An anti-electric breakdown structure of a circuit breaker arc extinguishing chamber, its design method, and the circuit breaker arc extinguishing chamber

Abstract

The present invention belongs to the technical field of the arc extinguishing chamber of a circuit breaker, and relates to an anti-electric breakdown structure for the arc extinguishing chamber of a circuit breaker. On the basis of the original linear shape of the nozzle throat, a divergent section is added. The shielding structure must be able to shield the divergent section, so it is necessary to ensure the distance dimension that the foremost end of the shielding structure extends beyond the downstream section of the nozzle. Through the coupling of fluid field simulation and electric field simulation calculations, the shielding structure extends beyond the upstream of the nozzle by a certain distance, which can shield the low-pressure area downstream of the nozzle, and transfer the point with the highest electric field from the static arc contact inside the nozzle to the shielding outside the nozzle; in the area near the downstream of the nozzle throat, a divergent section is added to better discharge the high-temperature arc gas before the static arc contact is pulled out of the nozzle throat, preventing the failure of interruption due to excessive accumulation of arc energy in the nozzle throat caused by the lengthening of the nozzle. It solves the problem that the self-energy circuit breaker is prone to electric breakdown under the transient recovery voltage when interrupting the current.

Description

Technical Field

[0001] The invention belongs to the technical field of circuit breaker arc extinguishing chambers, and particularly relates to an anti-electric breakdown structure of a circuit breaker arc extinguishing chamber, a design method thereof, and a circuit breaker arc extinguishing chamber. Background Art

[0002] In the power system, high-voltage self-energy SF6 circuit breakers are developing towards higher voltage levels and occupying an increasing market share. It uses the energy of the arc itself to assist in arc extinguishing and has advantages such as small operating power, light weight, and small volume compared to puffer circuit breakers.

[0003] The research on the characteristics of the gas flow field during the large-current arcing stage of self-energy SF6 circuit breakers has always been one of the research hotspots. Many scholars have done a lot of work in aspects such as the interaction between the gas flow field and the arc, turbulent flow and shock wave phenomena, and the influence of radiation and nozzle ablation. Rong Mingzhe et al. considered the influence of conduction heat dissipation on nozzle ablation, the arc, and the gas flow field, and also considered the influence of nozzle ablation vapor on the numerical calculation of the gas flow field, and studied and analyzed the transfer mode of arc energy in the self-energy arc extinguishing chamber and the influence of structural parameters on the breaking performance. Zhang Junmin used a mathematical model of the interaction between the nozzle arc and polytetrafluoroethylene (PTFE) vapor to simulate the breaking process of self-energy SF6 circuit breakers and found that PTFE vapor can accelerate the mixing of cold and hot airflows in the thermal expansion chamber, reduce the gas temperature drop rate in the post-arc nozzle, and is conducive to the rapid formation of a stagnation zone between the moving and static arc contacts. Yan J D et al. numerically simulated the gas flow field of self-expansion circuit breakers considering the nozzle ablation caused by arc radiation heat transfer and found that nozzle ablation and arc radiation during the large-current stage are the main reasons for the increase in pressure in the cylinder, and the nozzle structure will affect the gas flow cooling process before the arc current zero-crossing;

[0004] Pei Y et al. found through the calculation of the thermal breaking performance of self-expansion circuit breakers that the peak pressure in the expansion chamber lags behind the peak current, and the auxiliary nozzle is the key to improving the thermal breaking ability of self-expansion circuit breakers;

[0005] Zhang J L et al. found through the study of the thermal gas flow field in the self-energy arc extinguishing chamber that the arcing gas will burn in pure PTFE vapor or pure SF6 gas, and the heat brought by PTFE vapor into the expansion chamber is mainly used to establish pressure, and the calculated arc voltage and pressure changes are in good agreement with the test results;

[0006] Guo Ze et al. divided the motion forms of the valve into two categories: intermittent motion and continuous motion, established a more realistic valve motion model, and combined with the magnetohydrodynamics (MHD) model to simulate and analyze the temperature and pressure distribution in the arc extinguishing chamber, the nozzle ablation situation, and the motion characteristics of the check valve.

