A method and system for sleeving a power transmission line compression joint

Abstract

The application discloses a kind of transmission line crimping construction's sheath film method and system, it is related to electric power transmission and transformation engineering construction technical field.The method includes: cleaning the surface of aluminium pipe;3-4 layers of polyethylene preservative film are tightly wrapped on the outer surface of aluminium pipe;The aluminium pipe wrapped is placed in hydraulic press mould and is crimped;After crimping is completed, tear off preservative film.The application utilizes the non-polar, high crystallinity and weak surface layer characteristics of polyethylene preservative film, effectively solves the quality problems, such as flash, sticking mould, crimping pipe bending, existing in traditional crimping construction, realizes the standardization of crimping construction, and significantly improves the excellent rate of extra-high voltage transmission line crimping engineering.

Description

Technical Field

[0001] This invention relates to the field of power transmission and transformation engineering construction technology, specifically to a method and system for fabricating a membrane during transmission line crimping construction. Background Technology

[0002] With the rapid development of the power industry and the advancement of science and technology, ultra-high voltage (UHV) power transmission has become the main mode of energy transmission. In a buyer's market, competition among enterprises is essentially competition for quality, and quality is the lifeblood of any enterprise. For on-site construction in power transmission and transformation, the quality of crimping directly affects the success or failure of the entire project and the safety of the employees.

[0003] Currently, with the continuous increase in voltage levels, conductor cross-sections are constantly increasing, and the size of crimping connectors is also increasing accordingly. Taking the Mengxi-Tianjin South 1000 kV UHV AC transmission and transformation project as an example, it uses large-section conductors such as 8×JL / G1A-630 / 45 and 8×JL / G1A-630 / 55. Existing crimping technology mainly follows DL / T 5285-2013 "Hydraulic Crimping Process Specification for Overhead Conductors and Ground Wires in Transmission and Transformation Projects". However, in actual operation, it has been found that traditional crimping methods have many insurmountable technical defects: Severe flash phenomenon: Hydraulic crimping is essentially the transfer and conversion of energy. The chemical energy of gasoline is converted into the mechanical kinetic energy of the die, and during crimping, this mechanical kinetic energy is converted into the heat energy of the material, causing the temperature of the aluminum tube to rise instantaneously. The heat of fusion of aluminum is... J / kg, melting point 660.37℃. Under stress, aluminum crystals undergo plastic deformation. When the stress exceeds the elastic limit, a portion of the crystal slides relative to another portion along certain crystal planes and orientations (slippage). Due to the presence of die gaps, the aluminum crystals slip towards the die gaps before the die is closed, and at the recrystallization temperature (… For aluminum, recrystallization occurs below approximately 100.348℃, eventually forming irregular flash at the edge of the crimped tube. This not only affects the appearance but may also weaken the mechanical strength of the crimped tube.

[0004] The problem of mold sticking is prominent: After plastic deformation, the material exhibits flow laws (plastic potential theory). The combined effect of the adsorption force generated by the plastic potential and the internal friction force generated by the intermolecular forces leads to mold sticking. Specifically, under external pressure, the interface micro-elements of the steel mold and aluminum tube interlock, and the movement of electrons in the aluminum molecules generates instantaneous dipole moments, causing the adjacent molecules to become instantaneously polarized. This mutual coupling produces a net attraction, forming an internal friction force perpendicular to the contact surface. When this force exceeds the weight of the aluminum tube, severe mold sticking occurs, leading to difficulty in demolding and easy damage to the surface of the press-fit tube.

[0005] Bending deformation of crimped tubes: During the crimping process, the aluminum tube material is subjected to impact forces from the crimping die, and internal bending and shear forces exist. When the surface of the crimping die contacts the surface of the crimped tube, the frictional force is unevenly distributed. If the frictional force on one side is greater than that on the other side, it will cause the normal elongation and sliding speed of the material crystals to be inconsistent. The side with greater friction will have a faster crystal sliding speed, ultimately leading to uneven deformation and bending of the crimped tube. Existing solutions, such as creating a crimping operation platform, can improve the human factor, but cannot solve the problem of uneven stress at the material physical level.

[0006] Significant quality fluctuations and reliance on experience: Existing methods rely excessively on the experience of construction personnel. Due to the presence of burrs and bends, the outer diameter after pressing fluctuates greatly, often requiring a skilled and experienced crimper to control the crimping length on-site. The existing method of marking and crimping has too large a variable range, making it prone to errors and difficult to achieve standardized construction.

