Liquid metal current limiting protection device and short circuit protection method

Abstract

The present invention provides a liquid metal current limiting protection device and method, belonging to the field of electric power technology. The liquid metal current limiting protection device of the present invention includes a circuit breaker mechanism and a liquid metal current limiting mechanism; the liquid metal current limiting mechanism includes a limiting end cover, an insulating shell and a fixed electrode; the limiting end cover and the fixed electrode are symmetrically arranged at both ends of the insulating shell, and form a closed cavity with the insulating shell; an insulating partition is vertically arranged inside the closed cavity, and a flow hole is provided in the middle position of the insulating partition; the liquid metal current limiting mechanism also includes a movable electrode, and the movable electrode includes a main body located between the limiting end cover and the insulating partition and a connecting part located outside the closed cavity; liquid metal is filled between the insulating partition and the main body, and between the insulating partition and the fixed electrode. The connecting part is connected in series with the circuit breaker mechanism. The liquid metal current limiting mechanism also includes an insulating contact fixedly connected to the connecting part, and the insulating contact is arranged corresponding to the circuit breaker mechanism.

Description

Technical Field

[0001] The present invention belongs to the technical field of power systems, and in particular relates to a liquid metal current limiting protection device and a short-circuit protection method. Background Art

[0002] As the capacity of power systems increases year by year, the short-circuit capacity and short-circuit current of power grids are also increasing, which has greatly affected the development of power grids. Therefore, the research on effective short-circuit current limiting devices to limit short-circuit current and improve the reliability of power grid operation has become an urgent issue that will restrict the stable operation of power systems, power construction and development in the future. Summary of the Invention

[0003] The present invention aims to at least solve the problems in the prior art of the liquid metal current limiting protection device that arc extinguishing cannot be achieved and the self-recovery time of the liquid metal path cannot be controlled, and to provide a liquid metal current limiting protection device and a protection method.

[0004] In a first aspect, an embodiment of the present disclosure provides a liquid metal current limiting protection device, comprising a circuit breaker mechanism and a liquid metal current limiting mechanism; the liquid metal current limiting mechanism comprises a limiting end cap, an insulating housing, and a fixed electrode; the limiting end cap and the fixed electrode are symmetrically disposed at both ends of the insulating housing and form a closed cavity with the insulating housing; an insulating partition is vertically disposed within the closed cavity, and a flow hole is provided in the middle of the insulating partition;

[0005] The liquid metal current limiting mechanism further includes a movable electrode, the movable electrode including a main body located between the limiting end cover and the insulating partition and a connecting portion located outside the closed cavity; liquid metal is filled between the insulating partition and the main body, and between the insulating partition and the fixed electrode;

[0006] In which, the connecting part and the circuit-breaking mechanism are connected in series through a soft wire; the liquid metal current limiting mechanism also includes an insulating contact fixedly connected to the connecting part, and the insulating contact is arranged corresponding to the circuit-breaking mechanism and is used to provide a switching signal for the circuit-breaking mechanism; the circuit-breaking mechanism operates based on the switching signal provided by the insulating contact, automatically cutting off the circuit to achieve arc extinguishing.

[0007] Optionally, the liquid metal current limiting mechanism further includes a reset mechanism, and the reset mechanism is arranged between the limiting end cover and the main body of the movable electrode.

[0008] Optionally, the reset mechanism includes a reset spring.

[0009] Optionally, the material of the limiting end cover is insulating material.

[0010] Optionally, the connecting portion and the circuit breaker mechanism are connected in series via a soft wire.

[0011] Optionally, the insulating shell is a cylindrical structure.

[0012] Optionally, the circuit breaker mechanism includes a mechanical switch.

[0013] Optionally, the shape of the through-hole is circular, elliptical, triangular, rectangular or square.

[0014] Optionally, the material of the liquid metal includes a gallium-indium-tin metal alloy.

[0015] In a second aspect, the present invention further provides a protection method using the above-mentioned liquid metal current limiting protection device, comprising the following steps:

[0016] Connecting the liquid metal current limiting protection device in series with the circuit breaker;

[0017] When a short circuit fault occurs, the pressure generated by the vaporization of liquid metal inside the sealed cavity of the liquid metal current limiting protection device is used to push the movable electrode outward to provide a switching signal for the circuit breaker mechanism;

[0018] The circuit breaker mechanism operates based on the switching signal provided by the movable electrode, and automatically cuts off the circuit to extinguish the arc. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic structural diagram of a liquid metal current limiting protection device provided by an embodiment of the present invention;

[0020] Figure 2 A schematic structural diagram of a liquid metal current limiting mechanism provided by an embodiment of the present invention;

