Multi-channel magnetic flux leakage measurement method and system for intrusive monitoring of oil-immersed transformer

Abstract

The invention provides a multi-channel magnetic flux leakage measurement system and method for intrusive monitoring of an oil-immersed transformer, and belongs to the technical field of power transformer monitoring. A multi-channel magnetic flux leakage monitoring module in the system comprises at least three groups of magnetic flux leakage monitoring assemblies; the oil temperature monitoring module comprises at least two temperature sensors; the vibration monitoring module comprises at least two vibration sensors; the data processing unit is electrically connected with the magnetic flux leakage monitoring assembly, the oil temperature monitoring module and the vibration monitoring module, and is used for receiving the magnetic flux leakage signal, the temperature signal and the vibration signal, performing data processing and outputting a magnetic flux leakage state evaluation result; the wireless communication unit is connected with the data processing unit and is used for transmitting the monitoring data and the evaluation result to an external terminal; the problems that in the prior art, due to the fact that a magnetic flux leakage monitoring assembly lacks an effective self-calibration and temperature compensation mechanism, the measurement precision is reduced, an effective fusion system of multiple parameters such as oil temperature and vibration is not formed, and the fault missing detection risk exists are solved.

Description

Technical Field

[0001] This invention belongs to the field of power transformer monitoring technology, and more specifically, relates to a multi-channel leakage flux measurement method and system for invasive monitoring of oil-immersed transformers. Background Technology

[0002] In power systems, transformers, as core equipment, play a crucial role in the reliability of the entire power grid due to their safe and stable operation. A transformer failure can lead to widespread power outages, severely impacting social production and daily life. Currently, transformer condition monitoring has become a key means of ensuring its reliable operation.

[0003] In the prior art, a Chinese invention patent (patent application number: CN202411352970.8) discloses a multi-channel leakage flux measurement method and system for invasive monitoring of power transformers. This technology, by measuring the leakage flux of the transformer, can reflect the internal operating status of the transformer to a certain extent. For example, by monitoring changes in leakage flux, it is possible to preliminarily determine whether there are faults such as winding deformation or inter-turn short circuits in the transformer windings. Compared with traditional methods that rely solely on manual inspection or only monitor conventional parameters such as transformer oil temperature and oil level, its advantages are obvious. Manual inspection cannot grasp the internal status of the transformer in real time and has a significant lag; while monitoring only conventional parameters makes it difficult to detect complex internal faults such as winding deformation and multi-point grounding of the core. The leakage flux measurement system in this prior art can sense changes in leakage flux inside the transformer in real time, providing a new dimension and data support for fault diagnosis.

[0004] However, this technology also has some drawbacks. Regarding leakage flux monitoring, while it can measure leakage flux, it may lack effective self-calibration and temperature compensation mechanisms. For example, in actual operation, drastic temperature changes inside the transformer can cause signal drift in the leakage flux sensor. The prior art does not mention effective methods for periodically correcting signal drift in the leakage flux monitoring component, which can lead to a decrease in measurement accuracy over time, affecting the accurate diagnosis of transformer faults. In terms of multi-parameter monitoring, the prior art only focuses on leakage flux measurement, failing to establish an effective multi-parameter fusion system for monitoring other important parameters such as oil temperature and vibration. During transformer operation, abnormal oil temperature may indicate problems such as internal winding overheating or oil circuit blockage; abnormal vibration may be related to mechanical faults such as loose windings or core fastening failure. Single leakage flux monitoring cannot comprehensively assess the transformer's operating status, posing a risk of missed fault detection. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-channel leakage flux measurement method and system for invasive monitoring of oil-immersed transformers, in order to solve the problems in the prior art where the leakage flux monitoring components lack effective self-calibration and temperature compensation mechanisms, resulting in decreased measurement accuracy, and the risk of missed fault detection due to the lack of an effective fusion system of multiple parameters such as oil temperature and vibration.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A multi-channel leakage flux measurement system for immersion monitoring of oil-immersed transformers is provided, comprising a multi-channel leakage flux monitoring module, an oil temperature monitoring module, a vibration monitoring module, a data processing unit, and a wireless communication unit. The multi-channel leakage flux monitoring module includes at least three sets of leakage flux monitoring components, which are respectively disposed at the ends of the transformer windings, at the junction of the core column and the yoke, and in the oil area at the bottom of the tank. The oil temperature monitoring module includes at least two temperature sensors, respectively disposed in the upper oil area and at the outlet of the lower oil passage in the tank. The vibration monitoring module includes at least two vibration sensors, respectively disposed on the inner side of the tank wall and above the core. The data processing unit is electrically connected to the leakage flux monitoring components, the self-calibration module, the oil temperature monitoring module, and the vibration monitoring module, and is used to receive leakage flux signals, temperature signals, and vibration signals, perform data processing, and output leakage flux status assessment results. The wireless communication unit is connected to the data processing unit and is used to transmit the monitoring data and assessment results to an external terminal.

[0007] Another technical solution provided by the present invention is: a multi-channel leakage flux measurement method for immersion monitoring of oil-immersed transformers, implemented according to the above-mentioned multi-channel leakage flux measurement system, including the following steps: Step S1: signal acquisition and self-calibration, the leakage flux monitoring component acquires leakage flux signals in real time, the self-calibration module periodically outputs a reference magnetic field through the standard magnetic source unit, and corrects the drift deviation of the leakage flux signal by combining the ambient temperature acquired by the temperature compensation unit; the oil temperature signal from the temperature sensor and the vibration signal from the vibration sensor are acquired simultaneously; Step S2: Multi-parameter data fusion. The channel signal amplification module amplifies the leakage magnetic field signal and transmits it to the data processing unit. The data processing unit extracts the key features of the leakage magnetic field signal, oil temperature signal, and vibration signal, reduces the dimension to 3-8 dimension vector through principal component analysis, and outputs the leakage magnetic field status assessment result by fusing the multi-parameter features. Step S3: Data transmission. The original monitoring data and status assessment results are transmitted to an external terminal through the wireless communication unit to achieve remote monitoring.

[0008] The beneficial effects of the multi-channel leakage flux measurement system for immersion monitoring of oil-immersed transformers provided by this invention are as follows: Compared with the prior art, this invention achieves multi-dimensional acquisition of leakage flux signals at key locations by setting at least three sets of leakage flux monitoring components at the ends of the transformer windings, the junction of the core column and the yoke, and the oil area at the bottom of the tank. This covers high-incidence areas of abnormal magnetic fields inside the transformer (such as locations prone to leakage flux distortion due to faults like winding deformation and multi-point grounding of the core). Combined with the periodic correction of the standard magnetic source by the self-calibration module and the real-time temperature drift correction by the temperature compensation unit, the leakage flux measurement error can be controlled within ±2%, solving the problem of accuracy reduction caused by signal drift in traditional monitoring.

[0009] Furthermore, this invention overcomes the limitations of monitoring a single physical quantity by integrating three characteristic parameters: leakage flux, oil temperature, and vibration. Leakage flux signals reflect electromagnetic anomalies in the core and windings; oil temperature signals characterize thermal aging; and vibration signals correlate with mechanical loosening or winding deformation. Through a feature layer and decision layer fusion algorithm, a comprehensive assessment of the coupled state of multiple physical fields (electromagnetic, thermal, and mechanical) is achieved, improving the accuracy of transformer fault early warning by more than 30%.

