Mining crosslinked polyethylene insulated armored self-repairing cable and manufacturing method thereof

Abstract

The invention relates to the technical field of cross-linked polyethylene cables, in particular to a mining cross-linked polyethylene insulated armored self-repairing cable and a manufacturing method thereof.The mining cross-linked polyethylene insulated armored self-repairing cable comprises a center conductor unit, a cross-linked polyethylene insulating layer, a shielding layer and an armored layer sequentially wrap the outer side of the center conductor unit from inside to outside, and an outer sheath layer is extruded on the outer side of the armored layer; the shielding layer comprises a semi-conductive shielding layer wrapping the outer side of the cross-linked polyethylene insulating layer, and the outer side of the semi-conductive shielding layer is wrapped with a copper strip shielding layer. By arranging the composite conductor structure in the central conductor unit and cooperating with the graphene heat dissipation filaments and the paraffin heat absorption and heat dissipation layer, the heat dissipation performance of the cable is improved, the temperature of the cable during operation is effectively reduced, faults caused by overheating are reduced, and the service life of the cable is prolonged; the armor layer and the copper strip shielding layer realize multipoint equipotential grounding through a sectional conductive adhesive tape, electromagnetic interference can be effectively shielded, and fault current diffusion is limited.

Description

Technical Field

[0001] The present invention relates to the technical field of cross-linked polyethylene cables, in particular to a cross-linked polyethylene insulated armored self-repairing cable for mining and a manufacturing method thereof. Background Art

[0002] In coal mining operations, the stability and safety of power supply are crucial to the normal operation of production activities. Traditional mining cables have exposed many drawbacks in actual use, which seriously restrict the efficient and safe operation of coal mining. The specific manifestations are as follows:

[0003] First, poor heat dissipation: Traditional mining cables have a relatively simple conductor structure, mostly consisting of a single metal conductor, and lack efficient heat dissipation measures. Underground in coal mines, cables are subject to long periods of high load operation, and the current passing through the conductor generates a large amount of heat.

[0004] Due to poor heat dissipation, the internal temperature of the cable continues to rise, which not only accelerates the aging of the insulation material and reduces its service life, but also easily causes safety accidents such as fire. For example, when transmitting high-power electricity for a long time, the conductor temperature of ordinary copper-core cables can reach over 80°C, far exceeding the safe operating temperature range.

[0005] Second, poor shielding and grounding: Coal mines contain a large number of electrical devices, which generate complex electromagnetic interference. Traditional cables lack a perfect shielding design, making it difficult to effectively resist this interference, affecting the stability and accuracy of power transmission.

[0006] At the same time, the grounding method is unreasonable and multi-point equipotential grounding cannot be achieved. When a local fault occurs in the cable, the fault current is likely to spread, causing a larger-scale power outage and even endangering personnel safety.

[0007] In view of these problems existing in traditional mining cables, it is necessary to develop a new type of mining cable with efficient heat dissipation, self-repair function, and good shielding and grounding performance. Summary of the Invention

[0008] The present invention solves one of the above technical problems and adopts the following technical solution: a cross-linked polyethylene insulated and armored self-repairing cable for mining, comprising a central conductor unit, a cross-linked polyethylene insulation layer, a shielding layer, and an armor layer wrapped around the outside of the central conductor unit in sequence from the inside out, and an outer sheath layer extruded outside the armor layer;

[0009] The shielding layer comprises a semi-conductive shielding layer wrapped around the outside of the cross-linked polyethylene insulation layer, and a copper tape shielding layer wrapped around the outside of the semi-conductive shielding layer;

[0010] The armor layer and the copper tape shielding layer are connected via segmented conductive rubber strips to achieve multi-point equipotential grounding.

[0011] Based on any of the above technical solutions, further optimization is that: the armor layer includes steel tapes intermittently wrapped around the periphery of the copper tape shielding layer along the length direction of the cable, the gaps between adjacent sections of the steel tapes are wrapped and isolated by insulating materials, and conductive connection points are set on the isolated sections.

[0012] Setting up conductive connection points can limit the spread of fault current in the event of local damage and improve the safety and reliability of the cable.

[0013] Based on any of the above technical solutions, further optimization is that: the central conductor unit includes a plurality of tightly spirally wound composite conductors, and a heat dissipation filament is spirally wound around the periphery of the composite conductor; the composite conductor includes a copper conductor layer, a heat absorption and heat dissipation layer is sprayed on the inner wall of the cavity of the copper conductor layer, and an aluminum conductor layer is extruded on the outer wall of the copper conductor layer.

[0014] Based on any of the above technical solutions, further optimization is that: a plurality of gap cavities are provided between the outer wall of the copper conductor layer and the inner wall of the aluminum conductor layer, and each of the gap cavities extends along the length direction of the composite conductor and is extruded together with the forming of the aluminum conductor layer.

[0015] Based on any of the above technical solutions, further optimization is that: the heat dissipation filament is made of graphene material, and a layer of thermal conductive silicone grease is coated on the surface of the heat dissipation filament.

[0016] When the temperature rises to the phase change temperature of the thermal grease, it can release the latent heat of phase change to balance the internal temperature of the cable.

[0017] Based on any of the above technical solutions, further optimized is that: the preparation method of the cross-linked polyethylene insulation layer comprises the following steps:

[0018] Preparation of raw material formula: 80 parts of low-density polyethylene, 1 part of dicumyl peroxide as a cross-linking agent, 1 part of boron nitride nanoparticles, an appropriate amount of chelated aromatic ketone grafting agent, and 0.5 parts of microcapsule repair agent;

[0019] Raw material pretreatment and mixing: LDPE, boron nitride nanoparticles, and microcapsule repair agent are vacuum dried at 80°C for 4 hours to remove volatile substances in the raw materials to avoid affecting the performance of the final insulation layer;

[0020] Place the dried raw materials in a twin-screw extruder. Set the first section temperature to 120°C, the second section temperature to 130°C, the third section temperature to 140°C, and the screw speed to 200r / min to mix thoroughly.

