Preparation method and system of power cable suitable for desert area

Abstract

The invention relates to a preparation method and system of a power cable suitable for a desert area, and the method comprises the following steps: carrying out the wire drawing and twisting of a copper rod to obtain a conductor, and sequentially wrapping the conductor with a conductor shielding layer, an insulating layer and an insulating shielding layer to obtain an insulating wire core; a metal shielding layer and a temperature measuring optical fiber are twisted outside the insulating wire core to form a wire; a semi-conductive wrapping layer, an inner lining layer, an armor layer and a temperature-resistant layer are sequentially formed outside the wire in a wrapping mode, and the prepared cable is obtained. The temperature-resistant layer is extruded through a tube extrusion type mold, and the temperatures of 1-6 areas of an extruder are 145 + / -15 DEG C, 150 + / -15 DEG C, 160 + / -15 DEG C, 180 + / -15 DEG C, 180 + / -15 DEG C and 170 + / -15 DEG C respectively in the direction from feeding to discharging; the temperatures of the first zone to the fourth zone of the extruder head are 170 + / -5 DEG C, 170 + / -5 DEG C, 175 + / -5 DEG C and 175 + / -5 DEG C respectively. Through the optimization of the structure and the manufacturing process, the cable can adapt to the desert area environment.

Description

Technical Field

[0001] The present invention relates to the technical field of cable manufacturing, and specifically to a preparation method and system for power cables applicable to desert areas. Background Art

[0002] The statements in this part only provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] The cables used for connecting traditional distribution network equipment lack special design and optimization for the geographical environment and local climate of "desert, gobi, and barren mountains", resulting in accelerated insulation aging, sheath material deterioration due to high temperature, strong ultraviolet radiation, large day-night temperature difference, dust erosion, and humidity fluctuation in desert areas during the open-air laying and use of the cables. As a result, the insulation strength and electrical stability of the cables decrease, ultimately threatening their power supply stability. Summary of the Invention

[0004] In order to solve the technical problems existing in the above background art, the present invention provides a preparation method and system for power cables applicable to desert areas, enabling the cables to adapt to the desert environment through optimization in terms of structure and manufacturing process.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] The first aspect of the present invention provides a preparation method for power cables applicable to desert areas, including the following steps:

[0007] The copper rod is drawn and stranded to obtain a conductor, and a conductor shielding layer, an insulating layer, and an insulation shielding layer are sequentially wrapped outside the conductor to obtain an insulated wire core;

[0008] A metal shielding layer and a temperature-measuring optical fiber are stranded outside the insulated wire core to obtain a wire;

[0009] A semiconductive wrapping layer is obtained by wrapping outside the wire in sequence, an inner liner layer is obtained by extrusion, an armor layer is obtained by wrapping, and a temperature-resistant layer is obtained by extrusion to obtain the completed cable;

[0010] Among them, the temperature-resistant layer is extruded through an extrusion die. Along the feeding direction to the discharging direction, the temperatures of the 1-6 zones of the extruder are respectively: 145±15°C, 150±15°C, 160±15°C, 180±15°C, 180±15°C, and 170±15°C; the temperatures of the 1-4 zones of the extruder head are respectively: 170±5°C, 170±5°C, 175±5°C, and 175±5°C.

[0011] Further, the conductor shielding layer, the insulating layer, and the insulation shielding layer are sequentially wrapped outside the conductor to obtain an insulated wire core, specifically: the conductor shielding layer, the insulating layer, and the insulation shielding layer are used to obtain the insulated wire core by three-layer coextrusion.

[0012] Furthermore, the process parameters for three-layer coextrusion are as follows: along the direction from feeding to discharging, the temperatures of zones 1-9 of the extruder are respectively: 165±2°C, 170±2°C, 166±2°C, 168±2°C, 169±2°C, 169±2°C, 172±2°C, 170±2°C, and 169±2°C.

[0013] Furthermore, during three-layer coextrusion, the dimensions of the extrusion die are determined according to the outer diameter D of the conductor, specifically as follows:

[0014] Inner diameter of die core 1: D1 core = D + clearance value, and the clearance value is 0.5 - 0.7 mm;

[0015] Inner diameter of die core 2: D2 core = D1 core + 2 × nominal thickness of conductor shield;

[0016] Inner diameter of die sleeve: D sleeve = D2 core + 2 × nominal thickness of insulation + 2 × nominal thickness of insulation shield.

[0017] Furthermore, the insulating layer material is grafted polypropylene.

[0018] Furthermore, an inner lining layer is obtained by extrusion coating on the outer side of the semi-conductive wrapping layer, specifically as follows: extrusion is carried out using an extrusion tube die. Along the direction from feeding to discharging, the temperatures of zones 1-6 of the extruder are respectively: 125±15°C, 130±15°C, 150±15°C, 160±15°C, 160±15°C, 150±15°C;

[0019] Furthermore, along the direction from feeding to discharging, the temperatures of zones 1-4 of the extruder head are 160±5°C, 160±5°C, 165±5°C, and 165±5°C.

[0020] Furthermore, the temperature-resistant layer material is "high-performance nylon 12".

[0021] Furthermore, a conductor is obtained by stranding a metal shielding layer and a temperature-measuring optical fiber outside the insulated wire core, specifically as follows: according to the outer diameter of the insulated wire core, copper wires with a set diameter are selected and stranded equidistantly on the surface of the insulated wire core. During stranding, the temperature-measuring optical fiber is stranded together with the copper wires to obtain a conductor.

