Joint for cables and composite protection cover device for cables

Abstract

The application belongs to the technical field of power electronics, and provides a joint for cable and a composite protective cover device for cable, the joint for cable comprising: a composite shell comprising a composite material shell with four-proof function; wherein the composite shell is installed outside a prefabricated intermediate joint to form an outer protective layer of the prefabricated intermediate joint; and the length of the composite material shell completely covers the length of a corresponding insulation ring of the prefabricated intermediate joint; flanges respectively connected with two ends of the composite shell; metal lining pipes respectively arranged in inner holes of two ends of the composite shell; metal shells respectively located on two sides of the composite shell, and each metal shell is connected with a flange at two ends of the composite shell; wherein a grounding terminal is arranged on the metal shell; therefore, the straight-through joint and the insulation joint can be arranged in the same structure, and the switching between the two joint forms is realized by changing the internal grounding mode.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power electronics, in particular to a joint for cable and a composite protective cover device for cable. BACKGROUND

[0002] The joint protective shell commonly seen in the market is composed of a metal shell and an insulating ring, and is provided with grounding terminals at both ends. The surface of the metal shell is provided with an outer protective layer. The structure of the joint and the joint protective shell restores the body of the cable at the disconnected part, realizes the function of transmitting electric energy, and improves the mechanical protection capability of the cable. According to the actual procurement and use of the user engineering by the Southern Power Company, State Grid Corporation of China, and users, the joint below 220kV mostly does not have a good installation environment, a good ventilation tunnel, and safety measures during installation, and the failure rate of the joint is greater than that of the cable body. The loss caused by fire and explosion due to joint failure has attracted the attention of all parties.

[0003] Therefore, the protective shell corresponding to the joint should preferably have good waterproof, explosion-proof, fireproof, corrosion-proof and other properties. In order to make the joint protective shell have one or more of the aforementioned properties, the joint protective shell commonly seen in the market adopts the following structure forms:

[0004] 1. Metal protective shell + reinforced protective box (waterproof shell);

[0005] 2. Metal protective shell + fire extinguishing device;

[0006] 3. Metal protective shell + flexible fireproof mortar + fireproof blanket;

[0007] 4. Metal protective shell + fireproof partition + explosion-proof glass;

[0008] 5. Metal protective shell + fireproof plate slot box + suspension fire extinguishing system;

[0009] 6. Metal protective shell + intelligent explosion-proof joint;

[0010] However, the joint corresponding to the protective shell with the above structure has at least one of the following disadvantages:

[0011] 1. The practicability of the fire extinguishing device is low;

[0012] 2. The quality of the fireproof mortar product is uneven, the insulation performance is large, and local discharge is easy to occur;

[0013] 3. The fireproof partition + explosion-proof glass structure is complex, difficult to install and fix, and the explosion-proof glass itself has an explosion risk;

[0014] 4. The fireproof slot and the suspension fire extinguishing system require high manufacturing and installation requirements, need remote control operation, have a more complex structure, and have unstable fire extinguishing performance;

[0015] 5. The intelligent explosion-proof connector occupies a large space and is not easy to install

[0016] In addition to the above deficiencies, most of the structural forms may also have the characteristics of high cost and single performance. SUMMARY

[0017] In order to solve the single performance of the existing cable installation connector, the application provides a cable connector and a composite protective cover device for cable, which sets the straight-through connector and the insulation connector structure to be the same, and realizes the switching of the two connector forms by changing the internal grounding mode.

[0018] The first aspect of the application provides a cable connector, characterized in that it comprises:

[0019] The composite shell comprises a composite material shell with four-proof function; wherein the composite shell is installed outside the prefabricated intermediate connector to form an outer protective layer of the prefabricated intermediate connector; and the length of the composite material shell completely covers the length of the corresponding insulation ring of the prefabricated intermediate connector;

[0020] The flanges connected to the two ends of the composite shell, respectively;

[0021] The metal lining pipes arranged in the inner holes of the two ends of the composite shell, respectively;

[0022] The metal shells located on the two sides of the composite shell, respectively, each metal shell being connected with the flange at the two ends of the composite shell, respectively;

[0023] The metal shell is provided with a grounding terminal.

[0024] In the preferred embodiment of the application, each metal shell is provided with a grounding terminal, and each metal shell is provided with an insulating composite material on the outside.

[0025] In the preferred embodiment of the application, each metal shell is sealed and connected with the composite shell through the structure of the flange sealing ring.

