Low-loss energy-saving overhead insulated conductor and preparation method thereof

Abstract

The application relates to the technical field of electric wire and cable, and discloses a low-loss energy-saving overhead insulated conductor wire and a preparation method thereof. The method comprises the following steps: constructing a high-conductivity alloy core material through vacuum refining and electromagnetic stirring, and introducing a nucleating agent to refine the crystal grains; continuously casting and rolling the core material, performing multi-pass cold drawing, and cooperating with online induction annealing to reduce dislocation density by using a dynamic recrystallization mechanism; mixing functionalized nano fillers and a polymer matrix to prepare modified insulation materials; implementing a three-layer co-extrusion process to form a shielding layer, an insulation layer and a sheath layer outside the preheated core material; and finally performing controlled online crosslinking and segmented gradient cooling. By optimizing the microstructure of the core material and the components of the insulation material, the application effectively reduces the electronic scattering, skin effect and dielectric loss of the conductor, improves the mechanical strength and heat dissipation efficiency of the conductor wire, eliminates the interlayer air gap and partial discharge phenomenon, and significantly enhances the energy-saving characteristics, operation stability and service life of the conductor wire in a complex environment.

Description

Technical Field

[0001] This invention relates to the field of wire and cable technology, specifically to a low-loss, energy-saving overhead insulated conductor and its preparation method. Background Technology

[0002] With the accelerated construction of the global energy internet, overhead transmission lines, as the core carriers of energy transmission in the power system, have a decisive impact on the overall energy conservation and emission reduction of the power grid due to their operational efficiency and safety. Traditional overhead lines mainly use bare conductors, but with urbanization and complex weather conditions, insulated conductors are widely used because they can effectively reduce phase-to-phase distance, lower the risk of short circuits, and improve power supply reliability. Especially under the requirements of building resource-saving and environmentally friendly power grids, the current-carrying capacity, mechanical strength, and energy loss characteristics of transmission conductors during long-term operation have become key indicators for evaluating the technical level of distribution networks.

[0003] Among them, low-loss, energy-saving overhead insulated conductors aim to achieve lower unit resistance loss and stronger environmental adaptability through microstructure optimization of the conductive core material and modification of the outer insulation material. These conductors typically combine highly conductive alloy materials with polymer insulation materials possessing excellent dielectric properties, using a multi-layer composite structure design to balance electromagnetic shielding effectiveness and heat dissipation during operation. The research and development focus is on how to reduce the skin effect and dielectric loss under AC operation conditions by precisely controlling the material composition and interface structure while ensuring mechanical tensile strength, thereby improving the overall energy efficiency of power transmission.

[0004] However, traditional overhead insulated conductors suffer from insufficient precision in controlling impurities in the conductive core material and uneven microcrystalline grain distribution, resulting in high internal resistance and a high susceptibility to additional Joule heat loss during AC power transmission. Simultaneously, conventional insulation materials are prone to physical embrittlement under long-term heating and environmental stress, leading to an increased dielectric loss factor and a vicious cycle of excessive line temperature rise. Furthermore, existing manufacturing processes struggle to achieve complete molecular-level wetting at the conductor-insulation interface, easily creating micro-gaps in operating environments with large temperature fluctuations. This results in frequent partial discharges and significant power loss.

[0005] Therefore, a low-loss, energy-saving overhead insulated conductor and its preparation method are desired. Summary of the Invention

[0006] The purpose of this invention is to provide a low-loss, energy-saving overhead insulated conductor and its preparation method, which can effectively solve the problems in the background art.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for preparing a low-loss, energy-saving overhead insulated conductor, comprising the following specific steps: Step 1: Construct a high conductivity alloy core material. The melt is degassed and impurities are removed through vacuum refining and electromagnetic stirring. During solidification, a trace nucleating agent is introduced to obtain a uniformly distributed and refined grain structure. Step 2: The high conductivity alloy core material is subjected to continuous casting and rolling and multi-pass cold drawing, and online induction annealing is carried out between each pass to eliminate work hardening and reduce the dislocation density inside the material by utilizing the dynamic recrystallization mechanism. Step 3: Prepare high-performance modified insulating composite material by multi-stage screw mixing of polymer matrix resin, functionalized nanofiller, high-efficiency antioxidant and crosslinking accelerator under specific temperature control environment to achieve uniform dispersion of filler at the molecular level. Step 4: Implement a three-layer co-extrusion coating process to sequentially form an inner semi-conductive shielding layer, a modified insulation layer, and an outer anti-aging sheath layer on the core material after surface preheating treatment, forming a dense interlayer bonding structure. Step 5: Perform controlled online crosslinking and segmented gradient cooling. By adjusting the pressure and temperature distribution in the crosslinking chamber, the polymer chain segments are guided to form a stable network structure, and residual thermal stress between layers is eliminated.

[0008] Preferably, the process of constructing the high conductivity alloy core material in step 1 includes strict control of the chemical composition ratio of the raw materials. The high conductivity alloy core material uses a high-purity metal as the matrix and undergoes micro-alloying treatment by adding a specific proportion of rare earth elements. The rare earth elements can capture residual impurity atoms in the melt, removing harmful impurities from the grain boundaries by forming stable high-melting-point intermetallic compounds, thereby reducing the probability of electron scattering during operation. The electromagnetic stirring process generates a changing rotating magnetic field, causing controlled convection circulation inside the alloy melt, ensuring the macroscopic uniformity of the alloy elements and promoting gas escape. The particle size of the trace nucleating agent is within a specific range, and its lattice constant matches that of the matrix metal. It can provide a large number of non-spontaneous nucleation nuclei in the early stage of solidification, so that the final grains exhibit an isotropic equiaxed crystal morphology.

[0009] Preferably, the microstructure optimization of the conductive core material in step 1 involves precise control of grain boundary energy. The grain refinement process aims to shorten the mean free path of charge carriers within the crystal and capture defects that may cause local electric field distortion by increasing the total number of grain boundaries. The refined grain size distribution is within a preset range. This uniform microstructure can significantly improve the skin effect under AC operating conditions, making the current distribution on the conductor cross-section more stable, thereby reducing the equivalent AC resistance of the conductor.

