Method for connecting ultra-high voltage and large capacity submarine cable on site and installation platform thereof

Abstract

The application discloses a method for connecting an ultra-high-voltage and large-capacity submarine cable on a sea site and an installation platform thereof, and the method comprises the following steps: step 1, preparation before construction; step 2, approach of a leg pile lifting type water mobile installation platform; step 3, platform pile insertion positioning; step 4, self-lifting height adjustment; step 5, expansion of a submarine cable chute; step 6, salvage of a submarine cable end and fixation; step 7, erection of a joint manufacturing room and a purification room on the platform; step 8, cable end connection; step 9, installation of a cable soft joint protector; step 10, installation of a bending limiter; step 11, hoisting and launching of a joint; and step 12, pile pulling and site leaving. In the method, the installation platform is lifted to reduce the impact of sea waves, so that the platform is more stable, and the method has the characteristics of safety and reliability and high connection efficiency. The cable soft joint protector is improved, long-term protection function is realized, and the maintenance cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of submarine cable connection technology, specifically to a method for on-site connection of ultra-high voltage, high-capacity submarine cables at sea and its installation platform. Background Technology

[0002] During submarine cable laying, due to the long length of the cable, it is usually necessary to lay and connect sections. The mainstream technologies for submarine cable section connection are mainly divided into two categories: communication submarine cables and power submarine cables. For power submarine cable connection technologies, the following connection techniques are included: 1. Crimping technology Connection Principle: A specialized crimping tool is used to apply pressure to the cable conductor, causing plastic deformation and achieving a tight connection. The shape and size of the crimping die are precisely designed according to the cable conductor specifications. Technical Characteristics: Relatively simple operation, ensuring a good electrical connection between conductors, and possessing high mechanical strength and stability. However, the crimping quality is greatly affected by the performance of the crimping tool and the operator's skill level. Inadequate crimping may lead to increased contact resistance, affecting power transmission efficiency.

[0003] 2. Welding technology Connection principle: The cable conductors are heated to a molten state and then fused together. A common welding method is argon arc welding, which uses a shielding gas to prevent conductor oxidation during the welding process. Welded connections offer high reliability, ensuring excellent electrical and mechanical properties between the conductors, and can withstand significant current and mechanical stress. However, the welding process is complex, requiring highly skilled welding equipment and operators, and may potentially damage the cable insulation layer, necessitating appropriate protective measures.

[0004] 3. Prefabricated joint technology Connection Principle: The connector components are prefabricated in the factory; during on-site construction, they are simply installed at the cable connection point. The connector components typically utilize high-performance insulation materials and sealing structures, effectively restoring the cable's insulation and protective properties. Technical Features: Fast construction speed, stable quality, and minimal impact from on-site environmental factors. Prefabricated connectors offer superior insulation and sealing performance, effectively preventing moisture and humidity intrusion and improving cable reliability. However, prefabricated connectors are relatively expensive and require strict matching of cable specifications and models.

[0005] For ultra-high voltage, high-capacity submarine cable on-site connections, the cable ends need to be retrieved for splicing during segmented connections to ensure the continuity and stability of the cable. Submarine cables are typically laid on the seabed at depths of hundreds or even thousands of meters. Finding a relatively small diameter cable end in such a vast area is like finding a needle in a haystack; traditional retrieval methods are inefficient and inaccurate. Low retrieval efficiency: Traditional retrieval tools and methods may not be suitable for the complex seabed environment and the characteristics of the cable, resulting in a lengthy retrieval process and increased maintenance and time costs. For example, while simple inspections and repairs can be performed manually in shallow waters, manual operation is extremely difficult in deep waters.

[0006] In addition, existing submarine cable segmentation connections are usually carried out on floating vessels, which presents numerous challenges related to the environment, operations, equipment, and safety. • Rough seas: Rough seas are the norm at sea, causing floating vessels to rise and fall with the waves. This makes submarine cable connection operations extremely difficult, as workers struggle to maintain stable postures and pressure, which can easily lead to decreased connection accuracy. For example, during fiber optic splicing, shaking can increase splice loss. Moreover, rough seas can loosen already connected but not yet securely fixed parts, affecting connection quality and stability.

[0007] • Severe Weather: Severe weather such as heavy rain and typhoons can severely disrupt cable connection work on floating vessels. Heavy rain can wet equipment and cables, affecting electrical insulation performance and potentially damaging electronic equipment; strong winds and giant waves brought by typhoons can threaten the safety of floating vessels, potentially causing them to shift or tilt, forcing the connection work to be interrupted, and possibly damaging completed connections.

[0008] • Seawater corrosion: Seawater is highly corrosive. Floating vessels, constantly submerged, are susceptible to corrosion of their equipment and tools. Metal components used in the connection process, such as conductors and connectors, can rust and become damaged if not properly protected, affecting the conductivity and mechanical properties of the connection and shortening the lifespan of the submarine cable.

[0009] • Positioning difficulties: Precise positioning and splicing of submarine cables on a floating vessel is extremely difficult. Due to the swaying of the vessel, it is hard to ensure accurate alignment of the two ends of the cable, especially for connection methods with extremely high precision requirements, such as fiber optic splicing. Even a slight deviation can lead to excessive connection loss and affect signal transmission quality.

[0010] • Personnel Safety: Workers performing submarine cable connections on floating vessels face numerous safety risks. These include the risk of slipping and falling due to waves, mechanical injuries from improper equipment operation, and electrical safety risks such as electric shock. Furthermore, maritime rescue is relatively difficult, and in the event of a safety incident, the rescue process can be lengthy, posing a serious threat to the lives of personnel.

[0011] • Submarine cable safety: The movement and swaying of floating vessels may also cause excessive stretching, bending and other external forces to the submarine cable during the connection process, which may damage the internal structure of the submarine cable and affect its performance and service life.

[0012] In addition, after the cable expansion joint is connected, it needs to operate in the high-pressure, high-salt, and highly corrosive environment of the deep sea for a long time. Traditional protection solutions (such as rubber sealing sleeves and metal sheaths) have the following problems: 1. Sealing failure: High-pressure seawater penetration leads to a decrease in insulation performance and may even cause a short circuit; 2. Mechanical damage: The connector is easily damaged by ocean currents or impacts from foreign objects; 3. Accelerated corrosion: Salt spray and chemicals corrode metal parts, shortening their lifespan. Summary of the Invention

[0013] The purpose of this invention is to provide a safe, reliable, and highly efficient method for on-site connection of ultra-high voltage, high-capacity submarine cables at sea, as well as its installation platform.

[0014] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A method for on-site connection of ultra-high voltage, high-capacity submarine cables includes the following steps: Step 1, Pre-construction preparation: Select a jack-up type floating motorized installation platform as the installation platform for submarine cable connection; before the installation platform enters the sea area, the materials and machinery required for submarine cable connection should be transported to the installation platform to ensure the needs of joint fabrication; sufficient space should be reserved on the installation platform to meet the needs of submarine cable retrieval, fixing and fabrication site. Step 2: Deployment of the outrigger lifting-type water-mobile installation platform: Based on the location of the submarine cable end at sea, determine the offshore construction area and move the outrigger lifting-type water-mobile installation platform to the offshore construction area. Step 3, Platform Pile Positioning: After the outrigger-lifting mobile installation platform is moved to the offshore construction area, the vessel is positioned according to the buoy location, route coordinates, and sea conditions, and is parallel to and close to the centerline of the submarine cable route. The position of the outrigger piles is determined by the S-shaped curve of the cable being cast, to prevent accidental damage to the submarine cables on the seabed. In a floating state, the outrigger-lifting mobile installation platform first uses surveying equipment or divers to determine the position of the submarine cables on both sides of the installation platform, and then positions and inserts the outrigger piles. The lifting mechanism is activated to drive the outrigger piles down. When the outrigger pile shoe touches the seabed, the piling is completed. Step 4: Adjust the self-lifting height: After the pile driving is completed, continue to start the lifting mechanism. With the support of the outrigger piles, the installation platform will begin to rise and be adjusted to the preset height. Step 5: Unfold the cable chutes: Before salvage, unfold the cable chutes on both sides of the outrigger-supported, liftable, water-mobile installation platform and adjust the tilt angle of the cable chutes. Step 6: Salvage and secure the end of the submarine cable: The on-site salvage of the end mainly relies on the full-rotation crane on the outrigger boat; before construction, it is necessary to perform calculations based on the on-site water depth conditions and the weight of the submarine cable, and select appropriate lifting radius and tensile force parameters for salvage. Step 7: Construct a joint fabrication room and cleanroom on the platform: First, construct a fabrication room on the installation platform, and then construct a cleanroom inside the fabrication room; Step 8, Cable Termination Connection: The cable termination shall be connected using a flexible connector. Step 9: Install the cable expansion joint protector; Step 10: Install bend limiters: Install bend limiters on the cable at both ends of the protector; Step 11, Lowering the cable connector into the water: Use the main crane to lower the cable connector into the water, and finally place it on the seabed in an Ω shape; Step 12, Pile Removal and Site Retreat: Use the lifting mechanism to drive the outrigger piles upward and reset, and then drive the outrigger pile lifting water-powered installation platform away from the construction site.

