A 10kV-35kV medium-high voltage rare earth aluminum alloy power cable with a core-shell structure and a preparation method thereof

Abstract

The application discloses a 10kV-35kV medium and high voltage core-shell structure rare earth aluminum alloy power cable and a preparation method thereof, and belongs to the technical field of power transmission and medium and high voltage cable. The cable comprises a core-shell structure rare earth aluminum alloy conductor, a conductor shielding layer, a crosslinked polyethylene insulation layer, an insulation shielding layer, a metal shielding layer and a sheath layer; the conductor is composed of the following components: Ce 0.15-0.20%, Er 0.08-0.12%, Yb 0.05-0.08%, Zr 0.15-0.18%, Fe 0.10-0.13%, and the balance is Al. The microstructure comprises a core-shell structure nano precipitated phase of a rare earth-rich inner core and a zirconium-rich outer shell, the tensile strength of the conductor is greater than or equal to 182 MPa, the conductivity is greater than or equal to 61.5% IACS, the 300 DEG C strength residual rate is greater than or equal to 92%, and the creep resistance is better than that of a copper conductor. The application optimizes the voltage distribution electric field through a three-layer co-extrusion shielding structure, the local discharge amount is less than or equal to 5 pC under 1.73U0, and the requirement of GB / T 31840-2025 is met. The comprehensive cost of the cable is reduced by more than 50% compared with that of a copper core medium and high voltage cable, the weight is reduced by more than 55%, and the cable is suitable for medium and high voltage power transmission and distribution systems such as urban power distribution network reconstruction, park high voltage power distribution and 35kV urban main ring network.

Description

Technical Field

[0001] This invention belongs to the field of power transmission and medium- and high-voltage cable technology, specifically relating to a core-shell structure rare earth aluminum alloy power cable suitable for medium- and high-voltage (10kV-35kV) power transmission and distribution systems such as urban power distribution network renovation, industrial park high-voltage power distribution, and new energy power station collection lines, and its preparation method. Background Technology

[0002] With the deepening of the national three-year action plan for upgrading and transforming the power distribution network, the demand for replacement of existing medium and high voltage cables and for new installations is enormous. According to industry data, the annual output value of the medium and low voltage aluminum alloy cable industry has reached tens of billions of yuan. On February 1, 2026, the GB / T 31840-2025 series of national standards officially came into effect. Among them, GB / T 31840.2-2025 applies to 6kV~30kV medium voltage aluminum alloy cables, and GB / T 31840.3-2025 applies to 35kV aluminum alloy core extruded insulated power cables. China Southern Power Grid has taken the lead in achieving mass engineering application of 10kV aluminum alloy core cables in the power distribution network field.

[0003] The main technical problems currently existing in 10kV-35kV medium and high voltage cables are as follows:

[0004] Firstly, medium and high voltage cables have long used copper conductors almost exclusively, resulting in high costs and resource consumption. These cables are the backbone of urban power distribution network upgrades and industrial park power distribution, requiring a massive amount of copper. Aluminum core cables weigh only 40% of copper core cables, and their price for the same transmission capacity is about a quarter of that of copper core cables. However, existing aluminum alloy cable products are mainly concentrated in the low-voltage (1kV and below) field. The technological maturity and product variety of 10kV-35kV medium and high voltage aluminum alloy cables are still insufficient, and large-scale substitution has not yet been achieved.

[0005] Secondly, the use of aluminum alloy conductors in medium and high voltage cables poses a risk of partial discharge. The requirements for insulation systems and shielding structures in medium and high voltage cables are far higher than those for low-voltage cables. As a crucial structure for creating a uniform electric field and limiting partial discharge within the cable, the shielding layer's thickness, uniformity, and dimensional accuracy are critical. If these conditions are not met, partial discharge can easily occur at points of electric field concentration, leading to aging and breakdown of the insulation material. Existing aluminum alloy cable products largely adopt the shielding structure design of copper core cables, lacking optimized designs for the characteristics of aluminum alloy conductors (such as differences in surface roughness and coefficient of expansion).

[0006] Third, there are technical bottlenecks in the application of existing rare-earth aluminum alloy cables in medium and high voltage applications. Patents have been published for fire-resistant rare-earth aluminum alloy power cables for 35kV and below (e.g., CN120824069B), which use rare-earth aluminum alloy conductors combined with a multi-layer flame-retardant and fire-resistant structure. Other patents disclose rare-earth aluminum alloy cable materials containing 0.3-0.6wt% Er and 0.1-0.3wt% Yb. However, none of these solutions address the strengthening mechanism of core-shell structured nano-precipitates, nor do they systematically design for voltage equalization shielding and partial discharge suppression in medium and high voltage cables, and they do not extend the core-shell structure to urban trunk ring network scenarios at the 35kV voltage level.