[0010] Preferably, in step 2, the multi-pass cold drawing employs a continuously varying die aperture gradient to ensure that the flow stress of the material remains in equilibrium during deformation. The inner cavity of the drawing die adopts a streamlined structure with a specific curvature design to reduce frictional resistance and prevent the formation of microcracks or burrs on the core material surface. The online induction annealing utilizes a high-frequency induced current to rapidly heat the moving core material, causing the material temperature to quickly rise above the recrystallization temperature. Under this instantaneous high temperature, the distortion energy inside the crystal is released, and new grains begin to nucleate and grow at the original defects. By precisely adjusting the power of the induction power supply and the linear velocity of the core material, the degree of recrystallization can be controlled, allowing the conductive core material to maintain high mechanical strength while obtaining excellent ductility and conductivity.

[0011] Preferably, in step 3, when preparing the high-performance modified insulating composite material, the polymer matrix resin is selected from polyolefin materials with high dielectric strength. The functionalized nanofiller undergoes surface treatment with a silane coupling agent before addition, forming chemically active functional groups on the filler surface. These functional groups can chemically bond with the molecular chains of the matrix resin, enhancing the interfacial compatibility between inorganic particles and the organic matrix. The introduction of the functionalized nanofiller can significantly improve the heat resistance and mechanical modulus of the insulating material, and due to the nano-effect, forms a large number of trap energy levels within the material, effectively capturing free electrons and holes, inhibiting charge accumulation, and thus reducing dielectric loss during line operation.

[0012] Preferably, the synergistic effect of the high-efficiency antioxidant and the crosslinking accelerator in step 3 can significantly extend the service life of the conductor. The high-efficiency antioxidant eliminates free radicals generated by the thermal decomposition of the material, blocking the auto-oxidation cycle of the polymer chains and preventing physical embrittlement of the material. The crosslinking accelerator acts as a bridge in the subsequent crosslinking process, connecting the originally independent linear polymer chains into a three-dimensional network structure under the action of chemical bonds. This structure has extremely strong chemical corrosion resistance and thermal deformation stability, ensuring that the conductor does not deteriorate in insulation performance under long-term high current loads.

[0013] Preferably, the three-layer co-extrusion coating process in step 4 employs a co-extrusion die with a specific flow channel design. This co-extrusion die ensures that the three layers of material are at the same flow rate and pressure before leaving the die, avoiding interlayer shear stress caused by flow rate differences. The inner semiconductive shielding layer is in close contact with the core material surface. By adjusting the volume resistivity of the semiconductive material to a specific value, it effectively shields the electric field concentration phenomenon on the conductor surface, ensuring that the electric field lines are uniformly distributed within the insulation layer. The outer anti-aging sheath layer contains a high concentration of ultraviolet absorbers and antifungal agents, resisting ultraviolet radiation and biological erosion in harsh climatic environments, protecting the inner insulation layer from external damage.

[0014] Preferably, the surface preheating treatment of the core material in step 4 is achieved using a non-contact heating device. The preheating temperature is set within a specific range to remove moisture and volatile impurities from the core material surface. Simultaneously, the preheated core material generates stronger intermolecular thermal motion with the molten extruded material, achieving molecular-level wetting between the metal interface and the semiconductive layer. This tight interfacial bonding completely eliminates micro-gaps, fundamentally preventing partial discharge, reducing additional energy loss due to partial discharge, and improving system operational safety.

[0015] Preferably, the controlled online crosslinking in step 5 is completed within a crosslinking tube filled with a pre-pressurized protective gas. The protective gas prevents oxidation of the material during the high-temperature crosslinking process. The temperature distribution within the crosslinking tube is divided into a heating zone, a constant-temperature zone, and a cooling zone. In the heating zone, the crosslinking agent in the insulating material decomposes and releases active atoms; in the constant-temperature zone, the polymer chain segments undergo a complete crosslinking reaction; in the cooling zone, the conductor temperature is slowly reduced through segmented gradient cooling. This gradient cooling logic prevents shrinkage stress caused by excessive internal and external temperature differences in the conductor, ensuring the geometric stability and internal structural density of the finished conductor.

[0016] Preferably, the low-loss, energy-saving overhead insulated conductor and its preparation method further include performance monitoring of the finished conductor. This performance monitoring encompasses DC resistance testing, AC withstand voltage testing, partial discharge testing, and thermal cycling aging experiments. In the DC resistance test, high-precision measuring equipment verifies whether the resistance loss of the conductive core material meets the predetermined energy-saving target. In the partial discharge test, sensors monitor whether pulse signals are generated within the material under high-voltage conditions to assess the quality of the interface bonding. These monitoring steps ensure that each section of the conductor possesses excellent energy-saving characteristics and long-term operational reliability.

[0017] Preferably, the cross-sectional shape of the conductive core material is optimized, and a compact stranding process is used to achieve a preset high metal fill factor. This compact structure not only reduces the outer diameter of the conductor, lowering wind resistance and icing load, but also enhances the overall thermal conductivity of the conductor by increasing the metal contact area. When current flows, the generated Joule heat can be dissipated more quickly through the insulation layer, effectively reducing the conductor's equilibrium operating temperature. Based on the positive correlation between temperature and resistance, this further reduces the conductor's operating power loss.

[0018] Preferably, the modified insulating composite material further comprises a specific ratio of thermally conductive reinforcing filler. The thermally conductive reinforcing filler has a highly anisotropic thermal conductivity and is radially ordered during extrusion flow. This ordered arrangement forms phonon transport channels that significantly improve the lateral thermal conductivity of the insulation layer. By improving the heat dissipation efficiency of the insulation layer, the conductor can maintain a lower core temperature under the same current carrying capacity, thereby achieving macroscopic energy conservation and emission reduction goals.

[0019] Preferably, the surface of the outer anti-aging sheath layer has a micron-level hydrophobic structure. This structure is formed through a special mold surface texture transfer technology, which can significantly improve the self-cleaning ability and anti-icing flashover performance of the conductor surface. In rainy or snowy weather, moisture is unlikely to form a continuous water film on the conductor surface, thereby reducing the corona loss and creepage leakage current of the line. This multi-dimensional protection and energy-saving design together constitute the consistent advantage of the conductor of the present invention in complex and variable environments.

