CN121790068A - A high-heat-dissipation, high-performance low-voltage power cable - Google Patents

Abstract

The invention discloses a high-heat-dissipation high-performance power cable, and belongs to the technical field of power cables. The cable comprises a cable core and a flat plastic outer sheath wrapping the cable core. The cable core is formed by arranging a plurality of main wire cores or main wire cores and composite auxiliary wire cores in a flat adjacent contact manner, and no filler exists. The main line core conductor adopts a central hollow aluminum pipe and outer layer special-shaped copper type single-wire mortise-tenon stranding structure, and the composite auxiliary line core adopts a double-conductor double-insulation integrated structure. The main shielding reinforcing layer and the auxiliary shielding reinforcing layer are woven by aluminum-clad steel wires and are connected with each other. The invention omits the procedures of filling and cabling, improves the production efficiency, increases the heat dissipation area, optimizes the current-carrying capacity and the heat dissipation efficiency, saves the laying space by adopting a flat structure, enhances the heat deformation resistance and the mechanical protection performance, and is suitable for various laying environments of a three-phase power distribution system of 0.6/1kV and below.

Description

High-heat-dissipation high-performance low-voltage power cable

Technical Field

The invention relates to the technical field of power cables, in particular to a high-heat-dissipation and high-performance power cable suitable for a three-phase power distribution system with rated voltage of 0.6/1 kV and below.

Background

The performance of a low-voltage power cable, which is a key component for power transmission in a three-phase power distribution system, is directly related to power supply reliability, safety and economy. At present, most of traditional low-voltage power cables widely applied to the field are round to form a cable structure, conductors of the traditional low-voltage power cables adopt round compressed copper stranded wires, gaps between wire cores and cable cores are filled with a large amount of non-heat-absorbing filling materials, and then round outer jackets are extruded. The structure mainly has the following defects that firstly, the use of filling materials not only increases the material cost and the manufacturing process (such as cabling), but also prevents the direct contact heat dissipation of a wire core, so that the overall heat dissipation performance of the cable is poor, the current carrying capacity is limited, the operation temperature is higher, the insulation service life is influenced, secondly, the space utilization rate of a round cable core and a sheath structure laid in a limited space such as a bridge frame and a pipe gallery is low, the layout is irregular, the round sheath is easy to generate larger deformation due to dead weight in a high-temperature environment, and in addition, the shielding layers of the traditional cable are independently arranged, and circulation is possibly generated due to unbalanced induced voltage in the multi-core cable, so that the extra loss and the shielding effect are reduced.

Therefore, a new structure of the low-voltage power cable is needed, which can synchronously improve the heat dissipation efficiency, the production convenience, the space utilization rate and the operation stability.

In order to solve the problem of low space utilization of the round cable, a flat power cable such as a "rated voltage 1kV and below flat power cable" disclosed in chinese patent CN202584858U has been developed in the prior art, which eliminates round filling by arranging a plurality of cores side by side, thereby reducing the overall width of the cable and facilitating laying in a narrow space. However, such conventional flat cables generally employ a simple core parallel arrangement, and do not systematically optimize the internal conductors and core structure, which still suffer from the following significant drawbacks:

First, the neutral conductor (N) and the ground-protective conductor (PE) of a conventional flat cable are often designed as two separate cores, or only the PE core cross section is subjected to a small treatment, so that the flat cable becomes irregular and asymmetric. In order to accommodate the two cores with independent functions, the overall width of the cable cannot be made to be the most compact, and particularly under the large-section specification, the width redundancy is remarkable, and the space-saving potential of the flat structure cannot be fully exerted. Meanwhile, the independent PE wire cores are required to be treated independently in production and use, so that the process complexity and the installation cost are increased.

Secondly, the conductor of conventional flat cable adopts traditional circular single line transposition structure more, and its packing factor is low, inside has more clearance, is unfavorable for not only the promotion of electric current transmission efficiency, has also hindered inside heat conduction and the giving off, and the heat dispersion improves limitedly.

Thirdly, the shielding structure of the existing flat cable generally adopts the traditional design, the shielding layers of the wire cores are mutually independent, when the cable is electrified and operates, potential difference and circulation current can be generated between the shielding layers of each phase due to electromagnetic induction, so that extra energy loss and heat are caused, and the overall heat dissipation efficiency and operation stability of the cable are affected.

