Irradiation cross-linked polyethylene insulated copper core low-voltage cable

Abstract

The utility model relates to the technical field of wires and cables, in particular to an irradiation crosslinking polyethylene insulated copper core low-voltage cable, which comprises a plurality of mutually twisted wire cores, the filling strip is filled in an outer side gap between the two wire cores; the first flame-retardant wrapping layer wraps the outer sides of the wire cores and the filling strips and forms a cable core with a circular cross section; the inner sheath is extruded on the outer wall of the first flame-retardant wrapping layer; and the second flame-retardant wrapping layer is coated on the outer wall of the inner sheath. The graphite powder is filled between the stranded conductor and the insulating layer, so that the electric field on the inner wall of the insulating layer is more uniform, the heat conductivity between the stranded conductor and the insulating layer is good, local high heat of the insulating layer can be avoided, and in addition, the heat conduction filling strip is arranged between the wire core and the wrapping layer, so that channels for longitudinally transferring heat can be increased, and the heat conduction efficiency is improved. And the heat dissipation performance of the cable is integrally improved, so that the cable has better current-carrying and temperature-resistant performance.

Description

Technical Field

[0001] The utility model relates to the technical field of wire and cable, in particular to an irradiated cross-linked polyethylene insulated copper core low-voltage cable. Background Art

[0002] According to the requirements of the national standard "GB_12706.1-2008" and the civil building electrical design standard "GB51348-2019", the design of low-voltage cables needs to withstand a certain laying traction and tolerate a normal operating temperature of 90°C under the conditions of indoor, outdoor, and pipeline laying, and requirements are put forward for the structure, transmission capacity, and flame retardant and smoke suppression performance of the cables. The traditional PVC / polyvinyl chloride sheath polyethylene / polyvinyl chloride insulated copper core low-voltage cable is filled and stranded with a halogen-free filling rope, and is composed of an inner sheath, a shielding layer, an armor, and an outer sheath. In some applications with high flame retardant requirements, especially in places with high electrical performance and safety requirements such as high-rise buildings, computer control centers, security monitoring centers, rail transit, and fire protection terminals, cross-linked polyethylene insulation is used to transform thermoplastic polyethylene into thermosetting cross-linked polyethylene, so that the polyethylene molecules change from a linear structure to a three-dimensional network structure, thus greatly improving the mechanical properties and thermal aging properties, having a high working temperature, strong environmental stress resistance, being able to work normally at 125 degrees, and being able to withstand a momentary temperature of up to 300 degrees. The cable can still maintain long-term stable performance in a high-temperature environment. At the same time, the irradiated cross-linked polyethylene insulation material is environmentally friendly and non-toxic, and does not produce a large amount of smoke and toxic gases when burning, meeting the requirements of green modern environmental protection, and is applied to urban distribution lines, industrial and mining enterprises, and building power supply.

[0003] During the cable laying and operation process, the greatest risk comes from the high-temperature combustion and toxic high-temperature flue gas caused by line aging, insulation failure, and short circuit, which cause serious harm to the places and personnel where they are used. Despite the advantages of irradiated cross-linked polyethylene insulated low-voltage cables, due to factors such as long-term high transmission capacity, overload operation, and insulation aging, cable safety hazards are caused, and even fires are triggered. Therefore, by reasonably designing the cable current-carrying capacity, avoiding overloading, and regularly checking the temperature rise of the cable, such safety hazards can be reduced. In addition, since the flame retardant filling provided between the wire core and the insulation of the cable itself also makes it difficult for heat to dissipate inside the cable, improving the heat dissipation performance (active and / or passive) of the cable is an effective method to reduce safety hazards. Content of the Utility Model

[0004] In view of the temperature resistance and heat dissipation of low-voltage cables in the prior art, the utility model aims to improve the temperature resistance and heat dissipation performance of low-voltage cables, improve the long-term safety and stability of cable operation, and reduce the insulation caused by high temperature.

