A novel variable standoff liquid nitrogen switch

Abstract

This invention discloses a novel liquid nitrogen switch with adjustable opening distance, comprising a housing, and further comprising: a permanent magnet operating mechanism on the outside of the housing sidewall; a main shaft rotatably connected to the permanent magnet operating mechanism; a trip spring arm fixedly connected to the main shaft; a trip spring connected at one end to the trip spring arm; a vertically arranged channel steel; a positioning block fixed to the side of the channel steel; an insulating pull rod fixedly connected to the main shaft; two protrusions opposite each other at the lower end of the insulating pull rod; two annular vertical plates on the moving contact rod, with the protrusions abutting between the two annular vertical plates; a copper-tungsten alloy electrode disposed at the front end of the moving contact rod; and a stationary conductive element disposed opposite to the copper-tungsten alloy electrode. This invention uses a permanent magnet operating mechanism as the operating mechanism, and limits the range of motion of the main shaft by changing the size of the positioning block to achieve an adjustable switch opening distance. A high-pressure glass observation window is also provided to meet the need for observing the liquid nitrogen arc in experiments.

Description

Technical Field

[0001] This invention relates to the field of high-voltage switching technology, and specifically to a novel liquid nitrogen switch with variable opening distance. Background Technology

[0002] Sulfur hexafluoride (SF6) is currently widely used in high-voltage circuit breakers as an insulating and arc-quenching medium. However, SF6 is a greenhouse gas. Studies have shown that the greenhouse effect of SF6 is 23,900 times that of the same volume of carbon dioxide, and SF6 has a long atmospheric lifetime and is difficult to degrade naturally. Currently, SF6 emissions from the power equipment sector account for one-fifth of the world's total emissions. Therefore, finding alternatives to SF6 is of great significance for mitigating the greenhouse effect.

[0003] Research has shown that liquid nitrogen (LN2) possesses excellent insulation strength and arc-extinguishing ability, is readily available, and causes no environmental pollution. Therefore, liquid nitrogen can be considered a potential arc-extinguishing medium. Xiang Bin, Li Hongxu, Muhammad Junaid, and others from Xi'an Jiaotong University have previously constructed an experimental switch using liquid nitrogen as the arc-extinguishing medium and conducted breaking experiments on it, studying the voltage and current breaking characteristics of liquid nitrogen under DC and AC conditions. However, the current prototype liquid nitrogen switches used in experiments have some shortcomings. The opening distance of a high-voltage switch is related to its withstand voltage value; the larger the opening distance, the longer the arc and the higher the arc voltage. Currently used prototype switches typically have a fixed opening distance, which cannot be adjusted. This makes them unsuitable for experiments at multiple voltage levels. Secondly, most current liquid nitrogen switch prototypes adopt an open design without a closed arc-extinguishing chamber. While this design is simple, convenient, and relatively safe, the open design causes continuous evaporation of liquid nitrogen, requiring frequent replenishment during experiments. Furthermore, the open design makes it impossible to conduct breaking experiments of the liquid nitrogen switch under high-pressure conditions. To study the characteristics of liquid nitrogen arcs, current interruption experiments need to be conducted using liquid nitrogen switches. Currently, the prototype switch using liquid nitrogen as the arc-extinguishing medium overcomes some shortcomings of existing experimental liquid nitrogen switch prototypes. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention provides a novel liquid nitrogen switch with variable opening distance.

[0005] To achieve the above technical objectives, the present invention adopts the following technical solution: a novel liquid nitrogen switch with variable opening distance, comprising a housing, and further comprising:

[0006] The observation window is located on the top of the casing;

[0007] The permanent magnet operating mechanism is located on the outside of the housing side wall;

[0008] The main shaft is rotatably connected to the permanent magnet operating mechanism and extends through the housing and into the housing.

[0009] The opening and closing indicator is fixedly connected to the main shaft and located at the end of the main shaft away from the housing;

[0010] The trip spring arm is located outside the housing and is fixedly connected to the main shaft;

[0011] The trip spring has one end connected to the trip spring arm and the other end connected to the housing.

[0012] The channel steel is vertically installed between the housing and the permanent magnet operating mechanism;

[0013] The positioning block is fixed on the side of the channel steel near the housing; when the circuit is open, the opening spring arm abuts against the positioning block.

[0014] An insulating tie rod is fixedly connected to the main shaft; two protrusions are provided opposite each other at the lower end of the insulating tie rod.

