Copper-aluminum composite conductor with low cost and high conductivity and selection method

Abstract

The application discloses a low-cost high-conductivity copper-aluminum composite conductor and a selection method, and belongs to the technical field of cable conductors. The conductor is divided into three grades of large, medium and small according to a nominal cross-sectional area, and a concentric stranded structure of inner aluminum and outer copper is differentially adopted, and a circular and trapezoidal different-shaped single wire is matched to realize super-dense filling, so that the physical total cross-sectional area of the conductor is greater than the nominal cross-sectional area. The number ratio coefficient K of aluminum and copper single wires is set according to the gear, a cross-sectional area, resistance and copper material saving rate linkage calculation model is established, and electrical checking and calculation is completed in combination with a copper-aluminum parallel resistance formula. The product structure, outer diameter and single wire number all meet the standard of GB / T 3956-2008, the 20 DEG C direct current resistance is better than the national standard limit value, and the copper material saving rate reaches 19.60% to 39.79%. The scheme can directly replace the traditional pure copper conductor, is suitable for existing production equipment, effectively reduces raw material cost and reduces copper resource consumption, and has excellent conductivity and mass production performance.

Description

Technical Field

[0001] This invention relates to the field of cable technology, and in particular to a low-cost, high-conductivity copper-aluminum composite conductor and its selection method. Background Technology

[0002] In power frequency transmission and wiring scenarios of various electrical equipment, the current generally exhibits the skin effect, that is, when the current is not at full load, only the outer layer of the conductor carries current, and the inside carries almost no current. No matter what the purpose, it is impossible to achieve full load operation.

[0003] Under current operating conditions, wires and cables are in a non-full-load operating state for a long time. They may only briefly reach a momentary full-load operating state when the equipment is started, that is, the core is energized momentarily. Under normal operating conditions, the core inside the conductor is always in an idle conductive state.

[0004] Currently, the mainstream conductive conductors in the industry all adopt a pure copper stranded structure. As a scarce and high-priced strategic non-ferrous metal, copper has a large number of pure copper conductors with their cores left idle for a long time, resulting in a serious waste of copper resources. This leads to high production costs and low resource utilization for enterprises, which does not conform to the industry development trend of energy conservation, cost reduction, and green manufacturing.

[0005] The existing technology discloses some copper-aluminum composite conductor solutions, which are mainly divided into two categories: one type (CN 109903889A) is a copper-clad aluminum integrated cladding conductor, which adopts a structure of a single aluminum alloy rod with a seamless copper layer on the outside. This structure is not a stranded structure and cannot match the strand number, pitch, outer diameter and other parameters of the national standard pure copper conductor. It has poor mechanical properties and bending performance and cannot be directly used as a substitute for the national standard pure copper conductor.

[0006] Another type (CN 204577161 U) discloses a low skin effect composite copper-aluminum alloy conductor. The core technology of this patent is to use a central reinforcing core combined with multiple sets of copper-aluminum composite wire stranded structure. It relies on the skin effect to optimize the current distribution of large cross-section conductors, reduce conductor skin loss, and achieve lightweight and low-loss power transmission. The existing technology has several core defects: First, the conductor center is not a pure aluminum / aluminum alloy conductive core, but rather has an added carbon fiber reinforcing core. Furthermore, the outer layer is not pure copper wire stranded, but rather a copper-aluminum composite conductor stranded together, resulting in an overall copper-aluminum hybrid structure that cannot be equivalent to the conductive structure and electrical parameters of a pure copper conductor. Second, the structure is fixed and singular, only suitable for large-section special cables, and cannot flexibly adapt to single or multi-strand aluminum core structures according to different cable specifications, resulting in extremely poor versatility. Third, this patent only focuses on reducing skin loss and improving transmission efficiency, without referencing the key parameters of national standard pure copper conductors such as the number of strands, outer diameter, resistance, and stranding pitch. It cannot directly replace national standard pure copper conductors, requiring adaptation to specific production processes and usage scenarios, and cannot achieve universal and seamless replacement, failing to address the industry pain points of resource waste and high replacement costs associated with traditional pure copper conductors.

[0007] Meanwhile, none of the existing skin effect copper conductor technology solutions fully meet the requirements of the current national standard GB / T 3956-2008 regarding the number of strands, resistance, outer diameter, stranding structure, stranding direction, and stranding pitch of pure copper conductors. They cannot be directly and universally used to replace traditional pure copper cable conductors. They require adjustments to cable processing technology and equipment parameters, resulting in high replacement costs and difficulty in popularization, and thus they have not been able to replace traditional pure copper conductors on a large scale.

[0008] Secondly, traditional composite conductors strictly limit the total physical cross-sectional area to equal the nominal cross-sectional area, limiting the room for improvement in conductivity and making it difficult to simultaneously achieve the two major goals of "resistance better than the national standard" and "significantly saving copper materials".

[0009] Furthermore, there was no differentiated structural design for commonly used cable cross-sections of large, medium and small. Circular single wires and irregular single wires were mixed irregularly, resulting in low stranding and filling rates, poor structural compactness, and difficulty in consistently meeting the standards for finished product outer diameter and mechanical properties.

[0010] Fourth, the conductivity ratio of copper and aluminum cannot be precisely controlled, which can easily lead to problems such as excessive resistance and uneven conductivity, resulting in poor product consistency and difficulty in large-scale mass production.

[0011] CN120015399A discloses a low-cost, high-conductivity conductor, processing equipment, and processing technology. The conductor provided by this solution consists of an inner core, an inner support layer, and an outer cladding layer arranged sequentially from the inside out. The inner support layer is made of several stranded metal wires, and the outer cladding layer is made of several stranded copper wires.

[0012] This technology does not take cost-effectiveness into account, and the given fixed instruction is three layers of conductors.

[0013] Although the performance is good, the cost control is not good; regardless of the diameter, the cost-effectiveness of using this triple conductor is not high.

[0014] In summary, there is currently a lack of an integrated design solution that combines ultra-dense filling of irregularly shaped single wires, graded wire number ratios, precise calculation of single wire cross-sections, and coordinated control of parallel conductivity. The industry urgently needs a new type of composite stranded conductor that is structurally flexible, whose parameters fully comply with national standards, can directly and equivalently replace pure copper conductors, and significantly saves copper resources; furthermore, this system should, while achieving the desired effect, minimize costs as much as possible.

