An overhead insulated cable for power grids

Abstract

The application relates to the technical field of electric wire and cable, and particularly discloses an overhead insulated cable for power grid, which comprises a conductor, an insulation layer, a positioning sheath and a transposition protection assembly. The transposition protection assembly has a middle bearing section and a plurality of transposition bearing sections on both sides of the middle bearing section, which are collectively referred to as bearing sections. The lower parts of adjacent bearing sections are hingedly connected, and the width direction sides perpendicular to the cable axial direction are respectively locked through mutually independent time sequence failure connecting pieces. After two groups of connecting pieces at the same hinged position are both disabled, the transposition bearing sections located on the outside of the hinged position are rotated. The two sections after the breakage of the connecting pin are respectively limited by end caps and threading sleeves and by threaded sleeves and split pins, a flexible retaining piece is gradually tensioned and the maximum rotation angle is limited along with the rotation of the bearing section, so that the rigid bearing boundary and the main bending position of the cable are transferred in stages, and the wind vibration bending and local wear of the same position for a long time are reduced.

Description

Technical Field

[0001] This invention relates to the field of wire and cable technology, and more specifically to an overhead insulated cable for power grids. Background Technology

[0002] Overhead insulated cables typically consist of stranded conductors and an insulation layer covering the outside of the conductors. During installation, they are fixed to the crossarms of towers using insulators, suspension clamps, tension clamps, or other supporting hardware. Under the combined effects of their own weight, span tension, wind load, and temperature changes, the cable sags, transitioning from a constrained state to a free-suspension state near the supporting hardware. When repeated wind vibrations or swaying occur, the cable undergoes periodic bending near the support boundary, and there may also be slight relative displacement between the supporting structure and the cable's outer surface. Existing projects typically reduce localized damage by adding abrasion-resistant pads, sheathing, lengthening clamps, or installing vibration-damping components. However, these measures mostly maintain fixed clamping positions and fixed support boundaries, meaning the main bending areas of the cable remain concentrated in the same axial position for extended periods.

[0003] Chinese invention patent CN112103888A discloses a high-altitude cable and fixing device to prevent wind-induced swaying and wear. It uses a fixing mechanism, clamping and limiting mechanism, anti-wear tube, and extension support rod to separate and clamp the cables, reducing wear caused by multiple cables contacting each other under wind force. This solution improves the spacing between cables and fixes the anti-wear tube; however, the relative position between the clamping structure and the cables remains unchanged after installation. It primarily suppresses contact friction between cables and does not alter the position of a single cable during long-term repeated bending at the support boundary.

[0004] Chinese utility model patent CN216561131U discloses a lightning-proof pre-twisted wire tension clamp. It employs a double-layer structure with inner and outer pre-twisted wires, and the ends of the inner pre-twisted wires are bent away from the optical cable to prevent direct scratching. This structure reduces frictional damage between the clamp ends and the cable surface, but the stress transition position between the pre-twisted wires and the cable remains fixed, ensuring that the bending boundary of the cable or optical cable under long-term wind vibration conditions does not shift with usage.

[0005] Chinese utility model patent CN204391657U also discloses an insulating sheath for power transmission lines, which wraps multiple layers of insulating film around the outside of the conductor to achieve wear resistance, insulation, anti-aging, and water repellency. Such partial sheaths can improve the wear resistance of the cable's outer surface, but they mainly rely on increasing the number of material layers to withstand friction and cannot actively change the location of repeated stress and bending. When the external support structure continuously acts on the same area, the sheath and insulation layer still need to bear pressure, bending, and fretting loads within a fixed area for a long time.

[0006] Therefore, existing solutions can reduce the degree of local damage by adding wear-resistant layers, optimizing the clamp ends, or setting up vibration-damping structures. However, these solutions typically fix the cable in a long-term, unchanging clamping position, with the outer end of the support structure forming a fixed, rigid support boundary. As the number of wind-induced vibrations increases, the insulation layer and conductor near this boundary continuously endure alternating bending, and local padding is also prone to compression deformation and wear at the same location. If the clamp is directly slid along the cable axis for repositioning, the repositioning process may scrape the insulation layer, and there is also the problem of unstable load transfer. Therefore, there is a need for an installation and fixing structure integrated into the cable itself that can change the effective support length and major bending positions in a predetermined sequence without driving the clamp to slide along the insulation layer, and maintain continuous cable support and reliable anti-detachment at each stage. Summary of the Invention

[0007] This invention provides an overhead insulated cable for power grids, aiming to solve the problems of existing overhead insulated cables having fixed main bending positions after installation, resulting in the same local area being continuously subjected to wind vibration bending, compression and fretting wear, and the insulation layer being easily scratched when using sliding repositioning.

[0008] An overhead insulated cable for power grids includes a conductor and an insulation layer covering the outside of the conductor. A positioning sheath is fixedly installed on a portion of the outer side of the insulation layer, and a transposition protection assembly is installed on the outer side of the positioning sheath. The transposition protection assembly includes a central load-bearing section connected to the positioning sheath and multiple transposition support sections arranged sequentially along the axial direction of the overhead insulated cable on both sides of the central load-bearing section. The central load-bearing section is provided with an installation part for connecting external support members. The central load-bearing section and the transposition support sections are collectively referred to as support sections. The lower parts of adjacent support sections are hinged together, and the two support sections corresponding to each hinge position are connected to each other on both sides in the width direction perpendicular to the axial direction of the overhead insulated cable. Independent sequential failure connectors are used; the sequential failure connectors include a first connecting sleeve and a second connecting sleeve fixed to two adjacent support sections respectively, and a connecting pin passing through the first connecting sleeve and the second connecting sleeve. The connecting pin is provided with a corrosion failure section located in the second connecting sleeve, and the side wall of the second connecting sleeve is provided with a corrosion window corresponding to the corrosion failure section. The opening area of ​​the corrosion windows located on the same axial side of the middle support section and at different hinge positions decreases sequentially from the outside to the inside, so that after both sets of sequential failure connectors corresponding to the same hinge position fail, the transposition support section located outside the hinge position releases the upper connection and rotates around the hinge position.

