Compact three-position double-break isolating earthing switch

Abstract

The present invention relates to the technical field of high-voltage switchgear, and specifically discloses a compact three-station double-break isolating and grounding switch, in which a first static contact, a second static contact and a grounding static contact are fixed in a shell; a supporting structure composed of a first cylinder, a second cylinder, a third cylinder, a first telescopic rod, a second telescopic rod, a third telescopic rod, a fourth telescopic rod and a fifth telescopic rod is provided in the shell, so as to provide support for the first moving contact, the second moving contact and the grounding moving contact and realize position adjustment. This compact three-station double-break isolating and grounding switch has two breaks in an isolated state, and a grounding protection is provided between the two breaks, which can meet the technical requirements of non-power outage during expansion and installation operations and handover withstand voltage tests of GIS equipment. Its transmission design is relatively ingenious, and there is no need to set up transmission components and drive devices for the grounding moving contact, so that the overall structure is more compact and occupies less space, which is conducive to improving the air tightness of the shell and extending the service life.

Description

Technical Field

[0001] The invention relates to the technical field of high-voltage switchgear, and in particular to a compact three-station double-break isolating grounding switch. Background Art

[0002] With the advancement of electric power technology and the vigorous development of the national economy, the power transmission capacity continues to rise. Gas Insulated Switchgear (GIS) has been increasingly widely used due to its advantages of small footprint, high reliability and maintenance-free. In the traditional GIS structural design, there is often only a single isolation break between the standby expansion bay and the operating busbar. During the GIS standby bay expansion installation and handover withstand voltage test, in order to ensure the safety of personnel and equipment, it is usually necessary to shut down the busbar. This not only brings more inconvenience to power users, but also may cause great economic losses. In view of the current high dependence of social life and industrial production on power supply, designing GIS equipment that can realize live operation of the busbar during the expansion and installation process has become an important technical development trend.

[0003] At present, the industry generally adopts the method of configuring a double-break disconnector between the spare expansion interval and the operating busbar to realize live operation during the expansion and installation of GIS equipment. The structural design of existing double-break disconnectors is mostly unreasonable. For example, the patent with publication number CN206331958U discloses a double-break disconnector module that can meet the technical requirements of GIS expansion without power outage. However, the position adjustment of the grounding knife switch requires the setting of a separate transmission mechanism and drive device, which makes the overall equipment cumbersome and occupies a large space. The transmission mechanism needs to be set through the shell, which reduces the airtightness of the shell and affects the service life of the equipment. Summary of the invention

[0004] In order to solve the deficiencies in the prior art, the present invention provides a compact three-station double-break isolating grounding switch, which has two isolating breaks in the isolated state, and can meet the technical requirements of non-stop expansion of GIS. At the same time, based on the ingenious and reasonable structural design, it takes into account the technical advantages of high compactness, good airtightness and safer operation.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0006] A compact three-station double-break isolating grounding switch comprises a shell, in which a first static contact and a second static contact distributed at a front-to-back interval are fixed, and a grounding static contact is fixed on the upper side of the inner cavity of the shell; a first cylinder and a second cylinder extending forward and backward are fixed in the shell via an insulating bracket; the front and rear sides of the first cylinder are respectively provided with a first telescopic rod and a second telescopic rod which are plugged and sealed together, and the front and rear sides of the second cylinder are respectively provided with a third telescopic rod and a fourth telescopic rod which are plugged and sealed together, the front ends of the first telescopic rod and the third telescopic rod are jointly fixed with a first moving contact, and the rear ends of the third telescopic rod and the fourth telescopic rod are jointly fixed with a second moving contact, the first moving contact and the second moving contact are each fixedly connected with a rack extending forward and backward, the two racks are respectively meshed with the upper and lower sides of a gear, the gear is fixedly connected to a drive shaft, the drive shaft extends to the outside of the shell, and a third telescopic rod which extends upward and communicates with the first cylinder is fixed in the middle of the first cylinder. Three cylinders, the third cylinder is provided with a fifth telescopic rod which is plugged and sealed therewith, the upper end of the fifth telescopic rod extends to the top of the third cylinder and is fixedly connected to a grounding moving contact, the first cylinder is provided with a first piston and a second piston distributed on both sides of the third cylinder; the first cylinder is provided with a first pressure relief hole on the front side of the first piston, and a second pressure relief hole on the rear side of the second piston, the cavity formed between the first piston, the second piston and the fifth telescopic rod is filled with an insulating transmission medium, the middle part of the second cylinder is connected with a fourth cylinder fixed to the outside of the shell through a conduit, a switch valve is provided between the fourth cylinder and the conduit, the fourth cylinder is provided with a third piston, the cavity formed between the third telescopic rod, the fourth telescopic rod and the third piston is filled with an insulating transmission medium; the first cylinder, the second cylinder, the third cylinder, the first telescopic rod, the second telescopic rod, the third telescopic rod, the fourth telescopic rod and the fifth telescopic rod are all conductors.

