Self-luminous low-voltage cable and method for monitoring the temperature thereof

Abstract

The embodiment of the application provides a self-luminous low-voltage cable and a temperature monitoring method thereof, and belongs to the technical field of low-voltage cables. The self-luminous low-voltage cable comprises a cable core; a light-emitting functional layer is wrapped around the cable core, the light-emitting functional layer is composed of a polymer base material containing a light-storing luminescent material, and is used for active light emission; a transparent protective layer is wrapped around the light-emitting functional layer, the transparent protective layer is dispersedly provided with a temperature-sensitive color-changing material and an optical reference material, light emitted by the light-emitting functional layer is output as a first light beam with a first characteristic spectrum through the temperature-sensitive color-changing material, and the light emitted by the light-emitting functional layer is output as a second light beam with a second characteristic spectrum through the optical reference material; and a detection piece is used for detecting the first light beam and the second light beam, so as to determine the temperature of the cable core according to the characteristic spectra of the first light beam and the second light beam. The self-luminous low-voltage cable provided by the embodiment of the application can realize the self-luminous indication function, has the active temperature monitoring capability, and is beneficial to improving the accuracy of temperature monitoring.

Description

Technical Field

[0001] This application relates to cable technology, and more particularly to a self-illuminating low-voltage cable and a method for monitoring its temperature. Background Technology

[0002] In environments with insufficient lighting, such as tunnels, cable trenches, pipe galleries, and underground facilities, a large number of power cables are laid. To facilitate line identification during operation and maintenance, self-luminous cables have emerged. In related technologies, self-luminous cables have a fluorescent strip on the outside of the protective layer of each insulated core, and then a transparent polyethylene insulation layer is extruded, making each insulated core identifiable in dim environments, facilitating wiring and maintenance.

[0003] However, existing self-luminous cables can only achieve passive light-emitting indication function and are difficult to actively sense their own operating status. When the cable is abnormally heated due to overload, short circuit or external heat source, maintenance personnel still need to rely on external temperature measuring equipment for inspection, which is slow to respond and has monitoring blind spots. Summary of the Invention

[0004] This application provides a self-luminous low-voltage cable and a temperature monitoring method thereof to solve the technical problem in related technologies that self-luminous cables are difficult to actively sense their own temperature.

[0005] The self-illuminating low-voltage cable provided in this application embodiment includes:

[0006] Cable core;

[0007] A light-emitting functional layer, which covers the cable core, is composed of a polymer substrate containing a light-emitting material and is used for active light emission;

[0008] A transparent protective layer covers the light-emitting functional layer. A thermochromic material and an optical reference material are dispersed in the transparent protective layer. The light emitted by the light-emitting functional layer passes through the thermochromic material and outputs a first light beam with a first characteristic spectrum. The light emitted by the light-emitting functional layer passes through the optical reference material and outputs a second light beam with a second characteristic spectrum.

[0009] A detection element is used to detect the first beam and the second beam to determine the temperature of the cable core based on the characteristic spectra of the first beam and the second beam.

[0010] In some possible implementations, the thermochromic material is a color-reversible thermochromic microcapsule;

[0011] The thermochromic microcapsule includes a core and a capsule wall covering the core. The core contains a leuco dye, a color developer, and a melting point regulator. The melting point regulator is configured to be solid when the temperature is below the melting point, so that the leuco dye and the color developer combine to form a colored state; and to be liquid when the temperature is above the melting point, so that the color developer and the leuco dye separate to form a colorless state.

[0012] In some possible embodiments, the leuco dye is one or more of crystal violet lactone, fluorane compounds, or spiropyran compounds; the color developer is one or more of bisphenol A, p-hydroxybenzoate, or phenolic compounds; and the melting point regulator is one or more of fatty alcohols, fatty acid esters, or alkane compounds.

[0013] In some possible implementations, the optical reference material is one or more of inorganic oxide pigments or rare earth-doped inorganic phosphors;

[0014] Within the temperature range of 0℃ to 100℃, the peak wavelength shift of the reflection or emission spectrum of the optical reference material is less than 5nm, and the rate of change of reflectivity or luminescence intensity is less than 10%.

[0015] In some possible implementations, the detection element includes a first photodetector and a second photodetector, wherein the first photodetector is used to detect the light intensity of the first light beam and the second photodetector is used to detect the light intensity of the second light beam.

[0016] In some possible implementations, multiple first photodetectors and multiple second photodetectors are provided, and the multiple first photodetectors and multiple second photodetectors are spaced apart along the axial direction of the cable core;

[0017] Each terminal joint and each intermediate joint of the self-luminous low-voltage cable is provided with at least one first photodetector and at least one second photodetector.

[0018] In some possible implementations, it also includes:

[0019] A control component, connected to the first photodetector and the second photodetector, to receive the light intensity of the first beam detected by the first photodetector and the light intensity of the second beam detected by the second photodetector;

[0020] The control component is configured to determine the temperature of the cable core based on the ratio of the light intensity of the first beam to the light intensity of the second beam, and to issue an early warning signal indicating that the cable core temperature is abnormal when the ratio suddenly deviates from a preset value range.

