Ring main unit

Abstract

Provided in the present disclosure is a ring main unit (500). The ring main unit (500) comprises a gas tank (100), a fixed frame (1) fixed to an inner side wall of the gas tank, and a circuit breaker switch (2) and a three-position switch (3) that are located in the gas tank (100). Embedded poles (21) of the circuit breaker switch (2) each comprise a pole body (211), and a moving-end shielding seat (212) and a fixed-end shielding seat (213) that are located at two ends of the pole body (211), wherein the moving-end shielding seat (212) and the fixed-end shielding seat (213) can respectively cover the two ends of the pole body (211), thereby electrically isolating an electrical connection position of the pole body (211) from the external environment. The pole body (211), the moving-end shielding seat (212) and the fixed-end shielding seat (213) are cast into a whole by means of an insulating resin, thereby improving the consistency of the poles. A grounding shielding seat (33) is made of an integrally formed metal member, such that a plurality of grounding contacts (32) can be uniformly enclosed within a shielding space (301), thereby optimizing the electric field distribution of the grounding contacts. The ring main unit (500) disclosed in the present application can not only use dry air as an insulating gas, but also achieves the miniaturization of the ring main unit (500) and satisfies the corresponding insulation performance.

Description

Ring main unit

[0001] This application claims priority to Chinese Patent Application No. 2024212208762, filed on May 30, 2024, and Chinese Patent Application No. 2024106901734, filed on May 30, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to the field of switchgear technology, and mainly to a ring main unit. Background Technology

[0003] To improve power supply reliability and allow users to obtain power from two directions, the power grid is typically connected in a ring, also known as a ring network power supply system. This power supply method is simply called ring power supply. The switching equipment used in a ring network power supply system is generally referred to as a ring main unit.

[0004] SF6 gas is commonly used as a gas insulator in switchgear due to its excellent insulation and arc-quenching properties. However, as a greenhouse gas, its use is detrimental to environmental protection. Dry air also possesses certain insulating properties and could be considered as a replacement for SF6. However, air's insulation performance is lower than that of SF6, limiting its application in ring main units, especially for small ring main units where air insulation is insufficient to meet their insulation requirements due to their small size. Summary of the Invention

[0005] This disclosure provides a ring main unit with good insulation performance and small size.

[0006] According to one aspect of this application, a ring main unit is provided, comprising: an air box filled with dry air; a fixed frame fixed to the inner wall of the air box; a circuit breaker switch disposed on the fixed frame, comprising a sealed pole, which includes a pole body and a moving end shield and a stationary end shield located at both ends of the pole body, the pole body being fixed to the fixed frame, and the pole body, the moving end shield, and the stationary end shield being formed as a whole by casting insulating resin; and a three-position switch disposed on the fixed frame, the circuit breaker switch being arranged on the inner wall of the air box. The three-position switch is arranged in the middle layer of the fixed frame. The three-position switch includes: a grounding contact base, a plurality of grounding contacts disposed on the grounding contact base, and a grounding shield. The grounding contact base is disposed on the fixed frame, and the grounding shield covers the grounding contact base. The plurality of grounding contacts are located in the shielding space formed between the grounding shield and the grounding contact base. The grounding shield is configured as an integrally formed metal part. The grounding shield has a plurality of openings corresponding to the plurality of grounding contacts to expose each of the grounding contacts.

[0007] This disclosure provides a ring main unit, which includes a gas box, a fixed frame fixed to the inner wall of the gas box, a circuit breaker switch and a three-position switch located inside the gas box. The solid-sealed pole of the circuit breaker switch includes a pole body and moving-end shielding seats and stationary-end shielding seats located at both ends of the pole body. The moving-end shielding seats and stationary-end shielding seats partially cover both ends of the pole body, thereby better isolating the electrical connection points of the pole body from other adjacent electrical components. The pole body, moving-end shielding seats, and stationary-end shielding seats are formed as a whole by casting insulating resin. As an insulating material, the insulating resin not only allows for a tight connection between the pole body, moving-end shielding seats, and stationary-end shielding seats, but also covers the connection points of each component, thus providing good electrical isolation for the solid-sealed pole as a whole, providing a uniform electric field for the circuit breaker, and improving the overall insulation strength of the solid-sealed pole. Furthermore, the grounding shield in the three-position switch uses a one-piece molded metal component, which can uniformly enclose multiple grounding contacts within the shielding space formed between the grounding shield and the grounding contact seat. This optimizes the electric field distribution of the grounding contacts and provides excellent electromagnetic shielding. It also makes the structure on the grounding contact side more compact, improving the insulation strength of the three-position switch and reducing its overall size. In summary, the ring main unit of this application improves the insulation strength of the circuit breaker and the three-position switch by optimizing the electric field distribution, thereby enhancing the overall insulation level of the ring main unit. This allows the ring main unit to achieve miniaturization while meeting the corresponding insulation performance requirements, even when using dry air as the insulating gas. Attached Figure Description

[0008] The above and / or additional aspects and features of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0009] Figure 1 is a perspective view of a ring main unit according to some embodiments of this application from a first-view perspective.

[0010] Figure 2 is a perspective view of a ring main unit according to a second view of some embodiments of this application;

[0011] Figure 3 is a front view of the ring main unit shown in Figure 1;

[0012] Figure 4 is a right view of the ring main unit shown in Figure 1;

[0013] Figure 5 is a schematic diagram of the connection between the solid-sealed pole and the moving end of the pole in some embodiments of this application;

[0014] Figure 6 is a perspective view of a solid-sealed electrode post according to some embodiments of this application;

[0015] Figure 7 is a cross-sectional view of a solid-sealed electrode post according to some embodiments of this application;

[0016] Figure 8 is a magnified view of section C in Figure 7;

[0017] Figure 9 is a schematic diagram of one of the moving end shielding bases of some embodiments of this application;

[0018] Figure 10 is a second schematic diagram of a moving end shielding base according to some embodiments of this application;

[0019] Figure 11 is a schematic diagram of a stationary shielding base according to some embodiments of this application;

[0020] Figure 12 is a magnified view of part A in Figure 4;

[0021] Figure 13 is a magnified view of part D in Figure 5;

[0022] Figure 14 is a cross-sectional view of the connection between the solid-sealed pole and the moving end of the pole in some embodiments of this application;

[0023] Figure 15 is a magnified view of part E in Figure 14;

[0024] Figure 16 is a cross-sectional view of the connection structure between the side expansion sleeve and the main busbar in some embodiments of this application;

[0025] Figure 17 is a magnified view of part F in Figure 16;

[0026] Figure 18 is a schematic diagram of the side-expanding sleeve of some embodiments of this application;

[0027] Figure 19 is a cross-sectional view of the side-expanding sleeve of some embodiments of this application;

[0028] Figure 20 is a schematic diagram of a three-position switch according to some embodiments of this application;

[0029] Figure 21 is a schematic diagram of the installation of grounding contacts according to some embodiments of this application;

[0030] Figure 22 is a magnified view of part B in Figure 4.

[0031] Implementation of this disclosure

[0032] The embodiments of this application are described in detail below, and the embodiments described with reference to the accompanying drawings are exemplary.

