Superconducting current fault limiter with direct cooling structure

Abstract

The present invention relates to a superconducting current limiter, comprising a current limiter tank with an internally sealed interior, a cold head that is cooled to a cryogenic temperature, a cryogenic refrigerator arranged so that the cold head is introduced into the current limiter tank, and a refrigerant container that is sealed inside the current limiter tank, has a superconducting element installed inside, and contains a liquid refrigerant filled to a height greater than the height at which the superconducting element is installed for cooling the superconducting element, wherein one side of the refrigerant container protrudes to a position inside the current limiter tank into which the cold head is introduced and a protrusion formed to fill the liquid refrigerant is formed, and the cold head is introduced into the interior of the refrigerant container through the upper side of the protrusion, so that at least a portion of the introduced cold head is received in the liquid refrigerant filled in the protrusion.

Description

Technology Field

[0001] The present invention relates to a superconducting current limiter, and more specifically to a cooling structure of said superconducting current limiter. Background Technology

[0002] A superconductor refers to a material that loses electrical resistance below a specific temperature (superconducting critical temperature), and has the characteristic of becoming a perfect conductor with zero resistance (superconductivity) below the superconducting critical temperature. In this case, since the resistance is zero, it is possible to conduct electricity without power loss. On the other hand, at temperatures exceeding the superconducting critical temperature, the superconductivity is lost, and thus resistance occurs.

[0003] Meanwhile, fault current limiters are emerging that utilize superconductors exhibiting opposite phase change phenomena depending on temperature, enabling them to protect power system equipment from abnormal currents (fault currents) caused by accidents such as ground faults, short circuits, and lightning strikes while minimizing power loss during current flow.

[0004] A current limiter utilizing a superconductor in this manner is called a superconducting current fault limiter. In the case of the superconducting current limiter, it maintains superconducting characteristics in cryogenic environments where the temperature is maintained below the superconducting critical temperature, thereby enabling current flow without power loss. However, if a current exceeding the allowable value is introduced due to abnormal currents such as ground faults, short circuits, or lightning strikes, the superconductor exceeds the superconducting critical temperature and loses its superconductivity; the resistance resulting from this loss of superconductivity can limit the flow of current.

[0005] As such, superconducting current limiters utilize the resistance generated by the loss of superconductivity in superconductors, offering the advantage of limiting current within a very short time of a few milliseconds in the event of abnormal current. Furthermore, since current flow can be maintained without power loss when cryogenic conditions are maintained, they are gaining attention as ideal current limiters.

[0006] However, such a superconducting current limiter utilizes the phase change phenomenon of a superconductor depending on temperature, and must be able to maintain the superconductor at a temperature below the critical temperature. However, since the critical temperature is typically an ultra-low temperature of 77K (Kelvin) or lower, a cryogenic cooling system is required to maintain the superconductor in an ultra-low temperature state of 77K or lower. To this end, a conventional superconducting current limiter cools the superconductor by placing supercooled liquid nitrogen into a refrigerant, and has a configuration in which the heat load of the container containing the liquid nitrogen is removed through a cryogenic refrigerator operating in a closed cycle.

[0007] Meanwhile, a conventional superconducting current limiter has a configuration for cooling a liquid nitrogen container using a cryogenic refrigerator by attaching a thermally conductive member formed of a medium with high thermal conductivity to the outer wall of the container and connecting the cold head of the cryogenic refrigerator to the attached thermally conductive member, thereby cooling the liquid nitrogen container by a conduction cooling method. However, this conduction cooling method using a thermally conductive member has a problem in that, no matter how high the thermal conductivity is, the medium itself has a thermal resistance component, and the cooling efficiency is reduced due to this thermal resistance component. The problem to be solved

[0008] The present invention aims to solve the aforementioned problems and other problems by providing a superconducting current limiter having a cooling structure capable of maximizing the cooling efficiency of a cryogenic refrigerator when cooling a liquid nitrogen receiving container using a cryogenic refrigerator. means of solving the problem

[0009] According to one aspect of the present invention for achieving the above or other purposes, a superconducting current limiter according to an embodiment of the present invention comprises: a current limiter tank having an interior that is sealed; a cryogenic refrigerator having a cold head that is cooled to a cryogenic temperature and arranged so that the cold head is introduced into the current limiter tank; and a refrigerant container having a superconducting element installed inside the current limiter tank and a liquid refrigerant filled to a height greater than the height at which the superconducting element is installed for cooling the superconducting element, wherein one side of the refrigerant container protrudes to a position inside the current limiter tank into which the cold head is introduced and a protrusion formed to fill the liquid refrigerant is formed, and the cold head is introduced into the interior of the refrigerant container through the upper side of the protrusion, so that at least a portion of the introduced cold head is received in the liquid refrigerant filled in the protrusion.

