WO2023182668A1 - Superconducting fault current limiter having direct cooling structure and method for controlling same - Google Patents

Abstract

The present invention relates to a superconducting fault current limiter having a direct cooling structure and a method for controlling same. The superconducting fault current limiter having a direct cooling structure, according to the present invention, comprises: a cryogenic freezer having a cold head inserted into a fault current limiter tank; a refrigerant container containing a liquid refrigerant and an insulating gas; a freezer insertion part into which the cold head is inserted and which is filled with the liquid refrigerant and the insulating gas; a water level adjustment gas flow channel and a water level adjustment valve through which the insulating gas of the freezer insertion part is discharged or introduced; a pressure adjustment flow channel and a pressure adjustment valve connecting a main chamber of the refrigerant container to the water level control gas flow channel; and a control part for controlling the water level adjustment valve and the pressure adjustment valve so that, when the cryogenic freezer is driven, the liquid refrigerant is in contact with or separated from the cold head of the cryogenic freezer.

Description

Superconducting current limiter with direct cooling structure and its control method

The present invention relates to a superconducting current limiter, and more specifically to a cooling structure of the superconducting current limiter.

Superconductor refers to a material that loses electrical resistance below a certain temperature (superconductivity critical temperature). Below the superconductivity critical temperature, it has the characteristic of becoming a perfect conductor with a resistance of 0 (superconductivity). In this case, since the resistance is 0, it is possible to conduct electricity without loss of power. On the other hand, at temperatures exceeding the superconductivity critical temperature, the superconductivity is lost and resistance is generated.

Meanwhile, by using superconductors that have opposing phase changes depending on temperature, power loss is minimized when energized, while protecting power system devices in the event of fault currents that occur in accidents such as ground faults, short circuits, and lightning strikes. A fault current limiter is emerging.

The current limiter using a superconductor like this is called a superconducting current fault limiter. In the case of the superconducting current fault limiter, the superconducting characteristics are maintained in a cryogenic environment where the temperature is maintained below the superconducting critical temperature, so current is passed without power loss. Make this possible. However, if an abnormal current such as a ground fault, short circuit, or lightning occurs, and a current exceeding the allowable value is drawn, superconductivity is lost, and resistance generated due to the loss of superconductivity of the superconductor may limit the conduction of current.

In this way, the superconducting current limiter utilizes the phase change phenomenon of the 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 generally a cryogenic temperature of 77K (Kelvin) or lower, a cryogenic cooling system is needed to maintain the superconductor at a cryogenic temperature of 77K or lower. For this purpose, a typical superconducting current limiter cools the superconductor using supercooled liquid nitrogen as a refrigerant, and the heat load of the container containing the liquid nitrogen is removed through a cryogenic refrigerator operated in a closed cycle. .

Meanwhile, in the case of a superconducting current limiter, liquid nitrogen, a liquid refrigerant, absorbs the heat generated in the superconductor by the operating current, and the heat absorbed by the liquid refrigerant, that is, the heat load, is cooled through a cryogenic refrigerator. Therefore, the larger the operating current, that is, the closer to the maximum allowable current (rated current), the larger the heat load, and a cooling effect with greater output is required to remove the large heat load. Accordingly, a typical superconducting current limiter can achieve a sufficient cooling effect to remove the heat load by operating a plurality of cryogenic refrigerators in parallel.

However, the operating current may vary depending on the current load. For example, the operating current is proportional to the current flowing in the load, that is, the current load, and the operating current is also proportional to the heat load. Therefore, the smaller the operating current, the smaller the heat load, so when the current load is small, only weaker cold air may be sufficient to maintain the liquid refrigerant below the critical temperature.

However, in the case of a typical superconducting current limiter, the plurality of cryogenic refrigerators are configured to operate simultaneously in parallel regardless of the heat load. Therefore, since a plurality of cryogenic refrigerators are operated even with a small heat load, unnecessary operation may occur. In this case, the maintenance cost of the cryogenic refrigerator greatly increases depending on the operation time, so there is a problem that the maintenance cost of the superconducting current limiter increases due to the unnecessary operation of the cryogenic refrigerator.

The present invention aims to solve the above-described problems and other problems. When cooling a liquid nitrogen container using a cryogenic refrigerator, a superconducting current limiter having a cooling structure capable of maximizing the cooling efficiency of the cryogenic refrigerator, and the same. The purpose is to provide a control method for a superconducting current limiter.

Additionally, the present invention provides a superconducting current limiter and a control method for the superconducting current limiter that can further reduce maintenance costs by preventing excessive operation of a cryogenic refrigerator.

According to one aspect of the present invention to achieve the above or other objects, a superconducting current limiter according to an embodiment of the present invention includes a current limiter tank whose interior is sealed; A cryogenic refrigerator that is cooled to a very low temperature and has a cold head that is introduced into a current limiter tank; A refrigerant container that is sealed inside the current limiter tank and includes a liquid refrigerant filled to a height higher than the height at which the superconductor element is installed, and an insulating gas having a preset pressure and filled on the liquid refrigerant; The cold head is introduced at the top, the liquid refrigerant and the insulating gas are filled, and the insulating gas is filled in the refrigerant container by the liquid refrigerant formed on one side of the refrigerant container and filled with one side of the refrigerant container. A freezer inlet forming a space separated from the main room; A water level control gas flow path connected to the freezer inlet to discharge the insulating gas in the freezer inlet or to allow the insulating gas to flow into the freezer inlet, and a water level control valve that opens or closes the water level control gas flow path. ; a pressure control flow path connecting the main chamber of the refrigerant container and the level control gas flow path, and a pressure control valve that opens or closes the pressure control flow path; And, when the cryogenic refrigerator is operated, the water level control valve and the pressure control valve are controlled to change the level of the liquid refrigerant filled in the refrigerator inlet, so that the liquid refrigerant comes into contact with the cold head of the cryogenic refrigerator, or the cold It is characterized by including a control unit that separates the liquid refrigerant from the head.

