A cable and a method of manufacturing the same

Abstract

The application provides a cable and a preparation method thereof. The cable provided by the application comprises at least a conductor, an inner shielding layer, an insulation layer and an outer shielding layer; the inner shielding layer is arranged outside the conductor, the insulation layer is arranged outside the inner shielding layer, and the outer shielding layer is arranged outside the insulation layer; wherein the insulation layer comprises, by mass fraction, 100 parts of polypropylene, 3-5 parts of a first antioxidant; the first antioxidant is composed of antioxidant 1010, antioxidant 168 and antioxidant 330, and the mass ratio of the antioxidant 1010, the antioxidant 168 and the antioxidant 330 is (3-7):(1-3):(1-4). The cable has excellent electrical insulation performance (can be applied to a voltage level of 66 kV and above) and mechanical performance.

Description

Technical Field

[0001] This invention relates to a cable and its manufacturing method, belonging to the field of materials and cable technology. Background Technology

[0002] Currently, cross-linked polyethylene (XLPE) is commonly used as insulation material in insulated power cables. However, since XLPE is difficult to recycle and can only be incinerated or crushed and landfilled, it easily leads to energy waste and environmental pollution. Therefore, more and more cable manufacturers are turning their attention to polypropylene insulation materials. However, existing polypropylene insulation materials still cannot fully meet the requirements of power cable use due to defects such as low operating voltage and poor mechanical properties. Summary of the Invention

[0003] This invention provides a cable with excellent electrical insulation properties (suitable for voltage levels of 66kV and above) and mechanical properties.

[0004] This invention provides a method for preparing a cable, which can produce the aforementioned cable and is simple, easy to operate, and suitable for widespread application.

[0005] This invention provides a cable, which includes at least a conductor, an inner shielding layer, an insulation layer, and an outer shielding layer;

[0006] The inner shielding layer is disposed on the outside of the conductor, the insulating layer is disposed on the outside of the inner shielding layer, and the outer shielding layer is disposed on the outside of the insulating layer;

[0007] The insulating layer comprises, by weight, the following components:

[0008] 100 parts of polypropylene;

[0009] 3-5 parts of the first antioxidant;

[0010] The first antioxidant is composed of antioxidant 1010, antioxidant 168 and antioxidant 330, and the mass ratio of antioxidant 1010, antioxidant 168 and antioxidant 330 is (3-7):(1-3):(1-4).

[0011] The cable as described above, wherein the insulation layer further comprises, by weight, 2-5 parts of elastomer;

[0012] The elastomer is selected from at least one of BR, SBR, EPR, EVA, EPMD, POE, and SEBS.

[0013] The cable as described above, wherein the elastomer is selected from EPMD, EVA and SBR, and the mass ratio of EPMD, EVA and SBR is (3-6):(1-3):(1-4).

[0014] The cable as described above, wherein the inner shielding layer and / or the outer shielding layer comprises, by weight parts:

[0015] 100 parts of polypropylene;

[0016] 2-5 parts carbon black.

[0017] The cable as described above, wherein the inner shielding layer and / or the outer shielding layer further comprises, by weight parts:

[0018] Second antioxidant 2-6 parts;

[0019] Copper-resistant agent 2-5 parts.

[0020] The cable as described above, wherein the second antioxidant is composed of antioxidant 1010 and antioxidant 330;

[0021] The copper-resistant agent is copper-resistant agent 1024.

[0022] In the cable described above, the mass ratio of antioxidant 1010, antioxidant 330 and copper resistant agent 1024 in the inner shielding layer and / or the outer shielding layer is (1-5):(1-5):(1-4).

[0023] The present invention also provides a method for manufacturing the cable as described above, comprising the following steps:

[0024] The cable is obtained by sequentially wrapping an inner shielding layer, an insulation layer, and an outer shielding layer around the conductor using a three-layer co-extrusion die head.

[0025] In the preparation method described above, the extrusion temperature of the insulating layer is 155-255°C; and / or,

[0026] The extrusion temperature of the inner shielding layer and / or the outer shielding layer is 155-255℃; and / or,

[0027] The ratio of screw speed to linear speed of the extruder is 8-12.

[0028] In the preparation method described above, the cable is subjected to air cooling and water cooling treatment in sequence.

[0029] The cable of this invention has excellent electrical insulation properties (suitable for voltage levels of 66kV and above) and mechanical properties because the insulation layer of the cable includes a first antioxidant with a specific content and composition.

[0030] The cable manufacturing method of the present invention can produce the cable with excellent electrical insulation and mechanical properties as described above. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the accompanying drawings used in the description of the embodiments of the present invention or related technologies are briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the cross-sectional structure of a cable in some embodiments of the present invention.