[0026] In the preferred embodiment of the application, each metal shell is sealed and connected with the composite shell through welding.

[0027] In the preferred embodiment of the application, the composite material with four-proof function is fiber reinforced plastic or Kevlar fiber.

[0028] In the preferred embodiment of the application, the flange connected to the two ends of the composite shell is a metal flange or a flange made of a composite material with four-proof function.

[0029] In the preferred embodiment of the present application, the metal lining pipe is arranged in the inner hole of the cylinder end of the composite shell, a first annular groove is formed on the outer circumferential surface of the metal lining pipe, a second annular groove corresponding to the first annular groove in number and position is formed on the inner hole of the cylinder end, and a pouring cavity is formed between the first annular groove and the second annular groove, and the epoxy resin is poured in the pouring cavity to fix the metal lining pipe and the cylinder of the composite shell.

[0030] In the preferred embodiment of the present application, the composite shell comprises a first circular ring, a second circular ring, and an arc connecting the first circular ring and the second circular ring, and the first circular ring and the second circular ring are concentric shells.

[0031] In the preferred embodiment of the present application, the composite shell comprises a left shell and a right shell, the left shell and the right shell are symmetrical structures, and the left shell and the right shell are connected through a flange.

[0032] The second aspect of the present application also provides a composite protective cover device for cables, characterized in that it comprises:

[0033] The cable joint provided by the first aspect; and

[0034] A prefabricated intermediate joint installed in the cable joint, the prefabricated intermediate joint being used for installing cables.

[0035] The cable joint provided by the present application is provided with a composite shell, and the composite shell has good waterproof, explosion-proof, fireproof and corrosion-resistant properties due to the material properties of the cylinder. Moreover, the middle section of the protective shell of the composite shell is insulated, and the metal shells at both ends of the composite shell are provided with grounding terminals; therefore, by changing the grounding mode, the protective shell of the cable joint provided by the present application can be used for both insulated joints and straight-through joints.

[0036] Other features and advantages of the present application will be described in the following description, and some will become apparent from the description, or will be understood from the practice of the present application. The purpose and other advantages of the present application can be achieved and obtained by the structure and / or process specifically pointed out in the specification, claims and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 A cross-sectional view of a composite protective cover device for cables according to an embodiment of the present application Figure 1 .

[0038] Figure 2A cross-sectional view of a composite protective cover device for cables according to an embodiment of the present application Figure 2 .

[0039] Figure 3 A partial cross-sectional view of a composite protective cover device for cables according to an embodiment of the present application

[0040] Figure 4 A connection diagram of a cylinder and other components in a composite protective cover device for cables according to an embodiment of the present application Figure 1 .

[0041] Figure 5 A connection diagram of a cylinder and other components in a composite protective cover device for cables according to an embodiment of the present application Figure 2 .

[0042] Figure 6 A diagram of a metal lining pipe in a composite protective cover device for cables according to an embodiment of the present application

[0043] Figure 7 A connection diagram between a metal lining pipe and a cylinder in a composite protective cover device for cables according to an embodiment of the present application

[0044] Figure 8 A connection diagram of a composite protective cover device for cables as a ground for a straight-through joint according to an embodiment of the present application

[0045] Figure 9 A connection diagram of a composite protective cover device for cables as a ground for an insulation joint according to an embodiment of the present application

[0046] Figure 10 A structure diagram of a composite protective cover device for cables as an outer shielding treatment for a straight-through joint according to an embodiment of the present application

[0047] Figure 11 A partial enlarged diagram of Figure 10 .

[0048] Figure 12 A structure diagram of a composite protective cover device for cables as an outer shielding treatment for an insulation joint according to an embodiment of the present application

[0049] Figure 1 A partial enlarged diagram of Figure 12 .

[0050] Reference numerals

[0051]

[0052] DETAILED DESCRIPTION

[0053] The embodiments of the present application will be described in detail below with the accompanying drawings and examples, so that the application can be better understood and implemented. It should be noted that the specific description is only to make those skilled in the art more easily and clearly understand the present application, and is not a limiting interpretation of the present application; and as long as there is no conflict, each embodiment in the present application and each feature in each embodiment can be combined with each other, and the formed technical solutions are all within the protection scope of the present application.

[0054] The technical solutions of the present application will be described in detail below with the accompanying drawings and specific examples:

[0055] Embodiments

[0056] The inventors analyzed the requirements of Q / GDW 371-2009 "10(6)kV~500kV Cable Technical Standards", and creatively proposed the following implementation scheme for the cable joint:

[0057] 1. The outside of the straight-through joint and the insulating joint should be entirely covered by a protective layer; the protective layer should be tightly bonded with the outer sheath of the cable, and pouring insulating agent is recommended.