In one embodiment, when the cryogenic refrigerator is driven, the control unit controls the pressure control valve to close the pressure control passage, and controls the water level control valve in a state in which the pressure control passage is closed to cool the refrigerator. By discharging the insulating gas in the inlet, the liquid refrigerant level in the inlet of the refrigerator is adjusted using the difference between the gas pressure in the inlet of the refrigerator reduced by the discharged insulating gas and the insulating gas pressure in the main chamber of the refrigerant container. It is characterized by

In one embodiment, when the operation of the cryogenic refrigerator is stopped, the control unit controls the water level control valve to close the water level control gas flow path, and when the water level control gas flow path is closed, the refrigerant container is filled in the main chamber. The pressure control valve is controlled to open the pressure control flow path so that the insulating gas flows into the refrigerator inlet through the pressure control flow path.

In one embodiment, it further includes a pressure sensor that detects the gas pressure in the refrigerator inlet through the pressure of the water level control gas flow path, and the control unit is configured to detect the gas pressure in the refrigerator inlet according to the detection result of the pressure sensor. The liquid refrigerant level in the refrigerator inlet is determined based on the pressure, and the level control valve is controlled according to the determined liquid refrigerant level to close the level control gas flow path.

In one embodiment, the cryogenic refrigerator is plural, and the refrigerator inlet corresponding to each of the plurality of cryogenic refrigerators, the water level control gas flow path and the water level control valve, and the pressure control flow path and the pressure control valve are further provided. It is characterized by

In one embodiment, the control unit causes the liquid refrigerant to contact each of at least one cold head that is driven among the plurality of cryogenic refrigerators, or to separate the liquid refrigerant from each cold head. At least one of the pressure control valves and at least one of the plurality of pressure control valves are controlled to change the level of the liquid refrigerant filled in at least one refrigerator inlet.

In one embodiment, it further includes a current sensor that detects a current load applied to the superconducting current limiter, and the control unit drives at least one of the plurality of cryogenic refrigerators according to a detection result of the current sensor. do.

In one embodiment, the liquid refrigerant charged in the refrigerant container accommodates at least a portion of one side of the refrigerant container forming one side of the refrigerator inlet, and is lower than the height at which the cold head of the refrigerator inlet is introduced. It is characterized by being filled to have a water level.

In one embodiment, one side of the refrigerant container forming one side of the refrigerator inlet is at least partially separated into one side of the refrigerant container and one side of the freezer inlet, and one side of the separated refrigerant container It is characterized in that they are spaced apart from each other by a space formed between the side and one side of the refrigerator inlet.

In one embodiment, the cryogenic refrigerator is installed in the direction of gravity, and the cold head is introduced into the current limiter tank in the direction of gravity.

In one embodiment, the liquid refrigerant charged in the refrigerator inlet is,

When the water level rises according to the control of the water level control valve and the pressure control valve of the control unit and comes into contact with the cold head introduced into the refrigerator inlet, the cold air discharged from the cryogenic refrigerator is directly discharged through at least a portion of the contacted cold head. It is characterized by being delivered.

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

In one embodiment, the insulating gas is a mixed gas of gaseous nitrogen and gaseous non-condensable gas, and the non-condensable gas is any one of hydrogen, helium, and neon having a lower vaporization point than nitrogen. do.

Additionally, a method of controlling a superconducting current limiter according to another embodiment of the present invention includes detecting a current load of the superconducting current limiter based on a detection result of the current sensor; If the detected current load is above the preset threshold, all gas pressures in the plurality of refrigerator inlets are changed to increase the level of all liquid refrigerants in the plurality of refrigerator inlets so that the cold head of the cryogenic refrigerator reaches the inlet height. raising step; And, when the detected current load is less than a preset threshold, the gas pressure of some of the plurality of refrigerator inlets is changed to allow the liquid refrigerant in some of the refrigerator inlets to reach the height at which the cold head of the cryogenic refrigerator is introduced. It is characterized by comprising the step of raising the water level.

In one embodiment, the step of raising the level of all liquid refrigerants in the plurality of refrigerator inlets includes closing all of the plurality of pressure control passages and forming a plurality of level control gases in a state in which all of the plurality of pressure control passages are closed. Controlling the plurality of water level control valves and the plurality of pressure control valves so that all flow paths are opened; Checking whether the gas pressure in each refrigerator inlet detected by pressure sensors that detect the gas pressure in the refrigerator inlet through the pressure of the water level control gas flow path has reached a preset pressure; controlling the plurality of water level control valves so that all of the open water level control gas passages are closed according to the check results; And, it is characterized by including the step of driving all of the plurality of cryogenic refrigerators.

In one embodiment, the pressure control flow path connected to a part of the refrigerator inlet is closed, and a part of the water level control gas flow path connected to the part of the freezer inlet is opened while the part of the pressure control flow path is closed. Controlling some water level control valves and some pressure control valves; Checking whether the gas pressure in the partial refrigerator inlet reaches a preset pressure from at least one pressure sensor that detects the gas pressure in the partial refrigerator inlet; controlling the part of the water level control valve to close the part of the open water level control gas passage according to the check result; And, it characterized by comprising the step of driving at least one cryogenic refrigerator introduced into the part of the refrigerator inlet.

In one embodiment, the preset threshold is determined based on the rated current of the superconducting current limiter.

In addition, according to another field of the present invention, in a superconducting current limiter including a refrigerant container that accommodates a liquid refrigerant and an insulating gas and a superconductor is accommodated inside the liquid refrigerant, the refrigerant container includes a refrigerant container main chamber, and a cryogenic temperature limiter. It has a refrigerator inlet into which the refrigerator is introduced, the refrigerant container main chamber and the refrigerator inlet are connected to each other to allow the liquid refrigerant to flow, and the superconducting current limiter is provided in at least one of the refrigerant container main chamber and the refrigerator inlet, At least one pressure control unit capable of adjusting the pressure of the insulating gas contained in at least one of the refrigerant container main chamber and the refrigerator inlet; and a control unit for controlling the level of liquid refrigerant contained in the refrigerator inlet by controlling the at least one pressure control unit.