[0007] When a self - energized circuit breaker interrupts current, especially in a double - acting arc - extinguishing chamber, when interrupting a small current at a relatively low moving speed of the contact, the air pressure established in the compression chamber is relatively low. The expansion chamber has not accumulated enough arc energy, and the overall air pressure is low. The gas flow velocity in the expansion section downstream of the nozzle is large, and the air pressure decreases. Due to the heating of the arc in the entire internal area of the nozzle, the temperature is relatively high. The dielectric recovery strength after the arc increases with the increase of gas pressure and decreases with the increase of temperature. Therefore, the dielectric recovery strength in the low - pressure and high - temperature area downstream of the nozzle is relatively low, and it is prone to electrical breakdown under the transient recovery voltage.

[0008] Furthermore, when a high - voltage SF6 large - capacity circuit breaker interrupts a short - circuit current, a relatively high gas flow velocity is required at the nozzle to carry away a large amount of heat generated by the arc. However, the increase in flow velocity will lead to a decrease in pressure, resulting in a decline in insulation ability, thus leading to interruption failure. When a high - voltage SF6 large - capacity circuit breaker interrupts a small current, there is a problem that the gas flow area is insufficient after the one - way valve is opened. Summary of the Invention

[0009] The purpose of the present invention is to provide an anti - electrical - breakdown structure for a circuit breaker arc - extinguishing chamber, its design method, and a circuit breaker arc - extinguishing chamber, which solve the problem that a self - energized circuit breaker is prone to electrical breakdown under the transient recovery voltage when interrupting current.

[0010] The present invention is realized through the following technical solutions:

[0011] An anti - electrical - breakdown structure for a circuit breaker arc - extinguishing chamber, the circuit breaker arc - extinguishing chamber includes a large nozzle and a moving main contact; the large nozzle is connected inside the moving main contact;

[0012] The large nozzle includes a nozzle upstream section A, a nozzle throat B, and a nozzle downstream section C connected in sequence. The nozzle throat B is composed of a straight section B1 and an expansion section B2. The straight section B1 is connected to the nozzle upstream section A, and the expansion section B2 is connected to the nozzle downstream section C. The large - diameter end of the expansion section B2 faces the nozzle downstream section C;

[0013] A shielding structure is provided outside the large nozzle. The distance from the foremost end of the shielding structure exceeding the nozzle downstream section C is L1; the distance between the foremost end of the shielding structure and the moving main contact is L2;

[0014] The value of L1 is related to the voltage level. The higher the voltage level, the larger the value;

[0015] The included - angle value range of the expansion section B2 is related to the interrupting current. The larger the interrupting current, the larger the value;

[0016] The length of L2 needs to meet the insulation requirements of the lightning impulse voltage. The higher the voltage level, the longer the length of L2.

[0017] Furthermore, the value of L1 is 8 - 25 mm.

[0018] Furthermore, the value of L2 ranges from 50 to 130 mm.

[0019] Furthermore, the included angle range of the expansion section B2 is from 4 to 10°.

[0020] Furthermore, the shielding structure includes a guiding shield and a fracture shield;

[0021] The fracture shield includes a straight section and an arc section connected to each other. The straight section is connected to the guiding shield, and the arc section extends towards the B side of the nozzle throat.

[0022] Furthermore, the length of the fracture shield is controlled by two lengths L1 and L2;

[0023] The distance from the foremost end of the arc section to the downstream section C of the nozzle is L1;

[0024] The distance between the foremost end of the arc section and the moving main contact of the circuit breaker arc extinguishing chamber is L2.

