Overhead binding medium-voltage cable and preparation method thereof

Abstract

The invention relates to the technical field of wires and cables, and particularly provides an overhead binding medium-voltage cable and a preparation method thereof.The overhead binding medium-voltage cable comprises three cable core units twisted together, and each cable core unit comprises a conductor structure, an insulation structure, a metal shielding layer and a waterproof layer; the preparation method comprises the steps of conductor stranding, insulation co-extrusion and tooth groove forming, electrostatic coating of water-blocking powder, longitudinal wrapping of the metal shielding layer, extrusion and cooling type hot stamping of the waterproof layer, and three-core stranding and mechanical constraint. According to the invention, the outer surface of the insulation shielding layer is provided with the tooth socket biscuits to be filled with the semi-conductive water-blocking powder, so that a first water-blocking interface is formed; a second waterproof defense line can be formed by fusing and bonding the metal shielding layer and the waterproof layer; the conductor structure adopts a multi-layer twisting and chamfering design, so that permeation channels of water along gaps of the conductor can be reduced, multiple longitudinal waterproof barriers act synergistically, the water resistance of the cable can be remarkably improved, and the service life of the cable in a humid environment can be prolonged.

Description

Technical Field

[0001] This invention relates to the field of wire and cable technology, specifically to an overhead bundled medium-voltage cable and its preparation method. Background Technology

[0002] With the acceleration of my country's industrialization and urbanization, and the deepening of energy structure transformation, the demand for long-distance, large-capacity power transmission continues to grow, and power grid upgrading and large-scale grid connection projects for new energy sources are increasing. Against this backdrop, overhead insulated cables have been widely used in urban and rural power distribution networks and new energy collection lines due to their advantages such as simple installation, relatively low cost, and ease of maintenance.

[0003] Due to the inherent sag in overhead applications, traditional overhead cables are prone to developing "water trees" or "electrical trees" during long-term operation, especially in humid environments, due to longitudinal water seepage. "Water trees" refer to microscopic, dendritic water-filled channels formed within the cable insulation layer under the combined influence of moisture and an electric field. These channels are not true conductive pathways but rather a network of tiny water pores, cracks, or impurities. "Electrical trees," on the other hand, refer to tree-like, permanent conductive breakdown channels within the cable insulation layer, directly caused by extremely high localized electric field strength. This represents the final stage and direct manifestation of cable insulation failure. The formation of "water trees" or "electrical trees" leads to insulation aging and breakdown, severely impacting cable lifespan. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide an overhead bundled medium-voltage cable to solve the problem that overhead cables are prone to insulation failure during long-term operation, especially in humid environments.

[0005] To achieve the above and other related objectives, the present invention provides an overhead bundled medium-voltage cable, comprising three cable core units twisted together, wherein each cable core unit comprises, from the inside out, a conductor structure, an insulation structure, a metal shielding layer and a waterproof layer;

[0006] The insulating structure includes a conductor shielding layer, an insulating layer, and an insulating shielding layer that are co-extruded and coated on the outside of the conductor structure in sequence. The outer surface of the insulating shielding layer is provided with a plurality of grooves along the circumferential direction, and a semiconductor water-blocking powder layer is coated in the grooves. The metal shielding layer is coated on the outside of the insulating shielding layer.

[0007] In one embodiment of the present invention, the conductor structure includes a circular aluminum conductor core, an inner conductor layer, and an outer conductor layer. The inner conductor layer is made of multiple strands of monofilaments twisted together on the outside of the circular aluminum conductor core, and the outer conductor layer is made of multiple strands of monofilaments twisted together on the outside of the inner conductor layer.

[0008] In one embodiment of the present invention, the edges of the monofilaments constituting the inner layer of the conductor are provided with small chamfers, and the edges of the monofilaments constituting the outer layer of the conductor are provided with large chamfers.