In one embodiment, the at least one pressure regulator is provided with a pressure control valve provided in the main chamber of the refrigerant container, and the control unit is configured to cause a portion of the liquid refrigerant accommodated in the main chamber of the refrigerant container to be pushed into the refrigerator inlet to cool the refrigerator. The pressure control valve is controlled to provide additional insulating gas pressure to the main chamber of the refrigerant container so that the liquid refrigerant level in the inlet increases.

In one embodiment, the at least one pressure regulator is provided with a water level control valve provided in the refrigerator inlet, and the control unit is configured to cause a portion of the liquid refrigerant contained in the main chamber of the refrigerant container to be drawn to the refrigerator inlet to cool the refrigerator. The water level control valve is controlled to lower the insulating gas pressure at the refrigerator inlet so that the liquid refrigerant level at the inlet increases.

In one embodiment, the at least one pressure regulator includes a pressure control valve provided in the main chamber of the refrigerant container and a water level control valve provided in the refrigerator inlet, and the control unit is configured to control the liquid refrigerant contained in the main chamber of the refrigerant container. The pressure control valve is controlled to provide additional insulating gas pressure to the main chamber of the refrigerant container, and at the same time, the water level control valve is controlled so that a portion of the liquid refrigerant level in the freezer inlet increases. It is characterized by lowering the insulating gas pressure at the inlet.

The superconducting current limiter according to the present invention will be described as follows.

According to at least one of the embodiments of the present invention, the present invention transfers cold air from a cryogenic refrigerator directly to the liquid refrigerant contained in the container without a thermally conductive member, thereby dissipating liquid nitrogen in the container without thermal resistance due to the medium characteristics of the thermally conductive member. It has the advantage of being able to cool immediately. Therefore, the present invention has the effect of maximizing the cooling effect of a cryogenic refrigerator in a superconducting current limiter.

In addition, the present invention has the effect of reducing the maintenance cost of the superconducting current limiter by preventing the cryogenic refrigerators from being driven unnecessarily by limiting the number of cryogenic refrigerators driven according to the required current load.

In addition, the present invention, in a superconducting current limiter having a direct cooling structure that can directly transfer the cold air of the cryogenic refrigerator to the liquid refrigerant, the cold head of the non-driven cryogenic refrigerator is separated from the liquid refrigerant, thereby reducing the cold head of the non-driving cryogenic refrigerator. It has the effect of preventing heat from flowing in.

Figure 1 is a configuration diagram showing the structure of a superconducting current limiter according to an embodiment of the present invention, which includes a plurality of pressure valves and a pressure tank.

FIG. 2 is a block diagram showing the configuration of a superconducting current limiter according to an embodiment of the present invention shown in FIG. 1.

Figure 3 is an exemplary diagram showing examples of a condensation surface formed in the superconducting current limiter 10 according to an embodiment of the present invention and structures for limiting the area of the condensation surface.

Figure 4 is a flowchart showing an operation process in which a superconducting current limiter according to an embodiment of the present invention adjusts the liquid refrigerant level in the refrigerator inlet according to the current load.

5 to 7 are diagrams illustrating an example in which the liquid refrigerant level in the refrigerator inlet is adjusted according to valve control of the control unit in the superconducting current limiter according to an embodiment of the present invention.

Figure 8 is an exemplary diagram showing the structure of a superconducting current limiter according to an embodiment of the present invention, which further includes a pressure tank.

It should be noted that the technical terms used in this specification are only used to describe specific embodiments and are not intended to limit the present invention. Additionally, as used herein, singular expressions include plural expressions, unless the context clearly dictates otherwise. The suffixes “module” and “part” for components used in the following description are given or used interchangeably only for the ease of preparing the specification, and do not have distinct meanings or roles in themselves.

As used herein, “consists of.” or “including.” Terms such as these should not be construed as necessarily including all of the various components or steps described in the specification, and some of the components or steps may not be included, or additional components or steps may be included. It should be interpreted to include more.

Additionally, when describing the technology disclosed in this specification, if it is determined that a detailed description of a related known technology may obscure the gist of the technology disclosed in this specification, the detailed description will be omitted.

In addition, the attached drawings are only for easy understanding of the embodiments disclosed in this specification, and the technical idea disclosed in this specification is not limited by the attached drawings, and all changes included in the spirit and technical scope of the present invention are not limited. , should be understood to include equivalents or substitutes. In addition, each embodiment described below, as well as a combination of embodiments, are changes, equivalents, or substitutes included in the spirit and technical scope of the present invention, and of course, may fall within the spirit and technical scope of the present invention. .

Figure 1 is a configuration diagram showing the structure of a superconducting current limiter 10 according to an embodiment of the present invention, which includes a plurality of pressure valves and a pressure tank. And FIG. 2 is a block diagram showing the configuration of the superconducting current limiter 10 shown in FIG. 1.

First, referring to FIG. 1, the superconducting current limiter 10 according to an embodiment of the present invention includes a current limiter tank 210 whose inside is sealed as shown in FIG. 1, and an inside of the current limiter tank 210. A refrigerant container 200 that is sealed and stores liquid and gaseous refrigerants for cooling the HTS elements 213 that generate heat by operating current, and the refrigerant inside the refrigerant container 200. It may be formed to include a plurality of cryocoolers 251 and 252 that induce cooling of the HTS elements 213 by conducting and transferring cold air.

Looking more closely, the upper side of the current limiter tank 210 may be formed to be sealed with a cover and the inside may be vacuum treated. And it can be insulated to minimize heat transfer from the outside. Additionally, the upper cover of the sealed refrigerant container 200 may be exposed to the outside through a portion of the cover of the current limiter tank 210.

Additionally, the refrigerant container 200 may be provided in a sealed state inside the current limiter tank 210. Additionally, it may be insulated, and different liquid refrigerants 220 and insulating gases 230 may be filled therein.

