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Installation real shot
Installation real shot
Cable molded fusion joint (CMJ for short)
Technical Field
      The present technology relates to the technical field of XLPE insulated power cable connection, in particular to the latest method of cable molded welding joint "cable body" recovery tool - a domestic leading cable intermediate or straight connection technology, may be the current stage of heat shrinking An alternative to the intermediate connection of the collapsed, prefabricated cable is the ultimate product of the cable intermediate control attachment.
      Internationally, only Japan's Furukawa Electric had the "Extrusion Molded Joint" EMJ technology in 1993, which is used for the connection of long-distance cables of 550kV voltage class.
Background Technique
      With the continuous development of the social industry, the demand for electric energy is also increasing. A large number of XLPE insulated power cables are used in the power transmission process. The so-called power cables are insulated and entangled on the metal cores. Shielding and sealing with functional materials, special wires for transmitting and distributing high-power electric energy in the lines of power systems, including 3.6-1000kV XLPE insulated power cables of various voltage levels.
      Due to the limitation of production technology, site and transportation of XLPE insulated power cables, the length of XLPE insulated power cables is 500~1000 m/disk, with a diameter of 3.2 m and a disk width of 2.2 m. And the following weights of about 3 to 10 tons are convenient for production, storage, transportation, etc. However, due to the underground power grid of the city, the exit line of the power station, the internal power supply of industrial and mining enterprises, and the underwater transmission lines crossing the river and crossing the sea, there are several tens of meters, hundreds of meters, several kilometers, thousands of kilometers, so it is necessary to Each XLPE insulated power cable is connected to extend the connection to meet the design and construction requirements. Secondly, with the development of the power grid and the transformation of the city network, the proportion of power cables in the power grid lines is increasing. The quality of the corresponding cable body, the quality of cable installation, and the quality failure rate of cable accessories are also increasing. The reliability of electric power operation, so it is necessary to take high-quality preventive measures to comprehensively improve the operation level of distribution lines.
Power Cable And Acessories
      1, power cable
      Power cable is a special wire used to transmit and distribute electrical energy. Figure 1 is a physical diagram of power cable. Figure 2 is a structural diagram of power cable. It is commonly used in urban underground power grids, power station outlet lines, internal power supply for industrial and mining enterprises, and cross-river trans-water Lower transmission line.
      The main structure of the power cable consists of a core, an insulating layer, a shielding layer and a protective layer.
      ①wire core: is the conductive part of the power cable, used to transport electrical energy, - generally consists of copper or aluminum strands.
      ②Insulation layer: It is the inseparable component of the power cable structure that electrically isolates the core from the earth and the cores of different phases to ensure electrical energy transmission.
      ③Shielding layer: refers to the power cable conductor (inner) shielding layer and insulation (outer) shielding layer of voltage level of 10kV and above, which is a measure to improve the electric field distribution. Because the cable conductor is stranded by multiple strands of wire, the surface of the conductor is not smooth, which will cause electric field concentration or sharp angle discharge. It is easy to form an air gap with the insulating layer; a layer of semi-conductive material is added to the surface of the conductor. Forming a circular body, equipotential with the shielded conductor, and in good contact with the insulating layer, thereby avoiding partial discharge between the conductor and the insulating layer, called an inner shield layer; shielding the surface of the insulating layer with a layer of semiconductive material Layer, which has good contact with the insulating layer and equipotential with the metal sheath. As the center line, there is a capacitor current under normal conditions. When a fault occurs, the copper strip acts as a short-circuit fault current loop to avoid the occurrence between the insulating layer and the sheath. Partial discharge, called the outer shield.
      ④Protective layer: It is composed of inner sheath, armor layer and outer layer (or outer sheath) to protect the power cable from external impurities and moisture, and prevent direct damage to mechanical external damage. power cable.
