Method for improving current-carrying capacity of power transmission aluminum conductor based on phosphoric acid electrochemical treatment

Abstract

The invention discloses a method for improving the current-carrying capacity of a power transmission aluminum conductor based on phosphoric acid electrochemical treatment, which comprises the following steps of: putting a pretreated aluminum conductor serving as an anode into a phosphate electrolyte, applying direct-current voltage, performing anodic oxidation treatment, washing and drying after treatment, thereby obtaining the current-carrying capacity of the power transmission aluminum conductor. The current-carrying capacity of the aluminum conductor treated by the method at 70 DEG C is improved by more than 5% compared with that of an untreated aluminum conductor, meanwhile, the influence on the mechanical property of an aluminum stranded wire is small, the corrosion resistance of the conductor is reserved or enhanced, the process is simple, and the aluminum conductor is suitable for batch transformation of existing power transmission conductors. And process parameters can be adjusted according to different wire models, and the applicability is high.

Description

Technical Field

[0001] This invention belongs to the field of power transmission conductor processing technology, specifically relating to a method for increasing the current carrying capacity of aluminum power transmission conductors based on phosphoric acid electrochemical treatment. Background Technology

[0002] Transmission conductors are wires used for power transmission, widely used in high-voltage and ultra-high-voltage overhead transmission lines. Currently, the current-carrying capacity of transmission conductors (especially steel-cored aluminum stranded wire) during long-term operation is mainly limited by the conductor's allowable operating temperature and heat dissipation capacity. Conventional methods to increase current-carrying capacity mainly include replacing conductors with larger cross-section conductors, using new conductor materials, and increasing the capacity of conductor surface coatings. However, these methods are still subject to many limitations, such as: 1. Replacing conductors with larger cross-sections requires replacing the entire line's conductors, resulting in a long construction period, frequent power outages, high renovation costs, and increased weight placing higher demands on the load-bearing capacity of poles and fittings. Sometimes, it is also necessary to reinforce or replace the poles.

[0003] 2. Replace with new high-temperature, low-sag conductors (such as aluminum-clad steel and aluminum alloy core composite conductors ACCC / ACCR). These conductors are expensive, have complex processing techniques, and different core and outer materials have different coefficients of thermal expansion, posing a risk of contact fatigue during long-term operation. The installation process is also demanding, and there is insufficient experience in maintaining the corrosion resistance of some new materials under long-term operation.

[0004] 3. Capacitance treatment is applied to the surface coating of the conductor, such as coating with high thermal conductivity ceramic or metal coating. However, the coating is prone to aging, peeling or cracking when exposed to the outdoors for a long time. With the increase of coating thickness, the weight of the conductor increases and the flexibility decreases. Some coatings will affect the corrosion resistance of the conductor.

[0005] Furthermore, regarding surface treatment, some technologies attempt to improve heat dissipation efficiency by applying high thermal conductivity coatings or modifying the surface morphology through machining. However, coatings may reduce the corrosion resistance and long-term stability of the conductors, while machining can easily damage the structural integrity of the aluminum stranded wire and is costly. In summary, the current carrying capacity of conductors is currently mainly affected by their allowable operating temperature and heat dissipation capacity, and current technologies for increasing the current carrying capacity of transmission conductors are often limited by many factors and difficult to apply on a large scale.

[0006] To address the aforementioned issues, significant efforts have been made to achieve the goal of increasing the capacity of power transmission lines, for example: To improve the current carrying capacity of power transmission conductors, Chinese Patent No. CN119852035A discloses a heat-resistant, high-conductivity fiber-reinforced aluminum-based composite core aluminum stranded wire and its preparation method, including: (1) depositing a copper nanolayer on the surface of the fiber filament in the carbon fiber bundle and then performing ultrasound in the aluminum alloy liquid to obtain aluminum-based composite filament 1; (2) depositing a copper nanolayer on the aluminum-based composite filament 1 to obtain aluminum-based composite filament 2; (3) stranding the aluminum-based composite filament 2 to obtain aluminum-based composite stranded wire 1; (4) performing ultrasound on the aluminum-based composite stranded wire 1 in the aluminum alloy liquid to obtain aluminum-based composite stranded wire 2; (5) depositing a copper nanolayer on the aluminum-based composite stranded wire 2 to obtain aluminum-based composite core material; (6) stranding the aluminum-based composite core material with aluminum wire.