[0033] Explanation of reference numerals in the attached figures:

[0034] 1: Conductor;

[0035] 2: Inner shielding layer;

[0036] 3: Insulation layer;

[0037] 4: Outer shielding layer;

[0038] 5: Buffer layer;

[0039] 6: Metal sheath;

[0040] 7: Outer protective sleeve. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0042] Figure 1 This is a schematic diagram of the cross-sectional structure of a cable in some embodiments of the present invention. For example... Figure 1 As shown, in some embodiments of the present invention, the cable includes at least a conductor 1, an inner shielding layer 2, an insulation layer 3, and an outer shielding layer 4;

[0043] The inner shielding layer 2 is disposed on the outside of the conductor 1, the insulating layer 3 is disposed on the outside of the inner shielding layer 2, and the outer shielding layer 4 is disposed on the outside of the insulating layer 3.

[0044] The insulating layer 3 comprises, by weight, the following components:

[0045] 100 parts of polypropylene;

[0046] 3-5 parts of the first antioxidant;

[0047] The first antioxidant is composed of antioxidant 1010, antioxidant 168 and antioxidant 330, and the mass ratio of antioxidant 1010, antioxidant 168 and antioxidant 330 is (3-7):(1-3):(1-4).

[0048] In this invention, "covering" refers to the covering material completely enveloping and covering the axially extending exterior of the material to be covered. Using the inner shielding layer material as the covering material and conductor 1 as the material to be covered, this invention provides an example. "Inner shielding layer 2 covering the exterior of conductor 1" means that the inner shielding layer material completely envelops and covers the axially extending exterior of conductor 1, thereby forming an inner shielding layer 2 on the exterior of conductor 1. This invention does not particularly limit the specific method of covering. In some embodiments, the covering can be achieved by wrapping around the conductor, while in other embodiments, it can be achieved by nesting.

[0049] It is understood that the cable of the present invention comprises, from the core outwards, a conductor 1, an inner shielding layer 2, an insulation layer 3, and an outer shielding layer 4. The conductor 1 is used for conducting electricity, enabling the cable to transmit signals. The present invention does not impose any particular limitation on the conductor 1; the material and size of the conductor 1 can be determined according to actual needs. For example, the conductor 1 can be copper or aluminum, and its outer diameter can be 18-74 mm. The inner shielding layer 2 and the outer shielding layer 4 are used to achieve electrostatic shielding. In the present invention, the thickness of the inner shielding layer 2 and / or the outer shielding layer 4 can be selected according to actual needs. For example, the thickness of the inner shielding layer 2 can be 1.2-3 mm, and the thickness of the outer shielding layer 4 can be 0.8-2.1 mm. The insulation layer 3 serves as electrical insulation.

[0050] The insulating layer 3 of the present invention comprises 100 parts by weight of polypropylene and 3-5 parts by weight of a first antioxidant. Polypropylene is the base material of the insulating layer 3, and the first antioxidant is used to improve the thermal breakdown electrical strength, photo-aging performance and thermal aging performance of the insulating layer 3.

[0051] The first antioxidant of the present invention includes antioxidant 1010, antioxidant 168 and antioxidant 330 in a specific mass ratio. Compared with using only a single antioxidant, the first antioxidant of the present invention can greatly reduce the degree of decomposition of polypropylene (PP) molecular chains, increase the melting peak temperature of PP molecular chains, and improve the thermal breakdown electrical strength, anti-photoaging performance and anti-thermal aging performance of the insulation layer 3.

[0052] For example, when 1 part by weight of antioxidant 1010 is added to 100 parts by weight of polypropylene, the oxidation induction period of the resulting insulation layer is 30 minutes. However, when 2 or more parts by weight of antioxidant 1010 are added to 100 parts by weight of polypropylene, the oxidation induction period of the resulting insulation layer 3 remains essentially unchanged, indicating that the improvement of the anti-aging performance of the insulation layer 3 by a single antioxidant is limited.

[0053] Adding 1 part by weight of antioxidant 1010 and 1 part by weight of antioxidant 168 to 100 parts by weight of polypropylene resulted in an oxidation induction period of 36 minutes for the resulting insulation layer 3. However, adding 1 part by weight of antioxidant 1010 and 2 or more parts by weight of antioxidant 168 to 100 parts by weight of polypropylene did not change the oxidation induction period of the resulting insulation layer 3. This indicates that, compared with a single antioxidant, the addition of two antioxidants can further alleviate the auto-oxidative degradation process of polypropylene (PP) molecular chains to a certain extent and improve the anti-aging performance of the insulation layer 3, but the improvement performance is still limited.