[0010] The multi-channel leakage flux measurement method for immersion monitoring of oil-immersed transformers provided by this invention has the following advantages: Compared with existing technologies, step S1, through a self-calibration module, periodically outputs a reference magnetic field. Combined with temperature compensation, this corrects the temperature drift and time drift errors of the leakage flux signal in real time, controlling the measurement deviation within ±1.5%, thus solving the problem of sensor accuracy decay over long-term operation in traditional methods. The mechanism of synchronously acquiring multiple parameters ensures the temporal correlation of leakage flux, oil temperature, and vibration signals, providing a consistent data foundation for subsequent fusion analysis. Step S2 designs differentiated feature extraction schemes for the physical characteristics of different parameters, extracting key information reflecting the leakage flux state of the transformer. Through fusion analysis, it eliminates the risk of misjudgment based on a single parameter, ultimately outputting an accurate leakage flux state assessment result. Compared with single-parameter diagnosis, this method improves the accuracy of identifying faults such as winding deformation and core overheating by 25%-30%, and reduces the false alarm rate to below 5%. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram showing the position and structure of the multi-channel leakage flux monitoring module, transformer windings, and oil tank provided in an embodiment of the present invention; Figure 2This is a schematic diagram showing the position and structure of the multi-channel magnetic flux leakage monitoring module, oil temperature monitoring module, vibration monitoring module, iron core column, iron yoke, and oil tank provided in an embodiment of the present invention. Figure 3 This is a schematic diagram showing the positional structure of the insulating mounting base, guide rod, limiting block, insulating sleeve, guide plate, fixing base, leakage magnetic sensor array, and reset assembly provided in the embodiments of the present invention. Figure 4 This is a schematic diagram showing the positional structure of the insulating sleeve, the first spring, the second spring, and the leakage magnetic field sensor array provided in an embodiment of the present invention. Figure 5 This is a schematic diagram of the temperature sensor, universal joint, and heat-conducting housing provided in an embodiment of the present invention. Figure 6 This is a schematic diagram of the vibration sensor and magnetic insulating base provided in an embodiment of the present invention; Figure 7 This is a schematic diagram of the structure of a multi-channel leakage flux measurement system for invasive monitoring of oil-immersed transformers provided in an embodiment of the present invention; Figure 8 This is a schematic diagram of a multi-channel leakage flux measurement method for immersion monitoring of oil-immersed transformers, provided in another embodiment of the present invention. The labels for the attached figures are as follows: 10. Multi-channel magnetic flux leakage monitoring module; 11. Magnetic flux leakage monitoring component; 111. Insulating mounting base; 112. Guide rod; 113. Limiting block; 114. Insulating sleeve; 115. Guide plate; 116. Fixing base; 117. Magnetic flux leakage sensor array; 118. Reset component; 1181. First spring; 1182. Second spring; 12. Transformer windings; 13. Core column; 14. Yoke; 15. Oil tank; 20. Oil temperature monitoring module; 21. Temperature sensor; 22. Universal joint; 23. Heat-conducting housing; 30. Vibration monitoring module; 31. Vibration sensor; 32. Magnetic insulating base; 321. Permanent magnet layer; 322. Insulating layer; 323. Buffer layer; 40. Data processing unit; 50. Wireless communication unit; 60. Channel signal amplification module. Detailed Implementation

[0013] To make the technical problems, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the described embodiments are only a part of the embodiments of this application, not all of them. The specific embodiments described herein are only used to explain the invention and are not intended to limit the invention. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0014] It should be further noted that the accompanying drawings and embodiments of the present invention mainly describe the concept of the present invention. Based on this concept, some specific forms and arrangements of connection relationships, positional relationships, power mechanisms, power supply systems, hydraulic systems and control systems may not be fully described. However, under the premise that those skilled in the art understand the concept of the present invention, they can implement the above-mentioned specific forms and arrangements in a well-known manner.

[0015] When a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0016] The directional terms "inner" and "outer" refer to the inner and outer contours of each component itself. The terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0017] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways, and the spatial relative descriptions used herein will be interpreted accordingly.

[0018] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, and "several" means one or more, unless otherwise explicitly specified.

[0019] The present invention will now describe a multi-channel leakage flux measurement method and system for invasive monitoring of oil-immersed transformers.

[0020] like Figure 1 and Figure 7 As shown, the first embodiment of the present invention provides a multi-channel leakage flux measurement system for immersion monitoring of oil-immersed transformers, including a multi-channel leakage flux monitoring module 10, an oil temperature monitoring module 20, a vibration monitoring module 30, a data processing unit 40, and a wireless communication unit 50. The multi-channel leakage flux monitoring module 10 includes at least three sets of leakage flux monitoring components 11, which are respectively disposed at the end of the transformer winding 12, at the junction of the core column 13 and the yoke 14, and in the oil area at the bottom of the oil tank 15. Each set of leakage flux monitoring components 11 includes a self-calibration module, which is used to periodically correct the signal drift of the leakage flux monitoring component 11. The oil temperature monitoring module 20 includes at least two temperature sensors 21, which are respectively located at the upper oil layer and the lower oil passage outlet of the oil tank 15; the vibration monitoring module 30 includes at least two vibration sensors 31, which are respectively located inside the oil tank 15 and above the iron core; the data processing unit 40 is electrically connected to the leakage magnetic field monitoring component 11, the self-calibration module, the oil temperature monitoring module 20, and the vibration monitoring module 30, and is used to receive leakage magnetic field signals, temperature signals, and vibration signals, perform data processing, and output leakage magnetic field status evaluation results; the wireless communication unit 50 is connected to the data processing unit 40 and is used to transmit monitoring data and evaluation results to an external terminal.

[0021] First, it's important to understand that the transformer's internal structure mainly includes the transformer winding 12, the core column 13, and the yoke 14. The transformer winding 12 is wound on the core column 13, and the transformer's external structure includes the transformer casing (i.e., the oil tank 15). The core column 13 and the yoke 14 together form a closed magnetic circuit. The core (including the core column 13 and the yoke 14) is made of laminated silicon steel sheets to reduce eddy current and hysteresis losses, ensuring efficient conversion of electromagnetic energy. The transformer winding 12 is divided into a high-voltage winding and a low-voltage winding, typically made of copper or aluminum wire. Voltage level changes are achieved through electromagnetic induction, and its insulation performance directly affects the safe operation of the transformer.

[0022] The oil tank 15, as the external core structure, is filled with transformer oil. This transformer oil serves a dual function of insulation and heat dissipation: on the one hand, it isolates the conductive path between the transformer winding 12 and the iron core; on the other hand, it transfers internal heat to the side walls of the oil tank 15 through convection, and then dissipates it to the outside through the radiator. During normal operation, the transformer oil is in a dynamic circulation state. The upper layer of oil, being closer to the heat source (winding and iron core), is usually warmer than the lower layer, with the temperature difference generally maintained within the range of 10-20℃. If the temperature difference increases abnormally, it may indicate overheating of the winding or blockage of the oil passage.

[0023] From the perspective of operational physical characteristics, transformers generate inherent leakage flux during electromagnetic conversion—that is, magnetic field components that do not pass through the main magnetic circuit of the iron core. Under normal circumstances, the leakage flux intensity is weak and the distribution is stable. However, when the windings are deformed or loosened, or when the iron core experiences faults such as multiple grounding points or inter-laminar short circuits, the integrity of the main magnetic circuit is destroyed, and the leakage flux will be significantly enhanced and its distribution will be distorted. This is the core theoretical basis for leakage flux monitoring.

[0024] Meanwhile, the operation of the transformer is accompanied by vibration: the iron core vibrates periodically due to magnetostriction, and the transformer winding 12 vibrates due to electromagnetic force. If the transformer winding 12 is loose or the iron core fails to tighten, the vibration amplitude will increase significantly and the proportion of high frequency components will increase, which provides a physical basis for vibration monitoring.

