Safety warning cable with temperature sensing and production process thereof

Abstract

This invention relates to the field of cable technology and discloses a safety early warning cable with temperature sensing and its manufacturing process. The cable utilizes a core temperature sensing channel formed by a spiral metal sheath and a temperature-sensing optical fiber within the conductor, combined with a multi-core sensing optical cable to create a redundant temperature sensing system. Dual-path vibration sensing and AI signal recognition enable precise differentiation of vibration sources. Furthermore, a multi-layer composite isolation layer and a three-dimensional heat-conducting network are designed to achieve efficient heat dissipation. The manufacturing process employs a precisely temperature-controlled co-extrusion process, online thermal stress relaxation treatment, and optical fiber pre-fixation to improve cable insulation performance and sensing element stability. This invention significantly improves temperature sensing reliability and vibration identification accuracy, optimizes cable thermal management capabilities, extends service life, and the manufacturing process effectively reduces insulation eccentricity and pre-crosslinking defects, thus improving overall product quality.

Description

Technical Field

[0001] This invention relates to the field of cable technology, and in particular to a safety early warning cable with temperature sensing and its manufacturing process. Background Technology

[0002] As the core carrier of power transmission, the real-time monitoring and safety early warning of the operating status of power cables are crucial to the stability of the power system. Currently, the industry mainly uses the method of laying sensing optical fibers after the conventional cable is laid. That is, after the conventional cable is laid, the temperature sensing optical fiber and the vibration optical fiber are bundled on the cable surface and then connected to the monitoring host. This method has many drawbacks: the optical fiber can only detect the surface temperature of the cable and cannot reflect the core temperature of the conductor; the long heat conduction path leads to a response lag; the bonding between the optical fiber and the cable surface is not tight, making it susceptible to interference from the external environment, resulting in a high false alarm rate for temperature and vibration measurements; and vibration monitoring can only sense external vibrations and cannot identify micro-vibrations caused by internal cable faults.

[0003] To address the aforementioned issues, existing technologies integrate temperature-sensing optical fibers into the conductor and place vibration optical fibers within the protective layer, which improves monitoring accuracy to some extent. However, shortcomings remain: temperature measurement follows a single path without cross-verification mechanisms, and poor or damaged fiber contact can lead to measurement failure; vibration sensing cannot distinguish between internal and external vibration sources, easily resulting in false alarms or missed alarms; the isolation layer only provides electromagnetic shielding, and the filling layer only serves a supporting function without participating in thermal management, making it easy for conductor heat to accumulate locally and form hot spots, affecting cable current carrying capacity and service life.

[0004] Meanwhile, existing cable production processes present numerous challenges in quality control: during the insulation extrusion process, improper temperature control can easily lead to the formation of pre-crosslinked products, resulting in coke particles and impurities; the co-extrusion process can easily cause excessive insulation eccentricity, leading to electric field distortion; optical fibers are prone to misalignment and wear during processing, affecting sensing performance; and the thermal stress within the insulation layer after cable forming cannot be effectively eliminated, easily causing micro-cracks and reducing insulation strength.

[0005] In addition, existing monitoring systems can only perform simple time and intensity comparisons of vibration signals, and cannot accurately distinguish between environmental interference, external intrusion and internal faults, resulting in low early warning accuracy. Most graphene composite thermal conductive materials for cables are single materials, and it is difficult to balance thermal conductivity and flexibility, so they cannot simultaneously meet the requirements for thermal conduction and buffering. Summary of the Invention

[0006] The technical problems to be solved by this invention are: the current cable temperature measurement response is lagging, the vibration monitoring false alarm rate is high, thermal management is lacking, and there are defects in the production process quality.

[0007] The technical solution adopted by the present invention to solve its technical problem is: a safety early warning cable with temperature sensing, including a wrapping layer, multiple power wire insulated cores are arranged inside the wrapping layer, a protective layer is arranged outside the wrapping layer, a first vibration sensing element is arranged inside the protective layer, and an isolation layer is arranged between the wrapping layer and the protective layer.

[0008] Each power line insulated core includes a conductor and an insulation layer covering the conductor. Each conductor has a spiral metal sheath inside, and a temperature-sensing optical fiber is inserted inside the spiral metal sheath. The space between the inner wall of the spiral metal sheath and the temperature-sensing optical fiber is filled with high thermal conductivity nano-silicone grease to improve heat conduction efficiency. The outer wall of the spiral metal sheath has spiral microgrooves, and multiple strands of conductor copper wire are embedded in the spiral microgrooves to enhance the mechanical engagement and thermal contact area between the spiral metal sheath and the conductor.

[0009] A hollowed-out support is provided between the multiple insulated cores of the power lines. A filling layer is provided in the gap between the support and the multiple insulated cores of the power lines. The filling layer is filled with graphene composite thermal conductive material, which has both high thermal conductivity and flexibility. A copper-aluminum composite thermal conductive metal strip is provided on the surface of the insulation layer of each conductor. The copper-aluminum composite thermal conductive metal strip is in contact with the graphene composite thermal conductive material in the filling layer to form a radial thermal conduction path.

[0010] A multi-core sensing optical cable is located at the center of the filling layer. The multi-core sensing optical cable includes at least three multimode fiber cores and at least one single-mode fiber core based on Φ-OTDR technology. The multimode fiber cores are fused to the temperature-sensing fibers of each conductor at the cable end to form redundant temperature-sensing channels. The single-mode fiber core is used to sense internal vibrations. The outer surface of the multi-core sensing optical cable is tightly bonded to the graphene composite thermal conductive material in the filling layer through the holes of the bracket to realize the transfer of heat to the multi-core sensing optical cable.

