A wind power distribution cable resistant to torsional fatigue and its preparation method

Abstract

This invention relates to the field of cable manufacturing technology, and more particularly to a wind power distribution cable with torsional fatigue resistance and its manufacturing method. The manufacturing method includes: stranding tin-plated copper wires in layers to form a conductor; determining the initial strand density coefficient through resistance testing, and accordingly determining the initial torque amplitude of the cyclic torsional load; monitoring resistance changes during loading to determine the strand structure stability index; determining the annealing temperature based on this index and performing annealing treatment, using the microstructure characteristics of the annealed conductor as a transfer parameter; determining the insulation extrusion temperature based on the transfer parameter and performing encapsulation, applying a circumferential gradient cooling airflow during encapsulation; measuring the hardness values ​​of the insulation layer at various circumferential locations after encapsulation and adjusting the cooling intensity distribution curve accordingly; encapsulating the remaining conductors in the same batch according to the adjusted curve, and then manufacturing the finished cable through a shielding layer and an outer sheath. This invention achieves closed-loop parameter transfer and dynamic matching throughout the entire process, significantly improving the torsional fatigue life of the cable.

Description

Technical Field

[0001] This invention relates to the field of cable manufacturing technology, and in particular to a wind power distribution cable resistant to torsional fatigue and its manufacturing method. Background Technology

[0002] As a key component for power transmission in wind turbine generators, wind power distribution cables operate for extended periods in the torsional section between the nacelle and the tower, enduring frequent reciprocating torsional loads in both directions during turbine yaw. With the continuous increase in installed wind power capacity and the trend towards larger turbines, higher demands are placed on the torsional fatigue resistance of distribution cables. In existing technologies, the fabrication of distribution cables typically separates conductor stranding, annealing, and insulation extrusion processes. The process parameters for each process lack a dynamic matching mechanism based on conductor quality, resulting in conductors with poor stranding quality still undergoing subsequent processing with uniform parameters. This makes it difficult to compensate for the adverse effects of early stranding defects on the torsional resistance of the finished product. Simultaneously, the cooling method during insulation coating is singular, with cooling intensity uniformly distributed circumferentially. This leads to a uniform crystalline structure in all directions, preventing the insulation layer from buffering and dispersing stress through structural differences when subjected to torsional loads. This easily results in localized stress concentration and induces crack propagation, limiting the improvement of the overall torsional fatigue life of the cable. Furthermore, existing methods lack quantitative characterization of conductor stranding structure stability, making it difficult to effectively transfer stranding quality test results to subsequent processes to achieve precise control of process parameters.

[0003] Chinese Patent Publication No. CN115662678A discloses a non-circular high-power supercharging cable and its manufacturing method. The supercharging cable includes a non-circular body layer and an auxiliary layer disposed around the non-circular body layer. The non-circular body layer includes several non-circular bodies, which are arranged adjacently to form the non-circular body layer with an annular cross-section. Each non-circular body includes a non-circular conductor and a first auxiliary wire core covering the periphery of the non-circular conductor. Based on the cable structure, making part or all of the cable into a non-circular structure allows for close bonding between the cables, maximizing the use of space within the cable and improving heat transfer. Simultaneously, it allows for a smaller outer diameter, making the cable product lighter.

[0004] Therefore, the existing technology has the following problems: It does not address the dynamic matching of conductor stranding quality and subsequent process parameters, nor does it address the control of the insulation layer's crystal structure, thus failing to solve the fatigue failure problem of wind power distribution cables under reciprocating torsional conditions. Summary of the Invention

[0005] Therefore, the present invention provides a wind power distribution cable resistant to torsional fatigue and its preparation method, in order to overcome the problem that the prior art does not involve the dynamic matching of conductor stranding quality and subsequent process parameters, nor does it involve the control of the crystal structure of the insulation layer, and thus cannot solve the problem of fatigue failure of wind power distribution cables under reciprocating torsional conditions.

[0006] To achieve the above objectives, the present invention provides a method for manufacturing a wind power distribution cable resistant to torsional fatigue, comprising: Step S1: Several tin-plated copper wires are stranded in layers according to preset stranding parameters to form a conductor. The resistance of the stranded conductor is detected to obtain the conductor resistance value, and the initial stranding density coefficient of the conductor is determined based on the conductor resistance value. Step S2: Determine the initial torque amplitude of the torsional loading based on the initial strand density coefficient, apply a cyclic torsional load of the initial torque amplitude to the conductor, monitor the resistance change of the conductor under the cyclic torsional load, and determine the strand structure stability index of the conductor based on the number of cycles when the resistance change reaches the preset condition. Step S3: Determine the annealing temperature of the conductor according to the stranded structure stability index, and anneal the conductor according to the annealing temperature, using the microstructure characteristics of the conductor after annealing as the transfer parameter; Step S4: Determine the extrusion temperature for insulating layer extrusion coating according to the transmission parameters, coat the annealed conductor with insulating layer according to the extrusion temperature, apply gradient cooling airflow around the circumference of the insulating layer during the insulating layer coating process, measure the hardness value at each position of the circumference of the insulating layer after the insulating layer is coated, and adjust the cooling intensity distribution curve of the gradient cooling airflow according to the dispersion of each hardness value. Step S5: According to the adjusted cooling intensity distribution curve, the conductors in the same batch that have not yet been insulated are insulated, and then the insulated conductors are made into finished cables through shielding and outer sheath.

[0007] Further, in step S1, determining the initial strand density coefficient of the conductor based on the conductor resistance value includes: Step S11: Obtain the measured DC resistance value of the conductor and the theoretical DC resistance value of a solid standard conductor of the same material and cross-sectional area as the conductor, and determine the ratio of the theoretical DC resistance value to the measured DC resistance value as the density reference value. Step S12: Obtain the actual mass value per unit length of the stranded conductor and the theoretical mass value of a solid standard conductor of the same material and volume as the conductor, and determine the ratio of the actual mass value to the theoretical mass value as the mass fill rate. Step S13: The initial stranding density coefficient is obtained by weighted summation of the density reference value and the mass filling rate.

[0008] Further, in step S2, determining the initial torque amplitude of the torsional loading based on the initial twist density coefficient includes: Obtain the preset base torque amplitude and calculate the difference between the initial twist density coefficient and the preset standard density coefficient; The torque correction coefficient is determined based on the difference, and the product of the base torque amplitude and the torque correction coefficient is used as the initial torque amplitude.

