Special deep ground cable and cable preparation method thereof

Abstract

The invention provides a special deep ground cable and a cable preparation method thereof, and relates to the technical field of cable preparation, and the special deep ground cable comprises a buried cable and a special protection layer. According to the invention, through mutual cooperation of the prestressed tie bar and the double-layer embeddable steel tape armoring, the cable can be freely bent and is convenient to lay when the prestressed tie bar is in a loose state, and after the prestressed tie bar is tensioned by using the tie bar tensioning device, the double-layer steel tape armoring is extruded, so that the double-layer steel tape armoring is embedded into a whole with high rigidity; the interlocking structure significantly improves the compressive strength of the armor layer, effectively resists underground rock extrusion, soil side pressure and shear stress generated by geological movement, and prevents cable deformation or internal structure damage.

Description

Technical Field

[0001] The present invention relates to the technical field of cable manufacturing, and in particular to a special deep - earth cable and a method for manufacturing the cable. Background Art

[0002] With the growth of global energy demand and the in - depth development of underground space, deep - earth cables are increasingly widely used in fields such as geological exploration, oil and gas extraction, deep - seated mineral development, and underground power grid construction. The deep - earth environment is characterized by high pressure, high humidity, strong corrosion, and frequent geological movements, which pose stringent requirements on the mechanical strength, weather resistance, anti - deformation ability, and long - term reliability of cables.

[0003] Traditional cables face many problems in the deep - earth environment. Traditional deep - earth cables mostly use single - layer steel - tape armoring or metal sheaths, and their compressive strength and anti - deformation ability are limited. External forces such as underground rock extrusion and soil settlement are likely to cause the armoring layer to fracture or deform, thereby damaging the internal insulation structure and triggering short - circuits or signal interruptions. In addition, the strength of single - layer armoring is fixed during manufacturing. High strength rigidity will make it difficult to lay the cable, while high flexibility for easy laying will result in low strength rigidity, and it is difficult to balance the two. Summary of the Invention

[0004] The purpose of the present invention is to provide a special deep - earth cable and a method for manufacturing the cable, so as to solve the problem that the flexibility and strength of traditional cables are difficult to balance as mentioned in the above background.

[0005] To solve the above - mentioned technical problems, the technical solution adopted by the present invention is a special deep - earth cable, which includes an underground cable and a special protective layer. The special protective layer is wrapped outside the underground cable, and a foam buffer layer is filled between the special protective layer and the underground cable; The special protective layer includes an outer steel - tape armoring layer and an inner steel - tape armoring layer. The outer steel - tape armoring layer is wrapped outside the inner steel - tape armoring layer. The outer steel - tape armoring layer includes a first steel tape, and the outer steel - tape armoring layer is formed by winding the first steel tape. The first steel tape is roll - processed with a first step. The inner steel - tape armoring layer includes a second steel tape, and the inner steel - tape armoring layer is formed by winding the second steel tape. The second steel tape is roll - processed with a second step; The outside of the outer steel - tape armoring layer is wrapped with a first braided protective layer. Inside the inner steel - tape armoring layer, a second braided protective layer and a third braided protective layer are sequentially arranged. Six groups of first stitches and second stitches are sewn on the second braided protective layer and the third braided protective layer by a numerical - control sewing machine to form uniformly distributed limiting grooves, and prestressed tension bars are penetrated in the limiting grooves.

[0006] Further, the outermost layer of the underground cable is a composite sheath, an insulating inner lining is wrapped inside the composite sheath, a conductor core is wrapped inside the insulating inner lining, a conductor insulating sleeve is wrapped outside the conductor core, and a filling layer is arranged between the conductor insulating sleeve and the insulating inner lining.

[0007] Further, the tensioning of the prestressed tension bars is realized by a tension bar tensioning device. The tension bar tensioning device includes a first collar sleeved outside the underground cable. Six threaded rods are rotatably connected to the first collar in a circumferentially evenly distributed manner. The six threaded rods are fixedly connected with a second collar through threads. The second collar is sleeved outside the underground cable. A tension sensor is installed between the second collar and the prestressed tension bar, and the tension sensor is fixedly connected with the prestressed tension bar.

