Insulating bushing for an air chamber

Abstract

This application relates to an insulating sleeve for a gas-insulated switchgear, comprising an insulating casting body and a conductive rod. The insulating casting body is fitted over the conductive rod and integrally formed by casting. One end of the conductive rod has a first connecting hole with internal threads along its axial direction, and the other end has a second connecting hole with internal threads along its axial direction. A mounting sleeve is slidably fitted onto the outer periphery of the insulating casting body. A sealing washer is provided on the side of the mounting sleeve facing the first connecting hole, and the side of the sealing washer facing away from the mounting sleeve extends radially outward along the insulating casting body to form an annular sealing skirt. The sealing skirt is used to insert into the mounting hole of the gas-insulated switchgear and form an interference fit with the hole wall. A first external thread section is provided on the outer peripheral wall of the insulating casting body near the second connecting hole, and a fixing nut is threaded onto the first external thread section. This application effectively improves the problem of insufficient sealing reliability of existing insulating sleeves for gas-insulated switchgear through the synergistic effect of the above components.

Description

Technical Field

[0001] This application relates to the technical field of high-voltage switchgear, and in particular to an insulating bushing for gas-insulated switchgear. Background Technology

[0002] High-voltage switchgear, as the core device for power distribution, control, and protection in power systems, is widely used in substations, industrial distribution networks, and urban power grids. With the advancement of smart grid construction and increasingly stringent environmental protection requirements, gas-insulated metal-enclosed switchgear, especially gas-filled switchgear using sulfur hexafluoride (SF6) or its environmentally friendly alternative gases such as dry air, nitrogen mixtures, and fluorinated nitriles as the insulating medium, has shown significant advantages in terms of compactness, high reliability, and maintenance-free operation, and has become the mainstream choice in the medium-voltage power distribution field.

[0003] In the structure of a gas-insulated switchgear, the insulating bushing is a key component connecting the internal main circuit conductors to external cables or busbars, undertaking three core functions: electrical conduction, ground insulation, and gas chamber sealing. Its performance directly affects the safe operation and long-term stability of the entire switchgear. Typical insulating bushings for gas-insulated switchgear usually employ an integral structure with a conductive rod encased in epoxy resin and cast, then mechanically fastened to pre-drilled holes in the cabinet, while relying on sealing elements to achieve airtight isolation.

[0004] However, in practical applications, the insufficient sealing reliability of traditional insulating sleeves has become a major bottleneck restricting the long-term stable operation of equipment. Since insulating sleeves often employ a composite structure of a metal conductive rod and a non-metallic epoxy casting, the significant difference in their coefficients of thermal expansion makes them prone to internal stress accumulation under temperature cycling conditions. Furthermore, the curing shrinkage of epoxy materials themselves leads to the formation of micro-cracks at the interface or assembly gaps. When such structural errors are compounded by on-site installation deviations, conventional single O-rings or flat gaskets are insufficient to effectively compensate for deformation, easily causing slow leakage of high-cost insulating gases such as SF6. This not only increases maintenance costs but may also induce partial discharge or even insulation breakdown accidents due to pressure drop.

[0005] Therefore, there is an urgent need for a new type of insulating sleeve that can maintain high airtightness and good field maintainability throughout its entire life cycle. Utility Model Content

[0006] In order to improve the problem of insufficient sealing reliability of existing insulating sleeves for gas-filled switchgear, this application provides an insulating sleeve for gas-filled switchgear.

[0007] The insulating sleeve for a gas-insulated switchgear provided in this application adopts the following technical solution: An insulating sleeve for a gas-insulated switchgear includes an insulating casting body and a conductive rod. The insulating casting body is sleeved on the conductive rod and integrally formed by casting. One end of the conductive rod has a first connecting hole with internal threads along the axial direction, and the other end has a second connecting hole with internal threads along the axial direction. An installation sleeve is slidably fitted on the outer periphery of the insulating casting body. A sealing gasket is provided on the side of the installation sleeve facing the first connecting hole. The side of the sealing gasket away from the installation sleeve extends radially outward along the insulating casting body to form an annular sealing skirt. The sealing skirt is used to insert into the gas-insulated switchgear installation hole and form an interference fit with the hole wall. An external threaded section is provided on the outer peripheral wall of the insulating casting body near the second connecting hole, and a fixing nut is threaded onto the first external threaded section.

[0008] Furthermore, the thread direction of the first external thread segment is opposite to the thread direction of the internal thread in the first connecting hole.

[0009] Furthermore, a locking nut is also threaded onto the first external thread section, and the locking nut is located between the fixing nut and the second connecting hole.

[0010] Furthermore, the mounting sleeve has an annular groove on the side facing the sealing gasket, and the sealing gasket has an integrally formed snap-fit ​​protrusion that is interference-fitted with the annular groove.