[0007] In a preferred embodiment, the main body of the housing is cylindrical, and ports are provided at the front end and the rear end as well as the upper and lower sides of the middle part, and flanges are provided at the ports, and the ports are respectively fixed with a front end cover, a rear end cover, an upper end cover and a lower end cover that are sealed and matched; the first static contact and the second static contact are respectively fixed to the front end cover and the rear end cover via insulators; the grounding static contact is fixed to the upper end cover via an insulator; and the insulating bracket is fixed to the lower end cover via an insulator;

[0008] Furthermore, the insulating bracket is composed of a bow frame and a fixing seat. The first cylinder and the second cylinder are fixed on the fixing seat. The bow frame is located below the fixing seat and the two are fixedly connected by bolts. The bow frame is fixed to the lower end cover through an insulator.

[0009] In a preferred embodiment, the insulating transmission medium is insulating liquid or insulating gas.

[0010] In a preferred embodiment, the side wall of the fourth cylinder is provided with a transparent window;

[0011] Furthermore, the fourth cylinder is provided with a workstation mark cooperating with the third piston on one side of the transparent window.

[0012] In a preferred embodiment, a slideway is fixed to each of the first cylinder and the second cylinder, and the two racks are slidably matched with the two slideways respectively.

[0013] In a preferred embodiment, a square head portion is provided at one end of the drive shaft located outside the housing.

[0014] In a preferred embodiment, the ends of the first telescopic rod and the second telescopic rod that are plugged into the first cylinder are sleeved with sealing rings, the ends of the third telescopic rod and the fourth telescopic rod that are plugged into the second cylinder are sleeved with sealing rings, and the end of the fifth telescopic rod that is plugged into the third cylinder is sleeved with a sealing ring.

[0015] In a preferred embodiment, a first moving contact seat is commonly fixed to the front end of the first telescopic rod and the third telescopic rod, and the first moving contact is fixed to the front side of the first moving contact seat; a second moving contact seat is commonly fixed to the rear end of the third telescopic rod and the fourth telescopic rod, and the second moving contact is fixed to the rear side of the second moving contact seat; and the two racks are fixedly connected to the first moving contact seat and the second moving contact seat, respectively.

[0016] Compared with the prior art, this compact three-station double-break isolating grounding switch has the following beneficial technical effects:

[0017] (1) This compact three-station double-break isolating grounding switch has two breaks in the isolated state, and grounding protection is provided between the two breaks, which can meet the technical requirements of non-power outage during the expansion and installation of GIS equipment and the handover and withstand voltage test.

[0018] (2) The transmission design of this compact three-station double-break isolating and grounding switch is relatively ingenious. Based on the transmission coordination of gears and racks, it can realize automatic switching between the closed state, the isolated state and the grounding state without the need to set up additional transmission components and drive devices for the grounding moving contact. This makes the overall structure of this compact three-station double-break isolating and grounding switch more compact and occupies less space, which is conducive to improving the air tightness of the shell and extending the service life.

[0019] (3) The compact three-station double-break isolating and grounding switch is capable of locking and unlocking the switch by cleverly setting the switch valve, thereby avoiding the occurrence of misoperation and significantly improving operational safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present invention, but are not intended to limit the present invention.