[0015] June 12, 2025. Keywords: cable structure, aluminum inside, copper outside, different structures and ratios selected according to diameter requirements; cables are twisted together; different schemes are selected according to different diameters, mainly focusing on the internal structure of the cable; cable core, not involving the insulation layer;

[0016] ((TIAB = ("cable structure" OR "cable assembly" OR "cable configuration" OR "conductor arrangement" OR "electrical wiring design") AND technicalField =(cable core) AND disclosure = (The interior is aluminum,The external structure is copper OR different structures and ratios are selected according to diameter requirements OR the cable is stranded OR different schemes are selected according to different diameters OR mainly refers to the internal structure of the cable) AND backgroundArt = (not involving the insulation layer) AND (TIABC = ("conductor structure" OR "cable core" OR "stranded wire" OR "copper conductor" OR "aluminum conductor" OR "composite conductor" OR "conductor structure" OR "cable core" OR "stranded wire") OR TIABC = ("insulation material" OR "cable sheath" OR "polyethylene" OR "cross-linked polyethylene" OR "polyvinyl chloride" OR "fluoroplastic" OR "insulation material" OR "cable sheath" OR "XLPE" OR "PVC") OR TIABC = ("cable termination" OR "joint structure" OR "terminal connection" OR "sealing structure" OR "waterproof joint" OR "plug-in joint" OR "cable termination" OR "connector design" OR "sealing structure") OR TIABC = ("stranding process" OR "multi-strand stranding" OR "concentric stranding" OR "compound stranding structure") OR "Twisting Direction Control" OR "Twisting Pitch Adjustment" OR "Stranding Process" OR "Multi-Strand Cabling" OR "Lay Length Control") OR TIABC = ("Condition Monitoring" OR "Temperature Sensing" OR "Strain Sensing" OR "Fiber Optic Embedding" OR "Smart Cable" OR "Distributed Sensor" OR "Condition Monitoring" OR "Fiber Optic Sensing" OR "Smart Cable") ), with the option to allow synonym expansion selected, a search was conducted in the China Patent Publication Database, but no relevant literature was found. Summary of the Invention

[0017] Purpose of the invention: To provide a better, lower-cost, and more conductive copper-aluminum composite conductor and a method for selecting it. Specific objectives are detailed in the specific implementation section, which describes several substantial technical effects.

[0018] To achieve the above objectives, the present invention adopts the following technical solution:

[0019] Research Objective

[0020] 1. Reduce costs: Solve the problem of excessively high costs caused by the scarcity of copper resources in traditional pure copper conductors by optimizing the material composition to reduce the amount of copper used.

[0021] 2. Improve performance: Ensure that the conductor's electrical conductivity and mechanical properties (flexibility, tensile strength) meet national standards, while achieving lightweight design.

[0022] Invention content and core innovations

[0023] This invention uses GB / T 3956-2008 as the compliance benchmark, classifying commonly used conductors in power cables into three grades—large, medium, and small—based on their nominal cross-sectional area. For each grade, a specific aluminum / copper single-wire ratio coefficient is set, combined with differentiated combinations of round and irregularly shaped single wires to achieve ultra-dense stranding and filling, ensuring the total physical cross-sectional area of ​​the conductor exceeds the nominal cross-sectional area. Through a copper-aluminum parallel conductivity model, the resistance and conductivity distribution ratio are precisely calculated. Under the premise that the outer diameter of the finished product meets national standards, the DC resistance of the conductor is superior to the national standard limit for pure copper conductors, while significantly reducing the amount of copper used, forming a replicable and mass-producible standardized design system.

[0024] 1. Innovative Ultra-Dense Irregular Stranding Filling: Breaking away from the industry's inherent design thinking of "physical cross-sectional area = nominal cross-sectional area", this invention adopts a combination of circular + multi-specification irregular aluminum single wires and irregular copper single wires concentrically stranded. By utilizing the gap filling advantage of irregular wires, the overall filling rate is improved, making the total physical cross-sectional area of ​​the conductor greater than the nominal cross-sectional area. This enhances the overall conductivity without increasing the outer diameter of the finished product, which is the key feature that distinguishes this invention from existing technologies.

[0025] 2. Quantitative Innovation in Scale of Conductor Count: The conductors are divided into three grades according to their nominal cross-section. Each grade is configured with a fixed ratio coefficient K of the total number of aluminum core single wires / the total number of copper core single wires. This eliminates the need for experience-based trial matching and achieves a leap from case-by-case trial production to standardized formula design, resulting in strong versatility and portability.

[0026] 3. Multi-parameter linkage closed-loop design innovation: Construct a full-chain calculation model for nominal cross-section → grade division → number of wires ratio → single wire cross-sectional area → total cross-section of zone → parallel resistance → conductivity ratio → copper material saving rate. The number of wires, single wire size, electrical performance and economic indicators are mutually constrained and closed-loop verified, resulting in high design accuracy and strong product stability.

[0027] 4. Precise and Synergistic Innovation of Copper-Aluminum Parallel Conductivity: Based on the fixed resistivity parameters of the national standard, the conductivity distribution ratio of aluminum core and copper core is precisely controlled through structural ratio, so that the DC resistance of the composite conductor is stably better than the maximum allowable resistance of pure copper conductor in GB / T 3956-2008, and the conductivity performance has sufficient redundancy.

[0028] 5. Innovative process and standard adaptation: Differentiated cross-sections are achieved by using circular and irregular single-wire structures. The finished product's stranded outer diameter, total number of single wires, and stranding form all comply with the requirements of GB / T 3956-2008 composite conductors. It can be directly adapted to existing stranding and drawing equipment without the need to modify production lines, making it highly adaptable to mass production.

[0029] Core content

[0030] A method for selecting copper-aluminum composite concentric conductors, wherein the range of values ​​for the ratio coefficient K is:

[0031] The small cross-sectional area is no more than 25 mm², and the proportioning coefficient K ranges from 0.07 to 0.10.

[0032] The mid-section range is defined as having a nominal cross-sectional area between 35 mm² and 150 mm², and the proportioning coefficient K ranges from 0.55 to 0.65.

[0033] The large cross-section range has a nominal cross-sectional area of ​​not less than 185 mm², and the proportioning coefficient K ranges from 1.00 to 1.06.

[0034] A method for selecting copper-aluminum composite concentric conductors, wherein the number of single copper and aluminum wires is:

[0035] The number of single aluminum wires in the inner core of the small cross-section section is fixed at 1, while the number of single copper wires in the outer layer is 11 to 13.

[0036] The number of single aluminum wires in the inner core of the cross-section is 5 to 6, and the number of single copper wires in the outer layer is 9 to 11.

[0037] The number of single aluminum wires in the inner core of the large cross-section section is 19 to 22, and the number of single copper wires in the outer layer is 18 to 21.

[0038] A method for selecting copper-aluminum composite concentric conductors is disclosed. The designed composite conductor achieves a copper material saving rate of 19.60% to 39.79% compared to a pure copper conductor of the same specification; its standard DC resistance at 20℃ is superior to the limit value of pure copper conductors of the same specification in GB / T 3956-2008.

[0039] A method for selecting copper-aluminum composite concentric conductors.

