Conductor connection method for a submarine cable flexible joint

Abstract

The application belongs to the technical field of power cables, and discloses a conductor connecting method of a submarine cable flexible joint. The method comprises the following steps: respectively unfolding conductor filaments of a first flexible joint and a second flexible joint to be connected layer by layer, restoring the innermost conductor filaments to obtain a restored layer of the first conductor filaments and the second conductor filaments pre-connected; installing a heating coil and a sealing device in a welding area of the restored layer, continuously introducing nitrogen into the sealing device through a vent of the sealing device to replace air in the sealing device, then starting the heating coil to pyrolyze and gasify the water-blocking material, and the water-blocking material is removed with the nitrogen; when there is no visible object in the exhaust port and the nitrogen concentration exceeds 99.9% within a preset time, the heating of the heating coil is stopped; when the temperature of the restored layer is below 100 DEG C, the introduction of nitrogen is stopped, and then welding, post-welding treatment and restoration of the remaining outer conductor filaments layer by layer are performed, so that welding pores, impurities and other defects are effectively avoided, and the strength and reliability of the welded joint are ensured.

Description

Technical Field

[0001] This invention relates to the field of power cable technology, and in particular to a conductor connection method for a submarine cable flexible joint. Background Technology

[0002] In common land-based cables, there are gaps between the individual wires in the stranded conductor. When moisture enters the conductor, it will spread rapidly along the conductor. However, the operating environment of submarine cables is extremely harsh. In order to achieve the full water-blocking characteristics of the cable, in addition to the buffer water-blocking layer, it is also necessary to fill the gaps between the conductor cores by applying water-blocking grease or wrapping water-blocking yarn / rope during the stranding of the cable conductors, so as to meet the water-blocking performance requirements of submarine cables.

[0003] Submarine cable expansion joints, used for splicing submarine cables, enable the delivery of longer submarine cables to meet the needs of deep-sea and high-capacity power transmission. One of the key aspects of submarine cable expansion joint manufacturing is conductor connection. The quality of the conductor connection directly affects the electrical and mechanical properties of the joint. Conductor connection processing is the foundation for ensuring the long-term reliability of the joint. The conductor connection process mainly includes conductor unfolding, cleaning of water-blocking materials, conductor restoration, and conductor welding.

[0004] However, existing submarine cable flexible joint conductor connections consistently suffer from the following problems: First, water-blocking materials such as polyacrylic acid composite yarn and polyester fiber are difficult to completely remove, leaving behind powder or fibers that are difficult to see with the naked eye to adhere to the gaps between the conductor filaments, resulting in defects such as welding porosity and impurities; second, the high welding temperature can cause the water-blocking material that has not been completely removed from the inner layer of the conductor near the welding area to carbonize, directly contaminating the weld and affecting the welding quality. Furthermore, the quality of existing conductor connections cannot be quickly verified, and the conductor connection process cannot be reworked.

[0005] Therefore, how to reduce the impact of water-blocking materials inside the water-blocking conductor of submarine cables on the conductor connection quality in submarine cable flexible joints, avoid welding pores and impurity defects in the conductor, and make the conductor connection quality basically stable and controllable are the technical problems that urgently need to be solved. Summary of the Invention

[0006] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a conductor connection method for submarine cable flexible joints, so as to reduce the impact of water-blocking materials on the connection quality of submarine cable conductors.

[0007] To achieve the above objectives, the present invention provides a conductor connection method for a submarine cable flexible joint, comprising:

[0008] S1. Unfold the conductor wires of the first and second flexible connectors to be connected layer by layer, and pre-remove the water-blocking material on the unfolded conductor wires; S2. Restore the innermost conductor wires of the first and second flexible connectors to obtain a restored layer where the first and second conductor wires are pre-connected, with the first conductor wire being the innermost conductor wire of the first flexible connector and the second conductor wire being the innermost conductor wire of the second flexible connector; S3. Install a heating coil and a sealing device in the welding area of ​​the restored layer. The sealing device has a vent and an exhaust port; S4. Continuously introduce nitrogen into the sealing device through the vent to replace the air inside the sealing device. After the air replacement is completed, turn on the heating coil to heat the wire. The coil temperature is raised to the pyrolysis temperature of the water-blocking material to achieve pyrolysis and vaporization of the water-blocking material, and the pyrolyzed and vaporized water-blocking material is discharged out of the exhaust port along with nitrogen gas; S5, when there is no visible object at the exhaust port and the nitrogen concentration exceeds 99.9% within a preset time, the heating coil heating is stopped; S6, when the temperature of the restoration layer drops below 100℃, the nitrogen gas supply is stopped, and the gap between the first conductor wire and the second conductor wire is adjusted to 1-1.5mm; S7, the first conductor wire and the second conductor wire after the gap is adjusted are welded and post-weld processed. After the first conductor wire and the second conductor wire are welded, the remaining outer conductor wires are restored layer by layer. The restoration steps are the same as the restoration steps of the innermost conductor wire.

