A magnetic enhancement based cable partial discharge TMR current sensing device

Abstract

This invention relates to a magnetically enhanced cable partial discharge (TMR) current sensing device, comprising: a high-frequency mutual inductance module, including a ferrite magnetic ring and a secondary coil wound on the ferrite magnetic ring, used for current mutual inductance of the tested cable and outputting an induced current; a dual-parallel branch module, used for receiving the induced current and splitting the induced current into two symmetrical branch currents through a dual-branch structure; a composite magnetic field enhancement module, including two magnetically enhanced sensing sub-modules, respectively installed above the two branch lines of the dual-branch structure, each sub-module including a superconducting flux concentrator and a TMR sensor, the superconducting flux concentrator amplifying the magnetic field through a multi-stage narrow structure, and the TMR sensor installed in the magnetic field concentration area of ​​the superconducting flux concentrator; and an insulation shielding module for electromagnetic shielding using a multi-layered covering structure. Compared with the prior art, this invention significantly improves the detection capability and anti-interference capability of weak magnetic fields.

Description

Technical Field

[0001] This invention relates to the field of cable partial discharge detection technology, and in particular to a cable partial discharge TMR current sensing device based on magnetic enhancement. Background Technology

[0002] With the continuous improvement of power system voltage levels and transmission capacity, high-voltage cables, as the core transmission carriers of urban power grids, have made online monitoring of their insulation status a crucial link in ensuring power supply reliability. Partial discharge, as an early sign of cable insulation degradation, generates nanosecond-level pulse current signals containing rich information about defect characteristics. However, the strong electromagnetic interference, complex grounding conditions, and high-frequency signal attenuation in the cable operating environment place stringent demands on the sensitivity, interference immunity, and wideband response capabilities of current sensing devices.

[0003] Traditional partial discharge current detection techniques largely rely on the principle of electromagnetic induction, but face multiple technical bottlenecks in practical applications. Conventional current transformers are limited by the frequency response characteristics of the core material, making it difficult to effectively capture the complete waveform of high-frequency pulses. While non-contact sensors based on the magnetoresistive effect offer wide bandwidth advantages, they are susceptible to interference from stray magnetic fields, leading to a decrease in signal-to-noise ratio. In existing technologies, single-structure sensing devices often struggle to simultaneously meet the multiple requirements of weak signal enhancement, wide bandwidth detection, and electromagnetic shielding, thus limiting the accuracy of partial discharge feature extraction.

[0004] For example, the invention disclosed in publication number CN118731461A discloses a broadband signal fusion current sensor that uses a TMR magnetic sensing chip and a high-frequency current transformer for in-situ signal fusion. It achieves measurement frequency band coverage from DC to high frequency through a filtering and amplification circuit, reducing costs, and utilizes a magnetic core made of highly saturated magnetic material to avoid core saturation. While this scheme improves measurement frequency band coverage, it has a complex structure, high cost, and cannot suppress interference in all frequency bands, thus failing to achieve high-precision current measurement in complex electromagnetic environments. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing sensing devices with a single structure, which often cannot simultaneously meet the multiple requirements of weak signal enhancement, wideband detection and electromagnetic shielding, thus limiting the accuracy of partial discharge feature extraction, and to provide a cable partial discharge TMR current sensing device based on magnetic enhancement.

[0006] The objective of this invention can be achieved through the following technical solutions: A magnetically enhanced cable partial discharge (TMR) current sensing device includes: A high-frequency mutual inductance module, including a ferrite magnetic ring and a secondary coil wound on the ferrite magnetic ring, is used to perform current mutual inductance on the cable under test and output induced current. The dual parallel branch module is used to receive the induced current and split the induced current into two symmetrical branch currents through the dual branch structure. A composite magnetic field enhancement module includes at least two magnetic enhancement sensing sub-modules, which are respectively installed above the two branch lines of a dual-branch structure. Each magnetic enhancement sensing sub-module includes a superconducting flux concentrator and a TMR sensor. The superconducting flux concentrator amplifies the magnetic field through a multi-stage narrow structure, and the TMR sensor is installed in the magnetic field concentration area of ​​the superconducting flux concentrator. An insulating shielding module is used to electromagnetically shield the dual parallel branch module and the composite magnetic field enhancement module using a multi-layer encapsulation structure.