[0010] In one embodiment, the cryogenic refrigerator is characterized in that the cold head is introduced into the current limiter tank so that it reaches a height corresponding to the storage level of the liquid refrigerant filled in the refrigerant container.

[0011] In one embodiment, the refrigerant container is characterized by having a preset pressure and insulation thickness, and including an insulating gas to insulate between the upper cover of the refrigerant container and the liquid refrigerant.

[0012] In one embodiment, the cryogenic refrigerator is characterized in that the cold head is introduced into the current limiter tank in a direction perpendicular to gravity so as to be installed in a direction perpendicular to gravity.

[0013] In one embodiment, the liquid refrigerant is characterized by directly receiving cold air discharged from the cryogenic refrigerator through at least a portion of the cold head contained in the liquid refrigerant filled in the protrusion.

[0014] In one embodiment, the liquid refrigerant is characterized as being nitrogen in a supercooled liquid state.

[0015] In one embodiment, the adiabatic gas is a mixed gas of gaseous nitrogen and gaseous non-condensable helium, and the non-condensable gas is characterized as being one of hydrogen, helium, or neon having a vaporization point lower than that of nitrogen.

[0016] In one embodiment, the cryogenic refrigerator is characterized as being a GM refrigerator equipped with Gifford-McMahon (GM) refrigeration technology.

[0017] In addition, a superconducting current limiter according to another embodiment of the present invention comprises a current limiter tank with an interior sealed, a cold head that is cooled to a cryogenic temperature, a cryogenic refrigerator arranged so that the cold head is introduced into the current limiter tank, and a refrigerant container provided in a sealed state inside the current limiter tank, having a superconducting element installed inside and filled with a liquid refrigerant to a height greater than the height at which the superconducting element is installed for cooling the superconducting element, wherein the cryogenic refrigerator is connected to a refrigeration module that forms cold air and the cold head through an L-shaped arm, and one side of the refrigerant container has a hole formed to allow the cold head connected to the arm to be inserted, and the cold head is introduced into the interior of the refrigerant container through the hole so that at least a portion of the introduced cold head is received in the liquid refrigerant filled in the refrigerant container.

[0018] In one embodiment, the hole into which the cold head is inserted is characterized by being formed at a height below the level corresponding to the liquid refrigerant level filled in the refrigerant container.

[0019] In one embodiment, the liquid refrigerant is characterized by directly receiving cold air discharged from the cryogenic refrigerator through at least a portion of the cold head contained in the liquid refrigerant.

[0020] In one embodiment, the cryogenic refrigerator is characterized by being installed in a direction perpendicular to gravity. Effects of the invention

[0021] The superconducting current limiter according to the present invention is described as follows.

[0022] According to at least one embodiment of the present invention, the present invention has the advantage of being able to directly cool the liquid nitrogen contained in a container without thermal resistance caused by the medium characteristics of the thermally conductive member by directly transferring the cold air of a cryogenic refrigerator to the liquid nitrogen contained in the container without a thermally conductive member. Therefore, the present invention has the effect of maximizing the cooling effect of a cryogenic refrigerator in a superconducting current limiter. Brief explanation of the drawing

[0023] Figure 1 is a block diagram illustrating the general structure of a superconducting current limiter. Figure 2 is an example diagram illustrating a structure in which a cryogenic refrigerator and a liquid nitrogen receiving vessel are connected through a thermally conductive member in the above-mentioned general superconducting current limiter. FIG. 3 is a block diagram illustrating the structure of a superconducting current limiter according to an embodiment of the present invention. FIG. 4 is a block diagram illustrating the structure of a superconducting current limiter according to another embodiment of the present invention. FIG. 5 is a block diagram illustrating the structure of a superconducting current limiter according to another embodiment of the present invention. Specific details for implementing the invention

[0024] It should be noted that technical terms used in this specification are used merely to describe specific embodiments and are not intended to limit the invention. Additionally, singular expressions used in this specification include plural expressions unless the context clearly indicates otherwise. The suffixes "module" and "part" for components used in the following description are assigned or used interchangeably solely for the ease of drafting the specification and do not inherently possess distinct meanings or roles.

