Flexible direct-current wall bushing

Abstract

The invention relates to electric wires or cables and protection devices which penetrate through walls, floors or ceilings and are installed in buildings and the like, in particular to a flexible direct current wall bushing. The flexible direct-current wall bushing comprises a bushing body and a central conducting rod in the bushing body, a corrugated pipe extending in the axial direction of the direct-current wall bushing is axially fixed to the inner side of the central conducting rod, a sealing cover is fixed to the end, opposite to the central conducting rod, of the corrugated pipe, and a lead-out conductor is arranged on the sealing cover. A gap for the central conducting rod to stretch out and draw back is reserved between the central conducting rod and the sealing cover, the sealing cover is fixedly connected with the pipe body and completely wraps the corrugated pipe, a movable plate is arranged at one end of the corrugated pipe and connected with the central conducting rod, and the movable plate is in conductive sliding fit with the inner wall face of the sealing cover, so that the sealing reliability of the wall bushing is enhanced; the service life of the wall bushing is prolonged, the situation that the insulating property is affected by electric field distortion caused by sagging of the central conducting rod is avoided, and the possibility of flashover or disruptive discharge during working is reduced.

Description

Technical Field

[0001] The invention relates to an electric wire or cable and a protective device which is installed in a building through a wall, a floor or a ceiling, and in particular to a flexible DC wall bushing. Background Art

[0002] In DC power transmission and transformation projects, the DC wall bushing is the only electrical component connecting the inside and outside of the valve hall, carrying the full voltage and current of the entire line. Its performance reliability determines the safety and stability of the entire line. The current-carrying conductor of the DC wall bushing is the central conductive rod. Under high-voltage and ultra-high-voltage working conditions, the central conductive rod will expand and elongate in the axial direction due to the heat generated by the large current flow. In order to prevent the electric field distortion caused by the sagging caused by the expansion and elongation of the central conductive rod, a corrugated tube is generally used to connect the end of the wall bushing on the indoor side.

[0003] A Chinese invention patent application with application publication number CN11067679A and application publication date January 10, 2020 discloses a wall bushing, wherein a central conductive rod is arranged inside the wall bushing as a current-carrying conductor, and the outer tube body of the wall bushing is a hollow composite insulator, and a corrugated tube is installed at the indoor end of the wall bushing, and flanges and end covers are fixedly installed on the end faces of both ends of the corrugated tube, respectively. The corrugated tube is fixedly connected to the hollow composite insulator through the flange, and a mounting hole for inserting the central conductive rod is opened in the center of the flange and the end cover, and a split clamping ring is installed at the connection between the end cover facing away from the corrugated tube and the central conductive rod, and a clamping ring is provided on the inner surface of the clamping ring when used. The central conductive rod is provided with a positioning protrusion extending radially along the central conductive rod, and an annular groove serving as a positioning recess is provided on the central conductive rod. The clamping ring is embedded in the annular groove by the positioning protrusion to achieve relative fixation with the central conductive rod, and can maintain a high connection stability. A plurality of expansion joints are installed on the outside of the bellows between the flange and the end cover of the bellows, so that the end cover can move relative to the flange along the axial direction of the wall sleeve. The expansion joint includes a spring cylinder, one end of the spring cylinder is fixedly connected to the flange, and a push rod is installed on the end face of the other end along the axial direction of the spring cylinder. The push rod is installed on the end cover, and the tensioning effect on the central conductive rod is achieved by the push force applied to the end cover by the spring cylinder and the push rod structure.

[0004] The existing DC wall bushing adopts a bellows structure. When the central conductive rod is heated and elongated, the bellows drives the bellows end cover to straighten the elongated central conductive rod through the tensioning force provided by the spring tube, which can reduce the deflection change of the central conductive rod and avoid serious sagging problems that lead to electric field distortion. At the same time, the central conductive rod and the end covers on both sides are fixedly connected, avoiding the generation of metal particles due to friction or mechanical vibration at the joint of the central conductive rod due to the use of sliding electrical connection. However, the clamping ring structure of this structure will continue to be pushed by the spring in the spring tube when working, causing stress concentration, prone to deformation or breakage, and prone to end leakage, causing the insulating gas in the gas insulation structure to leak out, seriously affecting the insulation performance of the wall bushing. Summary of the invention

[0005] The object of the present invention is to provide a flexible DC wall bushing to solve the problem that the insulation performance of the DC wall bushing deteriorates due to air leakage caused by the use of a bellows connection at the indoor side of the wall bushing.