[0021] In some possible implementations, the transparent protective layer is a nylon layer or a polycarbonate layer, and the polymer substrate is a thermoplastic polyurethane.

[0022] In some possible implementations, the light-emitting functional layer is further provided with a plurality of light guide filaments, which are uniformly arranged around the circumference of the light-emitting functional layer, and the light guide filaments are transparent nylon filaments.

[0023] On the other hand, embodiments of this application also provide a temperature monitoring method for a self-illuminating low-voltage cable, used to monitor the temperature of the self-illuminating low-voltage cable as described in any of the preceding claims, the temperature monitoring method comprising:

[0024] The characteristic spectra of the first and second beams of light passing through the transparent protective layer from the light-emitting functional layer are detected by the testing device.

[0025] The temperature of the cable core is determined based on the difference in characteristic spectra between the first beam and the second beam.

[0026] The self-luminous low-voltage cable and its temperature monitoring method provided in this application embodiment include a light-emitting functional layer for active light emission, a transparent protective layer in which a thermochromic material and an optical reference material are dispersedly disposed, the light emitted by the light-emitting functional layer is output as a first beam with a first characteristic spectrum through the thermochromic material, and the light emitted by the light-emitting functional layer is output as a second beam with a second characteristic spectrum through the optical reference material.

[0027] Therefore, when the cable overheats due to overload or external heat source, the optical properties of the thermochromic material change, causing the characteristic spectrum of its first output beam to change, while the second output beam from the optical reference material remains relatively stable. The detection device can accurately determine the cable core temperature by comparing the characteristic spectra of the two beams, without relying on external temperature measuring equipment.

[0028] Furthermore, since the detection device determines the temperature state by comparing the optical characteristics of the first beam and the second beam, rather than directly measuring the absolute light intensity of a single beam, the dual-beam reference detection method can effectively eliminate misjudgments caused by common-mode factors such as light source brightness attenuation or environmental stray light interference, effectively improving the accuracy and reliability of temperature monitoring for self-illuminating low-voltage cables. Attached Figure Description

[0029] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0030] Figure 1 This is a schematic diagram of the structure of the self-illuminating low-voltage cable provided in the embodiments of this application;

[0031] Figure 2A schematic diagram showing the installation position of the detection component of the self-illuminating low-voltage cable provided in the embodiments of this application at the intermediate joint;

[0032] Figure 3 This is a schematic diagram showing the connection between the control component and the detection component provided in an embodiment of this application.

[0033] Explanation of reference numerals in the attached figures

[0034] 100. Cable core; 110. Insulation layer; 120. Cable sheath layer;

[0035] 200. Light-emitting functional layer; 210. Light guide filament;

[0036] 300. Transparent protective layer;

[0037] 400. Detection component; 410. First photodetector; 420. Second photodetector;

[0038] 500. Control components;

[0039] 600, intermediate joint.

[0040] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0042] The terms "first," "second," "third," "fourth," etc. (if present) in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented, for example, in orders other than those illustrated or described herein.

[0043] In this application, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0044] Furthermore, the terms "set up," "connect," and "fix" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this disclosure according to the specific circumstances.

[0045] Unless otherwise stated, the term "multiple" means two or more.

[0046] As mentioned in the background art, in related technologies, self-luminous cables have fluorescent strips on the outside of the protective layer of each insulated core, and then a transparent polyethylene insulation layer is extruded, so that each insulated core is identifiable in a dark environment, which facilitates wiring and maintenance.

[0047] However, existing self-luminous cables can only achieve passive light-emitting indication function and are difficult to actively sense their own operating status. When the cable is abnormally heated due to overload, short circuit or external heat source, maintenance personnel still need to rely on external temperature measuring equipment for inspection, which is slow to respond and has monitoring blind spots.

[0048] Based on this, one or more embodiments of this application provide a self-luminous low-voltage cable and a temperature monitoring method thereof. In the self-luminous low-voltage cable, a light-emitting functional layer is used for active light emission, and a thermochromic material and an optical reference material are dispersed in the transparent protective layer. The light emitted by the light-emitting functional layer passes through the thermochromic material and outputs a first light beam with a first characteristic spectrum, and the light emitted by the light-emitting functional layer passes through the optical reference material and outputs a second light beam with a second characteristic spectrum.

[0049] Therefore, when the cable overheats due to overload or external heat source, the optical properties of the thermochromic material change, causing the characteristic spectrum of its first output beam to change, while the second output beam from the optical reference material remains relatively stable. The detection device can accurately determine the cable core temperature by comparing the characteristic spectra of the two beams, without relying on external temperature measuring equipment.

[0050] The solutions provided in the embodiments of this application will be described below with reference to the accompanying drawings.