[0025] Furthermore, the circuit breaker arc extinguishing chamber further includes a thermal expansion chamber and a compression chamber. The thermal expansion chamber and the compression chamber are communicated, and a one-way valve is installed at the communication position;

[0026] The one-way valve includes a valve seat, a valve disc and a positioning bolt. The valve seat is installed at the end of the thermal expansion chamber; the valve disc is installed on one side of the valve seat through the positioning bolt, and the valve disc is located in the thermal expansion chamber;

[0027] The opening amplitude of the valve disc is determined by the length of the positioning bolt extending out of the valve seat;

[0028] The valve seat is prefabricated with ventilation holes and bolt holes arranged in a staggered manner, and the positioning bolt penetrates through the bolt holes.

[0029] Furthermore, one end of the positioning bolt away from the valve seat is a non-threaded section, and the end extending into the valve seat is a threaded section. The valve disc can freely slide on the non-threaded section of the positioning bolt.

[0030] The present invention also discloses a design method for the anti-electric breakdown structure of a circuit breaker arc extinguishing chamber, including the following process:

[0031] Based on the anti-electric breakdown structure of the circuit breaker arc extinguishing chamber, an arc extinguishing chamber simulation model is established, and the point with the highest electric field is transferred from the static arc contact inside the large nozzle to the shielding structure outside the large nozzle;

[0032] And through the coupling of fluid flow field simulation and electric field simulation calculation, the lengths of L1 and L2 are determined. Specifically:

[0033] The determination of L1 specifically includes the following steps:

[0034] First, obtain the distribution of post-arc gas pressure and temperature through the simulation of the arcing interruption stage. Based on the curve of the critical breakdown field strength varying with temperature and pressure, calculate the critical breakdown field strength E at each point. cr ;

[0035] Utilize electrostatic field simulation, apply the transient recovery voltage, and obtain the electric field strength value E at each point under the required working conditions. a , calculate the ratio of the two values E a / E cr ;

[0036] Adjust the length L1 such that the E a / E cr < 1 in region C of the downstream section of the nozzle. Then, the applied electric field strength is less than the critical breakdown field strength, and electrical breakdown will not occur in region C of the downstream section of the nozzle.

[0037] The determination of L2 specifically includes the following steps:

[0038] First, based on electrostatic field calculation, obtain the electric field strength E near the port shield under lightning impulse voltage. a , adjust the length of the nozzle throat B, control the length of L2, and make the electric field strength E a less than the critical breakdown field strength E cr under cold gas conditions. Then, electrical breakdown will not occur in region C of the downstream section of the nozzle.

[0039] The present invention also discloses a circuit breaker arc extinguishing chamber including the anti-electric breakdown structure described above.

[0040] Compared with the prior art, the present invention has the following beneficial technical effects:

[0041] The present invention discloses an anti-electric breakdown structure for a circuit breaker arc extinguishing chamber, and designs a new shape of the nozzle throat, that is, on the basis of the original linear nozzle throat shape, a divergent section is added, and requirements are put forward for the relationship between the shield and the divergent section, that is, the shielding structure must be able to shield the divergent section, so the dimension L1 must be ensured. Through the coupling of fluid field simulation and electric field simulation calculation, the shielding structure extends beyond the nozzle upstream by a certain distance, which can shield the low-pressure area downstream of the nozzle, and transfer the point with the highest electric field from the static arc contact inside the nozzle to the shield outside the nozzle; in the area of the nozzle throat close to the downstream, a divergent section is added to better discharge the high-temperature arc gas before the static arc contact is pulled out of the nozzle throat, preventing the interruption failure caused by excessive accumulation of arc energy in the nozzle throat due to the lengthening of the nozzle. Through design, there is a special dimensional fit between the shielding structure and the large nozzle. The position of the shielding structure must be able to effectively electrostatically shield the low-pressure area downstream of the nozzle. The distance L1 from the front end of the shielding structure beyond the downstream section C of the nozzle is 8-25 mm, and the higher the voltage, the larger the value; the included angle value range of the divergent section B2 is 4-10°, and the larger the interrupting current, the larger the value; the length of L2 needs to meet the insulation requirements of lightning impulse voltage, and the higher the voltage level, the longer the length of L2.