[0006] In order to solve the above problems, the flexible DC wall bushing of the present invention adopts the following technical solutions:

[0007] A flexible DC wall bushing comprises a tube body and a central conductive rod installed inside the tube body, wherein one end of the central conductive rod on the indoor side is axially fixedly connected to a corrugated tube extending axially along the DC wall bushing, one end of the corrugated tube facing away from the central conductive rod is fixedly connected to a sealing cover electrically connected to an indoor busbar joint, a lead-out conductor is provided on the sealing cover, a gap is reserved between the central conductive rod and the sealing cover for the telescopic movement of the central conductive rod, the sealing cover is fixedly connected to the tube body and completely wraps the corrugated tube to achieve sealing on the indoor side of the DC wall bushing, one end of the corrugated tube close to the central conductive rod is connected to the central conductive rod through a movable plate, and the movable plate is conductively slidably matched with the inner wall surface of the sealing cover.

[0008] Furthermore, the movable plate is a circular plate that fits the inner wall surface of the sealing cover.

[0009] Furthermore, a plug-in fitting section for axially fixing the central conductive rod is installed on the movable plate along the axial direction of the DC wall bushing, and the plug-in fitting section is a cylindrical structure.

[0010] Furthermore, an annular groove is formed on the inner wall of the plug-in fitting section, and a spring contact finger is arranged in the annular groove, and the spring contact finger abuts against the inner wall of the plug-in fitting section.

[0011] Furthermore, at least one plug-in sealing ring is provided between the plug-in fitting section and the central conductive rod to achieve sealing fit between the central conductive rod and the plug-in fitting section.

[0012] Furthermore, the cavity inside the sealing cover is in a double-layer structure, the inner surface of the larger radial section fits the side of the movable plate, and the smaller radial section cannot pass through the movable plate, so as to limit the movable plate.

[0013] Furthermore, an end cover is installed on the end surface of the bellows connected to the sealing cover, and the end cover is welded to the sealing cover.

[0014] Furthermore, a tube body sealing ring is provided at the connection portion between the sealing cover and the tube body.

[0015] Furthermore, the lead conductor is a terminal.

[0016] Furthermore, the tube body is a conical structure.

[0017] Beneficial effects: The present invention is an improved invention. The flexible DC wall bushing of the present invention includes a tube body and a central conductive rod installed inside the tube body. One end of the central conductive rod on the indoor side is axially fixedly connected to a bellows extending along the axial direction of the DC wall bushing. The bellows structure is arranged on the indoor side to adjust the expansion and contraction caused by the thermal expansion of the central conductive rod, so as to reduce the deflection change of the central conductive rod. At the same time, the metal particles generated by friction or mechanical vibration at the joint of the central conductive rod can be reduced, and the possibility of flashover or breakdown discharge during operation can be reduced. The end of the bellows facing away from the central conductive rod is fixedly connected to a sealing cover electrically connected to the indoor busbar joint. A lead conductor is arranged on the sealing cover for electrically connecting to the indoor busbar joint. The central conductive rod is electrically connected to the indoor busbar joint. A gap is reserved between the rod and the sealing cover for the telescopic movement of the center conductive rod to prevent the sealing cover from being subjected to a top thrust during operation, which may lead to air leakage or a reduction in service life. The sealing cover is fixedly connected to the tube body and completely wraps the bellows to achieve sealing on the indoor side of the DC wall bushing. The end of the bellows close to the center conductive rod is connected to the center conductive rod through a movable plate, and the movable plate and the inner wall surface of the sealing cover are conductively slidably matched to achieve flow through the center conductive rod and the sealing cover. This structure enhances the sealing reliability of the DC wall bushing, extends the service life of the DC wall bushing, avoids severe sagging of the center conductive rod and electric field distortion, and reduces the possibility of flashover or breakdown discharge during operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of an embodiment of the flexible DC wall bushing of the present invention;

[0019] Figure 2 for Figure 1 A schematic diagram of the structure of the tube body in the embodiment.

[0020] In the figure: 1. tube body; 2. center conductive rod; 3. bellows; 4. sealing cover; 5. movable plate; 6. mounting hole; 7. plug-in matching section; 8. ring groove; 9. spring contact finger; 10. plug-in sealing ring; 11. end cover; 12. tube body sealing ring; 13. lead-out conductor; 14. shielding cover. DETAILED DESCRIPTION

[0021] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0022] The bellows structure can suppress the generation of metal particles in the bushing, prevent flashover or breakdown discharge, and prevent the conductive rod from seriously sagging, causing electric field distortion and affecting insulation performance. However, the expansion and contraction of the bellows will reduce the sealing performance of the wall bushing, which may cause air leakage and affect insulation performance. The present invention is to add a sealing structure to the outside of the bellows on the indoor side of the DC wall bushing to ensure good sealing performance of the flexible connection part.