[0051] like Figure 1 and Figure 2As shown in the embodiment of this application, the self-luminous low-voltage cable includes a cable core 100, a light-emitting functional layer 200, a transparent protective layer 300, and a detection component 400.

[0052] A light-emitting functional layer 200 covers the cable core 100. The light-emitting functional layer 200 is composed of a polymer substrate containing a light-emitting material and is used for active light emission. A transparent protective layer 300 covers the light-emitting functional layer 200. A thermochromic material and an optical reference material are dispersed in the transparent protective layer 300. The light emitted by the light-emitting functional layer 200 passes through the thermochromic material and outputs a first light beam with a first characteristic spectrum. The light emitted by the light-emitting functional layer 200 passes through the optical reference material and outputs a second light beam with a second characteristic spectrum. A detection element 400 is used to detect the first light beam and the second light beam to determine the temperature of the cable core 100 based on the characteristic spectra of the first light beam and the second light beam.

[0053] like Figure 1 As shown, the cable core 100 is used to carry the current of the self-illuminating low-voltage cable and can adopt the load conductor structure in related technologies. For example, the cable core 100 is made of multiple copper or aluminum single wires twisted together, or it can be a single solid conductor. Depending on the application scenario, the cable core 100 can be selectively covered with functional layers such as insulation layer 110, shielding layer, and water-blocking layer. When a multi-core cable core structure is provided, the outermost layer of each cable core 100 is completely covered with cable sheath layer 120 to further enhance the constraint and protection effect on the cable core 100. These functional layers and cable sheath layer 120 do not affect the implementation of the technical solution of this application, and the specific structure and materials of the cable core 100 will not be described in detail here.

[0054] The light-emitting functional layer 200 is coaxially wrapped around the outside of the cable core 100. In terms of material selection, the polymer substrate should have good light transmittance and flexibility to allow the light emitted by the light-emitting material and the external excitation light to pass through efficiently, while avoiding the failure of the light-emitting function due to the deformation and cracking of the substrate during the bending, winding and laying of the cable.

[0055] For example, the polymer substrate can be thermoplastic polyurethane. Thermoplastic polyurethane combines the high elasticity of rubber with the processability of plastics. It has high light transmittance, excellent abrasion resistance and tear resistance, and good compatibility with various inorganic powder fillers. During the mixing process, the photoluminescent powder can be uniformly dispersed in the thermoplastic polyurethane melt to form a stable suspension system that is not prone to sedimentation.

[0056] As an alternative implementation, the polymer substrate can also be a polyethylene-vinyl acetate copolymer. This material has good flexibility and a lower processing temperature, which helps reduce the risk of thermal damage to the phosphorescent material during processing. In addition, the polymer substrate can also be made of styrene-based thermoplastic elastomers, polyolefin elastomers, and other polymer materials with good transparency and flexibility.

[0057] The photoluminescent material is dispersed in a polymer substrate. The basic working principle of the photoluminescent material is as follows: when irradiated by visible or ultraviolet light in the environment, the lattice defects or doped ions inside the material will store photogenerated electrons or holes. When the ambient light disappears, the captured charge carriers are slowly released under thermal disturbance and recombine with the luminescent center, radiating the stored energy in the form of visible light, thereby achieving long-term afterglow luminescence.

[0058] For example, the photoluminescent material is selected from rare earth aluminate long-afterglow luminescent powders, or silicate, sulfide, or titanate long-afterglow luminescent powders. The specific selection can be flexibly set according to factors such as the required emission color, afterglow time, and cost, and is not absolutely limited in this embodiment.

[0059] When preparing the luminescent functional layer 200, the photoluminescent material and the polymer substrate granules can be premixed, and then melt-mixed using a twin-screw extruder or internal mixer. During the mixing process, the shear force of the screw breaks down the agglomerates of the photoluminescent material and disperses them uniformly in the polymer melt. To prevent oxidation or lattice damage to the photoluminescent material during high-temperature mixing, the mixing temperature should not be too high, only higher than the melting temperature of the polymer substrate.

[0060] The light-emitting functional layer 200 can be coated onto the outside of the cable core 100 by extrusion molding. Specifically, a polymer substrate containing a light-emitting material that is mixed evenly is fed into the hopper of an extruder. Under the conveying and plasticizing action of the screw, a uniform melt is formed. The melt is then extruded through the die head and coated onto the surface of the moving cable core 100. After cooling and shaping, the light-emitting functional layer 200 is formed. The thickness of the light-emitting functional layer 200 can be adjusted according to the design requirements of the luminous brightness and the specifications of the overall outer diameter of the cable. This is not an absolute limitation in the embodiments of this application.

[0061] In some embodiments, the thermochromic material is a thermochromic microcapsule with reversible color; wherein the thermochromic microcapsule includes a core and a wall covering the core, the core containing a leuco dye, a color developer, and a melting point regulator, the melting point regulator being configured to be solid when the temperature is below the melting point, so that the leuco dye and the color developer combine to form a colored state; and liquid when the temperature is above the melting point, dissolving the color developer, so that the color developer and the leuco dye separate to form a colorless state.