[0025] In this specification, terms such as "composed of" or "comprising" should not be interpreted as necessarily including all of the various components or steps described in the specification, and should be interpreted as potentially excluding some of the components or steps, or including additional components or steps.

[0026] In addition, when describing the technology disclosed in this specification, if it is determined that a detailed description of related prior art could obscure the essence of the technology disclosed in this specification, such detailed description is omitted.

[0027] In addition, the attached drawings are intended only to facilitate understanding of the embodiments disclosed in this specification, and the technical concept disclosed in this specification is not limited by the attached drawings; it should be understood that they include all modifications, equivalents, and substitutions that fall within the concept and technical scope of the present invention. Furthermore, not only each of the embodiments described below, but also combinations of embodiments may fall within the concept and technical scope of the present invention as modifications, equivalents, and substitutions that fall within the concept and technical scope of the present invention.

[0028] FIG. 1 is a block diagram illustrating the general structure of a superconducting current limiter (1). FIG. 2 is an example diagram illustrating the structure in which a cryogenic refrigerator and a liquid nitrogen receiving vessel are connected through a thermally conductive member in the general superconducting current limiter (1).

[0029] First, referring to FIG. 1, a general superconducting current limiter (1) is equipped with a plurality of HTS (High Temperature Superconductivity) elements (13) which are superconductors having superconducting properties, and in order to maintain the superconducting properties of the HTS elements (13), the HTS elements (13) are stored in sub-cooled liquid nitrogen (Sub Cooled LN2 (Liquid Nitrogen 2)) so that the HTS elements (13) can maintain an ultra-low temperature state.

[0030] To this end, a conventional superconducting current limiter (1) may be formed by including a current limiter tank (20) with an internally sealed interior as shown in FIG. 1, a refrigerant container (10) that stores liquid and gaseous refrigerants for cooling HTS elements (13) that generate heat by operating current and is sealed inside the current limiter tank (20), and at least one cryocooler that induces cooling of the HTS elements (13) by conducting cold air to the refrigerant inside the refrigerant container (10).

[0031] Looking more closely, the upper side of the current limiter tank (20) can be formed to be sealed with a cover, and the interior (21) can be vacuum-sealed. It can also be insulated to minimize heat transfer from the outside. Furthermore, the upper cover of the sealed refrigerant container (10) can be exposed to the outside through a part of the cover of the current limiter tank (20).

[0032] And the above refrigerant container (10) may be provided in a sealed state inside the above current limiter tank (20). It may also be insulated, and may be filled with a refrigerant in a different liquid state (11, liquid refrigerant) and an insulating gas (12) inside.

[0033] Meanwhile, a plurality of HTS elements (13) may be installed inside the refrigerant container (10). Additionally, the upper cover of the refrigerant container (10) may be provided with a plurality of outer connecting parts (41) protruding outward. Furthermore, a plurality of inner connecting parts (42) connecting each of the plurality of HTS elements (13) and the plurality of outer connecting parts (41) may be provided. That is, the plurality of HTS elements (13) installed inside the refrigerant container (10) may be connected to the outer connecting parts protruding outward from the refrigerant container (10) through the inner connecting parts connected to each HTS element. Accordingly, the superconducting current limiter (1) may receive current (operating current) from outside the refrigerant container (10) through some of the outer connecting parts and some of the inner connecting parts, and may supply the supplied operating current to the outside of the refrigerant container (10) through other parts of the outer connecting parts and other parts of the inner connecting parts.

[0034] Meanwhile, the liquid refrigerant (11) filled into the refrigerant container (10) may be liquid nitrogen in a supercooled state as described above. In this case, the liquid refrigerant (11) may be filled to a height greater than the height at which the plurality of HTS elements (13) installed inside are installed, as shown in FIG. 1, so as to cool the plurality of HTS elements (13) that generate heat by the operating current. Accordingly, the plurality of HTS elements (13) are completely contained in the liquid refrigerant (11), and by absorbing the heat (joule heat) generated by the plurality of HTS elements (13) by the operating current, the superconducting characteristics of the plurality of HTS elements (13) can be maintained.

