Common box type normal pressure sealing air insulation ring main unit

Abstract

The utility model provides a common box type normal pressure sealing air insulation ring main unit which comprises at least two all-metal all-insulation closed subunits and at least two air boxes which are arranged in a common box mode. Each subunit is provided with a base module, a wire outlet sleeve, an isolation lower copper rod, a multi-station isolation switch, a vacuum circuit breaker, a circuit breaker mechanism, a mechanism chamber, an isolation mechanism, a cable chamber, a lower panel module, a vertical partition plate, a pressure relief channel and an upper panel module, and all the subunits share one gas box. The vertical partition plate is arranged in the middle of the base module. The beneficial effects of the utility model are that air insulation is adopted, insulating gas does not need to be processed additionally, potential greenhouse effect of SF6 is avoided, and energy conservation and environmental protection are realized; a common box structure is adopted, a common air box of the two subunits is not separated by a partition plate, and compared with two independent air insulation cabinet units, a part of electrical insulation space can be shared, and conditions are created for miniaturization. And the engineering cost is saved.

Description

Technical Field

[0001] The utility model relates to a ring main unit, in particular to a co - box type normal - pressure sealed air - insulated ring main unit. Background Art

[0002] With the acceleration of the new urbanization pace of the whole society, the terminal electricity load shows new trends of rapid growth, large changes and diversification. With the gradual promotion and implementation of the distribution network construction reform projects and projects, the market prospect of switchgear in China will become increasingly broad. At the same time, with the gradual enhancement of environmental protection awareness in the power industry and the gradual promotion of environmental governance, insulation methods harmful to the environment such as SF6 will be gradually replaced, which promotes the accelerated development of environmentally friendly switchgear.

[0003] The existing switchgear has the following defects:

[0004] 1. At present, power equipment with SF6 gas as the insulation method has a large range of use.

[0005] SF6 gas has stable chemical properties, excellent insulation and arc - extinguishing performance. The SF6 switchgear has a small volume and a small installation space. However, SF6 gas generates toxic gases under the action of high - power arcs, spark discharges and corona discharges, which is very harmful to the human body and the environment; SF6 gas exposed to the air has a potential hazard to the greenhouse effect.

[0006] 2. Traditional switchgear insulated with air has large dimensions and occupies a large space, such as the KYN series, etc., which is not conducive to the miniaturization and intelligent development of equipment.

[0007] Therefore, how to provide a ring main unit that can avoid using SF6 gas as the insulation method and is conducive to the miniaturization development of equipment is a technical problem urgently to be solved by those skilled in the art. Summary of the Invention

[0008] In order to solve the problems in the prior art, the utility model provides a co - box type normal - pressure sealed air - insulated ring main unit.

[0009] The utility model provides a common - box - type normal - pressure sealed air - insulated ring - main unit, which comprises a fully - metal and fully - insulated closed sub - unit and an air - box. There are at least two sub - units and the air - box is of a common - box structure. Each sub - unit is configured with a base module, an outgoing line bushing, an isolating lower copper bar, a multi - position disconnector, a vacuum circuit breaker, a circuit - breaker mechanism, a mechanism chamber, an isolating mechanism, a cable chamber, a lower - panel module, a vertical partition board, a pressure - relief channel and an upper - panel module. All the sub - units share one air - box. The vertical partition board is arranged in the middle of the base module. The vertical partition board divides the base module into a front part and a rear part. The front part of the base module is the cable chamber, and the rear part of the base module is the pressure - relief channel. The door panel of the cable chamber is the lower - panel module. The base modules of all the sub - units are connected as a whole, and the air - box is placed on the base modules of all the sub - units.

[0010] As a further improvement of the utility model, side - expansion bushings are respectively installed on the left and right sides above the interior of the air - box. An outgoing line bushing is installed at the front lower part of the air - box. A balance valve and an explosion - proof film are installed at the rear lower part of the air - box. The vacuum circuit breaker is installed in the upper half of the interior of the air - box. The vacuum circuit breaker is connected to the side - expansion bushing. The vacuum circuit breakers of all the sub - units are connected by a horizontal busbar. The multi - position disconnector is installed below the vacuum circuit breaker. The upper end of the multi - position disconnector is connected to the lower end of the vacuum circuit breaker. The lower end of the multi - position disconnector is connected to the outgoing line bushing through the isolating lower copper bar.

