Flame-retardant overhead insulated cable and production process thereof

Abstract

The invention discloses a flame-retardant overhead insulated cable and a production process thereof, the flame-retardant overhead insulated cable comprises a wire core and an insulating sheath wrapping the periphery of the wire core, a plurality of micropores are uniformly distributed in the insulating sheath, and the micropores are filled with flame-retardant gas. According to the invention, the insulating skin containing the micropore structure is adopted, and the micropores are filled with the flame-retardant gas, so that the flame retardant component can be assisted to improve the flame-retardant performance, the addition proportion of the flame retardant is reduced, the toughness of the cable is improved, and the cable is light in weight.

Description

Technical Field

[0001] The invention relates to the technical field of overhead insulated cables, and in particular to a flame-retardant overhead insulated cable and a production process thereof. Background Art

[0002] Overhead insulated cables are overhead conductors equipped with insulating protective sheaths. They are a special type of cable manufactured using a production process similar to that of cross-linked cables. They are a new way of transmitting electricity between overhead conductors and underground cables. Overhead insulated cables are generally single-core and are used in power transmission and distribution applications below 10KV. They have good safety performance in densely populated areas. In order to reduce the impact of fire on transmission cables, some overhead insulated cables have added flame retardant functions. The method generally adopted is to add flame retardants to the formula of the insulating protective sheath. Among them, aluminum hydroxide or magnesium hydroxide are two important inorganic flame retardants. Increasing the proportion of inorganic flame retardants can achieve better flame retardant properties, but it will reduce the toughness of the cable sheath and make it prone to brittle cracking; it will also affect the fluidity of the molten plastic material during the extrusion process, and it is easy to produce coating defects.

[0003] In order to overcome the above problems, a flame retardant overhead insulated cable and a production process thereof are needed. Summary of the invention

[0004] The purpose of the present invention is to provide a flame-retardant overhead insulated cable and its production process. By adopting an insulating sheath containing a microporous structure, and the micropores are filled with flame-retardant gas, the flame retardant component can be assisted to improve the flame retardant performance, reduce the proportion of flame retardant addition, improve the toughness of the cable and make it lightweight.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The invention discloses a flame-retardant overhead insulated cable, comprising a conductor core and an insulating sheath wrapped around the conductor core, wherein a plurality of micropores are evenly distributed in the insulating sheath and the micropores are filled with flame-retardant gas.

[0007] Furthermore, the insulating skin is formed by extrusion of a polyethylene-based material, and the raw material components of the insulating skin contain a flame retardant.

[0008] Furthermore, the flame retardant gas is specifically carbon dioxide or nitrogen.

[0009] Furthermore, the outer periphery of the insulating skin is also covered with an outer sheath, and the outer sheath is extruded by using a polyvinyl chloride material containing a flame retardant.

[0010] The present invention also discloses a flame-retardant overhead insulated cable production process. In the production process of the insulating sheath, the conductor core passes through a die cavity of a die head, and an extruder supplies material to the die head. The feed end of the extruder is also connected to a foaming agent supply unit through a pipeline, and the foaming agent supply unit supplies the foaming agent to the extruder and evenly mixes it into the extruded material.

[0011] Furthermore, the foaming agent supply unit is a carbon dioxide foaming agent supply unit.

[0012] Furthermore, the insulating skin guided out from the die head is subjected to surface cooling to improve the situation where holes appear on the surface.

[0013] Furthermore, it also includes a cooling conduit, which is coaxially installed on the output port of the die head, and the inner wall of the cooling conduit contacts the outer wall of the insulation skin for surface cooling.

[0014] Furthermore, the inner end of the cooling duct is positioned and connected to the outer mold of the die head through a positioning boss; the cooling duct is installed on the outer mold cover of the die head through a flange and bolts; an insulating pad is provided between the inner end surface of the cooling duct and the outer mold and the outer mold cover.

[0015] Furthermore, a cooling coil is wound around the outer wall of the cooling conduit, and the cooling coil is connected to a circulating cooling water supply unit; a coil shield is sleeved on the outer side of the cooling coil.

