Environment-friendly polypropylene insulating flame-retardant medium-voltage cable

Abstract

The utility model relates to the technical field of cables, and particularly discloses an environment-friendly polypropylene insulating flame-retardant medium-voltage cable, which comprises a cable core and a protective structure layer arranged outside the cable core. The cable core is provided with three power insulation wire cores and three tensile wire cores which are twisted together, and a flame-retardant filling rope which is filled in a twisting gap of the three power insulation wire cores and the three tensile wire cores, and each tensile wire core is arranged at a twisting outer side gap of two adjacent power insulation wire cores; each power insulation wire core is composed of a conductor, and a conductor shielding layer, a polypropylene insulation layer, an insulation shielding layer, a shielding isolation layer, a metal shielding composite layer and a conductor core fireproof layer which are sequentially arranged outside the conductor from inside to outside. According to the utility model, the medium-voltage cable formed based on the polypropylene insulating material effectively gives consideration to good tensile property and bending resistance, so that the convenience, flexibility and stability of the medium-voltage cable during use in a working condition environment are improved.

Description

Technical Field

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

[0002] Medium-voltage cables typically refer to power cables of 35kV and below. They are mainly used in practical applications in fields such as petrochemicals, transportation, wastewater treatment, and food processing, and are an important component of power transmission and distribution networks. Medium-voltage cables have high technical requirements for electrical performance, heat resistance, and flame retardancy.

[0003] Polypropylene (PP) is a lightweight, non-toxic, odorless, tasteless, and easily environmentally friendly milky-white highly crystalline polymer. It possesses not only excellent electrical properties but also good heat resistance (allowing the long-term operating temperature of cables to be increased from 90℃ to 105℃), making it highly suitable for the insulation structure molding of medium-voltage cables. Compared to the cross-linked polyethylene (XLPE) insulation material traditionally used in medium-voltage cables, it offers advantages in terms of light weight, environmental friendliness, and heat resistance. Therefore, the development of medium-voltage cables with polypropylene insulation has a promising market prospect. Based on this, the applicant previously disclosed a medium-voltage cable based on polypropylene insulation material, as detailed in the Chinese patent document entitled "An Environmentally Friendly Polypropylene Insulated Flame-Retardant and Fire-Resistant Medium-Voltage Cable," publication number CN 118609888 A, published on September 6, 2024.

[0004] However, the applicant discovered in the research that polypropylene insulation material has technical problems such as high hardness, high crystallinity and low flexibility during use. This results in poor performance of the molded medium-voltage cable in terms of tensile strength and bending resistance, which limits the convenience, flexibility and stability of the medium-voltage cable in the working environment and needs to be improved. Utility Model Content

[0005] The technical objective of this utility model is to provide an environmentally friendly polypropylene insulated flame-retardant medium-voltage cable with excellent tensile and bending resistance, based on polypropylene insulation material, addressing the special characteristics of the aforementioned medium-voltage cable and the shortcomings of existing technologies.

[0006] The technical objective of this utility model is achieved through the following technical solution: an environmentally friendly polypropylene insulated flame-retardant medium-voltage cable, comprising a cable core and a protective structural layer arranged outside the cable core.

[0007] The cable core has three power-insulated wire cores and three tensile wire cores twisted together, and flame-retardant filler rope filling the gap between the three power-insulated wire cores and the three tensile wire cores. Each tensile wire core is arranged at the outer gap of the twisting of two adjacent power-insulated wire cores.

[0008] The power insulated conductor core consists of a conductor and, from the inside out, a conductor shielding layer, a polypropylene insulation layer, an insulation shielding layer, a shielding isolation layer, a metal shielding composite layer, and a conductor core fireproof layer.

[0009] Furthermore, the conductor of the power insulated wire core is composed of multiple concentrically arranged round conductors, multiple concentrically arranged sector-shaped conductors surrounding the outermost round conductor, and conductor wrapping layers surrounding each sector-shaped conductor.

[0010] The concentrically arranged circular conductors and the sector-shaped conductors have a twisted structure;

[0011] The conductor wrapping layer is an overlapping wrapping structure of semiconducting strips on the outside of the sector-shaped conductor.

[0012] Furthermore, the power insulated wire core has a three-layer co-extruded structure consisting of a conductor shielding layer, a polypropylene insulation layer, and an insulation shielding layer.

[0013] Furthermore, the shielding layer of the power insulated conductor is an overlapping wrapping structure of semi-conductive tape outside the insulating shielding layer.

[0014] Furthermore, the metal shielding composite layer of the power insulated wire core is a composite structure of an inner copper wire loose winding layer and an outer copper strip wrapping layer.

[0015] Furthermore, the copper strip wrapping direction of the copper strip cladding layer is opposite to the copper wire unwound direction of the copper wire unwound layer.