[0009] Further, in step S2, the stability index of the conductor's strand structure is determined, including: The initial resistance value of the conductor before the cyclic torsional load is obtained. During the cyclic torsional load loading process, the dynamic resistance value of the conductor is collected at fixed intervals. The difference between the dynamic resistance value and the initial resistance value at each collection time is calculated as the resistance drift. A drift evolution curve is constructed with the number of cycles as the x-axis and the resistance drift as the y-axis. The first cycle number when the resistance drift first shows a positive increase, the second cycle number when the resistance drift enters the linear growth stage, and the third cycle number when the resistance drift reaches a preset drift threshold are extracted from the drift evolution curve. The difference between the second cycle number and the first cycle number is calculated as the steady-state duration interval, the difference between the third cycle number and the second cycle number is calculated as the linear growth interval, the ratio of the steady-state duration interval to the linear growth interval is calculated as the damage hysteresis coefficient of the stranded structure, and the damage hysteresis coefficient is used as the stranded structure stability index of the conductor.

[0010] Furthermore, the method for determining when the resistance drift enters the linear growth stage is as follows: Calculate the incremental value of resistance drift at adjacent acquisition times. When several consecutive incremental values ​​fall within a preset stable incremental range, the number of cycles at the starting acquisition time corresponding to the several consecutive incremental values ​​is taken as the second cycle number.

[0011] Further, in step S3, determining the annealing temperature of the conductor based on the stranded structure stability index includes: Obtain the preset base annealing temperature and calculate the difference between the stability index of the stranded structure and the preset standard stability index; In response to the difference being greater than zero, a first temperature compensation value is determined based on the difference, and the difference between the base annealing temperature and the first temperature compensation value is taken as the annealing temperature. In response to the difference being less than or equal to zero, a second temperature compensation value is determined based on the difference, and the sum of the base annealing temperature and the second temperature compensation value is taken as the annealing temperature.

[0012] Further, in step S4, determining the extrusion temperature during insulating layer extrusion coating based on the transmission parameters includes: Obtain the preset base extrusion temperature, and extract the microstructure characteristic value from the transfer parameter, wherein the microstructure characteristic value is the average grain size of the conductor after annealing; Calculate the difference between the average grain size and the preset standard grain size; In response to the difference being greater than zero, a third temperature compensation value is determined based on the difference, and the difference between the base extrusion temperature and the third temperature compensation value is taken as the extrusion temperature. In response to the difference being less than or equal to zero, a fourth temperature compensation value is determined based on the difference, and the sum of the base extrusion temperature and the fourth temperature compensation value is taken as the extrusion temperature.

[0013] Further, in step S4, adjusting the cooling intensity distribution curve of the gradient cooling airflow according to the dispersion of each hardness value includes: The difference between the maximum and minimum hardness values ​​at each circumferential location of the insulation layer is calculated as the hardness range. In response to the hardness range being greater than a preset upper limit value, the rate of change of cooling intensity of the gradient cooling airflow along the circumferential direction is reduced. In response to the hardness range being less than a preset lower limit, the rate of change of cooling intensity of the gradient cooling airflow along the circumferential direction is increased.

[0014] Furthermore, in step S4, the gradient cooling airflow is applied through several sets of annular jet nozzles arranged at intervals along the extrusion direction of the insulating layer. The cooling intensity of each set of annular jet nozzles increases progressively along the extrusion direction of the insulating layer. The jet nozzles at different circumferential positions in the same set of annular jet nozzles have different injection angles and injection pressures.

[0015] Furthermore, a power distribution cable prepared using the aforementioned method for manufacturing wind power-specific power distribution cables resistant to torsional fatigue includes: The device comprises, from the inside out, a conductor, an insulating layer, a shielding layer, and an outer sheath; the conductor is composed of several tin-plated copper wires twisted together in layers; the insulating layer covers the outer periphery of the conductor and has a differentiated crystalline structure in the circumferential direction; the shielding layer includes a conductor shielding layer and an insulating shielding layer, the conductor shielding layer covering the inner surface of the insulating layer and the insulating shielding layer covering the outer surface of the insulating layer; and the outer sheath covers the outer periphery of the insulating shielding layer.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention uses the ratio of the theoretical DC resistance value to the measured DC resistance value as the density benchmark value to reflect the tightness of the stranded structure; it uses the ratio of the actual mass value to the theoretical mass value as the mass filling rate to reflect the sufficiency of metal filling in the stranded structure; it obtains the initial stranding density coefficient by weighted summation of the density benchmark value and the mass filling rate, and comprehensively evaluates the stranding quality by integrating electrical and physical dual-dimensional information; and it maximizes the correlation between the density coefficient and the final torsional resistance performance by regression optimization of the weighting coefficient with torsional fatigue life as the target variable, providing a reliable quantitative input for the precise control of subsequent annealing temperature and extrusion temperature, overcoming the shortcomings of the prior art where single resistance detection is easily interfered with by contact resistance, the stranding quality characterization is incomplete, and stranding defects cannot be effectively transmitted to subsequent processes.

[0017] Furthermore, this invention determines the torque correction coefficient based on the difference between the initial strand density coefficient and the standard density coefficient, enabling the initial torque amplitude to adaptively adjust with the strand density. This overcomes the shortcomings of existing technologies where the torsional loading conditions are fixed and cannot match the actual stranding quality of the conductor, ensuring that the determination of the stranding structure stability index can truly reflect the stranding quality of the conductor. By constructing a drift evolution curve with the number of cycles as the abscissa and the resistance drift as the ordinate, the number of cycles at three key nodes—the first positive growth of the resistance drift, the entry into the linear growth stage, and the reaching of the drift threshold—is extracted. This quantifies the entire damage evolution process of the stranded structure into traceable numerical characteristics, overcoming the limitation of existing technologies that only use the number of failure cycles as a single evaluation index. By calculating the ratio of the steady-state continuation interval to the linear growth interval as the damage hysteresis coefficient, a larger ratio indicates that the stranded structure can maintain a longer stable degradation time after the onset of damage and has a stronger ability to resist accelerated damage propagation. Conversely, a smaller ratio indicates that the structure deteriorates rapidly once it degrades, thus achieving a comprehensive quantitative evaluation of the fatigue degradation resistance of the stranded structure.