[0054] Adding 3-5 parts by weight of a first antioxidant to 100 parts by weight of polypropylene, the first antioxidant comprising 5 parts by weight of antioxidant 1010, 2 parts by weight of antioxidant 168 and 3 parts by weight of antioxidant 330, results in an oxidation induction period of 90 minutes for the resulting insulating layer 3. This indicates that the first antioxidant with a specific composition in this invention can greatly improve the anti-aging properties of the insulating layer 3, thereby improving the mechanical properties of the insulating layer 3.

[0055] The first antioxidant of the present invention can also improve the mechanical properties of the insulation layer 3, thereby improving the mechanical properties of the cable.

[0056] For example, before the anti-aging test, the mechanical properties of the cable made according to the present invention were tested, and the elongation at break of the PP insulation was greater than 800%, and the tensile strength was greater than 42.4 N / mm. 2 After the cable of the present invention was subjected to an aging test in an air chamber (the temperature of the air chamber was 150°C, and the aging test time was 240 hours), the cable's elongation at break was greater than 780%, and its tensile strength was greater than 40.4 N / mm². 2 This demonstrates that the cable in this invention has excellent mechanical properties.

[0057] The first antioxidant of the present invention can also play a role in heterogeneous nucleation, increasing the number of crystal nuclei in the PP molecular chain, making the spherulites formed by PP smaller and more perfect, and the crystal distribution size more uniform, thereby improving the electrical insulation performance of the insulating layer 3.

[0058] For example, when the thickness of the insulating layer 3 is 0.2 mm, the insulating layer 3 of the present invention can achieve an electrical insulation strength of 150 kV / mm at 20°C, 120 kV / mm at 90°C, and 110 kV / mm at 105°C. In contrast, the existing polyethylene insulating layer (XLPE) can achieve an electrical insulation strength of 130 kV / mm at 20°C, 70 kV / mm at 90°C, and 20 kV / mm at 105°C. This demonstrates that the insulating layer 3 of the present invention with a specific composition has superior electrical insulation performance.

[0059] Furthermore, taking the cable of this invention with a voltage limit of 500kV as an example, the 500kV cable is combined with a straight connector, an insulated connector, a fully sealed plug-in dry GIS long terminal, a fully sealed plug-in dry GIS short terminal, a composite sleeve outdoor terminal, and a porcelain sleeve outdoor terminal to form a cable system. In the thermal cycling voltage test of the type test, the temperature of the conductor is increased from 95°C to 125°C, and the cable undergoes 30 thermal cycles. A voltage of 725kV (2.5U0) is applied to the cable, and the insulation layer does not break down, indicating that the cable has excellent electrical insulation performance.

[0060] A 500kV cable was subjected to a progressive lightning impulse test. The voltage was increased from 1550kV, with each increase being 150kV until the voltage reached 3050kV. The test was repeated 10 times on both positive and negative voltages. The insulation did not break down. Subsequently, the cable was subjected to a withstand voltage of 870kV (3U0) for 30 minutes. The insulation did not break down.

[0061] The insulation layer 3 of the present invention has a melting point of 160°C. In the type test of a 500kV cable with a conductor temperature of 125°C, after completing 30 thermal cycle voltage tests (2.5U0), it was subjected to a lightning impulse of 1800kV, 10 times positive and 10 times negative, without insulation breakdown or flashover. Subsequently, it withstood a withstand voltage of 3U0 for 30 minutes without insulation breakdown and without discharge exceeding the claimed sensitivity.

[0062] Furthermore, since the insulation layer 3 of the present invention has superior insulation properties, the thickness of the insulation layer 3 of the present invention can be thinner than that of the existing polyethylene insulation layer (XLPE) when meeting the same insulation requirements. The thinner thickness helps to reduce the outer diameter of the cable, save installation space, and reduce engineering costs.

[0063] For example, an insulating layer 3 with a thickness of 6-8 mm can be applied to a voltage of 66 kV, an insulating layer 3 with a thickness of 10-12 mm can be applied to a voltage of 110 kV, an insulating layer 3 with a thickness of 16-19 mm can be applied to a voltage of 220 kV, an insulating layer 3 with a thickness of 20-24 mm can be applied to a voltage of 330 kV, an insulating layer 3 with a thickness of 25-28 mm can be applied to a voltage of 500 kV, an insulating layer 3 with a thickness of 29-35 mm can be applied to a voltage of 640 kV, and an insulating layer 3 with a thickness of 36-40 mm can be applied to a voltage of 750 kV.

