Transition joint of crosslinked polyethylene submarine cable and oil-filled submarine cable and repairing method

Abstract

The invention discloses a cross-linked polyethylene submarine cable and oil-filled submarine cable transition joint and a repairing method, the cross-linked polyethylene submarine cable and oil-filled submarine cable transition joint comprises a connecting shell, the connecting shell is provided with an epoxy resin prefabricated body, a silicone rubber stress cone, an oil paper stress cone and a conductor connecting pipe, the epoxy resin prefabricated body is fixedly arranged in the connecting shell, and the silicone rubber stress cone is fixedly arranged in the conductor connecting pipe. The silicon rubber stress cone is located at one end of the epoxy resin prefabricated body, the oil paper stress cone is located at the other end of the epoxy resin prefabricated body, an epoxy bell-shaped opening is formed in the end, close to the oil paper stress cone, of the epoxy resin prefabricated body, and an oil way channel is formed in the epoxy bell-shaped opening. The center of the epoxy resin prefabricated body is provided with a conductor connecting pipe, and two ends of the conductor connecting pipe are respectively provided with a crosslinked polyethylene submarine cable interface and an oil-filled submarine cable interface. Through cooperation of the epoxy resin prefabricated body, the silicone rubber stress cone and the oil paper stress cone, dielectric constant transition of different insulating medium interfaces can be optimized, electric field distortion is reduced, the partial discharge risk is reduced, and the electrical insulation reliability is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of high-voltage submarine cable connection technology, and in particular to a transition joint and repair method for cross-linked polyethylene submarine cables and oil-filled submarine cables. Background Technology

[0002] Oil-filled submarine cables are widely used in large-scale core power transmission projects, such as airports, large power plants, and crossing straits and rivers. They are critical lifelines for ensuring the safety of regional power grids. However, the full life-cycle management technology for their submarine cable accessories has long been dependent on foreign countries, facing three major pain points: First, import dependence leads to high operation and maintenance costs and insufficient timeliness; second, existing domestic cable repair technologies cannot adapt to the heterogeneous connection between 500 kV cross-linked polyethylene (XLPE) submarine cables and oil-filled submarine cables, resulting in a significant risk of insulation interface failure; third, high-value submarine cable assets face significant potential losses, and the reliability of system power supply drops to a critical threshold. Against this backdrop, breakthroughs in the manufacturing technology of high-voltage cross-linked polyethylene-oil-filled submarine cable transition joints are of great strategic significance.

[0003] The current domestic oil-filled submarine cable repair technology faces the following bottlenecks: (1) High risk of multi-interface failure: Dielectric constant difference (XLPE ε≈2.3, oil-filled submarine cable oil paper insulation ε≈3.5) leads to interface electric field distortion >30%, causing partial discharge; (2) Deep-sea sealing failure: The leakage rate is high in the deep water of the marine environment, and leakage of insulating oil directly leads to insulation failure; (3) Lack of repair capabilities: Existing technologies only support the repair of homogeneous cables (XLPE-XLPE), and lack on-site repair solutions for oil-filled XLPE heterogeneous connections.

[0004] Therefore, there is an urgent need to develop an autonomous transition joint solution that is compatible with XLPE submarine cable technology, enables the connection of oil-filled submarine cables to cross-linked polyethylene submarine cables, and allows for rapid on-site repair. Summary of the Invention

[0005] In order to overcome the above-mentioned shortcomings of the prior art, the present invention provides a transition joint and repair method for cross-linked polyethylene submarine cable and oil-filled submarine cable, aiming to provide an XLPE-oil-filled submarine cable transition joint with high electrical insulation reliability and on-site construction capability.

[0006] The technical solution adopted by this invention to solve its technical problem is as follows: a transition joint for cross-linked polyethylene submarine cables and oil-filled submarine cables, comprising a connecting shell, wherein the connecting shell is equipped with an epoxy resin prefabricated body, a silicone rubber stress cone, an oil paper stress cone, and a conductor connecting tube. The epoxy resin prefabricated body is fixedly disposed within the connecting shell. The silicone rubber stress cone is located at one end of the epoxy resin prefabricated body, and the oil paper stress cone is located at the other end of the epoxy resin prefabricated body. An epoxy bell-shaped opening is provided at one end of the epoxy resin prefabricated body near the oil paper stress cone, and an oil passage is provided inside the epoxy bell-shaped opening. A conductor connecting tube is provided at the center of the epoxy resin prefabricated body, and a cross-linked polyethylene submarine cable interface and an oil-filled submarine cable interface are respectively provided at both ends of the conductor connecting tube. The silicone rubber stress cone is located on the side of the epoxy resin prefabricated body near the cross-linked polyethylene submarine cable interface, and the oil paper stress cone is located on the side of the epoxy resin prefabricated body near the oil-filled submarine cable interface.

