CN211376284U - Medium-voltage power cable for urban distribution network - Google Patents

Abstract

The utility model discloses a medium voltage power cable for urban distribution network, which comprises a cable core, wherein the cable core is formed by twisting three insulation wire cores, a fan-shaped filling strip is filled in the gap of the outer edge of the three insulation wire cores, and a soft bare conductor is arranged in the central gap tangent to the three insulation wire cores; the cable core is wrapped with a non-woven fabric belt, a polyethylene isolation layer is arranged outside the wrapping layer, an armor layer is arranged outside the isolation layer, and a low-smoke halogen-free polyolefin outer sheath is extruded outside the armor layer. The safe and reasonable shielding structure is designed to more effectively connect the capacitance current and the fault current into the ground, shield the magnetic field and the homogenized electric field, avoid the phenomenon of thermal insulation breakdown and finally achieve the purpose of ensuring the insulation electrical performance.

Description

Medium-voltage power cable for urban distribution network

Technical Field

The utility model relates to a wire and cable field specifically indicates a net is joined in marriage with middling pressure power cable in city.

Background

With the rapid development of cities, medium-voltage power cables are largely used for underground power cable lines in urban power supply and distribution networks. When the cable core has current circulation, there is the magnetic linkage on the metallic shield layer, and induced potential will appear at metallic shield layer both ends. The grounding of the metal shielding layer of the medium-voltage power cable can prevent the human body from electric shock, ensure the normal operation of a power system and protect circuits and electrical equipment from being damaged. The conventional medium-voltage power cable adopts a plurality of round monofilaments for compressing and stranding, the compressing degree is small, the contact resistance between conductor monofilaments is large, and the cable is easy to generate heat in the electrifying operation. The insulating layer is inseparable with copper strips shielding contact, because can appear expend with heat and contract with cold's phenomenon, the insulating layer can be flexible together with the copper strips, makes the copper strips fracture easily, and the electric current just can't flow in the ground smoothly to the cable is generating heat the in-process and appears thermal insulation breakdown phenomenon easily, leads to circuit system to break down, has caused huge economic loss for the enterprise.

SUMMERY OF THE UTILITY MODEL

The utility model aims to solve the technical problem that a net is joined in marriage with middling pressure power cable in city is provided, safe reasonable shielding structure design is more effectual inserts electric capacity current and fault current the earth, and shielding magnetic field, homogenization electric field can avoid thermal insulation breakdown phenomenon, finally reach the purpose of guaranteeing insulating electrical property.

In order to achieve the above object, the utility model adopts the following technical scheme: a medium-voltage power cable for a distribution network in a city comprises a cable core, wherein the cable core is formed by twisting three insulating wire cores, a fan-shaped filling strip is filled in a gap at the outer edge of each insulating wire core, and a soft bare conductor is arranged in a central gap tangent to the three insulating wire cores; the cable core is wrapped with a non-woven fabric belt, a polyethylene isolation layer is arranged outside the wrapping layer, an armor layer is arranged outside the isolation layer, and a low-smoke halogen-free polyolefin outer sheath is extruded outside the armor layer.

The improved structure of the cable is characterized in that the insulating wire core is composed of a combined conductor, a semiconductor inner shielding layer wrapped outside the combined conductor, a cross-linked polyethylene insulating layer extruded outside the semiconductor inner shielding layer, a semiconductor outer shielding layer wrapped outside the insulating layer and a metal shielding layer wrapped outside the semiconductor outer shielding layer.

The combined conductor is formed by sequentially compressing a circular oxygen-free copper monofilament in the center and an inner layer, an outer layer and an inner layer outside the circular oxygen-free copper monofilament, and twisting the circular oxygen-free copper monofilament layer and the circular oxygen-free copper monofilament which are concentric.

The inner diameter of the inner ring oxygen-free tile-shaped copper monofilament layer is equal to the diameter of the central circular oxygen-free copper monofilament, and the outer diameter of the inner ring oxygen-free tile-shaped copper monofilament layer is equal to the inner diameter of the middle ring oxygen-free tile-shaped copper monofilament layer; the outer diameter of the ring oxygen-free tile-shaped copper monofilament layer in the middle layer is equal to the inner diameter of the ring oxygen-free tile-shaped copper monofilament layer in the outer layer.

