Method for fusion jointing of high voltage cable soft joint insulation and submarine cable

Abstract

The application discloses a high-voltage cable soft joint insulation layer melting connection method and a submarine cable, and belongs to the technical field of high-voltage cable technology, and is characterized in that the method comprises the following steps: step S1, manufacturing a reaction force cone; step S2, opening a micro groove; step S3, filling uncrosslinked insulation particles; step S4, melting connection: a connection forms an integrated insulation layer; step S5, shaping the integrated insulation layer; and step S6, polishing the integrated insulation layer. In the vulcanization melting process, the micro groove and the nanoscale uncrosslinked XLPE insulation particles form a transition layer of cable connection, and the mechanical strength of the connection is greatly improved. Especially when the micro groove is filled, the nanoscale uncrosslinked XLPE insulation particles are bonded into a group by using a crosslinking initiator, so that the micro groove can be filled, and the insulation particles and the micro groove can be crosslinked, and therefore the crosslinking degree of the insulation layer melting connection is further improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of high-voltage cables, and particularly relates to a melting connection method for an insulation layer of a high-voltage cable soft joint and a submarine cable. BACKGROUND

[0002] A high-voltage cross-linked polyethylene insulated power cable is important infrastructure for power transmission, and especially for power transmission across a large sea area, since overhead lines cannot be laid, and a high-voltage cross-linked polyethylene insulated submarine cable becomes a necessary choice. For a high-voltage cross-linked polyethylene submarine cable, continuous length is one of the basic requirements. Since the manufacturing length of a single cable has a limit, and the laying of a submarine cable requires that a prefabricated cable intermediate joint is not used as much as possible, in order to achieve a sufficient transmission distance, a single section of cable must be connected to the required length by using a soft joint, which is also called a factory soft joint.

[0003] The most critical link of the soft joint is the process of "cross-linked polyethylene material extrusion or wrapping -> high-temperature and high-pressure insulation vulcanization". How to restore the XLPE insulation layer after the inner shielding is completed is the key to the success of the entire soft joint. There are two methods in the prior art.

[0004] Method one: the connection of the XLPE insulation layer of the soft joint is mainly to extrude the insulation material by using a special insulation forming mold, and to be formed by pressure and high-temperature vulcanization in a vulcanization pipe, so as to ensure that the injection-molded XLPE cable material and the cable body are fused together. The specific operation steps are as follows, including: the positions of the completed conductor joint and the conductor shielding joint are cleaned and treated, and then are placed in the insulation forming mold and preheated to 105 DEG C; the XLPE cable material is extruded into the insulation forming mold by using an extruder, and the extrusion is stopped when the cable material overflows from both ends of the forming mold, and the cable joint is cooled to room temperature. The forming mold is removed, and a vulcanization pipe is replaced, air is discharged and nitrogen is injected, and vulcanization is performed at 200 DEG C and 1.2 MPa, so as to complete the insulation layer joint.

[0005] Method two: the connection of the XLPE insulation layer of the soft joint is to first manufacture XLPE cable material into a film belt of a certain specification, and to process the XLPE cable material into a "pre-vulcanized irradiation cross-linked belt" by using a nuclear radiation process for standby use. When the joint is manufactured, the cross-linked belt is wound on the welded wire core layer by layer to reach a certain size, and then a forming mold is used for vulcanization forming at an air pressure of 0.6 MPa and a high temperature of about 160 DEG C.

[0006] No matter method one or method two, there is a common problem that cannot be solved. The basic principle of soft joint manufacturing is to cut the XLPE insulation of the cable body which has been crosslinked into a reaction force cone in the shape of a pencil tip, and to cover the surface of the reaction force cone with un-crosslinked XLPE insulation material by extrusion or wrapping molding. There will be a connection interface between the un-crosslinked XLPE insulation material and the cable body insulation material. Since the cable body insulation has completed the crosslinking reaction, the crosslinking initiator (i.e. dicumyl peroxide, DCP) in the material has been consumed. At the connection interface, due to the lack of crosslinking agent, the crosslinking degree is relatively low, which leads to low mechanical strength of the soft joint at the recovery interface, and thus the original mechanical properties of the cable body insulation cannot be achieved. Since the high-voltage submarine cable is used under strong water pressure for a long time, and the submarine cable will bear dragging and bending stress many times during installation, if the crosslinking degree at the recovery interface of the soft joint is not enough, repeated stress fatigue will cause stress defects in the insulation material at this place, which will eventually lead to failure of the soft joint. Therefore, how to improve the mechanical strength of the insulation layer connection is a problem to be solved at present. SUMMARY

[0007] The purpose of the present application is to provide a high-voltage cable soft joint insulation layer melting connection method and a submarine cable which can improve the mechanical strength of the connection.