[0009] In one embodiment of the present invention, the inner surface of the metal shielding layer is provided with embossed patterns and the outer surface is coated with an adhesive layer. The metal shielding layer engages with the grooves of the insulating shielding layer through the embossed patterns, and the metal shielding layer is bonded to the waterproof layer through the adhesive layer.

[0010] In one embodiment of the present invention, the metal shielding layer is formed by wrapping a metal strip material along the axial direction of the insulating shielding layer to form a tubular functional layer.

[0011] This invention provides a method for manufacturing an overhead bundled medium-voltage cable, comprising the following steps: S1. Conductor stranding: To prepare a circular aluminum conductor core, single wires with small chamfered edges on the cross-section are stranded on the outside of the circular aluminum conductor core to form the conductor inner layer; single wires with large chamfered edges on the cross-section are stranded on the outside of the conductor inner layer to form the conductor outer layer. S2. Insulation Co-extrusion and Groove Forming: Outside the conductor structure, a conductor shielding layer, an insulation layer, and an insulation shielding layer are formed sequentially through a co-extrusion process; and when forming the insulation shielding layer, a serrated die is used to form several circumferentially distributed grooves on the outer surface of the extruded insulation shielding layer. S3. Electrostatic coating water-blocking powder: Semiconductor water-blocking powder is coated onto the surface and grooves of the insulating shielding layer using an electrostatic coating process to form a semiconductor water-blocking powder layer. S4. Longitudinal wrapping of metal shielding layer: Provide a metal strip material with rolled patterns on the inner surface and an adhesive layer on the outer surface; use a longitudinal wrapping mold with positioning notches to longitudinally wrap the metal strip material along the axial direction of the insulating shielding layer, so that the rolled pattern surface and the powder layer in the grooves engage and contact to form a tubular metal shielding layer. S5. Extrusion and Cooling Heat Printing of Waterproof Layer: Molten polyolefin material is extruded over the metal shielding layer to form a waterproof layer. The heat from the extrusion melts the adhesive layer to achieve bonding with the waterproof layer. At the same time, a heat printing device with indirect cooling between rollers is used to continuously and stably heat print markings on the surface of the waterproof layer. S6. Three-core stranding and mechanical constraint: The three cable core units obtained in steps S1-S5 are stranded together without adding filler or wrapping tape during the stranding process; a tensioning ring is applied at the preset stranding length position using a fixed-length throwing and punching process to form a radial constraint on the stranded body, and finally the overhead bundled medium-voltage cable is obtained.

[0012] In one embodiment of the present invention, in step S2, the tooth profile design of the extrusion die is determined by simulation verification based on the heat shrinkage ratio of the insulating material to ensure that the tooth groove depth accumulates water-blocking powder.

[0013] In one embodiment of the present invention, in step S3, the electrostatic coating process controls the electrostatic voltage and powder delivery rate parameters to allow the electrostatically charged semiconductor water-blocking powder to be adsorbed into the tooth groove.

[0014] As described above, the overhead bundled medium-voltage cable and its preparation method of the present invention have the following beneficial effects: 1. This invention forms a first water-blocking interface by setting circumferential grooves on the outer surface of the insulating shielding layer and uniformly filling it with semi-conductive resistive water powder using an electrostatic coating process. The semi-conductive resistive water powder expands upon contact with water, effectively blocking the interface gaps. Furthermore, the inner surface of the metal shielding layer is embossed, allowing it to interlock with the water-blocking powder layer within the grooves, effectively enhancing the interface sealing. The adhesive layer coated on the outer surface of the metal shielding layer melts and bonds during the extrusion of the waterproof layer, achieving a chemical seal between the metal shielding layer and the waterproof layer, forming a second line of defense against water damage. The conductor structure employs a multi-layer stranded and chamfered design, reducing the channels for water penetration along conductor gaps. By constructing these multiple longitudinal waterproof barriers in a synergistic effect, this invention significantly improves the cable's water resistance, significantly inhibits the formation of "water trees" and "electrical trees," and extends the cable's service life in humid environments.