[0016] Compared with the prior art, the beneficial technical effects of the present invention are:

[0017] The flame-retardant overhead insulated cable of the present invention adopts an insulating sheath containing a microporous structure, and the micropores are filled with flame-retardant gas, which can assist the flame retardant component to improve the flame retardant performance, reduce the proportion of flame retardant addition, and ensure the toughness and strength of the cable. At the same time, the microporous structure also realizes the lightweight of the cable and reduces the dead weight of the overhead insulated cable. In addition, by adding an outer sheath made of polyvinyl chloride material, the insulating sheath can be closed and isolated for protection, while improving the UV resistance and weather resistance, and increasing the service life of the insulating sheath.

[0018] The flame-retardant overhead insulated cable production process of the present invention heats and plasticizes PE substrate particles in an extruder, and mixes them with supercritical carbon dioxide delivered by a foaming agent supply unit while stirring, so as to form a uniform expandable molten material that enters the die cavity of the die head and is coated on the periphery of the conductor core. When the expandable molten material enters the die cavity of the die head, the pressure drops suddenly, the carbon dioxide expands rapidly, and a microporous structure is formed, and the carbon dioxide gas is confined in a single microporous hole. A flow meter is required to control the proportion of the carbon dioxide foaming agent to be added to avoid excessive, large and interconnected micropores, which greatly reduces the strength of the insulation skin. By first cooling the surface of the insulation skin, the solidification of the cooled surface layer blocks the formation of bubbles of the carbon dioxide foaming agent on the surface, ensures that the surface of the insulation skin is continuous and smooth, and reduces the infiltration of rainwater and snow water during overhead use. By directly installing a cooling conduit on the output port of the die head, the surface of the insulation skin that has just been coated immediately contacts the cooling conduit, so that it is cooled and solidified before the inner material. The heat conduction from the die head to the cooling duct is reduced by the insulation pad, thereby ensuring the cooling effect of the cooling duct; the continuous and stable output of cold energy is ensured by adding a cooling coil, and the cooling coil is mechanically protected by the setting of a coil shield, while reducing the dissipation of cold energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below in conjunction with the accompanying drawings.

[0020] Figure 1 It is a schematic cross-sectional view of the flame-retardant overhead insulated cable of the present invention;

[0021] Figure 2 A cross-sectional schematic diagram of another embodiment of the flame-retardant overhead insulated cable of the present invention;

[0022] Figure 3 It is a schematic diagram of the extrusion process equipment of the flame-retardant overhead insulated cable of the present invention;

[0023] Figure 4 It is a schematic diagram of the front and cross-sectional structure of the extrusion die head of the flame-retardant overhead insulated cable of the present invention.

[0024] Explanation of the reference numerals: 1. conductor core; 2. insulation skin; 201. micropores; 3. outer sheath; 4. extruder; 5. die head; 501. outer mold; 502. outer mold cover; 6. foaming agent supply unit; 7. cooling duct; 701. cooling coil; 702. positioning boss; 703. insulation pad; 704. coil cover. DETAILED DESCRIPTION

[0025] The core of the present invention is to provide a flame-retardant overhead insulated cable and its production process. By adopting an insulating sheath containing a microporous structure, and the micropores are filled with flame-retardant gas, the flame retardant component can be assisted to improve the flame retardant performance, reduce the proportion of flame retardant addition, improve the toughness of the cable and make it lighter.

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0028] With reference to the accompanying drawings, Figure 1 It is a schematic cross-sectional view of the flame-retardant overhead insulated cable of the present invention; Figure 2 A cross-sectional schematic diagram of another embodiment of the flame-retardant overhead insulated cable of the present invention; Figure 3 It is a schematic diagram of the extrusion process equipment of the flame-retardant overhead insulated cable of the present invention; Figure 4 It is a schematic diagram of the front and cross-sectional structure of the extrusion die head of the flame-retardant overhead insulated cable of the present invention.

[0029] Example 1

[0030] like Figure 1 and Figure 2 As shown, the present invention discloses a flame-retardant overhead insulated cable, comprising a conductor core 1 and an insulating sheath 2 wrapped around the conductor core 1, wherein the insulating sheath 2 is evenly distributed with a plurality of micropores 201, that is, the insulating sheath 2 is a microporous insulating structure filled with micropores 201. Each micropore 201 is filled with a flame-retardant gas.