[0007] Fourth, while the standard system for medium and high voltage aluminum alloy cables is becoming increasingly comprehensive, the supply of high-performance products is insufficient. GB / T31840.3-2025 has clearly specified the material, structure, dimensions, and testing requirements for 35kV rated voltage aluminum alloy core extruded insulated power cables. High-performance medium and high voltage aluminum alloy cables that meet the new national standard have broad market prospects. However, existing products still cannot fully meet the reliability requirements of power grid companies for medium and high voltage trunk lines in terms of conductor strength (usually ≤160MPa), conductivity (usually ≤60%IACS), and partial discharge control.

[0008] Therefore, how to optimize the voltage-equalizing shielding structure of medium and high voltage cables to effectively suppress partial discharge (≤5pC) while ensuring high conductivity (≥61.5% IACS) and high strength (≥182MPa), and how to extend the core-shell structure rare earth aluminum alloy technology from the low voltage field to the 10kV-35kV medium and high voltage field, and develop medium and high voltage aluminum alloy power cables suitable for urban distribution network transformation and backbone ring networks, remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0009] (I) Purpose of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a 10kV-35kV medium-high voltage core-shell structure rare earth aluminum alloy power cable and its preparation method. This cable uses a core-shell structure rare earth aluminum alloy conductor, combined with an optimized voltage equalization shielding structure and insulation system design. While achieving high strength, high conductivity, lightweight, and low cost, it meets the stringent requirements of medium-high voltage cables for electric field uniformity, partial discharge suppression (≤5pC), and long-term operational reliability, filling the technological gap in the application of core-shell structure rare earth aluminum alloys in medium-high voltage urban backbone ring networks.

[0011] (II) Technical Solution

[0012] 1. Cable Structure

[0013] A 10kV-35kV medium-high voltage core-shell structure rare earth aluminum alloy power cable, characterized in that it comprises:

[0014] The cable core 1 is made of at least one core-shell structure rare earth aluminum alloy conductor; a conductor shielding layer 2 disposed outside the cable core; a cross-linked polyethylene insulation layer 3 disposed outside the conductor shielding layer; an insulation shielding layer 4 disposed outside the insulation layer; a metal shielding layer 5 disposed outside the insulation shielding layer; and an outermost sheath layer 6.

[0015] Preferably, the rated voltage of the cable is 10kV to 35kV, and it is suitable for medium and high voltage power transmission and distribution systems such as urban power distribution network renovation, high voltage power distribution in industrial parks, and power collection lines for new energy power plants.

[0016] Preferably, the cable core is made of multiple core-shell structure rare earth aluminum alloy monofilaments twisted together, with the twisting pitch ratio controlled at 10 to 14 times.

[0017] Furthermore, the cable meets all of the following technical requirements:

[0018] Conductor conductivity: ≥61.5% IACS;

[0019] Conductor tensile strength: ≥182MPa;

[0020] Conductor elongation: ≥22%;

[0021] Partial discharge quantity: ≤5pC at 1.73U0 (meets the requirements of GB / T 31840-2025);

[0022] Insulation withstand voltage: withstands 2.5U0 AC voltage for 30 minutes without breakdown;

[0023] Conductor operating temperature: Long-term operating temperature ≥90℃, short-circuit temperature ≥250℃;

[0024] Service life: more than 10 years longer than traditional copper core cables.

[0025] 2. Conductor materials

[0026] The core-shell structured rare-earth aluminum alloy conductor is characterized by comprising the following components by mass percentage:

[0027] Cerium (Ce): 0.15–0.20%

[0028] Erbium (Er): 0.08–0.12%

[0029] Ytterbium (Yb): 0.05–0.08%

[0030] Zirconium (Zr): 0.15–0.18%

[0031] Iron (Fe): 0.10–0.13%

[0032] The balance is aluminum (Al) and unavoidable impurities.

[0033] Furthermore, the microstructure of the conductor includes a core-shell structured nanoprecipitated phase and a nanoscale dispersed phase:

[0034] The core-shell structured nanoprecipitate is an Al3(RE,Zr) composite nanoprecipitate, which contains a rare earth element-rich core (Ce, Er, Yb) and a Zr-rich shell. The sum of the atomic concentrations of rare earth elements in the core accounts for more than 90% of the total number of atoms in the core of the precipitate, and the atomic concentration of Zr in the shell accounts for more than 85% of the total number of atoms in the shell of the precipitate.

[0035] The nanoscale dispersed phase is nanoscale Al that is encapsulated or pinned by the core-shell structured nanoscale precipitates. 13 The Fe4 dispersed phase has an equivalent spherical average diameter of no more than 50 nanometers.

[0036] Furthermore, the conductor has a tensile strength ≥182MPa, conductivity ≥61.5%IACS, elongation ≥22%, strength retention at 300℃ ≥92%, and creep deformation 40% less than that of copper conductors.

[0037] 3. Conductor shielding layer

[0038] The conductor shielding layer is disposed outside the cable core to uniformize the electric field on the conductor surface, eliminate the electric field concentration caused by surface unevenness generated by conductor stranding, and prevent partial discharge.