[0018] Furthermore, this invention calculates the difference between the stranded structure stability index and the standard stability index, and determines different temperature compensation directions based on the positive and negative values ​​of the difference. This allows for a reduction in annealing temperature when the stranded structure stability is better than the standard level to avoid excessive grain growth, and an increase in annealing temperature when the stranded structure stability is lower than the standard level to fully repair structural defects. This overcomes the shortcomings of existing technologies where the annealing temperature is fixed and cannot be differentiated according to the actual stranding state of the conductor, thus achieving a precise match between the annealing temperature and the stability of the conductor stranded structure.

[0019] Furthermore, this invention extracts the average grain size of the annealed conductor as a microstructure characteristic value and calculates the difference between it and the standard grain size. Based on the positive or negative value of the difference, different temperature compensation directions are determined. When the grains are coarse, the extrusion temperature is reduced to avoid excessive softening of the insulating material, and when the grains are fine, the extrusion temperature is increased to enhance interfacial wetting and bonding. This overcomes the shortcomings of the prior art, which has a fixed extrusion temperature and cannot be adjusted according to the differences in the conductor's microstructure. It achieves a precise match between the extrusion temperature and the conductor grain size.

[0020] Furthermore, this invention calculates the difference between the maximum and minimum hardness values ​​at various circumferential locations of the insulation layer as the hardness range, and presets an upper and lower limit value for the range to form an allowable interval. When the hardness range is greater than the upper limit value, the cooling intensity change rate is reduced to narrow the hardness difference; when the hardness range is less than the lower limit value, the cooling intensity change rate is increased to widen the hardness difference. This overcomes the shortcomings of the prior art, where uniform distribution of cooling intensity leads to a consistent circumferential crystalline structure in the insulation layer, making it impossible to buffer torsional stress through anisotropy. This keeps the hardness range within the allowable interval. By using progressively increasing annular jet nozzles along the extrusion direction, combined with differentiated jetting angles and pressures at different circumferential locations within the same group, a differentiated cooling intensity distribution is formed in the circumferential direction of the insulation layer to induce anisotropic crystalline structures. This allows the cable to decompose torsional stress into several local micro-strains through successive deformations of different hardness regions in the circumferential direction when subjected to torsional loads, avoiding stress concentration and thus significantly improving the torsional fatigue resistance of the insulation layer. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the method for preparing wind power distribution cables resistant to torsional fatigue in this embodiment; Figure 2 This is a flowchart illustrating the process of determining the initial stranding density coefficient in the fabrication method of wind power distribution cables resistant to torsional fatigue in this embodiment; Figure 3 This is a schematic diagram of the wind power distribution cable resistant to torsional fatigue in this embodiment; In the diagram, 1 is the conductor; 2 is the insulation layer; 3 is the shielding layer; and 4 is the outer sheath. Detailed Implementation

[0022] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0023] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0024] Please see Figures 1-2 As shown, Figure 1 This is a flowchart illustrating the method for preparing wind power distribution cables resistant to torsional fatigue in this embodiment; Figure 2 This is a flowchart illustrating the process of determining the initial stranding density coefficient in the preparation method of wind power distribution cables resistant to torsional fatigue in this embodiment.

[0025] This embodiment provides a method for manufacturing a wind power distribution cable resistant to torsional fatigue, including: Step S1: Several tin-plated copper wires are stranded in layers according to preset stranding parameters to form a conductor. The resistance of the stranded conductor is detected to obtain the conductor resistance value, and the initial stranding density coefficient of the conductor is determined based on the conductor resistance value. Step S2: Determine the initial torque amplitude of the torsional loading based on the initial strand density coefficient, apply a cyclic torsional load of the initial torque amplitude to the conductor, monitor the resistance change of the conductor under the cyclic torsional load, and determine the strand structure stability index of the conductor based on the number of cycles when the resistance change reaches the preset condition. Step S3: Determine the annealing temperature of the conductor according to the stranded structure stability index, and anneal the conductor according to the annealing temperature, using the microstructure characteristics of the conductor after annealing as the transfer parameter; Step S4: Determine the extrusion temperature for insulating layer extrusion coating according to the transmission parameters, coat the annealed conductor with insulating layer according to the extrusion temperature, apply gradient cooling airflow around the circumference of the insulating layer during the insulating layer coating process, measure the hardness value at each position of the circumference of the insulating layer after the insulating layer is coated, and adjust the cooling intensity distribution curve of the gradient cooling airflow according to the dispersion of each hardness value. Step S5: According to the adjusted cooling intensity distribution curve, the conductors in the same batch that have not yet been insulated are insulated, and then the insulated conductors are made into finished cables through shielding and outer sheath.

[0026] In this embodiment of the invention, firstly, multiple tin-plated copper wires are stranded according to a preset stranding pitch and layered structure to form a conductor. After the conductor stranding is completed, the measured DC resistance value of the stranded conductor is measured using a DC resistance tester under standard environmental conditions. Because contact resistance exists between individual wires during conductor stranding, and the current flows along the helical direction leading to current path growth, the measured DC resistance value of the stranded conductor is higher than the theoretical DC resistance value of a solid standard conductor of the same material and cross-sectional area. Therefore, obtaining the theoretical DC resistance value of a solid standard conductor of the same material and cross-sectional area as the conductor, and calculating the ratio of the theoretical DC resistance value to the measured DC resistance value as a density benchmark value, can quantify the initial tightness of the stranded structure. Simultaneously, the stranded conductor is weighed per unit length to obtain the actual mass value, and combined with the theoretical mass value of a solid standard conductor of the same material and volume, the ratio of the actual mass value to the theoretical mass value is calculated as the mass fill rate. By testing the mass per unit length of the conductor, its resistance can be determined quickly and accurately. The higher the conductor mass fill rate, the denser the stranding structure and the smaller the gap between the strands. The preset stranding pitch and layering structure can be preset according to the cable specifications and conventional stranding process requirements, and are not limited here.

[0027] Specifically, in step S1, determining the initial strand density coefficient of the conductor based on the conductor resistance value includes: Step S11: Obtain the measured DC resistance value of the conductor and the theoretical DC resistance value of a solid standard conductor of the same material and cross-sectional area as the conductor, and determine the ratio of the theoretical DC resistance value to the measured DC resistance value as the density reference value. Step S12: Obtain the actual mass value per unit length of the stranded conductor and the theoretical mass value of a solid standard conductor of the same material and volume as the conductor, and determine the ratio of the actual mass value to the theoretical mass value as the mass fill rate. Step S13: The initial stranding density coefficient is obtained by weighted summation of the density reference value and the mass filling rate.