[0009] Its effect is as follows: the positioning sleeve fixes the transposition protection component in the predetermined installation area of ​​the cable body, so that the installation load is first transferred to the middle load-bearing section through the installation part, and then distributed from the middle load-bearing section to the transposition support sections arranged on both sides in sequence, avoiding the formation of a single narrow pressing point on the insulation layer by the external support component. In the initial state, the connecting pins on both sides of the width direction of each hinge position cross the first connecting sleeve and the second connecting sleeve respectively, so that the upper part of the adjacent support section is connected, and together with the lower hinge relationship, they form a stable segmented support structure. The corrosion windows on the second connecting sleeves of each level gradually decrease from the outside to the inside, so that the sequential failure of the connecting components at different hinge positions forms a trend of sequential failure from the outside to the inside; the two sets of sequential failure connecting components at the same hinge position are independent of each other. Only after both sets fail will the transposition support section located outside the hinge position release the upper connection and rotate around the hinge position, avoiding the support section deflection caused by the failure of a single connecting component. After each outer transposition support joint rotates, the effective rigid support boundary moves towards the center, and the main bending area of ​​the cable shifts to the next axial position. When the above process is completed sequentially at different hinge positions, the bending position can be changed in stages without sliding the clamping structure along the insulation layer, reducing the long-term exposure of the same part to alternating bending and local wear. At the same time, the central load-bearing joint and the time-failed connectors that have not yet failed continue to maintain the installation load transfer and support stability.

[0010] Preferably, both the central bearing section and the transposition support section are U-shaped channels with their openings facing upwards. The cavities of multiple U-shaped channels are sequentially connected along the axial direction of the overhead insulated cable, and the overhead insulated cable is supported within the support channel formed by the multiple U-shaped channels. The effect is that the U-shaped channels can form an encircling support from below and both sides of the cable, facilitating assembly from below and preventing lateral cable detachment when the support section rotates; the sequential connection of multiple cavities ensures continuity of the support surface in the initial state and provides a structural basis for the subsequent formation of a segmented, approximately arc-shaped support surface.

[0011] Preferably, the inner walls of both the central support section and the transposition support section are provided with insulating and wear-resistant pads, and a clearance is provided between two adjacent insulating and wear-resistant pads to allow the corresponding transposition support section to rotate. The effect is that the insulating and wear-resistant pads isolate the metal support section from the cable insulation layer, disperse the pressure at the edge of the trough, and absorb small vibrations; the clearance prevents adjacent pads from pressing against each other or curling up during the rotation of the support section, allowing each support section to rotate independently at a set angle.

[0012] Preferably, the positioning sleeve includes a first sleeve body and a second sleeve body that interlock with each other. After the first sleeve body and the second sleeve body are interlocked, they together cover and radially tighten the outer side of the insulation layer. Positioning rings that abut against the insulation layer are respectively provided at both ends of the positioning sleeve, and the middle load-bearing section is fixed to the lower side of the positioning sleeve. The advantage is that the split positioning sleeve can be radially assembled after cable manufacturing or before line installation. The radial clamping force formed by the first sleeve body and the second sleeve body, together with the positioning rings, restricts the axial movement of the positioning sleeve relative to the insulation layer, keeping the transposition protection component in the predetermined installation position, and forming a stable integrated installation structure between the middle load-bearing section and the cable.

[0013] Preferably, the connecting pin includes an end cap, a pin shaft, and a threaded sleeve. The pin shaft passes sequentially through the first connecting sleeve and the second connecting sleeve. The corrosion failure section is formed on the portion of the pin shaft located inside the second connecting sleeve. The end cap is located at the end of the pin shaft extending out of the second connecting sleeve. The threaded sleeve is threadedly connected to the end of the pin shaft extending out of the first connecting sleeve. A connecting hole is provided on the pin shaft near the threaded sleeve. The corrosion window penetrates the side wall of the second connecting sleeve and corresponds to the position of the corrosion failure section. The effect is that the first and second connecting sleeves confine the pin shaft to a predetermined connection position on the upper part of adjacent support sections. The complete pin shaft spans the two support sections and prevents their upper parts from separating. After the corrosion failure section breaks, the pin shaft is divided into pin shaft segments located on the two sides of the connecting sleeves, thereby releasing the upper locking on that side. The sleeve wall of the second connecting sleeve, except for the corrosion window, shields the corrosion failure section. The corrosion window forms a confined channel for external moisture to contact the corrosion failure section, concentrating the corrosion effect at the predetermined failure position.

[0014] Preferably, the minimum cross-sectional area of ​​multiple corrosion-failed segments located on the same axial side of the central load-bearing section and at different hinge positions increases sequentially from the position furthest from the central load-bearing section to the position closest to the central load-bearing section. The effect is that the corrosion window area and the load-bearing cross-sectional area of ​​the corrosion-failed segment form a dual sequential control; the outer connectors have larger media contact conditions and smaller remaining load-bearing cross-sections, thus exhibiting a preferential failure tendency; connectors closer to the central load-bearing section have larger cross-sectional reserves, reducing the probability of simultaneous disengagement of connectors of different levels.

[0015] Preferably, each time-failure connector further includes a threaded sleeve, a flexible retainer, and a cotter pin. The threaded sleeve is fixed to the support section equipped with a second connecting sleeve. The flexible retainer passes through the threaded sleeve, with one end connected to the end cap and the other end connected to the cotter pin, which passes through the connecting hole. The flexible retainer is in a relaxed state when the connecting pin is intact, and gradually tightens as the transposed support section located outside the hinge position rotates after both sets of time-failure connectors at the same hinge position fail. After tightening, it limits the maximum rotation angle between two adjacent support sections. The effect is that the flexible retainer does not participate in rigid locking when the connecting pin is intact; after the corrosion-failed section breaks, the flexible retainer connects the end cap side pin section with another pin section held by the cotter pin, preventing the broken part from falling; after the support section is released from the upper connection and rotates, the effective length of the flexible retainer limits the maximum rotation angle between adjacent support sections, so that the released support section still supports the cable at a limited tilt angle.

[0016] Preferably, the two sets of sequentially failing connectors corresponding to the same hinge position have the same corrosion window opening area, minimum cross-sectional area of ​​the corrosion failure section, and corrosion failure section material; when the corrosion failure section of any set of sequentially failing connectors is not broken, the connecting pins of that set independently maintain the upper connection of the two adjacent support sections. The effect is that the two sets of connectors use the same nominal structural parameters, so that they are at similar predetermined failure levels, but are not required to actually break at the same time; when the connector on one side fails first, the intact connector on the other side can independently bear the upper constraint of the transition stage, avoiding unilateral sinking, twisting, or jamming of the support section, and the overall rotation is completed after both connectors on both sides fail.