[0007] Furthermore, the dual parallel branch module also includes a U-shaped main routing line. The dual branch structure includes two parallel branch routing lines extending from both ends of the U-shaped main routing line. The paths of the two branch routing lines are distributed vertically and horizontally in a mirror image. The ends of the two branch routing lines are connected to each other to form a closed loop structure.

[0008] Furthermore, the TMR sensor has two bridge arms, which are symmetrically distributed on the upper and lower edges of the corresponding branch traces.

[0009] Furthermore, the superconducting flux concentrator includes stacked insulating isolation layers and two parallel superconducting thin film layers, with the insulating isolation layer located between the two parallel superconducting thin film layers.

[0010] Furthermore, the TMR sensor is bonded to the surface of the uppermost superconducting thin film layer of the corresponding superconducting flux concentrator using a flip-chip bonding process.

[0011] Furthermore, the insulating layer has a current conduction window.

[0012] Furthermore, the superconducting thin film layer is provided with symmetrical spiral confinement grooves.

[0013] Furthermore, the secondary coil is an enameled wire coil, and an electrostatic shielding layer is provided between each group of secondary coils.

[0014] Furthermore, the insulating shielding module includes, from the inside out, a polytetrafluoroethylene insulating sleeve, a nanocrystalline alloy magnetic shielding layer, and an aluminized polyester film.

[0015] Furthermore, the device also includes a back-end signal processing module, which includes a differential amplification unit, a filtering unit, a signal conditioning unit, an analog-to-digital conversion unit, and a digital signal processing unit connected in sequence, wherein the differential amplification unit is connected to the TMR sensor.

[0016] Compared with the prior art, the present invention has the following advantages: (1) This invention splits the induced current into two symmetrical branch currents by setting up a dual parallel branch module, and actively counteracts the skin effect by using the reverse symmetry of the current, thereby reducing energy loss during the transmission of the induced current and effectively suppressing common-mode interference from external electromagnetic noise. A dual-path magnetic enhancement sensing submodule is also set up. The superconducting flux concentrator in the magnetic enhancement sensing submodule uses the flux superposition effect of a multi-level structure to focus weak magnetic signals onto the sensitive area, which significantly enhances the sensitivity to capture transient partial discharge magnetic fields. The TMR sensor is directly integrated into the magnetic field concentration area of ​​the superconducting flux concentrator for measurement. An insulating shielding module is set on the outside for electromagnetic shielding. The overall solution significantly improves the detection capability and anti-interference capability of weak magnetic fields through composite magnetic field enhancement technology, and solves the sensitivity and reliability problems of current measurement under high voltage and strong electromagnetic interference environment. It is suitable for partial discharge monitoring and dynamic current analysis of power cables.

[0017] (2) The present invention symmetrically sets the two bridge arms of the TMR sensor on the upper and lower edges of the branch trace, which can accurately capture the edge-enhanced magnetic field generated by the symmetrical branch current in the dual parallel branch structure, cancel common-mode electromagnetic interference through the differential response of the bridge arms, and improve the symmetry and uniformity of magnetic field coupling, significantly optimizing the sensor's response sensitivity and linearity to weak partial discharge current.

[0018] (3) The superconducting flux concentrator of the present invention is composed of two parallel superconducting thin film layers stacked alternately through an insulating isolation layer, which can amplify the magnetic field gain through the flux superposition effect of the multi-layer superconducting structure; the TMR sensor is directly bonded to the narrow channel surface of the uppermost superconducting thin film layer through flip-chip bonding process. The flip-chip bonding process can shorten the sensing distance, maximize the coupling efficiency between the TMR sensor and the enhanced magnetic field, and at the same time enhance the structural integration stability, so as to achieve efficient capture of nanosecond-level partial discharge pulse magnetic field.

[0019] (4) The superconducting thin film layers of the present invention are provided with symmetrical spiral confinement grooves to guide the supercurrent path in a directional manner. The electromagnetic confinement effect of the spiral structure further concentrates the magnetic field energy, so that the magnetic field is focused and strengthened in the narrow channel region. At the same time, it suppresses magnetic field diffusion and stray coupling, improves the magnetic field amplification factor and spatial resolution of the superconducting flux concentrator, and meets the high-precision detection requirements of weak partial discharge signals.

