Special high-voltage cable suitable for high-drop environment

Abstract

This utility model belongs to the field of cable technology and provides a special high-voltage cable suitable for high-drop environments. From the inside out, it comprises: a conductor, a conductor shielding layer, a cross-linked polyethylene insulation layer, an insulation shielding layer, a semi-conductive buffer water-blocking tape, a flat aluminum sheath, a semi-conductive butyl buffer tape, a stainless steel wire armor layer, a stainless steel strip, a water-blocking binding tape, a high flame-retardant polyethylene sheath, and a co-extruded semi-conductive PE layer. The stainless steel wire armor layer is composed of stainless steel wires with a diameter of 3.0±0.03mm and a wire pitch ratio of 20–23. The stainless steel strip is wound around the stainless steel wire armor layer in a reverse wrapping manner, with a wrapping gap of 60–80mm. Compared with existing technologies, this utility model significantly improves the overall tensile strength of the cable by incorporating a stainless steel wire armor layer composed of stainless steel wires with a diameter of 3.0±0.03mm and a pitch ratio of 20–23 in the cable structure. This effectively withstands axial tension in high-drop laying environments and prevents the cable from elongating, deforming, or breaking due to its own weight.

Description

Technical Field

[0001] This utility model belongs to the field of cable technology, specifically relating to a special high-voltage cable suitable for environments with high elevation differences. Background Technology

[0002] In large hydropower stations, there are often geographical drops of hundreds of meters. Power cables need to be laid under vertical or steep slope conditions. The resulting continuous axial tension poses a severe challenge to the mechanical strength and structural stability of the cables.

[0003] Currently, high-voltage power cables widely used at voltage levels of 110kV, 220kV, and 500kV typically employ cross-linked polyethylene (XLPE) as the main insulation layer, combined with a flat aluminum sheath or a corrugated aluminum sheath for metallic shielding and radial water-blocking structure. While these cables meet the electrical insulation requirements for high-voltage operation, they exhibit numerous structural defects in high-drop operating environments.

[0004] Specifically, the aluminum sheath of traditional cables has low tensile strength, making it prone to elongation, deformation, and even cracking under its own weight and long-term tension. This leads to stress damage to the insulation layer and affects the safe operation of the cable. Furthermore, conventional structures often use asphalt or hot melt adhesive as a buffer layer, which, while providing some corrosion protection, cannot achieve equipotential bonding between the aluminum sheath and the outer armor layer, making it susceptible to electrochemical corrosion in humid environments. Simultaneously, the outer sheath is typically made of 4.5mm or 5.0mm thick polyethylene material, offering limited mechanical protection. In complex laying environments such as those with rocks or gravel, it is easily scratched or damaged, allowing moisture intrusion and reducing insulation reliability.

[0005] Although existing technologies have attempted to introduce steel wire armor to improve tensile strength, if the armor structure is not designed properly (such as excessively large wire diameter or mismatched pitch ratio), it will lead to increased cable rigidity, decreased bending performance, which is not conducive to on-site laying and may cause local stress concentration.

[0006] In summary, existing high-voltage cables suffer from insufficient tensile strength, high risk of electrochemical corrosion, and susceptibility to damage to the outer sheath under conditions of high elevation drop, steep slope, and complex geological formations. Therefore, there is an urgent need for a special high-voltage cable with optimized structure, high tensile strength, corrosion resistance, and high mechanical protection to meet the long-term safe operation requirements under these special working conditions. Utility Model Content

[0007] The technical problem to be solved by this utility model is to provide a special high-voltage cable suitable for high-altitude environments, based on the current state of the existing technology.

[0008] The technical solution adopted by this utility model to solve the above-mentioned technical problems is as follows: a special high-voltage cable suitable for high drop environments is proposed, which includes, from the inside out: conductor, conductor shielding layer, cross-linked polyethylene insulation layer, insulation shielding layer, semi-conductive buffer water-blocking tape, flat aluminum sheath, semi-conductive butyl buffer tape, stainless steel wire armor layer, stainless steel tape, water-blocking binding tape, high flame-retardant polyethylene sheath and co-extruded semi-conductive PE layer.