[0016] Furthermore, the fireproof layer of the conductor core of the power insulated wire core is an extruded structure of ceramicized silicone rubber outside the metal shielding composite layer.

[0017] Furthermore, the tensile core is composed of a tensile core and a tensile core fireproof layer covering the outside of the tensile core;

[0018] The tensile core is a stranded structure of multiple aramid fiber strands;

[0019] The fireproof layer of the tensile core is an extruded structure of ceramicized silicone rubber on the outside of the tensile core.

[0020] Furthermore, the protective structure layer outside the cable core consists of a flame-retardant wrapping layer, an oxygen barrier layer, an inner sheath layer, a metal armor layer, and an outer sheath layer arranged sequentially from the inside out outside the cable core.

[0021] Furthermore, the flame-retardant wrapping layer is an overlapping wrapping structure of ceramicized silicone rubber mica composite tape outside the cable core;

[0022] The inner sheath layer is an extruded structure of low-smoke halogen-free flame-retardant polyolefin material outside the oxygen barrier layer.

[0023] The outer sheath layer is an extruded structure of low-smoke halogen-free flame-retardant polyolefin material outside the metal armor layer.

[0024] Furthermore, the metal armor layer is a double-layer loosely wound armor structure with metal strips on the outside of the inner sheath layer;

[0025] Alternatively, the metal armor layer may be a tightly wound armor structure consisting of multiple strands of metal wires outside the inner sheath layer.

[0026] The beneficial technical effects of this utility model are as follows: The above-mentioned technical measures are designed for the special characteristics of the medium-voltage cable. The insulation structure of the power insulated core is formed by using lightweight, environmentally friendly, and heat-resistant polypropylene insulation material. At the same time, in the cable core structure composed of the power insulated core, three tensile cores are arranged in a basically uniform manner between the stranding gaps of the three power insulated cores. On the one hand, the three tensile cores jointly bear the axial tensile task of the formed cable. On the other hand, the three circumferentially distributed tensile cores bear the traction force of the formed cable when bending and twisting according to their corresponding distribution positions. The tensile core with aramid fiber strand structure is particularly good because aramid fiber strand has the technical characteristics of high tensile strength and low elongation at break. While meeting the axial tensile performance, it is combined with three tensile cores distributed in different positions around the circumference to effectively bear the traction force when the cable is bent and twisted. This reliably makes up for the technical problem of poor tensile strength and bending resistance of the power insulation core formed by polypropylene insulation structure. As a result, the medium voltage cable formed by polypropylene insulation material can effectively take into account good tensile strength and bending resistance, so as to improve the convenience, flexibility and stability of this type of medium voltage cable when used in working environment.

[0027] Furthermore, in the above-mentioned technical measures, the tensile core is composed of a stranded structure of aramid fiber strands and an extruded structure of ceramicized silicone rubber. While meeting the above-mentioned tensile and bending resistance properties in medium-voltage cables, it is also suitable for the technical requirements of medium-voltage cables for heat resistance and flame retardancy, thereby forming a heat-resistant and flame-retardant structure to reliably improve the heat resistance and flame retardancy of the formed medium-voltage cable.

[0028] The conductor of the power insulated core is formed by concentrically arranged round conductors and sector conductors wrapped with a semi-conductive tape. This structure can effectively reduce the skin effect of medium-voltage cables during use and reliably improve the current carrying capacity of medium-voltage cables. At the same time, the semi-conductive tape wrapping structure can effectively prevent the three-layer co-extruded conductor shielding material and polypropylene insulation material from being embedded in the stranded structure of the conductor, so as to ensure that the aforementioned electrical performance of the conductor is not interfered with. Attached Figure Description

[0029] Figure 1This is a schematic diagram of one structure of the present utility model.

[0030] Figure 2 for Figure 1 A schematic diagram of the structure of the power insulated wire core.

[0031] Figure 3 for Figure 2 A schematic diagram of the conductor structure in the image.

[0032] Figure 4 for Figure 1 A schematic diagram of the tensile core structure.

[0033] The symbols in the diagram have the following meanings: 1—Power insulated core; 11—Conductor; 111—Round conductor; 112—Sector-shaped conductor; 113—Conductor wrapping layer; 12—Conductor shielding layer; 13—Polypropylene insulation layer; 14—Insulation shielding layer; 15—Shielding isolation layer; 16—Metallic shielding composite layer; 161—Copper wire loose winding layer; 162—Copper tape wrapping layer; 17—Conductor core fireproof layer; 2—Tension-resistant core; 21—Tension-resistant core; 22—Tension-resistant core fireproof layer; 3—Flame-retardant filler rope; 4—Flame-retardant wrapping layer; 5—Oxygen barrier layer; 6—Inner sheath layer; 7—Metallic armor layer; 8—Outer sheath layer. Detailed Implementation

[0034] This utility model relates to the field of cable technology, specifically an environmentally friendly polypropylene insulated flame-retardant medium-voltage cable. The main technical solution of this utility model will be described in detail below with reference to several embodiments. Embodiment 1 is illustrated in conjunction with the accompanying drawings. Figure 1 , Figure 2 , Figure 3 and Figure 4 The technical solution of this utility model is clearly and thoroughly explained; although other embodiments are not shown in separate drawings, their main structures can still be referred to the drawings of Embodiment 1.