[0008] A preparation method of a special deep underground cable for preparing the special deep underground cable includes the following steps: S1. Preparation of the conductor core and the conductor insulating sleeve: A high-conductivity copper alloy is used as the conductor core and is drawn to the required diameter by a wire drawing machine. Then, a conductor insulating sleeve is wrapped outside the conductor core. The insulating material is selected as cross-linked polyethylene and is uniformly coated by an extruder to form an insulating layer with a uniform thickness. S2. Processing of the insulating inner lining and the filling layer: The insulating inner lining uses low-density polyethylene and is covered outside the conductor insulating sleeve through an extrusion process. A polymer foaming material is filled between the insulating inner lining and the conductor insulating sleeve to form a filling layer. S3. Molding of the composite sheath: The composite sheath adopts a multi-layer co-extrusion technology. The inner layer is polyvinyl chloride and the outer layer is chloroprene rubber to ensure that the materials of each layer are tightly combined to form a uniform and bubble-free sheath structure. S4. Processing of the third braided protective layer and the second braided protective layer: A third braided protective layer and a second braided protective layer are sequentially sleeved outside the composite sheath, and a foam buffer layer is filled between the third braided protective layer and the composite sheath. Then, six groups of uniformly distributed first stitches and second stitches are sewn by a machine to form a limiting groove. S5. Installation of the prestressed tension bars: The prestressed tension bars are inserted into the limiting groove. The two ends of the prestressed tension bars protrude from the special protective layer and are fixed by a tension bar tensioning device to reserve an interface for subsequent tensioning operations. S6. Preparation of the inner steel tape armor layer and the outer steel tape armor layer: Inner steel tape armor layer: A second step is rolled on the surface of the second steel tape by a high-precision rolling device, and then it is wrapped outside the insulating inner lining in a spiral winding manner. Adjacent second steel tapes are overlapped through the second step to form an interlocking structure. Outer steel strip armor layer: After rolling out the first step, the first steel strip is wrapped around the outer side of the inner steel strip armor layer in a spiral winding manner, and adjacent ones are overlapped through the second step and the first step; S7. Processing of the first braided protective layer: The first braided protective layer is made of fiberglass braiding, and the first braided protective layer tightly wraps around the outer side of the outer steel strip armor layer through braiding.

[0009] Furthermore, both the first steel strip of the outer steel strip armor layer and the second steel strip of the inner steel strip armor layer are made of high-strength low-carbon steel strips, and the thickness of the steel strips is controlled between 1.5 mm and 2 mm.

[0010] Furthermore, the depth of the second step is the same as the thickness of the second steel strip, and the width of the second step is one-fifth of the width of the second steel strip.

[0011] Furthermore, the depth of the first step is the same as the thickness of the first steel strip, and the width of the first step is one-fifth of the width of the first steel strip.

[0012] Furthermore, the spiral directions of the second steel strip and the first steel strip are opposite when winding.

[0013] Furthermore, the winding pitch of the first steel strip is 1.5 - 2 times the width of the first steel strip, and the winding pitch of the second steel strip is 1.5 - 2 times the width of the second steel strip.

[0014] Furthermore, the first steel strip and the second steel strip are pre-galvanized, and after winding, an epoxy resin or polyurethane coating is sprayed on the surfaces of the inner steel strip armor layer and the outer steel strip armor layer.

