Magnetic shielding arrangement method and device for magnetic unbalance condition of power transformer

Abstract

The invention discloses a magnetic shielding arrangement method and device for the magnetic unbalance condition of a power transformer, and relates to the technical field of electrical engineering, and the method comprises the steps: analyzing the distribution of a leakage magnetic field of the power transformer, determining a magnetic shielding range, and setting a magnetic shielding plate in the magnetic shielding range. According to the method, firstly, the distribution of the leakage magnetic field of the power transformer is analyzed, the magnetic shielding range can be reasonably determined, then the magnetic shielding plate is arranged in the magnetic shielding range, the magnetic shielding effect is achieved, and the magnetic unbalance degree of the power transformer can be effectively reduced.

Description

Technical Field

[0001] The invention relates to the technical field of electrical engineering, and in particular to a magnetic shielding arrangement method and device for a power transformer with magnetic imbalance. Background Art

[0002] Large-capacity generators and interconnection transformers are mostly used in large power stations, nuclear power stations or important lines. Therefore, the operational reliability of large-capacity generators and interconnection transformers is extremely important. With the increase in transformer capacity, transportation conditions and on-site installation requirements have limited the emergence of large transformers with special structures such as core disintegration and yoke. Compared with general transformers, the magnetic field inside the core of such transformers is unbalanced. Accurately calculating the magnetic field, no-load loss and stray loss of the core of such transformers to avoid local overheating is of great significance for improving the reliability of transformer operation and ensuring the safe operation of the power system. With the increase in capacity and voltage level, the unreasonable distribution of the transformer's magnetic field and stray loss causes local loss concentration, which is the direct cause of local overheating and operational failures. Therefore, in order to ensure the safe operation of large-capacity magnetic unbalanced transformers and improve operational reliability, it is necessary to conduct in-depth research on the performance and parameters of such transformer products and reasonably install magnetic shielding devices. Summary of the invention

[0003] The technical problem to be solved by the present invention is to address the deficiencies of the prior art and specifically provide a magnetic shielding arrangement method and device for the magnetic imbalance of a power transformer, as follows:

[0004] 1) In the first aspect, the present invention provides a magnetic shielding arrangement method for a power transformer with magnetic imbalance. The specific technical solution is as follows:

[0005] Analyze the distribution of leakage magnetic field of power transformer and determine the magnetic shielding range;

[0006] A magnetic shielding plate is arranged within the magnetic shielding range.

[0007] The beneficial effects of the magnetic shielding arrangement method for the magnetic imbalance of the power transformer provided by the present invention are as follows:

[0008] First, by analyzing the distribution of the leakage magnetic field of the power transformer, the magnetic shielding range can be reasonably determined. Then, a magnetic shielding plate is set within the magnetic shielding range to achieve the magnetic shielding effect, which can effectively reduce the magnetic imbalance of the power transformer.

[0009] On the basis of the above scheme, the magnetic shielding arrangement method for the magnetic imbalance of the power transformer of the present invention can be improved as follows.

[0010] Furthermore, the magnetic shielding range is: a rectangular ring area located in the oil tank of the power transformer, one side of the rectangular ring area is parallel to the axial direction of the coil of the power transformer, and the other side of the rectangular ring area is perpendicular to the axial direction of the coil of the power transformer.

[0011] Furthermore, within the magnetic shielding range, a magnetic shielding plate is provided, including:

[0012] Magnetic shielding plates are laid in each pair of opposite rectangular frames in the rectangular ring area, and the four magnetic shielding plates are separated from each other, wherein a pair of opposite rectangular frames are arranged close to the coils on both sides of the power transformer, and another pair of opposite rectangular frames are arranged close to all the coils of the power transformer.

[0013] Furthermore, each magnetic shielding plate includes a plurality of magnetic shielding strips arranged in an array, and all the magnetic shielding strips are separated from each other.

[0014] Furthermore, the distribution of the leakage magnetic field of the power transformer is analyzed to determine the magnetic shielding range, including:

[0015] The distribution of the leakage magnetic field of the power transformer is measured by using a small coil measurement method to obtain the leakage magnetic field distribution measurement result;

[0016] Simulate the leakage magnetic field generated by the power transformer and obtain the simulation results of the leakage magnetic field distribution;

[0017] According to the leakage magnetic field distribution measurement results and leakage magnetic field distribution simulation results, the distribution of the leakage magnetic field of the power transformer is analyzed to determine the magnetic shielding range.