[0020] Preferably, the melting process in the preparation method is carried out in a vacuum induction furnace. During the melting process, by adjusting the vacuum level to a preset level, dissolved hydrogen, oxygen, and other gas molecules in the melt can be forced to escape from the liquid phase. By precisely controlling the melt overheating temperature and refining time, deep removal of non-metallic inclusions can be achieved, resulting in extremely high purity of the conductive core material matrix. This improvement in purity is a fundamental physical prerequisite for reducing the inherent resistance of the material and achieving low-loss goals.

[0021] Preferably, the cooling intensity during the continuous casting and rolling process is adjusted in real time by the circulating water system based on data from an infrared thermometer. By controlling the initial temperature of the billet before entering the rolling mill, it can be ensured that the material is in a good plastic state in the hot deformation zone. The deformation-induced precipitation technology during rolling enables microalloying elements to precipitate from the solid solution in the form of extremely fine particles. These precipitated phases can pin dislocations, which not only enhances the tensile strength of the conductor but also restores the conductivity of the conductive matrix by reducing the solid solubility after precipitation, thus achieving a synergistic improvement in strength, toughness, and high conductivity.

[0022] Preferably, the extrusion pressure in step 4 is maintained within a constant preset pressure range. By installing a pressure sensor and a speed closed-loop control system at the extruder die head, pressure pulsations caused by screw rotation can be eliminated. A constant pressure environment ensures the uniformity of the insulation layer wall thickness, avoiding uneven electric field distribution caused by wall thickness fluctuations. This precise control of the physical structure is a crucial process guarantee for ensuring consistent operating losses in long-distance lines.

[0023] Preferably, the formulation process of the insulating composite material involves real-time online monitoring of the dispersion state of the nanofiller. An ultrasonic dispersion monitoring system is used to sense the particle size distribution in the mixture in real time, ensuring the absence of large agglomerates. A uniform dispersion ensures a highly consistent dielectric constant throughout the material, preventing dielectric breakdown or energy dissipation induced by localized electric field concentration, thereby guaranteeing low-loss characteristics of the conductor at the microscopic level.

[0024] The present invention also provides a low-loss, energy-saving overhead insulated conductor, which is prepared by the above method.

[0025] Compared with the prior art, the beneficial effects achieved by the present invention are: 1. By refining the micrograin and rare-earth microalloying of the conductive core material, the electron scattering probability and skin effect under AC operation are effectively reduced, significantly reducing the unit resistance loss of the conductor and achieving efficient power transmission.

[0026] 2. By using nano-modified insulating materials and multi-layer co-extrusion process, trap energy levels are introduced into the material and the electric field distribution is optimized, which significantly suppresses the accumulation of space charge and partial discharge, reduces the dielectric loss factor, and improves energy utilization efficiency.

[0027] 3. The interface between the conductor and the insulation layer achieves a molecular-level tight bond through surface preheating and high-voltage extrusion, completely eliminating the tiny air gaps that may be caused by temperature fluctuations in the operating environment, and enhancing the performance stability of the line during long-term operation.

[0028] 4. By combining induction annealing and dynamic recrystallization control technology, the conductor maintains excellent mechanical strength while possessing higher conductivity, effectively balancing the contradiction between mechanical performance and energy-saving characteristics.

[0029] 5. The optimized thermal conductivity structure design and outer anti-aging protection system not only improve the heat dissipation efficiency of the conductor and further reduce the increase in resistance caused by the temperature rise during operation, but also significantly extend the service life of the conductor in complex weather environments and reduce the operation and maintenance costs throughout the entire life cycle. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the overall technical solution architecture of the low-loss energy-saving overhead insulated conductor and its preparation method proposed in this invention; Figure 2 This is a schematic diagram of the core principle framework of the present invention based on the microstructure control of conductive core material and the suppression of charge accumulation in insulating layer; Figure 3 This is a schematic diagram of the logic flow of refining and impurity removal, grain nucleation and refinement, and online induction annealing of the high conductivity alloy core material in this invention. Figure 4 This is a schematic diagram of the logical flow of the preparation of modified insulating composite materials, interfacial bonding of three-layer co-extrusion, and controlled online crosslinking in this invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1 In the preparation method of the low-loss energy-saving overhead insulated conductor, step 1 involves the process of constructing a high-conductivity alloy core material, specifically including strict control of the chemical composition ratio of raw materials. The high-conductivity alloy core material uses a high-purity metal as the matrix, and the purity of the high-purity metal is not less than 99.99%. During the smelting process, a specific proportion of rare earth elements is added for micro-alloying treatment, and the amount of rare earth elements added accounts for 0.05% to 0.15% of the total mass of the alloy. The rare earth elements include, but are not limited to, cerium, lanthanum, yttrium, etc., which can play a role in capturing residual impurity atoms in the melt. Specifically, the rare earth elements react chemically with harmful impurities such as oxygen, sulfur, lead, and bismuth in the melt to form stable high-melting-point intermetallic compounds. These compounds are removed in subsequent filtration and refining processes, or exist in the form of fine dispersed particles inside the grains, thereby removing harmful impurities from the grain boundaries and significantly reducing the scattering probability of electrons during operation.

[0033] In step 1, the process of constructing the high-conductivity alloy core material employs a vacuum refining process. This vacuum refining is carried out in a vacuum induction furnace, where the vacuum level is adjusted to a preset level of 0.1 Pa to 10 Pa. This high-vacuum environment allows dissolved hydrogen, oxygen, and nitrogen molecules in the melt to escape from the liquid phase, effectively preventing the formation of porosity defects. Simultaneously, an electromagnetic stirring process is used to generate a changing rotating magnetic field, creating controlled convection circulation within the alloy melt. The frequency of the magnetic field is set between 10 Hz and 50 Hz, and the magnetic induction intensity is distributed within the range of 0.05 Tesla to 0.2 Tesla. This controlled convection circulation not only ensures the macroscopic uniformity of the alloy elements but also promotes contact between the deep melt and the vacuum interface, improving degassing efficiency.