[0009] Preferably, step S1 includes: unfolding the conductor filaments of the first flexible connector and the second flexible connector layer by layer, with the unfolding points of adjacent conductor filaments between different layers being 15-25mm apart, and the unfolding length of each conductor filament being not less than 20mm; cleaning and adsorbing the water-blocking material on the surface of all unfolded conductor filaments to achieve pre-cleaning of the water-blocking material.

[0010] Preferably, the sealing device is a split-type half-sealing device, wherein the vent is connected to a nitrogen source for introducing nitrogen; and the exhaust port is connected to an activated carbon adsorption tank for adsorbing the water-blocking material after pyrolysis.

[0011] Preferably, an image acquisition device and a nitrogen concentration detector are built into the end of the exhaust port. The image acquisition device is used to determine whether there is a visible object at the exhaust port, and the nitrogen concentration detector is used to detect the nitrogen concentration at the exhaust port.

[0012] Preferably, the flow rate of nitrogen gas introduced in step S4 is 5-20 L / min.

[0013] Preferably, if the conductor wire is made of copper, a silver solder with a silver content of more than 15% is used to weld the first conductor wire and the second conductor wire after the gap is adjusted.

[0014] Preferably, the post-weld treatment includes grinding and polishing the weld, and the outer diameter of the conductor single wire is consistent with the outer diameter of the conductor body.

[0015] Preferably, in addition to the innermost and outermost conductor filaments, the post-weld treatment before grinding and polishing also includes uniformly hammering the weld and the adjacent 20mm area to compensate for weld shrinkage and relax the elastic strain of tensile residual stress.

[0016] The beneficial effects of this invention are: by unfolding and restoring the conductor layer by layer, combined with the triple cleaning guarantee of "manual cleaning, pyrolysis vaporization, and nitrogen purging" targeting the characteristics of water-blocking materials, the residual water-blocking materials on the conductor surface and inside the conductor layer near the weld can be thoroughly removed, effectively avoiding defects such as welding porosity and impurities, ensuring the strength and reliability of the welded joint, extending the service life of the submarine cable flexible joint, and each operation step can be standardized, making it easy to promote and apply in actual production. Attached Figure Description

[0017] Figure 1 This is a schematic flowchart of a flexible connector conductor connection method provided in an embodiment of the present invention;

[0018] Figure 2 This is a schematic diagram of a conductor single-wire unfolding structure provided in an embodiment of the present invention;

[0019] Figure 3 This is a schematic diagram of the overall structure of a conductor unfolding flexible joint provided in an embodiment of the present invention;

[0020] Figure 4 This is a partially enlarged schematic diagram of a conductor unfolding flexible joint provided in an embodiment of the present invention;

[0021] Figure 5 This is a schematic diagram of the restoration structure of a flexible connector conductor after connection, provided in an embodiment of the present invention.

[0022] Among them, 1-conductor monofilament, 2-water-blocking material, 3-conductor weld, 4-inner semiconducting layer, 5-insulating layer, 6-outer semiconductor layer, and 7-development point. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that in the description of the present invention, terms such as "upper," "lower," "left," "right," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only for the convenience of describing the present invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific manner. Therefore, they should not be construed as limitations on the present invention. Terms such as "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0024] Figure 1 This is a schematic flowchart of a flexible connector conductor connection method provided by an embodiment of the invention, as shown below. Figure 1 As shown.

[0025] S1, unfold the conductor wires of the first and second flexible connectors to be connected layer by layer, and pre-remove the water-blocking material on the unfolded conductor wires.