[0033] To improve power supply reliability and allow users to obtain power from two directions, the power grid is typically connected in a ring, also known as a ring network power supply system. This power supply method is simply called ring power supply. The high-voltage switchgear used in a ring network power supply system is generally referred to as a ring main unit.

[0034] Please refer to Figure 1. This disclosure provides a ring main unit, which includes a gas box 100, a fixed frame 1 fixed to the inner wall of the gas box 100, a circuit breaker switch 2 located inside the gas box 100, and a three-position switch 3.

[0035] As shown in Figures 1 and 2, the ring main unit includes a housing with multiple functional compartments inside. These functional compartments include an air chamber 100, a low-pressure compartment 200, a mechanism compartment 300, and a cable compartment 400. To more clearly illustrate the structure inside the air chamber 100, a portion of the housing is hidden in Figures 1 and 2.

[0036] In the ring main unit disclosed in this application, the gas box 100 is filled with dry air. Compared with the existing related technologies that mainly use SF6 gas as the insulating gas, this application uses dry air as the insulating gas for the ring main unit, which can not only reduce the adverse environmental impact of using the greenhouse gas SF6 gas and achieve environmental protection, but also reduce the manufacturing cost of the ring main unit.

[0037] As shown in Figure 3, the air box 100 is generally rectangular. The shape of the air box 100 can be modified according to actual use and requirements. The air box 100 can be welded by a welding robot using programmed rotary fixtures. This welding method ensures accurate positioning and uniform weld seams, effectively improving the precision and strength of the air box 100, while also reducing its leakage rate, thus giving the air box 100 good airtightness.

[0038] The inner wall of the gas box 100 is provided with a fixed frame 1, which can be fixedly connected to the inner wall of the ring main unit by welding. From the height direction of the ring main unit, the circuit breaker switch 2 is arranged on the upper layer of the fixed frame 1, and the three-position switch 3 is arranged on the middle layer of the fixed frame 1. The circuit breaker switch 2 and the three-position switch 3 are arranged vertically within the space of the gas box 100.

[0039] As shown in Figure 4, three solid-sealed poles 21 are provided on the fixed frame 1, and these three solid-sealed poles 21 can correspond to the three phases in the power supply network.

[0040] Referring to Figures 4 and 5, the circuit breaker switch 2 includes a solid-sealed pole 21, a moving end 22 of the pole, and a circuit breaker operating mechanism 23. The solid-sealed pole 21 is housed within the gas box 100, and the circuit breaker operating mechanism 23 is housed within the mechanism chamber 300. The circuit breaker operating mechanism 23 and the solid-sealed pole 21 are connected via the moving end 22. Driven by the circuit breaker operating mechanism 23, the stationary conductive rod and the moving conductive rod 211 within the solid-sealed pole 21 can be switched on and off.

[0041] As shown in Figures 5 and 6, the solidified electrode post 21 includes an electrode post body 211 and a moving end shielding seat 212 and a stationary end shielding seat 213 located at both ends of the electrode post body 211. The electrode post body 211 is fixed to the fixed frame 1, and the electrode post body 211, the moving end shielding seat 212, and the stationary end shielding seat 213 are formed into a whole by casting insulating resin. In this way, the design of the solidified electrode post 21 being integrally cast makes the contact between the electrode post body 211, the moving end shielding seat 212, and the stationary end shielding seat 213 tighter. Compared with setting the electrode post body 211, the moving end shielding seat 212, and the stationary end shielding seat 213 separately, the integral casting of these components with insulating resin can reduce the gaps or poor contact that may exist between the components, so that the three can form a tight connection.

[0042] The pole body 211 has a moving end and a stationary end at its two ends, respectively. The moving end shield 212 is located at the moving end of the pole body 211. The stationary end shield 213 is located at the stationary end of the pole body 211.

[0043] Among them, the insulating resin, as an insulating material, can tightly bond the pole body 211, the moving end shield 212 and the stationary end shield 213 together by integral casting, thereby forming an integral insulating resin layer 2113. This provides electrical isolation for the whole composed of the pole body 211, the moving end shield 212 and the stationary end shield 213, reduces the risk of arcing and breakdown caused by high voltage difference when the solid-sealed pole 21 is used in switchgear, achieves a more effective uniform electric field effect, and improves the insulation performance of the entire solid-sealed pole 21.

[0044] Optionally, epoxy resin may be used as the insulating resin.

[0045] As shown in Figure 7, the pole body 211 includes a cylinder 2111 with a vacuum interrupter 200 formed inside, a silicone sleeve 2112 wrapped around the outer surface of the cylinder 2111, and an insulating resin layer 2113 covering the outer surface of the silicone sleeve 2112.

[0046] A vacuum interrupter 200 is formed inside the pole body 211. The two ends of the vacuum interrupter 200 are respectively designated as a first end and a second end, which correspond to the first end and the second end of the pole body 211. A stationary conductive rod is correspondingly provided at the second end of the vacuum interrupter 200, and a moving conductive rod 221 of the pole moving end 22 is correspondingly provided at the second end of the vacuum interrupter 200. The moving conductive rod of the pole moving end 22 is used for transmission connection with the circuit breaker operating mechanism 23, thereby controlling the opening and closing coordination between the moving conductive rod and the stationary conductive rod.

[0047] A silicone sleeve 2112 is nested on the outer surface of the cylindrical body 2111 of the pole post 211, so that the insulating resin covers the silicone sleeve 2112. In this way, compared to directly casting the insulating resin together with the vacuum interrupter 200, which results in a low bonding rate and easy formation of air bubbles, first covering the surface of the vacuum interrupter 200 with the silicone sleeve 2112 allows for a tight connection between the silicone sleeve 2112 and the vacuum interrupter 200 due to the elasticity of the silicone sleeve 2112. Simultaneously, after the insulating resin cures on the outer surface of the silicone sleeve 2112, the silicone sleeve 2112 and the insulating resin bond more tightly, thus allowing the vacuum interrupter 200 to be more tightly encapsulated by the insulating resin. This forms a multi-layered, tightly connected integrated structure, resulting in better electrical isolation.

[0048] As shown in Figures 7 and 8, the moving end shield 212 has a protrusion 2124 protruding towards the vacuum interrupter 200, and the protrusion 2124 contacts the top surface of the silicone sleeve 2112.

[0049] As shown in Figures 8 and 10, the boss 2124 extends from the first connecting plate 2121 of the driven end shield 212 toward the vacuum interrupter 200 and abuts against the silicone sleeve 2112. Thus, during the integral casting of the driven end shield 212 and the pole body 211, the boss 2124 can more effectively block the insulating resin from entering the connection between the first connecting plate 2121 and the moving conductive rod 221 of the vacuum interrupter 200, preventing epoxy resin from seeping into the vacuum interrupter 200 through the connection between the driven end shield 212 and the pole body 211 and curing, thus affecting the movement of the moving conductive rod and reducing its flexibility. In this way, the boss 2124 reduces the problem of epoxy resin curing on the outside of the pole body 211, which could affect the operational performance of the sealed pole.