[0011] As a further improvement of the utility model, the circuit - breaker mechanism and the isolating mechanism are respectively installed above the front of each unit outside the air - box. The circuit - breaker mechanism corresponds to the vacuum circuit breaker, and the vacuum circuit breaker can be operated through the circuit - breaker mechanism. The isolating mechanism corresponds to the multi - position disconnector, and the multi - position disconnector can be operated through the isolating mechanism.

[0012] As a further improvement of the utility model, the mechanism chamber is an independent space formed by the space where the circuit - breaker mechanism and the isolating mechanism are located. The front panel of the mechanism chamber is the upper - panel module.

[0013] As a further improvement of the utility model, the multi - position disconnector adopts an air - insulated multi - position disconnector.

[0014] As a further improvement of the present utility model, the air-insulated multi-position disconnecting switch includes a mounting bracket, a main isolating static contact of the disconnecting switch main circuit, a disconnecting switch main shaft, a moving contact arm, and a main grounding static contact. The disconnecting switch main shaft is installed in the middle of the mounting bracket. The moving contact arm is installed on the mounting bracket and connected to the disconnecting switch main shaft. The main isolating static contact is installed on the mounting bracket and located above the disconnecting switch main shaft. The main grounding static contact is installed on the mounting bracket and located below the disconnecting switch main shaft. The disconnecting switch main shaft is driven to rotate by the isolating mechanism. The disconnecting switch main shaft drives the moving contact arm to move between the isolating main shaft closing position, the isolating main shaft opening position, and the isolating main shaft grounding position. When the moving contact arm stops at the isolating main shaft closing position, the moving contact arm contacts the main isolating static contact. When the moving contact arm stops at the isolating main shaft grounding position, the moving contact arm contacts the main grounding static contact.

[0015] As a further improvement of the present utility model, the minimum straight-line distance clearance between the main isolating static contact and the main grounding static contact is 280 mm.

[0016] As a further improvement of the present utility model, the upper part of the moving contact arm covers an isolating auxiliary protection plate towards the main isolating static contact.

[0017] As a further improvement of the present utility model, the isolating mechanism adopts a large-angle isolating mechanism. The large-angle isolating mechanism includes a closing operation shaft, a grounding operation shaft, a closing cam, a grounding cam, a fork, and a moving fit. The closing operation shaft is connected to the closing cam. The grounding operation shaft is connected to the grounding cam. The closing cam is connected to the fork through a closing slide rod. The grounding cam is connected to the fork through a grounding slide rod. The fork is connected to the disconnecting switch main shaft through the moving fit.

[0018] As a further improvement of the present utility model, the closing operation shaft drives the closing cam to rotate. The closing cam drives the fork to rotate. The fork drives the disconnecting switch main shaft to rotate through the moving fit, realizing closing and opening operations.

[0019] As a further improvement of the present utility model, the grounding operation shaft drives the grounding cam to rotate. The grounding cam drives the fork to rotate. The fork drives the disconnecting switch main shaft to rotate through the moving fit, realizing grounding and de-grounding operations.

[0020] As a further improvement of the present utility model, the multi-position disconnecting switch is preferably a three-position disconnecting switch, but not limited thereto. The number of positions can be selected according to actual situations.

[0021] As a further improvement of the present utility model, preferably, three sub-units are contained in a common box, but this is not a limitation, and the number of sub-units can be selected according to actual circumstances.

[0022] The beneficial effects of the present utility model are as follows: Air insulation is adopted, and the insulating gas does not require additional treatment, without the potential greenhouse effect of SF6, being energy-saving and environmentally friendly; The common box structure is adopted, and there is no partition in the common gas box of the two sub-units. Compared with two independent air-insulated cabinet units, a part of the electrical insulation space can be shared here, creating conditions for miniaturization and saving engineering costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other solutions can also be obtained based on these drawings.