[0007] As a further improvement of the present invention: a high-voltage electrode is embedded inside the epoxy resin preform, and the high-voltage electrode is fixedly connected to the conductor connecting pipe.

[0008] As a further improvement of the present invention: the silicone rubber stress cone is connected to the connecting housing by a compression fitting.

[0009] As a further improvement of the present invention: the dielectric constant of the silicone rubber stress cone is 2.5-3.0; the oil paper used to wrap the oil paper stress cone is crepe paper or Nomex paper, the wrapping overlap rate is 40-60%, and the cone angle is 15-30°.

[0010] As a further improvement of the present invention: the end of the connecting shell is provided with a sealing assembly, the sealing assembly including a fluororubber O-ring, a heat shrink tubing, a lead-tin alloy sealing layer and a modified epoxy resin sealing layer, the heat shrink tubing is located at both ends of the connecting shell and is respectively sleeved on the outside of the submarine cable, the fluororubber O-ring is located at both ends of the connecting shell and is disposed at the connection between the heat shrink tubing and the connecting shell, the lead-tin alloy sealing layer is disposed on the outside of the connection between the heat shrink tubing and the connecting shell, and the modified epoxy resin sealing layer is disposed on the outside of the lead-tin alloy sealing layer.

[0011] As a further improvement of the present invention: the heat shrink tubing is made of modified polyolefin material; the lead-tin alloy sealing layer is made by lead enamel process; the plastic deformation rate of the lead-tin alloy sealing layer is 10-25%; and the tensile strength of the modified epoxy resin sealing layer is ≥30MPa.

[0012] As a further improvement of the present invention: the oil passage is a straight type, a spiral type or a porous type; the cross-sectional area of ​​the oil passage is 15-35% of the oil passage of the oil-filled submarine cable conductor, and the oil flow resistance is <0.05MPa・s / L.

[0013] As a further improvement of the present invention: the oil passage includes an oil injection passage and an overflow passage.

[0014] As a further improvement of the present invention: the outer side of the transition joint is provided with a reinforcing layer, which is made of steel wire rope or aramid fiber.

[0015] This invention also provides a method for repairing cross-linked polyethylene (XLPE) submarine cables and oil-filled submarine cables, using the aforementioned transition joint for cross-linked polyethylene (XLPE) submarine cables and oil-filled submarine cables, comprising: Precast epoxy resin precast body, silicone rubber stress cone and sealing components; On-site wrapping of oil paper stress cone; The connecting shell, epoxy resin prefabricated body, silicone rubber stress cone, oil paper stress cone and conductor connecting tube are assembled in sequence. The cross-linked polyethylene submarine cable and oil-filled submarine cable are inserted into the two ends of the conductor connecting tube, and sealing components are assembled at both ends of the connecting shell.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention, through the combination of an epoxy resin prefabricated body, a silicone rubber stress cone, and an oil-paper stress cone, optimizes the dielectric constant transition at the interface of different insulating media, reduces electric field distortion, lowers the risk of partial discharge, and ensures the reliability of electrical insulation. The epoxy bell-shaped nozzle adapts to the oil-paper stress cone, providing stable support for the oil-paper insulation, while its internal oil channels ensure smooth circulation of the insulating oil in the oil-filled submarine cable, maintaining the insulation performance of the oil-filled submarine cable side. The epoxy resin prefabricated body is fixed to the connecting shell, resulting in a high degree of prefabrication of the component structure, facilitating on-site assembly, reducing on-site construction complexity, and at the same time, the connecting shell provides stable protection for the overall structure, improving the overall mechanical stability of the transition joint.

[0017] 2. This invention solves the insulation failure problem of heterogeneous submarine cables by controlling the interface electric field non-uniformity to ≤15% through epoxy resin prefabricated body, silicone rubber stress cone with specific dielectric constant, and parameterized oil paper stress cone, combined with dielectric constant gradient design. Sealing components (fluororubber O-rings, modified polyolefin heat shrink tubing, etc.) with clearly defined performance parameters achieve zero leakage at a water depth of 1400m, adapting to deep-sea environments. Oil channels (injection and overflow channels) and reasonable cross-sectional areas and oil flow resistance design ensure stable circulation of insulating oil. The outer reinforcing layer of the transition joint enhances mechanical strength. Prefabricated components and a simplified repair process (pretreatment, orderly assembly) reduce the on-site repair cycle to ≤7 days, balancing reliability, environmental adaptability, and construction efficiency, breaking the dependence on imports. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the present invention.