[0050] As shown in Figures 9 and 14, the moving end shielding seat 212 is provided with a first shielding cavity 201, which can make the connection between the moving end 22 of the pole post and the pole post body 211 located in the first shielding cavity 201. The moving end shielding seat 212 can uniformly distribute the electric field at the connection between the moving end 22 of the pole post and the pole post body 211.

[0051] As shown in Figures 9 and 10, the moving end shielding seat 212 includes a first connecting plate 2121 and three first shielding plates 2122 extending upward from the first connecting plate 2121. The first connecting plate 2121 and the first shielding plates 2122 together enclose a first shielding cavity 201.

[0052] Optionally, the moving end shielding base 212 can be formed by metal casting. The outer surface of the first shielding cavity 201, which is formed by the first connecting plate 2121 and the first shielding plate 2122, is covered with insulating resin, and the inner surface of the first shielding cavity 201 is a metal surface. The metal surface has good conductivity and electromagnetic shielding effect, which can further optimize the electric field at the connection between the moving end 22 of the pole and the pole body 211.

[0053] Furthermore, the moving end shielding base 212 is provided with a first opening 202, which communicates with the first shielding cavity 201. As shown in Figures 6 and 9, the first opening 202 is formed between two opposing first connecting plates 2121, allowing the moving end 22 of the pole post to extend into the first shielding cavity 201 through the first opening 202. This reduces the risk of the electric field spreading outward from the conductive connection between the pole post body 211 and the moving end 22, and also reduces the interference of interphase electric field interference or other externally generated electromagnetic fields on the moving end 22 in multiphase electrical equipment, thereby improving the insulation performance of the circuit breaker.

[0054] As shown in Figure 5, the moving end shielding base 212 is provided with a third opening 203, which communicates with the first shielding cavity 201. Specifically, the top of the three first connecting plates 2121 forms the third opening 203.

[0055] As shown in Figures 5 and 9, the moving end shielding base 212 is also provided with two protruding posts 2123, each with a first connecting hole 204. This allows the transmission crank arm 222 of the moving end 22 of the pole post to be fixed to the moving end shielding base 212 by locking the transmission pin 225 with the first connecting hole 204. This avoids the need to open a side hole on the pole post body 211 to connect the transmission pin 225, improving the consistency of the sealed pole post 21, effectively reducing potential insulation breakdown points, and thus improving the insulation performance of the circuit breaker switch 2. On the other hand, since there is no need to open through holes or process holes on the pole post body 211, the manufacturing process of the sealed pole post 21 can be simplified, and the assembly efficiency can be improved.

[0056] As shown in Figure 11, the stationary end shielding base 213 is provided with a second shielding cavity 205, which can partially surround the connection between the second end of the pole body 211 and the conductive element. The conductive element may include, but is not limited to, an isolating stationary contact, and a connecting component between the stationary end shielding base 213 and the second end of the vacuum interrupter 200.

[0057] As shown in Figures 4 and 12, the isolating stationary contact 34 of the three-position switch 3 is located inside the second shielding cavity 205, so that the electrical connection between the moving contact 36 and the isolating stationary contact 34 of the three-position switch 3 is located inside the second shielding cavity 205. The stationary shielding seat 213 can form a physical barrier for the electrical connection between the two, thus playing the role of electrical isolation.

[0058] As shown in Figure 11, the stationary shielding base 213 includes a second connecting plate 2131 and two second shielding plates 2132 extending downward from the second connecting plate 2131. The second shielding plates 2132 are disposed opposite to each other on opposite sides of the second connecting plate 2131, and the second connecting plate 2131 and the second shielding plates 2132 enclose a second shielding cavity 205. As shown in Figure 6, a second opening 208 is formed between the oppositely disposed second connecting plates 2131. The second opening 208 allows the moving contact 36 of the three-position switch 3 to extend into the second shielding cavity 205 and then make an electrical connection with the isolating stationary contact 34.

[0059] As shown in Figures 5, 6 and 7, a first insulating plate 24 protruding from the surface is provided on the surface of the electrode body 211. The first insulating plate 24 and the electrode body 211 are integrally connected by insulating resin casting. Thus, the surface of the first insulating plate 24 is covered with insulating resin. The provision of the first insulating plate 24 can increase the creepage distance on the surface of the electrode body 211, thereby improving the overall insulation level of the sealed electrode 21.

[0060] As shown in Figure 6, the first opening 202 of the moving end shielding seat 212 and the second opening 208 of the stationary end shielding seat 213 are located on the same side of the pole body 211. The first insulating plate 24 is located on the side where the circuit breaker operating mechanism 23 is connected to the crank arm shaft 224 of the moving end of the pole 22, and the first insulating plate 24 is located between the moving end shielding seat 212 and the stationary end shielding seat 213. In this way, the first insulating plate 24 can be located between the high-voltage metal and the grounding metal. The setting of the first insulating plate 24 can increase the creepage distance, improve the creepage level of the solidified pole 21, and more effectively reduce the risk of the insulating resin layer 2113 on the surface of the pole body 211 being polarized and becoming charged, thereby improving the overall insulation performance of the solidified pole 21.

[0061] Furthermore, two first insulating plates 24 are provided, and the two first insulating plates 24 are arranged opposite to each other, which further improves the creepage level and insulation performance of the surface of the solidified pole 21.

[0062] As shown in Figures 6 and 7, the surface of the pole body 211 is also provided with a second insulating plate 25 and a third insulating plate 26. The second insulating plate 25 and the third insulating plate 26 are both located on the side of the pole body 211 away from the first insulating plate 24. The second insulating plate 25 is correspondingly disposed on the end where the moving end shielding seat 212 is located, and the third insulating plate 26 is correspondingly disposed on the end of the stationary end shielding seat 213. The second insulating plate 25 and the third insulating plate 26 are both integrally connected to the pole body 211 by insulating resin.

[0063] The number of the second insulating plate 25 and the third insulating plate 26 can be set according to actual needs. For example, as shown in Figure 7, there are two of each of the second insulating plate 25 and the third insulating plate 26.

[0064] Thus, from the overall structure of the solidified pole 21, the pole body 211 is provided with a first insulating plate 24 on the side connected to the circuit breaker operating mechanism 23, and a second insulating plate 25 and a third insulating plate 26 on the side away from the circuit breaker operating mechanism 23, which can more comprehensively and effectively increase the creepage distance on the surface of the pole body 211.

[0065] From the positional layout of the first insulating plate 24, the second insulating plate 25, and the third insulating plate 26, since the first and second ends of the pole body 211 are the key parts for connecting the pole body 211 with the external circuit, the second insulating plate 25 and the third insulating plate 26 are respectively provided on the moving end shielding seat 212 and the stationary end shielding seat 213 at these two ends. At the same time, the first insulating plate 24 is provided on the side of the pole body 211 that is connected to the circuit breaker operating mechanism 23. The plate surfaces of the first insulating plate 24 on opposite sides face the high voltage metal and the grounding metal, respectively. This can effectively improve the creepage distance of the solidified pole 21 and further improve the insulation level of the solidified pole 21.