[0021] Figure 1 This is a schematic diagram of the external structure of a compact three-station double-break isolating and grounding switch.

[0022] Figure 2 This is a schematic diagram of the structure of a compact three-station double-break isolating and grounding switch after the shell is cut open.

[0023] Figure 3 It is a schematic diagram of the structure of a compact three-station double-break isolating and grounding switch after the shell is cut open and viewed from another direction.

[0024] Figure 4 It is a schematic diagram of the structure after the first cylinder, the second cylinder and the third cylinder are cut apart.

[0025] Figure 5 It is a schematic diagram of the structure of the fourth cylinder.

[0026] Figure 6 This is a schematic diagram of the isolation state of a compact three-station double-break isolating grounding switch.

[0027] Figure 7 This is a schematic diagram of the closed state of a compact three-station double-break isolating and grounding switch.

[0028] Figure 8 This is a schematic diagram of the grounding status of a compact three-station double-break isolating grounding switch.

[0029] Fig. 9 This is a schematic diagram of the coordination of various components during the process of switching from the closed state to the isolated state.

[0030] Fig.10 This is a schematic diagram of the coordination of various components in the process of switching from a grounded state to an isolated state.

[0031] In the figure: 1, housing, 2, drive shaft, 3, switch valve, 4, fourth cylinder, 5, first moving contact seat, 6, first static contact, 7, front end cover, 8, first telescopic rod, 9, rack, 10, third cylinder, 11, grounding moving contact, 12, first cylinder, 13, second telescopic rod, 14, second static contact, 15, rear end cover, 16, second moving contact seat, 17, fourth telescopic rod, 18, second cylinder, 19, lower end cover, 20, gear, 21, insulator Edge bracket, 211, fixing seat, 212, bow frame, 22, slide, 23, third telescopic rod, 24, grounding static contact, 25, upper end cover, 26, conduit, 27, first moving contact, 28, first pressure relief hole, 29, first piston, 30, fifth telescopic rod, 31, second piston, 32, second pressure relief hole, 33, second moving contact, 34, work station mark, 35, third piston, 36, transparent window, 37, first fracture, 38, second fracture. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] See also Figure 1-Figure 5As shown, the present embodiment discloses a compact three-station double-break isolating grounding switch, which includes a housing 1, wherein a first static contact 6 and a second static contact 14 are fixed inside the housing 1 and are spaced apart from each other, and a grounding static contact 24 is fixed on the upper side of the inner cavity of the housing 1; a first cylinder 12 and a second cylinder 18 extending forward and backward are fixed inside the housing 1 via an insulating bracket 21, and the first cylinder 12 and the second cylinder 18 are located between the first static contact 6 and the second static contact 14; the front and rear sides of the first cylinder 12 are respectively provided with a first telescopic rod 8 and a second telescopic rod 13 which are plugged and sealed therewith, and the front and rear sides of the second cylinder 18 are respectively provided with a third telescopic rod 23 and a third telescopic rod 24 which are plugged and sealed therewith. The fourth telescopic rod 17, the front ends of the first telescopic rod 8 and the third telescopic rod 23 are jointly fixed with a first moving contact 27, the first moving contact 27 is used to contact and cooperate with the first static contact 6, the rear ends of the third telescopic rod 23 and the fourth telescopic rod 17 are jointly fixed with a second moving contact 33, the second moving contact 33 is used to contact and cooperate with the second static contact 14, the first moving contact 27 and the second moving contact 33 are each fixed with a long strip-shaped rack 9 extending forward and backward, the two racks 9 are respectively located on the upper and lower sides of a gear 20 and are both meshed with the gear 20, the gear 20 is fixedly connected to a drive shaft 2, the drive shaft 2 extends to the outside of the housing 1, and the drive shaft 2 is used to contact with the housing 1 is connected to the driving device outside the first cylinder 12 for driving the gear 20 to rotate. A third cylinder 10 extending upward and communicating with the first cylinder 12 is fixed in the middle of the first cylinder 12. A fifth telescopic rod 30 plugged and sealed with the third cylinder 10 is provided in the third cylinder 10. The upper end of the fifth telescopic rod 30 extends to the top of the third cylinder 10 and is fixedly connected to a grounding moving contact 11. The grounding moving contact 11 is used to contact and cooperate with the grounding static contact 24. A first piston 29 and a second piston 31 distributed on both sides of the third cylinder 10 are provided inside the first cylinder 12. The first cylinder 12 is provided with a first pressure relief hole 28 on the front side of the first piston 29, and a second pressure relief hole 31 on the rear side of the second piston 31. The hole 32, the cavity formed between the first piston 29, the second piston 31 and the fifth telescopic rod 30 is filled with an insulating transmission medium, the middle of the second cylinder 18 is connected to a fourth cylinder 4 through a conduit 26, the fourth cylinder 4 is fixed to the outside of the shell 1, a switch valve 3 is provided between the fourth cylinder 4 and the conduit 26, a third piston 35 is provided in the fourth cylinder 4, and the cavity formed between the third telescopic rod 23, the fourth telescopic rod 17 and the third piston 35 is filled with an insulating transmission medium; the first cylinder 12, the second cylinder 18, the third cylinder 10, the first telescopic rod 8, the second telescopic rod 13, the third telescopic rod 23, the fourth telescopic rod 17, and the fifth telescopic rod 30 are all conductors;

