Electric appliance switch arc extinguishing system

Abstract

The utility model discloses an electric appliance switch arc extinguishing system, which belongs to the technical field of electric appliance equipment, and comprises an arc extinguishing grid sheet group and an arc guide piece, the arc extinguishing grid sheet group comprises arc extinguishing grid sheets which are arranged at intervals in the thickness direction, the arc outlet sides of the arc extinguishing grid sheets are arranged at intervals, and arc extinguishing grid sheet gaps are arranged between adjacent arc extinguishing grid sheets; the arc guiding piece comprises inserting structures, the arc inlet sides of the inserting structures are arranged at intervals in the long-short direction, the end faces of the inserting structures are attached to the end faces of the arc extinguishing grid pieces, air guiding openings are formed between the adjacent inserting structures, and the air guiding openings correspond to the gaps of the arc extinguishing grid pieces. According to the utility model, the weak structure of the sideline-to-sideline electric field of the arc-extinguishing grid sheet can be improved into an optimized sideline-to-plane electric field structure, the risk of breakdown short circuit at the tail end of the arc-extinguishing grid sheet is greatly reduced, and meanwhile, high-temperature gas and residual arc energy discharged from the tail end of the arc-extinguishing grid sheet can be effectively isolated from forming arc short circuit at the tail end of the arc-extinguishing grid sheet, so that the service life of the arc-extinguishing grid sheet is prolonged. And the effective utilization rate of the arc extinguishing grid plates is ensured.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of electrical equipment, in particular to a kind of electric switch arc extinguishing system. BACKGROUND

[0002] In power system, as the key equipment of controlling current on-off, the stability and safety of the performance of electric switch are crucial. In the action process of electric switch, due to the existence of voltage between contacts, air medium discharge will be caused, and then arc is formed. The generation of arc not only causes erosion to contact, affects the life of switch, but also can cause serious safety accidents such as short circuit. Therefore, in circuit breaker, disconnecting switch, contactor and other types of electric switch, arc extinguishing chamber is generally set to quickly extinguish arc, to ensure the normal operation and safety of electrical equipment.

[0003] As the core component in electric switch, arc extinguishing chamber undertakes the important task of limiting arc space position and accelerating arc extinguishing. The traditional arc extinguishing chamber design mainly consists of arc extinguishing grid and arc separation plate. By reasonably arranging these components, arc can be effectively guided into arc extinguishing chamber, and by the segmentation of arc extinguishing grid, arc can be lengthened and cooled, and finally extinguished. However, with the rapid development of new energy field, voltage level is continuously improved, which puts higher requirements on the design of arc extinguishing chamber.

[0004] Under high voltage working condition, after arc is extinguished in arc extinguishing chamber, high-temperature gas containing a large number of electric particles will be released. These gases still carry residual energy of arc, and if not properly handled, they are extremely easy to cause breakdown again at the weak electric field position at the end of arc extinguishing grid, forming arc-shaped short circuit. This phenomenon not only causes arc extinguishing grid to lose arc extinguishing effect, but also seriously affects the breaking performance of electric switch, and even causes greater safety accidents.

[0005] Therefore, how to optimize the electric field distribution between arc extinguishing grids and improve the anti-breakdown capability of the end of arc extinguishing grid has become an important problem to be solved in current electric switch design. UTILITY MODEL CONTENTS

[0006] The utility model aims at providing a kind of electric switch arc extinguishing system to solve the problems existing in the prior art. The arc outlet side of arc extinguishing grid is arranged in long-short interval, the arc inlet side of plug-in structure of arc guide piece is arranged in long-short interval, the end face of plug-in structure is attached to the end face of arc extinguishing grid, the weak electric field structure of traditional arc extinguishing grid edge line to edge line is improved to become the optimized electric field structure of edge line to plane, the risk of breakdown short circuit at the end of arc extinguishing grid is greatly reduced, and the high-temperature gas and residual arc energy discharged at the end of arc extinguishing grid can be effectively isolated to form arc short circuit at the end of arc extinguishing grid, to ensure the effective utilization rate of arc extinguishing grid.