[0066] As shown in Figures 6 and 7, a fixing insert 29 is also provided on the pole body 211. The fixing insert 29 is connected between the pole body 211 and the fixing frame 1. The fixing insert 29 is used to connect with the fixing frame 1, thereby fixing the pole body 211 on the fixing frame 1.

[0067] The fixing insert 29 and the pole body 211 are connected as one unit by casting insulating resin, which can form a tight connection between the fixing insert 29 and the pole body 211, avoid the fixing insert 29 affecting the electric field uniformity of the solidified pole 21, and further improve the overall insulation strength of the solidified pole 21.

[0068] Specifically, the fixing inserts 29 include three, and the positions of the three fixing inserts 29 form the three vertices of a triangle. The three positions of the fixing inserts can be indicated by the dashed triangle shown in Figure 7. In particular, the positions of the three fixing inserts 29 form the three vertices of a triangle, thus forming a triangular lock. The triangular structure has good stability, and the triangular lock further enhances the fixing effect between the sealing pole 21 and the fixing frame 1, preventing the sealing pole 21 from shifting or loosening during operation.

[0069] As shown in Figures 6 and 7, the fixing insert 29 is cylindrical in shape and has a curved surface. The shape design of the fixing insert 29 is conducive to optimizing the electric field distribution on the surface of the pole body and reducing the problem of electric field concentration caused by setting the fixing insert 29.

[0070] The interior of the fixing insert 29 has a sixth connecting hole 209, through which the connector 13 can pass so that the fixing insert 29 can be connected to the fixing frame 1.

[0071] Please refer to Figures 5 and 14. The moving end 22 of the pole includes a moving conductive rod 221, a transmission crank arm 222, an insulating pull rod 223, a crank arm shaft 224, a transmission pin 225, and a connecting cover plate 226.

[0072] One end of the moving conductive rod 221 passes through the first opening 202 of the moving end shield 212 and extends into the vacuum interrupter chamber 200 of the pole body 211.

[0073] As shown in Figures 10, 13, and 14, the first connecting plate 2121 of the moving end shielding base 212 has a through hole 210. One end of the moving conductive rod 221 passes through the through hole 210 and extends into the vacuum interrupter chamber 200 of the pole body 211. Driven by the circuit breaker operating mechanism 23, the moving conductive rod 221 can move up and down in the opening, thereby engaging or disengaging with the stationary conductive rod inside the vacuum interrupter chamber 200.

[0074] As shown in Figure 13, the transmission crank arm 222 includes a middle section and a first end and a second end located at both ends of the middle section. The middle section 2221 of the transmission crank arm is located between the first end 2222 and the second end 2223 of the transmission crank arm.

[0075] The first end 2222 of the transmission crank arm extends into the first shielding cavity 201 through the first opening 202, and then connects to the other end of the moving conductive rod 221. In this way, the part of the moving conductive rod 221 connected to the first end 2222 of the transmission crank arm is located in the first shielding cavity 201. The moving end shielding seat 212 can electrically isolate the connection between the moving conductive rod 221 and the transmission crank arm 222, thereby reducing the influence of the electric field on the electric field of the adjacent phase.

[0076] As shown in Figure 14, the second end 2223 of the transmission crank arm is connected to the insulating pull rod 223. The circuit breaker switch 2 also includes a first input shaft 27, which is connected between the second end 2223 of the transmission crank arm and the circuit breaker operating mechanism 23.

[0077] The first input shaft 27 is dynamically sealed at the connection between the gas box 100 and the mechanism chamber 300. This improves the sealing performance of the gas box 100 and reduces the risk of gas leakage between the moving end of the pole 22 and the transmission connection of the circuit breaker operating mechanism 23.

[0078] The middle part of the transmission crank arm 222 forms the fulcrum of the lever, and the second end 2223 of the transmission crank arm is connected to the insulating pull rod 223, serving as the power input end. When the circuit breaker operating mechanism 23 drives the first input shaft 27 to rotate, the insulating pull rod 223 rotates along with the first input shaft 27, thereby driving the transmission crank arm 222 to rotate around its middle part. At this time, the force is transmitted to the first end through the transmission crank arm 222, which serves as the power output end, thereby driving the moving conductive rod 221 to move and realize the opening and closing functions of the circuit breaker.

[0079] As shown in Figures 14 and 15, the other end of the movable conductive rod 221 has a first groove 206 with its opening facing upwards. The transmission pin 225 passes through the first end 2222 of the transmission crank arm and is installed inside the movable conductive rod 221 through the first groove 206. A connecting cover plate 226 is placed over the first groove 206 and connected to the movable conductive rod 221, so that the transmission pin 225 is confined within the first groove 206. In this way, the transmission pin 225 can be prevented from coming out of the first groove 206, thus confining the transmission pin 225 within the first groove 206.

[0080] The transmission pin 225, which passes through the transmission crank arm 222, can be first inserted into the other end of the moving conductive rod 221 through the first groove 206. Then, a connecting cover plate 226 is placed over the first groove 206 and installed on the other end of the moving conductive rod 221. The connecting cover plate 226 is positioned vertically opposite to the other end of the moving conductive rod 221, thus covering the opening of the first groove 206 and confining the transmission pin 225 within the first groove 206. When the transmission crank arm 222 is driven by the circuit breaker operating mechanism 23 to perform opening and closing operations, the first end 2222 of the transmission crank arm pulls the moving conductive rod 221 through the transmission pin 225, thereby causing the moving conductive rod 221 to engage or disengage with the stationary conductive rod.

[0081] Furthermore, since the connecting cover plate 226 is installed on the other end of the moving conductive rod 221, it can cover the electrical connection between the moving conductive rod 221 and the transmission crank arm 222, thereby reducing the exposed electrical connection parts. This reduces the problem of electric field concentration caused by the sharp point formed by the transmission connection with the transmission crank arm 222, thus improving the insulation performance of the transmission connection structure of the pole body 211.

[0082] As shown in Figure 15, the movable conductive rod 221 is provided with two third connecting holes (not shown) located on the outside of the first groove 206. The openings of the third connecting holes are set upwards, and the two third connecting holes are set opposite to each other on both sides of the first groove 206. The two ends of the connecting cover plate 226 are respectively provided with fourth connecting holes (not shown) corresponding to the third connecting holes, so that the connector 13 can pass through the third connecting holes and the fourth connecting holes to lock the connecting cover plate 226 and the movable conductive rod 221.

[0083] By providing a first groove 206 on the other end of the moving conductive rod 221, and connecting the moving conductive rod 221 to the transmission crank arm 222 through the connection of the moving conductive rod 221 to the connecting cover plate 226, it is possible to avoid drilling holes in the pole body 211 as connection holes, avoid disrupting the consistency of the pole body 211, reduce potential breakdown points, and reduce the likelihood of breakdown due to connection holes, thereby improving the overall insulation performance of the circuit breaker.