[0026] First, the submarine cable splice needs to be pre-treated before connection: the cable core to be welded is fixed on the workbench, the ends of the core are neatly cut, and then the conductor wires are unfolded layer by layer, such as... Figures 2 to 4 As shown, the unfolded dimensions of different layers are different so that they can be restored layer by layer. The unfolded dimensions of different layers can be controlled by the unfolding point. That is, the longer the unfolded dimension, the farther the unfolding point is from the end of the conductor core. Under the principle that the unfolded dimension is not less than 20mm and the interval between the flipping of each conductor wire is within 15 to 25mm, in order to ensure the economy and reliability of the conductor connection, the unfolded dimension of the conductor wire can be minimized as much as possible.

[0027] After unfolding the conductor wires of the first and second flexible connectors layer by layer, the water-blocking material on all conductor wires can be pre-removed. This pre-removal can be done manually, removing the water-blocking material from the surface of each conductor wire layer and cleaning the water-blocking material inside the gaps between the conductor wires with a fine brush and alcohol swabs. Throughout the process, a vacuum cleaner should be used to remove any remaining water-blocking material fragments and fibers from the welding area and surrounding air to prevent secondary adhesion to the conductor surface. The manually removed water-blocking material area should cover at least 20mm on each side of the welding point on each conductor wire layer. The welding area can be understood as the area near the welding points of each conductor wire layer in the first and second flexible connectors. The size of this area is not fixed and can be expanded or reduced based on the welding material or conductor material. After cleaning, each layer of conductor wires can be restored layer by layer for further water-blocking material removal and welding.

[0028] S2, restore the innermost conductor wires of the first flexible connector and the second flexible connector to obtain a restoration layer with the first conductor wire and the second conductor wire pre-connected. The first conductor wire is the innermost conductor wire of the first flexible connector, and the second conductor wire is the innermost conductor wire of the second flexible connector.

[0029] It should be noted that after the first and second conductor filaments are restored, they can be fixed with clamps or metal wires of the same material. When restoring the conductors, the direction of twist of the main filaments should be followed to avoid the filaments from flipping over.

[0030] S3, a heating coil and a sealing device are installed in the area to be welded in the restoration layer. The sealing device is equipped with a vent and an exhaust port.

[0031] Specifically, select a suitable induction heating coil and tightly and evenly wind 2-3 turns around each layer of conductor after restoration and the area to be welded. The winding range of the heating coil should cover the area to be welded. Of course, space can be reserved according to different welding materials to increase the winding area of ​​the heating coil, thereby increasing the area for removing water-blocking materials and avoiding the water-blocking materials from affecting the welding effect.

[0032] Then, after pretreatment (manual cleaning of water-blocking materials, etc.) and installation of the heating coil, a sealing device is installed on the conductor to wrap the welding area and the heating coil. For example, a split-type half-sealing device can be used. This split-type half-sealing device can use high-temperature fluororubber seals to seal the internal parts and the heating coil leads. A vent is provided on the split-type half-sealing device, which can be located at the bottom of the sealing device and connected to an external nitrogen source for introducing nitrogen. An exhaust port is provided at the top of the sealing device, which is connected to an external activated carbon adsorption tank to treat the waste gas after the pyrolysis of residual water-blocking materials on the conductor. This vent and exhaust port setting can remove as much waste gas as possible from inside the sealing device. An image acquisition device (such as a high-definition endoscopic camera) and a nitrogen concentration detector are built into the end of the exhaust port to observe the heating and purging process in real time and to detect the nitrogen concentration inside the device in real time. This allows for thorough detection of the water-blocking material in the welding environment before welding the submarine cable flexible joint, enabling pre-welding verification and avoiding the problem of subsequent inability to quickly verify and affect the conductor welding quality, thus improving the stability of the submarine cable conductor connection quality.

[0033] S4. Nitrogen gas is continuously introduced into the sealing device through the vent to replace the air inside the sealing device. After the air replacement is completed, the heating coil is turned on to raise the temperature of the heating coil to the pyrolysis temperature of the water-blocking material, thereby pyrolyzing and vaporizing the water-blocking material. The pyrolyzed and vaporized water-blocking material is then discharged out of the exhaust port along with the nitrogen gas.

[0034] Specifically, nitrogen can be introduced first to replace the air inside the sealing device. The completion of air replacement can be judged by the nitrogen concentration at the exhaust port. For example, if the nitrogen concentration at the exhaust port remains unchanged, it means that the air replacement is complete. Of course, the air replacement time can also be set directly based on experience or the water-blocking material. For example, nitrogen can be continuously introduced for 2 to 5 minutes, which is sufficient to replace the air. After that, the heating coil is turned on to raise the temperature of the heating coil to the pyrolysis temperature of the water-blocking material and maintain it for a certain period of time to allow the water-blocking material to fully pyrolyze.