[0058] 2. The cable joint should have a protective cover with good sealing performance and meet the requirements of relevant standards; the insulation level of the joint metal shielding layer to the protective cover should be consistent with the insulation level of the outer sheath of the cable.

[0059] 3. When the metal shielding layer of the 66kV and above cable line is cross-connected, the insulating joint should be used; otherwise, the straight-through joint is preferred.

[0060] The existing cable has at least one of the following deficiencies:

[0061] 1. The practicability of the fire extinguishing device is low;

[0062] 2. The quality of the fireproof mortar product is uneven, the insulation performance is large, and partial discharge is easy to occur;

[0063] 3. The fireproof partition + explosion-proof glass structure is complex, difficult to install and fix, and the explosion-proof glass itself has an explosion risk;

[0064] 4. The fireproof groove and the suspended fire extinguishing system require high production and installation requirements, need remote control operation, the structure is more complex, and the fire extinguishing performance is unstable;

[0065] 5. The space occupied by the intelligent explosion-proof joint is large, and it is not easy to install

[0066] In addition to the above deficiencies, most structural forms also have the characteristics of high cost and single performance.

[0067] To this end, the inventors combined the performance characteristics of metal protective shells, reinforced protective boxes, and intelligent explosion-proof shells to design a composite "four-proof joint (waterproof, explosion-proof, fireproof, and corrosion-resistant)" protective cover device that can effectively solve the above problems and meet the requirements of Appendix G of GB / T11017.1-2014.

[0068] For example, the present application provides a cable joint and a composite protective cover device for cables, which sets the straight-through joint and the insulation joint structure to be the same and realizes the switching of the two joint forms by changing the internal grounding mode; thereby better meeting the industry demand.

[0069] As Figure 1 A cross-sectional view of a composite protective cover device for cables according to an embodiment of the present application is shown in FIG. 2. Figure 1 A cross-sectional view of a composite protective cover device for cables according to an embodiment of the present application is shown in FIG. 2. Figure 2 , Figure 3 A partial cross-sectional view of a composite protective cover device for cables according to an embodiment of the present application is shown in FIG. 3. In a specific product structure design provided by the present embodiment, in an optional implementation scheme: referring to a traditional metal protective shell, there is a metal shell part, a composite shell part, and a grounding terminal, which is assembled on a prefabricated joint to form an outer protective layer of the joint. The metal shell and the composite shell are connected by flange surfaces, fastened by bolts, sealed by O-rings between the flange surfaces, and cross-connected to ground by the grounding terminals at both ends.

[0070] As Figures 1-3 shown, the present embodiment provides a cable joint, which includes:

[0071] The composite shell, in an optional way, adopts two composite tubes that are left-right symmetrical: a first composite tube 120 and a second composite tube 220; however, the present embodiment is not limited thereto, for example, a plurality of pipes made of similar shell materials can also be arranged between the first composite tube 120 and the second composite tube 220, and the middle section of the composite shell can also be set as an integrated type; these different implementation manners all belong to the protection scope of the present embodiment.

[0072] The composite shell comprises a composite material shell with four-proof function; the composite shell is mounted outside the prefabricated intermediate joint (i.e. the cable intermediate joint 500 for mounting cables needs to be prefabricated in advance to cooperate with the cable joint provided in the embodiment) to form the outer protective layer of the prefabricated intermediate joint; and the length of the composite material shell completely covers the length of the corresponding insulation ring of the prefabricated intermediate joint. Since the composite shell comprises a composite material shell with four-proof function, and the length of the composite material shell completely covers the length of the joint insulation ring, the overvoltage flashover failure between the metal sheaths at both ends is effectively avoided. For example, in order to avoid the induced voltage on the metal sheath being too high in long-distance AC power cable transmission, an insulation joint is designed. When the cable at both ends is disconnected, a certain overvoltage is also borne. When the overvoltage wave enters the metal sheath discontinuous point, a larger potential difference will be formed between the discontinuous points, and in severe cases, a breakdown flashover failure will occur. The conventional insulation joint is limited by the size of the insulation ring and the installation cooperation size, which will cause the insulation distance at the discontinuous point of the insulation joint to decrease. The design of the four-proof joint provided in the embodiment increases the insulation distance by about 1 / 3 by changing the form of the insulation ring and the cooperation position. Therefore, a better electrical insulation effect is achieved.