[0007] To achieve the above object, the utility model provides the following scheme:

[0008] The utility model provides a kind of electric appliance switch arc extinguishing system, including arc extinguishing grid piece group and arc guide piece, the arc extinguishing grid piece group includes the arc extinguishing grid piece being arranged at interval in thickness direction, the arc extinguishing grid piece's arc outlet side short interval arrangement, the arc extinguishing grid piece gap is between adjacent arc extinguishing grid piece;The arc guide piece includes plug-in structure, the arc outlet side short interval arrangement of the plug-in structure, the end face of the plug-in structure is attached the end face of the arc extinguishing grid piece, adjacent plug-in structure has guide port between them, the guide port corresponds with the arc extinguishing grid piece gap.

[0009] In an embodiment, the arc guide piece includes arc guide plate and the plug-in structure connected to the arc guide plate, the guide port is opened on the arc guide plate, and the plug-in structure includes long structure and short structure.

[0010] In an embodiment, the distance between the end face of the long structure and the end face of the short structure is greater than or equal to the thickness of the arc extinguishing grid piece.

[0011] In an embodiment, the arc extinguishing grid piece includes long grid piece and short grid piece, and the arc extinguishing grid piece's arc inlet side end face is arranged in alignment.

[0012] In an embodiment, the arc extinguishing grid pieces are of consistent length, and the arc inlet side of the arc extinguishing grid pieces is arranged in short interval.

[0013] In an embodiment, the guide port corresponds one-to-one with the arc extinguishing grid piece gap, and the inner side of the guide port is provided with a drainage inclined surface.

[0014] In an embodiment, the guide port is arranged in misalignment, the arc inlet side of the arc extinguishing grid piece is provided with an arc guide notch, and the direction of the arc guide notch is consistent with the guide port.

[0015] In an embodiment, it further includes an arc separation plate, the side of the arc extinguishing grid piece is provided with a plug-in protrusion, and the arc separation plate is provided with a plug-in port for plug-in connection of the plug-in protrusion.

[0016] In an embodiment, the arc outlet side of the arc separation plate is longer than the arc extinguishing grid piece, and the arc guide piece is partially located in the region between the arc separation plates.

[0017] In an embodiment, the plug-in protrusions of adjacent arc extinguishing grid pieces are arranged in misalignment.

[0018] The utility model has achieved the following technical effects compared with the prior art:

[0019] This invention arranges the arc-extinguishing grid at long and short intervals on the arc-exit side and the arc-inlet side of the arc-guiding component's insertion structure at long and short intervals. Simultaneously, the end face of the insertion structure is fitted to the end face of the arc-extinguishing grid. This transforms the traditional weak electric field structure of the arc-extinguishing grid's edge-to-edge into an optimized electric field structure of edge-to-plane, significantly reducing the risk of short circuit at the end of the arc-extinguishing grid. It also effectively isolates the high-temperature gas and residual arc energy emitted from the end of the arc-extinguishing grid from forming an arc short circuit at the end, ensuring the effective utilization rate of the arc-extinguishing grid.

[0020] Other technical solutions included in this utility model can also achieve the following technical effects:

[0021] The air inlet of this invention corresponds one-to-one with the gap of the arc-extinguishing grid plate. The inner side of the air inlet is provided with a flow guiding slope. The flow guiding slope can guide the airflow direction, reduce the adhesion of molten metal to the sharp corner of the end of the arc-extinguishing grid plate, and further prevent short circuit breakdown between the ends of the arc-extinguishing grid plates. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 The isometric view of Embodiment 1 of this utility model Figure 1 ;

[0024] Figure 2 The isometric view of Embodiment 1 of this utility model Figure 2 ;

[0025] Figure 3 The isometric view of the arc-extinguishing chamber in Embodiment 1 of this utility model Figure 1 ;

[0026] Figure 4 This is an isometric view of the arc-extinguishing grid plate of Embodiment 1 of this utility model;

[0027] Figure 5a This is a side view of the arc guide component in Embodiment 1 of this utility model;

[0028] Figure 5b This is a front view of the arc guide component in Embodiment 1 of this utility model;

[0029] Figure 5c This is an isometric drawing of the arc guide component in Embodiment 1 of this utility model;

[0030] Figure 6 The isometric view of the arc-extinguishing chamber in Embodiment 1 of this utility modelFigure 2 ;