[0017] Preferably, the effective lengths of the two flexible retainers corresponding to the same hinge position are the same. The effective lengths of the flexible retainers at each level on the same axial side of the central load-bearing section increase sequentially from the position closer to the central load-bearing section to the position farther away from the central load-bearing section. This allows multiple transposed support sections to rotate to the position where the flexible retainers are tensioned, collectively forming a segmented, approximately arc-shaped support surface that gradually slopes downwards away from the central load-bearing section. The effect is that the two flexible retainers at the same hinge position can jointly limit the rotation angle from both sides of the width direction of the U-shaped groove, reducing the lateral torsion after the support section rotates. Different effective lengths are used for different axial levels, so that the support section closer to the central load-bearing section maintains a smaller inclination angle, while the support section farther away from the central load-bearing section forms a larger inclination angle. Multiple support sections thus constitute a segmented, approximately arc-shaped support surface that gradually slopes downwards outwards.

[0018] Preferably, the threading sleeve is located on the side of the second connecting sleeve away from the first connecting sleeve, and the traction direction of the flexible retainer after being turned by the threading sleeve has an axial component that causes the pin section with the end cap to exit the second connecting sleeve; the inner diameter of the threading sleeve is smaller than the outer diameter of the end cap, and the threaded sleeve and the cotter pin are located on the axial sides of the first connecting sleeve respectively; after the corrosion failure section breaks, the pin section with the end cap exits the second connecting sleeve under the traction of the flexible retainer and moves until the end cap abuts against the threading sleeve, and the other pin section is jointly restricted in the first connecting sleeve by the threaded sleeve and the cotter pin; the corrosion window is a rectangular window opened on the side wall of the second connecting sleeve. Its effect is that the position and direction of the threaded sleeve cause the flexible retainer to generate an axial traction component on the pin section on the end cap side when the support section rotates. The size fit between the end cap and the threaded sleeve can prevent the pin section from continuing to disengage. The threaded sleeve and cotter pin axially limit the other pin section from both sides of the first connecting sleeve, so that both sections after the connecting pin breaks are reliably retained. The rectangular corrosion window is convenient for limiting the exposed length and opening area of ​​the corrosion failure section, and it is convenient to establish the relative failure sequence of different axial level connectors by changing the window size.

[0019] The beneficial effects of the present invention using the above technical solution are as follows: The present invention uses multiple rotatable support sections as a local installation and fixing structure integrated into the cable body. These sections are connected to external support components via a central support section, allowing the cable installation load to be transferred through the positioning sleeve and segmented support surfaces. Each hinge position employs independent sequential failure connectors on both sides of the U-shaped groove width direction. This ensures stable locking when both sides of the connectors are intact, and allows the upper connection of the support section to be maintained even if one side fails first, without requiring simultaneous failure of both sides. After the connecting pin breaks, the end cap and the threaded sleeve, and the screw sleeve and the cotter pin retain two sections of the pin shaft respectively. After both sides of the connectors fail, the flexible retaining member is tensioned as the support section rotates, limiting the rotation angle and allowing the released support section to continue forming a segmented, approximately arc-shaped, follow-up support. Each axial level of connector is released sequentially from the outside in, preventing any clamping component from sliding along the insulation layer. This effectively changes the rigid support length and the main bending positions of the cable, making it suitable for long-term overhead operation environments. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the present invention and its connection with external support components.

[0021] Figure 2 for Figure 1 A magnified view of a portion of point A in the middle.

[0022] Figure 3 This is a schematic diagram showing the state after the upper connection between adjacent support sections is disconnected.

[0023] Figure 4 This is a schematic diagram of the connecting pin of the present invention.

[0024] Figure 5 This is a schematic diagram of the positioning sleeve of the present invention.

[0025] Figure 6 This is a side view of the transposition support section of the present invention.

[0026] Figure 7 This is a schematic diagram of the end view structure of the cable body, positioning sheath and transposition support section of the present invention in the assembled state.

[0027] Figure label:

[0028] 1. Cable body; 2. Positioning sheath; 21. First sheath body; 22. Second sheath body; 23. Positioning ring; 3. Transposition protection assembly; 31. Middle load-bearing section; 311. Mounting part; 32. Transposition support section; 4. Sequence failure connector; 41. First connecting sleeve; 42. Second connecting sleeve; 421. Corrosion window; 43. Connecting pin; 431. End cap; 432. Pin shaft; 433. Corrosion failure section; 434. Screw sleeve; 435. Connecting hole; 44. Threaded sleeve; 45. Flexible retainer; 46. Cotter pin; 5. Hinge assembly; 51. Hinge lug; 52. Hinge shaft. Detailed Implementation

[0029] The structure, assembly method, and working process of the present invention will be described below with reference to the accompanying drawings. The dimensions and quantities shown in the drawings are for illustrating the fit between the components and do not constitute a limitation on the scope of protection.

[0030] like Figures 1 to 7 As shown, an overhead insulated cable for power grids includes a cable body 1, a positioning sheath 2, a transposition protection component 3, a timing failure connector 4, and a hinge assembly 5. The positioning sheath 2 is disposed in a predetermined suspension area of ​​the cable body 1. The transposition protection component 3 forms an integrated installation structure with the cable body 1 through the positioning sheath 2. The middle part of the transposition protection component 3 is used to connect with an external support, and the two sides are used to change the position of the cable body 1 from a supported state to a free suspension state in stages.

[0031] The cable body 1 includes a conductor and an insulation layer covering the outside of the conductor. The conductor can be aluminum stranded wire, aluminum alloy stranded wire, steel-cored aluminum stranded wire, or other conductor structures that meet the requirements of overhead power distribution. The insulation layer can be cross-linked polyethylene, weather-resistant polyethylene, or other insulation materials suitable for outdoor overhead lines. The transposition protection component 3 is located on a localized outer side of the insulation layer and does not change the conventional structure of the conductor and insulation layer over the remaining length.

[0032] The positioning sleeve 2 includes a first sleeve body 21 and a second sleeve body 22. The first sleeve body 21 and the second sleeve body 22 are interlocked along the radial direction of the cable body 1 to form a cylindrical structure surrounding the insulation layer. The two sleeve bodies can be fixed by means of clips, screws, clamps, or tenons, and together they radially tighten the insulation layer after being interlocked. The inner surfaces of the first sleeve body 21 and the second sleeve body 22 are provided with an anti-slip elastic layer. After being radially compressed, the anti-slip elastic layer forms a frictional fit with the insulation layer to improve the axial anti-slip capability of the positioning sleeve 2 and prevent the positioning sleeve 2 from exerting hard pressure on the insulation layer. The hardness of the anti-slip elastic layer is lower than that of the outer surface of the insulation layer, and it has weather resistance and creep resistance.

