Magnetostrictive sensor and detection device for power transmission conductor

Abstract

The invention provides a magnetostrictive sensor for a power transmission conductor and a detection device. The magnetostrictive sensor comprises a silicon steel yoke, at least one pair of permanent magnet assemblies, a support and an excitation coil. The silicon steel yoke is in a strip shape, the pair of permanent magnet assemblies are fixed at intervals in the length direction of the silicon steel yoke, and different magnetic pole ends of the two permanent magnet assemblies are oppositely arranged. The support is fixed on the silicon steel yoke and located between the two permanent magnet assemblies, the excitation coil is wound on the support in the length direction of the silicon steel yoke, a C-shaped groove deviating from one side of the silicon steel yoke is formed in the support, and the C-shaped groove is formed in the length direction of the silicon steel yoke so that the C-shaped groove can be attached to and close to the power transmission wire from the single side. The permanent magnet assembly induces an axial static bias magnetic field in the power transmission conductor and acts on the power transmission conductor together with a pulse dynamic magnetic field excited when high-frequency pulse current is introduced into the excitation coil, longitudinal modal ultrasonic guided waves are excited based on the inverse magnetostrictive effect, and the returned ultrasonic guided waves are received based on the positive magnetostrictive effect to detect the power transmission conductor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ultrasonic guided wave nondestructive testing, and specifically provides a magnetostrictive sensor and a detection device for a power transmission conductor. BACKGROUND

[0002] As a key carrier of the power system, the operation state of the power transmission conductor is directly related to the safety and stability of the power grid. With the continuous growth of power demand in China, long-distance and large-capacity power transmission has become the norm, which puts higher requirements on the carrying capacity and reliability of the conductor. Among all the links of the power transmission conductor, the tension stringing construction period is a high-risk stage for potential damage. Since the adjacent line layers of overhead bare conductors adopt a reverse stranding structure, there is significant stress stratification and relative fretting between the strands under the action of traction force. This mechanical behavior can cause stress concentration in the contact area, leading to fretting wear, fatigue and even fracture of the aluminum strands. Such damage has the characteristics of strong concealment and gradual development, which poses a safety hazard in the early stage of operation and significantly affects the long-term service life of the conductor and the overall safety of the power grid.

[0003] However, there is a serious lack of online monitoring technology for this critical stage. Existing nondestructive testing methods cannot meet the harsh requirements of the construction site: ultrasonic testing technology based on piezoelectric effect requires coupling agent and is complex to install, and cannot achieve rapid and dynamic detection; and traditional electromagnetic acoustic transducer (EMAT) has low acoustic energy conversion efficiency on non-ferromagnetic materials (such as aluminum) and is extremely sensitive to lift-off distance, resulting in low signal-to-noise ratio, poor stability, and difficulty in achieving reliable detection in a vibrating and shaking construction environment.

[0004] Therefore, there is an urgent need in the art for a non-contact, easy-to-install, and stable detection performance special sensor to realize real-time online monitoring of the internal stress and defects of the power transmission conductor during tension stringing and other construction processes. SUMMARY

[0005] The present application aims to solve the problem of inconvenient detection of the power transmission conductor by the existing sensor.

[0006] The purpose of the present application is achieved by the following technical solutions: The application provides a magnetostrictive sensor for a power transmission conductor, comprising a silicon steel yoke in a strip shape, at least one pair of permanent magnet assemblies fixed at intervals in the length direction of the silicon steel yoke, two permanent magnet assemblies oppositely arranged with different magnetic pole ends, a support fixed on the silicon steel yoke and located between the two permanent magnet assemblies, an excitation coil wound on the support in the length direction of the silicon steel yoke, the excitation coil being used for exciting a pulsed dynamic magnetic field when a high-frequency pulsed current is passed, a C-shaped groove provided on the side of the support away from the silicon steel yoke, the C-shaped groove being arranged in the length direction of the silicon steel yoke so that the magnetostrictive sensor is integrally attached to and close to the power transmission conductor from one side, the permanent magnet assemblies inducing an axial static bias magnetic field in the power transmission conductor, the static bias magnetic field and the pulsed dynamic magnetic field jointly acting on the power transmission conductor, exciting a longitudinal mode ultrasonic guided wave based on the inverse magnetostrictive effect, and receiving a returned ultrasonic guided wave based on the positive magnetostrictive effect.

[0007] Preferably, the permanent magnet assembly comprises a permanent magnet and a fixing plate, the fixing plate being fixed perpendicularly on the silicon steel yoke to surround the permanent magnet.

