Superconducting coil over-current protection device and circuit based on superconducting current-limiting cable

Abstract

The invention relates to the technical field of superconducting coil over-current protection devices, in particular to a superconducting coil over-current protection device and circuit based on a superconducting current-limiting cable, and the device comprises a low-temperature Dewar box body which is filled with liquid nitrogen; the superconducting current-limiting cable is positioned in the low-temperature Dewar box body; and the cable joint is connected with the tail end of the superconducting current limiting cable, and the top extends out of the low-temperature Dewar box body. The superconducting current-limiting cable comprises a framework and a superconducting strip which is spirally wound on the periphery of the framework. The round core type superconducting current-limiting cable has the characteristics of high critical current, low inductance and high thermal stability, and can quickly respond within a few milliseconds at the moment when a short-circuit fault occurs, so that the short-circuit current is limited at a relatively low level.

Description

Technical Field

[0001] The present invention relates to the technical field of superconducting coil overcurrent protection devices, and in particular to a superconducting coil overcurrent protection device and a circuit based on a superconducting current limiting cable. Background Art

[0002] The superconducting magnet quench protection system is an indispensable part of the fusion device. It is used to quickly disconnect the main circuit current and transfer and dissipate the magnet energy when the superconducting magnet quenches. The disconnection of the main circuit current mainly relies on mechanical DC switches, hybrid DC circuit breakers and other devices to segment the circuit. However, when the power supply system of the fusion device fails, the fault current is often very large. It is difficult for mechanical DC switches or hybrid DC circuit breakers to operate under large fault currents, which will lead to untimely protection and damage to the fusion magnet coil. Therefore, the current limiter is used in the superconducting magnet quench protection system to reduce the fault current and cooperate with the switch to protect the fusion device.

[0003] Traditional current limiters include resistor-type current limiters, inductor-type current limiters, and resistor-inductor hybrid current limiters. However, traditional current limiters are triggered by external signals to limit current, and usually have a long reaction time, and their response speed is reduced due to delays and aging of mechanical or electronic components. Traditional superconducting current limiters have relatively weak reset and repeat action capabilities, and may require manual intervention or a long time to restore the working state. It can be seen that traditional current limiters have a slow reaction speed and cannot quickly limit short-circuit current.

[0004] Therefore, how to improve the reaction rate of the current limiter and thus quickly limit the short-circuit current has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0005] The invention provides a superconducting coil overcurrent protection device and a circuit based on a superconducting current limiting cable, which are used to solve the problem of how to improve the reaction rate of a current limiter.

[0006] The present invention provides a superconducting coil overcurrent protection device based on a superconducting current limiting cable, comprising: Low temperature Dewar box, with liquid nitrogen flowing into it; Superconducting current-limiting cable, located in the cryogenic Dewar box; The cable connector is connected to the end of the superconducting current-limiting cable, and the top extends out of the low-temperature Dewar box.

[0007] In some embodiments, the superconducting current-limiting cable includes a skeleton and a superconducting tape spirally wound around the outer circumference of the skeleton.

[0008] In some of the embodiments, the number of superconducting current-limiting cables is 2 and they are arranged in parallel.

[0009] In some of the embodiments, the number of the cable connectors is 2, which are located at two ends of the superconducting current-limiting cable respectively.

[0010] In some of these embodiments, the cable connector clamps an end of the superconducting current-limiting cable.

[0011] In some of the embodiments, a copper tube is sleeved on the end of the superconducting current-limiting cable, and low-temperature solder is poured between the copper tube and the superconducting current-limiting cable to perform welded armoring.

[0012] In some embodiments, the cable connector includes: Lower plate; An upper connecting piece, the upper end of which extends out of the low-temperature Dewar box and is detachably connected to the lower plate; An accommodating hole is formed between the lower plate and the upper connecting piece, and the end of the superconducting current-limiting cable is inserted into the accommodating hole.

[0013] In some embodiments, it also includes: Epoxy support bracket, located at the bottom of the cable gland.

[0014] In some of the embodiments, a liquid nitrogen inlet, a nitrogen outlet and a mounting hole are provided on the top of the cryogenic Dewar box, and the top of the cable connector passes through the mounting hole.

[0015] The present invention also provides a superconducting coil overcurrent protection circuit based on a superconducting current limiting cable, comprising a fusion superconducting magnet, a power supply, a first switch and a superconducting coil overcurrent protection device connected in sequence, a parallel resistor at both ends of the fusion superconducting magnet and a second switch.

