Cable seamless welding method

Abstract

According to the cable seamless welding method provided by the invention, the two cables can be seamlessly connected in a mode of being integrally welded with the original cable body, the current-carrying performance and the strength of a connecting joint which is manufactured by the cable seamless welding method and is used for connecting the two cables are consistent with those of the cable body, and the cable seamless welding method is high in reliability. And the cable seamless welding method reduces the experience dependence on operators, and improves the consistency and reliability of cable connection work.

Description

Technical Field

[0001] This invention relates to the field of power engineering technology, and in particular to a method for seamless cable splicing. Background Technology

[0002] In the field of power engineering, the quality of cable connections directly affects the stability and reliability of power transmission. In recent years, with the continuous growth of electricity demand and the rapid advancement of power grid construction in my country, high-voltage cross-linked polyethylene insulated power cables have become the main artery of urban power lines, making their operational reliability crucial. Simultaneously, the connections between cables are becoming increasingly tight. However, the increasing cable density inevitably increases the frequency of cable damage incidents. For example, cables may be damaged during laying or operation due to external forces, aging, or other reasons, requiring professional operators to perform emergency repairs.

[0003] Mould Melt Joint (MMJ) is a cable restoration technology for connecting and repairing broken cables. Its key steps include welding the cable's copper core and creating an insulation layer. Current methods typically involve silver soldering the copper core, wrapping an inner semiconducting layer around the weld after soldering, and filling the inner semiconducting layer with hot-melt cross-linked polyethylene (XLPE) material. This allows the XLPE material to fuse with the cable's insulation layer, followed by an outer shielding layer and a protective layer. For example, Chinese invention patent application CN101068075A discloses a flexible joint for XLPE cables and its preparation method. Specifically, the process involves first stripping the insulation from both ends of the cable to expose the core, cleaning it with anhydrous ethanol, drying it, and then silver soldering to form the core connection. This silver soldering method is highly flexible and particularly suitable for repairing broken cables in outdoor environments. However, in practice, it relies heavily on the operator's experience, requiring high skill levels and making consistency difficult to guarantee. The welding process is lengthy, requiring a prolonged period of time to melt and adhere the solder between the copper cores using a welding torch. This necessitates maintaining the two copper cores in axial alignment and ensuring the welding torch remains stationary throughout the welding process, demanding high precision. Furthermore, while silver solder itself possesses good conductivity, ideally enabling the reconnected or repaired cable to match the original cable's performance, this welding method merely fills the space between the two copper cores without melting the copper cores during welding. Although the silver solder itself has good conductivity, contact resistance still exists at the joint between the copper cores and the silver solder, affecting current-carrying capacity and making the cable prone to overheating and melting under high current. Additionally, the mechanical strength at the copper core connection relies primarily on the silver solder; insufficient mechanical strength makes it inflexible and unable to withstand stress, leading to fatigue and a risk of breakage during use.

[0004] Furthermore, if there is an active interface between the cable copper core and the insulation layer, and this interface contains contaminants such as air gaps, micro-water, and impurities, and / or if air gaps exist within the insulation layer, partial discharge can easily occur, ultimately leading to insulation breakdown and hindering the safe operation of the cable. Simultaneously, air gaps in the insulation layer can also allow moisture and humidity to enter the cable, affecting its safe operation. Therefore, preventing air bubbles in the insulation layer is a crucial requirement in the insulation layer manufacturing process. For example, in the aforementioned patent disclosure, cross-linked polyethylene base material is filled into the insulation molding die using an extruder until overflow occurs at both ends, employing interference filling to reduce the possibility of air gaps. However, this method is only applicable to injection molding processes and is not suitable for processes involving winding cross-linked polyethylene insulation tape and then heating and welding. Currently, the welding process for manufacturing insulation layers also relies heavily on the operator's experience. Operators need to judge based on their experience and the different cable materials and specifications, and reasonably control the welding temperature and time. However, in actual operation, during the heating, melting, and cross-linking curing process of the cross-linked polyethylene insulation tape, residual trace amounts of air and adsorbed moisture will expand due to heat and attempt to escape. If the heating process is improper, such as insufficient heating time, the internal gas cannot be discharged in time and will be trapped in the insulation layer to form bubbles. Insufficient heating time or temperature can also lead to incomplete cross-linking of the material and uneven internal stress, which may result in voids later. When the welding temperature is too high or the time is too long, the insulation layer of the cable will be damaged, reducing the insulation performance of the cable and creating safety hazards.