[0035] It should be noted that the accompanying drawings of this utility model are schematic, and unnecessary details have been simplified to clarify the technical purpose of this utility model, so as to avoid obscuring the technical solution contributed by this utility model to the prior art. In addition, the expressions such as "about" and "basically" regarding quantity or fit relationship in the following text mean that reasonable assembly errors and processing errors are allowed in the industry, and do not literally describe absolute quantity or fit relationship.

[0036] Example 1

[0037] See Figure 1 As shown, the medium-voltage cable of this utility model includes a cable core and, from the inside out, a flame-retardant wrapping layer 4, an oxygen barrier layer 5, an inner sheath layer 6, a metal armor layer 7, and an outer sheath layer 8 arranged sequentially outside the cable core.

[0038] The cable core consists of three power-insulated cores 1 and three tensile cores 2 twisted together, and a flame-retardant filler rope 3 filling the gaps between the three power-insulated cores 1 and the three tensile cores 2. The twisting pitch ratio is approximately 30. Each tensile core 2 is arranged at the outer gap of the twisting of two adjacent power-insulated cores 1. Thus, in the use of the formed medium-voltage cable, the three tensile cores 2 jointly bear the axial tensile load—that is, form axial tensile resistance, while the three circumferentially distributed tensile cores 2 bear the traction force of the formed cable when bent and twisted according to their corresponding distribution positions—that is, form bending resistance.

[0039] See Figure 2 and Figure 3 As shown, the aforementioned power insulated core 1 is composed of a conductor 11 and, arranged sequentially from the inside out, a conductor shielding layer 12, a polypropylene insulation layer 13, an insulation shielding layer 14, a shielding isolation layer 15, a metal shielding composite layer 16, and a conductor core fireproof layer 17, forming a power insulated core based on polypropylene insulation material. Compared with traditional cross-linked polyethylene insulation material, this results in a lightweight, environmentally friendly, and heat-resistant power insulated core.

[0040] Among them, such as Figure 3 As shown, the conductor 11 of the power insulated core 1 consists of multiple concentrically arranged round conductors 111 (copper), multiple concentrically arranged sector-shaped conductors 112 (copper) surrounding the outermost round conductor 111, and conductor wrapping layers 113 surrounding each sector-shaped conductor 112. The concentrically arranged round conductors 111 and sector-shaped conductors 112 are stranded. The conductor wrapping layer 113 is a single-layer overlapping wrapping structure with a semi-conductive strip outside the sector-shaped conductors 112, with an overlap rate of approximately 30%. The conductor wrapping layer 113 tightly binds the stranded round conductors 111 and sector-shaped conductors 112. This conductor 11 structure not only effectively reduces the skin effect of the formed medium-voltage cable and reliably increases the current carrying capacity of the medium-voltage cable, but also effectively prevents the point discharge phenomenon caused by the conductor shielding material and insulation material being embedded in the stranding gap of the metal conductor, resulting in excellent electrical performance.

[0041] See Figure 4 As shown, the tensile core 2 consists of a tensile core 21 and a tensile core fireproof layer 22 covering the outside of the tensile core 21. The tensile core 21 is a stranded structure of multiple aramid fiber strands with high tensile strength and low elongation at break. The tensile core fireproof layer 22 is an extruded structure of heat-resistant and flame-retardant ceramicized silicone rubber on the outside of the tensile core 21. This structure of the tensile core 2 meets the technical requirements for tensile performance in the formed medium-voltage cable, and is also heat-resistant and flame-retardant, effectively adapting to the technical performance requirements of medium-voltage cables for heat resistance and flame retardancy.

[0042] In the above-mentioned molding structure of the power insulated conductor 1, the conductor shielding layer 12, the polypropylene insulation layer 13 and the insulation shielding layer 14 are semi-conductive and adopt a three-layer co-extrusion structure with polypropylene insulation material interspersed. This not only meets the insulation performance requirements, but also effectively balances the electric field of the conductor 11.

[0043] In the above-mentioned molding structure of the power insulated conductor 1, the shielding isolation layer 15 is a single-layer overlapping wrapping structure of a semi-conductive strip outside the insulating shielding layer 14, with an overlap wrapping rate of about 30%. While balancing the electric field of the conductor 11, it reliably separates the metal shielding composite layer and the insulating shielding layer 14, avoiding damage to the insulating shielding layer 14 and the internal polypropylene insulating layer 13 caused by the metal shielding composite layer 16.