[0039] Preferably, the conductor shielding layer is a semi-conductive cross-linked polyethylene material, tightly extruded onto the conductor, and cross-linked synchronously with the insulation layer.

[0040] Preferably, the thickness of the conductor shielding layer is 0.6 to 1.2 mm, and the volume resistivity is ≤100 Ω·m.

[0041] 4. Cross-linked polyethylene insulation layer

[0042] The cross-linked polyethylene insulation layer is placed outside the conductor shielding layer and is the core insulation structure of medium and high voltage cables, maintaining excellent electrical insulation performance at voltage levels of 10kV to 35kV.

[0043] Preferably, the thickness of the cross-linked polyethylene insulation layer is determined according to the rated voltage: the insulation layer thickness is ≥3.4mm for 10kV systems and ≥10.5mm for 35kV systems.

[0044] Furthermore, the cross-linked polyethylene insulation layer meets all the requirements of GB / T 31840—2025 for 35kV cable insulation materials.

[0045] 5. Insulating shielding layer

[0046] The insulating shielding layer is disposed outside the cross-linked polyethylene insulating layer to uniformly distribute the electric field on the surface of the insulating layer and eliminate the concentration of the interface electric field between the insulating layer and the metal shielding layer.

[0047] Preferably, the insulating shielding layer is a semi-conductive cross-linked polyethylene material, which is cross-linked synchronously with the insulating layer and can be peeled off or not peeled off.

[0048] Preferably, the thickness of the insulating shielding layer is 0.6 to 1.2 mm, and the volume resistivity is ≤100 Ω·m.

[0049] 6. Metal shielding layer

[0050] The metal shielding layer is disposed outside the insulating shielding layer and is used to carry the fault current when the system is grounded, while also serving as an electromagnetic shielding layer to suppress external electromagnetic interference.

[0051] Preferably, the metal shielding layer is a copper strip wrapped shielding layer or a copper wire braided shielding layer.

[0052] Preferably, the cross-section of the metal shielding layer meets the thermal stability requirements under a single-phase ground fault in the system.

[0053] 7. Sheath layer

[0054] The sheath layer is placed on the outermost layer of the cable to protect the internal structure of the cable and prevent mechanical damage and environmental corrosion.

[0055] Preferably, the sheath layer is a polyvinyl chloride (PVC) sheath, a polyethylene (PE) sheath, or a low-smoke halogen-free flame-retardant polyolefin (LSZH) sheath.

[0056] Furthermore, the thickness of the sheath layer is determined according to the cable specifications; for 35kV systems, it is generally ≥3.0mm.

[0057] 8. Preparation method

[0058] A method for preparing the above-mentioned 10kV-35kV medium-high voltage core-shell structure rare earth aluminum alloy power cable is characterized by comprising two stages: conductor material preparation and cable forming.

[0059] (I) Conductor Material Preparation Stage

[0060] Step 1, Melting and Casting: Prepare raw materials according to the stated composition ratio. The purity of the pure Al used is ≥99.99%, and the purity of the intermediate alloy is ≥99.5%. Melt and cast the raw materials into ingots under argon protection.

[0061] Step 2, Differentiated two-stage homogenization treatment: The ingot is subjected to the first stage homogenization treatment by heating to 420-425℃ and holding for 4.5-5.5 hours; then the second stage homogenization treatment is performed by heating to 540-545℃ and holding for 8-10 hours, and then air-cooled after being removed from the furnace.

[0062] Step 3, hot deformation processing: The homogenized ingot is heated to 460-500℃ and hot extruded or hot rolled to produce wire rod.

[0063] Step 4, Solution treatment and aging treatment: The wire blank is solution treated by heating to 560-565℃ and holding for 1.5-2.0 hours, then water quenched (cooling rate ≥80℃ / min); then aging treatment is performed by heating to 242-248℃ and holding for 6.5-7.5 hours.

[0064] Step 5, Annealing treatment: Anneal the aged wire by heating it to 310-330℃ and holding it for 2.0-3.0 hours, then cooling it in the furnace;

[0065] Step 6, cold working: The annealed wire is cold drawn to obtain the core-shell structure rare earth aluminum alloy monofilament of the required specifications.

[0066] (II) Cable Forming Stage

[0067] Step 7, Stranding: Strand multiple core-shell structure rare earth aluminum alloy monofilaments into a cable core at a stranding pitch ratio of 10 to 14, with a compression coefficient ≥0.92;

[0068] Step 8, conductor shielding extrusion: a semi-conductive cross-linked polyethylene conductor shielding layer is extruded onto the outside of the cable core;

[0069] Step 9, Insulation layer extrusion: Extruding a cross-linked polyethylene insulation layer over the conductor shielding layer;

[0070] Step 10, Extrusion of the insulating shielding layer: Extruding a semi-conductive cross-linked polyethylene insulating shielding layer (three-layer co-extrusion) over the insulating layer;

[0071] Step 11, Metal shielding layer wrapping: Wrap a copper strip or braided copper wire metal shielding layer around the insulating shielding layer;

[0072] Step 12, Sheath extrusion: Extruding a sheath layer over the metal shielding layer;

[0073] Step 13, Performance Testing: Perform cable performance testing according to GB / T 31840-2025, including partial discharge test (discharge amount ≤5pC at 1.73U0), power frequency withstand voltage test, etc.