[0015] Furthermore, the cable expansion joint protector includes a corrosion-resistant circular outer shell, which is formed by bolting an upper semi-circular shell and a lower semi-circular shell together. The upper semi-circular shell, lower semi-circular shell, and bolts are made of titanium alloy, and their surfaces are covered with a nano-ceramic composite material (Al2O3-SiC). Inside the corrosion-resistant circular outer shell are an elastic self-sealing sleeve, a shape memory alloy (SMA) buffer sleeve, and a high-strength aramid fiber braided sleeve. The elastic self-sealing sleeve is mounted on the cable expansion joint, the shape memory alloy (SMA) buffer sleeve is mounted on the elastic self-sealing sleeve, and the high-strength aramid fiber braided sleeve is mounted on the shape memory alloy (SMA) buffer sleeve. The corrosion-resistant circular outer shell covers the elastic self-sealing sleeve, the shape memory alloy (SMA) buffer sleeve, and the high-strength aramid fiber braided sleeve, with both ends of the elastic self-sealing sleeve extending outside the corrosion-resistant circular outer shell. The elastic self-sealing sleeve is used to adapt to cable bending and prevent seawater penetration. The shape memory alloy (SMA) buffer sleeve is used to reinforce the high-strength aramid fiber braided sleeve within the corrosion-resistant circular outer shell. The high-strength aramid fiber braided sleeve absorbs stress during deformation under pressure, preventing excessive compression of the cable joint. It enhances tensile strength and resists ocean current erosion and foreign object impact. The surface of the elastic self-sealing sleeve is coated with a hydrophobic nano-coating. The installation method of the elastic self-sealing sleeve involves wrapping the self-sealing material around the cable joint and achieving a tight fit through hot pressing. The self-sealing material is prepared by mixing silicone rubber and nano-SiO2 in a specific ratio and preparing a composite material using a sol-gel method, with the mass ratio of silicone rubber to nano-SiO2 between 90:10 and 95:5. The installation method of the shape memory alloy (SMA) buffer sleeve involves wrapping the shape memory alloy (SMA) layer around the elastic self-sealing sleeve and fixing it with laser welding. The shape memory alloy (SMA) layer is custom-shaped using 3D printing. The installation method of the high-strength aramid fiber braided sleeve involves wrapping the high-strength aramid fiber braided layer around the shape memory alloy (SMA) buffer sleeve and fixing it with laser welding. The high-strength aramid fiber braided layer is manufactured using an automated braiding process.

[0016] Furthermore, in step 6, the tensile force T applied during the specific salvage operation... d1 It can be obtained through the following formula:

[0017] The formula refers to the calculation formula for cable tension test in GB / T32346.1-2015: the coefficient 1.3 is to take into account the additional force generated by the submarine cable due to the influence of wind, waves and currents; considering the tension of the submarine cable at the mud contact point on the cable, 0.2WD is added as a constant.

[0018] Furthermore, in step 7, the internal dimensions of the joint fabrication room are 12 meters long, 7 meters wide, and 4 meters high. A static Class 1000 cleanroom, 3.5 meters long and 4 meters wide, is constructed inside the joint fabrication room. The joint fabrication room has doors at both ends, requiring no bottom beams and complete sealing. Several hanging rings are arranged at various positions on the top of the joint fabrication room, and the exterior of the joint fabrication room is covered with canvas. To ensure sufficient lighting on site, at least five 150-200 watt construction lights are provided, along with several spare bulbs. Air-cooled fans and dehumidifiers are provided to ensure the cleanroom environment meets the following requirements: temperature 10-30℃, relative humidity ≤70%, and cleanliness level reaching Class 1000. The indoor power supply requires two separate 220V 5kW power lines and two 380V 25kW independent power lines. The joint fabrication area needs to be equipped with lifting equipment of at least 5 tons to assist in the fabrication of flexible joints between the submarine cable ends.

[0019] Furthermore, in step 8, the specific steps for connecting the cable ends are as follows: Step 8.01, Cable End Pre-treatment: Before end connection, the submarine cable end needs to be heated and straightened. This helps control the insulation eccentricity during on-site flexible joint fabrication and also helps eliminate residual thermal stress during submarine cable manufacturing. When the submarine cable has large bending deformation, it can be preliminarily straightened with a submarine cable straightener before heating and straightening. Step 8.02, Conductor Welding: The welding of the conductor of the ultra-high voltage and high-capacity submarine cable adopts the flip-layer butt welding, and the welding strength can reach more than 180Mpa; Step 8.03, Roughing of the Reactive Cone: The stripping of the reactive cone uses a special high-voltage submarine cable main insulation layer sharpener. This sharpener can adjust the angle and length of the reactive cone stripping. After setting the angle parameters, the insulation is cut by rotation. While rotating, the cutter head continuously increases in height according to the set angle, and finally achieves the preset reactive cone shape. Step 8.04, Inner Semiconductor Shielding Layer Restoration: The inner shielding is restored by first wrapping and then molding. The surface of the conductor is wrapped with a wrapping tape. After the wrapping is completed, a half-type molding die is installed in the wrapping area. After the conductor shielding is restored, the insulating surface, including the reactive force cone, is finely polished. The wrapping tape is made of the same grade of semiconducting material as the conductor. Step 8.05: Reactive taper finishing; Step 8.06, Insulation Injection Molding Process: The insulation injection molding restoration process involves injecting insulation material of the same grade as the main body into a specially designed insulation injection mold using a dedicated extruder. Then, through heating and pressurization, the restored insulation is tightly fused with the main body insulation. This process has the highest environmental cleanliness requirements during on-site flexible joint fabrication. To prevent dust and other impurities from entering the insulation, it must be carried out in a mobile, Class 1000 cleanroom. Step 8.07, Insulation vulcanization process: Restoring insulation vulcanization requires heating and nitrogen pressurization; Step 8.08, Insulation Surface Treatment: To achieve the designed insulation and stress cone structure, after the insulation vulcanization is completed, excess insulation needs to be cut off and the surface needs to be polished. During cutting and polishing, the concentricity of the insulation must be ensured. When polishing, first use coarse sandpaper to polish, and then use fine sandpaper to polish until the insulation surface is smooth and flat. Finally, wipe the insulation surface with anhydrous alcohol or special insulation cleaning paper. Step 8.09, Restoration of the outer semiconductive shielding layer and water-blocking layer: The restoration of the outer semiconductive shielding layer adopts the same wrapping and molding restoration process as the inner shielding tape. The tape used is made of the same grade of semiconductive material as the body. After the outer semiconductive shielding layer is restored, a layer of semiconductive water-blocking buffer tape is wrapped around it as a water-blocking layer. Step 8.10, restoration of lead sleeve and PE sheath: The lead sleeve is restored using oxyhydrogen welding; the welding material used is the same alloy lead as the body; the PE sheath is restored using a special welding machine to weld the prefabricated sleeve to the body.

[0020] A type of outrigger-lifting water-based motorized installation platform includes a platform body. The platform body has cable chutes and chute deployment mechanisms on both sides. Before deployment, the cable chutes are tightly attached to the side walls of the platform body. The chute deployment mechanisms are installed within the platform body to move the lower end of the cable chutes. The upper end of the cable chutes is hinged to the platform body. Outrigger-lifting holes are located at the four corners of the platform body, and outrigger-piles are inserted into these holes. Pile shoes are installed at the lower ends of the outrigger-piles. Lifting mechanisms are located at the outrigger-piles lifting holes to fix and lift the outrigger-piles. The surface of the platform body is equipped with a main crane, an auxiliary crane, a general cargo crane, and a cable end retrieval device. The cable end retrieval device is used to retrieve the cable end from the seabed onto the platform body. The main crane and auxiliary crane are used to lift the cable.