[0064] It is worth mentioning that, due to the high insulation temperature resistance rating (operating temperature from 90°C to 120°C) of the cable of this invention, its current carrying capacity can be increased by 26%, resulting in excellent transmission capacity. Furthermore, since the insulation layer 3 is primarily made of PP, PP has the advantages of being recyclable, low-carbon, and environmentally friendly.

[0065] In some embodiments of the present invention, the insulating layer 3 further includes, by weight, 2-5 parts of elastomer;

[0066] The elastomer is selected from at least one of BR, SBR, EPR, EVA, EPMD, POE and SEBS.

[0067] In this invention, when the insulation layer 3 also includes an elastomer, the elastomer can improve the toughness of the insulation layer 3, improve the low-temperature resistance of the insulation layer 3, and thus improve the toughness and low-temperature resistance of the cable.

[0068] Furthermore, when the elastomer is selected from EPMD, EVA and SBR, and the mass ratio of EPMD, EVA and SBR is (3-6):(1-3):(1-4), the elastomer has a synergistic effect, which can maximize the improvement of the toughness and low temperature resistance of the insulation layer 3.

[0069] For example, when the mass ratio of EPMD, EVA and SBR in the elastomer is 5:2:3, the low-temperature impact test temperature of the insulation layer 3 can reach -80°C, indicating that the elastomer of the present invention can improve the low-temperature resistance of the insulation layer 3.

[0070] Furthermore, in an environment of -40℃ to -30℃, taking a 500kV cable as an example, the cable was subjected to three bending tests with a bending radius of 20 times the cable outer diameter, followed by partial discharge and voltage tests. At 3U0 (870kV), no discharge exceeding the claimed sensitivity was detected, and at 3U0 (870kV), the insulation did not break down after 60 minutes. This indicates that the cable of the present invention has excellent electrical insulation, mechanical properties, and low-temperature resistance.

[0071] In some embodiments of the present invention, the inner shielding layer 2 and / or the outer shielding layer 4 comprise, by weight:

[0072] 100 parts of polypropylene;

[0073] 2-5 parts carbon black.

[0074] It is understood that the inner shielding layer 2 of the present invention may include the specific components mentioned above, and the outer shielding layer 4 of the present invention may include the specific components mentioned above. Both the inner shielding layer 2 and the outer shielding layer 4 of the present invention may include the specific components mentioned above.

[0075] In this invention, when both the inner shielding layer 2 and / or the outer shielding layer 4 include the aforementioned specific components, the inner shielding layer 2 and / or the outer shielding layer 4 have excellent electrostatic shielding effects, which can improve the overall performance of the cable.

[0076] In some embodiments of the present invention, the inner shielding layer 2 and / or the outer shielding layer 4 further include, by weight:

[0077] Second antioxidant 2-6 parts;

[0078] Copper-resistant agent 2-5 parts.

[0079] It is understood that the inner shielding layer 2 of the present invention may also include the above-mentioned parts by weight of the second antioxidant and the copper inhibitor, and the outer shielding layer 4 of the present invention may also include the above-mentioned parts by weight of the second antioxidant and the copper inhibitor. Both the inner shielding layer 2 and the outer shielding layer 4 of the present invention may include the above-mentioned parts by weight of the second antioxidant and the copper inhibitor.

[0080] In this invention, when the inner shielding layer 2 and / or the outer shielding layer 4 further include the aforementioned amounts of a second antioxidant and a copper inhibitor, the inner shielding layer 2 and / or the outer shielding layer 4 can possess excellent antioxidant properties and mechanical properties.

[0081] Furthermore, the second antioxidant is composed of antioxidant 1010 and antioxidant 330;

[0082] When the copper-resistant agent is copper-resistant agent 1024, the inner shielding layer 2 and / or the outer shielding layer 4 have better antioxidant and mechanical properties, and at the same time improve the heat aging resistance of the insulation layer 3.

[0083] In particular, when the mass ratio of antioxidant 1010, antioxidant 330 and copper inhibitor 1024 in the inner shielding layer 2 and / or outer shielding layer 4 is (1-5):(1-5):(1-4), the inner shielding layer 2 and / or outer shielding layer 4 have superior antioxidant and mechanical properties.

[0084] In a specific embodiment, the mass ratio of antioxidant 1010, antioxidant 330 and copper resistant agent 1024 in the inner shielding layer 2 and / or outer shielding layer 4 is 3:3:2, and the inner shielding layer 2 and / or outer shielding layer 4 have superior oxidation and mechanical properties.