[0022] The second aspect of the present invention provides a preparation system for a power cable applicable to desert areas, including:

[0023] A wire drawing device for wire drawing treatment of the pre-treated copper rod;

[0024] A stranding device that receives the copper wires and strands them to obtain a conductor;

[0025] A three-layer coextrusion device for simultaneously extruding a conductor shield layer, an insulating layer, and an insulation shield layer outside the conductor to obtain an insulated wire core;

[0026] A shielding layer processing device is used to twist a metal shielding layer and a temperature-measuring optical fiber around an insulated wire core to obtain a wire;

[0027] A sheath and protective layer manufacturing unit is used to obtain a semiconductive wrapping layer around the wire through a wrapping device, obtain an inner liner through an extrusion device, obtain an armored layer through an armored layer processing device, obtain a temperature-resistant layer through an extruder, and after inspection, obtain a completed cable.

[0028] Compared with the prior art, the above one or more technical solutions have the following beneficial effects:

[0029] 1. A temperature-resistant layer is arranged outside the armored layer. By optimizing the process parameters during the manufacture of the temperature-resistant layer, the operating environment temperature of the cable is -40°C to 125°C, with good weather resistance and UV tolerance, and there will be no cracking problems in extreme temperature difference environments, and it can adapt to the desert environment.

[0030] 2. The first zone of the extruder is the feeding section. By setting a lower temperature, it prevents the premature melting and caking of the temperature-resistant layer raw materials, resulting in poor feeding. The second to fourth zones are the compression sections. By gradually raising the temperature to 180°C, the temperature-resistant layer raw materials are completely melted and homogenized. The fifth to sixth zones are the metering sections. By slightly lowering the temperature, the degradation risk of the temperature-resistant layer material is reduced, ensuring the melt stability. At the same time, the first zone of the die head corresponds to the connector. By setting a temperature slightly higher than the melt, it ensures the smooth transition of the melt. The second to third zones correspond to the die core / die sleeve. By precisely controlling the temperature, it ensures the stable extrusion shape of the temperature-resistant layer. The fourth zone corresponds to the die orifice. By slightly lowering the temperature, the exit swelling ("die swell" effect) is reduced. By optimizing the process parameters during the manufacture of the temperature-resistant layer, the weather resistance of the temperature-resistant layer raw materials is exerted to adapt to the desert environment.

[0031] 3. The insulating layer material is grafted polypropylene, and the melting temperature range is 160 - 175°C. During co-extrusion, the temperature is controlled at 165 - 172°C, which can not only ensure sufficient plasticization but also avoid high-temperature degradation. At the same time, the conductor shield, insulating layer, and insulation shield are all polypropylene (PP)-based materials, and a unified temperature window is required to ensure good fusion at the co-extrusion interface. The PP melt viscosity is sensitive to temperature. The narrow tolerance temperature control of ±2°C can avoid thickness unevenness or interlayer delamination caused by unstable flow, ensuring reliable cable performance and enabling long-term operation in the desert area.

[0032] 4. The temperature control parameters during co-extrusion generally show a wavy change. In zones 1-2, it is the initial heating stage to soften the polypropylene raw material and prevent cold material blockage. The temperature in zone 3 slightly decreases to compensate for the temperature rise caused by the shear of the extruder screw and prevent local overheating. In zones 4-6, the temperature slightly increases and is controlled within a relatively narrow tolerance range to homogenize the melt. The formed stable temperature enables the PP molecular chains to fully unfold and eliminates bubbles / unmelted particles. In zone 7, the temperature reaches the peak value, and the molecular diffusion during the co-extrusion of the three-layer material is enhanced through a short-term high temperature to strengthen the interlayer bonding. In the final zones 8-9, the temperature slightly decreases to reduce die swell and ensure dimensional accuracy.

[0033] 5. Electric tree (conductive channels) is likely to form at the defective parts of the cable insulation material, which will ultimately lead to breakdown. Since the cable operates in the desert area, the insulation aging speed is faster than that in general environments, making it more likely to be broken down. Therefore, introducing a semi-conductive wrapping layer between the metal shielding layer and the armor layer can ensure the long-term reliable operation of the cable. The existence of the semi-conductive layer can homogenize the surface charge distribution, reduce the charge accumulation on the surface of the insulation layer, and delay the growth of electric trees.

[0034] 6. The inner liner layer is obtained by extrusion coating on the outside of the semi-conductive wrapping layer. The set temperature parameters ensure the bonding strength between the inner liner layer and the wrapping layer, the uniform plasticization of the material, and adapt to the characteristics of the extrusion die.

[0035] 7. When the temperature-measuring optical fiber is directly exposed, it is easily damaged. After being stranded together with the copper wire serving as the shielding layer, the temperature-measuring optical fiber is embedded in the gaps naturally formed during the stranding of the copper wire, which can protect the temperature-measuring optical fiber from external force (extrusion, friction) damage by the copper wire and does not require additional occupation of the cable cross-sectional area. At the same time, the temperature-measuring optical fiber is in direct contact with the copper wire shielding, which can reflect the real temperature of the conductor in real time, and the copper wire shielding can also absorb external electromagnetic noise to protect the temperature-measuring signal from interference.

[0036] 8. There may be minute irregularities on the surface of the shielding layer or minute gaps between the shielding layer and the armor layer. These air gaps will cause electric field concentration and trigger partial discharge, which may break down the insulation in the long term. The semi-conductive nylon tape has a moderate conductivity and can fill the irregular surface of the shielding layer, enabling the electric field to smoothly transition from the insulation layer to the metal shielding layer and avoiding electric field distortion. Through the cooperation of the armor layer, the semi-conductive nylon tape wrapping, and the shielding layer, the internal electric field of the cable is homogenized, and at the same time, external electromagnetic field interference can be shielded. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0038] Figure 1 It is a schematic diagram of the preparation process of the power cable in the desert area provided by the present invention;

[0039] Figure 2 This is a schematic diagram of the power cable structure in desert areas provided by the present invention.