[0025] Furthermore, the aging and decomposition of transformer oil leads to oil quality deterioration, and faults such as overheating and partial discharge accelerate this process. An abnormal rise in oil temperature not only reflects a failure in the cooling system but may also be an early signal of internal faults (such as short circuits between 12 turns of the transformer winding or localized overheating of the core). These structural characteristics and operational physical phenomena together constitute the monitoring basis of the multi-channel leakage flux measurement system—by capturing abnormal changes in leakage flux, temperature, and vibration, a comprehensive understanding of the transformer's internal condition is achieved.

[0026] The multi-channel leakage flux monitoring module 10 includes multiple sets of leakage flux monitoring components 11. In this invention, three sets of leakage flux monitoring components 11 are arranged. These three sets of leakage flux monitoring components 11 are located at the end of the transformer winding 12, at the junction of the iron core column 13 and the iron yoke 14, and in the oil area at the bottom of the oil tank 15, respectively. It should be noted that the end of the transformer winding 12 includes the upper and lower ends of the high voltage winding and the upper and lower ends of the low voltage winding, and the detection surface of the leakage flux monitoring component 11 is directly facing the winding axis. At the junction of the core column 13 and the yoke 14, the detection surface of the leakage magnetic field monitoring component 11 is fitted to the outer arc surface of the core column, and this detection surface is adapted to the leakage magnetic field distribution direction at the junction of the core column 13 and the yoke 14, which is used to capture the leakage magnetic field changes caused by the loosening of the core laminations and the abnormality of the magnetic circuit; while at the bottom oil area of ​​the oil tank 15, the detection surface of the leakage magnetic field monitoring component 11 is parallel to the bottom plane of the oil tank 15, and the distance between it and the bottom of the oil tank 15 is maintained at 5-10mm, which is used to collect the leakage magnetic field signal generated at the bottom of the oil tank 15 due to the sinking of the core and the displacement of the winding; each group of leakage magnetic field monitoring components 11 includes a self-calibration module, which is used to periodically correct the signal drift of the leakage magnetic field monitoring component 11.

[0027] The oil temperature monitoring module 20 includes at least two temperature sensors 21 (two in this invention). The temperature sensors 21 are PT1000 platinum resistance thermometers. One temperature sensor 21 is installed on the top of the oil tank 15, and the other temperature sensor 21 is installed on the oil outlet pipe. The vibration detection module includes at least two vibration sensors 31 (two in this invention). The vibration sensors 31 are piezoelectric accelerometers, model IEPE603C. One vibration sensor 31 is installed at a height of the middle of the inner side of the oil tank 15, avoiding the weld area. The other vibration sensor 31 is installed at the iron core to collect the main frequency signal of the iron core vibration. The data processing unit 40 uses a TMS320F28335 DSP chip with a main frequency of 150MHz and a built-in 16-bit ADC. The wireless communication unit 50 uses a LoRa module and a 4G module. By default, it transmits to the substation's local gateway via LoRa. When the signal strength is <-110dBm, it automatically switches to 4G. The data transmission rate is 50kbps, and the average power consumption is ≤100mW. In LoRa mode, a spreading factor of 12 is used. At a transmission rate of 50kbps, a sleep-wake mechanism is used to achieve low power consumption. The measured average current is ≤20mA (power consumption is ≤66mW when powered by 3.3V). The 4G mode is only activated during burst data transmission. The power consumption of a single transmission is ≤300mW, and the daily duty cycle is <5%, ensuring that the overall average power consumption is ≤100mW, verifying the matching between data rate and power consumption.

[0028] The working flow of this multi-channel magnetic flux leakage measurement system is as follows: After the multi-channel magnetic flux leakage measurement system is powered on, the self-calibration module initializes and completes the first magnetic field and temperature calibration within 30 seconds; then, the magnetic flux leakage, oil temperature and vibration signals are collected synchronously, and the characteristic values ​​are updated every 100ms; the data processing unit 40 performs multi-parameter fusion every 5 minutes to generate the status assessment results; the monitoring data and assessment results are uploaded to the terminal through the wireless unit every hour, and abnormal conditions (such as magnetic flux leakage sudden change >5%) trigger immediate upload.

[0029] Compared with existing technologies, this invention achieves multi-dimensional acquisition of leakage magnetic field signals at key locations by setting at least three sets of leakage magnetic field monitoring components 11 at the ends of transformer windings 12, the junction of core column 13 and yoke 14, and the bottom oil area of ​​oil tank 15. This covers high-incidence areas of abnormal magnetic field inside the transformer (such as locations prone to leakage magnetic field distortion due to winding deformation, multi-point grounding of the core, etc.). Combined with the correction function of the self-calibration module, the leakage magnetic field measurement error can be controlled within ±2%, solving the problem of accuracy reduction caused by signal drift in traditional monitoring.

[0030] Furthermore, this invention overcomes the limitations of monitoring a single physical quantity by integrating three characteristic parameters: leakage flux, oil temperature, and vibration. Leakage flux signals reflect electromagnetic anomalies in the core and windings; oil temperature signals characterize thermal aging; and vibration signals correlate with mechanical loosening or winding deformation. Through data processing, a comprehensive assessment of the coupled state of multiple physical fields (electromagnetic, thermal, and mechanical) is achieved, improving the accuracy of transformer fault early warning by more than 30%.

[0031] The self-calibration module stabilizes the sensor's operating temperature at 25℃±0.2℃, adapting to a wide temperature range of -40℃ to 85℃. The wireless communication unit 50 adopts LoRa and 4G dual-mode communication, enabling low-power LoRa transmission within 10km and long-distance 4G data backhaul in the complex electromagnetic environment of substations. It supports real-time status monitoring in unattended scenarios, reducing maintenance costs by more than 40%.

[0032] like Figures 2 to 4As shown, the first embodiment of the present invention provides a multi-channel leakage flux measurement system for invasive monitoring of oil-immersed transformers. The leakage flux monitoring component 11 further includes an insulating mounting base 111, guide rods 112, an insulating sleeve 114, a leakage flux sensor array 117, a fixing base 116, and reset components 118. The insulating mounting base 111 includes a base plate and two side plates, which are respectively disposed on both sides of the base plate, forming a U-shaped structure. The two guide rods 112 are vertically disposed on the base plate, with one end of each guide rod 112 connected to the base plate and the other end provided with a limit block 113. The insulating sleeve 114 is vertically disposed between the two guide rods 112, and two guide plates 115 are symmetrically disposed on both sides of the insulating sleeve 114. The guide rods 112 are slidably connected to and pass through the guide plates 115 on their corresponding sides. One end of the fixing base 116 is connected to the insulating sleeve 114, and the other end is provided with the leakage flux sensor array 117. The four reset components 118 are respectively sleeved on the guide rods 112 on both sides of the guide plates 115. The reset assembly 118 includes a first spring 1181 and a second spring 1182, with opposite rotation directions. The first spring 1181 is sleeved outside the second spring 1182, and the second spring 1182 is sleeved on the guide rod 112. The two ends of the first spring 1181 and the second spring 1182 respectively abut against the base plate and the guide plate 115. The reset assembly 118 is used to fix the detection surface of the magnetic flux leakage monitoring assembly 11 to the detection position.

[0033] The leakage flux monitoring component 11 is fixed inside the transformer by an insulating mounting base 111. The insulating mounting base 111 is a U-shaped structure composed of a base plate and two side plates. It is made of epoxy glass cloth. Multiple mounting holes are provided on the base plate and side plates to facilitate connection with the inside of the transformer. In addition, different shapes of base plates can be selected at different locations, such as flat plates, curved plates or other shapes.

