Environment-friendly polypropylene medium voltage cable

Abstract

The utility model discloses an environmental protection type polypropylene medium voltage cable, including the cable that is formed by the stranding of three core wires, the filler strip of fan -shaped is arranged between the core wire, and the filler layer of the cable is formed to the cable outside, the wrapping layer, the isolating bush, the armoring layer and the outer sheath are sequentially arranged outside the filler layer, the filler strip includes two inner arc shape parts and an outer arc shape part, wherein two inner arc shape parts cooperate with the core wire respectively, and the gap filling part of the narrow strip structure is formed between the inner arc shape part and the outer arc shape part and between two inner arc shape parts respectively, the filling groove of setting along the axial setting of the filler strip is arranged at the end of the gap filling part, and the water -stop rope is arranged in the filling groove. The cable has good electrical performance, mechanical performance and weather resistance, and is suitable for long distance, high load scene, high temperature environment, offshore platform, sewage treatment plant and other humid / corrosive environment.

Description

Technical Field

[0001] This utility model belongs to the field of cable technology, specifically relating to an environmentally friendly polypropylene medium-voltage cable. Background Technology

[0002] Currently, most common power cables use cross-linked polyethylene (XLPE) insulation. During the production process, impurities such as cross-linking agents and byproducts generated during cross-linking may be introduced into the insulation layer, leading to more severe space charge accumulation under an electric field and thus accelerating insulation aging. The cross-linking process used in XLPE cables suffers from high energy consumption and low efficiency. The vulcanization and degassing during cross-linking not only complicates the process but also creates a harsh production environment, making recycling difficult. Furthermore, the time and cost of cross-linking and stress relief are much higher than for thermoplastic materials.

[0003] Polypropylene (PP) is a non-polar material with excellent insulation properties, high temperature resistance, and plasticity and reusability. It not only increases transmission capacity but also offers significant advantages in simplifying processing, reducing costs, and improving production efficiency, making PP insulated cables widely used in construction, transportation, power plants, automobiles, petrochemicals, and other fields. However, applications have revealed that PP is prone to air gaps or impurity defects under high-voltage electric fields, leading to partial discharge and affecting the long-term reliability of the cable. Furthermore, PP is susceptible to electrical aging under high-frequency or pulsed voltages, resulting in insulation layer deterioration. In humid environments, PP insulation is prone to water tree formation, reducing the cable's insulation life. Utility Model Content

[0004] The purpose of this invention is to provide an environmentally friendly polypropylene medium-voltage cable to solve the aforementioned problems existing in the application of polypropylene insulated cables.

[0005] This utility model is achieved through the following technical solution: An environmentally friendly polypropylene medium-voltage cable includes a cable formed by twisting three core wires together, with a fan-shaped filler strip disposed between the core wires to form a filler layer covering the cable. A wrapping layer, an isolation sleeve, an armor layer, and an outer sheath are arranged sequentially outside the filling layer; The filler strip includes two inner arc-shaped parts and one outer arc-shaped part. The two inner arc-shaped parts are respectively matched with the core wire. A narrow strip-shaped gap filling part is formed between the inner arc-shaped part and the outer arc-shaped part, and between the two inner arc-shaped parts. A filling groove is provided at the end of the gap filling part along the axial direction of the filler strip. A water-blocking rope is provided in the filling groove.

[0006] In some embodiments, the opening of the filling groove is smaller than the diameter of the water-blocking rope, so that the water-blocking rope can be embedded in the filling groove.

[0007] In some embodiments, a water-blocking yarn is provided between the inner arcuate portion and the corresponding core wire.

[0008] In some embodiments, a water-resistant coating is sprayed onto the surface of the filler layer.

[0009] In some embodiments, the core wire includes a conductor, and a conductor shielding layer, a polypropylene insulation layer, and an insulation shielding layer are sequentially disposed outside the conductor.

[0010] In some embodiments, a transition adhesive layer is provided between the conductor shielding layer and the polypropylene insulation layer.

[0011] In some embodiments, a nanocomposite layer with a dielectric constant of not less than 10 is disposed outside the insulating shielding layer.

[0012] In some embodiments, a metal shielding layer is provided outside the core wire.

[0013] In some embodiments, the conductor is formed by tightly stranding irregularly shaped monofilaments, and the compaction coefficient is not less than 0.92.

[0014] In some embodiments, a longitudinally wrapped water-resistant layer is disposed between the armor layer and the outer sheath.