[0040] In the figure: 1. Temperature-resistant layer, 201. Armor layer, 202. Inner lining layer, 203. Semi-conductive wrapping layer, 301. Metal shielding layer, 302. Temperature-measuring optical fiber, 303. Insulation shielding layer, 304. Insulation layer, 305. Conductor shielding layer, 306. Conductor. Specific embodiments

[0041] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0042] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0043] It should be noted that the terms herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0044] The following embodiments provide a preparation method and system for power cables applicable to desert areas, and propose DC cables for specific areas such as "deserts, gobi, and wastelands" for use in distribution network DC equipment. In order to solve the problem that in the prior art, while the DC cable meets normal working conditions, the cable body can resist the environment, and through structural optimization, material selection, and processing technology, the functional characteristics of weather resistance and aging resistance are achieved, which is suitable for open-air laying in environments such as "deserts, gobi, and wastelands" with high temperatures or large day-night temperature differences.

[0045] Embodiment 1:

[0046] As Figure 2 shown, the power cable applicable to desert areas includes a conductor 306, a conductor shielding layer 305, an insulation layer 304, an insulation shielding layer 303, a metal shielding layer 301, a semi-conductive wrapping layer 203, an inner lining layer 202, an armor layer 201, and a temperature-resistant layer 1 arranged in sequence from the inside to the outside; a temperature-measuring optical fiber 302 is provided in the metal shielding layer 301.

[0047] The above cable is prepared by the steps as Figure 1 shown, specifically:

[0048] The copper rod is drawn and stranded to obtain a conductor, and a conductor shield layer, an insulating layer, and an insulation shield layer are sequentially wrapped around the conductor to obtain an insulated core;

[0049] A metal shield layer and a temperature-measuring optical fiber are stranded outside the insulated core to obtain a wire;

[0050] A semiconductive wrapping layer is obtained by wrapping outside the wire, an inner liner layer is obtained by extrusion, an armor layer is obtained by wrapping, and a temperature-resistant layer is obtained by extrusion to obtain the completed cable.

[0051] As a further embodiment, the temperature-resistant layer 1 is made of high-performance nylon 12 material by extrusion. It has good weather resistance, will not crack in extreme temperature difference environments, and has UV tolerance, suitable for long-term outdoor open laying; at the same time, it has excellent mechanical properties, reducing construction costs.

[0052] As a further embodiment, high-performance nylon 12 (High-Performance Nylon 12) is an engineering plastic belonging to the long-chain polyamide family, and is polymerized from laurolactam or aminododecanoic acid monomers.

[0053] As a further embodiment, the armor layer 201 is a double-layer wrapped armor of high-strength non-magnetic stainless steel tape, improving the overall compressive performance.

[0054] As a further embodiment, the semiconductive wrapping layer 203 is wrapped with semiconductive nylon tape, which is used to equalize the overall electric field distribution of the cable and ensure the safety of the cable.

[0055] As a further embodiment, the wire part is composed of a conductor 306 and a shield layer wrapped outside the conductor 306. The shield layer includes a metal shield layer 301, an insulation shield layer 303, an insulating layer 304, and a conductor shield layer 305. The metal shield layer 301, the insulation shield layer 303, the insulating layer 304, and the conductor shield layer 305 are sequentially wrapped outside the conductor 306 from outside to inside.

[0056] As a further embodiment, the insulating layer 304 is made of grafted polypropylene material by extrusion, meeting the maximum service temperature of 110 °C; compared with cross-linked polyethylene, there is no need for a cross-linking process, saving production costs; the maximum operating temperature is high, which can increase the current-carrying capacity of the cable; it has thermoplasticity and is convenient for recycling.

[0057] As a further embodiment, grafted polypropylene (Grafted Polypropylene) refers to introducing other monomers or functional groups onto the polypropylene (PP) molecular chain through chemical methods to form a branched structure, thereby endowing the material with new properties (such as adhesiveness, polarity, compatibility, etc.).

[0058] As a further embodiment, the metal shielding layer 301 is composed of high-conductivity copper wires and its temperature measuring device, which plays a role in equalizing the electric field and can conduct the leakage current generated during operation.

[0059] As a further embodiment, a temperature measuring optical fiber 302 is buried in the metal shielding layer 301. By stranding at least two low-attenuation optical fibers, the temperature state of the cable during operation can be monitored, and an alarm can be given for abnormal temperature.

[0060] The temperature-resistant layer 1 is made of nylon 12 material, which has excellent properties such as low smoke, halogen-free, non-toxic, weather-resistant, oil-resistant, solvent-resistant, wear-resistant, good toughness, hardness ≥ Shore D 67, Vicat softening point of 170 °C, and smooth surface. It is suitable for laying in desert environments and reduces the laying difficulty at the same time.

[0061] The armor layer, semi-conductive nylon tape wrapping, and shielding layer work together to equalize the internal electric field of the cable and can shield external electromagnetic field interference at the same time; the shielding layer can also conduct the leakage current during the operation of the cable.

[0062] The temperature measuring device consists of two low-attenuation optical fibers, which can monitor the temperature of the cable during operation in real time and can also give an alarm for abnormal temperature during operation.