      2, power cable accessories
      Power cable accessories refer to the products connecting cables and transmission and distribution lines and related power distribution devices. - Generally refers to the intermediate connection and terminal connection of cables in cable lines. It forms a power transmission network together with cables; cable accessories are mainly based on cable structure. The characteristics can restore the performance of the cable, and ensure the extension of the cable length and the connection of the terminal.
      Cable accessories are generally divided into terminal connections and intermediate connections. Terminal connections are divided into indoor terminals and outdoor terminals. In general, outdoor terminals refer to open-air cable connectors, and indoor terminals refer to connectors for indoor connection cables and electrical devices; It is both straight-through and insulated. At this stage, the main product categories of cable accessories are: heat shrinkable, prefabricated, cold-shrinkable cable accessories. The three methods are to increase the stress tube and the stress cone to disperse the electric field stress control to achieve the operation of the cable. The production method may generate impurities, air gaps and active interfaces, which affect the insulation performance of the cable joint, which is invisibly reduced. Safety and reliability of grid operation.
      The most important technical problem that needs to be solved for cable accessories is to deal with the concentration of electric field at the fracture of the outer semi-conducting layer of the cable. Figure 3 shows the distribution of the electric field equipotential line at the cable cut-off. The electric stress control is to implement the electric field distribution and electric field strength inside the cable attachment. Control, that is, taking appropriate measures to optimize the electric field distribution and electric field strength, thereby improving the reliability and service life of the cable accessory operation. The most serious impact on the terminal operation reliability is the electric field ride, and the influence of the electric field change of the cable intermediate joint, in addition to the cable shield cut-off, and the cable end insulation cut-off. At present, there are two main solutions: one is to use a parametric electric field stress control tube, and the other is to use a geometric electric field stress control cone.
      The electric field stress control tube is a hose made of a material having a dielectric constant of 15 to 25 and a volume resistivity of 1010120.m. FIG. 4 is a physical diagram of an electric field stress control tube, and FIG. 5 is a principle of an electric field stress control tube. Figure. The electric field stress control tube is sleeved at the outer semi-conductive fracture to form an interface of different dielectric constants at the fracture, so that the electric power line is refracted at the interface, thereby achieving the effect of evacuating the electric field stress, but the electric field stress control tube is used. Although the high dielectric constant material is theoretically the higher the dielectric constant is, the higher the dielectric constant is, the larger the amount of heat is generated by the capacitor current, which promotes the stress control material, and the stress control material as a kind of In polymer multiphase structural composites, the dielectric constant and volume resistivity are contradictory bodies in the material itself. The higher the dielectric constant, the lower the volume resistivity, and the stability of the electrical parameters of the material. It is often affected by various factors. When operating in a long time electric field, the temperature and external environment changes will cause the stress control material to age. The volume resistivity of the stress control material after aging will change greatly, and the volume resistivity will become larger. The stress control material becomes an insulating material, which does not function to improve the electric field, the volume resistivity becomes small, and the stress control material becomes a conductive material. Cause the cable to malfunction.
      The electric field stress control cone is a structure with a bell mouth geometry, which is formed by a mold. Fig. 6 is a real-life stress control cone physical diagram, and Fig. 7 is an electric field stress control cone schematic diagram. The electric field stress control cone is lapped at the outer semiconducting fracture of the cable, and is also at a low potential position with the outer layer. The extension of the outer semiconducting fracture is performed so that the power line originally concentrated at the outer semiconducting fracture will follow the stress cone. The geometric shape is evenly distributed, the electric field distribution is improved, the possibility of corona generation is reduced, the damage to the insulation is reduced, but the volume of the cable is increased; since the electric field stress control cone is made in a factory mold, cold shrinkage The type must be expanded first, and the prefabricated field is expanded, which changes the original design size. The early support of the support tube causes the internal surface of the product to be uneven, resulting in instability of the product, and the electric field distribution cannot be solved satisfactorily.