[0009] The stainless steel wire armor layer is composed of stainless steel wires with a diameter of 3.0±0.03mm and a wire pitch ratio of 20–23 times.

[0010] The stainless steel strip is wound around the outside of the stainless steel wire armor layer in a reverse wrapping manner, with a wrapping gap of 60–80 mm.

[0011] The average thickness of the high flame-retardant polyethylene sheath is not less than 6.5 mm.

[0012] In the aforementioned special high-voltage cable suitable for high-drop environments, the semi-conductive butyl buffer tape has a thickness of 0.5 mm, a width of 100 mm, and a wrapping overlap of 10–20 mm.

[0013] In the aforementioned special high-voltage cable suitable for high-drop environments, the water-blocking binding tape has a thickness of 0.3mm, a width of 100mm, and an overlap of 20–30mm.

[0014] In the aforementioned special high-voltage cable suitable for high-altitude environments, the stainless steel strip has a thickness of 0.5±0.02mm and a width of 60mm.

[0015] In the aforementioned special high-voltage cable suitable for high-drop environments, the semi-conductive butyl buffer tape is used to ensure that the flat aluminum sheath and the outer stainless steel wire armor layer are at the same potential.

[0016] In the aforementioned special high-voltage cable suitable for high-drop environments, the semi-conductive PE layer is used for online detection of the integrity of the outer sheath.

[0017] In the aforementioned special high-voltage cable suitable for high-drop environments, both the stainless steel wire armor layer and the stainless steel strip are made of 304 stainless steel.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) By setting a stainless steel wire armor layer with a diameter of 3.0±0.03mm and a pitch ratio of 20–23 in the cable structure, the overall tensile strength of the cable is significantly improved, which can effectively withstand the axial tension in the high drop laying environment and prevent the cable from elongating, deforming or breaking due to its own weight. At the same time, the armor layer is tightened and fixed by using stainless steel strips with reverse wrapping and a gap of 60–80mm to prevent the steel wires from loosening and jumping during operation, which enhances the stability of the armor structure. The outer layer is set with a high flame-retardant polyethylene sheath with an average thickness of not less than 6.5mm, which not only improves the mechanical protection capability of the cable, making it less likely to be damaged when laid in complex terrains such as rocks and gravel, but also has excellent flame-retardant properties, meeting the fire protection requirements of high safety level places.

[0020] (2) The thickness of the water-blocking binding tape is 0.3mm, the width is 100mm, and the overlap is 20-30mm. This structural design achieves efficient longitudinal water blocking function. The overlap width is controlled at 20-30mm to ensure a reliable seal between adjacent tape layers, effectively preventing moisture from penetrating along the cable axis and preventing insulation from deteriorating due to moisture. The 0.3mm thickness ensures flexibility while providing sufficient mechanical strength, making it less prone to breakage during subsequent processing.

[0021] (3) The thickness of the stainless steel strip is 0.5±0.02mm and the width is 60mm. This size design takes into account both mechanical strength and wrapping processability: the thickness of 0.5mm is sufficient to provide enough rigidity and resistance to deformation, ensuring effective restraint of the stainless steel wire armor layer during reverse wrapping; the tolerance control of ±0.02mm ensures material uniformity and wrapping stability; the width of 60mm is moderate, which can cover enough armor surface and facilitates flat wrapping on the surface of cables with large curvature, avoiding wrinkles or curling edges. Attached Figure Description

[0022] Figure 1 This is a cross-sectional view of a special high-voltage cable suitable for high-altitude environments.

[0023] In the diagram, 1 is the conductor; 2 is the conductor shielding layer; 3 is the cross-linked polyethylene insulation layer; 4 is the insulation shielding layer; 5 is the semi-conductive buffer water-blocking tape; 6 is the flat aluminum sheath; 7 is the semi-conductive butyl buffer tape; 8 is the stainless steel wire armor layer; 9 is the stainless steel strip; 10 is the water-blocking binding tape; 11 is the high flame-retardant polyethylene sheath; and 12 is the semi-conductive PE layer. Detailed Implementation