[0034] Step 1 further includes introducing a trace nucleating agent during solidification to obtain a uniformly distributed, refined grain structure. The trace nucleating agent has a particle size within a specific range of 10 nm to 500 nm, and its material is selected from borides or carbides with specific lattice constants. The mismatch between the lattice constant of the nucleating agent and the matrix metal is less than 5%, enabling it to provide a large number of non-spontaneous nucleation nuclei in the early stages of solidification. By controlling the cooling rate between 10°C and 50°C per second, the final formed grains exhibit an isotropic equiaxed crystal morphology, with an average grain size controlled between 10 μm and 50 μm. This uniform microstructure significantly improves the skin effect under AC operating conditions. Due to the refined grains, the mean free path of charge carriers within the crystal is optimized, and the current distribution across the conductor cross-section tends to be more stable.

[0035] In the above method, step 1, the optimization of the microstructure of the conductive core material, also involves the precise control of grain boundary energy. The grain refinement process captures dislocations and vacancies that may cause local electric field distortion by increasing the total number of grain boundaries. The refined grain size is distributed within a predetermined narrow range, and this compact microstructure effectively reduces the inherent resistance of the material. In this way, the conductivity of the conductive core material at room temperature reaches between 61.5% and 63.5% of the nominal conductivity of annealed copper.

[0036] In step 2, the high conductivity alloy core material undergoes continuous casting and rolling followed by multi-pass cold drawing. The continuous casting process directly transforms the melt into a continuous billet, with the cooling intensity adjusted in real-time by the circulating water system based on data from an infrared thermometer. By controlling the initial temperature of the billet before entering the mill between 450°C and 520°C, the material is ensured to be in a good plastic state in the hot deformation zone. The multi-pass cold drawing process employs a continuously varying die aperture gradient, with the compression ratio between adjacent passes controlled between 15% and 25% to ensure that the flow stress of the material remains balanced during deformation. The inner cavity of the drawing die adopts a streamlined structure with a specific curvature design. The radius of curvature is dynamically optimized based on the distribution of the drawing force, reducing frictional resistance to prevent microcracks deeper than 5 micrometers from forming on the core material surface.

[0037] In step 2, in-line induction annealing is performed between each pass. This in-line induction annealing utilizes a high-frequency induced current with a frequency of 10 kHz to 30 kHz to rapidly heat the moving core material. The output power of the induction power supply is adjusted proportionally to the square of the core material's linear velocity, causing the material temperature to rapidly rise to the recrystallization temperature range of 350°C to 450°C. Under this instantaneous high temperature, the distortion energy accumulated within the crystal is released through a dynamic recrystallization mechanism. New grains nucleate and grow at the original dislocation density. By precisely controlling the heating time between 0.5 seconds and 2 seconds, the degree of recrystallization can be finely adjusted. This process eliminates work hardening and significantly reduces the dislocation density within the material, enabling the conductive core material to maintain a tensile strength of not less than 160 MPa while achieving an elongation of over 1.5%.

[0038] The rolling process in step 2 also incorporates deformation-induced precipitation technology. By controlling the coupling relationship between deformation and temperature, microalloying elements are precipitated from the solid solution as extremely fine particles with a particle size of less than 50 nanometers. These precipitated phases act as dislocation pinning agents, enhancing the tensile strength of the conductor and reducing lattice distortion due to the precipitation of solute atoms from the matrix, thereby restoring the conductivity of the conductive matrix and achieving a synergistic improvement in mechanical strength and electrical conductivity.

[0039] In step 3, a high-performance modified insulating composite material is prepared. This high-performance modified insulating composite material uses a polyolefin material with high dielectric strength as the polymer matrix resin, and its melt index is between 0.2 g / 10 min and 2.0 g / 10 min. The functionalized nanofiller is surface-treated with a silane coupling agent before addition, and the amount of the silane coupling agent added is 1% to 3% of the mass of the nanofiller. The surface treatment process is carried out under vacuum drying, which forms chemically active functional groups, such as amino, epoxy, or vinyl groups, on the surface of the filler.

[0040] In step 3, the functionalized nanofiller is selected from one or more combinations of layered silicates, nano-silica, or nano-alumina, and its addition amount accounts for 2% to 8% of the matrix resin mass. The filler is dispersed through a multi-stage screw mixing process under a specific temperature control environment of 160°C to 220°C. The multi-stage screw mixer has at least eight independent temperature control zones, with temperature fluctuations in each zone controlled within ±1°C. The high shear force of the screw ensures uniform dispersion of the nanofiller at the molecular level. The introduction of the functionalized nanofiller creates numerous trap energy levels within the material, with depths ranging from 0.8 eV to 1.2 eV. These traps effectively capture free electrons and holes generated during operation, suppressing the accumulation of space charge, thereby reducing the dielectric loss tangent during circuit operation to below 0.0005.

[0041] Step 3 also incorporates a high-efficiency antioxidant and a crosslinking accelerator. The high-efficiency antioxidant comprises a synergistic combination of hindered phenols and phosphites, which scavenge free radicals generated by the thermal decomposition of the material. The crosslinking accelerator is selected from monomers with multiple functional groups, such as triallyl isocyanurate, which acts as a bridge in subsequent crosslinking processes, promoting the transformation of linear polymer chains into a three-dimensional network structure. Furthermore, the modified insulating composite material also contains a specific ratio of thermally conductive reinforcing fillers, such as boron nitride or aluminum nitride, which have highly anisotropic thermal conductivity. During extrusion flow, these fillers are arranged radially in an ordered manner, forming phonon transport channels that increase the transverse thermal conductivity of the insulation layer by 50% to 100%.

[0042] During the preparation process in step 3 above, an ultrasonic dispersion monitoring system is used to sense the particle size distribution in the mixture in real time. An ultrasonic probe is installed at the head of the mixer, and the average particle size is calculated in real time by analyzing the attenuation spectrum and sound velocity changes of the ultrasonic waves in the melt. If the proportion of large agglomerates exceeds a preset threshold, the system automatically increases the screw speed or extends the cycle mixing time to ensure that there are no agglomerates larger than 1 micrometer in diameter, thereby guaranteeing a high degree of consistency in the dielectric constant of the insulating material.