[0016] The beneficial effects of the present invention are as follows: the superconducting coil overcurrent protection device based on the superconducting current limiting cable of the present invention adopts a round-core superconducting current limiting cable with high critical current, low inductance, and high thermal stability, and can respond quickly within a few milliseconds at the moment of a short-circuit fault, and limit the short-circuit current to a lower level. Compared with traditional superconducting current limiters, the round-core superconducting current limiting cable has better current limiting capability, and its superconducting layer can quickly lose superconductivity when a short-circuit fault occurs, and the fault current can be shunted through the skeleton, which can more effectively limit the short-circuit current and greatly improve the reaction rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of a superconducting coil overcurrent protection device based on a superconducting current limiting cable of the present invention; Figure 2 yes Figure 1 The structural schematic diagram of the superconducting current-limiting cable shown; Figure 3 yes Figure 2 The structural schematic diagram of the end surface of the superconducting current limiting cable shown; Figure 4The present invention is a schematic diagram of a superconducting coil overcurrent protection circuit based on a superconducting current limiting cable.

[0018] In the attached drawings, 1. low-temperature Dewar box; 11. liquid nitrogen inlet; 12. nitrogen outlet; 13. mounting hole; 2. superconducting current-limiting cable; 21. skeleton; 22. superconducting tape; 3. cable connector; 31. lower plate; 32. upper connecting piece; 33. receiving hole; 4. copper tube; 5. epoxy support frame; 6. fusion superconducting magnet; 7. first switch; 8. superconducting coil overcurrent protection device; 9. resistor; 10. second switch. DETAILED DESCRIPTION

[0019] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] As described in the background art, the traditional current limiter has a slow reaction speed and cannot quickly limit the short-circuit current. Therefore, how to improve the reaction speed of the current limiter and thus quickly limit the short-circuit current has become a technical problem that needs to be solved urgently by those skilled in the art.

[0021] To solve the above problems, refer to Figure 1-4 The present invention provides a superconducting coil overcurrent protection device based on a superconducting current limiting cable, the device comprising: a cryogenic Dewar box 1, a superconducting current limiting cable 2 and a cable connector 3, liquid nitrogen is introduced into the cryogenic Dewar box 1, the superconducting current limiting cable 2 is located in the cryogenic Dewar box 1, and both ends of the superconducting current limiting cable 2 are connected to the cable connector 3, the top of the cable connector 3 extends out of the cryogenic Dewar box 1 for connecting an external circuit.

[0022] Preferably, the superconducting current-limiting cable 2 includes a skeleton 21 and a superconducting tape 22 spirally wound around the outer periphery of the skeleton 21. The skeleton 21 is made of stainless steel and has a solid structure. In the axial direction of the skeleton 21, the superconducting tape 22 is spirally wound from one end of the skeleton 21 to the other end of the skeleton 21, forming a round-core superconducting cable. The round-core superconducting cable is a compact superconducting conductor with a certain flexibility. This conductor has the characteristics of high critical current, low inductance, high thermal stability, etc. More importantly, the round-core superconducting cable has good current-sharing characteristics, low heat capacity and high quench resistance, and can respond to fault currents instantly. This application utilizes the good characteristics of the round-core superconducting cable to design a superconducting coil overcurrent protection device, which can effectively prevent current overloads caused by short circuits and other faults, while taking into account the role of power transmission, and ensuring the safety and stable operation of the equipment in fusion experiments.

[0023] The round-core superconducting cable adopted in the present invention has the characteristics of high critical current, low inductance, high thermal stability and high mechanical strength. In view of the fact that the power system powered by the fusion coil is a high-power DC system, the superconducting coil overcurrent protection device and circuit designed have high current-carrying characteristics and can respond quickly to fault currents.

[0024] It should be noted that the number and winding method of the superconducting tape 22 are adjusted according to the changes in the performance parameters of the fusion magnet. The superconducting coil overcurrent protection device of the present application has high flexibility and reliability. The stainless steel skeleton 21 provides good mechanical support. At the same time, the stainless steel armored superconducting tape 22 and the stainless steel skeleton 21 are arranged, so that the superconducting current limiting cable 2 has a reliable high-impedance current limiting effect in the case of overcurrent.

[0025] Preferably, there are two superconducting current-limiting cables 2, which are arranged in parallel. There are two cable connectors 3, which are respectively located at the two ends of the superconducting current-limiting cables 2. That is, one end of the two superconducting current-limiting cables 2 is connected to one cable connector 3, and the other end is connected to another cable connector 3.

[0026] Preferably, the cable connector 3 clamps the end of the superconducting current-limiting cable 2. The cable connector 3 is provided with a receiving hole 33, and the two ends of the superconducting current-limiting cable 2 are respectively inserted into the receiving holes 33 of the two cable connectors 3. The receiving holes 33 have a certain clamping force on the ends of the superconducting current-limiting cable 2, thereby realizing a close connection between the superconducting current-limiting cable 2 and the cable connector 3, and reducing power loss.

