Self-energy-taking magnetic field sensor for monitoring leakage magnetic field of transformer and arrangement method of self-energy-taking magnetic field sensor

Abstract

The invention discloses a self-energy-taking magnetic field sensor for monitoring a leakage magnetic field of a transformer and an arrangement method of the self-energy-taking magnetic field sensor. The self-energy-taking magnetic field sensor comprises a Hall effect sensor and a vibration energy-taking device, the invention provides a new scheme for supplying power to a magnetic field sensor by using vibration energy of a transformer oil tank shell during working for the first time, and online measurement and self-energy-taking power supply of a leakage magnetic field of the transformer can be realized. Meanwhile, simulation analysis is carried out on the leakage magnetic field of the transformer, a sensor optimization arrangement scheme is given on the basis of leakage magnetic field distribution characteristics of a simulation result, the requirements for the specific arrangement number and positions of leakage magnetic field sensors are clarified, and efficient and accurate measurement of the leakage magnetic field of the transformer is achieved. The transformer fault on-line monitoring method can better reflect the operation condition of the transformer, is high in reliability and good in practicability, and facilitates improvement of the transformer fault on-line monitoring effect.

Description

Technical Field

[0001] The invention relates to a sensor and a layout method thereof, in particular to a self-energy magnetic field sensor for transformer leakage magnetic field monitoring and a layout method thereof. Background Art

[0002] Power transformers are the core equipment of power systems. They play a role in energy transmission and voltage conversion in power systems. The safe and stable operation of transformers is crucial to the transmission and distribution of electric energy. Real-time monitoring of transformer leakage magnetic field can help to detect potential faults in a timely and accurate manner, effectively reduce the failure rate of transformers, and help improve the safety, reliability and economy of power system operation. The structure of the transformer and the physical environment in which it is located are very complex. In the process of defects gradually developing into faults, the transformer leakage magnetic field will change. By monitoring the changes in the temporal and spatial distribution of the leakage magnetic field, the severity, location, type and other information of the transformer defects can be judged, the operating status of the transformer can be grasped in time, and corresponding maintenance measures can be taken in time.

[0003] With the development of sensor technology, more and more types of leakage magnetic field sensors are used for online monitoring of transformers. At present, the main types of magnetic field sensors are Hall effect magnetic field sensors, giant magnetoresistance magnetic field sensors, electromagnetic induction magnetic field sensors, magneto-optical rotation effect magnetic field sensors, etc. These sensors have low power consumption and all need to be powered by external power supplies. The additional power supply device will increase unnecessary costs and make maintenance more difficult. During the operation of the transformer, the body shell will vibrate, and the vibration energy generated is enough to power the sensor. At present, there is a lack of leakage magnetic field sensors that can use the vibration power supply during the operation of the transformer to achieve self-energy.

[0004] The use of self-energy magnetic field sensors can obtain the temporal and spatial distribution characteristics of the leakage magnetic field inside the transformer, which is conducive to understanding the operating status of the transformer. However, the heat sink, bushing and other structures of the transformer oil tank shell limit the installation location of the sensor, and the high cost limits the number of sensors installed. In addition, the measurement range of the sensor is limited, and defects or faults of different types and locations will cause changes in the leakage magnetic field at different locations, resulting in limited monitoring effects. At present, there is a lack of optimized layout solutions for transformer leakage magnetic field sensors.

[0005] Technology 1 related to the present invention: Existing transformer leakage magnetic detection device, the schematic diagram of the device is as follows Figure 1 As shown in Figure 2, the transformer leakage magnetic field is measured through the Hall effect, as shown in Figure 2. Figure 2As shown. A magnetic field amplifier and a filter are used to realize sensitive detection of the transformer leakage magnetic field and effectively filter out the frequency points of specific frequencies in the power line to obtain a power signal of specific frequency [Qian Chunnian, Hou Jianming, Fan Lei, et al. A transformer leakage magnetic field detection device [P]. Jilin: CN201820525323.6, 2018-11-30.]. However, the probe used to detect the magnetic field using the Hall effect contains metal materials. If installed inside the transformer, it will threaten its internal insulation and cause problems such as electric field distortion. The leakage magnetic field detection device still needs to be powered by an external power supply, and it is difficult to carry out power supply wiring in the limited space inside the transformer. The existing technology cannot realize self-powering of the sensor when measuring the leakage magnetic field.