Meanwhile, a plurality of HTS elements 213 may be installed inside the refrigerant container 200. Additionally, the upper cover of the refrigerant container 200 may be provided with a plurality of external connection parts 240 protruding outward. In addition, a plurality of internal connection parts may be provided to connect each of the plurality of HTS elements 213 and the plurality of external connection parts 240. That is, the plurality of HTS elements 213 installed inside the refrigerant container 200 have external connection parts 240 that protrude to the outside of the refrigerant container 200 through internal connections connected to each HTS element. can be connected Therefore, the superconducting current limiter 10 can receive current (operating current) from the outside of the refrigerant container 200 through some external connections and some internal connections connected to the power source, and other external connections connected to the load. The operating current supplied from the power source may be supplied to the outside of the superconducting current limiter 10 through another internal connection part.

Meanwhile, the liquid refrigerant 220 filled in the refrigerant container 200 may be liquid nitrogen in a supercooled state. In this case, the liquid refrigerant 220 is used to cool the plurality of HTS elements 213 generated by the operating current, as shown in FIG. 1, at a height greater than or equal to the height at which the plurality of HTS elements 213 are installed. Can be filled to full height. Accordingly, the plurality of HTS elements 213 are completely contained in the liquid refrigerant 220 and absorb the heat generated from the plurality of HTS elements 213 by the operating current, thereby Superconducting properties can be maintained.

Meanwhile, the insulating gas 230 is used to block heat transfer from the upper cover of the refrigerant container 200 exposed through the cover of the current limiter tank 210 to the liquid refrigerant 220, and is used at a preset pressure (e.g. : 3 Bar) It may be a gas with excellent insulation properties. For example, a mixed gas of gaseous nitrogen (GN2) and gaseous helium (GHe), as the insulating gas 230, is injected into the refrigerant container 200 with a sufficient thickness to block the heat transfer. can be filled.

Meanwhile, the liquid refrigerant 220 filled in the refrigerant container 200 can absorb heat generated from the plurality of HTS elements 213 by the operating current as described above. Therefore, in order to remove the heat absorbed from the liquid refrigerant 220, that is, the heat load, the superconducting current limiter 10 may further include a plurality of cryogenic refrigerators 251 and 252.

The cryogenic refrigerators 251 and 252 are each provided with coldheads 261 and 262 that are cooled to extremely low temperatures using a thermally circulating fluid, and cool the object being contacted by conducting cold air through the coldhead. It can be frozen at extremely low temperatures. The cryogenic refrigerators 251 and 252 may use refrigeration technology such as GM (Gifford-McMahon) for cryogenic freezing through the thermal cycle. Hereinafter, the cryogenic refrigerator using the Gifford-McMahon refrigeration technology will be referred to as a GM refrigerator.

However, in the indirect cooling method using a heat conductive member formed to surround the refrigerant container and a heat transfer member connected to the cold head of the cryogenic refrigerator, even if a medium made of a material with high thermal conductivity is used, there is a thermal resistance component inherent in the medium itself. There is a problem that the cooling efficiency of cryogenic refrigerators may decrease. In order to solve this problem, the superconducting current limiter 10 according to an embodiment of the present invention, as shown in FIG. 1, cools the cold heads 261 and 262 of the cryogenic refrigerators 251 and 252 with a liquid refrigerant ( By directly contacting the liquid refrigerant 220, the liquid refrigerant 220 can be cooled through a direct cooling structure that directly cools the liquid refrigerant 220.

For this purpose, the superconducting current limiter 10 is configured such that each side of the refrigerant container 200 adjacent to each of the cryogenic refrigerators 251 and 252 has a cold head 261 and 262 into which each of the cryogenic refrigerators 251 and 252 is introduced. It may have a structure that protrudes to a height corresponding to . In this case, the cold heads 261 and 262 of the cryogenic refrigerators 251 and 252 may be inserted into each end of the protrusions 201 and 202 formed on each side of the refrigerant container 200. And the other end of the protrusions 201 and 202 is connected to the refrigerant container 200, so that the liquid refrigerant charged in the refrigerant container 200 is in a part of the space formed by the protrusion of the protrusions 201 and 202. It can be formed to be filled. In this case, the remaining space of the protrusions 201 and 202 that is not filled with liquid refrigerant may be filled with the insulating gas 230.

That is, the protrusion 201 or 202 is formed to protrude in the form of an arm on one side of the refrigerant container 200, and one side of the arm is separated from one side wall of the adjacent refrigerant container 200. can be formed. That is, the protrusions 201 and 202 may be separated from the refrigerant container 200 and a partition 350 consisting of one side of the protrusions 201 and 202 and a side wall of the refrigerant container 200. Due to this separation structure, different pressures may be applied to the space inside each protrusion 201 and 202 from other spaces of the refrigerant container 200. Accordingly, the internal space of each protrusion 201 and 202 of the refrigerant container 200 is divided into another space of the refrigerant container 200, and the other space of the refrigerant container 200 is used as the main chamber of the refrigerant container 200. Let’s call it (231). That is, each protrusion 201, 202 and the main chamber 231 of the refrigerant container 200 are divided into different areas by partition walls 350 between each protrusion 201, 202 and the main chamber 231. It can be.

Meanwhile, the lower ends of each protrusion 201 and 202 may be connected to the main chamber 231. That is, the lower end of each partition 350 is open so that the main chamber 231 of the refrigerant container 200 and each of the protrusions 201 and 202 can be connected to each other.

In this case, the lower part of the main chamber 231 may be filled with liquid refrigerant 220 in which a plurality of HTS elements 213 are accommodated. The liquid refrigerant 220 filled in the refrigerant container 200 flows into each of the open protrusions 201 and 202 through the lower end of the partition wall 350 between the main chamber 231 and the main chamber 231. It can be.

Here, the liquid refrigerant 220 filled in the main chamber 231 may be filled to a height that accommodates the open area of each partition 350. That is, the main chamber 231 may be filled with the liquid refrigerant 220 to have a water level higher than the height corresponding to the lower end of each partition 350 from the base surface of the current limiter tank 210. Accordingly, the space not filled with the liquid refrigerant 220 in the main chamber 231 and the spaces not filled with the liquid refrigerant 220 in each of the protrusions 201 and 202 are connected to the partition wall 350 and the liquid refrigerant 220, respectively. can be isolated from each other.