[0005] Furthermore, during the entire hot-melt curing process, operators cannot monitor the internal state of the insulation layer in real time, nor can they dynamically adjust process parameters such as heating time and temperature according to the actual situation. They can only rely on experience to judge the current work progress. When defects exist inside the insulation layer, they can only be identified and remedial measures taken after the entire curing process is completed. Therefore, the presence of defects will significantly extend the overall work time and affect work efficiency. Summary of the Invention

[0006] One objective of this invention is to provide a seamless cable splicing method, wherein the seamless cable splicing method enables the solder to be integrated with the copper core of the cable, the resistivity of the copper core connection is close to that of the original conductor, the current carrying capacity is the same, and the reliability is high.

[0007] Another objective of this invention is to provide a seamless cable splicing method, wherein the seamless cable splicing method can effectively shorten the copper core welding time and reduce the process accuracy requirements.

[0008] Another objective of this invention is to provide a seamless cable splicing method, wherein the seamless cable splicing method uses exothermic welding to connect the cable copper core, and the weld joint is integrated with the cable copper core, avoiding the joint interface between the solder and the copper core present in the existing silver soldering method, thus ensuring the current carrying capacity of the combined cable.

[0009] Another objective of this invention is to provide a seamless cable welding method, wherein the seamless cable welding method uses a special mold for welding the copper core of the cable, reducing reliance on the operator's experience and improving the consistency of welding results.

[0010] Another objective of this invention is to provide a seamless cable splicing method, wherein the seamless cable splicing method applies radial pressure to the wrapped insulation material while splicing the insulation protective layer to assist gas migration and discharge, thereby reducing the possibility of air gaps in the insulation protective layer.

[0011] Another objective of this invention is to provide a seamless cable splicing method, wherein the seamless cable splicing method involves wrapping the cross-linked cable insulation tape in a staggered wrapping manner to expel air and reduce the possibility of air gaps in the insulation protective layer.

[0012] Another objective of this invention is to provide a seamless cable splicing method, wherein the seamless cable splicing method performs imaging detection on the insulation protective layer after the heat fusion time is reached to detect whether there is an air gap, and extends the heat fusion time if there is an air gap, so as to avoid the existence of air gaps in the insulation protective layer while ensuring work efficiency.

[0013] Another objective of this invention is to provide a seamless cable splicing method, wherein the seamless cable splicing method employs a stepped heating method to gradually increase the temperature to the splicing heating temperature, so as to promote the full escape of gas and effectively suppress the generation of air gaps in the insulation protective layer.

[0014] Another objective of this invention is to provide a seamless cable splicing method, wherein the seamless cable splicing method employs different heating rates at different heating stages to promote gas escape, avoid rapid heating to the splicing temperature which would cause the gas to vaporize into bubbles at high speed, and effectively suppress the generation of air gaps in the insulation protective layer.

[0015] According to one aspect of the present invention, a method for seamless cable splicing is provided, wherein the method includes the steps of:

[0016] A. Welding the copper core of the cable: Use conductive chemical exothermic solder to exothermically fuse the copper core.

[0017] B. Wrap the semi-conductive tape, starting from the middle of the copper core fusion joint and wrapping the semi-conductive tape to both sides in a semi-lapped manner, and lapping it to the inner semi-conductive layer of the cable body.

[0018] C. Wrap the insulating tape around the semi-conductive tape, starting from the middle of the copper core fusion joint and wrapping it to both sides in a semi-lapped manner, and lap it to the insulation layer of the cable body.

[0019] D. Perform a heating and melting treatment, melting the wrapped insulation tape at high temperature to fuse the insulation tape with the insulation layer of the cable body, and applying radial pressure to the wrapped insulation tape during the melting process;

[0020] E. After the molten insulating layer cools, an outer semiconductive layer is installed.

[0021] F. Install a protective layer for the joint.