[0063] In summary, for this embodiment, aiming at specific regions such as "deserts, gobi, and wastelands", a DC cable for distribution network DC equipment is proposed. The outermost layer of the cable uses nylon 12 material to form a temperature-resistant layer to address the problems of accelerated insulation aging and sheath material deterioration caused by factors such as high temperature, strong ultraviolet radiation, large temperature difference between day and night, dust erosion, and humidity fluctuations in desert areas. While meeting the normal operation of the cable, it improves the resistance of the cable body to the environment, and realizes the functional characteristics of weather resistance and aging resistance through structural optimization, material selection, and processing technology, which is suitable for open-air laying in environments such as "deserts, gobi, and wastelands" with high temperature or large temperature difference between day and night.

[0064] Embodiment 2:

[0065] A method for preparing a power cable suitable for desert areas, comprising the following steps:

[0066] 1) Prepare the conductor 306;

[0067] 2) Wrap the conductor shielding layer 305, insulation layer 304, and insulation shielding layer 303 outside the conductor 306 obtained in step 1) to obtain an insulated wire core;

[0068] 3) Stranding the metal shielding layer 301 and the temperature measuring optical fiber 302 outside the insulated wire core obtained in step 2) to obtain a wire;

[0069] 4) Wrap a semi-conductive wrapping layer 203 around the conductor obtained in step 3);

[0070] 5) Extrude an inner liner 202 outside the semiconductive wrapping layer 203 in step 4).

[0071] 6) Wrap an armor layer 201 outside the inner liner 202 obtained in step 5).

[0072] 7) Extrude a temperature-resistant layer 1 outside the armor layer 201 obtained in step 6) to obtain the required cable.

[0073] Specifically:

[0074] In step 1):

[0075] Manufacture copper single wires: Draw a copper rod with a diameter of Φ8.00 mm into copper single wires with a diameter of Φ2.97 mm. The tolerance requirements for the copper single wires are (0, ±0.02), the elongation rate of the single wires is 25%-30%, and the resistivity of the single wires does not exceed 0.017241 Ω·mm 2 / m.

[0076] Drawing the thick copper rod into thin copper single wires significantly reduces the stiffness of a single conductor. When the thin wires are bent, the stress is more dispersed, making the overall cable softer and facilitating installation and laying (especially in narrow spaces or scenarios with frequent bending).

[0077] Strand the copper single wires: Strand the copper single wires using regular concentric layer stranding.

[0078] Regular Concentric Lay Stranding means a process of stranding multiple single wires (such as copper single wires) around a center core in concentric circles layer by layer. The stranding direction of each layer is usually opposite to that of the adjacent layer (for example, the outer layer is left-handed and the adjacent inner layer is right-handed), and the number of single wires in each layer follows a fixed rule.

[0079] For example, arrange them in the order of 1+6+12+18 (from the inside out, there are 1, 6, 12, and 18 single wires in sequence), strand four layers, and compact them once after each stranding. The compacting is distributed to 6 wire reels, 12 wire reels, and 18 wire reels in sequence; for larger specifications, they can also be arranged in the way of 5+11+17+23. The stranding directions of the single wires are arranged in the order of Z, S, Z, that is, the stranding direction of the outermost layer is the Z direction, and the stranding direction of the second outermost layer is the S direction; the stranding pitch ratio of the outermost single wires is not greater than 13 times (Z and S represent the stranding directions, S is clockwise to the left, and Z is counterclockwise to the right).

[0080] Conductor requirements: The direct current resistance of the conductor (20 °C) meets the requirements of GB / T 3956-2008 standard, and the outer diameter of the conductor is controlled within 29.9±0.1 mm.

[0081] The twisting of multiple copper filaments further increases the cable's flexibility. When the twisted conductor is bent, the filaments can slightly slide between each other, avoiding localized stress concentration and extending its service life.

[0082] During the preparation of the conductor 306 , skin effect suppression and uniform current distribution are considered.

[0083] Skin effect suppression: High-frequency currents concentrate on the surface of a conductor (skin effect). Twisting multiple filaments increases the effective surface area, reduces high-frequency resistance, and reduces signal attenuation (especially for high-frequency cables or high-current applications).

[0084] Uniform current distribution: Regular concentric twisting ensures symmetrical helical angles within each layer of copper wire, evenly distributing current across the individual wires and preventing local overheating. When operating in desert regions, the temperature may rise faster than in non-desert areas due to ambient temperature. Regular concentric twisting ensures more uniform temperature distribution and minimizes local overheating.

[0085] Improved tensile strength: Desert regions experience stronger airflow, making overhead cables more susceptible to mechanical stress from cable movement. By twisting multiple filaments together, even if individual filaments break, the overall conductivity is maintained (redundant design). The twisted structure also shares mechanical tension, improving tensile strength.

[0086] Fatigue resistance: When a stranded cable is subjected to vibration or repeated bending, the tiny displacements between the individual filaments can absorb stress, making it more resistant to fatigue than a single solid conductor.

[0087] Structural stability: Each layer of copper wire is spirally arranged with a fixed pitch, and the directions between layers are opposite (such as right-handed in the outer layer and left-handed in the inner layer), which offsets the torque and prevents the cable from twisting or loosening spontaneously.

[0088] Geometric symmetry: Concentric twisting ensures that the conductor cross-section remains circular, making the insulation layer and outer sheath thickness uniform and avoiding electric field distortion (especially important for cables).

[0089] Production efficiency: The number of layers and the number of monofilaments in a regular twist follow mathematical rules (such as n 2 +1), facilitating standardized production and quality control.