[0023] Based on the above ideas, Figure 1 As shown, in a basic embodiment, the flexible DC wall bushing of the present invention includes a pipe body 1 and a central conductive rod 2 installed inside the pipe body 1, and one end of the central conductive rod 2 on the indoor side is axially fixedly connected to a corrugated pipe 3 along the axial direction of the DC wall bushing. The expansion and contraction caused by the thermal expansion of the central conductive rod 2 is adjusted by arranging the corrugated pipe 3 structure on the indoor side to reduce the deflection change of the central conductive rod 2, and at the same time, the metal particles generated by the friction or mechanical vibration at the joint of the central conductive rod 2 can be reduced, and the possibility of flashover or breakdown discharge during operation can be reduced. The end of the corrugated pipe 3 facing away from the central conductive rod 2 is fixedly connected to a sealing cover 4 electrically connected to the indoor busbar joint, and a lead conductor 13 is provided on the sealing cover 4 for electrically connecting to the indoor busbar joint. A gap is reserved between the central conductive rod 2 and the sealing cover 4 for the central conductive rod 2 to move telescopically, so as to prevent the sealing cover 4 from being subjected to a top thrust during operation, resulting in air leakage or a reduction in service life. The sealing cover 4 is fixedly connected to the tube body 1 and completely wraps the corrugated tube 3 to achieve sealing on the indoor side of the DC wall bushing. The end of the corrugated tube 3 close to the central conductive rod 2 is connected to the central conductive rod 2 through a movable plate 5. The movable plate 5 and the inner wall surface of the sealing cover 4 are conductively slidably matched to achieve the flow of current between the central conductive rod 2 and the sealing cover 4. This structure enhances the sealing reliability of the DC wall bushing, extends the service life of the DC wall bushing, avoids serious sagging of the central conductive rod 2 and electric field distortion, and reduces the possibility of flashover or breakdown discharge during operation.

[0024] In a preferred embodiment, the movable plate 5 is a circular plate that fits the inner wall of the sealing cover 4 to ensure good conductive connection. In other embodiments, the movable plate 5 can also be set to a square shape or the like, as long as it fits the inner wall of the sealing cover 4, it can work normally. The shielding cover 14 is fixedly connected to the movable plate 5 to achieve the electric field shielding function of the indoor end.

[0025] In a preferred embodiment, a plug-in fitting section 7 for axially fixing the central conductive rod 2 is installed on the movable plate 5 along the axial direction of the DC wall bushing on the side facing away from the indoors, and the plug-in fitting section 7 is a cylindrical structure, and plays a guiding role while being axially fixedly connected to the central conductive rod 2 through the plug-in fitting section 7. In other embodiments, the plug-in fitting section 7 is not provided, and the axially fixed connection with the central conductive rod 2 is made through the mounting hole 6, and normal operation can also be achieved.

[0026] In a preferred embodiment, an annular groove 8 is formed on the inner wall of the plug-in fitting section 7, and a spring contact finger 9 is disposed in the annular groove 8. The spring contact finger 9 abuts against the inner wall of the plug-in fitting section 7, so that the plug-in fitting section 7 is electrically connected to the end of the central conductive rod 2, and the equipotential of the indoor end assembly is maintained. In other embodiments, the annular groove 8 may not be provided, and a certain gap is ensured between the central conductive rod 2 and the plug-in fitting section 7. The spring contact finger 9 is pressed between the two, and the spring contact finger 9 can also be kept in a relatively fixed state to work normally.

[0027] In a preferred embodiment, at least one plug-in seal ring 10 is provided between the plug-in fitting section 7 and the central conductive rod 2 to achieve a sealed fit between the central conductive rod 2 and the plug-in fitting section 7. In other embodiments, the plug-in seal ring 10 may not be provided, and sealing may be achieved through the fit between the two, which may also work normally.

[0028] In a preferred embodiment, the shape of the cavity inside the sealing cover 4 is a double-layer structure, the inner surface of the larger radial cross section is in contact with the side of the movable plate 5, and flow is achieved through surface contact, and the smaller radial cross section cannot pass through the movable plate 5, so as to limit the movable plate 5. In other embodiments, the cavity adopts a same diameter design, although the sealing cover 4 may be impacted and its service life may be reduced, it can still work normally.

[0029] In a preferred embodiment, an end cover 11 is installed on the end surface where the bellows 3 is connected to the sealing cover 4. The end cover 11 is fixedly connected to the sealing cover 4 to increase the contact area between the bellows 3 and the sealing cover 4, reduce the pressure, and prevent the bellows 3 from being damaged or moving radially. In other embodiments, although the service life is shorter without the end cover 11, it can still work normally. A through hole corresponding to the central conductive rod 2 is opened on the end cover 11 to prevent the central conductive rod 2 from colliding with the bellows 3.