[0034] like Figure 6As shown, when the first moving contact 27 and the second moving contact 33 are in the isolation position and the grounding moving contact 11 and the grounding static contact 24 are in the open state, the first piston 29 is located at the rear side of the first pressure relief hole 28 and abuts against the first telescopic rod 8, and the second piston 31 is located at the front side of the second pressure relief hole 32 and abuts against the second telescopic rod 13.

[0035] When in use, this compact three-station double-break isolating grounding switch is connected to the transmission line using the first static contact 6 and the second static contact 14, and the grounding static contact 24 is connected to the earth; the first telescopic rod 8, the second telescopic rod 13, the third telescopic rod 23 and the fourth telescopic rod 17 can provide support and guidance for the first moving contact 27 and the second moving contact 33, so that the gear 20 and the two racks 9 can cooperate to simultaneously adjust the front and rear positions of the first moving contact 27 and the second moving contact 33; the fifth telescopic rod 30 can provide stable support and guidance for the grounding moving contact 11, so that the position of the grounding moving contact 11 can be adjusted up and down.

[0036] When switching from the isolated state to the closed state: see Figure 6 , Figure 7 As shown, based on the transmission effect of the gear and the two racks, the first moving contact 27 and the second moving contact 33 are driven to gradually move away from each other, and finally the first moving contact 27 contacts and cooperates with the first static contact 6, and at the same time, the second moving contact 33 contacts and cooperates with the second static contact 14 to achieve a closed state. In this state, the first static contact 6 and the second static contact 14 are connected through the first moving contact 27, the first cylinder 12, the second cylinder 18, the first telescopic rod 8, the second telescopic rod 13, the third telescopic rod 23, the fourth telescopic rod 17 and the second moving contact 33 is turned on, so that the power transmission line remains in a conducting state; in the above process, as the first moving contact 27 and the second moving contact 33 gradually move away from each other, the first telescopic rod 8 and the second telescopic rod 13 also gradually move away from each other, but because the inner cavity of the first cylinder 12 remains connected with the outside through the first pressure relief hole 28 and the second pressure relief hole 32, the first piston 29 and the second piston 31 will not move with the first telescopic rod 8 and the second telescopic rod 13. Therefore, when switching from the isolated state to the closed state, the position of the grounding moving contact 11 will not change.

[0037] When switching from isolated state to grounded state: See Figure 6 , Figure 8 As shown, based on the transmission action of the gear and the two racks, the first moving contact 27 and the second moving contact 33 are driven to gradually approach each other, and the first telescopic rod 8 and the second telescopic rod 13 respectively push the first piston 29 and the second piston 31 toward the middle, and under the pressure of the insulating transmission medium, the fifth telescopic rod 30 moves upward, and finally the grounding moving contact 11 contacts and cooperates with the grounding static contact 24 to achieve the grounding state.