[0007] Chinese Patent No. CN117987694A discloses a high-conductivity, high-corrosion-resistant aluminum monofilament, its production process, and its applications. The aluminum monofilament's composition, by mass percentage, is: Ce 0.06~0.08%, Ga 0.02~0.03%, Fe 0.10~0.25%, Si≤0.22%, Ti≤0.001%, with the remainder being Al and other unavoidable impurities. The production process includes the following steps: aluminum molten metal smelting, vacuum smelting, converter smelting, submerged refining, continuous casting and rolling, and drawing and scraping. This technology increases the current-carrying capacity of power transmission conductors by altering the composition of the aluminum monofilament.

[0008] Chinese Patent No. CN220709970U discloses a low-sag, high-capacity capacity-enhancing conductor, comprising a core support member, an inner aluminum wire layer, an outer aluminum wire layer, and a lubricating grease layer. The core support member is trapezoidal in shape and is disposed outside the core support member along the circumferential direction of the core support member. The outer aluminum wire layer is circular, facing away from the core support member, and is disposed outside the inner aluminum wire layer along the circumferential direction of the inner aluminum wire layer.

[0009] However, the transmission conductors prepared by the above methods are expensive, and due to differences in parameters such as weight, wire diameter, and operating temperature, they cannot be used to upgrade old lines, thus making large-scale application difficult. Summary of the Invention

[0010] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0011] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0012] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for increasing the current carrying capacity of aluminum transmission conductors based on phosphoric acid electrochemical treatment.

[0013] To solve the above-mentioned technical problems, the present invention provides the following technical solution: including, Using a pretreated aluminum wire as the anode, it is placed in a phosphoric acid electrolyte. The cathode is selected from lead plate, stainless steel or aluminum plate. A DC voltage is applied to perform anodizing treatment. After treatment, it is rinsed and dried to obtain an aluminum wire with a porous alumina structure.

[0014] As a preferred embodiment of the method for improving the current carrying capacity of transmission aluminum conductors based on phosphoric acid electrochemical treatment according to the present invention, the pretreatment includes surface cleaning treatment by degreasing with organic solvents, immersion in alkaline solution or rinsing with water to remove surface oil, oxides and impurities.

[0015] In a preferred embodiment of the method for increasing the current carrying capacity of aluminum transmission conductors based on phosphoric acid electrochemical treatment according to the present invention, the concentration of the phosphoric acid electrolyte is 0.3~0.6 mol / L.

[0016] In a preferred embodiment of the method for improving the current carrying capacity of aluminum transmission conductors based on phosphoric acid electrochemical treatment according to the present invention, the temperature of the phosphoric acid electrolyte is 0~20℃.

[0017] In a preferred embodiment of the method for increasing the current-carrying capacity of transmission aluminum conductors based on phosphoric acid electrochemical treatment according to the present invention, the current density of the DC voltage is 0.05~0.15 A / cm. 2 .

[0018] As a preferred embodiment of the method for improving the current carrying capacity of transmission aluminum conductors based on phosphoric acid electrochemical treatment according to the present invention, the anodizing treatment time is 10~30 min.

[0019] As a preferred embodiment of the method for improving the current carrying capacity of transmission aluminum conductors based on phosphoric acid electrochemical treatment according to the present invention, the current carrying capacity of the aluminum conductors treated by the method at 70°C is increased by more than 5% compared with the current carrying capacity of the untreated aluminum conductors.