[0090] In step 2):

[0091] The insulated wire core is made of thermoplastic polypropylene conductor shielding layer material, thermoplastic polypropylene insulation material and thermoplastic polypropylene insulation shielding material through CCV catenary wire three-layer co-extrusion, and the insulation color is natural color.

[0092] Extrusion process parameters: Along the direction from feeding to discharging, the temperatures of zones 1 - 9 of the extruder are respectively: 165 ± 2 °C, 170 ± 2 °C, 166 ± 2 °C, 168 ± 2 °C, 169 ± 2 °C, 169 ± 2 °C, 172 ± 2 °C, 170 ± 2 °C, 169 ± 2 °C. The screw speed of the extrusion equipment is 9.5 revolutions per minute;

[0093] Select an extrusion die and determine the die size according to the outer diameter of the conductor;

[0094] Calculation of die core 1: D1 core = D + clearance value, and the clearance value is generally 0.5 - 0.7 mm;

[0095] Calculation of die core 2: D2 core = D1 core + 2 × nominal thickness of the conductor shielding layer;

[0096] Calculation of die sleeve: D sleeve = D2 core + 2 × nominal thickness of insulation + 2 × nominal thickness of insulation shielding;

[0097] The wire drawing speed is generally 4.5 m / minute;

[0098] After extrusion, it is naturally cooled through a water tank and wound around a turnover spool.

[0099] The co - extruded insulated wire core has excellent electrical properties, high - temperature resistance, mechanical strength, chemical resistance, as well as environmental protection and cost advantages.

[0100] Excellent electrical properties: PP (thermoplastic polypropylene) has a low dielectric constant (~2.2) and low dielectric loss (tanδ < 0.0005), which can reduce signal attenuation and energy loss. Compared with traditional PVC or PE, PP has a higher insulation resistance and better corona resistance, and is suitable for medium - and high - voltage power cables.

[0101] High - temperature resistance: The long - term service temperature of PP can reach 90 °C - 105 °C (ordinary PE is only 70 °C), and it can withstand higher temperatures in the short term, suitable for high - temperature environments or high - current working conditions.

[0102] Mechanical strength and chemical resistance: The tensile strength and wear resistance of PP are better than those of PE, and it is resistant to acids, alkalis, and organic solvents, suitable for harsh industrial environments.

[0103] Thermoplastic PP is easy to process and does not require cross - linking (such as XLPE which requires irradiation or chemical cross - linking), simplifying the production process.

[0104] Environmental protection and cost advantages: PP can be recycled, in line with the environmental protection trend; and the raw material cost is lower than that of some high - performance materials (such as PTFE).

[0105] The conductor shielding layer (inner shielding) obtained by three-layer co-extrusion (conductor shielding + insulation + insulation shielding) serves to fill the minute irregularities on the conductor surface, making the electric field distribution uniform and avoiding partial discharge (especially in medium and high voltage cables). The insulation layer (main insulation) provides the core insulation performance, and the high purity and low defect rate of PP ensure high dielectric strength. The insulation shielding layer (outer shielding) is tightly bonded to the insulation layer, smoothing the electric field on the outer surface and preventing partial discharge between the cable insulation and the metal shielding layer.

[0106] During three-layer co-extrusion, the three materials are extruded simultaneously, with no contamination or air gaps between the interfaces, avoiding the risk of delamination (traditional step-by-step extrusion is prone to introducing impurities). It can be completed in one step, reducing the process steps, energy consumption, and reject rate.

[0107] The CCV (catenary) production line uses a catenary die to make the molten material sag naturally under the action of gravity, forming an insulation layer with a uniform thickness and avoiding eccentricity (which is crucial for the electric field uniformity of medium and high voltage cables).

[0108] The insulation layer of medium and high voltage cables requires extremely high purity. Colorants may introduce impurities (such as metal ions), affecting the dielectric properties or causing electrical tree aging. Therefore, the natural color is chosen without adding color masterbatch, avoiding fluctuations in insulation performance caused by uneven dispersion of the color masterbatch.

[0109] In step 3): The metal shielding layer is a high-conductivity copper wire shielding. The diameter and the number of copper wires stranded are selected according to the outer diameter of the insulated conductor core. Here, 28 copper wires with a diameter of 1.04 mm are preferably stranded equidistantly on the surface of the insulated conductor core. At the same time, the temperature measuring device is stranded together with the high-conductivity copper wires to obtain the conductor.

[0110] The copper wire shielding serves as an equipotential layer, eliminating the air gap between the insulation shielding layer and the metal sheath (or armor) and preventing partial discharge.

[0111] When a short circuit fault occurs in the cable, the copper wire shielding can quickly conduct the fault current and protect the insulation layer from being burned.

[0112] The copper wire shielding can also block external electromagnetic interference (such as the influence of power cables on communication cables) or prevent the leakage of the cable's own electromagnetic field.

[0113] The temperature measuring device in this embodiment is a temperature measuring optical fiber. After being stranded together with the high-conductivity copper wires, it can monitor the cable temperature in real time. When the temperature measuring optical fiber is directly exposed, it is easily damaged. Stranding it in the copper wires can avoid damage from external forces (such as extrusion and friction). Moreover, the gaps naturally formed during the stranding of the copper wires can accommodate the temperature measuring device without additional occupation of the cable cross-sectional area. In this way, the optical fiber serving as the temperature measuring device is in direct contact with the copper wire shielding and can reflect the true temperature of the conductor in real time. And the copper wire shielding can absorb external electromagnetic noise and protect the temperature measuring signal (such as the optical fiber signal) from interference.

