breaker

Abstract

This utility model provides a circuit breaker, including a plurality of parallel arc-extinguishing grid plates, a moving contact assembly, and a stationary contact assembly. The moving contact assembly has a pivot end and a free end. The free end includes a guide flange and a moving contact. The guide flange has an axis along its extension direction. Along its outer periphery, the guide flange is sequentially provided with a joint portion engaging with the moving contact, a first straight portion, a plurality of arc portions including at least a first arc portion and a second arc portion, and a second straight portion. The diameter of the first arc portion is larger than the diameter of the second arc portion, and the first arc portion extends through the axis. The first straight portion and the second straight portion are opposite to each other and extend along the axis. The stationary contact assembly includes a stationary contact and an arc-inducing portion disposed on a first arm. The arc-inducing portion extends from the first arm and is parallel to the plurality of arc-extinguishing grid plates.

Description

Technical Field

[0001] This utility model belongs to the field of circuit breaker technology, and in particular relates to a high-voltage, high-current circuit breaker. Background Technology

[0002] The statements in this section are merely to provide background information related to this utility model to aid in understanding it, and this background information does not necessarily constitute prior art.

[0003] In modern power systems, circuit breakers, as a key electrical protection device, control the opening and closing of circuits to provide protection, control, and monitoring functions for the power system. They are widely used in industrial and civil power systems. The working principle of a circuit breaker is based on a system of operable contacts. Under normal operation, the moving and stationary contact assemblies close to conduct the circuit, maintaining normal power supply. When abnormal conditions such as overload or short circuit occur, the circuit breaker can quickly detect the abnormal current signal and trigger the tripping mechanism, causing the moving and stationary contact assemblies to quickly separate, interrupting the fault current and thus preventing damage to electrical equipment and safety accidents such as fires.

[0004] However, despite the irreplaceable role of circuit breakers in the stable operation of modern power systems, there are still areas that need improvement to further enhance their performance and reliability. Utility Model Content

[0005] The purpose of this utility model is to provide a circuit breaker, comprising:

[0006] Multiple parallel arc-extinguishing grid plates, moving contact assemblies, and stationary contact assemblies, wherein:

[0007] The moving contact assembly has a pivot end and a free end. The free end includes a guide flange distal to the free end and a moving contact proximal to the free end. The guide flange has an axis along its extension direction. The guide flange is provided with a joint portion that engages with the moving contact, a first straight portion, a plurality of arc portions including at least a first arc portion and a second arc portion, and a second straight portion in sequence along its outer circumferential direction. The diameter of the first arc portion is larger than the diameter of the second arc portion, and the first arc portion extends through the axis. The first straight portion and the second straight portion are opposite to each other and extend along the axis.

[0008] The stationary contact assembly includes a stationary contact and an arc-inducing portion disposed on a first arm, the arc-inducing portion extending out from the first arm and parallel to the plurality of arc-extinguishing grid plates.

[0009] According to the circuit breaker of this utility model, preferably, the angle between the first straight portion and the second straight portion and the axis is less than 15 degrees.

[0010] According to the circuit breaker of this utility model, preferably, the diameter of the first arc portion is 1.5-3 times the diameter of the second arc portion.

[0011] According to the circuit breaker of this utility model, preferably, the engagement portion engages with the moving contact on a first side surface of the moving contact.

[0012] According to the circuit breaker of this utility model, preferably, there is an inclined connecting portion between the pivot end and the free end, the connecting portion having a second axis, the angle between the second axis and the axis being between 135 degrees and 165 degrees.

[0013] According to the circuit breaker of the present invention, preferably, the first arm portion includes a first planar portion and a first inclined portion; wherein, the first inclined portion is connected to the first planar portion and extends at a specified acute angle of inclination along a direction away from the moving contact assembly, and at least a portion of the stationary contact and the arc-starting portion are disposed on the surface of the first inclined portion.

[0014] According to the circuit breaker of this utility model, preferably, the tilt angle is between 5 degrees and 15 degrees.

[0015] According to the circuit breaker of this utility model, preferably, the stationary contact further includes a second arm and a support portion connected between the first arm and the second arm, wherein the first arm and the second arm are on the same side of the support portion and the height of the first arm relative to the support portion is greater than the height of the second arm relative to the support portion.