[0015] Compared with the prior art, the beneficial effects of the present invention include: A special deep-earth cable and its cable preparation method proposed by the present invention, through the mutual cooperation of prestressed tension bars and double-layer interlocking steel strip armors, when the prestressed tension bars are in a relaxed state, the cable can be freely bent, facilitating laying. After using the tension bar tensioning device to tension the prestressed tension bars, the double-layer steel strip armors will be extruded, making them interlock to form a rigid whole. This interlocking structure significantly improves the compressive strength of the armor layer, effectively resists the extrusion of underground rocks, the lateral pressure of soil, and the shear stress generated by geological movements, preventing the cable from deforming or the internal structure from being damaged. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematically shows a cross-sectional structure diagram of a special deep-earth cable proposed according to an embodiment of the present invention; Figure 2 Schematically shows a Figure 1 magnified structure diagram at position A in a special deep-earth cable proposed according to an embodiment of the present invention; Figure 3 Schematically shows a schematic diagram of the cable layer structure of a special deep - earth cable proposed according to an embodiment of the present invention; Figure 4 Schematically shows a schematic diagram of the outer steel - tape armor layer structure of a special deep - earth cable proposed according to an embodiment of the present invention; Figure 5 Schematically shows a schematic diagram of the inner steel - tape armor layer structure of a special deep - earth cable proposed according to an embodiment of the present invention; Figure 6 Schematically shows a schematic diagram of the cross - section structure of the outer steel - tape armor layer of a special deep - earth cable proposed according to an embodiment of the present invention; Figure 7 Schematically shows a special deep - earth cable proposed according to an embodiment of the present invention Figure 6 The enlarged structure schematic diagram at point B; Figure 8 Schematically shows a schematic diagram of the cross - section structure of the inner steel - tape armor layer of a special deep - earth cable proposed according to an embodiment of the present invention; Figure 9 Schematically shows a special deep - earth cable proposed according to an embodiment of the present invention Figure 8 The enlarged structure schematic diagram at point C; Figure 10 Schematically shows a schematic diagram of the structure of the tensioning device for the tensioning bars of a special deep - earth cable proposed according to an embodiment of the present invention.

[0017] Reference numerals in the figure: 1, buried cable; 101, composite sheath; 102, insulating lining; 103, conductor core; 104, conductor insulating sleeve; 105, filling layer; 2, special protective layer; 3, outer steel - tape armor layer; 301, first steel tape; 302, first step; 4, inner steel - tape armor layer; 401, second steel tape; 402, second step; 5, first braided protective layer; 6, second braided protective layer; 7, third braided protective layer; 8, first sewing thread; 9, second sewing thread; 10, limiting groove; 11, prestressed tensioning bar; 12, foam buffer layer; 13, tensioning device for tensioning bars; 1301, first collar; 1302, threaded rod; 1303, second collar; 1304, tension sensor. Specific embodiments

[0018] It is easy to understand that according to the technical solution of the present invention, without changing the essence of the present invention, those of ordinary skill in the art can propose various interchangeable structural forms and implementation methods. Therefore, the following specific embodiments and the accompanying drawings are only exemplary descriptions of the technical solution of the present invention, and should not be regarded as the whole of the present invention or as a limitation or restriction on the technical solution of the present invention.

[0019] In accordance with an embodiment of the present invention, it is combined with Figure 1-10 Shown. A special deep - buried cable mainly consists of two major parts: a buried cable 1 and a special protective layer 2, and the two achieve efficient and reliable performance through collaborative design.

[0020] As Figure 1 Shown, the buried cable 1, as the core of electric energy transmission, adopts a layered composite structure. The outermost layer is a composite sheath 101. The inner layer of it selects chlorinated polyethylene or chlorosulfonated polyethylene, and this material has excellent chemical corrosion resistance and can effectively resist the erosion of underground saline, acidic and alkaline soils; the middle layer is embedded with a fiberglass braided layer, significantly enhancing the tensile strength and puncture resistance of the sheath, and the breaking strength can reach more than 500 MPa; the outer layer is covered with low - density polyethylene added with carbon black, improving the wear resistance of the outer layer. This multi - layer composite design enables the composite sheath 101 to protect the internal structure while extending the overall service life of the cable.