[0011] The isolation layer comprises an inner shielding layer, a middle thermally conductive layer, and an outer buffer layer arranged sequentially from the inside out. The inner shielding layer is a semiconductor metal composite layer that effectively shields electromagnetic interference. The middle thermally conductive layer is a ring-shaped continuous structure composed of graphene film, which can uniformly diffuse heat along the circumference. The outer buffer layer is an EPDM elastomer material that absorbs mechanical stress. Multiple thermally conductive windows are spaced along the axial direction on the wrapping layer, so that the graphene composite thermally conductive material in the filling layer contacts the middle thermally conductive layer of the isolation layer to form a thermally conductive path, thereby realizing the outward diffusion of heat.

[0012] The first vibration sensing element and the single-mode fiber core signal in the multi-core sensing optical cable are connected to the same integrated AI algorithm early warning system. The early warning system uses the AI ​​algorithm to perform time-frequency analysis and pattern recognition on the two vibration signals, establishes a vibration feature library, and accurately distinguishes between internal fault vibration, external intrusion vibration and environmental interference vibration, with an effective early warning accuracy rate of ≥98%.

[0013] This invention also discloses the manufacturing process of the above-mentioned safety warning cable with temperature sensing, including the following steps:

[0014] S1. Pre-assembly of conductor and temperature measuring fiber: The conductor copper wire is embedded in the spiral microgroove of the spiral metal sheath. After filling the spiral metal sheath with high thermal conductivity nano silicone grease, the temperature measuring fiber is threaded through. The temperature measuring fiber is fixed in the center by the fiber positioning clamp of elastic silicone to prevent the fiber from shifting or wearing out, thus forming the temperature measuring conductor core.

[0015] S2. Power line insulated core extrusion: The temperature measuring conductor core is extruded through a three-layer co-extrusion machine to form an insulation layer and a copper-aluminum composite thermally conductive metal strip. The processing temperature of the insulation material and the shielding material is controlled. A combined extrusion die is used to ensure that the insulation eccentricity is ≤1%. At the same time, a three-stage filter structure is used to prevent the accumulation of pre-crosslinked products.

[0016] S3. Integration of the filling layer and multi-core sensing optical cable: Multiple insulated cores of power lines are placed in a hollow bracket, and graphene composite thermal conductive material is filled in the gaps of the bracket. At the same time, the multi-core sensing optical cable is fixed in the center of the bracket to ensure that the multi-core sensing optical cable and the copper-aluminum composite thermal conductive metal strip form a reliable thermal conductive path.

[0017] S4. Forming of the wrapping layer and the isolation layer: A wrapping layer is wrapped around the outside of the filler layer and a heat conduction window is opened. Then, the inner shielding layer, the middle heat conduction layer and the outer buffer layer are formed in one step through a co-extrusion process. The temperature uniformity of the co-extrusion die head is strictly controlled to ensure the interlayer bonding force.

[0018] S5. Assembly of protective layer and vibration sensing element: The protective layer is extruded on the outside of the isolation layer, and the first vibration sensing element is pre-embedded in the protective layer to ensure that the first vibration sensing element is connected to the single-mode fiber core signal of the multi-core sensing optical cable.

[0019] S6. Online thermal stress relaxation and testing: The formed cable undergoes online thermal stress relaxation treatment. It is heated to above the crystallization temperature of cross-linked polyethylene and then slowly cooled to effectively eliminate thermal stress in the insulation layer. Subsequently, temperature measurement, vibration signal detection and insulation performance testing are carried out to ensure product quality.

[0020] The beneficial effects of this invention are:

[0021] (1) This invention achieves direct and rapid monitoring of the core temperature of the conductor by setting a spiral metal sheath and a temperature measuring optical fiber inside the conductor, and using high thermal conductivity nano-silicone grease. At the same time, redundant temperature measuring channels are formed by copper-aluminum composite thermal conductive metal strip, graphene composite thermal conductive material and multimode optical fiber core of multi-core sensing optical cable. The two temperature measuring signals can be cross-verified, effectively avoiding false alarms or failures caused by single-point faults. The temperature measurement response time is ≤0.5s, and the reliability is significantly improved.

[0022] (2) The present invention uses a single-mode fiber core based on Φ-OTDR technology to sense internal vibration, and a first vibration sensing element in the protective layer to sense external vibration. Combined with an early warning system integrating AI algorithm, a vibration feature library is established through time-frequency analysis and pattern recognition to accurately distinguish between internal faults, external intrusions and environmental interference. The effective early warning accuracy rate is ≥98%, which greatly reduces the false alarm rate.

[0023] (3) The present invention designs a graphene composite thermal conductive material filling layer and a graphene film composite intermediate thermal conductive layer to form a three-dimensional thermal conductive network from the conductor to the central multi-core sensing optical cable and then to the outer isolation layer. At the same time, the intermediate thermal conductive layer is a ring-shaped continuous structure, which can diffuse heat evenly along the circumference, avoid local hot spot accumulation, effectively increase the cable current carrying capacity by ≥15%, and extend the service life.

[0024] (4) The production process of the present invention achieves precise centering and fixing of the temperature measuring fiber through the fiber positioning fixture, preventing offset or wear during processing and ensuring sensing performance; through the precise temperature-controlled co-extrusion process and combined extrusion mold, the insulation eccentricity of the insulation layer is controlled to ≤1%, avoiding electric field distortion; through three-stage filtration and regular replacement of the filter screen, the accumulation of pre-crosslinked products of the insulation material is prevented, and coke particles and impurity defects are eliminated; through online thermal stress relaxation treatment, the thermal stress of the insulation layer is effectively eliminated, the generation of micro-cracks is avoided, and the insulation strength is improved.