[0028] In this embodiment of the invention, the stranded conductor is placed between the measuring fixtures of a DC resistance tester. The four-terminal method is used to measure the actual DC resistance value of the conductor under standard environmental conditions. Simultaneously, based on the conductor's material and nominal cross-sectional area, the theoretical DC resistance value of a solid standard conductor of the same material and cross-sectional area is retrieved from a standard conductor resistance database. This theoretical DC resistance value is the ratio of the inherent resistivity of the material at standard temperature to the cross-sectional area per unit length of the conductor. The ratio of the theoretical DC resistance value to the measured DC resistance value is calculated and used as a density benchmark. The closer the ratio of the theoretical DC resistance value to the measured DC resistance value, the closer the actual conductivity of the stranded conductor is to the theoretical level of a solid conductor of the same specification, and the tighter the stranding structure.

[0029] A sample of a certain length of the stranded conductor is taken and weighed using a precision electronic balance. The actual mass per unit length is obtained by dividing the weighed mass by the sample length. Simultaneously, based on the conductor's nominal cross-sectional area and material density, the theoretical mass of the conductor at the same length when fully filled is calculated. The ratio of the actual mass to the theoretical mass is calculated as the mass fill rate. The closer the ratio of the actual mass to the theoretical mass, the more fully the metal is filled in the stranded structure, and the fewer the gaps between the strands.

[0030] The initial stranding density coefficient is obtained by assigning weight coefficients to the density reference value and the mass fill rate, and then summing them by weight. The weight coefficients are determined as follows: First, several groups of conductor samples with different stranding pitches and stranding tensions are prepared. The density reference value, mass fill rate, and torsional fatigue life of the finished cable are measured for each group of samples. Using torsional fatigue life as the target variable and density reference value and mass fill rate as independent variables, a multiple linear regression analysis is performed. The initial weight coefficients of density reference value and mass fill rate are determined based on the standardized regression coefficients of the independent variables in the regression analysis. Then, the weight coefficients are optimized and adjusted through cross-validation to maximize the correlation coefficient between the density coefficient obtained by weighted summation and torsional fatigue life. Finally, the optimized weight coefficients are used as the weights for the density reference value and mass fill rate.

[0031] This invention uses the ratio of theoretical DC resistance to measured DC resistance as the density benchmark value to reflect the tightness of the stranded structure; it uses the ratio of actual mass value to theoretical mass value as the mass filling rate to reflect the sufficiency of metal filling in the stranded structure; it obtains the initial stranding density coefficient by weighted summing of the density benchmark value and the mass filling rate, and comprehensively evaluates the stranding quality by integrating electrical and physical information; it maximizes the correlation between the density coefficient and the final torsional resistance performance by regressing the weighting coefficient with torsional fatigue life as the target variable, providing a reliable quantitative input for the precise control of subsequent annealing and extrusion temperatures, and overcoming the shortcomings of existing technologies such as susceptibility to contact resistance interference from single resistance detection, incomplete stranding quality characterization, and inability to effectively transfer stranding defects to subsequent processes.

[0032] Specifically, in step S2, determining the initial torque amplitude of the torsional loading based on the initial twist density coefficient includes: Obtain the preset base torque amplitude and calculate the difference between the initial twist density coefficient and the preset standard density coefficient; The torque correction coefficient is determined based on the difference, and the product of the base torque amplitude and the torque correction coefficient is used as the initial torque amplitude.

[0033] In this embodiment of the invention, firstly, a preset basic torque amplitude is obtained. This basic torque amplitude is determined based on the nominal cross-sectional area of ​​the conductor and the empirical value of conventional torsion tests of the material, and serves as a benchmark reference value for torque loading. Simultaneously, a standard density coefficient is preset. This standard density coefficient is a reference value when the stranded structure reaches an ideal tight state, and can be obtained through theoretical calculations of conductors of the same specification or through statistical measurements of a large number of qualified products.

[0034] Calculate the difference between the initial strand density coefficient and the standard density coefficient. If the difference is positive, it indicates that the current conductor's strand density is better than the standard level, the strand structure is tighter, the interlocking between strands is stronger, and it can withstand greater torsional loads without structural instability. In this case, a torque correction coefficient greater than 1 is determined based on the absolute value of the difference. If the difference is negative, it indicates that the current conductor's strand density is lower than the standard level, the strand structure is relatively loose, and a smaller loading torque is needed to avoid premature loosening of the conductor due to excessive loading conditions, which would prevent effective assessment of the strand structure's stability. In this case, a torque correction coefficient less than 1 is determined based on the absolute value of the difference. The specific method for determining the torque correction coefficient can be pre-established by creating a mapping table or fitting function relationship between the absolute value of the difference and the torque correction coefficient, and then calculated by looking up the table or substituting into the function. Finally, multiply the base torque amplitude by the torque correction coefficient to obtain the initial torque amplitude for the current conductor strand density state.

[0035] Specifically, in step S2, the stability index of the conductor's strand structure is determined, including: The initial resistance value of the conductor before the cyclic torsional load is obtained. During the cyclic torsional load loading process, the dynamic resistance value of the conductor is collected at fixed intervals. The difference between the dynamic resistance value and the initial resistance value at each collection time is calculated as the resistance drift. A drift evolution curve is constructed with the number of cycles as the x-axis and the resistance drift as the y-axis. The first cycle number when the resistance drift first shows a positive increase, the second cycle number when the resistance drift enters the linear growth stage, and the third cycle number when the resistance drift reaches a preset drift threshold are extracted from the drift evolution curve. The difference between the second cycle number and the first cycle number is calculated as the steady-state duration interval, the difference between the third cycle number and the second cycle number is calculated as the linear growth interval, the ratio of the steady-state duration interval to the linear growth interval is calculated as the damage hysteresis coefficient of the stranded structure, and the damage hysteresis coefficient is used as the stranded structure stability index of the conductor.

[0036] Specifically, the method for determining whether the resistance drift has entered the linear growth stage is as follows: Calculate the incremental value of resistance drift at adjacent acquisition times. When several consecutive incremental values ​​fall within a preset stable incremental range, the number of cycles at the starting acquisition time corresponding to the several consecutive incremental values ​​is taken as the second cycle number.