[0005] According to the first aspect of the object of the present utility model, a low-voltage copper-core cable with irradiated cross-linked polyethylene insulation is provided, including:

[0006] Multiple mutually stranded cores;

[0007] Filler strips, filled in the outer gaps between two cores;

[0008] A first flame-retardant wrapping layer, covering the outer sides of the cores and the filler strips, and forming a cable core with a circular cross-section;

[0009] An inner sheath, extruded on the outer wall of the first flame-retardant wrapping layer;

[0010] A second flame-retardant wrapping layer, covering the outer wall of the inner sheath;

[0011] An outer sheath, extruded on the outer wall of the second flame-retardant wrapping layer;

[0012] Wherein, the filler strip is configured as a strip shape, including a first surface, a second surface and a third surface. The first surface and the second surface are concave arc surfaces, respectively fitting with the outer walls of two adjacent cores. The third surface is a convex arc surface, and the third surface fits with the first flame-retardant wrapping layer. A heat-conducting structure is provided inside and / or on the surface of the filler strip. The core includes a stranded copper conductor and an insulating layer extruded on the surface of the copper conductor. A graphite powder filling structure is provided between the copper conductor and the insulating layer.

[0013] Preferably, the copper conductor is formed by stranding 7 fine copper wires according to a regular stranding structure of 1 + 6, forming six cavities between the six outer fine copper wires and the insulating layer. The graphite powder filling structure fills the cavities with a copolymer formed by graphite powder and polyolefin, especially a copolymer of spherical graphite powder and polypropylene.

[0014] Preferably, the insulating layer includes an irradiated cross-linked polyethylene insulating layer.

[0015] Preferably, a heat-conducting layer is provided on the surface of the filler strip, and the heat-conducting layer includes an aluminum foil or a copper foil or a heat-conducting particle coating.

[0016] Preferably, the heat-conducting particle coating includes a ceramic particle coating, and the thickness of the ceramic particle coating is 0.05 - 0.10 mm.

[0017] Preferably, the filler strip includes a cross-linked polyethylene extrusion strip, and heat-conducting microparticles are provided in the cross-linked polyethylene extrusion strip. The heat-conducting microparticles are ceramic particles, and the particle size range of the ceramic particles is 0.05 - 0.30 mm.

[0018] Preferably, the first flame-retardant wrapping layer is formed by wrapping with a first fiberglass tape, the number of wrapping layers is three, and the wrapping overlap rate is 50%.

[0019] Preferably, the second flame retardant wrapping layer is formed by wrapping with a second fiberglass tape, the number of wrapping layers is two, and the wrapping overlap rate is 20-30%.

[0020] Preferably, the inner sheath includes an irradiated cross-linked polyethylene insulating heat-conducting layer.

[0021] Preferably, the outer sheath includes a low-smoke and halogen-free polyolefin insulating layer.

[0022] Compared with the prior art, the advantages of the irradiated cross-linked polyethylene insulated copper core low-voltage cable of the present utility model are as follows:

[0023] In the design of the irradiated cross-linked polyethylene insulated copper core low-voltage cable, a graphite powder layer is filled between the stranded conductor and the insulating layer, and the cavity is filled with a copolymer formed by graphite powder and polyolefin, so that the electric field on the inner wall of the insulating layer is more uniform. The heat conductivity between the stranded conductor and the insulating layer is good, which can avoid local high heat accumulation in the insulating layer. At the same time, a heat-conducting filling strip is arranged between the wire core and the wrapping layer, which can increase the channel for heat to transfer longitudinally, and overall increase the heat dissipation performance of the cable, so that the cable has better current-carrying and temperature-resistant performances. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings are not intended to be drawn to scale. In the drawings, each identical or approximately identical component shown in each figure may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Now, embodiments of various aspects of the present utility model will be described by way of example and with reference to the drawings.

[0025] Figure 1 is a schematic structural diagram of the irradiated cross-linked polyethylene insulated copper core low-voltage cable shown in the present utility model.