[0042] Furthermore, a divergent section with an included angle of 6-10° is added to the nozzle throat to increase the exhaust during the arcing stage and improve the interrupting performance.

[0043] Furthermore, the one-way valve is changed to be positioned by a screw with half threads, and the part of the screw without threads is the opening and closing gap of the one-way valve. The improved structure makes the inner hole of the valve plate not directly cooperate with the shaft of the valve seat, thereby increasing the air flow channel inside the one-way valve. Without changing the diameter of the pressure cylinder, the flow area of the gas flowing from the pressure chamber to the expansion chamber is increased, and the air flow channel is increased, thereby improving the arc-blowing intensity and enhancing the interrupting ability of the circuit breaker.

[0044] The present invention also discloses a design method for an anti-electric breakdown structure of a circuit breaker arc extinguishing chamber. By the curve of the critical breakdown field strength varying with temperature and pressure, the critical breakdown field strength E of each point is obtained cr ; using electrostatic field simulation and applying a transient recovery voltage, the electric field strength value E of each point under the required working conditions is obtained a . Calculate the ratio E of the two values a / E cr . Adjust the length L1 of the fracture shield so that E in the downstream area of the nozzle a / E cr<1, that is, when the applied electric field strength is less than the critical breakdown field strength, no electric breakdown will occur in the downstream area of the nozzle. According to the calculation of the electrostatic field, the electric field strength near the fracture shield under lightning impulse voltage is obtained. Since the fracture shield is located outside the nozzle and the surrounding gas is almost in a cold state, its critical breakdown field strength is relatively high. However, the fracture shield is also closer to the moving main contact than the static arc contact. By adjusting the length of the nozzle throat and controlling the distance L2 between the fracture shield and the moving arc contact, the electric field strength can be made less than the critical breakdown field strength of the cold gas. Description of the Drawings

[0045] Figure 1 is a schematic structural diagram of the existing arc extinguishing chamber;

[0046] Figure 2 is a diagram showing the positional dimension relationship between the large nozzle and the port shield;

[0047] Figure 3 is a schematic structural diagram of the nozzle with an increased expansion section in the throat designed by the present invention;

[0048] Figure 4 is a schematic flow diagram of the design method for the shield length;

[0049] Figure 5 is a schematic structural diagram when the improved one-way valve is closed;

[0050] Figure 6 is a partial enlarged view when the improved one-way valve is closed;

[0051] Figure 7 is a schematic structural diagram when the improved one-way valve is open;

[0052] Figure 8 is a partial method diagram when the improved one-way valve is open;

[0053] Figure 9 is a schematic diagram of the relative positions of the improved one-way valve and the positioning bolt;

[0054] Figure 10 is a schematic diagram of the positioning screw;

[0055] Figure 11 is a schematic diagram of the one-way valve;

[0056] Figure 12 is a schematic structural diagram of the valve seat; Figure a is a side view; Figure b is a front view;

[0057] Figure 13 is a schematic diagram of the air flow after improving the one-way valve structure.

[0058] Figure 14 is the E a / E cr distribution diagram at the moment of 150 μs after the arc extinction zero-crossing at 13 ms in Scheme 1 of the application example;

[0059] Figure 15 For the E at 150 μs after the arc extinction zero-crossing of 20.5 ms in Solution 1 of the application example a / E cr distribution diagram;

[0060] Figure 16 For the comparison curve of the dielectric recovery strength of two solutions in the application example under different arc burning times.

[0061] Among them, 1. Moving main contact; 2. Large nozzle; 3. Shielding structure; 4. Thermal expansion chamber; 5. Varistor; 6. Compression chamber; 7. Valve seat; 8. Positioning bolt;

[0062] A. Upstream section of the nozzle; B. Throat of the nozzle; C. Downstream section of the nozzle; B1. Straight section; B2. Diverging section;

[0063] 71. Vent hole; 72. Bolt hole;

[0064] 81. Threaded section; 82. Threadless section. Detailed implementation manners

[0065] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention, that is, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments.