[0025] (5) The isolation layer of the present invention is formed in one step by a three-layer co-extrusion process. The micro-protrusion structure of the middle heat-conducting layer enhances the interlayer bonding force, the inner shielding layer realizes electromagnetic shielding, the middle heat-conducting layer realizes heat diffusion, and the outer buffer layer absorbs mechanical stress. It is a multi-functional layer, which simplifies the cable structure and improves the overall performance. Attached Figure Description

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] Figure 1 This is a schematic diagram of the cross-sectional structure of the temperature-sensing safety early warning cable of the present invention;

[0028] Figure 2 This is a schematic diagram showing the connection between the temperature-measuring optical fiber and the multi-core sensing optical fiber of the present invention and the support.

[0029] Figure 3 This is a schematic diagram of the cross-sectional structure of the insulated core of the power line of the present invention;

[0030] Figure 4 This is a schematic diagram of the cross-sectional structure of the isolation layer of the present invention;

[0031] Figure 5 This is a schematic diagram of the cross-sectional structure of the multi-core sensing optical cable of the present invention;

[0032] Figure 6 This is a process flow diagram of the present invention.

[0033] In the diagram: 1. Wrapping layer, 2. Power line insulated core, 3. Protective layer, 4. First vibration sensing element, 5. Isolation layer, 6. Conductor, 7. Insulation layer, 8. Spiral metal sheath, 9. Temperature measuring optical fiber, 10. Filling layer, 11. Graphene composite thermal conductive material, 12. Copper-aluminum composite thermal conductive metal strip, 13. Multi-core sensing optical cable, 14. Multimode optical fiber core, 15. Single-mode optical fiber core, 17. Inner shielding layer, 18. Intermediate thermal conductive layer, 19. Outer buffer layer, 20. Thermal conductive window, 21. High thermal conductivity nano-silicone grease, 22. Spiral microgroove, 23. Conductor copper wire, 24. Support. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0035] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0036] Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 The safety early warning cable with temperature sensing shown includes a wrapping layer 1, inside which are four insulated power wire cores 2, which are adapted to a three-phase four-wire power system. A protective layer 3 is provided outside the wrapping layer 1, and a first vibration sensing element 4 is provided inside the protective layer 3. An isolation layer 5 is provided between the wrapping layer 1 and the protective layer 3.

[0037] Each power line insulated core 2 includes a conductor 6 and a cross-linked polyethylene insulation layer 7 covering the conductor 6. Each conductor 6 is provided with a spiral metal sheath 8 made of 304 stainless steel. A single-mode temperature measuring optical fiber 9 is inserted inside the spiral metal sheath 8. The space between the inner wall of the spiral metal sheath 8 and the temperature measuring optical fiber 9 is filled with high thermal conductivity nano silicone grease 21 with a thermal conductivity of 8 W / (m·K).

[0038] In this embodiment, the spiral metal sheath 8 is made of 304 stainless steel, taking into account structural strength, corrosion resistance, and thermal conductivity. Its outer wall is machined with spiral microgrooves 22, 2mm wide and 1.5mm deep. The spiral direction of the microgrooves 22 is consistent with the twisting direction of the conductor 6. Multiple strands of φ2.5mm conductor copper wire 23 are embedded in the spiral microgrooves 22. The working principle is: through mechanical interlocking, a tight connection is achieved between the spiral metal sheath 8 and the conductor 6, preventing axial or radial displacement of the spiral metal sheath 8 within the conductor 6. To ensure the centered positioning of the temperature-sensing fiber optic cable 9 and increase the contact area between the spiral metal sheath 8 and the conductor 6, the heat generated by the conductor 6 can be quickly transferred to the body of the spiral metal sheath 8 through the conductor copper wire 23, thereby improving the heat conduction efficiency. The method is as follows: a spiral microgroove 22 is machined on the outer wall of the spiral metal sheath 8 using a precision CNC milling process, with the milling accuracy controlled within ±0.02mm. Then, the conductor copper wire 23 is embedded into the spiral microgroove 22 through a cold embedding process. After embedding, the surface is polished to ensure the roundness of the conductor 6.

[0039] The space between the inner wall of the spiral metal sheath 8 and the temperature-sensing optical fiber 9 is filled with high thermal conductivity nano-silicone grease 21 with a thermal conductivity of 8 W / (m·K). The working principle is as follows: the nano-scale filler of the nano-silicone grease can fill the tiny gaps between the spiral metal sheath 8 and the temperature-sensing optical fiber 9, eliminating the thermal resistance caused by the air gap. At the same time, the nano-silicone grease has good thermal conductivity and temperature resistance, which can transfer the core temperature of the conductor 6 transmitted by the spiral metal sheath 8 to the temperature sensing area of ​​the temperature-sensing optical fiber 9 without loss and quickly, so as to realize the direct monitoring of the core temperature. The implementation method is as follows: a vacuum negative pressure filling process is adopted. After sealing both ends of the spiral metal sheath 8, the vacuum is drawn to -0.098 MPa. Then, the high thermal conductivity nano-silicone grease 21 is injected from one end of the spiral metal sheath 8, with a filling density of ≥99%. After filling, both ends of the spiral metal sheath 8 are sealed to prevent the grease from overflowing.

[0040] A hollowed-out bracket 24 made of polypropylene is provided between the four insulated cores 2 of the power lines. The hollowing-out rate of the bracket 24 is 60%. A filling layer 10 is provided in the gap between the bracket 24 and the four insulated cores 2 of the power lines. A copper-aluminum composite thermally conductive metal strip 12 with a thickness of 0.3mm is provided on the surface of the insulation layer 7 of each conductor 6.