[0021] Figure 3 for Figure 2 A cross-sectional view of the liquid metal flow limiting mechanism shown;

[0022] Figure 4 for Figure 2 Schematic diagram of the principle of rapid contraction and arc starting of liquid metal in the liquid metal current limiting mechanism shown. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the technical solutions of the present disclosure, the present disclosure is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0024] Unless otherwise defined, the technical or scientific terms used in this disclosure should have the usual meanings understood by people with ordinary skills in the field to which this disclosure belongs. The words "first", "second" and similar words used in this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one", "an" or "the" do not indicate a quantity limitation, but rather indicate the existence of at least one. Words such as "include" or "comprise" mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0025] Current current limiting circuit breakers are divided into two types: solid-state fuses and liquid metal current limiters. Solid-state fuses are disposable. The Joule heat generated by excessive current increases the resistance of the solid fuse, thus limiting the current. When the line current overloads to a certain level, the fuse blows, and the only option is to replace the blown fuse, resulting in high overall operation and maintenance costs. Furthermore, the technology for liquid metal current limiters is still immature. Most rely on the self-contraction effect of liquid metal in small-diameter flow holes to achieve overcurrent limiting protection. However, short-circuit protectors designed based on this principle suffer from problems such as an inability to extinguish arcs and uncontrollable self-recovery time for the liquid metal path.

[0026] In order to solve at least one of the above technical problems, an embodiment of the present invention provides a liquid metal current limiting protection device and a protection method using the liquid metal current limiting protection device. The liquid metal current limiting protection device and the protection method using the liquid metal current limiting protection device provided by the embodiment of the present invention are further described in detail below in combination with the accompanying drawings and specific implementation methods.

[0027] Firstly, Figure 1 A schematic structural diagram of a liquid metal current limiting protection device provided by an embodiment of the present invention is shown in FIG. Figure 2 A schematic structural diagram of a liquid metal current limiting mechanism provided by an embodiment of the present invention is shown. Figure 3 for Figure 2 The cross-sectional view of the liquid metal flow limiting mechanism is shown in FIG. Figure 1-3 As shown, an embodiment of the present invention provides a liquid metal current limiting protection device, which includes a circuit breaker mechanism 1 and a liquid metal current limiting mechanism 2, wherein the liquid metal current limiting mechanism 2 includes a limiting end cover 21, an insulating shell 22, a fixed electrode 23, a movable electrode 26 and an insulating contact 27.

[0028] Specifically, the limiting end cap 21 and the fixed electrode 23 are symmetrically arranged at both ends of the insulating shell 22, and form a closed cavity with the insulating shell 22. An insulating partition 24 is vertically arranged inside the closed cavity, and a flow hole 25 is provided in the middle of the insulating partition 24. The movable electrode 26 includes a main body 261 located between the limiting end cap 21 and the insulating partition 24 and a connecting portion 262 located outside the closed cavity, and the space between the insulating partition 24 and the main body 261 of the movable electrode, and between the insulating partition 24 and the fixed electrode 23 is filled with liquid metal. The material of the liquid metal can be selected according to the situation and is not specifically limited here. Optionally, the material of the liquid metal includes but is not limited to gallium indium tin metal alloy and the like.

[0029] Continue to refer Figure 1-3 Connecting portion 262 is connected in series with circuit breaker mechanism 1, and insulating contact 27 is fixedly connected to connection 262 of the movable electrode. Insulating contact 27 is provided corresponding to circuit breaker mechanism 1 and is used to provide a switching signal to circuit breaker mechanism 1. Circuit breaker mechanism 1 operates based on the switching signal provided by insulating contact 27, automatically disconnecting the circuit and extinguishing the arc to achieve circuit protection. The switching signal can be a displacement signal of movable electrode 26 or a thrust signal, which is not specifically limited here.

[0030] The limiting end cap 21 is used to limit the position of the movable electrode 26. Its material can be selected according to the situation and is not specifically limited here. Optionally, the material of the limiting end cap 21 is an insulating material. The circuit breaker mechanism 1 can also be selected according to the situation. In the implementation of the present invention, the circuit breaker mechanism 1 is preferably a mechanical switch.