[0062] In the above embodiments, the capsule wall of the thermochromic microcapsule encapsulates the capsule core. The capsule wall can be made of melamine resin or polyurea, and the capsule core is encapsulated inside the microcapsule by the capsule wall. The leuco dye is one or more of crystal violet lactone, fluorane compounds, or spiropyran compounds. Crystal violet lactone is a classic thermochromic leuco dye, which is blue in the open ring state. Fluorane compounds have a wide chromatographic range and can be modified with different substituents to obtain color changes ranging from red to blue-violet. The specific selection can be adjusted according to the color and color-changing temperature required by the cable.

[0063] Here, the color developer is one or more of bisphenol A, parabens, or phenolic compounds. Bisphenol A has a moderately acidic phenolic hydroxyl group, and when used in combination with leuco dyes such as crystal violet lactone, the color development effect is obvious and reversible. Parabens are mildly acidic, and their binding-dissociation process with leuco dyes is rapid, resulting in a sensitive color change response. The type and amount of color developer can be adjusted according to the color depth and color change temperature.

[0064] The melting point regulator is one or more of fatty alcohols, fatty acid esters, or alkane compounds. The melting point regulator is solid at room temperature and melts into a liquid state when the temperature rises above its melting point. In its solid state, the melting point regulator does not have the ability to dissolve the color developer; the leuco dye is tightly bound to the color developer, and the entire core system is colored. When the melting point regulator melts, the liquid melting point regulator acts as a solvent, dissolving the color developer and separating it from the leuco dye. The leuco dye then reverts to its free, closed-ring structure, and the color disappears.

[0065] When the ambient temperature is below the melting point of the melting point regulator, the regulator is solid, and the solvent effect within the system is extremely weak. The chromogenic agent and the leuco dye undergo proton or electron transfer and bind tightly. The lactone ring of the leuco dye opens to form a colored conjugated structure, and the thermochromic microcapsule as a whole is colored. When the ambient temperature rises above the melting point of the melting point regulator, the regulator melts from solid to liquid. The liquid melting point regulator dissolves and surrounds the chromogenic agent, causing physical separation between the chromogenic agent and the leuco dye. After the leuco dye loses its proton or electron donor, the lactone ring closes again, the conjugated system shrinks, the colored absorption disappears, and the thermochromic microcapsule as a whole becomes colorless. When the ambient temperature falls back below the melting point of the regulator, it solidifies again. The chromogenic agent dissolved within it precipitates from the solidified regulator, re-contains and binds with the leuco dye, the lactone ring reopens, and the color is restored.

[0066] This shows that the color-changing process of thermochromic materials is reversible, and they can cycle between colored and colorless multiple times without significant performance degradation. This is beneficial for meeting the needs of self-luminous low-voltage cables for repeated overheating warnings during long-term operation.

[0067] In some embodiments, the optical reference material is one or more of inorganic oxide pigments or rare earth-doped inorganic phosphors; within the temperature range of 0℃-100℃, the peak wavelength shift of the reflection spectrum or emission spectrum of the optical reference material is less than 5nm, and the rate of change of reflectance or luminous intensity is less than 10%.

[0068] Optical reference materials are dispersed within the transparent protective layer 300, and their core function is to provide a reference standard whose optical properties do not change with temperature. Unlike thermochromic materials, optical reference materials maintain stable optical properties within the temperature range of normal cable operation and overheating conditions, thus providing a fixed comparison reference system for the test piece 400.

[0069] For example, the optical reference material is one or more of inorganic oxide pigments or rare earth-doped inorganic phosphors. The inorganic oxide pigments have a stable reflection spectrum in the visible light band, and their appearance color does not change with temperature. For example, the inorganic oxide pigments can be titanium dioxide, zinc oxide, or aluminum oxide, etc. Alternatively, the rare earth-doped inorganic phosphors can be rare earth doping systems such as cerium-doped yttrium aluminum garnet phosphors, europium aluminate strontium phosphors, and terbium aluminate yttrium phosphors.

[0070] Both inorganic oxide pigments and rare earth-doped inorganic phosphors are synthesized in a high-temperature solid-state process. Their preparation temperature is usually much higher than the extrusion processing temperature of the transparent protective layer 300 polymer. Therefore, no thermal decomposition, oxidation or crystal transformation will occur during the extrusion molding process, and they can completely maintain their original optical properties.

[0071] It should be noted that the optical reference material is introduced into the transparent protective layer 300 in powder form. During preparation, the optical reference material can be added as a masterbatch along with the thermochromic material during the polymer matrix compounding and granulation stage of the transparent protective layer 300. Uniform dispersion is achieved through shear mixing using a twin-screw extruder. The particle size of the optical reference material is typically in the micrometer range. After being dispersed in the transparent protective layer 300, it forms uniformly distributed light scattering or light conversion sites. The specific material type and concentration of the optical reference material can be adjusted according to different needs, as long as the peak wavelength shift of the reflection or emission spectrum of the optical reference material is less than 5 nm and the rate of change of reflectance or luminous intensity is less than 10% within the temperature range of 0℃-100℃.