[0019] Reference numerals: 1. Oil-filled submarine cable; 2. Cross-linked polyethylene submarine cable; 3. Connecting shell; 4. Epoxy resin prefabricated body; 5. Silicone rubber stress cone; 6. Oil paper stress cone; 7. Epoxy bell-shaped nozzle; 8. Oil passage; 9. High voltage electrode; 10. Conductor connecting tube; 11. Compression fitting; 12. Fluororubber O-ring; 13. Heat shrink tubing; 14. Lead-tin alloy sealing layer; 15. Oil paper. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or devices.

[0021] Please see Figure 1 A transition joint for a cross-linked polyethylene (XLPE) submarine cable and an oil-filled submarine cable includes a connecting shell 3. The connecting shell 3 is equipped with an epoxy resin prefabricated body 4, a silicone rubber stress cone 5, an oil paper stress cone 6, and a conductor connecting tube 10. The epoxy resin prefabricated body 4 is fixedly disposed within the connecting shell 3. The silicone rubber stress cone 5 is located at one end of the epoxy resin prefabricated body 4, and the oil paper stress cone 6 is located at the other end of the epoxy resin prefabricated body 4. An epoxy bell-shaped opening 7 is provided at one end of the epoxy resin prefabricated body 4 near the oil paper stress cone 6, and an oil passage 8 is provided inside the epoxy bell-shaped opening 7. A conductor connecting tube 10 is provided at the center of the epoxy resin prefabricated body 4. The two ends of the conductor connecting tube 10 are respectively provided with an XLPE submarine cable 2 interface and an oil-filled submarine cable 1 interface. The silicone rubber stress cone 5 is located on the side of the epoxy resin prefabricated body 4 near the XLPE submarine cable 2 interface, and the oil paper stress cone 6 is located on the side of the epoxy resin prefabricated body 4 near the oil-filled submarine cable 1 interface.

[0022] The conductor connecting tube 10 is equipped with a cross-linked polyethylene submarine cable interface and an oil-filled submarine cable interface at both ends, which can accurately adapt to the cross-linked polyethylene submarine cable 2 and the oil-filled submarine cable 1, achieving targeted connection and ensuring connection stability. Through the cooperation of epoxy resin prefabricated body 4, silicone rubber stress cone 5 and oil paper stress cone 6, the dielectric constant transition of different insulating media interfaces can be optimized, reducing electric field distortion, reducing the risk of partial discharge, and ensuring the reliability of electrical insulation. The epoxy bell-shaped port 7 adapts to the oil paper stress cone 6, which not only provides stable support for the oil paper insulation, but also ensures the smooth circulation of insulating oil in the oil-filled submarine cable 1 through its internal oil passage 8, maintaining the insulation performance of the oil-filled submarine cable 1 side. The epoxy resin prefabricated body 4 is fixed to the connecting shell 3. The component structure has a high degree of prefabrication, which is convenient for on-site assembly and reduces the complexity of on-site construction. At the same time, the connecting shell 3 provides stable protection for the overall structure and improves the overall mechanical stability of the transition joint.

[0023] In some embodiments, a high-voltage electrode 9 is embedded inside the epoxy resin preform 4, and the high-voltage electrode 9 is fixedly connected to the conductor connecting pipe 10.

[0024] The high-voltage electrode 9 is embedded in the epoxy resin prefabricated body 4 and fixed to the central conductor connecting tube 10. In conjunction with the dielectric properties of the epoxy resin prefabricated body 4, the silicone rubber stress cone 5 and the oil paper stress cone 6, the interface electric field distortion is further reduced and the insulation reliability is improved. The fixing design of the high-voltage electrode 9 and the conductor connecting tube 10 and the prefabricated epoxy resin prefabricated body 4 reduce on-site assembly errors, simplify the construction process, and enhance the overall stability.

[0025] In some embodiments, the silicone rubber stress cone 5 is connected to the connecting housing 3 by a compression fitting 11.

[0026] The silicone rubber stress cone 5 is directly connected to the connecting shell 3 through the compression fitting 11. The compression fitting 11 can help to form a tight fit between the silicone rubber stress cone 5 and the cross-linked polyethylene submarine cable 2, thereby improving the interface sealing. The connection method of the compression fitting 11 can ensure the stability of the position of the silicone rubber stress cone 5, and prevent it from shifting due to vibration or external force during the operation or construction of the cross-linked polyethylene submarine cable 2. This ensures the optimization effect of the silicone rubber stress cone 5 on the electric field and maintains the reliability of insulation.

[0027] In some embodiments, the dielectric constant of the silicone rubber stress cone 5 is 2.5-3.0; the oil paper 15 wrapped around the oil paper stress cone 6 is made of crepe paper or Nomex paper, with a wrapping overlap rate of 40-60% and a cone angle of 15-30°.