      At present, the power cable is usually connected to the metal core of the two power cables by crimping or screwing the intermediate connecting pipe to achieve the connection extension, and is controlled by the electric field stress control tube or the electric field stress control cone. Radial electric field. However, the crimping or screw fastening of the intermediate connecting pipe is structurally weak, easily broken, deformed, deformed, cannot be concentric, and the corner of the joint is discharged, the air gap is large, the physical and mechanical properties are small, and the radial direction is small. Large electric field loss, large heat generation, seriously affecting the current carrying capacity and mechanical performance of the power cable, and the connection construction is cumbersome and complicated; due to heat shrinkage, cold shrinkage, prefabricated cable accessories create gaps, internal air gaps, partial discharge and spread Enlarged deterioration, leading to insulation breakdown; moisture absorption or water ingress, moisture or tidal breathing effect and electrophoretic effect penetrate into the middle joint, interface resistance drops sharply, resulting in creeping discharge; insulation strength is reduced or aged, dendritic discharge carbonization Inspires accidents such as creepage and breakdown. Through the multi-year data analysis of the grid operation and maintenance department and CL/T1576-2016 (6~35 cable oscillation wave partial discharge test method), the on-site inspection requires partial discharge test, and it is known that cable faults occur mostly at the cable joints. The main reason is the cable. If the intermediate joint manufacturing process is unqualified, the insulation performance is not high, or the middle joint of the cable is not well sealed, so that the cable intermediate joint is damp and the insulation is broken. The cable attachment is much more complicated than the cable's own electric field distribution, which affects the safety and reliability of the overall cable system.   The root cause is mainly cable accessories.
      Therefore, the power market urgently needs a cable injection-welded X (CM) recovery cable structure to overcome the above problems.
Cmj Technical Content
      The purpose of the present technology is to provide a cable fusion joint technology, the cable fusion joint structure has a firm connection, high electrical conductivity at the joint, small radial electric field loss, low power loss, high current carrying capacity, copper core welding, and the cable can be bent. There is no need to worry about the influence of cable dragging, and the connection construction is simple and fast, and does not occupy the advantages of municipal land. The main structure of the cable is completely restored, and the cable body is approximately equal in diameter to reach the factory production level.
      At present, the production of cable joints at home and abroad generally adopts heat shrinkage, cold shrinkage, and prefabrication methods. The three methods are to increase the stress of the electric field by the stress tube and the stress cone to achieve the operation of the cable. The air gap and the active interface affect the insulation performance of the cable joint, which virtually reduces the safety and reliability of the grid operation. The cable fusion joint technology completely solves the fundamental problem of the interface between the cable accessory and the cable insulation, which can effectively reduce the fault of the cable line and its intermediate joint, and provides higher electrical stability and safety for the cable system. Sex. The cable fusion joint technology uses the equal-diameter conductor fusion welding connection for the cable, and the inner and outer shielding layers and insulation layers are restored according to the cable structure.
      The cable fusion joint technology is a new type of technology. This technology has many advantages over the common cable intermediate joint manufacturing method. It restores the cable to the new cable state by re-generating the cable structure. The cable intermediate joint is analyzed from Table 1. The measured value of the original copper core 17.36μQ.m is 17.97μQ.m~+, and the resistance is small, and the data before and after welding is similar, the data fluctuation is small, causing The influence of temperature rise on the insulation temperature is almost negligible, and the stability of the welded copper core DC resistance is high; from the analysis in Table 2: the ratio of the tensile force to the body of the copper core weld is 95%, and the tensile strength of the conductor-welded copper core The strength reaches more than 94% of the body strength, the amplitude is small, and the original mechanical strength is almost restored, which can greatly reduce the line fault frequency caused by the cable intermediate joint.