[0016] According to the circuit breaker of the present invention, preferably, each of the plurality of arc-extinguishing grids has a first guide portion and a second guide portion with different shapes, and a guide groove is provided between the first guide portion and the second guide portion. The arc-extinguishing grid has a first surface and a second surface, and the plurality of arc-extinguishing grids are arranged along the stacking direction such that the first surface or the second surface of two adjacent arc-extinguishing grids are opposite to each other.

[0017] According to the circuit breaker of this utility model, preferably, the plurality of arc-extinguishing grids include a first arc-extinguishing grid adjacent to the stationary contact assembly and a second arc-extinguishing grid adjacent thereto, and the minimum distance between the second arc-extinguishing grid and the guide flange is greater than the minimum distance between the first arc-extinguishing grid and the guide flange.

[0018] This utility model provides a circuit breaker that optimizes the structure of the moving contact assembly and the stationary contact assembly, adopts an asymmetrical arc-extinguishing grid arrangement and differentiates the spacing of the arc-extinguishing grids, and expands the arc-extinguishing space with a first arm having an inclined portion to increase the number of arc-extinguishing grids. This makes the arc movement path more reasonable and efficient, significantly increases the arc voltage, effectively disperses arc energy and reduces arc temperature, and ultimately greatly improves arc extinguishing efficiency. This enhances the reliability and stability of the contact system when breaking fault circuits and ensures stable operation of the circuit breaker under high load conditions. Attached Figure Description

[0019] The embodiments of this utility model will be further described below with reference to the accompanying drawings, wherein:

[0020] Figure 1 A schematic diagram of the structure of a circuit breaker according to an embodiment of the present invention is shown;

[0021] Figure 2 A schematic diagram of the moving contact assembly of a circuit breaker according to an embodiment of the present invention is shown;

[0022] Figure 3 A schematic diagram of the stationary contact assembly of a circuit breaker according to an embodiment of the present invention is shown;

[0023] Figure 4 A schematic diagram of the arc-extinguishing grid of a circuit breaker according to an embodiment of the present invention is shown. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates this application. It should be understood that the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0025] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

[0026] With the rapid development of technology and the booming rise of emerging industries, such as ultra-high voltage power transmission and new energy storage power stations, the demand for electricity continues to climb, and the operating voltage and current of electrical equipment are constantly increasing. This poses unprecedented challenges to the performance and reliability of circuit breakers. Especially under high voltage and high current conditions, a series of interrelated problems will arise when the circuit breaker breaks the circuit.

[0027] From the perspective of the arc generation mechanism, a strong arc will be formed at the moment of high voltage (e.g., 690V and higher), which will cause the arc to be more obstructed when it enters the arc extinguishing grid in the arc extinguishing device, and may even result in the arc not being able to enter some of the arc extinguishing grids, thus leading to a low arc voltage. Insufficient arc voltage will directly cause the arc to be difficult to extinguish quickly, thereby prolonging the arc burning time.

[0028] Meanwhile, the high temperature and energy generated by the electric arc will cause severe ablation of the moving contacts in the moving contact assembly. Although the moving contacts have good conductivity and resistance to arc burn-off, the material will be rapidly worn away under the continuous impact of the high-energy arc, and the increased contact resistance after the surface is eroded will further affect its conductivity; if the burn-off is aggravated, the moving contacts may even undergo contact welding, causing the circuit breaker to lose its breaking capacity.

[0029] Furthermore, prolonged arcing not only increases the thermal damage to internal components of the circuit breaker caused by the arc, but also leads to the continuous accumulation of arc energy, which in turn further worsens the burning of moving contacts and exacerbates the instability of arc voltage. These interacting problems create a vicious cycle, increasing the risk of circuit breaker failure and severely affecting its reliability and service life. If not addressed in a timely manner, this will hinder the safe and stable operation of the power system and the sustainable development of the industry.