[0041] The copper-aluminum composite thermally conductive metal strip 12 is spirally wound along the axial direction of the insulation layer 7, with a winding pitch of 1.2 times the outer diameter of the cable. The working principle is as follows: the copper-aluminum composite strip combines the high thermal conductivity of copper (thermal conductivity coefficient 401W / (m·K)) with the light weight and flexibility of aluminum. The spiral winding method can achieve full wrapping of the surface of the insulation layer 7 without any thermal dead corners. The radially extended end is tightly attached to the graphene composite thermally conductive material 11, forming a radial thermally conductive path from the conductor 6 insulation layer 7 to the filling layer 10, which quickly transfers the heat from the surface of the conductor 6 to the filling layer 10. The method of implementation is as follows: a continuous winding machine is used for spiral winding, and the winding tension is controlled at 5~8N to ensure that the copper-aluminum composite thermally conductive metal strip 12 is tightly attached to the insulation layer 7 without wrinkles. A 5mm length is reserved at the radially extended end to facilitate contact with the graphene composite thermally conductive material 11 of the filling layer 10.

[0042] The filling layer 10 is filled with a graphene / silicone rubber composite graphene composite thermally conductive material 11 with a thermal conductivity of 6 W / (m·K). It remains flexible within the range of -40℃ to 120℃. The working principle is as follows: graphene nanosheets form a three-dimensional thermally conductive network in the silicone rubber matrix, which can achieve rapid and uniform heat transfer. At the same time, the flexibility of the silicone rubber matrix can buffer the mechanical vibration of the power line insulation core 2 during operation, avoiding wear of the power line insulation core. In addition, the material also has sound transmission properties, which can transmit the micro-vibration signal inside the conductor 6 to the single-mode optical fiber core 15 in the form of sound waves, realizing acoustic coupling. The method of implementation is as follows: graphene nanosheets and silicone rubber matrix are mixed at a mass ratio of 15:85, and after being mixed by internal refining, a thermally conductive adhesive is made. The adhesive is injected into the gap between the bracket 24 and the power line insulation core 2 using a high-pressure injection process with an injection pressure of 0.8 MPa to ensure that the adhesive fills all the tiny gaps without bubbles or voids.

[0043] A multi-core sensing optical cable 13 is located at the center of the filling layer 10. The multi-core sensing optical cable 13 includes four multimode fiber cores 14 and one single-mode fiber core 15 based on Φ-OTDR technology. The multimode fiber cores 14 are connected to the temperature measuring optical fibers 9 of each conductor 6 at the cable end by fusion splicing to form redundant temperature measuring channels. The single-mode fiber core 15 is used to sense internal vibration. The outer surface of the multi-core sensing optical cable 13 is tightly bonded to the graphene composite thermal conductive material 11 in the filling layer 10 through the holes of the bracket 24. The graphene composite thermal conductive material 11 is in direct contact with the outer sheath of the multi-core sensing optical cable 13 to achieve efficient heat transfer.

[0044] The single-mode fiber core 15 inside the multi-core sensing optical cable 13 adopts Φ-OTDR (phase-sensitive optical time-domain reflectometry) technology. The working principle is as follows: Φ-OTDR technology injects continuous pulsed laser into the optical fiber and utilizes Rayleigh scattering of the laser in the optical fiber. When the optical fiber is subjected to micro-vibration, the phase of the scattered light will change. By detecting the phase change, high-sensitivity detection and accurate positioning of vibration signals can be achieved, with a positioning accuracy of ±1m. It can capture high-frequency micro-vibrations (frequency 50~500kHz) generated by partial discharge and insulation aging inside the conductor 6. The implementation method is as follows: the single-mode fiber core 15 adopts low-loss single-mode fiber (loss ≤0.2dB / km@1550nm) and is co-molded with the multi-mode fiber core 14 to form the multi-core sensing optical cable 13. The outer sheath of the multi-core sensing optical cable adopts low-modulus polyolefin material to improve the adhesion with the graphene composite thermal conductive material 11.

[0045] The multi-core sensing optical cable 13 is fixed at the center of the bracket 24, with a radial distance of ≤2mm between it and the copper-aluminum composite heat-conducting metal strip 12. The working principle is to shorten the heat conduction path and reduce heat loss during the transfer process, so that the heat transferred by the copper-aluminum composite heat-conducting metal strip 12 can quickly reach the multimode fiber core 14 of the multi-core sensing optical cable 13, ensuring the response speed and temperature measurement accuracy of the redundant temperature measurement channel. The implementation method is to set a positioning slot matching the multi-core sensing optical cable 13 at the center of the bracket 24. The distance between the slot and the positioning hole of each power line insulation core is precisely controlled to ≤2mm. The bracket 24 is integrally molded by injection molding process with a dimensional accuracy of ±0.05mm.

[0046] The isolation layer 5 comprises an inner shielding layer 17, an intermediate thermally conductive layer 18, and an outer buffer layer 19 arranged sequentially from the inside out. The inner shielding layer 17 is a semiconductor carbon black / aluminum foil composite layer with a thickness of 0.2 mm. The intermediate thermally conductive layer 18 is a continuous annular structure of graphene film / thermal conductive rubber composite with a thickness of 0.5 mm. The outer buffer layer 19 is an EPDM elastomer material with a thickness of 0.8 mm. The surface of the intermediate thermally conductive layer 18 has an array of micro-protrusion structures with a height of 0.3 mm, which are embedded in the outer buffer layer 19. The inner shielding layer 17, the intermediate thermally conductive layer 18, and the outer buffer layer 19 are formed in one step by a three-layer co-extrusion process, with an interlayer bonding force of 1.8 N / mm. A thermally conductive window 20 with a diameter of 5 mm is provided on the wrapping layer 1 at 30 cm intervals along the axial direction, so that the graphene composite thermally conductive material 11 in the filling layer 10 contacts the intermediate thermally conductive layer 18 of the isolation layer 5 to form a thermally conductive path, realizing the transfer of heat to the isolation layer 5 and uniform circumferential diffusion. The working principle is as follows: the heat-conducting window 20 allows the graphene composite heat-conducting material 11 of the filling layer 10 to directly contact the intermediate heat-conducting layer 18, forming a heat-conducting path from the filling layer 10 to the isolation layer 5, which conducts the heat inside the cable to the outside. At the same time, the uniformly distributed heat-conducting window 20 ensures that the heat is evenly diffused along the cable axis, avoiding local heat accumulation. The implementation method is as follows: the heat-conducting window 20 is opened on the wrapping layer 1 using laser drilling technology, with a hole diameter deviation of ≤0.1mm and a hole spacing deviation of ≤5mm. When wrapping, the heat-conducting window 20 is evenly distributed along the circumference of the cable, with 4 heat-conducting windows 20 opened in each circle, distributed at 90°.