[0020] (5) The insulating isolation layer of the present invention has a current conduction window to ensure the supercurrent continuity between the upper and lower superconducting thin film layers, forming a closed-loop supercurrent circuit, so that the magnetic field generated by each superconducting thin film layer can be directionally superimposed along the conduction window, avoiding the insulation layer from hindering the magnetic flux coupling, ensuring the magnetic field enhancement effect of the multilayer stacked structure is maximized, while maintaining the electrical isolation and mechanical stability of each layer structure.

[0021] (6) The insulating shielding module of the present invention comprises, from the inside out: a polytetrafluoroethylene insulating sleeve, a nanocrystalline alloy magnetic shielding layer and an aluminized polyester film, which can achieve multi-layer synergistic protection. The polytetrafluoroethylene insulating sleeve ensures the electrical insulation performance of the internal components, the nanocrystalline alloy magnetic shielding layer effectively blocks external stray magnetic field interference, and the aluminized polyester film suppresses electromagnetic radiation coupling. The combination of the three avoids internal signal leakage and resists the influence of complex external electromagnetic environment, providing a stable working environment for the dual parallel branch module and the composite magnetic field enhancement module, and further enhancing the anti-interference capability and measurement reliability of the device. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a superconducting thin film layer provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a superconducting flux concentrator provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the single-layer and double-layer magnetoresistive curves of a superconducting flux concentrator provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the position of a TMR bridge arm provided in an embodiment of the present invention; Figure 5 This is a diagram of a dual parallel branch structure provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of a cable partial discharge TMR current sensing device based on magnetic enhancement provided in an embodiment of the present invention; In the diagram, 1 is the high-frequency mutual inductance module, 2 is the dual parallel branch module, 3 is the magnetic enhancement sensing sub-module, and 4 is the insulation shielding module. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0025] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0026] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed during use. They are only for the convenience of describing this 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 this invention.

[0027] It should be noted that 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. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0028] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," not that the structure must be completely horizontal, but can be slightly tilted.

[0029] Example 1 like Figure 6 As shown, this embodiment provides a cable partial discharge (TMR) current sensing device based on magnetic enhancement, comprising: The high-frequency mutual inductance module 1 includes a ferrite magnetic ring and a secondary coil wound on the ferrite magnetic ring, which is used to perform current mutual inductance on the cable under test and output induced current. The dual parallel branch module 2 is used to receive the induced current and split the induced current into two symmetrical branch currents through the dual branch structure. The composite magnetic field enhancement module includes at least two magnetic enhancement sensing sub-modules 3, which are respectively installed above the two branch lines of the dual-branch structure. Each magnetic enhancement sensing sub-module 3 includes a superconducting magnetic flux concentrator and a TMR sensor. The superconducting magnetic flux concentrator amplifies the magnetic field through a multi-stage narrow structure, and the TMR sensor is installed in the magnetic field concentration area of ​​the superconducting magnetic flux concentrator. The insulating shielding module 4 is used to electromagnetically shield the dual parallel branch module 2 and the composite magnetic field enhancement module using a multi-layer encapsulation structure.

[0030] Specifically, the high-frequency mutual inductance module 1 includes: A toroidal ferrite core, the inner circumferential wall of which is coaxially fitted with the cable conductor; The secondary coil is wound in segments and consists of enameled wire coils, with an electrostatic shielding layer between each group of coils.

[0031] The dual-parallel branch module 2 is used to receive the induced current and design a dual-branch structure in the PCB structure to split the induced current into two symmetrical branch currents, including: U-shaped main traces are symmetrically arranged on the PCB, with the middle part used to receive induced current. The dual-branch structure includes two parallel branch lines extending from both ends of the U-shaped main line, with their routing paths distributed vertically in a mirror-symmetric manner; the ends of the two branch lines are interconnected to form a closed loop structure.

[0032] Two magnetically enhanced sensing sub-modules 3 are respectively positioned directly above the two branch lines of the dual parallel branch module 2.

[0033] Preferably, the two bridge arms of the TMR sensor in the magnetic enhancement sensing submodule 3 are symmetrically distributed on the upper and lower edges of the two branch traces.