[0022] In one embodiment, step A includes:

[0023] A1. Assemble the ends of the two copper cores of the cable into a welding mold;

[0024] A2. The conductive chemically exothermic solder and combustion accelerator are loaded into the welding mold;

[0025] A3. Ignite the combustion aid, and the conductive chemical exothermic solder generates high-temperature molten copper that melts the surface of the cable copper core. After cooling, it solidifies in the gap between the two cable copper cores and combines with the cable copper core as one.

[0026] A4. After cold cutting, remove the welding mold and grind the solidified fusion material to the same diameter as the copper core of the cable.

[0027] In one embodiment, the conductive chemically exothermic solder is a solder powder composed of a mixture of copper oxide and aluminum.

[0028] In one embodiment, the combustion improver is magnesium powder.

[0029] In one embodiment, the welding mold includes an assembly body and a mold cover. The assembly body includes a first half-mold and a second half-mold, which are assembled to form the assembly body. The assembly body has a welding cavity and an upper cavity section and a lower cavity section extending from the upper and lower ends of the welding cavity, as well as a left opening and a right opening connecting the welding cavity to the external space. The diameter of the welding cavity is larger than the diameter of the upper cavity section and the lower cavity section. The assembly body has a solder hopper connecting to the upper end of the upper cavity section. The solder hopper has a top opening, and the mold cover is used to cover the top opening. In step A1, the ends of the two cable copper cores are respectively inserted into the left opening and the right opening. In step A2, the conductive chemical exothermic solder and the combustion accelerator are poured into the solder hopper through the top opening. The conductive chemical exothermic solder fills the upper cavity section, the welding cavity, and the lower cavity section.

[0030] In one embodiment, prior to step E, the method further includes the steps of: performing imaging and / or ultrasonic inspection on the molten insulating layer to identify the presence of air gap defects, and if present, extending the heating time.

[0031] In one embodiment, step D includes:

[0032] D1. Heat the temperature to T1 and maintain it for 5 to 30 minutes, wherein T1 is greater than or equal to 60°C and less than or equal to 85°C;

[0033] D2. Increase the temperature from T1 to T2 and maintain it for 5 to 30 minutes, wherein T2 is greater than or equal to 120°C and less than or equal to 140°C;

[0034] D3. Increase the temperature from T2 to T3 and maintain it for more than 60 minutes, wherein T3 is greater than or equal to 150°C.

[0035] In one embodiment, prior to step C, the step further includes: heat-treating the wrapped semiconducting strip.

[0036] In one embodiment, step E includes:

[0037] E1. After the molten insulation layer cools to below 50°C, use sandpaper with a grit from low to high to polish the insulation layer in sequence.

[0038] E2. Apply semi-conductive paint from one end of the cooled insulating layer to the other end, and dry the semi-conductive paint layer with fire.

[0039] E3. Wrap the semiconductive strip around the semiconductive paint layer in a semi-lapped manner and overlap it to the outer semiconductive layer of the cable body.

[0040] In one embodiment, step F includes:

[0041] F1. Wrap the copper mesh in a half-lap manner and overlap it with the copper shielding layer of the cable body by at least 30mm.

[0042] F2. Wrap PVC tape around the copper mesh using a semi-lapping method.

[0043] The further objects and advantages of the invention will become fully apparent from the following description and accompanying drawings. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the cable structure to be connected.

[0045] Figure 2 This is a schematic diagram of a seamless cable splicing method according to an embodiment of the present invention, showing the welding of the copper core of a cable.

[0046] Figure 3 This is a partial structural diagram of a welding mold used for welding the copper core of a cable in the cable seamless welding method according to the above embodiments of the present invention.

[0047] Figure 4 This is a schematic diagram of the cable structure after copper core welding is performed according to the seamless cable welding method described in the above embodiments of the present invention.

[0048] Figure 5 This is a schematic diagram of the cable structure after the cable is connected according to the seamless fusion splicing method of the above embodiments of the present invention.

[0049] Figure 6 This is a schematic diagram of the internal electric field distribution of a cable after it has been connected using the seamless cable splicing method described in the above embodiments of the present invention.

