Double busbar air switchgear and its maintenance method

Abstract

This application discloses a double-busbar gas-filled switchgear and its maintenance method, belonging to the technical field of power distribution switchgear. It includes a housing, a lower circuit breaker gas chamber, a front isolation gas chamber, and a rear isolation gas chamber; both the front and rear isolation gas chambers are equipped with top-expanded incoming bushings. A voltage transformer and a disconnecting switch assembly are connected in series at the outgoing end of the lower circuit breaker gas chamber. Two sets of disconnecting switch mechanisms are installed at the front of the housing, wherein the front direct-acting three-position mechanism is directly driven and connected to the three-position switch in the front isolation gas chamber, and the rear direct-acting three-position mechanism is driven and connected to the three-position switch in the rear isolation gas chamber through a sprocket and chain drive assembly. The maintenance method is also disclosed, which isolates the voltage transformer from the main circuit by operating the disconnecting switch assembly, allowing maintenance of the voltage transformer to be completed under continuous power supply conditions of the double busbars. This application achieves uninterrupted maintenance of the voltage transformer, reliable rear busbar drive, and directional pressure relief function, with a compact structure and high safety.

Description

Technical Field

[0001] This application belongs to the technical field of power distribution switchgear, and specifically relates to a double busbar gas-filled switchgear and its maintenance method. Background Technology

[0002] Cylinder gas-insulated switchgear (C-GIS) is widely used in medium-voltage power systems due to its compact structure and strong environmental adaptability. Among them, double-busbar gas-insulated switchgear enables uninterrupted busbar maintenance and fault redundancy switching, which is of great significance for improving power supply continuity. However, existing double-busbar gas-insulated switchgear has significant shortcomings in the connection method of potential transformers (PTs): the voltage transformers are usually directly connected to the main circuit, lacking an independent electrical isolation structure. When a PT needs to be checked or replaced, the power supply to the connected busbar or even the entire feeder unit must be interrupted, resulting in load outages and failing to meet the core load's requirement for "zero-outage" operation and maintenance.

[0003] Furthermore, the design of the operating mechanism and transmission structure of the three-position switch on the rear busbar is not reasonable. To facilitate centralized front-end operation, the operating mechanism of the rear busbar gas chamber is often located at the front of the cabinet. However, the transmission path often requires multiple reversing stages, resulting in a lengthy structure, high transmission losses, and a tendency to jam, affecting the smoothness and long-term reliability of dual busbar switching. Simultaneously, the explosion-proof pressure relief structure of existing equipment is mostly a simple opening or a shared channel. When an arcing fault occurs in the busbar gas chamber, the high-temperature, high-pressure gas is difficult to release directionally and rapidly, easily impacting adjacent gas chambers or weak points in the cabinet, causing secondary damage to the equipment or even personal injury.

[0004] Therefore, it is evident that, under the premise of ensuring flexible switching between the two busbars, achieving uninterrupted maintenance of voltage transformers, optimizing the reliability of the rear busbar transmission, and improving the safety of pressure relief are technical problems that urgently need to be solved in this field. Summary of the Invention

[0005] The purpose of this application is to provide a double-busbar gas-filled switchgear and its maintenance method. This addresses the technical problems in existing double-busbar gas-filled switchgear, such as the need to interrupt the main circuit power supply for voltage transformer maintenance, unreliable and easily jammed transmission of the rear busbar three-position switch, and poor safety of arcing and pressure relief in the busbar gas chamber.

[0006] To achieve the above objectives, this application adopts the following technical solution: A dual-busbar gas-filled switchgear, comprising: case; The lower circuit breaker air chamber is disposed within the housing; The front isolation chamber and the rear isolation chamber are stacked on top of the lower circuit breaker chamber and are assembled together in the housing. The top walls of the front isolation chamber and the rear isolation chamber are each equipped with a top-expanded inlet bushing for connecting to the external busbar. A voltage transformer and a disconnecting switch assembly for electrically isolating the voltage transformer from the main circuit are connected in series at the outlet terminal of the lower circuit breaker chamber. And two sets of disconnecting switch mechanisms installed at the front of the housing, including a front direct-acting three-position mechanism and a rear direct-acting three-position mechanism; The front direct-acting three-position mechanism is directly connected to the three-position switch in the front isolation air chamber; The rear direct-acting three-position mechanism is connected to the three-position switch in the rear isolation chamber via a transmission assembly.