[0007] In summary, a new method is needed that can fundamentally solve the problems of flash, sticking, and bending at the material physics level, and can standardize the control of pressing quality. Summary of the Invention

[0008] The present invention aims to solve the above-mentioned technical problems by providing a method and system for fabricating a membrane during the crimping construction of power transmission lines.

[0009] To solve the above-mentioned technical problems, the technical solution provided by the present invention is: a method for fabricating a membrane during the crimping construction of ultra-high voltage transmission lines, comprising the following steps: Step 1: Pre-treatment of the crimping tube: Select the aluminum tube to be crimped and clean its outer surface; Step 2, Film Coating: A specific number of layers of cling film are tightly wrapped around the outer surface of the aluminum tube. The cling film is made of polyethylene (PE), and its molecular structure formula is... The carbon atoms are arranged in a zigzag pattern, all atoms are connected by σ bonds, all carbon atoms are sp3 hybridized, and the plastic wrap is treated with an opening agent, antistatic agent, plasticizer and stabilizer to form a weak surface layer. Step 3, Hydraulic pressing: The aluminum tube wrapped in plastic wrap is placed in the pressing mold of the hydraulic press for pressing. During the pressing process, the mechanical energy generated by the hydraulic press is converted into heat energy, causing the temperature of the aluminum tube to rise instantly. However, due to the isolation of the plastic wrap, the surface of the aluminum tube does not come into direct contact with the mold. Step 4, Demolding and Cleaning: After pressing, remove the plastic wrap remaining on the surface of the aluminum tube.

[0010] Preferably, in step two, the critical surface tension of the plastic wrap is... The thickness of the plastic wrap is 1.1 micrometers (0.11 millimeters). The cling film must undergo surface treatment before printing or laminating to increase its surface tension so that it can be smoothly wetted by ink or adhesive, but in this invention it is used as an isolation layer.

[0011] Preferably, in step two, the number of layers of the cling film is 3 to 4. When the number of wrapping layers is 3 or 4, the bending phenomenon of the crimped pipe is completely eliminated, and the edge distance and elongation are qualified. When the number of wrapping layers is 1-2, bending or flash still exists; when the number of wrapping layers is 5-6, the elongation after crimping occasionally exceeds the standard.

[0012] Preferably, in step three, the hydraulic crimping pressure is set according to the wire type. For conductors of model JL / G1A-630 / 45, the rated tensile strength is ≥150.45kN, and the tensioning tension during construction is calculated as 45kN; For conductors of model JL / G1A-630 / 55, the rated tensile strength is ≥164.32kN, and the tensioning tension during construction shall be in accordance with the corresponding standards.

[0013] Preferably, in step three, the non-polar polymer properties of the plastic wrap are used to block the instantaneous dipole moment coupling between aluminum molecules and the steel mold, eliminating the internal friction force generated by intermolecular forces, thereby solving the problem of sticking to the mold; the non-polar polymer material does not generate a net attraction effect due to the mutual coupling of dipole moments.

[0014] Preferably, in step three, the high crystallinity and thermodynamic stability of the plastic wrap are utilized to create a hoop effect during the plastic deformation of the aluminum tube, preventing aluminum crystals from sliding into the die gap and thus eliminating flash. The hoop effect is achieved by the surface tension of the plastic wrap, which is much greater than the intermolecular forces that cause flash.

[0015] Preferably, in step three, the good geometric stability of the plastic wrap ensures that the aluminum tube surface is subjected to uniform force during the pressing process, resulting in a consistent crystal slip rate and thus reducing the probability of the pressing tube bending. Geometric stability refers to the fact that the plastic wrap is not easily stretched or deformed under mechanical force or heat.

[0016] Preferably, in step four, due to the non-polarity and weak surface layer characteristics of the cling film, its adsorption force on the surface of the aluminum tube is much smaller than that between the aluminum tube and the steel mold, so it can be easily peeled off, and the surface of the aluminum tube is smooth and without residue after peeling; the cohesive strength of the weak surface layer is much lower than that of the main body.