[0021] Furthermore, the submarine cable end retrieval device includes an underwater mobile unit, a biomimetic octopus-style flexible gripping system, and an acoustic-optical-magnetic composite navigation and positioning system. The biomimetic octopus-style flexible gripping system and the acoustic-optical-magnetic composite navigation and positioning system are mounted on the underwater mobile unit. The acoustic-optical-magnetic composite navigation and positioning system includes sonar, lidar, and a magnetometer. The sonar is used for long-range detection of the cable end location and seabed topography. The lidar provides high-precision three-dimensional point cloud data to assist the device in obstacle avoidance and path planning. The magnetometer detects the weak magnetic field generated by the current at the cable end to achieve precise positioning. The biomimetic octopus-style flexible gripping system is used to grip the submarine cable end. This system employs multiple flexible silicone arms as gripping mechanisms. Each silicone arm has a built-in micro-hydraulic or pneumatic drive unit, which can independently control bending and extension to achieve a gripping fit to complex shapes. The surface is covered with a micro-nano-scale biomimetic suction cup structure, which fixes the cable end through the dual action of negative pressure adsorption and friction, reducing slippage and damage during the grasping process. The underwater mobile device is equipped with a self-powered energy system, which adopts a solar-wave energy composite power generation self-powered energy system. The energy self-powered energy system includes a flexible solar panel and a wave energy conversion device. The flexible solar panel is located on the upper surface of the underwater mobile device, and the wave energy conversion device adopts an oscillating water column type or pendulum type wave energy conversion device. The underwater mobile device is equipped with a wireless charging system. The top of the underwater mobile device is equipped with a lifting lug, which is connected to the recovery rope on the winch. The winch is located on a levitation-type water-mobile installation platform with outrigger piles. The recovery rope is made of carbon fiber. A thruster is located at the rear of the underwater mobile device, and two lifting thrusters are located at the bottom of the underwater mobile device. A telescopic support frame is located at the bottom of the underwater mobile device.

[0022] Furthermore, the front, rear, left, and right sides of the outrigger pile are respectively provided with a row of equally spaced front pin holes, a row of equally spaced rear pin holes, a row of equally spaced left pin holes, and a row of equally spaced right pin holes. The left or right pin holes are staggered with the front or rear pin holes. The front and rear pin holes correspond to each other, and the left and right pin holes correspond to each other. The hole spacing between adjacent front pin holes is equal to the hole spacing between adjacent rear pin holes, adjacent left pin holes, and adjacent right pin holes, all being 2L. In the axial direction of the outrigger pile, the distance between the front or rear pin holes and the left or right pin holes is L.

[0023] Furthermore, the lifting mechanism includes a square frame, a front hydraulic cylinder lifting device, a rear hydraulic cylinder lifting device, a left hydraulic cylinder lifting device, and a right hydraulic cylinder lifting device. The square frame is composed of an upper square frame, a lower square frame, and four columns. The four corners of the upper square frame are fixedly connected to the lower square frame via the four columns. The lower and upper square frames are parallel to each other. The outriggers to be lifted pass through the upper and lower square frames of the square frame. The front, rear, left, and right hydraulic cylinder lifting devices are respectively installed on the front, rear, left, and right sides of the square frame. The front and rear hydraulic cylinder lifting devices synchronously drive the outriggers to rise and fall, and the left and right hydraulic cylinder lifting devices synchronously drive the outriggers to rise and fall. The lifting devices for the front hydraulic cylinder, rear hydraulic cylinder, left hydraulic cylinder, and right hydraulic cylinder are structurally identical. The front hydraulic cylinder lifting device includes two front hydraulic cylinders, a slide rail, a slider, and a pin positioning device. The two front hydraulic cylinders are vertically mounted on the upper front side of the square frame. The slide rail is located on the front beam of the square frame. The two front hydraulic cylinders simultaneously drive the slider to move along the slide rail. The pin positioning device is fixed on the slider. The pin positioning device includes a positioning pin, a return spring, and an electromagnet. The positioning pin is horizontally installed in the pin hole of the slider. When the electromagnet is energized, it pulls the positioning pin out of the front pin hole of the outrigger pile through magnetic force, and the return spring is compressed. When the electromagnet is de-energized, the positioning pin is pushed into the front pin hole of the outrigger pile under the action of the return spring.

[0024] Furthermore, the platform body is equipped with a thruster, a main generator set, and an emergency / berthing generator. The thruster is used to drive the platform body to move at sea, and the thruster is a Rolls Royce 355 / P50. The platform is equipped with a 3250kW electric azimuth thruster. The platform body has a length of 95m, a width of 46m, a depth of 10m, a draft of 5.7m, outrigger pile diameter of 3.8m, outrigger length of 96m, and pile shoe dimensions of 12.6m x 8.2m x 2.5mm. The maximum operating water depth is 55m. The main generator set consists of four diesel generator sets with a rated power of 800kw, and an emergency / parking generator with a rated power of 300kw. The main crane is 1000t, the auxiliary crane is 300t, the utility crane is 25t, the single pile lifting force is 5000t, the single pile supporting force is 6000t, the rated lifting platform speed is 15m / h, and the capacity is 50 people.

[0025] The beneficial effects of this invention are as follows: In this application, the segmented submarine cable end connection operation is carried out on a levitation-type water-powered installation platform with outrigger piles. During connection, the installation platform can be raised, reducing the impact of waves and making the platform more stable, greatly reducing the swaying amplitude, and laying the foundation for precise connection of the submarine cable. In particular, the method of building a joint fabrication room on the platform and building a clean room in the fabrication room not only avoids seawater corrosion during the connection process, but also improves the safety of construction personnel.

[0026] This application improves the cable expansion joint protector, which can fully withstand the high pressure of deep sea and has excellent sealing reliability. The multi-layer protection structure significantly reduces the risk of seawater penetration and can adapt to the bending and thermal expansion and contraction of the cable expansion joint. This invention has long-term protection function with a design life of ≥20 years, reducing maintenance costs.

[0027] This application designs a submarine cable end retrieval device that integrates cutting-edge technologies such as bionics and acoustic-optical-magnetic composite navigation, overcoming the design limitations of traditional retrieval devices. It maintains high positioning accuracy even in low-visibility or turbid waters, reducing reliance on manual marking and featuring precise positioning and high retrieval efficiency. The silicone arm secures the cable end through a combination of negative pressure adsorption and friction, minimizing slippage and damage during the retrieval process. Attached Figure Description

[0028] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort: Figure 1 This is a flowchart of the method for on-site connection of ultra-high voltage high-capacity submarine cables according to the present invention; Figure 2 This is a schematic diagram of the cable expansion joint protector of the present invention; Figure 3 for Figure 2 The side view shown; Figure 4 for Figure 2 The longitudinal section shown; Figure 5 for Figure 1 The flowchart for cable end connection in step 7 is shown below. Figure 6 for Figure 1 The diagram shows a structural schematic of a mobile, water-based installation platform with lifting outriggers. Figure 7 for Figure 6 A schematic diagram of the submarine cable end retrieval device shown. Figure 8 for Figure 6A schematic diagram of the lifting mechanism and outrigger piles shown; Figure 9 for Figure 8 The top view shown; Figure 10 for Figure 8 The diagram shows the structure of the square frame shown. Figure 11 for Figure 8 The diagram shows the structure of the front hydraulic cylinder lifting device. Figure 12 for Figure 11 The diagram shows the structure of the insertion / removal pin positioning device.

[0029] In the diagram: 1. Corrosion-resistant circular outer shell; 2. Upper semi-circular shell; 3. Lower semi-circular shell; 4. Bolt; 5. Elastic self-sealing sleeve; 6. Shape memory alloy (SMA) buffer sleeve; 7. High-strength aramid fiber braided sleeve; 8. Cable joint; 9. Nano-ceramic composite material (Al2O3-SiC) layer; 10. Hydrophobic nano-coating; 11. Platform body; 12. Submarine cable chute; 13. Chute deployment mechanism; 14. Outrigger pile lifting hole; 15. Support 16. Leg pile; 17. Pile shoe; 18. Lifting mechanism; 19. Main crane; 20. Auxiliary crane; 21. Submarine cable end retrieval device; 22. Underwater mobile device; 23. Bionic octopus-style flexible grasping system; 24. Acoustic-optical-magnetic composite navigation and positioning system; 25. Telescopic support frame; 26. Silicone arm; 27. Self-supplied energy system; 28. Wireless charging system; 29. ​​Lifting lug; 30. Thruster; 31. Lifting thruster; 22. Square frame; 32. Front hydraulic cylinder lifting device; 33. Rear hydraulic cylinder lifting device; 34. Left hydraulic cylinder lifting device; 35. Right hydraulic cylinder lifting device; 36. Upper square frame; 37. Lower square frame; 38. Column; 39. Front pin hole; 40. Left pin hole; 41. Right pin hole; 42. Front hydraulic cylinder; 43. Slide rail; 44. Slider; 45. Insertion and removal pin positioning device; 46. Positioning pin; 47. Return spring; 48. Electromagnet; 49. Stepped hole. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of this application can be combined with each other.

[0031] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper surface," "lower surface," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "forward," "reverse," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0032] like Figure 1 As shown, a method for on-site connection of ultra-high voltage, high-capacity submarine cables includes the following steps: Step 1, Pre-construction preparation: Select a jack-up type floating motorized installation platform as the installation platform for submarine cable connection; before the installation platform enters the sea area, the materials and machinery required for submarine cable connection should be transported to the installation platform to ensure the needs of joint fabrication; sufficient space should be reserved on the installation platform to meet the needs of submarine cable retrieval, fixing and fabrication site.