[0073] Flanges connected to both ends of the composite shell, respectively; for example Figures 1-3 The first flange 130 on the left side and the second flange 230 on the right side;

[0074] Metal lining pipes respectively arranged in the inner holes of both ends of the composite shell; for example Figures 1-3 The first metal lining pipe 121 on the left side and the third metal lining pipe on the right side;

[0075] Metal shells respectively located on both sides of the composite shell: the first metal shell 110 on the left side and the second metal shell 210 on the right side, each metal shell 110, 210 is connected with the flanges 130, 230 at both ends of the composite shell;

[0076] The metal shell is provided with a grounding terminal 300.

[0077] In the preferred embodiment of the present embodiment, the composite shell comprises a first circular ring, a second circular ring and an arc connecting the first circular ring and the second circular ring; the first circular ring and the second circular ring are concentric circular shells.

[0078] In the preferred embodiment of the present embodiment, the composite shell comprises a left side shell 100 and a right side shell 200, the left side shell 100 and the right side shell 200 are symmetrical structures, and the left side shell 100 and the right side shell 200 are connected through flanges.

[0079] In this embodiment, the cable connector is provided with a composite shell. This composite shell, relying on the material properties of the cylinder, provides excellent waterproof, explosion-proof, fireproof, and corrosion-resistant properties. Furthermore, the middle section of the composite shell is insulated, while grounding terminals are provided on the metal shells at both ends. Therefore, by simply changing the grounding method, the protective shell of the cable connector provided by this invention can be used for both insulated and straight-through connectors. The straight-through and insulated connectors are structurally identical, differing only in the grounding wire connection method during installation in the product circuit. In other words, this product can be used as both an insulated connector and a straight-through connector.

[0080] like Figure 8 This embodiment provides a schematic diagram of a composite protective cover device for cables as a grounding connection for a straight-through connector. For example, it can be connected by two layers of waterproof tape 700, including the grounding cable. Figure 9 This invention provides a schematic diagram of a composite protective cover device for cables used as an insulating joint grounding device. As a method of insulating joint grounding, the component is provided with two layers of waterproof tape 700, heat shrink tubing 710, wire core 720, and rolled tape 730 in sequence.

[0081] In this embodiment, intermediate joints are categorized into straight-through joints and insulated joints. A straight-through joint is defined as an accessory that connects two cables to form a continuous circuit; specifically, it refers to a joint where the metal sheath of the joint is electrically continuous with the metal shield and insulation shield of the connected cables. An insulated joint is defined as a joint that electrically disconnects (discontinuously separates) the metal sheath, metal shield, and insulation shield of the connected cables.

[0082] Straight-through connectors and insulated connectors are structurally identical; the difference lies in the internal material treatment during installation (e.g., ...). Figures 10-13 As shown) and grounding connection method (such as Figure 8 , Figure 9 (As shown) are different.

[0083] Figure 10 This embodiment provides a schematic diagram of a composite protective cover device for cables as an external shielding treatment structure for straight-through connectors. Figure 11 for Figure 10 A partially enlarged schematic diagram; such as Figure 10 , Figure 11 As shown, the corresponding external shielding structure includes, in sequence: copper wire 810, semi-conductive tape 820, first insulating tape 830, electric wrapping 840, PVC tape 850 (e.g., 2 layers); waterproof tape 860 (e.g., 2 layers); second insulating tape 870 (e.g., 2 layers), conductive tape 880 (e.g., 2 layers), and copper mesh 890 (e.g., 1 layer).

[0084] Figure 12 A composite protective cover device for a cable is provided as an outer shielding treatment structure diagram for an insulation joint, Figure 1 3 is Figure 12 a partial enlarged schematic view. As shown in Figure 10 , Figure 11 , the corresponding outer shielding treatment structure includes in sequence: 900-insulation shielding section, centering block 910, copper wire 920, third insulation tape 930, insulation tape wrapping 940, PVC tape 952, waterproof tape 954, second insulation tape 956, copper mesh 958, conductive tape 960, electric wrapping 970, copper mesh 982, semi-conductive tape 984, waterproof tape 986.

[0085] As shown in Figures 1-3 , in the preferred embodiment of the present embodiment, each metal shell (first metal shell 110 on the left, second metal shell 210 on the right) is provided with a grounding terminal, and each metal shell is provided with an insulating composite material on the outside.