[0024] Figure 1 It is an internal schematic view from the side of a common box type atmospheric pressure sealed air-insulated ring main unit of the present utility model;

[0025] Figure 2 It is a front view of a common box type atmospheric pressure sealed air-insulated ring main unit of the present utility model;

[0026] Figure 3 It is a schematic view from the left rear perspective of the opened rear cover plate of a common box type atmospheric pressure sealed air-insulated ring main unit of the present utility model;

[0027] Figure 4 It is a schematic view from the rear front perspective of the opened rear cover plate of a common box type atmospheric pressure sealed air-insulated ring main unit of the present utility model;

[0028] Figure 5 It is a schematic view from the right front perspective of the opened mechanism chamber of a common box type atmospheric pressure sealed air-insulated ring main unit of the present utility model;

[0029] Figure 6 It is a three-dimensional schematic view of the three-position disconnector of a common box type atmospheric pressure sealed air-insulated ring main unit of the present utility model;

[0030] Figure 7 It is a schematic view of the output angle of the disconnector main shaft of the three-position disconnector of a common box type atmospheric pressure sealed air-insulated ring main unit of the present utility model;

[0031] Figure 8 It is a closing schematic view of the three-position disconnector of a common box type atmospheric pressure sealed air-insulated ring main unit of the present utility model;

[0032] Figure 9 It is a schematic diagram of the opening of the three-position disconnector of a coaxial type normally pressurized and sealed air-insulated ring main unit of the present utility model;

[0033] Figure 10 It is a grounding schematic diagram of the three-position disconnector of a coaxial type normally pressurized and sealed air-insulated ring main unit of the present utility model;

[0034] Figure 11 It is a partial schematic diagram of the three-position disconnector of a coaxial type normally pressurized and sealed air-insulated ring main unit of the present utility model.

[0035] Figure 12 It is a front view of the isolating mechanism of a coaxial type normally pressurized and sealed air-insulated ring main unit of the present utility model;

[0036] Figure 13 It is a side view of the isolating mechanism of a coaxial type normally pressurized and sealed air-insulated ring main unit of the present utility model;

[0037] Figure 14 It is Figure 13 sectional view A-A of;

[0038] Figure 15 It is a side view of the isolating mechanism of a coaxial type normally pressurized and sealed air-insulated ring main unit of the present utility model;

[0039] Figure 16 It is Figure 15 sectional view B-B of;

[0040] Figure 17 It is a schematic diagram of the closing of the isolating mechanism of a coaxial type normally pressurized and sealed air-insulated ring main unit of the present utility model;

[0041] Figure 18 It is a schematic diagram of the opening of the isolating mechanism of a coaxial type normally pressurized and sealed air-insulated ring main unit of the present utility model;

[0042] Figure 19 It is a grounding schematic diagram of the isolating mechanism of a coaxial type normally pressurized and sealed air-insulated ring main unit of the present utility model.

[0043] Figure 20 It is a schematic diagram of the movement of the fork of the isolating mechanism of a coaxial type normally pressurized and sealed air-insulated ring main unit of the present utility model. Specific embodiments

[0044] It should be noted that, without conflict, the embodiments in the present utility model and the features in the embodiments can be combined with each other.

[0045] In the description of the present utility model, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the protection scope of the present utility model. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present utility model, unless otherwise stated, the meaning of "a plurality" is two or more.

[0046] In the description of the present utility model, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", "coupling" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a direct connection, or an indirect connection through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood through specific circumstances.

[0047] The present utility model will be further described below in conjunction with the drawings and specific embodiments.

[0048] As Figures 1 to 20 shown, a common box type normally - pressurized sealed air - insulated ring - main unit with rated parameters of 12 kV / 630 A / 25 kA is designed and developed in accordance with but not limited to the following standards.