[0072] In preparing the transparent protective layer 300, the thermochromic microcapsules and optical reference materials are first premixed in a preset ratio, and then fed together with the polymer substrate granules of the transparent protective layer 300 into a mixing equipment for melt blending. Both the thermochromic microcapsules and the optical reference materials are micron-sized powders with similar particle sizes. During the melt blending process, they are subjected to the combined action of screw shearing, which enables the synchronous and uniform dispersion of the two.

[0073] The second beam output by the optical reference material has a characteristic spectrum that does not change with temperature. This forms a dual-beam comparison with the first beam output by the temperature-sensitive color-changing material, which changes with temperature. The control component 500 can accurately determine the temperature status of the cable by comparing the differences in the characteristic spectra of the two beams. This fundamentally eliminates temperature misjudgments caused by common-mode factors such as aging and decay of the light-emitting functional layer 200, dust accumulation and wear of the transparent protective layer 300, and interference from stray light in the environment. This helps to improve the reliability and accuracy of the self-monitoring light-emitting cable during long-term operation.

[0074] like Figure 2 As shown, in some embodiments, the detection element 400 includes a first photodetector 410 and a second photodetector 420. The first photodetector 410 is used to detect the light intensity of the first beam, and the second photodetector 420 is used to detect the light intensity of the second beam.

[0075] In the above embodiments, the first photodetector 410 and the second photodetector 420 are respectively provided with a beam splitting element and a photoelectric conversion element. The beam splitting element can be a bandpass filter. The bandpass filter of the first photodetector 410 only allows light in the first characteristic spectrum band to pass through, and the bandpass filter of the second photodetector 420 only allows light in the second characteristic spectrum band to pass through, thereby realizing independent detection of dual channels.

[0076] Photoelectric conversion elements are used to convert received optical signals into measurable electrical signals. For example, photodiodes can be selected as photoelectric conversion elements. Photodiodes have fast response speed, good linearity, and small size, making them suitable for integrated design.

[0077] Furthermore, multiple first photodetectors 410 and second photodetectors 420 are provided, and multiple first photodetectors 410 and second photodetectors 420 are spaced apart along the axial direction of the cable core 100; at least one first photodetector 410 and at least one second photodetector 420 are provided at each terminal joint and each intermediate joint 600 position of the self-luminous low-voltage cable.

[0078] In this embodiment, multiple first photodetectors 410 and second photodetectors 420 are sequentially arranged along the cable axis at a certain interval. The spacing between adjacent detection points can be determined comprehensively based on factors such as the temperature monitoring accuracy requirements of the cable laying environment, cable length, and maintenance costs.

[0079] For example, in sections with large temperature gradients or high risk of overheating, the spacing between detection points can be appropriately reduced to improve monitoring resolution; in sections with gentle temperature changes or low risk of overheating, the spacing can be appropriately increased to reduce system costs.

[0080] In the above embodiments, the first photodetector 410 and the second photodetector 420 at each detection point are configured in a group to simultaneously acquire the light intensity of the first beam and the light intensity of the second beam at that location. When the light intensity ratio at a certain detection point deviates from the preset reference range, it can be determined that there is a temperature anomaly in the section where the detection point is located, and maintenance personnel can quickly locate the abnormal section based on the location of the detection point that issued the alarm.

[0081] Cable termination joints and intermediate joints 600 are critical nodes connecting different sections of a cable line, and are also high-risk areas prone to localized overheating due to increased contact resistance. Therefore, at each termination joint and each intermediate joint 600 of the self-illuminating low-voltage cable, at least one first photodetector 410 and at least one second photodetector 420 are respectively installed to achieve key temperature monitoring of the joint locations.

[0082] Terminal joints are located at the beginning and end of cable lines and serve as transition areas for the connection of cables to other electrical equipment. Intermediate joints 600 are located at the connection between two sections of self-illuminating low-voltage cables. They are usually fabricated and installed on-site, and their connection quality is greatly affected by construction techniques and the on-site environment. They are also frequent locations for overheating faults. Detection elements 400 are installed at each terminal joint and each intermediate joint 600 to ensure effective online monitoring of every potential overheating risk point in the cable line.

[0083] like Figure 2 As shown, at the connector, the first photodetector 410 and the second photodetector 420 can be aligned with the end face of the transparent protective layer 300. Since the transparent protective layer 300 also functions as an optical waveguide, the light emitted by the light-emitting functional layer 200 is conducted along the cable axis within the transparent protective layer 300 and concentrated at the end face of the transparent protective layer 300 at the connector. The detection element 400 is aligned with the end face to receive the optical signal. The light collection efficiency is high and the signal strength is sufficient, which is beneficial to improving detection accuracy and signal-to-noise ratio.