[0084] As shown in Figures 5 and 13, the first end 2222 of the transmission crank arm is provided with a second groove 207. The opening direction of the second groove 207 is from the outside to the inside, and the second groove 207 has a first sidewall and a second sidewall arranged opposite to each other. The other end of the moving conductive rod 221 and the connecting cover plate 226 are both inserted into the second groove 207. In this way, the first sidewall, the second sidewall of the transmission crank arm 222, and the connecting cover plate 226 can enclose the other end of the moving conductive rod 221, reducing the exposed electrical connection portion and further optimizing the electric field distribution at the connection between the pole body 211 and the moving end 22 of the pole.

[0085] As shown in Figures 9 and 13, a crank arm shaft 224 is inserted through the middle part of the transmission crank arm 222, and two protrusions 2123 are formed on the moving end shield seat 212. The two protrusions 2123 are respectively provided with first connecting holes 204. The axial ends of the crank arm shaft 224 extending to the outside of the transmission crank arm 222 are inserted into the two first connecting holes 204 of the moving end shield seat 212 through the connector 13 and locked.

[0086] In this way, the transmission crank arm 222 is connected to the moving end shielding seat 212 via the crank arm shaft 224 and the connector 13, instead of directly creating through holes or process holes in the pole body 211 for pin connection. This avoids drilling holes in the pole body 211, thus maintaining the consistency of the pole body 211, effectively reducing potential insulation breakdown points, and improving the insulation performance of the pole body 211. On the other hand, since there is no need to create through holes or process holes in the pole body 211, the manufacturing process of the circuit breaker is simplified, and the assembly process of the circuit breaker is also simpler, which is conducive to improving assembly efficiency.

[0087] Furthermore, as shown in Figure 9, the first connecting hole 204 is located inside the first shielding cavity 201, so that the fixed connection point of the middle part of the transmission crank arm 222 can be located inside the first shielding cavity 201. The moving end shielding seat 212 can provide electrical isolation for the fixed connection end of the transmission crank arm 222, thereby improving the insulation level.

[0088] In another embodiment, as shown in FIG13, a baffle is also provided at the location where the two first shielding plates 2122 form the first opening 202, and the two protruding posts 2123 are arranged adjacent to the baffle and located on the inner side of the baffle.

[0089] As shown in Figures 9 and 13, the crank arm shaft 224 is provided with second connecting holes (not shown) at both ends of the axial direction. The first connecting hole 204 is provided in correspondence with the second connecting hole so that the connector 13 can be inserted from above into the second connecting hole and the first connecting hole 204 to lock the crank arm shaft 224 and the protrusion 2123.

[0090] As shown in Figure 13, the middle part of the transmission crank arm 222 is provided with a through hole for the crank arm shaft 224 to pass through. The crank arm shaft 224 is fixedly connected to the protrusion 2123. Under the drive of the insulating pull rod 223, the transmission crank arm 222 can rotate relative to the crank arm shaft 224.

[0091] Referring to Figure 14, the circuit breaker switch 2 also includes a flexible connection 28. One end of the flexible connection 28 is connected to the pole body 211 via a fixing member. The connection point between the flexible connection 28 and the pole body 211 is located within the first shielding cavity 201. The other end of the flexible connection 28 extends upward through a third opening 203 to connect to a conductive circuit. Thus, the portion forming the electrical connection between the flexible connection 28 and the pole body 211 is located within the first shielding cavity 201. The moving end shielding seat 212 can provide electric field isolation at the electrical connection point between the flexible connection 28 and the pole body 211, thereby further improving the insulation level of the circuit breaker.

[0092] Specifically, the moving conductive rod 221 of the moving end 22 of the pole column passes through one end of the flexible connection 28 and extends into the vacuum interrupter 200 inside the pole column body 211. A fixing member is connected to the moving conductive rod 221, which fixes the flexible connection 28 to the moving end of the pole column body 211. The other end of the flexible connection 28 extends upward through the opening at the top of the moving end shield 212 and is connected to the conductive circuit.

[0093] Please refer to Figure 16. The air box 100 also includes a side expansion sleeve 7, a main busbar 9, and a branch copper busbar 10.

[0094] The two side expansion sleeves 7 are respectively installed on the two side walls of the air box 100 and located above the solid sealing pole 21. The side expansion sleeves 7 are equipped with conductive rods 8. The conductive rods 8 include a first end and a second end arranged along the axial direction. The first end 81 of the conductive rod is used to connect with the bus coupler. The two ends of the main busbar 9 are electrically connected to the second ends 82 of the conductive rods on both sides to form a conductive circuit.

[0095] One end of the branch copper busbar 10 is connected to the main busbar 9, and the other end of the branch copper busbar 10 is connected to the flexible connector 28.

[0096] The first end 81 of the conductive rods installed inside the two side expansion sleeves 7 can be connected to the busbars of their adjacent ring main units, and the second end 82 of the conductive rods installed inside the two side expansion sleeves 7 can be connected to both ends of the main busbar 9, thus forming a conductive circuit. One end of the branch copper busbar 10 is connected to the main busbar 9, and the other end of the branch copper busbar 10 is connected to the flexible connection 28, so that the circuit breaker switch 2 can form an electrical connection with the conductive circuit. In this way, the power supply system can supply power to each ring main unit. When the circuit breaker switch 2 in the ring main unit receives the power from the power supply system, it can distribute the power according to the preset control logic to realize the power supply function.

[0097] Please refer to Figures 17 to 19. The side expansion sleeve 7 includes an insulating partition 71 and a second outer sleeve 72. The axial ends of the second outer sleeve 72 are a first end and a second end. The insulating partition 71 is provided on the first end, and the second end is used for installation on the ring main unit. The conductive rod 8 is arranged axially inside the second outer sleeve 72. The second end 82 of the conductive rod extends out of the second outer sleeve 72 and extends to the insulating partition 71. The first end 81 of the conductive rod is configured as a ball for connection with the bus coupler.

[0098] An insulating partition 71 is disposed on one end face 703 of the side-expanding sleeve 7 facing the other side-expanding sleeve 7. Specifically, the insulating partition 71 is disposed on one end face 703 of the second outer sleeve 72. The insulating partition 71 includes three shielding surfaces 702, which together form a uniform electric field cavity 701. The end face 703 of the second outer sleeve 72 and the three shielding surfaces 702 form four faces of a hexahedral structure. The other two faces of the hexahedral structure are open. One of the open faces 704 faces downwards from the side-expanding sleeve and is opposite to the solid-sealing pole 21. The fifth connecting hole 801 faces one of the open faces 704.

[0099] The insulating partition 71 encloses a uniform electric field cavity 701. The second end 82 of the conductive rod is located within the uniform electric field cavity 701, and the second end 82 of the conductive rod is provided with a fifth connecting hole 801 with its opening facing downward relative to the horizontal installation direction of the side expansion sleeve 7. One end of the main busbar 9 is inserted into the fifth connecting hole 801 of one of the conductive rods 8 from below and locked by a connector 13. The other end of the main busbar 9 is inserted into the fifth connecting hole 801 of another conductive rod 8 from below and locked by a connector 13. By providing the fifth connecting hole 801 on the conductive rod 8 with its opening facing downward, the main busbar 9 can be inserted into and locked from below by the connector 13. In this way, when installing the main busbar 9 on the side expansion sleeve 7, it will not be restricted by the installation space between the two side expansion sleeves 7.