[0114] In step 4): To ensure the smooth operation of the product and reduce the breakdown risk, the manufactured wire is wrapped with a semi-conductive nylon tape; for example, wrap it with a 0.12×40 mm semi-conductive nylon tape for one layer, and its minimum overlapping width is not less than 8 mm.

[0115] Wrapping the semi-conductive nylon tape around the outer layer of the wire can optimize the electric field distribution, enhance mechanical protection, and ensure the long-term reliable operation of the cable.

[0116] There may be slight irregularities on the surface of the metal shielding layer 301, or there may be slight gaps between it and the armor layer. These air gaps will cause electric field concentration, triggering partial discharge (PD), and may break down the insulation in the long term.

[0117] The semi-conductive nylon tape has moderate conductivity (the resistivity is usually 103 - 105 Ω·cm), which can fill the irregular surface of the metal shielding layer 301, making the electric field transition smoothly from the insulation layer to the metal shielding layer and avoiding electric field distortion.

[0118] When the metal shielding layer is bent or pressed, it may directly rub against the insulation layer, damaging the insulation in the long term. The semi-conductive nylon tape has flexibility, can absorb mechanical stress, and prevent the metal shielding layer from cutting other nearby functional layers.

[0119] Electrical tree (conductive channels) is likely to form at the defective parts of the cable insulation material, eventually leading to breakdown. The existence of the semi-conductive layer can equalize the surface charge distribution, reduce the charge accumulation on the surface of the insulation layer, and delay the growth of electrical trees. Since the cable operates in the desert area, the insulation aging speed is faster than that in the general environment, making it more likely to be broken down. Introducing the semi-conductive wrapping layer 203 between the metal shielding layer 301 and the armor layer 201 can ensure the long-term reliable operation of the cable.

[0120] In step 5): The extruded inner liner material is medium density polyethylene (MDPE), and an extrusion die is used for extrusion to ensure that the internal temperature measurement device of the cable is not damaged; along the feeding to discharging direction, the temperatures of the 1 - 6 zones of the extruder are 125±15 °C, 130±15 °C, 150±15 °C, 160±15 °C, 160±15 °C, 150±15 °C respectively; the temperatures of the 1 - 4 zones of the head are 160±5 °C, 160±5 °C, 165±5 °C, 165±5 °C, the screw speed of the extrusion equipment is 4.2 revolutions per minute; the wire outlet speed is generally 1 m / minute.

[0121] When the armor layer (such as steel wire or steel strip) is in direct contact with the semi-conductive nylon tape, it may damage the temperature measurement device (such as optical fiber or thermocouple) in contact with the semi-conductive nylon tape due to extrusion or bending. The MDPE inner liner layer, as a flexible isolation layer, absorbs the stress from the armor layer to avoid the breakage of the temperature measurement device or signal distortion.

[0122] When the armored layer moves (such as during laying or vibration), it may rub against the semiconductive nylon tape, and the lubricity of MDPE reduces wear.

[0123] The semiconductive nylon tape has weak conductivity. If it directly contacts the metal armored layer, a leakage current path may be formed, while using MDPE (an insulating material) can block this path.

[0124] The armored layer is usually in a helical winding or intermittent structure. The MDPE inner lining layer can fill the gap between the armor and the inner layer to prevent the structure from becoming loose when the cable deforms.

[0125] In step 6): The armored material is a high-strength non-magnetic stainless steel tape. While improving the overall mechanical properties of the cable, it further enhances the anti-interference ability against external electromagnetic fields and is wound around the surface of the inner lining layer by a double-layer intermittent wrapping method.

[0126] Example: Use a 0.5×35mm high-strength non-magnetic stainless steel tape, with double-layer intermittent wrapping and a gap width of 14 - 17mm.

[0127] Stainless steel tapes (such as materials 304 and 316) have high strength (tensile strength ≥520 MPa), can resist external mechanical forces such as the pulling force during laying, rock extrusion, and rodent gnawing (for buried laying), etc., and protect the internal insulation layer and temperature measuring device.

[0128] The magnetic permeability of non-magnetic stainless steel (such as austenitic 304) is close to that of a vacuum (μ≈1), avoiding eddy current losses and hysteresis losses in an alternating magnetic field.

[0129] The conductivity of stainless steel (resistivity about 7.3×10 -7 Ω·m) can reflect external electromagnetic waves and suppress the influence of external interference (such as from substations, lightning strikes) on internal signals.

[0130] In step 7): The temperature-resistant layer material uses nylon 12 (PA12) material and is extruded using an extrusion die. Along the direction from feed to discharge, the temperatures of zones 1 - 6 of the extruder are 145±15°C, 150±15°C, 160±15°C, 180±15°C, 180±15°C, 170±15°C respectively; the temperatures of zones 1 - 4 of the die head are 170±5°C, 170±5°C, 175±5°C, 175±5°C, the screw speed of the extrusion equipment is 4 RPM; the wire outlet speed is generally 1 m / min, and the nominal thickness of the extruded temperature-resistant layer is 4.0 mm.

[0131] PA12 has a low flexural modulus (about 1.4 GPa), is suitable for cables that need to be frequently bent, and resists corrosion by grease, fuel, and weak acids and alkalis. The performance of the material itself can meet the operating requirements of cables in desert areas.

[0132] The tube extrusion die makes the molten PA12 first form a tube and then coat the cable core, avoiding direct extrusion from damaging the internal armor layer, temperature measuring device or insulation layer (the high pressure of the contrast extrusion die may flatten the metal shielding layer).