[0035] And the insulating gas (12) is intended to block heat transfer to the liquid refrigerant (11) from the upper cover of the refrigerant container (10) exposed through the cover of the current limiter tank (20), and may be a gas with excellent insulating properties filled to have a preset pressure (e.g., 3 Bar). For example, a mixture of gaseous nitrogen (GN2) and gaseous non-condensing gas helium (GHe) may be filled into the refrigerant container (10) with a sufficient thickness (d) (15) to block the heat transfer as the insulating gas (12). Here, the non-condensing gas may be any one of hydrogen gas, helium gas, and neon gas having a vaporization point lower than that of nitrogen.

[0036] Meanwhile, the liquid refrigerant (11) filled in the refrigerant container (10) can absorb heat generated by the plurality of HTS elements (13) by the operating current as described above. Therefore, in order to remove the heat absorbed by the liquid refrigerant (11), i.e., the heat load, the superconducting current limiter (1) may further include at least one cryogenic refrigerator (30).

[0037] The above cryogenic refrigerator (30) is equipped with a cold head (31) that is cooled to a cryogenic temperature using a heat-circulating fluid, and can freeze an object in contact to a cryogenic temperature by means of cold conduction through the cold head. The above cryogenic refrigerator (30) may use refrigeration technology such as GM (Gifford-McMahon) for cryogenic freezing through the heat circulation. Hereinafter, a cryogenic refrigerator using the above Gifford-McMahon refrigeration technology will be referred to as a GM refrigerator.

[0038] In order to remove the heat load of the liquid refrigerant (11) using the cryogenic refrigerator (30) as described above, a conventional superconducting current limiter (1) has a configuration in which a heat-conducting member (23) formed of a medium with high thermal conductivity is attached to the outer surface of a refrigerant container (10), and the attached heat-conducting member (23) and the cold head (31) of the cryogenic refrigerator (30) are connected through a heat transfer member (22), thereby transferring the cold air of the cold head (31) to the heat-conducting member (23) through the heat transfer member (22). Then, the heat-conducting member (23), cooled by the cold air of the cold head (31), cools the refrigerant container (10), thereby removing the heat load of the liquid refrigerant (11).

[0039] To this end, referring to FIG. 2 for a more detailed view, inside the current tank (20) as shown in FIG. 2 (a), a heat-conducting member (23) formed to surround a refrigerant container (10) can be formed to be connected to a heat transfer member (22) connected to a cold head (31) of a cryogenic refrigerator (30), as shown in FIG. 2 (b) and FIG. 2 (c), which illustrates FIG. 2 (b) in more detail. Thus, cold air is propagated throughout the heat-conducting member (23) through a point of the heat-conducting member (23) connected to the heat transfer member (22), and the liquid refrigerant (11) inside the refrigerant container (10) can be cooled by the heat-conducting member (23) attached to surround the refrigerant container (10).

[0040] However, in this indirect cooling method using a heat-conducting member (23) and a heat transfer member (22), even if a medium made of a material with high thermal conductivity is used, there is a thermal resistance component inherent to the medium itself. Therefore, due to this thermal resistance component, the cooling efficiency of the cryogenic refrigerator (30) may be reduced. This reduction in cooling efficiency can cause a decrease in the cooling performance of the liquid refrigerant (11), and furthermore, in the case of cryogenic temperatures, there is a problem that a large difference in cooling performance occurs even with a small temperature difference. In order to compensate for the reduced cooling efficiency, the cryogenic refrigerator (30) must be driven so that the cold head (31) is cooled to a lower temperature, which causes a problem of increased power consumption of the cryogenic refrigerator (30).

[0041] To solve this problem, the superconducting current limiter according to an embodiment of the present invention allows the liquid refrigerant (11) to be cooled through a direct cooling structure that directly cools the liquid refrigerant (11) by bringing the cold head (31) of the cryogenic refrigerator (30) into direct contact with the liquid refrigerant (11).

[0042] However, due to the operating principle, the cryogenic refrigerator (30) must be used in a vertical position from top to bottom, that is, perpendicular to gravity, to enable high-efficiency operation. And when the cryogenic refrigerator (30) is installed in a direction perpendicular to gravity, if the cryogenic refrigerator is positioned on the upper part of the refrigerant container (300), it may be adjacent to the part where current flows (outer connection part (41)), which may cause insulation problems.

[0043] In addition, due to the structure of a conventional superconducting current limiter (1), the length of the cold head (31) protruding from the cryogenic refrigerator (30) is short. Therefore, when the liquid refrigerant (11) level is raised so that the liquid refrigerant (11) can come into direct contact with the cold head (31), the thickness of the insulating gas (12) above the liquid refrigerant (11) may be reduced. However, since the insulating gas (12) has a significant effect on insulation, if the thickness of the insulating gas (12) is reduced, the insulation effect is lowered and heat inflow may increase. Therefore, the thickness (d) of the insulating gas (12) must be maintained, and accordingly, the maximum level of the liquid refrigerant (11) may be limited.