[0035] As some examples, the pyrolysis temperatures and pyrolysis times of different water-blocking materials are shown in the table below:

[0036]

[0037] Therefore, when the water-blocking material is a water-blocking grease, the heating coil temperature can be set to 180℃. To save costs, continuous heating can be started after 20 minutes, and the state of the object at the exhaust port and the nitrogen concentration can be observed at any time. The heating coil temperature can be adjusted at any time. For example, if the exhaust concentration has not reached 99.9% after 50 minutes of pyrolysis, it indicates that the pyrolysis effect is not good, and the temperature of the heating coil can be increased. This process can be completed by a nitrogen concentration detector. The nitrogen concentration detector can also only perform observation and alarm functions. When the pyrolysis effect of the water-blocking material is abnormal, an alarm will be issued. Of course, it can also be preset to directly analyze the current pyrolysis status and dynamically adjust the temperature of the heating coil according to the current status when the pyrolysis effect is abnormal. The same applies to other water-blocking materials, which will not be explained in detail here.

[0038] Nitrogen gas is introduced throughout the heating process of the heating coil. By combining the positions of the vent and exhaust ports, the welding area of ​​the cable core conductor can be purged from bottom to top. The nitrogen flow rate can be set to 5-20 L / min. The specific flow rate can be determined based on the pyrolysis effect of the water-blocking material. For example, if the water-blocking material is difficult to pyrolyze or there is too much water-blocking material on the surface, the nitrogen flow rate can be increased to enhance the purging effect of nitrogen on the water-blocking material, completely removing the vaporized water-blocking material from the welding area and preventing the water-blocking material from re-solidifying on the surface of the conductor welding area and causing contamination during the welding process.

[0039] S5. When there is no visible object at the exhaust port and the nitrogen concentration exceeds 99.9% within a preset time, the heating coil will stop heating.

[0040] Specifically, when the image acquisition device (such as a high-definition camera) does not capture any visible volatile substances such as smoke or oil vapor, and the nitrogen detector shows that the nitrogen concentration exceeds 99.9% for a preset time (e.g., within 3 minutes), it is determined that the pyrolysis of the water-blocking material is complete, and the heating coil is stopped. However, the nitrogen supply will not be stopped at this time. Nitrogen should continue to be purged until the temperature of the conductor restoration layer drops below 100°C to prevent conductor oxidation.

[0041] It should also be noted that, in order to save on labor costs, algorithms can be used to analyze image data to determine whether there is any smoke, oil vapor, etc., which will not be elaborated here.

[0042] S6. When the temperature of the restoration layer drops below 100°C, stop the nitrogen gas supply and adjust the gap between the first conductor filament and the second conductor filament to 1-1.5 mm.

[0043] S7, Weld the first conductor wire and the second conductor wire after adjusting the gap and perform post-weld processing. After the first conductor wire and the second conductor wire are welded, restore the remaining outer conductor wire layer by layer. The restoration steps are the same as the restoration steps of the innermost conductor wire.

[0044] After the water-blocking material has been pyrolyzed and the conductor wires have cooled down, welding can be prepared. Before welding, adjust the positions of the female and male conductors, confirm that the first and second conductor wires are accurately connected, and control the gap between them to 1-1.5 mm. Then, a high-frequency argon arc welding machine can be used for welding.

[0045] The welding rods can be selected according to different conductor materials. For example, when the core of the submarine cable is a copper conductor, silver welding rods with a silver content of more than 15% are preferred, as they have good wettability and fluidity and can obtain higher bonding strength. For aluminum, aluminum-based welding rods with corresponding strength are preferred, and for aluminum alloy conductors, aluminum alloy-based welding rods are preferred.

[0046] After welding, use a flat, elongated, round-headed hammer to quickly and evenly hammer the weld and the adjacent 20mm area. Hammering causes lateral plastic stretching of the weld metal, compensating for weld shrinkage, relaxing the elastic strain of tensile residual stress, and preventing weld cracks. In this way, the mechanical force of the hammering adds a compressive stress on top of the existing tensile residual stress, causing controllable plastic deformation ("expanding" or "upsetting") in the weld area. This deformation compensates for weld shrinkage and offsets the shrinkage tensile stress generated during weld cooling, thus reducing or even converting harmful "residual tensile stress" into beneficial "compressive stress." In multi-layer welding, the innermost and outermost weld layers are generally not hammered, but each of the remaining layers must be hammered to compensate for weld shrinkage and relax the elastic strain of tensile residual stress.