[0033] Positioning rings 23 are provided at both ends of the positioning sleeve 2. The positioning rings 23 can be integrally formed with the first sheath body 21 or the second sheath body 22, or they can be installed as independent rings at the ends of the positioning sleeve 2. The two positioning rings 23 abut against the insulation layer, and together with the radial clamping force formed by the first sheath body 21 and the second sheath body 22, they restrict the axial movement of the positioning sleeve 2 along the cable body 1. The edges of the positioning rings 23 that contact the insulation layer are rounded to avoid forming new sharp indentations at the ends of the positioning sleeve 2. In actual manufacturing, the axial length of the positioning sleeve 2 is greater than the axial length of the central load-bearing section 31, so that the load generated by the central load-bearing section 31 can be distributed over a longer range through the positioning sleeve 2.

[0034] The transposition protection assembly 3 includes a central support section 31 and multiple transposition support sections 32 located on both sides of the central support section 31. The central support section 31 and the transposition support sections 32 are hereinafter collectively referred to as support sections. Both the central support section 31 and the transposition support sections 32 are U-shaped channels with their openings facing upwards. The channels can be made of aluminum alloy, stainless steel, fiber-reinforced composite materials, or other materials with sufficient mechanical strength and weather resistance. The two side walls of the U-shaped channel are higher than the axis of the cable body 1, ensuring that the cable body 1 remains confined within the support channel when subjected to lateral wind forces. The upper edge of the side walls is provided with an outwardly folded arc edge to prevent cutting action when the upper edge of the side walls contacts the insulation layer.

[0035] The lower part of the central bearing section 31 is fixedly connected to the positioning sleeve 2. Specifically, the central bearing section 31 can be fixed to the connecting seat at the bottom of the positioning sleeve 2 by bolts, or it can be integrally formed with the second sleeve body 22 of the positioning sleeve 2. The upper groove of the central bearing section 31 is adapted to the shape of the positioning sleeve 2, so that the positioning sleeve 2 is stably embedded in the central bearing section 31. The central bearing section 31 is provided with a mounting part 311, which can be a mounting ear extending upward or to the side. The mounting ear is provided with a mounting hole for connecting to the external support through an insulator string, hanging plate, U-ring or other hardware. The mounting part 311 can also be set as a hook or connecting seat that cooperates with the external support, but it maintains a fixed relationship with the central bearing section 31.

[0036] Multiple transposition support sections 32 are arranged sequentially along the axial direction of the cable body 1. The number of transposition support sections 32 located on one side of the central support section 31 can be two to six, with the number on both sides preferably being the same to ensure the support structure is symmetrical relative to the central support section 31. The axial length of each transposition support section 32 can be the same, or it can gradually increase from the center outwards. When using the same length, the distance the rigid support boundary moves after each unlocking is similar; when using different lengths, the bending positions at each stage can have different spacing according to predetermined fatigue distribution requirements.

[0037] The cavities of the central support section 31 and multiple transposition support sections 32 are sequentially connected to form a support channel extending axially along the cable body 1. In the initial installation state, the bottom of each transposition support section 32 and the central support section 31 are approximately located on the same support surface, and the cable body 1 is supported along the entire length of the transposition protection assembly 3. The transposition protection assembly 3 does not rigidly clamp the cable body 1 circumferentially; the top of the U-shaped channel remains open, allowing the support structure to primarily bear the downward gravity of the cable body 1 and the lateral force generated by its swing.

[0038] The lower parts of two adjacent transposition support sections 32 are connected by a hinge assembly 5, and the lower part of the transposition support section 32 adjacent to the middle support section 31 is also connected to the middle support section 31 by a hinge assembly 5. The hinge assembly 5 includes hinge ears 51 respectively disposed at the lower part of the adjacent support sections and a hinge shaft 52 passing through the hinge ears 51. The axis of the hinge shaft 52 extends along the width direction of the U-shaped groove, allowing the transposition support section 32 to rotate in the vertical plane where the cable body 1 is located. Limiting heads or independent anti-detachment pins are provided at both ends of the hinge shaft 52 to prevent the hinge shaft 52 from axially dislodging.

[0039] Insulating and wear-resistant pads are installed on the inner walls of each intermediate bearing section 31 and transposition support section 32. The insulating and wear-resistant pads are adapted to the shape of the U-shaped trough inner wall and can be made of silicone rubber, EPDM rubber, thermoplastic elastomer, or wear-resistant insulating composite material. The insulating and wear-resistant pads are fixed to the trough by embedding, bonding, or mechanical fastening to prevent the pads from shifting relative to the trough when the cable body 1 swings. The surface of the pads in contact with the cable body 1 is a continuous arc surface, and the radius of the arc is not less than the outer radius of the cable body 1. For the sake of simplicity in the accompanying drawings, the clearance between the insulating and wear-resistant pads and their adjacent positions is not separately marked.

[0040] A clearance gap is provided between two adjacent insulating wear-resistant pads, and a clearance gap is also provided between the insulating wear-resistant pad adjacent to the middle support section 31 and the insulating wear-resistant pad inside the middle support section 31. The clearance gap extends along the width direction of the transposition protection assembly 3, and its axial width can accommodate the relative displacement of the pad ends when adjacent support sections rotate. Each pad end is provided with a bevel or arc surface, so that when the transposition support section 32 rotates, the ends of adjacent pads form a smooth transition without forming a sharp corner towards the cable body 1.

[0041] The upper parts of adjacent support sections are connected by a time-failure connector 4. Each hinge position corresponds to two sets of identical and independent time-failure connectors 4, which are located on both sides of the width of the U-shaped groove. Each set of time-failure connectors 4 includes a first connecting sleeve 41, a second connecting sleeve 42, a connecting pin 43, a threading sleeve 44, a flexible retainer 45, and a cotter pin 46. The first connecting sleeve 41 is fixed to the upper part of one of the support sections, and the second connecting sleeve 42 is fixed to the upper part of the adjacent support section, so that the two connection positions are opposite to each other along the axial direction of the cable body 1. The threading sleeve 44 is fixed to the support section where the second connecting sleeve 42 is provided, and is located on the side of the second connecting sleeve 42 away from the first connecting sleeve 41. Its threading channel allows the traction direction of the flexible retainer 45 after it turns to have a component along the axial direction of the connecting pin 43, causing the end cap side pin shaft section to exit the second connecting sleeve 42.

