A shielding assembly for an optical unit of an optical fiber current sensor and a sensing system

Abstract

This invention discloses a shielding assembly and sensing system for the optical unit of a fiber optic current sensor, comprising an outer shield and an inner shield coaxially nested therein. The outer shield is made of a material with high saturation magnetization, and the inner shield is made of a material with high magnetic permeability. A magnetic isolation gap is defined between the two by non-magnetic support pillars, forming a composite shielding structure. An accommodating cavity is formed inside the inner shield to completely house the core optical unit, including the fiber optic slide and reflector. The mating surfaces of the shield's cover plate and base are sealed in a labyrinthine manner by isolation strips and isolation grooves, and a conductive gasket is provided to ensure magnetic circuit continuity. This invention places the magnetic field-sensitive optical unit within a double-layer shield, isolating it from external magnetic field interference and improving the sensor's measurement accuracy and long-term stability in strong magnetic field environments.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensing technology, and more specifically to a shielding component and sensing system for an optical unit of a fiber optic current sensor. Background Technology

[0002] In fiber optic current sensors with reflective interferometer structures, optical elements such as quarter-glass slides are typically introduced to achieve effective signal modulation and demodulation. These elements, together with the reflector, form the core of optical signal reflection and processing. However, an inherent challenge in existing technologies is that when the glass slide is composed of polarization-maintaining fibers several centimeters long, it is difficult to form a physically seamless and magnetically closed structure between it and the reflector. This unavoidable "closed gap" or non-closed region is exposed to the external environment. When the sensor operates in environments with strong DC or slowly varying magnetic fields, such as electrolytic smelting or fusion devices, stray magnetic fields penetrating this gap will also produce the Faraday effect, introducing a non-reciprocal noise phase difference independent of the measured current. This error is directly superimposed on the actual measurement signal, forming zero-point drift, affecting the sensor's measurement accuracy and long-term stability.

[0003] Based on the above, this application proposes a shielding component and sensing system for the optical unit of an optical fiber current sensor, which can effectively solve the above problems. Summary of the Invention

[0004] To address the problem that existing fiber optic current sensors suffer from non-reciprocal phase errors in their core optical units due to magnetic field penetration under strong magnetic field conditions, leading to zero-point drift and decreased accuracy, this application proposes a shielding component and sensing system for the optical unit of a fiber optic current sensor.

[0005] A shielding assembly and sensing system for an optical unit of a fiber optic current sensor, comprising:

[0006] An outer shielding body, the outer shielding body including a first cover plate and a first base detachably engaged with the first cover plate;

[0007] The inner shield includes a second cover plate and a second base detachably fitted with the second cover plate, and is housed within the outer shield. A first magnetic isolation gap is defined between the outer shield and the inner shield. A receiving cavity is defined inside the inner shield. A wiring channel is formed inside the inner shield and the outer shield, and the wiring channel connects to the outside and the receiving cavity.

[0008] The outer shielding material has a higher saturation magnetization than the inner shielding material, and the inner shielding material has a higher initial permeability than the outer shielding material.

[0009] By setting up double-layered nested inner and outer shields of different materials, a composite shielding structure that balances high saturation magnetization and high permeability is constructed, providing an efficient magnetic field shielding environment for the optical unit inside the cavity. At the same time, by setting up a wiring channel connecting the inside and outside, the entry and exit paths of the optical fiber are guaranteed.

[0010] In one embodiment, a non-magnetic support column is provided on the inner bottom surface of the first base, and the second base is supported on the non-magnetic support column to define the first magnetic isolation gap. By providing the non-magnetic support column and defining the first isolation gap, the inner and outer shielding bodies are physically separated, preventing the magnetic properties of the outer shielding body from being directly conducted to the inner shielding body when it becomes saturated due to a strong magnetic field, thereby enhancing the shielding effectiveness of the inner high-permeability material.

[0011] In one embodiment, a flexible liner is provided on the inner wall of the receiving cavity. The flexible liner has a first wiring port communicating with the wiring channel. The second base has a second wiring port corresponding to the wiring channel. A magnetic isolation plate is provided on the second wiring port, defining a wiring hole between the magnetic isolation plate and the second wiring port. By providing the flexible liner, stress buffering and mechanical decoupling are provided for the optical components placed on it, mitigating optical performance degradation caused by assembly stress or vibration. Simultaneously, along the critical paths of fiber optic entry and exit, the magnetic isolation plate locally strengthens the magnetic shielding of the wiring channel itself, further suppressing magnetic field leakage.