[0024] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0025] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in this utility model embodiment are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0026] like Figure 1 As shown, this technical solution proposes a special high-voltage cable suitable for high-drop environments. Its structure, from the inside out, includes: a conductor, a conductor shielding layer, a cross-linked polyethylene insulation layer, an insulation shielding layer, a semi-conductive buffer water-blocking tape, a flat aluminum sheath, a semi-conductive butyl buffer tape, a stainless steel wire armor layer, a stainless steel strip, a water-blocking binding tape, a high flame-retardant polyethylene sheath, and a co-extruded semi-conductive PE layer. The stainless steel wire armor layer is composed of spirally wound stainless steel wires with a diameter of 3.0±0.03mm, with a wire pitch ratio controlled between 20 and 23. The stainless steel strip is wound around the armor layer in a reverse wrapping manner, maintaining a gap of 60–80mm between adjacent strips. The average thickness of the high flame-retardant polyethylene sheath is not less than 6.5mm, ensuring the reliability of the outer protection layer.

[0027] The stainless steel wire armor layer uses steel wire with a diameter of 3.0±0.03mm and controls the pitch ratio to 20–23 times. This ensures sufficient tensile strength to withstand the axial tension generated by high drop laying, while also taking into account the cable's flexibility, making it easy to bend and lay in complex terrain.

[0028] Stainless steel wire is wound in a spiral around the outer layer of the cable. When subjected to tensile or bending loads, it generates axial tension and radial outward "expansion force" (similar to the outward expansion of a spring when stretched). Without effective restraint, this can easily lead to increased gaps between the steel wires, "strand skipping" (detachment from its original position), loosening of the armor layer, uneven stress and cracking of the outer sheath, and even deformation of the entire cable structure.

[0029] To address this, this solution incorporates a reverse-wrapped stainless steel strip around the stainless steel wire armor layer. This strip's winding direction is opposite to that of the wire armor, forming a "cross-locking" structure that effectively inhibits axial slippage and radial expansion of the wire. A 60-80mm gap is maintained during the wrapping of the stainless steel strip, with non-continuous overlap, ensuring effective tightening while preventing excessive cable stiffness and maintaining good bending performance. Both the stainless steel strip and the wire armor layer are made of 304 stainless steel, ensuring consistent material composition and preventing electrochemical corrosion caused by dissimilar metal contact. The strip also possesses high strength and excellent corrosion resistance.

[0030] The reverse-wrapped stainless steel strip significantly enhances the overall stability of the armor structure, effectively preventing the steel wires from loosening and shifting during transportation, laying, and long-term operation, and improving the structural reliability of the cable under high tensile conditions.

[0031] In this design, the high flame-retardant polyethylene sheath serves as the outermost layer of the cable. It not only possesses flame-retardant properties but also integrates mechanical protection, fire safety, environmental tolerance, and long-term reliability. When the cable is heated due to overload, short circuit, or external fire source, this sheath can slow down the combustion rate, reduce the release of toxic fumes, and effectively prevent the flame from spreading along the cable, meeting the requirements of flame-retardant standards such as IEC 60332.

[0032] The average thickness of the sheath is not less than 6.5mm, significantly thicker than that of conventional cables (usually 4.5mm or 5.0mm). This thickened design significantly improves resistance to external damage, effectively resisting scratches from rocks and gravel piles, as well as impacts from construction machinery. It also prevents damage caused by friction or falls during high-altitude laying, thus protecting the internal structure and extending the cable's service life.

[0033] Furthermore, to enhance the electrochemical stability between the aluminum sheath and the outer metal layer, the cable in this design has a semi-conductive butyl buffer strip outside the flat aluminum sheath, with a thickness of 0.5 mm and a width of 100 mm. During the spiral wrapping process, the overlap width between adjacent strips is controlled to be 10–20 mm.

[0034] These dimensions are optimized to ensure a continuous, seamless coverage of the aluminum sheath surface with the buffer strip, preventing uneven potential due to exposed areas, while avoiding material waste or increased structural thickness caused by excessive overlap. The 0.5mm thickness provides excellent elasticity and cushioning, absorbing stress during cable bending or vibration and preventing sheath cracking.