[0086] For example, the metal shell part is combined by a metal shell and a rotational molding layer. For example, the first metal shell 110 on the left includes a first metal pipe 111 and a first insulating composite layer outside the first metal pipe 111; the second metal shell 210 on the right includes a second metal pipe 211 and a second insulating composite layer outside the second metal pipe 211. In this way, the metal shell corresponds to the metal sheath of the cable, and the rotational molding layer corresponds to the outer sheath of the cable. The grounding terminals at both ends are welded on the metal shell as outgoing lines for cross-connection grounding in the power system, and are reliably connected with the grounding cable 400 in a crimping manner.

[0087] As a preferred embodiment, each metal shell (for example, first metal shell 110, second metal shell 210) is sealed and connected between the composite shell (for example, first composite pipe 120, second composite pipe 220) through the structure of the flange sealing ring. For example, the metal shell and the composite shell are connected through the flange surface, fastened by bolts, sealed between the flange surfaces by O-rings, and the grounding terminals at both ends realize the cross-connection grounding of the metal sheath.

[0088] As another preferred way, each metal shell can also be sealed and connected with the composite shell through welding. That is, the metal flange and the composite shell can be connected by composite technology, or by metal flange and epoxy resin pouring technology; as an alternative, the connection between the metal shell and the composite shell can also be realized by welding.

[0089] In the preferred embodiment of the present embodiment, the composite material with four-proof function is fiber reinforced plastic or Kevlar fiber.

[0090] In which, fiber reinforced plastic is also high-strength glass steel, which has:

[0091] Light and hard, not conductive, stable performance, high mechanical strength, good thermal performance, resistant to ablation, corrosion resistant.

[0092] Light and hard, widely used in storage tanks, transformer housings and other fields, so it is suitable as a shell material for protective shells.

[0093] Non-conductive, excellent insulation performance, can be used as a capacitor divider shell, insulating rod, high-voltage insulating tube, etc., suitable for making joint insulation rings.

[0094] High mechanical strength, good thermal performance, resistant to ablation, can be used as an explosion-proof, flame-retardant material, also used in arc extinguishing equipment, and the protective shell made has explosion-proof and fireproof capabilities.

[0095] Good corrosion resistance, can be used as corrosion-resistant pipes, corrosion-resistant pumps, corrosion-resistant valves, sewage and wastewater treatment equipment, and the protective shell made has corrosion-resistant and waterproof performance.

[0096] In this embodiment, the main core material of the composite shell is fiber reinforced plastic, and other fiber materials with the same performance can be used as substitutes, such as Kevlar fiber.

[0097] In addition, the technical solution provided in this embodiment can be made into two forms of shell with waterproof insulating agent and without waterproof insulating agent according to actual needs.

[0098] The technical solution provided in this embodiment can replace the existing'metal protective shell + reinforced protective box double-shell structure', but the cable joint size provided in this embodiment is smaller, lighter and lower in cost. Moreover, its parts can be assembled in the factory or assembled on site, and the structure is flexible.

[0099] In this embodiment, the performance, mechanical properties and electrical properties of the composite shell material meet the requirements of Table 1.

[0100]

[0101] Table 1. Performance test table of composite shell

[0102] As Figure 4 A composite protective cover device for cables is provided in this embodiment Figure 1 , Figure 5 A composite protective cover device for cables is provided in this embodiment Figure 2 , Figure 6 A composite protective cover device for cables is provided in this embodimentFigure 7 This invention provides a schematic diagram of the connection between the metal liner and the cylinder in a composite protective cover device for cables. (See diagram below.) Figures 4-7 As shown, the further implementation methods for the cylinder, flange, and metal liner are as follows:

[0103] In a preferred embodiment of this invention, the flanges connected to both ends of the composite shell are metal flanges or flanges made of a composite material with four protective functions.

[0104] For example, such as Figure 4 As shown, taking the first composite pipe 120 on the left as an example, the composite shell includes a cylinder 122. Both ends of the cylinder 122 are provided with flanges of the same material as the cylinder (e.g., the first flange sidewall 132 and the third flange wall 610). The flanges are integrally manufactured with the cylinder 122 or the flanges are bonded to one end of the cylinder.

[0105] For example, such as Figure 5 , Figure 6 As shown, taking the first composite pipe 120 on the left as an example, the composite shell includes a cylindrical body 122. Metal liners (e.g., the first metal liner 121 and the second metal liner 123) are inserted into the inner holes at both ends of the cylindrical body 122. The outer ends of the metal liners are provided with metal flanges. This composite shell structure is easy to manufacture and the metal flanges have good strength. The first metal liner 121 is provided with a first annular groove 124, which can be used to cast epoxy resin.