[0021] The inner side of the composite sheath 101 is wrapped with an insulating inner lining 102, which is molded by epoxy resin or polyimide materials. Epoxy resin has good insulation performance and mechanical strength, while polyimide is resistant to high temperature and chemical corrosion. Both can provide stable support for the internal structure. The surface of the insulating inner lining 102 is provided with annular grooves, which not only enhance the mechanical bite with the composite sheath 101, but also can accommodate filling materials during the manufacturing process, improving the stability of the overall structure.

[0022] Inside the insulating inner lining 102 is a conductor core 103, which is stranded by multiple strands of shaped wires. By optimizing the cross - sectional shape of the single wire such as fan - shaped, tile - shaped and the stranding direction, the filling coefficient can be increased to more than 0.92, significantly reducing the outer diameter of the core and reducing the material loss. The surface of the conductor is drawn by a precision die, and the roughness is controlled below 0.1 μm. This treatment effectively avoids partial discharge phenomena under high - voltage electric fields and improves the electrical performance of the cable.

[0023] The outside of the conductor core 103 is wrapped with a conductor insulating sleeve 104, and high - insulation materials such as cross - linked polyethylene or ethylene - propylene rubber (EPR) are selected. These materials have excellent insulation performance and heat resistance and can withstand high temperatures above 120 °C. In addition, by adding fillers such as nano - silica and silicon nitride, the anti - electrical tree aging ability of the insulating layer is significantly enhanced, ensuring that the breakdown strength ≥ 30 kV / mm, thereby extending the service life of the insulating layer.

[0024] Between the conductor insulation sleeve 104 and the insulation lining 102, the filling layer 105 is made of low-density foamed polyurethane or nitrile rubber. This closed-cell filling material can effectively absorb external impact and protect the internal conductor and insulation layer from mechanical damage; at the same time, the closed-cell structure can also block the water penetration path and prevent groundwater from corroding the inside of the cable. The Shore hardness of the filling layer 105 is controlled at 40-50A, taking into account both buffering performance and structural support, ensuring that the cable can still maintain a stable shape when squeezed by external force.

[0025] like Figure 2 and Figure 3 As shown, the special protective layer 2 serves as the mechanical protection core of the cable and is composed of a double-layer steel belt armor layer, a three-layer braided protective layer and a tensioning system.

[0026] like Figure 2 - Figure 9 As shown, the outer steel belt armor layer 3 on the outside is wound by the first steel belt 301, and the thickness of the steel belt is 1.5-2.0mm. The first step 302 formed during rolling makes the adjacent steel belts overlap closely, forming a "canine teeth staggered" mechanical interlocking effect. This design significantly improves the compressive strength of the armor layer, increasing the overall compressive strength by more than 40%. The inner steel belt armor layer 4 is wound by the second steel belt 401, and is also overlapped by the second step 402 to form an interlocking structure, which further improves the mechanical strength of the armor layer. The winding direction of the outer steel belt armor layer 3 is opposite to that of the inner steel belt armor layer 4 on the inside. This reverse winding design can effectively offset the torque stress generated when the cable is bent and enhance the bending resistance of the cable. The surfaces of the two layers of steel belt armor layers are sprayed with epoxy resin powder to form an anti-corrosion coating with a thickness of 50-80μm, which can withstand the erosion of chloride ions and sulfides in the underground environment, and the salt spray corrosion resistance time exceeds 1000 hours, ensuring the long-term stability of the armor layer.

[0027] like Figure 2 As shown, the outer side of the outer steel belt armor layer 3 is wrapped with a first braided protective layer 5, which is made of anti-corrosion and anti-rust materials. Its function is to protect the steel belt armor layer from direct erosion by the external environment and further extend the service life of the armor layer. The second braided protective layer 6 and the third braided protective layer 7 are arranged in sequence on the inner side of the inner steel belt armor layer 4, both of which are woven from high-strength aramid fibers. Aramid fibers have the characteristics of high tensile strength, high modulus, excellent chemical resistance and flame retardancy, and can provide additional mechanical protection for the internal structure. Six groups of first stitches 8 and second stitches 9 are sewn on the surface of the braided layer by a CNC sewing machine to form evenly distributed limit grooves 10. The function of these limit grooves 10 is to accurately fix the position of the prestressed reinforcement 11 to ensure that the reinforcement is evenly distributed inside the cable, thereby generating uniform stress when tensioned.