The further improvement, the semiconductor inner shielding layer and the semiconductor outer shielding layer are extruded cross-linked polyolefin semiconductor shielding layers, the flatness of the inner surface and the outer surface of the insulating layer is guaranteed, the surface field intensity can be uniform, and the premature electrical aging of the insulation caused by field intensity concentration is avoided.

The further improvement is that the metal shielding layer is an annealed soft copper strip, the thickness is 0.10-0.12mm, and the lapping overlapping rate is more than 15%.

In a further improvement, the soft bare conductor is formed by stranding a plurality of soft copper monofilaments.

The armor layer is a wrapped double-layer galvanized steel strip, the thickness of the galvanized steel strip is 0.2-0.8mm, and the wrapping gap rate is not more than 50%.

Further improved, the number of the oxygen-free tile-shaped copper monofilaments on the same annular oxygen-free tile-shaped copper monofilament layer is M, and the tile-shaped angle of the cross section of each oxygen-free tile-shaped copper monofilament is 360 degrees/M.

The beneficial effects of the utility model reside in that:

compared with the prior art, a net is joined in marriage in city and is used middling pressure power cable, contact resistance is minimum between the conductor monofilament, can effectively reduce cable operation in-process conductor phenomenon of generating heat, safe reasonable shielding structure design is more effectual inserts electric capacity current and fault current the earth, shielding magnetic field, homogenization electric field can avoid thermal insulation breakdown phenomenon, finally reaches the purpose of guaranteeing insulating electrical property.

Drawings

Fig. 1 is a schematic structural diagram of the present invention.

Detailed Description

As shown in fig. 1, a medium voltage power cable for distribution networks in cities comprises a combined conductor 1, a semiconductor inner shielding layer 2 is wrapped outside the combined conductor, a cross-linked polyethylene insulating layer 3 is extruded outside the semiconductor inner shielding layer, a semiconductor outer shielding layer 4 is wrapped outside the insulating layer, a metal shielding layer 5 is wrapped outside the semiconductor outer shielding layer, the metal shielding layer is an annealed soft copper strip, the thickness is 0.10-0.12mm, and the wrapping overlapping rate is more than 15%, so that an insulating wire core is formed; tightly and tangentially twisting the three insulated wire cores into a cable core, and filling a fan-shaped filling strip 7 in gaps at the outer edges of the three insulated wire cores to ensure the roundness of the cable; a soft bare conductor 6 is arranged at the central gap where the three insulated wire cores are tangent, the soft bare conductor is formed by stranding a plurality of soft copper monofilaments, the metal shielding layer outside the three insulated wire cores is tangent and closely contacted, after the cable runs for a long time, the copper strips are overlapped and lapped at the joint, because the contact surface is oxidized and the copper strips are not tightly contacted after being bent, cooled and deformed by a cable, the joint of the copper strips has larger contact resistance, the resistance of a metal shielding layer is inevitably increased, capacitance current and fault current can be forced to pass through a semi-conductive outer shielding layer, so that the insulation wire core is seriously heated and thermally broken down, the soft bare conductor is arranged to be tangent to and closely contacted with the metal shielding layer outside the three insulated wire cores, so that the effective cross section of shielding is increased, the contact resistance of the shielding layer is reduced, and capacitive current and fault current can be directly and safely led to the ground along the axial direction of the cable;

the non-woven fabric belt 8 is wound outside the cable core, the polyethylene isolation layer 9 is arranged outside the wrapping layer, the cable can expand with heat and contract with cold when being electrified in the use process, the isolation layer can also stretch together with the copper belt, the copper belt is easy to break, and the arrangement reduces the tight contact between the isolation layer and the copper belt, and plays a role in buffering; the isolation layer can isolate oxygen and prevent moisture from entering, so that the internal metal shielding layer element can be protected from being oxidized quickly; the armor layer 10 is arranged outside the isolation layer and is a wrapped double-layer galvanized steel strip, the thickness of the galvanized steel strip is 0.2-0.8mm, the wrapping gap rate is not more than 50%, and the cable can resist mechanical external force and also can block or reduce the influence of eddy current on the interior of the cable; a low-smoke halogen-free polyolefin outer sheath 11 is extruded outside the armor layer;