[0042] The connecting pin 43 includes an end cap 431, a pin 432, a corrosion-damaged section 433, a threaded sleeve 434, and a connecting hole 435. The pin 432 passes sequentially through the first connecting sleeve 41 and the second connecting sleeve 42. The corrosion-damaged section 433 is located within the second connecting sleeve 42. The end cap 431 is fixed to the end of the pin 432 extending out of the second connecting sleeve 42. The threaded sleeve 434 is threadedly connected to the end of the pin 432 extending out of the first connecting sleeve 41. The connecting hole 435 is located on the pin 432 near the threaded sleeve 434. In the assembled state, the threaded sleeve 434 and the connecting hole 435 are located on opposite axial sides of the first connecting sleeve 41, and the end cap 431 is located on the side of the second connecting sleeve 42 away from the first connecting sleeve 41. When the connecting pin 43 is intact, the pin 432 bridges the first connecting sleeve 41 and the second connecting sleeve 42, preventing the upper parts of adjacent support sections from separating.

[0043] The second connecting sleeve 42 is fitted onto the outside of the corrosion-failed section 433. Its sidewall has a rectangular corrosion window 421 that penetrates the wall thickness, and the corrosion window 421 corresponds to the position of the corrosion-failed section 433. A gap is left between the inner wall of the second connecting sleeve 42 and the corrosion-failed section 433 to allow external moisture to enter. Rainwater, moisture, and air enter the second connecting sleeve 42 through the corrosion window 421 and come into contact with the corrosion-failed section 433. The sleeve wall of the second connecting sleeve 42, except for the corrosion window 421, reduces direct contact between other parts of the pin 432 and the external environment, concentrating the corrosion process at the predetermined failure location.

[0044] To establish a sequential failure relationship from the outside in, the opening areas of the corrosion windows 421 at different hinge positions on the same axial side of the central bearing section 31 decrease sequentially from the outside in, while the minimum cross-sectional area of ​​the corrosion failure segments 433 at each level increases sequentially from the outside in. The two sets of sequentially failing connectors 4 at the same hinge position use the same nominal window size, corrosion failure segment 433 cross-section, and material, but the two sets of connectors are independent of each other, and their actual failure time is allowed to have a time difference due to local humidity, orientation, and manufacturing errors. When the corrosion failure segment 43 of any set of connecting pins 43 has not broken, it is designed under the load condition that it can independently maintain the upper connection of adjacent bearing sections. The independent maintaining load condition means that when another set of connecting pins 43 at the same hinge position fails, its shear bearing capacity is greater than the design upper constraint load of that hinge position.

[0045] The specific dimensions of corrosion window 421 and corrosion failure section 433 can be determined based on the cable's rated load, the corrosion environment of the installation area, and the predetermined transposition stage. During the design phase, salt spray tests or cyclic damp heat tests can be conducted for different combinations of corrosion window area and minimum cross-sectional area of ​​corrosion failure section. Static load bearing tests can be performed on the connecting pins 43 after the tests. The window size and cross-sectional size of each level of connector are calibrated according to the order in which they reach the predetermined remaining load capacity, so that the predetermined failure time of the outer level connector is earlier than that of the adjacent inner level connector. The same calibration parameters are used for two sets of connectors at the same hinge position, but the simultaneous failure of the two sets of connectors is not taken as a design condition.

[0046] The pin 432 can be made of coated carbon steel, zinc alloy, aluminum alloy, or other metal materials whose strength gradually decreases under the action of a predetermined environmental medium. The corrosion failure section 433 is the reduced diameter section on the pin 432. An anti-corrosion layer can be applied to the surface of the pin 432, except for the corrosion failure section 433. The first connecting sleeve 41, the second connecting sleeve 42, and the main body of the support section are made of materials with higher corrosion resistance than the corrosion failure section 433, or are coated with a corrosion-resistant coating, so that corrosion mainly occurs in the corrosion failure section 433. The second connecting sleeve 42 also provides mechanical shielding for the corrosion failure section 433, preventing it from being directly impacted by external objects.

[0047] After the corrosion-damaged section 433 breaks, the connecting pin 43 splits into two segments. Since the threaded sleeve 44 is located on the side of the second connecting sleeve 42 opposite to the first connecting sleeve 41, the traction direction of the flexible retainer 45 after being turned by the threaded sleeve 44 has a component along the axial direction of the connecting pin 43. The pin segment 432 with the end cap 431 rotates relative to the support section where the second connecting sleeve 42 is located, and under the traction of the flexible retainer 45, it exits the second connecting sleeve 42 and moves until the end cap 431 abuts against the threaded sleeve 44. The inner diameter of the threaded sleeve 44 is smaller than the outer diameter of the end cap 431 to prevent the pin segment 432 from further disengaging. The other pin segment 432 retains the threaded sleeve 434 and the connecting hole 435. The cotter pin 46 passes through the connecting hole 435. The threaded sleeve 434 and the cotter pin 46 are located on opposite sides of the axial direction of the first connecting sleeve 41, thus jointly confining the pin segment 432 within the first connecting sleeve 41. Therefore, neither segment of the broken connecting pin 43 will fall off the support section.

[0048] The two sets of sequentially failed connectors 4 at the same hinge position operate independently. When the corrosion-failed segment 433 on one side disconnects first, the intact connecting pin 43 on the other side still spans the corresponding first connecting sleeve 41 and second connecting sleeve 42, independently restricting the upper parts of adjacent support sections from separating from each other. Therefore, the transposition support section 32 located outside the hinge position will not immediately rotate downwards due to unilateral failure. Only after the corrosion-failed segment 433 on the other side subsequently disconnects is the upper connection at the hinge position completely released, and the transposition support section 32 located outside the hinge position can rotate as a whole around the hinge axis 52.