[0012] In one embodiment, the first base has a third wiring port at the location corresponding to the wiring channel. The diameter of the third wiring port gradually increases from the inner wall to the outer wall of the first base. The first cover plate has a fourth wiring port at the location corresponding to the wiring channel. Symmetrical mating plates are arranged on both sides of the fourth wiring port to partially block the third wiring port. By setting a variable-diameter third wiring port, it facilitates the insertion of optical fibers during assembly, avoiding damage. Furthermore, it collects and guides minute amounts of electromagnetic waves that may intrude from external gaps, directing their energy to a magnetic isolation plate on the inner shield, where it is concentrated and attenuated. The mating plates physically block the largest diameter location of the three wiring ports from the outside, reducing the effective area where electromagnetic waves can directly incident. The combination of "guided absorption" and "direct blocking" mechanisms enhances the overall shielding performance of the wiring channel.

[0013] In one embodiment, a first isolation strip extends from the lower bottom surface of the first cover plate, and a first isolation groove is formed on the upper surface of the first base to cooperate with the first isolation strip. A conductive electromagnetic gasket is provided on the mating surface of the first isolation strip and the first isolation groove. This solution forms a labyrinth-like sealing structure by setting the isolation strip and the isolation groove in a stepped overlapping manner, which prolongs the leakage path of magnetic lines of force and reduces magnetic resistance. The conductive electromagnetic gasket ensures good electrical contact between the cover plate and the base, provides a low-impedance path for the formation of induced eddy currents, and enhances the shielding effect against alternating magnetic fields and electromagnetic waves.

[0014] In one embodiment, a surrounding disk is disposed at the center of the second base, and at least one isolation strip is disposed on the inner top surface of the second cover plate. The receiving cavity is defined by the surrounding disk and the at least one isolation strip. A second isolation strip and a third isolation strip are disposed at intervals on the inner top surface of the second cover plate, and a second isolation groove and a third isolation groove are correspondingly formed on the upper surface of the second base. By setting the surrounding disk and isolation strip, a receiving cavity for accommodating optical components and coiled optical fibers is defined inside the inner shield, making the layout of internal components more regular and compact, and providing a structural basis for subsequent internal labyrinth sealing. At the same time, this scheme also adopts a double labyrinth sealing structure similar to that of the outer shield on the inner shield, realizing a progressive improvement in shielding effectiveness.

[0015] In one embodiment, conductive electromagnetic pads are provided on the mating surfaces of the second isolation strip and the second isolation groove, as well as the third isolation strip and the third isolation groove. This solution further enhances the magnetic circuit continuity of the inner shield by also providing conductive electromagnetic pads on the mating surfaces of the inner shield, enabling it to more efficiently attenuate residual magnetic fields entering the gap between the inner and outer shields.

[0016] In one embodiment, the bottom surfaces of the second and third isolation strips are provided with multiple mating teeth, and the inner bottom surfaces of the second and third isolation grooves are correspondingly provided with multiple mating grooves that can mate with the mating teeth. The mating surfaces of the mating teeth and the mating grooves are filled with a non-magnetic thermally conductive medium. This solution increases the contact area by setting a micro-groove structure and filling it with a thermally conductive medium, thus constructing an efficient heat dissipation channel while ensuring electrical isolation between the inner shielding components. This solves the problem of temperature drift that the core optical unit may experience due to changes in operating or ambient temperature.

[0017] In one embodiment, the sidewall of the second cover plate is supported by a ring of bearing plates extending radially outward from the bottom surface of the second base, and a second magnetic isolation gap is formed between the sidewall of the second cover plate and the sidewall of the second base. The design of the bearing plates provides a stable support structure for the assembly of the inner shield, while also creating a radial magnetic isolation gap, ensuring that the entire inner shield is completely enclosed within the magnetic isolation gap, further enhancing the magnetic isolation effect in three-dimensional space.

[0018] In one embodiment, a fiber optic current sensing system is provided, characterized by comprising: a shielding component as described in any of the preceding claims; an optical unit housed within the housing cavity; a fiber optic sensing ring; and a demodulation unit; wherein the optical unit includes a polarization-maintaining transmission fiber, a fiber optic slide, a lead fiber, and a reflector; the polarization-maintaining transmission fiber is led out from the demodulation unit, enters the housing cavity via the routing channel, and is sequentially connected to the fiber optic slide and the lead fiber; the lead fiber is led out of the shielding component via the routing channel, wraps around the fiber optic sensing ring, and is then reintroduced into the housing cavity via the routing channel; the end of the introduced lead fiber is connected to the reflector. This solution clarifies the specific application method and optical path routing of the shielding component in the entire fiber optic current sensing system. By placing the optical unit, which is most sensitive to magnetic fields, inside the shielding component, and allowing the lead fiber used for sensing to "lead out-wrap-lead back," protection of the core component is achieved, and the non-reciprocal noise problem caused by the exposure of the slide-reflector closed gap to a strong magnetic field is solved.