[0008] To solve the above technical problems, the technical scheme adopted by the present application is:

[0009] A high-voltage cable soft joint insulation layer melting connection method, comprising the following steps:

[0010] Step S1, making a reaction force cone: after completing the connection of the inner shielding layer, the insulation layer of the cable connection end is cut into a conical structure to form a reaction force cone;

[0011] Step S2, opening a micro groove: a micro groove is created on the surface of the reaction force cone, so that the micro groove covers the entire surface of the reaction force cone;

[0012] Step S3, filling un-crosslinked insulation particles: nano-sized un-crosslinked XLPE insulation particles are filled into the micro groove, and all the micro grooves on the surface of the reaction force cone are filled;

[0013] Step S4, melting connection: the two reaction force cones of the insulation layer of the cable connection end are melted and connected together by using un-crosslinked XLPE insulation material, so that the connection forms an integrated insulation layer;

[0014] Step S5, shaping the integrated insulation layer: the roundness of the integrated insulation layer is adjusted by polishing;

[0015] Step S6, polishing the integrated insulation layer: polishing the integrated insulation layer to make the roughness of the surface of the integrated insulation layer not greater than 0.9 μm.

[0016] Further, in the step S2, the surface of the reaction force cone is subjected to laser scanning treatment by using the forging laser head of the laser forging system, and a spiral micro groove is formed on the surface of the reaction force cone, and the pitch of the spiral micro groove is 50 μm.

[0017] Further, the related parameters of the laser scanning treatment are as follows: the defocusing amount is 2.8 mm; the laser power is 110 W; the repetition frequency is 100 kHz; the scanning speed is 1530 mm / s, and the spot overlap rate is 86%.

[0018] Further, in the step S3, the method for filling the nanoscale uncrosslinked XLPE insulation particles is as follows: after the nanoscale uncrosslinked XLPE insulation particles are mixed with a solvent to form a briquette, the briquette is filled into the micro groove. The nanoscale uncrosslinked XLPE insulation particles can be agglomerated by adding the solvent, so that the micro groove can be filled.

[0019] Further, the solvent is a crosslinking initiator. The crosslinking initiator can not only agglomerate the nanoscale uncrosslinked XLPE insulation particles, but also improve the crosslinking degree of the melt connection of the insulation layer and improve the tensile strength of the connection of the insulation layer.

[0020] Further, the crosslinking initiator is dicumyl peroxide (DCP).

[0021] Further, in the step S6, the surface of the integrated insulation layer is subjected to laser polishing treatment by using the forging laser head of the laser forging system.

[0022] Further, the related parameters of the laser polishing treatment are as follows: the defocusing amount is 3.3 mm; the laser power is 80 W; the repetition frequency is 88 kHz; the scanning speed is 1200 mm / s, and the spot overlap rate is 81%.

[0023] Further, in the step S4, the melt connection is an extrusion and vulcanization process in which the hot melt uncrosslinked XLPE insulation material is extruded and covered on the surface of the reaction force cone by using an insulation forming die, or is a wrapping and vulcanization process in which the uncrosslinked XLPE insulation tape is wrapped on the surface of the reaction force cone.

[0024] A submarine cable comprises a high-voltage cable soft joint made by using the melt connection method of the high-voltage cable soft joint insulation layer.

[0025] The beneficial effects of the present application are as follows:

[0026] The micro groove is filled with the nanoscale uncrosslinked XLPE insulating particles, and in the vulcanization and melting process, the micro groove and the nanoscale uncrosslinked XLPE insulating particles form a transition layer for cable connection, and through the crosslinking of the nanoscale uncrosslinked XLPE insulating particles in the transition layer and the uncrosslinked XLPE insulating material covering the surface of the reaction force cone, the mechanical strength of the connection is greatly improved.

[0027] The nanoscale uncrosslinked XLPE insulating particles are bonded into groups by using a crosslinking initiator when filling the micro groove, which not only ensures that the micro groove can be filled, but also enables the nanoscale uncrosslinked XLPE insulating particles to be crosslinked with the micro groove, thereby further improving the crosslinking degree of the melting connection of the insulating layer, and improving the tensile strength and bending resistance of the connection of the insulating layer.