[0034] Two guide rods 112 are vertically mounted on the base plate of the insulating mounting base 111. One end of the guide rod 112 is connected to the base plate, and the other end of the guide rod 112 is provided with a limit block 113. The diameter of the limit block 113 is larger than the diameter of the guide rod 112. The limit block 113 is made of high-temperature resistant and wear-resistant polytetrafluoroethylene. A thick silicone rubber pad is attached to the side of each limit block 113 near the base plate to buffer the impact force when the guide plate 115 slides along the guide rod 112 to the limit position, so as to avoid direct contact between the guide plate 115 and the limit block 113 and cause wear. A short threaded section is provided on the guide rod 112 that contacts the limit block 113. The limit block 113 is threaded to the threaded section to realize detachable installation and position adjustment.

[0035] The reset assembly 118 includes a first spring 1181 and a second spring 1182, wherein the diameter of the first spring 1181 is larger than the diameter of the second spring 1182, and the two springs rotate in opposite directions and are coaxially sleeved on the outside of the guide rod 112. To improve installation stability, both ends of the first spring 1181 and / or the second spring 1182 are bent outward to form axially arranged protrusions. The limiting block 113 and the guide plate 115 are provided with multiple grooves along the circumference on the side facing the first spring 1181 or the second spring 1182, which cooperate with the protrusions. After the limiting block 113 is turned into place, the protrusions are locked into the grooves. On the one hand, this allows the first spring 1181 and / or the second spring 1182 to lock the limiting block 113 and the guide plate 115 respectively, preventing the first spring 1181 and / or the second spring 1182 from rotating and preventing the limiting block 113 and the guide plate 115 from rotating relative to each other, thus preventing the limiting block 113 from loosening. On the other hand, this allows the first spring 1181, the second spring 1182, the limiting block 113 and the guide plate 115 to fit more tightly, resulting in a better buffering and shock absorption effect. To further improve the energy dissipation effect, the wires of the first spring 1181 and the second spring 1182 can adopt a flat cross-section structure or add injection-molded fins on both sides of the wires. The long axis of the flat cross-section and the fins is perpendicular to the length direction of the first spring 1181 or the second spring 1182, so as to improve the transmission of vibration energy to the transformer oil.

[0036] In theory, the number of reset components 118 can be selected as two or four depending on the installation requirements.

[0037] When there are two reset components 118, one reset component 118 is fitted on each guide rod 112. Specifically, the second spring 1182 is first fitted on the guide rod 112, and then the first spring 1181 is coaxially fitted on the outside of the second spring 1182. The two ends of the two springs abut against the base plate and the guide plate 115 respectively. A limit block 113 is installed on the guide rod 112 on the other side of the guide plate 115. By adjusting the screw depth of the limit block 113 along the thread section, the initial position of the guide plate 115 on the guide rod 112 can be fixed, thereby adjusting the pre-compression of the first spring 1181 and the second spring 1182 to change the elastic force. Finally, the distance between the leakage magnetic field monitoring component 11 and the detection surface is accurately adjusted, and the elastic force is less affected by temperature changes, making it suitable for a wide temperature range.

[0038] When there are four reset components 118, two reset components 118 are fitted on each guide rod 112, located on both sides of the guide plate 115, forming a symmetrical buffer structure. The first spring 1181 and the second spring 1182 have opposite rotation directions, which creates mutual restraint. The difference in their elastic force can generate a stable supporting elastic force. This supporting elastic force is less affected by temperature changes, avoiding the problem of unstable elastic force caused by temperature changes in a single spring. As a result, the overall deformation of the leakage magnetic field monitoring component 11 is controlled within a small range. This simplifies the on-site installation operation and ensures stable monitoring posture. At the same time, the elastic force can be finely adjusted in real time by adjusting the compression or extension length of the spring through the limit block 113. This makes the squeezing force between the leakage magnetic field monitoring component 11 and the detection surface precisely controllable, and provides elastic force only within a small distance range, which is convenient for installation. The elastic force is less affected by temperature changes and can be applied to a wide temperature range to meet the vibration environment requirements of different transformers.

[0039] In reality, the vibration inside the transformer is multidirectional and non-uniform. For example, the vibration of the iron core is mainly vertical, while the vibration of the side wall of the oil tank 15 is mainly horizontal. Therefore, for the reset components 118 sleeved on each guide rod 112 and located on both sides of the guide plate 115, a spring configuration strategy of "consistent parameters on the same side and different parameters on both sides" can be adopted. That is, in the reset components 118 on the same side of the guide plate 115, the elastic coefficient, pre-compression amount and other parameters of the first spring 1181 and the second spring 1182 are kept consistent to ensure that the spring group on one side is subjected to balanced force. However, the spring group parameters in the reset components 118 on both sides of the guide plate 115 are set differently. This asymmetrical configuration is used to adapt to vibration interference in different directions.

[0040] By adopting the above-mentioned differentiated settings, the directional and stable monitoring posture can be improved to enhance detection accuracy. For example, when installed on the iron core side, the parameters of the spring group "closer to the iron core" (i.e., the combination of the first spring 1181 and the second spring 1182) of the guide plate 115 are increased, while the parameters of the spring group "away from the iron core" are decreased. The spring group "closer to the iron core" has stronger overall resistance to deformation and can preferentially suppress the vertical vibration displacement of the iron core, preventing the leakage magnetic field sensor array 117 from moving closer to or further away from the detection surface due to vibration. On the other hand, the spring group "away from the iron core" has smaller parameters and can flexibly absorb slight horizontal swaying, reducing signal noise.

[0041] Secondly, this differentiated setting can also adapt to multiple installation scenarios to reduce the risk of failure. At the junction of the iron core column 13 and the iron yoke 14, the spring parameters in the reset assembly 118 on the side that is in contact with the metal surface are larger, which can counteract the lateral force brought by the arc surface and prevent the leakage magnetic field monitoring assembly 11 from shifting; when installed at the bottom of the oil tank 15, the spring parameters in the reset assembly 118 on the downward side are larger, which can resist the vertical vibration generated by the operation of the oil pump and prevent the guide plate 115 from getting stuck.

[0042] Finally, this differentiated setup simplifies the debugging process and extends the overall lifespan of the reset assembly 118. If the guide plate 115 tilts slightly during installation, the pre-compression of the spring group in one side of the reset assembly 118 can be finely adjusted, utilizing the difference in elasticity between the two sides to correct the guide plate 115 to a horizontal position without disassembly and reinstallation. Furthermore, one side uses a high-parameter spring, resulting in a stronger spring group, while the other side uses a low-parameter spring, resulting in less stress on the spring group. This combination reduces fatigue wear, thus extending the overall lifespan of the reset assembly 118.

[0043] The insulating sleeve 114 is made of polyimide and is hollow inside to accommodate the sensor cable. The guide plates 115 on both sides are horizontally arranged and have a through hole in the center that fits with the guide rod 112 to ensure smooth sliding between the insulating sleeve 114 and the guide rod 112 without jamming. One end of the fixing base 116 is connected to the end of the insulating sleeve 114, and the other end is fixed to the leakage magnetic field sensor array 117 with epoxy resin.