[0019] In summary, this application includes at least one of the following beneficial technical effects:

[0020] 1. By setting an outer shield made of a material with high saturation magnetization and an inner shield made of a material with high magnetic permeability, and setting a first magnetic isolation gap between the two, a composite shielding structure that takes into account both the strong magnetic field anti-saturation capability and the efficient magnetic field attenuation capability is realized, thereby improving the shielding effectiveness.

[0021] 2. By setting isolation strips and isolation groove labyrinth structures on the joint surface of the outer and inner shielding bodies, and using conductive electromagnetic pads, the leakage path of magnetic fields and electromagnetic waves along the joint is blocked, ensuring the integrity of the shielding body.

[0022] 3. By setting up a single cable routing channel that runs through the double-layer shield, and designing structures such as magnetic isolation plates and labyrinthine openings inside and at the openings, the magnetic field penetration at the weak points of the structure is suppressed to the maximum extent while ensuring the necessity of fiber optic entry and exit.

[0023] 4. By completely housing the core optical units, including the fiber optic plate and the reflector, within the housing cavity and designing a "lead-encircle-lead-back" sensing optical path, stray magnetic field sources that cause non-reciprocal phase errors are isolated from the source, thereby improving the zero-point stability and measurement accuracy of the fiber optic current sensor in a strong magnetic field environment.

[0024] 5. By combining the mating teeth and grooves set at the joints of the inner shield with the heat-conducting medium, a highly efficient heat dissipation channel is constructed, which achieves strong magnetic shielding while ensuring the temperature stability of the core optical unit. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the shielding component and sensing system embodiment 1 for an optical unit of an optical fiber current sensor provided in this application.

[0026] Figure 2 A schematic diagram of a shielding assembly and sensing system embodiment 1 for an optical unit of an optical fiber current sensor provided in this application, taken from a first blast angle.

[0027] Figure 3 A schematic diagram of a shielding assembly and sensing system embodiment 1 for an optical unit of a fiber optic current sensor provided in this application, taken from a second blast angle.

[0028] Figure 4 This is a schematic diagram of the structure of the first base and the second base in Embodiment 1 of a shielding assembly and sensing system for an optical unit of an optical fiber current sensor provided in this application.

[0029] Figure 5 A schematic diagram of a shielding assembly and sensing system embodiment 1 for an optical unit of an optical fiber current sensor provided in this application, viewed from a first cross-sectional perspective.

[0030] Figure 6 for Figure 5 Enlarged diagram of point A in the middle.

[0031] Figure 7 for Figure 5 Enlarged diagram of point B in the middle.

[0032] Figure 8 for Figure 5 Enlarged diagram of point C in the middle.

[0033] Figure 9 A schematic diagram of a shielding assembly and sensing system embodiment 1 for an optical unit of an optical fiber current sensor provided in this application from a second cross-sectional view.

[0034] Figure 10A cross-sectional schematic diagram of a shielding component and sensing system for an optical unit of a fiber optic current sensor provided in this application, according to Embodiment 2.

[0035] Figure 11 for Figure 10 Enlarged diagram of point D in the middle.

[0036] Figure 12 This application provides a shielding component for an optical unit of a fiber optic current sensor and an optical path diagram in a sensing system.

[0037] Explanation of reference numerals in the attached figures:

[0038] 1. Outer shield; 11. First cover plate; 111. Fourth wiring port; 112. Mating plate; 113. First isolation strip; 12. First base; 121. Non-magnetic support column; 122. Third wiring port; 123. First isolation groove; 13. First magnetic isolation gap; 2. Inner shield; 21. Second cover plate; 211. Second isolation strip; 212. Third isolation strip; 213. Mating tooth; 214. First weight reduction groove; 22. Second base; 221. Second wiring port; 222. Wiring hole; 223. Surrounding disk; 224. Second isolation groove; 225. Third isolation groove; 226. Mating groove; 227. Bearing plate; 228. Second weight reduction groove; 23. Receiving cavity; 24. Second magnetic isolation gap; 3. Wiring channel; 4. Flexible pad; 41. First wiring port; 5. Magnetic isolation plate; 6. Conductive electromagnetic pad; 7. Thermal conductive medium; 8. Optical unit; 81. Polarization-maintaining transmission fiber; 82. Fiber optic slide; 83. Lead fiber; 84. Reflector; 9. Fiber optic sensing ring; 10. Demodulation unit. Detailed Implementation

[0039] This application provides a shielding component and sensing system for the optical unit of a fiber optic current sensor, as detailed below. Figure 1-12 This application will be described in further detail.