[0040] Basic parameters and complete set of calculation formulas

[0041] 1. National standard fixed physical property parameters

[0042] Resistivity of copper conductor: ρ Cu =17.241Ω·mm² / km

[0043] Resistivity of aluminum conductor: ρ Al =28.264Ω·mm² / km

[0044] Baseline length: L = 1km

[0045] 2. Basic Definitions

[0046] S 标称 : Nominal cross-sectional area of ​​the conductor (mm²);

[0047] S Al : Total cross-sectional area of ​​the inner aluminum conductor (mm²);

[0048] S Cu : Total cross-sectional area of ​​the outer copper conductor (mm²);

[0049] S 物理总 : Total physical cross-sectional area of ​​the conductor (mm²);

[0050] N Al Total number of aluminum single wires;

[0051] N Cu Total number of copper wires;

[0052] s Al Cross-sectional area of ​​a single aluminum wire (mm²);

[0053] s Cu Cross-sectional area of ​​a single copper wire (mm²);

[0054] K: Aluminum-copper ratio coefficient ;

[0055] Filling constraints:

[0056] S 物理总 =S Al +S Cu

[0057] S 物理总 >S 标称

[0058] 3. Core Calculation Formula

[0059] 1) Formula linking the number of strands to the cross-sectional area of ​​a single filament

[0060] All single wires in the copper core have the same specifications:

[0061] s Cu =

[0062] The aluminum core uses a multi-specification single-wire layered combination:

[0063] S Al =∑(N Ali s Ali )

[0064] Where: N Ali s Ali These represent the number of individual wires and the cross-sectional area of ​​each layer of the aluminum core.

[0065] 2) DC resistance of a single conductor material

[0066]

[0067] 3) Total resistance of copper and aluminum in parallel

[0068]

[0069] 4) Copper material saving rate and target total cross-section of copper core

[0070] Copper saving rate = 100%

[0071] = (1 - Copper material saving rate)

[0072] Segmentation structure, parameters, and complete verification (based on experimental data)

[0073] 1. Gear Classification Rules

[0074] Small cross-section: ≤25mm², representing a specification of 10mm²

[0075] Mid-section: 35mm²≤ ≤150mm², representing a specification of 70mm²

[0076] Large cross-section: ≥185mm², representing a specification of 240mm²

[0077] 2. Nominal cross-section 240 mm² (large cross-section range)

[0078] (1) Structure and monofilament parameters

[0079] Inner core aluminum (19 in total): 1 round aluminum wire with a single wire cross-sectional area of ​​5.14 mm²; 6 irregularly shaped aluminum wires with a single wire cross-sectional area of ​​7.48 mm²; 12 irregularly shaped aluminum wires with a single wire cross-sectional area of ​​8.33 mm².

[0080] Outer copper layer (18 in total): 18 irregularly shaped copper strands, each with a cross-sectional area of ​​7.65 mm².

[0081] Total number of single wires: 37; Outer diameter of finished stranded wire: 19.1mm.

[0082] (2) Cross-section calculation

[0083] S Al =5.14+6×7.48+12×8.33=150mm²

[0084] S Cu =18×7.65=137.7mm²

[0085] S 物理总 =150 + 137.7 = 287.7 mm²

[0086] (3) Theoretical verification of resistance

[0087] Inner core aluminum conductor resistance:

[0088] Resistance of the outer copper conductor:

[0089] Overall parallel resistance:

[0090]

[0091]

[0092] = 13.295

[0093]

[0094] (4) Performance and benefits

[0095] National standard limits: The theoretical value is 0.27% better than the national standard;

[0096] Measured resistance after correction at 20℃: It is 1.57% better than the national standard;

[0097] Copper material savings rate: 100% = 39.79%

[0098] (5) Proportioning coefficient

[0099] K= 1.056; Standard coefficient range for large cross-section intervals: 1.00~1.06

[0100] 3. Nominal cross-section 70 mm² (mid-section range)

[0101] (1) Structure and monofilament parameters

[0102] Inner core aluminum (6 in total): 1 round aluminum wire with a single wire cross-sectional area of ​​5.31 mm²; 5 irregularly shaped aluminum wires with a single wire cross-sectional area of ​​5.30 mm².

[0103] Outer copper layer (10 in total): 10 irregularly shaped copper strands, with a single wire cross-sectional area of ​​4.53 mm².

[0104] Total number of single wires: 16; Outer diameter of finished stranded wire: 9.95mm.

[0105] (2) Cross-section calculation

[0106] S Al =5.31 + 5 × 5.3 = 31.81 mm²

[0107] S Cu =10×4.53=45.30mm²

[0108] S 物理总 =31.81 + 45.30 = 77.11 mm²

[0109] (3) Theoretical verification of resistance

[0110] Inner core aluminum conductor resistance:

[0111] Resistance of the outer copper conductor:

[0112] Overall parallel resistor

[0113]

[0114]

[0115] =3.7535

[0116]

[0117] (4) Performance and benefits

[0118] National standard limits: The theoretical value is 0.6% better than the national standard;

[0119] Measured resistance after correction at 20℃: It is 0.74% better than the national standard;

[0120] Copper material savings rate: 100% = 30.80%

[0121] (5) Proportioning coefficient

[0122] K= 0.6; Standard coefficient range for the mid-section interval: 0.55~0.65

[0123] 4. Nominal cross-section 10 mm² (small cross-section range)

[0124] (1) Structure and monofilament parameters

[0125] Inner core aluminum (1 piece in total): 1 round aluminum wire with a single wire cross-sectional area of ​​3.14 mm².

[0126] Outer copper layer (12 in total): 12 round copper wires, each with a cross-sectional area of ​​0.65 mm².

[0127] Total number of single wires: 13; Finished stranded outer diameter: 3.8mm.