[0043] In step 4, a three-layer co-extrusion coating process is implemented. First, the core material, after drawing and annealing, undergoes surface preheating. This preheating is achieved using a non-contact induction heating device, with the preheating temperature set between 80 and 120 degrees Celsius, aiming to remove physically adsorbed water and volatile organic impurities from the core material surface. The preheated core material then enters a three-layer co-extrusion die with a specific flow channel design. The co-extrusion die has three independent flow channel branches, corresponding to the inner semi-conductive shielding layer, the modified insulation layer, and the outer anti-aging sheath layer, respectively.

[0044] In step 4, the thickness of the inner semiconductive shielding layer is controlled between 0.5 mm and 1.0 mm. By adjusting the structure and amount of carbon black added to the semiconductive material, its volume resistivity is stabilized between 10 ohm·cm and 100 ohm·cm. This layer effectively shields the electric field concentration caused by burrs on the conductor surface, ensuring a uniform distribution of electric field strength within the insulation layer. The modified insulation layer, as the core electrical protection layer, has a thickness determined according to the rated voltage level of the conductor. The outer anti-aging sheath layer contains a high concentration of ultraviolet absorbers, such as benzophenone derivatives, and antifungal agents. Its surface has a micron-level hydrophobic structure formed through a special mold texture transfer technology. The height of the micro-protrusions in the hydrophobic structure is distributed between 5 microns and 20 microns, and the spacing is between 10 microns and 50 microns. This structure gives the static contact angle of the conductor surface greater than 150 degrees, exhibiting excellent self-cleaning ability and anti-icing flashback performance.

[0045] In step 4, the extrusion pressure is maintained within a constant preset pressure range of 20 MPa to 40 MPa. A melt pressure sensor and a speed closed-loop control system installed at the extruder die head compensate for pressure pulsations caused by screw rotation in real time. This precise pressure control ensures that the insulation layer wall thickness deviation is less than 5% of the rated wall thickness, avoiding partial discharge induction factors caused by wall thickness fluctuations. Simultaneously, the high-pressure extrusion environment induces intense intermolecular thermal motion between the preheated core material and the molten material at the interface, forming a molecular-level wetting layer with a thickness of 10 to 30 micrometers, completely eliminating micro-gaps.

[0046] In step 5, controlled online crosslinking and segmented gradient cooling are performed. The controlled online crosslinking is completed within a crosslinking tube filled with a nitrogen protective gas at a pressure of 1.0 MPa to 1.5 MPa. The nitrogen protective gas is circulated through a purification system to ensure an oxygen content below 100 ppm. The crosslinking tube is divided into a heating zone, a constant temperature zone, and a cooling zone. In the heating zone, the ambient temperature is gradually increased from 200 degrees Celsius to 300 degrees Celsius, causing the peroxide crosslinking agent in the insulating material to decompose and release active free radicals. In the constant temperature zone, the temperature is maintained between 280 degrees Celsius and 320 degrees Celsius for 1 to 5 minutes, guiding the polymer chain segments to form a stable network structure, achieving a gel content between 75% and 85%.

[0047] In step 5, the cooling zone employs a segmented gradient cooling method. The cooling logic is as follows: first, primary slow cooling is achieved using high-temperature nitrogen gas at 200°C to 150°C; then, hot water spray cooling at 100°C to 60°C is applied; finally, the product enters a room-temperature circulating water tank. This gradient cooling rate is controlled between 20°C and 40°C per minute. This precise cooling curve guides the polymer chains to slowly align during crystallization, preventing shrinkage stress caused by internal and external temperature differences. After this process, the residual thermal stress inside the finished wire is reduced to below 5 MPa, ensuring dimensional stability during long-term operation.

[0048] The method also includes multi-dimensional performance monitoring of the finished conductor. This performance monitoring includes DC resistance testing, using a 6.5-digit digital multimeter combined with a four-terminal measurement method to verify whether the resistivity of the conductive core material at 20 degrees Celsius is better than the predetermined index. AC withstand voltage testing is conducted on a power frequency high-voltage test bench, applying twice the rated voltage for 5 minutes without breakdown. Partial discharge testing uses a broadband sensor for monitoring; at 1.73 times the rated voltage, the discharge value is no greater than 5 picoctaves. Thermal cycling aging tests simulate the conductor's performance under load fluctuations; after 200 thermal cycles, the rate of change in both mechanical strength and insulation resistance is less than 10%.

[0049] In the physical structure design of the conductive core material, a compact stranding process is employed. By adjusting the pressure of the compaction rollers and the die size of the stranding machine, the metal filling factor is increased from 0.75 in the traditional structure to over 0.90. This compact structure increases the contact area between the individual wires and reduces the contact resistance. Simultaneously, by increasing the metal content, the overall equivalent thermal conductivity of the conductor is improved. When the current carrying capacity is 500 amperes, the surface temperature rise of the conductor is 5 to 8 degrees Celsius lower than that of traditional conductors. Since the resistivity of the metal increases with temperature, the lower operating temperature further reduces Joule losses, achieving energy savings at the macroscopic level.

[0050] Example 2 To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0051] In Embodiment 2, a preparation scheme for a low-loss, energy-saving overhead insulated conductor suitable for ultra-high voltage levels is provided. In step 1, the composition of the high-conductivity alloy core material is adjusted. The base metal is ultra-high purity aluminum with a purity of 99.999%. Scandium is added to the rare earth microalloying elements, and its addition amount is controlled between 0.02% and 0.08% of the total alloy mass. The intermetallic compound formed by scandium and the aluminum matrix has extremely high thermal stability and can strongly pin dislocations. In the refining stage, the vacuum degree of the vacuum induction furnace is reduced to 0.01 Pa to 0.1 Pa, and the refining time is extended to 30 to 60 minutes. The magnetic field of the electromagnetic stirrer adopts a bidirectional alternating mode, switching the rotation direction every 10 seconds to further improve the homogenization of the melt.

[0052] In step 2, the number of passes in the multi-pass cold drawing is set to 12. The compression rate of the first pass is set to 30%, and the compression rate of subsequent passes decreases progressively to 10%. The die lubrication uses a high-pressure forced oil supply system, maintaining the lubricating oil pressure at 0.5 MPa. The frequency of online induction annealing is increased to 50 kHz, utilizing the skin effect to achieve selective and rapid heating of the core material surface. The cooling process after recrystallization annealing is carried out in a sealed chamber filled with dry compressed air, with the cooling rate precisely controlled at 15 degrees Celsius per second by adjusting the airflow. This process results in a nanoscale ultrafine crystalline structure on the core material surface, with a thickness of approximately 50 to 100 micrometers, which can significantly reduce skin effect losses in ultra-high voltage power transmission.