[0034] The composite magnetic field enhancement module is composed of a superconducting flux concentrator and a TMR sensor. The superconducting flux concentrator amplifies the magnetic field through a multi-stage narrow structure, and the TMR sensor is directly integrated into the magnetic field concentration area of ​​the superconducting flux concentrator. The composite magnetic field enhancement module is placed on the two branches of the dual parallel branch module 2. Specifically, it includes: A superconducting flux concentrator is composed of two parallel superconducting thin film layers stacked alternately with an insulating layer between the two parallel superconducting thin film layers. The TMR sensor is directly bonded to the narrow channel surface of the uppermost superconducting thin film layer using a flip-chip bonding process.

[0035] Preferably, an insulating layer is disposed between adjacent superconducting thin film layers and has a current conduction window to ensure the continuity of supercurrent between upper and lower superconducting thin film layers, forming a closed-loop supercurrent circuit. This allows the magnetic fields generated by each superconducting thin film layer to be directionally superimposed along the conduction window, avoiding the insulation layer's obstruction of magnetic flux coupling, ensuring the maximum magnetic field enhancement effect of the multilayer stacked structure, while maintaining the electrical isolation and mechanical stability of each layer.

[0036] Preferably, both superconducting thin film layers are provided with symmetrical spiral confinement grooves to guide the supercurrent path in a directional manner. The electromagnetic confinement effect of the spiral structure further concentrates the magnetic field energy, enabling the magnetic field to be focused and strengthened in the narrow channel region. At the same time, it suppresses magnetic field diffusion and stray coupling, improves the magnetic field amplification factor and spatial resolution of the superconducting flux concentrator, and meets the high-precision detection requirements of weak partial discharge signals.

[0037] The insulation shielding module 4 employs a multi-layered encapsulation structure to provide electromagnetic shielding for the dual parallel branch module 2 and the magnetically enhanced sensing module. The following structure is preferred: The system comprises a PTFE insulating sleeve, a nanocrystalline alloy magnetic shielding layer, and an aluminized polyester film, forming a multi-layered, synergistic protection layer. The PTFE insulating sleeve ensures the electrical insulation performance of internal components, the nanocrystalline alloy magnetic shielding layer effectively blocks external stray magnetic field interference, and the aluminized polyester film suppresses electromagnetic radiation coupling. The combination of these three elements prevents internal signal leakage and resists the influence of complex external electromagnetic environments, providing a stable operating environment for the dual-parallel branch modules and the composite magnetic field enhancement module, further strengthening the device's anti-interference capability and measurement reliability.

[0038] Example 2 This embodiment is largely the same as Embodiment 1, except that the device further includes a back-end signal processing module 5, which includes a differential amplification unit, a filtering unit, a signal conditioning unit, an analog-to-digital conversion unit, and a digital signal processing unit connected in sequence. The differential amplification unit is connected to the TMR sensor.

[0039] The following is a specific implementation example: A wide-frequency-domain, high-sensitivity partial discharge magnetic field detection system was constructed using a composite structure of an Nb / AlO_x / NiFe superconducting flux concentrator and dual parallel PCB current paths.

[0040] In the fabrication of the superconducting module, a 150 nm thick Nb film was deposited on a quartz substrate by magnetron sputtering, and a double-layer stacked structure was formed using reactive ion etching. Each layer had a width of 10 μm and an interlayer spacing of 0.5 μm. Figure 1 , 2 Superconducting thin-film layer structures and superconducting flux concentrator structures were respectively developed; a magnetic field gain of 332 times was achieved in a 4.2K liquid helium environment, which is 1.52 times higher than that of traditional single-layer structures. Figure 3 The figures show the magnetoresistance curves for single-layer and double-layer magnetoresistance.

[0041] The current sensing unit uses a TMR2583 tunnel magnetoresistive chip, with the two bridge arms D2 and D2 symmetrically distributed on the upper and lower edges of the two branch traces. Figure 4 The diagram shows the location of the TMR bridge arm. The dual 726um wide PCB copper traces are laid out in parallel with a spacing of 0.9mm. Figure 5 The diagram shows a dual-parallel branch structure. Simulation results demonstrate that the edge magnetic field strength of the dual-path structure is 61.3% higher than that of the single-path structure.