[0008] Preferably, the permanent magnet assembly further comprises a wear-resistant sliding shoe, the wear-resistant sliding shoe being fixed on the permanent magnet or the fixing plate, the wear-resistant sliding shoe being provided with an arc-shaped groove matched with the power transmission conductor in the radial direction, and the magnetostrictive sensor is integrally attached to the power transmission conductor from one side so as to keep a radial interval distance between the excitation coil and the power transmission conductor.

[0009] Preferably, the fixing plate is made of a non-ferromagnetic material.

[0010] Preferably, the fixing plate is made of an aluminum alloy material.

[0011] Preferably, the permanent magnet is made of a neodymium-iron-boron material.

[0012] Preferably, the support is made of an engineering plastic.

[0013] Preferably, the size of the silicon steel yoke is 300mm*50mm*20mm.

[0014] Preferably, the size of the permanent magnet is 100mm*50mm*35mm.

[0015] Based on the same inventive concept, the application further provides a detection device for a power transmission conductor, characterized in that the detection device comprises at least one magnetostrictive sensor for a power transmission conductor according to any one of claims 1 to 9 and an ultrasonic guided wave excitation collector electrically connected with the magnetostrictive sensor.

[0016] Compared with the prior art, the present application has the following beneficial technical effects: The present application provides a magnetostrictive sensor for power transmission conductor, which comprises a silicon steel yoke, at least one pair of permanent magnet assemblies, a bracket and an excitation coil. The silicon steel yoke is in a strip shape, and the pair of permanent magnet assemblies are fixed at intervals in the length direction of the silicon steel yoke, with the opposite poles of the two permanent magnet assemblies facing each other. The bracket is fixed on the silicon steel yoke and located between the two permanent magnet assemblies. The excitation coil is wound on the bracket in the length direction of the silicon steel yoke and is used to excite a pulsed dynamic magnetic field when a high-frequency pulse current is passed through. The bracket is provided with a C-shaped groove on the side facing away from the silicon steel yoke, which is arranged in the length direction of the silicon steel yoke so that the magnetostrictive sensor as a whole is attached to and close to the power transmission conductor from one side. Through such arrangement, the permanent magnet assemblies induce an axial static bias magnetic field in the power transmission conductor, which acts on the power transmission conductor together with the pulsed dynamic magnetic field, excites longitudinal mode ultrasonic guided waves based on the inverse magnetostrictive effect, and detects the power transmission conductor based on the positive magnetostrictive effect. Based on the inverse magnetostrictive effect, longitudinal mode ultrasonic guided waves propagating along the axis of the power transmission conductor are excited, and based on the positive magnetostrictive effect, guided wave signals reflected back by defects in the power transmission conductor are received, thereby realizing detection and positioning of defects in the power transmission conductor and improving the convenience of detection.

[0017] The magnetostrictive sensor adopts a unique one-sided and open magnetic circuit design, and only needs to be close to the power transmission conductor from one side to complete the arrangement of the sensor, without the need to wrap or wind the power transmission conductor, greatly simplifying the installation process and improving the convenience of use in dynamic scenes such as stringing construction. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a working schematic view of the magnetostrictive sensor of the present application installed on the power transmission conductor from one side; Figure 2 is an exploded schematic view of the magnetostrictive sensor of the present application; Figure 3 is a top view schematic view of the magnetostrictive sensor of the present application.

[0019] Figure 4 is Figure 3 is a cross-sectional view in the A-A direction; Figure 5 is Figure 3 is a cross-sectional view of the bracket in the B-B direction; Figure 6 is a winding schematic view of the excitation coil of the magnetostrictive sensor of the present application on the bracket; Figure 7 is a detection signal curve of the magnetostrictive sensor of the present application.

[0020] Reference signs: 1-wear-resistant sliding shoe; 2-bracket; 3-side fixing plate; 4-inner fixing plate; 5-silicon steel yoke; 6-end fixing plate; 7-first permanent magnet; 8-second permanent magnet; 9-static bias magnetic field; 10-excitation coil; 11-power transmission conductor. DETAILED DESCRIPTION

[0021] The preferred embodiments of the present application will be described below with reference to the accompanying drawings. Those skilled in the art will understand that these embodiments are only used to explain the technical principles of the present application, and are not intended to limit the protection scope of the present application. Those skilled in the art can make adjustments as needed to adapt to specific application occasions.

[0022] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0023] It should be noted that in the description of the present application, the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and other terms indicating direction or positional relationship are based on the direction or positional relationship shown in the drawings, which is only for the convenience of description, and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0024] Example 1 As shown in Figure 1 and Figure 6 , the magnetostrictive sensor for power transmission conductor provided by the present embodiment includes a silicon steel yoke 5, at least one pair of permanent magnet assemblies, a bracket 2 and an excitation coil 10.