[0053] In step 3, the polymer matrix resin of the high-performance modified insulating composite material is a mixture of high-density polyethylene and low-density polyethylene in a mass ratio of 7:3. The functionalized nanofiller is montmorillonite nanosheets grafted with a silane coupling agent, with a thickness between 1 and 5 nanometers and a radial dimension between 100 and 500 nanometers. The mixing process uses a three-screw mixer, whose shear strength is more than 40% higher than that of a twin-screw mixer. This high-intensity shearing causes the montmorillonite nanosheets to form a highly exfoliated morphology within the polyolefin matrix. These exfoliated nanosheets not only improve the electrical breakdown strength but also construct complex tortuous paths within the material, extending the migration path of charge carriers and thus shortening the space charge decay time by more than 60%.

[0054] In step 4, the parameters of the three-layer co-extrusion process were optimized for ultra-high pressure requirements. Graphene conductive filler was added to the inner semi-conductive shielding layer, with a mass percentage of 2% to 5%. Due to graphene's extremely high aspect ratio, the preset volume resistivity can be achieved with a relatively low filler content, while maintaining the material's flexibility. The thickness of the modified insulation layer was increased to 15 mm to 25 mm, and a three-stage pressure gradient control was adopted during extrusion, with the die pressure smoothly transitioning from 35 MPa to 40 MPa. Fluorocarbon modified resin was introduced into the outer anti-aging sheath layer, which was blended with the polyolefin matrix to form an island structure. This structure gives the sheath layer not only excellent weather resistance, but also a hydrophobic surface structure with lower surface energy, and a critical surface tension of less than 20 mN / m.

[0055] In step 5, controlled online crosslinking employs electron beam irradiation crosslinking as a supplement to thermal crosslinking. After passing through a nitrogen-protected thermal crosslinking tube, the conductor immediately enters the electron beam irradiation area. The accelerating voltage of the electron beam is set between 1.5 MV and 2.5 MV, and the absorbed dose is controlled between 100 kGrey and 150 kGrey. The electron beam can penetrate the thick insulation layer, initiating free radical reactions in deep molecules, ensuring the uniformity of crosslinking in the thick-walled insulated conductor. In the gradient cooling stage, an infrared temperature compensation zone is added, using an infrared lamp array to locally compensate for the surface temperature of the conductor, ensuring that the axial temperature difference of the conductor is less than 2 degrees Celsius.

[0056] In the performance monitoring phase, a scanning test was added to measure the change of dielectric loss tangent with temperature for ultra-high voltage conductors. Within the test range of 30°C to 100°C, the fluctuation range of the loss tangent was less than 0.0002. The partial discharge initiation voltage was tested using the high-frequency pulsed current method, and the initiation voltage value was 1.5 times higher than the rated operating voltage. Furthermore, the interface wetting layer was microscopically characterized using scanning electron microscopy, verifying that the bonding thickness between the metal core and the shielding layer reached 25 micrometers, and that no visible bubbles or delamination were present at the interface.

[0057] Example 3 To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0058] In Example 3, a method for preparing a low-loss, energy-saving overhead insulated conductor suitable for harsh icy and snowy environments is highlighted. In step 1, the preparation of the high-conductivity alloy core material enhances the control of impurity segregation. During the smelting process, in addition to rare earth elements, a trace amount of the intermediate alloy aluminum-titanium-boron is added. The addition amount of aluminum-titanium-boron is 0.2%, which contains a large number of titanium diboride particles. These particles, acting as heterogeneous nucleation cores, can further refine the grain size to 5 to 15 micrometers. The electromagnetic stirring process employs a variable-frequency pulsed magnetic field with a pulse duty cycle of 0.4. This unsteady flow field effectively breaks up growing dendrites and promotes the transformation to equiaxed crystals.

[0059] In step 2, the cooling intensity during continuous casting and rolling is nonlinearly regulated by the circulating water system. The water flow rate is adjusted based on the initial heat release rate to maintain the temperature difference between the core and surface of the billet within 20 degrees Celsius. The die surface during cold drawing is coated with a diamond-like carbon film to further reduce the coefficient of friction. An ultrasonic vibration-assisted module is added to the in-line induction annealing process. By applying 20 kHz mechanical vibration before the core material enters the inductor, the movement and annihilation of dislocations within the crystal are accelerated, allowing the recrystallization process to be fully completed at a lower temperature (approximately 320 degrees Celsius), thus better preserving the microstructure of the material.

[0060] In step 3, high aspect ratio carbon nanotubes are introduced as a synergistic modifier into the high-performance modified insulating composite material. The carbon nanotubes undergo strong acid oxidation treatment, and hydroxyl functional groups are grafted onto their surface; the addition amount is controlled between 0.1% and 0.3%. Although carbon nanotubes are conductive, their uniform dispersion in the insulating matrix at extremely low concentrations, forming deep trap centers rather than a conductive network, significantly enhances the insulating layer's ability to suppress charge accumulation. The mixing process employs supercritical carbon dioxide-assisted technology. Supercritical carbon dioxide at a pressure of 8 MPa is introduced into the mixer. Utilizing its extremely strong dissolving and plasticizing effects, the viscosity of the melt is significantly reduced, allowing the functionalized nanofillers to achieve molecular-level dispersion at lower temperatures, avoiding thermal degradation of the matrix resin at high temperatures.

[0061] In step 4, the three-layer co-extrusion process adds a plasma activation process after the core material surface is preheated. An atmospheric pressure plasma nozzle scans the core material surface, introducing oxygen-containing functional groups and increasing the metal surface energy from 40 millijoules per square meter to over 70 millijoules per square meter. This ensures that the subsequently extruded inner semiconductive shielding layer can bond with the metal core material through stronger covalent bonds. The manufacturing process of the micron-level hydrophobic structure on the surface of the outer anti-aging sheath layer employs a roller embossing method. While the sheath layer is still partially cooled after leaving the co-extrusion die, a pair of cooling rollers with micro / nano structures etched on their surfaces transfer a specific texture to the sheath surface. This texture has a stepped morphology, capable of trapping air to form a stable air cushion layer, maintaining its hydrophobicity even at 95% ambient humidity.