[0047] The isolation layer 5 consists of an inner shielding layer 17 (0.2mm thick semiconductor carbon black / aluminum foil composite layer), an intermediate thermally conductive layer 18 (0.5mm thick graphene film / thermal conductive rubber composite layer), and an outer buffer layer 19 (0.8mm thick EPDM elastomer). Its working principle is as follows: the semiconductor carbon black layer of the inner shielding layer 17 eliminates electric field distortion inside the cable; the aluminum foil layer provides electromagnetic shielding, preventing electromagnetic interference with sensing signals; the graphene film of the intermediate thermally conductive layer 18 forms a continuous annular thermally conductive surface, uniformly diffusing the heat transferred from the filling layer 10 along the circumference, avoiding localized heat. Point; the outer buffer layer 19 absorbs the external mechanical stress on the protective layer 3, protecting the internal power line insulation core; the array-type micro-protrusion structure increases the contact area between the middle heat-conducting layer 18 and the outer buffer layer 19, improves the interlayer bonding force, and prevents interlayer peeling; the implementation method is: a three-layer co-extrusion process is used for one-time molding. When the middle heat-conducting layer 18 is extruded, an array-type micro-protrusion is formed through the micro-protrusion texture on the mold surface. After extrusion, it is immediately co-extruded with the outer buffer layer 19, so that the micro-protrusion is embedded in the uncured EPDM elastomer. The interlayer bonding force of the three-layer co-extrusion is ≥1.8N / mm.

[0048] The first vibration sensing element 4 is a distributed vibration optical fiber, which is connected to the same integrated AI algorithm early warning system as the single-mode optical fiber core 15 in the multi-core sensing optical cable 13. The early warning system has a built-in vibration feature library of mechanical excavation, manual touch, partial discharge, wind and rain interference, etc. Through AI algorithm, it performs time and frequency analysis and pattern recognition on the two vibration signals, accurately distinguishes the vibration source type, and achieves an effective early warning accuracy rate of 99%. The working principle is as follows: The early warning system first collects two vibration signals. The single-mode fiber core 15 collects the micro-vibration signal inside the cable, and the first vibration sensing element 4 collects the vibration signal outside the cable. Then, the AI ​​algorithm performs time-frequency analysis on the two signals, extracting features such as frequency, amplitude, and duration. It then performs pattern matching with the system's built-in vibration feature library (which includes six typical vibration features such as mechanical excavation, manual contact, partial discharge, insulation aging, wind and rain interference, and vehicle vibration). By comparing the timing, intensity, and feature matching degree of the two signals, the vibration source type is accurately distinguished. The implementation method is as follows: The early warning system adopts an FPGA+ARM hardware architecture. The FPGA realizes high-speed signal acquisition and preprocessing with an acquisition rate of 1GS / s. The ARM realizes the operation of the AI ​​algorithm and pattern recognition. The vibration feature library is trained with a large amount of vibration data from actual working conditions and uses a convolutional neural network (CNN) for feature recognition, achieving an effective early warning accuracy of 99%.

[0049] The first vibration sensing element 4 is connected to the single-mode fiber core 15 via a fiber optic coupler. The signal loss is ≤0.2dB / km. The working principle is to reduce the attenuation of the signal during transmission, ensuring that weak vibration signals (especially internal micro-vibration signals) can be transmitted completely to the early warning system, and avoiding identification errors caused by signal attenuation. The implementation method is to use a low-loss fiber optic coupler (loss ≤0.1dB), and the fiber optic connection is fused. The fusion splicing loss is ≤0.02dB / point. All fiber optic connection points are sealed to prevent dust and moisture from entering and increasing the loss.

[0050] This embodiment also provides the manufacturing process of the above-mentioned safety early warning cable with temperature sensing, including the following steps:

[0051] S1. Pre-assembly of conductor and temperature-sensing optical fiber 9: The conductor copper wire 23 is embedded in the spiral microgroove 22 of the spiral metal sheath 8. High thermal conductivity nano silicone grease 21 is filled into the spiral metal sheath 8 by vacuum filling, with a filling density of ≥99%. Then, the temperature-sensing optical fiber 9 is threaded through. The temperature-sensing optical fiber 9 is fixed in the center by an optical fiber positioning clamp made of elastic silicone material. The inner wall of the clamp is provided with a spiral groove that matches the spiral metal sheath 8. The positioning deviation of the temperature-sensing optical fiber 9 is controlled within 0.08mm to prevent the temperature-sensing optical fiber 9 from shifting or wearing during subsequent processing, forming a temperature-sensing conductor core.

[0052] In step S1, an elastic silicone fiber positioning clamp is used to center and fix the temperature-sensing fiber 9. The inner wall of the clamp has a spiral groove that matches the spiral metal sheath 8. The positioning deviation of the temperature-sensing fiber 9 is ≤0.08mm. The working principle is as follows: the flexibility of the elastic silicone clamp can conform to the surfaces of the temperature-sensing fiber 9 and the spiral metal sheath 8, avoiding wear of the temperature-sensing fiber 9 caused by hard contact. The spiral groove matches the spiral structure of the spiral metal sheath 8, realizing the circumferential positioning of the clamp on the spiral metal sheath 8, preventing the clamp from shifting axially, thereby ensuring the stability of the temperature-sensing fiber. 9. At the center of the spiral metal sheath 8, temperature measurement deviation caused by the temperature measuring fiber 9 adhering to the wall is avoided. The method is as follows: the clamp size is designed according to the inner diameter of the spiral metal sheath 8 and the outer diameter of the temperature measuring fiber 9. The spiral groove direction and pitch of the clamp inner wall are completely consistent with the spiral metal sheath 8. It is formed by silicone molding process. After the temperature measuring fiber 9 is inserted into the clamp, it is embedded into the spiral metal sheath 8 together. After filling with high thermal conductivity nano silicone grease 21, the clamp is removed, or the clamp is left directly inside the spiral metal sheath 8 (the silicone material does not affect the thermal conductivity).