[0033] Step 2: Deployment of the outrigger pile lifting-type water-powered installation platform: Based on the location of the submarine cable end at sea, determine the offshore construction area and move the outrigger pile lifting-type water-powered installation platform to the offshore construction area.

[0034] Step 3, Platform Pile Positioning: After the outrigger pile lifting-type water-mobile installation platform is moved to the offshore construction area, the vessel is positioned according to the buoy position, route coordinates and sea conditions, and is parallel to and close to the centerline of the submarine cable route. The position of the outrigger pile is determined according to the S-shaped curve of the cable being thrown to prevent accidental damage to the submarine cable on the seabed. When the outrigger pile lifting-type water-mobile installation platform is floating, the position of the submarine cables on both sides of the installation platform is first determined by scanning equipment or divers. Then, the positioning piles are inserted, and the lifting mechanism is activated to drive the outrigger piles to move down. When the outrigger pile shoes touch the seabed, the insertion of the piles is completed.

[0035] Step 4: Adjust the self-lifting height: After the piles are inserted, continue to start the lifting mechanism. With the support of the outrigger piles, the installation platform will begin to rise and be adjusted to the preset height.

[0036] Step 5: Unfold the cable chutes: Before salvage, unfold the cable chutes on both sides of the outrigger-supported, liftable, water-mobile installation platform and adjust the tilt angle of the cable chutes.

[0037] Step 6: Salvage and Secure the Cable End: Before salvage, install cable chutes on both sides of the outrigger-mounted, lift-type, water-powered installation platform. On-site cable end salvage is primarily accomplished using a full-rotation crane on the outrigger vessel. Before construction, calculations must be performed based on the on-site water depth and the weight of the cable to select the appropriate lifting radius and the tension parameters for salvage. The specific tension for salvage is calculated using the following formula:

[0038] The formula refers to the calculation formula for cable tension test in GB / T32346.1-2015: the coefficient 1.3 is to take into account the additional force generated by the submarine cable due to the influence of wind, waves and currents; considering the tension of the submarine cable at the mud contact point on the cable, 0.2WD is added as a constant; when W0=1.56kN, Ws=0.8kN, H1=25m, H2=10m, H3=35m, Tdl=128kN, that is, the crane must meet the load of 12.8T when performing single-head salvage within the allowable turning radius.

[0039] Step 7: Build a joint fabrication room and cleanroom on the platform: First, build a fabrication room on the installation platform, and then build a cleanroom inside the fabrication room.

[0040] The internal dimensions of the joint fabrication room are 12 meters long, 7 meters wide, and 4 meters high. The joint fabrication room has doors at both ends, and the doors are required to be without bottom beams and fully sealed. Several hanging rings are arranged at various positions on the top of the joint fabrication room, and the exterior of the joint fabrication room is covered with canvas.

[0041] Set up a cleanroom: Build a static Class 1000 cleanroom, 3.5 meters long and 4 meters wide, inside the joint fabrication room.

[0042] To ensure adequate lighting on site, at least five 150-200 watt construction lights should be provided, along with several spare bulbs. Air-cooled fans and dehumidifiers should be installed to ensure the cleanroom environment meets the following requirements: temperature 10-30℃, relative humidity ≤70%, and cleanliness level of Class 1000.

[0043] Indoor power supply: Two separate 220V 5kW power lines and two 380V 25kW power lines are required. The cleanroom must be equipped with lifting equipment of at least 5 tons to assist in the fabrication of flexible joints between the submarine cable ends.

[0044] Step 8, Cable end connection: The cable end is connected using a flexible connector.

[0045] Step 9: Install cable expansion joint protector: like Figure 2 , Figure 3 , Figure 4As shown, the cable expansion joint protector includes a corrosion-resistant circular housing 1, which is formed by connecting an upper semi-circular housing 2 and a lower semi-circular housing 3 via bolts 4. Specifically, the upper semi-circular housing 1, the lower semi-circular housing 2, and the bolts 3 are made of titanium alloy, and their surfaces are covered with a nano-ceramic composite material (Al2O3-SiC) layer 9. The purpose of this design is that the nano-ceramic composite material provides chemical inertness and resistance to seawater corrosion, while the titanium alloy material is lightweight and high-pressure resistant, making it suitable for deep-sea environments.

[0046] The corrosion-resistant circular outer shell 1 contains an elastic self-sealing sleeve 5, a shape memory alloy (SMA) buffer sleeve 6, and a high-strength aramid fiber braided sleeve 7. The elastic self-sealing sleeve 5 is mounted on the cable joint 8, the shape memory alloy (SMA) buffer sleeve 6 is mounted on the elastic self-sealing sleeve 5, and the high-strength aramid fiber braided sleeve 7 is mounted on the shape memory alloy (SMA) buffer sleeve 6. The corrosion-resistant circular outer shell 1 covers the elastic self-sealing sleeve 5, the shape memory alloy (SMA) buffer sleeve 6, and the high-strength aramid fiber braided sleeve 7, with both ends of the elastic self-sealing sleeve 5 extending outside the corrosion-resistant circular outer shell 1. The elastic self-sealing sleeve 5 is used to adapt to cable bending and prevent seawater penetration. The shape memory alloy (SMA) buffer sleeve 6 is used to absorb stress when the corrosion-resistant circular outer shell deforms under high pressure, preventing excessive compression of the cable joint. The high-strength aramid fiber braided sleeve 7 is used to improve tensile strength and resist ocean current erosion and foreign object impact.

[0047] The surface of the elastic self-sealing sleeve 5 is coated with a hydrophobic nano-coating 10, such as a fluorinated polymer, which is used to inhibit salt crystallization and microbial adhesion.

[0048] The installation method of the elastic self-sealing sleeve 5 is as follows: wrap the self-sealing material around the cable joint and achieve a tight fit by hot pressing. The preparation method of the self-sealing material is as follows: mix silicone rubber and nano SiO2 in a certain proportion and prepare a composite material by sol-gel method. The mass ratio of silicone rubber to nano SiO2 is between 90:10 and 95:5.

[0049] Principle: Silicone rubber itself possesses excellent flexibility and insulation, enabling it to adapt to cable bending and provide basic sealing performance. Nano-SiO2 fills the pores of silicone rubber, improving the material's density and resistance to seawater penetration. When the proportion of nano-SiO2 is within a certain range, it ensures that the flexibility of the silicone rubber is not significantly affected while significantly improving the material's barrier performance against high-pressure seawater. Multiple experiments have shown that when the mass ratio of silicone rubber to nano-SiO2 is 92:8, the seawater penetration rate of the material under simulated 1000-meter water pressure is reduced by 80% compared to pure silicone rubber, while the material's flexibility still meets the requirements for cable bending.

[0050] The installation method of the shape memory alloy (SMA) buffer sleeve 6 is as follows: the shape memory alloy (SMA) layer is wrapped around the elastic self-sealing sleeve and fixed by laser welding. The shape memory alloy (SMA) layer is customized by 3D printing.

[0051] The installation method of the high-strength aramid fiber braided sleeve 7 is as follows: the high-strength aramid fiber braided layer is wrapped around the shape memory alloy (SMA) buffer sleeve and fixed by laser welding. The high-strength aramid fiber braided layer is made by an automated braiding process.

[0052] Key innovations of this invention: • Self-sealing mechanism: The elastic self-sealing sleeve is made of a composite material of silicone rubber and nano-SiO2. Under high pressure, it undergoes micro-deformation to fill the gap between the cable and the connector, forming a dynamic seal; the hydrophobic nano-coating can reduce the contact area between seawater and the material surface, thus reducing the permeation rate.

[0053] • Adaptive compensation: The SMA buffer layer automatically adjusts its deformation according to pressure changes to maintain a balanced stress on the joint; the aramid fiber braided layer allows for a certain degree of bending to avoid stress concentration.

[0054] • Long-lasting corrosion resistance: A dense oxide layer forms on the surface of the nano-ceramic sheath, preventing chloride ion penetration; the titanium alloy sheath undergoes anodizing treatment to further enhance corrosion resistance.

[0055] Test and verification: • High pressure test: Apply 10MPa pressure in a simulated deep-sea pressure chamber for 72 hours to check the sealing performance.

[0056] • Corrosion test: Expose the sheath to 5% NaCl salt spray for 1000 hours to assess the corrosion rate.

[0057] • Bending test: Simulate cable bending scenarios to verify adaptive compensation capabilities.

[0058] After the above tests and verifications, the present invention can fully withstand the high pressure of the deep sea, such as a water depth of 1000 meters and a pressure of about 10MPa; it also has good corrosion resistance and can resist seawater, salt spray and microbial adhesion; the present invention can adapt to the bending and thermal expansion and contraction of cable joints; the present invention has a long-term protection function with a design life of ≥20 years, reducing maintenance costs.

[0059] Step 10: Install bend limiters: Install bend limiters on the cable and at both ends of the protector.