[0011] Furthermore, the end of the sealing skirt away from the sealing gasket is provided with a guide slope.

[0012] Furthermore, the mounting sleeve is provided with a second external thread section, on which a protective cap for covering the second connecting hole is threadedly connected.

[0013] Furthermore, the openings of both the first and second connecting holes have been chamfered.

[0014] In summary, the beneficial technical effects of this application are as follows: 1. A dual seal, both radial and axial, is achieved through the combination of a sliding mounting sleeve and a sealing gasket with a sealing skirt. The interference fit between the sealing skirt and the cabinet mounting holes effectively compensates for manufacturing and assembly errors, significantly suppresses the leakage of insulating gases (such as SF6 or environmentally friendly gases), and prevents the intrusion of external pollutants. 2. By setting the internal thread direction of the first connecting hole to the opposite direction of the external thread direction, a dynamic reverse torque feedback mechanism is formed. When the conductive rod tends to loosen due to vibration or thermal cycling during operation, the loosening torque is converted into an additional tightening torque of the fixing nut, which causes the mounting sleeve to further press the sealing structure, forming a self-tightening anti-loosening mechanism. With the addition of the locking nut, a double mechanical locking is formed, which greatly improves the connection stability and long-term reliability in vibration environment. 3. The step-by-step installation process, with electrical connections first followed by mechanical fastening, simplifies on-site operations and facilitates maintenance; the interference fit design of the snap-fit ​​protrusion and annular groove ensures the consistency and firmness of the connection between the sealing gasket and the mounting sleeve; the guide bevel and chamfering of the connection hole reduce the difficulty of centering and the requirements for installation accuracy, improve assembly efficiency and adaptability, and are especially beneficial for on-site operations. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall structure of an embodiment of this application; Figure 2 This is a top view of an embodiment of this application; Figure 3 It is along Figure 2 A partial cross-sectional view of the middle AA line; Figure 4 This is a schematic diagram of the structure of the protective cap assembled in an embodiment of this application.

[0016] Explanation of reference numerals in the attached figures: 1. Insulating casting body; 11. First external thread section; 111. Fixing nut; 112. Locking nut; 2. Conductive rod; 21. First connecting hole; 211. Chamfer; 22. Second connecting hole; 3. Mounting sleeve; 31. Annular groove; 32. Second external thread section; 321. Protective cap; 4. Sealing gasket; 41. Sealing skirt; 411. Guide bevel; 42. Snap-fit ​​protrusion. Detailed Implementation

[0017] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0018] This application discloses an insulating sleeve for a gas-insulated switchgear. (Refer to...) Figures 1 to 3It includes an insulating casting body 1 and a conductive rod 2. The insulating casting body 1 is coated onto the outside of the conductive rod 2 using an epoxy resin casting process to form an integral structure, ensuring good electrical insulation performance and mechanical strength. The conductive rod 2 is preferably made of copper, with a first connecting hole 21 with internal threads at one end along the axial direction and a second connecting hole 22 with internal threads at the other end, used to connect to the busbar or contacts inside the cabinet, respectively.

[0019] An installation sleeve 3 is slidably fitted onto the outer periphery of the insulating casting body 1. A sealing washer 4 is provided on the side of the installation sleeve 3 facing the first connecting hole 21. The side of the sealing washer 4 facing away from the installation sleeve 3 extends radially outward along the insulating casting body 1 to form an annular sealing skirt 41. This sealing skirt 41 is used to insert into the gas chamber mounting hole and form an interference fit with the hole wall. Specifically, the outer diameter of the sealing skirt 41 is slightly larger than the inner diameter of the gas chamber mounting hole to achieve elastic deformation and tight fit with the hole wall during installation.

[0020] In addition, the outer peripheral wall of the insulating casting body 1 near the second connecting hole 22 is provided with a first external thread section 11, and a fixing nut 111 is threadedly connected to the first external thread section 11.

[0021] During installation, the conductive rod 2 with the first connecting hole 21 is first inserted into the gas-filled cabinet mounting hole, and the mounting sleeve 3 is initially positioned away from the first connecting hole 21. Then, the insulating casting body 1 is rotated, allowing the conductive rod 2 to achieve a threaded connection with the electrical components (such as spline contacts) inside the cabinet through the first connecting hole 21, ensuring reliable electrical conductivity. Next, the fixing nut 111 is rotated, driving the mounting sleeve 3 axially towards the cabinet body, causing the sealing skirt 41 to insert into the mounting hole and undergo elastic deformation, thus tightly fitting the hole wall. Simultaneously, the sealing gasket 4 is pressed between the mounting sleeve 3 and the cabinet surface, forming a double seal in both the radial and axial directions. The interference fit design of the sealing skirt 41 effectively compensates for the assembly gap between the insulating casting body 1 and the metal cabinet mounting hole, preventing leakage of insulating gas (such as sulfur hexafluoride or environmentally friendly alternative gases) inside the gas-filled cabinet and blocking the intrusion of external moisture, dust, and other contaminants. The fixing nut 111 provides continuous clamping force, preventing loosening of the connection due to vibration or temperature changes.