[0044] In the above-mentioned molding structure of the power insulated conductor 1, the metal shielding composite layer 16 is a composite structure of an inner copper wire loose winding layer 161 and an outer copper strip wrapping layer 162. The copper strip wrapping layer 162 is a single-layer overlapping wrapping structure of copper strip, with an overlap rate of approximately 30%. Moreover, the copper strip wrapping direction of the copper strip wrapping layer 162 is opposite to the copper wire loose winding direction of the copper wire loose winding layer 161, so that the molding structure of the metal shielding composite layer 16 is compact, stable, and not easily loosened, ensuring that its electromagnetic shielding performance is maintained for a long time.

[0045] In the above-mentioned molding structure of the power insulated core 1, the conductor core fireproof layer 17 is an extrusion structure of ceramicized silicone rubber on the outside of the metal shielding composite layer 16, so that the molded power insulated core 1 can obtain heat resistance and flame retardant properties, effectively meeting the technical performance requirements of medium voltage cables for heat resistance and flame retardant properties.

[0046] In the above-mentioned medium-voltage cable forming structure, the flame-retardant wrapping layer 4 is a single-layer overlapping wrapping structure of ceramicized silicone rubber mica composite tape outside the cable core, with an overlap wrapping rate of about 30%. On the one hand, it tightens and rounds the forming structure of the cable core, and on the other hand, it enables the cable core to obtain heat resistance and flame retardant properties, effectively meeting the technical performance requirements of medium-voltage cables for heat resistance and flame retardancy.

[0047] In the above-mentioned medium-voltage cable molding structure, the oxygen barrier layer 5 is an extrusion structure of fluoroplastic outside the flame-retardant wrapping layer 4.

[0048] In the above-mentioned medium-voltage cable molding structure, the inner sheath layer 6 is an extrusion structure of low-smoke halogen-free flame-retardant polyolefin material outside the oxygen barrier layer 5.

[0049] In the above-mentioned medium-voltage cable forming structure, the metal armor layer 7 is a double-layer loosely wound armor structure with metal strips outside the inner sheath layer 6, which can obtain a certain degree of flexibility while obtaining impact resistance structural strength.

[0050] In the above-mentioned medium-voltage cable molding structure, the outer sheath layer 8 is an extrusion structure of low-smoke halogen-free flame-retardant polyolefin material outside the metal armor layer 7.

[0051] The above-mentioned medium-voltage cable is prepared according to the following process steps:

[0052] Step 1. Preparation of power-insulated wire cores; obtain three power-insulated wire cores;

[0053] Preparation of tensile cores; three tensile cores were obtained;

[0054] Step 2. On a 3150 reel cable forming machine, three power insulated wire cores and three tensile wire cores are stranded together with flame-retardant filler rope of parallel strand structure according to the phase-to-phase distribution method described above, and the stranded structure is twisted together according to the designed pitch ratio to obtain a stranded cable core.

[0055] Step 3. Wrap a ceramicized silicone rubber mica composite tape around the outside of the cable core according to the designed overlap ratio to obtain a flame-retardant wrapping layer;

[0056] Step 4. Extrude fluoroplastic to the outside of the flame-retardant wrapping layer to the designed thickness to obtain an oxygen barrier layer;

[0057] Step 5. On the outside of the oxygen barrier layer, extrude an inner sheath layer of low-smoke halogen-free flame-retardant polyolefin material according to the designed extrusion thickness;

[0058] Step 6. On the outside of the inner sheath layer, according to the designed loose winding pitch, a double-layer loosely wound metal strip structure metal armor layer is sequentially applied;

[0059] Step 7. Extrude an outer sheath of low-smoke halogen-free flame-retardant polyolefin material to the outside of the metal armor layer according to the designed extrusion thickness;

[0060] Obtain flame-retardant medium-voltage cables.

[0061] In step 1 above, the preparation of the power-insulated wire core includes the following process steps:

[0062] Step ①. Using a double-head continuous annealing wire drawing machine, the φ8mm copper rod is stretched and shaped into a round wire of the required specifications through 7 passes of dies, resulting in multiple round conductors;

[0063] Using a double-head continuous annealing wire drawing machine, through 7 passes of dies, the φ8mm copper rod is stretched and shaped into a fan-shaped wire of the required specifications to obtain multiple fan-shaped conductors;

[0064] Step ②. Arrange the multiple circular wires of the conductor into concentric circles;

[0065] Multiple fan-shaped conductors with a fan-shaped wire structure are distributed on the outer periphery of the circular conductors distributed in the concentric circle structure;

[0066] The conductor is stranded into strands using a frame-type stranding machine, and a semiconducting strip is wrapped around the outside of the stranded metal conductor to obtain a conductor wrapping layer.