Meanwhile, the cold head of the cryogenic refrigerator may be introduced into the upper part of each protrusion 201 and 202. And when the liquid refrigerant 220 filled inside the protrusions 201 and 202 comes into contact with at least a portion of the cold head introduced into the upper part of the protrusions 201 and 202, the cold air of the cold head contacts the cold head. It can be delivered directly to the liquid refrigerant (220). Therefore, in the following description, the protrusions 201 and 202 will be referred to as the part where the freezer is introduced, that is, the 'freezer inlet part'.

Meanwhile, the main chamber 231 may be filled with the insulating gas 230 after the liquid refrigerant 220 is filled. Therefore, as shown in FIG. 1, the lower part of the main chamber 231 is filled with liquid refrigerant 220 containing a plurality of HTS elements 213, and above it, that is, in the upper part of the main chamber 231, an insulating gas ( 230) can be filled. In this case, the insulating gas 230 may be filled to have a preset pressure (eg, 3 BAR).

In addition, each of the refrigerator inlets 201 and 202 has a flow path (first level control gas) through which gas for adjusting the level of the liquid refrigerant 220 filled in each of the refrigerator inlets 201 and 202 is introduced or discharged. A flow path 271 and a second water level control gas flow path 272) may be formed. And in the first water level control gas flow path 271 and the second water level control gas flow path 272, a first gas flow path for opening or closing the first water level control gas flow path 271 and the second water level control gas flow path 272. A water level control valve 131 and a second water level control valve 132 may be provided. Here, the first water level control valve 131 and the second water level control valve 132 are each connected to a first water level control gas flow path ( At least one of the 271) and the second water level control gas passage 272 may be opened or closed.

Meanwhile, between each of the refrigerator inlets 201 and 202 and each of the first and second water level control valves 132, there is a flow path (first pressure control) connected to the main chamber 231 of the refrigerant container 200. The flow path 211 and the second pressure control flow path 212) may be connected. And in the first pressure control flow path 211 and the second pressure control flow path 212, a first pressure control valve for opening or closing the first pressure control flow path 211 and the second pressure control flow path 212 ( 121) and a second pressure control valve 122 may be provided.

Therefore, as shown in FIG. 1, in a state in which both the first pressure control flow path 211 and the second pressure control flow path 212 are open, the first water level control valve 121 and the second water level control valve 122 When the insulating gas 230 is filled in the upper part of the main chamber 231 in a closed state, the first pressure adjustment passage 211, the second pressure adjustment passage 122 and the first water level adjustment gas passage 271, Through the second water level control gas flow path 272, the insulating gas 230 filled in the main chamber 231 may flow into the first refrigerator inlet 201 and the second refrigerator inlet 202.

Therefore, if the insulating gas 230 filled in the upper part of the main chamber 231 has a pressure of 3 BAR as shown in FIG. 1, the upper part of the first and second refrigerator inlets 201 and 202 into which the cold head is introduced is also The insulating gas 230 having a pressure of 3 BAR may be filled. Therefore, as shown in FIG. 1, the liquid refrigerant 220 filled in each refrigerator inlet 201 and 202 is higher than the height of the lower end of the partition wall 350 from the base surface of the current limiter tank 210, and each The refrigerator inlets 201 and 202 may be filled to have a water level lower than the height at which the cold heads 261 and 262 are introduced.

In this way, if the cold head of any cryogenic refrigerator is not in contact with the liquid refrigerant 220, it is a state in which neither cryogenic refrigerator is operating, that is, the superconducting current limiter 10 has not started operating. You can.

Meanwhile, in this state, when the first water level control gas flow path 271 is opened by the first water level control valve 121, the insulating gas filled in the first refrigerator inlet 201 is discharged to the outside of the superconducting current limiter 10. It can be. Then, the pressure at the top of the first refrigerator inlet 201 may decrease, and the level of the liquid refrigerant 220 may increase by the reduced pressure of the insulating gas 230. And, when the level of the charged liquid refrigerant rises, the liquid refrigerant whose level has risen comes into contact with at least a part of the cold head introduced into the upper end of the first refrigerator inlet 201, and therefore, when the cryogenic refrigerator is driven, the cryogenic refrigerator The cold air from the refrigerator can be transferred directly to the liquid refrigerant.

That is, when the cryogenic refrigerator introduced into the first refrigerator inlet 201 is driven, the control unit 100 of the superconducting current limiter 10 according to an embodiment of the present invention operates the first water level control valve 131 and By controlling the first pressure control valve 121 to change the filling level of the liquid refrigerant 220 by changing the pressure at the top of the first refrigerator inlet 201, cold air can be directly delivered from the inlet cold head. Let it happen.

On the other hand, when stopping the operation of the introduced cryogenic refrigerator, the control unit 100 controls the first water level control valve 131 to close the first water level control gas flow path 271 and opens the first pressure control valve 121. The first pressure adjustment passage 211 can be controlled to open. Then, the insulating gas 230 filled in the main chamber 231 of the refrigerant container 200 may flow back into the first refrigerator inlet 201. Therefore, the pressure at the top of the first freezer inlet 201, which was depressurized due to the discharge of the insulating gas, is restored to be equal to the pressure of the insulating gas 230 filled in the main chamber 231, and the first freezer inlet 201 is restored. The level of the liquid refrigerant 220 filled in may be lowered again. Accordingly, the cold head and the liquid refrigerant 220 introduced into the upper part of the first refrigerator inlet 201 may be spaced apart from each other. In this case, since the insulating gas 230 is filled between the cold head and the liquid refrigerant 220, the space between the cold head and the liquid refrigerant 220 can be insulated. Therefore, when the cryogenic refrigerator is not operated, heat conducted to the cold head due to the upper part of the cryogenic refrigerator leaking out of the current limiter tank 210 can be blocked from being transferred to the liquid refrigerant 220.