[0006] Technology 2 related to the present invention: [Gao Tingyu. Research on transformer magnetic field sensor based on tapered micro-nano optical fiber [D]. North China Electric Power University (Beijing), 2023.] Taking advantage of the high dispersion stability of magnetic fluid and its difficulty in precipitation and agglomeration, a magnetic fluid-coated tapered micro-nano optical fiber magnetic field sensor is designed. Light is used as the carrier of sensing information, and the magnetic fluid is coated on the outside of the optical fiber. The change in the external magnetic field causes the change in the refractive index of the magnetic fluid, thereby realizing the measurement of the magnetic field. It has a simple structure, high sensitivity, and is easy to monitor remotely. Device and test platform such as Figure 3 As shown in the figure, the tapered micro-nano optical fiber structure coated with magnetic fluid is encapsulated on both sides with insulating cardboard to form a "sandwich" packaging structure. However, due to the magnetic saturation characteristics of magnetic fluid, the dynamic range of the sensor is limited by the saturation magnetic field of the magnetic fluid. At the same time, the interference wavelength of the sensor is greatly affected by temperature, which will cause certain measurement errors.

[0007] Technology 3 related to the present invention: [Sun Lu, Gao Shuguo, Wang Lili, et al. Sensor, device and monitoring method for online monitoring of transformer leakage magnetic field [P]. Hebei Province: CN202410818148.X, 2024-10-08.] It relates to a sensor, device and monitoring method for online monitoring of transformer leakage magnetic field, which uses an optical fiber structure as a sensing unit and reflects the magnetic field change through the change in the polarization state of light. The principle is as follows Figure 4 and Figure 5 As shown, the laser first passes through the polarization controller, is adjusted to linear polarized light, and then enters the sensor. The light polarization conversion caused by the Faraday effect causes the grating bandwidth to change, and then it is emitted into the photodetector through the analyzer, and finally the transformer leakage magnetic measurement result is determined by the signal processing device. This patent has the advantages of being free from electromagnetic interference and easy to install, and can realize online monitoring of transformer leakage magnetic, but the power supply of the sensor needs to be connected from the outside, the power supply equipment has a limited life, high maintenance cost, and low conversion efficiency. At the same time, it increases the size of the device and has certain requirements for the installation location.

[0008] Technology 4 related to the present invention [Ji Mao, Qi Bo, Zheng Wei, et al. Research on the leakage magnetic distribution law and coding identification method of typical transformer winding defects [J]. Power System Technology, 2024, 48(05): 2133-2142.] established a 110kV true transformer model, set winding deformation and turn-to-turn short-circuit faults of different degrees, positions and forms for transformer winding defects, and performed simulation analysis, and obtained the change law of leakage magnetic distribution during faults. It not only proved the significance of the research and development of leakage magnetic sensors, but also provided a reference for the sensor layout. However, the actual research and development of magnetic field sensors capable of monitoring the transformer leakage magnetic field has not been completed. Summary of the invention

[0009] The present invention relates to a transformer magnetic leakage sensor that can realize self-power supply, proposes an optimized arrangement method of sensors in transformer magnetic leakage field monitoring, and provides the optimized installation quantity and position of the magnetic leakage field sensor. The present invention discloses the following technical solutions: A self-energy magnetic field sensor for transformer leakage magnetic field monitoring, comprising: a Hall effect magnetic field sensor, a vibration energy acquisition device, wherein the vibration energy acquisition device utilizes the energy of transformer vibration to generate electrical energy to supply the Hall effect magnetic field sensor; the characteristic is that: the vibration energy acquisition device comprises: a base, a cantilever I, a cantilever II, a cantilever III, a weight I, a weight II, and a weight III; the base is connected to the cantilever I, cantilever II, and cantilever III; the base is fixed to the wall of the transformer oil tank by hot melt adhesive, vibrates with the transformer, and drives the cantilever I, cantilever II, and cantilever III to vibrate; the cantilever I is connected to the weight I; the cantilever II is connected to the weight II; the cantilever III is connected to the weight III.