[0053] S2. Power line insulated core extrusion: The temperature measuring conductor core is extruded through a three-layer co-extrusion machine to form a cross-linked polyethylene insulation layer 7 and a copper-aluminum composite thermally conductive metal strip 12. The processing temperature of the insulation material is controlled at 118℃, and the processing temperature of the shielding material is controlled at 114℃. The extrusion die adopts a combined extrusion die with a die concentricity error of ≤0.05mm to ensure that the insulation eccentricity is 0.8%. The filter screen of the three-layer co-extrusion machine adopts a three-stage filtration structure with mesh sizes of 80 mesh, 120 mesh, and 200 mesh respectively. The filter screen is replaced every 5 days of continuous production to prevent the accumulation of pre-cross-linked insulation products, forming coke particles and impurities.

[0054] In step S2, the filter screen of the three-layer co-extrusion machine adopts a three-stage filtration structure of 80 mesh → 120 mesh → 200 mesh. The filter screen is replaced every 5 days of continuous production. The working principle is as follows: the 80 mesh filter screen filters large particulate impurities (particle size ≥ 200 μm) in the insulation material, the 120 mesh filter screen filters medium particulate impurities (particle size ≥ 100 μm), and the 200 mesh filter screen filters tiny particulate impurities (particle size ≥ 50 μm). The three-stage filtration can effectively remove impurities and pre-crosslinked products in the insulation material, and prevent impurities from forming breakdown points inside the insulation layer 7. Regularly replacing the filter screen can prevent uneven material flow caused by filter screen blockage and ensure the molding quality of the insulation layer 7. The implementation method is as follows: a three-stage filtration device is set at the barrel outlet of the three-layer co-extrusion machine. The filter screen is made of stainless steel, and the mesh number increases sequentially. The filtration device adopts a quick-release structure to facilitate the replacement of the filter screen. After replacement, the barrel is cleaned to prevent residual impurities.

[0055] In step S2, the processing temperature of the insulation material is controlled at 118℃ and the processing temperature of the shielding material is controlled at 114℃. A combined extrusion die is used, and the insulation eccentricity is controlled within 0.8%. The working principle is as follows: The processing temperature of cross-linked polyethylene insulation material needs to be precisely controlled. If the temperature is too low, the material flow will be obstructed, and the insulation layer 7 will not be densely formed. If the temperature is too high, the insulation material will be pre-crosslinked, affecting the degree of crosslinking. The combined extrusion die can realize the synchronous extrusion of the insulation material and the shielding material, ensuring the concentricity of the shielding layer and the insulation layer, thereby controlling the insulation eccentricity, avoiding electric field distortion caused by insulation eccentricity, and preventing local insulation breakdown of the cable. The implementation method is as follows: The three-layer co-extruder adopts zoned temperature control. The barrel is divided into a feeding zone, a plasticizing zone, and a homogenizing zone. The temperature of each zone is precisely controlled with an error of ±1℃. The combined extrusion die adopts a concentricity adjustable structure. By adjusting the position of the die mandrel, the insulation eccentricity is controlled within ≤1%.

[0056] S3. Integration of the filling layer and multi-core sensing optical cable: Four insulated cores 2 of the power line are placed in the hollow bracket 24. Graphene composite thermal conductive material 11 is filled into the gaps of the bracket 24 by high-pressure injection at a pressure of 0.8 MPa to ensure dense filling. At the same time, the multi-core sensing optical cable 13 is fixed to the center of the bracket 24 by a buckle to ensure that the radial distance between the multi-core sensing optical cable 13 and the copper-aluminum composite thermal conductive metal strip 12 is ≤2 mm, forming a reliable heat conduction path.

[0057] S4. Forming of the wrapping layer and the isolation layer: The polyimide wrapping layer 1 is wrapped around the outside of the filler layer 10 using an overlapping wrapping method, with a wrapping overlap rate of 50%. Thermally conductive windows 20 are opened on the wrapping layer 1 by laser perforation, with a hole diameter deviation of ≤0.1mm. Subsequently, the inner shielding layer 17, the middle thermally conductive layer 18 and the outer buffer layer 19 are formed in one step through a co-extrusion process. The co-extrusion die head temperature is controlled at 125℃, and the temperature uniformity error is ±1.5℃ to ensure the interlayer bonding force.

[0058] S5. Assembly of protective layer and vibration sensing element: Extruding polyvinyl chloride protective layer 3 on the outside of isolation layer 5 at an extrusion temperature of 160℃, and fixing the first vibration sensing element 4 of distributed vibration optical fiber in the protective layer 3 with a pre-embedded clamp at a depth of 1 / 2 of the thickness of the protective layer 3, ensuring that the first vibration sensing element 4 of distributed vibration optical fiber and the single-mode optical fiber core 15 of multi-core sensing optical cable 13 are connected by an optical fiber coupler, with a signal loss ≤0.2dB / km;

[0059] In step S5, the first vibration sensing element 4 is pre-embedded in the protective layer 3 at a depth of 1 / 2 of the thickness of the protective layer 3. The working principle is as follows: if the pre-embedding depth is too shallow, the first vibration sensing element 4 is easily damaged by external mechanical forces and is susceptible to interference from ambient temperature, direct sunlight, etc.; if the pre-embedding depth is too deep, the external vibration signal must pass through a thicker protective layer 3 to reach the sensing element, resulting in signal attenuation and reduced sensitivity; pre-embedding at 1 / 2 of the thickness of the protective layer 3 can balance signal sensitivity and element protection. The implementation method is as follows: a sensing element positioning groove is set in the extrusion mold of the protective layer, and the depth of the positioning groove is 1 / 2 of the designed thickness of the protective layer 3. After the first vibration sensing element 4 is inserted into the positioning groove, it is extruded synchronously with the protective layer 3. After extrusion, it is pulled at a constant speed by a traction machine to ensure the straightness of the sensing element.