[0031] Figure 7 This is an exploded view of Embodiment 1 of this utility model;

[0032] Figure 8 This is an isometric sectional view of the arc guide component in Embodiment 1 of this utility model;

[0033] Figure 9 The isometric view of the arc-extinguishing chamber in Embodiment 1 of this utility model Figure 3 ;

[0034] Figure 10 This is a cross-sectional view along the airflow direction of Embodiment 1 of this utility model;

[0035] Figure 11a This is a side view of Embodiment 1 of the present utility model;

[0036] Figure 11b for Figure 11a CC section view;

[0037] Figure 11c for Figure 11a DD section view;

[0038] Figure 12 This is an exploded view of Embodiment 2 of this utility model;

[0039] Figure 13a This is a side view of Embodiment 2 of the present invention;

[0040] Figure 13b for Figure 13a Sectional view of AA;

[0041] Figure 13c for Figure 13a BB section view;

[0042] Figure 14a The airflow motion principle of Embodiment 2 of this utility model Figure 1 ;

[0043] Figure 14b The airflow motion principle of Embodiment 2 of this utility model Figure 2 ;

[0044] Figure 15 This is a cross-sectional view along the airflow direction of Embodiment 2 of this utility model;

[0045] Figure 16 This is a diagram showing the electric field distribution at the end of the arc-extinguishing grid plate of this utility model;

[0046] Figure 17 This is a diagram showing the electric field distribution at the end of an existing arc-extinguishing grid.

[0047] Among them, 1. exhaust port; 2. arc guide; 3. arc isolation plate; 4. arc inlet; 5. long grid plate; 6. short grid plate; 7. arc extinguishing chamber cavity; 8. air guide port; 9. plug-in structure; 10. Y-shaped arc extinguishing grid plate; 11. flow guiding slope; 12. arc extinguishing chamber; 13. staggered arrangement structure. Detailed Implementation

[0048] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0049] The purpose of this invention is to provide an arc-extinguishing system for electrical switches to solve the problems existing in the prior art. The arc-extinguishing grid is arranged with long and short intervals on the arc outlet side, and the arc-guiding component's insertion structure is also arranged with long and short intervals on the arc inlet side. By attaching the end face of the insertion structure to the end face of the arc-extinguishing grid, the traditional weak electric field structure of the arc-extinguishing grid edge-to-edge can be improved into an optimized electric field structure of edge-to-plane, which significantly reduces the risk of short circuit at the end of the arc-extinguishing grid. At the same time, it can effectively isolate the high-temperature gas and residual arc energy discharged from the end of the arc-extinguishing grid from forming an arc short circuit at the end of the arc-extinguishing grid, ensuring the effective utilization rate of the arc-extinguishing grid.

[0050] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] In this utility model, the front end refers to the direction of entering the arc, i.e., the side of the arc inlet, and the end end refers to the direction of exiting the arc, i.e., the side of the arc outlet.

[0052] like Figures 1 to 17As shown, this utility model provides an arc-extinguishing system for an electrical switch, including an arc-extinguishing grid assembly and an arc-guided component 2. The arc-guided component 2 is attached to the arc-exiting port side of the arc-extinguishing grid assembly. The arc-extinguishing grid assembly includes arc-extinguishing grids spaced apart in the thickness direction. The arc-exiting port side of the arc-extinguishing grids is arranged with long and short intervals (the arc-inlet side of the arc-extinguishing grids is not specifically required; they can be arranged with long and short intervals or aligned). There is an arc-extinguishing grid gap between adjacent arc-extinguishing grids. The arc-inlet side of the arc-extinguishing grid gap is an air inlet, and the arc-exiting port side of the arc-extinguishing grid gap is an exhaust port 1. The arc-guided component 2 includes a plug-in structure 9. The arc-inlet side of the plug-in structure 9 is arranged with long and short intervals. The long and short interval arrangement of the plug-in structure 9 is exactly opposite to that of the arc-extinguishing grids, complementing each other, so that the end face of the plug-in structure 9 can fit against the end face of the arc-extinguishing grids. There is an air guide port 8 between adjacent plug-in structures 9. The air guide port 8 corresponds to the gap of the arc extinguishing grid plate. It can be that multiple gaps of the arc extinguishing grid plate correspond to one air guide port 8, or one gap of the arc extinguishing grid plate corresponds to multiple air guide ports 8, or the air guide port 8 and the gap of the arc extinguishing grid plate can be in one-to-one correspondence.

