis for judging whether the winding is unstable. At the same time, this method is combined with actual short-circuit tests to further verify the accuracy of the simulation results and improve the reliability of the evaluation.

[0013] Furthermore, the two-dimensional pancake-by-pancake model constructed in step S2 is simplified by ignoring the stays and the spacers and evenly distributing the winding compression height to each oil channel.

[0014] By ignoring the stays and pads and evenly distributing the winding compression height to each oil channel, the construction process of the two-dimensional pancake-by-pancake model is simplified, the computational complexity is reduced, and the simulation efficiency is improved. At the same time, this simplification does not significantly affect the accuracy of the simulation results.

[0015] Furthermore, the three-dimensional single-line pie model in step S4 imposes boundary constraints on the stays and pads, and the constraints include spring support and fixed constraints.

[0016] Furthermore, in step S5, a short-circuit impedance tester is used to measure the short-circuit impedance after each short-circuit impact.

[0017] Using a new power transformer to conduct multiple short-circuit impact accumulation tests can more directly verify the accuracy of the simulation results. At the same time, using a short-circuit impedance tester to measure the short-circuit impedance after each short-circuit impact can more accurately evaluate the changes in the electrical performance of the winding under short-circuit impact. This test method combined with simulation analysis can more comprehensively evaluate the strength of the transformer winding.

[0018] On the other hand, the present invention provides a transformer winding strength detection system based on a short-circuit test, comprising:

[0019] A parameter determination module is used to determine the winding coil parameters according to the transformer parameter table, and obtain the transformer single coil size, the support bar size and the spacer block size;

[0020] A model testing module is used to construct a two-dimensional coil-by-coil model and a three-dimensional winding model according to winding coil parameters, respectively, to perform short-circuit impulse current excitation on the two-dimensional coil-by-coil model and the three-dimensional winding model, respectively, to obtain the displacement deformation distribution of each coil in the two-dimensional coil-by-coil model and the cumulative short-circuit electromagnetic force body density distribution of the three-dimensional winding model, respectively, to calculate the short-circuit impedance and the relative impedance change rate of the three-dimensional winding model after each short-circuit impulse current excitation, to select the coil with the largest variable after the two-dimensional coil-by-coil model test to construct a three-dimensional single-coil model, to apply the short-circuit electromagnetic force body density distribution obtained from the three-dimensional winding model test to the three-dimensional single-coil model, and to calculate the maximum cumulative deformation change rate of the three-dimensional single-coil model;

[0021] A data interface module is used to obtain the short-circuit impedance calculated after the short-circuit test of the actual power transformer and calculate the relative impedance change rate;

[0022] The comparison and analysis module compares the data obtained by the data interface module, the data calculated by the three-dimensional winding model test module, and the data calculated by the three-dimensional single-wire model test module to determine whether the winding strength meets the standard.

[0023] Furthermore, the data comparison of the comparison and analysis module includes: if the short-circuit impedance and the relative impedance change rate calculated by the three-dimensional winding model test module and the three-dimensional single-wire cake model test module are both above the target values ​​in a certain short-circuit impact, and the maximum cumulative deformation change rate of the three-dimensional single-wire cake model is above the limit value, then it is judged that the winding strength is insufficient.

[0024] Furthermore, the method of obtaining the repeated short-circuit electromagnetic force body density distribution of the three-dimensional winding model includes: applying multiple short-circuit impulse current excitations to the three-dimensional winding model of the transformer, and saving the deformation result after each short-circuit impulse current excitation as the initial geometric model of the next impulse.

[0025] Further, the calculation of the maximum cumulative deformation change rate of the three-dimensional single-wire cake model includes: applying the repeated short-circuit electromagnetic force body density distribution of the three-dimensional winding model to the three-dimensional single-wire cake model, and saving the deformation change rate after each calculation as the next initial geometric model.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. This method combines finite element simulation and short-circuit test to comprehensively and accurately evaluate the strength of transformer windings. Through gradual and in-depth simulation analysis, from two-dimensional to three-dimensional, and then to the single-wire pancake model, it can accurately capture the deformation of the winding under short-circuit impact, providing a reliable basis for judging whether the winding is unstable.