[0017] As a preferred embodiment, it includes: a conductor selection module, used to determine the type and parameters of the conductors used in the project, the parameters including conductor type, structure, calculated cross-sectional area, outer diameter and rated tensile strength; The film-wrapping parameter setting module is used to set the number of layers of cling film according to the cross-section of the wire and the type of the compression tube. The number of layers is set to 3 or 4 layers. The crimping control module is used to control the crimping stroke and pressure of the hydraulic press to ensure that the crimping process meets the preset standards. The quality inspection module is used to perform grip strength testing and appearance inspection on the crimped pipe. The grip strength test requires that it be no less than 95% of the design tension.

[0018] Preferably, the quality inspection module's judgment criteria are: for JL / G1A-630 / 45 conductors, the measured gripping force must be ≥142.58kN; For the JLB20A-170 grounding wire, the measured gripping force must be ≥133.4kN; and the surface of the crimped connector must be free of burrs, adhesive residue, and bending. The system will ultimately output a statistical report on the overall line pressure pipe quality rate, requiring a quality rate of no less than 99.75%.

[0019] The advantages of this invention compared to the prior art are: 1. Fundamentally solves flash and mold sticking: Utilizing the high crystallinity and thermodynamic stability of plastic wrap, it acts as a "hoop"-like constraint during the plastic deformation of the aluminum tube, preventing aluminum crystals from sliding into the die gap and fundamentally eliminating flash. At the same time, since plastic wrap is a typical non-polar polymer material with a weak surface layer, it blocks the instantaneous dipole moment coupling between aluminum molecules and the steel die, eliminating the internal friction force generated by intermolecular forces and solving the problem of mold sticking.

[0020] 2. Effectively suppresses pipe bending: The plastic wrap has good geometric stability, allowing it to continue functioning as the pipe extends. Due to its strong inertia and structural stability, the intermolecular forces change little under the same structural influence, resulting in a more uniform distribution of frictional force. This solves the problem of inconsistent crystal slip velocity caused by uneven frictional force, significantly reducing the probability of pipe bending.

[0021] 3. Achieving standardized and regulated construction: By fixing the number of wrapping layers (3-4 layers), the elongation and edge distance data after crimping are highly consistent. Because of the wrapping with plastic wrap, waste edges generated after crimping are eliminated, and this waste edge extends towards the conductor side, increasing the gripping force between the crimped pipe and the conductor. Furthermore, this construction method is not only applicable to crimped pipes for UHV transmission lines but also to crimped pipes for all transmission lines, and even similar crimping conditions. This reduces reliance on operator experience, significantly lowering the requirements for plan preparation and on-site operation while ensuring quality. It helps to standardize construction procedures and solves the previous problem of "the variable range of the marking and crimping process being too large, often leading to errors."

[0022] 4. Significantly improves project quality and economic benefits: Actual application verification in the Mengxi-Tianjin South project showed that all 543 conductor splice pipes along the entire line were of excellent quality, and the excellent rate of 816 tension-resistant compression fittings reached 99.75%. This method greatly improved the pass rate of compression fitting quality, laying a solid foundation for achieving high quality on the first attempt, reducing rework losses, and demonstrating significant economic benefits and promotional value. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the route of the present invention; Figure 2 This is a tension diagram of the present invention; Figure 3 This is the first test report on the crimping grip of the conductor grounding wire according to the present invention; Figure 4 This is the second test report on the crimping grip of the conductor grounding wire according to the present invention; Figure 5 This is the third test report on the crimping grip of the conductor grounding wire according to the present invention; Figure 6 This is a flowchart illustrating the overall method of the present invention; Figure 7 This is a detailed flowchart of the film processing of the present invention; Figure 8 This is a flowchart explaining the hydraulic crimping principle of the present invention. Detailed Implementation

[0024] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[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] This invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of this invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not be construed as limiting the scope of protection of this invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0028] Furthermore, in the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used solely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In addition, the terms "first," "second," or "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0029] Unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" in this invention should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; similarly, they can refer to mechanical connections, electrical connections, or direct connections, or indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0030] Example 1