[0028] The dielectric constant of the silicone rubber stress cone 5 is limited to 2.5-3.0. When paired with the oil paper stress cone 6 with specific parameters (crepe paper / Nomex paper, overlap rate 40-60%, cone angle 15-30°), it can precisely match the dielectric properties of XLPE and epoxy resin prefabricated body 4.

[0029] By precisely designing the curvature of the annular bell-shaped aperture and the geometric parameters of the oil paper stress cone 6, a gradient transition of dielectric constant is formed between the three media: XLPE (ε≈2.3), epoxy resin (ε≈3.5), and oil paper (ε≈3.8), with a gradient change rate ≤0.3 / mm. This reduces the non-uniformity of the interfacial electric field from >30% in the traditional structure to ≤15%, completely eliminating the risk of partial discharge.

[0030] In some embodiments, the high-voltage electrode 9 is fixedly connected to the conductor connecting tube 10 by bolts.

[0031] The high-voltage electrode 9 and the conductor connecting tube 10 are fixed by bolts. The bolt connection has reliable mechanical fastening, which can ensure that the connection between the two is stable under the conditions of submarine cable operation vibration and deep sea pressure changes, avoid electrical connection failure caused by relative displacement, and ensure the stability of current transmission.

[0032] In some embodiments, the end of the connecting housing 3 is provided with a sealing assembly, which includes a fluororubber O-ring 12, a heat shrink tubing 13, a lead-tin alloy sealing layer 14, and a modified epoxy resin sealing layer (not shown in the figure). The heat shrink tubing 13 is located at both ends of the connecting housing 3 and is respectively sleeved on the outside of the submarine cable. The fluororubber O-ring 12 is located at both ends of the connecting housing 3 and is disposed at the connection between the heat shrink tubing 13 and the connecting housing 3. The lead-tin alloy sealing layer 14 is disposed on the outside of the connection between the heat shrink tubing 13 and the connecting housing 3, and the modified epoxy resin sealing layer is disposed on the outside of the lead-tin alloy sealing layer 14.

[0033] The sealing components work in layers. Fluororubber O-rings 12 initially seal the connection between the heat shrink tubing 13 and the connecting housing 3, adapting to vibration scenarios. The heat shrink tubing 13 then reinforces the radial seal on the outside of the submarine cable. A lead-tin alloy sealing layer 14 buffers pressure on the outside, while a modified epoxy resin sealing layer provides rigid protection. These four independent seals effectively block external moisture and water pressure, improving sealing reliability. The heat shrink tubing 13 fits the outer side of the submarine cable, and the O-ring focuses on the connection gap. The lead-tin alloy sealing layer 14 and the modified epoxy resin sealing layer provide external reinforcement, precisely addressing areas prone to leakage at the cable joint end, suitable for complex environments such as deep seas. Assembly is done layer by layer, with a clear operating procedure, facilitating standardized on-site construction and ensuring consistent sealing performance.

[0034] In some embodiments, the heat shrink tubing 13 is made of modified polyolefin material; the lead-tin alloy sealing layer 14 is made using a lead-plating process.

[0035] The heat shrink tubing 13 is made of modified polyolefin material, which has stable heat shrink performance. After heating, it can tightly fit the outer side of the submarine cable and the connecting shell 3, enhancing the radial sealing effect. The lead-tin alloy sealing layer 14 is made of lead-plating process, which is easy to shape and has good fit. It can be adapted to the irregular structure at the end of the transition joint, improving the sealing adaptability.

[0036] In some embodiments, the plastic deformation rate of the lead-tin alloy sealing layer 14 is 10-25%, and the tensile strength of the modified epoxy resin sealing layer is ≥30MPa.

[0037] The lead-tin alloy sealing layer has a plastic deformation rate of 10-25%, which can absorb deep-sea pressure fluctuations and prevent hard and brittle fracture; the modified epoxy resin sealing layer has a tensile strength of ≥30MPa, forming rigid protection. The combination of the two takes into account both buffering and tensile strength, making it suitable for the high-pressure environment of the deep sea.

[0038] In some embodiments, the cross-sectional area of ​​the oil passage 8 is 15-35% of the conductor oil passage of the oil-filled submarine cable 1, and the oil flow resistance is <0.05MPa・s / L.

[0039] By limiting the cross-sectional area of ​​the oil passage 8 to 15-35% of the conductor oil passage of the oil-filled submarine cable 1, a balance is achieved between oil flow smoothness and structural strength. This is because an excessively small cross-sectional area would lead to a sharp increase in oil flow resistance, affecting the circulation of insulating oil, while an excessively large cross-sectional area would prevent weakening the mechanical strength of the connecting shell 3 and the epoxy bell-shaped nozzle 7. With an oil flow resistance of <0.05MPa・s / L, efficient circulation of insulating oil between the oil passage 8 and the conductor oil passage of the oil-filled submarine cable 1 is ensured, effectively removing heat and maintaining stable insulation performance, thus preventing insulation failure due to poor oil flow.