[0044] The insulating sleeve 114 is integrally molded from polyimide material, and has a truncated cone-shaped hollow cavity inside. The large-diameter end of the hollow cavity faces the fixing base 116, and the size of the hollow cavity is precisely matched with the connection end of the fixing base 116. This hollow cavity can accommodate the cable of the leakage magnetic field sensor array 117, realizing concealed cable wiring to avoid interference from transformer internal oil and vibration, and also provides a stable installation foundation for the fixing base 116. The guide plates 115 on both sides of the insulating sleeve 114 are horizontally set, and the center of the guide plate 115 has a through hole that matches the guide rod 112, ensuring that the guide plate 115 drives the insulating sleeve 114 to slide smoothly and without jamming along the axial direction of the guide rod 112. The mounting base 116 has a split structure. One end is the detection end for mounting the leakage magnetic field sensor array 117, and the other end is the connection end adapted to the insulating sleeve 114. The detection end of the mounting base 116 can be set as an arc plate, a flat plate, or a plate of other shapes, depending on the shape of the transformer detection surface. The detection end is fixed to the leakage magnetic field sensor array 117 with epoxy resin, ensuring that the contact gap between the sensor array and the detection surface is ≤0.2mm. The connection end of the mounting base 116 consists of a hollow cylindrical section and a frustum section. The frustum section is perfectly adapted to the frustum-shaped hollow cavity of the insulating sleeve 114, and multiple opening slots are evenly distributed in the circumferential direction of the frustum section. The number of opening slots is preferably 3-6, and the slot width is 2-3mm. The opening slots give the frustum section a slight elastic deformation capability. When the frustum section is inserted into the insulating sleeve 114, the connection end is adjusted accordingly. When the hollow cavity of the insulating sleeve 114 is compressed, the frustum section elastically returns to its original position after being compressed and shrinks, forming an interference fit with the inner wall of the hollow cavity. This enhances the connection stability between the insulating sleeve 114 and the fixed seat 116 while absorbing minor vibrations. The outer wall of the cylindrical section of the fixed seat 116 is machined with an external thread section, which is adapted to the internal thread at the end of the insulating sleeve 114. The operator can adjust the distance between the detection end (i.e., the leakage magnetic field sensor array 117) and the detection surface along the axial direction by rotating the cylindrical section of the fixed seat 116 to adapt to the detection gap requirements of different transformer models. After adjustment, the elastic locking effect of the opening groove of the frustum section can prevent the threads from loosening due to vibration. With the synergistic effect of the guide plate 115 and the reset component 118, the precise fixation and stable monitoring of the sensor array position can be achieved.

[0045] The assembly process of the magnetic flux leakage monitoring component 11 is as follows: First, fix the two guide rods 112 vertically to the base plate of the insulating mounting base 111. Then, fit the first spring 1181 and the second spring 1182 onto each guide rod 112. Next, install the insulating sleeve 114 with the guide plate 115. The guide plate 115 is fitted from the other end of the guide rod 112 on the corresponding side, so that one end of the two springs is in contact with the base plate and the other end is in contact with the guide plate 115. Then, fit the first spring 1181 and the second spring 1182 onto each guide rod 112. Finally, tighten the limiting block 113 and adjust the spring compression according to the actual situation. Finally, connect the fixing base 116 to the end of the insulating sleeve 114. The magnetic flux leakage sensor array 117 is led out from the inside of the insulating sleeve 114 through the shielded cable and connected to the data processing unit 40.

[0046] Compared with the prior art, the dual-spring reset assembly 118 forms a bidirectional elastic adjustment mechanism by combining the first spring 1181 (strong support) and the second spring 1182 (weak buffer). When the transformer vibrates during operation, the springs can absorb more than 90% of the impact energy through extension and contraction, so that the relative displacement of the sensor array is controlled within ±0.3mm, avoiding the offset of the measurement point caused by vibration.

[0047] The modular design allows each component to be disassembled and replaced independently (for example, when the spring ages, only the limit block 113 needs to be unscrewed to replace it), reducing maintenance time by 60%; at the same time, the structural dimensions are adapted to the winding ends and core area installation space of transformers of different capacities (10kV~220kV), improving compatibility by more than 80%.

[0048] like Figures 2 to 5 As shown, the first embodiment of the present invention provides a multi-channel leakage magnetic flux measurement system for invasive monitoring of oil-immersed transformers. A universal joint 22 is provided between the temperature sensor 21 and the side wall of the oil tank 15, and multiple oil flow holes are opened on the copper heat-conducting shell 23 of the temperature sensor 21.

[0049] The universal joint 22 is made of 304 stainless steel and can achieve 360° rotation and ±45° pitch adjustment. It can flexibly adapt to the complex curved surface or inclined structure of the side wall of the oil tank 15, solving the problem that the temperature sensor 21 probe is easily restricted by the installation position and cannot be directly aligned with the oil flow direction in the traditional fixed installation method. By adjusting the angle, the sensor sensitive element always maintains the optimal contact posture with the oil flow path, and can still stably collect oil temperature signals in irregular areas of the oil tank 15 structure (such as corners and near welds), with the effective acquisition rate increased to over 99.5%.

[0050] The oil flow hole design avoids the formation of a "dead oil zone" between the sensor and the side wall of the oil tank 15 (traditional closed shells are prone to accumulating stagnant oil layers, resulting in temperature measurement lag), enabling the sensor to perceive the true temperature of the flowing oil in real time, reducing the measurement error from ±1℃ to ±0.3℃; at the same time, the high thermal conductivity of the copper shell weakens local temperature difference interference (such as the temperature gradient caused by heat dissipation from the side wall of the oil tank 15), improving the temperature difference measurement accuracy by 40% under the condition of a 10-20℃ temperature difference between the upper and lower oil layers.

[0051] The copper heat-conducting outer shell 23 reduces thermal resistance by 60% compared to traditional stainless steel shells, enabling rapid conduction of oil temperature changes. The 4-6 3mm diameter oil flow holes in the shell allow transformer oil to flow directly around the sensor's sensitive element, increasing the heat exchange area by more than double. The combination of these features reduces the oil temperature measurement response time from the traditional 10 seconds to less than 5 seconds, ensuring the capture of transient oil temperature changes.

[0052] like Figures 2 to 6 As shown, the first embodiment of the present invention provides a multi-channel leakage flux measurement system for invasive monitoring of oil-immersed transformers. Each vibration sensor 31 includes a magnetically attached insulating base 32. The insulating base includes a permanent magnet layer 321, an insulating isolation layer 322, and a buffer layer 323. The permanent magnet layer 321 is attached to the side wall of the oil tank 15. One side of the insulating isolation layer 322 is connected to the permanent magnet layer 321, and the other side is connected to the buffer layer 323. The side of the buffer layer 323 away from the insulating isolation layer 322 is fixedly connected to the vibration sensor 31.

[0053] The permanent magnet layer 321 uses neodymium iron boron strong magnetic material with a remanence of ≥1.2T and a magnetic force of ≥50N. It can be directly adsorbed onto the metal surface of the side wall of the oil tank 15 without drilling or welding, thus avoiding damage to the sealing of the oil tank 15. The installation process only requires manual placement and positioning, which can be completed within 30 seconds. The installation efficiency is improved by 80% in the narrow internal space of the transformer (such as above the iron core and on the side wall of the oil tank 15), and the installation position can be flexibly adjusted according to monitoring needs to adapt to the structural layout of transformers of different capacities.

[0054] The insulating layer 322 is made of 5mm thick epoxy glass cloth, which can block the conductive path between the side wall of the oil tank 15 and the sensor, preventing interference from the high-voltage electric field of the transformer through the base. At the same time, the low magnetic permeability of the insulating material can reduce the coupling effect of the magnetic field on the vibration signal, ensuring that the signal-to-noise ratio of the vibration data in the 100-500Hz frequency band collected by the sensor is ≥30dB, solving the signal distortion problem caused by electromagnetic induction in traditional metal bases.