[0026] Figure 2 is a schematic cross-sectional structural diagram of the irradiated cross-linked polyethylene insulated copper core low-voltage cable shown in the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] In order to better understand the technical content of the present utility model, specific embodiments are hereby given and described in conjunction with the accompanying drawings as follows.

[0028] Combined with Figure 1 and Figure 2As shown in the figure, a first aspect of the present utility model provides a low-voltage copper-core cable with irradiated cross-linked polyethylene insulation, which includes multiple mutually twisted cores 1, a filling strip 2, a first flame-retardant wrapping layer 3, an inner sheath 4, a second flame-retardant wrapping layer 5, and an outer sheath 6. The core is formed by twisting the cores 1 and wrapping the filling strip 2 filled in the gaps outside the cores 1 with a flame-retardant wrapping tape. Among them, the core includes 3 to 6 mutually twisted cores 1, which meet the requirements of different power transmissions for single-phase, three-phase, and four-wire systems. The inner and outer sheaths and the flame-retardant wrapping layer provide flame-retardant and insulating protection for the outside of the core.

[0029] The core 1 includes a twisted copper conductor 11 and an insulating layer 13 extruded on the surface of the copper conductor, forming a bundle of insulated conductors. Currently, most cores use twisted conductors. The gaps between the conductors are not conducive to heat conduction, and an uneven electric field is formed between the conductor and the insulating layer, which is likely to cause local aging of the insulation. Therefore, in the embodiments of the present utility model, a graphite powder filling structure 12 is provided between the copper conductor 11 and the insulating layer 13. Particularly preferably, the graphite powder filling structure is in the form of a copolymer formed by graphite powder and polyolefin, filling the cavity structure. Among them, in this embodiment, a copolymer of spherical graphite powder with a particle size of 50 - 200 um and polypropylene (commercially available, with the graphite proportion less than 2 - 5%) is used.

[0030] In this way, since the copper conductor 11 has good thermal conductivity and electrical properties, it can reduce the heat generated when current passes through. At the same time, using the graphite powder between the copper conductor 11 and the insulating layer 13, a good heat conduction path can be formed between the copper conductor 11 and the insulating layer 13, enabling heat to have a channel for outward conduction, avoiding the concentration of heat at the contact points between the copper conductor 11 and the insulating layer 13. The graphite powder also plays a role in evenly distributing the electric field.

[0031] Optionally, the insulating layer 13 includes an irradiated cross-linked polyethylene insulating layer. The irradiated cross-linked polyethylene insulating layer has good heat resistance and aging resistance. Through the effects of uniform heat conduction and uniform electric field, the aging of the insulating layer 13 can be further delayed to maintain its insulation.

[0032] In a specific embodiment, the copper conductor 11 is formed by twisting 7 fine copper wires according to a regular stranding structure of 1 + 6, forming six cavities between the six outer fine copper wires and the insulating layer 13, and the graphite powder filling structure 12 fills the cavities.

[0033] During production, the twisted fine copper wires can be passed through a filling box with graphite powder. After passing through the filling box, the surface of the stranding structure is covered with graphite powder. An insulating extruder is connected behind the filling box to coat the graphite powder to form the core 1.

[0034] Further, filling with a flame-retardant rope between the conductor 1 and the first flame-retardant wrapping layer 3 is not conducive to the radial heat transfer along the cable. Therefore, the filling strip 2 is filled in the outer gap between two conductors 1, and the filling strip 2 is used as a heat transfer path.

[0035] Among them, the filling strip 2 is constructed in a strip shape. The filling strip 2 includes a first surface, a second surface and a third surface. The first surface and the second surface are concave arc surfaces, which are respectively attached to the outer walls of two adjacent conductors 1. The third surface is a convex arc surface, and the third surface is attached to the first flame-retardant wrapping layer 3. A heat conduction structure is provided inside and / or on the surface of the filling strip 2.