[0025] Specifically, as shown in Figure 1 , the silicon steel yoke 5 is in the form of a strip, with dimensions of 300mm x 50mm x 20mm. The silicon steel yoke 5 is pre-provided with a plurality of mounting holes (not shown in the figure) for mounting the permanent magnet assemblies and the bracket 2. In addition, the middle position of the silicon steel yoke 5 can also be provided with a positioning groove (not shown in the figure) for fixing the bracket 2 according to actual needs.

[0026] As shown in Figure 1As shown, a pair of permanent magnet assemblies are fixed at intervals along the length of the silicon steel yoke 5, and two of the permanent magnet assemblies are arranged with opposite poles of the same name. Specifically, the permanent magnet assembly includes a permanent magnet and a fixed plate, and the permanent magnet is made of neodymium iron boron material with a size of 100mmx50mmx35mm. The permanent magnet includes a first permanent magnet 7 and a second permanent magnet 8, which are respectively installed at both ends of the same side of the silicon steel yoke 5 through the fixed plate. It should be noted that the permanent magnet can also be directly fixed to the yoke 5 at both ends by adhesive means.

[0027] As shown, the silicon steel yoke 5 and the pair of permanent magnet assemblies arranged with opposite poles of the same name are arranged at intervals. The overall function of the pair of permanent magnet assemblies is to induce a strong and stable axial static bias magnetic field 9 in the surface layer of the adjacent power transmission conductor 11, which is used to magnetize the power transmission conductor 11 and determine the magnetic domain direction.

[0028] As shown in Figure 2 and Figure 3 , the fixed plate is fixed vertically on the silicon steel yoke 5 to surround and protect the permanent magnet. The fixed plate includes an end fixed plate 6, an inner fixed plate 4 arranged opposite to the end fixed plate 6, and side fixed plates 3 located on both sides. The two side fixed plates 3, the inner fixed plate 4 and the end fixed plate 6 are fixed around the permanent magnet in the thickness direction of the permanent magnet to fix the two ends of the silicon steel yoke 5. Among them, the two side fixed plates 3 have a flange structure arranged inwardly, which firmly encapsulates and fixes the permanent magnet on the silicon steel yoke 5 to play a protection and positioning role.

[0029] As shown, the fixed plate is made of non-ferromagnetic materials such as aluminum alloy and is machined, and is matched with the mounting hole on the yoke 5 through the screw. The two permanent magnets (the first permanent magnet 7 and the second permanent magnet 8) are fixed at the two ends of the yoke 5 in a manner of opposite poles of the same name to form a closed magnetic circuit, thereby generating a concentrated and axial static magnetic field 9 in the area near the power transmission conductor 11 of the magnetostrictive sensor. That is, the N pole of the first permanent magnet 7 and the S pole of the second permanent magnet 8 are arranged opposite to each other along the length of the silicon steel yoke 5.

[0030] As shown in Figure 4 , the bracket 2 is fixed on the silicon steel yoke 5 and located between the two permanent magnet assemblies, and the bracket 2 is made of engineering plastic and is fixed in the middle of the silicon steel yoke 5 through the screw or buckle.

[0031] As shown in Figure 1 , Figure 5 and Figure 6As shown, the excitation coil 10 is wound on the support 2 along the length direction of the silicon steel yoke 5, and is used to excite the pulsed dynamic magnetic field when a high-frequency pulse current is passed. The support 2 has a C-shaped groove on the side away from the silicon steel yoke 5, which is arranged along the length direction of the silicon steel yoke 5 so that the magnetostrictive sensor is attached to and close to the power transmission conductor 11 from one side. The excitation coil 10 is tightly wound in the C-shaped groove of the support 2 in the form of a solenoid using Litz wire, and the number of turns and wire diameter are determined according to the required frequency and power of the excitation magnetic field.

[0032] The static bias magnetic field 9 and the pulsed dynamic magnetic field jointly act on the power transmission conductor 11, and the magnetostrictive sensor can excite longitudinal mode ultrasonic guided waves based on the inverse magnetostrictive effect, and also receive the returned ultrasonic guided waves based on the positive magnetostrictive effect.