[0028] 2. In the construction of the two-dimensional pancake-by-pancake model, the model is simplified by ignoring the stays and pads and evenly distributing the winding compression height to each oil channel, which reduces the calculation complexity and improves the simulation efficiency. At the same time, this simplification does not significantly affect the accuracy of the simulation results.

[0029] 3. By coupling the electromagnetic-structural field to calculate the displacement and deformation distribution of the coil under a single short-circuit impact, the actual short-circuit impact process can be simulated more accurately, and the dynamic response of the winding under the short-circuit impact can be captured. This helps to better understand the behavioral characteristics of the winding under short-circuit conditions and provides more abundant information for evaluating the winding strength.

[0030] 4. In multiple short-circuit impulse current excitations, the deformation results after each short-circuit impulse are saved as the initial geometric model for the next impulse, taking into account the impact of the cumulative effect on the winding strength. This cumulative effect analysis is crucial for evaluating the stability of the winding in long-term operation and helps to improve the accuracy and comprehensiveness of the evaluation.

[0031] 5. By calculating the short-circuit impedance and the relative change rate of impedance after each short-circuit impulse current excitation, the change in the electrical performance of the winding under the short-circuit impulse can be evaluated. This helps to more accurately determine whether the winding is damaged or unstable due to the short-circuit impulse, providing a strong guarantee for the safe operation of the transformer.

[0032] 6. The boundary constraints of the support bars and pads are considered in the three-dimensional single-wire model, which can more accurately simulate the stress of the winding under short-circuit impact. This simulation analysis considering boundary constraints can more realistically reflect the deformation and stress distribution of the winding under short-circuit impact, providing more reliable data support for evaluating the winding strength.

[0033] 7. By selecting a new power transformer for short-circuit test and comparing it with the simulation results, the accuracy and reliability of the simulation method can be verified. This test verification method helps to further improve the accuracy and credibility of the evaluation results and provide strong support for the design and manufacture of transformers. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a flow chart of the transformer winding strength detection method based on short-circuit test of the present invention;

[0035] Figure 2 A schematic diagram of a two-dimensional pancake-by-pancake finite element model of a transformer according to an embodiment of the present invention;

[0036] Figure 3 A schematic diagram of a three-dimensional winding model of a transformer according to an embodiment of the present invention;

[0037] Figure 4 A schematic diagram of a three-dimensional single-line pie model according to an embodiment of the present invention;

[0038] Figure 5 It is a partial enlarged view of the three-dimensional single-line pie model of an embodiment of the present invention.

[0039] In the figure: 1. Iron core; 2. Low-voltage inner winding; 3. High-voltage winding; 4. Low-voltage outer winding; 5. Winding; 6. Support bar; 7. Spacer. DETAILED DESCRIPTION

[0040] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] like Figure 1 —5, the specific scheme of the embodiment is as follows: A transformer winding strength detection method based on a short-circuit test comprises the following steps:

[0042] S1: According to the transformer parameter table (Table 1):

[0043]

[0044] Determine the winding coil parameters, which include the compression ratio, reactance height, single coil size and oil channel gap of the low voltage inner winding, high voltage winding and low voltage outer winding, and obtain the transformer single coil size, support bar size and spacer size accordingly;

[0045] Specifically: According to the transformer parameter table, the compression rates of the low voltage inner winding, high voltage winding and low voltage outer winding are 7.54%, 7.68% and 7.94% respectively, and the reactance heights are 455mm, 455mm and 415mm respectively;

[0046] The single-wire size of the low-voltage inner winding is 15×11.82mm, and the oil channel gaps are 3×16.84mm, 11×12.84mm, and 3×16.84mm from top to bottom, respectively. The low-voltage inner winding is modeled as 18 wires.

[0047] The single-wire size of the high-voltage winding is 36×9.1mm, and the oil channel gaps are 5×8.7mm, 28×2.7mm, and 2×3.88mm from top to bottom. The high-voltage winding is modeled as 36 wires.