[0053] This invention arranges the arc-extinguishing grid at long and short intervals on the arc-exit side and the arc-inlet side of the insertion structure 9 of the arc-guiding component 2 at long and short intervals. At the same time, the end face of the insertion structure 9 is attached to the end face of the arc-extinguishing grid. This can improve the traditional weak electric field structure of the arc-extinguishing grid edge-to-edge into an optimized electric field structure of edge-to-plane, which greatly reduces the risk of short circuit at the end of the arc-extinguishing grid. At the same time, it can effectively isolate the high-temperature gas and residual arc energy discharged from the end of the arc-extinguishing grid from forming an arc short circuit at the end of the arc-extinguishing grid, thus ensuring the effective utilization rate of the arc-extinguishing grid.

[0054] like Figure 16 and Figure 17 As shown, traditional arc-extinguishing grid layout design methods are insufficient to effectively address the issue of arc-extinguishing grid end breakdown in arc-extinguishing chamber 12 caused by factors such as concentrated electric field distribution and weak insulation at the arc-extinguishing grid end edges under complex electric field environments. By adopting an alternating arrangement of arc-extinguishing grids, the electric field pattern between the edge edges can be improved to a plane-to-edge pattern, optimizing the electric field distribution at the arc-extinguishing grid ends, preventing excessive concentration of the electric field at the edge edges, and significantly reducing the risk of short circuits due to grid end breakdown.

[0055] like Figures 1 to 3 As shown, the arc-extinguishing system consists of an arc-extinguishing chamber 12 and an arc-guiding component 2. The arc-extinguishing chamber 12 is enclosed by two spaced-apart arc-blocking plates 3. The arc-extinguishing chamber 12 has an arc inlet 4 and an exhaust outlet 1.

[0056] like Figure 10 As shown, the arc guide 2 is connected to one end of the exhaust port 1 of the arc extinguishing chamber 12, and the arc guide 2 is arranged in close contact with the arc extinguishing chamber 12.

[0057] In one embodiment, the arc guide 2 includes an arc guide plate and a plug-in structure 9 connected to the arc guide plate. The arc guide plate is a plate-shaped structure, and the air vent 8 is opened on the arc guide plate. The plug-in structure 9 includes a long structure and a short structure, which are distributed alternately to form a structure with long and short intervals.

[0058] In one embodiment, the distance between the end face of the long structure and the end face of the short structure is greater than or equal to the thickness of the arc-extinguishing grid, so as to increase the distance between the end faces of adjacent arc-extinguishing grids, form an electric field pattern between the edge and the plane, and improve the weak electric field structure between the edge and the edge.

[0059] like Figure 5a , Figure 5b , Figure 5c and Figure 10 As shown, the arc guide 2 is provided with a plug-in structure 9. The distance between the long and short structures is more than 1 times the thickness of the arc-extinguishing grid. The plug-in structure 9 is embedded in the arc-extinguishing chamber cavity 7 and is arranged in close contact with the ends of the long grid 5 and the short grid 6. This close contact arrangement can significantly reduce the risk of short circuit at the end of the arc-extinguishing grid, improve the anti-breakdown capability of the end of the arc-extinguishing grid, and effectively isolate the high-temperature gas and residual arc energy discharged from the end of the arc-extinguishing grid from forming an arc short circuit at the end of the arc-extinguishing grid, thus ensuring the effective utilization rate of the arc-extinguishing grid.

[0060] In one embodiment, such as in Example 1, the arc-extinguishing grid includes a long grid 5 and a short grid 6. The end faces of the arc-inlet side of the arc-extinguishing grid are aligned, so that the arc-outlet side of the arc-extinguishing grid is distributed with long and short intervals.

[0061] like Figure 1 , Figure 5a , Figure 5b , Figure 5c , Figure 7 as well as Figure 11a , Figure 11b and Figure 11c As shown, the arc-extinguishing grid adopts a U-shaped arc-extinguishing grid, which can be divided into long grid 5 and short grid 6.