[0027] Preferably, a copper tube 4 is sleeved at the end of the superconducting current-limiting cable 2, and low-temperature solder is poured between the copper tube 4 and the superconducting current-limiting cable 2 to perform welding armoring. With this design, on the one hand, the copper tube 4 can protect the superconducting tape 22 in the cable joint 3 from extrusion damage; on the other hand, the superconducting current-limiting cable 2 is in close contact with the copper tube 4, thereby reducing the loss of electric energy. Specifically, in the exemplary embodiment, the copper tube 4 can be a hollow thick copper tube, and the outer periphery of the superconducting current-limiting cable 2 can be wrapped with high-performance insulating paper, that is, the two ends of the superconducting current-limiting cable 2 inserted into the cable joint 3 are not wrapped with insulating paper, and the part of the superconducting current-limiting cable 2 that is exposed to the superconducting tape 22 on the outer periphery includes insulating paper, which can prevent breakdown between the two superconducting current-limiting cables 2 and improve the safety and reliability of the superconducting coil overcurrent protection device.

[0028] Preferably, the cable connector 3 comprises: a lower plate 31 and an upper connector 32 which are detachably connected, a receiving hole 33 is formed between the lower plate 31 and the upper connector 32, and the end of the superconducting current limiting cable 2 is inserted into the receiving hole 33. The upper end of the upper connector 32 extends out of the cryogenic Dewar box 1, and the upper connector 32 can be connected to an external circuit. Specifically, in the exemplary embodiment, two parallel semicircular through grooves are provided on the upper surface of the lower plate 31, and the upper connector 32 comprises a horizontal plate and two vertical plates mounted on the horizontal plate, and two parallel semicircular through grooves are provided on the lower surface of the horizontal plate, and the horizontal plate is connected to the lower plate 31 by bolts, and two receiving holes 33 are formed between the horizontal plate and the lower plate 31, which are respectively used to clamp one end of two superconducting current limiting cables 2. The two vertical plates pass through the cryogenic Dewar box 1, and the top exposes the upper surface of the cryogenic Dewar box 1, and can be connected to an external circuit.

[0029] It should be noted that the cable connector 3 is made of copper and is galvanized on the surface of the copper material. Its main function is to provide mechanical support for the superconducting current limiting cable 22, and to guide the current from the cable connector 3 into the superconducting current limiting cable 2, and then to guide the current from the superconducting current limiting cable 2. The structure of the upper connector 32 is designed to be able to be wired to the outside of the low-temperature Dewar box 1, which is convenient for the connection operation of the equipment.

[0030] Preferably, the superconducting coil overcurrent protection device of the present invention also includes an epoxy support frame 5, which is a U-shaped structure and is located at the bottom of the cable connector 3. It is used to support the cable connector 3 to prevent the cable connector 3 from directly contacting the low-temperature Dewar box 1. The epoxy support frame 5 is made of epoxy resin material. The epoxy resin material has good mechanical strength and insulation properties at low temperatures. Its main function is to provide stable mechanical support for the superconducting current limiting cable 2. Due to its good insulation properties, it can prevent the superconducting current limiting cable 2 from having a grounding fault, thereby providing safety protection for the superconducting coil overcurrent protection device.

[0031] Preferably, the cryogenic Dewar box 1 is made of stainless steel, including a sealed upper cover and a box body, the top of the upper cover is provided with a liquid nitrogen inlet 11, a nitrogen outlet 12 and a mounting hole 13, the top of the cable connector 3 passes through the mounting hole 13, the number of the mounting holes 13 is 4, the mounting hole 13 is a strip structure, and the top of the cable connector 3 passes through the mounting hole 13 to connect with the external circuit. Liquid nitrogen is introduced into the liquid nitrogen inlet 11, and the liquid nitrogen enters the cryogenic Dewar box 1 to provide a 77K working environment for the superconducting current limiting cable 2. The liquid nitrogen is vaporized to form nitrogen, which is discharged from the nitrogen outlet 12. On the one hand, the discharge of nitrogen is convenient for balancing the pressure in the cryogenic Dewar box 1; on the other hand, it is convenient for the recycling of nitrogen.

[0032] The present invention also provides a superconducting coil overcurrent protection circuit based on a superconducting current limiting cable, referring to Figure 4The circuit includes a fusion superconducting magnet 6, a power supply, a first switch 7 and a superconducting coil overcurrent protection device 8 connected in sequence, and a heat dissipation resistor 9 and a second switch 10 are connected in parallel at both ends of the fusion superconducting magnet 6.

[0033] It should be noted that after the superconducting coil is energized, it becomes the fusion superconducting magnet 6. In practical applications, the superconducting coil needs to be energized, so the fusion superconducting magnet 6 is connected to the circuit, and the superconducting coil overcurrent protection circuit of the present application is used to protect the fusion superconducting magnet 6 from overcurrent.