[0015] The movable contact rod has two annular vertical plates, and the protrusion abuts between the two annular vertical plates;

[0016] A copper-tungsten alloy electrode is positioned at the front end of the moving contact rod;

[0017] The first conductive rod horizontally penetrates the housing and extends to the outside of the housing, and the first conductive rod is sleeved inside the moving contact rod;

[0018] The stationary conductive element is positioned opposite to the copper-tungsten alloy electrode. When the circuit is closed, the stationary conductive element abuts against the copper-tungsten alloy electrode.

[0019] The second conductive rod extends horizontally through the housing and out of the housing, and the front end of the second conductive rod is connected to the stationary conductive component.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] This invention proposes a novel liquid nitrogen switch with variable contact gap, employing a closed structure for adjustable contact gap operation. Based on a traditional SF6 circuit breaker, it utilizes a permanent magnet operating mechanism. By adjusting the size of the positioning block to limit the main shaft's movement, the switch contact gap can be adjusted. A high-voltage glass observation window is included to allow for observation of the liquid nitrogen arc during experiments. Compared to previous open-type liquid nitrogen switches, this invention offers advantages such as adjustable contact gap, high breaking capacity, and fast breaking speed. Furthermore, this invention can also perform liquid nitrogen breaking experiments under high-pressure conditions. Attached Figure Description

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

[0023] Figure 1 This is a perspective view of the present invention;

[0024] Figure 2 This is a perspective view of the invention from another angle;

[0025] Figure 3 This is a top view of the circuit breaker in the open state of the present invention;

[0026] Figure 4 This is a top view of the device in the closed state.

[0027] Figure 5 for Figure 3 A cross-sectional view along the AA direction;

[0028] Figure 6 for Figure 4 A cross-sectional view along the AA direction;

[0029] Figure 7 for Figure 3 A cross-sectional view along the BB direction;

[0030] Figure 8 for Figure 4 A cross-sectional view along the BB direction;

[0031] Figure 9 This is a schematic diagram of the internal structure of the present invention in the open state;

[0032] Figure 10 This is a schematic diagram of the internal structure of the present invention in the closed state;

[0033] Figure 11 This is a schematic diagram of the insulating pull rod and the moving contact rod.

[0034] Figure 12 This is a schematic diagram showing the connection method between the insulating pull rod and the moving contact rod;

[0035] Figure 13 This is the circuit diagram for the liquid nitrogen switch opening and closing experiment.

[0036] In the diagram: 1-glass observation window, 2-liquid nitrogen injection port, 3-pressure relief valve, 4-pressure gauge, 5-valve, 6-housing, 7-permanent magnet operating mechanism, 8-channel steel, 9-opening / closing indicator, 10-main shaft, 11-insulator, 12-positioning block, 13-insulating pull rod, 14-moving contact rod, 15-stationary conductive part, 16-opening spring, 17-opening spring arm, 18-first conductive rod, 19-copper-tungsten alloy electrode, 20-second conductive rod, 21-protrusion, 22-annular vertical plate. Detailed Implementation

[0037] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0038] like Figure 1-12As shown, a novel liquid nitrogen switch with variable opening distance includes a housing 6, using liquid nitrogen as the insulating and arc-extinguishing medium. Liquid nitrogen, as a cryogenic liquid with a temperature of 77K, causes conventional metals to become embrittled upon contact. Therefore, to meet the requirements for containing liquid nitrogen, the housing 6 is made of 304 stainless steel, which can withstand the cryogenic temperature of liquid nitrogen for extended periods. Liquid nitrogen also generates significant pressure. Experimental tests show that the housing 6 maintains good sealing performance when filled with 0.6 MPa of gas. The top of the housing 6 also features a liquid nitrogen inlet 2 and a pressure relief valve 3, which has manual and automatic modes. When the internal pressure of the switch housing 6 exceeds 0.6 MPa, the pressure relief valve 3 automatically begins to release pressure, maintaining a stable pressure within the housing 6. A pressure gauge 4 and a valve 5 are also located on the external side wall of the housing 6. The valve 5 is used to pressurize the interior of the housing 6. The switch also includes an observation window 1, located on the top of the housing 6; in liquid nitrogen arc experiments, the shape, brightness, area, volume, and other parameters of the liquid nitrogen arc can be observed to further understand the characteristics of the liquid nitrogen arc. After adopting a closed structure, an observation window 1 is opened to observe the arc phenomenon in the liquid nitrogen switch. A permanent magnet operating mechanism 7 is located on the outside of the side wall of the housing 6; a main shaft 10 is rotatably connected to the permanent magnet operating mechanism 7 and extends through the housing 6 into its interior; a circuit breaker indicator 9 is fixedly connected to the main shaft 10 and located at the end of the main shaft 10 furthest from the housing 6; a circuit breaker spring arm 17 is located outside the housing 6 and fixedly connected to the main shaft 10; a circuit breaker spring 16 is connected at one end to the circuit breaker spring arm 17 and at the other end to the housing 6; a channel steel 8 is vertically positioned between the housing 6 and the permanent magnet operating mechanism 7; a positioning block 12 is fixed to the side of the channel steel 8 near the housing 6; in the open state, the circuit breaker spring arm 17 abuts against the positioning block 12; an insulating pull rod 13 is fixedly connected to the main shaft 10; two protrusions 21 are provided opposite each other at the lower end of the insulating pull rod 13. The protrusion 21 is a cylindrical head bolt with a cross-sectional circle diameter of 12mm; the moving contact rod 14 has two annular vertical plates 22 with a width of 12.5mm between them, and the protrusion 21 abuts against the two annular vertical plates 22; a copper-tungsten alloy electrode 19 is located at the front end of the moving contact rod 14; a first conductive rod 18 horizontally penetrates the housing 6 and extends to the outside of the housing 6, and is sleeved inside the moving contact rod 14; a stationary conductive element 15 is positioned opposite the copper-tungsten alloy electrode 19, and abuts against the copper-tungsten alloy electrode 19 when the circuit is closed; a second conductive rod 20 horizontally penetrates the housing 6 and extends to the outside of the housing 6, and its front end is connected to the stationary conductive element 15. Insulators 11 are sleeved on the first conductive rod 18 and the second conductive rod 20 located outside the housing 6.