[0060] Step 11, Lowering the cable connector into the water: Use the main crane to lower the cable connector into the water, and finally place it on the seabed in an Ω shape.

[0061] Step 12, Pile Removal and Site Retreat: Use the lifting mechanism to drive the outrigger piles upward and reset, and then drive the outrigger pile lifting water-powered installation platform away from the construction site.

[0062] like Figure 5 As shown, the specific steps for connecting the cable ends in step 8 are as follows: Step 8.01, Cable End Pre-treatment: Before end connection, the submarine cable end needs to be heated and straightened. This helps control the insulation eccentricity during on-site flexible joint fabrication and also helps eliminate residual thermal stress during submarine cable manufacturing. When the submarine cable has large bending deformation, it can be preliminarily straightened with a submarine cable straightener before heating and straightening. Step 8.02, Conductor Welding: The welding of the conductor of the ultra-high voltage and high-capacity submarine cable adopts the flip-layer butt welding, and the welding strength can reach more than 180Mpa; Step 8.03, Reactive Cone Roughing: The reactive cone is stripped using a specialized high-voltage submarine cable main insulation layer sharpener. This sharpener can adjust the stripping angle and length of the reactive cone. After setting the angle parameters, the insulation is cut by rotation. While rotating, the cutter head continuously increases in height according to the set angle, ultimately achieving the preset reactive cone shape. The functions of the reactive cone are: firstly, to increase the contact area between the main insulation and the restoring insulation, thereby increasing their adhesion; secondly, since the interface between the main insulation and the restoring insulation has the weakest electric field resistance, increasing the cone length significantly reduces the tangential electric field along the cone surface, greatly reducing the possibility of breakdown along the cone surface. Step 8.04, Inner Semiconductor Shielding Layer Restoration: The inner shielding is restored using a wrapping-then-molding method. A wrapping tape is used to wrap the surface of the conductor. After wrapping, a half-type molding die is installed in the wrapping area. After the conductor shielding is restored, the insulating surface, including the reactive force cone, is precision-machined. The wrapping tape is made of the same grade of semiconducting material as the conductor. A calendering process is used, resulting in uniform thickness, good flatness, and high tensile strength. Temperature is strictly controlled during the tape manufacturing process to prevent premature cross-linking. Step 8.05: Reactive force taper finishing; Step 8.06, Insulation Injection Molding Process: The insulation injection molding restoration process involves injecting insulation material of the same grade as the main body into a specially designed insulation injection mold using a dedicated extruder. Then, through heating and pressurization, the restored insulation is tightly fused with the main body insulation. This process has the highest environmental cleanliness requirements during on-site flexible joint fabrication. To prevent dust and other impurities from entering the insulation, it must be carried out in a mobile, Class 1000 cleanroom. Step 8.07, Insulation vulcanization process: Restoring insulation vulcanization requires heating and nitrogen pressurization; Step 8.08, Insulation Surface Treatment: To achieve the designed insulation and stress cone structure, after the insulation vulcanization is completed, excess insulation needs to be cut off and the surface needs to be polished. During cutting and polishing, the concentricity of the insulation must be ensured. When polishing, first use coarse sandpaper to polish, and then use fine sandpaper to polish until the insulation surface is smooth and flat. Finally, wipe the insulation surface with anhydrous alcohol or special insulation cleaning paper. Step 8.09, Restoration of the outer semiconductive shielding layer and water-blocking layer: The restoration of the outer semiconductive shielding layer adopts the same wrapping and molding restoration process as the inner shielding tape. The tape used is made of the same grade of semiconductive material as the body. After the outer semiconductive shielding layer is restored, a layer of semiconductive water-blocking buffer tape is wrapped around it as a water-blocking layer. Step 8.10, Lead sleeve and PE sheath restoration: The lead sleeve is restored using oxyhydrogen welding, which has the advantages of concentrated flame and low heat, effectively avoiding the impact on internal insulation; the welding material used is the same alloy lead as the body; the PE sheath is restored using a special welding machine to weld the prefabricated sleeve to the body.

[0063] In this embodiment, the connected ultra-high voltage, high-capacity submarine cable is a newly improved 500kV submarine cable by the applicant. The insulation layer of this 500kV submarine cable uses a novel composite insulation material with a thickness of 34mm. This material is made of cross-linked polyethylene (XLPE) mixed with nano-level insulating additives. The nano-level insulating additives are nano-cellulose with a mass percentage content of 4-7%. The nano-level insulating additives can effectively inhibit the accumulation of space charge, improve the insulation performance of the insulation layer under DC voltage, and enhance the mechanical strength and heat resistance of the insulation layer. An anti-corrosion and anti-bioadhesion layer is provided on the surface of the submarine cable. The anti-corrosion and anti-bioadhesion layer includes a nano-anti-corrosion coating and an epoxy resin-based nano-silver coating. The nano-anti-corrosion coating is applied to the surface of the protective adhesive layer. After the anti-corrosion coating dries, the epoxy resin-based nano-silver coating is applied. The mass percentage content of silver in the epoxy resin-based nano-silver coating is 0.20%-0.40%. Experiments have shown that in marine environments, coatings with a silver content of 0.30% significantly reduce microbial adhesion, while silver content below 0.20% results in insufficient anti-corrosion and anti-biological capabilities due to low silver content; and silver content above 0.40% weakens corrosion resistance due to decreased bonding.

[0064] The conductor in the 500kV submarine cable is a water-blocking conductor, which is made of multiple strands of water-blocking wire twisted together. The water-blocking wire includes aluminum alloy wire and water-blocking tape, with the water-blocking tape wrapped around the surface of the aluminum alloy wire. The aluminum alloy wire used in the water-blocking conductor has high conductivity and tensile strength, which can effectively withstand the tension of the submarine cable during laying and operation, while reducing the weight of the submarine cable and facilitating laying.

[0065] like Figure 6As shown, a type of outrigger-lifting water-based motorized installation platform includes a platform body 11. The platform body 11 has cable chutes 12 and chutes deployment mechanisms 13 on both sides. Before deployment, the cable chutes are tightly attached to the side walls of the platform body 11. The chutes deployment mechanism 13 is installed inside the platform body 11 to move the lower end of the cable chutes 12. The upper end of the cable chutes 12 is hinged to the platform body 11. Outrigger-lifting holes 14 are provided at the four corners of the platform body 11. Outrigger piles 15 are inserted into the outrigger-lifting holes 14, and pile shoes 16 are installed at the lower ends of the outrigger piles 15. A lifting mechanism 17 is provided at the outrigger-lifting holes 14 to fix and lift the outrigger piles 15.

[0066] The surface of the platform body 11 is equipped with a main crane 18, an auxiliary crane 19, a miscellaneous crane (not shown in the figure), and a submarine cable end retrieval device 20. The submarine cable end retrieval device 20 is used to retrieve the submarine cable end from the seabed onto the platform body 11. The main crane 18 and the auxiliary crane 19 are used to lift the submarine cable.

[0067] In this embodiment, the technical parameters of the outrigger pile lifting-type water-mobile installation platform are as follows: The thrusters installed on the platform body 11 are ROLLS ROYCE 355 / P50 3250kW electric azimuth thrusters.

[0068] The platform body 11 has a length of 95m, a width of 46m, a depth of 10m, and a draft of 5.7m.

[0069] The diameter of the support pile 15 is 3.8m, and the length of the support leg is 96m.

[0070] The dimensions of the pile shoe are 12.6m x 8.2m x 2.5mm, and the maximum operating water depth is 55m.

[0071] The main generator set consists of four diesel generator sets with a rated power of 800 kWh.

[0072] The emergency and parking generator is a generator with a rated power of 300 kWh.

[0073] The main crane has a capacity of 1000 tons.

[0074] The auxiliary crane has a capacity of 300 tons.

[0075] The hoist for miscellaneous items is 25t.

[0076] The lifting force of a single pile of the lifting mechanism is 5000t, and the support force of a single pile is 6000t.

[0077] The rated speed of the lifting platform is 15m / h.

[0078] The capacity is 50 people.

[0079] like Figure 7 As shown, the submarine cable end retrieval device includes an underwater mobile device 21, a biomimetic octopus-style flexible grasping system 22, and an acoustic-optical-magnetic composite navigation and positioning system 23. The biomimetic octopus-style flexible grasping system 22 and the acoustic-optical-magnetic composite navigation and positioning system 23 are located at the front of the underwater mobile device 21. A thruster 29 is located at the rear of the underwater mobile device 21. Two lifting thrusters 30 are located at the bottom of the underwater mobile device 21. Telescopic support frames 24 are also located on both sides of the bottom of the underwater mobile device 21.

[0080] The acoustic-optical-magnetic composite navigation and positioning system 23 includes a sonar, a lidar, and a magnetometer. The sonar is used to detect the position of the cable end and the seabed topography at a long distance. The lidar is used to provide high-precision three-dimensional point cloud data to assist the device in obstacle avoidance and path planning. The magnetometer is used to detect the weak magnetic field generated by the current at the cable end to achieve accurate positioning.