[0015] 2. The metal shielding layer adopts a longitudinal wrapping molding process, which can form a continuous, low-resistance equipotential shielding body, effectively balancing the electric field on the cable surface, eliminating the risk of electric shock, and improving electromagnetic compatibility; in addition, the metal shielding layer can ensure the continuity and stability of the electrical connection of the shielding layer by the interlocking of the grooves of the insulating shielding layer through the rolling embossing.

[0016] 3. The manufacturing process of this invention, specifically the toothed groove forming, is based on material thermal shrinkage ratio simulation design, ensuring that the groove depth can both accumulate water-blocking powder and avoid electric field concentration. The electrostatic coating process can overcome the influence of gravity, achieving uniform adhesion of water-blocking powder on the cable circumference, especially in the lower toothed groove. The longitudinal wrapping mold has a positioning notch, solving the problem of loose longitudinal wrapping joints of double-sided tapes and improving the integrity of the shielding layer. In this manufacturing process, the overhead bundled medium-voltage cable is manufactured using a mechanical constraint method of three-core stranding and fixed-length throwing and tightening rings. The overall structure is compact, effectively preventing structural loosening due to internal water accumulation or temperature changes. In this solution, the tightening ring can provide continuous radial constraint force, ensuring the structural stability of the cable under overhead suspension, wind vibration, and temperature changes, thereby improving the reliability of overhead applications. The overhead bundled medium-voltage cable formed by this manufacturing process has a compact overall structure, is lightweight, and is easy to install. It is suitable for medium-voltage overhead applications such as urban and rural power distribution networks and new energy collection lines, and has good environmental adaptability and long-term operational reliability. Attached Figure Description

[0017] Figure 1 The diagram shown is a three-dimensional structural schematic of the overhead bundled medium-voltage cable disclosed in this invention.

[0018] Figure 2 The diagram shown is an enlarged structural schematic of a single cable core unit in an overhead bundled medium-voltage cable disclosed in this invention.

[0019] Figure 3 The diagram shown is a cross-sectional structural schematic of the overhead bundled medium-voltage cable disclosed in this invention.

[0020] Figure 4 The diagram shows a schematic of the preparation process of the overhead bundled medium-voltage cable preparation method disclosed in this invention.

[0021] Component designation explanation Cable core unit 1; conductor structure 2; circular aluminum conductor inner core 21; conductor inner layer 22; conductor outer layer 23; insulation structure 3; conductor shielding layer 31; insulation layer 32; insulation shielding layer 33; toothed groove 331; metal shielding layer 4; embossed 41; adhesive layer 42; waterproof layer 5; semiconductor water-blocking powder layer 6. Detailed Implementation

[0022] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0023] Please see Figures 1 to 3 It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, provided they do not affect the effectiveness or purpose of the invention, should fall within the scope of the disclosed technical content. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0024] Example 1, please refer to Figures 1-3This embodiment provides an overhead bundled medium-voltage cable, including three cable core units 1 twisted together. Each cable core unit 1 includes a conductor structure 2, an insulation structure 3, a metal shielding layer 4, and a waterproof layer 5 arranged sequentially from the inside out. The metal shielding layer 4 is formed by wrapping a metal strip material along the axial direction of the insulation shielding layer 33 to form a tubular or near-tubular functional layer. The metal shielding layer adopts a longitudinal wrapping forming process, which can form a continuous, low-resistance equipotential shield, effectively balancing the electric field on the cable surface, eliminating the risk of electric shock, and improving electromagnetic compatibility. Furthermore, the metal shielding layer can ensure the continuity and stability of the electrical connection of the shielding layer by the interlocking of the grooves of the insulation shielding layer through the knurling.