[0031] This example demonstrates the application of JL / G1A-630 / 45 conductor crimping in the Mengxi-Tianjin South 1000 kV UHV AC transmission and transformation project, specifically in Section 2 of the line construction. This section begins at Chijiayao and ends in Qiantanggou and Houtanggou within Pinglu District, with the entire route consisting entirely of mountainous terrain and difficult transportation. First, based on the engineering design drawings, the conductor type was confirmed as JL / G1A-630 / 45, with the following parameters: aluminum single wire 45 / 4.22mm, galvanized steel wire 7 / 2.81mm, total cross-section 672.81mm², outer diameter 33.75mm, and rated tensile strength ≥150.45kN. During construction, the aluminum tube to be crimped was cleaned and tightly wrapped with three layers of commercially available standard polyethylene cling film (approximately 1.1 micrometers thick). The wrapped aluminum tube was then placed into the crimping mold, and the hydraulic press was started for crimping. During the pressing process, the cling film deforms synchronously with the aluminum tube, utilizing its non-polar properties to block intermolecular coupling. After pressing, the surface of the pressed tube was found to be smooth, without burrs, and easy to demold. Subsequently, a third-party testing agency was commissioned to conduct a grip strength test, and the test results are shown in the table below:

[0032] The results showed that after using plastic wrap, all indicators of the compression fitting met the requirements of DL / T 5285-2013 standard, and the appearance quality was significantly improved.

[0033] Example 2

[0034] JLB20A-170 Grounding Wire Crimping and Multi-Layer Comparison Test: This embodiment applies to the grounding wire crimping of the same project, using the JLB20A-170 grounding wire. The grounding wire parameters are: 19 / 3.40mm diameter, total cross-sectional area 172.50mm², outer diameter 17.0mm, and rated tensile strength ≥203.38kN. For the grounding wire crimping tube, the method of wrapping with four layers of cling film was also used. After crimping, the common sticking phenomenon disappeared, and the cling film adhered tightly to the aluminum tube, making it easy to remove. To verify the optimal number of wrapping layers, the inventors conducted multiple comparative tests in the laboratory, recording the crimping effects after wrapping with different numbers of cling film layers as shown in the table below:

[0035] As shown in the table, the crimped tube quality is optimal when the number of wrapping layers reaches 3 or 4. If the number of layers is too few (1-2 layers), the aluminum tube surface cannot be completely covered, resulting in bending or burrs; if the number of layers is too many (5-6 layers), the elongation after crimping may occasionally exceed the standard. Therefore, the present invention preferably uses 3 or 4 layers.

[0036] Example 3: Large-Scale Engineering Application Data Statistics This example demonstrates the large-scale application effect of the method of the present invention in the Mengxi-Tianjin South 1000kV UHV AC transmission line project (Section 2). In this project, the optimized film-coating crimping scheme was used throughout, meaning that the crimping pipe must be covered with three layers of plastic wrap before crimping. After final acceptance by the Shanxi Provincial Inspection and Quarantine Bureau, the statistical data is as follows: All 543 conductor splices along the entire line were in excellent condition; The excellent rate of 816 tension-resistant pipes was 99.75% (814 / 816). All 24 grounding conduits were of excellent quality; All 34 grounding wire tension pipes were of excellent quality.

[0037] This result fully demonstrates the effectiveness and stability of the method of the present invention. Compared with the traditional method of applying electrical grease (which can improve adhesion but leads to unsightly crimped pipes and a small amount of flash), the film-coating technology of the present invention not only meets the mechanical performance standards, but also achieves a breakthrough in process aesthetics, providing a strong guarantee for the high-quality construction of ultra-high voltage projects.

[0038] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A method for using a liner in the crimping construction of transmission lines, characterized in that, Includes the following steps: Step 1: Pre-treatment of the crimping tube: Select the aluminum tube to be crimped and clean its outer surface; Step 2, Film Coating: A specific number of layers of cling film are tightly wrapped around the outer surface of the aluminum tube. The cling film is made of polyethylene (PE), and its molecular structure formula is... The carbon atoms are arranged in a zigzag pattern, all atoms are connected by σ bonds, all carbon atoms are sp3 hybridized, and the plastic wrap is treated with an opening agent, antistatic agent, plasticizer and stabilizer to form a weak surface layer. Step 3, Hydraulic pressing: The aluminum tube wrapped in plastic wrap is placed in the pressing mold of the hydraulic press for pressing. During the pressing process, the mechanical energy generated by the hydraulic press is converted into heat energy, causing the temperature of the aluminum tube to rise instantly. However, due to the isolation of the plastic wrap, the surface of the aluminum tube does not come into direct contact with the mold. Step 4, Demolding and Cleaning: After pressing, remove the plastic wrap remaining on the surface of the aluminum tube.