[0010] The present invention also discloses a method for arranging leakage magnetic field sensors, which is characterized by comprising the following steps: Step 1: Use simulation software based on the finite-difference time-domain method to build a two-dimensional axisymmetric model of a three-winding transformer at a ratio of 10:1, set parameters such as the relative dielectric constant and magnetic permeability of each part of the material, ignore the mutual influence of the magnetic field between phases, and only take one phase for analysis; Step 2: Through simulation analysis, the transformer leakage magnetic field distribution under three conditions: normal, winding deformation, and inter-turn short circuit; when simulating the normal condition of the transformer, the corresponding current is directly applied to the winding; when simulating the inter-turn short circuit, a short-circuit current 20 times the normal current is applied to the short-circuited turn; winding deformation faults are divided into radial deformation and axial deformation; Step 3: Process the simulation results of different fault types and fault locations to obtain the overlapping area of ​​the maximum magnetic field intensity of each surface of the outer wall of the transformer tank under different faults, so as to preliminarily determine the range of sensor layout positions, and then compare the magnetic field intensity of each overlapping area, and combine it with the actual number of sensors to obtain the specific layout position of the leakage magnetic field sensor; Step 4: Based on the position information obtained in step 3, stick the leakage magnetic field sensor to the corresponding position of the transformer with hot melt adhesive to start monitoring the temporal and spatial distribution of the transformer leakage magnetic field. Beneficial Effects

[0011] (1) A vibration energy harvesting device is added to use the vibration energy generated during the operation of the transformer to power the sensor. It has a simple structure, can achieve long-term self-energy harvesting, and reduce maintenance costs.

[0012] (2) An optimal arrangement scheme for the number and location of leakage magnetic field sensors is proposed. The leakage magnetic field of the transformer under normal and fault conditions is analyzed in advance through simulation software to obtain the optimal arrangement number and location of the sensors to achieve the best monitoring effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of a leakage magnetic field detection device of prior art 1; Figure 2 This is a schematic diagram of measuring magnetic field through Hall effect in prior art 1; Figure 3 Schematic diagram of transformer magnetic field sensor device and test platform based on tapered micro-nano optical fiber; Figure 4 This is a schematic diagram of the principle of the fiber laser magnetic field sensor; Figure 5 The structure diagram of the sensor used for online monitoring of transformer leakage magnetic field; Figure 6 It is a schematic diagram of the sensor of the present invention; Figure 7 It is a structural schematic diagram of the vibration energy extraction device of the present invention; Figure 8 It is a schematic diagram of the structure of cantilever I of the present invention; Fig. 9 This is a schematic diagram of the simulated fault setting of the present invention. DETAILED DESCRIPTION Example