Meanwhile, in the same manner, the control unit 100 controls the second water level control valve 132 and the second pressure control valve 122 to open or close the second water level control gas flow path 272, and the second pressure control valve By controlling (122) to open or close the second pressure control passage 212, the level of the liquid refrigerant 220 filled in the second refrigerator inlet 202 can be adjusted. That is, as necessary, the control unit 100 adjusts the pressure of the insulating gas in at least one refrigerator inlet corresponding to the at least one driven cryogenic refrigerator, so that the at least one is in contact with at least a portion of the cold head of the driven cryogenic refrigerator. The level of the liquid refrigerant 220 filled in the refrigerator inlet can be controlled.

In addition, when one of the cryogenic refrigerators is not driven, insulating gas can be injected into the refrigerator inlet corresponding to the cryogenic refrigerator that is not driven so that the cold head of the introduced cryogenic refrigerator is separated from the liquid refrigerant. Therefore, it is possible to prevent the cold head of a cryogenic refrigerator that is not operating from acting as a heat load of the liquid refrigerant.

Meanwhile, Figure 1 assumes that the superconducting current limiter 10 according to an embodiment of the present invention is provided with two cryogenic refrigerators 251 and 252. However, it goes without saying that the present invention is not limited to this. In other words, a greater number of cryogenic refrigerators can be provided.

And according to the above description, since the present invention is assumed to have two cryogenic refrigerators, as shown in FIG. 1, two protrusions 201 and 202 corresponding to each cryogenic refrigerator 251 and 252 are formed. An example was assumed. Therefore, if a greater number of cryogenic refrigerators are provided in the superconducting current limiter 10, it goes without saying that corresponding protrusions can be formed depending on the number of each cryogenic refrigerator. However, in the following description, for convenience of explanation, it is assumed that two cryogenic refrigerators are provided.

Meanwhile, the volume of the main chamber 231 of the refrigerant container 200 may be sufficiently large to allow the volume inside each refrigerator inlet 201 and 202 to be ignored. Therefore, when the main chamber 231 is filled with the insulating gas 230 corresponding to a sufficient pressure (e.g. 3 BAR), the main chamber 231 is filled with the insulating gas 230 filled in each of the refrigerator inlets 201 and 202. It can serve as a pressure tank that provides filling pressure. Therefore, the superconducting current limiter 10 according to an embodiment of the present invention may not be provided with a separate pressure tank.

For convenience of explanation, in the following description, opening or closing of the first water level control gas flow path 271 by driving the first water level control valve 131 is referred to as opening or closing of the first water level control valve 131. Do this. In addition, opening or closing of the second water level control gas passage 272 by driving the second water level control valve 132 will be referred to as opening or closing of the second water level control valve 132. In addition, opening or closing of the first pressure control passage 211 by driving the first pressure control valve 121 will be referred to as opening or closing of the first pressure control valve 131. Additionally, opening or closing of the second pressure control passage 212 by driving the second pressure control valve 122 will be referred to as opening or closing of the second pressure control valve 132.

Meanwhile, the flow path inlet where each refrigerator inlet (201, 202) and the first and second water level control gas flow paths (271, 272) are connected is connected to the liquid refrigerant (220) when the water level of the liquid refrigerant (220) rises. It may be formed around the location where the cold head is introduced to prevent it from entering. In addition, the control unit 100 may detect the level of the liquid refrigerant 220 and control the water level control valve and the pressure control valve according to the detected level so that the level of the liquid refrigerant does not rise to the level where the flow path inlet is formed.

Here, the level of the liquid refrigerant is determined according to the pressure of the insulating gas filled in the upper part of the refrigerator inlet, as described above. Therefore, the control unit 100 is provided with a pressure sensor to detect the pressure of the insulating gas filled in the upper part of the refrigerator inlet, and when the water level control valve is opened, the level of the liquid refrigerant charged in the upper part of the refrigerator inlet is measured from the pressure sensor. The pressure corresponding to can be detected. And by closing the open water level control valve according to the detected pressure, the water level of the liquid refrigerant can be prevented from rising to the height where the flow path inlet is formed.

FIG. 2 is a block diagram showing each configuration of the control unit 100 and the superconducting current limiter 10 connected to the control unit 100. Referring to FIG. 2, the superconducting current limiter 10 includes a control unit 100, a detection unit 110 connected to the control unit 100, a valve unit 120, and a refrigerator unit 250. It can be configured.

As described above, the detection unit 110 may include a pressure detection unit 111 including at least one pressure sensor for detecting pressure and a current detection unit 112 for detecting a current load.

First, each of the pressure sensors 111-1 and 111-2 of the pressure sensing unit 111 may be a sensor for detecting the pressure of the insulating gas filled in the upper part of each refrigerator inlet 201 and 202. To this end, each pressure sensor may be provided in a pressure control flow path connected to the water level control gas flow path, between a pressure control valve formed on the pressure control flow path and the water level control gas flow path. In this case, when the pressure control valves 121 and 122 are closed, each pressure sensor (111-1, 111-2) is connected to the water level control gas flow path (271, 272) and the pressure control flow path (211, 212). Based on the gas pressure, the pressure of the insulating gas filled in the upper part of each refrigerator inlet (201, 202) can be detected. And the pressure detection result can be provided to the control unit 100.

And the current detection unit 112 can detect the current supplied to or from the superconducting current limiter 10 as a current load. For this purpose, the current sensing unit 112 may include at least one current sensor. And the current value detected by the at least one current sensor, that is, the current load, can be provided to the control unit 100.

And the refrigerator unit 250 may include at least one cryogenic refrigerator. As an example, as shown in FIG. 1, when two cryogenic refrigerators are introduced into the superconducting current limiter 10 through two refrigerator inlets, the refrigerator portion 250 includes a first cryogenic refrigerator 251 and a second cryogenic refrigerator ( 252) may be included. In addition, the first cryogenic refrigerator 251 and the second cryogenic refrigerator 252 may be partially or fully driven under the control of the control unit 100.