[0018] Furthermore, it also includes:

[0019] Calculate the current applied to each coil of the power transformer in a magnetic-circuit coupled manner;

[0020] Applying a corresponding current to each coil of the power transformer so that the power transformer generates a leakage magnetic field;

[0021] In the simulation software, a corresponding current is applied to each coil of the power transformer to cause the power transformer to generate a leakage magnetic field.

[0022] 2) In the second aspect, the present invention also provides a magnetic shielding device for the magnetic imbalance of a power transformer, and the specific technical solution is as follows:

[0023] It comprises a magnetic shielding plate, and a magnetic shielding range is set within the magnetic shielding range, wherein the distribution of the leakage magnetic field of the power transformer is analyzed to determine the magnetic shielding range.

[0024] The beneficial effects of the magnetic shielding device for the magnetic imbalance of the power transformer of the present invention are as follows:

[0025] First, by analyzing the distribution of the leakage magnetic field of the power transformer, the magnetic shielding range can be reasonably determined. Then, a magnetic shielding plate is set within the magnetic shielding range to achieve the magnetic shielding effect, which can effectively reduce the magnetic imbalance of the power transformer.

[0026] On the basis of the above solution, the magnetic shielding device for the magnetic imbalance of the power transformer of the present invention can also be improved as follows.

[0027] Furthermore, the magnetic shielding range is: a rectangular ring area located in the oil tank of the power transformer, one side of the rectangular ring area is parallel to the axial direction of the coil of the power transformer, and the other side of the rectangular ring area is perpendicular to the axial direction of the coil of the power transformer.

[0028] Furthermore, within the magnetic shielding range, a magnetic shielding plate is provided, including:

[0029] Magnetic shielding plates are laid in each pair of opposite rectangular frames in the rectangular ring area, and the four magnetic shielding plates are separated from each other, wherein a pair of opposite rectangular frames are arranged close to the coils on both sides of the power transformer, and another pair of opposite rectangular frames are arranged close to all the coils of the power transformer.

[0030] Furthermore, each magnetic shielding plate includes a plurality of magnetic shielding strips arranged in an array, and all the magnetic shielding strips are separated from each other.

[0031] Furthermore, the distribution of the leakage magnetic field of the power transformer is analyzed to determine the magnetic shielding range, including:

[0032] The distribution of the leakage magnetic field of the power transformer is measured by using a small coil measurement method to obtain the leakage magnetic field distribution measurement result;

[0033] Simulate the leakage magnetic field generated by the power transformer and obtain the simulation results of the leakage magnetic field distribution;

[0034] According to the leakage magnetic field distribution measurement results and leakage magnetic field distribution simulation results, the distribution of the leakage magnetic field of the power transformer is analyzed to determine the magnetic shielding range.

[0035] Furthermore, the current applied to each coil of the power transformer is calculated in a magnetic-circuit coupling manner; a corresponding current is applied to each coil of the power transformer so that the power transformer generates a leakage magnetic field; in the simulation software, a corresponding current is applied to each coil of the power transformer so that the power transformer generates a leakage magnetic field. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments of the present invention:

[0037] Figure 1 A schematic flow chart of a magnetic shielding arrangement method for a power transformer magnetic imbalance according to an embodiment of the present invention;

[0038] Figure 2 Schematic diagram of measuring magnetic position;

[0039] Figure 3 One of the schematic diagrams of the magnetic shielding plate provided;

[0040] Figure 4 The second schematic diagram of the magnetic shielding plate is set up. DETAILED DESCRIPTION

[0041] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0042] The technical solution of the present invention and how the technical solution of the present invention solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present invention will be described below in conjunction with the accompanying drawings.

[0043] like Figure 1 As shown, a magnetic shielding arrangement method for a power transformer magnetic imbalance according to an embodiment of the present invention comprises the following steps:

[0044] S1. Analyze the distribution of the leakage magnetic field of the power transformer and determine the magnetic shielding range;

[0045] The power transformer may be a single-phase large-capacity power transformer such as a three-column parallel structure power transformer, or may be other types of power transformers.

[0046] S2. A magnetic shielding plate is installed within the magnetic shielding range.