[0040] Example 1

[0041] Reference Figure 1-9 and Figure 12 This embodiment provides a shielding assembly for the optical unit of a fiber optic current sensor. This shielding assembly is designed to provide a highly effective static magnetic environment for the core optical components of the reflective fiber optic current sensor, resisting interference from external strong magnetic fields.

[0042] In this embodiment, a shielding assembly for an optical unit of a fiber optic current sensor includes an outer shield 1 and an inner shield 2 housed therein. Both the outer shield 1 and the inner shield 2 are detachable cylindrical box structures. The outer shield 1 includes a first cover plate 11 and a first base 12, while the inner shield 2 includes a second cover plate 21 and a second base 22. The outer shield 1 is made of a soft magnetic material with high saturation magnetization. High saturation magnetization refers to a soft magnetic material with a saturation magnetic flux density higher than 1.5T. In this embodiment, silicon steel is preferred. This type of material is not easily saturated under high magnetic fields and can serve as the first line of defense against strong external magnetic fields, diverting and shielding most of the magnetic flux. The inner shield 2 is made of a soft magnetic material with extremely high initial permeability. High permeability material refers to a soft magnetic material with an initial permeability higher than 50,000. In this embodiment, permalloy is preferred. This material has good magnetic permeability and shielding performance under weak magnetic field, and is used to attenuate the residual weak magnetic field after penetrating the outer shield 1.

[0043] Specifically, to ensure the continuity of the magnetic circuit at the interface between the two, a first isolation strip 113 is integrally formed on the lower bottom surface of the first cover plate 11, and correspondingly, a first isolation groove 123 is machined on the upper surface of the first base 12 to match it. This forms a "labyrinthine" overlapping structure, which increases magnetic resistance and prevents magnetic lines of force from leaking from the joint. A conductive electromagnetic pad 6 is provided on the interface between the first isolation strip 113 and the first isolation groove 123, which is preferably a beryllium copper finger spring in this embodiment. In this embodiment, the conductive electromagnetic pad 6 is provided for two main purposes: First, when dealing with alternating magnetic fields in the environment, its high conductivity and elastic structure can ensure that a low-impedance electrical connection path is formed between the first cover plate 11 and the first base 12. When the alternating magnetic field passes through the outer shield 1, eddy currents are induced. This low-impedance path provides a closed loop for the flow of eddy currents, thereby generating a reverse magnetic field sufficient to cancel most of the incident field, achieving efficient shielding against alternating magnetic fields. Secondly, when dealing with DC or slowly changing magnetic fields, although the pad 6, which is a non-magnetic material, itself constitutes a magnetic blocking point, its good elasticity can ensure a tight mechanical fit between the high magnetic permeability material body of the first cover plate 11 and the first base 12, thereby minimizing the physical gap size of the joint on a macroscopic level and playing a certain role in suppressing the leakage path of DC magnetic lines.

[0044] Specifically, the inner shield 2 and the outer shield 1 are not in direct contact. Multiple non-magnetic support pillars 121 are provided on the inner bottom surface of the first base 12. In this embodiment, the non-magnetic support pillars 121 are preferably made of non-magnetic stainless steel. The second base 22 is directly supported on these non-magnetic support pillars 121, thus naturally forming an annular first magnetic isolation gap 13 between the bottom and sidewalls of the inner shield 2 and the outer shield 1. The first magnetic isolation gap 13 can be filled with air or other non-magnetic media. Even if the outer shield 1 experiences local saturation under an extremely strong magnetic field, the first magnetic isolation gap 13 can effectively prevent the saturation state from being transmitted to the inner shield 2, ensuring that the inner shield 2 always operates in its linear high permeability region and achieves optimal shielding performance. In this embodiment, the first magnetic isolation gap 13 is filled with air.

[0045] Specifically, the inner shield 2 defines a receiving cavity 23. At the center of the second base 22, a disc-shaped surrounding disk 223 is integrally machined. The surrounding disk 223 is used to coil the optical fiber entering the receiving cavity 23. To protect the fragile optical fiber, a flexible liner 4 is laid on the inner wall of the receiving cavity 23; in this embodiment, the flexible liner 4 is preferably made of polytetrafluoroethylene film.