[0007] Furthermore, the front isolation gas chamber is a welding sealing gas chamber, which includes a first welding gas box. The first welding gas box is connected to a pressure relief channel, and the free end of the pressure relief channel is provided with an explosion-proof plate for directionally releasing the fault pressure in the front isolation gas chamber to the arc chamber.

[0008] Furthermore, the pressure relief channel is a seamless steel pipe structure, which is sealed to the explosion-proof plate via a flange.

[0009] In one preferred embodiment, the transmission assembly includes a transmission support, a transmission link, and a sprocket and chain assembly; The transmission support is fixed inside the housing. The output shaft of the rear direct-acting three-position mechanism is connected to the sprocket and chain assembly through the transmission link. The sprocket and chain assembly is connected to the three-position switch in the rear isolation chamber.

[0010] In a preferred embodiment, the disconnector assembly is a knife-type disconnector, which includes a live base, disconnecting contacts, a rotating mechanism, and a manual operating handle; The live base is connected to the circuit breaker output terminal in the lower circuit breaker chamber, the isolating contact is connected to the primary side of the voltage transformer, and the manual operation handle drives the isolating contact to open and close through the rotation mechanism.

[0011] In a preferred embodiment, the front isolation chamber and the rear isolation chamber are arranged in a high-low structure, with the installation height of the front isolation chamber being higher than that of the rear isolation chamber, so as to form a reserved space below or to the side of the front isolation chamber for arranging a pressure relief channel.

[0012] As a preferred embodiment, the front isolation chamber and the rear isolation chamber are each provided with independent access doors.

[0013] In a preferred embodiment, a circuit breaker mechanism is provided in the lower circuit breaker chamber, which is mechanically interlocked with the three-position switches in the front and rear isolation chambers.

[0014] As a preferred embodiment, the interior of the housing is filled with SF6 gas or environmentally friendly insulating gas as an insulating and arc-extinguishing medium.

[0015] In addition, this application also provides a method for uninterrupted maintenance of the PT based on the above-mentioned switchgear, including the following steps: By operating the disconnecting switch assembly, the voltage transformer is electrically isolated from the main circuit; While maintaining continuous power supply to the dual busbars connected to the front and rear isolation chambers, the isolated voltage transformers are inspected, verified, or replaced. After the maintenance is completed, operate the disconnect switch assembly to reconnect the voltage transformer to the main circuit.

[0016] Compared with the prior art, this application has the following beneficial effects: A dual-busbar gas-filled switchgear is defined by a top-parallel structure in which the front and rear isolation chambers are stacked on top of the lower circuit breaker chamber, and an overall architecture consisting of a voltage transformer and a dedicated disconnecting switch assembly connected in series at the outgoing terminals, along with two sets of front-mounted three-position mechanisms. This solution enables independent control and flexible switching of the two busbars, while utilizing the disconnecting switch assembly to provide an independent electrical isolation point for the voltage transformer, laying the foundation for uninterrupted maintenance. The top-parallel layout significantly reduces the equipment width and floor space, improving space utilization.

[0017] In one possible implementation, a pressure relief channel with an explosion-proof diaphragm is added to the front isolation gas chamber. When an arcing failure occurs inside this gas chamber, the high-temperature, high-pressure gas can be released directionally into the arcing chamber through the channel, preventing disorderly airflow from impacting adjacent gas chambers or cabinets, thus preventing damage to secondary equipment and personnel injury, and significantly improving the safety protection level of the equipment.

[0018] In one possible implementation, the pressure relief channel is specifically defined as a seamless steel pipe, sealed with an explosion-proof disc via a flange. This structure features high strength, impact resistance, and reliable sealing, capable of withstanding the high temperature and pressure impact during a fault, ensuring a stable and reliable pressure relief process, while also facilitating the installation and replacement of the explosion-proof disc.

[0019] In one possible implementation, the disconnector assembly is specifically defined as a knife switch structure with an integrated manual operating handle. This structure is mature, intuitive to operate, and clearly defines the open and closed positions. Maintenance personnel can manually achieve electrical isolation and switching between the PT and the main circuit without special tools. It is convenient to operate, low in cost, and particularly suitable for on-site maintenance work.

[0020] In one possible implementation, independent access doors are provided for the front isolation chamber, the rear isolation chamber, and the lower circuit breaker chamber. When a chamber requires maintenance, its access door can be opened individually without compromising the sealing of other chambers, reducing maintenance difficulty and downtime scope, and facilitating fault isolation and modular maintenance.