[0047] Optionally, in the above technical solution, the magnetic shielding range is: a rectangular ring area located in the oil tank of the power transformer, one side of the rectangular ring area is parallel to the axial direction of the coil of the power transformer, and the other side of the rectangular ring area is perpendicular to the axial direction of the coil of the power transformer.

[0048] Optionally, in S2, a magnetic shielding plate is provided within the magnetic shielding range, including:

[0049] S20. Magnetic shielding plates are laid in each pair of opposite rectangular frames in the rectangular ring area, and the four magnetic shielding plates are separated from each other, wherein a pair of opposite rectangular frames are arranged close to the coils on both sides of the power transformer, and another pair of opposite rectangular frames are arranged close to all the coils of the power transformer.

[0050] Optionally, in the above technical solution, each magnetic shielding plate includes a plurality of magnetic shielding strips arranged in an array, and all the magnetic shielding strips are separated from each other.

[0051] Optionally, in S1, analyzing the distribution of the leakage magnetic field of the power transformer to determine the magnetic shielding range includes:

[0052] S10. Using a small coil measurement method to measure the distribution of the leakage magnetic field of the power transformer, to obtain a leakage magnetic field distribution measurement result, specifically:

[0053] When the oil tank of the power transformer is not filled with oil, the inside of the oil tank is entered through the transformer entry hole to install magnetic measuring plates. The positions with large leakage magnetic fields such as clamps, pull plates, and coil main air channels are selected for measurement. A total of 8 magnetic measuring plates are installed, and the distribution of the leakage magnetic field of the power transformer is measured using the small coil measurement method. The leakage magnetic field distribution measurement results are obtained to provide data support for the magnetic shielding range. Figure 2 There are 8 magnetic measuring positions in total, which are marked with reference numerals 1 to 8 respectively. The magnetic measuring positions can also be set according to actual conditions.

[0054] The magnetic measuring board is composed of an electrical wood board and a group of small coils in different directions, and the magnetic measuring boards are of different lengths such as 1000mm, 500mm and 200mm. Since the directions of leakage magnetic field measured on the surfaces of different structural parts in the oil tank are different, the small coils are made into waist-shaped and circular shapes respectively. The diameter of the winding wire on the small coil is 0.05mm, and each small coil is wound with at least 300 turns. The external connecting wire of the magnetic measuring board is 15m long, which is convenient for leading out through the upper part of the oil tank.

[0055] S11, simulating the leakage magnetic field generated by the power transformer to obtain a simulation result of the leakage magnetic field distribution;

[0056] S12. Analyze the distribution of the leakage magnetic field of the power transformer according to the leakage magnetic field distribution measurement results and the leakage magnetic field distribution simulation results, and determine the magnetic shielding range.

[0057] Select multiple magnetic fields at the same position from the leakage magnetic field distribution simulation results and the leakage magnetic field distribution simulation results to verify whether they are all within the preset magnetic field deviation. If so, analyze the leakage magnetic field distribution simulation results to determine the preliminary magnetic shielding range, as well as the preliminary distance between two adjacent magnetic shielding plates, the preliminary distance between two adjacent magnetic shielding strips, the preliminary width of each magnetic shielding plate, and the preliminary width of each magnetic screen strip and other parameters. Then, based on these parameters, perform simulation calculations of the shielding effectiveness in the simulation software until the shielding effectiveness reaches the preset decibel (dB). Then, determine the magnetic shielding range, as well as the distance between the magnetic shielding range and the coil, the distance between two adjacent magnetic shielding plates, the distance between two adjacent magnetic shielding strips, the width of each magnetic shielding plate, and the length, width and thickness of each magnetic screen strip, and set the magnetic shielding plate within the magnetic shielding range based on these parameters.

[0058] The material of the magnetic screen strip may be Permalloy or the like, or other materials may be selected in combination with simulation calculation results.

[0059] When the result of verifying whether they are all within the preset magnetic field deviation is no, the simulation result of the leakage magnetic field distribution is taken as the basis, and the simulation result of the leakage magnetic field distribution is corrected. According to the simulation result of the leakage magnetic field distribution, the simulation result of the leakage magnetic field distribution is analyzed to determine the preliminary magnetic shielding range, as well as the preliminary distance between two adjacent magnetic shielding plates, the preliminary distance between two adjacent magnetic shielding strips, the preliminary width of each magnetic shielding plate, and the preliminary width of each magnetic shield strip. Then, according to these parameters, the simulation calculation of the shielding effectiveness is performed in the simulation software until the shielding effectiveness reaches the preset decibel (dB). Then, the magnetic shielding range, the distance between the magnetic shielding range and the coil, the distance between two adjacent magnetic shielding plates, the distance between two adjacent magnetic shielding strips, the width of each magnetic shielding plate, and the width of each magnetic shield strip are determined, and according to these parameters, the magnetic shielding plate is set within the magnetic shielding range.