[0028] like Figure 1 , Figure 3 andFigure 10 As shown in the figure, six prestressed tension members 11 penetrate through the limiting groove 10. Carbon fiber reinforced composite material is selected, and its tensile strength ≥ 2000 MPa. The specific strength of the carbon fiber composite material is more than 5 times that of traditional steel, and the linear expansion coefficient is only 1 / 4 of that of steel. This enables the prestressed tension members 11 to effectively reduce the stress fluctuation caused by temperature changes while withstanding high tension. Both ends of the prestressed tension members 11 protrude from the special protective layer 2 and are used in conjunction with the tensioning device 13 for the tension members. By applying prestress, the steel tape armor layer is changed from a loose state to a tight whole, significantly improving the anti-extrusion and anti-tensile properties of the cable.

[0029] As Figure 10 shown, the tensioning of the prestressed tension members 11 is achieved through the tensioning device 13 for the tension members. The tensioning device 13 for the tension members includes a first collar 1301 sleeved on the outer side of the underground cable 1. The collar is made of high-strength aluminum alloy material, and its inner diameter is precisely matched with the outer diameter of the cable to avoid local damage to the cable during the tensioning process. Six threaded rods 1302 are rotatably connected to the first collar 1301 in a circumferential and evenly distributed manner. The threaded rods 1302 convert the rotational motion into axial displacement through precision screw pairs. A second collar 1303 is in threaded cooperation with the threaded rods 1302 and can move axially along the cable. A tension sensor 1304 is installed between the second collar 1303 and the prestressed tension members 11. A high-precision strain gauge sensor is used, with a measuring range of 0 - 500 kN and an accuracy of ±0.5%, which can monitor the tension of the tension members in real time and feedback it to the control system.

[0030] During the cable laying stage, the prestressed tension members 11 are in a relaxed state, and the steel tape armor layer is not fully engaged. At this time, the cable can be freely bent, facilitating laying in complex underground paths. After a section of the cable is laid and the connection is completed, a special tool is used to rotate the threaded rods 1302 to drive the second collar 1303 to move away from the first collar 1301, and tension is applied to the prestressed tension members 11 through the tension sensor 1304. At the same time, the first collar 1301 applies an axial pressure to the special protective layer 2, causing the first steel tapes 301 of the outer steel tape armor layer 3 to be embedded in each other through the first steps 302, and the second steel tapes 401 of the inner steel tape armor layer 4 to be interlocked through the second steps 402. The originally loose steel tape armor layer thus forms a rigid whole, significantly enhancing the mechanical strength of the cable, making it more difficult to bend, and thereby strengthening the protection effect on the underground cable 1. The tension sensor 1304 monitors the tension of the six prestressed tension members 11 in real time to ensure that the uniformity is controlled within ±5%. When the underground cable 1 is disturbed by external factors in the later stage, the tensions of the six prestressed tension members 11 will change differently. The tension sensor 1304 can capture these changes in time and give an early warning, providing real-time monitoring for the safe operation of the cable.

[0031] A preparation method for a special deep underground cable includes the following steps: 1. Preparation of the conductor core 103 and the conductor insulating sheath 104: Use a highly conductive copper alloy or aluminum alloy as the conductor core 103, draw it to the required diameter through a wire drawing machine to ensure a smooth and defect-free surface, and then wrap the conductor insulating sheath 104 around the conductor core 103. The insulating material is selected from cross-linked polyethylene or polytetrafluoroethylene and uniformly coated through an extruder to form an insulating layer with a uniform thickness, improving the voltage resistance and corrosion resistance.