[0037] In this embodiment of the invention, before applying a cyclic torsional load, the initial resistance value of the conductor is first measured and recorded using a DC resistance tester. Then, a cyclic torsional load is applied to the conductor according to the initial torque amplitude determined in the above manner. During the loading process, the dynamic resistance value of the conductor is collected at fixed cycle intervals (e.g., after a certain number of cycles). For each collection moment, the difference between the dynamic resistance value at that moment and the initial resistance value before loading is calculated; this difference is the resistance drift. With the number of cycles as the x-axis and the resistance drift as the y-axis, all collected data points are plotted as a drift evolution curve. This curve visually reflects the gradual degradation of the conductor's internal structure under cyclic torsional load. Three key points are extracted from the curve: the first cycle number is the number of cycles when the resistance drift first shows a positive increase. During the preceding cycles, the resistance drift remains at zero or fluctuates slightly around zero, indicating that the stranded structure has not yet suffered substantial damage, and the contact state between the strands remains stable. When the drift first turns positive and continues to increase, it signifies that irreversible damage accumulation has begun in the stranded structure.

[0038] The second cycle count marks the starting point when the resistance drift enters the linear growth phase. In this phase, the resistance drift increases approximately linearly with the number of cycles, indicating that damage to the stranded structure accumulates at a stable rate, and the contact resistance between the strands gradually increases. Specifically, the determination method is as follows: calculate the increment of the resistance drift at adjacent sampling times (i.e., the slope between two adjacent points). When several consecutive increments fall within a preset stable increment range, it indicates that the drift has entered a stable linear growth state. The cycle count at the starting sampling time corresponding to these consecutive increments is taken as the second cycle count. The stable increment range can be preset based on the slope statistics of the linear growth phase from a large amount of historical experimental data. The third cycle count is the number of cycles required for the resistance drift to reach a preset drift threshold. The preset drift threshold is determined based on the maximum allowable rate of change of conductor resistance. When the drift reaches this threshold, it indicates that the stranded structure has undergone severe degradation and is close to failure.

[0039] After extracting the number of cycles mentioned above, the difference between the second and first cycle counts is calculated to obtain the steady-state duration interval. A longer interval indicates that the stranded structure can maintain a stable degradation rate for a longer period after damage begins, reflecting good progressive failure characteristics. Simultaneously, the difference between the third and second cycle counts is calculated to obtain the linear growth interval. This interval reflects the time span from stable degradation to rapid deterioration of the stranded structure. Finally, the ratio of the steady-state duration interval to the linear growth interval is calculated as the damage hysteresis coefficient of the stranded structure, and this coefficient is used as the stability index of the conductor's stranded structure. A larger ratio indicates that the stranded structure can maintain a longer stable degradation time after entering the linear degradation stage, exhibiting stronger resistance to accelerated damage propagation; conversely, a smaller ratio indicates that the stranded structure rapidly deteriorates to failure once it enters the linear degradation stage, exhibiting poor fatigue resistance.

[0040] This invention determines the torque correction coefficient based on the difference between the initial strand density coefficient and the standard density coefficient, enabling the initial torque amplitude to adaptively adjust with the strand density. This overcomes the shortcomings of existing technologies where the torsional loading conditions are fixed and cannot match the actual stranding quality of the conductor, ensuring that the determination of the stranding structure stability index can truly reflect the stranding quality of the conductor. By constructing a drift evolution curve with the number of cycles as the x-axis and the resistance drift as the y-axis, the invention extracts the number of cycles at three key nodes: the first positive growth of the resistance drift, the entry into the linear growth stage, and the reaching of the drift threshold. This quantifies the entire damage evolution process of the stranded structure into traceable numerical characteristics, overcoming the limitation of existing technologies that only use the number of failure cycles as a single evaluation index. By calculating the ratio of the steady-state continuation interval to the linear growth interval as the damage hysteresis coefficient, a larger ratio indicates that the stranded structure can maintain a longer stable degradation time after the onset of damage and has a stronger ability to resist accelerated damage propagation. Conversely, a smaller ratio indicates that the structure deteriorates rapidly once it degrades, thus achieving a comprehensive quantitative evaluation of the fatigue degradation resistance of the stranded structure.

[0041] Specifically, in step S3, determining the annealing temperature of the conductor based on the stranded structure stability index includes: Obtain the preset base annealing temperature and calculate the difference between the stability index of the stranded structure and the preset standard stability index; In response to the difference being greater than zero, a first temperature compensation value is determined based on the difference, and the difference between the base annealing temperature and the first temperature compensation value is taken as the annealing temperature. In response to the difference being less than or equal to zero, a second temperature compensation value is determined based on the difference, and the sum of the base annealing temperature and the second temperature compensation value is taken as the annealing temperature.

[0042] In this embodiment of the invention, firstly, a preset base annealing temperature is obtained. This base annealing temperature is the conventional annealing temperature value for conductors of this material and specification in conventional annealing processes in the art. Simultaneously, a standard stability index is preset. This standard stability index is a reference value when the stranded structure reaches an ideal stable state, and can be obtained through statistical measurements of the stranded structure stability index of a large number of qualified products. The difference between the above-mentioned stranded structure stability index and the standard stability index is calculated. If the difference is positive, it indicates that the stranded structure stability of the current conductor is better than the standard level, indicating good interlocking between strands, uniform residual stress distribution, and low lattice distortion during the stranding process. Only a lower annealing temperature is needed to eliminate residual stress and promote appropriate grain growth. At this time, a first temperature compensation value is determined based on the absolute value of the difference. The base annealing temperature is subtracted from the first temperature compensation value to obtain the annealing temperature applicable to the current conductor.

[0043] If the difference is negative, it indicates that the current stranding structure stability of the conductor is lower than the standard level, suggesting that more dislocations, lattice distortions, or micro-damage may have occurred during the stranding process. A higher annealing temperature is needed to promote atomic migration and lattice rearrangement, thereby achieving structural repair. In this case, a second temperature compensation value is determined based on the absolute value of the difference. Adding the second temperature compensation value to the base annealing temperature yields the annealing temperature suitable for the current conductor. The specific method for determining the temperature compensation value can be pre-established by creating a mapping table or fitting function between the absolute value of the difference and the temperature compensation value, and then calculating it by looking up the table or substituting into the function. The larger the absolute value of the difference, the larger the corresponding temperature compensation value, enabling linear or nonlinear continuous adjustment of the annealing temperature according to the degree of deviation of the stranding structure stability index.