In addition, the shielding and armouring structure of the conventional cable are separated, so that the cable has the problems of more production flow, complex structure, larger outer diameter, large laying difficulty, large installation occupation space and the like.

In summary, although the flat structure improves the laying space problem to a certain extent, the existing low-voltage power cable, whether it is a round or flat structure, cannot systematically solve the problems of conductor heat dissipation, structural stability, production convenience, integration of neutral conductors and ground protection functions, and the integration of shielding structure and armor structure. Therefore, there is still an urgent need in the art for a new solution for a low-voltage power cable that can achieve high heat dissipation, high current carrying, high stability, high space utilization and easy production at the same time.

Disclosure of Invention

1. Object of the invention

Aiming at the problems of low heat dissipation efficiency, complicated production procedures, insufficient laying space utilization rate, shielding performance to be optimized and the like of the existing low-voltage power cable, the invention aims to provide the high-heat dissipation high-performance low-voltage power cable. The cable is designed through an innovative structure, and aims to remarkably improve the current-carrying capacity and the heat dissipation effect, simplify the production process, and enhance the laying adaptability and the long-term operation reliability.

2. Technical proposal

In order to achieve the above purpose, the invention adopts the following technical scheme:

The core of the high-heat-dissipation high-performance low-voltage power cable is a flattened integral structural design and multifunctional integration. The cable comprises a cable core and a flat plastic outer sheath tightly coated outside the cable core. The cable core is formed by arranging a plurality of (e.g. 3, 4 and 5) main wire cores or three main wire cores and one composite auxiliary wire core in flat adjacent contact, and the arrangement is compact, and no filler exists in the cable core. The design directly increases the exposed heat dissipation surface of the cable core and eliminates the traditional cable filling procedure. The main line core is used as a core conductive unit and sequentially comprises a main conductor, a main insulating layer, a main semi-conductive layer and a main shielding reinforcing layer from inside to outside. The main conductor adopts a composite structure, the center is a hollow aluminum pipe, one or more copper single wire layers are wrapped on the center of the hollow aluminum pipe in a twisting mode, and the whole body is compressed, so that the compression coefficient is not less than 0.97. The hollow aluminum tube has the advantages that the weight of the conductor is reduced, the cost is saved, and meanwhile, the internal cavity of the hollow aluminum tube can form a potential air convection channel to assist in heat dissipation. The copper single wire is of a special-shaped structure, the cross section of the copper single wire is preferably trapezoidal, Z-shaped, S-shaped or tile-shaped, close engagement is achieved between adjacent single wires through mortise and tenon joint, relative displacement is effectively prevented, smooth and round conductor surfaces are guaranteed, and chamfering of 0.1 mm-0.2 mm is arranged at edges and corners of the single wire to reduce local electric field concentration. The composite auxiliary wire core is a unit integrating the functions of grounding protection and neutral conductor, and sequentially comprises an auxiliary inner conductor, an auxiliary inner insulating layer, an auxiliary outer conductor, an auxiliary outer insulating layer, an auxiliary semiconductive layer and an auxiliary shielding reinforcing layer from inside to outside. The auxiliary inner conductor comprises a central layer and an outer layer, the central layer is a solid soft round copper wire, the outer layer is one or more copper single wire layers, the nominal sectional area of the auxiliary outer conductor is the same as or similar to that of the auxiliary inner conductor, and the nominal sectional area of the auxiliary outer conductor is about half of that of the corresponding main wire core. The double-layer insulation design enhances the insulation reliability and mechanical protection thereof. The main shielding reinforcing layer and the auxiliary shielding reinforcing layer are both of aluminum-clad steel wire weaving structures, the weaving density is not less than 80%, and the nominal diameter of the aluminum-clad steel wire is preferably 0.4 mm. The main shielding reinforcing layer and the auxiliary shielding reinforcing layer are electrically connected to form a continuous shielding loop when the cable is electrified, so that induced voltage generated by three-phase unbalance and other factors is effectively counteracted or weakened, circulation loss of the shielding layer is reduced, the overall heat dissipation efficiency is further improved, the aluminum-clad steel wire has good electric conductivity and tensile strength, and the shielding reinforcing layer combines a shielding structure and an armor structure into a whole, so that the cable is fine and functions are integrated. The flat plastic outer sheath is formed by tightly wrapping a cable core by adopting polyvinyl chloride, polyethylene or halogen-free low-smoke flame-retardant polyolefin and other materials through a tube extrusion process. The flat structure makes the deformation capability of the cable bridge against self weight stronger when bearing high temperature (such as in the cable bridge), the bearing pressure per unit area is smaller, and the cable bridge is more space-saving when laid, and is orderly arranged. In order to further optimize conductor performance, the multi-layer copper single wire layers of the main conductor and the auxiliary inner conductor adopt a twisting mode that adjacent layers are twisted in opposite directions, the twisting pitch diameter ratio of the outermost layer is controlled to be 17-21, the pitch diameter ratio of the adjacent inner layers is increased by 8-12 and the total pitch diameter ratio is not more than 49, and the number of copper single wires of each layer is 4-6 more than that of the adjacent inner layers. The main insulating layer, the auxiliary inner insulating layer and the auxiliary outer insulating layer are made of crosslinked polyethylene, and the eccentricity of the main insulating layer, the auxiliary inner insulating layer and the auxiliary outer insulating layer is strictly controlled to be not more than 10%, so that the electric field is uniformly distributed.