The valve unit 120 may include a driving unit for driving each valve described in FIG. 1 above. For example, the valve unit 120 includes a first pressure control valve unit (hereinafter referred to as first pressure control valve 121) for driving the first pressure control valve 121, and a second pressure control valve 122. It may include a second pressure control valve unit (hereinafter referred to as the second pressure control valve 122) for driving. In addition, the valve unit 120 operates a first water level control valve unit (hereinafter referred to as first water level control valve 131) for driving the first water level control valve 131 and a second water level control valve 132. It may include a second water level control valve unit (hereinafter referred to as the second water level control valve 132).

Meanwhile, the control unit 100 can control other connected components based on the detection result of the detection unit 110. First, the control unit 100 detects the current load based on the detection result of the current detection unit 112, and some of the cryogenic refrigerators 251 and 252 provided in the freezer unit 250 are operated based on the detected current load. It can drive only cryogenic freezers or all cryogenic freezers. For convenience of explanation below, when only some cryogenic refrigerators are operated, it will be assumed that only the first cryogenic refrigerator 251 is operated.

When the cryogenic refrigerator to be driven is determined, the control unit 100 may control the valve unit 120 to lower the insulating gas pressure at the freezer inlet where the cold head of the determined cryogenic refrigerator is introduced.

For example, when the detected current load is close to the rated current and all cryogenic refrigerators are required to be driven, the control unit 100 closes the first and second pressure control valves 121 and 122 and adjusts the first and second water levels. The valve unit 120 can be controlled so that both valves 131 and 132 are opened. Then, in each of the first water level control gas flow path 271 and the second water level control gas flow path 272 connected to each of the first refrigerator inlet 201 and the second refrigerator inlet 202, the first refrigerator inlet ( 201) and the second refrigerator inlet 202, the insulating gases may be discharged, thereby lowering the gas pressure in the first refrigerator inlet 201 and the second refrigerator inlet 202. Accordingly, the level of the liquid refrigerant rises in each of the first refrigerator inlet 201 and the second refrigerator inlet 202, and accordingly, the upper portions of the first refrigerator inlet 201 and the second refrigerator inlet 202 At least a portion of each of the first cold head 261 of the first cryogenic refrigerator 251 and the second cold head 262 of the second cryogenic refrigerator 252 may be in contact with the liquid refrigerant whose water level has risen. . Therefore, when the first cryogenic refrigerator 251 and the second cryogenic refrigerator 252 are driven, cold air can be directly transferred to the liquid refrigerant from both the first cold head 261 and the second cold head 262.

However, if the detected current load is less than the critical current and the operation of any one cryogenic refrigerator is sufficient, the control unit 100 closes the first pressure control valve 121 and opens the first water level control valve 131. The valve unit 120 can be controlled as much as possible. On the other hand, the valve unit 120 can be controlled to open the second pressure control valve 122 and close the second water level control valve 132.

Then, the insulating gas filled in the first refrigerator inlet 201 can be discharged from the first water level control gas flow path 271 connected to the first refrigerator inlet 201. Accordingly, the gas pressure within the first refrigerator inlet 201 may be lowered. Therefore, the level of the liquid refrigerant in the first refrigerator inlet 201 rises, and at least a portion of the first cold head 261 of the first cryogenic refrigerator 251 introduced into the upper end of the first refrigerator inlet 201 You may come into contact with liquid refrigerant whose level has risen. Therefore, cold air resulting from the operation of the first cryogenic refrigerator 251 may be directly transferred to the liquid refrigerant through the first cold head 261.

On the other hand, as the second water level control gas valve 132 is closed, the gas pressure in the second refrigerator inlet 202 may be maintained at its initial state. Additionally, as the second pressure control valve 122 is opened, the gas pressure in the second refrigerator inlet 202 can be maintained at the same pressure as the gas pressure in the main chamber 231 of the refrigerant container 200. Accordingly, the liquid refrigerant in the second refrigerator inlet 202 can maintain the initial level, and accordingly, the liquid refrigerant and the second cold head 262 of the second cryogenic refrigerator 252 are separated from each other by the heat insulating gas. Delivery may be blocked. Therefore, it is possible to prevent the introduced cold head from acting as a heat load having heat resistance to the liquid refrigerant due to the cryogenic refrigerator not operating.

Meanwhile, of course, the control unit 100 may drive only one cryogenic refrigerator based on the current load detected by the current detection unit 112 while all cryogenic refrigerators are in operation. In this case, the control unit 100 can lower the liquid refrigerant level in the refrigeration unit inlet where the cold head of one of the non-operating cryogenic refrigerators is introduced by normalizing the gas pressure in the inlet of one of the refrigerating units.

For example, the control unit 100 controls the valve unit 120 to close the first and second pressure control valves 121 and 122 and open both the first and second water level control valves 131 and 132. In one state, the second water level control valve 132 may be closed and the second pressure control valve 122 may be opened. Then, gas discharge from the second water level control gas flow path 272 may be terminated. And since the gas pressure in the second refrigerator inlet 202 is lower than the gas pressure in the main chamber 231 of the refrigerant container 200, the second pressure control valve 122 is opened and the second pressure control flow path connected to each other ( 212) and the second water level control gas flow path 272, the insulating gas in the main chamber 231 of the refrigerant container 200 may flow into the second refrigerator inlet 202.

Accordingly, the gas pressure in the second refrigerator inlet 202 can be restored, and the liquid refrigerant level that had risen can be lowered again. Then, the liquid refrigerant and the second cold head 262 may be separated as the water level drops, and may be insulated from each other by the insulating gas. Therefore, it is possible to prevent the second cryogenic refrigerator 252 that is not driven from acting as a heat load.

Meanwhile, according to the above description, in the superconducting current limiter 10 according to an embodiment of the present invention, each refrigerator inlet 201, 202 and the refrigerant container 200 are separated by a partition 350. It was also explained that the level of liquid refrigerant may rise or fall within the refrigerator inlet.

Therefore, the first side of the partition 350, that is, the side on the side of the refrigerant container 200, is in contact with the insulating gas of the main chamber 231 of the refrigerant container 200, and the second side of the partition 350 is inside the refrigerator inlet. It may come into contact with liquid refrigerant whose water level rises. Accordingly, the second side of the partition 350 in contact with the liquid refrigerant is cooled by the liquid refrigerant, and this may cause the insulating gas to condense on the first side. That is, a condensation surface can be formed.