[0049] GB / T 1985 - 2014 High - voltage alternating - current disconnectors and earthing switches;

[0050] GB / T 4208 - 2017 Degrees of protection provided by enclosures (IP code);

[0051] GB / T 3906 3.6 kV to 40.5 kV alternating - current metal - enclosed switchgear and controlgear;

[0052] GB / T 1984 - 2014 High - voltage alternating - current circuit - breakers;

[0053] GB / T 11022 Common technical requirements for high - voltage switchgear and controlgear standards.

[0054] The common - box type normal - pressure sealed air - insulated ring - main unit cabinet has an overall structure that is fully metal and fully insulated and enclosed. It adopts a three - unit common - box structure. In this embodiment, the three - unit common - box structure is taken as an example for illustration, but it is not limited thereto.

[0055] The common - box type normal - pressure sealed air - insulated ring - main unit cabinet mainly includes the following modules:

[0056] Base module 1, outgoing line bushing 2, lower isolating copper bar 3, three - position disconnector 4, vacuum circuit breaker 5, side - expansion bushing 6, gas box (switch box) 7, circuit - breaker mechanism 8, mechanism chamber 9, isolating mechanism 10, cable chamber 11, balance valve 12, explosion - proof film 13, lower - panel module 14, vertical partition 15, pressure - relief channel 16, horizontal busbar 17, and upper - panel module 18.

[0057] In the common - box type normal - pressure sealed air - insulated ring - main unit cabinet, each unit is equipped with its own base module 1, outgoing line bushing 2, lower isolating copper bar 3, three - position disconnector 4, vacuum circuit breaker 5, circuit - breaker mechanism 8, mechanism chamber 9, isolating mechanism 10, cable chamber 11, lower - panel module 14, vertical partition 15, pressure - relief channel 16, and upper - panel module 18.

[0058] The common - box type normal - pressure sealed air - insulated ring - main unit cabinet shares a single gas box, namely the gas box (switch box) 7. The gas box (switch box) 7 shares the balance valve 12 and the explosion - proof film 13. The gas box (switch box) 7 shares a set of side - expansion bushings 6, which are led out from the left and right sides of the gas box 7 to the expansion positions. The horizontal busbar 17 is used for the connection at the upper end of the vacuum circuit breaker 5.

[0059] The cabinet assembly structure is as follows:

[0060] 1. The base module 1 is separated by the vertical partition 15. The front part is the cable chamber 11, and the rear part is the pressure - relief channel 16. The lower - panel module 14 is the door panel of the cable chamber 11.

[0061] 2. After the three base modules 1 are put together, they are screwed together with bolts, and the gas box (switch box) 7 is placed on them.

[0062] 3. On the upper left and right sides inside the gas box (switch box) 7, side - expansion bushings 6 are installed. On the front lower part, the outgoing line bushing 3 is installed. On the rear lower part, the balance valve 12 and the explosion - proof film 13 are installed. The vacuum circuit breaker 5 is installed in the upper half of the inside of the gas box (switch box) 7 and is directly connected to the side - expansion bushing 6. The vacuum circuit breakers 5 are connected to each other through the horizontal busbar 17. The three - position disconnector 4 is installed below the vacuum circuit breaker 5. Its upper end is connected to the lower end of the vacuum circuit breaker 5, and its lower end is connected to the outgoing line bushing 2 through the lower isolating copper bar 3.

[0063] 4. The circuit - breaker mechanism 8 and the isolating mechanism 10 are installed in the front upper part of the gas box (switch box) 7, corresponding to the vacuum circuit breaker 5 and the three - position disconnector 4 respectively.

[0064] 5. The mechanism chamber 9 is formed by the space where the circuit breaker mechanism 8 and the isolating mechanism 10 are located, covers the upper panel module 18, and forms an independent space.

[0065] The functions of each component are as follows:

[0066] 1. The cable chamber 11 and the pressure relief channel 16 are formed by separating the base module 1 with a vertical partition 15. It realizes the functions of cable connection and pressure relief for switch arcing faults. The gas tank (switch cabinet) 7 is seated on the base module 1, and the explosion-proof membrane 13 corresponds to the pressure relief channel 16 in one of the base modules 1. At the same time, it relies on the base module 1 for load-bearing. The balance valve 12 has an internal and external gas pressure balancing device to prevent external humid air from entering the box body.