[0067] Step ③. The semiconductive conductor shielding material, polypropylene insulation material, and semiconductive insulating shielding material are sequentially extruded over the conductor in step ② using a three-layer co-extrusion method to obtain a three-layer co-extruded structure of conductor shielding layer, polypropylene insulation layer, and insulating shielding layer.

[0068] Meanwhile, the core wire of the aforementioned output head is cooled in stages and gradually by nitrogen pressurization (nitrogen pressure is 1.0MPa) + water cooling; the nitrogen pressurization cooling area is divided into 8 sections, the water vapor transition area is divided into 2 sections, and the water cooling area is divided into 12 sections.

[0069] The temperature distribution of each section of the nitrogen pressurization and cooling zone is shown in Table 1 below:

[0070]

[0071] Step 4. Wrap the semiconducting tape around the outside of the insulating shielding layer according to the designed overlap rate to obtain the shielding isolation layer;

[0072] Step 5. Loosely wind the copper wires around the outside of the shielding layer according to the designed pitch to obtain a loosely wound copper wire layer;

[0073] Step 6. Wrap the copper strip around the outside of the loosely wound copper wire layer according to the designed overlap rate and wrapping direction to obtain the copper strip wrapping layer;

[0074] Step 7. On a 120 extruder, ceramicized silicone rubber is extruded onto the outside of the copper strip wrapping layer according to the designed thickness to obtain the conductor core fireproof layer;

[0075] A heat-resistant, flame-retardant, power-insulated wire core with polypropylene insulation structure was obtained.

[0076] In step 1 above, the preparation of the tensile core includes the following process steps:

[0077] Step ①. Twist the aramid yarn into strands to obtain multiple aramid strands;

[0078] Step 2. Twist the multiple aramid strands together in a concentric circle arrangement;

[0079] Step ③. Extrude ceramicized silicone rubber onto the outside of the aramid strand stranded structure from step ② to obtain a tensile core.

[0080] The above-mentioned segmented cooling method of nitrogen pressurization + water cooling for power insulation cores, as shown by comparative tests (the only difference in the comparative tests is the change in cooling method, and everything else is the same), can effectively prevent the phenomenon of internal stress accumulation and plastic delamination caused by rapid cooling of the power insulation cores, and at the same time effectively reduce the adverse effects of gravity on the eccentricity of cable insulation.

[0081] Comparative Example 1 directly used water cooling, and the distribution of the cooling zones in each section is shown in Table 2 below:

[0082]

[0083] Comparative Example 2 used an unsegmented nitrogen pressurization (nitrogen pressure 1.0 MPa) + water cooling method; the temperature distribution of each segment of the nitrogen pressurization and cooling zone is shown in Table 3 below:

[0084]

[0085] Comparative Example 3 employed nitrogen pressurization (nitrogen pressure 1.0 MPa) + water cooling under different temperature conditions; the temperature distribution of each section of the nitrogen pressurization and cooling zone is shown in Table 4 below:

[0086]

[0087] The cooling method and temperature conditions of this utility model, along with the structure and performance parameters of the power-insulated wire core obtained from the three comparative examples mentioned above, are shown in Table 5 below:

[0088]

[0089] As can be clearly seen from Table 5, this utility model adopts a segmented nitrogen pressurization cooling + water cooling method under specific temperature conditions. On the one hand, the specific nitrogen pressurization can increase the pressure on the surface of the power insulated wire core, making the bonding between the insulation shielding layer, polypropylene insulation layer and conductor shielding layer tighter and preventing delamination. On the other hand, nitrogen is an inert gas, which plays a good protective role for the power insulated wire core.

[0090] Example 2

[0091] The medium-voltage cable of this utility model includes a cable core and, from the inside out, a flame-retardant wrapping layer, an oxygen barrier layer, an inner sheath layer, a metal armor layer, and an outer sheath layer arranged sequentially outside the cable core.

[0092] The cable core consists of three power-insulated cores and three tensile cores twisted together, along with flame-retardant filler rope filling the gaps between the three power-insulated cores and the three tensile cores. The twisting pitch ratio is approximately 25. Each tensile core is positioned at the outer gap of the twisted sections of two adjacent power-insulated cores. Thus, in the use of the formed medium-voltage cable, the three tensile cores jointly bear the axial tensile load—that is, they form axial tensile resistance—while the three circumferentially distributed tensile cores, according to their corresponding positions, bear the traction force of the formed cable during bending and torsion—that is, they form bending resistance.

[0093] The aforementioned power insulated wire core consists of a conductor and, from the inside out, a conductor shielding layer, a polypropylene insulation layer, an insulation shielding layer, a shielding isolation layer, a metal shielding composite layer, and a conductor core fireproof layer, forming a power insulated wire core based on polypropylene insulation material. Compared to traditional cross-linked polyethylene insulation material, this results in a lightweight, environmentally friendly, and heat-resistant power insulated wire core.