[0044] FIG. 3 illustrates a refrigerant container (300) according to an embodiment of the present invention that can satisfy these conditions and has a direct cooling structure in which the cold head (31) of the cryogenic refrigerator (30) can directly cool the liquid refrigerant (11).

[0045] Referring to FIG. 3, the superconducting current limiter (100) according to an embodiment of the present invention may be positioned such that the cold head (31) of the cryogenic refrigerator (30) can come into direct contact with the liquid refrigerant (11) while maintaining the thickness (d) (15) of the insulating gas (12), and the cryogenic refrigerator (30) may be positioned at a lower position, i.e., closer to the HTS element (13) or the liquid refrigerant (11). Additionally, the insulating gas (12) may be filled to have the same pressure (e.g., 3 BAR) as a conventional superconducting current limiter (1). Accordingly, the insulating gas (12) may have the same insulating performance as a conventional superconducting current limiter (1).

[0046] More specifically, the cryogenic refrigerator (30) can be positioned such that the cold head (31) of the cryogenic refrigerator (30) is positioned at a height corresponding to the level of the liquid refrigerant (11) while maintaining the thickness (d) (15) of the insulating gas (12).

[0047] In addition, the refrigerant container (300) of the superconducting current limiter (100) according to an embodiment of the present invention may have a structure in which each side of the refrigerant container (300) adjacent to the cryogenic refrigerator (30) protrudes up to a height in which the cold head (31) of each cryogenic refrigerator (30) is inserted. In this case, the cold head (31) of the cryogenic refrigerator (30) may be inserted into each of the upper sides of the protrusions (301, 302) formed on each side of the refrigerant container (300).

[0048] Meanwhile, liquid refrigerant (11) can be filled into each of the above protrusions (301, 302). Accordingly, at least a portion of the cold head (100) can be accommodated in the liquid refrigerant (11) filled into each of the above protrusions (301, 302), and accordingly, each of the above cold heads (31) can come into direct contact with the liquid refrigerant (11).

[0049] As such, the ultra-low temperature current limiter (100) according to an embodiment of the present invention is configured such that the cold head (31) is positioned at a height corresponding to the liquid refrigerant (11) while maintaining the thickness (d) (15) of the insulating gas (12), and the refrigerant container (300) can be extended within the current limiter tank (310) to the portion into which the cold head (31) is inserted through protrusions (301, 302) that protrude to the position into which the cold head (31) of the ultra-low temperature refrigerator (30) is inserted. Additionally, by having a configuration in which the liquid refrigerant (11) is filled to the portion extended through the protrusions (301 or 302), the cold head (31) of the ultra-low temperature refrigerator (30) is configured to come into direct contact with the liquid refrigerant (11). Therefore, the present invention has the advantage that since the cold head (31) directly transfers cold air to the liquid refrigerant (11) without a medium, a decrease in cooling efficiency due to the thermal resistance characteristics of the thermally conductive member or the heat transfer member does not occur.

[0050] Meanwhile, the above description assumes that the length and shape of the cold head (31) protruding from the cooling module of the cryogenic refrigerator (30) are limited. However, if the length of the protruding cold head (31) can be extended, it is obvious that the cold head (31) can be extended to directly cool the liquid refrigerant (11) inside the refrigerant container (300).

[0051] FIG. 4 is a block diagram illustrating the structure of a superconducting current limiter (200) according to another embodiment of the present invention.

[0052] Referring to FIG. 4, the superconducting current limiter (200) according to the embodiment of the present invention is shown as being formed in an arm (401) of a cryogenic refrigerator (30) such that the cold head (31) is formed to be bent into an 'L' shape. In this case, the refrigerant container (400) of the superconducting current limiter (200) according to the embodiment of the present invention may have a hole formed on each side where each cryogenic refrigerator (30) is placed, so that the cold head (31) of each cryogenic refrigerator (30) can be inserted. In this case, the refrigerant container (400) with the hole formed therein may have a structure that is sealed due to the insertion of the cold head (31).