[0074] Step 14, winding and packaging: winding and packaging the qualified cables.

[0075] (III) Beneficial Effects

[0076] Compared with the prior art, the present invention has the following significant advantages:

[0077] 1. Filling the gap in medium and high voltage core-shell structure rare earth aluminum alloy cable technology: This invention is the first to extend the core-shell structure rare earth aluminum alloy technology from the low voltage field to the 10kV-35kV medium and high voltage field, realizing the breakthrough application of core-shell structure in medium and high voltage urban trunk ring network cables.

[0078] 2. Excellent overall conductor performance: The core-shell structure rare-earth aluminum alloy conductor of this invention has a tensile strength ≥182MPa, conductivity ≥61.5% IACS, and strength retention rate ≥92% at 300℃. Compared with traditional electrical aluminum (tensile strength 120MPa, conductivity 61.0% IACS), the tensile strength is increased by more than 50%; compared with existing rare-earth aluminum alloys (tensile strength approximately 160MPa), the tensile strength is increased by more than 14%. The weight is only 30% of that of copper conductors, and the overall cost is reduced by more than 50% compared to copper cables.

[0079] 3. Precise Partial Discharge Control: This invention utilizes an optimized three-layer co-extruded shielding structure (conductor shielding layer + insulation layer + insulation shielding layer) to effectively and uniformly distribute the electric field, eliminating electric field concentration at the conductor stranding surface and the insulation layer interface. The finished cable exhibits a partial discharge of ≤5pC at 1.73U0, meeting the stringent requirements of GB / T 31840—2025 for medium and high voltage cables.

[0080] 4. Fully compliant with national standards: The cable structure, materials, and test methods of this invention comply with the requirements of GB / T31840.2-2025 (6kV~30kV medium voltage) and GB / T 31840.3-2025 (35kV), and can be directly applied to the power distribution network renovation projects of State Grid and Southern Power Grid.

[0081] 5. Superior creep resistance: The core-shell structure nano-precipitates effectively pin dislocations, resulting in 40% less creep deformation than copper conductors. This makes the connection points more reliable in long-term operation and extends the service life by more than 10 years compared to traditional copper core cables.

[0082] 6. Broad Market Prospects: China Southern Power Grid has taken the lead in achieving mass engineering application of 10kV aluminum alloy core cables. With the ongoing national three-year action plan for power distribution network upgrading and transformation, there is a huge potential for replacing existing medium and high voltage cables. The cable of this invention is suitable for urban power distribution network transformation, high-voltage power distribution in industrial parks, transformer substation incoming and outgoing lines, and 10kV-35kV municipal underground pipelines, among other scenarios.

[0083] 7. Aligns with the national strategy of "replacing copper with aluminum": Aluminum core cables weigh only 40% of copper core cables, and their price is about one-quarter of that of copper core cables for the same transmission capacity. This invention can significantly reduce the construction cost of medium and high voltage cables and alleviate the pressure of copper resource shortages. Attached Figure Description

[0084] Figure 1 This is a schematic diagram of the cross-sectional structure of a 135kV medium-high voltage power cable according to Embodiment 1 of the present invention. In the figure: 1-core-shell structure rare earth aluminum alloy conductor; 2-conductor shielding layer; 3-crosslinked polyethylene insulation layer; 4-insulation shielding layer; 5-metallic shielding layer; 6-sheath layer.

[0085] Figure 2 This is a transmission electron microscope (TEM) image of the core-shell structured rare-earth aluminum alloy conductor of Example 1 of the present invention, showing the core-shell structured nano-precipitates. In the image: 1-Rare-earth-rich core (Ce / Er / Yb ≥ 90%); 2-Zr-rich outer shell (Zr ≥ 85%); 3-Al 13 Fe4 dispersed phase (≤50nm); 4-Al matrix. Scale bar is 50nm.

[0086] Figure 3 The figure shows the partial discharge test results of Embodiment 1 of the present invention (discharge amount ≤ 5pC at 1.73U0). Detailed Implementation

[0087] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be described in further detail below with reference to the accompanying drawings and embodiments. However, the following embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0088] Test method description:

[0089] The performance tests of the embodiments and comparative examples of this invention were all conducted in accordance with the following standards:

[0090] Tensile strength: Tested according to GB / T 228.1-2021 "Metallic materials, tensile testing - Part 1: Test method at room temperature";

[0091] Conductivity: Tested according to GB / T 351-2019 "Methods for Measurement of Resistivity of Metallic Materials";

[0092] Conductor elongation: Tested according to GB / T 228.1-2021;

[0093] High-temperature strength residual rate: tested according to GB / T 20957.1-2007 "High-Temperature Tensile Test Method";

[0094] Partial discharge test: Performed according to GB / T 31840-2025 (discharge quantity measured at 1.73U0, ≤5pC);

[0095] Power frequency withstand voltage test: conducted according to GB / T 31840-2025 (2.5U0 AC voltage held for 30 minutes without breakdown);

[0096] Insulation resistance measurement: Performed according to GB / T 31840-2025;

[0097] Creep resistance: Tested according to GB / T 2039-2012 "Metallic materials uniaxial tensile creep test method".