[0047] After cooling, the welded surfaces of each conductor layer are uniformly ground and polished to restore the conductor surface flatness. Simultaneously, it is ensured that the outer diameter of the welded restoration layer is consistent with the outer diameter of the conductor body after grinding. For welding of multi-layer conductor monofilament submarine cable joints, the above restoration steps can be performed layer by layer to achieve the connection of the submarine cable flexible joint, avoiding the influence of water-blocking materials on the conductor welding effect. The restored joint conductor structure is as follows: Figure 5 As shown.

[0048] This allows for the removal of powders or fibers that are difficult to distinguish with the naked eye by introducing nitrogen gas, thus avoiding defects such as welding porosity and impurities. Furthermore, the temperature control of the heating coil vaporizes any remaining water-blocking material between the conductor filaments, preventing carbonization and contamination of the weld during welding, thereby improving welding quality and stability.

[0049] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for conductor connection of a submarine cable flexible joint, characterized in that, Includes the following steps: S1, unfold the conductor wires of the first and second flexible connectors to be connected layer by layer, and pre-remove the water-blocking material on the unfolded conductor wires. S2, restore the innermost conductor wires of the first flexible connector and the second flexible connector to obtain a restoration layer with the first conductor wire and the second conductor wire pre-connected. The first conductor wire is the innermost conductor wire of the first flexible connector, and the second conductor wire is the innermost conductor wire of the second flexible connector. S3, Install a heating coil and a sealing device in the area to be welded of the restoration layer. The sealing device is provided with a vent and an exhaust port. S4. Nitrogen gas is continuously introduced into the sealing device through the vent to replace the air inside the sealing device. After the air replacement is completed, the heating coil is turned on to raise the temperature of the heating coil to the pyrolysis temperature of the water-blocking material, thereby pyrolyzing and vaporizing the water-blocking material. The pyrolyzed and vaporized water-blocking material is then discharged out of the exhaust port along with the nitrogen gas. S5, when there is no visible object at the exhaust port and the nitrogen concentration exceeds 99.9% within a preset time, the heating coil heating is stopped; S6, when the temperature of the recovery layer drops below 100°C, stop the nitrogen gas supply and adjust the gap between the first conductor wire and the second conductor wire to 1-1.5 mm; S7, Weld the first conductor wire and the second conductor wire after adjusting the gap and perform post-weld processing. After the first conductor wire and the second conductor wire are welded, restore the remaining outer conductor wire layer by layer. The restoration steps are the same as the restoration steps of the innermost conductor wire.

2. The method according to claim 1, characterized in that, Step S1 includes: The conductor wires of the first and second flexible connectors are unfolded layer by layer, with the unfolding points of adjacent conductor wires between different layers being 15 to 25 mm apart, and the unfolding length of each conductor wire being not less than 20 mm. The water-blocking material on the surface of all the unfolded conductor filaments is cleaned and adsorbed to achieve pre-cleaning of the water-blocking material.

3. The method according to claim 1, characterized in that, The sealing device is a split-type half-sealing device. The vent is connected to a nitrogen source to introduce nitrogen. The exhaust port is connected to an activated carbon adsorption tank, which is used to adsorb the water-blocking material after pyrolysis.

4. The method according to claim 3, characterized in that, An image acquisition device and a nitrogen concentration detector are built into the end of the exhaust port. The image acquisition device is used to determine whether there is a visible object at the exhaust port, and the nitrogen concentration detector is used to detect the nitrogen concentration at the exhaust port.

5. The method according to claim 1, characterized in that, In step S4, the flow rate of nitrogen gas introduced is 5–20 L / min.

6. The method according to claim 1, characterized in that, If the conductor wire is made of copper, then a silver solder with a silver content of more than 15% is used to weld the first conductor wire and the second conductor wire after the gap is adjusted.

7. The method according to claim 1, characterized in that, The post-welding treatment includes grinding and polishing the weld, and the outer diameter of the conductor single wire is consistent with the outer diameter of the conductor body.

8. The method according to claim 7, characterized in that, In addition to the innermost and outermost conductor filaments, the post-weld treatment before grinding and polishing also includes uniformly hammering the weld and the adjacent 20mm area.

Images