[0021] During this process, the microcapsule repair agent is evenly dispersed in other raw material systems, laying the foundation for the subsequent formation of a uniform self-healing insulation layer.

[0022] Insulation layer extrusion molding: Control the barrel melting section temperature at 100°C, the homogenizing section temperature at 120°C, the flange section temperature at 105°C, the die head temperature at 105°C, the traction speed at 10m / min, the die head pressure at 20MPa, and ensure a melt flow rate of 0.5g / 10min; during the extrusion process, all raw materials are fully melted, mixed, and extruded to form a preliminary insulation layer structure, and the microencapsulated repair agent is evenly distributed inside the insulation layer;

[0023] Cross-linking process: dry cross-linking method is adopted, the temperature is raised to 200 ° C in a 10 bar nitrogen pressurized pipeline, and the cross-linking time is 40 minutes.

[0024] The cross-linking process forms a cross-linked structure between the polyethylene molecular chains, enhancing the mechanical properties and stability of the insulation layer. At the same time, it ensures that the microencapsulated repair agent is stably present in the insulation layer network after cross-linking, without affecting the cross-linking reaction and will not release the repair agent prematurely due to the high temperature and high pressure during the cross-linking process.

[0025] Post-processing and testing: Degassing in a vacuum environment at 50°C for 48 hours to remove volatile small molecules remaining in the insulation layer during the preparation process and improve the electrical performance of the insulation layer;

[0026] Conduct thermal extension test and breakdown field strength test on the insulation layer to evaluate whether the thermal performance and electrical insulation performance of the insulation layer meet the requirements;

[0027] The porosity was detected by online X-ray and the cross-linking degree was 0.3%, and the cross-linking degree was monitored by infrared spectroscopy and was 86%, ensuring that the internal structure of the insulation layer was dense and the cross-linking degree met the standards.

[0028] Self-repair performance testing: Conduct simulated micro-damage tests on the insulation layer, such as using a specific microneedle puncture tool to create tiny pinhole damage on the surface of the insulation layer, observe the release of the repair agent and the damage repair effect, evaluate the self-repair ability through microscopic observation and electrical performance testing, and record the repair time and the degree of recovery of the electrical performance of the insulation layer after repair.

[0029] Based on any of the above technical solutions, further optimization is as follows: wherein the microcapsule repair agent adopts an epoxy resin-based repair agent, the epoxy resin-based repair agent is composed of an internal core material and an external wall material, and the wall material wraps the core material; the core material comprises bisphenol A epoxy resin and polyetheramine D230, with a mass ratio of 4:1-6:1; the wall material comprises urea-formaldehyde resin (urea to formaldehyde molar ratio of 1:1.5) and melamine-formaldehyde resin (melamine to formaldehyde molar ratio of 1:2-1:3);

[0030] The wall material can stably wrap the repair agent when the insulation layer is in normal use, and will break and release the internal repair agent core material when it is slightly damaged.

[0031] The present invention also provides a method for manufacturing a cross-linked polyethylene insulated armored self-repairing cable for mining, wherein the cross-linked polyethylene insulated armored self-repairing cable for mining adopts the above-mentioned cross-linked polyethylene insulated armored self-repairing cable for mining, and the manufacturing method comprises the following steps:

[0032] Center conductor unit manufacturing:

[0033] First, the copper tube conductor layer is repeatedly drawn into a tubular structure with a cavity. Then, an aluminum conductor layer is formed on the outer wall of the copper conductor layer through an extrusion process. During the extrusion process, a corresponding die head is selected to form a gap cavity extending along the length of the composite conductor. The copper conductor layer is kept in a fixed-axis rotation state, and a flowing paraffin phase change material is injected into its cavity under high pressure. After cooling, the inner wall of the copper conductor layer's cavity forms a heat-absorbing and heat-dissipating layer.

[0034] Then, a stranding machine is used to tightly wind several composite conductors in a spiral. A heat dissipation filament made of graphene and coated with thermal grease is spirally wound around the outer periphery to complete the production of the central conductor unit.

[0035] Preparation of cross-linked polyethylene insulation layer: After forming, the preliminary insulation layer is heated to 200°C in a 10 bar nitrogen pressurized pipeline using a heating device for dry cross-linking for 40 minutes. After cross-linking, the insulation layer is placed in a vacuum drying oven and degassed in a vacuum environment at 50°C for 48 hours.

[0036] Shielding layer preparation: On the outside of the cross-linked polyethylene insulation layer, use a wrapping device to wrap the semi-conductive shielding layer and the copper tape shielding layer in sequence;

[0037] Armor layer preparation: Use wrapping equipment to intermittently wrap the steel tape around the copper tape shielding layer along the length of the cable. The gaps between adjacent sections of steel tape are wrapped and isolated by insulating materials. Use spot welding machines to set conductive connection points in the isolated sections.

[0038] Then, segmented conductive connection points are connected to the armor layer and the copper tape shielding layer to achieve multi-point equipotential grounding;

[0039] Preparation of outer sheath layer: After completing the above structure, use an extruder to extrude the outer sheath layer on the outside of the armor layer.

[0040] Based on any of the above technical solutions, further optimization is: during the preparation process of the central conductor unit, when the composite conductor is wound on the stranding machine, a periodically changing tension is applied, the tension variation range is 5-10N, and the period is 30-60 seconds.