[0014] In order to overcome the problem that the existing transformer leakage magnetic field monitoring device needs external power supply and cannot realize self-energy supply, and the problem that the sensor arrangement position is unclear and cannot realize accurate and efficient measurement of the leakage magnetic field, the present invention improves the existing monitoring device and designs a self-energy magnetic field sensor suitable for transformer leakage magnetic field monitoring. The piezoelectric piece is periodically deformed by using a cantilever and a weight installed on the transformer housing and vibrating with the transformer, and the vibration energy is converted into electrical energy, thereby powering the sensor. The technical solution is as follows: A self-energy magnetic field sensor for transformer leakage magnetic field monitoring includes: a Hall effect magnetic field sensor and a vibration energy extraction device; the sensor schematic diagram is shown in the attached invention Figure 6 The Hall effect magnetic field sensor 1 is attached to the transformer oil tank shell by hot melt adhesive. Figure 7 The vibration energy harvesting device includes a base 21, a cantilever Ⅰ22, a cantilever Ⅱ23, a cantilever Ⅲ24, a weight Ⅰ25, a weight Ⅱ26, and a weight Ⅲ27. The base 21 is connected to the cantilever Ⅰ22, the cantilever Ⅱ23, and the cantilever Ⅲ24; the base 21 is fixed to the wall of the transformer oil tank by hot melt adhesive, vibrates with the transformer, and drives the cantilever Ⅰ22, the cantilever Ⅱ23, and the cantilever Ⅲ24 to vibrate. It is required that the vibration energy harvesting device 2 can utilize the energy of the transformer vibration to generate electrical energy to supply the Hall effect magnetic field sensor 1. The cantilever Ⅰ22 is connected to the weight Ⅰ25, the cantilever Ⅱ23 is connected to the weight Ⅱ26, and the cantilever Ⅲ24 is connected to the weight Ⅲ27. Since the cantilever Ⅰ22, the cantilever Ⅱ23, and the cantilever Ⅲ24 have the same structure, the three cantilever structures are explained by taking the cantilever Ⅰ22 as an example. The schematic diagram of the structure of the cantilever Ⅰ22 is shown in the appendix of the invention. Figure 8 The cantilever I 22 includes piezoelectric ceramic I 31, piezoelectric ceramic II 32 and a central plate 33. Under the action of a heavy object, the piezoelectric sheets on both sides of the cantilever produce periodic deformation, thereby generating electrical energy.

[0015] The measurement principle of the sensor of the present invention is consistent with the prior art, but the power supply principle is different. The improvements are mainly in: (1) capturing the vibration energy during the operation of the transformer to power the sensor; (2) simulating the distribution of the transformer leakage magnetic field to obtain the optimal sensor layout plan. Example

[0016] In the existing transformer leakage magnetic field monitoring method, the distribution characteristics of the leakage magnetic field are not studied, so the optimized specific arrangement quantity and position scheme of the leakage magnetic field sensor cannot be given. In order to further improve the sensor detection effect while reducing costs and realize efficient measurement of the transformer leakage magnetic field, the present invention pre-simulates the temporal and spatial distribution of the transformer leakage magnetic field to obtain the optimal arrangement scheme of the position and quantity of the leakage magnetic field sensor.

[0017] The optimal arrangement method for monitoring transformer leakage magnetic field using the above sensors is as follows: Step 1: Use simulation software based on the finite-difference time-domain method to build a two-dimensional axisymmetric model of a three-winding transformer at a ratio of 10:1. Set the parameters such as the relative dielectric constant and magnetic permeability of each part of the material, ignore the mutual influence of the magnetic field between phases, and only take one phase for analysis.

[0018] Because the three phases of the transformer are symmetrical and the conditions are similar, that is, the leakage magnetic field at different positions (angles) along the axial symmetry axis is approximately equal. Therefore, only one phase is taken for analysis. Compared with the three-dimensional model, the two-dimensional model is simpler and faster in calculation, and can significantly reduce the consumption of computing resources. This is particularly important for optimization in engineering design and product development. The two-dimensional modeling method is simple and easy to promote and apply in product design, and the calculation results can meet the requirements of engineering design. Therefore, it is chosen to build a two-dimensional axisymmetric model of a three-winding transformer.

[0019] The reason for selecting parameters such as dielectric constant and magnetic permeability is that dielectric constant and magnetic permeability are key parameters for describing the electromagnetic properties of materials. Dielectric constant affects the behavior of materials in electric fields, while magnetic permeability affects the behavior of materials in magnetic fields. In the simulation of transformer leakage magnetic field, these parameters determine the propagation and distribution of electromagnetic fields in different materials. By accurately setting the dielectric constant and magnetic permeability, the electromagnetic field distribution inside the transformer can be calculated more accurately, which is crucial for the simulation of transformer leakage magnetic field. Specifically, the core material in the simulation model is 30QG105 silicon steel sheet, and the oil tank material is Q235 steel. The BH curves of the two materials are added to the simulation model. Except for the core and the oil tank wall, the relative magnetic permeability of other materials is 1.