[0050] Figure 7 This is a schematic diagram illustrating temperature control during cable insulation layer welding according to the above-described embodiment of the present invention. Detailed Implementation

[0051] The following description is intended to disclose the present invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. The basic principles of the invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the invention.

[0052] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and 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 orientation. Therefore, the above terms should not be construed as limiting this invention.

[0053] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0054] This invention provides a seamless cable splicing method, which can seamlessly connect two cables by fusing them into the original cable body. The connection joint made by the seamless cable splicing method has the same current carrying capacity and strength as the cable body, and has high reliability. Furthermore, the seamless cable splicing method reduces the dependence on the operator's experience and improves the consistency and reliability of cable connection work.

[0055] refer to Figure 1 As shown, the two ends of the two cables L to be connected are schematically represented. The cables L include phase A, phase B, and phase C cables. Each cable, from the inside out, includes a copper core L1, an inner semiconducting layer L2, an insulation layer L3, an outer semiconducting layer L4, and a protective layer L5. The seamless cable splicing method involves sequentially and seamlessly connecting the copper core L1, the inner semiconducting layer L2, the insulation layer L3, the outer semiconducting layer L4, and the protective layer L5 of the two cables L together. This makes the two cables L approximate the original long cable, ensuring that the performance and structural strength of the two cables L after connection or repair are similar to a single cable or the cable before breakage. This guarantees the reliability of cable operation. Furthermore, since the performance and structural strength of the connected cables are similar to the original long cable, cable layout can be more flexible, which helps reduce costs and is of great significance for power grid construction.

[0056] Specifically, in combination Figures 1 to 7 The seamless cable splicing method includes the following steps:

[0057] A. Weld the copper core L1 of the cable using conductive chemical exothermic solder to exothermically fuse the copper core L1.

[0058] B. Wrap semiconductive tape 200, wrap the semiconductive tape 200 from the middle position of the copper core fusion joint 100 to both sides in a semi-lapped manner, and overlap it to the inner semiconductive layer L2 of the cable body.

[0059] C. Wrap the insulating tape 300 around the semi-conductive tape 200 from the middle of the copper core fusion joint 100 to both sides in a semi-lapped manner, and overlap it to the insulation layer L3 of the cable body.

[0060] D. Perform heating and melting treatment, melt the wrapped insulation tape 300 at high temperature, so that the insulation tape 300 is melted and bonded to the insulation layer L3 of the cable body, and apply radial pressure to the wrapped insulation tape 300 during the melting process;

[0061] E. After the molten insulating layer cools, an outer semiconductive layer is installed.

[0062] F. Install a protective layer for the joint.

[0063] Specifically, the seamless cable splicing method uses a conductive chemical exothermic solder to fuse the two copper cores L1 of the cable through an exothermic reaction, achieving fusion between the copper conductors. This results in the DC resistivity of the connection point 100 between the two copper cores L1 being the same as that of the cable copper core L1, and there is no connection interface between them. This avoids the contact resistance generated by existing silver soldering methods, ensuring that the current carrying capacity of the cable L at the copper core connection point 100 does not change significantly after the connection or repair. At the same time, the copper core connection point 100 is essentially the same as the cable copper core L1, and the mechanical strength of the cable L at the copper core connection point 100 after the connection or repair is not significantly weakened, allowing it to bend and withstand force like the overall cable.

[0064] Specifically, step A includes:

[0065] A1. Assemble the ends of the two copper cores L1 of the cable into a welding mold 10;

[0066] A2. The conductive chemical exothermic solder and combustion accelerator are loaded into the welding mold 10;

[0067] A3. Ignite the combustion aid, and the conductive chemical exothermic solder generates high-temperature molten copper that melts the surface of the cable copper core L1. After cooling, it solidifies in the gap between the two cable copper cores L1 and combines with the cable copper core L1 as one.

[0068] A4. After cold cutting, remove the welding mold 10 and grind the fused solidified material to the same diameter as the copper core of the cable.