[0055] The buffer layer 323 is used to filter interference vibrations from the sidewalls of the oil tank 15, improving the accuracy of vibration signal acquisition. The buffer layer 323 is made of silicone rubber, whose elastic modulus can effectively absorb high-frequency vibration noise transmitted from the inner wall of the oil tank 15, reducing the vibration transmission rate to below 30% through the material's damping characteristics. For the inherent vibrations during transformer operation, the buffer layer 323 can attenuate more than 90% of stray vibration interference, reducing the root mean square value measurement error of the vibration signal from ±5% to 1.5%, accurately capturing the characteristic frequencies of faults such as winding loosening and core resonance.

[0056] Each layer is connected by a stepped snap-fit ​​structure, allowing for individual replacement of aged buffer layer 323 or permanent magnets, thus reducing maintenance costs. When periodic sensor calibration is required (e.g., annually), no special tools are needed; disassembly and reassembly can be completed by a single person, reducing calibration time to one-third of traditional mechanical fixing methods.

[0057] like Figures 2 to 7 As shown, the first embodiment of the present invention provides a multi-channel leakage flux measurement system for immersion monitoring of oil-immersed transformers. The self-calibration module includes a standard magnetic source unit and a temperature compensation unit. The standard magnetic source unit includes a miniature electromagnet element, a Hall element and a permanent magnet element, which are used to output a reference magnetic field with variable magnetic field strength. The Hall element is used to monitor the magnetic field strength in real time and provide feedback calibration. The temperature compensation unit includes a temperature sensor 21 and a temperature drift correction circuit. It collects the operating temperature of the leakage flux sensor array 117 in real time and establishes a sensitivity temperature drift correction model: B 校准 =B 实测 ·(1+k1·ΔT+k2·ΔB) where, B 校准 B is the corrected leakage flux strength. 实测 The original measured value of the sensor is given by k1, which is the temperature drift coefficient, ΔT is the deviation between the actual temperature and the 25℃ reference temperature, k2 is the magnetic field drift coefficient, and ΔB is the deviation between the measured magnetic field and the reference magnetic field. The temperature drift correction circuit stabilizes the operating temperature of the leakage magnetic field sensor sensitive element within the range of 25℃±0.2℃ through the feedback control loop composed of the semiconductor cooling chip and the temperature sensor 21, so as to compensate for the influence of temperature change on the magnetic sensitivity characteristics.

[0058] Specifically, the main function of the standard magnetic source unit is to provide a reference standard for the multi-channel leakage flux measurement system, outputting a reference magnetic field with variable magnetic field strength to calibrate the measurement results of the leakage flux sensor array 117, ensuring the accuracy and reliability of the measurement data. Specifically, the standard magnetic source unit can output a continuously adjustable reference magnetic field of 0.1-10mT, covering the leakage flux intensity range under normal transformer operation (0.1-2mT) and fault conditions (2-10mT). Real-time monitoring and feedback adjustment via Hall effect elements ensure the long-term stability of the reference magnetic field, solving the problem that traditional fixed magnetic sources cannot adapt to different operating conditions and reducing the leakage flux measurement error to within ±2% across the entire range. The temperature compensation unit, on the other hand, is mainly designed for the complex and variable temperature environment inside the transformer. It collects the operating temperature of the leakage flux sensor array 117 in real time, establishes a sensitivity temperature drift correction model to compensate for the influence of temperature changes on the magnetic sensitivity characteristics, avoids measurement errors caused by temperature fluctuations, and ensures that the leakage flux sensor array 117 operates stably and accurately at different temperatures.

[0059] The standard magnetic source unit includes miniature electromagnets, Hall effect sensors, and permanent magnets. The miniature electromagnets generate varying magnetic fields when different currents are applied; the permanent magnets provide a stable base magnetic field. Together, they form a composite magnetic field with variable strength. The Hall effect sensors monitor the current magnetic field strength in real time and feed the data back to the system control unit. The system adjusts the current applied to the miniature electromagnets to precisely control the overall reference magnetic field strength, outputting a variable reference magnetic field that meets calibration requirements.

[0060] The temperature compensation unit includes a temperature sensor 21 and a temperature drift correction circuit. The temperature sensor 21 collects the operating temperature of the location of the leakage flux sensor array 117 in real time and converts the temperature signal into an electrical signal, which is then transmitted to the temperature drift correction circuit. The temperature drift correction circuit uses the established sensitivity temperature drift correction model B. 校准 =B 实测 The operation is performed using (1 + k1 ΔT + k2 ΔB), where B... 校准 B is the corrected leakage flux strength. 实测 The values ​​are the original sensor measurements, k1 is the temperature drift coefficient, ΔT is the deviation between the actual temperature and the 25℃ reference temperature, k2 is the magnetic field drift coefficient, and ΔB is the deviation between the measured magnetic field and the reference magnetic field. The corrected leakage magnetic flux density is obtained through model calculation. This is achieved by strictly limiting the drift coefficient (k1 ≤ 3 × 10⁻⁶). -4 / ℃、k2≤2×10 -The model (3 / mT) enables precise quantitative correction of the cross-interference between temperature and magnetic field. Compared with the traditional method that relies solely on hardware compensation, this model can reduce the additional temperature error in a wide temperature range of -40℃ to 85℃ from ±5% to ±1.2%, making it particularly suitable for scenarios with drastic temperature fluctuations caused by transformer oil cooling and heating cycles.

[0061] In addition, the temperature drift correction circuit forms a feedback control loop with the thermoelectric cooler and the temperature sensor 21. When the temperature is higher than 25°C, the thermoelectric cooler starts cooling to reduce the temperature of the sensitive element of the leakage magnetic field sensor. When the temperature is lower than 25°C, the thermoelectric cooler is controlled to stop cooling or perform appropriate heating to stabilize the operating temperature of the sensitive element of the leakage magnetic field sensor within the range of 25°C ± 0.2°C, thereby reducing the influence of temperature on the magnetic sensitivity characteristics from the hardware level.

[0062] In practical applications, the 0.1-10mT adjustable reference magnetic field output by the standard magnetic source unit is used to verify the accuracy of the magnetic field measured by the leakage flux sensor array 117. The temperature compensation unit, through a dual approach of "model correction + hardware temperature control," corrects the impact of temperature and magnetic field cross-interference on the sensor measurement results in real time. Simultaneously, the self-calibration module supports a programmable calibration cycle, defaulting to every 30 minutes, but adjustable from 1 to 60 minutes. The calibration process is fully automatic and does not interrupt normal monitoring. Compared to traditional manual calibration requiring shutdown, this function reduces maintenance costs by 90% and avoids calibration errors introduced by manual operation, making it particularly suitable for the long-term operation requirements of unattended substations. The components work together; the standard magnetic source unit provides a stable and adjustable magnetic field reference, and the temperature compensation unit ensures the stability of the sensor's magnetic sensitivity characteristics. These two components complement each other, jointly improving the measurement accuracy of the multi-channel leakage flux measurement system, reducing measurement errors caused by inaccurate magnetic field calibration and temperature changes. This provides more reliable and accurate data for leakage flux monitoring of oil-immersed transformers, helping to promptly detect potential transformer faults and ensuring stable transformer operation.

[0063] like Figure 2 and Figure 7 As shown, the first embodiment of the present invention provides a multi-channel leakage flux measurement system for invasive monitoring of oil-immersed transformers. The multi-channel leakage flux measurement system also includes a channel signal amplification module 60. The input side of the channel signal amplification module 60 is electrically connected to the leakage flux sensor array 117, and the output side is connected to the input side of the data processing unit 40, for amplifying the acquired leakage flux signals.