[0062] like Figure 4 , Figure 9 , Figure 11a , Figure 11b and Figure 11c As shown, U-shaped long grid plates 5 and U-shaped short grid plates 6 are arranged alternately in the arc-extinguishing chamber 12, with each grid plate parallel or nearly parallel to the others. This arrangement of the arc-extinguishing grid plates makes the electric field distribution between them more uniform, improving the electric field pattern from edge-to-edge to edge-to-plane, and reducing the arc-extinguishing grid plate ablation caused by excessive concentration of local electric field intensity.

[0063] In one embodiment, such as in Example 2, the arc-extinguishing grid plates are of uniform length, and in order to achieve a long-short interval distribution on the arc exit side, the arc-extinguishing grid plates are arranged with long-short intervals on the arc inlet side.

[0064] like Figure 12 , Figure 13a , Figure 13b , Figure 13c and Figure 15 As shown, the difference between Embodiment 2 and Embodiment 1 is that the arc-extinguishing grid plates connected between the two arc-isolating plates 3 in the arc-extinguishing chamber 12 are of equal length. The arc-extinguishing grid plates can be either Y-shaped arc-extinguishing grid plates 10 or U-shaped arc-extinguishing grid plates (such as long grid plates 5 and short grid plates 6). Adjacent arc-extinguishing grid plates within the arc-extinguishing chamber 12 are arranged in a staggered pattern along the line connecting the arc inlet 4 and the exhaust outlet 1, forming a staggered arrangement structure 13 at both the front and rear ends of the arc-extinguishing grid plates. By setting the staggered arrangement structure 13, in addition to achieving the technical effects of Embodiment 1, the magnetic resistance of the arc entering the arc-extinguishing grid plates can be reduced, the arc length can be lengthened, and the arc's movement path can be optimized.

[0065] In one embodiment, the air guide port 8 corresponds one-to-one with the gap of the arc extinguishing grid plate, and the inner side of the air guide port 8 is provided with a flow guiding slope 11.

[0066] like Figure 5a , Figure 5b , Figure 5c , Figure 8 and Figure 10 As shown, the arc guide component 2 has air vents 8, which are arranged longitudinally and have a certain length in the horizontal direction. All air vents 8 are parallel to each other. The gaps between the exhaust port 1 and the air vents 8 are arranged in a one-to-one correspondence. The air vents 8 are provided with a guiding slope 11, which can guide the direction of the airflow discharged from the exhaust port 1, reducing the adhesion of molten metal to the surface and sharp corners of the arc-extinguishing grid, and further preventing short-circuit breakdown between the ends of the arc-extinguishing grid.

[0067] In one embodiment, the air inlets 8 are staggered, and an arc-initiating notch is provided on the arc-inlet side of the arc-extinguishing grid plate, with the orientation of the arc-initiating notch consistent with that of the air inlets 8. The staggered arrangement of the air inlets 8 increases the spacing of the discharged airflow and improves the arc-extinguishing effect.

[0068] In one embodiment, an arc-blocking plate 3 is also included. The side of the arc-extinguishing grid is provided with a plug-in protrusion. The arc-blocking plate 3 is provided with a plug-in interface for the plug-in protrusion to be plugged in. By plugging the plug-in protrusion into the plug-in interface, the arc-blocking plate 3 supports and fixes the arc-extinguishing grid.

[0069] In one embodiment, the arc-exiting side of the arc-blocking plate 3 is longer than the arc-extinguishing grid plate, which can be part of the arc-extinguishing chamber 12, namely the arc-extinguishing chamber cavity 7. The arc-guided member 2 is located in the area between the arc-blocking plates 3 (i.e., the arc-extinguishing chamber cavity 7).

[0070] likeFigure 6 , Figure 7 As shown, the arc guide component 2 is partially embedded in the arc extinguishing chamber cavity 7.

[0071] In one embodiment, the staggered arrangement of the insertion protrusions of adjacent arc-extinguishing grid plates can improve the insertion stability of the arc-extinguishing grid plates and increase the spacing between the insertion protrusions of adjacent arc-extinguishing grid plates.