[0030] In a preferred embodiment, a pipe body sealing ring 12 is provided at the connection between the sealing cover 4 and the pipe body 1 to ensure the sealing performance in the flexible DC wall bushing cavity. In other embodiments, the two are connected by welding, although the sealing performance is reduced, they can still work normally.

[0031] In a preferred embodiment, the lead conductor 13 is a terminal post to realize the electrical connection between the indoor end and the busbar connector. The current starts from the central conductive rod 2 and enters the indoor busbar connector through the plug-in matching section 7, the movable plate 5, the sealing cover 4, and the lead conductor 13. In another embodiment, a terminal block can also be used as the lead conductor. Although the corresponding busbar connector needs to be modified, it can still work normally.

[0032] like Figure 2 As shown, in a preferred embodiment, the pipe body 1 is a conical structure, which reduces the weight of the pipe body 1 while ensuring the creepage distance, improves the situation where the DC wall bushing is subjected to excessive mechanical stress, and can save space. In other embodiments, a columnar pipe body 1 is used, which increases the mechanical stress on the DC wall bushing, but can also work normally.

[0033] During operation, as a large current flows, the temperature of the central conductive rod 2 rises, and it begins to stretch in the axial direction due to the temperature. Since the central conductive rod 2 is fixedly connected to the movable plate 5, the movable plate 5 is pushed to move toward the lead-out conductor, compressing the bellows 3 until the movable plate 5 can no longer move. When the current flow decreases and the temperature drops, the central conductive rod 2 begins to shorten, pulling the movable plate 5 to move away from the lead-out conductor 13 until the movable plate 5 contacts the tube body 1 and stops moving.

[0034] During this process, the current flows in from the outdoor end, passes through the central conductive rod 2, passes through the central conductive rod 2 and the spring contact finger 9 of the plug-in mating section 7, flows through the plug-in mating section 7 and the movable plate 5, and the side of the movable plate 5 is in close contact with the sealing cover 4 for conduction, flows through the lead-out conductor 13, and enters the indoor power network.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. The patent protection scope of the present invention shall be based on the claims. All equivalent structural changes made using the contents of the description and drawings of the present invention should also be included in the protection scope of the present invention.

Claims

1. A flexible DC wall bushing, comprising a tube body and a central conductive rod installed inside the tube body, wherein one end of the central conductive rod indoors is axially fixedly connected to a corrugated tube extending along the axial direction of the DC wall bushing, characterized in that: The end of the corrugated tube facing away from the central conductive rod is fixedly connected to a sealing cover electrically connected to the indoor busbar joint, and a lead-out conductor is provided on the sealing cover. A gap is reserved between the central conductive rod and the sealing cover for the telescopic movement of the central conductive rod. The sealing cover is fixedly connected to the tube body and completely wraps the corrugated tube to achieve sealing on the indoor side of the DC wall bushing. The end of the corrugated tube close to the central conductive rod is connected to the central conductive rod through a movable plate, and the movable plate is in conductive sliding cooperation with the inner wall surface of the sealing cover.

2. The flexible DC wall bushing according to claim 1, characterized in that: The movable plate is a circular plate which is fitted with the inner wall surface of the sealing cover.

3. The flexible DC wall bushing according to claim 1 or 2, characterized in that: A plug-in fitting section for axially fixing the central conductive rod is installed on the movable plate on the side facing away from the indoors along the axial direction of the DC wall bushing, and the plug-in fitting section is a cylindrical structure.

4. The flexible DC wall bushing according to claim 3, characterized in that: The inner wall of the plug-in fitting section is provided with an annular groove, in which a spring contact finger is arranged, and the spring contact finger abuts against the inner wall of the plug-in fitting section.

5. The flexible DC wall bushing according to claim 3, characterized in that: At least one plug-in sealing ring is arranged between the plug-in fitting section and the central conductive rod to achieve sealing fit between the central conductive rod and the plug-in fitting section.

6. The flexible DC wall bushing according to claim 1 or 2, characterized in that: The cavity shape in the sealing cover is a double-layer structure, the inner surface of the larger radial section is in contact with the side of the movable plate, and the smaller radial section cannot pass through the movable plate, so as to limit the movable plate.

7. The flexible DC wall bushing according to claim 1 or 2, characterized in that: An end cover is installed on the end surface of the bellows connected to the sealing cover, and the end cover is welded to the sealing cover.

8. The flexible DC wall bushing according to claim 1 or 2, characterized in that: A tube body sealing ring is provided at the connection portion between the sealing cover and the tube body.

9. The flexible DC wall bushing according to claim 1 or 2, characterized in that: The lead conductor is a terminal.

10. The flexible DC wall bushing according to claim 1 or 2, characterized in that: The tube body is a conical structure.

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