[0030] Therefore, considering the aforementioned challenges faced by existing circuit breakers under high-voltage and high-current conditions, this invention provides an innovative circuit breaker by optimizing and improving core components such as the moving contact assembly, stationary contact assembly, and arc-extinguishing device. Furthermore, experimental verification has shown that the circuit breaker provided by this application has significantly enhanced breaking capacity and can be stably applied to overload and short-circuit protection scenarios for high-voltage and high-current electrical equipment such as ultra-high-voltage power transmission lines and new energy storage power stations, providing a solid guarantee for the reliable operation of the power system.

[0031] Figure 1 A schematic diagram of the structure of a circuit breaker according to an embodiment of the present invention is shown. Figure 1 As shown, the circuit breaker 100 includes a plurality of arc-extinguishing grid plates 12 parallel to each other, a moving contact assembly 10, and a stationary contact assembly 11, etc. The moving contact assembly 10 and the stationary contact assembly 11 each have at least a partially conductive portion to conduct current between them.

[0032] Figure 2 A schematic diagram of the stationary contact assembly of a circuit breaker according to an embodiment of the present invention is shown. Figure 2 As shown, the moving contact assembly 10 has a pivot end 101, a free end 102, and a connecting portion 103 connecting the pivot end 101 and the free end 102. The pivot end 101 can be rotatably or movably connected to the housing or base of the circuit breaker 100 via an insulating support. The free end 102 includes a guide flange 1021 distal to the free end 102 and a moving contact 1022 proximal to the free end 102. The guide flange 1021 has an axis D1 along its extending direction, and the guide flange 1021 is provided sequentially along its outer circumference with a joining portion L1 that engages with the moving contact 1022, a first straight portion L2, a plurality of arcuate portions including at least a first arcuate portion L3 and a second arcuate portion L4, and a second straight portion L5. The diameter R1 of the first arcuate portion L3 is larger than the diameter R2 of the second arcuate portion L4, and the first arcuate portion L3 extends through the axis D1. The first straight portion L2 and the second straight portion L5 are opposite to each other and extend along the axis D1.

[0033] Figure 3 A schematic diagram of the stationary contact assembly of a circuit breaker according to an embodiment of the present invention is shown. Figure 3 As shown, the stationary contact assembly 11 includes a first arm 111, a second arm 112, a support portion 113 connecting the first arm 111 and the second arm 112, and a stationary contact 114 and an arc-starting portion 115 disposed on the first arm 111. The first arm 111 and the second arm 112 are on the same side of the support portion 113. Furthermore, as... Figure 1 As shown, the arc-inducing portion 115 extends from the first arm portion 111 and is parallel to the plurality of arc-extinguishing grid plates 12.

[0034] When an overload or short circuit occurs in the circuit, the circuit breaker 100 can quickly detect the abnormal current signal and trigger the moving contact assembly 10 and the stationary contact assembly 11 to quickly separate, cutting off the faulty circuit. During the process of the moving contact assembly 10 and the stationary contact assembly 11 disconnecting the faulty circuit, when the moving contact 1022 separates from the stationary contact 114, the high voltage between the contacts breaks down the air, generating an electric arc. If the high temperature of the arc (reaching several thousand degrees Celsius) continues to act on the moving contact 1022, it will cause the contact material to evaporate and erode rapidly, seriously affecting the service life and breaking performance of the moving contact.

[0035] According to the circuit breaker 100 of this utility model, by optimizing and improving the moving contact assembly 10, an efficient arc transfer and arc extinguishing path is provided.

[0036] First, after the electric arc is generated, based on the arc's own "skin effect" and electromagnetic force, it will preferentially transfer to the first straight section L2 through the junction of the moving contact 1022 and the junction L1. The first straight section L2 adopts a short-distance smooth transition design, and its low impedance characteristics can effectively reduce the energy loss of the arc during the transfer process, so that the arc can be guided to the first circular section L3 with minimal resistance.

