A superconducting current-limiting fuse switch with a narrow neck

Abstract

The present invention discloses a superconducting current-limiting fuse switch with a narrow neck, comprising a cryogenic liquid nitrogen container, an end cap, a connecting contact, a superconducting melt, and an auxiliary arc-extinguishing device. The switch comprises two different arc-extinguishing methods: a filler arc-extinguishing method in which a solid arc-extinguishing filler is placed around the superconducting melt, and a grid arc-extinguishing method in which an insulating grid and a magnetic field generator are used to assist in arc-extinguishing. Under normal current flow conditions, the superconducting melt of the superconducting current-limiting fuse switch maintains a superconducting state. After a short-circuit fault occurs, the superconducting melt quenches and generates an arc, which is then extinguished by the arc-extinguishing medium, and the superconducting current-limiting fuse switch completes the short-circuit fault interruption. The present invention has a large rated current capacity, low on-state loss, high breaking capacity, and high response speed, effectively providing short-circuit protection for power equipment and possessing high practical value.

Description

Technical Field

[0001] The present invention relates to the technical field of power system and equipment protection, and in particular to a superconducting current-limiting fuse switch with a narrow neck. Background Art

[0002] With the continuous development of smart grids and the vigorous promotion of new energy grid integration, various emerging power technologies are constantly emerging to improve operational efficiency and ensure the safety and stability of grid operations. Furthermore, with the further development of high-temperature superconducting materials, superconducting power technology, due to its low loss, high reliability, and rapid response speed, has become a key technology for solving grid operation problems. A variety of superconducting power equipment, such as superconducting cables, superconducting motors, superconducting magnetic energy storage, and superconducting transformers, has been put into use.

[0003] When a short-circuit fault occurs in a power system, the short-circuit current rises rapidly within a short period of time. Once the critical current of the superconducting tape is reached, causing a quench, localized heating and overvoltage in the tape can cause irreversible damage to the superconducting device, resulting in severe economic losses. Therefore, how to quickly limit the development of the short-circuit current and remove the superconducting device from the system to prevent damage caused by a quench is a crucial issue.

[0004] Patent CN102522277A discloses a high-temperature superconducting fuse. The high-temperature superconducting fuse places a YBCO superconducting tape in liquid nitrogen and suspends a heavy hammer below the tape. When a short circuit occurs, the YBCO superconducting tape melts and disconnects under the action of the heavy hammer, thereby protecting the system.

[0005] HS Choi, Huang Xinjian, and others studied the arcing characteristics of superconducting tape in liquid nitrogen. They studied the fundamental properties of arcing in superconducting tape in liquid nitrogen and analyzed the relationship between applied voltage, current limiting time, and discharge time. Huang Xinjian and others fabricated a narrow neck structure on the superconducting tape and experimentally determined the effects of the prospective current and the geometry of the narrow neck on the AC interrupting characteristics of the superconducting fuse.

[0006] The above patents and documents all use liquid nitrogen to extinguish the arc generated by the melting of the superconducting tape, and there are no other auxiliary arc extinguishing means. However, the arc extinguishing ability of liquid nitrogen is limited. For larger short-circuit current faults, it will be difficult to interrupt due to the long arcing time, and the superconducting equipment cannot be effectively protected. Summary of the Invention

[0007] In view of the above-mentioned deficiencies and defects of the prior art, the purpose of the present invention is to propose a superconducting current-limiting fuse switch with a narrow neck, which can effectively protect superconducting equipment in the event of a short circuit and, as a power switch, has a wide range of application scenarios.

[0008] The present invention achieves the above-mentioned purpose through the following technical means:

[0009] A superconducting current-limiting fuse switch with a narrow neck, comprising a cryogenic liquid nitrogen container 1, an end cover 2, a connecting contact 3, a superconducting melt 4, and an auxiliary arc extinguishing device 5;