[0020] The reason for not considering other parameters is that the settings of other parameters will not affect the accuracy of the simulation results. By simplifying and assuming, we can reduce the consumption of computing resources and improve the efficiency of the simulation while ensuring the accuracy of the simulation results. For example, we assume that the change of the electromagnetic field is sinusoidal, ignore the influence of high-order harmonics, and set the conductivity of the metal wire to a constant to further simplify the model. We ignore factors such as eddy currents in the core, displacement currents, circulating currents in the windings, and the hysteresis characteristics of the metal component materials, and focus on the analysis and research of the core, windings, and oil tanks.

[0021] Step 2: There are few existing studies on winding defect simulation of three-winding transformers. The leakage magnetic field distribution characteristics of three-winding transformers under two types of winding defects, winding deformation and inter-turn short circuit, are unclear, and no sensor optimization layout scheme that can realize online monitoring of leakage magnetic field under winding defects can be given. Therefore, the present invention conducts research on the leakage magnetic field distribution of three-winding transformers under three conditions: normal, winding deformation, and inter-turn short circuit.

[0022] The transformer leakage magnetic field distribution under three conditions of normal, winding deformation and inter-turn short circuit is simulated and analyzed. When simulating the normal condition of the transformer, the corresponding current is directly applied to the winding; when simulating the inter-turn short circuit, a short-circuit current 20 times the normal current is applied to the short-circuit turn based on the simulation of the normal condition. Finally, the winding deformation is set. Due to the symmetry of the model, the winding deformation is only set in the middle and upper part of the winding. According to the simulation results when the upper part of the winding is defective, the leakage magnetic field distribution law when the lower part of the winding is defective can be obtained. Radial deformation and axial deformation are set in the upper and middle parts of the winding: when radially deformed, the deformed winding produces a radial offset relative to the normal winding. According to the stress condition of the transformer winding, the offset direction of the radial deformation of the high-voltage winding points to the tank wall, while the offset direction of the medium-voltage winding and the low-voltage winding points to the iron core; when axially deformed, the spacing between the cakes of the deformed winding decreases. The existing description of the degree of winding deformation directly uses numerical values, which makes it difficult to make a horizontal comparison of radial deformation or axial deformation. Therefore, when the deformation amount is the same percentage (taken as 20%) relative to the winding size (thickness or width) in the deformation direction, it is the same degree of winding deformation, and the distribution law of the leakage magnetic field when the transformer winding is deformed is analyzed. Therefore, the present invention simulates the same degree of radial and axial deformation at different positions, and analyzes the distribution of the leakage magnetic field when the winding is deformed. The simulation model when the same degree of winding deformation occurs in the middle of the high-voltage winding is shown in the attached figure. Fig. 9 .

[0023] According to the simulation results, under normal circumstances, in the area outside the iron core and the oil tank wall, the transformer leakage magnetic field has a radial distribution. At the height position corresponding to the winding coil, the oil gap leakage magnetic field between the high-voltage winding and the medium-voltage winding has the maximum leakage flux density, and the leakage flux density gradually decreases along both sides, and the leakage flux between the iron core and the low-voltage winding reaches the minimum; at the height position corresponding to the insulation of the winding end, there is a maximum leakage flux between the iron core and the low-voltage winding, and as it approaches the oil tank wall, the leakage flux gradually decreases, and the leakage flux reaches the minimum near the oil tank wall.

[0024] In terms of winding deformation, the number of winding deformation cakes is taken as 8 cakes. According to the simulation results, the winding deformation at different positions has the maximum and minimum leakage flux changes in the area near the defective winding, and the farther away from the defective winding, the closer the leakage flux change is to 0. Therefore, without considering the number of built-in leakage magnetic field sensors installed, arranging sensors on the oil tank at the same height as the winding can effectively realize the monitoring of transformer winding deformation.