[0031] In a specific embodiment of the present invention, the insulating skin 2 is extruded from a polyethylene-based material, and the raw material components of the insulating skin 2 contain a flame retardant. The flame retardant is an inorganic flame retardant. For the insulating skin of a common flame-retardant cable, the content of the inorganic flame retardant is generally not less than 25%. In order to ensure the flame retardant performance, it is often necessary to add about 30% of the inorganic flame retardant. A high proportion of inorganic flame retardant will lead to a decrease in the toughness and strength of the insulating skin 2. In this embodiment, a micropore 201 structure for injecting flame-retardant gas into the insulating skin 2 can reduce the proportion of the inorganic flame retardant to 15-20%, and can achieve the same flame retardant effect.

[0032] Specifically, the flame retardant gas is carbon dioxide or nitrogen.

[0033] The flame-retardant overhead insulated cable of the present invention adopts an insulating sheath containing a microporous structure, and the micropores are filled with flame-retardant gas, which can assist the flame retardant component to improve the flame retardant performance, reduce the proportion of flame retardant addition, and ensure the toughness and strength of the cable. At the same time, the microporous structure also realizes the lightweight of the cable and reduces the dead weight of the overhead insulated cable.

[0034] In a specific implementation of this embodiment, Figure 2 As shown, the outer periphery of the insulating skin 2 is also covered with an outer sheath 3, and the outer sheath 3 is extruded and molded by using polyvinyl chloride material containing flame retardant. The outer sheath 3 is extruded and molded on the outer side of the insulating skin 2 for a second time.

[0035] By adding an outer sheath 3 made of polyvinyl chloride, the insulating sheath 2 can be isolated and protected in a closed manner, while the UV resistance and weather resistance are improved, thereby increasing the service life of the insulating sheath.

[0036] The working principle of the flame-retardant overhead insulated cable of this embodiment is as follows: during the open flame combustion test, after the flame is removed, the insulating skin 2 can achieve self-extinguishing of the open flame within 2 to 5 seconds, wherein the decomposition of the inorganic flame retardant absorbs heat, reduces the surface temperature of the material, and delays combustion. At the same time, when the micropore 201 structure is burned through, the wrapped carbon dioxide gas is released, which blocks the contact between the combustible substrate and the air, and also plays a role in extinguishing the fire. It should be noted that overhead cables are often in contact with the air around them and often have good oxygen conditions. The carbon dioxide gas released by the micropores 201 in this application isolates the burning material and the air nearby, which can play a good role in isolating and extinguishing the fire.

[0037] Example 2

[0038] The present invention also discloses a flame retardant overhead insulated cable production process, such as Figure 3As shown, it is used to produce the flame-retardant overhead insulated cable in the above embodiment. The important difference between the production process and the existing overhead insulated cable is that: in the production process of the insulating skin 2, the conductor core 1 passes through the die cavity of the die head 5, and the extruder 4 supplies the material to the die head 5. The feed end of the extruder 4 is also connected to the foaming agent supply unit 6 through a pipeline, and the high-pressure pump of the foaming agent supply unit 6 supplies the foaming agent to the extruder 4 and evenly mixes it into the extruded material. In the die cavity of the die head 5, the molten material mixed with the foaming agent is released from pressure, and the foaming agent is quickly released and gasified to form a micropore 201 structure.

[0039] Specifically, if Figure 3 As shown, the foaming agent supply unit 6 is a supercritical carbon dioxide foaming agent supply unit, which is transported to the extruder 4 by a high-pressure pump and a high-pressure pipeline and is measured by a flow meter.

[0040] The PE substrate particles are heated and plasticized in the extruder 4, and mixed with the supercritical carbon dioxide delivered from the foaming agent supply unit 6 while stirring, to form a uniform expandable molten material that enters the mold cavity of the die head 5 and is coated on the outer periphery of the conductor core 1. When the expandable molten material enters the mold cavity of the die head 5, the pressure drops suddenly, and the carbon dioxide expands rapidly to form a micropore 201 structure, and the carbon dioxide gas is confined in a single micropore 201. A flow meter is required to control the proportion of the carbon dioxide foaming agent to avoid excessive, large, and interconnected micropores 201, which would significantly reduce the strength of the insulation skin 2.

[0041] In a specific implementation of this embodiment, Figure 3 and Figure 4 As shown, the surface of the insulation skin 2 output from the die head 5 is cooled to improve the situation of holes on the surface.