[0020] Another object of the present invention is to provide a method for improving the current carrying capacity of aluminum transmission conductors based on phosphoric acid electrochemical treatment.

[0021] Beneficial effects of this invention: The method of this invention prepares a porous alumina structure on the surface of aluminum stranded wire through phosphoric acid anodizing, which not only significantly improves the surface heat dissipation performance, thereby increasing the current carrying capacity of the conductor at rated temperature, but also has the following advantages: 1. The process is simple and suitable for the batch modification of existing power transmission lines; 2. While retaining the corrosion resistance of the conductor, it has minimal impact on the mechanical properties of the aluminum stranded wire; 3. Process parameters can be adjusted according to different wire types, making it highly adaptable. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 These are surface microstructure images of the aluminum wires in Embodiments 1, 2 and Comparative Example 1 of the present invention.

[0023] Figure 2 The temperature of the aluminum wires in Embodiments 1, 2 and Comparative Example 1 of the present invention under different currents. Detailed Implementation

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0025] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0026] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0027] Unless otherwise specified, all raw materials used in this invention are commercially available in the field.

[0028] The method for determining the current carrying capacity and actual breaking force of the aluminum conductor at 70°C in this invention refers to: Current carrying capacity measurement method: Select a 120mm long wire with a length of 1.5m. 2Aluminum-clad steel-cored aluminum stranded wire is tested. Copper lugs are connected to both ends of the conductor, and temperature sensors are placed on the conductor surface to monitor the conductor temperature in real time. A current-temperature-rise device is then connected to both ends of the conductor to apply current. The current is gradually increased from 0 A. Before the conductor temperature reaches 60°C, the current is increased by 20 A at a time. Once the conductor temperature stabilizes (no temperature change within 10 minutes), the current is increased further until the conductor temperature exceeds 60°C. Subsequently, the current is increased by 1 A at a time until the conductor temperature reaches 70°C and remains constant. At this point, the conductor current represents the maximum current-carrying capacity at 70°C.

[0029] Actual breaking force measurement method: Step 1: Sample Preparation 1. Sampling: Cut a straight and undamaged sample from the entire reel of wire. The sample length must meet the requirements of the testing machine for clamping and measuring gauge length, and is usually no less than 8 to 10 meters.

[0030] 2. End Fabrication: This is the most crucial step, designed to ensure that the wire does not fail prematurely due to stress concentration at the clamping point, thus preventing breakage within the effective length. Common methods include: Casting method: Using casting materials such as metal (e.g., zinc) or epoxy resin, the end of the wire is cast into a specially designed sleeve (e.g., a steel anchor). The cast body can evenly distribute the clamping force and protect the internal steel wire.

[0031] Crimping method: Using specially made aluminum or steel pipes, the fittings are crimped onto the ends of the wires using a hydraulic press to form a strong connection.

[0032] Pre-twisted wire ends: Multiple pre-formed wires are wound around the wire ends to increase friction with the clamps and distribute stress. This method requires skilled operation.

[0033] Step 2: Test Equipment Universal testing machine: It must have sufficient capacity (the tensile force should be greater than the expected breaking force of the conductor) and the accuracy should meet the standard requirements (usually grade 1 or 0.5).

[0034] Fixtures: Wedge-shaped fixtures or hydraulic push-pull fixtures are used to ensure that the prepared end is firmly held and will not slip during the stretching process.

[0035] Extensometer: Used to accurately measure the elongation of a conductor, which helps in plotting stress-strain curves.

[0036] Step 3: Experimental Procedure Install the specimen: Install the prepared specimen at the center of the upper and lower clamps of the testing machine, ensuring good alignment and avoiding skewing that could generate additional bending moment.

[0037] Apply initial load: First apply a small initial tension (typically 1%-5% of RTS) to eliminate initial bending and slack in the conductor. Take this state as the "zero point".

[0038] Measure the gauge length: Mark a distance (e.g., 500 mm or 1 m) in the effective section of the middle of the specimen as the original gauge length (L0).