[0022] In summary, this insulating sleeve for gas-insulated switchgear, with its sliding mounting sleeve 3 and standardized threaded interface, can adapt to different cabinet structures and electrical connection requirements, improving installation flexibility and reducing manufacturing complexity. Its combined sealing design (combining sealing gasket 4 and sealing skirt 41) effectively addresses differences in material shrinkage rates (such as between the metal conductive rod 2 and the epoxy resin casting) and installation errors, ensuring long-term reliable sealing performance. The step-by-step installation process (electrical connection first, followed by mechanical fastening) simplifies on-site operations, particularly facilitating replacement work in enclosed cabinets or during on-site maintenance, without requiring specialized tools or destructive removal. This effectively addresses the issue of insufficient sealing reliability in existing insulating sleeves for gas-insulated switchgear.

[0023] Specifically, refer to Figures 1 to 3 The thread direction of the first external thread section 11 is opposite to that of the internal thread in the first connecting hole 21. Based on this opposite thread direction design, when the gas-insulated cabinet is in operation and factors such as vibration or temperature changes cause a tendency for the threaded connection at the first connecting hole 21 to loosen, the fixing nut 111 connected to the first external thread section 11 will be subjected to a reverse torque. The direction of this torque is consistent with the tightening direction of the fixing nut 111, thereby causing the fixing nut 111 to tighten further rather than loosen. For example, in a vibration environment, if the threaded connection in the first connecting hole 21 tends to loosen, the torque applied to the conductive rod 2 will be transmitted to the first external thread section 11, and then converted into an additional tightening force on the fixing nut 111, so that the mounting sleeve 3 is pressed more tightly against the cabinet. This mechanism effectively suppresses the risk of loosening of the insulating sleeve due to long-term vibration or thermal cycling, and further improves the stability and reliability of the installation.

[0024] Furthermore, referring to Figures 1 to 3 A locking nut 112 is also threaded onto the first external thread section 11, and the locking nut 112 is located between the fixing nut 111 and the second connecting hole 22. After the fixing nut 111 is tightened and the mounting sleeve 3 is pressed and fixed to the gas cabinet body, the locking nut 112 is further tightened. Through the mutual cooperation of the locking nut 112 and the fixing nut 111, a double mechanical locking structure is formed.

[0025] The locking nut 112 effectively restricts the rotational movement of the fixing nut 111 under vibration or impact conditions, significantly improving the installation stability and vibration resistance of the insulating bushing on the gas-insulated switchgear. Simultaneously, tightening the locking nut 112 applies additional preload to the first external thread section 11. This preload, in conjunction with the clamping force generated by the fixing nut 111, helps optimize the stress distribution of the overall structure, allowing stress to be more evenly transmitted to the conductive rod 2, the insulating casting 1, the mounting sleeve 3, and all connection interfaces. This design reduces localized stress concentration caused by internal pressure fluctuations in the gas-insulated switchgear or external mechanical impacts, thereby reducing the fatigue risk of critical components and improving the reliability and durability of the insulating bushing under long-term operating conditions.

[0026] Furthermore, referring to Figure 2 and Figure 3 The mounting sleeve 3 has an annular groove 31 on the side facing the sealing gasket 4. The sealing gasket 4 has an integrally formed snap-fit ​​protrusion 42 that interferes with the annular groove 31, and the shape of the snap-fit ​​protrusion 42 matches the annular groove 31. During assembly, a certain axial force is applied to the sealing gasket 4, causing the snap-fit ​​protrusion 42 to elastically deform and press into the annular groove 31. Due to the interference fit design, the snap-fit ​​protrusion 42 is subjected to radial constraint force from the groove wall after entering the annular groove 31, while the inner wall of the annular groove 31 is also subjected to a counterforce from the snap-fit ​​protrusion 42, thus forming a strong mechanical connection between the two. Simultaneously, because the sealing gasket 4 and the mounting sleeve 3 achieve a stable connection through this snap-fit ​​structure, the sealing skirt 41 maintains more uniform deformation and positional consistency when inserted into the gasket mounting hole, thereby improving the uniformity of contact with the mounting hole wall and enhancing the interface sealing effect.