[0060] Optionally, in the above technical solution, it also includes:

[0061] S010. Calculating the current applied to each coil of the power transformer in a magnetic-circuit coupling manner;

[0062] The power transformer includes a high-voltage coil, a medium-voltage coil and a low-voltage coil. The high-voltage coil and the medium-voltage coil are connected in a self-coupling manner and are both connected to the voltage regulating coil. The low-voltage coil and the excitation coil are connected in parallel. When the high-voltage coil and the medium-voltage coil of the power transformer are in operation, the voltage regulating coil participates in the operation, and in order to achieve magnetic potential balance, the excitation coil also participates in the operation. Since the low-voltage coil is connected in parallel with the excitation coil, when the high-voltage coil and the medium-voltage coil of the power transformer are in operation, current also flows through the low-voltage coil. At this time, the excitation coil is equivalent to the power supply, and the low-voltage coil is equivalent to the load of the excitation coil. Compared with the excitation coil, the length of the magnetic circuit of the low-voltage coil is different, that is, the magnetic resistance is different. Therefore, the current generated by the high-voltage coil and the medium-voltage coil connected in parallel on the two columns will be different. According to the transformer magnetic potential balance principle, the current of the high-voltage coil and the medium-voltage coil connected in parallel on the two columns is also different due to the influence of the current of the low-voltage coil. Therefore, this type of power transformer must calculate the distribution of the current in each coil in a magnetic-circuit coupling manner, that is, calculate the current applied to each coil of the power transformer in a magnetic-circuit coupling manner.

[0063] S011. Apply a corresponding current to each coil of the power transformer so that the power transformer generates a leakage magnetic field. In the simulation software, apply a corresponding current to each coil of the power transformer so that the power transformer generates a leakage magnetic field.

[0064] Taking the three-column parallel structure power transformer as an example, Figure 3 and Figure 4 ( Figure 4 The “tank magnetic shielding” includes four magnetic shielding plates, namely a first magnetic shielding plate 9, a second magnetic shielding plate 10, a third magnetic shielding plate 11 and a fourth magnetic shielding plate 12) The magnetic shielding plate of the present invention is described, specifically:

[0065] The power transformer includes three iron cores (iron cores are also called side poles), which are marked as the first side pole (I pole), the second side pole (II pole) and the third side pole (III pole) in sequence. Three layers of coil windings are arranged on each side pole from the inside to the outside. The height of each coil winding is equal. The three layers of coil windings from the inside to the outside are respectively high-voltage coil windings, medium-voltage coil windings and low-voltage coil windings. That is to say, the high-voltage coil includes three high-voltage coil windings, the medium-voltage coil includes three medium-voltage coil windings, and the low-voltage coil includes three low-voltage coil windings.

[0066] The magnetic shielding range is: a rectangular ring area located inside the oil tank of the power transformer, one side of the rectangular ring area is parallel to the axial direction of the coil of the power transformer (the axial directions of the high-voltage coil, medium-voltage coil and low-voltage coil are the same), and the other side of the rectangular ring area is perpendicular to the axial direction of the coil of the power transformer.

[0067] Magnetic shielding plates are laid in each pair of rectangular frames that are opposite to each other in the rectangular ring area, and the four magnetic shielding plates are separated from each other, wherein a pair of rectangular frames that are opposite to each other are arranged close to the coils on both sides of the power transformer, and another pair of rectangular frames that are opposite to each other are arranged close to all the coils of the power transformer, wherein the coils on both sides of the power transformer refer to: the coils of the first side pole and the coils of the third side pole, specifically refer to: the outermost low-voltage coil on the first side pole and the outermost low-voltage coil on the third side pole, and the four magnetic shielding plates are respectively recorded as the first magnetic shielding plate 9, the second A magnetic shielding plate 10, a second magnetic shielding plate 11 and a fourth magnetic shielding plate 12, the first magnetic shielding plate 9 and the second magnetic shielding plate 11 are arranged opposite to each other, the second magnetic shielding plate 10 and the fourth magnetic shielding plate 12 are arranged opposite to each other, the first magnetic shielding plate 9 and the second magnetic shielding plate 11 are perpendicular to the axial direction of the coil of the power transformer, the second magnetic shielding plate 10 and the fourth magnetic shielding plate 12 are parallel to the axial direction of the coil of the power transformer, the second magnetic shielding plate 10 is arranged close to the outermost low-voltage coil on the first side column, and the fourth magnetic shielding plate 12 is arranged close to the outermost low-voltage coil on the third side column.