[0098] Raw material description:

[0099] The purity of the raw materials used in the embodiments of the present invention is as follows:

[0100] Pure Al: Purity ≥ 99.99%;

[0101] Al-10%Ce, Al-5%Er, Al-5%Yb, Al-4%Zr, and Al-10%Fe master alloys: all with a purity ≥99.5%.

[0102] Core-shell structure characterization methods:

[0103] In this embodiment of the invention, the microstructure and elemental distribution of the core-shell structured nanoprecipitates were characterized using transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDS), in accordance with GB / T 47182-2026 "Microbeam analysis and analytical electron microscopy for measuring the shell wall thickness of core-shell particles".

[0104] Example 1 (35kV medium and high voltage power cable, suitable for urban main ring network)

[0105] 1. Preparation of core-shell structured rare earth aluminum alloy conductors

[0106] 1.1 Batching: Take pure Al (purity ≥99.99%), Al-10%Ce (purity ≥99.5%), Al-5%Er (purity ≥99.5%), Al-5%Yb (purity ≥99.5%), Al-4%Zr (purity ≥99.5%), and Al-10%Fe (purity ≥99.5%) master alloys and mix them according to the final composition of Ce 0.18%, Er 0.10%, Yb 0.06%, Zr 0.16%, Fe 0.12%, and the balance Al.

[0107] 1.2 Melting and casting: Melting is carried out at 750℃ under argon protection, and after being stirred evenly, it is cast into ingots.

[0108] 1.3 Differentiated two-stage homogenization: The ingot is placed in a homogenization furnace, first held at 423℃ for 5.0 hours, then heated to 542℃ and held for 9.0 hours, and then removed from the furnace and air-cooled.

[0109] 1.4 Hot Deformation: The homogenized ingot is heated to 480℃ and hot extruded to form... Wire rod.

[0110] 1.5 Solution treatment and aging: The wire blank was solution treated at 562℃ for 1.8 hours and then water quenched (cooling rate ≥80℃ / min); then aged at 245℃ for 7.0 hours.

[0111] 1.6 Annealing treatment: The aged wire is kept at 320℃ for 2.5 hours and then cooled to room temperature in the furnace.

[0112] 1.7 Cold working: Cold drawing the annealed wire to... Core-shell structured rare earth aluminum alloy monofilament.

[0113] 2. Cable forming (35kV level)

[0114] 2.1 Twisting: Twisting 37 strands The core is made of rare-earth aluminum alloy monofilaments with a core-shell structure, twisted together at a pitch ratio of 12 to form the cable core, with a compression factor ≥0.92 and a nominal cross-section of 95mm². 2 .

[0115] 2.2 Conductor shielding extrusion: A semi-conductive cross-linked polyethylene conductor shielding layer with a thickness of 1.0 mm is extruded onto the outside of the cable core.

[0116] 2.3 Insulation layer extrusion: A cross-linked polyethylene insulation layer with a thickness of 10.5 mm is extruded over the conductor shielding layer (meeting the requirements of a 35kV system).

[0117] 2.4 Extrusion of insulating shielding layer: A semi-conductive cross-linked polyethylene insulating shielding layer with a thickness of 1.0 mm is extruded on the outside of the insulating layer (three-layer co-extrusion process).

[0118] 2.5 Metal shielding layer wrapping: A copper strip metal shielding layer is wrapped around the outside of the insulating shielding layer.

[0119] 2.6 Sheath extrusion: A polyethylene (PE) sheath layer with a thickness of 3.0 mm is extruded over the metal shielding layer.

[0120] 2.7 Cooling and winding: The formed cable is cooled by passing it through a cooling water tank and then wound up and packaged.

[0121] 3. Performance Testing

[0122] 3.1 Conductor properties: The obtained core-shell structure rare earth aluminum alloy monofilament was tested and found to have a tensile strength of 184 MPa, a conductivity of 61.6% IACS, an elongation of 23.2%, and a strength retention rate of 92.8% at 300℃ / 1h.

[0123] 3.2 Creep resistance: Tests show that the creep deformation of the conductor of this invention is about 40% smaller than that of copper conductor.

[0124] 3.3 Partial discharge test: The partial discharge test (at 1.73U0) was conducted according to GB / T 31840-2025. The discharge quantity was 3.8pC, ≤5pC, which meets the standard requirements.

[0125] 3.4 Power frequency withstand voltage test: Hold at 2.5U0 AC voltage for 30 minutes. If the insulation does not break down, the test is passed.