[0042] In the back-end signal processing module 5, the differential amplification unit uses the low-temperature drift instrumentation amplifier AD8421, with a common-mode rejection ratio of 120dB. Its input is directly connected to the output of the dual-path TMR sensor via a symmetrical twisted-pair cable. The filtering unit is designed as a programmable second-order active filter network, using a MAX7407 chip to achieve dynamic bandwidth switching from 0.1Hz to 2MHz. It features dual modes of power frequency notch filtering and high-frequency harmonic suppression, effectively eliminating inherent harmonic interference in the power system. The signal conditioning unit integrates an AD8251 programmable gain amplifier and an ADG5412 analog switch, constructing a 16-level dynamic range adaptive adjustment mechanism capable of peak hold and baseline restoration for partial discharge pulses. The analog-to-digital converter uses the AD7768 24-bit converter, whose internal digital noise reduction engine can eliminate periodic interference caused by the switching power supply. The digital signal processing unit is based on the Xilinx Zynq-7000 SoC platform and incorporates a convolutional neural network feature extraction algorithm.

[0043] In actual testing, when partial discharge occurs in the joint of the cross-linked polyethylene cable, the sensor outputs a signal-to-noise ratio of 49dB within an effective bandwidth of 1.2MHz, and can stably detect discharge pulse currents on the order of 0.9mA, thus realizing accurate monitoring of the partial discharge current of high-voltage cables.

[0044] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A cable partial discharge TMR current sensing device based on magnetic enhancement, characterized in that, include: The high-frequency mutual inductance module (1) includes a ferrite magnetic ring and a secondary coil wound on the ferrite magnetic ring, which is used to perform current mutual inductance on the cable under test and output induced current. The dual parallel branch module (2) is used to receive the induced current and to split the induced current into two symmetrical branch currents through the dual branch structure. The composite magnetic field enhancement module includes at least two magnetic enhancement sensing sub-modules (3), which are respectively installed above the two branch lines of the dual-branch structure. Each magnetic enhancement sensing sub-module (3) includes a superconducting magnetic flux concentrator and a TMR sensor. The superconducting magnetic flux concentrator amplifies the magnetic field through a multi-stage narrow structure, and the TMR sensor is installed in the magnetic field concentration area of ​​the superconducting magnetic flux concentrator. An insulating shielding module (4) is used to electromagnetically shield the dual parallel branch module (2) and the composite magnetic field enhancement module using a multi-layer covering structure.

2. The cable partial discharge TMR current sensing device based on magnetic enhancement according to claim 1, characterized in that, The dual parallel branch module (2) also includes a U-shaped main routing line. The dual branch structure includes two parallel branch routing lines extending from both ends of the U-shaped main routing line. The paths of the two branch routing lines are distributed vertically and horizontally in a mirror symmetry. The ends of the two branch routing lines are connected to each other to form a closed loop structure.

3. The cable partial discharge TMR current sensing device based on magnetic enhancement according to claim 2, characterized in that, The TMR sensor has two bridge arms, which are symmetrically distributed on the upper and lower edges of the corresponding branch lines.

4. The cable partial discharge TMR current sensing device based on magnetic enhancement according to claim 2, characterized in that, The superconducting flux concentrator includes stacked insulating layers and two parallel superconducting thin film layers, with the insulating layer located between the two parallel superconducting thin film layers.

5. The cable partial discharge TMR current sensing device based on magnetic enhancement according to claim 4, characterized in that, The TMR sensor is bonded to the surface of the uppermost superconducting thin film layer of the corresponding superconducting flux concentrator using a flip-chip bonding process.

6. The cable partial discharge TMR current sensing device based on magnetic enhancement according to claim 4, characterized in that, The insulating layer has a current conduction window.

7. The cable partial discharge TMR current sensing device based on magnetic enhancement according to claim 4, characterized in that, The superconducting thin film layer is provided with symmetrical spiral confinement grooves.

8. The cable partial discharge TMR current sensing device based on magnetic enhancement according to claim 1, characterized in that, The secondary coil is an enameled wire coil, and an electrostatic shielding layer is provided between each group of secondary coils.

9. The cable partial discharge TMR current sensing device based on magnetic enhancement according to claim 1, characterized in that, The insulating shielding module (4) includes, from the inside out, a polytetrafluoroethylene insulating sleeve, a nanocrystalline alloy magnetic shielding layer, and an aluminized polyester film.

10. A cable partial discharge TMR current sensing device based on magnetic enhancement according to claim 1, characterized in that, The device also includes a back-end signal processing module (5), which includes a differential amplification unit, a filtering unit, a signal conditioning unit, an analog-to-digital conversion unit, and a digital signal processing unit connected in sequence. The differential amplification unit is connected to the TMR sensor.

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