[0046] Specifically, to ensure reliable fixation of the inner shield 2, the second cover plate 21 and the second base 22 are connected by non-magnetic screws. At the center of the second cover plate 21, a downward-facing first weight-reducing groove 214 is integrally formed along the axial direction, and the bottom surface of the first weight-reducing groove 214 has a threaded hole for threaded connection. Correspondingly, on the surrounding disc 223 of the second base 22, a second weight-reducing groove 228 is radially formed from the axis. The bottom surface of the second weight-reducing groove 228 also has a threaded hole corresponding to the threaded hole of the first weight-reducing groove 214.

[0047] Specifically, at least one ring of isolation strips is formed on the inner top surface of the second cover plate 21. In this embodiment, concentric second isolation strips 211 and third isolation strips 212 are preferably spaced apart. The structure of the second isolation strips 211 and third isolation strips 212 is similar to that of the first isolation strip 113. When the second cover plate 21 is closed on the second base 22, the second isolation strips 211 and third isolation strips 212 respectively cooperate with the second isolation grooves 224 and third isolation grooves 225 correspondingly opened on the upper surface of the second base 22. In this embodiment, the sealing method is the same as that of the outer shield 1. Conductive electromagnetic pads 6 are also provided on the joint surfaces of the second isolation strip 211 and the second isolation groove 224, and the third isolation strip 212 and the third isolation groove 225, to ensure the magnetic circuit integrity of the inner shield 2 itself and achieve precise shielding of the receiving cavity 23. The space of the receiving cavity 23 is defined by the surrounding disk 223, the flexible pad 4, and the second isolation strip 211.

[0048] Specifically, a ring-shaped support plate 227 extends radially outward from the bottom surface of the second base 22. When the second cover plate 21 mates with the second base 22, the side wall of the second cover plate 21 falls precisely on the support plate 227, thus forming a ring-shaped second magnetic isolation gap 24 between the side wall of the second cover plate 21 and the side wall of the second base 22.

[0049] In this embodiment, to allow the optical fiber to enter and exit the receiving cavity 23 and connect with the external structure, a single, shared wiring channel 3 is provided on the shielding assembly. This wiring channel 3 passes sequentially through the outer shielding body 1 and the inner shielding body 2. On the side wall of the flexible pad 4, corresponding to the position of the wiring channel 3, a first wiring opening 41 is provided.

[0050] Specifically, a second wiring port 221 is provided at the corresponding position of the second base 22 on the inner shield 2. To enhance the shielding at this location, a magnetic isolation plate 5 is also provided on the second wiring port 221. In this embodiment, the magnetic isolation plate 5 is made of the same material as the second base 22. A wiring hole 222, which allows only a few optical fibers to pass through, is defined between the magnetic isolation plate 5 and the bottom edge of the second wiring port 221, thus reducing the magnetic flux cross-section at this location.

[0051] Specifically, on the outer shield 1, a third cable routing port 122 is provided at the corresponding position of the first base 12. The third cable routing port 122 is flared from the inner wall to the outer wall, that is, the diameter gradually increases. This flared structure has a dual function: first, its smooth, non-sharp-angled bevel facilitates the insertion of optical fibers during assembly or adjustment, avoiding scratches or micro-bending losses to the fragile fiber core; second, this structure has the effect of collecting and guiding minute electromagnetic waves that may invade from external gaps, and can guide and focus their energy onto the magnetic isolation plate 5 set on the inner shield 2, so that the isolation plate 5 can perform concentrated absorption and attenuation, thereby improving the shielding efficiency.

[0052] More specifically, to further enhance the shielding performance of the wiring channel 3, the first cover plate 11 has a smaller fourth wiring port 111 at a corresponding position, and mating plates 112 are symmetrically arranged on both sides of the fourth wiring port 111. These two mating plates 112 partially block the large, trumpet-shaped opening of the lower third wiring port 122 from the outside. With this arrangement, the mating plates 112 act as a "direct block," forming a limited-size, non-straight-through external opening together with the fourth wiring port 111, reducing the effective area where electromagnetic waves can directly enter and physically limiting the entry of electromagnetic waves. This design, combined with the "guided absorption" function of the third wiring port 122, strengthens the overall shielding performance of the wiring channel 3, a structurally weak point.

[0053] Embodiments of this application also provide an optical fiber current sensing system, including the shielding assembly for the optical unit of the optical fiber current sensor described above, an optical unit 8, an optical fiber sensing ring 9, and a demodulation unit 10.