[0133] After the tube is extruded, it is sized by vacuum to ensure that the thickness of the temperature-resistant layer is consistent (such as 1.0±0.1 mm), avoiding a decrease in temperature resistance performance due to local thinning.

[0134] The temperature-rising logic of the extruder by zones is as follows:

[0135] Zone 1 (feeding section): lower temperature (145°C), preventing the PA12 particles from prematurely melting and caking, which may cause poor feeding.

[0136] Zones 2-4 (compression section): gradually increase the temperature to 180°C to completely melt and homogenize the PA12.

[0137] Zones 5-6 (metering section): slightly lower the temperature (170°C) to reduce the risk of degradation and ensure the melt stability.

[0138] Precise temperature control: PA12 is sensitive to temperature. Too high temperature will cause thermal degradation (releasing caprolactam monomer), and too low temperature will result in poor melt fluidity.

[0139] The temperature gradient of the head in zones 1-4 is as follows:

[0140] Zone 1 (connector): slightly higher than the melt temperature (170°C) to ensure a smooth transition of the melt.

[0141] Zones 2-3 (die core / die sleeve): precisely controlled (170-175°C) to ensure a stable shape of the tube extrusion.

[0142] Zone 4 (die lip): slightly lower the temperature (175°C) to reduce the exit swelling ("die swell" effect).

[0143] The melt viscosity of PA12 is 200-500 Pa·s at 200°C. The balance between fluidity and strength is adjusted through the above temperature gradient.

[0144] The crystallinity of PA12 (about 25%) is affected by the cooling rate. The mechanical properties can be optimized through the above temperature control.

[0145] During the extrusion process of the temperature-resistant layer, a power frequency spark test is carried out, and the test voltage is 15 kV.

[0146] The main components of the temperature-resistant layer are composed of nylon 12 and additives. Among them, PA12 accounts for 96%, the main antioxidant (1076+1098) accounts for 0.6%, phosphite accounts for 0.4%, light stabilizer accounts for 0.5%, calcium stearate accounts for 0.8%, nucleating agent accounts for 0.2%, and tackifier accounts for 0.5%.

[0147] The formulation of the temperature-resistant layer aims to optimize material properties, extend service life, and adapt to processing techniques to meet the operating requirements of cables in desert areas.

[0148] The main antioxidants (1076 + 1098) account for 0.6%. Specifically:

[0149] 1076 (phenolic antioxidant): Captures free radicals and prevents oxidative degradation during high-temperature processing or use.

[0150] 1098 (amine antioxidant): Works in synergy with 1076 to provide long-term thermal stability, especially inhibiting chain scission of PA12 during long-term thermal aging.

[0151] The total amount of 0.6% is an optimal choice to balance cost and efficacy. Excessive amounts may migrate and precipitate, while insufficient amounts cannot provide effective protection.

[0152] Phosphite (0.4%) is used as a secondary antioxidant to decompose peroxides, delay yellowing of the material and decline of mechanical properties. It works in synergy with the main antioxidant to form a dual protection mechanism of "free radical capture + peroxide decomposition".

[0153] The light stabilizer (0.5%) can inhibit the photo-oxidation reaction induced by ultraviolet (UV) light to cope with long-term UV irradiation in desert areas. The commonly used type is hindered amine light stabilizer (HALS), which works in synergy with antioxidants to enhance weather resistance.

[0154] Calcium stearate (0.8%) is used as a lubricant to reduce the melt viscosity, improve the processing fluidity of PA12, and reduce the torque energy consumption of the extruder.

[0155] The mold release agent prevents the melt from adhering to the mold and improves the surface finish of the extrusion die. 0.8% can balance the lubrication effect and the impact on the mechanical properties of the material (excessive amounts will reduce the strength of PA12).

[0156] The nucleating agent (0.2%) is used to promote the uniformity and speed of PA12 crystallization, and improve its rigidity and heat distortion temperature (HDT). The commonly used types are inorganic nanoparticles (such as talc powder) or organic acid salts. Since the nucleating agent is highly efficient, excessive amounts will cause the material to become brittle, so it is set at 0.2%.

[0157] The tackifier (0.5%) is used to enhance the adhesion between PA12 and adjacent layers (such as the armor layer or sheath layer) to avoid delamination. Commonly used maleic anhydride grafted polymers (such as POE-g-MAH) react with the polar groups of PA12 to form chemical bonds.

[0158] In this embodiment, the performance indicators of the temperature-resistant layer are shown in the following table. The performance of the temperature-resistant layer of the cable produced by adjusting the extrusion process is superior to common products on the market, and the relevant experimental data are shown in Table 1.

[0159] Table 1 Comparison of the Performance of the Temperature-Resistant Layer

[0160]

[0161]

[0162] The temperature-resistant layer of the cable is made by extrusion of high-performance nylon 12 material. The operating environment temperature is from -40°C to 125°C. It has good weather resistance and UV tolerance, and will not crack in extreme temperature difference environments. At the same time, it has excellent mechanical properties, reducing construction costs. The armor layer, semi-conductive nylon tape wrapping, and shielding layer work together to equalize the electric field inside the cable and can also shield external electromagnetic field interference. The shielding layer can also conduct the leakage current during the operation of the cable. The temperature measurement device consists of two low-attenuation optical fibers, which can monitor the temperature of the cable during operation in real time and can also alarm for abnormal temperatures during operation. The insulation layer is made of polypropylene material, and the maximum operating temperature of 110°C is better than that of traditional cross-linked polyethylene material (90°C), which can increase the cable ampacity. Thermoplastic polypropylene does not require cross-linking reaction, which can reduce production costs. At the same time, thermoplastic polypropylene can be recycled and reused, which is environmentally friendly.