[0068] Preferably, a line between a center point of the second magnetic shielding plate 10 and a center point of the first side pillar is perpendicular to the surface where the second magnetic shielding plate 10 is located, a line between a center point of the fourth magnetic shielding plate 12 and a center point of the first side pillar is perpendicular to the surface where the fourth magnetic shielding plate 12 is located, a line between a center point of the first magnetic shielding plate 9 and an axis line of the second side pillar is perpendicular to the surface where the first magnetic shielding plate 9 is located, and a line between a center point of the first magnetic shielding plate 9 and an axis line of the second side pillar is flush with the top surface of each coil winding, a line between a center point of the second magnetic shielding plate 11 and an axis line of the second side pillar is perpendicular to the surface where the second magnetic shielding plate 10 is located, and a line between a center point of the second magnetic shielding plate 11 and an axis line of the second side pillar is flush with the top surface of each coil winding.

[0069] Each magnetic shielding plate includes a plurality of magnetic shielding bars arranged in an array, and all magnetic shielding bars are separated from each other. For example, each magnetic shielding plate includes 7 magnetic shielding bars arranged in an array, and the specific number can be set according to actual conditions.

[0070] In the present invention, the horizontally placed magnetic shielding plates (the first magnetic shielding plate 9 and the second magnetic shielding plate 11) reduce the magnetic resistance between the I column and the III column, thereby increasing the mutual inductance between the I column and the III column, that is, reducing the mutual inductance deviation between the I column and the III column. Vertical magnetic shielding plates (the second magnetic shielding plate 10 and the fourth magnetic shielding plate 12) are placed at corresponding positions of the I column and the III column to increase the magnetic permeability, thereby increasing the self-inductance value of the I column and the III column itself. By reasonably arranging the oil tank magnetic shielding, the deviation of the short-circuit impedance between the coils of each column of the power transformer with a three-column parallel structure can be effectively reduced.

[0071] Take ODFPS-500000kVA / 750kV autotransformer as an example for explanation.

[0072] The calculation results of each selected current of ODFPS-500000kVA / 750kV autotransformer are shown in Table 1.

[0073] Table 1:

[0074]

[0075] As can be seen from Table 1, the currents in the high-voltage coil, medium-voltage coil, and low-voltage coil are not the same. The maximum current deviation of the low-voltage coil is 5.6%, the maximum current deviation of the medium-voltage coil is 3.0%, and the maximum current deviation of the high-voltage coil is 2.1%, and the current of the X column is greater than the current of the A column. The main reason for the difference in the current of the two columns is that the product structure is a high-voltage coil, a medium-voltage coil, and a low-voltage coil in parallel, and the low-voltage coil is in parallel with the excitation coil. The magnetic path lengths of the low-voltage coil and the excitation coil are different, so the current distribution is different. In the traditional transformer design, the circuit method is used to calculate the current without considering the influence of the magnetic circuit. The calculated coil current is exactly the same for the two columns. Therefore, in order to accurately calculate the coil current value of this magnetic circuit unbalanced structure transformer, the three-dimensional transient magnetic circuit coupling method must be used to calculate the current applied to each coil of the autotransformer in a magnetic-circuit coupling manner.

[0076] The magnetic measuring board is composed of an electrical wood board and a group of small coils in different directions, forming magnetic measuring boards of different lengths such as 1000mm, 500mm and 200mm. Since the directions of leakage magnetic field measured on the surfaces of different structural parts are different, the small coils are made into waist-shaped and circular shapes respectively. The diameter of the winding wire on the small coil is 0.05mm, and each small coil is wound with at least 300 turns. The external connecting wire of the magnetic measuring board is 15m long so that it can be led out through the upper part of the oil tank.