[0066] The components described and illustrated in the accompanying drawings and embodiments of the present invention can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the present invention provided in the following drawings is not intended to limit the scope of the claimed present invention, but only represents a selected embodiment of the present invention. Based on the accompanying drawings and embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts fall within the protection scope of the present invention.

[0067] It should be noted that the term "comprising", "including" or any other variant is intended to cover non-exclusive inclusion, such that a process, element, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to the process, element, method, article or device.

[0068] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0069] Arc extinguishing chamber structure of high-voltage SF6 large-capacity circuit breaker, including large nozzle 2, small nozzle, moving main contact 1, static main contact, shielding structure 3, moving arcing contact, static arcing contact, cylinder, piston, piston rod, air valve, valve seat 7 and other parts. The overall structure is shown in Figure 1 . The space enclosed by the partition on the piston rod and the cylinder is the air compression chamber 6, and the space enclosed by the partition on the piston rod and the moving main contact 1 is the thermal expansion chamber 4. During the movement of the moving-side parts, the volume of the air compression chamber 6 changes with the movement of the moving-side parts, while the volume of the thermal expansion chamber 4 remains unchanged. When interrupting large current, the arc extinguishing chamber extinguishes the arc using the self-energy principle of the thermal expansion chamber 4, that is, the arc heats the gas in the thermal expansion chamber 4, causing its pressure to increase instantaneously, and the relatively high gas pressure can directly blow out the arc; when interrupting small current, the arc extinguishing chamber uses the method of compressing air in the air compression chamber 6 to increase the gas pressure, so that the air flow passes through the thermal expansion chamber 4 to extinguish the arc.

[0070] In the improved structural scheme of the present invention, first, there is a special cooperation between the shielding structure 3 and the large nozzle 2, and the position of the shielding structure 3 must be able to effectively electrostatically shield the low-pressure area downstream of the nozzle.

[0071] As Figure 3 shown, the large nozzle 2 includes a nozzle upstream section A, a nozzle throat B, and a nozzle downstream section C connected in sequence. The nozzle throat B consists of a straight section B1 and a divergent section B2. The straight section B1 is connected to the nozzle upstream section A, and the divergent section B2 is connected to the nozzle downstream section C. The approximate well port of the divergent section B2 faces the nozzle downstream section C.

[0072] As Figure 2 shown, a shielding structure 3 is provided outside the large nozzle 2. The distance from the foremost end of the shielding structure 3 beyond the nozzle downstream section C is L1; the distance between the foremost end of the shielding structure 3 and the moving main contact 1 of the circuit breaker arc extinguishing chamber is L2.

[0073] Specifically, the shielding structure 3 includes a guiding shield and a breaking shield; the breaking shield includes a straight section and an arc section connected to each other. The straight section is connected to the guiding shield, and the arc section extends towards the nozzle throat B side.

[0074] As Figure 2 shown, the length of the breaking shield is controlled by two lengths L1 and L2; the distance from the foremost end of the arc section beyond the nozzle downstream section C is L1; the distance between the foremost end of the arc section and the moving main contact 1 of the circuit breaker arc extinguishing chamber is L2.

[0075] The distance L1 from the foremost end of the breaking shield beyond the downstream of the nozzle is 8 - 25 mm, and the higher the voltage, the larger the value; the included angle value range of the divergent section B2 is 4 - 10°, and the larger the breaking current, the larger the value; the length of L2 needs to meet the insulation requirements of lightning impulse voltage, and the higher the voltage level, the longer the length of L2.