[0060] S6. Online thermal stress relaxation and testing: The formed cable undergoes online thermal stress relaxation treatment. The cable is heated to 135℃ through a hot drying tunnel and held at that temperature for 6 minutes. Then, it is slowly cooled by water at a cooling rate of 2.5℃ / min to effectively eliminate radial thermal stress in the insulation layer 7. After cooling, the cable is tested for the temperature signal response speed of the temperature measuring fiber 9, the vibration signal recognition accuracy of the single-mode fiber core 15 and the first vibration sensing element 4, and the insulation withstand voltage performance of the insulation layer 7. The temperature response time is ≤0.5s and the insulation withstand voltage value is ≥35kV / mm. After passing the test, the cable is wound and packaged.

[0061] In step S6, the formed cable undergoes online thermal stress relaxation treatment, heated to 135℃, held for 6 minutes, and cooled at a rate of 2.5℃ / min. The working principle is as follows: During the extrusion molding process, the polymer material of the insulation layer 7 will generate orientation and internal stress. The internal stress will cause micro-cracks in the insulation layer 7 during long-term operation, affecting the insulation performance. Heating the cable to above the crystallization temperature of cross-linked polyethylene (130~140℃) enhances the mobility of the polymer chain segments, releasing the internal stress. Slow cooling allows the polymer chain segments to realign evenly, eliminating the internal stress. The implementation method is as follows: a hot drying tunnel and a cooling water tank are set up on the cable production line. The hot drying tunnel uses hot air heating, with the temperature controlled at 135℃±2℃. The length of the heat preservation section is designed to be 30m according to the cable production speed (5m / min). The cooling water tank uses staged water cooling, with the water temperature gradually decreasing from 80℃ to 25℃ to achieve slow cooling at a rate of 2.5℃ / min.

[0062] In step S6, temperature measurement, vibration measurement, and insulation performance detection are performed on the cooled cable. The working principle is as follows: By quantifying the detection, the sensing performance and insulation performance of the cable are verified to ensure that the product meets the design requirements. The temperature measurement response time ≤ 0.5 s ensures the rapidity of temperature measurement, and the insulation withstand voltage value ≥ 35 kV / mm ensures the insulation reliability of the cable. The implementation method is as follows: The DTS distributed temperature measurement system is used to detect the temperature measurement response time. A laser signal is injected into the temperature measurement optical fiber 9 and the multi-mode optical fiber core 14. The conductor 6 is heated by a heating source, and the time when the temperature change is detected by the temperature measurement optical fiber 9 is recorded. The DAS distributed vibration measurement system is used to detect the recognition accuracy of vibration measurement signals. Different types of vibration signals are simulated to verify the recognition accuracy of the early warning system. The power frequency withstand voltage tester is used to detect the insulation withstand voltage performance. A 50 kV power frequency voltage is applied at both ends of the cable for 1 minute. No breakdown or flashover is qualified.

[0063] In this embodiment, the first vibration sensing element 4 is a distributed vibration optical fiber. The protective layer 3 is made of polyvinyl chloride, the insulation layer 7 is made of cross-linked polyethylene, and the support 24 is made of polypropylene with a hollowing rate of 60%, which not only ensures the support strength but also provides space for the filling of the graphene composite heat-conducting material 11.

[0064] Enlightened by the ideal embodiment of the present invention described above, through the above description, relevant staff can make various changes and modifications completely within the scope not deviating from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A safety early warning cable with temperature sensing, comprising a wrapping layer (1), characterized in that, The wrapping layer (1) contains multiple insulated cores (2) of power lines, and a protective layer (3) is provided outside the wrapping layer (1). A first vibration sensing element (4) is provided inside the protective layer (3), and an isolation layer (5) is provided between the wrapping layer (1) and the protective layer (3). The insulated core (2) of the power lines includes a conductor (6) and an insulation layer (7) covering it. A spiral metal tube (8) with spiral microgrooves (22) is inserted inside the conductor (6). A temperature-sensing optical fiber (9) is inserted inside the spiral metal tube (8), and a high thermal conductivity nano-silicone grease (21) is filled between the inner wall of the spiral metal tube (8) and the temperature-sensing optical fiber (9). A conductor copper wire (23) is embedded in the spiral microgrooves (22). A perforated pattern is provided between the multiple insulated cores (2). A hollow support (24) is provided. A filling layer (10) filled with graphene composite thermal conductive material (11) is provided in the gap between the support (24) and the power line insulation core (2). A copper-aluminum composite thermal conductive metal strip (12) in contact with the graphene composite thermal conductive material (11) is provided on the surface of the insulation layer (7). A multi-core sensing optical cable (13) is provided in the center of the filling layer (10). The multi-core sensing optical cable (13) contains at least three multimode fiber cores (14) and at least one single-mode fiber core (15) based on Φ-OTDR technology. The multimode fiber cores (14) are fused to the ends of the temperature measuring optical fiber (9) one by one. The outer surface of the multi-core sensing optical cable (13) is tightly attached to the graphene composite thermal conductive material (11) through the holes of the support (24).