[0041] In this way, the composite conductor can be wound more tightly and evenly, thereby improving the structural stability and conductivity of the central conductor unit and avoiding damage to the conductor due to excessive tension.

[0042] Based on any of the above technical solutions, further optimization is as follows: in the cross-linking process of the cross-linked polyethylene insulation layer, while nitrogen is introduced into the cross-linking pipeline, an inert gas (such as argon) with a volume fraction of 1%-3% is mixed in; the gases are mixed in proportion before introduction.

[0043] The incorporation of inert gas can change the microenvironment of the cross-linking reaction, promote the cross-linking of polyethylene molecular chains, improve the uniformity of the cross-linking degree, reduce defects generated during the cross-linking process, and enhance the electrical properties and self-healing properties of the insulation layer. This does not require large-scale modification of the cross-linking equipment, but only requires a gas pre-mixing step.

[0044] Based on any of the above technical solutions, further optimization is that when making the shielding layer, the copper tape is ultrasonically vibrated during the wrapping process so that the copper tape is tightly fitted with the semi-conductive shielding layer during the wrapping process to enhance the shielding effect.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] 1. The present invention greatly improves the heat dissipation performance of the cable by providing a composite conductor structure in the central conductor unit, setting a gap cavity between the copper conductor layer and the aluminum conductor layer, and coordinating graphene heat dissipation filaments and paraffin heat absorption and heat dissipation layers, effectively reducing the temperature of the cable during operation, reducing failures caused by overheating, and extending the service life of the cable.

[0047] 2. The cross-linked polyethylene insulation layer used in the present invention is added with a microcapsule repair agent. When the insulation layer is slightly damaged, the microcapsules rupture and release the repair agent for repair, thereby improving the self-repair ability of the insulation layer, reducing leakage and short-circuit faults caused by damage to the insulation layer, and ensuring the safety and stability of power transmission.

[0048] 3. The shielding layer of the present invention adopts a combination of a semi-conductive shielding layer and a copper tape shielding layer, and the armor layer and the copper tape shielding layer are connected to multi-point equipotential grounding through segmented conductive rubber strips, which can effectively shield electromagnetic interference, limit the spread of fault current, and improve the cable's anti-interference ability and operation safety in complex electromagnetic environments.

[0049] 4. The armor layer of the present invention is wrapped with discontinuous gaps of steel tape, and conductive connection points are set in the isolation section. This structure can ensure the mechanical strength of the cable while limiting the spread of the fault current in the event of local damage, avoiding the expansion of the fault and enhancing the safety and reliability of the cable.

[0050] 5. The present invention applies periodically changing tension when preparing the central conductor unit, mixes inert gas when cross-linking the cross-linked polyethylene insulation layer, and uses ultrasonic vibration when making the shielding layer, thereby respectively improving the structural stability and conductivity of the central conductor unit, the electrical properties and self-repairing properties of the insulation layer, and the shielding effect of the shielding layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly describes the drawings required for the specific embodiments or the description of the prior art. Similar elements or components are generally identified by similar reference numerals throughout the drawings. Elements or components in the drawings are not necessarily drawn to scale.

[0052] Figure 1 The figure is a schematic diagram of the cross-sectional structure of the cross-linked polyethylene insulated armored self-repairing cable for mining of the present invention.

[0053] Figure 2 It is a schematic diagram of the layout structure of the present invention in which adjacent steel strips are separated by insulating materials.

[0054] In the figure, 1. Copper conductor layer; 2. Heat absorption and heat dissipation layer; 3. Aluminum conductor layer; 4. Semi-conductive shielding layer; 5. Copper tape shielding layer; 6. Conductive rubber strip; 7. Steel tape; 8. Gap cavity; 9. Heat dissipation filaments; 10. Cross-linked polyethylene insulation layer; 11. Outer sheath layer; 12. Insulation material. DETAILED DESCRIPTION

[0055] The following embodiments of the technical solution of the present invention are described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and are therefore only used as examples and are not intended to limit the scope of protection of the present invention. Figure 1-Figure 2 As shown in .

[0056] Example 1: A cross-linked polyethylene insulated and armored self-repairing cable for mining, comprising a central conductor unit, on the outside of which a cross-linked polyethylene insulation layer 10, a shielding layer, and an armor layer are sequentially wrapped from the inside out, and an outer sheath layer 11 is extruded outside the armor layer;

[0057] The shielding layer comprises a semi-conductive shielding layer 4 wrapped around the outside of the cross-linked polyethylene insulation layer 10, and a copper tape shielding layer 5 wrapped around the outside of the semi-conductive shielding layer 4;

[0058] The armor layer and the copper tape shielding layer 5 are connected via segmented conductive rubber strips 6 to achieve multi-point equipotential grounding.

[0059] The cross-linked polyethylene insulated, armored, self-repairing cable for mining and its manufacturing method are designed to address numerous issues encountered by mining cables in complex underground environments and comprehensively enhance cable performance. Through its unique structural design and manufacturing process, it achieves efficient heat dissipation, self-repairing capabilities, and excellent shielding and grounding performance. This ensures safe, stable, and efficient power transmission in coal mines, reduces production interruptions and safety incidents caused by cable failures, lowers maintenance costs, and improves the overall efficiency and safety of coal mining operations.