      Cable melting technology through wire core welding, wire core grinding; semiconductor film melting and other diameter recovery; main insulation layer melting recovery, main insulation layer grinding. Equal diameter recovery; outer semiconductor layer melting equal diameter recovery, cable outer sheath recovery Wait for multiple steps to restore the cable to its original appearance. The biggest advantage of this technology is the fusion of copper wire core, inner shield, main insulation and outer shield by fusion technology to enhance the waterproof and insulation performance of the cable and prolong the life of the cable intermediate joint. According to the cable raw material, main structure and specification requirements, the extrusion molding process is used to insulate and crosslink the process, the cable is shielded, and the electric field distribution characteristics of the cable body are combined, and no additional stress cone, stress insulation and external shield are melted and combined to form the body characteristics. If there is no 1 cable, if it is not handled well at the copper core cable joint, it will cause great safety concealment; the pipe structure and the joint without the interface air gap fully recover the concept. At present, the main network power supply and distribution cable fusion joint of the State Grid Power Supply Company restores the cable body connection technology, and the treated joint has much improved conductivity and tensile performance than the copper cable itself.
      Wire core welding of cable melting technology, simple structure setting, convenient operation, no external power source and heat source, low welding cost, fast calculation in seconds, overall welding section without bubbles, and repeated use of mold more than 200 times. The quality is stable and reliable. It is very suitable for the welding operation of the field cable core. It is applicable to the field of equal core and unequal core connection protection between copper core and copper core, aluminum core and aluminum core cable.
      Through years of data analysis and cable oscillation wave partial discharge test of power grid operation and maintenance department, cable faults occur mostly with cable intermediate joints. Due to the unqualified manufacturing process of cable intermediate joints, insufficient insulation performance leads to cable intermediate joint failure; if cable intermediate joint sealing performance Not good, resulting in moisture in the middle of the cable joint, insulation breakdown. Cable accessories are much more complicated than the electric field distribution of the cable itself, which affects the safety and reliability of the overall cable system. It mainly comes from the cable accessories. The connection technology of the CMJ recovery cable body can be completely solved. The CMJ technology for restoring the cable body is The concept of making the cable connectorless. The breakthrough of this technology will provide safe operation for high-voltage and ultra-high-voltage cable systems, and solve the high-end technology of soft joints of submarine cables and soft joints of positive and negative DC cables. This new cable fusion technology will gradually restore the cable construction. To achieve the absolute sealing effect, Asia-Europe Electric guarantees that the safety operation of the cable intermediate joint made by the melting technology and the life of the cable will not fail, providing a major technical leap for the safety and reliability of the cable system in the power grid, with significant The milestone of reality.
      Cable melting technology through wire core welding, wire core grinding; semiconductor film melting and other diameter recovery; main insulation layer melting recovery, main insulation layer grinding, equal diameter recovery; outer semiconductor layer melting equal diameter recovery, cable outer sheath recovery, etc. Multiple processes are required to restore the cable to its original appearance. The biggest advantage of this technology is that the copper wire core, the inner shield, the main insulation and the outer shield are melt-bonded into a body by the melting technology, which enhances the waterproof and insulating properties of the cable and prolongs the life of the cable intermediate joint. According to the cable raw material, main structure and specification requirements, the cable-injection molding insulation cross-linking process is used to fuse the cable shielding, insulation and outer shield to form a cable electric field shield with uniform body characteristics without stress treatment and no air gap interface. The electric field distribution of CMJ is completely equivalent to the electric field distribution characteristics of the cable body, and there is no additional stress cone, stress tube structure, joint recovery concept without joint air gap. At present, the cable trench for power supply and distribution of the main network of the State Grid Power Supply Company uses a 630mm copper core cable with a cross section of 300mm or more. If the copper core cable joint is not handled well, it will cause great safety hazards; the cable fusion joint restores the cable body connection technology. The treated joints are greatly improved in electrical conductivity and tensile properties than the copper cables themselves.