[0025] The conductor structure 2 includes a circular aluminum conductor core 21, an inner conductor layer 22, and an outer conductor layer 23. The inner conductor layer 22 is made of multiple strands of monofilaments twisted together on the outside of the circular aluminum conductor core 21, and the edges of the monofilaments forming the inner conductor layer 22 are provided with small chamfers. The outer conductor layer 23 is made of multiple strands of monofilaments twisted together on the outside of the inner conductor layer 22, and the edges of the monofilaments forming the outer conductor layer 24 are provided with large chamfers. The conductor structure 2 adopts a multi-layer twisting and chamfering design, which can reduce the seepage channels of water along the conductor gaps and form a third anti-seepage structure.

[0026] The insulating structure 3 includes a conductor shielding layer 31, an insulating layer 32, and an insulating shielding layer 33, which are co-extruded and coated on the outside of the conductor structure 2 in sequence. The outer surface of the insulating shielding layer 33 has a plurality of circumferential grooves 331, and a semiconductor water-blocking powder layer 6 is coated in the grooves 331. The metal shielding layer 4 covers the outside of the insulating shielding layer 33. This invention forms a first water-blocking interface by providing circumferential grooves 331 on the outer surface of the insulating shielding layer 33 and uniformly filling it with semiconducting resistive water-blocking powder using an electrostatic coating process. The semiconducting resistive water-blocking powder expands upon contact with water, effectively blocking the interface gaps.

[0027] The inner surface of the metal shielding layer 4 is provided with embossed patterns 41, and the outer surface is coated with an adhesive layer 42. The metal shielding layer 4 engages with the grooves 331 of the insulating shielding layer 33 through the embossed patterns 41, and the metal shielding layer 4 is bonded to the waterproof layer 5 through the adhesive layer 42. The embossed patterns 41 on the inner surface of the metal shielding layer 4 and the water-blocking powder layer 6 in the grooves 331 through the embossed patterns 41 effectively enhance the interface sealing. The adhesive layer 42 coated on the outer surface of the metal shielding layer 4 can melt and bond during the extrusion of the waterproof layer 5, achieving a chemical seal between the metal shielding layer 4 and the waterproof layer 5, forming a second line of waterproof defense.

[0028] This invention forms a multi-layered longitudinal waterproof barrier by constructing a first water-blocking interface, a second waterproof defense line, and reducing the penetration channels of water along conductor gaps. This significantly improves the water resistance of cables, significantly inhibits the generation of "water trees" and "electrical trees," and extends the service life of cables in humid environments.

[0029] Example 2, please refer to Figure 4 This embodiment provides a method for preparing an overhead bundled medium-voltage cable, used to manufacture the overhead bundled medium-voltage cable described in Embodiment 1, comprising the following steps: S1. Conductor stranding: Prepare a circular aluminum conductor core 21, and use a single wire with a small chamfer on the edge of the cross section to strand on the outside of the circular aluminum conductor core 21 to form a conductor inner layer 22; use a single wire with a large chamfer on the edge of the cross section to strand on the outside of the conductor inner layer 22 to form a conductor outer layer 23.

[0030] S2. Insulation Co-extrusion and Groove Forming: Outside the conductor structure 2, a conductor shielding layer 31, an insulation layer 32, and an insulation shielding layer 33 are formed sequentially through a co-extrusion process; and when forming the insulation shielding layer 33, a serrated die is used to form a number of circumferentially distributed grooves 331 on the outer surface of the extruded insulation shielding layer 33; the tooth shape design of the extrusion die is determined by simulation verification based on the heat shrinkage ratio of the insulating material to ensure that the groove 331 depth accumulates water-blocking powder, and the groove forming is based on the material heat shrinkage ratio simulation design to ensure that the groove depth can both accumulate water-blocking powder and avoid electric field concentration.

[0031] S3. Electrostatic Coating of Water-Blocking Powder: Semiconductor water-blocking powder is coated onto the surface of the insulating shielding layer 33 and the groove 331 using an electrostatic coating process to form a semiconductor water-blocking powder layer 6. The electrostatic coating process controls the electrostatic voltage and powder delivery rate parameters to allow the electrostatically charged semiconductor water-blocking powder to be adsorbed into the groove 331. The electrostatic coating process can overcome the influence of gravity and achieve uniform adhesion of the water-blocking powder on the circumference of the cable, especially in the lower groove.