[0094] The conductor of the power insulated core consists of multiple concentrically arranged round conductors (copper), multiple concentrically arranged sector-shaped conductors (copper) surrounding the outermost round conductor, and conductor wrapping layers surrounding each sector conductor. The concentrically arranged round conductors and sector conductors are stranded. The conductor wrapping layer is a single-layer overlapping structure with a semi-conductive strip wrapped around the sector conductors, with an overlap rate of approximately 45%. The conductor wrapping layer tightly binds the stranded round and sector conductors. This conductor structure not only effectively reduces the skin effect of the formed medium-voltage cable and reliably increases the current carrying capacity of the medium-voltage cable, but also effectively prevents tip discharge caused by the conductor shielding and insulation materials embedding in the stranding gaps of the metal conductors, resulting in excellent electrical performance.

[0095] The tensile core consists of a tensile core and a fire-resistant layer covering the outside of the tensile core. The tensile core is a stranded structure of multiple aramid fiber strands with high tensile strength and low elongation at break. The fire-resistant layer is an extruded structure of heat-resistant and flame-retardant ceramicized silicone rubber on the outside of the tensile core. This tensile core structure meets the technical requirements for tensile strength in the formed medium-voltage cable, and is also heat-resistant and flame-retardant, effectively adapting to the technical performance requirements of medium-voltage cables for heat resistance and flame retardancy.

[0096] In the above-mentioned molding structure of the power insulated conductor, the conductor shielding layer, the polypropylene insulation layer and the insulation shielding layer are semi-conductive and adopt a three-layer co-extrusion structure with polypropylene insulation material interspersed. This structure not only meets the insulation performance requirements, but also effectively balances the electric field of the conductor.

[0097] In the above-mentioned forming structure of the power insulated conductor, the shielding isolation layer is a single-layer overlapping wrapping structure of semi-conductive strip outside the insulating shielding layer, with an overlap wrapping rate of about 45%. While balancing the conductor electric field, it reliably separates the metal shielding composite layer from the insulating shielding layer, avoiding damage to the insulating shielding layer and the internal polypropylene insulation layer caused by the metal shielding composite layer.

[0098] In the above-mentioned forming structure of the power insulated wire core, the metal shielding composite layer is a composite structure of an inner copper wire loose winding layer and an outer copper strip wrapping layer. The copper strip wrapping layer is a single-layer overlapping wrapping structure of copper strip with an overlap rate of about 45%. Moreover, the copper strip wrapping direction of the copper strip wrapping layer is opposite to the copper wire loose winding direction of the copper wire loose winding layer, so as to make the forming structure of the metal shielding composite layer compact, stable and not easy to loosen, ensuring that its electromagnetic shielding performance is maintained for a long time.

[0099] In the above-mentioned molding structure of the power insulated conductor core, the fireproof layer of the conductor core is an extrusion structure of ceramicized silicone rubber outside the metal shielding composite layer, so that the molded power insulated conductor core has heat resistance and flame retardant properties, effectively meeting the technical performance requirements of medium voltage cables for heat resistance and flame retardancy.

[0100] In the above-mentioned medium-voltage cable forming structure, the flame-retardant wrapping layer is a single-layer overlapping wrapping structure of ceramicized silicone rubber mica composite tape outside the cable core, with an overlap wrapping rate of about 45%. On the one hand, it tightens and rounds the forming structure of the cable core, and on the other hand, it enables the cable core to obtain heat resistance and flame retardant properties, effectively meeting the technical performance requirements of medium-voltage cables for heat resistance and flame retardancy.

[0101] In the above-mentioned medium-voltage cable molding structure, the oxygen barrier layer is an extrusion structure of fluoroplastic outside the flame-retardant wrapping layer.

[0102] In the above-mentioned medium-voltage cable molding structure, the inner sheath layer is an extrusion structure of low-smoke halogen-free flame-retardant polyolefin material outside the oxygen barrier layer.

[0103] In the above-mentioned medium-voltage cable molding structure, the metal armor layer is a tightly wound armor structure with multiple strands of metal wires outside the inner sheath layer. While obtaining impact resistance structural strength, it can also obtain a certain degree of flexibility.

[0104] In the above-mentioned medium-voltage cable molding structure, the outer sheath layer is an extrusion structure of low-smoke halogen-free flame-retardant polyolefin material outside the metal armor layer.

[0105] Example 3

[0106] The medium-voltage cable of this utility model includes a cable core and, from the inside out, a flame-retardant wrapping layer, an oxygen barrier layer, an inner sheath layer, a metal armor layer, and an outer sheath layer arranged sequentially outside the cable core.