[0036] In this way, since the filling strip 2 is attached to the surfaces of the conductor 1 and the first flame-retardant wrapping layer 3, the contact area is large, which is conducive to heat exchange between the two. And through the heat conduction structure arranged on the surface or inside of the filling strip 2, the heat conductivity of the present application can be increased, so that the heat of the conductor can be transferred out more effectively.

[0037] In an optional embodiment, the filling strip 2 includes a cross-linked polyethylene extrusion strip, and heat-conducting particles are provided in the cross-linked polyethylene extrusion strip. The heat-conducting particles are ceramic particles.

[0038] Specifically, between the extrusion of the filling strip 2, the insulating material and the heat-conducting particles are mixed. Optionally, the weight ratio of the heat-conducting particles is 5% - 10%, and the particle size range of the ceramic particles is 0.05 - 0.30 mm. The filling strip 2 formed in this way has better heat conductivity compared with the flame-retardant rope or the foamed strip.

[0039] In an optional embodiment, a heat conduction layer is provided on the surface of the filling strip 2. The heat conduction layer can be selected from aluminum foil or copper foil or a heat-conducting particle coating. Among them, the aluminum foil or copper foil is adhered to the surface of the filling strip 2 with glue. The heat-conducting particle coating can be selected as a ceramic particle coating. The ceramic particle coating is formed by mixing ceramic particles, a binder and a curing agent. The thickness of the ceramic particle coating is 0.05 - 0.10 mm, and the particle size of the ceramic particles is about 0.03 mm.

[0040] The heat conduction efficiency from the conductor 1 to the first flame-retardant wrapping layer 3 can be further improved through the heat conduction layer on the surface of the filling strip 2.

[0041] Further, the first flame-retardant wrapping layer 3 covers the outside of the conductor 1 and the filling strip 2, and forms a cable core with a circular cross-section. Among them, the first flame-retardant wrapping layer 3 is formed by wrapping with a first glass fiber tape, the number of wrapping layers is three, and the wrapping overlap rate is 50%.

[0042] The flame-retardant wrapping layer structure formed in this way is dense, has a good flame-retardant effect, and can conduct heat outwards.

[0043] Further, the inner sheath 4 is extruded on the outer wall of the first flame-retardant wrapping layer 3; the second flame-retardant wrapping layer 5 is wrapped on the outer wall of the inner sheath 4; the outer sheath 6 is extruded on the outer wall of the second flame-retardant wrapping layer 5.

[0044] Among them, the second flame-retardant wrapping layer 5 is formed by wrapping with a second fiberglass tape, the number of wrapping layers is two, and the wrapping overlap rate is 20-30%. The structure of the second flame-retardant wrapping layer 5 is looser and thinner than that of the first flame-retardant wrapping layer 3.

[0045] Among them, the inner sheath 4 includes an irradiated cross-linked polyethylene insulating and heat-conducting layer. The outer sheath 6 includes a low-smoke and halogen-free polyolefin insulating layer.

[0046] Specifically, the irradiated cross-linked polyethylene insulating and heat-conducting layer can be formed by mixing polyethylene insulating material and heat-conducting particles during extrusion. Optionally, the heat-conducting particles can be selected as talcum powder, and the weight ratio of talcum powder is less than 5%. This is beneficial to improving the heat conductivity of the irradiated cross-linked polyethylene insulating and heat-conducting layer.

[0047] Combined with the above embodiments, the utility model fills graphite powder between the stranded conductor and the insulating layer, making the electric field on the inner wall of the insulating layer more uniform. At the same time, the heat conductivity between the stranded conductor and the insulating layer is good, which can avoid local high heat in the insulating layer. In addition, a heat-conducting filling strip is arranged between the wire core and the wrapping layer, which can increase the channels for heat to transfer longitudinally, and overall increase the heat dissipation performance of the cable, so that the cable has better current-carrying and temperature-resistant performances.