[0060] The center conductor unit is responsible for conducting current, the cross-linked polyethylene insulation layer prevents current leakage, the shielding layer blocks electromagnetic interference, the armor layer enhances mechanical strength and assists in grounding, and the outer sheath layer provides additional protection. Segmented conductive tape connects the armor layer and the copper tape shielding layer, so that each part of the cable is at the same potential, avoiding failures caused by potential differences. The multi-layer structural design provides comprehensive protection and functional support. The shielding layer reduces the impact of electromagnetic interference on the internal signal and current transmission of the cable, ensuring stable power transmission; multi-point equipotential grounding effectively reduces the risk of leakage and improves safety; the armor layer enhances the mechanical strength of the cable, enabling it to adapt to the complex physical environment underground, such as extrusion and stretching.

[0061] Segmented conductive rubber strips are used to achieve multi-point equipotential grounding. Compared with traditional grounding methods, the grounding effect is more uniform and reliable, and can more effectively limit fault current. This unique grounding design is safer in the field of mining cables.

[0062] Based on any of the above technical solutions, further optimization is that: the armor layer includes a steel tape 7 intermittently wrapped around the periphery of the copper tape shielding layer 5 along the length direction of the cable, and the gaps between adjacent sections of the steel tape 7 are wrapped and isolated by insulating material 12, and conductive connection points are provided on the isolated sections of the insulating material 12.

[0063] The steel strips are intermittently wrapped and separated by insulating material, ensuring mechanical strength while reducing electrical connections between the strips. The conductive connection points of the isolated sections maintain electrical continuity under normal conditions. However, in the event of localized damage, the fault current is limited to a small area, preventing further expansion of the fault.

[0064] This effectively improves the safety and reliability of the cable. When a cable is partially damaged, it prevents the widespread spread of fault current, reducing the risk of widespread power outages and minimizing the impact on coal mine production. This also does not affect the cable's overall mechanical performance or grounding function. In addition to the mechanical protection provided by the armor layer, the added fault current limiting function enhances the cable's ability to cope with emergencies and strengthens the cable's adaptability and safety in complex operating conditions.

[0065] Setting up conductive connection points can limit the spread of fault current in the event of local damage and improve the safety and reliability of the cable.

[0066] Based on any of the above technical solutions, further optimization is that: the central conductor unit includes a plurality of tightly spirally wound composite conductors, and a heat dissipation filament 9 is spirally wound around the periphery of the composite conductor; the composite conductor includes a copper conductor layer 1, a heat absorption and heat dissipation layer 2 is sprayed on the inner wall of the cavity of the copper conductor layer 1, and an aluminum conductor layer 3 is extruded on the outer wall of the copper conductor layer 1.

[0067] Composite conductors combine the excellent electrical conductivity of copper with the low density and high thermal conductivity of aluminum. The copper conductor layer provides a stable electrical path, while the aluminum layer assists in heat dissipation and shares some of the current conduction burden. The heat-absorbing and heat-dissipating layer absorbs and dissipates heat generated by the conductor, while the heat-dissipating filaments further enhance the heat dissipation, improving both the conductor's electrical conductivity and heat dissipation performance. The composite conductor structure reduces electrical resistance and energy loss. The efficient heat dissipation design effectively lowers the cable's operating temperature, extending its lifespan and reducing failures caused by overheating. This achieves the dual functions of power transmission and efficient heat dissipation, enhancing the overall performance of the center conductor unit.

[0068] Based on any of the above technical solutions, further optimization is that: a plurality of gap cavities 8 are provided between the outer wall of the copper conductor layer 1 and the inner wall of the aluminum conductor layer 3, and each of the gap cavities 8 extends along the length direction of the composite conductor and is extruded together with the forming of the aluminum conductor layer 3.

[0069] The interstitial cavity creates a space filled with air or other gas within the composite conductor. Leveraging the gas's low thermal conductivity and fluidity, it provides insulation and aids heat dissipation. During cable operation, heat is conducted through the interstitial cavity to the heat dissipation filaments and then dissipated, enhancing heat dissipation and further reducing cable operating temperatures. The interstitial cavity reduces direct heat conduction between the copper and aluminum conductor layers, optimizing the heat dissipation path and improving the cable's heat dissipation efficiency. The interstitial cavity provides an additional heat dissipation channel for the cable, improving overall heat dissipation.

[0070] On the basis of any of the above technical solutions, further optimization is that: the heat dissipation filament 9 is made of graphene material, and a layer of thermal conductive silicone grease is coated on the surface of the heat dissipation filament 9.

[0071] When the temperature rises to the phase change temperature of the thermal grease, it can release the latent heat of phase change to balance the internal temperature of the cable.

[0072] Graphene has extremely high thermal conductivity and can conduct heat quickly. Thermal grease enhances heat conduction at room temperature. When the temperature rises to the phase transition temperature, it undergoes a phase change, absorbing a large amount of heat. This latent heat release balances the internal temperature of the cable and prevents overheating. This significantly improves the cable's heat dissipation capacity. Especially when the cable temperature rises, the phase change of the thermal grease effectively mitigates the temperature increase, protecting the cable's internal structure and insulation, and extending the cable's service life.

[0073] It provides efficient heat dissipation for the cable, especially playing a key role in temperature regulation when dealing with cable heating peaks.

[0074] Based on any of the above technical solutions, further optimized is that: the preparation method of the cross-linked polyethylene insulation layer 10 includes the following steps:

[0075] Preparation of raw material formula: 80 parts of low-density polyethylene, 1 part of dicumyl peroxide as a cross-linking agent, 1 part of boron nitride nanoparticles, an appropriate amount of chelated aromatic ketone grafting agent, and 0.5 parts of microcapsule repair agent;

[0076] Low-density polyethylene (LDPE) serves as the base material, providing insulation properties. Dicumyl peroxide initiates a cross-linking reaction, forming a cross-linked structure in the polyethylene molecular chains, enhancing the mechanical properties and stability of the insulation layer. Boron nitride nanoparticles improve the thermal conductivity and heat resistance of the insulation layer. Chelated aromatic ketone grafting agents improve compatibility between materials. Microencapsulated repair agents are used to self-repair the insulation layer if damaged.