[0037] The design of the first arc section L3 and the second arc section L4 is a crucial component of the entire arc-extinguishing system. Specifically, the diameter R1 of the first arc section L3 is larger than the diameter R2 of the second arc section L4, and its extension path passes through the axis D1. This geometric design utilizes the stretching and cooling characteristics of the electric arc: when the arc enters the first arc section L3, the larger radius of curvature increases the arc stretching length, directly increasing the arc gap; based on the positive correlation between arc voltage and arc length, the increase in arc gap significantly increases the arc voltage, making it more difficult to maintain arc combustion. Simultaneously, the larger arc diameter increases the arc diffusion angle (i.e., the arc initiation angle), forming a funnel-like expansion shape that guides the arc to accelerate along the expansion direction, effectively dispersing arc energy and reducing local temperature.

[0038] When the electric arc enters the second arc section L4 from the first arc section L3, the smaller diameter R2 and shorter arc length create a "contraction effect." This structure forces the arc to climb upwards within a limited space. Combined with the guiding design of the second straight section L5, the arc is precisely guided into the array of multiple arc-extinguishing grid plates 12. The arc-extinguishing grid plates 12 are typically made of highly magnetically and thermally conductive materials. When the arc enters the gap between the grid plates, it is divided into multiple short arcs. Utilizing the near-cathode effect and the heat dissipation of the grid plates, the arc voltage rises sharply and the arc temperature drops rapidly, ultimately achieving rapid arc extinguishing, significantly improving arc extinguishing efficiency, and ensuring reliable disconnection of the contact system.

[0039] In some embodiments of this utility model, preferably, the diameter of the first arc portion L3 is 1.5-3 times the diameter of the second arc portion L4.

[0040] In some embodiments of this utility model, the joint L1 and the moving contact 1022 can be joined on the first side surface P1 of the moving contact 1022, so that the joint L1 partially wraps around the moving contact 1022 to form protection for it, thereby reducing the ablation of the moving contact 1022 by the electric arc.

[0041] In some embodiments of this invention, the angle between the first straight section L2 and the second straight section L5 and the axis is less than 15 degrees, which is more conducive to the diffusion and extinguishing of the electric arc.

[0042] In some embodiments of this utility model, preferably, the length of the first straight section L2 is less than the length of the second straight section L5.

[0043] In some embodiments of this utility model, preferably, the first straight section L2 is tangent to the first circular arc section L3.

[0044] In some embodiments of this utility model, preferably, the second straight portion L5 is tangent to the second circular arc portion L4.

[0045] In some embodiments of this utility model, preferably, the guide flange 1021 may have multiple arcuate portions.

[0046] Through the above improvements, the embodiments of this utility model can make the arc transfer path smoother and the resistance smaller, thereby accelerating the speed at which the arc enters the arc-extinguishing grid and improving the arc-extinguishing efficiency.

[0047] In some embodiments of this invention, an inclined connecting portion 103 is provided between the pivot end 101 and the free end 102. The connecting portion 103 has a second axis D2, and the angle θ1 between the second axis D2 and the axis D1 is an obtuse angle, preferably between 135 degrees and 165 degrees. Thus, the free end 102 tilts upward relative to the connecting portion 103, thereby increasing the arc gap.

[0048] In some embodiments of the present invention, the first arm portion 111 may include a first flat portion 1111 and a first inclined portion 1112; wherein, the first inclined portion 1112 is connected to the first flat portion 1111 and extends along a direction away from the moving contact assembly 10 at a specified acute angle of inclination θ2, and at least a portion of the stationary contact 114 and the arc-drawing portion 115 are disposed on the surface of the first inclined portion 1112.

[0049] Therefore, the tilt angle θ2 allows for a further increase in the arc-starting angle. A larger arc-starting angle allows the arc to diffuse towards the arc-extinguishing grid 12 at a greater angle, reducing arc deflection and energy loss in the path, thereby accelerating the arc's entry into the arc-extinguishing grid and improving arc-extinguishing efficiency. Simultaneously, the first tilted portion 1112 also optimizes space utilization. Its tilted extension expands the space between the arc-starting portion 115 and the multiple arc-extinguishing grids 12, allowing for the inclusion of more arc-extinguishing grids (e.g., from 9 to 11). More arc-extinguishing grids mean the arc will be divided into more short arcs. According to the short-arc extinguishing theory, increasing the number of short arcs significantly enhances the near-cathode effect, while also improving the grid's heat dissipation capacity, further increasing the arc voltage and accelerating the arc temperature drop, ultimately resulting in a significant increase in arc-extinguishing speed and effectively ensuring the reliability and stability of the contact system during fault disconnection.