[0100] Because it uses a bottom-insertion locking method, workers do not need to perform complex operations in confined spaces. They can simply insert and lock the connector 13, simplifying the installation process and improving efficiency. On the other hand, it facilitates the design of smaller ring main units, and even with limited space on both sides, it does not affect the effective installation between the main busbar 9 and the side expansion sleeve 7.

[0101] Furthermore, the insulating partition 71 encloses a uniform electric field cavity 701, which provides electrical isolation for the electrical connection structure within the cavity. Essentially, the uniform electric field cavity 701 formed by the insulating partition 71 isolates the overlap between the conductive rod 8 and the main busbar 9 from external electrical interference, thus preventing external electrical interference from affecting the electrical connection and preventing electrical leakage at the connection point between the conductive rod 8 and the main busbar 9. This improves the insulation strength of the electrical connection structure of the main busbar 9. In this way, while reducing the overall size of the ring main unit, the uniformity of the electric field and the interphase insulation strength are improved to meet the corresponding insulation performance requirements of small ring main units.

[0102] The insulating partition 71 can be made of an insulating material. For example, the insulating material used for the insulating partition 71 can be epoxy resin. The insulating partition 71 can be designed to be integrally cast with the second outer sleeve 72 using epoxy resin.

[0103] Please refer to Figure 18. The insulating partition 71 is formed by two oppositely arranged partitions and a third partition connecting the two oppositely arranged partitions. The two oppositely arranged partitions are located on both sides of the overlap between the main busbar 9 and the conductive rod 8. The electrical connection structure between the main busbar 9 and the conductive rod 8 arranged adjacent to each other on the same side can be separated by the insulating partition 71, further increasing the interphase insulation strength.

[0104] The connection between the shielding surfaces 702 of the insulating partition 71 is a rounded transition. In this way, the rounded transition between the shielding surfaces 702 can reduce the abrupt change of the electric field at the connection of the shielding surfaces 702, so that the electric field distribution is more uniform and the electric field is not too concentrated at the connection of the shielding surfaces 702 of the insulating partition 71. This can improve the electrical insulation performance of the main busbar 9 and the ring main unit in the uniform electric field cavity 701.

[0105] Please refer to Figures 18 and 19. The top outer surface of the second end 82 of the conductive rod is set as an arc surface 803.

[0106] As shown in Figure 19, the top outer surface of the second end 82 of the conductive rod, which is also the surface of the end of the conductive rod 8, is set as an arc surface 803. This allows the electric field to transition smoothly on the end surface of the conductive rod 8, thereby reducing electric field concentration and making the electric field distribution more uniform. Moreover, the arc surface also has better electrical insulation properties, making it less prone to charge accumulation, thus optimizing the electric field distribution at the electrical connection between the side expansion sleeve 7 and the conductive rod 8.

[0107] As shown in Figures 16 and 19, a cut surface 802 is formed on the circumferential sidewall of the second end 82 of the conductive rod. The cut surface 802 is used to fit against the main busbar 9 when it is installed, and the fifth connecting hole 801 is located at the cut surface 802. In this way, when the main busbar 9 is installed, the cut surface 802 can fit tightly against the main busbar 9, which not only increases the contact area and improves the efficiency of current transmission, but also reduces the risk of electrical faults caused by poor contact. Moreover, after the main busbar 9 is assembled at the cut surface 802 and locked with the conductive rod 8, it can avoid the connection structure between the main busbar 9 and the conductive rod 8 being too thin, and more effectively reduce the occurrence of electric field concentration at the tip of the main busbar 9.

[0108] The fifth connecting hole 801 provided on the second end 82 of the conductive rod is configured as a blind hole so that the end of the connector 13 is covered inside the conductive rod 8, and the part after the other end of the connector 13 passes through the fifth connecting hole 801 and passes through the conductive rod 8 forms a sharp electric field concentration.

[0109] Please refer to Figures 3, 4, and 20. The ring main unit also includes a three-position switch 3 installed in the gas box 100 and a three-position operating mechanism 4 installed in the mechanism room 300. The three-position switch 3 includes a grounding contact base 31, a plurality of grounding contacts 32 and a grounding shield base 33 installed on the grounding contact base 31, as well as an isolating stationary contact 34, a moving contact base 35, and a moving contact 36 rotatably installed on the moving contact base 35.

[0110] Among them, there are three grounding contacts 32, three isolating stationary contacts 34 and three moving contacts 36, which correspond to the three phases in the power supply network respectively.

[0111] As shown in Figure 20, the three-position operating mechanism 4 is connected to the moving contact 36 of the three-position switch 3. Under the drive of the three-position operating mechanism 4, the moving contact 36 can be selectively connected to the isolating stationary contact 34 or the grounding contact 32 by rotation.

[0112] The three-position switch 3 includes three working states: the closed position where the moving contact 36 is connected to the disconnector, that is, the moving contact 36 is electrically connected to the isolating stationary contact 34; the grounding position where the moving contact 36 is electrically connected to the grounding contact 32; and the isolation position where the main break is separated, that is, the moving contact 36 is not connected to either the isolating stationary contact 34 or the grounding contact 32.

[0113] As shown in Figure 21, the grounding contact seat 31 is mounted on the fixed frame 1, and the grounding shield seat 33 covers the grounding contact seat 31. The three grounding contacts 32 are located within the shielding space 301 formed between the grounding shield seat 33 and the grounding contact seat 31. The grounding shield seat 33 is configured as an integrally formed metal part, and the grounding shield seat 33 has multiple openings 302 corresponding to the multiple grounding contacts 32 to expose each grounding contact 32.

[0114] The grounding shield 33 is made of conductive metal. By uniformly wrapping the three-phase grounding contacts 32 with the same metal piece, the electric field distribution of the grounding contacts 32 can be evenly distributed, reducing the risk of excessive local electric field. Moreover, the metal material of the grounding shield 33 can provide good electromagnetic shielding for the grounding contacts 32, reducing the risk of electric field diffusion during the electrical connection between the moving contact 36 and the grounding contact 32, which is beneficial to the electrical stability of the three-position switch 3.

[0115] Furthermore, compared to the separate shielding of the single-phase grounding contact 32 in related technologies, the integrated metal shielding base 33 reduces manufacturing and installation costs and eliminates assembly and welding processes. Traditional separate shielding of single phases may increase the risk of electrical faults due to assembly or connection issues; the integrated design of the grounding shielding base 33 reduces this risk and improves the insulation performance and reliability of the three-position switch 3. Considering the overall size of the three-position switch 3, the integrated grounding shielding base 33 can more compactly enclose the grounding contact 32, which helps reduce the overall size of the three-position switch 3, making the structure more compact and suitable for small-sized ring main units.

[0116] For example, the grounding shield 33 can be made of one piece of sheet metal.