[0107] The cable core consists of three power-insulated cores and three tensile cores twisted together, along with flame-retardant filler rope filling the gaps between the three power-insulated cores and the three tensile cores. The twisting pitch ratio is approximately 35. Each tensile core is positioned at the outer gap of the twisted sections of two adjacent power-insulated cores. Thus, in the use of the formed medium-voltage cable, the three tensile cores jointly bear the axial tensile load—that is, they form axial tensile resistance—while the three circumferentially distributed tensile cores, according to their corresponding positions, bear the traction force of the formed cable during bending and torsion—that is, they form bending resistance.

[0108] The aforementioned power insulated wire core consists of a conductor and, from the inside out, a conductor shielding layer, a polypropylene insulation layer, an insulation shielding layer, a shielding isolation layer, a metal shielding composite layer, and a conductor core fireproof layer, forming a power insulated wire core based on polypropylene insulation material. Compared to traditional cross-linked polyethylene insulation material, this results in a lightweight, environmentally friendly, and heat-resistant power insulated wire core.

[0109] The conductor of the power insulated core consists of multiple concentrically arranged round conductors (copper), multiple concentrically arranged sector-shaped conductors (copper) surrounding the outermost round conductor, and conductor wrapping layers surrounding each sector conductor. The concentrically arranged round conductors and sector conductors are stranded. The conductor wrapping layer is a single-layer overlapping structure with a semi-conductive strip wrapped around the sector conductors, with an overlap rate of approximately 50%. The conductor wrapping layer tightly binds the stranded round and sector conductors. This conductor structure not only effectively reduces the skin effect of the formed medium-voltage cable and reliably increases the current carrying capacity of the medium-voltage cable, but also effectively prevents point discharge caused by the conductor shielding material and insulation material embedding in the stranding gaps of the metal conductors, resulting in excellent electrical performance.

[0110] The tensile core consists of a tensile core and a fire-resistant layer covering the outside of the tensile core. The tensile core is a stranded structure of multiple aramid fiber strands with high tensile strength and low elongation at break. The fire-resistant layer is an extruded structure of heat-resistant and flame-retardant ceramicized silicone rubber on the outside of the tensile core. This tensile core structure meets the technical requirements for tensile strength in the formed medium-voltage cable, and is also heat-resistant and flame-retardant, effectively adapting to the technical performance requirements of medium-voltage cables for heat resistance and flame retardancy.

[0111] In the above-mentioned molding structure of the power insulated conductor, the conductor shielding layer, the polypropylene insulation layer and the insulation shielding layer are semi-conductive and adopt a three-layer co-extrusion structure with polypropylene insulation material interspersed. This structure not only meets the insulation performance requirements, but also effectively balances the electric field of the conductor.

[0112] In the above-mentioned forming structure of the power insulated conductor, the shielding isolation layer is a single-layer overlapping wrapping structure of semi-conductive strip outside the insulating shielding layer, with an overlap wrapping rate of about 50%. While balancing the conductor electric field, it reliably separates the metal shielding composite layer from the insulating shielding layer, avoiding damage to the insulating shielding layer and the internal polypropylene insulating layer caused by the metal shielding composite layer.

[0113] In the above-mentioned forming structure of the power insulated wire core, the metal shielding composite layer is a composite structure of an inner copper wire loose winding layer and an outer copper strip wrapping layer. The copper strip wrapping layer is a single-layer overlapping wrapping structure of copper strip with an overlap rate of about 50%. Moreover, the copper strip wrapping direction of the copper strip wrapping layer is opposite to the copper wire loose winding direction of the copper wire loose winding layer, so as to make the forming structure of the metal shielding composite layer compact, stable and not easy to loosen, ensuring that its electromagnetic shielding performance is maintained for a long time.

[0114] In the above-mentioned molding structure of the power insulated conductor core, the fireproof layer of the conductor core is an extrusion structure of ceramicized silicone rubber outside the metal shielding composite layer, so that the molded power insulated conductor core has heat resistance and flame retardant properties, effectively meeting the technical performance requirements of medium voltage cables for heat resistance and flame retardancy.

[0115] In the above-mentioned medium-voltage cable forming structure, the flame-retardant wrapping layer is a single-layer overlapping wrapping structure of ceramicized silicone rubber mica composite tape outside the cable core, with an overlap wrapping rate of about 50%. On the one hand, it tightens and rounds the forming structure of the cable core, and on the other hand, it enables the cable core to obtain heat resistance and flame retardant properties, effectively meeting the technical performance requirements of medium-voltage cables for heat resistance and flame retardancy.

[0116] In the above-mentioned medium-voltage cable molding structure, the oxygen barrier layer is an extrusion structure of fluoroplastic outside the flame-retardant wrapping layer.

[0117] In the above-mentioned medium-voltage cable molding structure, the inner sheath layer is an extrusion structure of low-smoke halogen-free flame-retardant polyolefin material outside the oxygen barrier layer.