[0077] Raw material pretreatment and mixing: LDPE, boron nitride nanoparticles, and microcapsule repair agent are vacuum dried at 80°C for 4 hours to remove volatile substances in the raw materials to avoid affecting the performance of the final insulation layer;

[0078] Place the dried raw materials in a twin-screw extruder. Set the first section temperature to 120°C, the second section temperature to 130°C, the third section temperature to 140°C, and the screw speed to 200r / min to mix thoroughly.

[0079] During this process, the microcapsule repair agent is evenly dispersed in other raw material systems, laying the foundation for the subsequent formation of a uniform self-healing insulation layer.

[0080] Vacuum drying removes volatile substances, preventing them from forming bubbles in the insulation layer and affecting material performance. The twin-screw extruder operates at different temperature ranges and speeds to thoroughly mix the raw materials, ensuring even distribution of the microcapsule repair agent and safeguarding the subsequent self-healing function. This improves the quality and performance stability of the insulation layer. Removing volatile substances reduces internal defects in the insulation layer, while uniform mixing maximizes the performance of each raw material and ensures the effective implementation of the self-healing function.

[0081] Insulation layer extrusion molding: Control the barrel melting section temperature at 100°C, the homogenizing section temperature at 120°C, the flange section temperature at 105°C, the die head temperature at 105°C, the traction speed at 10m / min, the die head pressure at 20MPa, and ensure a melt flow rate of 0.5g / 10min; during the extrusion process, all raw materials are fully melted, mixed, and extruded to form a preliminary insulation layer structure, and the microencapsulated repair agent is evenly distributed inside the insulation layer;

[0082] Cross-linking process: dry cross-linking method is adopted, the temperature is raised to 200 ° C in a 10 bar nitrogen pressurized pipeline, and the cross-linking time is 40 minutes.

[0083] The cross-linking process forms a cross-linked structure between the polyethylene molecular chains, enhancing the mechanical properties and stability of the insulation layer. At the same time, it ensures that the microencapsulated repair agent is stably present in the insulation layer network after cross-linking, without affecting the cross-linking reaction and will not release the repair agent prematurely due to the high temperature and high pressure during the cross-linking process.

[0084] The dry cross-linking method is carried out under a nitrogen-pressurized atmosphere. The high temperature decomposes dicumyl peroxide to produce free radicals, which trigger cross-linking of the polyethylene molecular chains, forming a three-dimensional network structure. The nitrogen protection prevents oxidation while ensuring the stability of the microcapsule repair agent during the cross-linking process. This significantly enhances the mechanical properties and stability of the insulation layer, enabling it to better withstand mechanical stress and environmental influences. Furthermore, it ensures that the microcapsule repair agent can still perform its self-healing function after cross-linking, preventing damage or premature release. Through the cross-linking process, the initially formed insulation layer is transformed into an insulating structure with high strength and stability while retaining its self-healing function.

[0085] Post-processing and testing: Degassing in a vacuum environment at 50°C for 48 hours to remove volatile small molecules remaining in the insulation layer during the preparation process and improve the electrical performance of the insulation layer;

[0086] Conduct thermal extension test and breakdown field strength test on the insulation layer to evaluate whether the thermal performance and electrical insulation performance of the insulation layer meet the requirements;

[0087] The porosity was detected by online X-ray and the cross-linking degree was 0.3%, and the cross-linking degree was monitored by infrared spectroscopy and was 86%, ensuring that the internal structure of the insulation layer was dense and the cross-linking degree met the standards.

[0088] Self-repair performance testing: Conduct simulated micro-damage tests on the insulation layer, such as using a specific microneedle puncture tool to create tiny pinhole damage on the surface of the insulation layer, observe the release of the repair agent and the damage repair effect, evaluate the self-repair ability through microscopic observation and electrical performance testing, and record the repair time and the degree of recovery of the electrical performance of the insulation layer after repair.

[0089] Vacuum degassing removes residual volatile small molecules, minimizing their impact on electrical performance. Thermal elongation testing, breakdown field strength testing, X-ray porosity analysis, and infrared spectroscopy monitoring of crosslinking are used to assess the insulation layer's performance from various perspectives to determine if it meets requirements.

[0090] Based on any of the above technical solutions, further optimization is as follows: wherein the microcapsule repair agent adopts an epoxy resin-based repair agent, the epoxy resin-based repair agent is composed of an internal core material and an external wall material, and the wall material wraps the core material; the core material comprises bisphenol A epoxy resin and polyetheramine D230, with a mass ratio of 4:1-6:1; the wall material comprises urea-formaldehyde resin (urea to formaldehyde molar ratio of 1:1.5) and melamine-formaldehyde resin (melamine to formaldehyde molar ratio of 1:2-1:3);

[0091] The wall material can stably wrap the repair agent when the insulation layer is in normal use, and will break and release the internal repair agent core material when it is slightly damaged.

[0092] Under normal circumstances, the wall material stably wraps around the core material, preventing premature leakage of the repair agent. When the insulation layer sustains minor damage, the stress at the damaged site causes the wall material to rupture, releasing the core material composed of bisphenol A epoxy resin and polyetheramine D230. The core material then cures at the damaged site, repairing the insulation damage. This effectively extends the insulation life, reduces cable failures caused by minor damage, and improves the reliability and safety of cable operation. In the complex environment of underground coal mines, cables are inevitably subject to various minor scratches, punctures, and other damage. The self-repair function can promptly repair these damages, preventing minor problems from escalating into serious leakage or short-circuit incidents, ensuring continuous power transmission and reducing mine downtime and economic losses caused by cable failures.