[0048] Although the present utility model has been disclosed above with preferred embodiments, it is not intended to limit the present utility model. Those with ordinary knowledge in the technical field to which the present utility model belongs can make various modifications and refinements without departing from the spirit and scope of the present utility model. Therefore, the protection scope of the present utility model shall be subject to that defined by the claims.

Claims

1. A low-voltage copper-core cable with irradiated cross-linked polyethylene insulation, characterized in that, Comprising: Multiple mutually stranded core wires (1), the core wires (1) comprising stranded copper conductors (11) and insulating layers (13) extruded on the surfaces of the copper conductors, and a graphite powder filling structure (12) being provided between the copper conductors (11) and the insulating layers (13); Filling strips (2), filled in the outer gaps between two core wires (1); A first flame-retardant wrapping layer (3), wrapped on the outer sides of the core wires (1) and the filling strips (2) and forming a cable core with a circular cross-section; An inner sheath (4), extruded on the outer wall of the first flame-retardant wrapping layer (3); A second flame-retardant wrapping layer (5), wrapped on the outer wall of the inner sheath (4); An outer sheath (6), extruded on the outer wall of the second flame-retardant wrapping layer (5); Wherein, the filling strips (2) are configured as strips, including a first surface, a second surface and a third surface, the first surface and the second surface being concave arc surfaces, respectively fitting with the outer walls of two adjacent core wires (1), the third surface being a convex arc surface, the third surface fitting with the first flame-retardant wrapping layer (3), and a heat conduction structure being provided inside and / or on the surface of the filling strips (2).

2. The irradiated crosslinked polyethylene insulated copper core low-voltage cable according to claim 1, wherein, The copper conductor (11) is formed by stranding 7 fine copper wires according to a regular stranding structure of 1 + 6, six cavities being formed between the six outer fine copper wires and the insulating layer (13), and the graphite powder filling structure (12) filling the cavities with a copolymer formed by graphite powder and polyolefin.

3. The irradiated cross-linked polyethylene insulated copper core low-voltage cable according to claim 2, wherein, The insulating layer (13) includes an irradiated cross-linked polyethylene insulating layer.

4. The irradiated crosslinked polyethylene insulated copper core low voltage cable according to claim 1, characterized in that, A heat conduction layer is provided on the surface of the filling strips (2), and the heat conduction layer includes an aluminum foil or a copper foil or a heat conduction particle coating.

5. The irradiated crosslinked polyethylene insulated copper core low-voltage cable according to claim 4, wherein The heat conduction particle coating includes a ceramic particle coating, and the thickness of the ceramic particle coating is 0.05 - 0.10 mm.

6. The irradiated crosslinked polyethylene insulated copper core low-voltage cable according to claim 1 or 4, characterized in that, The filling strips (2) include cross-linked polyethylene extrusion strips, and heat conduction fine particles are provided in the cross-linked polyethylene extrusion strips, the heat conduction fine particles being ceramic particles, and the particle size range of the ceramic particles is 0.05 - 0.30 mm.

7. The irradiated crosslinked polyethylene insulated copper core low-voltage cable according to claim 1, wherein, The first flame-retardant wrapping layer (3) is formed by wrapping with a first glass fiber tape, the number of wrapping layers being three, and the wrapping overlapping rate being 50%.

8. The irradiated crosslinked polyethylene insulated copper core low-voltage cable according to claim 1, wherein, The second flame-retardant wrapping layer (5) is formed by wrapping with a second glass fiber tape, the number of wrapping layers being two, and the wrapping overlapping rate being 20 - 30%.

9. The irradiated crosslinked polyethylene insulated copper core low-voltage cable according to claim 1, characterized in that, The inner sheath (4) includes an irradiated cross-linked polyethylene insulating and heat conduction layer.

10. The irradiated crosslinked polyethylene insulated copper core low-voltage cable according to claim 1, characterized in that, The outer sheath (6) includes a low-smoke and halogen-free polyolefin insulating layer.

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