[0054] In this embodiment, the optical unit 8 is integrally installed and housed within the receiving cavity 23 inside the shielding assembly. The optical unit 8 includes a polarization-maintaining transmission fiber 81, a fiber optic plate 82, a lead fiber 83, and a reflector 84. One end of the polarization-maintaining transmission fiber 81 is connected to the external demodulation unit 10, and the other end enters the receiving cavity 23 through the wiring channel 3 of the shielding assembly and is connected to the front end of the fiber optic plate 82. The rear end of the fiber optic plate 82 is connected to the lead fiber 83.

[0055] Specifically, the fiber optic sensing ring 9 is a ring structure disposed outside the shielding assembly. In this embodiment, it is preferably a ring skeleton made of non-magnetic material, which is placed around the bus conductor through which the current to be measured flows during use.

[0056] Specifically, the demodulation unit 10 is the signal processing center of the system, and it is connected to the polarization-maintaining transmission fiber 81 in the shielding assembly via an optical fiber link. The demodulation unit 10 is responsible for generating the probe light signal, receiving the returned signal carrying phase information, and calculating the magnitude of the current using a specific algorithm.

[0057] More specifically, the polarization-maintaining transmission fiber 81 is led out from the demodulation unit 10, enters the receiving cavity 23 via the wiring channel 3, and connects to the fiber optic plate 82. The lead fiber 83 is led out from the end of the fiber optic plate 82, and then leads out to the outside of the shielding assembly via the wiring channel 3. On the outside, the lead fiber 83 is tightly wound around the fiber optic sensing ring 9 for a specified number of turns to form a sensing coil. After winding, the lead fiber 83 returns again via the wiring channel 3 and is introduced into the receiving cavity 23. The end of the introduced lead fiber 83 is connected to the reflector 84. The fixed position of the reflector 84 in the receiving cavity 23 is spatially adjacent to the front end of the fiber optic plate 82, thus forming a compact reflective optical circuit.

[0058] The working principle of the shielding component and sensing system for the optical unit of the fiber optic current sensor provided in this embodiment is as follows:

[0059] Optical Path Principle: The signal light is emitted from the external demodulation unit 10, passes through the polarization-maintaining transmission fiber 81, and enters the receiving cavity 23 via the wiring channel 3 on the shielding assembly. Upon entry, the polarization-maintaining transmission fiber 81 is first wound several times on the surrounding disk 223 to relieve stress. Subsequently, the fiber is connected sequentially to the fiber optic plate 82 and the lead fiber 83. The connected lead fiber 83 is then led out of the shielding assembly from the wiring channel 3 and wound onto the external fiber sensing ring 9 to sense the magnetic field generated by the external bus current. After winding, the end of the lead fiber 83 re-enters the receiving cavity 23 from the wiring channel 3, and its end is connected to a reflector 84, which is fixed adjacent to the initial position of the fiber optic plate 82. After being reflected by the reflector 84, the signal light returns along the original path, passing again through the fiber sensing ring 9, the fiber optic plate 82, and the polarization-maintaining transmission fiber 81, finally returning to the demodulation unit 10. The demodulation unit 10 calculates the current magnitude by analyzing the data generated when the optical signal returns.

[0060] Magnetic shielding principle: When the shielding component is placed in a strong magnetic field environment, the principle of action of the external DC or slowly varying magnetic field is as follows:

[0061] First, the outer shield 1, made of a material with high saturation magnetization, serves as the first line of defense. Utilizing its resistance to saturation, it bypasses most of the magnetic flux from the external strong magnetic field. During this process, the labyrinthine structure of the "first isolation strip 113-first isolation groove 123" at the joint surface between the first cover plate 11 and the first base 12 increases magnetic resistance by extending the leakage path of the magnetic lines of force. Meanwhile, the conductive electromagnetic pad 6 placed on top provides a low-impedance continuous path for the eddy currents induced by the alternating magnetic field within the shield. The two work together to ensure the structural integrity and shielding effectiveness of the outer shield 1 itself.

[0062] Secondly, a small amount of residual magnetic field penetrating the outer shield 1 will enter the first magnetic isolation gap 13 defined by the non-magnetic support pillar 121. The magnetic permeability of this gap is much lower than that of the shielding material, forming a high magnetic resistance layer. Its key function is to decouple the inner and outer shields in the magnetic circuit, preventing the saturation state from being conducted to the inner shield 2 through direct contact in the event of local magnetic saturation of the outer shield 1 under extreme conditions.

[0063] Secondly, the weak residual magnetic field, after being attenuated by the gap, reaches the inner shield 2 made of a material with high initial permeability, where it undergoes precise secondary absorption and bypassing. The inner shield 2 also employs a sealing structure of "isolation strip-isolation groove" and conductive electromagnetic gasket 6 to ensure precise shielding of the receiving cavity 23.