[0010] The shell of the cryogenic liquid nitrogen container 1 has an inner and outer two-layer structure, including an outer layer 101 of the cryogenic liquid nitrogen container and an inner layer 102 of the cryogenic liquid nitrogen container. The outer layer 101 of the cryogenic liquid nitrogen container and the inner layer 102 of the cryogenic liquid nitrogen container are isolated by an insulating material and evacuated, and liquid nitrogen is stored in the cryogenic liquid nitrogen container 1; the end cover 2 includes a first end cover 201 and a second end cover 202 embedded in the shell of the cryogenic liquid nitrogen container 1; the connecting contact 3 includes a first connecting contact 301 and a second connecting contact 302 respectively connected to the outer sides of the first end cover 201 and the second end cover 202, and the first connecting contact 301 and the second connecting contact 302 are punched with through holes as a connection method for the superconducting current limiting fuse switch and the external circuit; both ends of the superconducting melt 4 are connected to the first end cover 201 and the inner side of the second end cover 202, one or more narrow neck structures 401 connected in series and parallel are formed on the superconducting melt 4 by cutting; according to different arc extinguishing methods, the auxiliary arc extinguishing device 5 includes a filler shell 501 used in the filler arc extinguishing method or an insulating grid 502 and a magnetic field generating device 503 used in the grid arc extinguishing method; under normal current flow conditions, the superconducting melt 4 of the superconducting current limiting fuse switch maintains a superconducting state; when a short circuit fault occurs, when the short circuit current reaches the critical current value of the superconducting melt, the superconducting melt quenches and rapidly heats up under the action of the Joule effect, first reaching the melting point at the narrow neck structure 401 and generating an arc, and then the arc is extinguished under the action of the arc extinguishing medium, and the superconducting current limiting fuse switch completes the disconnection of the short circuit fault.

[0011] The filler shell 501 used in the filler arc extinguishing method is connected to the inner sides of the first end cover 201 and the second end cover 202 to form an internal closed structure. The internal closed structure is filled with arc extinguishing filler. A shrinkage space is reserved between the first end cover 201, the second end cover 202 and the filler shell 501 according to the thermal expansion coefficient, and low-temperature resistant sealant is used for casting and sealing.

[0012] The arc-extinguishing filler in the filler shell 501 is a mixture of one or more of quartz sand, ceramic beads, alumina ceramics, aluminum oxide sand, talcum powder, sodium borate, silica gel, etc.; the arc-extinguishing filler is powdery or granular, and is wrapped around the superconducting melt 4 by reaching a preset filling density. While serving as an arc-extinguishing medium, it also fixes and supports the superconducting melt 4.

[0013] The material of the filler shell 501 is one of alumina ceramics, epoxy resin, melamine, and polytetrafluoroethylene; the low-temperature resistant sealant is polyimide or polybenzimidazole.

[0014] The filler shell 501 is connected to the inner side of the first end cover 201 and the second end cover 202 by screw connection or welding.

[0015] The grid arc extinguishing method uses an insulating grid 502 and a magnetic field generating device 503. The insulating grid 502 is located above the horizontally placed superconducting melt 4. The magnetic field generating device 503 provides a transverse magnetic field perpendicular to the direction of the current. When a short circuit fault occurs, the arc generated by the melting of the superconducting melt 4 causes the surrounding liquid nitrogen to evaporate to form a nitrogen gas cloud, which is driven upward by the gas cloud. The magnetic field generated by the magnetic field generating device 503 exerts an upward force on the arc, accelerating the movement of the arc. The arc is then divided into multiple short arcs by the insulating grid 502, thereby accelerating the arc extinguishing and improving the short-circuit current breaking capability of the superconducting current-limiting fuse switch.

[0016] The magnetic field generating device 503 uses one of a permanent magnet and a coil.

[0017] The superconducting melt 4 is made of a second generation high temperature superconducting tape, such as a REBCO tape or a YBCO tape; the shape of the narrow neck structure 401 is one of a circular narrow neck, a rectangular narrow neck, a diamond narrow neck, and a trapezoidal narrow neck.

[0018] The first connecting contact blade 301 and the second connecting contact blade 302 are respectively connected to the outer sides of the first end cover 201 and the second end cover 202 by means of snap connection, screw connection or welding connection.

[0019] Both ends of the superconducting melt 4 are connected to the inner sides of the first end cover 201 and the second end cover 202 by means of heat fusion connection or welding.

[0020] One or more narrow neck structures 401 connected in series and in parallel are formed on the superconducting melt 4 by mechanical cutting or laser cutting.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1) Compared with conventional fuses, due to the use of superconducting fuses, there is zero resistance under normal current flow conditions, so the rated current carrying capacity is greatly enhanced and the on-state loss is significantly reduced;

[0023] 2) The superconducting melt can automatically and quickly switch from zero resistance to resistance under short circuit conditions, and has stronger current limiting capability;

[0024] 3) When protecting other superconducting equipment in the power system, the temperature rise at the narrow neck of the superconducting current-limiting fuse switch after quenching is much greater than the temperature rise of the strip in the superconducting equipment. It quickly interrupts the short-circuit current after arcing and bears the overvoltage caused by the short circuit, ensuring high reliability of protection for superconducting equipment.