3. Advantageous effects

Compared with the prior art, the invention has the following remarkable beneficial effects:

(1) The production is efficient, the cost is optimized, the filling material and the corresponding cabling procedure are canceled, the process flow is simplified, the production period is shortened, and the material and manufacturing cost is reduced.

(2) The heat dissipation is excellent, the current carrying capacity is improved, the heat dissipation surface area of the flat unfilled cable core structure is obviously increased (the estimated heat dissipation surface area can be increased by more than 30%), the auxiliary heat dissipation of the central hollow aluminum pipe and the optimized current distribution of the special-shaped conductor are matched, and the heat dissipation efficiency and the long-term allowable current carrying capacity of the cable are jointly improved.

(3) The structure is stable, flat, regular and symmetrical, the performance is reliable, the high compactness and stability of the conductor are ensured by the mortise and tenon twisting of the special-shaped copper wire, the connection of the main shielding layer and the auxiliary shielding layer effectively inhibits induced voltage, the electromagnetic performance is optimized, the deformation resistance of the flat sheath is strong, and better mechanical protection is provided.

(4) The flat cable has the advantages of convenient laying, strong adaptability, high space utilization rate of the section of the flat cable, convenient laying and regular layout in a narrow channel, special adaptation to complex environments with fall and tension requirements and wide application scenes.

Drawings

Fig. 1 is a schematic diagram of the overall cross-section structure of the cable of the present invention (conductor type single line is trapezoidal).

Fig. 2 is a schematic diagram of the overall cross-section structure of the cable of the present invention (the conductor type single line is Z-shaped + S-shaped).

Fig. 3 is a schematic view of the overall cross-section of the cable of the present invention (the conductor type single wire is tile-shaped).

Fig. 4 is a schematic view of various structural forms of copper type single wires used for conductors of the cable of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. The following examples are intended to illustrate the invention, but not to limit the scope thereof. The high-heat-dissipation high-performance low-voltage power cable has the rated voltage of 0.6/1 kV, is suitable for a three-phase power distribution system with the voltage level and below, can be widely applied to various laying modes such as direct burial, brackets, cable bridges and the like, and is particularly suitable for being used in environments with vertical drop or needing to bear certain tensile force.