[0085] Understandable, such as Figure 1 As shown, the cable of the present invention may further include a buffer layer 5, a metal sheath 6, and an outer sheath 7; wherein the buffer layer 5 covers the outside of the outer shielding layer 4, the metal sheath 6 covers the outside of the buffer layer 5, and the outer sheath 7 covers the outside of the metal sheath 6. In the present invention, the buffer layer 5, the metal sheath 6, and the outer sheath 7 can all be buffer layers 5, metal sheath 6, and outer sheath 7 commonly used in the art.

[0086] In this invention, the buffer layer 5 can be a common buffer layer 5 in the art. For example, the material of the buffer layer 5 can be a low volume resistivity buffer strip with a volume resistivity of no more than 3 Ω·m and a surface resistivity of no more than 50 Ω. The thickness of the buffer layer 5 can be 1.5-2.5 mm.

[0087] The metal sheath 6 can be at least one of the following: corrugated aluminum sheath, smooth aluminum sheath, corrugated copper sheath, smooth copper sheath, lead sheath, and non-magnetic stainless steel sheath. When the metal sheath 6 is a corrugated aluminum sheath or a smooth aluminum sheath, the thickness of the metal sheath 6 is 1.6-4.5 mm. When the metal sheath 6 is a corrugated copper sheath or a smooth copper sheath, the thickness of the metal sheath 6 is 0.8-2.2 mm. When the metal sheath 6 is a lead sheath, the thickness of the metal sheath 6 is 2.5-5 mm. When the metal sheath 6 is a non-magnetic stainless steel sheath, the thickness of the metal sheath 6 is 0.8-2.2 mm.

[0088] The outer sheath 7 can be made of PE or PVC. PE can be low-smoke halogen-free flame-retardant PE. When the thickness of the outer sheath 7 is 3.5-4mm, it can be used for 66kV voltage; when the thickness of the outer sheath 7 is 4-5.5mm, it can be used for 110kV voltage; when the thickness of the outer sheath 7 is 5.5-6.5mm, it can be used for 220kV voltage; when the thickness of the outer sheath 7 is 6-7mm, it can be used for 330kV voltage; when the thickness of the outer sheath 7 is 7-8mm, it can be used for 500kV voltage; when the thickness of the outer sheath 7 is 7.5-8.5mm, it can be used for 640kV voltage; and when the thickness of the outer sheath 7 is not specified, it can be used for 750kV voltage.

[0089] A second aspect of the present invention provides a method for preparing the above-described cable, comprising the following steps:

[0090] Using a three-layer co-extrusion die head, an inner shielding layer 2, an insulation layer 3, and an outer shielding layer 4 are sequentially wrapped around the conductor 1 to obtain a PP insulated cable core.

[0091] Specifically, conductor 1, inner shielding layer material, insulation layer material (insulation layer material includes 100 parts of polypropylene; 3-5 parts of a first antioxidant, the first antioxidant is composed of antioxidant 1010, antioxidant 168 and antioxidant 330, and the mass ratio of antioxidant 1010, antioxidant 168 and antioxidant 330 is ((3-7):(1-3):(1-4)) and outer shielding layer material are all placed in corresponding positions in an extruder, and the inner shielding layer 2, insulation layer 3 and outer shielding layer 4 are sequentially wrapped around the outside of conductor 1 using a three-layer co-extrusion die head, thereby obtaining the cable of the present invention.

[0092] The cable preparation method of the present invention can produce the above-mentioned cable, and the preparation method is simple and suitable for widespread application.

[0093] In this invention, the melting temperature of the insulating layer 3, which includes the above-mentioned specific components, is 190-210°C, which allows the extrusion temperature of the insulating layer 3 to be 155-255°C, thereby improving the extrusion performance of the insulating layer 3 and thus improving the overall performance (anti-aging performance, mechanical properties, etc.) of the insulating layer 3.

[0094] In this invention, when the inner shielding layer 2 and / or the outer shielding layer 4 include polypropylene, carbon black, a second antioxidant, and a copper inhibitor with a specific composition, the melting temperature of the inner shielding layer and / or the outer shielding layer is 180-210°C, which allows the extrusion temperature of the inner shielding layer 2 and / or the outer shielding layer 4 to be 155-255°C, thereby improving the extrusion performance of the inner shielding layer 2 and / or the outer shielding layer 4, and thus improving the overall performance (anti-aging performance, mechanical properties) of the inner shielding layer 2 and / or the outer shielding layer 4.