[0040] In some embodiments, the oil passage 8 includes an oil injection passage and an overflow passage.

[0041] The oil passage 8 is equipped with dual channels for oil injection and overflow. The oil injection channel can directionally replenish insulating oil to the oil-filled submarine cable 1 side to meet the oil replenishment needs. The overflow channel can promptly drain excess oil or oil that has expanded due to temperature changes from the oil passage, preventing excessive pressure within the oil passage from damaging the sealing or insulation structure and achieving dynamic oil balance. The dual-channel design forms a closed-loop circulation path, which, compared to a single channel, makes it easier to ensure smooth flow of insulating oil, reduces dead zones in oil flow, and ensures that the insulating oil evenly covers the insulating components on the oil-filled submarine cable 1 side, maintaining stable insulation performance.

[0042] In some embodiments, the oil passage 8 is a straight-through type, a spiral type, or a porous type.

[0043] The oil passage 8 offers three structural options: straight, spiral, and perforated. It can be flexibly adapted to the actual working conditions of the oil-filled submarine cable 1 (such as oil flow requirements and internal space of the connecting shell 3). The straight type has low resistance and is suitable for high oil flow requirements; the spiral type can extend the oil flow path and help the oil to fully contact the insulating components; the perforated type can disperse the oil flow and avoid local oil flow concentration.

[0044] In some embodiments, the outer side of the transition joint is provided with a reinforcing layer (not shown in the figure), which is made of steel wire rope or aramid fiber.

[0045] The outer reinforcing layer of the transition joint is made of steel wire rope or aramid fiber braid. Both materials have high tensile strength, which significantly improves the overall mechanical load-bearing capacity of the joint and effectively resists the tensile forces generated by water flow impact and self-weight pulling during submarine cable laying and operation, preventing joint deformation or breakage. The braiding process allows the reinforcing layer to conform to the outer contour of the transition joint, adapting to the irregular structure of the joint, while also possessing a certain degree of flexibility. It does not restrict the slight bending of the transition joint during construction due to excessive rigidity, balancing mechanical protection and construction adaptability. Steel wire rope and aramid fiber are resistant to seawater corrosion and aging, and can maintain stable performance even after long-term immersion in the marine environment, extending the service life of the transition joint.

[0046] The cross-linked polyethylene submarine cable 2 and oil-filled submarine cable 1 transition joint of the present invention can achieve electric field homogenization and solve the problem of partial discharge caused by interface electric field distortion; the transition joint can withstand 1.4MPa water pressure (equivalent to 1400m water depth) with zero leakage, achieving deep-sea level sealing; the prefabrication technology can quickly shorten the on-site repair cycle and achieve rapid repair; the transition joint can keep the insulating oil of the oil-filled submarine cable 1 circulating smoothly.

[0047] A method for repairing a cross-linked polyethylene submarine cable 2 and an oil-filled submarine cable 1, comprising a transition joint for the cross-linked polyethylene submarine cable 2 and the oil-filled submarine cable 1, including: 4. Precast epoxy resin precast body, 5. Silicone rubber stress cone and sealing components; On-site wrapping of oil paper stress cone 6; The connecting shell, epoxy resin prefabricated body, silicone rubber stress cone, oil paper stress cone and conductor connecting tube are assembled in sequence. The cross-linked polyethylene submarine cable 2 and oil-filled submarine cable 1 are inserted into the two ends of the conductor connecting tube, and sealing components are assembled at both ends of the connecting shell.

[0048] Using the above-mentioned transition joint, the pretreatment only requires wrapping the oil paper stress cone 6, the epoxy resin prefabricated body 4, the silicone rubber stress cone 5 and the sealing components are prefabricated parts, and there is no need to spend time making core components on site. The repair can be completed quickly, shortening the downtime of the submarine cable, improving the repair efficiency, and adapting to the emergency repair scenario on the seabed. This shortens the repair cycle of 500kV heterogeneous submarine cables to ≤7 days (more than 5 times faster than the imported solution).

[0049] Detailed description of the invention: The cross-linked polyethylene submarine cable and oil-filled submarine cable transition joint of the present invention integrates insulation, mechanics, current carrying and sealing, and must ensure uniform electric field distribution, reasonable structural stress, reliable electrical connection and smooth oil circulation.

[0050] The overall structure of the transition joint between cross-linked polyethylene submarine cable and oil-filled submarine cable mainly includes: an epoxy resin prefabricated body, a silicone rubber stress cone, compression fittings, a connecting shell, an oil-paper stress cone, and a lead seal. A gradient insulation component is installed in the center of the transition joint to form an oil-blocking barrier, with "dry and wet separation" on both sides. The connecting shell, located on the oil-filled submarine cable side, is filled with insulating oil and connected to the oil channels of the oil-filled submarine cable.