[0128] (2) Cross-section calculation

[0129] S Al =3.14mm²

[0130] S Cu =12×0.65=7.8mm²

[0131] S 物理总 =3.14 + 7.8 = 10.94 mm²

[0132] (3) Theoretical verification of resistance

[0133] Inner core aluminum conductor resistance:

[0134] Resistance of the outer copper conductor:

[0135] Overall parallel resistance:

[0136]

[0137]

[0138] =0.5635

[0139]

[0140] (4) Performance and benefits

[0141] National standard limits: The theoretical value is 3.3% better than the national standard;

[0142] Measured resistance after correction at 20℃: It is 2.19% better than the national standard;

[0143] Copper material savings rate: 100% = 19.6%

[0144] (5) Proportioning coefficient

[0145] K= 0.083; Standard coefficient range for small cross-section intervals: 0.07~0.10

[0146] Summary Table of Tier Parameters

[0147] Large cross section ≥185mm² 1.00～1.06 19～22 18～21 Round aluminum + irregularly shaped aluminum + irregularly shaped copper 38%～40% Mid-section 35~150mm² 0.55～0.65 5～6 9～11 Round aluminum + irregularly shaped aluminum + irregularly shaped copper 29%～31% Small cross-section ≤25mm² 0.07～0.10 1 11～13 Single round aluminum + round copper 19%～20%

[0148] Standardized design steps

[0149] 1. Gear Determination: Based on the nominal cross-sectional area of ​​the target conductor, it is divided into large, medium, and small corresponding design ranges;

[0150] 2. Number of wires: retrieve the aluminum-copper wire ratio coefficient K for the corresponding interval, calculate and determine the total number of inner core aluminum wires and the total number of outer copper wires;

[0151] 3. Calculation of cross-section in zones: Calculate the total cross-sectional area of ​​the target copper core based on the preset copper material saving rate; determine the total cross-sectional area of ​​the aluminum core by combining the ultra-dense filling constraint (the total cross-sectional area of ​​the conductive material is greater than the nominal cross-sectional area);

[0152] 4. Calculation of cross-sectional area of ​​single wire: Calculate the cross-sectional area of ​​a single copper wire using the number of wires and the single wire cross-section algorithm; for the layered design of the aluminum core, calculate the cross-sectional area of ​​the single aluminum wire in each layer separately, and verify that the wire size is in line with industry-standard specifications and national tolerances.

[0153] 5. Structural Assembly: The large and medium sections adopt a "central circular aluminum + outer irregular aluminum + outer irregular copper" structure, while the small section adopts a "single circular aluminum + outer circular copper" concentric twisted structure to ensure that the outer diameter of the finished product meets the national standard.

[0154] 6. Electrical verification: The total DC resistance is calculated using the resistance formula and parallel resistance model to ensure that the theoretical resistance does not exceed the limit value of pure copper conductors of the same specification in GB / T3956-2008.

[0155] 7. Actual test and verification: Produce a sample and perform temperature correction. Test the standard resistance at 20℃, the number of single wires, and the outer diameter of the strand. After all indicators are qualified, the product is finalized.

[0156] The present invention, employing the above technical solution, has the following beneficial effects compared to the prior art:

[0157] 1. Technical Effects

[0158] (1) Adopting the irregular single-wire ultra-dense stranding technology, the overall filling area and conductivity of the conductor are improved without increasing the outer diameter of the finished product. This breaks through the limitations of traditional cross-section design. The copper-aluminum composite structure is lightweight, reducing construction difficulty. The irregular single-wire design improves the stranding tightness, reduces eddy currents, and has better conduction efficiency. The DC resistance of the conductor is superior to the national standard, with sufficient conductivity redundancy and safe and reliable operation.

[0159] (2) The graded and quantitative proportioning system realizes parameter standardization, and the number of strands, single filament cross section and electrical conductivity ratio can be precisely controlled, resulting in high product consistency and completely solving the performance fluctuation problem caused by traditional experience design.

[0160] (3) The structure, number of single wires, resistance and outer diameter of the finished product strictly comply with the requirements of GB / T 3956-2008. The mechanical strength, bending performance and stranding stability of the conductor meet the requirements of cable laying and long-term operation. It can be used as a new type of conductor to replace pure copper conductors in wires and cables.

[0161] 2. Economic Effects

[0162] (1) Under the premise of ensuring that the conductivity and mechanical properties (flexibility and tensile strength) are equivalent to those of pure copper conductors, the copper material reduction of all conductors is achieved in a gradient manner, and the copper material saving rate can reach up to 20%-40%, which greatly reduces the procurement cost of precious metal copper and has significant economic benefits.

[0163] (2) Standardized design process shortens the new product development cycle, reduces material loss and labor costs caused by repeated trial production, and further reduces the overall production cost.

[0164] 3. Mass production effect of the process

[0165] With different cross-sectional sizes and the combination of round and irregularly shaped single wires, it is fully compatible with existing cable drawing and concentric stranding production equipment, requiring no production line modification; the structure is uniform, the process is simple, and the mass production difficulty is low, enabling rapid large-scale production of the entire series of specifications.

[0166] 4. Industry and Social Benefits

[0167] This invention constructs a brand-new quantitative design theory and ultra-dense stranding technology for copper-aluminum composite conductors, filling a technological gap in the industry; it significantly reduces copper resource consumption, aligns with industrial policies of green manufacturing and energy conservation and carbon reduction, and has a strong industry demonstration effect and promotion value.

[0168] The accompanying drawings illustrate the technical solution of this invention.

[0169] Based on the above current principle, an irregular conductor with an outer core layer consisting of multiple round / irregularly shaped copper wires stranded together and an inner core layer consisting of a single or multiple round / irregularly shaped (aluminum / aluminum alloy) stranded together was designed, thereby reducing the waste of precious copper resources.

[0170] This invention fully meets the requirements of current national standards for the number of strands, resistance, outer diameter, stranding structure, stranding direction, and stranding pitch of copper conductors, and serves as a new type of conductor to replace copper conductors used in wires and cables. Attached Figure Description

[0171] To further illustrate the present invention, the following description is provided in conjunction with the accompanying drawings:

[0172] Figure 1 This is a cross-sectional view of a 240mm² copper-aluminum composite stranded conductor. The top image is a physical picture, and the bottom image is a structural diagram.

[0173] Figure 2 This is a cross-sectional view of a 70mm² copper-aluminum composite stranded conductor. The top image is a physical picture, and the bottom image is a structural diagram.

[0174] Figure 3 This is a cross-sectional view of a 10mm² copper-aluminum composite stranded conductor. The top image is a physical picture, and the bottom image is a structural diagram.

[0175] Figure 4 This is a detailed parameter table for each layer. Detailed Implementation

[0176] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0177] Experimental Records

[0178] 240mm² Copper-Aluminum Composite Stranded Conductor Prototype Development and Testing Record

[0179] I. Basic Experimental Information

[0180] (I) Experimental Objective

[0181] 1. Verify whether the structural parameters of the self-developed 240mm² copper-aluminum composite stranded conductor meet the requirements of GB / T 3956-2008 "Conductors of Cables" standard.

[0182] 2. Calculate and measure the DC resistance per unit length of the composite conductor, evaluate whether its conductivity is better than the national standard for copper conductors, and calculate the copper material saving benefits.

[0183] (II) Experimental Equipment

[0184] Digital DC bridge QJ36B-2, vernier caliper

[0185] II. Core Specifications of the Conductor Under Test

[0186] (I) Overall Structure

[0187] The conductor is a double-layered, irregularly shaped, single-wire stranded structure with an inner aluminum and outer copper core. Its nominal cross-sectional area is 240 mm², while the actual total cross-sectional area is 287.7 mm². It contains 37 single wires and has a stranded outer diameter of 19.1 mm. (Reference) Figure 1 .