[0038] When switching from the closed state to the isolated state: see Figure 6 , Figure 7 , Fig. 9 As shown, based on the transmission effect of the gear and the two racks, the first moving contact 27 and the second moving contact 33 are driven to gradually approach each other. When the first telescopic rod 8 and the second telescopic rod 13 are respectively in contact with the first piston 29 and the second piston 31, the first moving contact 27 is separated from the first static contact 6 to form a first break 37. At the same time, the second moving contact 33 is separated from the second static contact 14 to form a second break 38, thereby realizing an isolated state with two isolated breaks. In the process of the first telescopic rod 8 and the second telescopic rod 13 gradually approaching each other, since the inner cavity of the first cylinder 12 is connected to the outside through the first pressure relief hole 28 and the second pressure relief hole 32, the pressure on the first piston 29 and the second piston 31 does not change. Therefore, when the closed state is switched to the isolated state, the position of the grounding moving contact 11 does not change.

[0039] When switching from grounded state to isolated state: See Figure 6 , Figure 8 , Fig.10 As shown, based on the transmission action of the gear and the two racks, the first moving contact 27 and the second moving contact 33 are driven to gradually move away from each other. In the process of the first telescopic rod 8 and the second telescopic rod 13 moving away from each other, the first piston 29 and the second piston 31 are driven to move away from each other based on the negative pressure. Under the pressure of the insulating transmission medium, the fifth telescopic rod 30 will drive the grounding moving contact 11 to move downward. When the first moving contact 27 and the second moving contact 33 reach the isolation position, the grounding moving contact 11 and the grounding static contact 24 are separated to the open state.

[0040] When this compact three-station double-break isolating grounding switch is used in a GIS system, it has two breaks in the isolated state, and grounding protection is provided between the two breaks. Even if one break breaks down, the breakdown current can be discharged by the grounding system, and the other break still plays a role of safe isolation, which can meet the technical requirements of non-power outage during expansion and installation operations and handover voltage tests of GIS equipment.

[0041] Based on the transmission cooperation between the gear 20 and the rack 9, the compact three-station double-break isolating and grounding switch can adjust the positions of the first moving contact 27 and the second moving contact 33, and can indirectly adjust the position of the grounding moving contact 11. Therefore, only the drive shaft 2 needs to be connected to a power device outside the shell 1 to realize the automatic switching of all working states of the compact three-station double-break isolating and grounding switch, and there is no need to set a separate transmission component and drive device for the position adjustment of the grounding moving contact 11, so that the overall structure of the compact three-station double-break isolating and grounding switch is more compact, reduces the occupied space, and is conducive to improving the airtightness of the shell 1.

[0042] In the present compact three-station double-break isolating and grounding switch, a switch valve 3 is provided between the fourth cylinder 4 and the conduit 26, and an insulating transmission medium is filled in the chamber formed between the third telescopic rod 23, the fourth telescopic rod 17 and the third piston 35; when the switch valve 3 is in an open state, the insulating transmission medium can flow accordingly with the position change of the third telescopic rod 23 and the fourth telescopic rod 17, and thus will not affect the position change of the third telescopic rod 23 and the fourth telescopic rod 17, that is, the working state of the present compact three-station double-break isolating and grounding switch can be adjusted; and when the switch valve 3 is in a closed state, the insulating transmission medium cannot flow, and the positions of the third telescopic rod 23 and the fourth telescopic rod 17 cannot be adjusted, that is, the working state of the present compact three-station double-break isolating and grounding switch is in a locked state, and its working state cannot be switched; based on this design, the working state of the present compact three-station double-break isolating and grounding switch can be locked and unlocked by adjusting the state of the switch valve 3 to avoid misoperation and improve safety.