[0039] Under the action of the permanent magnet operating mechanism 7, the tripping spring arm 17 rotates around the main shaft 10. Simultaneously, the main shaft 10 drives the insulating pull rod 13, which in turn drives the moving contact rod 14 to move horizontally along the direction of the first conductive rod 18. When the switch is in the closed state, the tripping spring 16 is in a stretched, energy-storing state. Under the action of the permanent magnet operating mechanism 7, the upward electromagnetic force on the tripping spring arm 17 is greater than the downward pulling force applied by the tripping spring 16, causing the copper-tungsten alloy electrode 19 and the stationary conductive element 15 to contact each other. Upon receiving the tripping command, the upward electromagnetic force on the tripping spring arm 17 is less than the downward pulling force applied by the tripping spring 16, causing the tripping spring 16 to drive the tripping spring arm 17 downward. The tripping spring arm 17 drives the main shaft 10 to move the moving contact rod 14 via the insulating pull rod 13. Simultaneously, the two protrusions 21 move upward between the annular vertical plate 22, separating the copper-tungsten alloy electrode 19 and the stationary conductive element 15, generating an electric arc between the two electrodes. At this time, the high-speed camera installed on the upper part of the outer shell 6 can capture images of the liquid nitrogen arc through the glass observation window 1. The tripping spring arm 17 moves downward continuously until it abuts against the positioning block 12. The opening distance refers to the distance between the switch copper-tungsten alloy electrode 19 and the stationary conductive part 15. At this time, the switch reaches the maximum opening distance, and the tripping action ends.

[0040] Observation window 1 is a glass observation window, and the glass thickness is calculated as follows:

[0041]

[0042] Where t is the minimum glass thickness in mm; P is the maximum operating pressure in bar; D is the glass diameter in cm; and σ is the flexural strength of the glass in kg / cm². 2 According to the manual, it is 1800 kg / cm². 2 In this embodiment, the maximum opening distance of the switch contacts is 40mm. To ensure better observation of the liquid nitrogen arc, the diameter of the observation window is set to 15cm. Based on the internal pressure requirement of 0.6MPa (6bar) of the switch, the calculated minimum glass thickness t is 12.13mm. To further ensure safety, a 15mm thick glass is ultimately used as the observation window.

[0043] To facilitate experiments with liquid nitrogen switches at different voltage levels, a replaceable positioning block 12 is used in the liquid nitrogen switch. By changing the size of the positioning block 12, the movement range of the main shaft 10 is limited when the liquid nitrogen switch is opened. By replacing the positioning block 12 with different sizes, the switch opening distance can be adjusted. The positioning block 12 is 10mm thick, has a trapezoidal cross-section, and a height of 35mm. The upper base of the trapezoid is positioned away from the main shaft 10 and is vertical. The calculation process for the size of the trapezoid is as follows:

[0044] x=101.052sinα-19.094cosα+19.094

[0045]

[0046]

[0047] Where a is the length of the upper base of the trapezoid in mm; b is the length of the lower base of the trapezoid in mm; x is the opening distance of the switch in mm; and α is the angle of rotation of the main shaft 10 in degrees.