the combined conductor is formed by twisting a circular oxygen-free copper monofilament 12 at the center and an inner, middle and outer three layers of circular oxygen-free tile-shaped copper monofilament layers 13 which are sequentially pressed outside the circular oxygen-free copper monofilament and are concentric with the circular oxygen-free copper monofilament; each ring oxygen-free tile-shaped copper monofilament layer is formed by combining a plurality of oxygen-free tile-shaped copper monofilaments 14, the inner diameter of the inner ring oxygen-free tile-shaped copper monofilament layer is equal to the diameter of the central circular oxygen-free copper monofilament, and the outer diameter of the inner ring oxygen-free tile-shaped copper monofilament layer is equal to the inner diameter of the middle ring oxygen-free tile-shaped copper monofilament layer; the outer diameter of the ring oxygen-free tile-shaped copper monofilament layer of the middle layer is equal to the inner diameter of the ring oxygen-free tile-shaped copper monofilament layer of the outer layer; the number of the oxygen-free tile-shaped copper monofilaments on the same annular oxygen-free tile-shaped copper monofilament layer is M, and the tile-shaped angle of the cross section of each oxygen-free tile-shaped copper monofilament is 360 degrees/M; the number of the anaerobic tile-shaped copper monofilaments on the inner layer is 6, so that the tile-shaped angle of the cross section of the anaerobic tile-shaped copper monofilaments on the inner layer is 360 degrees/6 degrees and is 60 degrees; the number of the middle oxygen-free tile-shaped copper monofilaments is 6, so that the tile-shaped angle of the cross section of the middle oxygen-free tile-shaped copper monofilaments is 360 degrees/12 degrees and is 30 degrees; the number of the outer oxygen-free tile-shaped copper monofilaments is 18, so that the tile-shaped angle of the cross section of the middle oxygen-free tile-shaped copper monofilament is 360 degrees/18 degrees and is 20 degrees; the axle that the tile type monofilament of every layer used central circular monofilament is the axis of symmetry axle evenly distributed in order to enclose into the ring for seamless between two arbitrary adjacent annuluses in an arbitrary intraformational, the coefficient of stiction is more than 98%, when tile type monofilament is parallel with central circular monofilament, theoretically compresses the coefficient and reaches 100%, thereby guarantees the utility model discloses a seamless between the conductor monofilament has avoided having the contact resistance increase that the space arouses because of there is the monofilament between, has reduced cable conductor heating phenomenon, and electric conductive property is better.

Example 1:

the first step, adopt the conventional stranded conductor apparatus to strand a central oxygen-free copper round monofilament and several oxygen-free copper tile type monofilaments to form, the ring internal diameter that the tile type monofilament of the first layer constitutes equals the diameter of central round monofilament, the ring external diameter that the tile type monofilament constitutes equals the ring internal diameter that adjacent layer tile type monofilament constitutes, make between central round monofilament and the first layer ring shape, between the adjacent ring of arbitrary layer ring seamless, the quantity of the tile type monofilament on the same layer is M, the tile type angle of the cross section of the tile type monofilament is 360/M, the tile type monofilament of each layer regards central round monofilament's axis as the symmetry axis evenly distributed to enclose into the ring, make between arbitrary two adjacent rings in an arbitrary layer seamless, thus guarantee the utility model discloses a conductor monofilament is seamless, has avoided because of having the contact resistance increase that the space arouses between the monofilament, the heating phenomenon of the cable conductor is reduced, and the conductivity is better;

secondly, extruding the semiconductor inner shielding layer, the insulating layer and the semiconductor outer shielding layer simultaneously by using the conventional three-layer co-extrusion crosslinking equipment through a high-temperature high-pressure dry crosslinking process, wherein the eccentricity of the insulating layer is controlled within 8 percent, so that the uniformity of insulation is ensured;

thirdly, lapping a metal shielding layer in a single-layer overlapping lapping mode of an annealed soft copper strip, wherein the thickness of the copper strip is 0.10-0.12mm, and the lapping overlapping rate is more than 15%;

and fourthly, stranding, namely forming a soft bare conductor by a plurality of soft copper monofilaments, wherein a central orifice of stranding equipment in a stranding process is parallel to the central gap at the inner side of the three insulated wire cores and is tangent to the metal shielding layers outside the three insulated wire cores at the same time, so that the soft bare conductor is in close contact with the metal shielding layers, the effective cross section of shielding is increased, the contact resistance of the shielding layers is reduced, and the capacitive current and the fault current can be directly and safely led into the ground along the axial direction of the cable. The single-layer non-woven fabric belt is lapped and wrapped on the outer side of the cable core in a lapping mode while cabling is carried out, the cable can expand with heat and contract with cold when being electrified in the using process, the isolation layer can also stretch together with the copper belt, the copper belt is easy to break, the arrangement reduces the phenomenon that the isolation layer is tightly contacted with the copper belt, and the buffering effect is achieved;