[0035] This buffer strip structure plays a crucial role in actual operation. Its semi-conductive properties maintain the flat aluminum sheath and the outer stainless steel wire armor layer at the same potential, fundamentally eliminating the risk of electrochemical corrosion caused by the potential difference between the two metals. Especially in humid, groundwater-rich, or salt spray environments, this design significantly extends the service life of the metal sheath, preventing moisture intrusion and insulation performance degradation due to corrosion perforation. Simultaneously, the butyl rubber material itself possesses excellent sealing and aging resistance, further enhancing the corrosion protection capabilities of the aluminum sheath and improving the long-term operational reliability of the cable in harsh environments.

[0036] To achieve longitudinal water-blocking functionality and further secure the armor layer, a water-blocking binding tape with a thickness of 0.3 mm and a width of 100 mm is incorporated into the structure. During the wrapping process, the overlap width is controlled at 20–30 mm. This design ensures that the tape forms a fully overlapping, sealed structure during spiral winding, effectively preventing moisture penetration along the cable's axial direction and protecting the insulation from moisture degradation. The 0.3 mm thickness provides sufficient mechanical strength while ensuring flexibility and ease of installation, making it less prone to breakage during subsequent extrusion processes.

[0037] This water-blocking binding tape not only possesses excellent water-blocking performance but also plays a supporting role in structural fastening. Its tightly overlapping wrapping method creates uniform compression force on the inner stainless steel wire armor layer, preventing loosening or strand skipping of the wires during transportation, laying, or long-term operation. Simultaneously, this layer tightly integrates with the outer sheath, enhancing the overall compactness and stability of the cable structure. It is particularly suitable for engineering environments with high groundwater levels and long laying paths, significantly improving the cable's moisture resistance and mechanical reliability.

[0038] In terms of the constraint design of the armor structure, the stainless steel strip adopts a thickness of 0.5±0.02mm and a width of 60mm, and is wound around the outside of the stainless steel wire armor layer in a reverse spiral manner. This size design takes into account both material strength and process adaptability: the 0.5mm thickness provides sufficient rigidity to achieve effective binding, and the ±0.02mm tolerance control ensures material uniformity and wrapping flatness; the 60mm width is moderate, which can cover enough armor surface and facilitates stable wrapping on cable surfaces with large curvature changes, avoiding wrinkles or curling edges.

[0039] This stainless steel strip exhibits excellent structural restraint capabilities in practical applications. Its reverse wrapping method, combined with the spiral direction of the steel wire armor, forms a cross-locking structure, effectively suppressing the "expansion" tendency of the steel wire under axial tension and preventing the armor layer from loosening. Simultaneously, the 60–80mm wrapping gap design ensures a tight binding effect while retaining a certain degree of bending performance in the cable, preventing excessive tightening from increasing cable rigidity and affecting laying. This composite structure of "primary load-bearing + secondary restraint" significantly improves the structural integrity and operational safety of the cable under high tensile conditions.

[0040] It is worth noting that both the stainless steel wire armor layer and the stainless steel strip are made of 304 stainless steel, ensuring complete material consistency. 304 stainless steel possesses high strength, excellent corrosion resistance, and good processing performance, making it suitable for complex environments such as high humidity and weak acids and alkalis. More importantly, using the same material avoids the galvanic corrosion problems that may occur when dissimilar metals come into contact, ensuring the electrochemical stability of the armoring system during long-term operation.

[0041] The choice of this material significantly enhances the overall durability of the cable. In high-corrosion environments such as hydropower stations, underground caverns, and coastal areas, 304 stainless steel exhibits excellent corrosion resistance, effectively preventing the armor layer from failing due to corrosion. Simultaneously, its high strength further enhances the cable's tensile strength, working synergistically with the optimized pitch ratio helical structure to ensure safe and stable operation even under drops of hundreds of meters, fully meeting the stringent requirements of modern large-scale hydropower projects for special cables.

[0042] Furthermore, to enable real-time monitoring of the outer sheath's condition, the outermost layer of the cable employs a co-extrusion structure of a high flame-retardant polyethylene sheath and a semi-conductive PE layer. This design not only enhances the sheath's mechanical and fire-resistant properties but also provides it with a detection capability. The semi-conductive layer is connected to a monitoring device via a grounding system, allowing for real-time detection of any damage to the outer sheath during operation.