[0067] 2. The gas tank (switch cabinet) 7 is installed with side expansion bushings 6, the vacuum circuit breaker 5 is connected to the horizontal busbar 17, and the three-position disconnector 4 is connected to the outgoing line bushing 2 through the isolating lower copper bar 3. That is, the installation of the main components of the primary electrical circuit is completed, and this part is collectively referred to as the primary energized part.

[0068] 3. The circuit breaker mechanism 8 and the isolating mechanism 10 are installed above the front of the gas tank (switch cabinet) 7, corresponding to the vacuum circuit breaker 5 and the three-position disconnector 4 respectively, and operate them.

[0069] 4. Before the switchgear actually works: the vacuum circuit breaker 5 is in the off position and the three-position disconnector 4 is in the grounded position.

[0070] 4.1. When performing a closing operation, the isolating mechanism 10 drives the three-position disconnector 4 to perform a grounding opening, then operates the three-position disconnector 4 to close; then operates the vacuum circuit breaker 5 to close.

[0071] 4.2. When performing an opening operation, first operate the vacuum circuit breaker 5 to open, then operate the three-position disconnector 4 to open, and then operate the three-position disconnector 4 to ground.

[0072] The three-position disconnector 4 adopts an air-insulated three-position disconnector, including an installation bracket 45, a main static contact 43 of the disconnector main circuit, a disconnector main shaft 41, a moving contact arm 42, and a main static contact 44 for grounding.

[0073] The main shaft 41 of the disconnecting switch is installed in the middle of the mounting bracket 45. The moving contact arm 42 is installed on the mounting bracket 45 and connected to the main shaft 41 of the disconnecting switch. The main static contact 43 of the isolation is installed on the mounting bracket 45 and above the main shaft 41 of the disconnecting switch. The main static contact 44 of the grounding is installed on the mounting bracket 45 and below the main shaft 41 of the disconnecting switch. The isolation mechanism 10 drives the main shaft 41 of the disconnecting switch to rotate. The main shaft 41 of the disconnecting switch drives the moving contact arm 42 to move between the closing position 401 of the isolation main shaft, the opening position 402 of the isolation main shaft and the grounding position 403 of the isolation main shaft, as Figure 7 shown. When the moving contact arm 42 stops at the closing position 401 of the isolation main shaft, the moving contact arm 42 contacts the main static contact 43 of the isolation, as Figure 8 shown. When the moving contact arm 42 stops at the grounding position 403 of the isolation main shaft, the moving contact arm 42 contacts the main static contact 44 of the grounding, as Figure 10 shown.

[0074] The phase-to-phase distance in the cabinet depth direction adopts a large-span phase-to-phase distance of 180 mm, so that it can still be greater than 125 mm after subtracting the width of the busbar; the closest linear distance clearance between the main static contact 43 of the isolation in the main circuit of the disconnecting switch and the main static contact 44 of the grounding is 280 mm, as Figure 9 shown. The upper part of the moving contact arm 42 covers the isolation auxiliary protection plate 46 in the direction of the closing static contact, as Figure 11 shown, further improving the electrical performance.

[0075] The output angle of the main shaft 41 of the three-position disconnecting switch 4 can reach 148 degrees. By redesigning the swing angle of the moving contact arm 42 and the length of the moving contact arm 42 itself, the moving contact arm 42 can stop at the corresponding working position and meet the electrical distance, as Figures 7 to 10 shown.

[0076] The isolation mechanism 10 adopts a large-angle isolation mechanism. The large-angle isolation mechanism includes a closing operation shaft 101, a grounding operation shaft 102, a closing cam 103, a grounding cam 104, a fork 105 and a moving fit 106, as Figures 12 to 16 shown.

[0077] The closing operation shaft 101 is connected to the closing cam 103. The grounding operation shaft 102 is connected to the grounding cam 104. The closing cam 103 is connected to the fork 105 through a closing slide bar. The grounding cam 104 is connected to the fork 105 through a grounding slide bar. The fork 105 is connected to the main shaft 41 of the disconnecting switch through the moving fit 106.