[0025] 4) When protecting other superconducting equipment in the power system, because of the common liquid nitrogen environment, it can form a combined electrical appliance with other superconducting equipment to reduce the floor space and further save space

[0026] 5) High breaking capacity and high response speed. In addition to protecting superconducting equipment, it has a wide range of application scenarios and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention is a three-dimensional schematic diagram of a superconducting current-limiting fuse switch with a narrow neck, illustrating the overall structure of the present invention.

[0028] Figure 2 The figure is a schematic structural plan view of a superconducting current-limiting fuse switch with a narrow neck, illustrating the specific structure of the present invention.

[0029] Figure 3 This is a schematic diagram of the structural principle of Example 1 of the filler arc extinguishing method.

[0030] Figure 4 This is a schematic diagram of the structural principle of Example 2 of the filler arc extinguishing method.

[0031] Figure 5 Schematic diagram of the structural principle of the grid arc extinguishing method.

[0032] Figure 6 Schematic diagram of the principle of the grid arc extinguishing method.

[0033] Figure 7 Schematic diagram of different narrow neck shapes on the superconducting melt.

[0034] Explanation of symbols:

[0035] 1: Cryogenic liquid nitrogen container; 2: End cover;

[0036] 3: Connecting contact blade; 4: Superconducting melt;

[0037] 5: Auxiliary arc extinguishing device.

[0038] 101: outer layer of cryogenic liquid nitrogen container; 102: inner layer of cryogenic liquid nitrogen container;

[0039] 201: first end cover; 202: second end cover;

[0040] 301: first contact blade; 302: second contact blade;

[0041] 401: Narrow neck structure; 501: Filling shell;

[0042] 502: Insulation grid; 503: Magnetic field generating device. DETAILED DESCRIPTION

[0043] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] like Figure 1 As shown, a superconducting current-limiting fuse switch with a narrow neck of the present invention includes a low-temperature liquid nitrogen container 1, an end cover 2, a connecting contact 3, a superconducting melt 4, and an auxiliary arc extinguishing device 5.

[0045] like Figure 2 As shown, the shell of the cryogenic liquid nitrogen container 1 has an inner and outer layer structure, including an outer layer 101 of the cryogenic liquid nitrogen container and an inner layer 102 of the cryogenic liquid nitrogen container. The outer layer 101 and the inner layer 102 of the cryogenic liquid nitrogen container are separated by an insulating material and evacuated to store liquid nitrogen in the cryogenic liquid nitrogen container 1. The first end cap 201 and the second end cap 202 are embedded in the shell of the cryogenic liquid nitrogen container 1. The first connecting contact blade 301 and the second connecting contact blade 302 are respectively connected to the outer sides of the first end cap 201 and the second end cap 202 by snap connection, screw connection or welding. The first connecting contact blade 301 and the second connecting contact blade 302 are provided with through holes as a connection method for the superconducting current limiting fuse switch to the external circuit. The two ends of the superconducting melt 4 are connected to the inner sides of the first end cap 201 and the second end cap 202 by hot melt connection or welding. One or more narrow neck structures 401 connected in series and parallel are formed on the superconducting melt 4 by mechanical cutting or laser cutting.

[0046] According to different arc extinguishing methods, the auxiliary arc extinguishing device 5 includes a filler shell 501 used in the filler arc extinguishing method or an insulating grid 502 and a magnetic field generating device 503 used in the grid arc extinguishing method.

[0047] like Figure 3 The figure shows an embodiment of the filler arc extinguishing method. In this embodiment, a filler shell 501 is used, and the material is one of alumina ceramic, epoxy resin, melamine, polytetrafluoroethylene, etc.; the filler shell 501 is connected to the inner side of the first end cover 201 and the second end cover 202 by screw connection or welding, forming an internal closed structure filled with arc extinguishing filler; in order to reduce the stress of the shell and improve the sealing performance in the low-temperature environment of liquid nitrogen, a shrinkage space is reserved between the first end cover 201, the second end cover 202 and the filler shell 501 according to the thermal expansion coefficient, and a low-temperature resistant sealant is used for casting. The gap between the cast body and the shell of the low-temperature liquid nitrogen container 1 is sealed with a low-temperature resistant sealant such as polyimide or polybenzimidazole to prevent liquid nitrogen from entering the interior of the fuse switch. The cast body also strengthens the structural strength of the fuse switch shell and prevents the shell from rupturing when the short-circuit current is interrupted.