[0064] Finally, to address the potential weak point in shielding, the wiring channel 3, this application employs a composite structure for reinforcement. The external mating plate 112 and the fourth wiring port 111 reduce the incident aperture of electromagnetic waves through physical shielding; the flared third wiring port 122 guides and concentrates the incoming minute magnetic field; and finally, the magnetic isolation plate 5, located at the opening of the inner shield 2, concentrates and absorbs the guided magnetic flux.

[0065] Example 2

[0066] Reference Figure 10-12 This embodiment provides another shielding assembly for the optical unit of a fiber optic current sensor. The structure of this embodiment is basically the same as that of Embodiment 1. The difference lies in the differentiated design of the labyrinthine sealing structure of the inner shield 2 and the outer shield 1, aiming to achieve synergistic optimization of electromagnetic shielding and thermal management functions.

[0067] In this embodiment, the sealing structure of the inner shield 2 has been adaptively improved. Multiple arrayed mating teeth 213 are machined on the bottom surfaces of the second isolation strip 211 and the third isolation strip 212 using precision machining or etching processes. Correspondingly, multiple mating grooves 226 that can mesh with the mating teeth 213 are also machined on the inner bottom surfaces of the second isolation groove 224 and the third isolation groove 225. This tooth-groove meshing structure can macroscopically ensure the positioning accuracy of the cover plate and the base, and increase the effective contact surface area between the two on the mating surfaces.

[0068] Specifically, a non-magnetic thermally conductive medium 7 is filled on the mating surface formed by the mating teeth 213 and the mating groove 226. The thermally conductive medium 7 can be a paste-like thermally conductive grease, or a thermally conductive putty or phase change thermally conductive sheet with a certain degree of plasticity. In this embodiment, thermally conductive grease is preferred. When the second cover plate 21 and the second base 22 are pressed together, the thermally conductive medium 7 can fill the gap between the mating teeth 213 and the mating groove 226, expelling air, thereby creating a continuous, low-thermal-resistance thermally conductive path between the components.

[0069] The working principle of the shielding component and sensing system for the optical unit of a fiber optic current sensor provided in this application embodiment is as follows:

[0070] The optical path working principle and the basic principle of its double-layer magnetic shielding in this embodiment are the same as those in Embodiment 1.

[0071] The unique feature of this embodiment is that, through differentiated design of the joint treatment methods of the inner and outer shielding layers, the electromagnetic shielding performance and thermodynamic performance are simultaneously optimized.

[0072] In terms of thermal management, the inner shield 2 integrates efficient heat dissipation. The optical unit 8 generates heat during operation, which is transferred through its own structure to the cover plate 21 and base 22 of the inner shield 2, which have a large surface area. Because a non-magnetic thermally conductive medium 7 is filled between the mating teeth 213 and the mating groove 226 at the joint, a continuous, low-thermal-resistance thermal conduction path is constructed, allowing heat to be rapidly and uniformly distributed throughout the entire inner shield 2. The inner shield 2 thus becomes a highly efficient heat sink surrounding the core device, quickly and uniformly dissipating heat, which is then radiated and convectioned through the first magnetic isolation gap 13 to the outer shield 1, and finally dissipated into the environment. This active temperature control scheme directly suppresses the temperature drift of the core device caused by internal heat sources, ensuring the measurement accuracy and stability of the fiber optic current sensor during long-term operation.

[0073] Regarding electromagnetic performance, this invention employs a synergistic design of double-layer shielding. The outer shield 1 is responsible for resisting and shielding the vast majority of strong external magnetic fields. Therefore, the magnetic field penetrating to the inner shield 2 is a significantly weakened, residual magnetic field. Under this premise, the main task of the inner shield 2 becomes the precise absorption and shielding of this weak magnetic field. The locally high magnetic reluctance gap formed by filling its seams with a non-magnetic thermally conductive medium 7 keeps the impact on the overall shielding effectiveness of the inner shield within an acceptable range. Ultimately, this design solves the heat dissipation problem of the core components while ensuring magnetic shielding performance, achieving a balance between the two.