[0118] In the above-mentioned medium-voltage cable forming structure, the metal armor layer is a double-layer loosely wound armor structure with metal strips outside the inner sheath layer, which can obtain both impact resistance and structural strength, as well as a certain degree of flexibility.

[0119] In the above-mentioned medium-voltage cable molding structure, the outer sheath layer is an extrusion structure of low-smoke halogen-free flame-retardant polyolefin material outside the metal armor layer.

[0120] The above embodiments are only used to illustrate the present invention and are not intended to limit it.

[0121] Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications can still be made to the above embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the present invention.

Claims

1. An environmentally friendly polypropylene insulated flame-retardant medium voltage cable, comprising a cable core and a protective structure layer arranged outside the cable core; characterized in that: the cable core has three power insulated wire cores (1) and three tensile wire cores (2) twisted together, and a flame-retardant filling rope (3) filled in the twisting gap between the three power insulated wire cores (1) and the three tensile wire cores (2), each tensile wire core (2) is arranged at the twisting outside gap of the adjacent two power insulated wire cores (1); the power insulated wire core (1) is composed of a conductor (11) and, from inside to outside of the conductor (11), a conductor shielding layer (12), a polypropylene insulation layer (13), an insulation shielding layer (14), a shielding isolation layer (15), a metal shielding composite layer (16) and a conductor core fireproof layer (17); the tensile wire core (2) is composed of a tensile core (21) and a tensile core fireproof layer (22) wrapped outside the tensile core (21), the tensile core (21) is a twisted structure of a plurality of aramid fiber strands, and the tensile core fireproof layer (22) is an extrusion wrapping structure of ceramicized silicone rubber outside the tensile core (21).

2. The environmentally friendly polypropylene insulated flame-retardant medium voltage cable according to claim 1, characterized in that: the conductor (11) of the power insulated wire core (1) is composed of a plurality of concentrically arranged round conductors (111), a plurality of fan-shaped conductors (112) concentrically arranged around the outermost round conductor (111), and a conductor wrapping layer (113) arranged around each fan-shaped conductor (112); the concentrically arranged round conductors (111) and the fan-shaped conductors (112) are in a twisted structure; the conductor wrapping layer (113) is a superimposed wrapping structure of a semi-conductive tape outside the fan-shaped conductors (112).

3. The environmentally friendly polypropylene insulated flame-retardant medium voltage cable according to claim 1, characterized in that: the conductor shielding layer (12), the polypropylene insulation layer (13) and the insulation shielding layer (14) of the power insulated wire core (1) are a three-layer co-extrusion structure.

4. The environmentally friendly polypropylene insulated flame-retardant medium voltage cable according to claim 1, characterized in that: the shielding isolation layer (15) of the power insulated wire core (1) is a superimposed wrapping structure of a semi-conductive tape outside the insulation shielding layer (14).

5. The environmentally friendly polypropylene insulated flame-retardant medium voltage cable according to claim 1, characterized in that: the metal shielding composite layer (16) of the power insulated wire core (1) is a composite structure of an inner copper wire sparse winding layer (161) and an outer copper tape wrapping layer (162); and the copper tape wrapping direction of the copper tape wrapping layer (162) is opposite to the copper wire sparse winding direction of the copper wire sparse winding layer (161).

6. The environmentally friendly polypropylene insulated flame-retardant medium voltage cable according to claim 1, characterized in that: the conductor core fireproof layer (17) of the power insulated wire core (1) is an extrusion wrapping structure of ceramicized silicone rubber outside the metal shielding composite layer (16).

7. The environmentally friendly polypropylene insulated flame-retardant medium voltage cable according to claim 1, characterized in that: The protective structure layer outside the cable core is composed of a flame-retardant wrapping layer (4), an oxygen barrier layer (5), an inner sheath layer (6), a metal armor layer (7) and an outer sheath layer (8) arranged in sequence from inside to outside of the cable core. 8.The environmentally-friendly polypropylene insulated flame-retardant medium-voltage cable according to claim 7, characterized in that: The flame-retardant wrapping layer (4) is an overlapping wrapping structure of ceramicized silicone rubber mica composite tape outside the cable core. The inner sheath layer (6) is an extrusion coating structure of low-smoke halogen-free flame-retardant polyolefin material outside the oxygen barrier layer (5). The outer sheath layer (8) is an extrusion coating structure of low-smoke halogen-free flame-retardant polyolefin material outside the metal armor layer (7). 9.The environmentally-friendly polypropylene insulated flame-retardant medium-voltage cable according to claim 7, characterized in that: The metal armor layer (7) is a double-layer sparse winding armor structure of metal tape outside the inner sheath layer (6). Alternatively, the metal armor layer (7) is a dense winding armor structure of multiple metal wires outside the inner sheath layer (6).

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