[0095] Furthermore, the extrusion temperatures of the insulation layer 3, the inner shielding layer 2, and the outer shielding layer 4 mentioned above can ensure a smooth interface between the insulation layer 3 and the inner shielding layer 2, and a smooth interface between the insulation layer 3 and the outer shielding layer 4, thereby improving the electrical insulation strength of the cable.

[0096] In this invention, when extruding 66kV-110kV conductors, a 330-mesh filter is used for the insulation material and a 110-mesh filter is used for the inner and / or outer shielding material; when extruding 220kV-330kV conductors, a 430-mesh filter is used for the insulation material and a 210-mesh filter is used for the inner and / or outer shielding material; when extruding 500kV-750kV conductors, a 530-mesh filter is used for the insulation material and a 310-mesh filter is used for the inner and / or outer shielding material. This invention improves the extrusion performance of the insulating layer 3, inner shielding layer 2, and outer shielding layer 4 by filtering the insulating layer material, inner shielding layer material, and outer shielding layer material through a filter screen. It also improves the purity of the insulating layer material during extrusion, increases the extrusion pressure, and makes the extruded colloid of inner shielding layer 2 and / or outer shielding layer 4 smooth and well plasticized. This enhances the smoothness of the interface between inner shielding layer 2 and / or outer shielding layer 4 and insulating layer 3, making the protrusion size of the interface <10μm.

[0097] In some embodiments, the insulating material is filtered using a 530-mesh filter. The filtered insulating material is then placed in the extruder head. 150 tons of insulating material can be extruded at a temperature of 155-255°C and can run continuously for 17 days. The extrusion pressure of the insulating layer 3 is uniform and stable (the increase in extrusion pressure does not exceed 5%). 100 tons of XLPE material can be placed in the extruder and run continuously for 10 days. This demonstrates that the insulating material of the present invention has excellent anti-scorching properties in the extruder.

[0098] In some embodiments of the present invention, when the ratio of the screw speed to the linear speed of the extruder is 8-12, the optimal extrusion performance can be achieved, so that the extrusion pressure fluctuation of the insulation layer, the inner shielding layer and the outer shielding layer is within 10 bar.

[0099] In this invention, insulating layer materials, inner shielding layer materials, and outer shielding layer materials of specific compositions are extruded under specific process conditions (extrusion temperature, linear speed, and screw speed). The insulating layer materials, inner shielding materials, and outer shielding materials exhibit good flowability, making it easy to control the eccentricity of the formed insulating layer 3, inner shielding layer 2, and outer shielding layer 4. Furthermore, the adsorption between the inner shielding layer 2 and conductor 1 is strong, the adsorption between the insulating layer 3 and inner shielding layer 2 is strong, and the adsorption between the outer shielding layer 4 and insulating layer 3 is strong. In some embodiments, the maximum extrusion thickness of the insulating layer 3 can be 40 mm, and the eccentricity of the insulating layer 3 can be controlled within 3%.

[0100] In some embodiments of the present invention, the method for manufacturing the cable further includes sequentially subjecting the cable to air cooling and water cooling treatments.

[0101] In this invention, the extruded cable has a certain temperature, and the extruded cable can be subjected to air cooling and water cooling in sequence. The combination of air cooling and water cooling can not only improve cooling efficiency and save cooling costs, but also gradually reduce the temperature of the cable, more evenly eliminate the stress of the insulation layer 3, inner shielding layer 2 and outer shielding layer 4, reduce the partial discharge of the cable, and improve the insulation performance of the cable.

[0102] In some implementations, a nitrogen circulating cooling system can be used for gas cooling. Existing XLPE vertical VCV production lines can be improved by adding a primary nitrogen circulating cooling system between the first vulcanizing pipe and the water vapor balance tank. This system uses a high-pressure circulating fan and a plate heat exchanger to circulate and cool the nitrogen, thereby achieving gas cooling of the cables. The gas-cooled cables can then be water-cooled.

[0103] In this invention, the insulation performance of the cable can be further improved by adjusting the temperature difference between air cooling and water cooling. For example, an extruded 500kV cable is subjected to air cooling and then water cooling sequentially. When the water cooling temperature is 120°C lower than the air cooling temperature, the partial discharge of the cable at 1.5U0 (U0 = 290V) is 30pC, indicating insulation breakdown. When the water cooling temperature is 100°C lower than the air cooling temperature, the partial discharge of the cable at 1.5U0 (U0 = 290V) is 24pC, indicating insulation breakdown. When the water cooling temperature is 70°C lower than the air cooling temperature, the partial discharge of the cable at 1.5U0 (U0 = 290V) is 13pC, indicating discharge but insulation breakdown. When the water cooling temperature is 40°C lower than the air cooling temperature, no discharge exceeding the background level is detected at 1.5U0 (U0 = 290V), indicating no insulation breakdown. Therefore, it can be concluded that when the water cooling temperature is 40°C lower than the air cooling temperature, the cable has superior electrical insulation performance.