[0033] Specifically, when the two magnetic fields jointly act on the ferromagnetic power transmission conductor 11 (such as the steel core of the steel-cored aluminum stranded wire), an elastic wave is excited through the inverse magnetostrictive effect. Since the direction of the magnetic field is designed to be consistent with the axial direction of the power transmission conductor 11, the longitudinal mode (L mode) ultrasonic guided wave is preferentially excited, which propagates along the axial direction of the power transmission conductor 11 and is sensitive to axial stress and defect changes. Similarly, the ultrasonic guided wave propagating back causes the power transmission conductor 11 to deform, which disturbs the static magnetic field 9 on the surface of the power transmission conductor 11 through the positive magnetostrictive effect, and is received and detected by the same magnetostrictive sensor or another magnetostrictive sensor of the same type, thereby realizing the detection of stress or defects.

[0034] Therefore, the magnetostrictive sensor only needs to be arranged and installed on one side during operation, without the need for circumferential wrapping of the entire power transmission conductor 11, and the ultrasonic guided wave signal with high signal-to-noise ratio can be obtained. In addition, by accurately controlling the axial direction of the static bias magnetic field 9 and the pulsed dynamic magnetic field, the longitudinal mode guided wave can be efficiently excited and received, with high signal-to-noise ratio and strong anti-interference ability.

[0035] As shown in Figure 2 and Figure 3 The permanent magnet assembly further includes a wear-resistant sliding shoe 1 fixed on the permanent magnet, and the wear-resistant sliding shoe 1 is provided with an arc-shaped groove matched with the power transmission conductor 11 in the radial direction, so that the magnetostrictive sensor is fixed on the power transmission conductor 11 from one side.

[0036] The wear-resistant sliding shoe 1 is installed on the side of the permanent magnet away from the silicon steel yoke 5, and the arc-shaped groove of the wear-resistant sliding shoe 1 is sprayed with a Teflon coating to increase wear resistance. The wear-resistant sliding shoe 1 is used to limit the position of the power transmission conductor 11 in the radial direction, so that the excitation coil 10 and the power transmission conductor 11 maintain a spacing distance, and the spacing distance is not less than 0.1 mm, so as to reduce the friction and damage between the excitation coil 10 and the power transmission conductor 11 during movement. The wear-resistant sliding shoe 1 is installed on the fixed plate by screws or directly pasted on the permanent magnet.

[0037] In addition, the wear-resistant sliding shoe 1 can also be provided with a buckle or sleeve structure for detachable structure, so as to facilitate the replacement of the wear-resistant sliding shoe 1 with different arc-shaped grooves matching different diameters of the power transmission conductor 11. The wear-resistant sliding shoe 1 is made of engineering plastic with low friction coefficient and high wear resistance.

[0038] When the power transmission conductor 11 (such as a coaxial cable) is detected, only the power transmission conductor 11 needs to be placed in the arc-shaped groove of the wear-resistant sliding shoe 1, and the excitation coil 10 in the C-shaped groove support 2 of the magnetostrictive sensor is close to the power transmission conductor 11 on one side in an open and non-contact manner, without the need for wrapping or disassembling along the circumference of the power transmission conductor 11, thereby improving the installation and detection efficiency of the magnetostrictive sensor in a complex construction site (especially in the process of tensioning and paying off). Alternatively, the wear-resistant sliding shoe 1 of the magnetostrictive sensor can also be in contact with the power transmission conductor 11, and the magnetostrictive sensor can be bound on the power transmission conductor 11 through a fastener to realize real-time, online and non-destructive monitoring of the internal defects and stress state of the power transmission conductor 11.

[0039] Embodiment 2 The embodiment provides a detection device for a power transmission conductor, which comprises an ultrasonic guided wave excitation collector and the magnetostrictive sensor of embodiment 1, and the ultrasonic guided wave excitation collector is electrically connected with the magnetostrictive sensor.

[0040] Specifically, as shown in Figure 1 When the excitation coil 10 in the ultrasonic guided wave excitation collector is electrically connected with the excitation electrode of the ultrasonic guided wave excitation collector, a single magnetostrictive sensor works in a "self-excitation and self-reception" mode, and the magnetostrictive sensor can be installed and fixed on a mechanical arm or a support frame with the aid of a shell auxiliary part or directly, the position is adjusted so that the power transmission conductor 11 is embedded in the grooves of the two wear-resistant sliding shoes 1 of the magnetostrictive sensor to make the excitation coil 10 close to the power transmission conductor 11 for detection.

[0041] If long-distance online monitoring of the power transmission conductor 11 is required, two identical magnetostrictive sensors need to be arranged at a certain distance along the axis of the power transmission conductor 11, one is set as a transmitting end, and the other is set as a receiving end, the excitation coil 10 of the magnetostrictive sensor in the transmitting end and the receiving end is respectively electrically connected with the excitation electrode and the receiving electrode of the ultrasonic guided wave excitation collector, thereby forming a "one transmitting and one receiving" monitoring network. By analyzing the propagation time, wave speed, amplitude attenuation and other characteristic parameters of the guided wave signal excited by the transmitting end, the stress distribution inside the conductor can be inversely calculated.