[0049] Each set of timing failure connectors 4 is equipped with a flexible retainer 45. The flexible retainer 45 passes through the threaded sleeve 44, with one end connected to the end cap 431 and the other end connected to the cotter pin 46, which passes through the connecting hole 435. When the connecting pin 43 remains intact, the flexible retainer 45 is in a relaxed state and does not participate in the rigid locking of the upper part of the support section. After the corrosion failure section 433 breaks, the flexible retainer 45 maintains the connection relationship between the end cap 431 and the cotter pin 46. After both sets of connecting pins 43 at the same hinge position fail, the transposition support section 32 located outside the hinge position rotates around the hinge axis 52. The two flexible retainers 45 located on both sides of the width direction of the U-shaped groove gradually tighten as the relative distance increases, and after reaching the tension state, they restrict the transposition support section 32 from continuing to rotate.

[0050] The flexible retainer 45 can be made of aramid fiber rope, metal braided rope with an insulating layer, weather-resistant polymer tape, or other low-elongation flexible components. The effective length of the flexible retainer 45 refers to its usable working length when transitioning from a relaxed state to a tensioned state between the connection point of the end cap 431, the turning point of the threaded sleeve 44, and the connection point of the cotter pin 46. The flexible retainer 45 extends from the end cap 431 through the threaded sleeve 44 to the cotter pin 46. Its effective length and the arrangement position of the threaded sleeve 44 together limit the maximum rotation angle between adjacent support sections and bear the self-weight and wind-induced additional load of the corresponding transposed support section 32. The two flexible retainers 45 at the same hinge position have the same effective length, so that both sides of the support section have the same angular constraint in the width direction after tensioning.

[0051] Since the two sets of timing-failure connectors 4 do not require synchronous failure, a transition phase exists between the failure of one connector and the failure of the other. During this transition phase, the intact connector bears the main upper constraint; the connecting pin 43 on the failed side is divided into two sections, one of which is limited by the end cap 431 and the threaded sleeve 44, and the other is restricted within the first connecting sleeve 41 by the threaded sleeve 434 and the cotter pin 46. The flexible retainer 45 holds the two pin sections 432 but is not yet fully tensioned. This structure allows the corrosion release process to accommodate a time difference while avoiding significant twisting of the support joint caused by unilateral release.

[0052] The flexible retaining members 45 located on the same axial side of the central bearing section 31 can be configured with different effective lengths, with shorter effective lengths near the central bearing section 31 and longer effective lengths further away. After the various transposition bearing sections 32 are released, the inner bearing section forms a smaller angle, and the outer bearing section forms a larger angle. The multiple transposition bearing sections 32 together form a segmented, approximately arc-shaped bearing surface that gradually slopes outward and downward, allowing the cable body 1 to smoothly transition from the fixed central position to the free suspension position.

[0053] The maximum rotation angle limited by each level of flexible retainer 45 is determined based on the minimum allowable bending radius of the cable body 1, the axial length of the transposition support section 32, the connection position of the flexible retainer 45, and its effective length. During design, the minimum radius of curvature corresponding to the segmented support curve after rotation of each level of transposition support section 32 is not less than the minimum allowable bending radius of the cable of this specification, and a smooth transition is maintained between adjacent transposition support sections 32.

[0054] During assembly, the insulating wear-resistant pads are pre-fixed to the inner walls of the central bearing section 31 and each transposition support section 32; the first sheath 21 and the second sheath 22 are installed in the predetermined suspension area of ​​the cable body 1, so that the two positioning rings 23 abut against the two ends of the positioning area respectively; then the central bearing section 31 is fixed to the lower side of the positioning sheath 2, and the mounting part 311 faces the external support; then the transposition support sections 32 are installed sequentially on both sides of the central bearing section 31, and the lower part of each support section is connected by the hinge shaft 52, with the width of the U-shaped groove at each hinge position being... First connecting sleeve 41, second connecting sleeve 42 and connecting pin 43 are installed on both sides of the direction, so that the corrosion failure section 433 corresponds to the corrosion window 421 on the second connecting sleeve 42, and the threaded sleeve 434 and connecting hole 435 are located on both sides of the axial direction of the first connecting sleeve 41, respectively; then the threaded sleeve 44 is installed on the side of the second connecting sleeve 42 away from the first connecting sleeve 41, and the flexible retainer 45 is passed through the threaded sleeve 44, so that one end is connected to the end cap 431 and the other end is connected to the cotter pin 46, and the cotter pin 46 is passed through the connecting hole 435.

[0055] After assembly, check whether the two sets of sequentially failing connectors 4 at the same hinge position have the same nominal corrosion window 421 size and corrosion failure segment 433 size, and check whether different axial levels satisfy the relationship of gradually increasing resistance to failure from the outside to the inside. Using the same specifications for the two sets of connectors is only to make their failure trends similar, and does not guarantee simultaneous failure. The corrosion window 421 on the second connecting sleeve 42 is preferably set to the side or obliquely downward, and the corrosion window 421 is aligned with the corrosion failure segment 433 to allow external moisture to enter and facilitate inspection and observation.

[0056] After the mounting section 311 is connected to the external support, the vertical component of the force generated by the self-weight of the cable body 1 and the span tension is first borne by the insulating wear-resistant liner, and then transmitted to the mounting section 311 through the transposition support section 32 and the middle support section 31. The positioning sleeve 2, through the radial clamping action of the first sleeve body 21 and the second sleeve body 22 on the insulation layer, and together with the positioning rings 23 at both ends, restricts the transposition protection component 3 from moving axially along the cable body 1, while dispersing the middle load along the outer surface of the insulation layer. In the initial state, the connecting pins 43 on both sides of each hinge position remain intact, the transposition support section 32 cannot rotate around the hinge axis 52, and multiple support sections together form the longest rigid support section.

[0057] During the initial operation phase, the cable body 1 experiences slight vibrations or swaying due to wind force, and the transposition protection assembly 3 moves along with the cable body 1 as a whole. Since the outermost transposition support section 32 forms the first transition boundary between the rigid support section and the free suspension section, the main bending deformation is concentrated outside this boundary. The insulating wear-resistant liner disperses the contact pressure, and the outermost transposition support section 32 provides a larger transition radius for the cable body 1.

[0058] External moisture comes into contact with the corrosion failure section 433 through the corrosion window 421 on the outermost second connecting sleeve 42. Since the outermost corrosion window 421 has the largest opening area and the corrosion failure section 433 has the smallest minimum cross-sectional area, after testing and calibration, the two sets of sequentially failing connectors 4 in this stage have a predetermined tendency to fail earlier than the adjacent inner-stage connectors. When the corrosion failure section 433 on one side disconnects first, the connecting pin 43 on the other side remains independently locked at the top; after the corrosion failure section 433 on the other side at the same hinge position also disconnects, all upper connections on both sides are released, and the outermost transposition support section 32 enters a rotatable state.