[0032] 2. Processing of the insulating inner lining 102 and the filling layer 105: The insulating inner lining 102 is made of low-density polyethylene or ethylene propylene rubber and is covered on the outside of the conductor insulating sheath 104 through an extrusion process to form a buffer structure. A polymer foaming material or asbestos fiber is filled between the insulating inner lining 102 and the conductor insulating sheath 104 to form the filling layer 105, which is used to absorb external impact energy and enhance the anti-vibration and anti-bending capabilities of the cable.

[0033] 3. Molding of the composite sheath 101: The composite sheath 101 adopts a multi-layer co-extrusion technology. The inner layer is made of polyvinyl chloride or thermoplastic polyurethane to provide basic mechanical protection; the outer layer is made of chloroprene rubber or silicone rubber to enhance weather resistance and chemical corrosion resistance, ensuring that the materials of each layer are tightly combined to form a uniform and bubble-free sheath structure.

[0034] 4. Processing of the third braided protective layer 7 and the second braided protective layer 6: The third braided protective layer 7 and the second braided protective layer 6 are successively sleeved on the outside of the composite sheath 101, and a foam buffer layer 12 is filled between the third braided protective layer 7 and the composite sheath 101. The third braided protective layer 7 and the second braided protective layer 6 are made of high-strength polyester fiber or nylon fiber, and six groups of evenly distributed first stitches 8 and second stitches 9 are sewn through a machine to form a limiting groove 10. This braided structure not only provides positioning for the subsequent prestressed tension bars 11 but also enhances the anti-friction and anti-impact performance inside the cable.

[0035] 5. Installation of the prestressed tension bars 11: The prestressed tension bars 11 are inserted into the limiting groove 10. The tension bar material is selected from high-strength carbon fiber composite materials or titanium alloys with a diameter of 3 - 5 mm, ensuring that its tensile strength exceeds 1.5 times the design tension of the cable. Both ends of the prestressed tension bars 11 protrude from the special protective layer 2 and are fixed through the tension bar tensioning device 13, reserving an interface for subsequent tensioning operations. The uniform distribution design of the tension bars can ensure that the cable is evenly stressed after tensioning, improving the overall structural stability.

[0036] 6. Preparation of the inner steel tape armor layer 4 and the outer steel tape armor layer 3: Inner steel tape armor layer 4: High-strength low-carbon steel tape with a thickness of 1.5 mm - 2 mm is used. Through high-precision rolling equipment, a second step 402 with a depth equal to the steel tape thickness and a width of one-fifth of the steel tape width is rolled on the surface of the second steel tape 401. Subsequently, it is wrapped around the outside of the insulating lining 102 in a left-handed helical winding manner, and adjacent steel tapes are overlapped through the second step 402 to form an interlocking structure. The outer steel tape armor layer 3 also uses high-strength low-carbon steel tape. After rolling out the first step 302, it is wrapped around the outside of the inner steel tape armor layer 4 in a right-handed helical winding manner, and the winding pitch is 1.5 - 2 times the width of the steel tape. Adjacent steel tapes are overlapped through the first step 302. The reverse winding design of the two layers of steel tapes utilizes the torque cancellation effect to significantly enhance the overall rigidity of the armor layer. The surface of the steel tape is pre-galvanized or aluminized, and after winding, an epoxy resin or polyurethane coating is sprayed on the surface of the armor layer to improve the chemical corrosion resistance and antioxidant ability.

[0037] 7. Processing of the first braided protective layer 5: The first braided protective layer 5 is made of glass fiber or aramid fiber and is tightly wrapped around the outside of the outer steel tape armor layer 3. This braided layer can not only protect the steel tape armor layer from external puncture damage but also further enhance the tensile and shear resistance of the cable to adapt to the complex stresses in the deep underground environment.