1. The overall structure and design principle are shown in fig. 4, the cable of the invention is flat, and consists of an inner cable core C100 and an outer tightly covered flat plastic outer sheath D100. The cable core C100 adopts a flat adjacent contact arrangement mode, and this embodiment is illustrated by a structure of "3 main line cores a100+1 composite auxiliary line cores B100" which is most commonly used (as shown in fig. 1). All the wire cores are closely adjacent, and no filling gap exists. The layout has larger outer surface area than the traditional round cable core under the condition of the same total sectional area of the conductors, and is beneficial to heat dissipation to surrounding media. Meanwhile, the elimination of the filler avoids the obstruction of heat conduction. The core heat dissipation design also comprises that the main conductor of the main line core A100 adopts a hollow aluminum pipe and special-shaped copper wire structure (as shown in figure 1), and the hollow aluminum pipe A10 can reduce the weight and simultaneously promote weak air convection in the inner cavity. The special-shaped copper single wire A201 is spliced through mortise and tenon joints, so that extremely high compression coefficient (more than or equal to 0.97) is realized, conductor gaps are reduced, alternating current resistance is reduced, and heating is reduced from the source. The electromagnetic shielding optimal design is characterized in that the main shielding reinforcing layer A50 and the auxiliary shielding reinforcing layer B70 are woven by adopting high-density (more than or equal to 80%) aluminum-clad steel wires, and the electric communication of the main shielding reinforcing layer A50 and the auxiliary shielding reinforcing layer B is ensured in the grounding design of a cable system. The connection can offset or greatly reduce the induced voltages on the main and auxiliary wire core shielding layers to form equipotential, and basically eliminates the circulation of the shielding layers and the additional loss and heat caused by the circulation.

2. Detailed example 1 of the components the main wire core a100 example takes main wire cores with nominal cross-sectional areas of 150mm 2, 185 mm2, 240 mm2, 300 mm2, 400 mm2 as examples, and its specific structural parameters are as follows:

150 mm2 main line core:

The main conductor center layer A10 is a hollow aluminum tube with an inner diameter of 3.50 mm and an outer diameter of 7.1 mm.

The main conductor outer layer A20 is stranded by two layers of special-shaped trapezoidal copper single wires (A201). Inner layer 12 and outer layer 18. The outer diameter of the twisted main body is 14.5 mm. The adjacent layers are twisted in opposite directions, and the pitch diameter ratio of the outer layer is 19.

The main insulation A30 is crosslinked polyethylene, the average thickness is 1.4 mm-1.5 mm, and the eccentricity is less than or equal to 10%.

The main semiconductive layer A40 is wrapped by overlapping semiconductive buffer belts with the thickness of 0.2 mm and the width of 40 mm which are 1 layer thick.

The main shielding reinforcing layer A50 is formed by adopting a 32-ingot braiding machine, wherein each ingot comprises 3 aluminum-clad steel wires (LB 14 or LB 20) with the nominal diameter of 0.4 mm, the braiding pitch is about 42.6 mm-43.7 mm, and the braiding density is more than or equal to 81%. The main core has an average outer diameter of about 19.7 mm.

185 The mm2 main line core comprises a hollow aluminum pipe with the same size as 150 mm2, an A20 structure of 12+18 pieces, an insulation thickness of 1.6 mm-1.7 mm, 4 wires per spindle of shielding braiding, a pitch of about 66.0 mm-68.1 mm and an outer diameter of about 21.6 mm.

240 The mm2 main line core comprises a hollow aluminum pipe with the inner diameter of 4.00 mm, the outer diameter of 8.0 mm and an A20 structure of 15+21, the insulation thickness of 1.7 mm-1.8 mm, 4 lines per spindle in shielding braiding, the pitch of 59.4 mm-61.1 mm and the outer diameter of about 24.1 mm.

300 The mm2 main line core is a hollow aluminum pipe with the same size as 240mm 2, the A20 is of a 15+21-root structure, the insulation thickness is 2.0 mm-2.2 mm, the shielding braiding pitch is about 56.1-mm-57.1 mm, and the outer diameter is 26.5 mm.

400 The mm2 main line core comprises a hollow aluminum pipe with an inner diameter of 5.00 mm and an outer diameter of 9.0 mm, wherein the A20 is of a three-layer 12+18+24 structure, the insulation thickness is 2.0 mm-2.2 mm, the shielding weaving pitch is about 53.2 mm-54.4 mm, and the outer diameter is 29.5 mm. The compression coefficient of all specifications of main conductors is more than or equal to 0.97, the copper single-wire chamfer angle is 0.1 mm-0.2 mm, and the strand extension coefficient is controlled to be 1.04-1.07.