[0051] The gradient insulation assembly comprises an epoxy resin precast body, a silicone rubber stress cone, an oil-paper stress cone, and a conductor connector. The epoxy resin precast body is typically cast from thermosetting resin. The gradient insulation assembly is cylindrical and contains an embedded high-voltage metal electrode, which is bolted to the conductor connector to form an oil seal. Paper insulation is applied manually to the oil-filled submarine cable, usually followed by a stress cone cast from thermosetting resin, thus forming an oil-paper stress cone. The insulation on the cross-linked polyethylene submarine cable side can employ a "precast assembly" design, in which the silicone rubber stress cone is pressed into the holes of the epoxy resin precast body by compression fittings.

[0052] The transition joint between the cross-linked polyethylene submarine cable and the oil-filled submarine cable includes the following aspects: 1. Dry and wet separation double insulation system The transition joint adopts a zoned insulation design, setting up a physical isolation barrier between the cross-linked polyethylene (XLPE) submarine cable side and the oil-filled submarine cable side to achieve dry and wet separation of the insulation medium.

[0053] (1) Cross-linked polyethylene submarine cable side insulation structure: It is composed of epoxy resin prefabricated body and silicone rubber stress cone, wherein the dielectric constant of silicone rubber stress cone is controlled within the range of 2.5-3.0. It is tightly bonded to the cross-linked polyethylene submarine cable conductor by compression fitting to ensure uniform electric field distribution.

[0054] (2) Insulation structure of oil-filled submarine cable: The epoxy resin prefabricated body is equipped with an epoxy bell-shaped opening, combined with a stress cone of oil paper manually wrapped on site. The oil paper is made of crepe paper or Nomex paper, and the wrapping parameters are strictly limited to an overlap rate of 40-60%, a cone angle of 15-30°, and a single layer thickness of 0.05-0.15mm, forming a continuous conical insulation layer after wrapping. The epoxy bell-shaped opening of the epoxy resin prefabricated body has a pre-set oil passage for the flow of insulating oil, ensuring communication with the oil-filled submarine cable.

[0055] (3) Interface electric field optimization: By precisely designing the curvature of the epoxy bell-shaped opening and the geometric parameters of the oil paper stress cone, the three media XLPE (ε≈2.3), epoxy resin (ε≈3.5), and oil paper (ε≈3.8) form a gradient transition of dielectric constant with a gradient change rate ≤0.3 / mm. This reduces the non-uniformity of the interface electric field from >30% in the traditional structure to ≤15%, completely eliminating the risk of partial discharge.

[0056] 2. Multi-layer sealing system For high-pressure environments with a water depth of 1400m (equivalent to 1.4MPa), a multi-level sealing scheme with independent failure modes is adopted; (1) First-level dynamic seal: Fluororubber O-rings are installed in vibration-sensitive parts, with a compression permanent deformation rate of <15% and resistance to high-frequency mechanical vibration; (2) Second-stage radial seal: Radial compression seal is achieved by using heat shrink tubing, and the material is modified polyolefin to ensure the reliability of static seal; (3) Third-level pressure buffer seal: A lead-tin alloy sealing layer is formed by lead-plating process, with a plastic deformation rate of 10-25%, which absorbs deep-sea pressure fluctuations; (4) Fourth-stage curing seal: Modified epoxy resin (tensile strength ≥30MPa) is poured externally to form a rigid modified epoxy resin sealing layer, which completely blocks external water pressure penetration. Each stage of the seal works independently, and the failure of a single stage does not affect the overall sealing performance.

[0057] 3. Oil circuit circulation design The epoxy resin prefabricated body on the oil-filled submarine cable side integrates oil channels (including oil injection channels and overflow channels). The structure of the oil channels can adopt a straight-through type, spiral type, or multi-hole type design. The cross-sectional area of ​​a single oil channel is strictly controlled within the range of 15-35% of the cross-sectional area of ​​the oil channel of the conductor of the oil-filled submarine cable: below 15% will cause a sharp increase in oil flow resistance, and above 35% will weaken mechanical strength. This design ensures that the insulating oil forms a closed loop circulation between the transition joint and the oil-filled submarine cable, maintaining stable insulation performance.

[0058] 4. Mechanical tensile strength (1) Tensile armor layer: The transition joint is wrapped with a reinforcing layer woven from steel wire rope or aramid fiber, and is connected to the original armor of the cross-linked polyethylene submarine cable through titanium alloy compression fittings. The tensile strength is >200kN. (2) Flexible bending section: A dedicated flexible transition section with a length of 1-3 times the diameter of the transition joint is set at both ends of the transition joint. The flexible bending section integrates a stainless steel braided mesh or spring armor bending limit structure to limit the bending radius to >3m, so as to avoid micro-cracks in the insulation layer of cross-linked polyethylene submarine cable and oil-filled submarine cable due to excessive bending.