[0048] The single-wire coil of the low-voltage outer winding is 14.5×11.9 in this village, and the oil channel gaps are 6×7.1mm, 4×9.1mm and 9×13.1mm from top to bottom respectively. The low-voltage outer winding is modeled as 20 coils;

[0049] S2: Based on the single coil size obtained in step S1, ignoring the stays and pads, the winding compression height is evenly distributed to each oil channel, and a two-dimensional coil-by-coil model is constructed. The two-dimensional coil-by-coil model is subjected to a single short-circuit impact current excitation, and the displacement deformation distribution of each coil is obtained by coupling electromagnetic-structural field calculation. In this way, the displacement deformation distribution of each coil under a single short-circuit impact can be obtained;

[0050] In this embodiment, COMSOL finite element software is generally used to construct the model. The two-dimensional pancake model ignores the struts and pads, and the winding compression height is evenly distributed to each oil channel to achieve the effect of establishing a simplified two-dimensional pancake model.

[0051] S3: According to the winding coil parameters in step S1, hollow cylinders with different inner and outer diameters are respectively established as low-voltage inner windings, high-voltage windings and low-voltage outer windings to participate in electromagnetic calculations, material parameters and constraints are set, and a three-dimensional winding model of the transformer is constructed. Multiple short-circuit impulse current excitations are applied to the three-dimensional winding model of the transformer. After each short-circuit impulse current excitation, the deformation result is saved as the initial geometric model for the next impulse, and the short-circuit electromagnetic force body density distribution under the repeated short-circuit impulse current excitations is obtained, and the short-circuit impedance and the relative impedance change rate after each short-circuit impulse current excitation are calculated;

[0052] The specific calculation method of short-circuit impedance and relative impedance change rate is as follows:

[0053] The two formulas are as follows:

[0054]

[0055]

[0056] Calculate the short-circuit impedance and relative change rate after each short-circuit impulse current excitation calculation;

[0057] Where Uk is the short-circuit impedance, is the relative change rate of impedance, D is the equivalent magnetic leakage area, r is the Rockwell coefficient, IN1 is the rated current; K is the additional reactance coefficient; H K12 is the winding reactance height; et is the turn potential; w is the number of winding turns; is the operating frequency; L is the transformer reactance value; W1 is the total magnetic field energy; Zk and Zk-1 are the short-circuit impedance values ​​calculated by the model twice before and after respectively;

[0058] S4: According to the winding coil parameters obtained in step S1 and the displacement deformation distribution obtained in step S2, the coil with the largest deformation is selected to construct a three-dimensional single coil model, and the short-circuit electromagnetic force body density distribution obtained in step S3 is applied to the constructed three-dimensional single coil model. The three-dimensional single coil model includes the winding 5, and boundary constraints are imposed on the stays 6 and the pads 7. The constraints include spring support and fixed constraints, and the deformation change rate after each calculation is saved as the initial geometric model for the next time;

[0059] After each short-circuit impulse current excitation of the three-dimensional single-line cake model, the calculation result will show the maximum deformation change of the cake. Since the simulation is cumulative, the maximum cumulative deformation change of the single-line cake is obtained. In fact, the simulation result can show the deformation of each position of the single-line cake model in a circle. The cumulative maximum deformation Am of each simulation result can be directly read out. The previous maximum deformation change is recorded as Am-1, and the next maximum deformation change is recorded as Am, according to the following formula:

[0060]

[0061] Get the maximum cumulative deformation change rate X ;

[0062] It should be noted that the three-dimensional winding model of the transformer established in step S5 is used to calculate the density distribution of the winding short-circuit electromagnetic force body under repeated short-circuit impacts, which can avoid the huge amount of calculation and model non-convergence caused by multi-field coupling analysis in the subsequent single-line fine modeling;

[0063] S5: Select a brand new power transformer to conduct a short-circuit test, apply a short-circuit current that is consistent with the short-circuit impulse current excitation in step S2 and step S3, measure the short-circuit impedance and calculate the relative impedance change rate;

[0064] Specific: After each short-circuit test, the short-circuit impedance is measured using an impedance tester and according to the following formula:

[0065]

[0066] Calculate the relative rate of change of impedance obtained from the experiment.

[0067] S6: Compare the short-circuit impedance, impedance relative change rate and the maximum cumulative deformation change rate calculated by the three-dimensional single-wire cake model obtained in step S3 and step S5. If the short-circuit impedance and impedance relative change rate obtained by the test and simulation are both above the target values ​​in a certain short-circuit impact, and the maximum cumulative deformation change rate of the three-dimensional single-wire cake model is above the limit value, it is judged that the winding strength is insufficient.