[0074] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A shielding assembly for an optical unit of a fiber optic current sensor, characterized in that, include: The outer shield (1) includes a first cover plate (11) and a first base (12) that is detachably engaged with the first cover plate (11); The inner shield (2) includes a second cover plate (21) and a second base (22) detachably fitted with the second cover plate (21), and is housed within the outer shield (1). A first magnetic isolation gap (13) is defined between the outer shield (1) and the inner shield (2). A receiving cavity (23) is defined inside the inner shield (2). A wiring channel (3) is opened inside the inner shield (2) and the outer shield (1). The wiring channel (3) connects the outside and the receiving cavity (23). The outer shield (1) has a higher saturation magnetization than the inner shield (2), and the inner shield (2) has a higher initial permeability than the outer shield (1).

2. The shielding assembly for an optical unit of a fiber optic current sensor according to claim 1, characterized in that, A non-magnetic support column (121) is provided on the inner bottom surface of the first base (12), and the second base (22) is supported on the non-magnetic support column (121) to define the first magnetic isolation gap (13).

3. A shielding assembly for an optical unit of a fiber optic current sensor according to claim 1, characterized in that, A flexible liner (4) is provided on the inner wall of the receiving cavity (23). A first wiring port (41) communicating with the wiring channel (3) is provided on the flexible liner (4). A second wiring port (221) is provided on the second base (22) at the position corresponding to the wiring channel (3). A magnetic isolation plate (5) is provided on the second wiring port (221). A wiring hole (222) is defined between the magnetic isolation plate (5) and the second wiring port (221).

4. A shielding assembly for an optical unit of a fiber optic current sensor according to claim 3, characterized in that, The first base (12) has a third wiring port (122) at the position corresponding to the wiring channel (3). The diameter of the third wiring port (122) gradually increases from the inner wall to the outer wall of the first base (12). The first cover plate (11) has a fourth wiring port (111) at the position corresponding to the wiring channel (3). The fourth wiring port (111) has symmetrical mating plates (112) on both sides to cover part of the third wiring port (122).

5. A shielding assembly for an optical unit of a fiber optic current sensor according to claim 1, characterized in that, The bottom surface of the first cover plate (11) extends with a first isolation strip (113), and the upper surface of the first base (12) is provided with a first isolation groove (123) that cooperates with the first isolation strip (113). A conductive electromagnetic pad (6) is provided on the joint surface of the first isolation strip (113) and the first isolation groove (123).

6. A shielding assembly for an optical unit of a fiber optic current sensor according to claim 1, characterized in that, A surrounding disk (223) is provided at the center of the second base (22), and at least one isolation strip is provided on the inner top surface of the second cover plate (21). The receiving cavity (23) is defined by the surrounding disk (223) and the at least one isolation strip. A second isolation strip (211) and a third isolation strip (212) are provided at intervals on the inner top surface of the second cover plate (21). A second isolation groove (224) and a third isolation groove (225) are correspondingly opened on the upper surface of the second base (22).

7. A shielding assembly for an optical unit of a fiber optic current sensor according to claim 6, characterized in that, Conductive electromagnetic pads (6) are provided on the joint surfaces of the second isolation strip (211) and the second isolation groove (224), as well as the third isolation strip (212) and the third isolation groove (225).

8. A shielding assembly for an optical unit of a fiber optic current sensor according to claim 6, characterized in that, The bottom surfaces of the second isolation strip (211) and the third isolation strip (212) are provided with a plurality of mating teeth (213), and the inner bottom surfaces of the second isolation groove (224) and the third isolation groove (225) are provided with a plurality of mating grooves (226) that can mate with the mating teeth (213). The mating surfaces of the mating teeth (213) and the mating grooves (226) are filled with a non-magnetic thermally conductive medium (7).

9. A shielding assembly for an optical unit of a fiber optic current sensor according to claim 1, characterized in that, The sidewall of the second cover plate (21) is supported by a ring of bearing plates (227) extending radially outward from the bottom surface of the second base (22), and a second magnetic isolation gap (24) is formed between the sidewall of the second cover plate (21) and the sidewall of the second base (22).

10. A fiber optic current sensing system, characterized in that, include: The shielding assembly as described in any one of claims 1-9; An optical unit (8) is housed within the receiving cavity (23); A fiber optic sensing loop (9); and One demodulation unit (10); The optical unit (8) includes a polarization-maintaining transmission fiber (81), a fiber optic plate (82), a lead fiber (83), and a reflector (84). The polarization-maintaining transmission fiber (81) is led out from the demodulation unit (10), enters the receiving cavity (23) through the wiring channel (3), and is sequentially connected to the fiber optic plate (82) and the lead fiber (83). The lead fiber (83) is led out from the shielding component through the wiring channel (3), wraps around the fiber optic sensing ring (9), and is then introduced into the receiving cavity (23) again through the wiring channel (3). The end of the introduced lead fiber (83) is connected to the reflector (84).

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