[0076] AsFigure 4 As shown in the figure, the present invention proposes a design method for the fracture shielding length. For the determination of L1, first, the distribution of gas pressure and temperature after the arc is obtained through the opening simulation in the arcing stage. Through the curve of the critical breakdown field strength varying with temperature and pressure, the critical breakdown field strength E of each point is obtained. cr ;

[0077] Using electrostatic field simulation, applying the transient recovery voltage, the electric field strength value E of each point under the required working conditions is obtained. a . Calculate the ratio of the two values E a / E cr .

[0078] Adjust the fracture shielding length L1 so that E in the downstream area of the nozzle a / E cr <1, that is, the applied electric field strength is less than the critical breakdown field strength, and electrical breakdown will not occur in the downstream area of the nozzle.

[0079] Because E in the process on the left a and E cr are both unevenly distributed in space. In order to be able to compare E a and E cr at each spatial point, therefore, the calculation of E a / E cr of each spatial point is carried out, and then it is checked whether there are points greater than 1. The cold-state E on the right cr is considered a constant in the whole space. So E a and E cr can be directly compared.

[0080] For the determination of L2, first, according to the electrostatic field calculation, the electric field strength near the fracture shielding under the lightning impulse voltage is obtained. Since the fracture shielding is located outside the nozzle and the surrounding gas is almost in the cold state, its critical breakdown field strength is relatively high. However, the fracture shielding is also closer to the moving main contact 1 than the static arc contact. Adjust the nozzle throat length to control the distance L2 between the fracture shielding and the moving main contact 1 so that the electric field strength is less than the critical breakdown field strength of the cold-state gas. The flow chart of the above design method is shown in Figure 3 .

[0081] The design method of the nozzle is to add an expansion section B2 with an included angle of 4° - 10° downstream of the lengthened nozzle throat, as shown in Figure 3 . Before the static arc contact is pulled out of the nozzle throat, it can better discharge the high-temperature arc gas, preventing the failure of interruption due to excessive accumulation of arc energy in the nozzle throat caused by the lengthening of the nozzle.

[0082] The following introduces an application example of using the design method proposed by the present invention to improve the structure of a certain 126 kV arc extinguishing chamber.

[0083] Application example:

[0084] Post-arc electric field E a and critical breakdown field strength E cr The distribution of the ratio in the flow field is shown in Figure 14 and Figure 15 , Figure 14 and Figure 15 are the distribution diagrams of E a / E cr at 150 μs after the current zero-crossing at 13 ms and 20.5 ms in the original scheme (Scheme 1), respectively. It can be seen from Figure 14 that at 150 μs after the current zero-crossing at 13 ms, E a / E cr < 1 in the entire fracture region, and its maximum value is 0.819. This indicates that electric breakdown will not occur between the contacts at this moment.

[0085] It can be seen from Figure 15 that at 150 μs after the current zero-crossing at 20.5 ms, in the region near the top of the static arc contact, E a / E cr > 1, and its maximum value is 1.47. That is to say, electric breakdown will occur in the gas gap near the top of the static arc contact at this moment. Research tests found that Scheme 1 can successfully interrupt near 13 ms short arc, but has poor interrupting ability near 20.5 ms long arc, and electric breakdown will occur, and its breakdown voltage is often below 250 kV. To prevent electric breakdown near the top of the static arc contact, L1 should be optimized to avoid excessive field strength and poor dielectric recovery in this region.

[0086] Figure 16 The comparison of the dielectric recovery strength and the test TRV after the current zero-crossing of Scheme 2 and Scheme 1 after improving L1 under 13 ms and 20.5 ms arcing is given. It can be seen that in Scheme 1 under 20.5 ms arcing, before 38 μs after the current zero-crossing, the dielectric recovery strength is higher than TRV, and it can be judged that electric breakdown will not occur between the contacts. After 38 μs after the current zero-crossing, the dielectric recovery strength is lower than TRV, that is to say, electric breakdown will occur between the contacts. Under the condition of 13 ms arcing in Scheme 1 and under the conditions of 13 ms and 20.5 ms arcing in Scheme 2, the dielectric recovery strength after zero-crossing is higher than TRV throughout the time, and it can be judged that electric breakdown will not occur during the TRV stage. Research tests found that Scheme 2 successfully passed the OP2 test and solved the problem of non-interruption of long arc in Scheme 1.