[0188] (II) Detailed parameters of each layer

[0189] Inner core layer aluminum 1 circular wire + 6 irregularly shaped wires + 12 irregularly shaped wires concentrically twisted Circular monofilament: 1 (5.14 mm²); Shaped monofilament: 6 (7.48 mm² / filament); Shaped monofilament: 12 (8.33 mm² / filament). Circular monofilament: 5.14 mm²; 6 irregular filaments: 44.88 mm²; 12 irregular filaments: 99.96 mm² 150mm² 13.82mm outer core layer copper 18 heteromorphic concentric strands Shaped monofilaments: 18 strands (7.65mm² / strand) 137.7mm² 137.7mm² 19.1mm

[0190] III. Compliance Verification of Structural Parameters

[0191] According to the requirements of GB / T 3956-2008 standard, the key indicators of the conductor structure were verified, and the results are as follows:

[0192] 1. Number of single wires: The total number of single wires in the conductor is 37, which meets the requirement of "minimum number of single wires ≥ 34" for the second type of stranded copper conductor of 240mm² specification in Table 2 of the standard, ensuring the mechanical flexibility and structural stability of the conductor.

[0193] 2. Stranding diameter: The overall stranding outer diameter of the conductor is 19.1mm, which conforms to the allowable diameter range of 240mm² tightly stranded round conductors in Table C2 of Appendix C of GB / T3956-2008 standard, and can be adapted to subsequent cable cabling processes.

[0194] IV. Theoretical Calculation of Conductivity

[0195] (a) Basis for Calculation

[0196] 1. Formula for DC resistance of a conductor: (L=1km, the standard length for cable industry measurement; ρ is conductor resistivity; S is conductor cross-sectional area)

[0197] 2. Standard resistivity value: Aluminum conductor Copper conductor .

[0198] 3. Formula for parallel resistors: (The inner aluminum core and the outer copper core are connected in parallel for electrical conduction.)

[0199] (II) Step-by-step calculation

[0200] 1. Single-layer resistor

[0201] Inner core aluminum conductor resistance:

[0202] Resistance of the outer copper conductor:

[0203] 2. Overall parallel resistor

[0204]

[0205]

[0206] = 13.295

[0207]

[0208] 3. Theoretical performance comparison: Compared with the maximum allowable resistance of 240mm² annealed copper conductor (0.0754Ω / km) in GB / T3956-2008, the theoretically calculated value is about 0.27% better than the national standard.

[0209] V. Experimental Measurement of Electrical Conductivity

[0210] (a) Test conditions

[0211] • Test ambient temperature: 22℃

[0212] • Test conductor length: 1m

[0213] • Testing instrument: QJ36B-2 digital DC bridge

[0214] (II) Measured Results

[0215] Measured resistance at 1.22℃:

[0216] Resistance after correction at standard temperature of 2.20℃:

[0217] 3. Measured performance advantages: Compared with the national standard requirement of 0.0754Ω / km, the measured resistance is about 1.57% better than the national standard, and the performance is better than the theoretical calculation value.

[0218] VI. Core Benefit Analysis

[0219] 1. Conductivity distribution: According to calculations, the conductivity of the inner aluminum conductor accounts for 39.92% of the total conductivity, while the conductivity of the outer copper conductor accounts for 60.08% of the total conductivity, achieving efficient synergy between the conductivity of copper and aluminum.

[0220] 2. Copper saving: Compared with pure copper conductors of the same specification, the copper cross-sectional area of ​​this composite conductor is only 137.7 mm², saving 39.79% of copper usage. It meets the material requirements for composite conductors in Clause 5.2.3 of GB / T3956-2008, and has both economic and practical advantages.

[0221] VII. Experimental Conclusions

[0222] The structural parameters of the 1.240mm² copper-aluminum composite stranded conductor, such as the number of single wires and the stranding diameter, all meet the requirements of GB / T3956-2008 standard, and have the structural basis for mass production.

[0223] 2. The measured resistance per unit length of the conductor at 20℃ is 0.074219Ω / km, which is 1.57% better than the national standard for copper conductors. The conductivity meets the standard and has performance redundancy.

[0224] 3. While ensuring conductivity, the product achieves a 39.79% reduction in copper material, balancing power transmission requirements with raw material cost control, and has high engineering promotion value.

[0225] 70mm² Copper-Aluminum Composite Stranded Conductor Prototype Development and Testing Record

[0226] I. Basic Experimental Information

[0227] (I) Experimental Objective

[0228] 1. Verify whether the structural parameters of the self-developed 70mm² copper-aluminum composite stranded conductor meet the requirements of GB / T 3956-2008 "Conductors of Cables" standard.

[0229] 2. Calculate and measure the DC resistance per unit length of the composite conductor, evaluate whether its conductivity is better than the national standard for copper conductors, and calculate the copper material saving benefits.

[0230] (II) Experimental Equipment

[0231] Digital DC bridge QJ36B-2, vernier caliper

[0232] II. Core Specifications of the Conductor Under Test

[0233] (I) Overall Structure

[0234] The conductor is a double-layered, irregularly shaped, stranded single-wire structure with an inner aluminum and outer copper core. Its nominal cross-sectional area is 70 mm², the actual total cross-sectional area is 77.13 mm², and it has 16 single wires with a stranded outer diameter of 9.95 mm. (Reference) Figure 2 .

[0235] (II) Detailed parameters of each layer

[0236] Inner core layer aluminum 1 circular strand + 5 irregularly shaped concentric strands Circular monofilament: 1 (5.31mm²); Shaped monofilament: 5 (5.30mm² / filament); Circular monofilament: 5.31 mm²; 5 irregularly shaped filaments: 26.52 mm²; 31.83mm² 6.37mm outer core layer copper 10 heteromorphic concentric strands Shaped monofilaments: 10 strands (4.53mm² / strand) 45.3mm² 45.3mm² 9.95mm

[0237] III. Compliance Verification of Structural Parameters

[0238] According to the requirements of GB / T 3956-2008 standard, the key indicators of the conductor structure were verified, and the results are as follows:

[0239] 1. Number of single wires: The total number of single wires in the conductor is 16, which meets the requirement of "minimum number of single wires ≥ 12" for the second type of stranded copper conductor of 70mm² specification in Table 2 of the standard, ensuring the mechanical flexibility and structural stability of the conductor.

[0240] 2. Stranding diameter: The overall stranding outer diameter of the conductor is 9.95mm, which conforms to the allowable diameter range of 70mm² tightly stranded round conductors in Table C2 of Appendix C of the standard, and can be adapted to subsequent cable cabling processes.