[0050] In some embodiments of this utility model, preferably, the tilt angle θ2 is between 5 degrees and 15 degrees.

[0051] In some embodiments of this utility model, such as Figure 1 and Figure 3 As shown, the height of the first arm 111 of the stationary contact assembly 11 relative to the support 113 is greater than the height of the second arm 112 relative to the support 113. This design allows for a more ample longitudinal space in the arc-extinguishing region, enabling the installation of more arc-extinguishing grids.

[0052] Figure 4 A schematic diagram of the arc-extinguishing grid of a circuit breaker according to an embodiment of the present invention is shown. Figure 4 As shown, in some embodiments of this utility model, the arc-extinguishing grid 12 has a first guide portion 1201 and a second guide portion 1202 with different shapes, and a guide groove 1203 is provided between the first guide portion 1201 and the second guide portion 1202. The arc-extinguishing grid 12 has a first surface (front) and a second surface (back). Multiple arc-extinguishing grids 12 are arranged along the stacking direction such that the first surface or second surface of two adjacent arc-extinguishing grids 12 are opposite to each other. That is, the arc-extinguishing grids 12 are not arranged in the same direction but are staggered. For example, the back side of the first arc-extinguishing grid is facing down and the front side is facing up. The front side of the second arc-extinguishing grid is opposite to or adjacent to the front side of the first arc-extinguishing grid, and the back side of the third arc-extinguishing grid is opposite to or adjacent to the back side of the second arc-extinguishing grid, and so on. Thus, multiple arc-extinguishing grids 12 can form an asymmetrical arrangement structure.

[0053] When the electric arc enters the region of asymmetrically arranged arc-extinguishing grid plates, it needs to constantly adapt to the changing electric field direction and spatial distance between the grid plates, making the arc's shape more complex and distorted. As the arc moves along this complex path, its length is further elongated. Based on the positive correlation between arc voltage and arc length, the arc voltage also increases significantly. Simultaneously, the asymmetrical structure diversifies the contact patterns between the arc and the grid plate surface, enhancing the grid plate's heat dissipation effect and the intensity of the near-cathode effect. Under the combined effect of these multiple factors, maintaining arc combustion becomes even more difficult, thus significantly improving arc-extinguishing efficiency and ensuring that the arc is quickly extinguished during circuit breaking, effectively protecting the contact system for safe and stable operation.

[0054] In some embodiments of this invention, the plurality of arc-extinguishing grid plates 12 include a first arc-extinguishing grid plate adjacent to the stationary contact assembly 11 and a second arc-extinguishing grid plate adjacent to the first arc-extinguishing grid plate, and the minimum distance between the second arc-extinguishing grid plate and the guide flange 1021 is greater than the minimum distance between the first arc-extinguishing grid plate 12 and the guide flange 1021. This layout design cleverly utilizes the motion characteristics of the electric arc during the breaking process.

[0055] When the arc transfers from the driven contact assembly 10 to the arc-extinguishing grid 12, the first arc-extinguishing grid, being closest to the guiding flange 1021, is able to utilize its strong magnetic field characteristics to attract the arc, quickly "capturing" it into the grid gap. At this point, the arc is initially divided into short arcs at the first arc-extinguishing grid, reducing the arc energy. Meanwhile, the second arc-extinguishing grid maintains a relatively greater distance from the guiding flange 1021, reducing the obstruction to the arc entering the arc-extinguishing grid array. This allows the arc to quickly enter the gap between the arc-extinguishing grids and be rapidly cut into short arcs, thus significantly improving the arc-extinguishing efficiency.

[0056] According to embodiments of this utility model, by optimizing the structure of the moving and stationary contact assemblies, adopting an asymmetric arrangement of arc-extinguishing grid plates and a differentiated spacing layout of the arc-extinguishing grid plates, and simultaneously expanding the space of the first arm with an inclined portion to increase the number of arc-extinguishing grid plates, the arc movement path becomes more reasonable and efficient, the arc voltage is significantly increased, thereby effectively dispersing arc energy and reducing arc temperature, ultimately greatly improving arc extinguishing efficiency, enhancing the reliability and stability of the contact system when breaking fault circuits, and ensuring stable operation of the circuit breaker under high voltage and high current conditions.