[0015] Compared with the prior art, this utility model has the following advantages and beneficial effects: The cable of this invention has good electrical, mechanical and weather resistance properties, can reduce energy loss during power transmission, and is suitable for long-distance, high-load scenarios; the long-term operating temperature can reach 105℃, making it suitable for high-temperature environments; and it has better resistance to high-frequency pulse voltage, making it suitable for power supply of frequency converters and frequency conversion motors; through the design of the anti-water tree structure, it can be used in humid / corrosive environments such as offshore platforms and sewage treatment plants. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this utility model, the accompanying drawings in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of an environmentally friendly polypropylene medium-voltage cable according to an embodiment of this utility model.

[0018] Figure 2 This is a schematic diagram of the filling strip structure in an embodiment of the present invention.

[0019] Figure 3 This is a schematic diagram of the core wire structure in an embodiment of the present utility model.

[0020] in: 11. Conductor; 12. Conductor shielding layer; 13. Polypropylene insulation layer; 14. Insulating shielding layer; 15. Transition bonding layer; 16. Nanocomposite layer; 17. Metal shielding layer. 20. Filler strip; 21. Inner arc-shaped part; 22. Outer arc-shaped part; 23. Gap filling part; 24. Filling groove; 25. Water-blocking rope. 31. Wrapping layer; 32. Isolation layer; 33. Armor layer; 34. Longitudinal waterproof layer; 35. Outer sheath. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this utility model, but not all embodiments.

[0022] In view of the problems existing in the practical application of polypropylene insulated cables, this utility model aims to provide an environmentally friendly polypropylene medium-voltage cable with good insulation performance, good electrical resistance, and good weather resistance.

[0023] Reference Figure 1 and Figure 2 In some embodiments of this utility model, the environmentally friendly polypropylene medium-voltage cable includes a cable formed by twisting three core wires together, with a fan-shaped filler strip 20 disposed between the core wires, forming a filler layer covering the cable through the filler strip. A wrapping layer 31, an isolation sleeve 32, an armor layer 33, and an outer sheath 34 are sequentially arranged outside the filling layer; The filler strip 20 includes two inner arc-shaped portions 21 and one outer arc-shaped portion 22. The two inner arc-shaped portions are respectively engaged with the core wire. A narrow strip-shaped gap filling portion 23 is formed between the inner arc-shaped portion and the outer arc-shaped portion, and between the two inner arc-shaped portions. A filling groove 24 is provided at the end of the gap filling portion 23 along the axial direction of the filler strip. A water-blocking rope 25 is provided in the filling groove 24.

[0024] After the three core wires are twisted together to form a cable, three fan-shaped empty areas will be formed on the outside, and the cross-section of the filler strip will match the cross-section of the empty area.

[0025] This invention employs fan-shaped filler strips to fill the gaps between the core wires. The three filler strips are wrapped around the outside of the cable to form a filler layer, which can prevent moisture from penetrating along the filler layer and effectively solve the problem that polypropylene insulation layers are prone to water treeing in humid environments, thus reducing insulation life.

[0026] like Figure 2 The fan-shaped filler strip has three pointed corners forming gap filling sections to fill the gaps between wire cores and between adjacent filler strips. A filling groove is set at the end of the gap filling section, and a water-blocking rope is set in the filling groove. The water-blocking rope is effectively fixed on the filler strip through the filling groove, and the gap is filled by the water-blocking rope. When the water-blocking rope expands when it comes into contact with water, it can effectively prevent the continued penetration of water, so as to solve the problem of water tree formation in PP insulation layer in humid environment and ensure the cable insulation life.

[0027] By filling the gaps between the core wires with filler strips, the roundness of the cable can be well guaranteed.

[0028] The filler strip is made of foamed polypropylene material through extrusion molding. During the core wire stranding process, it is stranded together with the three core wires to form a cable. By placing the water-blocking rope inside the filling groove, it facilitates the filling of gaps during the stranding of the filler strip and core wires. With the water-blocking rope placed inside the filling groove, when the filler strip is subjected to stranding and compressive force, the water-blocking rope can be extruded from the filling groove under this compressive force, thus achieving better filling of the gaps under external pressure.

[0029] In some embodiments, the opening of the filling groove 24 is smaller than the diameter of the water-blocking rope 25, allowing the water-blocking rope 25 to be embedded within the filling groove 24. The diameter of the water-blocking rope matches the diameter of the filling groove. When the water-blocking rope is embedded in the filling groove, it can be effectively fixed to the filling strip. Furthermore, when the filling strip is subjected to compressive force, the water-blocking rope can be squeezed out of the filling groove, thereby effectively filling the gaps.

[0030] Water-blocking rope 25 typically uses superabsorbent polymer (SAP) filled into fibers. SAP has excellent water absorption, with a water absorption capacity greater than 50 mL / g and a water absorption rate greater than 40 mL / g / 1 min. It can expand more than 10 times within 1 min and form a water-blocking gel, which prevents water penetration.