[0069] It is worth mentioning that the conductive chemical exothermic solder is a solder powder made of copper oxide and aluminum. In step A, a violent exothermic reaction occurs between aluminum and copper oxide to produce high-temperature copper liquid. After cooling, a solid copper core connection 100 is formed, which is integrated with the copper core L1 of the cable. The copper core connection 100 forms a molecular bond, and its conductivity is consistent with that of the conductor. The resistance change rate of the cable at the copper core connection 100 is close to zero.

[0070] Specifically, in step A2, the combustion accelerator is added to ignite the conductive chemical exothermic solder. The combustion accelerator can be ignited at a relatively low temperature and instantly provides the initial energy for the thermally conductive chemical exothermic solder to undergo an exothermic reaction. In this embodiment of the invention, the combustion accelerator is magnesium powder, which can generate a temperature of over 2000°C during combustion to promote the reaction of the thermally conductive chemical exothermic solder. At the same time, the combustion accelerator reacts first during the reaction and does not leave any residue after the reaction is completed, thus not affecting the resistance of the copper core connection 100.

[0071] It is worth mentioning that, in specific combinations Figures 2 to 4 The welding mold 10 includes an assembly body 11 and a mold cover 12. The assembly body 11 includes a first half mold 111 and a second half mold 112, which are assembled to form the assembly body 11. The assembly body 11 has a welding cavity 101 and an upper cavity section 102 and a lower cavity section 103 extending from the upper and lower ends of the welding cavity 101, as well as a left opening 1011 and a right opening 1012 connecting the welding cavity 101 with the external space. A solder hopper 104 is connected to the upper end of the upper cavity section 101. The solder hopper 104 has a top opening, and the mold cover 12 is used to cover the top opening. In step A1, the ends of the two cable copper cores L1 are respectively inserted into the left opening 1011 and the right opening 1012. In step A2, the conductive chemical exothermic solder and the combustion accelerator are poured into the solder hopper 104 through the top opening. The conductive chemical exothermic solder fills the upper cavity section 102, the welding cavity 101, and the lower cavity section 103. (Reference) Figure 4After cooling and demolding, the size of the weld solidified solid formed by the melting and solidification of the conductive chemical exothermic solder is significantly larger than that of the cable copper core L1. In particular, due to the setting of the upper cavity section 102 and the lower cavity section 103, the weld solidified solid has two protruding sections, which ensures that the molten copper can fully wrap and melt the surfaces of the two cable copper cores L1 during the welding process, avoiding the failure of the bonding surface to fuse or the formation of micro-interfaces due to insufficient metal content. Furthermore, impurities such as slag and pores generated during the reaction can float and sink based on the upper cavity section 102 and the lower cavity section 103, ensuring the purity of the copper core connection 100 and avoiding defects such as slag inclusion, pores, and honeycomb at the copper core connection 100.

[0072] Specifically, the diameter of the welding cavity 101 is larger than the diameter of the upper cavity section 101 and the lower cavity section 102, so as to avoid defects such as shrinkage or looseness between the copper cores L1 of the cable due to the volume shrinkage of the copper liquid during cooling. The copper core connection 100 is located at the geometric center of the weld solidified body. The consistency of the copper core connection 100 is ensured by polishing in step A4.

[0073] It is worth mentioning that, in order to ensure that the two copper cores L1 of the cable remain aligned during welding, the welding mold 10 further includes a mold base 13, wherein the assembly body 11 is placed on the mold base 13 and supported by the mold base 13, wherein the left opening 1011 and the right opening 1012 are aligned, and will remain aligned when the two copper cores L1 of the cable are inserted into the left opening 1011 and the right opening 1012.

[0074] Specifically, prior to step A1, a pre-processing step is included, wherein the pre-processing step includes stripping each layer of the cable L to expose the cable copper core L1, heating the cable copper core L1 to remove moisture, heating the first half mold 111 and the second half mold 112 to remove moisture, aligning the two cable copper cores L1 with a preset gap, and assembling the first half mold 111 and the second half mold 112.

[0075] Specifically, a hot air gun or a gas gun can be used to heat the first half mold 111, the second half mold 112, and the copper core of the cable L1 to remove moisture. The first half mold 111 and the second half mold 112 have matching screw holes. After assembling the first half mold 111 and the second half mold 112, screws are used to tighten the first half mold 111 and the second half mold 112.