Design Principle
      The safety and reliability of the cable in the actual application process is much higher than the safety reliability of the cable accessory to which it is connected. From the structural principle, the cable body is composed of an insulating layer of uniform thickness and an inner and outer semi-conductive layer. The conductors of equal diameter form a cylindrical and stable cable body. Therefore, the customization of the structure makes the electrical properties of the cable, that is, the electric field distribution, more stable and uniform, so that the cable has high electrical safety reliability and long use. According to this principle, the CMJ completely restores the original cable body structure at the cable joint in the field, so that the electrical performance after the CMJ is connected with the cable and the electrical performance of the cable body are equally high. The cable conductor, the inner semi-conductive layer, the main insulation and the outer semi-conductive layer at the CMJ joint completely restore the body according to the original structure of the cable, and the assembly structure of the external object without the stress cone and the stress tube makes the cable joint become a complete cable without The connector realizes the concept of restoring the structure of the cable body. The insulating material and semi-conducting material used in CMJ are exactly the same material as the insulating material and semi-conducting material of the production cable. The combination of CMJ and cable has good compatibility and stability in chemical, physical properties and structure, and the heat of the molten interface. Performance and mechanical properties have been extensively tested and tested. All of them fully meet the standard requirements; and the CMJ in the Dali operation also shows its superior practicability. The technology is made on the spot according to the copper core, inner shield, insulation, inner shield structure, specification, and the same shielding and insulating material of the cable, and realizes the electric field shielding body which is continuously and equivalently matched with the original cable, so that the shielding and the insulation have no air gap. The interface is melt-bonded, forming a uniform structure with the cable without obvious joint shape, the insulation strength is consistent with the original cable, and has higher electrical insulation performance and operational durability, so that the electric field distribution and electric field strength are optimal. The natural state highlights the stable electrical performance and reliable operation of the CMJ.
Design Features
      The characteristics of CMJ and cross-linked cable are the same, its electrical performance is connected with the connected cable or higher safety and reliability; CMJ's manufacturing technology and process are different from the production of cable, but the principle and production are realized. The standards implemented by the process are consistent; CMJ's insulation level, current carrying behavior, mechanical properties, sealing effect and other properties fully meet the cable requirements, and ensure long-term safe operation in harsh environments, fully in line with international IEC, The relevant standards of the national GB; CMJ can also be made into the same connection with the cable insulation according to the different needs of users, such as the submarine cable joint requirements must be equal to the connected cable structure; from the CMJ structure, It is consistent with the structure of the cable, has no movable objects, and has its insulated joints and straight-through joints to achieve cross-connecting.
Comparison Of Cable Intermediate Connections
      (1) Must have 220V power supply, work shed and other construction conditions.
      (2) During the installation process, the ambient temperature should be above 10C and the relative humidity is 85% or less; to avoid condensation on the insulation surface, and to take remedial measures when the ambient temperature is low and the humidity is too high.
      (3) If the cable is found to be ingress or damp, remedial measures should be taken, otherwise construction cannot be carried out.
      (4) Rain, fog, wind and sand must be constructed in a closed shed.
      (5) For the protection of patented technology, only the stripping cable, the core wire is welded, and the main insulation cross-linking is completed, allowing the product to be viewed or photographed.
Certifications
      Acceptance requirements and precautions
      Please specify the order number and product name model when ordering; please check the supporting products according to the matching table after opening the box;
      Please carefully read the product installation process and operate in strict accordance with the process before installation and use; bulk inventory, product moisture, dust, pressure, puncture.
Pledge
      ■Service on-site, on-site service + telephone consultation or fax;
      ■After receiving the response from the user, the response will be processed within 2 hours. The emergency personnel will arrive at the scene within 24 hours in Guangdong Province, and will be rushed to the scene within 48 hours outside Guangdong Province.
      ■Ensure that the dispatched staff obey the various rules and regulations on the site, and are obliged to train the operation and maintenance personnel for the customer; provide all the technical materials stipulated in the contract or agreement to the customer in a timely manner;
      ■Strengthen contact with users, develop user product quality tracking information, and return visits to products to ensure long-term safe operation of products;
      ■Any problem at any time, in order to solve the user's problem, to provide users with safe, reliable, high-quality and satisfactory service.
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