[0062] In step 5, the controlled online crosslinking process employs variable pressure control logic. At the inlet of the crosslinking tube, the pressure is maintained at 1.2 MPa, gradually decreasing to 0.8 MPa as the conductor moves towards the outlet. This pressure gradient matches the density change of the polymer during crosslinking, reducing the likelihood of internal pore formation. The segmented gradient cooling section incorporates a cold air curtain isolation zone to prevent interference from turbulent external airflow on the cooling curve. Low-temperature impact testing at -40 degrees Celsius and anti-ice adhesion testing were added to the finished product monitoring. Experimental results show that the ice adhesion strength on the surface of this conductor is only 15% to 20% of that of traditional conductors, significantly reducing mechanical load and creepage loss under extreme weather conditions.

[0063] In the compact stranding process of the conductive core material, the cross-sectional shape of the monofilaments is pre-treated into a trapezoidal or S-shaped interlocking structure. This irregularly shaped monofilament reduces the porosity to below 3% after stranding. Through this extremely high compaction design, the tensile strength of the conductor is increased by more than 15% compared to conventional conductors of the same cross-section. Simultaneously, due to the extremely low contact thermal resistance between the monofilaments, the radial equivalent thermal conductivity of the entire conductor is increased by an order of magnitude. In actual operation, this structure can evenly distribute and rapidly dissipate the heat generated when current flows through it, resulting in a long-term operating temperature reduction of approximately 10 degrees Celsius for the insulation layer. According to the Arrhenius equation, this is equivalent to extending the service life of the conductor by more than double.

[0064] In the formulation of the modified insulating composite material, an anisotropic thermally conductive sheet is also added. These sheets are oriented and aligned in the strong shear field of screw extrusion. Through the control of this micro-alignment, efficient radial heat transfer within the insulation layer is achieved. Simultaneously, the online ultrasonic dispersion monitoring system incorporates a multi-channel echo analysis algorithm, capable of distinguishing between macroscopic packing aggregation and localized concentration fluctuations, and accordingly performing millisecond-level closed-loop compensation for the pressure in the mixing zone and the screw back pressure.

[0065] In the aforementioned three-layer co-extrusion coating process, the inner wall of the co-extrusion die's runner is fluorinated to reduce the wall slip resistance of the melt. This design eliminates stress concentration in the melt at the die exit, resulting in a clear interface and no material mixing in the extruded three-layer structure. A very small amount of hindered amine light stabilizer is also added to the material of the inner semiconductive shielding layer, which works synergistically with the UV absorber in the sheath layer to protect the semiconductive layer from the small amount of UV light that may be transmitted.

[0066] In the aforementioned controlled online crosslinking process, the temperature control of the crosslinking tube employs a predictive control algorithm based on an expert system. By integrating real-time rheological data of the material, extrusion speed, and ambient temperature changes, the algorithm can predictively adjust the power distribution of the electric heater, ensuring that temperature fluctuations in the isothermal zone are controlled within ±0.5 degrees Celsius. This extreme temperature uniformity ensures the density and uniformity of the polymer network structure, avoiding the generation of local weaknesses.

[0067] The performance monitoring of the finished conductor also included a comprehensive simulation of the line's energy-saving effect. Rated current was applied to the simulated line, and the temperature distribution along the entire conductor segment was monitored using an infrared imager. The data showed that the conductor of this invention exhibits an extremely uniform temperature field during operation, with no localized hot spots. Combined with DC resistance measurement data, the overall energy loss was reduced by 12% to 18% compared to the benchmark conductor. In the partial discharge test, even at the extreme operating temperature of 120 degrees Celsius, the discharge level remained at an extremely low level of less than 5 picocoos, fully demonstrating its excellent energy-saving characteristics and long-term operational reliability.

[0068] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a low-loss, energy-saving overhead insulated conductor, characterized in that, Includes the following steps: Step 1: Construct a high conductivity alloy core material. The raw materials are chemically proportioned. The melt is degassed and impurities are removed through vacuum refining and electromagnetic stirring. A trace nucleating agent is introduced during solidification to obtain a uniformly distributed and refined grain structure. Step 2: The high conductivity alloy core material is subjected to continuous casting and rolling and multi-pass cold drawing, and online induction annealing is carried out between each pass to eliminate work hardening and reduce the dislocation density inside the material by utilizing the dynamic recrystallization mechanism. Step 3: Prepare high-performance modified insulating composite material by multi-stage screw mixing of polymer matrix resin, functionalized nanofiller, high-efficiency antioxidant and crosslinking accelerator under temperature control to achieve dispersion of filler at the molecular level. Step four: Implement a three-layer co-extrusion coating process to sequentially form an inner semi-conductive shielding layer, a modified insulation layer, and an outer anti-aging sheath layer on the core material after surface preheating treatment, forming an interlayer bonding structure. Step 5 involves controlled online crosslinking and segmented gradient cooling. By adjusting the pressure and temperature distribution in the crosslinking chamber, the polymer chain segments are guided to form a network structure, and residual thermal stress between layers is eliminated.

2. The method for preparing a low-loss, energy-saving overhead insulated conductor according to claim 1, characterized in that, The process of constructing the high conductivity alloy core material in step one includes: High-purity metals are provided as the base material, and rare earth elements in a preset proportion are added during the smelting process for micro-alloying treatment; The rare earth elements are guided to capture residual impurity atoms in the melt, and through the chemical reaction between the rare earth elements and the harmful impurities in the melt, a stable high-melting-point intermetallic compound is formed. The harmful impurities are removed from the grain boundaries to reduce the probability of electron scattering during operation; An electromagnetic stirring device is used to generate a changing rotating magnetic field, which creates a controlled convection circulation inside the melt, ensuring the macroscopic uniformity of alloying elements and promoting the escape of gases.