[0076] It is worth mentioning that, after step A1 and before step A2, there is also a step of sealing the gap of the welding mold 10. By filling the gap between the copper core L1 of the cable and the left opening 1011 and the right opening 1012 with sealing mud, the high-temperature copper liquid is prevented from being exposed during welding, which could damage the cable or cause injury to the operator, thereby improving the safety of operation.

[0077] In other words, through step A, the seamless cable splicing method can seamlessly splice the copper cores L1 of two cables L together, and the splice joint is integrated with the copper core L1 and made of the same material. It is equivalent to the copper core L1 in terms of performance and structural strength, eliminating the contact resistance and heat generation hazards at the connection point caused by the traditional silver soldering method, and ensuring the stable operation of the cable L.

[0078] It is also worth mentioning that, in step A, the exothermic reaction of step A3 is completed in just a few seconds, which avoids the need for long time and high operator experience and process precision required by the existing silver welding method, and also helps to ensure the consistency of the welding effect.

[0079] Furthermore, the seamless cable splicing method can also be integrated with the cable L in other layers, making the connected or repaired cable equivalent to the integrated cable or the cable before breakage. Specifically, in step B, the semi-conductive strip 200 is wrapped in a half-lap manner. The half-lap manner means that the upper layer of semi-conductive strip 200 covers half of the lower layer of semi-conductive strip 200. Specifically, in step B, the first layer of semi-conductive strip 200 is first wrapped around the middle of the copper core connection 100, and then the second layer of semi-conductive strip 200 is wrapped to the left or right to cover the first layer of semi-conductive strip 200. In this way, the semi-conductive strip 200 is wrapped in a staggered manner to expel air and reduce the possibility of air gaps in the semi-conductive strip 200.

[0080] In particular, in some embodiments of the present invention, before step C, the method further includes the step of heating the wrapped semiconductive tape 200 so that the wrapped semiconductive tape 200 is tightly attached together, and the air gap of the semiconductive tape 200 is eliminated before wrapping the insulating tape 300.

[0081] It is worth mentioning that in step C, the insulating tape 300 is also wrapped in a semi-lapped manner. By wrapping the insulating tape 300 in a staggered manner, air is squeezed out, reducing the possibility of air gaps in the insulating tape 300.

[0082] In particular, step C involves gradually increasing the temperature to the welding temperature in a stepped manner to promote the full escape of gas and effectively suppress the formation of air gaps in the insulating protective layer.

[0083] Specifically, in combination Figure 7 Step D includes:

[0084] D1. Heat from the initial temperature T0 to T1 and maintain for 5 to 30 minutes, wherein T1 is greater than or equal to 60°C and less than or equal to 85°C, thereby evaporating the residual moisture in the insulating tape 300 and the semiconducting tape 200 at a lower temperature. The temperature of T1 is low, and the insulating tape 300 has not yet melted at this temperature, so the gas channel is open and the moisture can escape.

[0085] D2. Increase the temperature from T1 to T2 and maintain it for 5 to 30 minutes, wherein T2 is greater than or equal to 120°C and less than or equal to 140°C. At this time, the insulating tape 300 begins to soften and its fluidity increases. Air bubbles that may exist inside the insulating tape 300 are easy to move and merge under stress. In step D, radial pressure is further applied to the wrapped insulating tape 300 at this time to assist the air bubbles to migrate and be discharged.

[0086] D3. Increase the temperature from T2 to T3 and maintain it for more than 60 minutes, wherein T3 is greater than or equal to 150°C. At this time, the insulation tape 300 and the insulation layer L3 of the cable L melt and cross-link. At the same time, the remaining tiny moisture can be evaporated and discharged. After most of the water vapor is removed by the steps D1 and D2, the pores formed by the evaporation of moisture are small in size and few in number. They can be covered and filled during the melting process of the insulation tape 300, effectively avoiding the formation of air gaps.