[0028] The roundness of the integrated insulating layer is adjusted by polishing, so that the electric field distribution is more uniform, and especially the integrated insulating layer is polished, thereby eliminating the protrusions and depressions on the surface of the insulating layer at the connection, to avoid partial discharge at the contact surface between the cable insulating layer and the outer semiconductive shielding layer, thereby causing the electric tree phenomenon and the insulating layer breakdown phenomenon, and greatly improving the safety and reliability of the cable connection. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 A flowchart of the melting connection method of the insulating layer of the high-voltage cable flexible joint. DETAILED DESCRIPTION

[0030] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be further described in detail below in combination with the drawings and specific embodiments, and it should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0031] In the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper surface", "lower surface", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "forward rotation", "reverse rotation", "axial", "radial", "circumferential" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0032] As shown in Figure 1 A melting connection method of an insulating layer of a high-voltage cable flexible joint, comprising the following steps:

[0033] Step S1, making reaction force cone: after the connection of the inner shielding layer is completed, the insulating layer of the cable connection end is cut into a conical structure to form a reaction force cone.

[0034] Step S2, opening micro-groove: micro-grooves are created on the surface of the reaction force cone, so that the micro-grooves cover the entire surface of the reaction force cone.

[0035] Specifically, the surface of the reaction force cone is processed by laser scanning using a forging laser head of a laser forging system, and a spiral micro-groove is formed on the surface of the reaction force cone, and the pitch of the spiral micro-groove is 50 μm.

[0036] The related parameters of the laser scanning processing are as follows: the defocusing amount is 2.8 mm; the laser power is 110 W; the repetition frequency is 100 kHz; the scanning speed is 1530 mm / s, and the spot overlap rate is 86%.

[0037] Step S3, filling uncrosslinked insulating particles: nanoscale uncrosslinked XLPE insulating particles are filled into the micro-grooves, and all the micro-grooves on the surface of the reaction force cone are filled.

[0038] Specifically, the method of filling nanoscale uncrosslinked XLPE insulating particles is as follows: after the nanoscale uncrosslinked XLPE insulating particles are mixed with a solvent to form a mass, the mass is filled into the micro-grooves. The addition of the solvent can make the nanoscale uncrosslinked XLPE insulating particles form a mass, so as to ensure that the micro-grooves are filled.

[0039] In this embodiment, the solvent is a crosslinking initiator, and the crosslinking initiator is dicumyl peroxide (DCP). The crosslinking initiator not only makes the nanoscale uncrosslinked XLPE insulating particles form a mass, but also improves the crosslinking degree of the insulating layer melt connection and the tensile strength of the insulating layer connection.

[0040] Step S4, melt connection: the two reaction force cones of the cable connection end insulating layer are melt connected together by using uncrosslinked XLPE insulating material, so that the connection forms an integrated insulating layer.

[0041] In this embodiment, the melt connection adopts the existing technology, specifically, an insulating forming mold is used to extrude the hot melt uncrosslinked XLPE insulating material and cover it on the surface of the reaction force cone.

[0042] Of course, the wrapping vulcanization process of wrapping the uncrosslinked XLPE insulating tape on the surface of the reaction force cone can also be used.

[0043] Step S5, shaping the integrated insulating layer: the roundness of the integrated insulating layer is adjusted by polishing;

[0044] Step S6, polishing the integrated insulation layer: polishing the integrated insulation layer to make the roughness of the surface of the integrated insulation layer not more than 0.9 mu m.

[0045] Specifically, the surface of the integrated insulation layer is subjected to laser polishing treatment by using a forging laser head of a laser forging system, and the related parameters of the laser polishing treatment are as follows: the defocusing amount is 3.3 mm; the laser power is 80 W; the repetition frequency is 88 kHz; the scanning speed is 1200 mm / s, and the spot overlap rate is 81%.

[0046] A submarine cable comprising a high-voltage cable joint made using the method for fusion bonding of the insulation layer of a high-voltage cable joint according to the present application.

[0047] Working principle: The micro groove is created on the surface of the reaction force cone, so that the micro groove covers the entire surface of the reaction force cone, and then the nano-scale uncrosslinked XLPE insulation particles are filled into the micro groove, when the vulcanization fusion is carried out, not only the crosslinking between the nano-scale uncrosslinked XLPE insulation particles is carried out, but also the crosslinking between the nano-scale uncrosslinked XLPE insulation particles and the uncrosslinked XLPE insulation material of the extruded or wrapped layer is carried out, and in the vulcanization fusion process, the micro groove and the nano-scale uncrosslinked XLPE insulation particles form a transition layer for cable connection, which greatly improves the mechanical strength of the connection; especially when filling the micro groove, the nano-scale uncrosslinked XLPE insulation particles are bonded into a group by using a crosslinking initiator, which not only ensures that the micro groove can be filled, but also enables the nano-scale uncrosslinked XLPE insulation particles to be crosslinked with the micro groove, thereby further improving the crosslinking degree of the insulation layer fusion connection, so as to improve the mechanical strength of the insulation layer connection, and when the present application is used in high-voltage submarine cables, the high-voltage submarine cables can adapt to the working environment under long-term strong water pressure, and the submarine cables also have the ability to withstand multiple dragging and bending during installation.