fifthly, extruding a polyethylene isolation layer with the thickness of 1.0-2.0mm, wherein the polyethylene isolation layer can isolate oxygen, prevent moisture from entering and protect the internal metal shielding layer element from being oxidized quickly;

sixthly, uniformly wrapping a double-layer high-strength non-magnetic steel strip on the outer layer of the isolation layer by using a steel strip armoring machine, wherein the wrapping is tight and uniform, the thickness of the steel strip is 0.2-0.8mm, and the wrapping clearance of the steel strip is not more than 50%; the armor layer can resist mechanical external force and also can block or reduce the influence of eddy current on the interior of the cable;

and seventhly, extruding and wrapping the low-smoke halogen-free polyolefin sheath material to form an outer sheath, thereby obtaining the medium-voltage power cable for the urban distribution network.

The utility model discloses the concrete application way is many, and the above-mentioned only is the preferred embodiment of the utility model, should point out, to ordinary skilled person in this technical field, under the prerequisite that does not deviate from the utility model discloses the principle, can also make a plurality of improvements, and these improvements also should be regarded as the utility model discloses a scope of protection.

Claims (9)

1. The utility model provides a net is joined in marriage in city and is used middling pressure power cable which characterized in that: the cable core is formed by twisting three insulated wire cores, a fan-shaped filling strip is filled in a gap at the outer edge of each insulated wire core, and a soft bare conductor is arranged in a central gap tangent to the three insulated wire cores; the cable core is wrapped with a non-woven fabric belt, a polyethylene isolation layer is arranged outside the wrapping layer, an armor layer is arranged outside the isolation layer, and a low-smoke halogen-free polyolefin outer sheath is extruded outside the armor layer.

2. The medium voltage power cable for urban distribution networks according to claim 1, wherein the insulated wire core is composed of a combined conductor, a semiconductor inner shielding layer wrapped outside the combined conductor, a cross-linked polyethylene insulating layer extruded outside the semiconductor inner shielding layer, a semiconductor outer shielding layer wrapped outside the insulating layer, and a metal shielding layer wrapped outside the semiconductor outer shielding layer.

3. The medium voltage power cable for urban distribution networks according to claim 2, wherein the combined conductor is formed by stranding a central circular oxygen-free copper monofilament, an inner, middle and outer three layers of circular oxygen-free tile-shaped copper monofilament layers which are sequentially compressed outside the circular oxygen-free copper monofilament and are concentric with the circular oxygen-free copper monofilament.

4. The medium voltage power cable for urban distribution networks according to claim 3, wherein each ring oxygen-free tile-shaped copper monofilament layer is formed by combining a plurality of oxygen-free tile-shaped copper monofilaments, the inner diameter of the inner ring oxygen-free tile-shaped copper monofilament layer is equal to the diameter of the central ring oxygen-free copper monofilament, and the outer diameter of the inner ring oxygen-free tile-shaped copper monofilament layer is equal to the inner diameter of the middle ring oxygen-free tile-shaped copper monofilament layer; the outer diameter of the ring oxygen-free tile-shaped copper monofilament layer in the middle layer is equal to the inner diameter of the ring oxygen-free tile-shaped copper monofilament layer in the outer layer.

5. The medium voltage power cable for urban distribution networks according to claim 2, wherein the semiconductor inner shielding layer and the semiconductor outer shielding layer are extruded cross-linked polyolefin semiconductor shielding layers.

6. The medium voltage power cable for urban distribution networks according to claim 2, wherein the metal shielding layer is an annealed soft copper tape, the thickness is 0.10-0.12mm, and the lapping overlapping rate is greater than 15%.

7. The medium voltage power cable for urban distribution networks according to claim 1, wherein said soft bare conductor is stranded from a plurality of soft copper monofilaments.

8. The medium voltage power cable for urban distribution networks according to claim 1, wherein the armor layer is a wrapped double-layer galvanized steel strip, the thickness of the galvanized steel strip is 0.2-0.8mm, and the wrapping gap rate is not more than 50%.

9. The medium voltage power cable for urban distribution networks according to claim 4, wherein the number of oxygen-free tile-shaped copper monofilaments on each annular oxygen-free tile-shaped copper monofilament layer is M, and the tile-shaped angle of the cross section of each oxygen-free tile-shaped copper monofilament is 360 °/M.

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