[0025] In terms of inter-turn short circuit, in order to obtain the transformer leakage magnetic field distribution under severe conditions to determine the requirements for the layout of the leakage magnetic sensor, the inter-turn short circuit degree is taken as 5%. According to the simulation results, when the inter-turn short circuit occurs in the low-voltage winding and the medium-voltage winding, the maximum leakage flux is near the short-circuited turn, and the leakage flux near the tank wall will also increase. When it occurs in the high-voltage winding, the maximum leakage flux is relatively small, and the leakage flux near the tank wall is reduced, and the minimum is reduced to 0mT.

[0026] By building an axisymmetric two-dimensional model of a three-winding transformer, the leakage magnetic field distribution under three conditions, normal, winding deformation, and inter-turn short circuit, was obtained through simulation analysis. The area with the largest change in leakage magnetic field under different working conditions was obtained, providing a basis for the arrangement of sensors.

[0027] Step 3: Process the simulation results of different fault types and fault locations to obtain the overlapping area of ​​the maximum magnetic field intensity on each surface of the outer wall of the transformer oil tank under different faults, so as to preliminarily determine the range of sensor layout positions. Then compare the magnetic field intensity of each overlapping area, and combine it with the actual number of sensors to obtain the specific layout position of the leakage magnetic field sensor.

[0028] The low, medium and high windings are divided into upper, middle and lower parts respectively. Three specific fault types, namely radial deformation of winding, axial deformation of winding and inter-turn short circuit, are set in the upper and middle parts and simulated (the simulation results of the lower part can be obtained by symmetry); then the simulation results of the leakage magnetic field distribution of the four oil tank walls of the front, rear, left and right of the transformer are compared. Since the maintenance and arrangement of the sensor on the upper wall of the oil tank are relatively difficult, even if it is installed, it will cause certain inconvenience to the maintenance work, so the upper wall of the oil tank is not considered. The simulation results of different fault types and fault locations are processed as follows: each surface is divided into 6 rectangular areas and numbered 1-6; then the absolute value of the maximum leakage flux of each area of ​​each surface of the tank wall under different faults is coded. When the absolute value of the leakage flux is greater than 4mT, the corresponding code is 2, when the absolute value of the leakage flux is between 0.3mT and 4mT, the corresponding code is 1, and when the absolute value of the leakage flux is less than 0.3mT, the corresponding code is 0; then the maximum magnetic field intensity coding results of the same surface of the outer wall under different faults are superimposed, and the two areas with the largest coding values ​​in the 6 rectangular areas are selected to preliminarily determine the range of sensor layout positions. Further compare the maximum magnetic field intensity coding superposition values ​​of the two largest areas of different surfaces horizontally, and sort them from large to small. If the corresponding position does not meet the installation conditions in actual situations (such as the presence of heat sinks or sleeve structures, etc.), this area is eliminated in the sequence, and the order of the remaining areas in the sequence is postponed. Then, combined with the actual number of sensors (assuming N), the center position of the first N areas is selected as the specific layout position of the leakage magnetic field sensor.

[0029] Step 4: Based on the position information obtained in step 3, stick the leakage magnetic field sensor to the corresponding position of the transformer with hot melt adhesive to start monitoring the temporal and spatial distribution of the transformer leakage magnetic field.

[0030] The present invention improves the power supply mode of the transformer leakage magnetic field sensor, and protects the leakage magnetic field sensor through a self-energy extraction solution of extracting energy through vibration during the operation of the transformer; by simulating the transformer leakage magnetic field, the sensor position and quantity are determined according to the simulation results, and the optimal arrangement of the sensors is obtained.

[0031] The basic principles, main features and advantages of the present invention are shown and described above.