[0031] The principle of the liquid metal current limiting protection device of the present invention is as follows:

[0032] like Figure 1-4 As shown, the liquid metal current limiting protection device is connected to the circuit through one end of the movable electrode 26 and one end of the fixed electrode 23. The fixed electrode 23, the liquid metal, and the movable electrode 26 form a path. When the current in the circuit is within the normal range, the three are normally conductive. When the current in the circuit increases abnormally due to a short circuit or other conditions, the local magnetic field at the flow hole 25 will increase accordingly, causing the liquid metal at the flow hole 25 to be affected by the lower Figure 4The Lorentz force F shown in the figure. When the current increases to a certain level, the liquid metal at the flow hole 25 shrinks under the action of the Lorentz force F, and the effective cross-sectional area of ​​the liquid metal in the flow hole 25 becomes smaller, resulting in an increase in the overall resistance of the liquid metal, resulting in a current limiting effect. As the current continues to increase and the liquid metal continues to shrink, the liquid metal breaks and arcs at the flow hole 25. The Joule heat generated by the current flow and the heat generated at the moment of arcing cause part of the liquid metal at the flow hole 25 to vaporize, generating a certain pressure. This pressure pushes the movable electrode 26 to move toward the limit end cover 21, releasing a switch signal (such as a displacement signal or a force signal) to the circuit breaker mechanism 1. After receiving the signal, the circuit breaker mechanism 1 immediately cuts off the circuit, thereby achieving arc extinguishing.

[0033] In this embodiment, since the liquid metal current limiting protection device includes a circuit breaker mechanism 1 and a liquid metal current limiting mechanism 2, the liquid metal current limiting mechanism 2 includes a limiting end cover 21, an insulating shell 22, a fixed electrode 23, a movable electrode 26 and an insulating contact 27, the limiting end cover 21 and the fixed electrode 23 are symmetrically arranged at both ends of the insulating shell 22, and form a closed cavity with the insulating shell 22, the closed cavity is filled with liquid metal, and an insulating partition 24 is vertically arranged inside the closed cavity, and a flow hole 25 is provided in the middle of the insulating partition 24. Therefore, when the current increases to a certain level, the liquid metal is discharged. When the current is increased, the liquid metal at the flow hole 25 shrinks under the action of the Lorentz force, and the effective cross-sectional area of ​​the liquid metal in the flow hole 25 becomes smaller, resulting in an increase in the overall resistance of the liquid metal and a current limiting effect. As the current continues to increase and the liquid metal continues to shrink, part of the liquid metal at the flow hole 25 vaporizes and generates pressure, pushing the movable electrode 26 toward the limit end cover 21, thereby releasing the switch signal to the circuit breaker mechanism 1. After receiving the signal, the circuit breaker mechanism 1 immediately cuts off the circuit, completely interrupting the flow, and then extinguishing the arc, ensuring the safety of operation and maintenance work when the line is abnormal. In addition, since the deformable conductor filled in the closed cavity is liquid metal, it can be reused, saving operation and maintenance costs.

[0034] In some embodiments, as Figure 1-3 As shown, the movable electrode 26 is made of a material with good conductivity and is designed as a cylindrical piston structure. It forms a sealing effect with the interior of the insulating shell 22, but can move axially relative to the insulating shell 22 to conduct electricity and push the insulating contact 27 to move. A through hole is opened on the connecting portion 262 of the movable electrode 26, which can be connected to an external conductive terminal. The fixed electrode 23 is also made of a material with good conductivity and is tightly connected to the end of the insulating shell 22 to form a good sealing effect. The fixed electrode 23 also has a through hole and can also be connected to an external conductive terminal. The shape of the insulating shell 22 can be selected according to the situation and is not specifically limited here. Preferably, the shape of the insulating shell 22 is cylindrical.

[0035] Optionally, the limiting end cover 21 and the insulating shell 22 , as well as the fixed electrode 23 and the insulating shell 22 are connected by fastening bolts.

[0036] In this embodiment, since the liquid metal flow limiting mechanism 2 is in the form of a cylindrical cylinder, it has the advantages of good sealing, high reliability, small size, and can be installed and placed in any direction.

[0037] In some embodiments, as Figure 3 As shown, the liquid metal current limiting mechanism 2 further includes a reset mechanism 28, which is disposed between the limiting end cap 21 and the main body 261 of the movable electrode. The reset structure may be an elastic sheet, a spring, or the like with a reset function. In this embodiment, the reset structure is preferably a reset spring.

[0038] During the complete circuit-breaking period, as the arc is extinguished within the liquid metal current-limiting mechanism 2, the vaporized liquid metal gradually condenses, and the internal pressure gradually decreases. Consequently, the movable electrode 26, under the action of the reset mechanism 28, gradually returns to its initial state, and the movable electrode 26, the liquid metal, and the fixed electrode 23 are once again conductive. However, because the circuit-breaking mechanism 1 is completely disconnected, no current flows within the liquid metal current-limiting mechanism 2. The circuit will resume normal operation until the fault is resolved and the circuit-breaking mechanism 1 is closed.