[0059] Working principle of the invention: The transition joint of this invention integrates "gradient insulation + four-level sealing + dual oil circuit" to solve the technical problems of heterogeneous interface discharge (≤15% non-uniformity) of XLPE-oil-filled submarine cable, 1400m deep-sea sealing (zero leakage), and oil circuit blockage (oil resistance <0.05MPa·s / L), and achieves rapid on-site repair.

[0060] (1) Dry and wet zone insulation structure The physical isolation between the cross-linked polyethylene (XLPE) submarine cable side and the oil-filled submarine cable side is achieved through the gradient insulation component in the center of the transition joint: the XLPE submarine cable side adopts a combination of epoxy resin prefabricated body and silicone rubber stress cone (dielectric constant 2.5-3.0), and the oil-filled submarine cable side uses the epoxy bell-shaped opening of the epoxy resin prefabricated body and the field-wrapped oil paper stress cone (crepe paper / Nomex paper, overlap rate 40-60%, cone angle 15-30°) to ensure that the two insulation media do not permeate each other.

[0061] (2) Three-dielectric gradient electric field control By precisely designing the geometric transition interface of XLPE (ε≈2.3), epoxy resin (ε≈3.5), and oil paper (ε≈3.8), and controlling the gradient change rate of dielectric constant to ≤0.3 / mm, the non-uniformity of the electric field at the interface of heterogeneous materials is reduced from >30% to ≤15%, thus completely eliminating the risk of partial discharge.

[0062] (3) Four-stage deep-sea sealing system The system is sequentially equipped with a fluororubber O-ring dynamic seal (compression deformation <15%), a heat shrink tubing radial seal, a lead-tin alloy sealing layer (plastic deformation 10-25%), and a modified epoxy resin sealing layer (tensile strength ≥30MPa). The four independent seals can withstand 1.4MPa / 24h (equivalent to 1400m water depth) with zero leakage.

[0063] (4) Dual-channel oil circuit design The epoxy resin prefabricated body on the side of the oil-filled submarine cable integrates dual channels for oil injection and overflow (straight / spiral / multi-hole type). The cross-sectional area of ​​a single channel is strictly controlled within 15-35% of the oil channel of the conductor of the oil-filled submarine cable, and the oil flow resistance is <0.05MPa·s / L, ensuring smooth circulation of insulating oil.

[0064] (5) Tensile armor transition structure The armor layer is made of steel wire rope or aramid fiber and is connected to the original armor of the cross-linked polyethylene submarine cable through titanium alloy compression fittings (yield strength ≥800MPa). The tensile strength is >200kN, ensuring the mechanical reliability of deep-sea laying.

[0065] (6) Flexible bending protection mechanism Flexible transition sections with a length of 1-3 times the diameter are set at both ends of the transition joint, with built-in stainless steel braided mesh or spring armor bending limit structure to forcibly limit the minimum bending radius to ≥3m, preventing micro-cracks from forming in the insulation layer of cross-linked polyethylene submarine cables and oil-filled submarine cables due to bending.

[0066] (7) Prefabricated on-site repair process The epoxy resin prefabricated body, silicone rubber stress cone, and sealing components are all prefabricated in the factory. On-site, only the oil paper stress cone needs to be wrapped and modularly assembled. The connecting shell, epoxy resin prefabricated body, silicone rubber stress cone, oil paper stress cone, and conductor connecting tube are assembled in sequence. The cross-linked polyethylene submarine cable and oil-filled submarine cable are inserted into the two ends of the conductor connecting tube, and sealing components are installed at both ends of the connecting shell. This shortens the repair cycle of 500kV heterogeneous submarine cable to ≤7 days (more than 5 times faster than the imported solution).

[0067] The main functions of this invention are: This invention, through the combination of materials with gradient dielectric constants and geometric optimization, achieves for the first time an electric field non-uniformity of ≤15% at the interface of XLPE, epoxy resin, and oil-paper, thus homogenizing the electric field and avoiding the problem of partial discharge caused by interfacial electric field distortion due to differences in dielectric constants. The sealing assembly passed a 1.4MPa / 24h pressure test (equivalent to a water depth of 1,400m) with zero leakage, demonstrating deep-sea sealing reliability. The prefabricated epoxy resin prefabricated body and modular sealing assembly shorten the repair cycle to within 7 days, more than 5 times faster than imported solutions, enabling on-site splicing repair of cross-linked polyethylene submarine cables and oil-filled submarine cables with high reliability.