[0057] References to "various embodiments," "some embodiments," "one embodiment," or "embodiment," etc., in this specification refer to a specific feature, structure, or property described in connection with the said embodiment, included in at least one embodiment. Therefore, the appearance of the phrases "in various embodiments," "in some embodiments," "in one embodiment," or "in an embodiment," etc., throughout this specification does not necessarily refer to the same embodiment. Furthermore, specific features, structures, or properties can be combined in any suitable manner in one or more embodiments. Therefore, a specific feature, structure, or property shown or described in connection with one embodiment can be combined, in whole or in part, with features, structures, or properties of one or more other embodiments without limitation, provided that the combination is not illogical or inoperable.

[0058] The terms "comprising," "having," and similar expressions used in this specification are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses. Furthermore, the elements in the accompanying drawings are for illustrative purposes only and are not drawn to scale.

[0059] Although the present invention has been described through preferred embodiments, the present invention is not limited to the embodiments described herein, and includes various changes and variations without departing from the scope of the present invention.

Claims

1. A circuit breaker characterized by, It includes multiple parallel arc-extinguishing grid plates, a moving contact assembly, and a stationary contact assembly, wherein: The moving contact assembly has a pivot end and a free end. The free end includes a guide flange distal to the free end and a moving contact proximal to the free end. The guide flange has an axis along its extension direction. The guide flange is provided with a joint portion that engages with the moving contact, a first straight portion, a plurality of arc portions including at least a first arc portion and a second arc portion, and a second straight portion in sequence along its outer circumferential direction. The diameter of the first arc portion is larger than the diameter of the second arc portion, and the first arc portion extends through the axis. The first straight portion and the second straight portion are opposite to each other and extend along the axis. The stationary contact assembly includes a stationary contact and an arc-inducing portion disposed on a first arm, the arc-inducing portion extending out from the first arm and parallel to the plurality of arc-extinguishing grid plates.

2. The circuit breaker of claim 1, wherein, The angle between the first straight section and the second straight section and the axis is less than 15 degrees.

3. The circuit breaker of claim 1, wherein, The diameter of the first arc portion is 1.5 to 3 times the diameter of the second arc portion.

4. The circuit breaker according to claim 1, characterized in that, The engagement portion engages with the moving contact on the first side of the moving contact.

5. The circuit breaker of claim 1, wherein, The pivot end and the free end have an inclined connecting portion, the connecting portion having a second axis, the angle between the second axis and the axis being between 135 degrees and 165 degrees.

6. The circuit breaker of claim 1, wherein, The first arm portion includes a first planar portion and a first inclined portion; wherein the first inclined portion is connected to the first planar portion and extends at a specified acute angle of inclination in a direction away from the moving contact assembly, and at least a portion of the stationary contact and the arc-drawing portion are disposed on the surface of the first inclined portion.

7. The circuit breaker of claim 6, wherein, The tilt angle is between 5 and 15 degrees.

8. The circuit breaker of claim 1, wherein, The stationary contact further includes a second arm and a support portion connected between the first arm and the second arm, wherein the first arm and the second arm are on the same side of the support portion and the height of the first arm relative to the support portion is greater than the height of the second arm relative to the support portion.

9. The circuit breaker of claim 1, wherein, Each of the plurality of arc-extinguishing grids has a first guide portion and a second guide portion with different shapes, and a guide groove is provided between the first guide portion and the second guide portion. The arc-extinguishing grid has a first surface and a second surface. The plurality of arc-extinguishing grids are arranged along the stacking direction such that the first surface or the second surface of two adjacent arc-extinguishing grids are opposite to each other.

10. The circuit breaker of claim 1, wherein, The plurality of arc-extinguishing grids includes a first arc-extinguishing grid adjacent to the stationary contact assembly and a second arc-extinguishing grid adjacent to it, and the minimum distance between the second arc-extinguishing grid and the guide flange is greater than the minimum distance between the first arc-extinguishing grid and the guide flange.

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