[0077] The magnetic field leakage on the surface of the oil tank, clamps, pull plates, etc. is measured by using magnetic measuring plates. The leakage magnetic flux passes through these small coils, generating a measurable electromotive force E on the coils:

[0078] E=4.44×f×B×A×N (1)

[0079] According to formula (1), we can get

[0080] B=E / (4.44×f×A×N)=C×E (2)

[0081] Among them, B is the magnetic induction intensity at the measuring point, E is the electromotive force generated on the coil, f is the frequency, A is the average cross-sectional area of ​​the coil, N is the number of turns of the coil, and C is the constant of each coil.

[0082] The C value of each small coil on the magnetic measuring plate at 50Hz is given after calibration, and a more accurate electromotive force E can be measured, which can obtain a more accurate magnetic induction intensity B.

[0083] The test process is as follows:

[0084] 1) When the body of the power transformer (autotransformer) is dry and the lowering of the box is completed, but the oil tank is not filled with oil, the magnetic measuring plate is installed inside the oil tank through the transformer entry hole. The positions with large leakage magnetic field, such as clamps, pull plates, and main air channels of the coil, are selected for measurement. A total of 8 magnetic measuring plates are installed, and the distribution of the leakage magnetic field of the power transformer is measured using the small coil measurement method. The leakage magnetic field distribution measurement results are obtained to provide data support for the magnetic shielding range.

[0085] 2) After the magnetic plate is installed, oil the power transformer (autotransformer). When the power transformer (autotransformer) is higher than the coil, stop. Install the box cover and ensure that the contact between the box cover and the box edge is the same as during operation. It is not necessary to install low-voltage and neutral point bushings, oil storage cabinets and other accessories.

[0086] 3) Carry out wiring according to the temperature rise test of power transformer (autotransformer);

[0087] 4) Apply rated current:

[0088] 5) The measurement takes about 30 minutes, and the voltage data obtained is recorded;

[0089] 6) Drain the oil tank and remove the magnetic measuring plate;

[0090] 7) The experiment is over.

[0091] The present invention uses a field-circuit coupling method to calculate the resistance value of each coil of the transformer. In the calculation, a DC voltage is applied to the coil to obtain the DC current of each coil winding. The resistance can be calculated using formula (3):

[0092]

[0093] Among them, U is the DC voltage across the coil, I is the DC current of the coil, and R is the DC resistance of the coil.

[0094] The calculation results are shown in Table 2.

[0095] Table 2:

[0096]

[0097] The short-circuit impedance of the coil can be calculated based on the calculation results of the transient current of each coil. Due to the short circuit on the secondary side, for a traditional ordinary double-winding transformer, its short-circuit impedance can be calculated using formula (4):

[0098]

[0099] Among them, U1 is the short-circuit test voltage applied on the primary side, I1 is the primary winding current, and Z k is the short-circuit impedance of the coil.

[0100] However, since the autotransformer adopts a high-voltage coil-medium-voltage coil auto-coupling connection structure, according to the characteristics of the external circuit, formula (4) can be improved to:

[0101]

[0102] Among them, U 1h is the measured voltage of the primary side high voltage winding, I1 is the measured current of the high voltage winding, and U2 is the measured voltage of the medium voltage winding.

[0103] Based on the resistance and reactance values ​​of each coil, the leakage inductance of each coil can be calculated, specifically using formula (6):

[0104]

[0105] Where L is the coil inductance.

[0106] According to the above-mentioned calculation method of short-circuit impedance, the present invention calculates the short-circuit impedance and leakage inductance of the three-column parallel coil when the transformer has and does not have oil tank magnetic shielding. Table 3 shows the calculated short-circuit impedance of each coil when the transformer does not have oil tank magnetic shielding. Table 4 shows the comparison between the calculated short-circuit impedance of each coil and the test value when the transformer has oil tank magnetic shielding. Table 5 shows the calculated short-circuit reactance when the transformer has and does not have oil tank magnetic shielding:

[0107] Table 3:

[0108]

[0109] Table 4:

[0110]

[0111]

[0112] Table 5:

[0113]