[0104] The present invention will be further described below with reference to specific embodiments.

[0105] Example 1

[0106] like Figure 1 As shown, the cable in this embodiment is prepared by a method including the following steps:

[0107] Using a three-layer co-extrusion die head, an inner shielding layer 2, an insulation layer 3, and an outer shielding layer 4 are sequentially wrapped around the conductor 1. A buffer layer 5, a metal sheath 6, and an outer sheath 7 are sequentially wrapped around the outer shielding layer 4 to obtain a cable.

[0108] The insulating layer is divided into seven zones and then extruded after heating. The temperature of the first zone is 168℃, the temperature of the second zone is 178℃, the temperature of the third zone is 185℃, the temperature of the fourth zone is 190℃, the temperature of the fifth zone is 200℃, the temperature of the sixth zone is 200℃, and the temperature of the seventh zone is 200℃ (extrusion temperature). The inner shielding layer and the outer shielding layer are both divided into four zones and then extruded after heating. The temperature of the first zone is 160℃, the temperature of the second zone is 170℃, the temperature of the third zone is 180℃, and the temperature of the fourth zone is 200℃ (extrusion temperature).

[0109] The ratio of the screw speed to the linear velocity of the extruder is 10;

[0110] The cables obtained above were subjected to air cooling and water cooling treatments in sequence. The air cooling treatment was nitrogen cooling treatment at a temperature of 75°C, and the water cooling treatment was at a temperature of 40°C.

[0111] The cable in this embodiment includes: conductor 1, inner shielding layer 2, insulation layer 3, outer shielding layer 4, buffer layer 5, metal sheath 6, and outer sheath 7;

[0112] The inner shielding layer 2 is disposed on the outside of the conductor 1, the insulation layer 3 is disposed on the outside of the inner shielding layer 2, the outer shielding layer 4 is disposed on the outside of the insulation layer 3, the buffer layer 5 is disposed on the outside of the outer shielding layer 4, the metal sheath 6 is disposed on the outside of the buffer layer 5, and the outer sheath 7 is disposed on the outside of the metal sheath 6.

[0113] Conductor 1 is made of copper, and its outer diameter is 60.7 mm.

[0114] The inner shielding layer 2 and the outer shielding layer 4 comprise, by weight, 100 parts of polypropylene and 4 parts of carbon black; the thickness of the inner shielding layer 2 is 2.7 mm and the thickness of the outer shielding layer 4 is 1.6 mm.

[0115] The insulation layer 3 comprises, by weight parts: 100 parts polypropylene; 3 parts first antioxidant; and 5 parts elastomer. The first antioxidant is composed of antioxidant 1010, antioxidant 168, and antioxidant 330, and the mass ratio of antioxidant 1010, antioxidant 168, and antioxidant 330 is 5:2:3. The elastomer is a mixture of EPMD, EVA, and SBR, and the mass ratio of EPMD, EVA, and SBR is 5:2:3.

[0116] The thickness of insulating layer 3 is 28 mm;

[0117] The material of buffer layer 5 is a low volume resistivity buffer strip with a volume resistivity of 3Ω·m and a surface resistivity of 50Ω. The thickness of the buffer layer is 2.3mm.

[0118] Metal sleeve 6 is an aluminum sleeve with a thickness of 3.3mm;

[0119] The outer sheath 7 is made of low-smoke halogen-free flame-retardant PE (ST12), and the thickness of the outer sheath is 8mm.

[0120] Example 2

[0121] The cable preparation method in this embodiment is basically the same as that in Embodiment 1, except that the composition of the insulation layer 3 is different.

[0122] The cable in this embodiment is basically the same as that in embodiment 1, except that the elastomer in the insulation layer 3 is EPMD.

[0123] Example 3

[0124] The cable preparation method in this embodiment is basically the same as that in embodiment 1, except that the composition of the inner shielding layer 2 and the outer shielding layer 4 is different.

[0125] The cable in this embodiment is basically the same as that in embodiment 1, except that...

[0126] The inner shielding layer 2 and the outer shielding layer 4 further include, by weight: 6 parts of a second antioxidant; 2 parts of a copper inhibitor; the second antioxidant is composed of antioxidant 1010 and antioxidant 330; the copper inhibitor is copper inhibitor 1024; the mass ratio of antioxidant 1010, antioxidant 330 and copper inhibitor 1024 is 3:3:2.