2. The safety early warning cable with temperature sensing according to claim 1, characterized in that, The isolation layer (5) includes an inner shielding layer (17), an intermediate heat-conducting layer (18), and an outer buffer layer (19) arranged sequentially from the inside to the outside. The inner shielding layer (17) is a semiconductor metal composite layer, the intermediate heat-conducting layer (18) is a continuous ring structure of graphene film composite, and the outer buffer layer (19) is an EPDM elastomer material. The wrapping layer (1) is provided with multiple heat-conducting windows (20) spaced along the axial direction, so that the graphene composite heat-conducting material (11) in the filling layer (10) contacts the intermediate heat-conducting layer (18) of the isolation layer (5) to form a heat-conducting path. The first vibration sensing element (4) and the single-mode fiber core (15) in the multi-core sensing optical cable (13) are connected to the early warning system of the same integrated AI algorithm.

3. The safety early warning cable with temperature sensing according to claim 1, characterized in that, The single-mode optical fiber core (15) in the multi-core sensing optical cable (13) forms an acoustic coupling path with the surface of the insulation layer (7) of each conductor (6) through the graphene composite thermal conductive material (11) of the filling layer (10). The graphene composite thermal conductive material (11) has both sound transmission and heat conduction functions, and its thermal conductivity is ≥5W / (m·K). It also maintains flexibility in the range of -40℃ to 120℃.

4. The safety early warning cable with temperature sensing according to claim 2, characterized in that, The surface of the intermediate heat-conducting layer (18) is provided with an array of micro-protrusion structures. The micro-protrusion structures are embedded in the outer buffer layer (19). The inner shielding layer (17), the intermediate heat-conducting layer (18) and the outer buffer layer (19) are formed in one step by a three-layer co-extrusion process, and the interlayer bonding force is ≥1.5N / mm.

5. The safety early warning cable with temperature sensing according to claim 2, characterized in that, The early warning system uses AI algorithms to perform time-frequency analysis and pattern recognition on the signals of the first vibration sensing element (4) and the single-mode fiber core (15), establishes a vibration feature library, and achieves accurate differentiation between internal fault vibration, external intrusion vibration and environmental interference vibration, with an effective early warning accuracy rate of ≥98%.

6. The safety early warning cable with temperature sensing according to claim 1, characterized in that, The copper-aluminum composite thermal conductive metal strip (12) is a copper-aluminum composite strip that is spirally wound along the axial direction of the insulation layer (7). The winding pitch is 1 to 1.5 times the outer diameter of the cable. The radially extended end of the copper-aluminum composite thermal conductive metal strip (12) is tightly bonded to the graphene composite thermal conductive material (11) of the filling layer (10) to form a radial thermal conductive path.

7. A manufacturing process for a safety early warning cable with temperature sensing as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Pre-assembly of conductor and temperature measuring fiber (9): The conductor copper wire (23) is embedded in the spiral microgroove (22) of the spiral metal sheath (8). After filling the spiral metal sheath (8) with high thermal conductivity nano silicone grease (21), the temperature measuring fiber (9) is inserted. The temperature measuring fiber (9) is fixed in the center by the fiber positioning clamp to form the temperature measuring conductor core. S2, Extrusion of power line insulated core: The temperature measuring conductor core is extruded through a three-layer co-extrusion machine to form an insulation layer (7) and a copper-aluminum composite thermally conductive metal strip (12). The processing temperature of the insulation material is controlled at 115~120℃, and the processing temperature of the shielding material is controlled at 112~116℃. The extrusion die adopts a combined extrusion die to ensure that the insulation eccentricity is ≤1%. S3. Integration of the filling layer and the multi-core sensing optical cable: Multiple power line insulated cores (2) are placed inside the hollow bracket (24), and graphene composite thermal conductive material (11) is filled in the gaps of the bracket (24). At the same time, the multi-core sensing optical cable (13) is fixed in the center of the bracket (24) to ensure that the multi-core sensing optical cable (13) and the copper-aluminum composite thermal conductive metal strip (12) form a thermal conductive path. S4. Forming of wrapping layer and isolation layer: Wrap wrapping layer (1) around the outside of filler layer (10) and open heat conduction window (20). Then, form inner shielding layer (17), middle heat conduction layer (18) and outer buffer layer (19) in one step through co-extrusion process. The temperature uniformity error of co-extrusion die head is ≤ ±2℃. S5. Assembly of protective layer and vibration sensing element: Extrude protective layer (3) on the outside of isolation layer (5), and embed the first vibration sensing element (4) in the protective layer (3) to ensure signal communication between the first vibration sensing element (4) and the single-mode fiber core (15) of multi-core sensing optical cable (13). S6. Online thermal stress relaxation and testing: The formed cable is subjected to online thermal stress relaxation treatment. The cable is heated to above the crystallization temperature of cross-linked polyethylene and then slowly cooled. Subsequently, temperature measurement, vibration signal detection and insulation performance testing are performed.

8. The production process according to claim 7, characterized in that, The fiber positioning fixture mentioned in step S1 is an elastic silicone fixture. The inner wall of the fixture is provided with a spiral groove that matches the spiral metal tube (8), which can prevent the temperature measuring fiber (9) from shifting or wearing during subsequent processing. The positioning deviation of the temperature measuring fiber (9) is ≤0.1mm.

9. The production process according to claim 7, characterized in that, The heating temperature of the online thermal stress relaxation treatment in step S6 is 130~140℃, the holding time is 5~8min, and the cooling rate is controlled at 2~3℃ / min, which effectively eliminates the radial thermal stress in the insulation layer (7) and avoids the generation of micro cracks.

10. The production process according to claim 7, characterized in that, The filter screen of the three-layer co-extrusion machine in step S2 adopts a three-stage filtration structure, with the mesh sizes being 80 mesh, 120 mesh, and 200 mesh respectively. The filter screen is replaced every 5 consecutive days of production to prevent the pre-crosslinked products of the insulating material from accumulating and forming coke particles and impurities.

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