[0117] Please refer to Figure 21. The grounding shield 33 is an arched plate formed by bending a metal part. The arched plate and the grounding contact seat 31 enclose a shielding space 301. The grounding contacts 32 are spaced apart within the shielding space 301, and each grounding contact 32 is exposed through an opening 302 in the arched plate. The arched plate is formed by bending a metal part, and the manufacturing process of the grounding shield 33 is relatively simple and the cost is low.

[0118] As shown in Figures 4 and 12, each isolating stationary contact 34 is located in the second shielding cavity 205 of the corresponding stationary end shielding seat 213. The stationary end shielding seat 213 can provide electrical isolation for the isolating stationary contact 34, thereby isolating the electric field between the three phases of the circuit breaker and improving the insulation performance.

[0119] As shown in Figure 20, the moving contact 36 includes a middle portion and a first end and a second end located at both ends of the middle portion. The middle portion 361 of the moving contact is disposed between the first end 362 and the second end 363 of the moving contact. The first end 362 of the moving contact is rotatably mounted on the moving contact seat 35, and the second end 363 of the moving contact is used for selective electrical connection with the grounding contact 32 or the isolating stationary contact 34. The middle portion is used for transmission connection with the three-position operating mechanism 4.

[0120] The three-position switch 3 also includes a connecting crank arm 37 and a second input shaft 38. The two ends of the connecting crank arm 37 are respectively connected between the middle part of the moving contact 36 and the three-position operating mechanism 4.

[0121] The second input shaft 38 is dynamically sealed at the connection between the air box 100 and the mechanism chamber 300. This improves the sealing performance of the air box 100, thereby reducing the risk of gas leakage at the transmission connection between the three-position switch 3 and the three-position operating mechanism 4.

[0122] Specifically, driven by the three-position operating mechanism 4, the second input shaft 38 can rotate around its axis. For example, if the second input shaft 38 rotates clockwise around its axis, it will drive the connecting crank arm 37 and the moving contact 36 connected to the connecting crank arm 37 to rotate clockwise. The second end 363 of the moving contact can rotate clockwise to the grounding shield 33 and extend into the shielding space 301 through the opening 302 of the grounding shield 33, connecting with the grounding contact 32 located in the shielding space 301. If the second end 363 of the moving contact rotates counterclockwise, it can rotate to the bottom of the stationary shield 213 and extend into the second shielding cavity 205 through the second opening 208 of the stationary shield 213, connecting with the isolating stationary contact 34 located in the second shielding cavity 205. Thus, the three-position switch 3 disclosed in this application can optimize the electric field at the electrical connection positions of the moving contact 36, the grounding contact 32, and the isolating stationary contact 34, thereby reducing the risk of electric field interference between multiple phases or other external electromagnetic field interference, and thus improving the insulation level of the three-position switch 3.

[0123] As shown in Figure 20, a first shielding cover 5 is provided at the connection between the first end 362 of each moving contact and the moving contact base 35, so that the first end 362 of the moving contact is located within the space enclosed by the first shielding cover 5, thereby improving the electric field distribution at the first end of the moving contact 36.

[0124] The second end 363 of the moving contact is provided with a second shield 6. The second shield 6 is used to uniform the electric field of the second end, and the second shield 6 can extend into the stationary end shield 213 or the grounding shield 33 as the second end rotates.

[0125] Please refer to Figures 1 and 22. The ring main unit also includes an outgoing sleeve 11, which is located below the three-position switch 3. The outgoing sleeve 11 includes a first outer sleeve 111 and an outgoing conductive end 112 disposed within the first outer sleeve 111. One end of the first outer sleeve 111 is connected to the side wall of the ring main unit's gas box 100.

[0126] Please refer to Figures 4 and 22. The ring main unit also includes a copper rod 12. One end of the copper rod 12 is electrically connected to the moving contact 36, and the other end of the copper rod 12 is connected to the outgoing conductive terminal 112. The connection between the copper rod 12 and the outgoing conductive terminal 112 is located inside the first outer sleeve 111. As shown in Figure 3, the first outer sleeve 111 can wrap the electrical connection between the copper rod 12 and the outgoing conductive terminal 112, thereby forming a physical barrier at the electrical connection between the two and playing a role in electrical isolation.

[0127] In this application, the electric field distribution is optimized at locations where electric field accumulation may occur in the circuit breaker switch 2 and the three-position switch 3, in order to meet the insulation performance requirements of a small-sized ring main unit filled with dry air as the insulating gas. In the circuit breaker switch 2, the solid-sealed pole 21 is integrally formed by casting the pole body 211, the moving end shielding seat 212, and the stationary end shielding seat 213 at both ends of the pole body 211 with insulating resin. The transmission crank arm 222 is connected to the moving end shielding seat 212 through the crank arm shaft 224, avoiding the need for connection holes in the pole body 211. This maintains the consistency of the solid-sealed pole 21 and effectively improves the insulation performance of the circuit breaker switch 2. By uniformly wrapping the grounding contact 32 in the three-position switch 3 within the shielding space 301 formed by the grounding shielding seat 33 and the grounding contact seat 31, the electric field distribution of the grounding contact 32 can be uniformly distributed, reducing the risk of excessive local electric field. Moreover, the integrally formed grounding shielding seat 33 can more compactly wrap the grounding contact 32 and reduce the size of the three-position switch 3. Furthermore, the electric field is also optimized at the incoming and outgoing ends of the ring main unit. At the incoming end of the ring main unit, the main busbar 9 and the side expansion bushing 7 are fastened together by connecting them vertically. This facilitates the design of a smaller ring main unit, ensuring effective installation between the main busbar 9 and the side expansion bushing 7 even with limited space on both sides. Furthermore, the electric field at the electrical connection between the main busbar 9 and the side expansion bushing 7 is optimized to further improve the insulation performance at this connection. At the outgoing end of the ring main unit, the electrical connection between the copper rod 12 and the outgoing conductive end 112 is wrapped to uniformly distribute the electric field at the connection. Through these structural improvements, the size of the ring main unit is reduced while still meeting the insulation requirements for filling the ring main unit with dry air as the insulating gas. The depth of the ring main unit disclosed in this invention can be reduced to 865mm, the width to 450mm, and the height to 1800mm. Compared to traditional ring main units with a depth of over 900mm and a width of over 550mm, the size of the ring main unit disclosed herein is significantly reduced, and the use of dry air in the air box 100 is also more environmentally friendly.

[0128] It is understood that those skilled in the art can make equivalent substitutions or changes based on the technical solutions and inventive concepts of this disclosure, and all such changes or substitutions should fall within the protection scope of this disclosure.

Claims

1. A ring main unit, comprising: An air chamber, wherein the air chamber is filled with dry air; A fixed frame is fixed to the inner wall of the air box; A circuit breaker switch, wherein the circuit breaker switch is mounted on the fixed frame, and comprises: A sealed pole includes a pole body and a moving end shield and a stationary end shield located at both ends of the pole body. The pole body is fixed to the fixed frame. The pole body, the moving end shield and the stationary end shield are formed into a whole by casting insulating resin. A three-position switch is mounted on the fixed frame. The circuit breaker switch is arranged on the upper layer of the fixed frame, and the three-position switch is arranged on the middle layer of the fixed frame. The three-position switch includes: The system includes a grounding contact base, multiple grounding contacts mounted on the grounding contact base, and a grounding shield. The grounding contact base is mounted on the fixed frame, and the grounding shield covers the grounding contact base. The multiple grounding contacts are located within a shielding space formed between the grounding shield and the grounding contact base. The grounding shield is configured as an integrally formed metal part, and the grounding shield has multiple openings corresponding to the multiple grounding contacts to expose each grounding contact.