[0044] This invention calculates the difference between the stranded structure stability index and the standard stability index, and determines different temperature compensation directions based on the positive or negative value of the difference. When the stranded structure stability is better than the standard level, the annealing temperature is reduced to avoid excessive grain growth; when the stranded structure stability is lower than the standard level, the annealing temperature is increased to fully repair structural defects. This overcomes the shortcomings of existing technologies where the annealing temperature is fixed and cannot be adjusted according to the actual stranding state of the conductor, and achieves a precise match between the annealing temperature and the stability of the conductor stranded structure.

[0045] Specifically, in step S4, determining the extrusion temperature during insulating layer extrusion coating based on the transmission parameters includes: Obtain the preset base extrusion temperature, and extract the microstructure characteristic value from the transfer parameter, wherein the microstructure characteristic value is the average grain size of the conductor after annealing; Calculate the difference between the average grain size and the preset standard grain size; In response to the difference being greater than zero, a third temperature compensation value is determined based on the difference, and the difference between the base extrusion temperature and the third temperature compensation value is taken as the extrusion temperature. In response to the difference being less than or equal to zero, a fourth temperature compensation value is determined based on the difference, and the sum of the base extrusion temperature and the fourth temperature compensation value is taken as the extrusion temperature.

[0046] In this embodiment of the invention, firstly, a preset base extrusion temperature is obtained. This base extrusion temperature is a conventional extrusion temperature value used in conventional extrusion processes in the art for this type of insulating material and conductor specification. The microstructure characteristic value is extracted from the transfer parameters. This microstructure characteristic value is the average grain size of the conductor after annealing. The average grain size of the conductor after annealing can be obtained by observation using a metallographic microscope or measurement using electron backscatter diffraction technology. The average grain size reflects the effect of the annealing process on the microstructure of the conductor. A larger grain size indicates that the annealing temperature is too high, resulting in significant grain growth; a smaller grain size indicates that the annealing temperature is too low or moderate, resulting in grain refinement.

[0047] Simultaneously, a standard grain size is preset. This standard grain size is a reference value for the grain size when the stranded structure reaches an ideal annealing state, and can be obtained through statistical measurements of grain size from a large number of qualified products. The difference between the average grain size and the standard grain size is calculated. If the difference is positive, it indicates that the average grain size of the conductor after annealing is larger than the standard value, and the annealing temperature is relatively high, leading to excessive grain growth. When the grains are coarse, the number of grain boundaries on the conductor surface decreases, and the surface activity decreases, allowing the insulating material to fully spread and wet the conductor surface at a lower temperature. At this time, a third temperature compensation value is determined based on the absolute value of this difference. The third temperature compensation value is then subtracted from the base extrusion temperature to obtain the extrusion temperature applicable to the current conductor.

[0048] If the difference is negative, it indicates that the average grain size of the conductor after annealing is smaller than the standard value, the annealing temperature is relatively low, the grains are refined, and the number of grain boundaries increases. Fine-grained structures have higher surface energy, and the conductor surface has more high-energy grain boundaries and defects, resulting in higher activity. Therefore, the extrusion temperature needs to be increased to enhance the fluidity and wetting ability of the insulating material, ensuring that the insulating material can fully penetrate the microscopic uneven structure of the conductor surface and achieve good interfacial bonding. In this case, a fourth temperature compensation value is determined based on the absolute value of the difference. Adding the fourth temperature compensation value to the base extrusion temperature yields the extrusion temperature applicable to the current conductor. Regarding the specific method for determining the temperature compensation value, a mapping table or fitted function relationship between the absolute value of the difference and the temperature compensation value can be established in advance, and the value can be obtained by looking up the table or substituting into the function for calculation.

[0049] This invention extracts the average grain size of the conductor after annealing as a microstructure characteristic value and calculates the difference between it and the standard grain size. Different temperature compensation directions are determined according to the positive and negative values ​​of the difference. When the grains are coarse, the extrusion temperature is reduced to avoid excessive softening of the insulating material, and when the grains are fine, the extrusion temperature is increased to enhance interfacial wetting and bonding. This overcomes the shortcomings of the prior art, which has a fixed extrusion temperature and cannot be adjusted according to the differences in the conductor's microstructure. It achieves a precise match between the extrusion temperature and the conductor grain size.

[0050] Specifically, in step S4, adjusting the cooling intensity distribution curve of the gradient cooling airflow according to the dispersion of each hardness value includes: The difference between the maximum and minimum hardness values ​​at each circumferential location of the insulation layer is calculated as the hardness range. In response to the hardness range being greater than a preset upper limit value, the rate of change of cooling intensity of the gradient cooling airflow along the circumferential direction is reduced. In response to the hardness range being less than a preset lower limit, the rate of change of cooling intensity of the gradient cooling airflow along the circumferential direction is increased.

[0051] Specifically, in step S4, the gradient cooling airflow is applied through several sets of annular jet nozzles arranged at intervals along the extrusion direction of the insulating layer. The cooling intensity of each set of annular jet nozzles increases progressively along the extrusion direction of the insulating layer. The jet nozzles at different circumferential positions in the same set of annular jet nozzles have different injection angles and injection pressures.

[0052] In this embodiment of the invention, after the insulating layer is coated, multiple measurement positions are uniformly selected around the circumference of the insulating layer, and a hardness tester is used to measure the hardness at each position to obtain hardness value distribution data for each position around the circumference of the insulating layer. The difference between the maximum and minimum hardness values ​​at all measurement positions is calculated as the hardness range. The hardness range reflects the uniformity of the circumferential crystalline structure of the insulating layer. Simultaneously, an upper limit and a lower limit for the range are preset, which constitute the allowable range of the hardness range. The upper limit is the maximum allowable hardness difference; exceeding this value indicates excessive hardness difference at each position around the circumference and excessive anisotropy. The lower limit is the minimum hardness difference required to ensure that anisotropy functions effectively; falling below this value indicates that the circumferential hardness is homogeneous and the anisotropy is insufficient.