[0031] In some embodiments, a water-blocking yarn is provided between the inner arc-shaped portion and the corresponding core wire. The water-blocking yarn fills the gap between the filler strip and the core wire, and expands when exposed to water to prevent moisture penetration.

[0032] In some embodiments, a water-resistant coating is sprayed onto the surface of the filler layer. Before wrapping, SAP powder or water-resistant adhesive is sprayed onto the surface of the filler layer formed by the filler strip to form a water-resistant coating on the surface of the filler layer, so as to achieve better water resistance.

[0033] This invention uses filler strips to fill the wrapping gaps between core wires, achieving dry cabling without oil or solvents, thus enabling cable recycling and ensuring the cable's environmental performance.

[0034] A central hole is provided in the middle of the filler strip. The central hole reduces the weight of the filler strip, thereby reducing the weight of the cable. At the same time, the central hole provides space for other components to be installed inside the cable.

[0035] The sheath 31 is made of a non-hygroscopic polymer material to improve the cable's moisture resistance and provide protection for the internal cables.

[0036] The isolation sleeve 32 is made of polyvinyl chloride to reduce the impact of electromagnetic interference on signal transmission, buffer external pressure and friction, and prevent damage to internal cables.

[0037] The armor layer 33 is made of galvanized steel strip, which provides protection for the internal cables of the cable and is used as a grounding conductor.

[0038] The outer sheath 34 can be made of polyvinyl chloride to be suitable for various laying environments.

[0039] A longitudinally wrapped water-blocking layer 34 is disposed between the armor layer 33 and the outer sheath 35. The longitudinally wrapped water-blocking layer 34 is made of water-blocking non-woven fabric tape. The longitudinally wrapped water-blocking layer is formed on the outside of the armor layer using a longitudinal wrapping device before the outer sheath is formed. The setting of the longitudinally wrapped water-blocking layer does not increase the production process and prevents the outer sheath from directly contacting the metal armor layer, thus playing a buffering role and effectively avoiding stress concentration in the outer sheath and cracking during laying and operation. The longitudinally wrapped water-blocking layer can expand rapidly after water enters, thereby blocking the penetration of water along the inner wall of the outer sheath in the length direction of the cable.

[0040] In some embodiments, such as Figure 3 As shown, the core wire includes a conductor 11, and a conductor shielding layer 12, a polypropylene insulation layer 13, and an insulation shielding layer 14 are sequentially disposed outside the conductor 11.

[0041] Conductor 11 is formed by tightly stranding irregularly shaped monofilaments with a compaction coefficient of over 0.92; the outer surface is smooth and burr-free, which can effectively reduce the risk of insulation breakdown, and there are no extra gaps, so that moisture cannot penetrate along the longitudinal direction of the conductor.

[0042] The conductor shielding layer 12 is made of semi-conductive polypropylene or cross-linked semi-conductive material, used to fill the gap between the conductor and the insulation layer, eliminate partial discharge, and uniformize the electric field.

[0043] The polypropylene insulation layer 13 is made of polypropylene or modified polypropylene, such as a PP / PE blend. Modifications to the polypropylene material, such as the addition of antioxidants and voltage stabilizers, further enhance its heat resistance and anti-aging properties. The use of polypropylene gives the insulation layer high dielectric strength, low dielectric loss, and high temperature resistance, while also providing good environmental performance, enabling the cable to be recycled and reused.

[0044] The thickness of the polypropylene insulation layer is set according to the voltage level. Taking a 10kV cable as an example, the thickness of the polypropylene insulation layer can usually be set to 4.3-4.5mm.

[0045] The insulating shielding layer 14 is made of semi-conductive polypropylene or cross-linked semiconductor material, which works in conjunction with the conductive shielding layer to further homogenize the electric field and prevent surface discharge.

[0046] Semiconducting water-resistant tape and / or aluminum-plastic composite longitudinal wrapping layer can be set outside the insulating shielding layer 14 to achieve longitudinal water blocking.

[0047] In some embodiments, a transition adhesive layer 15 is provided between the conductor shielding layer and the polypropylene insulation layer. The transition adhesive layer 15 is made of polypropylene material that has been polarly grafted to improve the compatibility between the polar conductor shielding layer and the non-polar insulation layer and reduce the porosity between the interfaces.