[0241] IV. Theoretical Calculation of Conductivity

[0242] (a) Basis for Calculation

[0243] 1. Formula for DC resistance of a conductor: (L=1km, the standard length for cable industry measurement; ρ is conductor resistivity; S is conductor cross-sectional area)

[0244] 2. Standard resistivity value: Aluminum conductor Copper conductor .

[0245] 3. Formula for parallel resistors: (The inner aluminum core and the outer copper core are connected in parallel for electrical conduction.)

[0246] (II) Step-by-step calculation

[0247] 1. Single-layer resistor

[0248] Inner core aluminum conductor resistance:

[0249] Resistance of the outer copper conductor:

[0250] 2. Overall parallel resistor

[0251]

[0252]

[0253] =3.7535

[0254]

[0255] 3. Theoretical performance comparison: Compared with the maximum allowable resistance of 70mm² annealed copper conductor (0.268Ω / km) in GB / T3956-2008, the theoretically calculated value is about 0.6% better than the national standard.

[0256] V. Experimental Measurement of Electrical Conductivity

[0257] (a) Test conditions

[0258] • Test ambient temperature: 26℃

[0259] • Test conductor length: 1m

[0260] • Testing instrument: QJ36B-2 digital DC bridge

[0261] (II) Measured Results

[0262] Measured resistance at 1.26℃:

[0263] Resistance after correction at standard temperature of 2.20℃:

[0264] 3. Actual performance advantages: Compared with the national standard requirement of 0.268Ω / km, the actual resistance is about 0.74% better than the national standard, and the performance is better than the theoretical calculation value.

[0265] VI. Core Benefit Analysis

[0266] 1. Conductivity distribution: According to calculations, the conductivity of the inner aluminum conductor accounts for 29.98% of the total conductivity, while the conductivity of the outer copper conductor accounts for 70.02% of the total conductivity, achieving efficient synergy between the conductivity of copper and aluminum.

[0267] 2. Copper saving: Compared with pure copper conductors of the same specification, the copper cross-sectional area of ​​this composite conductor is only 45.3mm², saving 30.8% of copper usage. It meets the material requirements for composite conductors in Clause 5.2.3 of GB / T3956-2008, and has both economic and practical advantages.

[0268] VII. Experimental Conclusions

[0269] The structural parameters of the 1.70mm² copper-aluminum composite stranded conductor, such as the number of single wires and the stranding diameter, all meet the requirements of GB / T3956-2008 standard, and have the structural basis for mass production.

[0270] 2. The measured resistance per unit length of the conductor at 20℃ is 0.26602Ω / km, which is 0.74% better than the national standard for copper conductors. The conductivity meets the standard and has performance redundancy.

[0271] 3. While ensuring conductivity, the product achieves a 30.8% reduction in copper material, balancing power transmission requirements with raw material cost control, and has high engineering promotion value.

[0272] 10mm² Copper-Aluminum Composite Stranded Conductor Prototype Development and Testing Record

[0273] I. Basic Experimental Information

[0274] (I) Experimental Objective

[0275] 1. Verify whether the structural parameters of the self-developed 10mm² copper-aluminum composite stranded conductor meet the requirements of GB / T 3956-2008 "Conductors of Cables" standard.

[0276] 2. Calculate and measure the DC resistance per unit length of the composite conductor, evaluate whether its conductivity is better than the national standard for copper conductors, and calculate the copper material saving benefits.

[0277] (II) Experimental Equipment

[0278] Digital DC bridge QJ36B-2, vernier caliper

[0279] II. Core Specifications of the Conductor Under Test

[0280] (I) Overall Structure

[0281] The conductor is a double-layered, circular, single-wire stranded structure with an inner aluminum and an outer copper core. Its nominal cross-sectional area is 10 mm², the actual total cross-sectional area is 10.94 mm², and it has 13 single wires with a stranded outer diameter of 3.8 mm. (Reference) Figure 3 .

[0282] (II) Detailed parameters of each layer

[0283] Inner core layer aluminum 1 round Circular monofilament: 1 piece (3.14mm²); Circular monofilament: 3.14 mm²; 3.14mm² 2.0mm outer core layer copper 12 circular concentric twisted Circular monofilaments: 12 strands (0.65mm² / strand) 7.8mm² 7.8mm² 3.8mm

[0284] III. Compliance Verification of Structural Parameters

[0285] According to the requirements of GB / T 3956-2008 standard, the key indicators of the conductor structure were verified, and the results are as follows:

[0286] 1. Number of single wires: The total number of single wires in the conductor is 13, which meets the requirement of "minimum number of single wires ≥ 6" for the second type of stranded copper conductor of 10mm² specification in the standard, ensuring the mechanical flexibility and structural stability of the conductor.

[0287] 2. Stranding diameter: The overall stranding outer diameter of the conductor is 3.8mm, which conforms to the allowable diameter range of 10mm² tightly stranded round conductors in Table C2 of Appendix C of the standard, and can be adapted to subsequent cable cabling processes.

[0288] IV. Theoretical Calculation of Conductivity

[0289] (a) Basis for Calculation

[0290] 1. Formula for DC resistance of a conductor: (L=1km, the standard length for cable industry measurement; ρ is conductor resistivity; S is conductor cross-sectional area)

[0291] 2. Standard resistivity value: Aluminum conductor Copper conductor .

[0292] 3. Formula for parallel resistors: (The inner aluminum core and the outer copper core are connected in parallel for electrical conduction.)

[0293] (II) Step-by-step calculation

[0294] 1. Single-layer resistor

[0295] Inner core aluminum conductor resistance:

[0296] Resistance of the outer copper conductor:

[0297] 2. Overall parallel resistor

[0298]

[0299]

[0300] =0.5635

[0301]

[0302] 3. Theoretical performance comparison: Compared with the maximum permissible resistance of 10mm² annealed copper conductor (1.83Ω / km) in GB / T3956-2008, the theoretically calculated value is about 3.03% better than the national standard.

[0303] V. Experimental Measurement of Electrical Conductivity

[0304] (a) Test conditions

[0305] • Test ambient temperature: 18℃

[0306] • Test conductor length: 1m

[0307] • Testing instrument: QJ36B-2 digital DC bridge

[0308] (II) Measured Results

[0309] Measured resistance at 1.18℃:

[0310] Resistance after correction at standard temperature of 2.20℃:

[0311] 3. Actual performance advantages: Compared with the national standard requirement of 1.83Ω / km, the actual resistance is about 2.19% better than the national standard, and the performance is better than the theoretical calculation value.

[0312] VI. Core Benefit Analysis

[0313] 1. Conductivity distribution: According to calculations, the conductivity of the inner aluminum conductor accounts for 20% of the total conductivity, while the conductivity of the outer copper conductor accounts for 80% of the total conductivity, achieving efficient synergy between the conductivity of copper and aluminum.