[0163] Example 3:

[0164] A preparation system for a power cable applicable to desert areas, comprising:

[0165] A wire drawing device for wire drawing treatment of the pretreated copper rod;

[0166] A stranding device for receiving copper wires and stranding them to obtain a conductor;

[0167] A three-layer co-extrusion device for simultaneously extruding a conductor shielding layer, an insulation layer, and an insulation shielding layer outside the conductor to obtain an insulated wire core;

[0168] A shielding layer processing device for stranding a metal shielding layer and a temperature measurement optical fiber outside the insulated wire core to obtain a wire;

[0169] A sheath and protective layer manufacturing unit for obtaining a semi-conductive wrapping layer outside the wire through a wrapping device, obtaining an inner liner layer through an extrusion device, obtaining an armor layer through an armor layer processing device, obtaining a temperature-resistant layer through an extrusion machine, and obtaining a completed cable after inspection.

[0170] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. Preparation method of power cable applicable to desert areas, characterized in that, It includes the following steps: The copper rod is drawn and stranded to obtain a conductor, and a conductor shielding layer, an insulating layer, and an insulation shielding layer are sequentially wrapped outside the conductor to obtain an insulated core; A metal shielding layer and a temperature-measuring optical fiber are stranded outside the insulated core to obtain a wire; A semiconductive wrapping layer is obtained by wrapping outside the wire in sequence, an inner liner layer is obtained by extrusion, an armor layer is obtained by wrapping, and a temperature-resistant layer is obtained by extrusion to obtain the completed cable; Among them, the temperature-resistant layer is extruded through an extrusion tube die. Along the feeding direction to the discharging direction, the temperatures of the 1-6 zones of the extruder are respectively: 145±15°C, 150±15°C, 160±15°C, 180±15°C, 180±15°C, and 170±15°C; the temperatures of the 1-4 zones of the extruder head are respectively: 170±5°C, 170±5°C, 175±5°C, and 175±5°C.

2. The preparation method of the power cable applicable to desert areas according to claim 1, wherein The conductor shielding layer, the insulating layer, and the insulation shielding layer are sequentially wrapped outside the conductor to obtain an insulated core. Specifically, the conductor shielding layer, the insulating layer, and the insulation shielding layer are used to obtain the insulated core by three-layer coextrusion.

3. The preparation method of the power cable applicable to desert areas according to claim 2, characterized in that, The process parameters of the three-layer coextrusion are: along the feeding direction to the discharging direction, the temperatures of the 1-9 zones of the extruder are respectively: 165±2°C, 170±2°C, 166±2°C, 168±2°C, 169±2°C, 169±2°C, 172±2°C, 170±2°C, and 169±2°C.

4. The preparation method of the power cable applicable to desert areas according to claim 2, characterized in that, During the three-layer coextrusion, the size of the extrusion die is determined according to the outer diameter D of the conductor. Specifically: Inner diameter of die core 1: D1 core = D + clearance value, and the clearance value is 0.5-0.7mm; Inner diameter of die core 2: D2 core = D1 core + 2×nominal thickness of conductor shielding; Inner diameter of die sleeve: D sleeve = D2 core + 2×nominal thickness of insulation + 2×nominal thickness of insulation shielding.

5. The preparation method of the power cable applicable to desert areas as described in claim 1, wherein The material of the insulating layer is grafted polypropylene.

6. The preparation method of the power cable applicable to desert areas according to claim 1, wherein The inner liner layer is obtained by extrusion outside the semiconductive wrapping layer. Specifically: an extrusion tube die is used for extrusion. Along the feeding direction to the discharging direction, the temperatures of the 1-6 zones of the extruder are respectively: 125±15°C, 130±15°C, 150±15°C, 160±15°C, 160±15°C, 150±15°C.

7. The preparation method of the power cable applicable to desert areas as described in claim 6, characterized in that, Along the feeding direction to the discharging direction, the temperatures of the 1-4 zones of the extruder head are 160±5°C, 160±5°C, 165±5°C, and 165±5°C.

8. The preparation method of the power cable applicable to desert areas as described in claim 1, wherein, The material of the temperature-resistant layer is "high-performance nylon 12".

9. The preparation method of the power cable applicable to desert areas as described in claim 1, characterized in that, A metal shielding layer and a temperature-measuring optical fiber are stranded outside the insulated core to obtain a wire. Specifically: according to the outer diameter of the insulated core, copper wires with a set diameter are selected and equally spaced and stranded on the surface of the insulated core. During the stranding, the temperature-measuring optical fiber is stranded together with the copper wires to obtain a wire.

10. A system for the preparation method of power cables applicable to desert areas, which is used to implement the preparation method described in any one of claims 1-9, characterized in that, It includes: A wire drawing device for drawing the pretreated copper rod; A stranding device for receiving the copper wires and stranding them to obtain a conductor; A three-layer coextrusion device for synchronously extruding a conductor shielding layer, an insulating layer, and an insulation shielding layer outside the conductor to obtain an insulated core; A shielding layer processing device for stranding a metal shielding layer and a temperature-measuring optical fiber outside the insulated core to obtain a wire; Sheath and protective layer manufacturing unit, which is used to obtain a semiconductive wrapping layer outside the conductor through a wrapping device, obtain an inner lining layer through an extrusion device, obtain an armored layer through an armored layer processing device, obtain a temperature-resistant layer through an extruder, and after inspection, obtain a completed cable.

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