[0043] For details, see Figure 2 , Figure 3 , Figure 4 As shown, in order to facilitate the assembly of various components in the compact three-station double-break isolating and grounding switch, the main body of the housing 1 is cylindrical, and ports are provided at the front end and the rear end as well as the upper and lower sides of the middle part, and flanges are provided at the ports, and these ports are respectively installed and fixed with a sealed front cover 7, a rear cover 15, an upper end cover 25 and a lower end cover 19; the first static contact 6 and the second static contact 14 are respectively fixed to the front end cover 7 and the rear end cover 15 through insulators; the grounding static contact 24 is fixed to the upper end cover 25 through an insulator; the insulating bracket 21 is fixed to the lower end cover 19 through an insulator;

[0044] Furthermore, the insulating bracket 21 is composed of a bow frame 212 and a clamping seat 211. The first cylinder 12 and the second cylinder 18 are clamped and fixed by the clamping seat 211. The bow frame 212 is located below the clamping seat 211 and the two are fixedly connected by bolts. The bow frame 212 is fixed to the lower end cover 19 through an insulator. According to actual conditions, the bow frame 212 and the clamping seat 211 can be assembled in the shell.

[0045] Specifically, the insulating transmission medium is insulating liquid or insulating gas.

[0046] Optional, see Figure 1 , Figure 4 , Figure 5As shown, a transparent window 36 is provided on the side wall of the fourth cylinder 4, through which the operator can observe the position of the third piston 35. Based on the aforementioned structural design, the position of the third piston 35 in the fourth cylinder 4 is substantially corresponding to the positions of the third telescopic rod 23 and the fourth telescopic rod 17. By observing the position of the third piston 35 through the transparent window 36, the station state of the compact three-station double-break isolating grounding switch can be determined, achieving an effect equivalent to visible breaks; further, in order to facilitate observation and judgment, the fourth cylinder 4 is provided with a station mark 34 that cooperates with the third piston 35 on one side of the transparent window 36.

[0047] Optional, see Figure 2 , Figure 3 , Figure 4 As shown, a slideway 22 is fixed to each of the first cylinder 12 and the second cylinder 18, and the two racks 9 are slidably matched with the two slideways 22, respectively, thereby significantly reducing the strength requirement of the racks 9.

[0048] Optional, such as Figure 1 As shown, one end of the driving shaft 2 located outside the housing 1 is provided with a square head to facilitate transmission connection with the driving device.

[0049] Optional, see Figure 4 As shown, the first telescopic rod 8 and the second telescopic rod 13 are plugged and sealed with the first cylinder 12. In order to ensure good sealing performance, pistons that are sealed with the first cylinder 12 can be installed at the corresponding ends of the first telescopic rod 8 and the second telescopic rod 13. A more preferred embodiment is that the ends of the first telescopic rod 8 and the second telescopic rod 13 that are plugged and matched with the first cylinder 12 are sleeved with sealing rings; similarly, the ends of the third telescopic rod 23 and the fourth telescopic rod 17 that are plugged and matched with the second cylinder 18 are sleeved with sealing rings, and the ends of the fifth telescopic rod 30 that are plugged and matched with the third cylinder 10 are sleeved with sealing rings.

[0050] Optional, see Figure 2 , Figure 4 As shown, the front ends of the first telescopic rod 8 and the third telescopic rod 23 are jointly fixed with the first moving contact seat 5, and the first moving contact 27 is fixed to the front side of the first moving contact seat 5; the rear ends of the third telescopic rod 23 and the fourth telescopic rod 17 are jointly fixed with the second moving contact seat 16, and the second moving contact 33 is fixed to the rear side of the second moving contact seat 16; the two racks 9 are respectively fixedly connected to the first moving contact seat 5 and the second moving contact seat 16.