[0042] Specifically, a cooling conduit 7 is also provided at the outlet end of the die head 5 . The cooling conduit 7 is coaxially installed on the output port of the die head 5 . The inner wall of the cooling conduit 7 contacts the outer wall of the insulating skin 2 for surface cooling.

[0043] By first cooling the surface of the insulation skin 2, the solidification of the cooled surface layer blocks the formation of bubbles on the surface of the carbon dioxide foaming agent, ensuring that the surface of the insulation skin 2 is continuous and smooth, and reducing the infiltration of rainwater and snow water during overhead use. By directly installing the cooling conduit 7 on the output port of the die head 5, the surface of the insulation skin 2 that has just been coated immediately contacts the cooling conduit 7, so that it is cooled and solidified before the inner material.

[0044] In a specific implementation of this embodiment, Figure 4As shown, the inner end of the cooling conduit 7 is positioned and connected with the outer mold 501 of the die head 5 through the positioning boss 702. The positioning boss 702 is a circular boss, and the corresponding outer mold 501 port is provided with an annular groove. The cooperation of the two ensures coaxiality. The cooling conduit 7 is installed on the outer mold cover 502 of the die head 5 through a flange and bolts. An insulating pad 703 is provided between the inner end surface of the cooling conduit 7 and the outer mold 501 and the outer mold cover 502. The insulating pad 703 is specifically a composite pad with heat-resistant rubber as the base material, which has good thermal insulation performance.

[0045] Specifically, if Figure 4 As shown, a cooling coil 701 is wound around the outer wall of the cooling conduit 7, and the cooling coil 701 is connected to a circulating cooling water supply unit. The cooling water supply unit can use the cooling water system of the workshop or a separate chiller. A coil shield 704 is sleeved on the outer side of the cooling coil 701. The coil shield 704 is a cylindrical shield buckled on the outer periphery of the outer wall of the cooling conduit 7, and a heat insulation layer is attached to the inner wall of the coil shield 704.

[0046] The heat conduction from the die head 5 to the cooling duct 7 is reduced by the insulation pad 703, thereby ensuring the cooling effect of the cooling duct 7; the continuous and stable output of cold energy is ensured by adding a cooling coil 701, and the cooling coil 701 is mechanically protected by the setting of the coil shield 704, while reducing the dissipation of cold energy.

[0047] Specifically, if Figure 4 As shown, an anti-adhesion coating is applied on the inner wall of the cooling conduit 7 to prevent the surface layer of the insulated skin 2 that is not fully cooled from adhering to the inner wall of the cooling conduit 7 .

[0048] The extrusion coating process of the flame-retardant overhead insulated cable production process of the present invention is as follows: the foaming agent supply unit 6 delivers a quantitative amount of supercritical carbon dioxide foaming agent to the extruder 4 through a high-pressure pump. The plasticized polyethylene material and the carbon dioxide foaming agent in the spiral cavity of the extruder 4 are stirred, conveyed and mixed to form a uniform expandable molten material that enters the mold cavity of the die head 5, and then is coated on the outer periphery of the conductor core 1 that continuously passes through the mold cavity. Among them, when the expandable molten material enters the mold cavity of the die head 5, the pressure drops suddenly, and the carbon dioxide expands rapidly, forming a micropore 201 structure inside the molten material, and the carbon dioxide gas is confined in a single micropore 201. In the process of the insulation skin 2 that has just been coated being transported backward, its surface layer immediately contacts the cooling conduit 7, so that the surface layer is cooled and solidified before the inner material, and the cooled surface layer solidification blocks the carbon dioxide foaming agent from forming bubbles on the surface layer, ensuring that the outer wall of the surface layer of the insulation skin 2 is continuous and smooth.

[0049] In summary, the flame-retardant overhead insulated cable of the present invention, by adopting an insulating sheath containing a microporous structure, and the micropores are filled with flame-retardant gas, can assist the flame retardant component to improve the flame retardant performance, reduce the proportion of flame retardant addition, and ensure the toughness and strength of the cable. At the same time, the microporous structure also realizes the lightweight of the cable and reduces the dead weight of the overhead insulated cable. In addition, by adding an outer sheath 3 made of polyvinyl chloride material, the insulating sheath 2 can be closed and isolated for protection, while improving the UV resistance and weather resistance, and increasing the service life of the insulating sheath.