2. The nominal cross-sectional areas of the composite auxiliary core B100 in the embodiment of the composite auxiliary core are respectively adapted to the main core, and are generally about 1/2 of the cross-sectional area of the main core, specifically taking 70 mm2 (150 mm 2), 95 mm2 (185 mm 2), 120 mm2 (240 mm 2), 150 mm2 (300 mm 2) and 185 mm2 (400 mm 2) as examples:

2×70 mm2 composite secondary core (150 mm2 main core is adapted):

and the auxiliary inner conductor center layer B10 is a solid soft round copper wire with the diameter of about 3.80 mm.

The outer layer B20 of the auxiliary inner conductor is formed by twisting 6 special-shaped copper single wires with the outer diameter of about 9.25 mm.

The auxiliary inner insulation B30 is crosslinked polyethylene, and the thickness is about 1.2 mm-1.3 mm.

The auxiliary outer conductor layer B40 is formed by stranding 24 special-shaped copper single wires, and the outer diameter of the auxiliary outer conductor layer B is about 15.0 mm.

The auxiliary outer insulation B50 is crosslinked polyethylene, and the thickness is about 1.2 mm-1.3 mm.

The secondary semiconductive layer B60 is wrapped by overlapping semiconductive buffer strips with the thickness of 0.2 mm and the width of 40 mm which are 1 layer thick.

The specification of the auxiliary shielding reinforcing layer B70 is completely the same as the A50 of the 150 mm2 main wire core, and the average outer diameter is about 19.7 mm.

The composite auxiliary wire cores with other specifications (2×95 mm2, 2×120 mm2, 2×150 mm2 and 2×185 mm 2) are similar in structure, and the number of conductor stranding layers, the insulation thickness and the shielding layer specification are matched and designed corresponding to the main wire core matched with the composite auxiliary wire cores, so that the outer diameters are coordinated, and the composite auxiliary wire cores are convenient to be arranged flatly. All the insulation eccentricities are less than or equal to 10 percent.

3. The cable core C100 and the outer sheath D100 embodiment abut the 3 main wire cores a100 and the 1 composite secondary wire core B100 of the corresponding specifications in parallel to form the flat-arrangement cable core C100 without any filling. And then the flat outer sheath D100 is extruded. The outer sheath material can be polyvinyl chloride (PVC), polyethylene (PE) or halogen-free low-smoke flame-retardant polyolefin (WDZ) according to the requirements. The thickness of the sheath and the external dimension of the cable are determined according to the dimension of the cable core so as to ensure necessary mechanical protection and electrical insulation. Taking the 3+1 structure of the main line core and the composite auxiliary line core as an example, the external dimensions and the sheath thickness of part of the specifications are as follows:

150 mm2 + 2 x 70 mm2, the width of the cable core after arrangement is about 82.9 mm, and the height is about 23.8 mm. The nominal thickness of the outer sheath D100 is about 2.0 mm-2.2 mm.

185 The external dimension is about 90.8 mm multiplied by 26.0 mm, and the sheath thickness is about 2.1 mm-2.3 mm.

240 The external dimension is about 101.2 mm multiplied by 28.9 mm, and the sheath thickness is about 2.3 mm to 2.5 mm.

300 The external dimension is about 111.0 mm multiplied by 31.5 mm, and the sheath thickness is about 2.4 mm-2.6 mm.

400 The external dimension is about 123.6 mm multiplied by 35.1 mm, and the sheath thickness is about 2.7 mm to 2.9 mm. The flat sheath structure is calculated to have the permanent deformation resistance under high temperature pressure (such as long-term running in a cable bridge) which is obviously better than that of a round sheath made of the same material. When the depth of the high-temperature pressure mark is 50%, the section of the bottom of the outer sheath bearing the weight of the outer sheath is increased by 45% or more, the dead weight pressure of the cable in unit area can be reduced by 40% or more, the sheath deformation caused by dead weight is effectively reduced, and the protection reliability of the outer sheath of the cable is greatly improved.