[0126] 3.5 Insulation resistance measurement: The insulation resistance value meets the requirements of GB / T 31840-2025.

[0127] 3.6 Overall Performance: The overall weight of the cable is reduced by approximately 55% compared to copper core medium- and high-voltage cables, and the overall cost is reduced by approximately 52%. It is suitable for 35kV main ring networks in urban distribution network upgrades.

[0128] Example 2 (10kV medium-voltage power cable, suitable for urban power distribution network renovation)

[0129] 1. Preparation of core-shell structured rare earth aluminum alloy conductors

[0130] 1.1 Ingredients: The ingredients were prepared according to the final composition of Ce 0.15%, Er 0.12%, Yb 0.05%, Zr 0.17%, Fe 0.11%, with the balance Al. The purity and source of the raw materials were the same as in Example 1.

[0131] 1.2 Melting and casting: Same as in Example 1.

[0132] 1.3 Differentiated two-stage homogenization: heat at 421℃ for 5.5 hours, then heat at 541℃ for 8.5 hours.

[0133] 1.4 Thermal deformation: Same as in Example 1.

[0134] 1.5 Solution treatment and aging: Solution treatment at 561℃ for 1.5 hours followed by water quenching; aging treatment at 243℃ for 7.2 hours.

[0135] 1.6 Annealing treatment: Hold at 315℃ for 2.8 hours, then cool with the furnace.

[0136] 1.7 Cold working: Cold drawing to Core-shell structured rare earth aluminum alloy monofilament.

[0137] 2. Cable forming (10kV level)

[0138] 2.1 Twisting: Twisting 19 strands The core is made of rare-earth aluminum alloy monofilaments with a core-shell structure, twisted together at a pitch ratio of 12 to form the cable core, with a compression factor ≥0.92 and a nominal cross-section of 35mm².2 .

[0139] 2.2 Extrusion of conductor shielding layer: Extrusion of semi-conductive cross-linked polyethylene conductor shielding layer with a thickness of 0.8 mm.

[0140] 2.3 Insulation layer extrusion: Extrusion of cross-linked polyethylene insulation layer, 3.4mm thick (meeting the requirements of 10kV system).

[0141] 2.4 Extrusion of insulating shielding layer: Extrusion of semi-conductive cross-linked polyethylene insulating shielding layer, 0.8 mm thick (three-layer co-extrusion process).

[0142] 2.5 Metal shielding layer wrapping: A copper strip metal shielding layer is wrapped around the outside of the insulating shielding layer.

[0143] 2.6 Sheath extrusion: A polyvinyl chloride (PVC) sheath layer with a thickness of 2.5 mm is extruded over the metal shielding layer.

[0144] 3. Performance Testing

[0145] 3.1 Conductor properties: The obtained core-shell structure rare earth aluminum alloy monofilament was tested and found to have a tensile strength of 182 MPa, a conductivity of 61.8% IACS, an elongation of 23.8%, and a strength retention rate of 93.1% at 300℃ / 1h.

[0146] 3.2 Creep resistance: Tests show that the creep deformation of the conductor of this invention is about 40% smaller than that of copper conductor.

[0147] 3.3 Partial discharge test: The partial discharge test (at 1.73U0) was conducted according to GB / T 31840-2025. The discharge quantity was 3.2pC, ≤5pC, which meets the standard requirements.

[0148] 3.4 Power frequency withstand voltage test: Hold at 2.5U0 AC voltage for 30 minutes without insulation breakdown.

[0149] 3.5 Overall Performance: The overall weight of the cable is reduced by approximately 55% compared to copper core medium-voltage cables, and the overall cost is reduced by approximately 50%. Suitable for 10kV upgrade projects in urban power distribution networks.

[0150] Example 3 (35kV large cross-section medium and high voltage power cable, suitable for capacity expansion and renovation of the main power grid)

[0151] 1. Preparation of core-shell structured rare earth aluminum alloy conductors

[0152] 1.1 Ingredients: The ingredients were prepared according to the final composition of Ce 0.20%, Er 0.08%, Yb 0.08%, Zr 0.15%, Fe 0.13%, with the balance being Al. The purity and source of the raw materials were the same as in Example 1.

[0153] 1.2 Melting and casting: Same as in Example 1.

[0154] 1.3 Differentiated two-stage homogenization: heat at 424℃ for 4.8 hours, then heat at 544℃ for 9.5 hours.

[0155] 1.4 Thermal deformation: Same as in Example 1.

[0156] 1.5 Solution treatment and aging: Solution treatment at 564℃ for 2.0 hours followed by water quenching; aging treatment at 247℃ for 6.8 hours.

[0157] 1.6 Annealing treatment: Hold at 325℃ for 2.2 hours, then cool with the furnace.

[0158] 1.7 Cold working: Cold drawing to Core-shell structured rare earth aluminum alloy monofilament.