[0048] The matrix of the transition adhesive layer is made of high melt strength polypropylene. By introducing polar grafted segments, such as maleic anhydride-grafted PP, polar anchors are provided to improve the compatibility between the polypropylene insulation layer and the conductor shielding layer. This also creates a modulus gradient, buffers thermal stress, and reduces interfacial surface tension. Nano-SiO2 can be filled within the transition adhesive layer to enhance hydrophobic properties and block water tree channels.

[0049] The thickness of the transition bonding layer 15 can be set to 0.2-0.4mm, and it can be co-extruded with the conductor shielding layer and the polypropylene insulation layer in one step to ensure that there are no gaps between the layers.

[0050] In some embodiments, a nanocomposite layer 16 with a dielectric constant of not less than 10 is disposed outside the insulating shielding layer 14. The nanocomposite layer 16 is made by filling PP material with TiO2 or BaTiO3. The nanocomposite layer is used to form an electric field gradient, reduce the local electric field strength of the PP insulating layer, and suppress charge injection. The dielectric constant of the nanocomposite layer is 10-20.

[0051] In some embodiments, a metal shielding layer 17 is provided outside the core wire. The metal shielding layer 17 is formed by wrapping copper tape or loosely winding copper wire with copper tape wrapping, and is used to provide a short-circuit current path, shield external electromagnetic interference, and meet the grounding requirements of medium-voltage cables.

[0052] The performance of the environmentally friendly polypropylene medium-voltage cable in this embodiment was tested, and the performance test data are shown in Table 1.

[0053] Table 1. Cable performance test data for this embodiment. The cable of this invention has good electrical, mechanical and weather resistance properties, can reduce energy loss during power transmission, and is suitable for long-distance, high-load scenarios; the long-term operating temperature can reach 105℃, making it suitable for high-temperature environments; and it has better resistance to high-frequency pulse voltage, making it suitable for power supply of frequency converters and frequency conversion motors; through the design of the anti-water tree structure, it can be used in humid / corrosive environments such as offshore platforms and sewage treatment plants.

[0054] In the description of this utility model, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", and "outer" used to indicate the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the utility model product is usually placed in during use. They are only used to facilitate the description of this utility model and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0055] Furthermore, the use of terms such as "horizontal" or "vertical" in the description of this utility model does not imply that the component is required to be absolutely horizontal or suspended, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0056] In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0057] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present utility model shall fall within the protection scope of the present utility model.

Claims

1. An environmentally friendly polypropylene medium-voltage cable, characterized in that, The cable includes a cable formed by twisting three core wires together, with a fan-shaped filler strip located between the core wires to form a filler layer covering the cable. A wrapping layer, an isolation sleeve, an armor layer, and an outer sheath are arranged sequentially outside the filling layer; The filler strip includes two inner arc-shaped parts and one outer arc-shaped part. The two inner arc-shaped parts are respectively matched with the core wire. A narrow strip-shaped gap filling part is formed between the inner arc-shaped part and the outer arc-shaped part, and between the two inner arc-shaped parts. A filling groove is provided at the end of the gap filling part along the axial direction of the filler strip. A water-blocking rope is provided in the filling groove.

2. The environmentally friendly polypropylene medium-voltage cable according to claim 1, characterized in that, The opening of the filling groove is smaller than the diameter of the water-blocking rope, so that the water-blocking rope can be embedded in the filling groove.

3. The environmentally friendly polypropylene medium-voltage cable according to claim 1, characterized in that, A water-blocking yarn is provided between the inner arc-shaped part and the corresponding core wire.

4. The environmentally friendly polypropylene medium-voltage cable according to claim 1, characterized in that, A water-resistant coating is sprayed onto the surface of the filler layer.

5. The environmentally friendly polypropylene medium-voltage cable according to claim 1, characterized in that, The core wire includes a conductor, and a conductor shielding layer, a polypropylene insulation layer, and an insulation shielding layer are sequentially disposed outside the conductor.

6. The environmentally friendly polypropylene medium-voltage cable according to claim 5, characterized in that, A transition adhesive layer is provided between the conductor shielding layer and the polypropylene insulation layer.

7. The environmentally friendly polypropylene medium-voltage cable according to claim 5, characterized in that, A nanocomposite layer with a dielectric constant of not less than 10 is disposed outside the insulating shielding layer.

8. The environmentally friendly polypropylene medium-voltage cable according to claim 5, characterized in that, A metal shielding layer is provided outside the core wire.

9. The environmentally friendly polypropylene medium-voltage cable according to claim 5, characterized in that, The conductor is formed by tightly stranding irregularly shaped monofilaments, and the compaction coefficient is not less than 0.

92.

10. The environmentally friendly polypropylene medium-voltage cable according to claim 1, characterized in that, A longitudinally wrapped water-blocking layer is installed between the armor layer and the outer sheath.

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