[0042] A 60 kHz square wave signal is fed into a transmitting end sensor to excite longitudinal mode ultrasonic guided waves in the steel-cored aluminum stranded wire power transmission conductor 11. As shown in Figure 7 Figure 7 ​Distance (m) is the distance, amplitude is the amplitude of the ultrasonic wave, about 0.25 ms later, another receiving end sensor arranged at a distance of 1.2 m from the transmitting end receives a pure direct ultrasonic wave signal.

[0043] Wherein, the on-line real-time monitoring magnetostrictive sensor adopts a wear-resistant shoe 1 design and a non-coupling mode, so that the magnetostrictive sensor can be installed on the power transmission conductor 11 for a long time, and continuous, on-line and non-destructive monitoring of stress during construction or operation is realized.

[0044] The permanent magnets (the first permanent magnet 7 and the second permanent magnet 8) in the magnetostrictive sensor adopt a protective structure design of fixed plates (the side fixed plate 3, the inner fixed plate 4 and the end fixed plate 6), which effectively protects the internal permanent magnets (the first permanent magnet 7 and the second permanent magnet 8) and the excitation coil 10, and improves the service life and reliability of the magnetostrictive sensor in harsh industrial environments.

[0045] The above is only an embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application is included in the scope of the claims of the present application.

Claims

1. A magnetostrictive sensor for power transmission lines, characterized in that, include: Silicon steel yoke (5), which is in strip shape; At least one pair of permanent magnet components are fixedly spaced along the length of the silicon steel yoke (5), with the magnetic ends of the two permanent magnet components of opposite names arranged opposite each other; The bracket (2) is fixed to the silicon steel yoke (5) and located between the two permanent magnet components. An excitation coil (10) is wound on the bracket (2) along the length of the silicon steel yoke (5). The excitation coil (10) is used to generate a pulse dynamic magnetic field when a high-frequency pulse current is applied. The bracket (2) is provided with a C-shaped groove on the side away from the silicon steel yoke (5). The C-shaped groove is arranged along the length direction of the silicon steel yoke (5) so that the magnetostrictive sensor as a whole is attached to and close to the power transmission line (11) from one side. The permanent magnet component induces an axial static bias magnetic field (9) in the power transmission line (11). The static bias magnetic field (9) and the pulse dynamic magnetic field act together on the power transmission line (11) to excite longitudinal mode ultrasonic guided waves based on the inverse magnetostrictive effect and receive the returned ultrasonic guided waves based on the positive magnetostrictive effect.

2. The magnetostrictive sensor for power transmission lines according to claim 1, characterized in that, The permanent magnet assembly includes a permanent magnet and a fixing plate, wherein the fixing plate is vertically fixed on the silicon steel yoke (5) to fix the permanent magnet around it.

3. The magnetostrictive sensor for power transmission lines according to claim 1, characterized in that, The permanent magnet assembly also includes a wear-resistant slipper (1), which is fixed to the permanent magnet or the fixed plate. The wear-resistant slipper (1) is provided with an arc-shaped groove that radially matches the power transmission line (11). The magnetostrictive sensor is attached and fixed to the power transmission line (11) from one side so that the excitation coil (10) and the power transmission line (11) maintain a radial spacing distance.

4. The magnetostrictive sensor for power transmission lines according to claim 1, characterized in that, The fixing plate is made of non-ferromagnetic material.

5. The magnetostrictive sensor for power transmission lines according to claim 4, characterized in that, The fixing plate is made of aluminum alloy.

6. The magnetostrictive sensor for power transmission lines according to claim 2, characterized in that, The permanent magnet is made of neodymium iron boron material.

7. The magnetostrictive sensor for power transmission lines according to claim 1, characterized in that, The bracket (2) is made of engineering plastic.

8. The magnetostrictive sensor for power transmission lines according to claim 1, characterized in that, The dimensions of the silicon steel yoke (5) are 300mm×50mm×20mm.

9. The magnetostrictive sensor for power transmission lines according to claim 2, characterized in that, The permanent magnet has dimensions of 100mm × 50mm × 35mm.

10. A detection device for power transmission lines, characterized in that, It includes at least one magnetostrictive sensor for power transmission lines as described in any one of claims 1 to 9 and an ultrasonic guided wave excitation acquisition device electrically connected to said magnetostrictive sensor.

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