3. When the production process and the performance overview are produced, firstly, preparing special-shaped copper single wires and aluminum-clad steel wires. And manufacturing the main wire core (stranded conductor, extrusion insulation, wrapping semi-conductive layer and braiding shielding) and the composite auxiliary wire core (similar flow and double insulation extrusion) sequentially. And then the appointed number of wire cores are gathered in parallel to form a flat cable core, and the flat cable core is not required to be filled by a cable former. Finally, directly extruding and wrapping the cable core to form a flat outer sheath. According to the cable disclosed by the invention, compared with the similar traditional round cable in the GB/T12706.1 standard, the surface heat dissipation area is increased by about 30% -40% under the condition of the same conductor material and cross section, the long-term allowable current-carrying capacity can be expected to be improved by 5% -10%, the production cost is reduced due to the simplified process, and the laying space is saved by about 20% -30%. The unique structure of the solar heat collector has obvious advantages in the aspects of heat dissipation, current carrying, production efficiency and laying adaptability.

Claims (10)

1. A high-heat-dissipation, high-performance, low-voltage power cable, characterized in that it comprises a cable core and a flat plastic outer sheath covering the cable core; the cable core is composed of multiple main conductors arranged in a flat, adjacent contact, and there is no filler material in the cable core; The main conductor, from the inside out, includes a main conductor, a main insulation layer, a main semiconducting layer, and a main shielding reinforcement layer. The main body comprises a hollow aluminum tube and one or more layers of copper single wire strands stranded and wrapped around the aluminum tube. 2. The high heat dissipation, high performance, low voltage power cable according to claim 1, characterized in that the cable core is composed of three main conductors and one composite auxiliary conductor arranged in a flat, adjacent contact configuration; The composite sub-core, from the inside out, includes an inner sub-conductor, an inner sub-insulation layer, an outer sub-conductor, an outer sub-insulation layer, a semiconducting sub-layer, and a shielding reinforcement layer. 3. The high heat dissipation, high performance, low voltage power cable according to claim 1, wherein the compression coefficient of the main body is not less than 0.97. 4. The high heat dissipation, high performance, low voltage power cable according to claim 2, characterized in that the secondary inner conductor comprises a central layer and an outer layer, the central layer being a solid soft round copper wire, and the outer layer being one or more copper-type single-wire layers; the nominal cross-sectional area of the secondary outer conductor is the same as or approximately the nominal cross-sectional area of the secondary inner conductor. 5. The high heat dissipation, high performance, low voltage power cable according to claim 1 or 4, characterized in that the cross-sectional shape of the copper single wire is a trapezoidal, Z-shaped, S-shaped, or tile-shaped irregular structure, and adjacent single wires are joined together in a tenon-and-mortise manner; the corners of the copper single wire are provided with a chamfer of 0.1 mm to 0.2 mm. 6. The high heat dissipation, high performance, low voltage power cable according to claim 1 or 2, characterized in that the main shielding reinforcement layer and the secondary shielding reinforcement layer are both aluminum-clad steel wire braided structures with a braiding density of not less than 80%; the main shielding reinforcement layer and the secondary shielding reinforcement layer are electrically connected. 7. The high heat dissipation, high performance, low voltage power cable according to claim 1, wherein the material of the flat plastic outer sheath is polyvinyl chloride, polyethylene, or halogen-free, low-smoke, flame-retardant polyolefin. 8. The high heat dissipation, high performance, low voltage power cable according to claims 3 and 4, characterized in that the multi-layer copper single-wire layers of the main conductor and the secondary inner conductor adopt a stranding method with opposite stranding directions of adjacent layers, the stranding diameter ratio of the outermost layer is 17~21, the stranding diameter ratio of the adjacent inner layers increases from 8 to 12 and is not greater than 49; the number of copper single wires in each layer is 4~6 more than that in its adjacent inner layer. 9. The high heat dissipation, high performance, low voltage power cable according to claim 1, wherein the main insulation layer and the secondary inner and outer insulation layers are both made of cross-linked polyethylene, and the eccentricity of the insulation layer is not greater than 10%. 10. The high heat dissipation, high performance, low voltage power cable according to claim 1, characterized in that the rated voltage of the cable is 0.6/1 kV and below, and it is suitable for direct burial, support, cable tray, and laying in environments with drops and tension.