[0039] Smooth loading: Apply tensile force at a constant rate. The loading rate should increase the tensile stress in the specimen at a rate between 10 and 100 MPa / s. For example, the movement speed of the testing machine beam can be controlled between 1 and 50 mm / min.

[0040] Continuous recording: The testing machine automatically records the tensile force-displacement (or tensile force-strain) curve until the specimen breaks.

[0041] Observe the fracture phenomenon: Observe and record the fracture location: Valid fracture: The fracture occurred within the gauge length and was far from the clamp. This data is valid.

[0042] Invalid fracture: Fracture occurring within or too close to the fixture (e.g., within one pitch) may be due to improper end preparation. This data should be discarded, and resampling and testing are required.

[0043] Read the breaking force (Fb): Read the maximum tensile force value from the recorded curve, which is the actual breaking force. Example 1 This embodiment provides a method for increasing the current carrying capacity of aluminum transmission conductors based on phosphoric acid electrochemical treatment, specifically: 1) Preprocessing: The aluminum stranded wire to be processed in this embodiment (diameter is 120mm) 2 The aluminum-clad steel core aluminum stranded wire undergoes surface cleaning treatment. The wire is immersed in a sodium hydroxide solution with a concentration of 1 mol / L and a temperature of 30°C for 45 seconds, then rinsed with distilled water, and then immersed in a phosphoric acid solution with a concentration of 0.1 mol / L for 10 seconds to remove residual sodium hydroxide. Finally, it is ultrasonically cleaned with distilled water for 60 seconds to remove oil, oxides and impurities, thus obtaining the pretreated aluminum stranded wire.

[0044] 2) Electrochemical treatment with phosphoric acid: A 0.3 mol / L phosphoric acid electrolyte was prepared. Pretreated aluminum stranded wire was used as the anode and placed in the phosphoric acid electrolyte at a temperature of 20°C. A lead plate was used as the cathode, and a current density of 0.1 A / cm² was applied. 2 The anodizing process was performed using a DC voltage for 20 minutes.

[0045] 3) Post-processing: After completing the phosphoric acid electrochemical treatment, the aluminum stranded wire is removed, rinsed with deionized water, and dried to obtain the aluminum wire with a porous alumina structure in this embodiment.

[0046] Example 2 The difference between this embodiment and Embodiment 1 is that the current density in step 2) is adjusted to 0.05 A / cm. 2 The remaining steps and processes are the same as in Example 1, resulting in the aluminum conductor of this example.

[0047] Comparative Example 1 This comparative example uses a diameter of 120mm without any treatment. 2 Aluminum-clad steel core aluminum stranded wire was used as a blank control.

[0048] Comparing the surface microstructures of the aluminum wires in Example 1, Example 2, and Comparative Example 1, the results are as follows: Figure 1 As shown, the aluminum stranded wire treated with phosphoric acid electrochemically forms a regular and uniformly distributed porous alumina structure on its surface, which significantly improves the radiation and convection heat dissipation performance of the conductor, thereby increasing the current carrying capacity of the transmission conductor at the rated operating temperature, while maintaining its mechanical properties and corrosion resistance.

[0049] The temperatures of the aluminum wires in Examples 1, 2, and 1 under different currents were compared, and the results are as follows: Figure 2 As shown, under the same current, the temperatures of both Example 1 and Example 2 are lower than those of Comparative Example 1, and the temperature of Example 1 is even lower. When the current reaches the maximum allowable operating current of 420A for ordinary conductors, the temperature of the conductor in Comparative Example 1 is 70.6℃, that in Example 1 is 51.7℃, and that in Example 2 is 58.1℃. This indicates that Example 1 has better heat dissipation performance and a larger current carrying capacity under the same conditions.

[0050] The current carrying capacity and mechanical properties of the aluminum conductors in Example 1, Example 2 and Comparative Example 1 at 70°C are compared, and the results are shown in Table 1.