[0038] Working principle: When the cable is laid and connected, the threaded rod 1302 of the tensioning device 13 of the tensioning tendon is rotated by a special tool. The threaded rod 1302 is rotationally connected to the first collar 1301, and its rotational motion is converted into the axial displacement of the second collar 1303 through the screw pair. When the second collar 1303 moves axially along the buried cable 1, a tension is applied to the prestressed tendon 11 through the tension sensor 1304. The tension sensor 1304 monitors the tension value in real time to ensure that the force uniformity of the six prestressed tendons 11 is controlled within ±5%. As the tension increases, the prestressed tendon 11 is gradually straightened and undergoes elastic deformation. At the same time, the first collar 1301 applies an axial pressure to the special protective layer 2, prompting the steel tape armor layer to undergo mechanical interlocking.

[0039] The first steel strip 301 of the outer steel strip armor layer 3 and the second steel strip 401 of the inner steel strip armor layer 4 respectively form a first step 302 and a second step 402 during rolling. When an axial pressure acts on the special protective layer 2, the first steel strip 301 of the outer steel strip armor layer 3 undergoes a slight displacement due to extrusion, and the first steps 302 of adjacent steel strips are embedded in each other, forming a "dog-tooth interlocking" interlocking structure; similarly, the second steel strip 401 of the inner steel strip armor layer 4 is fitted through the second step 402. Due to the opposite winding directions of the two layers of steel strips, this fitting not only enhances the longitudinal bonding force of the armor layer, but also forms a rigid whole in the axial direction of the entire armor layer through the reverse torque cancellation effect. In the underground environment, cables often bear external forces such as soil side pressure and rock extrusion. After the steel strip armor layer forms a rigid whole, its compressive strength is increased by more than 40%, which can effectively disperse the external pressure and prevent the cable from deforming due to extrusion or the internal structure from being damaged. Deep geological activities may also cause the cable to be subjected to tensile or shear stresses. The rigid armor layer distributes the local stress evenly throughout the cable through the mechanical interlocking structure, avoiding single-point stress concentration, thereby extending the service life of the cable. At the same time, the rigid whole reduces the creep phenomenon of the cable underground. Especially in a high-voltage environment, it can maintain the geometric shape stability of the cable and prevent the insulation layer from fatigue aging or poor conductor contact caused by long-term deformation.

[0040] The technical scope of the present invention is not limited to the content described above. Those skilled in the art can make various deformations and modifications to the above embodiments without departing from the technical idea of the present invention, and these deformations and modifications should all fall within the protection scope of the present invention.

Claims

1. A special deep-earth cable, characterized in that, It includes an underground cable and a special protective layer. The special protective layer wraps around the outside of the underground cable, and a foam buffer layer is filled between the special protective layer and the underground cable; The special protective layer includes an outer steel tape armor layer and an inner steel tape armor layer. The outer steel tape armor layer wraps around the inner steel tape armor layer. The outer steel tape armor layer includes a first steel tape, and the outer steel tape armor layer is formed by winding the first steel tape. The first steel tape is roll - processed with a first step. The inner steel tape armor layer includes a second steel tape, and the inner steel tape armor layer is formed by winding the second steel tape. The second steel tape is roll - processed with a second step; A first braided protective layer is wrapped outside the outer steel tape armor layer. A second braided protective layer and a third braided protective layer are sequentially arranged inside the inner steel tape armor layer. Six groups of first stitches and second stitches are sewn on the second braided protective layer and the third braided protective layer by a numerical control sewing machine to form uniformly distributed limiting grooves, and prestressed tension bars penetrate through the limiting grooves.

2. A special deep - earth cable as claimed in claim 1, wherein, The outermost layer of the underground cable is a composite sheath. An insulating lining is wrapped inside the composite sheath. A conductor core is wrapped inside the insulating lining. A conductor insulating sleeve is wrapped outside the conductor core, and a filling layer is arranged between the conductor insulating sleeve and the insulating lining.

3. The special deep-earth cable according to claim 2, characterized in that, The tensioning of the prestressed tension bars is realized by a tension bar tensioning device. The tension bar tensioning device includes a first collar sleeved outside the underground cable. Six threaded rods are rotatably connected to the first collar in a circumferentially evenly distributed manner. The six threaded rods are fixedly connected to a second collar through threads. The second collar is sleeved outside the underground cable. A tension sensor is installed between the second collar and the prestressed tension bars, and the tension sensor is fixedly connected to the prestressed tension bars.