[0034] In specific applications, the voltage fluctuation at the upper end of the cable connector 3 can be monitored by a computer to determine whether there is an overcurrent phenomenon. If the preset voltage threshold is reached, the computer sends a signal to disconnect the first switch 7, close the second switch 10, and connect the heat dissipation resistor 9 to the circuit, so that the energy in the fusion superconducting magnet 6 is transferred to the heat dissipation resistor 9 to prevent further damage to the fusion superconducting magnet 6. It is also necessary to monitor the temperature of the fusion superconducting magnet 6 to determine whether the fusion superconducting magnet is in a quenched state. If the superconducting state is restored, the computer sends a signal to close the first switch 7 and disconnect the second switch 10 at the same time. It is also necessary to check whether the superconducting coil overcurrent protection device and the heat dissipation resistor 9 can work normally to ensure the safety and reliability of the superconducting coil overcurrent protection circuit.

[0035] Compared with the prior art, the superconducting coil overcurrent protection device of the present application has the following beneficial effects: 1. Compared with the traditional current limiter, the superconducting coil overcurrent protection device of the present application has a fast response speed and better safety and reliability. The superconducting current limiting cable can respond quickly within a few milliseconds at the moment of the short-circuit fault, limiting the short-circuit current to a lower level. The superconducting current limiting cable of the present application has a better current limiting capability. Its superconducting tape can quickly quench when a short-circuit fault occurs, and the fault current can be shunted through the skeleton, which can more effectively limit the short-circuit current. 2. The superconducting coil overcurrent protection device of the present application is small in size and has more flexible usage scenarios. It has high current-carrying characteristics and high mechanical stability. It can both transmit current and limit fault current. The superconducting current-limiting cable has a simple structure and integrates detection, triggering, and current limiting, which is convenient for installation and subsequent equipment maintenance.

[0036] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0037] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0038] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0039] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples" or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0040] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A superconducting coil overcurrent protection device based on a superconducting current limiting cable, characterized in that: include: Low temperature Dewar box, with liquid nitrogen flowing into it; A superconducting current-limiting cable is located in the cryogenic Dewar box; A cable connector is connected to the end of the superconducting current-limiting cable, and the top thereof extends out of the low-temperature Dewar box.

2. The superconducting coil overcurrent protection device based on the superconducting current limiting cable according to claim 1 is characterized in that: The superconducting current-limiting cable comprises a skeleton and a superconducting tape spirally wound around the outer circumference of the skeleton.

3. The superconducting coil overcurrent protection device based on superconducting current limiting cable according to claim 1 is characterized in that: The number of the superconducting current-limiting cables is 2 and they are arranged in parallel.

4. The superconducting coil overcurrent protection device based on the superconducting current limiting cable according to claim 1 is characterized in that: The number of the cable connectors is 2, which are respectively located at the two ends of the superconducting current-limiting cable.

5. The superconducting coil overcurrent protection device based on superconducting current limiting cable according to claim 1 is characterized in that: The cable joint clamps the end of the superconducting current-limiting cable.

6. The superconducting coil overcurrent protection device based on a superconducting current limiting cable according to any one of claims 1 to 5, characterized in that: A copper tube is sleeved on the end of the superconducting current-limiting cable, and low-temperature solder is poured between the copper tube and the superconducting current-limiting cable to perform welding armoring.

7. The superconducting coil overcurrent protection device based on a superconducting current limiting cable according to any one of claims 1 to 5, characterized in that: The cable connector comprises: Lower plate; An upper connecting piece, the upper end of which extends out of the low-temperature Dewar box and is detachably connected to the lower plate; A receiving hole is formed between the lower plate and the upper connecting piece, and the end of the superconducting current-limiting cable is inserted into the receiving hole.

8. The superconducting coil overcurrent protection device based on a superconducting current limiting cable according to any one of claims 1 to 5, characterized in that: Also includes: An epoxy support frame is located at the bottom of the cable connector.

9. The superconducting coil overcurrent protection device based on a superconducting current limiting cable according to any one of claims 1 to 5, characterized in that: A liquid nitrogen inlet, a nitrogen outlet and a mounting hole are arranged on the top of the low-temperature Dewar box, and the top of the cable connector passes through the mounting hole.

10. A superconducting coil overcurrent protection circuit based on a superconducting current limiting cable, characterized in that: The invention comprises a fusion superconducting magnet, a power supply, a first switch and a superconducting coil overcurrent protection device as claimed in any one of claims 1 to 9 which are connected in sequence, and a resistor and a second switch are connected in parallel at both ends of the fusion superconducting magnet.

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