[0043] This feature greatly enhances the operation and maintenance capabilities of cable systems. Once the outer sheath develops cracks due to mechanical damage, aging, or external force, the monitoring system will detect a decrease in insulation resistance or abnormal leakage current, promptly issuing an early warning signal. Maintenance personnel can then quickly locate the fault and repair it, preventing minor defects from escalating into major accidents. This "monitorable" feature is particularly suitable for projects with long laying paths and high elevation differences where inspection is difficult, significantly improving the safety and maintenance efficiency of the power supply system.

[0044] In summary, this technical solution, through the collaborative design of a multi-layered composite structure, constructs a special high-voltage cable optimized for high-drop environments. This cable not only achieves comprehensive improvements in tensile strength, mechanical protection, and environmental tolerance in its structure, but also features refined control over material selection and process parameters, effectively solving key technical challenges of traditional high-voltage cables prone to armor loosening, sheath damage, electrochemical corrosion, and water-blocking failure during large-drop laying. The combination of stainless steel wire armor and reverse-wrapped stainless steel strip significantly enhances the cable's structural stability under continuous axial tension; the equipotential design of the semi-conductive butyl buffer strip fundamentally suppresses electrochemical corrosion between metal layers; and the combination of a thickened, high-flame-retardant polyethylene sheath and a co-extruded semi-conductive layer enhances the physical and fire-resistant properties of the outer sheath while enabling online monitoring of operational status. The overall solution is structurally sound, technologically feasible, safe, and reliable, possessing outstanding practicality and promotional value. It is particularly suitable for high-voltage, steep-slope power transmission requirements in complex conditions such as hydropower stations, long tunnels, and mountain power transmission, providing strong support for the safe and stable operation of power systems in high-drop environments.

[0045] It should be noted that in this utility model, the use of terms such as "first," "second," and "a" is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of those features. In the description of this utility model, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly defined. The terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two elements or the interaction between two elements, unless otherwise explicitly defined. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0046] Furthermore, the technical solutions of the various embodiments of this utility model can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0047] The specific embodiments described herein are merely illustrative examples illustrating the spirit of this utility model. Those skilled in the art to which this utility model pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of this utility model or exceeding the scope defined by the appended claims.

Claims

1. A special high-voltage cable suitable for environments with high elevation differences, characterized in that, From the inside out, it includes: conductor, conductor shielding layer, cross-linked polyethylene insulation layer, insulation shielding layer, semi-conductive buffer water-blocking tape, flat aluminum sheath, semi-conductive butyl buffer tape, stainless steel wire armor layer, stainless steel tape, water-blocking binding tape, high flame-retardant polyethylene sheath, and co-extruded semi-conductive PE layer. The stainless steel wire armor layer is composed of stainless steel wires with a diameter of 3.0±0.03mm and a wire pitch ratio of 20–23 times. The stainless steel strip is wound around the outside of the stainless steel wire armor layer in a reverse wrapping manner, with a wrapping gap of 60–80 mm. The average thickness of the high flame-retardant polyethylene sheath is not less than 6.5 mm.

2. The special high-voltage cable suitable for high-altitude environments as described in claim 1, characterized in that, The semi-conductive butyl buffer tape has a thickness of 0.5 mm, a width of 100 mm, and an overlap of 10–20 mm.

3. A special high-voltage cable suitable for high-altitude environments as described in claim 1, characterized in that, The water-blocking strap has a thickness of 0.3mm, a width of 100mm, and an overlap of 20–30mm.

4. A special high-voltage cable suitable for high-altitude environments as described in claim 1, characterized in that, The stainless steel strip has a thickness of 0.5±0.02mm and a width of 60mm.

5. A special high-voltage cable suitable for high-altitude environments as described in claim 1, characterized in that, The semi-conductive butyl buffer strip is used to ensure that the flat aluminum sheath and the outer stainless steel wire armor layer are at the same potential.

6. A special high-voltage cable suitable for high-altitude environments as described in claim 1, characterized in that, The semi-conductive PE layer is used for online detection of the integrity of the outer sheath.

7. A special high-voltage cable suitable for high-altitude environments as described in claim 1, characterized in that, Both the stainless steel wire armor layer and the stainless steel strip are made of 304 stainless steel.

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