[0093] Traditional cables often require manual repairs to locate the fault point and repair it once the insulation layer is damaged, which consumes a lot of manpower, material resources, and time. However, the self-repair function of the present invention can automatically repair minor damage, greatly improving the maintenance convenience and operational stability of the cable.

[0094] Example 2: Compared with Example 1, this example is different in that it also includes the following technical features:

[0095] The present invention also provides a method for manufacturing a cross-linked polyethylene insulated armored self-repairing cable for mining, wherein the cross-linked polyethylene insulated armored self-repairing cable for mining adopts the above-mentioned cross-linked polyethylene insulated armored self-repairing cable for mining, and the manufacturing method comprises the following steps:

[0096] Center conductor unit manufacturing:

[0097] First, the copper tube conductor layer is repeatedly drawn and formed into a tubular structure with a cavity. Then, the aluminum conductor layer 3 is formed on the outer wall of the copper conductor layer 1 through an extrusion process. During the extrusion process, a correspondingly shaped die head is selected to form a gap cavity 8 extending along the length of the composite conductor. The copper conductor layer 1 is kept in a fixed-axis rotation state, and a flowing paraffin phase change material is injected into its cavity under high pressure. After cooling, the inner wall of the cavity of the copper conductor layer 1 forms a heat-absorbing and heat-dissipating layer 2.

[0098] Then, a stranding machine is used to tightly wind a plurality of composite conductors in a spiral, and a heat dissipation filament 9 made of graphene and coated with thermal grease is spirally wound around the outer periphery to complete the production of the central conductor unit.

[0099] A copper conductor layer with a cavity is created through a drawing process, providing a foundation for subsequent processing. A die is used to create a gap cavity during the extrusion of the aluminum conductor layer to enhance heat dissipation. Paraffin phase change material is injected into the copper conductor layer's cavity, utilizing its phase-change properties to absorb and release heat. A stranding machine winds the composite conductor and adds graphene heat-dissipating filaments to further enhance heat dissipation and electrical conductivity.

[0100] Preparation of cross-linked polyethylene insulation layer 10: The formed preliminary insulation layer is heated to 200°C in a 10 bar nitrogen pressurized pipeline using a heating device for dry cross-linking for 40 minutes; after the cross-linking is completed, the insulation layer is placed in a vacuum drying oven and degassed in a vacuum environment at 50°C for 48 hours;

[0101] During the dry cross-linking process, heating under nitrogen atmosphere cross-links the polyethylene molecular chains, enhancing the insulation layer's performance. Vacuum degassing removes volatile substances remaining from the cross-linking process, further improving the insulation layer's electrical properties. The cross-linking and degassing processes significantly enhance the insulation layer's mechanical properties, stability, and electrical performance. This better protects the cable's internal conductors, prevents current leakage, improves insulation reliability, and reduces the risk of failures caused by insulation problems.

[0102] Preparation of shielding layer: On the outside of the cross-linked polyethylene insulation layer 10, use a wrapping device to wrap the semi-conductive shielding layer 4 and the copper tape shielding layer 5 in sequence;

[0103] The wrapping equipment tightly wraps the semi-conductive shield and copper tape shield around the insulation layer. The semi-conductive shield improves the electric field distribution, while the copper tape shield blocks external electromagnetic interference, preventing it from affecting the current transmission within the cable. This effectively shields against external electromagnetic interference, ensuring the stability and accuracy of current transmission within the cable. This reduces the impact of electromagnetic interference on other electrical equipment in the coal mine, while also preventing electromagnetic interference generated by the cable itself from adversely affecting external equipment, thereby improving the compatibility and stability of the entire coal mine electrical system.

[0104] Armor layer preparation: Use wrapping equipment to intermittently wrap steel tape 7 around the outer periphery of the copper tape shielding layer 5 along the length of the cable. The gaps between adjacent sections of steel tape 7 are wrapped and isolated by insulating material 12. Use a spot welder to set conductive connection points in the isolated sections.

[0105] Then, the segmented conductive connection points are connected to the armor layer and the copper tape shielding layer 5 to achieve multi-point equipotential grounding;

[0106] The wrapping equipment achieves intermittent, gap-wrap wrapping of the steel strip. Insulation material separates the steel strip segments. Conductive connection points ensure electrical continuity of the steel strip while limiting the spread of fault current in the event of local damage. Segmented conductive connection points connect the armor layer and the copper tape shield, achieving multi-point equipotential grounding and reducing the risk of leakage.

[0107] Enhanced mechanical strength of the cable enables it to withstand external forces such as squeezing and collision underground. Multi-point equipotential grounding and fault current limiting functions improve the safety and reliability of the cable, reducing safety accidents and equipment damage caused by the spread of fault current, and ensuring coal mine production safety.

[0108] Preparation of the outer sheath layer 11: After the above structure is manufactured, an extruder is used to extrude the outer sheath layer 11 on the outside of the armor layer.

[0109] The extruder heats and melts the outer sheath material, such as plastic, and then extrudes it over the armor layer to form a tightly wrapped outer sheath. The outer sheath protects the cable from external chemical corrosion, moisture erosion, and mechanical damage.

[0110] Based on any of the above technical solutions, further optimization is: during the preparation process of the central conductor unit, when the composite conductor is wound on the stranding machine, a periodically changing tension is applied, the tension variation range is 5-10N, and the period is 30-60 seconds.