[0081] The acoustic-optical-magnetic composite navigation and positioning system achieves the fusion of multi-source information. Its advantages are: it can maintain high positioning accuracy in low visibility or turbid waters and reduce reliance on manual markers.

[0082] The biomimetic octopus-style flexible gripping system 22 is used to grip the end of a submarine cable. The biomimetic octopus-style flexible gripping system uses multiple flexible silicone arms 25 as the gripping mechanism.

[0083] The advantages of multiple flexible silicone arms 25 are: they adapt to cable ends of different diameters and materials, the gripping process is gentle, and they avoid the rigid impact of traditional mechanical grippers. Each silicone arm has a built-in micro hydraulic or pneumatic drive unit, which can independently control bending and extension, achieving a close gripping of complex shapes.

[0084] The surface of the silicone arm is covered with a micro-nano biomimetic suction cup structure, which fixes the cable end through the dual action of negative pressure adsorption and friction, reducing slippage and damage during the gripping process.

[0085] The underwater mobile device 21 is equipped with a self-sufficient energy system 26, which employs a solar-wave energy hybrid power generation system. The self-sufficient energy system includes flexible solar panels and wave energy conversion devices. The flexible solar panels are located on the upper surface of the underwater mobile device 21, and the wave energy conversion devices are located on both sides of the underwater mobile device 21. The wave energy conversion devices are pendulum-type wave energy conversion devices. The advantages are: reduced dependence on external energy sources and the ability to achieve long-term autonomous operation.

[0086] The underwater mobile device 21 is equipped with a wireless charging system 27, which uses a pre-set charging base station on the seabed for wireless charging to extend the range of the vehicle.

[0087] The underwater mobile device is equipped with a lifting lug 28 on its top, which is connected to the recovery rope on the winch. The winch is located on a levitation-type water-mobile installation platform with outriggers. The recovery rope is made of carbon fiber.

[0088] Working principle and operating procedure: 1. Deployment phase: The self-reconfigurable modular framework and biomimetic grasping system are assembled by the ship, and the self-powered energy supply system is activated.

[0089] 2. Search and location phase: Activate the acoustic-optical-magnetic composite navigation system to scan the seabed and locate the cable end.

[0090] In the group collaboration mode, multiple devices work together to search different areas and share the positioning results.

[0091] 3. Grasping phase: After the device approaches the target, the bionic octopus arm unfolds and adheres to the cable end, and the suction cup structure initiates negative pressure adsorption.

[0092] 4. Lifting and Recovery Phase: Activate the wireless charging module (if power is insufficient) or directly lift the cable end to the surface platform using a winch. In group collaborative mode, multiple devices work alternately to achieve continuous salvage.

[0093] 5. Autonomous Maintenance and Charging Phase: After completing the mission, the device returns to the underwater charging base station for wireless charging and self-test maintenance.

[0094] like Figure 8 , 9 As shown in Figure 10, the lifting mechanism 17 includes a square frame 31, a front hydraulic cylinder lifting device 32, a rear hydraulic cylinder lifting device 33, a left hydraulic cylinder lifting device 34, and a right hydraulic cylinder lifting device 35. The square frame 31 is composed of an upper square frame 36, a lower square frame 37, and four columns 38. The four corners of the upper square frame 36 are fixedly connected to the lower square frame 37 through the four columns 38. The lower square frame 37 and the upper square frame 36 are parallel to each other. The outrigger 15 being lifted passes through the upper and lower square frames of the square frame 31. The front hydraulic cylinder lifting device 32, the rear hydraulic cylinder lifting device 33, the left hydraulic cylinder lifting device 34, and the right hydraulic cylinder lifting device 35 are respectively installed on the front, rear, left, and right sides of the square frame 31. The front hydraulic cylinder lifting device 32 and the rear hydraulic cylinder lifting device 33 drive the outrigger 15 to lift synchronously, and the left hydraulic cylinder lifting device 34 and the right hydraulic cylinder lifting device 35 drive the outrigger 15 to lift synchronously. The front hydraulic cylinder lifting device 32 and the rear hydraulic cylinder lifting device 33 synchronously drive the outrigger piles to rise and fall, and the left hydraulic cylinder lifting device 34 and the right hydraulic cylinder lifting device 35 have the same structure.

[0095] On the front, rear, left, and right sides of the support pile 15, there are a row of equally spaced front pin holes 39, a row of equally spaced rear pin holes (not shown in the figure), a row of equally spaced left pin holes 40, and a row of equally spaced right pin holes 41. The left pin holes 40 or right pin holes 41 are staggered with the front pin holes 39 or rear pin holes. The front pin holes 39 and rear pin holes correspond to each other, and the left pin holes 40 and right pin holes 41 correspond to each other. The hole spacing between adjacent front pin holes 39 is equal to the hole spacing between adjacent rear pin holes, adjacent left pin holes 40, and adjacent right pin holes 41, all being 2L. In the axial direction of the support pile 15, the distance between the front pin hole or rear pin hole and the left pin hole or right pin hole is L. The pile shoe and the outrigger pile are cylindrical structures. The material of the pile shoe and the outrigger pile is NV-D690 high-strength steel. The yield strength of the outrigger pile 15 is 690MPa. The inner diameter of the outrigger pile is 5m and the wall thickness is 50mm.

[0096] like Figure 11 As shown, the front hydraulic cylinder lifting device includes two front hydraulic cylinders 42, a slide rail 43, a slider 44, and a pin positioning device 45. The two front hydraulic cylinders 42 are vertically mounted on the upper part of the front side of the square frame 31. The slide rail is provided on the square frame 31. The two front hydraulic cylinders 42 simultaneously drive the slider 44 to move along the slide rail 43. The pin positioning device 45 is provided on the slider 44.

[0097] like Figure 12 As shown, the insertion and removal pin positioning device 45 includes a positioning pin 46, a return spring 47, and an electromagnet 48. The positioning pin 46 is horizontally installed in the stepped hole 49 of the slider. When the electromagnet 48 is energized, the electromagnet 48 pulls the positioning pin 46 out of the front pin hole of the outrigger pile 15 by magnetic force, and the return spring 47 is compressed. When the electromagnet 48 is de-energized, the positioning pin 46 is pushed into the front pin hole of the outrigger pile 15 under the action of the return spring 47.

[0098] During the pile extraction and site clearance process, the lifting mechanism 17 raises the outrigger piles 15 as follows: First, the front hydraulic cylinder lifting device, rear hydraulic cylinder lifting device, left hydraulic cylinder lifting device, and right hydraulic cylinder lifting device respectively insert positioning pins into the front pin hole, rear pin hole, left pin hole, and right pin hole on the outrigger pile through the insertion and removal pin positioning device. At this time, the initial state is different. The front hydraulic cylinder lifting device and the rear hydraulic cylinder lifting device are synchronized, and the left hydraulic cylinder lifting device and the right hydraulic cylinder lifting device are synchronized. However, the front and rear hydraulic cylinders and the left and right hydraulic cylinders cannot be at the same working stroke position. The left and right hydraulic cylinders are set to the middle stroke, and the front and rear hydraulic cylinders are in the 0 stroke state.

[0099] Secondly, the front hydraulic cylinder lifting device, rear hydraulic cylinder lifting device, left hydraulic cylinder lifting device, and right hydraulic cylinder lifting device are activated simultaneously, each driving the outrigger pile upwards via the pin-positioning device. Only when the left and right positioning pins are pulled out does the front and rear hydraulic cylinders continue lifting. That is, when the left and right hydraulic cylinders reach their maximum stroke, the left and right hydraulic cylinder lifting devices pull the positioning pins out of the left and right pin holes on the outrigger pile via the pin-positioning device. At this point, under the combined action of the front and rear hydraulic cylinder lifting devices, the outrigger pile continues to move upwards. The left and right positioning pins are inserted into the next pin hole, and all four cylinders lift simultaneously. In other words, the left and right hydraulic cylinder lifting devices drive the pin-positioning device downwards rapidly. After detecting the next left and right pin hole, the positioning pin is inserted, and the left hydraulic cylinder... The front and rear hydraulic cylinder lifting devices start in opposite directions simultaneously, together with the front and rear hydraulic cylinder lifting devices, to move the outrigger pile upwards. When the front and rear hydraulic cylinders reach their maximum stroke, the front and rear hydraulic cylinder lifting devices pull out the positioning pins from the front and rear pin holes on the outrigger pile using the insertion and removal pin positioning device. At this time, under the action of the left and right hydraulic cylinder lifting devices, the outrigger pile continues to move upwards. The left and right hydraulic cylinder lifting devices drive the insertion and removal pin positioning device to move downwards quickly. After detecting the next front and rear pin holes, the positioning pin is inserted. The front and rear hydraulic cylinder lifting devices start in opposite directions simultaneously, together with the left and right hydraulic cylinder lifting devices, to move the outrigger pile upwards until the left and right hydraulic cylinders reach their maximum stroke. Then, repeat the above steps until the pile reaches the required lifting height, then stop working.