[0048] Before conducting the liquid nitrogen switch opening and closing experiment, an air pump was used to pressurize the inside of the switch through valve 5 to ensure the good sealing of the switch housing 6. Then, 18L of liquid nitrogen was injected into the housing 6 through the liquid nitrogen injection port 2, immersing the stationary conductive component 15 and the copper-tungsten alloy electrode 19 in liquid nitrogen. Subsequently, the first conductive rod 18 and the second conductive rod 20 of the liquid nitrogen switch were connected to the experimental circuit, as follows... Figure 13 As shown in the diagram, a capacitor C and an inductor L connected in series are used as the current source, with capacitor C pre-charged. The left side shows the charging circuit, and the right side shows the discharging circuit. At the start of the experiment, switch S1 is closed, switch S2 is open, and the liquid nitrogen switch is in the closed state. At this time, current flows through capacitor C, inductor L, switch S1, and the liquid nitrogen switch to form a circuit. Subsequently, a tripping command is issued to the liquid nitrogen switch, and it begins to trip. A high-speed camera placed on top of housing 6 captures images of the liquid nitrogen arc at a fixed frequency. After a few milliseconds, the liquid nitrogen switch successfully extinguishes the arc. Then, switch S2 is closed, discharging through resistor R1.

[0049] Compared to traditional gas circuit breakers, this invention uses liquid nitrogen as the arc-extinguishing medium. Liquid nitrogen has the advantage of being environmentally friendly and pollution-free compared to sulfur hexafluoride. This invention employs a permanent magnet operating mechanism, resulting in a faster switch separation speed of up to 2 m / s. A positioning block is also incorporated within the mechanism, allowing adjustment of the maximum opening distance of the switch by replacing the positioning block. This invention utilizes a closed structure, enabling experiments under high-pressure conditions compared to existing liquid nitrogen switch prototypes. Furthermore, the observation window on the top facilitates the capture of images of the liquid nitrogen arc using a high-speed camera.

[0050] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A novel liquid nitrogen switch with variable opening distance, comprising a housing (6), characterized in that, Also includes: An observation window (1) is located on the top of the housing (6); a liquid nitrogen injection port (2) and a pressure relief valve (3) are also provided on the top of the housing (6); a pressure gauge (4) and a valve (5) are also provided on the outside of the side wall of the housing (6); the observation window (1) is a glass observation window (1), and the glass thickness is calculated as follows: in, t Minimum glass thickness, in mm; P is maximum operating pressure, in bar. D The diameter of the glass is in cm. The flexural strength of glass, expressed in kg / cm². 2 ; The permanent magnet operating mechanism (7) is located on the outside of the side wall of the housing (6); The main shaft (10) is rotatably connected to the permanent magnet operating mechanism (7) and the main shaft (10) passes through the housing (6) and extends into the interior of the housing (6); The opening and closing indicator (9) is fixedly connected to the main shaft (10) and is located at the end of the main shaft (10) away from the housing (6); The trip spring arm (17) is set outside the housing (6) and fixedly connected to the main shaft (10); The trip spring (16) is connected at one end to the trip spring arm (17) and at the other end to the housing (6); Channel steel (8) is vertically arranged between the housing (6) and the permanent magnet operating mechanism (7); The positioning block (12) is fixed on the side of the channel steel (8) near the housing (6); when the circuit is open, the opening spring arm (17) abuts against the positioning block (12); the thickness of the positioning block (12) is 10mm, the cross section of the positioning block (12) is trapezoidal, the height of the trapezoid is 35mm, the upper bottom edge of the trapezoid is set away from the main shaft (10), and the upper bottom edge of the trapezoid is set vertically. The calculation process of the size of the trapezoid is as follows: in, a This is the length of the upper base of the trapezoid, in mm; b x is the length of the lower base of the trapezoid, in mm; x is the opening distance of the switch, in mm. The angle of rotation of the main shaft (10) is expressed in degrees. An insulating pull rod (13) is fixedly connected to the main shaft (10); two protrusions (21) are provided at the lower end of the insulating pull rod (13); The movable contact rod (14) has two annular vertical plates (22) on it, and the protrusion (21) abuts between the two annular vertical plates (22); A copper-tungsten alloy electrode (19) is disposed at the front end of the moving contact rod (14); The first conductive rod (18) penetrates horizontally through the housing (6) and extends to the outside of the housing (6), and the first conductive rod (18) is sleeved inside the moving contact rod (14); The stationary conductive element (15) is arranged opposite to the copper-tungsten alloy electrode (19). When the circuit is closed, the stationary conductive element (15) abuts against the copper-tungsten alloy electrode (19). The second conductive rod (20) penetrates horizontally through the housing (6) and extends to the outside of the housing (6), and the front end of the second conductive rod (20) is connected to the stationary conductive component (15); an insulator (11) is sleeved on the first conductive rod (18) and the second conductive rod (20) located outside the housing (6).

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