[0027] Furthermore, referring to Figures 1 to 4 The sealing skirt 41, at the end furthest from the sealing gasket 4, is provided with a guide slope 411. The inclination angle and curved profile of the guide slope 411 have been precisely calculated and optimized to ensure smooth contact with the edge of the gasket mounting hole during installation. The guide slope 411 reduces the difficulty of centering the sealing skirt 41 when it enters the gasket mounting hole, avoiding assembly interference caused by hole axis deviation, which is especially suitable for rapid on-site installation or applications with limited precision. Furthermore, the slope structure transforms the contact between the sealing skirt 41 and the edge of the mounting hole from an impact collision to a gradual sliding in, effectively reducing surface scratches, extrusion deformation, or material wear, and helping to maintain the structural integrity and sealing reliability of the sealing skirt 41.

[0028] At the same time, refer to Figures 1 to 4The mounting sleeve 3 is provided with a second external thread section 32, on which a protective cap 321 for covering the second connecting hole 22 is threadedly connected. The protective cap 321 is made of insulating materials such as silicone rubber or epoxy resin, and its interior has an internal thread structure that matches the second external thread section 32. Through screw-on connection, the protective cap 321 can completely cover the second connecting hole 22, forming a physical isolation barrier. During the transportation, storage, or when the gas cabinet is not in use, the protective cap 321 can effectively prevent dust, oil, moisture, and other contaminants from entering the interior of the second connecting hole 22, avoiding oxidation or contamination of the conductive rod 2 surface, thereby maintaining good electrical connection performance.

[0029] Additionally, refer to Figures 1 to 3 Both the openings of the first connecting hole 21 and the second connecting hole 22 are chamfered 211, forming a guide bevel 411 structure. When an electrical connection component with external threads (such as a bolt or connector) is screwed into the connecting hole, the chamfer 211 provides initial alignment guidance. The end of the connecting component first contacts the chamfer 211, and under rotation, it smoothly slides into the hole along the bevel, avoiding rigid collision or jamming with the edge of the hole, significantly reducing installation difficulty. Especially in installation scenarios with limited space or restricted visibility, the guiding effect of the chamfer 211 reduces the requirements for installation accuracy, making it easier for operators to achieve quick and accurate docking, thereby improving on-site assembly efficiency.

[0030] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "first," "second," "third," and similar terms used in this application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. The terms "a" or "an," and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "comprising," "including," and similar terms mean that the elements or objects preceding "comprising" encompass the elements or objects listed following "comprising" or "including," and their equivalents, but do not exclude other elements or objects. "Above," "below," "left," "right," etc., are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0031] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. An insulating sleeve for a gas-insulated switchgear, comprising an insulating casting body (1) and a conductive rod (2), wherein the insulating casting body (1) is sleeved over the conductive rod (2) and integrally formed by casting, characterized in that, One end of the conductive rod (2) is provided with a first connecting hole (21) with internal thread along the axial direction, and the other end is provided with a second connecting hole (22) with internal thread along the axial direction; the outer periphery of the insulating casting body (1) is slidably fitted with an installation sleeve (3), and a sealing gasket (4) is provided on the side of the installation sleeve (3) facing the first connecting hole (21). The side of the sealing gasket (4) away from the installation sleeve (3) extends along the radial outer side of the insulating casting body (1) to form an annular sealing skirt (41). The sealing skirt (41) is used to insert into the gas cabinet installation hole and form an interference fit with the hole wall. An insulating casting body (1) has a first external thread section (11) on its outer peripheral wall near the second connecting hole (22), and a fixing nut (111) is threaded onto the first external thread section (11).

2. The insulating sleeve for a gas-insulated switchgear according to claim 1, characterized in that, The direction of the thread of the first external thread segment (11) is opposite to the direction of the internal thread in the first connecting hole (21).

3. An insulating sleeve for a gas-insulated switchgear according to claim 2, characterized in that, A locking nut (112) is also threaded onto the first external thread section (11), and the locking nut (112) is located between the fixing nut (111) and the second connecting hole (22).

4. An insulating sleeve for a gas-insulated switchgear according to claim 1, characterized in that, The mounting sleeve (3) has an annular groove (31) on the side facing the sealing gasket (4), and the sealing gasket (4) has an integrally formed snap-fit ​​protrusion (42) that is interference fit with the annular groove (31).

5. An insulating sleeve for a gas-insulated switchgear according to claim 1, characterized in that, The end of the sealing skirt (41) away from the sealing gasket (4) is provided with a guide slope (411).

6. An insulating sleeve for a gas-insulated switchgear according to claim 1, characterized in that, The mounting sleeve (3) is provided with a second external thread section (32), and a protective cap (321) for covering the second connecting hole (22) is threaded onto the second external thread section (32).

7. An insulating sleeve for a gas-insulated switchgear according to claim 1, characterized in that, The openings of the first connecting hole (21) and the second connecting hole (22) are both chamfered (211).

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