4. A method for preparing a special deep - earth cable, which is used to prepare the special deep - earth cable as described in claim 3, characterized in that, It includes the following steps: S1. Preparation of the conductor core and the conductor insulating sleeve: A high - conductivity copper alloy is used as the conductor core, which is drawn to the required diameter by a wire drawing machine, and then a conductor insulating sleeve is wrapped outside the conductor core. The insulating material is cross - linked polyethylene, which is uniformly coated by an extruder to form an insulating layer with a uniform thickness; S2. Processing of the insulating lining and the filling layer: The insulating lining uses low - density polyethylene, which is covered outside the conductor insulating sleeve through an extrusion process. A polymer foaming material is filled between the insulating lining and the conductor insulating sleeve to form a filling layer; S3. Molding of the composite sheath: The composite sheath adopts a multi - layer co - extrusion technology, with a polyvinyl chloride inner layer and a chloroprene rubber outer layer, ensuring that the materials of each layer are tightly combined to form a uniform and bubble - free sheath structure; S4. Processing of the third braided protective layer and the second braided protective layer: The third braided protective layer and the second braided protective layer are sequentially sleeved outside the composite sheath, and a foam buffer layer is filled between the third braided protective layer and the composite sheath. Then, six groups of uniformly distributed first stitches and second stitches are sewn by a machine to form limiting grooves; S5. Installation of the prestressed tension bars: The prestressed tension bars are inserted into the limiting grooves. The two ends of the prestressed tension bars protrude from the special protective layer and are fixed by the tension bar tensioning device, reserving an interface for subsequent tensioning operations; S6. Preparation of the inner steel tape armor layer and the outer steel tape armor layer: Inner steel tape armor layer: A second step is rolled on the surface of the second steel tape by a high-precision rolling equipment, and then it is wrapped around the outer side of the insulating lining in a spiral winding manner. Adjacent second steel tapes are overlapped through the second step to form an interlocking structure; Outer steel tape armor layer: After rolling out the first step, the first steel tape is wrapped around the outer side of the inner steel tape armor layer in a spiral winding manner, and adjacent ones are overlapped through the first step by passing through the second step; S7. Processing of the first braided protective layer: The first braided protective layer is made of glass fiber braiding, and the first braided protective layer is tightly wrapped around the outer side of the outer steel tape armor layer through braiding.

5. The preparation method of a special deep-earth cable according to claim 4, characterized in that, The first steel tape of the outer steel tape armor layer and the second steel tape of the inner steel tape armor layer both adopt high-strength low-carbon steel tapes, and the thickness of the steel tapes is controlled between 1.5 mm and 2 mm.

6. The preparation method of a special deep-earth cable according to claim 4, characterized in that, The depth of the second step is the same as the thickness of the second steel tape, and the width of the second step is one-fifth of the width of the second steel tape.

7. The preparation method of a special deep-earth cable according to claim 4, characterized in that, The depth of the first step is the same as the thickness of the first steel tape, and the width of the first step is one-fifth of the width of the first steel tape.

8. The preparation method of a special deep-earth cable as claimed in claim 4, wherein, The spiral directions of the second steel tape and the first steel tape are opposite when winding.

9. The preparation method of a special deep-earth cable as described in claim 4, characterized in that The winding pitch of the first steel tape is 1.5 - 2 times the width of the first steel tape, and the winding pitch of the second steel tape is 1.5 - 2 times the width of the second steel tape.

10. The preparation method of a special deep-earth cable according to claim 4, characterized in that, The first steel tape and the second steel tape are pre-galvanized, and after winding, an epoxy resin or polyurethane coating is sprayed on the surfaces of the inner steel tape armor layer and the outer steel tape armor layer.

Images