[0064] The raw signal acquired by the leakage flux sensor array 117, especially during normal transformer operation, has a weak amplitude (typically in the mV or even μV range) and is easily drowned out by electromagnetic noise. The channel signal amplification module 60, through a programmable gain amplifier (adjustable gain range of 10-1000 times), can linearly amplify the weak leakage flux signal to the input range adapted to the data processing unit 40, increasing the signal amplitude by 100-1000 times. This process effectively highlights the minute changes in leakage flux caused by early faults such as slight winding deformation and localized core anomalies, solving the problem of missed fault detection due to weak signals in traditional systems and improving the sensitivity of early fault identification.

[0065] As shown in Figure 8, the second embodiment of the present invention provides a multi-channel leakage flux measurement method for immersion monitoring of oil-immersed transformers, comprising the following steps: Step S1: Signal acquisition and self-calibration. The leakage magnetic field monitoring component 11 acquires the leakage magnetic field signal in real time. The self-calibration module periodically outputs a reference magnetic field through the standard magnetic source unit and, combined with the ambient temperature acquired by the temperature compensation unit, corrects the drift deviation of the leakage magnetic field signal. Simultaneously, the oil temperature signal from the temperature sensor 21 and the vibration signal from the vibration sensor are acquired. Step S2: Multi-parameter data fusion. The channel signal amplification module 60 amplifies the leakage magnetic field signal and transmits it to the data processing unit 40. The data processing unit 40 extracts the key features of the leakage magnetic field signal, oil temperature signal, and vibration signal, reduces the dimension to a 3-8 dimension vector through principal component analysis, and outputs the leakage magnetic field status assessment result by fusing the multi-parameter features.

[0066] Step S3: Data transmission. The original monitoring data and status assessment results are transmitted to an external terminal through the wireless communication unit 50 to achieve remote monitoring.

[0067] In step S1, the three sets of leakage magnetic field monitoring components 11 are located at the winding end, the junction of the iron core column 13 and the yoke 14, and the bottom of the oil tank 15, respectively, and collect leakage magnetic field signals through the leakage magnetic field sensor array 117. The self-calibration module is started simultaneously: the standard magnetic source unit outputs an adjustable reference magnetic field of 0.1-10mT, and the Hall element monitors the magnetic field strength in real time and provides feedback correction; the temperature compensation unit obtains the operating temperature of the leakage magnetic field sensor through the PT1000 sensor and substitutes it into the temperature drift correction formula "B". 校准 =B 实测The leakage magnetic field signal is corrected by "(1+k1·ΔT+k2·ΔB)", where k1=2.5×10-4 / ℃ and k2=1.6×10-3 / mT. The semiconductor cooling chip stabilizes the temperature of the leakage magnetic field sensor at 25℃±0.2℃. Simultaneously, the calibrated data is transmitted to the data processing unit 40 via the SPI bus. Meanwhile, the oil temperature monitoring module 20 and the vibration monitoring module 30 collect oil temperature and vibration signals, respectively. The oil temperature signal is collected by the temperature sensor 21 and synchronized to the data processing unit 40 via the 485 bus. A timestamp is used to align the upper and lower oil temperature signals. The vibration signal is collected by the piezoelectric sensor 31 at a sampling rate of 10kHz to measure vibration acceleration.

[0068] Compared with existing technologies, this step outputs a reference magnetic field periodically through a self-calibration module. Combined with temperature compensation, it can correct the temperature drift and time drift errors of the leakage magnetic signal in real time, controlling the measurement deviation within ±1.5%, thus solving the problem of sensor accuracy decay over long-term operation in traditional methods. The mechanism of synchronously acquiring multiple parameters ensures the temporal correlation of leakage magnetic, oil temperature, and vibration signals, providing a consistent data foundation for subsequent fusion analysis.

[0069] The core function of "Step S2: Multi-parameter Data Fusion" is to process the multi-source signals of "leakage flux, oil temperature, and vibration" collected in "Step S1," extract key information reflecting the transformer's leakage flux status, eliminate the risk of misjudgment based on a single parameter through fusion analysis, and finally output accurate leakage flux status assessment results. It connects "raw data" with "fault diagnosis." The core components are implemented as follows: First, the channel signal amplification module 60 receives the leakage magnetic signal (each of the three leakage magnetic monitoring components 11 outputs one signal, for a total of three) after self-calibration correction in step S1. A low-noise operational amplifier is used to amplify the signal, preventing distortion due to attenuation or noise interference when the signal is transmitted to the data processing unit 40. Second, the data processing unit 40 receives the amplified leakage magnetic signal, the timestamped oil temperature signal, and the vibration signal with a 10kHz sampling rate, respectively, and extracts key features for these three types of signals. Specifically: for the leakage magnetic signal, the leakage magnetic peak values ​​of the three monitoring points are extracted; the leakage magnetic peak values ​​reflect the leakage magnetic intensity; the main peak frequency of the 50-200Hz frequency band is used to reflect the leakage magnetic change corresponding to abnormal vibration of the winding / core; the distortion rate of the signal waveform is used to reflect the uniformity of the leakage magnetic distribution, totaling 3×3=9. The data processing unit 40 performs dimensionality reduction on the 13 original features (9+2+2=13 dimensions) for the oil temperature signal. For the oil temperature signal, it calculates the temperature difference between the upper and lower layers (normal difference ≤ 5℃; excessive difference may be accompanied by abnormal heating due to leakage flux) and the oil temperature rise rate within 10 minutes (normal ≤ 0.5℃ / 10min; excessively rapid rise indicates a potential fault). For the vibration signal, it calculates the root mean square value of vibration acceleration (reflecting vibration intensity) and peak frequency (matching the vibration frequency corresponding to abnormal leakage flux) in the 100-500Hz frequency band (the main frequency band of transformer fault vibration). Finally, the data processing unit 40 uses principal component analysis (PCA) to reduce the dimensionality of these features—retaining a cumulative contribution rate ≥ 90%. The principal components are used to obtain 3-8 dimensional feature vectors (e.g., the peak value of core leakage flux and the root mean square value of vibration are highly correlated, so they can be combined into 1 dimensional principal components; oil temperature difference and leakage flux distortion rate are independent, so each retains 1 dimension); then, based on the dimensionality-reduced feature vectors, a weighted fusion algorithm (leakage flux feature weight 0.5, oil temperature 0.3, vibration 0.2) is used to calculate the comprehensive evaluation value, and compared with preset thresholds (e.g., normal threshold ≤0.3, suspected fault 0.3-0.6, fault >0.6), the three-level leakage flux status evaluation results of "normal / suspected fault / fault" are output.

[0070] Step S3: Data transmission. The core function of this step is to ensure that the monitoring data and evaluation results output in step S2 are transmitted securely and in real time to the external terminal to meet the remote operation and maintenance needs of unattended substation scenarios. The wireless communication unit 50 transmits the monitoring data and evaluation results to the external terminal in a dual-mode LoRa (prioritizing low power consumption) or 4G (remote / weak signal scenario) manner, thereby realizing unattended remote monitoring. Furthermore, the wireless communication unit 50 adopts a dual-mode communication strategy of LoRa and 4G. In scenarios with stable signals and short-distance transmission within the substation, LoRa communication (low-power mode) is prioritized to reduce system energy consumption. In scenarios with long-distance transmission or weak signals within the substation, it automatically switches to 4G communication to ensure real-time data transmission. Simultaneously, a "tiered data transmission + compression encryption" mechanism is employed: raw monitoring data (leakage magnetic flux, oil temperature, and vibration signals) are transmitted at fixed intervals to reduce redundant data. Leakage magnetic flux status assessment results (especially "suspected fault" and "fault" levels) are pushed immediately when an anomaly is detected, avoiding delays in fault information. All transmitted data is first compressed using the LZ77 compression algorithm (compression rate ≥30%) and then encrypted using the AES-128 encryption algorithm, achieving a 99.9% transmission success rate in the complex electromagnetic environment inside the transformer, with an overall transmission delay ≤10s. Finally, the data and assessment results are transmitted to external terminals, such as maintenance monitoring platforms and mobile apps, enabling unattended remote monitoring and fault early warning.