[0068] In the description of this invention, it should be understood that the terms "upper end face," "lower end face," "top," "bottom," "left," and "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention. Therefore, they should not be construed as limiting the actual direction of use of this invention. The above embodiments are only used to illustrate the technical solutions of this invention, and not to limit it. Although this invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this invention, and they should all be covered within the scope of the claims and specification of this invention.

Claims

1. A transition joint for cross-linked polyethylene submarine cable and oil-filled submarine cable, characterized in that: The device includes a connecting housing, which houses an epoxy resin prefabricated body, a silicone rubber stress cone, an oil-paper stress cone, and a conductor connecting tube. The epoxy resin prefabricated body is fixedly disposed within the connecting housing. The silicone rubber stress cone is located at one end of the epoxy resin prefabricated body, and the oil-paper stress cone is located at the other end. The epoxy resin prefabricated body has an epoxy bell-shaped opening at the end near the oil-paper stress cone, and an oil passage is provided inside the epoxy bell-shaped opening. A conductor connecting tube is located at the center of the epoxy resin prefabricated body, and a cross-linked polyethylene submarine cable interface and an oil-filled submarine cable interface are respectively provided at both ends of the conductor connecting tube. The silicone rubber stress cone is located on the side of the epoxy resin prefabricated body near the cross-linked polyethylene submarine cable interface, and the oil-paper stress cone is located on the side of the epoxy resin prefabricated body near the oil-filled submarine cable interface.

2. The transition joint between a cross-linked polyethylene submarine cable and an oil-filled submarine cable according to claim 1, characterized in that: A high-voltage electrode is embedded inside the epoxy resin prefabricated body, and the high-voltage electrode is fixedly connected to the conductor connecting pipe.

3. The transition joint between a cross-linked polyethylene submarine cable and an oil-filled submarine cable according to claim 1, characterized in that: The silicone rubber stress cone is connected to the connecting housing via a compression fitting.

4. The transition joint between a cross-linked polyethylene submarine cable and an oil-filled submarine cable according to claim 1, characterized in that: The dielectric constant of the silicone rubber stress cone is 2.5-3.0; the oil paper used to wrap the oil paper stress cone is crepe paper or Nomex paper, with a wrapping overlap rate of 40-60% and a cone angle of 15-30°.

5. The transition joint between a cross-linked polyethylene submarine cable and an oil-filled submarine cable according to claim 1, characterized in that: The end of the connecting shell is provided with a sealing assembly, which includes a fluororubber O-ring, a heat shrink tubing, a lead-tin alloy sealing layer, and a modified epoxy resin sealing layer. The heat shrink tubing is located at both ends of the connecting shell and is respectively sleeved on the outside of the submarine cable. The fluororubber O-ring is located at both ends of the connecting shell and is disposed at the connection between the heat shrink tubing and the connecting shell. The lead-tin alloy sealing layer is disposed on the outside of the connection between the heat shrink tubing and the connecting shell. The modified epoxy resin sealing layer is disposed on the outside of the lead-tin alloy sealing layer.

6. The transition joint between a cross-linked polyethylene submarine cable and an oil-filled submarine cable according to claim 5, characterized in that: The heat shrink tubing is made of modified polyolefin material; the lead-tin alloy sealing layer is made using a lead-plating process.

7. The transition joint between a cross-linked polyethylene submarine cable and an oil-filled submarine cable according to claim 1, characterized in that: The oil passage can be straight, spiral, or porous; the cross-sectional area of ​​the oil passage is 15-35% of the oil passage of the oil-filled submarine cable conductor, and the oil flow resistance is <0.05MPa・s / L.

8. The transition joint between a cross-linked polyethylene submarine cable and an oil-filled submarine cable according to claim 1, characterized in that: The oil passage includes an oil injection passage and an overflow passage.

9. The transition joint between a cross-linked polyethylene submarine cable and an oil-filled submarine cable according to claim 1, characterized in that: The transition joint has a reinforcing layer on its outer side, which is made of steel wire rope or aramid fiber.

10. A method for repairing a cross-linked polyethylene submarine cable and an oil-filled submarine cable, using a transition joint for a cross-linked polyethylene submarine cable and an oil-filled submarine cable as described in any one of claims 1-9, characterized in that: include: Precast epoxy resin precast body, silicone rubber stress cone and sealing components; On-site wrapping of oil paper stress cone; The connecting shell, epoxy resin prefabricated body, silicone rubber stress cone, oil paper stress cone and conductor connecting tube are assembled in sequence. The cross-linked polyethylene submarine cable and oil-filled submarine cable are inserted into the two ends of the conductor connecting tube, and sealing components are assembled at both ends of the connecting shell.

Images