[0059] After the outermost transposition support section 32 is disconnected from the upper connection, it rotates around the hinge axis 52 under the downward load of the cable body 1. During rotation, the clearance between adjacent insulating wear-resistant pads provides space for the pad ends, preventing the pads from pressing against each other. The two flexible retaining members 45 located on both sides of the width direction of the U-shaped groove extend from the end cap 431 through the cable sleeve 44 to the cotter pin 46, and gradually tighten as the support section rotates; when the flexible retaining members 45 reach the tensioned state, the support section stops rotating, and the two flexible retaining members 45 together limit its maximum rotation angle.

[0060] At this point, the outermost transposition support section 32 transforms from a rigid extension into an inclined support section that can move relative to the inner support section. The rigid support boundary moves towards the center by the axial length of one support section, and the main bending position of the cable body 1 shifts from the outer end of the outermost support section to the vicinity of the adjacent inner support section. The outermost support section still supports the cable body 1 from below and forms a gentle transition together with the inner support section, so the transposition does not cause the cable body 1 to suddenly become suspended.

[0061] As the operating time continues to increase, the two sets of timing failure connectors 4 at the next level fail sequentially according to the predetermined relative failure order. The transposition support section 32 located outside the corresponding hinge position releases its upper lock after both sets of connectors fail and rotates to the position where the flexible retainer 45 is tensioned. The transposition support sections 32 at each level are released sequentially from the outside to the inside, causing the rigid support boundary to move towards the center step by step. The cable body 1 bears the main alternating bending in different axial regions at different stages. The released support sections are arranged into segmented approximately arc-shaped support surfaces according to the angles defined by the flexible retainers 45 at each level, maintaining the bending radius and support continuity of the cable body 1.

[0062] The sequential failure connectors 4 on both sides of each hinge position in the width direction are allowed to fail sequentially, but the corresponding support section will only rotate as a whole after both sides of the connectors have failed. The transposition process on both sides of the central support section 31 in the axial direction can also be carried out simultaneously or with a time difference; even if one side of the axial support chain completes a certain level of transposition first, the connection between the central support section 31 and the external support will not be severed, and the other side in the axial direction will still maintain its original support state. Each hinge position and the two axial support chains are independent of each other, and local release will not cause other support sections to go out of control.

[0063] When the sequential failure connectors 4 closest to the central load-bearing section 31 finally fail, all the transposition support sections 32 on both sides are in a rotational support state defined by the flexible retainer 45. The central load-bearing section 31 is still fixed to the cable body 1 by the positioning sleeve 2 and the mounting part 311. At this time, the transposition protection assembly 3 forms a segmented approximately arc-shaped support structure that extends gradually downward to both sides with the central load-bearing section 31 as the center. This final state can still bear the self-weight of the cable body 1 and provide multiple rotational transition nodes between the central fixed position and the free suspension section.

[0064] This invention is a one-time graded transposition structure. Each failed connector 4 does not require automatic reset after completing its corresponding stage of release. During line maintenance, the completed transposition stage can be determined by observing the angle of the transposition support section 32. When restoring to the initial state is required, the cotter pin 46 and threaded sleeve 434 can be removed under power outage and unloading conditions, and the connecting pin 43 can be replaced. If necessary, the second connecting sleeve 42 can be replaced, and the transposition support section 32 can be rotated back to its initial position and relocked. The positioning sleeve 2, the middle bearing section 31, the hinge assembly 5, the wire threading sleeve 44, the flexible retainer 45, and the insulating wear-resistant pad can be reused or replaced together based on the inspection results.

[0065] For ease of maintenance, maintenance personnel can inspect the condition of the corrosion-damaged section 433 through the corrosion window 421 on the side wall of the second connecting sleeve 42, and replace the connecting pin 43 under power outage and unloading conditions. The corrosion-damaged section 433 is housed within the second connecting sleeve 42 and is not directly impacted by external objects during normal operation. After the corrosion-damaged section 433 breaks, the end cap 431 cooperates with the threaded sleeve 44 to restrict one section of the pin 432, and the threaded sleeve 434 cooperates with the cotter pin 46 passing through the connecting hole 435 to restrict the other section of the pin 432. The flexible retainer 45 connects the end cap 431 and the cotter pin 46, thereby preventing the broken part of the connecting pin 43 from becoming a free-falling component.

[0066] In alternative embodiments, the opening area of ​​the corrosion window 421 can be kept the same, while the failure sequence from the outside to the inside can be established by changing the amount of moisture-absorbing and guiding material provided in the second connecting sleeve 42, the length of the corrosion failure section 433, or the thickness of the surface anti-corrosion layer; alternatively, the minimum cross-sectional area of ​​the corrosion failure section 433 can be kept the same, and the sequence difference can be formed only by the area of ​​the corrosion window 421 or the thickness of the surface anti-corrosion layer of the corrosion failure section 433. All of the above methods are based on the principle that the connector 4 has gradually increasing resistance to failure at different levels of sequential failure.

[0067] In alternative embodiments, the transposition support section 32 can be a semi-circular groove, an approximately V-shaped groove, or an open groove consisting of two side support arms and a bottom connecting plate, as long as it can provide support from below the cable body 1 and allow adjacent support sections to rotate around the lower hinge position. The mounting portion 311 of the middle support section 31 can be detachably connected to the external support member, or it can be permanently connected to the external support member through an insulating connector.

[0068] In alternative implementations, the number of transposition support sections 32 on both sides can be different to adapt to different usage scenarios with different spans, sags, or prevailing wind directions on both sides of the tower; however, the sequential failure connectors 4 on the same side are still arranged in order from the outside to the inside. If the cable body 1 only forms a significant free sag transition on one side of the installation point, multiple transposition support sections 32 can be set only on one side of the middle support section 31, and a fixed support section can be set on the other side.