[0072] The working principle of this utility model is as follows:

[0073] like Figure 14a and Figure 14b As shown, when the circuit breaker trips, the electric arc enters the arc-extinguishing chamber 12 under the combined action of the magnetic field and airflow to extinguish the arc. After the arc is extinguished, the discharged high-temperature gas carrying charged particles still has residual arc energy. The high-temperature gas with residual arc energy in the gap between the arc-extinguishing grid plates is discharged through the exhaust port 1 of the arc-extinguishing chamber 12 into the air guide port 8 of the arc-guiding component 2. Because the insertion structure 9 of the arc-guiding component 2 is arranged in close contact with the end of the arc-extinguishing grid plate, and the gaps between the exhaust port 1 of the arc-extinguishing chamber 12 and the air guide port 8 of the arc-guiding component 2 are arranged in a one-to-one correspondence, an optimized electric field structure is formed between the edge of the arc-extinguishing grid plate and the plane of the arc-extinguishing grid plate. This increases the difficulty of the high-temperature gas forming a breakdown between the arc-extinguishing grid plates and significantly reduces the risk of arc short circuit at the end of the arc-extinguishing grid plate. Meanwhile, this optimized electric field structure can reduce the risk of short circuit at the end of the arc-extinguishing grid plate even if the arc is not completely extinguished in the arc-extinguishing chamber 12 and a small portion of the arc overflows into the arc-guiding component 2 under particularly harsh operating conditions.

[0074] This utility model uses specific examples to illustrate its principles and implementation methods. The above description of the embodiments is only for the purpose of helping to understand the method and core idea of ​​this utility model. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the idea of ​​this utility model. In summary, the content of this specification should not be construed as a limitation of this utility model.

Claims

1. An electric appliance switch arc extinguishing system, characterized by, The application relates to an arc extinguishing device. The arc extinguishing device comprises an arc extinguishing grid group and an arc guiding member. The arc extinguishing grid group comprises arc extinguishing grid pieces arranged in a thickness direction, and the arc entrance sides of the arc extinguishing grid pieces are arranged in a long-short interval mode.

2. The electrical switch arc quenching system of claim 1, wherein: The arc guiding member comprises an insertion structure, and the insertion structure is arranged in a long-short interval mode on the arc entrance side.

3. The electrical switch arc quenching system of claim 2, wherein: The end surface of the insertion structure is matched with the end surface of the arc extinguishing grid piece.

4. The electrical switch arc extinction system of claim 1, wherein: The arc guiding member comprises an arc guiding plate and the insertion structure connected to the arc guiding plate.

5. The electrical switch arc extinction system of claim 1, wherein: The air guiding hole is arranged on the arc guiding plate.

6. The electrical switch arc extinction system of claim 1, wherein: The insertion structure comprises a long structure and a short structure.

7. The electrical switch arc extinction system of claim 1, wherein: The interval between the end surface of the long structure and the end surface of the short structure is greater than or equal to the thickness of the arc extinguishing grid piece.

8. The electrical switch arc extinction system of claim 1, wherein: The arc extinguishing grid piece comprises a long grid piece and a short grid piece.

9. The electrical switch arc extinction system of claim 8, wherein: The arc entrance side end surfaces of the arc extinguishing grid pieces are arranged in an alignment mode.

10. The electrical switch arc extinction system of claim 8, wherein: The arc extinguishing grid pieces have the same length. The arc entrance sides of the arc extinguishing grid pieces are arranged in a long-short interval mode. The air guiding hole corresponds to the arc extinguishing grid gap. The inner side of the air guiding hole is provided with a flow guiding inclined surface. The air guiding hole is arranged in a dislocation mode. The arc entrance side of the arc extinguishing grid piece is provided with an arc guiding gap. The arc guiding gap is arranged in a direction consistent with the air guiding hole. The arc extinguishing device further comprises an arc separating plate. The side of the arc extinguishing grid piece is provided with an insertion protrusion. The arc separating plate is provided with an insertion port for the insertion protrusion. The arc entrance side of the arc separating plate is longer than the arc extinguishing grid piece. The arc guiding member is partially arranged in the region between the arc separating plates. The insertion protrusions of the adjacent arc extinguishing grid pieces are arranged in a dislocation mode.

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