[0087] Change the installation and limiting method of the one-way valve. Use a screw with half of its length threaded for positioning. The non-threaded part of the screw is the opening and closing clearance of the one-way valve. The improved structure enables the inner hole of the one-way valve not to directly cooperate with the axis of the piston rod, thereby increasing the air flow channel at the lower edge of the air valve of the one-way valve. Without changing the diameter of the pressure cylinder, the flow area of the gas flowing out from the pressure chamber 6 to the thermal expansion chamber 4 is increased.

[0088] As Figures 5 - 9 shown, the arc extinguishing chamber of the circuit breaker further includes a thermal expansion chamber 4 and a pressure chamber 6. The thermal expansion chamber 4 and the pressure chamber 6 are connected, and a one-way valve is installed at the connection. The one-way valve includes a valve seat 7, a valve plate 5, and a positioning bolt 8. The valve plate 5 is installed on the valve seat 7 through the positioning bolt 8. The opening amplitude of the one-way valve is determined by the length of the positioning bolt 8 extending out of the valve seat 7.

[0089] In the prior art, when the one-way valve is closed, the valve plate 5 closely adheres to the valve seat 7. When the one-way valve is opened, the valve plate 5 closely adheres to the step on the axis of the valve seat 7. Therefore, when the one-way valve is opened, the gas can only flow out from the outside of the one-way valve and cannot flow out from the inside of the one-way valve.

[0090] For the improved structure of the one-way valve, as Figure 5 and Figure 6 shown, when the one-way valve is closed, the valve plate 5 closely adheres to the valve seat 7; as Figure 7 and Figure 8 shown, when the one-way valve is opened, the valve plate 5 closely adheres to the positioning bolt 8. There is enough clearance between the inside of the one-way valve and the axis of the valve seat 7, enabling the air flow to flow out both from the inside and the outside. The specific air flow is as Figure 13 shown. Such a structural design can not only increase the gas flow area but also reduce the ablation of the valve plate 5 by the hot air flow.

[0091] As Figure 12 a and Figure 12 b shown, the structure of the valve seat 7 is also improved. A bolt hole 72 is drilled on the rib in the middle of the vent hole 71 of the valve seat 7, and the positioning bolt 8 is installed in the bolt hole 72.

[0092] As Figure 10 shown, the part of the positioning bolt 8 close to the head has no thread, which is the non-threaded section 82; the part close to the tail has a thread, which is the threaded section 81. Correspondingly, as Figure 11 shown, multiple mounting holes for installing the positioning bolt 8 are also drilled at the corresponding positions on the valve plate 5. The valve plate 5 can slide freely on the non-threaded section 82 of the positioning bolt 8.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: it is still possible to modify the specific implementation manners of the present invention or make equivalent replacements, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. An anti-electric breakdown structure of a circuit breaker arc extinguishing chamber, characterized in that: The circuit breaker arc extinguishing chamber comprises a large nozzle (2) and a moving main contact (1); the large nozzle (2) is connected to the inner side of the moving main contact (1); The large nozzle (2) comprises a nozzle upstream section A, a nozzle throat B and a nozzle downstream section C which are connected in sequence, the nozzle throat B is composed of a straight section B1 and a diverging section B2, the straight section B1 is connected to the nozzle upstream section A, the diverging section B2 is connected to the nozzle downstream section C, and the large diameter end of the diverging section B2 faces the nozzle downstream section C; A shielding structure (3) is provided outside the large nozzle (2), the front end of the shielding structure (3) exceeds the downstream section C of the nozzle by a distance L1; the distance between the front end of the shielding structure (3) and the moving main contact (1) is L2; The value of L1 is related to the voltage level. The higher the voltage level, the larger the value. The range of the opening angle of the expansion section B2 is related to the breaking current. The larger the breaking current, the larger the value. The length of L2 must meet the insulation requirements of lightning impulse voltage. The higher the voltage level, the longer the length of L2; The value of L1 is 8~25mm, the value of L2 is 50~130mm, and the opening angle of the expansion section B2 ranges from 4~10°; The shielding structure (3) includes a guide shield and a break shield; The fracture shield includes a straight line segment and an arc segment connected to each other, the straight line segment is connected to the guide shield, and the arc segment extends to the nozzle throat B side.