2. The ring main unit according to claim 1, wherein, The ring main unit has a width of 450mm, a depth of 865mm, and a height of 1800mm.

3. The ring main unit according to claim 1 or 2, wherein, Two protrusions are formed on the moving end shielding seat. The protrusions are located in the first shielding cavity of the moving end shielding seat. The two protrusions are provided with first connecting holes. The circuit breaker switch further includes a moving terminal of the pole, which includes a moving conductive rod, one end of which passes through the moving terminal shield and extends into the vacuum interrupter chamber of the pole body; and A transmission crank arm includes a middle part and a first end and a second end located at both ends of the middle part, and the other end of the moving conductive rod is connected to the first end of the transmission crank arm. as well as An insulating pull rod is connected to the second end of the transmission crank arm; as well as A crank arm shaft passes through the middle part of the transmission crank arm, and the axial ends of the crank arm shaft extending to the outside of the transmission crank arm are inserted into the two first connecting holes of the moving end shield seat and locked by a connector.

4. The ring main unit according to claim 3, wherein, The moving end of the pole post also includes a transmission pin and a connecting cover plate. The transmission pin and the connecting cover plate are both located in the first shielding cavity of the moving end shielding seat. The transmission pin passes through the first end of the transmission crank arm. The other end of the moving conductive rod is provided with a first groove with the opening facing upward. The transmission pin is installed in the moving conductive rod through the first groove. The connecting cover plate is placed above the first groove and connected to the moving conductive rod, so that the transmission pin is limited to the first groove.

5. The ring main unit according to claim 3, wherein, The circuit breaker switch also includes a circuit breaker operating mechanism, and the ring main unit is also provided with a mechanism chamber. The circuit breaker operating mechanism is located in the mechanism chamber. The circuit breaker switch also includes a first input shaft, which is connected to the insulating pull rod for transmission, so as to drive the moving conductive rod to move in the vacuum interrupter chamber under the drive of the circuit breaker operating mechanism. The first input shaft dynamic seal is installed at the connection between the air box and the mechanism chamber.

6. The ring main unit according to claim 3, wherein, The moving end shielding seat is located at the moving end of the pole body. The moving end shielding seat is provided with a first shielding cavity and a first opening. The protruding post, the moving conductive rod and the crank arm shaft are located in the first shielding cavity. The transmission crank arm extends into the first shielding cavity through the first opening. The stationary shielding base is located at the stationary end of the pole body. The stationary shielding base is provided with a second shielding cavity and a second opening. The three-position switch also includes an isolating stationary contact, a moving contact base, and a moving contact rotatably disposed on the moving contact base. The isolating stationary contact is located in the second shielding cavity. The moving contact can rotate relative to the moving contact base to selectively engage with the isolating stationary contact or the grounding contact.

7. The ring main unit according to claim 6, wherein, The surface of the pole body is provided with a first insulating plate protruding from the surface. The first opening and the second opening are both located on the same side of the pole body. The first insulating plate is located on the side where the circuit breaker operating mechanism is connected to the crank arm shaft drive. The first insulating plate is disposed between the moving end shielding seat and the stationary end shielding seat. The first insulating plate is integrally connected to the pole body by the insulating resin.

8. The ring main unit according to claim 6, wherein, The moving contact includes a middle portion and a first end and a second end located at both ends of the middle portion. The first end of the moving contact is rotatably connected to the moving contact seat, and the second end of the moving contact is used to selectively connect to the grounding contact or the isolating stationary contact. The three-position switch also includes a connecting crank arm and a second input shaft. The ring main unit also includes a three-position operating mechanism installed in the mechanism chamber. The two ends of the connecting crank arm are respectively connected between the middle part of the moving contact and the three-position operating mechanism. The second input shaft is dynamically sealed at the connection between the air box and the mechanism chamber.

9. The ring main unit according to claim 1 or 2, wherein, The circuit breaker switch also includes a flexible connection. One end of the flexible connection is connected to the pole body through a fixing member. The connection point between the flexible connection and the pole body is located in the first shielding cavity of the moving end shielding seat. The moving end shielding seat has a third opening above it that communicates with the first shielding cavity. The other end of the flexible connection extends upward through the third opening to connect to the conductive circuit.

10. The ring main unit according to claim 9, wherein, The gas box also includes: The two side expansion sleeves are respectively installed on the two side walls of the gas box and located above the solid sealing pole. A conductive rod is inserted inside the side expansion sleeve. The conductive rod includes a first end and a second end arranged along the axial direction. The first end of the conductive rod is used to connect with the bus coupler. The main busbar has its two ends electrically connected to the second ends of the conductive rods on both sides to form the conductive circuit; A branch copper busbar is connected between the flexible connection and the main busbar; The side-expanding sleeve is provided with a uniform electric field cavity, which is enclosed by an insulating partition. The second end of the conductive rod extends into the uniform electric field cavity. The second end of the conductive rod is provided with a fifth connecting hole with its opening facing downward relative to the horizontal installation direction of the side-expanding sleeve. One end of the main busbar is locked from below by inserting a connector into the fifth connecting hole of one of the conductive rods. The other end of the main busbar is locked from below by inserting a connector into the fifth connecting hole of the other conductive rod.

11. The ring main unit according to claim 10, wherein, The top outer surface of the second end of the conductive rod is set as an arc surface; and / or A cut surface is formed on the circumferential sidewall of the second end of the conductive rod. The cut surface is used to fit against the main busbar when the main busbar is installed. The fifth connecting hole is located at the cut surface.

12. The ring main unit according to claim 10, wherein, The insulating partition is disposed on one end face of the side expansion sleeve facing the other side expansion sleeve. The insulating partition includes three shielding surfaces, which enclose the uniform electric field cavity. The end face of the side expansion sleeve and the three shielding surfaces form four faces of a hexahedron structure. The other two faces of the hexahedron structure are open. One of the open faces faces downward of the side expansion sleeve and is opposite to the solid-sealing pole. The fifth connecting hole faces the open face.

13. The ring main unit according to claim 1 or 26, wherein, Also includes: The outgoing sleeve is located below the three-position switch. The outgoing sleeve includes a first outer sleeve and an outgoing conductive end disposed inside the first outer sleeve. as well as A copper rod, one end of which is electrically connected to the moving contact, and the other end of which is connected to the outgoing conductive end, with the connection point between the copper rod and the outgoing conductive end located inside the first outer sleeve.

14. The ring main unit according to claim 1 or 2, wherein, The pole body is also provided with a fixing insert, which is connected between the pole body and the fixing frame. The fixing insert and the pole body are connected as one piece by casting with insulating resin. The fixed inserts include three, and the positions of the three fixed inserts form the three vertices of a triangle.

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