[0039] In this embodiment, since a reset mechanism 28 is also provided inside the liquid metal current limiting mechanism 2, when the line fault is eliminated, the liquid metal current limiting mechanism 2 can be reset and turned on normally without manual reset, thereby saving labor resources and reducing operation and maintenance costs.

[0040] In some embodiments, as Figure 1 As shown, the connecting portion 262 of the movable electrode 26 is connected in series with the circuit breaker mechanism 1 via a flexible wire 3 .

[0041] In this embodiment, the circuit breaker mechanism 1 and the liquid metal current limiting mechanism 2 are connected via a flexible conductor 3. This does not affect the transmission of the displacement signal or force signal of the liquid metal current limiting device to the circuit breaker mechanism 1, thereby ensuring timely shutdown of the circuit breaker mechanism 1. Optionally, the flexible conductor 3 can be connected to the circuit breaker mechanism 1 and the liquid metal current limiting mechanism 2 respectively by crimping terminals followed by screw fastening, or by direct welding or other methods not specifically limited herein.

[0042] Optionally, the shape of the through-hole is circular, elliptical, triangular, rectangular or square.

[0043] In a second aspect, an embodiment of the present invention provides a method for protection using the above-mentioned liquid metal current limiting protection device, comprising the following steps:

[0044] S100. Connect the liquid metal current limiting protection device and the circuit breaker in series.

[0045] S200 , when a short circuit fault occurs, the pressure generated by the vaporization of liquid metal inside the sealed cavity is used to push the movable electrode outward, thereby providing a switching signal for the circuit breaker mechanism.

[0046] S300: The circuit breaker mechanism 1 operates based on the switch signal provided by the movable electrode, and automatically cuts off the circuit to extinguish the arc.

[0047] It will be understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present invention, and the present invention is not limited thereto. Those skilled in the art will appreciate that various modifications and improvements can be made without departing from the spirit and substance of the present invention, and such modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A liquid metal current limiting protection device, characterized in that: The device comprises: a circuit breaker mechanism and a liquid metal current limiting mechanism; the liquid metal current limiting mechanism comprises a limiting end cover, an insulating shell, and a fixed electrode; the limiting end cover and the fixed electrode are symmetrically arranged at both ends of the insulating shell and form a closed cavity with the insulating shell; an insulating partition is vertically arranged inside the closed cavity, and a flow hole is provided in the middle of the insulating partition; The liquid metal current limiting mechanism further includes a movable electrode, the movable electrode including a main body located between the limiting end cover and the insulating partition and a connecting portion located outside the closed cavity; liquid metal is filled between the insulating partition and the main body, and between the insulating partition and the fixed electrode; In which, the connecting part and the circuit-breaking mechanism are connected in series through a soft wire; the liquid metal current limiting mechanism also includes an insulating contact fixedly connected to the connecting part, and the insulating contact is arranged corresponding to the circuit-breaking mechanism and is used to provide a switching signal for the circuit-breaking mechanism; the circuit-breaking mechanism operates based on the switching signal provided by the insulating contact, automatically cutting off the circuit to achieve arc extinguishing.

2. The liquid metal current limiting protection device according to claim 1, characterized in that: The liquid metal current limiting mechanism further includes a reset mechanism, which is arranged between the limiting end cover and the main body of the movable electrode.

3. The liquid metal current limiting protection device according to claim 2, characterized in that: The reset mechanism includes a reset spring.

4. The liquid metal current limiting protection device according to claim 1, characterized in that: The material of the position-limiting end cover is insulating material.

5. The liquid metal current limiting protection device according to claim 1, characterized in that: The connecting portion and the circuit breaker mechanism are connected in series via a flexible wire.

6. The liquid metal current limiting protection device according to claim 1, characterized in that: The insulating shell is a cylindrical structure.

7. The liquid metal current limiting protection device according to claim 1, characterized in that: The circuit breaker mechanism includes a mechanical switch.

8. The liquid metal current limiting protection device according to claim 1, characterized in that: The shape of the through-flow hole is circular, elliptical, triangular, rectangular or square.

9. The liquid metal current limiting protection device according to claim 1, characterized in that: The material of the liquid metal includes a gallium-indium-tin metal alloy.

10. A short circuit protection method using the liquid metal current limiting protection device according to any one of claims 1 to 9, characterized in that: The short-circuit protection method comprises the following steps: Connecting the liquid metal current limiting protection device in series with the circuit breaker; When a short circuit fault occurs, the pressure generated by the vaporization of liquid metal inside the sealed cavity of the liquid metal current limiting protection device is used to push the movable electrode outward to provide a switching signal for the circuit breaker mechanism; The circuit breaker mechanism operates based on the switching signal provided by the movable electrode, and automatically cuts off the circuit to extinguish the arc.

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