2. The method for using a liner in the crimping construction of transmission lines according to claim 1, characterized in that: In step two, the critical surface tension of the plastic wrap is The thickness of the plastic wrap is 1.1 micrometers (0.11 millimeters). The cling film must undergo surface treatment before printing or laminating to increase its surface tension so that it can be smoothly wetted by ink or adhesive, but in this invention it is used as an isolation layer.

3. The method for fabricating a membrane during the crimping construction of an ultra-high voltage transmission line according to claim 1, characterized in that: In step two, the number of layers of the plastic wrap is 3 to 4. When the number of wrapping layers is 3 or 4, the bending phenomenon of the crimped pipe is completely eliminated, and the edge distance and elongation are qualified. When the number of wrapping layers is 1-2, bending or flash still exists; when the number of wrapping layers is 5-6, the elongation after crimping occasionally exceeds the standard.

4. The method for fabricating a membrane during the crimping construction of an ultra-high voltage transmission line according to claim 1, characterized in that: In step three, the hydraulic crimping pressure is set according to the wire type; For conductors of model JL / G1A-630 / 45, the rated tensile strength is ≥150.45kN, and the tensioning tension during construction is calculated as 45kN; For conductors of model JL / G1A-630 / 55, the rated tensile strength is ≥164.32kN, and the tensioning tension during construction shall be in accordance with the corresponding standards.

5. The method for using a liner in the crimping construction of transmission lines according to claim 1, characterized in that: In step three, the non-polar polymer properties of the plastic wrap are used to block the instantaneous dipole moment coupling between aluminum molecules and the steel mold, eliminating the internal friction force generated by intermolecular forces, thereby solving the problem of sticking to the mold; the non-polar polymer material does not generate a net attraction effect due to the mutual coupling of dipole moments.

6. The method for using a liner in the crimping construction of transmission lines according to claim 1, characterized in that: In step three, the high crystallinity and thermodynamic stability of the plastic wrap are utilized to create a hoop effect during the plastic deformation of the aluminum tube, preventing aluminum crystals from sliding into the die gap and thus eliminating flash. The hoop effect is achieved by the surface tension of the plastic wrap, which is much greater than the intermolecular forces that cause flash.

7. The method for using a liner in the crimping construction of transmission lines according to claim 1, characterized in that: In step three, the good geometric stability of the plastic wrap ensures that the aluminum tube surface is subjected to uniform force during the pressing process, resulting in a consistent crystal slip rate and thus reducing the probability of the pressing tube bending. Geometric stability refers to the fact that the plastic wrap is not easily stretched or deformed under mechanical force or heat.

8. The method for fabricating a membrane during the crimping construction of an ultra-high voltage transmission line according to claim 1, characterized in that: In step four, due to the non-polarity and weak surface layer characteristics of the plastic wrap, its adsorption force on the surface of the aluminum tube is much smaller than that between the aluminum tube and the steel mold. Therefore, it can be easily peeled off, and the surface of the aluminum tube is smooth and without residue after peeling. The cohesive strength of the weak surface layer is much lower than that of the main body.

9. A membrane system for crimping construction of ultra-high voltage transmission lines, characterized in that, include: The conductor selection module is used to determine the type and parameters of the conductors used in the project. The parameters include conductor type, structure, calculated cross-sectional area, outer diameter and rated tensile strength. The film-wrapping parameter setting module is used to set the number of layers of cling film according to the cross-section of the wire and the type of the compression tube. The number of layers is set to 3 or 4 layers. The crimping control module is used to control the crimping stroke and pressure of the hydraulic press to ensure that the crimping process meets the preset standards. The quality inspection module is used to perform grip strength testing and appearance inspection on the crimped pipe. The grip strength test requires that it be no less than 95% of the design tension.

10. The method for fabricating a membrane during the crimping construction of an ultra-high voltage transmission line according to claim 9, characterized in that: The quality inspection module's judgment criteria are as follows: for JL / G1A-630 / 45 conductors, the measured gripping force must be ≥142.58kN; For the JLB20A-170 grounding wire, the measured gripping force must be ≥133.4kN; and the surface of the crimped connector must be free of burrs, adhesive residue, and bending. The system will ultimately output a statistical report on the overall line pressure pipe quality rate, requiring a quality rate of no less than 99.75%.

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