[0068] In this embodiment, when the relative change rate of the short-circuit impedance obtained from the test and simulation is above 2% in a certain short-circuit impact, and the maximum cumulative deformation change rate of the three-dimensional single-wire pancake model is above 40%, it can be determined that the winding is unstable, that is, the winding strength is insufficient.

[0069] This method combines finite element simulation and short-circuit test to comprehensively and accurately evaluate the strength of transformer windings. Through gradually in-depth simulation analysis (from two-dimensional to three-dimensional, and then to the single-wire pancake model), the deformation of the winding under the impact of short circuit can be accurately captured, providing a reliable basis for judging whether the winding is unstable. At the same time, this method is combined with actual short-circuit tests to further verify the accuracy of the simulation results and improve the reliability of the evaluation.

[0070] The two-dimensional pancake-by-pancake model constructed in step S2 is simplified by ignoring the stays and pads and evenly distributing the winding compression height to each oil channel. By ignoring the stays and pads and evenly distributing the winding compression height to each oil channel, the construction process of the two-dimensional pancake-by-pancake model is simplified, the calculation complexity is reduced, and the simulation efficiency is improved. At the same time, this simplification does not significantly affect the accuracy of the simulation results.

[0071] In this embodiment, in step S2, a low-voltage winding short-circuit impulse current excitation is given under a steady-state field, and the displacement deformation distribution of the coil under a single short-circuit impulse is calculated by coupling the electromagnetic-structural field. Given a low-voltage winding short-circuit impulse current excitation under a steady-state field, the displacement deformation distribution of the coil under a single short-circuit impulse is calculated by coupling the electromagnetic-structural field, which can more accurately simulate the actual short-circuit impulse process and improve the accuracy of the simulation results. At the same time, this method can also capture the dynamic response of the winding under a short-circuit impulse, providing richer information for evaluating the winding strength.

[0072] In this embodiment, in step S2, a single short-circuit impulse current excitation is applied through a two-dimensional transformer winding model established one by one, and the structural mechanics interface is coupled to calculate the displacement deformation degree of each unit pie number of the winding under a single short-circuit impulse, thereby laying a foundation for establishing a refined three-dimensional single-line pie model.

[0073] The three-dimensional winding model of the transformer subjected to multiple short-circuit impacts in step S3 of the embodiment of the present invention saves the calculation results after a single impact electromagnetic-structural field coupling calculation, and serves as the initial geometric model for the next short-circuit impact, in order to obtain the short-circuit electromagnetic force distribution density at each position of the winding after each short-circuit impact. The three-dimensional winding model of the transformer here also ignores the stays and pads. Since the deformation calculation interface is not used, ignoring the above-mentioned support members does not affect the electromagnetic force calculation results, and at the same time has the effect of greatly reducing the amount of model calculation.

[0074] It should be noted that the calculation results of the three-dimensional winding model of the transformer after multiple short-circuit shocks in step S3 need to be saved as the initial geometric model for the next short-circuit shock. Saving the calculation results of the three-dimensional winding model of the transformer after multiple short-circuit shocks as the initial geometric model for the next short-circuit shock can consider the impact of the cumulative effect on the winding strength. This cumulative effect analysis is crucial for evaluating the stability of the winding in long-term operation and helps to improve the accuracy and comprehensiveness of the evaluation.

[0075] In addition, in step S3, a hollow cylindrical power transformer cumulative impact winding model is established, multiple short-circuit impact currents are applied in sequence, the structural mechanics interface is coupled, the short-circuit electromagnetic force body density distribution of the winding is extracted, and the result after each calculation is saved as the initial geometric model for the next short-circuit impact. This step can achieve the calculation of the electromagnetic force distribution after each short-circuit impact based on the cumulative effect of the winding force, and also pave the way for the calculation of the three-dimensional single-line pancake model.

[0076] The three-dimensional single-wire model in step S4 takes into account the boundary constraints of the stays and pads. The calculation results of the three-dimensional winding model of the transformer after multiple short-circuit shocks are saved as the initial geometric model for the next short-circuit shock, which can consider the impact of the cumulative effect on the winding strength. This cumulative effect analysis is crucial for evaluating the stability of the winding in long-term operation and helps to improve the accuracy and comprehensiveness of the evaluation.