[0053] If the hardness range exceeds the upper limit, it indicates an excessively large difference in circumferential hardness, with some areas being either too soft or too hard. During torsion, the significant difference in deformation capacity between different regions leads to premature yielding in soft areas and insufficient deformation in hard areas. This mismatch in performance results in severe stress concentration, which in turn accelerates the initiation and propagation of fatigue cracks. In this case, it is necessary to reduce the rate of change of cooling intensity along the circumferential direction of the gradient cooling airflow to make the cooling conditions in each circumferential location more uniform, thereby reducing the hardness difference and bringing the range back within the allowable range.

[0054] If the hardness range is less than the lower limit, it indicates that the circumferential hardness tends to be uniform, failing to form an effective anisotropic crystalline structure in the insulation layer. When the cable is subjected to torsional loads, the torsional stress is concentrated at a single interface, and the stress cannot be coordinated and dispersed through differentiated deformation in different areas, easily inducing crack initiation. In this case, it is necessary to increase the rate of change of cooling intensity along the circumferential direction of the gradient cooling airflow, enhance the cooling difference between different circumferential positions, thereby increasing the hardness difference and raising the range to within the allowable range.

[0055] The gradient cooling airflow is applied using several sets of annular nozzles spaced apart along the extrusion direction of the insulation layer. The cooling intensity of each set of annular nozzles increases progressively along the extrusion direction, causing the insulation layer to undergo a gradient cooling process from weak to strong along the axial direction during extrusion, thus achieving gradual solidification of the insulation layer in the axial direction. Within the same set of annular nozzles, nozzles at different circumferential positions have different injection angles and injection pressures, causing different parts of the insulation layer to experience different cooling intensities at the same time. This induces differentiated crystallization behavior in the circumferential direction of the insulating material, ultimately forming a non-uniform crystalline structure with anisotropic hardness.

[0056] This invention calculates the difference between the maximum and minimum hardness values ​​at various circumferential locations of the insulation layer as the hardness range, and presets an upper and lower limit value for the range to form an allowable interval. When the hardness range is greater than the upper limit value, the cooling intensity change rate is reduced to narrow the hardness difference; when the hardness range is less than the lower limit value, the cooling intensity change rate is increased to widen the hardness difference. This overcomes the shortcomings of existing technologies where uniform cooling intensity distribution leads to a consistent circumferential crystalline structure in the insulation layer, making it impossible to buffer torsional stress through anisotropy. The hardness range is thus constrained within the allowable interval. By using progressively increasing annular jet nozzles along the extrusion direction, combined with differentiated jetting angles and pressures at different circumferential locations within the same group, a differentiated cooling intensity distribution is formed in the circumferential direction of the insulation layer to induce anisotropic crystalline structure. This allows the cable to decompose torsional stress into several local micro-strains through successive deformations of different hardness regions in the circumferential direction when subjected to torsional loads, avoiding stress concentration and thus significantly improving the torsional fatigue resistance of the insulation layer.

[0057] In this embodiment of the invention, after hardness testing and adjustment of the cooling intensity distribution curve, an optimized cooling intensity distribution curve suitable for the stranding quality of the current batch of conductors is obtained. Since stranded conductors in the same batch have the same stranding parameter settings, and the entire process of testing and parameter optimization, from strand density testing, torsion loading, annealing to insulation coating and hardness feedback, has been completed for representative conductor samples in this batch, the optimized cooling intensity distribution curve is applicable to all remaining conductors in the same batch. According to the adjusted cooling intensity distribution curve, insulation extrusion coating is performed on each conductor in the same batch that has not yet been coated. During the coating process, each group of annular nozzles, spaced apart along the insulation extrusion direction, operates according to the optimized cooling intensity distribution curve. The cooling intensity of each group of annular nozzles increases progressively along the extrusion direction. Nozzles at different circumferential positions within the same group operate according to their respective set spray angles and spray pressures, causing the insulation layer of each conductor to form a differentiated crystalline structure consistent with the sample in the circumferential direction, ensuring the consistency of the insulation layer quality of the entire batch of products.

[0058] After the insulation layer is applied, the shielding layer and outer sheath are sequentially applied around the conductor covered with the insulation layer. The shielding layer, formed by wrapping or extruding a semi-conductive material, includes a conductor shielding layer covering the inner surface of the insulation layer and an insulating shielding layer covering the outer surface of the insulation layer, used to uniform the electric field and prevent partial discharge. The outer sheath is made of weather-resistant polymer material extruded and applied around the insulating shielding layer to protect the internal structure from mechanical damage and environmental corrosion. These steps complete the finished cable.

[0059] Please see Figure 3 As shown, Figure 3 This is a schematic diagram of the wind power distribution cable resistant to torsional fatigue in this embodiment.

[0060] Specifically, a power distribution cable prepared by the method for manufacturing wind power-specific power distribution cables resistant to torsional fatigue includes: The conductor 1, insulation layer 2, shielding layer 3, and outer sheath 4 are arranged sequentially from the inside out. The conductor 1 is composed of several tin-plated copper wires twisted together in layers. The insulation layer 2 covers the outer periphery of the conductor and has a differentiated crystalline structure in the circumferential direction. The shielding layer 3 includes a conductor shielding layer and an insulation shielding layer. The conductor shielding layer covers the inner surface of the insulation layer, and the insulation shielding layer covers the outer surface of the insulation layer. The outer sheath 4 covers the outer periphery of the insulation shielding layer.

[0061] In this embodiment of the invention, The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for manufacturing a wind power distribution cable resistant to torsional fatigue, characterized in that, include: Step S1: Several tin-plated copper wires are stranded in layers according to preset stranding parameters to form a conductor. The resistance of the stranded conductor is detected to obtain the conductor resistance value, and the initial stranding density coefficient of the conductor is determined based on the conductor resistance value. Step S2: Determine the initial torque amplitude of the torsional loading based on the initial strand density coefficient, apply a cyclic torsional load of the initial torque amplitude to the conductor, monitor the resistance change of the conductor under the cyclic torsional load, and determine the strand structure stability index of the conductor based on the number of cycles when the resistance change reaches the preset condition. Step S3: Determine the annealing temperature of the conductor according to the stranded structure stability index, and anneal the conductor according to the annealing temperature, using the microstructure characteristics of the conductor after annealing as the transfer parameter; Step S4: Determine the extrusion temperature for insulating layer extrusion coating according to the transmission parameters, coat the annealed conductor with insulating layer according to the extrusion temperature, apply gradient cooling airflow around the circumference of the insulating layer during the insulating layer coating process, measure the hardness value at each position of the circumference of the insulating layer after the insulating layer is coated, and adjust the cooling intensity distribution curve of the gradient cooling airflow according to the dispersion of each hardness value. Step S5: According to the adjusted cooling intensity distribution curve, the conductors in the same batch that have not yet been insulated are insulated, and then the insulated conductors are made into finished cables through shielding and outer sheath.