[0078] Figure 13The cross-section A-A therein is the cam position in the front direction of the mechanism, Figure 15 and the cross-section B-B therein is the position of the toggle plate in the rear view direction of the mechanism. During operation, the closing cam 103 is driven to rotate by the closing operation shaft 101, the closing cam 103 drives the fork 105 to rotate, and the fork 105 drives the main shaft 41 of the disconnector to rotate through the moving fit 106 to realize closing and opening operations. The grounding cam 104 is driven to rotate by the grounding operation shaft 102, the grounding cam 104 drives the fork 105 to rotate, and the fork 105 drives the main shaft 41 of the disconnector to rotate through the moving fit 106 to realize grounding and dis-grounding operations.

[0079] In the open state, the closing operation shaft 101 is operated counterclockwise to close, and vice versa to open; the grounding operation shaft 102 is operated clockwise to ground, and vice versa to dis-ground.

[0080] During closing, the fork 105 stops at position 1051. During opening, the fork 105 stops at position 1053. During grounding, the fork 105 stops at position 1052. When the isolating mechanism is closed and grounded, the included angle of the stop positions of the fork 105 is 148 degrees, which corresponds to the output angle of the main shaft 41 of the disconnector of the three-position disconnector 4, as Figure 20 shown.

[0081] A coaxial type normally pressurized sealed air-insulated ring main unit provided by the present utility model realizes the characteristics of environmental protection and miniaturization, and has the following advantages:

[0082] First, air insulation is adopted, and the insulating gas does not require additional treatment, without the potential greenhouse effect of SF6, which is energy-saving and environmentally friendly.

[0083] Second, this coaxial type scheme is a three-unit coaxial structure with a width of 1200 mm, that is, each unit has an average width of 400 mm. It is much smaller than the width requirements of the normally pressurized sealed air-insulated ring main unit by the State Grid or the Southern Power Grid.

[0084] Third, the coaxial structure is adopted, and there is no partition between the two units. Compared with two independent air-insulated cabinet units, a part of the electrical insulation space can be shared here. Conditions are created for miniaturization. Engineering costs are saved.

[0085] Fourth, the primary energized part is arranged in the sealed box body. The main insulation medium between the energized conductors and between the phases and relative to the ground is air, and the arc extinguishing method is vacuum arc extinguishing. The air pressure in the sealed box body always remains the same as the ambient atmospheric pressure. The sealed box body is equipped with an internal and external gas pressure balance device to prevent external humid air from entering the box body. The safety distances between the energized components such as the circuit breaker, disconnector, busbar, and disconnector contact in the sealed gas box relative to the ground and between the phases are not less than 125 mm, meeting the requirements of relevant national and industrial standards.

[0086] V. Make comprehensive use of the limited space inside the common box gas tank, appropriately distribute and combine, uniform the electric field, and meet the electrical distance requirements.

[0087] The above content is a further detailed description of the present utility model in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present utility model is only limited to these descriptions. For those of ordinary skill in the technical field to which the present utility model belongs, without departing from the concept of the present utility model, several simple deductions or substitutions can still be made, and all should be regarded as belonging to the protection scope of the present utility model.

Claims

1. A common box type normal pressure sealed air insulated ring main unit, characterized in that: It includes a fully metal and fully insulated enclosed subunit and a gas tank. There are at least two subunits and they share the same gas tank. Each subunit is configured with a base module, an outlet bushing, an isolating lower copper bar, a multi-position disconnect switch, a vacuum circuit breaker, a circuit breaker mechanism, a mechanism chamber, an isolating mechanism, a cable chamber, a lower panel module, a vertical partition, a pressure relief channel and an upper panel module. All the subunits share one gas tank. The vertical partition is arranged in the middle of the base module. The vertical partition divides the base module into a front part and a rear part. The front part of the base module is the cable chamber, and the rear part of the base module is the pressure relief channel. The door panel of the cable chamber is the lower panel module. The base modules of all the subunits are connected as a whole. The gas tank is placed on the base modules of all the subunits.