[0071] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-channel magnetic flux leakage measurement system for invasive monitoring of oil-immersed transformers, characterized in that, The utility model relates to a kind of transformer oil tank monitoring system, including: Multi-channel magnetic flux leakage monitoring module (10), including at least three groups of magnetic flux leakage monitoring components (11), three groups of the magnetic flux leakage monitoring component (11) are respectively arranged at transformer winding (12) end, iron core column (13) and iron yoke (14) junction and oil tank (15) bottom; Oil temperature monitoring module (20), including at least two temperature sensors (21), is respectively arranged in oil tank (15) upper oil domain and lower oil passage export place; Vibration monitoring module (30), including at least two vibration sensors (31), is respectively arranged in oil tank (15) wall inside and iron core top; Data processing unit (40) is electrically connected with the magnetic flux leakage monitoring component (11), the oil temperature monitoring module (20) and the vibration monitoring module (30) respectively, for receiving magnetic flux leakage signal, temperature signal and vibration signal and carrying out data processing, and outputting magnetic flux leakage state evaluation result; Wireless communication unit (50) is connected with the data processing unit (40), for transmitting monitoring data and evaluation result to external terminal.

2. A multi-channel magnetic flux leakage measurement system for invasive monitoring of oil-immersed transformers according to claim 1, characterized in that, The magnetic flux leakage monitoring component (11) further includes: Insulating mounting seat (111), including a bottom plate and two side plates, two side plates are respectively arranged on the both sides of the bottom plate, and the bottom plate and the two side plates form U-shaped structure; Two guide rods (112) are vertically arranged on the bottom plate, one end of each guide rod (112) is connected with the bottom plate, and the other end is provided with a limiting block (113); Insulating sleeve (114) is vertically arranged between the two guide rods (112), two guide plates (115) are symmetrically arranged on the both sides of the insulating sleeve (114), and the guide rod (112) is slidingly limitedly connected with the guide plate (115) on the corresponding side thereof; Fixed seat (116) is connected with the insulating sleeve (114) at one end, and a magnetic flux leakage sensor array (117) is arranged at the other end; Four reset components (118) are respectively sleeved on the guide rods (112) on the both sides of the guide plate (115).

3. A multi-channel magnetic flux leakage measurement system for invasive monitoring of an oil-immersed transformer according to claim 2, characterized in that, The reset component (118) includes first spring (1181) and second spring (1182), the rotation directions of the first spring (1181) and the second spring (1182) are opposite, the first spring (1181) is sleeved outside the second spring (1182), the second spring (1182) is sleeved on the guide rod (112), and the two ends of the first spring (1181) and the second spring (1182) are respectively abutted with the bottom plate and the guide plate (115).

4. A multi-channel magnetic flux leakage measurement system for invasive monitoring of oil-immersed transformers according to claim 2, characterized in that: Universal joint (22) is arranged between the temperature sensor (21) and the inner wall of the oil tank (15), and a plurality of oil flow holes are formed in the copper heat-conducting shell (23) of the temperature sensor (21).

5. A multi-channel magnetic flux leakage measurement system for invasive monitoring of oil-immersed transformers according to claim 1, characterized in that: Each of the vibration sensors (31) comprises a magnetic insulation base (32) comprising a permanent magnet layer (321), an insulation isolation layer (322) and a buffer layer (323), the permanent magnet layer (321) is attached to the wall of the oil tank (15) and is connected by magnetic force adsorption, one side of the insulation isolation layer (322) is connected with the permanent magnet layer (321), the other side is connected with the buffer layer (323), and the buffer layer (323) is fixedly connected with the vibration sensor (31) away from the insulation isolation layer (322).

6. A multi-channel magnetic flux leakage measurement system for invasive monitoring of oil-immersed transformers according to claim 2, characterized in that: Each of the magnetic flux leakage monitoring assemblies (11) comprises a self-calibration module for periodically correcting signal drift of the magnetic flux leakage monitoring assembly (11); The self-calibration module comprises a standard magnetic source unit and a temperature compensation unit; the standard magnetic source unit comprises a micro electromagnet element, a Hall element and a permanent magnet element, and is used for outputting a reference magnetic field with variable magnetic field strength, wherein the Hall element is used for monitoring the magnetic field strength in real time and feeding back calibration; The temperature compensation unit comprises a temperature sensor (21) and a temperature drift correction circuit, which is used for collecting the working temperature of the magnetic flux leakage sensor array (117) in real time, and establishing a sensitivity temperature drift correction model: B 校准 = B 实测 · (1 + k1 · ΔT + k2 · ΔB) where B 校准 is the corrected magnetic flux density, B 实测 is the sensor raw measurement, k1 is the temperature drift coefficient, ΔT is the deviation of the actual temperature from the 25°C reference temperature, k2 is the magnetic field drift coefficient, and ΔB is the deviation of the measured magnetic field from the reference magnetic field. The temperature drift correction circuit stabilizes the working temperature of the magnetic flux leakage sensor sensitive element in the range of 25℃±0.2℃ through a feedback control loop composed of a semiconductor refrigeration sheet and a temperature sensor (21), so as to compensate the influence of temperature change on the magnetic sensitive characteristic.

7. A multi-channel magnetic flux leakage measurement system for invasive monitoring of oil-immersed transformers according to claim 2, characterized in that: The multi-channel magnetic flux leakage measurement system further comprises a channel signal amplification module (60), the input side of the channel signal amplification module (60) is electrically connected with the magnetic flux leakage sensor array (117), and the output side is connected with the input side of the data processing unit (40), which is used for amplifying and processing the obtained magnetic flux leakage signals.

8. A multi-channel magnetic flux leakage measurement system for invasive monitoring of oil-immersed transformers according to claim 4, characterized in that: The magnetic flux leakage sensor array (117) comprises a plurality of Hall sensors, and the diameter of the oil flow hole is 2-5mm.

9. A multi-channel magnetic flux leakage measurement system for invasive monitoring of oil-immersed transformers according to claim 1, characterized in that: The wireless communication unit (50) adopts LoRa and 4G dual-mode communication.

10. A multi-channel magnetic flux leakage measurement method for oil-immersed transformer invasive monitoring, implemented by the multi-channel magnetic flux leakage measurement system according to any one of claims 1-9, characterized in that, The method comprises the following steps: Step S1: signal acquisition and self-calibration, the magnetic flux leakage monitoring assembly (11) collects the magnetic flux leakage signal in real time, the self-calibration module periodically outputs the reference magnetic field through the standard magnetic source unit, and corrects the drift deviation of the magnetic flux leakage signal in combination with the ambient temperature collected by the temperature compensation unit; the oil temperature signal of the temperature sensor (21) and the vibration signal of the vibration sensor (31) are collected synchronously; Step S2: multi-parameter data fusion, the channel signal amplification module (60) amplifies the magnetic flux leakage signal and transmits it to the data processing unit (40); the data processing unit extracts the key features of the magnetic flux leakage signal, the oil temperature signal and the vibration signal, reduces the dimension to 3-8 dimensional vectors through principal component analysis, and outputs the magnetic flux leakage state evaluation result by fusing the multi-parameter features; Step S3: data transmission, the original monitoring data and the state evaluation result are transmitted to the external terminal through the wireless communication unit (50), and remote monitoring is realized.

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