[0053] Meanwhile, the above-described cryogenic refrigerator (30) has a structure in which a cold head (31) is inserted into the side of a refrigerant container (400) according to the above-described 'L'-shaped arm (401), and can be positioned in a direction perpendicular to gravity. Therefore, the cryogenic refrigerator (30) can also be operated with high efficiency. In addition, the hole into which the cold head (31) is inserted is formed at a height below the level corresponding to the liquid refrigerant (11) while maintaining the thickness (d) (15) of the insulating gas (12), so the cold head (31) can come into direct contact with the liquid refrigerant (11) filled in the refrigerant container (400). Accordingly, the superconducting current limiter (200) according to another embodiment of the present invention also has the advantage that, since the cold head (31) directly transmits cold air to the liquid refrigerant (11) without a medium, a decrease in cooling efficiency due to the thermal resistance characteristics of the medium (thermal conductive member or heat transfer member) does not occur.

[0054] Meanwhile, although the above description explains a form in which a protrusion protrudes from the side of the refrigerant container, it goes without saying that the present invention is not limited thereto. For example, it goes without saying that a part of the refrigerant container, rather than the side, may be recessed to a height close to the liquid refrigerant level, and a cryogenic refrigerator may be installed in the recessed part.

[0055] FIG. 5 is a block diagram illustrating the structure of a superconducting current limiter (300) according to an embodiment of the present invention.

[0056] Referring to FIG. 5, a superconducting current limiter (500) according to another embodiment of the present invention may have a current limiter tank (510) having a refrigerant container (500) in which at least a portion is recessed. In this case, a portion of the refrigerant container (500) may be recessed to a height adjacent to the height (vertical distance from the base surface of the current limiter tank (510)) in which the liquid refrigerant (11) containing the plurality of HTS elements (13) is filled. And a cryogenic refrigerator (30) may be introduced in the direction of gravity into the recessed portion.

[0057] Accordingly, as shown in FIG. 5, the cold head (31) of the cryogenic refrigerator (30) introduced into a portion of the recessed refrigerant container (500) can come into contact with at least a portion of the liquid refrigerant (11). Therefore, the coldness of the cold head (31) can be directly transferred to the liquid refrigerant (11).

[0058] The foregoing detailed description of the present invention shall not be interpreted as restrictive in all respects and shall be considered as exemplary. The scope of the present invention shall be determined by a reasonable interpretation of the appended claims, and all modifications within the equivalent scope of the present invention are included within the scope of the present invention.

Claims

Claim 1 delete Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 delete Claim 6 delete Claim 7 delete Claim 8 delete Claim 9 A superconducting current limiter comprising: a current limiter tank having an interior that is sealed; a cryogenic refrigerator having a cold head that is cooled to a cryogenic temperature and arranged so that the cold head is introduced into the current limiter tank; and a refrigerant container having a superconducting element installed inside the current limiter tank and containing a liquid refrigerant filled to a height greater than the height at which the superconducting element is installed for cooling the superconducting element, wherein the cryogenic refrigerator is connected to a refrigeration module that forms cold air and the cold head through an L-shaped arm, and one side of the refrigerant container has a hole formed to allow the cold head connected to the arm to be inserted, and the cold head is introduced into the interior of the refrigerant container through the hole so that at least a portion of the introduced cold head is received in the liquid refrigerant filled in the refrigerant container. Claim 10 A superconducting current limiter according to claim 9, characterized in that the hole into which the cold head is inserted is formed at a height below the level corresponding to the liquid refrigerant level filled in the refrigerant container. Claim 11 A superconducting current limiter according to claim 9, characterized in that the liquid refrigerant directly receives cold air discharged from the cryogenic refrigerator through at least a portion of the cold head contained in the liquid refrigerant. Claim 12 In claim 9, the superconducting current limiter is characterized in that the cryogenic refrigerator is installed in a direction perpendicular to gravity. Claim 13 A superconducting current limiter comprising: a cryogenic refrigerator having a cold head that is cooled to a cryogenic temperature and arranged so that the cold head is introduced into the tank of the current limiter; a refrigerant container having a superconducting element installed inside and containing a liquid refrigerant filled to a height greater than the height at which the superconducting element is installed for cooling the superconducting element, wherein a portion of the upper cover of the refrigerant container has a recess formed that is recessed downward in the direction of the refrigerant container up to a height adjacent to the height at which the liquid refrigerant is filled, and the cryogenic refrigerator is introduced through the recessed upper cover of the refrigerant container so that at least a portion of the cold head is contained in the liquid refrigerant.

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