[0084] like Figure 3 As shown, in some embodiments, the self-illuminating low-voltage cable also includes a control component 500.

[0085] The control unit 500 is connected to the first photodetector 410 and the second photodetector 420 to receive the light intensity of the first beam detected by the first photodetector 410 and the light intensity of the second beam detected by the second photodetector 420. The control unit 500 is configured to determine the temperature of the cable core 100 based on the ratio of the light intensity of the first beam to the light intensity of the second beam, and to issue an early warning signal of abnormal temperature of the cable core 100 when the ratio suddenly deviates from a preset value range.

[0086] In this embodiment, the control component 500 may be an electronic device with data processing capabilities, such as a microcontroller, digital signal processor, field programmable gate array, or industrial control computer. The control component 500 may be integrated into the terminal distribution cabinet of the cable, the local control box, or an independent monitoring instrument, or it may serve as a node in a distributed monitoring system to interact with the host computer via a bus or network. No absolute limitation is made in this regard.

[0087] The control unit 500 can be connected to the output terminals of each of the first photodetectors 410 and the second photodetectors 420 via signal cables. The signal cables can be laid along the cable laying path or integrated into the cable sheath structure. Alternatively, a wireless transmission module can be set at each detection point to wirelessly transmit the electrical signals converted by each photodetector to the control unit 500, thereby reducing the amount of wiring work and eliminating the need to modify the internal structure of the self-illuminating low-voltage cable, making the setup easier.

[0088] The control unit 500 calculates the real-time ratio of the received light intensity values ​​of the first beam and the second beam. For example, if the light intensity of the first beam is A and the light intensity of the second beam is B, then the real-time ratio of the first beam and the second beam is R = A / B.

[0089] During the cable manufacturing or initial commissioning phase, a standard ratio can be calibrated under known normal operating temperature conditions, and the ratio of the intensity of the first beam to the intensity of the second beam at this time is recorded as a reference ratio. The reference ratio corresponds to the normal operating temperature state of the cable. During actual operation, the control unit 500 continuously calculates the real-time ratio and compares the real-time ratio with the reference ratio.

[0090] When the cable temperature changes, the optical properties of the thermochromic material change, causing a change in the light intensity A of the first beam, while the light intensity B of the second beam output by the optical reference material remains basically stable. Therefore, the real-time ratio R changes accordingly with temperature. The control unit 500 determines the current temperature state of the cable core 100 based on the magnitude and direction of the change in the real-time ratio R relative to the reference ratio.

[0091] It should be noted that the preset value range is the allowable fluctuation range of the ratio set in advance during the calibration stage or the initial system setup stage. This range is centered on the reference ratio value, with a certain tolerance above and below it. The tolerance range can be set according to the sensitivity and false alarm rate requirements of temperature monitoring.

[0092] For example, under normal temperature calibration, the reference ratio of the intensity of the first beam to the intensity of the second beam is measured to be 0.5. A tolerance of ±10% is set around this reference value, forming a preset value range of 0.45-0.55. During normal cable operation, the real-time ratio fluctuates slightly between 0.47 and 0.53, always remaining within this range. When the cable core 100 overheats, causing a sudden change in the color of the temperature-sensitive color-changing material, the intensity of the first beam increases abruptly, and the real-time ratio jumps to 0.8, exceeding the upper limit of the preset value range. The control unit 500 then issues a warning signal. Of course, the above specific values ​​are merely illustrative examples.

[0093] During normal cable operation, the optical properties of the thermochromic material may fluctuate slightly due to diurnal or seasonal changes in ambient temperature. Small variations in the real-time ratio within the preset range are normal and do not trigger an alarm. However, when the cable overheats abnormally due to overload, short circuit, poor joint contact, or external heat sources, the temperature of the thermochromic material exceeds its color-changing temperature threshold, causing a sudden change in color state. This results in a significant jump in the intensity of the first light beam, causing the real-time ratio R to abruptly shift out of the preset range. Upon detecting this shift, the control unit 500 determines that the cable core 100 temperature is abnormal and immediately issues an alarm signal.

[0094] Here, the warning signal can be an audible and visual alarm or uploaded to the remote monitoring center via a communication interface, as long as it can alert maintenance personnel to abnormal cable temperature.

[0095] The brightness of the luminescent functional layer 200 may decrease over long-term use, or the transmittance of the transparent protective layer 300 may decrease due to dust accumulation, or the optical window of the detection component 400 may become contaminated. These factors can all affect the normal detection accuracy. However, due to the presence of an optical reference material, the light intensities of the first and second beams will decrease approximately proportionally. Although the light intensities A and B of the first and second beams respectively decrease, their ratio remains essentially unchanged, staying within the preset value range, and the control component 500 will not issue a false alarm. Only when temperature changes cause a change in the optical properties of the thermochromic material, resulting in a change in the light intensity of the first beam independent of the second beam, will the ratio shift and trigger an alarm. This design effectively eliminates the impact of common-mode interference such as light source attenuation and dust accumulation on temperature judgment, which is beneficial to improving the sensitivity of temperature monitoring and long-term operational reliability.