[0114] The short-circuit impedance of the three-column coils of the three-column parallel power transformer is different. The impedance of column I and column III is smaller than that of column II. This is mainly because the coil of column II is located between the coils of columns I and III, and the mutual inductance between the two columns I and III is larger. When there is no oil tank magnetic shielding, the impedance deviation between the three columns is 3.08%, while the short-circuit impedance deviation between the three main coils is only 1.01% when the oil tank shielding is provided. Therefore, from the above calculation results, it can be seen that the oil tank magnetic shielding reduces the short-circuit impedance deviation between the three-column parallel coils. The main reasons are: first, the horizontal magnetic shielding reduces the magnetic resistance between column I and column III, which increases the mutual inductance between the two columns, that is, reduces the mutual inductance deviation with column II; second, the vertical magnetic shielding is placed at the corresponding position of column I and column III, which increases its magnetic permeability, so that the self-inductance value of column I and column III can be increased. It can be seen that the reasonable arrangement of the oil tank magnetic shielding can effectively reduce the deviation of the short-circuit impedance between the coils of each column of this type of three-column parallel structure transformer.

[0115] It can also be seen from Tables 3 and 4 that the short-circuit impedance increases by 1.6% when the oil tank magnetic shielding is considered compared to when the oil tank magnetic shielding is not considered. The impedance voltage percentage is 17.7% when the magnetic shielding is not considered, and the impedance voltage percentage is 18% when the magnetic shielding is considered. This is mainly because the magnetic shielding increases the magnetic permeability of the leakage magnetic path. The calculation error between the calculated value and the test value of the short-circuit impedance when the oil tank magnetic shielding is considered is 0.55%, which shows the accuracy and feasibility of this calculation method.

[0116] In the above embodiments, although the steps are numbered S1, S2, etc., these are only specific embodiments given by the present invention. Those skilled in the art may adjust the execution order of S1, S2, etc. according to actual conditions, which is also within the protection scope of the present invention. It can be understood that in some embodiments, some or all of the above embodiments may be included.

[0117] A magnetic shielding device for a magnetic imbalance of a power transformer according to an embodiment of the present invention includes a magnetic shielding plate, and a magnetic shielding range is set within the magnetic shielding range, wherein the distribution of the leakage magnetic field of the power transformer is analyzed to determine the magnetic shielding range. First, by analyzing the distribution of the leakage magnetic field of the power transformer, the magnetic shielding range can be reasonably determined, and then, a magnetic shielding plate is set within the magnetic shielding range to achieve a magnetic shielding effect, which can effectively reduce the magnetic imbalance of the power transformer.

[0118] Optionally, in the above technical solution, the magnetic shielding range is: a rectangular ring area located in the oil tank of the power transformer, one side of the rectangular ring area is parallel to the axial direction of the coil of the power transformer, and the other side of the rectangular ring area is perpendicular to the axial direction of the coil of the power transformer.

[0119] Optionally, in the above technical solution, a magnetic shielding plate is provided within the magnetic shielding range, including:

[0120] Magnetic shielding plates are laid in each pair of opposite rectangular frames in the rectangular ring area, and the four magnetic shielding plates are separated from each other, wherein a pair of opposite rectangular frames are arranged close to the coils on both sides of the power transformer, and another pair of opposite rectangular frames are arranged close to all the coils of the power transformer.

[0121] Optionally, in the above technical solution, each magnetic shielding plate includes a plurality of magnetic shielding strips arranged in an array, and all the magnetic shielding strips are separated from each other.

[0122] Optionally, in the above technical solution, analyzing the distribution of the leakage magnetic field of the power transformer to determine the magnetic shielding range includes:

[0123] The distribution of the leakage magnetic field of the power transformer is measured by using a small coil measurement method to obtain the leakage magnetic field distribution measurement result;

[0124] Simulate the leakage magnetic field generated by the power transformer and obtain the simulation results of the leakage magnetic field distribution;

[0125] According to the leakage magnetic field distribution measurement results and leakage magnetic field distribution simulation results, the distribution of the leakage magnetic field of the power transformer is analyzed to determine the magnetic shielding range.

[0126] Optionally, in the above technical solution, the current applied to each coil of the power transformer is calculated in a magnetic-circuit coupling manner; a corresponding current is applied to each coil of the power transformer so that the power transformer generates a leakage magnetic field; and in the simulation software, a corresponding current is applied to each coil of the power transformer so that the power transformer generates a leakage magnetic field.