2. The method for manufacturing wind power distribution cables resistant to torsional fatigue according to claim 1, characterized in that, In step S1, determining the initial strand density coefficient of the conductor based on the conductor resistance value includes: Step S11: Obtain the measured DC resistance value of the conductor and the theoretical DC resistance value of a solid standard conductor of the same material and cross-sectional area as the conductor, and determine the ratio of the theoretical DC resistance value to the measured DC resistance value as the density reference value. Step S12: Obtain the actual mass value per unit length of the stranded conductor and the theoretical mass value of a solid standard conductor of the same material and volume as the conductor, and determine the ratio of the actual mass value to the theoretical mass value as the mass fill rate. Step S13: The initial stranding density coefficient is obtained by weighted summation of the density reference value and the mass filling rate.

3. The method for preparing wind power distribution cables resistant to torsional fatigue according to claim 1, characterized in that, In step S2, determining the initial torque amplitude of the torsional loading based on the initial twist density coefficient includes: Obtain the preset base torque amplitude and calculate the difference between the initial twist density coefficient and the preset standard density coefficient; The torque correction coefficient is determined based on the difference, and the product of the base torque amplitude and the torque correction coefficient is used as the initial torque amplitude.

4. The method for preparing wind power distribution cables resistant to torsional fatigue according to claim 1, characterized in that, In step S2, the stability index of the conductor's strand structure is determined, including: The initial resistance value of the conductor before the cyclic torsional load is obtained. During the cyclic torsional load loading process, the dynamic resistance value of the conductor is collected at fixed intervals. The difference between the dynamic resistance value and the initial resistance value at each collection time is calculated as the resistance drift. A drift evolution curve is constructed with the number of cycles as the x-axis and the resistance drift as the y-axis. The first cycle number when the resistance drift first shows a positive increase, the second cycle number when the resistance drift enters the linear growth stage, and the third cycle number when the resistance drift reaches a preset drift threshold are extracted from the drift evolution curve. The difference between the second cycle number and the first cycle number is calculated as the steady-state duration interval, the difference between the third cycle number and the second cycle number is calculated as the linear growth interval, the ratio of the steady-state duration interval to the linear growth interval is calculated as the damage hysteresis coefficient of the stranded structure, and the damage hysteresis coefficient is used as the stranded structure stability index of the conductor.

5. The method for preparing wind power distribution cables resistant to torsional fatigue according to claim 4, characterized in that, The method for determining whether the resistance drift has entered the linear growth stage is as follows: Calculate the incremental value of resistance drift at adjacent acquisition times. When several consecutive incremental values ​​fall within a preset stable incremental range, the number of cycles at the starting acquisition time corresponding to the several consecutive incremental values ​​is taken as the second cycle number.

6. The method for preparing wind power distribution cables resistant to torsional fatigue according to claim 1, characterized in that, In step S3, the annealing temperature of the conductor is determined based on the stranded structure stability index, including: Obtain the preset base annealing temperature and calculate the difference between the stability index of the stranded structure and the preset standard stability index; In response to the difference being greater than zero, a first temperature compensation value is determined based on the difference, and the difference between the base annealing temperature and the first temperature compensation value is taken as the annealing temperature. In response to the difference being less than or equal to zero, a second temperature compensation value is determined based on the difference, and the sum of the base annealing temperature and the second temperature compensation value is taken as the annealing temperature.

7. The method for preparing wind power distribution cables resistant to torsional fatigue according to claim 1, characterized in that, In step S4, determining the extrusion temperature during insulation layer extrusion coating based on the transmission parameters includes: Obtain the preset base extrusion temperature, and extract the microstructure characteristic value from the transfer parameter, wherein the microstructure characteristic value is the average grain size of the conductor after annealing; Calculate the difference between the average grain size and the preset standard grain size; In response to the difference being greater than zero, a third temperature compensation value is determined based on the difference, and the difference between the base extrusion temperature and the third temperature compensation value is taken as the extrusion temperature. In response to the difference being less than or equal to zero, a fourth temperature compensation value is determined based on the difference, and the sum of the base extrusion temperature and the fourth temperature compensation value is taken as the extrusion temperature.

8. The method for preparing wind power distribution cables resistant to torsional fatigue according to claim 1, characterized in that, In step S4, the cooling intensity distribution curve of the gradient cooling airflow is adjusted according to the dispersion of each hardness value, including: The difference between the maximum and minimum hardness values ​​at each circumferential location of the insulation layer is calculated as the hardness range. In response to the hardness range being greater than a preset upper limit value, the rate of change of cooling intensity of the gradient cooling airflow along the circumferential direction is reduced. In response to the hardness range being less than a preset lower limit, the rate of change of cooling intensity of the gradient cooling airflow along the circumferential direction is increased.

9. The method for preparing wind power distribution cables resistant to torsional fatigue according to claim 1, characterized in that, In step S4, the gradient cooling airflow is applied through several sets of annular jet nozzles arranged at intervals along the extrusion direction of the insulating layer. The cooling intensity of each set of annular jet nozzles increases progressively along the extrusion direction of the insulating layer. The jet nozzles at different circumferential positions in the same set of annular jet nozzles have different injection angles and injection pressures.

10. A power distribution cable prepared using the torsional fatigue resistant wind power distribution cable manufacturing method according to any one of claims 1-9, characterized in that, include: The conductor, insulation layer, shielding layer, and outer sheath are arranged sequentially from the inside out; the conductor is composed of several tin-plated copper wires twisted together in layers. The insulating layer covers the outer periphery of the conductor and has a differentiated crystalline structure in the circumferential direction; the shielding layer includes a conductor shielding layer and an insulating shielding layer, the conductor shielding layer covers the inner surface of the insulating layer and the insulating shielding layer covers the outer surface of the insulating layer; The outer sheath covers the outer periphery of the insulating shielding layer.

Images