[0051] Table 1

[0052] As shown in Table 1, the current carrying capacity of aluminum stranded wires treated with phosphoric acid electrochemically is significantly improved compared to blank wires, with an increase of up to 10%. This is because the porous alumina structure formed on the surface of the wires after phosphoric acid electrochemical treatment enhances radiative and convective heat dissipation, enabling the wires to carry a larger current at the same temperature, while the actual breaking force does not change significantly. This indicates that the treatment method of the present invention does not cause significant damage to the wire matrix structure, effectively maintaining mechanical performance stability while greatly improving the current carrying capacity. Example 3 The difference between this comparative example and Example 1 is that the current density was adjusted to 0.025 A / cm². 2 0.2 A / cm 2 The remaining steps are the same as in Example 1, to obtain aluminum wires with different current densities in this example.

[0053] The current carrying capacity and mechanical properties of aluminum wires obtained by different current density treatments in this embodiment are compared with those in Embodiments 1 and 2 at 70°C. The results are shown in Table 2.

[0054] Table 2

[0055] As can be seen from Table 2, the conductor exhibits the highest current carrying capacity and superior mechanical properties when the current density of the present invention is 0.1 A / cm². This is because the oxidation reaction rate is moderate at this density, enabling the formation of a uniform alumina layer with a reasonable pore structure, thus maximizing heat dissipation. However, when the current density is too low (0.025 A / cm²), the conductor's performance is significantly improved. 2 If the oxidation reaction is insufficient, the porous structure is not fully developed, the pore structure is small, the heat dissipation performance is limited, and the current carrying capacity increases only slightly. When the density is too high (0.2A / cm²), the reaction is too violent, which may lead to damage to the surface porous structure, cracking of the alumina layer or damage to the conductor substrate, thereby reducing the current carrying capacity and mechanical properties.

[0056] Example 4 The difference between this comparative example and Example 1 is that the electrolyte concentrations were adjusted to 0.1 mol / L and 1 mol / L, respectively. All other steps were the same as in Example 1, resulting in aluminum wires treated with different electrolyte concentrations in this example.

[0057] The current carrying capacity, mechanical properties, and corrosion resistance of aluminum wires treated with different electrolyte concentrations in this embodiment and in Implementation 1 at 70°C are compared, and the results are shown in Table 3.

[0058] Table 3

[0059] As can be seen from Table 3, the performance is optimal when the electrolyte concentration is 0.3 mol / L. At this concentration, phosphoric acid can provide sufficient electrolyte for the oxidation reaction, ensuring the stable progress of the reaction and forming a well-structured porous alumina layer. When the concentration is too low, insufficient electrolyte leads to a higher voltage during the oxidation process, and the porous structure on the aluminum surface is damaged, making it difficult to form an effective heat dissipation porous structure. The current carrying capacity and mechanical properties are also poor. Further increasing the concentration may cause excessive corrosion and damage the integrity of the conductor surface structure.

[0060] Example 5 The difference between this comparative example and Example 1 is that the electrolyte temperature was adjusted to 10°C and 30°C respectively, while the remaining steps were the same as in Example 1, resulting in aluminum wires treated with different electrolyte temperatures in this example.

[0061] The current carrying capacity, mechanical properties, and corrosion resistance of aluminum wires obtained by different electrolyte temperature treatments in this embodiment and in Example 1 at 70°C are compared, and the results are shown in Table 4.

[0062] Table 4

[0063] As shown in Table 4, the current carrying capacity and mechanical properties are optimal when the electrolyte temperature is 20℃, because the reaction rate and reaction controllability are balanced at this temperature, allowing for the precise formation of the desired porous structure. When the temperature drops to 10℃, the reaction rate slows down, the oxidation process is insufficient, the porous structure is not fully developed, and the current carrying capacity decreases slightly. When the temperature rises to 30℃, the reaction rate is too fast, which may lead to uneven growth of the alumina layer or even local peeling, resulting in decreased heat dissipation performance and impaired mechanical properties, further verifying the necessity of temperature control between 0 and 20℃.