[0021] In one possible implementation, a mechanical interlock is provided between the circuit breaker mechanism and the three-position switches in the front and rear isolation chambers. This interlock prevents accidental closing of the circuit breaker when the three-position switch is not in the correct operating position, and also prevents accidental operation of the three-position switch when the circuit breaker is closed, fundamentally eliminating the risk of misoperation and ensuring equipment and personal safety.

[0022] A method for overhauling switchgear allows for the complete overhaul of the PT (Power Transmission Unit) without interrupting the power supply to the dual busbars after electrically isolating the PT from the main circuit using a disconnecting switch assembly. This completely solves the problem of traditional equipment PT maintenance requiring power outages and meets the stringent requirements of core loads such as data centers, hospitals, and semiconductor factories for "zero-power-outage" operation and maintenance. Attached Figure Description

[0023] Figure 1 A schematic diagram of the overall structure of the dual-busbar gas-filled switchgear provided in this application; Figure 2 This is a structural schematic diagram of the front isolation chamber provided in this application; Figure 3 This is a structural schematic diagram of the rear isolation chamber provided in this application; Figure 4 A schematic diagram of the lower circuit breaker gas chamber provided in this application; Figure 5 This is a schematic diagram of the transmission assembly provided in this application; Figure 6 This is a schematic diagram of the structure of the disconnector assembly provided in this application.

[0024] The attached diagram shows the following labels: 1. Front isolation chamber; 2. Rear isolation chamber; 3. Lower circuit breaker chamber; 4. Equipment cabinet. 11. Front direct-acting three-position mechanism; 12. Front isolation gas chamber inspection door; 13. First top-expanding inlet bushing; 14. Pressure relief channel; 15. First welding gas box; 21. Rear-acting three-station mechanism; 22. Transmission assembly; 23. Second top-expanding inlet bushing; 24. First inspection door; 25. Second welding gas box; 221. Transmission support; 222. Transmission connecting rod; 223. Sprocket and chain assembly; 31. Circuit breaker mechanism; 32. Disconnecting switch assembly; 33. Second inspection door; 34. Voltage transformer; 321. Live base; 322. Isolation contact finger; 323. Rotation mechanism; 324. Manual operation handle. Detailed Implementation

[0025] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0026] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0027] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0028] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0029] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. 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.

[0031] Example 1 like Figure 1 As shown, this embodiment provides a dual-busbar gas-filled switchgear, including a housing 4, and a front isolation chamber 1, a rear isolation chamber 2, and a lower circuit breaker chamber 3 assembled inside the housing. The front isolation chamber 1 and the rear isolation chamber 2 are stacked on top of the lower circuit breaker chamber 3, forming a top-parallel integrated structure. The entire device is a fully enclosed gas-filled design, with SF6 gas or environmentally friendly insulating gas filling the housing 4 as the insulation and arc-extinguishing medium. This top-parallel layout significantly reduces the overall width and footprint of the device by stacking the chambers, which could otherwise be arranged side-by-side, making it particularly suitable for installation in space-constrained scenarios such as compact urban substations and new energy power plants.

[0032] like Figure 2 As shown, the front isolation chamber 1 is a welded sealed chamber, formed by laser welding of 3mm stainless steel plates to create a first welded gas box 15, ensuring sufficient mechanical strength and long-term airtightness. A first top-expanding inlet bushing 13 is installed on the top wall of the front isolation chamber 1. The inner conical surface of this bushing is embedded with conductive copper terminals for electrical connection to adjacent switchgear or external main busbars via a top-mounted busbar connector. A front direct-acting three-position mechanism 11 is located on the front side of the front isolation chamber 1 (i.e., the front of the housing). This mechanism is operated electrically or manually, and its output shaft is directly and rigidly connected to the moving conductive rod of the three-position switch within the chamber, achieving direct transmission. By eliminating intermediate transmission links, the operation response is fast, transmission loss is low, and positional accuracy is high.