[0127] It should be noted that the beneficial effects of the magnetic shielding device for the magnetic imbalance of the power transformer provided in the above embodiment are the same as the beneficial effects of the magnetic shielding arrangement method for the magnetic imbalance of the power transformer provided in the above embodiment, which will not be repeated here. In addition, the device and method embodiments provided in the above embodiment belong to the same concept, and the specific implementation process is detailed in the method embodiment, which will not be repeated here.

[0128] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects and represent the definition of a specific order or sequence. The order of use of similar objects can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than the order shown or described.

[0129] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A magnetic shielding arrangement method for a power transformer with magnetic imbalance, characterized in that: include: Analyze the distribution of leakage magnetic field of power transformer and determine the magnetic shielding range; A magnetic shielding plate is arranged in the magnetic shielding range.

2. A magnetic shielding arrangement method for a power transformer magnetic imbalance according to claim 1, characterized in that: The magnetic shielding range is: a rectangular ring area located in the oil tank of the power transformer, one side of the rectangular ring area is parallel to the axial direction of the coil of the power transformer, and the other side of the rectangular ring area is perpendicular to the axial direction of the coil of the power transformer.

3. A magnetic shielding arrangement method for a power transformer magnetic imbalance according to claim 2, characterized in that: In the magnetic shielding range, a magnetic shielding plate is arranged, including: Magnetic shielding plates are laid in each pair of opposite rectangular frames in the rectangular ring area, and the four magnetic shielding plates are separated from each other, wherein a pair of opposite rectangular frames are arranged close to the coils on both sides of the power transformer, and another pair of opposite rectangular frames are arranged close to all the coils of the power transformer.

4. The magnetic shielding arrangement method for the magnetic imbalance of a power transformer according to claim 3 is characterized in that: Each magnetic shielding plate comprises a plurality of magnetic shielding strips arranged in an array, and all the magnetic shielding strips are separated from each other.

5. A magnetic shielding arrangement method for a power transformer with magnetic imbalance according to any one of claims 1 to 4, characterized in that: Analyze the distribution of the leakage magnetic field of the power transformer and determine the magnetic shielding range, including: The distribution of the leakage magnetic field of the power transformer is measured by using a small coil measurement method to obtain the leakage magnetic field distribution measurement result; Simulate the leakage magnetic field generated by the power transformer and obtain the simulation results of the leakage magnetic field distribution; According to the leakage magnetic field distribution measurement results and the leakage magnetic field distribution simulation results, the distribution of the leakage magnetic field of the power transformer is analyzed to determine the magnetic shielding range.

6. A magnetic shielding arrangement method for a power transformer magnetic imbalance according to claim 5, characterized in that: Also includes: Calculate the current applied to each coil of the power transformer in a magnetic-circuit coupled manner; Applying a corresponding current to each coil of the power transformer so that the power transformer generates a leakage magnetic field; In the simulation software, a corresponding current is applied to each coil of the power transformer so that the power transformer generates a leakage magnetic field.

7. A magnetic shielding device for the magnetic imbalance of a power transformer, characterized in that: It comprises a magnetic shielding plate, and the magnetic shielding range is set within the magnetic shielding range, wherein the distribution of the leakage magnetic field of the power transformer is analyzed to determine the magnetic shielding range.

8. A magnetic shielding device for the magnetic imbalance of a power transformer according to claim 7, characterized in that: The magnetic shielding range is: a rectangular ring area located in the oil tank of the power transformer, one side of the rectangular ring area is parallel to the axial direction of the coil of the power transformer, and the other side of the rectangular ring area is perpendicular to the axial direction of the coil of the power transformer.

9. A magnetic shielding device for the magnetic imbalance of a power transformer according to claim 8, characterized in that: In the magnetic shielding range, a magnetic shielding plate is arranged, including: Magnetic shielding plates are laid in each pair of opposite rectangular frames in the rectangular ring area, and the four magnetic shielding plates are separated from each other, wherein a pair of opposite rectangular frames are arranged close to the coils on both sides of the power transformer, and another pair of opposite rectangular frames are arranged close to all the coils of the power transformer.

10. A magnetic shielding device for the magnetic imbalance of a power transformer according to claim 9, characterized in that: Each magnetic shielding plate comprises a plurality of magnetic shielding strips arranged in an array, and all the magnetic shielding strips are separated from each other.

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