[0159] 2. Cable forming (35kV large cross-section)

[0160] 2.1 Twisting: Twisting 61 strands The core is made of rare-earth aluminum alloy monofilaments with a core-shell structure, twisted together at a pitch ratio of 12 to form the cable core, with a compression factor ≥0.92 and a nominal cross-section of 185mm². 2 .

[0161] 2.2 Extrusion of conductor shielding layer: Extrusion of semi-conductive cross-linked polyethylene conductor shielding layer with a thickness of 1.2 mm.

[0162] 2.3 Insulation layer extrusion: Extrusion of cross-linked polyethylene insulation layer, 10.5 mm thick.

[0163] 2.4 Extrusion of insulating shielding layer: Extrusion of semi-conductive cross-linked polyethylene insulating shielding layer, 1.2mm thick (three-layer co-extrusion process).

[0164] 2.5 Metal shielding layer wrapping: Wrap copper tape metal shielding layer.

[0165] 2.6 Sheath extrusion: Extrusion of a low-smoke halogen-free flame-retardant polyolefin (LSZH) sheath layer with a thickness of 3.5 mm.

[0166] 3. Performance Testing

[0167] 3.1 Conductor properties: The obtained core-shell structure rare earth aluminum alloy monofilament was tested and found to have a tensile strength of 185 MPa, a conductivity of 61.5% IACS, an elongation of 22.5%, and a strength retention rate of 92.5% at 300℃ / 1h.

[0168] 3.2 Creep resistance: Tests show that the creep deformation of the conductor of this invention is about 40% smaller than that of copper conductor.

[0169] 3.3 Partial discharge test: The partial discharge test (at 1.73U0) shall be conducted in accordance with GB / T 31840-2025. The discharge quantity shall be 3.5pC, ≤5pC, which meets the standard requirements.

[0170] 3.4 Overall performance: Applicable to 35kV capacity expansion and renovation projects of urban main power grids.

[0171] Comparative Example 1 (Traditional copper core medium-high voltage cable - 35kV)

[0172] Referring to mainstream copper core 35kV medium and high voltage cable products on the market, a nominal cross-section of 95mm² is selected. 2 A copper cable was used as a comparative example. Tests showed that the copper conductor had a tensile strength of approximately 240 MPa, a conductivity of 100% IACS, and a partial discharge quantity ≤5 pC. The overall weight of the cable was approximately 2.2 times that of Example 1 of this invention, and the cost was approximately 2.1 times higher.

[0173] Comparative Example 2 (Ordinary Aluminum Alloy Medium-Voltage Cable - Coreless Shell Structure)

[0174] Referring to common aluminum alloy 35kV medium and high voltage cables on the market, a nominal cross-section of 95mm² is selected. 2 (Equivalent current carrying capacity) is used as a comparative example. The aluminum conductor is made of AA8000 series aluminum alloy, with a tensile strength of approximately 150 MPa, a conductivity of approximately 57% IACS, and a strength retention rate of approximately 70% at 300℃ / 1h. The partial discharge quantity is ≤10 pC, slightly higher than the standard requirement. The creep resistance test value is significantly worse than that of the embodiment of the present invention.

[0175] Summary of Performance of Examples and Comparative Examples

[0176]

[0177] Conclusion: The 10kV-35kV medium-high voltage core-shell structure rare earth aluminum alloy power cables of this invention (Examples 1-3) are close to copper cables in terms of tensile strength and conductivity, but significantly superior in weight and cost. The partial discharge quantity (≤3.8pC) meets the requirements of GB / T 31840-2025 standard (≤5pC). Compared with ordinary aluminum alloy cables, the tensile strength is increased by more than 20%, the conductivity by more than 4 percentage points, and the high-temperature performance (300℃ residual rate ≥92.5%) is significantly better than ordinary aluminum alloy cables (70%), with more precise partial discharge control. The cables of this invention fully comply with the requirements of GB / T 31840.2-2025 and GB / T31840.3-2025 standards and are suitable for urban power distribution network renovation, industrial park high-voltage power distribution, 35kV urban main ring networks, and other scenarios.

[0178] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A 10kV-35kV medium-high voltage core-shell structure rare earth aluminum alloy power cable, characterized in that, include: At least one cable core is made of a core-shell structured rare-earth aluminum alloy conductor; A conductor shielding layer disposed on the outside of the cable core; A cross-linked polyethylene insulation layer disposed outside the conductor shielding layer; An insulating shielding layer placed outside the insulating layer; A metal shielding layer disposed outside the insulating shielding layer; And the outermost sheath layer; The core-shell structured rare earth aluminum alloy conductor is composed of the following components by mass percentage: Ce 0.15-0.20%, Er 0.08-0.12%, Yb 0.05-0.08%, Zr 0.15-0.18%, Fe 0.10-0.13%, with the balance being Al and unavoidable impurities.