[0314] 2. Copper saving: Compared with pure copper conductors of the same specification, the copper cross-sectional area of ​​this composite conductor is only 7.8mm², saving 19.60% of copper usage. It meets the material requirements for composite conductors in Clause 5.2.3 of GB / T3956-2008, and has both economic and practical advantages.

[0315] VII. Experimental Conclusions

[0316] The structural parameters of the 1.10mm² copper-aluminum composite stranded conductor, such as the number of single wires and the stranding diameter, all meet the requirements of GB / T3956-2008 standard, and have the structural basis for mass production.

[0317] The measured resistance per unit length of the conductor at 2.20℃ is 1.7899Ω / km, which is better than the national standard for copper conductors by 2.19%, indicating that the conductivity meets the standard and has performance redundancy.

[0318] 3. While ensuring conductivity, the product achieves a 19.60% reduction in copper material, balancing power transmission requirements with raw material cost control, and has high engineering promotion value.

[0319] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims.

Claims

1. A low-cost, high-conductivity copper-aluminum composite conductor, characterized in that: Based on the nominal cross-sectional area of ​​the target conductor, the conductor is divided into three specifications: large cross-section, medium cross-section, and small cross-section; by utilizing the gap filling advantage of irregularly shaped wires, the total physical cross-sectional area of ​​the conductor is made greater than the nominal cross-sectional area. Large and medium cross-sections use a central circular aluminum single wire combined with an outer irregular aluminum single wire and an outer irregular copper single wire; Small cross-sections use a single circular aluminum wire paired with an outer circular copper wire to construct a concentric stranded structure of inner aluminum and outer copper. The small cross-sectional area is no more than 25 mm², and the proportioning coefficient K ranges from 0.07 to 0.

10. The mid-section range is defined as having a nominal cross-sectional area between 35 mm² and 150 mm², and the proportioning coefficient K ranges from 0.55 to 0.

65. The large cross-section range has a nominal cross-sectional area of ​​not less than 185 mm², and the proportioning coefficient K ranges from 1.00 to 1.

06. The number of single aluminum wires in the inner core of the small cross-section section is fixed at 1, while the number of single copper wires in the outer layer is 11 to 13. The number of single aluminum wires in the inner core of the cross-section is 5 to 6, and the number of single copper wires in the outer layer is 9 to 11. The number of single aluminum wires in the inner core of the large cross-section section is 19 to 22, and the number of single copper wires in the outer layer is 18 to 21.

2. The method for selecting the low-cost, high-conductivity copper-aluminum composite conductor as described in claim 1, characterized in that: By using a combination of round single wires and irregularly shaped single wires concentrically twisted together, and taking advantage of the gap filling of the irregularly shaped wires, the total physical cross-sectional area of ​​the conductor is greater than the nominal cross-sectional area, thereby improving the overall conductivity without increasing the outer diameter of the finished product. It adopts a concentric stranded and parallel conductive structure of inner aluminum and outer copper, and combines round single wires with irregularly shaped single wires to achieve ultra-dense filling. The total physical cross-sectional area of ​​the conductor is greater than the nominal cross-sectional area. The ratio of aluminum to copper single wires is configured according to the nominal cross-section. The outer diameter and number of single wires of the finished product meet the GB / T3956-2008 standard. The DC resistance of the conductor at 20℃ is better than the national standard requirements. The amount of copper used is 19.60% to 39.79% less than that of pure copper conductors of the same specification. It is used in power transmission and distribution cable conductors.

3. The method for selecting a low-cost, high-conductivity copper-aluminum composite conductor as described in claim 2, characterized in that: Includes the following steps: S1. Based on the nominal cross-sectional area of ​​the target conductor, divide the conductor into three design zones: large cross-section, medium cross-section, and small cross-section. S2. Pre-set the aluminum-copper single wire ratio coefficient K for each interval, wherein the ratio coefficient K is equal to the ratio of the total number of aluminum single wires to the total number of copper single wires; S3. Determine the number of inner core aluminum single wires and outer layer copper single wires based on the ratio coefficient K of the target conductor's interval; calculate the total cross-sectional area of ​​the copper core based on the preset copper material saving rate, determine the total cross-sectional area of ​​the aluminum core based on the ultra-dense filling constraint, and then calculate the cross-sectional area of ​​a single aluminum single wire and a single copper single wire using the linkage algorithm of the number of wires and the cross-sectional area of ​​a single wire; use a combination of round single wires and irregular single wires for ultra-dense concentric stranding to make the total physical cross-sectional area of ​​the conductor greater than the nominal cross-sectional area, while controlling the finished stranded outer diameter to meet the requirements of GB / T 3956-2008; S4. Match the corresponding single-wire structure according to the cross-sectional area: large and medium cross-sections use a central circular aluminum single wire with an outer irregular aluminum single wire and an outer irregular copper single wire; small cross-sections use a single circular aluminum single wire with an outer circular copper single wire to construct a concentric stranded structure of inner aluminum and outer copper. S5. Conduct electrical verification using the DC resistance formula for conductors and the parallel resistance model of copper and aluminum to ensure that the DC resistance of the composite conductor at 20℃ is not greater than the maximum allowable resistance value of pure copper conductors of the same specification in GB / T 3956-2008. S6. Perform temperature correction and performance testing on the trial samples to confirm that the number of single wires, stranded outer diameter, and DC resistance all meet the standards, and complete the conductor design.

4. The method for selecting a low-cost, high-conductivity copper-aluminum composite conductor as described in claim 2, characterized in that: The calculation formula is: 1) Calculation of the number of wires and the cross-sectional area of ​​a single copper wire: The cross-sectional area of ​​a single copper wire is equal to the total cross-sectional area of ​​the copper core divided by the total number of copper wires; the total cross-sectional area of ​​the aluminum core is the sum of the products of the number of single wires in each layer of the aluminum core and the corresponding cross-sectional area of ​​the single wire. 2) Formula for calculating the total cross-sectional area of ​​the copper core: The total cross-sectional area of ​​the copper core is equal to the nominal cross-sectional area multiplied by (1 - copper material saving rate); 3) The resistivity of copper conductor is taken as 17.241 Ω·mm² / km, and the resistivity of aluminum conductor is taken as 28.264 Ω·mm² / km. The measured length is taken as 1 km. The resistance of a single conductor material is equal to the resistivity multiplied by the length and then divided by the corresponding cross-sectional area. The total resistance of copper and aluminum in parallel meets the formula for calculating parallel resistance, i.e., the overall parallel resistance. 4) Ultra-dense filling constraint: The total physical cross-sectional area of ​​the conductor is greater than the nominal cross-sectional area.