[0100] Working principle: The segmented submarine cable end connection of this application is carried out on a levitation-type water-powered installation platform with outrigger piles. During the connection, the installation platform can be raised, reducing the impact of sea waves, thereby making the platform more stable and greatly reducing the sway amplitude, laying the foundation for the precise connection of the submarine cable. In particular, the method of building a joint fabrication room on the platform and building a clean room in the fabrication room not only avoids seawater corrosion during the connection process, but also improves the safety of construction personnel.

[0101] This application improves the cable expansion joint protector, which can fully withstand the high pressure of deep sea and has excellent sealing reliability. The multi-layer protection structure significantly reduces the risk of seawater penetration and can adapt to the bending and thermal expansion and contraction of the cable expansion joint. This invention has long-term protection function with a design life of ≥20 years, reducing maintenance costs.

[0102] This application designs a submarine cable end retrieval device that integrates cutting-edge technologies such as bionics and acoustic-optical-magnetic composite navigation, overcoming the design limitations of traditional retrieval devices. It maintains high positioning accuracy even in low-visibility or turbid waters, reducing reliance on manual marking and featuring precise positioning and high retrieval efficiency. The silicone arm secures the cable end through a combination of negative pressure adsorption and friction, minimizing slippage and damage during the retrieval process.

[0103] The submarine cable end retrieval device adopts a biomimetic octopus-style flexible gripping system. The biomimetic octopus-style flexible gripping system uses multiple flexible silicone arms as gripping mechanisms, which can adapt to cable ends of different diameters and materials. The gripping process is gentle, avoiding the rigid impact of traditional mechanical grippers.

[0104] Furthermore, those skilled in the art can combine and integrate the different embodiments or examples described herein, as well as the features of those embodiments or examples, without contradiction. Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for on-site connection of ultra-high voltage, high-capacity submarine cables at sea, characterized in that, Includes the following steps: Step 1, Preparations before construction: Select a jack-up type water-powered installation platform as the installation platform for submarine cable connection; before the installation platform enters the sea area, transport the materials and machinery required for submarine cable connection to the installation platform. Step 2: Deployment of the outrigger lifting-type water-mobile installation platform: Based on the location of the submarine cable end at sea, determine the offshore construction area and move the outrigger lifting-type water-mobile installation platform to the offshore construction area. Step 3, Platform Pile Positioning: After the outrigger-lifting water-powered installation platform is moved to the offshore construction area, the vessel is positioned according to the buoy location, route coordinates, and sea conditions, and is parallel to and close to the centerline of the submarine cable route. The position of the outrigger piles is determined based on the S-shaped curve of the cable deployment. While the outrigger-lifting water-powered installation platform is floating, the position of the submarine cables on both sides of the installation platform is first determined using survey equipment or divers, and then the positioning and piling are carried out. The lifting mechanism is activated to drive the outrigger piles to move down. When the piling shoe of the outrigger pile touches the seabed, the piling is completed. Step 4: Adjust the self-lifting height: After the pile driving is completed, continue to start the lifting mechanism. With the support of the outrigger piles, the installation platform will begin to rise and be adjusted to the preset height. Step 5: Unfold the cable chutes: Before salvage, unfold the cable chutes on both sides of the outrigger-supported, liftable, water-mobile installation platform and adjust the tilt angle of the cable chutes. Step 6: Salvage and secure the end of the submarine cable: The on-site salvage of the end is accomplished using a full-rotation crane on the outrigger vessel; before construction, calculations are performed based on the on-site water depth and the weight of the submarine cable to select the appropriate lifting radius and tension parameters for salvage. Step 7: Construct a joint fabrication room and cleanroom on the platform: First, construct a fabrication room on the installation platform, and then construct a cleanroom inside the fabrication room; Step 8, Cable Termination Connection: The cable termination shall be connected using a flexible connector. Step 9: Install the cable expansion joint protector; Step 10: Install bend limiters: Install bend limiters on the cable at both ends of the protector; Step 11, Lowering the cable connector into the water: Use the main crane to lower the cable connector into the water, and finally place it on the seabed in an Ω shape; Step 12, Pile Removal and Site Retreat: Use the lifting mechanism to drive the outrigger piles upward and reset, and then drive the outrigger pile lifting water-powered installation platform away from the construction site.

2. The method for on-site connection of ultra-high voltage, high-capacity submarine cables according to claim 1, characterized in that: The cable expansion joint protector includes a corrosion-resistant circular outer shell, which is formed by bolting an upper semi-circular shell and a lower semi-circular shell together. The upper and lower semi-circular shells and bolts are made of titanium alloy, and their surfaces are covered with a nano-ceramic composite material (Al2O3-SiC). Inside the corrosion-resistant circular outer shell are an elastic self-sealing sleeve, a shape memory alloy (SMA) buffer sleeve, and a high-strength aramid fiber braided sleeve. The elastic self-sealing sleeve is mounted on the cable expansion joint, the shape memory alloy (SMA) buffer sleeve is mounted on the elastic self-sealing sleeve, and the high-strength aramid fiber braided sleeve is mounted on the shape memory alloy (SMA) buffer sleeve. The corrosion-resistant circular outer shell covers the elastic self-sealing sleeve, the shape memory alloy (SMA) buffer sleeve, and the high-strength aramid fiber braided sleeve, with both ends of the elastic self-sealing sleeve extending outside the corrosion-resistant circular outer shell. The elastic self-sealing sleeve is used to adapt to cable bending and prevent seawater penetration. The shape memory alloy (SMA) buffer sleeve is used to withstand high pressure under the corrosion-resistant circular outer shell. The elastic self-sealing sleeve absorbs stress during deformation, preventing excessive compression of the cable joint; the high-strength aramid fiber braided sleeve improves tensile strength and resists ocean current erosion and foreign object impact; the surface of the elastic self-sealing sleeve is coated with a hydrophobic nano-coating; the installation method of the elastic self-sealing sleeve is: wrapping the self-sealing material around the cable joint and achieving a tight fit through hot pressing; the preparation method of the self-sealing material is: mixing silicone rubber and nano-SiO2 in a certain proportion and preparing a composite material through the sol-gel method, wherein the mass ratio of silicone rubber to nano-SiO2 is between 90:10 and 95:5; the installation method of the shape memory alloy (SMA) buffer sleeve is: wrapping the shape memory alloy (SMA) layer around the elastic self-sealing sleeve and fixing it with laser welding; the shape memory alloy (SMA) layer is customized by 3D printing; the installation method of the high-strength aramid fiber braided sleeve is: wrapping the high-strength aramid fiber braided layer around the shape memory alloy (SMA) buffer sleeve and fixing it with laser welding; the high-strength aramid fiber braided layer is made by an automated braiding process.

3. The method for on-site connection of ultra-high voltage, high-capacity submarine cables according to claim 1, characterized in that: In step 6, the tensile force T applied during the specific salvage operation... d1 It can be obtained through the following formula: The formula refers to the calculation formula for cable tension test in GB / T32346.1-2015: the coefficient 1.3 is to take into account the additional force generated by the submarine cable due to the influence of wind, waves and currents; considering the tension of the submarine cable at the mud contact point on the cable, 0.2WD is added as a constant.

4. The method for on-site connection of ultra-high voltage, high-capacity submarine cables according to claim 1, characterized in that: In step 7, the internal dimensions of the joint fabrication room are 12 meters long, 7 meters wide, and 4 meters high. A static Class 1000 cleanroom, 3.5 meters long and 4 meters wide, is constructed inside the joint fabrication room. The joint fabrication room has doors at both ends, requiring no bottom beams and complete sealing. Several hanging rings are arranged at various positions on the top of the joint fabrication room, and the exterior of the joint fabrication room is covered with canvas. To ensure sufficient lighting on site, at least five 150-200 watt construction lights are provided, along with several spare bulbs. Air-cooled fans and dehumidifiers are provided to ensure the cleanroom environment meets the following requirements: temperature 10-30℃, relative humidity ≤70%, and cleanliness level reaching Class 1000. The indoor power supply requires two separate 220V 5kW power lines and two 380V 25kW power lines. The joint fabrication area needs to be equipped with lifting equipment of at least 5 tons to assist in the fabrication of flexible joints between the submarine cable ends.