[0077] When calculating the deformation displacement of the three-dimensional single-wire model in step S4, the result after each short-circuit impact needs to be saved as the initial geometric model for the next short-circuit impact. Saving the calculation results of the three-dimensional winding model of the transformer after multiple short-circuit impacts as the initial geometric model for the next short-circuit impact can consider the impact of the cumulative effect on the winding strength. This cumulative effect analysis is crucial for evaluating the stability of the winding in long-term operation and helps to improve the accuracy and comprehensiveness of the evaluation.

[0078] The electromagnetic force body density applied to the three-dimensional single-wire model in step S4 is derived from the short-circuit electromagnetic force body density distribution calculated in step S3. The calculation results of the three-dimensional winding model of the transformer after multiple short-circuit shocks are saved as the initial geometric model of the next short-circuit shock, which can consider the impact of the cumulative effect on the winding strength. This cumulative effect analysis is crucial for evaluating the stability of the winding in long-term operation and helps to improve the accuracy and comprehensiveness of the evaluation.

[0079] In step S4, the detection method of the present application establishes a refined three-dimensional single-wire cake model including the support bar 6 and the spacer block 7, and the electromagnetic force body density distribution obtained in the previous stage is intercepted according to the wire cake unit number and height as the excitation of the three-dimensional single-wire cake model. The three-dimensional single-wire cake model is much less computationally intensive than the complete transformer model taking into account various insulating parts and supporting structures, and avoids the problems of huge model calculation amount and non-convergence caused by the use of electromagnetic-structural multi-physics field coupling calculation in short-circuit impulse current excitation.

[0080] In step S5, a new power transformer is used to perform multiple short-circuit impact cumulative tests, and the short-circuit impedance after each short-circuit impact is measured using a short-circuit impedance tester. Using a new power transformer to perform multiple short-circuit impact cumulative tests can more directly verify the accuracy of the simulation results. At the same time, using a short-circuit impedance tester to measure the short-circuit impedance after each short-circuit impact can more accurately evaluate the changes in the electrical performance of the winding under the short-circuit impact. This test method combined with simulation analysis can more comprehensively evaluate the strength of the transformer winding.

[0081] In step S5 and step S6, the detection method of the present application performs a short-circuit prototype test on a brand-new power transformer, applies a short-circuit current that is consistent with the simulation calculation for multiple times, and uses an impedance tester to measure the short-circuit impedance after each test, and compares it with the model impedance value, which can verify the accuracy of the model. At the same time, by calculating the relative change rate of the short-circuit impedance and comparing it with the maximum deformation change rate of the three-dimensional single-wire model, the mechanical strength state of the winding at this time can be determined.

[0082] On the other hand, based on the same technical concept of the above embodiment, the present invention provides a transformer winding strength detection system based on a short-circuit test, comprising:

[0083] A parameter determination module is used to determine the winding coil parameters according to the transformer parameter table, and obtain the transformer single coil size, the support bar size and the spacer block size;

[0084] A model testing module is used to construct a two-dimensional coil-by-coil model and a three-dimensional winding model according to winding coil parameters, respectively, to perform short-circuit impulse current excitation on the two-dimensional coil-by-coil model and the three-dimensional winding model, respectively, to obtain the displacement deformation distribution of each coil in the two-dimensional coil-by-coil model and the cumulative short-circuit electromagnetic force body density distribution of the three-dimensional winding model, respectively, to calculate the short-circuit impedance and the relative impedance change rate of the three-dimensional winding model after each short-circuit impulse current excitation, to select the coil with the largest variable after the two-dimensional coil-by-coil model test to construct a three-dimensional single-coil model, to apply the short-circuit electromagnetic force body density distribution obtained from the three-dimensional winding model test to the three-dimensional single-coil model, and to calculate the maximum cumulative deformation change rate of the three-dimensional single-coil model;

[0085] A data interface module is used to obtain the short-circuit impedance calculated after the short-circuit test of the actual power transformer and calculate the relative impedance change rate;

[0086] The comparison and analysis module compares the data obtained by the data interface module, the data calculated by the three-dimensional winding model test module, and the data calculated by the three-dimensional single-wire model test module to determine whether the winding strength meets the standard.