[0033] A pressure relief channel 14 is welded or flanged onto the rear or side wall of the first welded gas chamber 15. In a preferred embodiment, the pressure relief channel 14 is made of seamless steel pipe with an inner diameter of not less than 50 mm to ensure sufficient pressure relief flow. A flange is welded to the free end of the pressure relief channel 14 (the end furthest from the first welded gas chamber 15), and the flange is tightened to the explosion-proof diaphragm with bolts and a gasket. The explosion-proof diaphragm is made of high borosilicate tempered glass or stainless steel with a punctured diaphragm, and its burst pressure is set to 1.2 to 1.5 times the design pressure of the gas chamber. When an arcing fault occurs inside the current isolation gas chamber 1, the instantaneous arc causes the insulating gas to expand rapidly, the pressure rises rapidly, and it ruptures the explosion-proof diaphragm. The high-temperature, high-pressure gas is directed through the pressure relief channel 14 to the arcing chamber at the top of the equipment, and then discharged outside the cabinet through the top pressure relief port, without laterally impacting the adjacent rear isolation gas chamber 2 or downwards impacting the circuit breaker gas chamber 3, thus avoiding secondary damage. Since the front isolation chamber 1 and the rear isolation chamber 2 adopt a high-low structure layout, the installation height of the front isolation chamber 1 is higher than that of the rear isolation chamber 2, which naturally forms a height difference space below or to the side of the front isolation chamber 1. The pressure relief channel 14 is just arranged in this reserved space, without the need to increase the cabinet size.

[0034] like Figure 3 As shown, the rear isolation chamber 2 is also formed by welding stainless steel plates to create a second welded air box 25. A second top-expanding inlet sleeve 23 is installed on its top wall for connecting to another spare busbar. A rear direct-acting three-position mechanism 21 is located on the front side of the rear isolation chamber 2. Since the rear isolation chamber 2 is located behind the front isolation chamber 1 in the front-rear direction, placing its operating mechanism directly at the rear would be inconvenient for daily operation. Therefore, this embodiment adopts a front-mounted operation + remote transmission scheme. Specifically, the rear direct-acting three-position mechanism 21 is installed on the same operating panel at the front of the housing (located next to the front direct-acting three-position mechanism 11). Its output shaft does not directly extend into the rear isolation chamber 2, but is connected to the three-position switch inside the rear isolation chamber 2 via a transmission assembly 22.

[0035] Combination Figure 5 As shown, the transmission assembly 22 specifically includes a transmission support 221, a transmission connecting rod 222, and a sprocket and chain assembly 223. The transmission support 221 is a metal casting or welded part, fixed to a crossbeam located between the front and rear isolation chambers inside the housing 4 by bolts. The output shaft of the rear direct-acting three-position mechanism 21 is connected to the front end of the transmission connecting rod 222 via a coupling or key. The transmission connecting rod 222 extends in the front-rear direction, and its rear end is connected to the drive sprocket (or input shaft) of the sprocket and chain assembly 223. The sprocket and chain assembly 223 includes a drive sprocket, a driven sprocket, and a chain fitted on the two sprockets. The drive sprocket is installed at the rear end of the transmission connecting rod 222, and the driven sprocket is installed on the operating shaft of the three-position switch of the rear isolation chamber 2.

[0036] When the rear direct-acting three-position mechanism 21 is activated, its output shaft rotates, driving the transmission link 222 to rotate. This rotational motion is then transmitted to the three-position switch operating shaft within the rear isolation chamber 2 via the sprocket and chain assembly 223, driving the three-position switch to switch between the "closing," "isolation," and "grounding" positions. Compared to bevel gear drives, sprocket and chain transmission offers advantages such as adjustable center distance, adaptability to longer transmission distances, lower impact, and no need for precise alignment. Furthermore, fewer transmission links reduce the likelihood of jamming, ensuring smooth operation and long-term reliability of the rear busbar three-position switch. Simultaneously, since both three-position operating mechanisms are concentrated at the front of the housing, maintenance personnel can complete the switching operation of both busbars on a single interface, significantly improving the human-machine interface experience.

[0037] like Figure 4 As shown, the lower circuit breaker chamber 3 is located below the front isolation chamber 1 and the rear isolation chamber 2. Inside, the circuit breaker mechanism 31, voltage transformer 34, and disconnector assembly 32 are installed. The lower circuit breaker chamber 3 is an independent sealed chamber, electrically connected to the two upper isolation chambers via a wall bushing or isolation bushing. A conductive busbar is installed at the output end of the lower circuit breaker chamber 3 (i.e., the port connecting to external cables or busbars). The voltage transformer 34 and disconnector assembly 32 are connected in series on this conductive busbar. Specifically, the circuit breaker output copper busbar is first connected to the energized base 321 of the disconnector assembly 32, and then led out from the isolation contact 322 to the primary side of the voltage transformer 34. The secondary side of the voltage transformer 34 is then led to the instrument room for measurement or protection. This "series connection" makes the disconnector assembly 32 a controllable gateway for the voltage transformer 34 to access the main circuit.