[0048] The arc-extinguishing filler is a mixture of one or more of quartz sand, ceramic beads, alumina ceramics, aluminum oxide sand, talcum powder, sodium borate, silica gel, etc. The arc-extinguishing filler is in powder or granular form and is wrapped around the superconducting melt 4 to achieve a certain filling density. While serving as an arc-extinguishing medium, it also fixes and supports the superconducting melt 4.

[0049] like Figure 4 Another embodiment of the filler arc extinguishing method is shown, in which the arc extinguishing filler is solidified so that the arc extinguishing filler is fixed around the superconducting melt 4 and is in direct contact with the liquid nitrogen filled in the low-temperature liquid nitrogen container 1.

[0050] like Figure 5 The figure shows an embodiment of the grid arc extinguishing method, which uses an insulating grid 502 and a magnetic field generating device 503; the superconducting melt 4 is placed horizontally, and the insulating grid 502 is located above the superconducting melt 4; the magnetic field generating device 503 uses one of a permanent magnet and a coil to provide a transverse magnetic field perpendicular to the direction of the current.

[0051] like Figure 6 As shown, when a short circuit fault occurs, the arc generated by the melting of the superconducting melt 4 causes the surrounding liquid nitrogen to evaporate to form a nitrogen gas mass, which is driven upward by the gas mass. The magnetic field generated by the magnetic field generating device 503 generates an upward force on the arc, accelerating the movement of the arc. Subsequently, the arc is divided into multiple short arcs by the insulating grid 502, thereby accelerating the extinction of the arc and improving the short-circuit current breaking capability of the superconducting current limiting fuse switch.

[0052] The superconducting melt 4 is made of second-generation high-temperature superconducting tape, including but not limited to REBCO tape and YBCO tape;

[0053] Resistivity of superconducting tape ρ The functional relationship is described by formula (1), formula (2), and formula (3):

[0054] (1)

[0055] (2)

[0056] Where, J c is the critical current density of the superconducting coil, which varies with temperature; T c is the critical temperature of the superconducting coil; n is the characteristic constant of the superconducting tape; E c is the quench terminal voltage of the superconducting coil; T op is the operating temperature of the superconducting coil;T c is the critical temperature of the superconducting coil; T is the temperature of the superconducting coil; J c0 is the critical current density of the superconducting coil at the operating temperature; f ( T ) is the change of resistance with temperature after the superconducting tape is completely quenched.

[0057] like Figure 6 Shown are different shapes of the narrow neck structure 401 , where the shape of the narrow neck structure 401 is one of a circular narrow neck, a rectangular narrow neck, a diamond-shaped narrow neck, a trapezoidal narrow neck, and the like.

[0058] Under normal current flow conditions, the current value and temperature value of the superconducting melt of the superconducting current limiting fuse switch are both less than the critical value, maintaining the superconducting state, the resistance is 0, and there is no conduction loss; when a short circuit fault occurs, when the short circuit current reaches the critical current value of the superconducting melt, the superconducting melt quenches and rapidly heats up under the action of the Joule effect, first reaching the melting point at the narrow neck and generating an arc, and then the arc is extinguished under the action of the arc extinguishing medium, and the superconducting current limiting fuse switch completes the disconnection of the short circuit fault.

[0059] The present invention has been described in detail above in conjunction with specific preferred embodiments, but the specific embodiments of the present invention are not limited thereto. Without departing from the scope of protection of the claims of the present invention, several simple modifications or replacements should be deemed to fall within the scope of protection of the present invention determined by the submitted claims.

Claims

1. A superconducting current-limiting fuse switch with a narrow neck, characterized in that: It includes a cryogenic liquid nitrogen container (1), an end cover (2), a connecting contact (3), a superconducting melt (4), and an auxiliary arc extinguishing device (5); The shell of the cryogenic liquid nitrogen container (1) has an inner and outer two-layer structure, including an outer layer (101) of the cryogenic liquid nitrogen container and an inner layer (102) of the cryogenic liquid nitrogen container. The outer layer (101) of the cryogenic liquid nitrogen container and the inner layer (102) of the cryogenic liquid nitrogen container are isolated by an insulating material and evacuated to store liquid nitrogen in the cryogenic liquid nitrogen container (1). The end cover (2) includes a first end cover (201) and a second end cover (202) embedded in the shell of the cryogenic liquid nitrogen container (1). The connecting contact blade (3) includes a first connecting contact blade (301) and a second connecting contact blade (302) respectively connected to the outer sides of the first end cover (201) and the second end cover (202). Through holes are punched on the first connecting contact blade (301) and the second connecting contact blade (302) as a connection method for the superconducting current limiting fuse switch and the external circuit. The two ends of the superconducting melt (4) The ends are connected to the inner sides of the first end cover (201) and the second end cover (202), and one or more narrow neck structures (401) connected in series and parallel are formed on the superconducting melt (4) by cutting; according to different arc extinguishing methods, the auxiliary arc extinguishing device (5) includes a filler shell (501) used in the filler arc extinguishing method or an insulating grid (502) used in the grid arc extinguishing method and a magnetic field generating device (503); under normal current flow, the superconducting melt (4) of the superconducting current limiting fuse switch maintains a superconducting state; when a short circuit fault occurs, when the short circuit current reaches the critical current value of the superconducting melt, the superconducting melt quenches and rapidly heats up under the action of the Joule effect, first reaching the melting point at the narrow neck structure (401) and generating an arc, and then the arc is extinguished under the action of the arc extinguishing medium, and the superconducting current limiting fuse switch completes the disconnection of the short circuit fault.