[0032] S4. Longitudinal wrapping of metal shielding layer: Provide a metal strip material with rolled patterns 41 on the inner surface and an adhesive layer 42 on the outer surface; use a longitudinal wrapping mold with a positioning notch to longitudinally wrap the metal strip material along the axial direction of the insulating shielding layer 33, so that the rolled pattern 41 surface and the powder layer in the groove 331 engage and contact, forming a tubular metal shielding layer 4; the longitudinal wrapping mold is set with a positioning notch to solve the problem of loose joints in the longitudinal wrapping of double-sided strips and improve the integrity of the shielding layer.

[0033] S5. Extrusion and Cooling Heat Printing of Waterproof Layer: Molten polyolefin material is extruded over the metal shielding layer 4 to form a waterproof layer 5. The heat of extrusion melts the adhesive layer 42 to achieve bonding with the waterproof layer 5. At the same time, a heat printing device with indirect cooling is used to continuously and stably heat print markings on the surface of the waterproof layer 5. S6. Three-core stranding and mechanical constraint: The three cable core units 1 obtained in steps S1-S5 are stranded together without adding filler or wrapping tape during the stranding process; a tension ring is applied at a preset stranding length using a fixed-length throwing and punching process to form radial constraint on the stranded body, ultimately producing the overhead bundled medium-voltage cable; This manufacturing process uses three-core stranding and a fixed-length throwing and punching tension ring as a mechanical constraint method to prepare the overhead bundled medium-voltage cable, resulting in a compact overall structure that effectively avoids loosening of the knots due to internal water accumulation or temperature changes; the tension ring can provide continuous radial constraint force, ensuring the structural stability of the cable under overhead suspension, wind vibration, and temperature changes, thereby improving the reliability of overhead applications.

[0034] The overhead bundled medium-voltage cable formed by this manufacturing process has a compact overall structure, is lightweight, and is easy to install. It is suitable for medium-voltage overhead applications such as urban and rural power distribution networks and new energy power collection lines, and has good environmental adaptability and long-term operational reliability.

[0035] In summary, this invention effectively suppresses water treeing and electrical treeing by constructing a multi-layered synergistic water-blocking system, significantly extending cable life. The use of a longitudinally wrapped metal shielding layer 4 achieves continuous electric field balance and electromagnetic compatibility. The innovative use of a mechanically constrained three-core stranded structure with a tightening ring in the manufacturing process enhances structural stability and resistance to loosening in overhead environments. Combined with precision-controlled toothed groove forming, electrostatic coating, and a dedicated longitudinal wrapping mold, the invention ensures consistent product performance and high production efficiency, ultimately resulting in a cable solution suitable for medium-voltage overhead applications that combines high reliability, long lifespan, and good safety. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and possesses high industrial application value.

[0036] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. An aerial bundled medium voltage cable, characterized in that, It comprises three cable core units (1) twisted together, and each cable core unit (1) comprises, from inside to outside, a conductor structure (2), an insulation structure (3), a metal shielding layer (4) and a waterproof layer (5); The insulation structure (3) comprises a conductor shielding layer (31), an insulation layer (32) and an insulation shielding layer (33) which are successively co-extruded on the outside of the conductor structure (2), and the outer surface of the insulation shielding layer (33) is circumferentially provided with a plurality of tooth grooves (331), and a semiconductor water-blocking powder layer (6) is coated in the tooth grooves (331); the metal shielding layer (4) is coated on the outside of the insulation shielding layer (33).

2. An overhead bundled medium voltage cable according to claim 1, characterized in that: The conductor structure (2) comprises a circular aluminum conductor inner core (21), a conductor inner layer (22) and a conductor outer layer (23), the conductor inner layer (22) is twisted outside the circular aluminum conductor inner core (21) by a plurality of monofilaments, and the conductor outer layer (23) is twisted outside the conductor inner layer (22) by a plurality of monofilaments.