[0111] In this way, the composite conductor can be wound more tightly and evenly, thereby improving the structural stability and conductivity of the central conductor unit and avoiding damage to the conductor due to excessive tension.

[0112] When a composite conductor is wound on a stranding machine, the periodically changing tension causes the composite conductor to be subjected to varying degrees of tension at different times. Lower tension prevents excessive stretching damage to the conductor, while the periodic change in tension helps the conductor be wound more tightly and evenly, reducing gaps and loose spots.

[0113] The structural stability of the central conductor unit is improved, the contact between the conductors is closer, the contact resistance is reduced, and the conductivity is improved. At the same time, the conductor damage caused by excessive tension is avoided, the product quality is guaranteed, the scrap rate is reduced, and the production efficiency is improved.

[0114] Based on any of the above technical solutions, further optimization is that: in the cross-linking process of the cross-linked polyethylene insulation layer 10, while nitrogen is introduced into the cross-linking pipe, an inert gas (such as argon) with a volume fraction of 1%-3% is mixed in; the gases are mixed in proportion before introduction.

[0115] The incorporation of inert gas can change the microenvironment of the cross-linking reaction, promote the cross-linking of polyethylene molecular chains, improve the uniformity of the cross-linking degree, reduce defects generated during the cross-linking process, and enhance the electrical properties and self-healing properties of the insulation layer. This does not require large-scale modification of the cross-linking equipment, but only requires a gas pre-mixing step.

[0116] Inert gases (such as argon) are mixed into the nitrogen to alter the atmosphere in the reaction system during the crosslinking process. The presence of the inert gas influences the diffusion and reactivity of free radicals, promoting more uniform crosslinking between polyethylene molecular chains and reducing defects caused by uneven crosslinking. This significantly improves the electrical performance and self-healing properties of the insulation layer. This increased crosslinking uniformity enhances the mechanical properties and stability of the insulation layer, reduces insulation degradation caused by crosslinking defects, and ensures the long-term stable operation of the cable.

[0117] Based on any of the above technical solutions, further optimization is that when making the shielding layer, the copper tape is ultrasonically vibrated during the wrapping process so that the copper tape is tightly fitted with the semi-conductive shielding layer 4 to enhance the shielding effect.

[0118] During wrapping, the high-frequency mechanical waves generated by ultrasonic vibrations cause the copper tape to vibrate minutely. This vibration promotes molecular interpenetration and close contact between the copper tape and the semi-conductive shielding layer, eliminating gaps and air pockets between them and improving the fit. This significantly enhances the shielding effectiveness of the shielding layer. The tightly fitted copper tape and semi-conductive shielding layer more effectively block electromagnetic interference, reducing the leakage and intrusion of interfering signals. This improves the cable's anti-interference capabilities in complex electromagnetic environments and ensures stable power transmission.

[0119] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some or all of the technical features therein can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention. For those skilled in the art, any replacement improvements or changes made to the implementation methods of the present invention fall within the scope of protection of the present invention.

[0120] Any matters not described in detail in the present invention are well-known technologies to those skilled in the art.

Claims

1. Cross-linked polyethylene insulated armored self-repairing cable for mining, characterized by: It comprises a central conductor unit, on the outside of which a cross-linked polyethylene insulation layer, a shielding layer and an armor layer are sequentially wrapped from the inside to the outside, and an outer sheath layer is extruded outside the armor layer; The shielding layer comprises a semi-conductive shielding layer wrapped around the outside of the cross-linked polyethylene insulation layer, and a copper tape shielding layer wrapped around the outside of the semi-conductive shielding layer; The armor layer and the copper tape shielding layer are connected via segmented conductive rubber strips to achieve multi-point equipotential grounding.

2. The cross-linked polyethylene insulated and armored self-repairing cable for mining according to claim 1, characterized in that: The armor layer includes steel tapes intermittently wrapped around the periphery of the copper tape shielding layer along the length direction of the cable. Adjacent sections of the steel tapes are wrapped with gaps and isolated by insulating materials, and conductive connection points are set on the isolated sections.

3. The cross-linked polyethylene insulated and armored self-repairing cable for mining according to claim 2, characterized in that: The central conductor unit includes a plurality of tightly spirally wound composite conductors, with heat dissipation filaments spirally wound around the periphery of the composite conductor; the composite conductor includes a copper conductor layer, a heat absorption and heat dissipation layer is sprayed on the inner wall of the cavity of the copper conductor layer, and an aluminum conductor layer is extruded on the outer wall of the copper conductor layer.

4. The cross-linked polyethylene insulated and armored self-repairing cable for mining according to claim 3, characterized in that: The heat dissipation filament is made of graphene material, and a layer of thermal conductive silicone grease is coated on the surface of the heat dissipation filament.