[0087] refer to Figure 7 As shown, in step D, different heating rates are used at different heating stages to promote gas escape and avoid rapid heating to the welding temperature, which would cause the gas to vaporize into bubbles at high speed. This effectively suppresses the formation of air gaps in the insulating protective layer. Specifically, in steps D1 and D2, the temperature is heated from T0 to T1 and from T1 to T2 at a relatively slow heating rate, which is beneficial to promote the escape of gas and water vapor during the heating process. In step D3, the temperature is heated from T2 to T3 at a relatively fast heating rate to promote the rapid evaporation of the remaining moisture and promote the melting of the insulating tape 300.

[0088] Specifically, after maintaining the temperature T3 for a set time, the seamless cable welding method performs imaging and / or ultrasonic inspection on the molten insulation layer to identify any air gap defects. If any are found, the heating time is extended. In other words, the seamless cable welding method performs inspection before the insulation layer cools and extends the heating time if air gap defects are present, avoiding rework after cooling, improving work efficiency, and reducing raw material waste.

[0089] In other words, the seamless cable splicing method gradually eliminates any possible moisture and air bubbles by step-by-step heating, avoiding the problem of excessive reliance on operator experience caused by traditional rapid heating to the melting temperature and relying on the operator's experience to judge the splicing progress and air bubble removal. This reduces subjective judgment errors, lowers the reliance on operator experience, and improves the consistency and reliability of cable connection work.

[0090] refer to Figure 5 As shown, the cable after insulation layer fusion is as follows Figure 5 As shown in the figure, it can be understood that the boundary PL between the insulation layer formed by the insulation tape 300 and the insulation layer L3 of the cable L itself, and the boundary between the copper core connection 100 and the cable copper core L1 are shown only to demonstrate that the two sections of the cable L are fused together. In reality, these two boundaries do not exist. The copper core connection 100 and the cable copper core L1 are fused together, and the insulation tape 300 and the insulation layer L3 are fused together.

[0091] Specifically, refer to Figure 6 As shown, after the two cables L are connected by the seamless cable splicing method, the electric field distribution at the connection point is consistent with that of the cables themselves, exhibiting equivalent electrical properties and stable performance and structural strength. Simply put, the seamless cable splicing method is equivalent to regenerating a section of cable with identical performance between the two cables L.

[0092] Further, step E includes:

[0093] E1. After the molten insulation layer cools to below 50°C, use sandpaper with grit from low to high to polish the insulation layer. Specifically, use 240# and 600# sandpaper to polish the insulation layer in sequence to gradually remove the pits on the surface of the insulation layer and improve the adhesion of the insulation layer surface.

[0094] E2. Apply semi-conductive paint from one end of the cooled insulation layer to the other end, and dry the semi-conductive paint layer with fire. Specifically, dry the semi-conductive paint with a hot air gun or gas gun, and apply it three times to ensure that the surface of the insulation layer is covered with semi-conductive paint.

[0095] E3. Wrap the semiconductive strip around the semiconductive paint layer in a semi-lapped manner and overlap it to the outer semiconductive layer of the cable body, thereby completing the setting of the outer semiconductive layer of the joint.

[0096] Further, wherein step F includes:

[0097] F1. Wrap the copper mesh in a half-lap manner and overlap it with the copper shielding layer of the cable body by at least 30mm to ensure that the protective layer is connected to the protective layer of the cable L.

[0098] F2. Wrap PVC tape around the copper mesh using a semi-lapping method.

[0099] Further, after completing step F, the A-phase cable, B-phase cable, and C-phase cable are combined, filled with filler, wrapped with PVC tape and self-adhesive insulating tape, connected to the cable armor with grounding braided tape and fixed with constant force springs, and then wrapped with self-adhesive insulating tape and waterproof tape in sequence. Waterproof tape is wrapped at the break point, and armor tape is wrapped at the joint to the cable L with a half overlap. Finally, a layer of black PVC tape is wrapped.

[0100] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0101] Those skilled in the art should understand that the embodiments of the present invention described above and shown in the accompanying drawings are merely examples and do not limit the present invention. The objectives of the present invention have been fully and effectively achieved. The functions and structural principles of the present invention have been demonstrated and explained in the embodiments, and any variations or modifications may be made to the implementation of the present invention without departing from the stated principles.