3. The method for preparing a low-loss, energy-saving overhead insulated conductor according to claim 1, characterized in that, The process of obtaining a uniformly distributed refined grain structure in step one includes: A trace nucleating agent with a particle size within a first preset particle size range is selected, and the lattice constant of the trace nucleating agent matches the lattice constant of the matrix metal. In the early stage of solidification, the trace nucleating agent provides non-spontaneous nucleation nuclei, and the cooling rate is controlled within the first preset cooling rate range, so that the final formed grains exhibit an isotropic equiaxed crystal morphology. The grain refinement process increases the total number of grain boundaries. By utilizing the defects caused by grain boundary trapping leading to local electric field distortion, the size of the refined grains is controlled within a preset size distribution range. This improves the skin effect under AC operation and makes the current distribution on the conductor cross-section more stable.

4. The method for preparing a low-loss, energy-saving overhead insulated conductor according to claim 1, characterized in that, The continuous casting and rolling and multi-pass cold drawing process in step two includes: The cooling intensity during the continuous casting and rolling process is adjusted by using a circulating water system based on real-time temperature data fed back by an infrared thermometer, so as to control the initial temperature of the billet before entering the rolling mill to be within the first preset temperature range. In the multi-pass cold drawing process, a continuously varying die aperture gradient is used to control the compression ratio between adjacent passes within a first preset compression ratio range, so as to ensure that the flow stress of the material is in a balanced state during the deformation process. Drawing is performed using a drawing die with a streamlined internal structure, which reduces frictional resistance and suppresses the formation of micro-cracks on the surface of the core material.

5. The method for preparing a low-loss, energy-saving overhead insulated conductor according to claim 1, characterized in that, The online induction annealing process in step two includes: The core material in motion is rapidly heated by using a high-frequency induced current. By adjusting the power of the induced power supply and the linear velocity of the core material, the temperature of the core material is raised to above the recrystallization temperature. The distortion energy inside the crystal is released by the dynamic recrystallization mechanism, so that the new grains nucleate and grow at the defects. By adjusting the degree of recrystallization, the core material can maintain the preset mechanical strength while having the preset ductility. Deformation-induced precipitation technology is used to guide microalloying elements to precipitate from the solid solution in the form of precipitated phases. The precipitated phases pin dislocations and reduce the solid solubility of solute atoms inside the matrix to restore the electrical conductivity of the matrix.

6. The method for preparing a low-loss, energy-saving overhead insulated conductor according to claim 1, characterized in that, The process of preparing the high-performance modified insulating composite material in step three includes: A polyolefin material with a preset dielectric strength is selected as the polymer matrix resin; The functionalized nanofiller is subjected to surface modification treatment to form chemically active functional groups on the surface of the functionalized nanofiller, which guides the functional groups to chemically bond with the molecular chains of the polymer matrix resin. The functionalized nanofillers are used to form trap energy levels inside the high-performance modified insulating composite material. Free electrons and holes are captured through the trap energy levels to suppress charge accumulation and reduce dielectric loss during line operation. A high-efficiency antioxidant and a crosslinking promoter are added to the high-performance modified insulating composite material, and the high-efficiency antioxidant is used to remove free radicals generated by thermal decomposition.

7. The method for preparing a low-loss, energy-saving overhead insulated conductor according to claim 1, characterized in that, The multi-stage screw compounding process in step three includes: In a screw mixer with multiple independent temperature control zones, the temperature fluctuation range of each zone is controlled within a preset temperature difference threshold. The functionalized nanofiller and the polymer matrix resin are mixed at the molecular level through the shearing action of the screw. The particle size distribution in the mixture is sensed in real time by using an ultrasonic dispersion monitoring system. The average particle size is calculated in real time by analyzing the attenuation spectrum and sound velocity changes of ultrasonic waves in the melt. Based on the calculated average particle size, the screw speed or the cycle mixing time is automatically adjusted to eliminate large agglomerates.

8. The method for preparing a low-loss, energy-saving overhead insulated conductor according to claim 1, characterized in that, The three-layer co-extrusion coating process in step four includes: The core material is preheated using a non-contact heating device to remove moisture and volatile impurities from its surface by setting a preheating temperature. The surface of the preheated core material is scanned using atmospheric pressure plasma to enhance the surface energy of the core material and introduce oxygen-containing functional groups. A co-extrusion die with a specific flow channel design is used to guide the inner semiconductive shielding layer, the modified insulating layer, and the outer anti-aging sheath layer to be at the same flow rate and pressure state before leaving the die orifice.

9. The method for preparing a low-loss, energy-saving overhead insulated conductor according to claim 1, characterized in that, The process of forming the interlayer bonding structure in step four also includes: Adjust the volume resistivity of the inner semiconductive shielding layer to shield the electric field concentration phenomenon on the surface of the core material; UV absorbers and antifungal agents are added to the outer anti-aging sheath layer, and a micron-scale hydrophobic structure is formed on the surface of the outer anti-aging sheath layer using mold surface texture transfer technology. By utilizing a pressure sensor and a speed closed-loop control system at the extruder die head, pressure pulsation caused by screw rotation is eliminated, and the extrusion pressure is maintained within a preset pressure range to ensure the uniformity of the wall thickness of the modified insulation layer. By utilizing the intermolecular thermal motion between the preheated core material and the molten extruded material, a molecular-level wetting layer is formed between the metal interface and the inner semiconductive shielding layer. The controlled online crosslinking and segmented gradient cooling process in step five includes: Online cross-linking is performed in a cross-linking tube filled with a protective gas at a preset pressure, and the temperature distribution inside the cross-linking tube is divided into a heating zone, a constant temperature zone, and a cooling zone. In the heating zone, the crosslinking agent in the modified insulation layer is decomposed to release active atoms, and in the constant temperature zone, the polymer chain segments are guided to undergo a crosslinking reaction and form a three-dimensional spatial network structure. The cooling zone employs a segmented gradient cooling logic, first undergoing primary slow cooling with high-temperature nitrogen, followed by hot water spray cooling, and finally entering a normal-temperature circulating water tank. By controlling the cooling rate at each stage, shrinkage stress is prevented from being generated in the conductor.

10. A low-loss, energy-saving overhead insulated conductor, characterized in that, Prepared using the method described in any one of claims 1-9.

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