[0048] The present application also adjusts the roundness of the integrated insulation layer by polishing, so that the electric field distribution is more uniform, and especially the integrated insulation layer is subjected to polishing treatment, so that the roughness of the surface of the integrated insulation layer is not more than 0.9 mu m, so as to eliminate the protrusions and depressions on the surface of the insulation layer at the connection, so as to avoid the occurrence of partial discharge at the contact surface between the cable insulation layer and the outer semiconductive shielding layer, thereby causing the electric tree phenomenon and the insulation layer breakdown phenomenon, and greatly improving the safety and reliability of the cable connection.

[0049] In addition, the different embodiments or examples described in the specification and the features of the different embodiments or examples can be combined and combined by those skilled in the art without contradiction. Although the embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and cannot be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A method of fusion jointing of a high voltage cable soft joint insulation layer, characterized in that, It comprises the following steps: Step S1, making reaction force cone: after the connection of the inner shielding layer is completed, the insulating layer of the cable connection end is cut into a conical structure to form a reaction force cone; Step S2, opening microgrooves: microgrooves are created on the surface of the reaction force cone, so that the microgrooves cover the entire surface of the reaction force cone; a forging laser head of a laser forging system is used to perform laser scanning treatment on the surface of the reaction force cone to form helical microgrooves on the surface of the reaction force cone, and the pitch of the helical microgrooves is 50 μm; Step S3, filling uncrosslinked insulation particles: nanoscale uncrosslinked XLPE insulation particles are filled into the microgrooves and fill all the microgrooves on the surface of the reaction force cone; Step S4, fusion connection: the two reaction force cones of the insulating layer of the cable connection end are fused and connected together by using uncrosslinked XLPE insulation material, so that the connection forms an integrated insulating layer; Step S5, shaping the integrated insulating layer: the roundness of the integrated insulating layer is adjusted by polishing; Step S6, polishing the integrated insulating layer: the integrated insulating layer is polished to make the roughness of the surface of the integrated insulating layer not greater than 0.9 μm.

2. The fusion connection method of the insulating layer of the high-voltage cable flexible joint according to claim 1, characterized in that: The relevant parameters of the laser scanning treatment are as follows: the defocusing amount is 2.8 mm; the laser power is 110 W; the repetition frequency is 100 kHz; the scanning speed is 1530 mm / s, and the spot overlap rate is 86%.

3. The method of fusion bonding of the insulation of a high voltage cable joint according to claim 1, characterized in that: In the step S3, the method for filling the nanoscale uncrosslinked XLPE insulation particles is as follows: the nanoscale uncrosslinked XLPE insulation particles are mixed with a solvent to form a mass, and then the mass is filled into the microgrooves.

4. The method of fusion jointing of a high voltage cable soft joint insulation layer according to claim 3, characterized in that: The solvent is a crosslinking initiator.

5. A method of fusion jointing of a high voltage cable soft joint insulation layer according to claim 4, characterized in that: The crosslinking initiator is dicumyl peroxide (DCP).

6. The method of fusion bonding of the insulation of a high voltage cable joint according to claim 1, characterized in that: In the step S6, the surface of the integrated insulating layer is subjected to laser polishing treatment by using the forging laser head of the laser forging system.

7. A method of fusion jointing of a high voltage cable soft joint insulation layer according to claim 6, characterized in that: The relevant parameters of the laser polishing treatment are as follows: the defocusing amount is 3.3 mm; the laser power is 80 W; the repetition frequency is 88 kHz; the scanning speed is 1200 mm / s, and the spot overlap rate is 81%.

8. The method of fusion bonding of the insulation of a high voltage cable joint according to claim 1, characterized in that: In step S4, the fusion connection is achieved by using an insulating forming mold to extrude hot-melt uncrosslinked XLPE insulation material and cover it on the surface of the reaction force cone, or by using a wrapping vulcanization process in which uncrosslinked XLPE insulation tape is wrapped around the surface of the reaction force cone.

9. A subsea cable characterised in that: It comprises a high-voltage cable flexible joint made by using any one of the methods of claims 1 to 8.

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