[0050] The flame-retardant overhead insulated cable production process of the present invention heats and plasticizes the PE base material particles in the extruder 4, and mixes them with the supercritical carbon dioxide delivered by the foaming agent supply unit 6 while stirring, so as to form a uniform expandable molten material, which enters the mold cavity of the die head 5 and is coated on the outer periphery of the conductor core 1. When the expandable molten material enters the mold cavity of the die head 5, the pressure drops suddenly, and the carbon dioxide expands rapidly to form a micropore 201 structure, and the carbon dioxide gas is confined in a single micropore 201. A flow meter is required to control the proportion of the carbon dioxide foaming agent to be added to avoid excessive, large and interconnected micropores 201, which greatly reduces the strength of the insulation skin 2. By first cooling the surface of the insulation skin 2, the solidification of the cooled surface layer blocks the formation of bubbles on the surface by the carbon dioxide foaming agent, ensuring that the surface of the insulation skin 2 is continuous and smooth, and reducing the infiltration of rainwater and snow water during overhead use. By directly installing the cooling conduit 7 on the output port of the die head 5, the surface of the insulation skin 2 that has just been coated can immediately contact the cooling conduit 7, so that it can be cooled and solidified before the inner material. The heat conduction from the die head 5 to the cooling conduit 7 is reduced by the insulation pad 703, ensuring the cooling effect of the cooling conduit 7; the continuous and stable output of the cooling amount is ensured by adding the cooling coil 701, and the cooling coil 701 is mechanically protected by the setting of the coil shield 704, while reducing the dissipation of the cooling amount.

[0051] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0052] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A flame-retardant overhead insulated cable, comprising a conductor core (1) and an insulating sheath (2) wrapped around the conductor core (1), characterized in that: A plurality of micropores (201) are evenly distributed in the insulating skin (2), and the micropores (201) are filled with flame-retardant gas.

2. The flame-retardant overhead insulated cable according to claim 1, characterized in that: The insulating skin (2) is formed by extrusion of a polyethylene-based material, and the raw material components of the insulating skin (2) contain a flame retardant.

3. The flame-retardant overhead insulated cable according to claim 1, characterized in that: The flame retardant gas is specifically carbon dioxide or nitrogen.

4. The flame-retardant overhead insulated cable according to claim 1, characterized in that: The outer periphery of the insulating skin (2) is also covered with an outer sheath (3), and the outer sheath (3) is extruded from a polyvinyl chloride material containing a flame retardant.

5. A flame retardant overhead insulated cable production process, characterized in that: Used to produce the flame-retardant overhead insulated cable according to any one of claims 1 to 4, in the production process of the insulating sheath (2), the conductor core (1) passes through the mold cavity of the die head (5), and the extruder (4) supplies materials to the die head (5); the feed end of the extruder (4) is also connected to the foaming agent supply unit (6) through a pipeline, and the foaming agent supply unit (6) supplies the foaming agent to the extruder (4) and evenly mixes it into the extruded material.

6. The flame retardant overhead insulated cable production process according to claim 5, characterized in that: The foaming agent supply unit (6) is a carbon dioxide foaming agent supply unit.

7. The flame retardant overhead insulated cable production process according to claim 5, characterized in that: The insulating skin (2) output from the die head (5) is subjected to surface cooling to improve the situation where holes appear on the surface.

8. The flame retardant overhead insulated cable production process according to claim 7, characterized in that: It also includes a cooling conduit (7), which is coaxially installed on the output port of the die head (5), and the inner wall of the cooling conduit (7) contacts the outer wall of the insulation skin (2) for surface cooling.

9. The flame retardant overhead insulated cable production process according to claim 8, characterized in that: The inner end of the cooling duct (7) is positioned and connected to the outer mold (501) of the die head (5) via a positioning boss (702); the cooling duct (7) is mounted on the outer mold cover (502) of the die head (5) via a flange and bolts; and an insulating pad (703) is provided between the inner end surface of the cooling duct (7) and the outer mold (501) and the outer mold cover (502).

10. The flame retardant overhead insulated cable production process according to claim 9, characterized in that: A cooling coil (701) is wound around the outer wall of the cooling conduit (7), and the cooling coil (701) is connected to a circulating cooling water supply unit; a coil shield (704) is sleeved on the outer side of the cooling coil (701).

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