[0069] The working principle of this invention is as follows: In the initial state, the sequentially failing connectors 4 on both sides of the width direction of each hinge position, together with the hinge assembly 5, lock the adjacent transposition support section 32, forming the longest rigid support section. During operation, the outer-stage connector, after testing and calibration, has a priority failure tendency due to the larger corrosion window 421 and the smaller cross-section of the corrosion failure section 433. After the corrosion failure section 433 breaks, the connecting pin 43 splits into two parts. One part with the end cap 431 is pulled out of the second connecting sleeve 42 under the axial traction component formed by the flexible retainer 45 after being turned by the threaded sleeve 44, and is limited by the end cap 431 and the threaded sleeve 44. The other part is restricted in the first connecting sleeve 41 by the threaded sleeve 434 and the cotter pin 46 passing through the connecting hole 435. When the connector on either side of the same hinge position fails first, the complete connector on the other side continues to independently maintain the upper locking. Only after both connectors on both sides fail does the transposition support section 32 located outside the hinge position rotate around the hinge axis 52. As the two flexible retainers 45 gradually tension, the transposition support section 32 stops rotating and maintains its inclined support, causing the rigid support boundary and main bending position to shift inward. Subsequent connecting sections repeat the above process in a predetermined relative order, and finally, multiple transposition support sections 32 form a segmented approximately arc-shaped support surface, distributing the alternating bending concentrated in a single location to multiple axial positions and maintaining continuous support during the transposition process.

Claims

1. An overhead insulated cable for power grids, comprising a conductor and an insulating layer covering the outside of the conductor, characterized in that, A positioning sleeve is fixed to the outer side of a portion of the insulation layer, and a transposition protection assembly is provided on the outer side of the positioning sleeve. The transposition protection assembly includes a central bearing section connected to the positioning sleeve and multiple transposition support sections arranged along the cable axis on both sides of the central bearing section. The central bearing section has an installation part for connecting external support members. The central bearing section and the transposition support sections are collectively referred to as support sections. The lower parts of adjacent support sections are hinged together, and the two support sections corresponding to each hinge position are connected on both sides of the width direction perpendicular to the cable axis by independent sequential failure connectors. The sequential failure connector includes a first connecting sleeve and a second connecting sleeve fixed to two adjacent support sections and a connecting pin passing through the two connecting sleeves. The connecting pin has a corrosion failure section located in the second connecting sleeve, and the side wall of the second connecting sleeve has a corrosion window corresponding to the corrosion failure section. The opening area of ​​each level of corrosion window on the same axial side decreases sequentially from the outside to the inside. After both sets of sequential failure connectors at the same hinge position fail, the transposition support section located outside the hinge position releases the upper connection and rotates around the hinge position.

2. The overhead insulated cable for power grids according to claim 1, characterized in that, Both the central bearing section and the transposition support section are U-shaped grooves with their openings facing upwards. The cavities of the multiple U-shaped grooves are connected sequentially along the axial direction of the overhead insulated cable, and the overhead insulated cable is supported in the support channel formed by the multiple U-shaped grooves.

3. The overhead insulated cable for power grids according to claim 2, characterized in that, The inner walls of both the central bearing section and the transposition support section are provided with insulating and wear-resistant pads, and a clearance is left between two adjacent insulating and wear-resistant pads to allow the corresponding transposition support section to rotate.

4. The overhead insulated cable for power grids according to claim 1, characterized in that, The positioning sleeve includes a first sleeve body and a second sleeve body that are interlocked. After the first sleeve body and the second sleeve body are interlocked, they together cover and radially hug the outside of the insulation layer. Positioning rings that abut against the insulation layer are respectively provided at both ends of the positioning sleeve. The middle bearing section is fixed to the lower side of the positioning sleeve.

5. An overhead insulated cable for power grids according to claim 1, characterized in that, The connecting pin includes an end cap, a pin shaft, and a threaded sleeve. The pin shaft passes through the first connecting sleeve and the second connecting sleeve in sequence. The corrosion failure section is formed on the part of the pin shaft located inside the second connecting sleeve. The end cap is disposed at the end of the pin shaft extending out of the second connecting sleeve. The threaded sleeve is threadedly connected to the end of the pin shaft extending out of the first connecting sleeve. A connecting hole is provided on the pin shaft near the threaded sleeve. The corrosion window penetrates the side wall of the second connecting sleeve and corresponds to the position of the corrosion failure section.

6. The overhead insulated cable for power grids according to claim 5, characterized in that, The minimum cross-sectional area of ​​multiple corrosion-failed segments located on the same axial side of the central load-bearing section and at different hinge positions increases sequentially from the position farthest from the central load-bearing section to the position closest to the central load-bearing section.

7. An overhead insulated cable for power grids according to claim 5, characterized in that, Each of the aforementioned timing failure connectors further includes a threaded sleeve, a flexible retainer, and a cotter pin. The threaded sleeve is fixed to the support section provided with the second connecting sleeve. The flexible retainer passes through the threaded sleeve, with one end connected to the end cap and the other end connected to the cotter pin. The cotter pin passes through the connecting hole. The flexible retainer is in a relaxed state when the connecting pin is intact, and gradually tightens as the transposition support section located outside the hinge position rotates after both sets of timing failure connectors at the same hinge position fail. After tightening, it limits the maximum rotation angle between two adjacent support sections.

8. An overhead insulated cable for power grids according to claim 5, characterized in that, Two sets of sequentially failing connectors corresponding to the same hinge position have the same corrosion window opening area, minimum cross-sectional area of ​​corrosion failure section, and corrosion failure section material; when the corrosion failure section of any set of sequentially failing connectors is not broken, the connecting pins of that set independently maintain the upper connection of the two adjacent support sections.

9. An overhead insulated cable for power grids according to claim 7, characterized in that, The effective lengths of the two flexible retainers corresponding to the same hinge position are the same. The effective lengths of the flexible retainers at each level located on the same axial side of the central bearing section increase sequentially from the position closer to the central bearing section to the position farther away from the central bearing section, so that after the multiple transposition support sections rotate to the position where the flexible retainers are tensioned, they together form a segmented approximately arc-shaped support surface that gradually slopes downward in the direction away from the central bearing section.

10. An overhead insulated cable for power grids according to claim 7, characterized in that, The threaded sleeve is located on the side of the second connecting sleeve opposite to the first connecting sleeve. The traction direction of the flexible retainer after being turned by the threaded sleeve has an axial component that causes the pin section with the end cap to exit the second connecting sleeve. The inner diameter of the threaded sleeve is smaller than the outer diameter of the end cap. The threaded sleeve and the cotter pin are located on opposite axial sides of the first connecting sleeve. After the corrosion failure section breaks, the pin section with the end cap exits the second connecting sleeve under the traction of the flexible retainer and moves until the end cap abuts against the threaded sleeve. The other pin section is restricted within the first connecting sleeve by the threaded sleeve and the cotter pin. The corrosion window is a rectangular window opened on the side wall of the second connecting sleeve.

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