[0032] Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and the specification only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention, and these changes and improvements fall within the scope of the present invention to be protected. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A self-energy magnetic field sensor for transformer leakage magnetic field monitoring, comprising: A Hall effect magnetic field sensor (1), a vibration energy harvesting device (2), wherein the vibration energy harvesting device (2) utilizes the energy of transformer vibration to generate electrical energy to supply the Hall effect magnetic field sensor (1); the characteristics are as follows: the vibration energy harvesting device comprises: a base (21), a cantilever I (22), a cantilever II (23), a cantilever III (24), a weight I (25), a weight II (26), and a weight III (27); the base (21) is connected to the cantilever I (22), the cantilever II (23), and the cantilever III (24); the base (21) is fixed to the wall of the transformer oil tank by hot melt adhesive, vibrates with the transformer, and drives the cantilever I (22), the cantilever II (23), and the cantilever III (24) to vibrate; the cantilever I (22) is connected to the weight I (25); the cantilever II (23) is connected to the weight II (26); the cantilever III (24) is connected to the weight III (27).

2. The self-energy magnetic field sensor for transformer leakage magnetic field monitoring according to claim 1 is characterized in that: The cantilever I (22), cantilever II (23) and cantilever III (24) have different lengths so as to increase the natural frequency of the vibration energy harvesting device (2) and improve the power generation efficiency of the piezoelectric energy harvesting device.

3. The self-energy magnetic field sensor for transformer leakage magnetic field monitoring according to claim 1 is characterized in that: The cantilever I (22), cantilever II (23) and cantilever III (24) adopt a piezoelectric bimorph structure; The cantilever I (22) comprises: a piezoelectric ceramic I (31), a piezoelectric ceramic II (32) and a central electrode plate (33); the piezoelectric ceramic I (31) and the piezoelectric ceramic II (32) are respectively connected via the central electrode plates (33), and are connected in parallel in terms of electrode lead-out.

4. A method for arranging leakage magnetic field sensors using the self-powered magnetic field sensor for transformer leakage magnetic field monitoring according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1: Use simulation software based on the finite-difference time-domain method to build a two-dimensional axisymmetric model of a three-winding transformer at a ratio of 10:1, set parameters such as the relative dielectric constant and magnetic permeability of each part of the material, ignore the mutual influence of the magnetic field between phases, and only take one phase for analysis; Step 2: Through simulation analysis, the transformer leakage magnetic field distribution under three conditions: normal, winding deformation, and turn-to-turn short circuit; When simulating the normal condition of the transformer, the corresponding current is directly applied to the winding; when simulating the inter-turn short circuit, a short-circuit current 20 times the normal current is applied to the short-circuited turn; winding deformation faults are divided into radial deformation and axial deformation; Step 3: Process the simulation results of different fault types and fault locations to obtain the overlapping area of ​​the maximum magnetic field intensity of each surface of the outer wall of the transformer tank under different faults, so as to preliminarily determine the range of sensor layout positions, and then compare the magnetic field intensity of each overlapping area, and combine it with the actual number of sensors to obtain the specific layout position of the leakage magnetic field sensor; Step 4: Based on the position information obtained in step 3, stick the leakage magnetic field sensor to the corresponding position of the transformer with hot melt adhesive to start monitoring the temporal and spatial distribution of the transformer leakage magnetic field.

5. A method for arranging leakage magnetic field sensors according to claim 4, characterized in that: In the process of simulating the transformer leakage magnetic field distribution, the transformer model is meshed and boundary conditions are set, wherein the left side of the transformer model is set as an axisymmetric boundary, i.e., the first type of boundary condition; the upper side, lower side and right side of the transformer model, i.e., the outer side of the oil tank wall, are set as the second type of boundary conditions.

6. A method for arranging leakage magnetic field sensors according to claim 4, characterized in that: Due to the symmetry of the transformer model, winding deformation is set only in the middle and upper part of the winding. According to the simulation results when the upper part of the winding is defective, the leakage magnetic field distribution law when the lower part of the winding is defective is obtained, and radial deformation and axial deformation are set in the upper and middle parts of the winding.

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