3. An overhead bundled medium voltage cable according to claim 2, characterized in that: The edges of the monofilaments constituting the conductor inner layer (22) are provided with small chamfers, and the edges of the monofilaments constituting the conductor outer layer (24) are provided with large chamfers.

4. An overhead bundled medium voltage cable according to claim 1, characterized in that: The inner surface of the metal shielding layer (4) is provided with a rolling pattern (41), and the outer surface is coated with a glue layer (42), the metal shielding layer (4) is engaged with the tooth grooves (331) of the insulation shielding layer (33) through the rolling pattern (41), and the metal shielding layer (4) is bonded with the waterproof layer (5) through the glue layer (42).

5. An overhead bundled medium voltage cable according to claim 1, characterized in that: The metal shielding layer (4) is formed into a tubular functional layer by wrapping a metal strip material along the axial direction of the insulation shielding layer (33).

6. A method of preparing an aerial bundled medium voltage cable, characterized in that, The method for manufacturing the overhead bundled medium voltage cable according to any one of claims 1-5 comprises the following steps: S1, conductor twisting: preparing a circular aluminum conductor inner core (21), twisting a conductor inner layer (22) outside the circular aluminum conductor inner core (21) by monofilaments with small chamfers on the cross-sectional edges, and twisting a conductor outer layer (23) outside the conductor inner layer (22) by monofilaments with large chamfers on the cross-sectional edges; S2, insulation co-extrusion and tooth groove forming: forming a conductor shielding layer (31), an insulation layer (32) and an insulation shielding layer (33) outside the conductor structure (2) by a co-extrusion process, and forming a plurality of circumferentially arranged tooth grooves (331) on the outer surface of the insulation shielding layer (33) by using a mold with sawtooth when the insulation shielding layer (33) is formed; S3, electrostatic coating of water-blocking powder: coating a semiconductor water-blocking powder in the surface of the insulation shielding layer (33) and the tooth grooves (331) by an electrostatic coating process to form a semiconductor water-blocking powder layer (6); S4, longitudinal wrapping of the metal shielding layer: providing a metal strip material with a rolling pattern (41) on the inner surface and a glue layer (42) coated on the outer surface; using a longitudinal wrapping mold with a positioning gap, longitudinally wrapping the metal strip material along the axial direction of the insulation shielding layer (33) to make the rolling pattern (41) surface engage with the powder layer in the tooth grooves (331), and forming a tubular metal shielding layer (4); S5, extrusion of waterproof layer and cooling hot stamping: extruding molten polyolefin material outside the metal shielding layer (4) to form a waterproof layer (5), and the extrusion heat melts the glue layer (42) to achieve adhesion with the waterproof layer (5); at the same time, a hot stamping device with indirect cooling between the wheels is used to continuously and stably hot stamp the surface of the waterproof layer (5); S6, three-core stranding and mechanical constraint: three cable core units (1) prepared by steps S1-S5 are stranded, and no filler or wrapping tight belt is added during stranding; a fixed-length throwing process is used to apply a tightening ring at a predetermined stranding length position to form radial constraint on the stranded body, and finally the overhead bundled medium-voltage cable is prepared.

7. A process for the preparation of overhead bundled medium voltage cables according to claim 6, characterized in that: In step S2, the tooth profile design of the extrusion die is simulated and verified based on the thermal shrinkage ratio of the insulating material to ensure that the tooth groove (331) depth accumulates water-blocking powder.

8. A method of preparing an overhead bundled medium voltage cable according to claim 6, characterized in that: In step S3, the electrostatic coating process controls the electrostatic voltage and powder delivery rate parameters, so that the electrostatically charged semiconductor water-blocking powder is adsorbed to the inside of the tooth groove (331).

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