2. The 10kV-35kV medium-high voltage core-shell structure rare earth aluminum alloy power cable according to claim 1, characterized in that, The microstructure of the conductor includes a core-shell structured nanoprecipitated phase and a nanoscale dispersed phase; The core-shell structured nanoprecipitate is an Al3(RE,Zr) composite nanoprecipitate, which contains a rare earth element-rich core and a Zr-rich shell. The sum of the atomic concentrations of rare earth elements in the core accounts for more than 90% of the total number of atoms in the core of the precipitate, and the atomic concentration of Zr in the shell accounts for more than 85% of the total number of atoms in the shell of the precipitate. The nanoscale dispersed phase is nanoscale Al that is encapsulated or pinned by the core-shell structured nanoscale precipitates. 13 The Fe4 dispersed phase has an equivalent spherical average diameter of no more than 50 nm.

3. The 10kV-35kV medium-high voltage core-shell structure rare earth aluminum alloy power cable according to claim 1, characterized in that, The cable has a partial discharge of ≤5pC at 1.73U0, which meets the requirements of GB / T 31840-2025.

4. The 10kV-35kV medium-high voltage core-shell structure rare earth aluminum alloy power cable according to claim 1, characterized in that, Both the conductor shielding layer and the insulating shielding layer are made of semi-conductive cross-linked polyethylene material with a thickness of 0.6–1.2 mm and a volume resistivity of ≤100 Ω·m.

5. The 10kV-35kV medium-high voltage core-shell structure rare earth aluminum alloy power cable according to claim 1, characterized in that, The thickness of the cross-linked polyethylene insulation layer is determined according to the rated voltage; the insulation layer thickness is ≥3.4mm for 10kV systems and ≥10.5mm for 35kV systems.

6. The 10kV-35kV medium-high voltage core-shell structure rare earth aluminum alloy power cable according to claim 1, characterized in that, The cable core is made of multiple core-shell structure rare earth aluminum alloy monofilaments twisted together, with a twisting pitch ratio of 10 to 14 times and a compression coefficient ≥0.

92.

7. The 10kV-35kV medium-high voltage core-shell structure rare earth aluminum alloy power cable according to claim 1, characterized in that, The metal shielding layer is a copper strip wrapped shielding layer or a copper wire braided shielding layer.

8. The 10kV-35kV medium-high voltage core-shell structure rare earth aluminum alloy power cable according to claim 1, characterized in that, The conductor has a tensile strength ≥182MPa, conductivity ≥61.5%IACS, elongation ≥22%, and strength retention rate at 300℃ / 1h ≥92%.

9. The 10kV-35kV medium-high voltage core-shell structure rare earth aluminum alloy power cable according to claim 1, characterized in that, The rated voltage of the cable is 10kV to 35kV, and it is suitable for urban power distribution network renovation, high-voltage power distribution in industrial parks, and power collection lines for new energy power plants.

10. The 10kV-35kV medium-high voltage core-shell structure rare earth aluminum alloy power cable according to claim 1, characterized in that, The cable meets the requirements of GB / T 31840.2-2025 and GB / T 31840.3-2025.

11. A method for preparing a 10kV-35kV medium-high voltage core-shell structure rare earth aluminum alloy power cable as described in any one of claims 1 to 10, characterized in that, Includes the following steps: Step 1, casting: Prepare raw materials according to the stated composition ratio, melt them under a protective atmosphere, and cast them into ingots; Step 2, Differentiated two-stage homogenization treatment: The ingot is subjected to the first stage homogenization treatment by heating to 420-425℃ and holding for 4.5-5.5 hours; then the second stage homogenization treatment is performed by heating to 540-545℃ and holding for 8-10 hours. Step 3, hot deformation processing: The homogenized ingot is heated to 460-500℃ and hot extruded or hot rolled to produce wire rod. Step 4, Solution treatment and aging treatment: The wire blank is solution treated by heating to 560-565℃ and holding for 1.5-2.0 hours, then water quenched at a cooling rate of ≥80℃ / min; then aging treatment is performed by heating to 242-248℃ and holding for 6.5-7.5 hours. Step 5, Annealing treatment: Anneal the aged wire by heating it to 310-330℃ and holding it for 2.0-3.0 hours; Step 6, cold working: The annealed wire is cold drawn to obtain a core-shell structure rare earth aluminum alloy monofilament; Step 7, Stranding: Strand multiple core-shell structure rare earth aluminum alloy monofilaments into a cable core; Step 8, conductor shielding extrusion: a semi-conductive cross-linked polyethylene conductor shielding layer is extruded onto the outside of the cable core; Step 9, Insulation layer extrusion: Extruding a cross-linked polyethylene insulation layer over the conductor shielding layer; Step 10, Extrusion of insulating shielding layer: Extruding a semi-conductive cross-linked polyethylene insulating shielding layer over the insulating layer; Step 11, Metal shielding layer wrapping: Wrap a metal shielding layer around the outside of the insulating shielding layer; Step 12, Sheath extrusion: Extruding a sheath layer over the metal shielding layer; Step 13, Performance Testing: Perform cable performance testing according to GB / T 31840-2025; Step 14, winding and packaging: winding and packaging the qualified cables.

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