5. The method for selecting a low-cost, high-conductivity copper-aluminum composite conductor as described in claim 2, characterized in that: The nominal cross-sectional area of ​​a single copper or aluminum tube is as follows: 1) Nominal cross-section 240mm² large cross-section conductor: the cross-sectional area of ​​a single round aluminum conductor is 5.14 mm², the cross-sectional areas of a single irregularly shaped aluminum conductor are 7.48 mm² and 8.33 mm² respectively, and the cross-sectional area of ​​a single irregularly shaped copper conductor is 7.65 mm². 2) Nominal cross-section 70mm² conductor: single circular aluminum cross-section area is 5.31mm², single irregular aluminum cross-section area is 5.30mm², single irregular copper cross-section area is 4.53mm². 3) Nominal cross-section 10mm² small cross-section conductor: The cross-sectional area of ​​a single circular aluminum conductor is 3.14mm², and the cross-sectional area of ​​a single circular copper conductor is 0.65mm².

6. The method for selecting a low-cost, high-conductivity copper-aluminum composite conductor as described in claim 2, characterized in that: The cross-section of the irregularly shaped lines is trapezoidal or trapezoidal, and the irregularly shaped lines are in close contact with each other.

7. The method for selecting a low-cost, high-conductivity copper-aluminum composite conductor as described in claim 2, characterized in that: During the selection process, a full-chain calculation model is constructed, which includes nominal cross-section, grade division, number of wires ratio, single wire cross-sectional area, total cross-section of the zone, parallel resistance, conductivity ratio, and copper material saving rate. The number of wires, single wire size, electrical performance, and economic indicators are mutually constrained and verified in a closed loop.

8. The method for selecting a low-cost, high-conductivity copper-aluminum composite conductor as described in claim 2, characterized in that: The following series of formulas are used in the selection process: National standard fixed physical property parameters Resistivity of copper conductor: ρ Cu =17.241Ω·mm² / km Resistivity of aluminum conductor: ρ Al =28.264Ω·mm² / km Baseline length: L = 1km Basic Definition S 标称 : Nominal cross-sectional area of ​​the conductor (mm²); S Al : Total cross-sectional area of ​​the inner aluminum conductor (mm²); S Cu : Total cross-sectional area of ​​the outer copper conductor (mm²); S 物理总 : Total physical cross-sectional area of ​​the conductor (mm²); N Al Total number of aluminum single wires; N Cu Total number of copper wires; s Al Cross-sectional area of ​​a single aluminum wire (mm²); s Cu Cross-sectional area of ​​a single copper wire (mm²); K: Aluminum-copper ratio coefficient ; Filling constraints: S 物理总 =S Al +S Cu S 物理总 >S 标称 Core calculation formula 1) Formula linking the number of strands to the cross-sectional area of ​​a single filament All single wires in the copper core have the same specifications: s Cu = The aluminum core uses a multi-specification single-wire layered combination: S Al =∑(N Ali s Ali ) Where: N Ali s Ali These are the number of single wires and the cross-sectional area of ​​a single wire in each layer of the aluminum core; DC resistance of a single-material conductor Total resistance of copper and aluminum in parallel Copper material saving rate and target total cross-section of copper core Copper saving rate = 100% = (1 - Copper material saving rate) VI. Segmentation Structure, Parameters, and Complete Verification (Based on Experimental Data) Gear Classification Rules Small cross-section: ≤25mm², representing a specification of 10mm² Mid-section: 35mm²≤ ≤150mm², representing a specification of 70mm² Large cross-section: ≥185mm², representing a specification of 240mm² Nominal cross-section 240 mm² (large cross-section range) (1) Structure and monofilament parameters Inner core aluminum (19 in total): 1 round aluminum wire with a single wire cross-sectional area of ​​5.14 mm²; 6 irregularly shaped aluminum wires with a single wire cross-sectional area of ​​7.48 mm²; 12 irregularly shaped aluminum wires with a single wire cross-sectional area of ​​8.33 mm². Outer copper layer (18 in total): 18 irregularly shaped copper wires, with a single wire cross-sectional area of ​​7.65 mm²; Total number of single wires: 37; Finished stranded outer diameter: 19.1mm; (2) Cross-section calculation S Al =5.14+6×7.48+12×8.33=150mm² S Cu =18×7.65=137.7mm² S 物理总 =150+137.7=287.7mm² (3) Theoretical verification of resistance Inner core aluminum conductor resistance: Resistance of the outer copper conductor: Overall parallel resistance: = 13.295 (4) Performance and benefits National standard limits: The theoretical value is 0.27% better than the national standard; Measured resistance after correction at 20℃: It is 1.57% better than the national standard; Copper material savings rate: 100% = 39.79% (5) Proportioning coefficient K= 1.056; Standard coefficient range for large cross-section intervals: 1.00~1.06 Nominal cross-section 70 mm² (mid-section range) (1) Structure and monofilament parameters Inner core aluminum (6 in total): 1 round aluminum wire with a single wire cross-sectional area of ​​5.31 mm²; 5 irregularly shaped aluminum wires with a single wire cross-sectional area of ​​5.30 mm². Outer copper layer (10 strands in total): 10 irregularly shaped copper strands, with a single wire cross-sectional area of ​​4.53 mm²; Total number of single wires: 16; Finished stranded outer diameter: 9.95mm; (2) Cross-section calculation S Al =5.31+5×5.3=31.81mm² S Cu =10×4.53=45.30mm² S 物理总 =31.81+45.30=77.11mm² (3) Theoretical verification of resistance Inner core aluminum conductor resistance: Resistance of the outer copper conductor: Overall parallel resistor =3.7535 (4) Performance and benefits National standard limits: The theoretical value is 0.6% better than the national standard; Measured resistance after correction at 20℃: It is 0.74% better than the national standard; Copper material savings rate: 100% = 30.80% (5) Proportioning coefficient K= 0.6; Standard coefficient range for the mid-section interval: 0.55~0.65 Nominal cross-section 10 mm² (small cross-section range) (1) Structure and monofilament parameters Inner core aluminum (1 piece in total): 1 round aluminum wire with a single wire cross-sectional area of ​​3.14 mm²; Outer copper layer (12 in total): 12 round copper wires, each with a cross-sectional area of ​​0.65 mm². Total number of single wires: 13; Finished stranded outer diameter: 3.8mm; (2) Cross-section calculation S Al =3.14mm² S Cu =12×0.65=7.8mm² S 物理总 =3.14+7.8=10.94mm² (3) Theoretical verification of resistance Inner core aluminum conductor resistance: Resistance of the outer copper conductor: Overall parallel resistance: =0.5635 (4) Performance and benefits National standard limits: The theoretical value is 3.3% better than the national standard; Measured resistance after correction at 20℃: It is 2.19% better than the national standard; Copper material savings rate: 100% = 19.6% (5) Proportioning coefficient K= 0.083； The standard coefficient range for small cross-section intervals is 0.07 to 0.10.

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