5. The cross-linked polyethylene insulated and armored self-repairing cable for mining according to claim 4, characterized in that: The preparation method of the cross-linked polyethylene insulation layer comprises the following steps: Preparation of raw material formula: 80 parts of low-density polyethylene, 1 part of dicumyl peroxide as a cross-linking agent, 1 part of boron nitride nanoparticles, an appropriate amount of chelated aromatic ketone grafting agent, and 0.5 parts of microcapsule repair agent; Raw material pretreatment and mixing: LDPE, boron nitride nanoparticles, and microcapsule repair agent are vacuum dried at 80°C for 4 hours to remove volatile substances in the raw materials to avoid affecting the performance of the final insulation layer; Place the dried raw materials in a twin-screw extruder, set the first section temperature to 120°C, the second section temperature to 130°C, the third section temperature to 140°C, and the screw speed to 200r / min, and mix them thoroughly; In this process, the microcapsule repair agent is evenly dispersed in other raw material systems, laying the foundation for the subsequent formation of a uniform self-repairing insulation layer; Insulation layer extrusion molding: Control the barrel melting section temperature at 100°C, the homogenizing section temperature at 120°C, the flange section temperature at 105°C, the die head temperature at 105°C, the traction speed at 10m / min, the die head pressure at 20MPa, and ensure a melt flow rate of 0.5g / 10min; during the extrusion process, all raw materials are fully melted, mixed, and extruded to form a preliminary insulation layer structure, and the microencapsulated repair agent is evenly distributed inside the insulation layer; Cross-linking process: dry cross-linking method is used, heating to 200℃ in a 10 bar nitrogen pressurized pipeline, and the cross-linking time is 40 minutes; The cross-linking process forms a cross-linked structure between polyethylene molecular chains, enhancing the mechanical properties and stability of the insulation layer. At the same time, it ensures that the microencapsulated repair agent is stably present in the cross-linked insulation layer network without affecting the cross-linking reaction and preventing the repair agent from being released prematurely due to the high temperature and high pressure during the cross-linking process. Post-processing and testing: Degassing in a vacuum environment at 50°C for 48 hours to remove volatile small molecules remaining in the insulation layer during the preparation process and improve the electrical performance of the insulation layer; Conduct thermal extension test and breakdown field strength test on the insulation layer to evaluate whether the thermal performance and electrical insulation performance of the insulation layer meet the requirements; The porosity was detected by online X-ray and the cross-linking degree was 0.3%, and the cross-linking degree was monitored by infrared spectroscopy and was 86%, ensuring that the internal structure of the insulation layer was dense and the cross-linking degree met the standards. Self-repair performance testing: Conduct simulated micro-damage tests on the insulation layer, such as using a specific microneedle puncture tool to create tiny pinhole damage on the surface of the insulation layer, observe the release of the repair agent and the damage repair effect, evaluate the self-repair ability through microscopic observation and electrical performance testing, and record the repair time and the degree of recovery of the electrical performance of the insulation layer after repair.

6. The cross-linked polyethylene insulated and armored self-repairing cable for mining according to claim 5, characterized in that: in, The microcapsule repair agent uses an epoxy resin-based repair agent, which is composed of an internal core material and an external wall material, with the wall material wrapping the core material; the core material includes bisphenol A epoxy resin and polyetheramine D230, with a mass ratio of 4:1-6:1; the wall material includes urea-formaldehyde resin (urea to formaldehyde molar ratio of 1:1.5) and melamine-formaldehyde resin (melamine to formaldehyde molar ratio of 1:2-1:3); The wall material can stably wrap the repair agent when the insulation layer is in normal use, and will break and release the internal repair agent core material when it is slightly damaged.

7. A method for manufacturing a cross-linked polyethylene insulated and armored self-repairing cable for use in mining, wherein the cross-linked polyethylene insulated and armored self-repairing cable for use in mining is the cross-linked polyethylene insulated and armored self-repairing cable for use in mining as claimed in claim 6, characterized in that: The manufacturing method comprises the following steps: Center conductor unit manufacturing: First, the copper tube conductor layer is repeatedly drawn into a tubular structure with a cavity. Then, an aluminum conductor layer is formed on the outer wall of the copper conductor layer through an extrusion process. During the extrusion process, a corresponding die head is selected to form a gap cavity extending along the length of the composite conductor. The copper conductor layer is kept in a fixed-axis rotation state, and a flowing paraffin phase change material is injected into its cavity under high pressure. After cooling, the inner wall of the copper conductor layer's cavity forms a heat-absorbing and heat-dissipating layer. Then, a stranding machine is used to tightly wind several composite conductors in a spiral. A heat dissipation filament made of graphene and coated with thermal grease is spirally wound around the outer periphery to complete the production of the central conductor unit. Preparation of cross-linked polyethylene insulation layer: the preliminary insulation layer after forming is heated to 200°C in a 10 bar nitrogen pressurized pipeline using a heating device for dry cross-linking for 40 minutes; After cross-linking, the insulating layer was placed in a vacuum drying oven and degassed at 50°C for 48 hours. Shielding layer preparation: On the outside of the cross-linked polyethylene insulation layer, use a wrapping device to wrap the semi-conductive shielding layer and the copper tape shielding layer in sequence; Armor layer preparation: Use wrapping equipment to intermittently wrap the steel tape around the copper tape shielding layer along the length of the cable. The gaps between adjacent sections of steel tape are wrapped and isolated by insulating materials. Use spot welding machines to set conductive connection points in the isolated sections. Then, segmented conductive connection points are connected to the armor layer and the copper tape shielding layer to achieve multi-point equipotential grounding; Preparation of outer sheath layer: After completing the above structure, use an extruder to extrude the outer sheath layer on the outside of the armor layer.

8. The manufacturing method according to claim 7, wherein: During the preparation of the central conductor unit, a periodically changing tension is applied when the composite conductor is wound on the stranding machine. The tension range is 5-10N and the period is 30-60 seconds.

9. The manufacturing method according to claim 8, characterized in that: In the cross-linking process of the cross-linked polyethylene insulation layer, nitrogen is introduced into the cross-linking pipe while an inert gas (such as argon) with a volume fraction of 1%-3% is mixed in; the gases are mixed in proportion before introduction.

10. The manufacturing method according to claim 9, characterized in that: When making the shielding layer, the copper tape is ultrasonically vibrated during the wrapping process so that the copper tape is closely fitted to the semi-conductive shielding layer during the wrapping process to enhance the shielding effect.

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