[0106] like Figure 7 As shown, in a preferred embodiment, a first metal liner 121 is inserted into the inner hole at the end of the cylindrical body 122 of the composite shell. A first annular groove 127 is formed on the outer circumferential surface of the first metal liner 121. A second annular groove 126, which is the same number as the first annular groove and corresponding in position, is formed on the inner hole at the end of the cylindrical body 122. A casting cavity 125 is formed between the first annular groove 127 and the second annular groove 126. Epoxy resin is poured into the casting cavity 125 to fix the metal liner to the cylindrical body of the composite shell.

[0107] It should be noted that the serial numbers mentioned in this embodiment—first, second, third, fourth—can be interchanged. For example, the serial numbers before different components such as flanges, composite pipes, metal liners, annular grooves, and cylinders can be interchanged, and their specific structures can be the same or different. Moreover, both the first annular groove 127 and the first annular groove 124 are referred to as "first," indicating that both annular grooves are set on the metal liner; their specific structures can be set to be the same or different depending on different application scenarios.

[0108] This embodiment also provides a composite protective cover device for cables, which includes:

[0109] Any one of the cable joints as Figures 1-7 Any one of the cable joints as

[0110] The prefabricated intermediate joint is installed in the cable joint and is used for installing the cable.

[0111] Therefore, by using the above technical solution provided by the embodiment, the cable joint is provided with the composite shell, the material characteristics of the barrel make the protective shell of the composite shell have good waterproof, explosion-proof, fireproof and corrosion-proof performance. Moreover, the middle section of the protective shell is insulated, and the metal shell at both ends of the composite shell is provided with the grounding terminal; therefore, by changing the grounding mode, the protective shell of the cable joint provided by the embodiment can be used for both insulated joints and straight-through joints.

[0112] Finally, it needs to be explained that the above description is only the best embodiment of the present application, and does not limit the present application in any form. Any person skilled in the art can make many possible changes and simple replacements to the technical solution of the present application without departing from the scope of the technical solution of the present application, which belongs to the protection scope of the technical solution of the present application.

Claims

1. A joint for electrical cables, characterized in that The composite shell comprises a composite material shell with four-proof function, which is fiber reinforced plastic or Kevlar fiber; wherein the composite shell is mounted outside the prefabricated intermediate joint to form an outer protective layer of the prefabricated intermediate joint, the composite shell comprises a first circular ring, a second circular ring and an arc connecting the first circular ring and the second circular ring, the first circular ring and the second circular ring are concentric circular shells; and the length of the composite material shell completely covers the length of the corresponding insulation ring of the prefabricated intermediate joint; Flanges connected to the two ends of the composite shell respectively; Metal lining pipes arranged in the inner holes of the two ends of the composite shell respectively; Metal shells located on the two sides of the composite shell, each metal shell is connected with the flange at the two ends of the composite shell respectively, and an insulating composite material is arranged outside each metal shell; Wherein, the metal shell is provided with a grounding terminal, by changing the grounding mode of the grounding terminal, the cable joint is switched to be used as a straight-through joint or an insulated joint. Each metal shell is sealed and connected with the composite shell through the structure of a flange sealing ring.

2. The joint of claim 1, wherein Each metal shell is sealed and connected with the composite shell through welding.

3. The fitting of claim 1, wherein The flanges connected to the two ends of the composite shell are metal flanges or flanges made of composite materials with four-proof function.

4. The fitting of claim 1, wherein The metal lining pipe is inserted into the inner hole of the cylinder end of the composite shell, a first annular groove is formed on the outer circumferential surface of the metal lining pipe, a second annular groove corresponding in number and position to the first annular groove is formed on the inner hole of the cylinder end, a pouring cavity is formed between the first annular groove and the second annular groove, and epoxy resin is poured in the pouring cavity to fix the metal lining pipe and the cylinder of the composite shell.

5. The fitting of claim 1, wherein The composite shell comprises a left shell and a right shell, the left shell and the right shell are symmetrical structures, and the left shell and the right shell are connected through flanges.

6. The joint of any of claims 1-5, wherein, The cable joint comprises:

7. A composite protective cover device for an electrical cable, characterized by The cable joint according to any one of claims 1-6; And The prefabricated intermediate joint mounted in the cable joint, the prefabricated intermediate joint is used for installing cables. ​

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