[0038] Further as Figure 6As shown, the disconnector assembly 32 is a knife-type disconnector, including a live base 321, disconnecting contacts 322, a rotating mechanism 323, and a manual operating handle 324. The live base 321 is a copper block structure, bolted to an insulating support within the lower circuit breaker chamber 3, and electrically connected to the circuit breaker's outgoing terminals. The disconnecting contacts 322 are a set of spring-loaded contact assemblies mounted on rotatable moving blades. The rotating mechanism 323 includes a shaft, a fork, or a gear pair, one end of which is connected to the manual operating handle 324, and the other end drives the moving blades to rotate. The manual operating handle 324 extends to the front or side panel of the housing and is equipped with clear open / closed indicator marks. When voltage transformer 34 needs maintenance, the maintenance personnel rotate the manual operating handle 324, which drives the moving blade to rotate via the rotating mechanism 323. This disengages the isolating contact 322 from the energized base 321 and simultaneously closes it with an auxiliary grounding contact (optional), thus completely electrically isolating the voltage transformer 34 from the main circuit and reliably grounding it. At this time, even if the main busbar is energized and the circuit breaker is closed, the voltage transformer 34 side remains completely de-energized, allowing for safe maintenance. Throughout the entire operation, the double busbars connected to the front isolation chamber 1 and the rear isolation chamber 2 remain in normal power supply mode, and the downstream load is unaffected. After maintenance, the voltage transformer 34 can be reconnected to the main circuit by reversing the manual operating handle 324.

[0039] In addition, such as Figure 1 As shown, the front isolation chamber 1, rear isolation chamber 2, and lower circuit breaker chamber 3 are each equipped with independent maintenance doors: front isolation chamber maintenance door 12, first maintenance door 24, and second maintenance door 33. These maintenance doors employ a sealing ring and clamping bolt structure to ensure airtightness during normal operation. During maintenance, a single chamber can be opened without damaging the seals of the other chambers. A mechanical interlock device is installed between the circuit breaker mechanism 31 in the lower circuit breaker chamber 3 and the three-position switches in the front isolation chamber 1 and rear isolation chamber 2. This ensures that the circuit breaker can only be closed when the three-position switch is in the closed or isolated position. Conversely, when the circuit breaker is closed, the three-position switch is locked and cannot be operated, preventing the circuit breaker from being disconnected under load or closed with grounding, further improving operational safety.

[0040] Based on the above-mentioned switching equipment, the present invention also provides a method for uninterrupted maintenance of a voltage transformer. When it is necessary to maintain or replace the voltage transformer 34, the following steps are performed: Step 1: The maintenance personnel manually operate the manual operation handle 324 to drive the rotation mechanism 323 of the disconnecting switch assembly 32, causing the disconnecting contact 322 to separate from the live base 321, thus electrically isolating the voltage transformer 34 from the main circuit. At this time, a clear "open" indicator can be observed on the housing panel, and the reading of the secondary side voltmeter of the voltage transformer 34 returns to zero.

[0041] Step two: While maintaining continuous power supply to the dual busbars connected to the front isolation chamber 1 and the rear isolation chamber 2 (i.e., both busbars I and II are operating normally, and the downstream load is being supplied with power normally), open the second inspection door 33 of the lower circuit breaker chamber 3 to inspect, verify, or replace the voltage transformer 34, which is now completely isolated and grounded. Since the voltage transformer 34 is disconnected from the high-voltage circuit, operators can safely perform wiring disconnection, insulation testing, and other operations.

[0042] Step three: After maintenance is completed, close the second maintenance door 33 and restore the gas chamber seal. Reverse the operation of the manual operating handle 324 to re-engage and close the isolating contact finger 322 with the live base 321. The voltage transformer 34 is then reconnected to the main circuit, restoring the voltage monitoring function. The entire process requires no power outage to the dual busbars or any feeders, ensuring complete power supply continuity.

[0043] The above maintenance methods are particularly suitable for critical load power supply scenarios such as data centers, hospitals, and semiconductor factories where power outages are not permitted. They transform voltage transformer maintenance from planned power outages into online operations, greatly improving power supply reliability.