Claims

1. A compact three-station double-break isolating grounding switch, comprising a housing, a first static contact and a second static contact arranged at intervals in front and behind are fixed in the housing, and a grounding static contact is fixed on the upper side of the housing inner cavity; characterized in that: A first cylinder and a second cylinder extending forward and backward are fixed in the shell through an insulating bracket; a first telescopic rod and a second telescopic rod which are plugged and sealed together are respectively provided on the front and rear sides of the first cylinder, and a third telescopic rod and a fourth telescopic rod which are plugged and sealed together are respectively provided on the front and rear sides of the second cylinder, a first moving contact is fixed to the front ends of the first telescopic rod and the third telescopic rod, and a second moving contact is fixed to the rear ends of the third telescopic rod and the fourth telescopic rod, the first moving contact and the second moving contact are each fixedly connected to a rack extending forward and backward, the two racks are respectively meshed with the upper and lower sides of a gear, the gear is fixedly connected to a drive shaft, the drive shaft extends to the outside of the shell, a third cylinder which extends upward and is communicated with the first cylinder is fixed in the middle part, a fifth telescopic rod which is plugged and sealed together is provided in the third cylinder, and the fifth telescopic rod The upper end extends to the top of the third cylinder and is fixedly connected to a grounding moving contact. A first piston and a second piston are arranged inside the first cylinder and are distributed on both sides of the third cylinder. The first cylinder is provided with a first pressure relief hole on the front side of the first piston, and a second pressure relief hole on the rear side of the second piston. The cavity formed by the first piston, the second piston and the fifth telescopic rod is filled with an insulating transmission medium. The middle part of the second cylinder is connected to a fourth cylinder fixed to the outside of the shell through a conduit. A switch valve is arranged between the fourth cylinder and the conduit. The third piston is arranged in the fourth cylinder. The cavity formed by the third telescopic rod, the fourth telescopic rod and the third piston is filled with an insulating transmission medium. The first cylinder, the second cylinder, the third cylinder, the first telescopic rod, the second telescopic rod, the third telescopic rod, the fourth telescopic rod and the fifth telescopic rod are all conductors.

2. The compact three-station double-break isolating and grounding switch according to claim 1 is characterized in that: The main body of the shell is cylindrical, and ports are opened at the front end, the rear end, and the upper and lower sides of the middle part. Flanges are provided at the ports, and these ports are respectively installed and fixed with a sealed front cover, a rear end cover, an upper end cover and a lower end cover; the first static contact and the second static contact are respectively fixed to the front end cover and the rear end cover via insulators; the grounding static contact is fixed to the upper end cover via an insulator; the insulating bracket is fixed to the lower end cover via an insulator.

3. The compact three-station double-break isolating and grounding switch according to claim 2 is characterized in that: The insulating bracket is composed of a bow frame and a clamping seat. The first cylinder and the second cylinder are fixed on the clamping seat. The bow frame is located below the clamping seat and the two are fixedly connected by bolts. The bow frame is fixed to the lower end cover through an insulator.

4. The compact three-station double-break isolating and grounding switch according to claim 1 is characterized in that: The insulating transmission medium is insulating liquid or insulating gas.

5. The compact three-station double-break isolating and grounding switch according to claim 1 is characterized in that: The side wall of the fourth cylinder is provided with a transparent window.

6. The compact three-station double-break isolating and grounding switch according to claim 5 is characterized in that: The fourth cylinder is provided with a workstation mark matched with the third piston on one side of the transparent window.

7. The compact three-station double-break isolating and grounding switch according to claim 1 is characterized in that: A slideway is fixed on each of the first cylinder and the second cylinder, and the two racks are slidably matched with the two slideways respectively.

8. The compact three-station double-break isolating and grounding switch according to claim 1 is characterized in that: One end of the driving shaft located outside the shell is provided with a square head.

9. The compact three-station double-break isolating and grounding switch according to claim 1, characterized in that: The ends of the first telescopic rod and the second telescopic rod that are plugged into the first cylinder are sleeved with sealing rings, the ends of the third telescopic rod and the fourth telescopic rod that are plugged into the second cylinder are sleeved with sealing rings, and the end of the fifth telescopic rod that is plugged into the third cylinder is sleeved with a sealing ring.

10. The compact three-station double-break isolating and grounding switch according to claim 1, characterized in that: A first moving contact seat is fixed to the front ends of the first telescopic rod and the third telescopic rod, and the first moving contact is fixed to the front side of the first moving contact seat; a second moving contact seat is fixed to the rear ends of the third telescopic rod and the fourth telescopic rod, and the second moving contact is fixed to the rear side of the second moving contact seat; and two racks are fixedly connected to the first moving contact seat and the second moving contact seat, respectively.

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