[0064] Example 6 The difference between this comparative example and Example 1 is that the processing time was adjusted to 10 min and 30 min respectively, while the remaining steps were the same as in Example 1, resulting in aluminum wires processed for different processing times in this example.

[0065] The current carrying capacity, mechanical properties, and corrosion resistance of aluminum wires obtained by different processing times in this embodiment and in Example 1 at 70°C are compared, and the results are shown in Table 5.

[0066] Table 5

[0067] As can be seen from Table 5, the performance is optimal when the processing time is 20 minutes. This duration ensures that the oxidation reaction proceeds fully, forming an alumina layer with suitable thickness and porosity, perfectly matching the heat dissipation requirements. If the time is too short, the oxidation is incomplete, the porous structure is not fully formed, the heat dissipation improvement is limited, and the current carrying capacity is low. If the time is too long, excessive oxidation will lead to an excessively thick alumina layer or excessive consumption of the conductor substrate, damaging the conductor structure, resulting in a decrease in current carrying capacity and a significant reduction in mechanical properties.

[0068] In summary, this invention creatively constructs a porous alumina structure on the surface of aluminum conductors through phosphoric acid anodizing. This not only overcomes the limitations of existing line replacement, new material, or coating technologies, such as high cost and complex processes, but also improves current carrying capacity. The process is simple and can be adapted to the batch renovation of existing conductors without large-scale line replacement or complex installation. It has little impact on the mechanical properties of aluminum conductors, and can also retain or even enhance corrosion resistance. Furthermore, the process parameters can be adjusted according to the conductor type, making it highly applicable and effectively solving the problem of upgrading old lines. It provides a practical new path for increasing the capacity of power transmission conductors.

[0069] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for increasing the current-carrying capacity of aluminum transmission conductors based on phosphoric acid electrochemical treatment, characterized in that: include, Using a pretreated aluminum wire as the anode, it is placed in a phosphoric acid electrolyte. The cathode is selected from lead plate, stainless steel or aluminum plate. A DC voltage is applied to perform anodizing treatment. After treatment, it is rinsed and dried to obtain an aluminum wire with a porous alumina structure.

2. The method for increasing the current-carrying capacity of aluminum transmission conductors based on phosphoric acid electrochemical treatment as described in claim 1, characterized in that: The pretreatment includes surface cleaning treatment by degreasing with organic solvents, immersion in alkaline solutions, or rinsing with water to remove surface oil, oxides, and impurities.

3. The method for increasing the current-carrying capacity of aluminum transmission conductors based on phosphoric acid electrochemical treatment as described in claim 1, characterized in that: The concentration of the phosphoric acid electrolyte is 0.3~0.6 mol / L.

4. The method for increasing the current carrying capacity of aluminum transmission conductors based on phosphoric acid electrochemical treatment as described in claim 4, characterized in that: The temperature of the phosphoric acid electrolyte is 0~20℃.

5. The method for increasing the current-carrying capacity of aluminum transmission conductors based on phosphoric acid electrochemical treatment as described in claim 1, characterized in that: The current density of the DC voltage is 0.05~0.15 A / cm. 2 .

6. The method for increasing the current-carrying capacity of aluminum transmission conductors based on phosphoric acid electrochemical treatment as described in claim 1, characterized in that: The anodizing treatment time is 10~30 min.

7. The method for increasing the current-carrying capacity of aluminum transmission conductors based on phosphoric acid electrochemical treatment as described in claims 1-6, characterized in that: The current carrying capacity of the aluminum conductor treated by the method at 70°C is increased by more than 5% compared with that of the untreated aluminum conductor.

8. The power transmission aluminum conductor obtained by the method for increasing the current carrying capacity of power transmission aluminum conductors based on phosphoric acid electrochemical treatment as described in claim 7.

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