[0127] Example 4

[0128] The cable preparation method in this embodiment is basically the same as that in Embodiment 1, except that:

[0129] The ratio of the screw speed to the linear speed of the extruder is 7.

[0130] The cable in this embodiment is prepared by the method described above.

[0131] Example 5

[0132] The cable preparation method in this embodiment is basically the same as that in Embodiment 1, except that it does not include air cooling treatment.

[0133] The cable in this embodiment is prepared by the method described above.

[0134] Comparative Example 1

[0135] The preparation method of the cable in this comparative example is basically the same as that in Example 1, except that the composition of the insulation layer 3 is different.

[0136] The cable in this comparative example is basically the same as that in Example 1, except that the insulation layer 3 includes, by mass parts: 100 parts of polypropylene; 3 parts of the first antioxidant; the first antioxidant is composed of antioxidant 1010, antioxidant 168 and antioxidant BHT, and the mass ratio of antioxidant 1010, antioxidant 168 and antioxidant BHT is 1:4:2.

[0137] Comparative Example 2

[0138] The preparation method of the cable in this comparative example is basically the same as that in Example 1, except that the composition of the insulation layer 3 is different.

[0139] The cable in this comparative example is basically the same as that in Example 1, except that the insulation layer 3 includes, by weight, 100 parts of polypropylene and 3 parts of antioxidant 1010.

[0140] Performance testing

[0141] The cables in the examples and comparative examples were subjected to performance tests, and the test results are shown in Table 1.

[0142] 1. Electrical insulation performance

[0143] Referring to GB / T 1408.1-2016 "Test Methods for Electrical Strength of Insulating Materials - Part 1: Tests at Power Frequency", the insulation layer in the cable is cut into 0.2mm samples.

[0144] 2. Mechanical properties

[0145] Refer to GB / T 2951.11-2008 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Fibers - Part 11: General Test Methods - Measurement of Thickness and Dimensions - Mechanical Properties Tests".

[0146] 3. Low temperature shock

[0147] Refer to GB / T 5470 "Determination of embrittlement temperature of plastics by impact method".

[0148] Table 1

[0149]

[0150] As can be seen from Example 1 and Comparative Examples 1-2 in Table 1, including antioxidants with specific compositions in the insulation layer can improve the mechanical properties and electrical insulation properties of the cable.

[0151] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cable, characterized in that, It includes at least a conductor, an inner shielding layer, an insulating layer, and an outer shielding layer; The inner shielding layer is disposed on the outside of the conductor, the insulating layer is disposed on the outside of the inner shielding layer, and the outer shielding layer is disposed on the outside of the insulating layer; The insulating layer comprises, by weight, the following components: 100 parts of polypropylene; 3-5 parts of the first antioxidant; The first antioxidant is composed of antioxidant 1010, antioxidant 168 and antioxidant 330, and the mass ratio of antioxidant 1010, antioxidant 168 and antioxidant 330 is (3-7):(1-3):(1-4). The inner shielding layer and / or the outer shielding layer comprise, by weight: 100 parts polypropylene; 2-5 parts carbon black; 2-6 parts secondary antioxidant; 2-5 parts copper inhibitor; The second antioxidant consists of antioxidant 1010 and antioxidant 330; The copper-resistant agent is copper-resistant agent 1024; in the inner shielding layer and / or the outer shielding layer, the mass ratio of antioxidant 1010, antioxidant 330 and copper-resistant agent 1024 is (1-5):(1-5):(1-4).

2. The cable according to claim 1, characterized in that, The insulating layer further includes, by weight, 2-5 parts of elastomer; The elastomer is selected from at least one of BR, SBR, EPR, EVA, EPMD, POE, and SEBS.

3. The cable according to claim 2, characterized in that, The elastomer is selected from EPMD, EVA and SBR, and the mass ratio of EPMD, EVA and SBR is (3-6):(1-3):(1-4).

4. A method for preparing a cable according to any one of claims 1-3, characterized in that, Includes the following steps: The cable is obtained by sequentially wrapping an inner shielding layer, an insulation layer, and an outer shielding layer around the conductor using a three-layer co-extrusion die head.

5. The preparation method according to claim 4, characterized in that, The extrusion temperature of the insulating layer is 155-255℃; and / or, The extrusion temperature of the inner shielding layer and / or the outer shielding layer is 155-255℃; and / or, The ratio of screw speed to linear speed of the extruder is 8-12.

6. The preparation method according to claim 4 or 5, characterized in that, The cable was subjected to air cooling and water cooling treatment in sequence.

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