[0096] like Figure 1 As shown, in some embodiments, a plurality of light guide filaments 210 are also dispersedly disposed in the light-emitting functional layer 200. The plurality of light guide filaments 210 are uniformly disposed around the circumference of the light-emitting functional layer 200, and the light guide filaments 210 are transparent nylon filaments.

[0097] In the above embodiments, the nylon material has good light transmittance and flexibility, and its refractive index is higher than that of the polymer substrate of the light-emitting functional layer 200. It can form a total internal reflection condition inside the light guide filament 210, so that the light entering the light guide filament 210 is efficiently transmitted along its axis and the scattering loss of light energy in the radial direction is reduced.

[0098] The circumferentially distributed nylon filaments ensure uniform brightness distribution when viewed from any angle of the cable, avoiding dark areas or bright spots. During the fabrication of the light-emitting functional layer 200, the light guide filament 210 is introduced simultaneously during the extrusion molding of the light-emitting functional layer 200. A guide filament introduction device is installed at the extruder head to guide the light guide filament 210 from the pay-off reel and through the die core. While the polymer substrate melt covers the cable core 100, the light guide filament 210 is uniformly embedded in the light-emitting functional layer 200, and after cooling and setting, it forms an integral light-emitting functional layer 200.

[0099] The light emitted by the photoluminescent material in the polymer substrate is partly transmitted directly in the radial direction and output outward through the transparent protective layer 300, and partly enters the light guide filament 210. The light entering the light guide filament 210 undergoes total internal reflection and is confined inside the light guide filament 210 and conducted along the cable axis. During the light conduction process, some light will be scattered or leaked from the side wall of the light guide filament 210, making the light emission brightness distribution along the cable more uniform and effectively compensating for the brightness attenuation caused by the distance from the light source or the bending of the cable.

[0100] An exemplary working process of the self-illuminating low-voltage cable provided in this application embodiment is as follows:

[0101] After the cable is laid and put into operation, the light-emitting material in the light-emitting functional layer 200 absorbs and stores light energy during the day or under artificial light source illumination, and continuously emits visible light in the dark environment. This light radiates outward from the light-emitting functional layer 200 and enters the transparent protective layer 300 covering it. The transparent protective layer 300 contains thermochromic material and optical reference material uniformly dispersed in it.

[0102] As the light emitted from the light-emitting functional layer 200 passes through the transparent protective layer 300, part of it interacts with the thermochromic material and, influenced by its temperature-dependent optical properties, forms a first beam with a first characteristic spectrum. The other part interacts with the optical reference material, and, because the optical properties of the optical reference material remain stable within the cable's operating temperature range, forms a second beam with a second characteristic spectrum that is unaffected by temperature. Both beams of light exit from the outer surface or end face of the transparent protective layer 300.

[0103] Detection elements 400 are spaced apart at each terminal joint and intermediate joint 600 along the cable axis. They receive composite light emitted from the transparent protective layer 300 in real time. The first photodetector 410 in the detection element 400 separates the first beam through a corresponding filter and measures its light intensity. The second photodetector 420 separates the second beam through a corresponding filter and measures its light intensity. The two sets of light intensity signals are transmitted to the control component 500. The control component 500 calculates the ratio of the light intensity of the first beam to the light intensity of the second beam in real time.

[0104] When the cable is at its normal operating temperature, the thermochromic material maintains its initial color state, and the real-time ratio remains stable within the preset value range. When the cable overheats due to overload or other reasons, and the temperature of the cable core 100 exceeds the color-changing temperature threshold of the thermochromic material, the thermochromic material undergoes a sudden color change, and the intensity of the first beam changes significantly, while the intensity of the second beam remains basically unchanged. The real-time ratio instantly deviates from the preset value range. After the control component 500 detects this change, it determines that the temperature of the cable core 100 is abnormal, issues a warning signal, and can link a circuit breaker or load switch to cut off the power supply. When the temperature drops below the threshold, the thermochromic material returns to its initial state, the ratio returns to the normal range, and the warning is lifted. The entire monitoring process uses the ratio method to eliminate light source attenuation and dust interference, achieving highly reliable online monitoring of cable temperature.

[0105] Another embodiment of this application provides a temperature monitoring method for a self-illuminating low-voltage cable, used to monitor the temperature of the self-illuminating low-voltage cable as described in any of the above claims. The temperature monitoring method includes:

[0106] The characteristic spectra of the first and second light beams that penetrate the transparent protective layer 300 through the light-emitting functional layer 200 are detected by the detection element 400.

[0107] The temperature of cable core 100 is determined based on the difference in characteristic spectra between the first beam and the second beam.