[0087] Among them, the data comparison of the comparison and analysis module includes: if the short-circuit impedance and the relative impedance change rate calculated by the three-dimensional winding model test module and the three-dimensional single-wire cake model test module are both above the target value in a certain short-circuit impact, and the maximum cumulative deformation change rate of the three-dimensional single-wire cake model is above the limit value, then it is judged that the winding strength is insufficient.

[0088] Secondly, obtaining the repeated short-circuit electromagnetic force body density distribution of the three-dimensional winding model includes: applying multiple short-circuit impulse current excitations to the three-dimensional winding model of the transformer, and saving the deformation result after each short-circuit impulse current excitation as the initial geometric model of the next impulse.

[0089] Calculating the maximum cumulative deformation change rate of the three-dimensional single-wire pancake model includes: applying the repeated short-circuit electromagnetic force body density distribution of the three-dimensional winding model to the three-dimensional single-wire pancake model, and saving the deformation change rate after each calculation as the next initial geometric model.

[0090] The following is a specific example of the short-circuit impact test of the A-pillar high-voltage winding-low-voltage outer winding and the corresponding finite element simulation of a new single-phase double-pillar three-winding D-400kVA / 6.3kV:

[0091] First, according to the transformer parameters in the calculation sheet, establish Figure 2The two-dimensional pancake-by-pancake model of the A-pillar has 24, 378 and 24 turns of the low-voltage inner-high-voltage-low-voltage outer winding, respectively, which are modeled according to 18, 36 and 20 pancakes, respectively. Other parameters are shown in Table 1. The reactance height keeps the top flush, and the compression rate is evenly distributed in the oil channel between every two pancakes. The two-dimensional pancake-by-pancake model ignores the pads and stays, and does not consider the outer insulation of a single transformer wire to simplify the model calculation amount. The short-circuit impulse current excitation of 45%, 50%, 55% and 60% is given in turn, and the structural mechanics field is coupled. The Lorentz force coupling term generated by the interaction between the current and the magnetic field is loaded on the two-dimensional winding model as a volume force. According to the deformation interface, the coil unit number with the largest coil displacement under a single impact is determined.

[0092] Continue to build a three-dimensional transformer model of a hollow cylinder, in which the reactance height of the A-pillar low-voltage inner-high-voltage = low-voltage outer winding is 455mm, and the winding radius is modeled as shown in Table 1. Set the number of winding turns to the same as the two-dimensional pancake model, select the circuit-magnetic field coupling interface, draw the short-circuit equivalent circuit of the low-voltage inner-high-voltage winding in the circuit module, and select the current source in the circuit interface. Set the peak current to 45%, 50%, 55% and 60% of the short-circuit current. Add the structural mechanics coupling term to calculate the electromagnetic force distribution of the winding after each short-circuit current loading. Save the deformation result of each short circuit as the initial geometric configuration for the next calculation. At the same time, in one step, calculate the short-circuit impedance size after each short-circuit impact according to the formula, and calculate the relative change rate of the short-circuit impedance obtained by the simulation model.

[0093] The three-dimensional single-wire pancake model was constructed using COMSOL software. The model includes a brace and a pad. The boundary constraint condition is set as a fixed constraint on one side of the brace, the contact surface between the upper end of the winding and the pad is set as a preload, and the contact surface between the lower end of the winding and the pad is set as a fixed constraint. The brace and pad are both 16 levels. In the load setting, the electromagnetic force distribution body density calculated in the previous step is used as the excitation. According to the winding height and the coil unit number, the electromagnetic force distribution body density at the coil position corresponding to the maximum displacement is found by the probe and loaded onto the three-dimensional single-wire pancake model. The single physical field calculation of the structural field is performed in the steady-state field of COMSOL. The displacement and stress distribution of the corresponding three-dimensional single-wire pancake model are solved, and the calculation results of each time are also saved as the initial geometric configuration of the next short-circuit impact. The maximum displacement change rate of the three-dimensional single-wire pancake model is calculated according to the simulation results.