Claims

1. A method for seamless cable splicing, characterized in that, include: A. Welding the copper core of the cable: Use conductive chemical exothermic solder to exothermically fuse the copper core. B. Wrap the semi-conductive tape, starting from the middle of the copper core fusion joint and wrapping the semi-conductive tape to both sides in a semi-lapped manner, and lapping it to the inner semi-conductive layer of the cable body. C. Wrap the insulating tape around the semi-conductive tape, starting from the middle of the copper core fusion joint and wrapping it to both sides in a semi-lapped manner, and lap it to the insulation layer of the cable body. D. Perform a heating and melting treatment, melting the wrapped insulation tape at high temperature to fuse the insulation tape with the insulation layer of the cable body, and applying radial pressure to the wrapped insulation tape during the melting process; E. After the molten insulating layer cools, an outer semiconductive layer is installed. F. Install a protective layer for the joint.

2. The seamless cable splicing method according to claim 1, wherein step A includes: A1. Assemble the ends of the two copper cores of the cable into a welding mold; A2. The conductive chemically exothermic solder and combustion accelerator are loaded into the welding mold; A3. Ignite the combustion aid, and the conductive chemical exothermic solder generates high-temperature molten copper that melts the surface of the cable copper core. After cooling, it solidifies in the gap between the two cable copper cores and combines with the cable copper core as one. A4. After cold cutting, remove the welding mold and grind the solidified fusion material to the same diameter as the copper core of the cable.

3. The seamless cable splicing method according to claim 2, wherein the conductive chemical exothermic solder is a solder powder composed of copper oxide and aluminum.

4. The seamless cable welding method according to claim 3, wherein the combustion aid is magnesium powder.

5. The seamless cable splicing method according to claim 3, wherein the welding mold includes an assembly body and a mold cover, wherein the assembly body includes a first half mold and a second half mold, the first half mold and the second half mold are assembled to form the assembly body, the assembly body has a welding cavity and an upper cavity section and a lower cavity section extending from the upper and lower ends of the welding cavity, and a left opening and a right opening communicating the welding cavity with the external space, wherein the diameter of the welding cavity is larger than the diameter of the upper cavity section and the diameter of the lower cavity section, wherein the assembly body has a solder hopper communicating with the upper end of the upper cavity section, the solder hopper has a top opening, the mold cover is used to cover the top opening, wherein in step A1, the ends of the two cable copper cores are respectively inserted into the left opening and the right opening, and in step A2, the conductive chemical exothermic solder and the combustion accelerator are poured into the solder hopper from the top opening, the conductive chemical exothermic solder fills the upper cavity section, the welding cavity and the lower cavity section.

6. The seamless cable splicing method according to claim 1, wherein prior to step E, it further includes the step of: performing imaging inspection and / or ultrasonic inspection on the molten insulation layer to identify whether there is an air gap defect, and if so, extending the heating time.

7. The seamless cable splicing method according to claim 1, wherein step D comprises: D1. Heat the temperature to T1 and maintain it for 5 to 30 minutes, wherein T1 is greater than or equal to 60°C and less than or equal to 85°C; D2. Increase the temperature from T1 to T2 and maintain it for 5 to 30 minutes, wherein T2 is greater than or equal to 120°C and less than or equal to 140°C; D3. Increase the temperature from T2 to T3 and maintain it for more than 60 minutes, wherein T3 is greater than or equal to 150°C.

8. The seamless cable splicing method according to claim 1, wherein before step C, it further includes the step of: heat-treating the wrapped semiconductive strip.

9. The seamless cable splicing method according to claim 1, wherein step E comprises: E1. After the molten insulation layer cools to below 50°C, use sandpaper with a grit from low to high to polish the insulation layer in sequence. E2. Apply semi-conductive paint from one end of the cooled insulating layer to the other end, and dry the semi-conductive paint layer with fire. E3. Wrap the semiconductive strip around the semiconductive paint layer in a semi-lapped manner and overlap it to the outer semiconductive layer of the cable body.

10. The seamless cable splicing method according to claim 1, wherein step F comprises: F1. Wrap the copper mesh in a half-lap manner and overlap it with the copper shielding layer of the cable body by at least 30mm. F2. Wrap PVC tape around the copper mesh using a semi-lapping method.

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