[0108] The core principle of the temperature monitoring method for the self-luminous low-voltage cable mentioned above is to obtain the characteristic spectra of the first beam output by the temperature-sensitive color-changing material and the second beam output by the optical reference material through the detection element 400, and to determine the temperature state of the cable core 100 based on the difference between the two characteristic spectra.

[0109] Since the temperature monitoring method for self-luminous low-voltage cables is used to monitor the temperature of self-luminous low-voltage cables as described above, all the advantages of self-luminous low-voltage cables can be realized by applying this temperature monitoring method.

[0110] The technical solutions of this application have been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it is readily understood by those skilled in the art that the scope of protection of this application is obviously not limited to these specific embodiments. The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A self-illuminating low-voltage cable, characterized in that, include: Cable core (100); A light-emitting functional layer (200) covers the cable core (100). The light-emitting functional layer (200) is made of a polymer substrate containing a light-emitting material and is used for active light emission. A transparent protective layer (300) covers the light-emitting functional layer (200). The transparent protective layer (300) contains a thermochromic material and an optical reference material. The light emitted by the light-emitting functional layer (200) passes through the thermochromic material and outputs a first light beam with a first characteristic spectrum. The light emitted by the light-emitting functional layer (200) passes through the optical reference material and outputs a second light beam with a second characteristic spectrum. A detection element (400) is used to detect the first beam and the second beam to determine the temperature of the cable core (100) based on the characteristic spectra of the first beam and the second beam.

2. The self-illuminating low-voltage cable according to claim 1, characterized in that, The thermochromic material is a thermochromic microcapsule with reversible color. The thermochromic microcapsule includes a core and a capsule wall covering the core. The core contains a leuco dye, a color developer, and a melting point regulator. The melting point regulator is configured to be solid when the temperature is below the melting point, so that the leuco dye and the color developer combine to form a colored state; and to be liquid when the temperature is above the melting point, so that the color developer and the leuco dye separate to form a colorless state.

3. The self-illuminating low-voltage cable according to claim 2, characterized in that, The leuco dye is one or more of crystal violet lactone, fluorane compounds, or spiropyran compounds; the color developer is one or more of bisphenol A, p-hydroxybenzoic acid esters, or phenolic compounds; and the melting point regulator is one or more of fatty alcohols, fatty acid esters, or alkane compounds.

4. The self-illuminating low-voltage cable according to claim 1, characterized in that, The optical reference material is one or more of inorganic oxide pigments or rare earth-doped inorganic phosphors. Within the temperature range of 0℃ to 100℃, the peak wavelength shift of the reflection or emission spectrum of the optical reference material is less than 5nm, and the rate of change of reflectivity or luminescence intensity is less than 10%.

5. The self-illuminating low-voltage cable according to any one of claims 1 to 4, characterized in that, The detection device (400) includes a first photodetector (410) and a second photodetector (420). The first photodetector (410) is used to detect the light intensity of the first beam, and the second photodetector (420) is used to detect the light intensity of the second beam.

6. The self-illuminating low-voltage cable according to claim 5, characterized in that, Multiple first photodetectors (410) and multiple second photodetectors (420) are provided, and multiple first photodetectors (410) and multiple second photodetectors (420) are spaced apart along the axial direction of the cable core (100); At each terminal joint and each intermediate joint (600) of the self-luminous low-voltage cable, at least one first photodetector (410) and at least one second photodetector (420) are respectively provided.

7. The self-illuminating low-voltage cable according to claim 5, characterized in that, Also includes: A control unit (500) is connected to the first photodetector (410) and the second photodetector (420) to receive the light intensity of the first beam detected by the first photodetector (410) and the light intensity of the second beam detected by the second photodetector (420). The control unit (500) is configured to determine the temperature of the cable core (100) based on the ratio of the light intensity of the first beam to the light intensity of the second beam, and to issue an early warning signal that the temperature of the cable core (100) is abnormal when the ratio suddenly deviates from a preset value range.

8. The self-illuminating low-voltage cable according to any one of claims 1 to 4, characterized in that, The transparent protective layer (300) is a nylon layer or a polycarbonate layer, and the polymer substrate is thermoplastic polyurethane.

9. The self-illuminating low-voltage cable according to any one of claims 1 to 4, characterized in that, The light-emitting functional layer (200) is further provided with a plurality of light guides (210), which are uniformly arranged around the circumference of the light-emitting functional layer (200). The light guides (210) are transparent nylon filaments.

10. A method for monitoring the temperature of a self-illuminating low-voltage cable, characterized in that, The temperature monitoring method for monitoring the temperature of a self-illuminating low-voltage cable as described in any one of claims 1 to 9 includes: The characteristic spectra of the first and second beams of light passing through the transparent protective layer (300) of the light-emitting functional layer (200) are detected by the detection device (400); The temperature of the cable core (100) is determined based on the difference in characteristic spectra between the first beam and the second beam.

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