[0094] A new power transformer with the same simulation parameters was subjected to multiple short-circuit impact tests. It should be noted that the short-circuit tests conducted by the present invention all loaded current on the low-voltage side, and the high-voltage side maintained a short circuit. The two-column three-winding transformer in this test, each column from the inside to the outside is low-voltage inner-high-voltage-low-voltage outer winding. The experiment studies the cumulative effect of short-circuit impact of high and low voltage windings, so four groups of short-circuit impact tests are required, namely H-LVA1, H-LVA2, H-LVB1 and H-LVB2, where H and L represent high and low voltage windings, A and B represent the two columns of the transformer, and the numbers represent the low-voltage winding numbers. The mechanical strength of the transformer winding is explored by gradually increasing the current. The H-LVA1 group of short-circuit prototype tests were loaded from 45% of the withstand current. Combined with the short-circuit impedance between the high and low voltage windings measured after each short-circuit test, the absolute change rate and relative change rate of the short-circuit impedance were calculated to analyze the deformation of the winding and determine whether to continue to increase the loading current value. The low-voltage side of the two-dimensional finite element model was loaded with steady-state current values ​​of 10.69kA, 11.88kA, 13.07kA, 13.07kA and 14.25kA in turn, and the simulation model leakage magnetic field under the five tests was calculated respectively, and the short-circuit impedance was obtained. The A-pillar low-voltage inner coil was subjected to a total of 5 short-circuit impact tests. Since the absolute change rate and relative change rate of the short-circuit impedance measured after the third short-circuit impact test changed greatly compared with the second, the short-circuit current value was maintained unchanged during the fourth current loading to continue to impact the winding to prevent the coil from being rapidly damaged in mechanical properties.

[0095] The coil unit number with the maximum displacement is obtained according to the two-dimensional coil model, and the electromagnetic force body density distribution is calculated according to the hollow cylindrical winding model and loaded onto the corresponding three-dimensional single coil model. Compared with the traditional fine modeling method of coupling electromagnetic-structural field, it is more flexible and reduces the amount of calculation on the basis of multiple modeling. On the one hand, the short-circuit impedance calculated from the hollow cylindrical winding model is compared with the short-circuit impedance obtained from the test to verify the accuracy of the model. On the other hand, the relative change rate of the short-circuit impedance obtained from the simulation model and the maximum deformation change rate obtained from the three-dimensional single coil model are compared with the relative change rate of the experimental short-circuit impedance to judge the winding strength state. If the relative change rate of the short-circuit impedance obtained from the test and simulation is above 2% in a short-circuit impact, and the maximum cumulative deformation change rate of the three-dimensional single coil model is above 40%, it is concluded that the winding is unstable.

[0096] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A transformer winding strength detection method based on short-circuit test, characterized in that: The following steps are involved: S1: According to the transformer parameter table, the winding coil parameters are determined, wherein the winding coil parameters include the compression rate, reactance height, single coil size and oil channel gap of the low voltage inner winding, the high voltage winding and the low voltage outer winding, and the transformer single coil size, the support bar size and the spacer block size are obtained according to the winding coil parameters; S2: Based on the single coil size obtained in step S1, ignoring the stays and pads, the winding compression height is evenly distributed to each oil channel, a two-dimensional coil-by-coil model is constructed, a single short-circuit impulse current excitation is applied to the two-dimensional coil-by-coil model, and the displacement deformation distribution of each coil is obtained by coupling electromagnetic-structural field calculation; S3: According to the winding coil parameters in step S1, hollow cylinders with different inner and outer diameters are respectively established as low-voltage inner windings, high-voltage windings and low-voltage outer windings to participate in electromagnetic calculations, material parameters and constraints are set, and a three-dimensional winding model of the transformer is constructed. Multiple short-circuit impulse current excitations are applied to the three-dimensional winding model of the transformer. After each short-circuit impulse current excitation, the deformation result is saved as the initial geometric model for the next impulse, and the short-circuit electromagnetic force body density distribution under the repeated short-circuit impulse current excitations is obtained, and the short-circuit impedance and the relative impedance change rate after each short-circuit impulse current excitation are calculated; The specific calculation method of short-circuit impedance and relative impedance change rate is as follows: The two formulas are as follows: ， ； Calculate the short-circuit impedance and relative change rate after each short-circuit impulse current excitation calculation; Among them, U k is the short-circuit impedance, is the relative change rate of impedance, D is the equivalent magnetic leakage area, r is the Rockwell coefficient, I N1 is the rated current; K is the additional reactance coefficient; H K12 is the winding reactance height; e t is the turn potential; w is the number of winding turns; is the operating frequency; W1 is the total magnetic field energy; Z k , Z k-1 They are the short-circuit impedance values ​​obtained by the model calculations twice before and after; S4: According to the winding coil parameters obtained in step S1 and the displacement deformation distribution obtained in step S2, the coil with the largest deformation is selected to construct a three-dimensional single coil model, the short-circuit electromagnetic force body density distribution obtained in step S3 is applied to the three-dimensional single coil model, and the deformation change rate after each calculation is saved as the initial geometric model for the next time; S5: Select a brand new power transformer to conduct a short-circuit test, apply a short-circuit current that is consistent with the short-circuit impulse current excitation in step S2 and step S3, measure the short-circuit impedance and calculate the relative impedance change rate; S6: Compare the short-circuit impedance, relative impedance change rate and maximum cumulative deformation change rate calculated by the three-dimensional single-wire cake model in step S3 and step S5. If the short-circuit impedance and relative impedance change rate obtained in step S3 and step S5 are both above the target values ​​in a short-circuit impact, and the maximum cumulative deformation change rate of the three-dimensional single-wire cake model is above the limit value, it is judged that the winding strength is insufficient.