2. The anti-electrical breakdown structure of the arc extinguishing chamber of a circuit breaker according to claim 1, characterized in that: The length of the break shield is controlled by the two lengths L1 and L2; The distance that the front end of the arc segment exceeds the downstream segment C of the nozzle is L1; The distance between the front end of the arc segment and the moving main contact (1) of the arc extinguishing chamber of the circuit breaker is L2.

3. The anti-electrical breakdown structure of the arc extinguishing chamber of a circuit breaker according to claim 1 or 2, characterized in that: The circuit breaker arc extinguishing chamber further comprises a thermal expansion chamber (4) and a compressed air chamber (6), the thermal expansion chamber (4) and the compressed air chamber (6) are connected, and a one-way valve is installed at the connection point; The one-way valve comprises a valve seat (7), a valve plate (5) and a positioning bolt (8), wherein the valve seat (7) is mounted at the end of the thermal expansion chamber (4); the valve plate (5) is mounted on one side of the valve seat (7) via the positioning bolt (8), and the valve plate (5) is located in the thermal expansion chamber (4); The opening range of the valve plate (5) is determined by the length of the positioning bolt (8) extending from the valve seat (7); The valve seat (7) is prefabricated with ventilation holes (71) and bolt holes (72) arranged in a staggered manner, and the positioning bolts (8) penetrate through the bolt holes (72).

4. The anti-electrical breakdown structure of the arc extinguishing chamber of a circuit breaker according to claim 3, characterized in that: The end of the positioning bolt (8) away from the valve seat (7) is a non-threaded section (82), and the end extending into the valve seat (7) is a threaded section (81). The valve plate (5) can slide freely on the non-threaded section (82) of the positioning bolt (8).

5. The design method of the anti-electrical breakdown structure of the arc extinguishing chamber of the circuit breaker according to any one of claims 1 to 4, characterized in that: The process includes: An arc extinguishing chamber simulation model is established based on the anti-electrical breakdown structure of the arc extinguishing chamber of the circuit breaker, and the point with the highest electric field is transferred from the static arc contact inside the large nozzle (2) to the shielding structure (3) outside the large nozzle (2); And through the coupling of flow field simulation and electric field simulation calculation, the lengths of L1 and L2 are determined, specifically: The determination of L1 specifically includes the following steps: First, the distribution of gas pressure and temperature after the arc is obtained through the arcing stage breaking simulation. The critical breakdown field strength E at each point is calculated through the curve of critical breakdown field strength changing with temperature and pressure. cr ; Using electrostatic field simulation, apply transient recovery voltage to obtain the electric field strength value E at each point under the required working condition. a , calculate the ratio of the two values ​​E a / E cr ; Adjust the length L1 so that the E of the downstream section C of the nozzle a / E cr <1, the applied electric field strength is less than the critical breakdown field strength, and no electrical breakdown will occur in the region C downstream of the nozzle; The determination of L2 specifically includes the following steps: First, according to the electrostatic field calculation, the electric field strength E near the fracture shield under the lightning impulse voltage is obtained. a , adjust the length of the nozzle throat B and control the length of L2 so that the electric field strength E a Less than the critical breakdown field strength E under cold gas cr , then no electrical breakdown will occur in the area C downstream of the nozzle.

6. An arc extinguishing chamber of a circuit breaker comprising the anti-electrical breakdown structure according to any one of claims 1 to 4.

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