[0044] In summary, this invention, through its unique top-parallel three-layer air chamber structure, front-direct-acting three-position mechanism, sprocket and chain rear drive design, dedicated knife-switch disconnector assembly for voltage transformers, and independent directional pressure relief channel, achieves multiple beneficial effects for dual-busbar gas-filled switchgear, including uninterrupted maintenance of voltage transformers, flexible and reliable switching of dual busbars, and directional pressure relief during faults. It features a compact structure, safe operation, and efficient maintenance, meeting the requirements of modern medium-voltage distribution networks for high reliability and maintenance without power outages.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications to the technical solutions described in the foregoing embodiments, or equivalent substitutions for some or all of the technical features, do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A double-busbar gas-filled switchgear, characterized in that, include: Shell (4); The lower circuit breaker air chamber (3) is disposed inside the housing (4); The front isolation chamber (1) and the rear isolation chamber (2) are stacked on top of the lower circuit breaker chamber (3) and are assembled together in the housing (4). The top walls of the front isolation chamber (1) and the rear isolation chamber (2) are both equipped with top-expanded inlet bushings for connecting external busbars. A voltage transformer (34) and a disconnecting switch assembly (32) for electrically isolating the voltage transformer (34) from the main circuit are connected in series at the outlet of the lower circuit breaker chamber (3). And two sets of disconnecting switch mechanisms installed at the front of the housing (4), including a front direct-acting three-position mechanism (11) and a rear direct-acting three-position mechanism (21). The front direct-acting three-position mechanism (11) is directly connected to the three-position switch in the front isolation air chamber (1); The rear direct-acting three-position mechanism (21) is connected to the three-position switch in the rear isolation chamber (2) via a transmission assembly (22).

2. The dual-busbar gas-filled switchgear according to claim 1, characterized in that, The front isolation gas chamber (1) is a welding sealing gas chamber, which includes a first welding gas box (15). The first welding gas box (15) is connected to a pressure relief channel (14). The free end of the pressure relief channel (14) is provided with an explosion-proof plate, which is used to release the fault pressure in the front isolation gas chamber (1) to the arc chamber in a directional manner.

3. The dual-busbar gas-filled switchgear according to claim 2, characterized in that, The pressure relief channel (14) is a seamless steel pipe structure, which is sealed to the explosion-proof plate through a flange.

4. The dual bus airswitch apparatus of claim 1, wherein, The transmission assembly (22) includes a transmission support (221), a transmission link (222), and a sprocket and chain assembly (223). The transmission support (221) is fixed inside the housing (4). The output shaft of the rear direct-acting three-position mechanism (21) is connected to the sprocket and chain assembly (223) through the transmission link (222). The sprocket and chain assembly (223) is connected to the three-position switch in the rear isolation chamber (2).

5. The dual-busbar gas-filled switchgear according to claim 1, characterized in that, The disconnector assembly (32) is a knife-type disconnector, which includes a live base (321), a disconnecting contact finger (322), a rotating mechanism (323), and a manual operating handle (324). The live base (321) is connected to the circuit breaker output terminal in the lower circuit breaker chamber (3), the isolation contact (322) is connected to the primary side of the voltage transformer (34), and the manual operation handle (324) drives the isolation contact (322) to open and close through the rotation mechanism (323).

6. The dual-busbar gas-filled switchgear according to claim 1, characterized in that, The front isolation chamber (1) and the rear isolation chamber (2) are arranged in a high-low structure, and the installation height of the front isolation chamber (1) is higher than that of the rear isolation chamber (2) so as to form a reserved space for arranging the pressure relief channel (14) below or to the side of the front isolation chamber (1).

7. The dual-busbar gas-filled switchgear according to claim 1, characterized in that, The front isolation chamber (1) and the rear isolation chamber (2) are each equipped with independent inspection doors.

8. The dual-busbar gas-filled switchgear according to claim 1, characterized in that, The lower circuit breaker chamber (3) is equipped with a circuit breaker mechanism (31), which is mechanically interlocked with the three-position switches in the front isolation chamber (1) and the rear isolation chamber (2).

9. The dual-busbar gas-filled switchgear according to any one of claims 1-8, characterized in that, The housing (4) is filled with SF6 gas or environmentally friendly insulating gas as an insulating and arc-extinguishing medium.

10. A maintenance method for a double-busbar gas-insulated switchgear according to any one of claims 1-9, characterized in that, Includes the following steps: Step 1: By operating the disconnecting switch assembly (32), the voltage transformer (34) is electrically isolated from the main circuit; Step 2: While maintaining continuous power supply to the dual busbars connected to the front isolation chamber (1) and the rear isolation chamber (2), inspect, verify or replace the isolated voltage transformer (34). Step 3: After the maintenance is completed, operate the disconnect switch assembly (32) to reconnect the voltage transformer (34) to the main circuit.

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