2. The transformer winding strength detection method based on short-circuit test according to claim 1 is characterized in that: The two-dimensional pancake-by-pancake model constructed in step S2 is simplified by ignoring the stays and spacers and evenly distributing the winding compression height to each oil channel.

3. The transformer winding strength detection method based on short-circuit test according to claim 1 is characterized in that: In the three-dimensional single-line pie model in step S4, boundary constraints are imposed on the stays and pads, and the constraints include spring support and fixed constraints.

4. The transformer winding strength detection method based on short-circuit test according to claim 1 is characterized in that: In step S5, a short-circuit impedance tester is used to measure the short-circuit impedance after each short-circuit impulse current excitation.

5. A detection system for a transformer winding strength detection method based on a short-circuit test according to any one of claims 1 to 4, characterized in that: include: A parameter determination module is used to determine the winding coil parameters according to the transformer parameter table, and obtain the transformer single coil size, the support bar size and the spacer block size; A model testing module is used to construct a two-dimensional coil-by-coil model and a three-dimensional winding model according to winding coil parameters, respectively, to perform short-circuit impulse current excitation on the two-dimensional coil-by-coil model and the three-dimensional winding model, respectively, to obtain the displacement deformation distribution of each coil in the two-dimensional coil-by-coil model and the cumulative short-circuit electromagnetic force body density distribution of the three-dimensional winding model, respectively, to calculate the short-circuit impedance and the relative impedance change rate of the three-dimensional winding model after each short-circuit impulse current excitation, to select the coil with the largest variable after the two-dimensional coil-by-coil model test to construct a three-dimensional single-coil model, to apply the short-circuit electromagnetic force body density distribution obtained from the three-dimensional winding model test to the three-dimensional single-coil model, and to calculate the maximum cumulative deformation change rate of the three-dimensional single-coil model; A data interface module is used to obtain the short-circuit impedance calculated after the short-circuit test of the actual power transformer and calculate the relative impedance change rate; The comparison and analysis module compares the data obtained by the data interface module, the data calculated by the three-dimensional winding model test module, and the data calculated by the three-dimensional single-wire model test module to determine whether the winding strength meets the standard.

6. The detection system according to claim 5, characterized in that: The data comparison of the comparison and analysis module includes: if the short-circuit impedance and the relative impedance change rate calculated by the three-dimensional winding model test module and the three-dimensional single-wire cake model test module are both above the target values ​​in a certain short-circuit impact, and the maximum cumulative deformation change rate of the three-dimensional single-wire cake model is above the limit value, then it is judged that the winding strength is insufficient.

7. The detection system according to claim 5, characterized in that: Obtaining the repeated short-circuit electromagnetic force body density distribution of the three-dimensional winding model includes: applying multiple short-circuit impulse current excitations to the three-dimensional winding model of the transformer, and saving the deformation result after each short-circuit impulse current excitation as the initial geometric model of the next impulse.

8. The detection system according to claim 7, characterized in that: Calculating the maximum cumulative deformation change rate of the three-dimensional single-wire cake model includes: applying the repeated short-circuit electromagnetic force body density distribution of the three-dimensional winding model to the three-dimensional single-wire cake model, and saving the deformation change rate after each calculation as the next initial geometric model.

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