5. The method for on-site connection of ultra-high voltage, high-capacity submarine cables according to claim 1, characterized in that, In step 8, the specific steps for connecting the cable ends are as follows: Step 8.01, Cable End Pre-treatment: Before end connection, the submarine cable end needs to be heated and straightened. This helps control the insulation eccentricity during on-site flexible joint fabrication and also helps eliminate residual thermal stress during submarine cable manufacturing. When the submarine cable has large bending deformation, it can be preliminarily straightened with a submarine cable straightener before heating and straightening. Step 8.02, Conductor Welding: The welding of the conductor of the ultra-high voltage and high-capacity submarine cable adopts the flip-layer butt welding, and the welding strength is above 180Mpa; Step 8.03, Roughing of the Reactive Cone: The stripping of the reactive cone uses a special high-voltage submarine cable main insulation layer sharpener. This sharpener can adjust the angle and length of the reactive cone stripping. After setting the angle parameters, the insulation is cut by rotation. While rotating, the cutter head continuously increases in height according to the set angle, and finally achieves the preset reactive cone shape. Step 8.04, Inner Semiconductor Shielding Layer Restoration: The inner shielding is restored by first wrapping and then molding. The surface of the conductor is wrapped with a wrapping tape. After the wrapping is completed, a half-type molding die is installed in the wrapping area. After the conductor shielding is restored, the insulating surface, including the reactive force cone, is finely polished. The wrapping tape is made of the same grade of semiconducting material as the conductor. Step 8.05: Reactive force taper finishing; Step 8.06, Insulation Injection Molding Process: The insulation injection molding restoration process involves injecting insulation material of the same grade as the main body into a specially made insulation injection mold using a dedicated extruder. Then, through heating and pressurization, the restored insulation is tightly fused with the main body insulation. This process has the highest environmental purification requirements during the on-site flexible joint manufacturing process. To prevent dust and other impurities from entering the insulation, it needs to be carried out in a mobile cleanroom of Class 1000. Step 8.07, Insulation vulcanization process: Restoring insulation vulcanization requires heating and nitrogen pressurization; Step 8.08, Insulation Surface Treatment: To achieve the designed insulation and stress cone structure, after the insulation vulcanization is completed, excess insulation needs to be cut off and the surface needs to be polished. During cutting and polishing, the concentricity of the insulation must be ensured. When polishing, first use coarse sandpaper to polish, and then use fine sandpaper to polish until the insulation surface is smooth and flat. Finally, wipe the insulation surface with anhydrous alcohol or special insulation cleaning paper. Step 8.09, Restoration of the outer semiconductive shielding layer and water-blocking layer: The restoration of the outer semiconductive shielding layer adopts the same wrapping and molding restoration process as the inner shielding tape. The tape used is made of the same grade of semiconductive material as the body. After the outer semiconductive shielding layer is restored, a layer of semiconductive water-blocking buffer tape is wrapped around it as a water-blocking layer. Step 8.10, restoration of lead sleeve and PE sheath: The lead sleeve is restored using oxyhydrogen welding; the welding material used is the same alloy lead as the body; the PE sheath is restored using a special welding machine to weld the prefabricated sleeve to the body.

6. A mobile, waterborne installation platform with lifting outriggers as described in claim 1, characterized in that: The system includes a platform body, on both sides of which are provided submarine cable chutes and chute deployment mechanisms. Before deployment, the submarine cable chutes are tightly attached to the side walls of the platform body. The chute deployment mechanisms are installed inside the platform body to move the lower end of the submarine cable chutes. The upper end of the submarine cable chutes is hinged to the platform body. The platform body has outrigger pile lifting holes at its four corners, through which outrigger piles are inserted. Pile shoes are installed at the lower ends of the outrigger piles. Lifting mechanisms are provided at the outrigger pile lifting holes to fix and lift the outrigger piles. The surface of the platform body is equipped with a main crane, an auxiliary crane, a general cargo crane, and a submarine cable end retrieval device. The submarine cable end retrieval device is used to retrieve the submarine cable end from the seabed onto the platform body. The main crane and the auxiliary crane are used to lift the submarine cable.

7. The outrigger pile lifting type water-mobile installation platform according to claim 6, characterized in that: The submarine cable end retrieval device includes an underwater mobile unit, a biomimetic octopus-style flexible gripping system, and an acoustic-optical-magnetic composite navigation and positioning system. The biomimetic octopus-style flexible gripping system and the acoustic-optical-magnetic composite navigation and positioning system are mounted on the underwater mobile unit. The acoustic-optical-magnetic composite navigation and positioning system includes sonar, lidar, and a magnetometer. The sonar is used for long-range detection of the cable end location and seabed topography. The lidar provides high-precision three-dimensional point cloud data to assist the device in obstacle avoidance and path planning. The magnetometer detects the weak magnetic field generated by the current at the cable end to achieve precise positioning. The biomimetic octopus-style flexible gripping system is used to grip the submarine cable end. This system employs multiple flexible silicone arms as gripping mechanisms. Each silicone arm has a built-in micro-hydraulic or pneumatic drive unit, which can independently control bending and extension to achieve a gripping fit to complex shapes. The surface of the silicone arm... The underwater vehicle features a micro-nano biomimetic suction cup structure that uses both negative pressure adsorption and friction to secure the cable end, reducing slippage and damage during the grasping process. It is equipped with a self-supplied energy system, employing a solar-wave energy hybrid power generation system. This system includes a flexible solar panel on the upper surface of the underwater vehicle, and the wave energy conversion device is either an oscillating water column type or a pendulum type. The vehicle also features a wireless charging system. A lifting lug is located at the top of the underwater vehicle, connecting to a recovery rope on a winch. The winch is mounted on a levitation-type water-mobile installation platform with outriggers. The recovery rope is made of carbon fiber. A thruster is located at the rear of the underwater vehicle, and two lifting thrusters are located at the bottom. A telescopic support frame is also located at the bottom of the underwater vehicle.

8. The outrigger pile lifting type water-mobile installation platform according to claim 6, characterized in that: The front, rear, left, and right sides of the outrigger pile are respectively provided with a row of equally spaced front pin holes, a row of equally spaced rear pin holes, a row of equally spaced left pin holes, and a row of equally spaced right pin holes. The left or right pin holes are staggered with the front or rear pin holes. The front and rear pin holes correspond to each other, and the left and right pin holes correspond to each other. The hole spacing between adjacent front pin holes is equal to the hole spacing between adjacent rear pin holes, adjacent left pin holes, and adjacent right pin holes, all being 2L. In the axial direction of the outrigger pile, the distance between the front or rear pin holes and the left or right pin holes is L.

9. The outrigger pile lifting type water-mobile installation platform according to claim 8, characterized in that: The lifting mechanism includes a square frame, a front hydraulic cylinder lifting device, a rear hydraulic cylinder lifting device, a left hydraulic cylinder lifting device, and a right hydraulic cylinder lifting device. The square frame is composed of an upper square frame, a lower square frame, and four columns. The four corners of the upper square frame are fixedly connected to the lower square frame via the four columns. The lower and upper square frames are parallel to each other. The outriggers to be lifted pass through the upper and lower square frames of the square frame. The front, rear, left, and right hydraulic cylinder lifting devices are respectively installed on the front, rear, left, and right sides of the square frame. The front and rear hydraulic cylinder lifting devices synchronously drive the outriggers to rise and fall, and the left and right hydraulic cylinder lifting devices synchronously drive the outriggers to rise and fall. The lifting device, rear hydraulic cylinder lifting device, left hydraulic cylinder lifting device, and right hydraulic cylinder lifting device have the same structure. The front hydraulic cylinder lifting device includes two front hydraulic cylinders, a slide rail, a slider, and a pin positioning device. The two front hydraulic cylinders are vertically mounted on the upper part of the front side of the square frame. The slide rail is located on the front beam of the square frame. The two front hydraulic cylinders simultaneously drive the slider to move along the slide rail. The pin positioning device is fixed on the slider. The pin positioning device includes a positioning pin, a return spring, and an electromagnet. The positioning pin is horizontally installed in the pin hole of the slider. When the electromagnet is energized, the electromagnet pulls the positioning pin out of the front pin hole of the outrigger pile through magnetic force, and the return spring is compressed. When the electromagnet is de-energized, the positioning pin is pushed into the front pin hole of the outrigger pile under the action of the return spring.

10. The outrigger pile lifting type water-based motorized installation platform according to claim 6, characterized in that: The platform is equipped with a thruster, a main generator set, and an emergency / berthing generator. The thruster is used to propel the platform at sea; the thruster is a Rolls Royce 355 / P50. The platform is equipped with a 3250kW electric azimuth thruster. The platform body has a length of 95m, a width of 46m, a depth of 10m, a draft of 5.7m, outrigger pile diameter of 3.8m, outrigger length of 96m, and pile shoe dimensions of 12.6m x 8.2m x 2.5mm. The maximum operating water depth is 55m. The main generator set consists of four diesel generator sets with a rated power of 800kw, and an emergency / parking generator with a rated power of 300kw. The main crane is 1000t, the auxiliary crane is 300t, the utility crane is 25t, the single pile lifting force is 5000t, the single pile supporting force is 6000t, the rated lifting platform speed is 15m / h, and the capacity is 50 people.

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