2. A superconducting current-limiting fuse switch with a narrow neck according to claim 1, characterized in that: The filler shell (501) used in the filler arc extinguishing method is connected to the inner sides of the first end cover (201) and the second end cover (202) to form an internal closed structure, and the internal closed structure is filled with arc extinguishing filler. A shrinkage space is reserved between the first end cover (201), the second end cover (202) and the filler shell (501) according to the thermal expansion coefficient, and low-temperature resistant sealant is used for casting and sealing; The arc-extinguishing filler in the filler shell (501) is a mixture of one or more of quartz sand, ceramic beads, alumina ceramics, aluminum oxide sand, talcum powder, sodium borate, and silica gel; the arc-extinguishing filler is in powder or granular form, and is wrapped around the superconducting melt (4) by achieving a preset filling density, serving as an arc-extinguishing medium while also fixing and supporting the superconducting melt (4).

3. A superconducting current-limiting fuse switch with a narrow neck according to claim 2, characterized in that: The material of the filler shell (501) is one of alumina ceramics, epoxy resin, melamine, and polytetrafluoroethylene; and the low-temperature resistant sealant is polyimide or polybenzimidazole.

4. A superconducting current-limiting fuse switch with a narrow neck according to claim 2, characterized in that: The filler shell (501) is connected to the inner sides of the first end cover (201) and the second end cover (202) by screw connection or welding.

5. The superconducting current-limiting fuse switch with a narrow neck according to claim 1, characterized in that: The grid arc extinguishing method uses an insulating grid (502) and a magnetic field generating device (503), wherein the insulating grid (502) is located above a horizontally placed superconducting melt (4); the magnetic field generating device (503) provides a transverse magnetic field perpendicular to the current direction; when a short circuit fault occurs, the arc generated by the melting of the superconducting melt (4) causes the surrounding liquid nitrogen to evaporate to form a nitrogen gas mass, which is driven upward by the gas mass. The magnetic field generated by the magnetic field generating device (503) generates an upward force on the arc, accelerating the movement of the arc. Subsequently, the arc is divided into multiple short arcs by the insulating grid (502), thereby accelerating the extinguishing of the arc and improving the breaking capability of the superconducting current limiting fuse switch for short circuit current.

6. A superconducting current-limiting fuse switch with a narrow neck according to claim 5, characterized in that: The magnetic field generating device (503) uses one of a permanent magnet and a coil.

7. The superconducting current-limiting fuse switch with a narrow neck according to claim 1, characterized in that: The superconducting melt (4) is made of a second-generation high-temperature superconducting tape, using a REBCO tape or a YBCO tape; the shape of the narrow neck structure (401) is one of a circular narrow neck, a rectangular narrow neck, a diamond narrow neck, and a trapezoidal narrow neck.

8. The superconducting current-limiting fuse switch with a narrow neck according to claim 1, characterized in that: The first connecting contact blade (301) and the second connecting contact blade (302) are respectively connected to the outer sides of the first end cover (201) and the second end cover (202) by means of a snap connection, a screw connection or a welding connection.

9. The superconducting current-limiting fuse switch with a narrow neck according to claim 1, characterized in that: The two ends of the superconducting melt (4) are connected to the inner sides of the first end cover (201) and the second end cover (202) by means of heat melting or welding.

10. The superconducting current-limiting fuse switch with a narrow neck according to claim 1, characterized in that: One or more narrow neck structures (401) connected in series and in parallel are formed on the superconducting melt (4) by mechanical cutting or laser cutting.

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