2. The common-box type normally-closed air-insulated ring main unit according to claim 1, wherein: On the left and right sides above the interior of the gas tank, side expansion bushings are respectively installed. The outlet bushing is installed at the front lower part of the gas tank. A balance valve and an explosion-proof membrane are installed at the rear lower part of the gas tank. The vacuum circuit breaker is installed in the upper half of the interior of the gas tank. The vacuum circuit breaker is connected to the side expansion bushing. The vacuum circuit breakers of all the subunits are connected by a horizontal busbar. The multi-position disconnect switch is installed below the vacuum circuit breaker. The upper end of the multi-position disconnect switch is connected to the lower end of the vacuum circuit breaker. The lower end of the multi-position disconnect switch is connected to the outlet bushing through the isolating lower copper bar.

3. The common-box type normally-closed air-insulated ring main unit according to claim 1, wherein: The circuit breaker mechanism and the isolating mechanism are respectively installed above the front of each unit outside the gas tank. The circuit breaker mechanism corresponds to the vacuum circuit breaker, and the vacuum circuit breaker can be operated through the circuit breaker mechanism. The isolating mechanism corresponds to the multi-position disconnect switch, and the multi-position disconnect switch can be operated through the isolating mechanism.

4. The compartmentalized type normally-closed air-insulated ring main unit according to claim 3, wherein: The mechanism chamber is an independent space formed by the space where the circuit breaker mechanism and the isolating mechanism are located. The front panel of the mechanism chamber is the upper panel module.

5. The co-box type normal pressure sealed air-insulated ring main unit according to claim 1, wherein: The multi-position disconnect switch adopts an air-insulated multi-position disconnect switch.

6. The common box type normally-closed air-insulated ring main unit according to claim 5, wherein: The air-insulated multi-position disconnect switch includes a mounting bracket, an isolating main static contact of the disconnect switch main circuit, a disconnect switch main shaft, a moving contact arm and a grounding main static contact. The disconnect switch main shaft is installed in the middle of the mounting bracket. The moving contact arm is installed on the mounting bracket and connected to the disconnect switch main shaft. The isolating main static contact is installed on the mounting bracket and located above the disconnect switch main shaft. The grounding main static contact is installed on the mounting bracket and located below the disconnect switch main shaft. The disconnect switch main shaft is driven to rotate by the isolating mechanism. The disconnect switch main shaft drives the moving contact arm to move among the isolating main shaft closing position, the isolating main shaft opening position and the isolating main shaft grounding position. When the moving contact arm stops at the isolating main shaft closing position, the moving contact arm contacts the isolating main static contact. When the moving contact arm stops at the isolating main shaft grounding position, the moving contact arm contacts the grounding main static contact.

7. The common-box type normally-closed air-insulated ring main unit according to claim 6, wherein: The upper part of the moving contact arm covers an isolating auxiliary protection plate towards the isolating main static contact.

8. The common-box type normally-closed air-insulated ring main unit according to claim 6, wherein: The isolation mechanism adopts a large-angle rotation isolation mechanism, which includes a closing operation shaft, a grounding operation shaft, a closing cam, a grounding cam, a fork and a moving fit. The closing operation shaft is connected to the closing cam, the grounding operation shaft is connected to the grounding cam, the closing cam is connected to the fork through a closing slide bar, the grounding cam is connected to the fork through a grounding slide bar, and the fork is connected to the main shaft of the disconnecting switch through the moving fit.

9. The co - box type normal - pressure sealed air - insulated ring - main unit according to claim 8, wherein: The closing operation shaft drives the closing cam to rotate, the closing cam drives the fork to rotate, and the fork drives the main shaft of the disconnecting switch to rotate through the moving fit, realizing the closing and opening operations.

10. The compartmentalized type normally-closed air-insulated ring main unit according to claim 8, characterized in that: The grounding operation shaft drives the grounding cam to rotate, the grounding cam drives the fork to rotate, and the fork drives the main shaft of the disconnecting switch to rotate through the moving fit, realizing the grounding and dis-grounding operations.

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