Figure 3 is an exemplary diagram showing examples of a condensation surface formed in the superconducting current limiter 10 according to an embodiment of the present invention and structures for limiting the area of the condensation surface.

Referring to FIG. 3, FIG. 3(a) shows an example in which the above-described concave surface is formed. In this case, when the gas pressure in the first refrigerator inlet 201 is lowered due to the opening of the first water level control valve 131, the liquid in the first refrigerator inlet 201 as shown in (a) of FIG. The water level of the refrigerant 220 may rise.

Therefore, in the partition 350, based on the water level of the liquid refrigerant 220 filled in the main chamber 231 of the refrigerant container 200, below the water level of the liquid refrigerant 220 in the main chamber 231 of the refrigerant container 200 Since both the side surface of the portion 351 on the first refrigerator inlet 201 side and the side surface on the main chamber 231 of the refrigerant container 200 are in contact with the liquid refrigerant, condensation may not occur.

However, in the case of the portion 352 above the level of the liquid refrigerant 220 in the main chamber 231 of the refrigerant container 200, the side of the first refrigerator inlet 201 is raised within the first refrigerator inlet 201. It is in contact with the liquid refrigerant 220, and the side of the main chamber 231 of the refrigerant container 200 is in contact with the insulating gas 230 in the main chamber 231 of the refrigerant container 200. Accordingly, the upper portion 352 of the partition 350 can be cooled by the liquid refrigerant contacted from the side of the first refrigerator inlet 201. Therefore, condensation may occur on the side of the upper portion 352 of the partition wall 350 on the side of the main chamber 231 of the refrigerant container 200. In other words, condensation surfaces may occur.

In order to limit the occurrence of such condensation surfaces, the superconducting current limiter 10 according to an embodiment of the present invention may have a configuration in which at least a portion of the partition wall 350 is separated.

For example, as shown in (b) of FIG. 3, the outer wall of the refrigerant container 200 and the outer wall of the refrigerator inlet can be separated from each other through a branch structure in which a portion of the partition wall 350 is physically separated. In this case, the outer wall of the refrigerant container 200 and the outer wall of the refrigerator inlet may be spatially separated as shown in (b) of FIG. 3.

Meanwhile, in the branch structure, the point corresponding to the branch where separation of the partition begins may be a point corresponding to a height higher than the water level of the liquid refrigerant 220 in the refrigerant container 200. In this case, the refrigerant container 200 and the refrigerator inlet have one partition at a height (meaning the vertical distance from the base of the current limiter tank 210) below the level of the liquid refrigerant 220 charged in the refrigerant container 200. (350) is shared, but at a height above the level of the liquid refrigerant (220) charged in the refrigerant container (200), they are spatially separated (360) through the branch structure, resulting in an increase in the level of the liquid refrigerant at the refrigerator inlet. The outer wall of the refrigerator inlet being cooled and the outer wall of the refrigerant container 200 in the part filled with the insulating gas may be disconnected. Therefore, since the refrigerant container 200 and the refrigerator inlet do not share one partition, the formation of the condensation surface may be limited.

Meanwhile, in Figure 3 (b), a case where only a part of the partition wall 350 is separated through the branch structure was explained, but as shown in Figure 3 (c), the entire side of the refrigerator inlet is separated through the arm structure. It may have a configuration that is separated from the refrigerant container 200. In this case, unlike the partition wall 350 structure in which the freezer inlet and the main chamber of the refrigerant container 200 share at least some of the side surfaces, the side of the freezer inlet and the side of the refrigerant container 200 are completely separated, so the condensation may not occur.

In the above description, the structure of the superconducting current limiter 10 and the function of each component of the superconducting current limiter 10 according to an embodiment of the present invention have been described in detail. In the following description, we will look at an operation process in which the valve unit 120 is controlled according to the operation of the control unit 100 in the above-described superconducting current limiter 10 to adjust the liquid refrigerant level in at least one refrigerator inlet.

Figure 4 is a flowchart showing an operation process in which the superconducting current limiter 10 according to an embodiment of the present invention adjusts the liquid refrigerant level in the refrigerator inlet according to the current load. 5 to 7 are diagrams illustrating an example in which the liquid refrigerant level in the refrigerator inlet is adjusted according to the valve control of the control unit 100.

First, the superconducting current limiter 10 according to an embodiment of the present invention can be filled with an appropriate amount of liquid refrigerant 220 in the refrigerant container 200. In this case, the control unit 100 may open both the first and second pressure control valves 121 and 122 and the first and second water level control valves 131 and 132. In addition, charging of the liquid refrigerant 220 may be performed with both the first and second pressure control valves 121 and 122 and the first and second water level control valves 131 and 132 open.

Meanwhile, when the liquid refrigerant 220 is charged with all valves 121, 122, 131, and 132 open, the pressure of each refrigerator inlet 201, 202 and the main chamber 231 of the refrigerant container 200 is Therefore, the level of the liquid refrigerant 220 filled in each refrigerator inlet 201 and 202 and the main chamber 231 of the refrigerant container 200 may be the same.

In this case, the liquid refrigerant 220 can be filled to a level sufficient to accommodate the plurality of HTS elements 213 installed inside the refrigerant container 200, and the cryogenic refrigerator ( It can be filled to a height that does not contact the cold heads 261 and 262 of 251 and 252). In this case, as shown in FIG. 5, the liquid refrigerant 220 can be accommodated in a part of each partition 350 that separates the main chamber 231 of the refrigerant container 200 and each refrigerator inlet 201 and 202. Accordingly, the main chamber 231 of the refrigerant container 200 and the refrigerator inlets 201 and 202 may be separated from each other by each partition 350 and the liquid refrigerant 220.

Meanwhile, as shown in FIG. 5, when the liquid refrigerant 220 is charged, none of the cold heads may be in contact with the filled liquid refrigerant 220. This state is a state in which the cold of any cold head is not transferred to the liquid refrigerant, and may be a state in which both the first cryogenic refrigerator 251 and the second cryogenic refrigerator 252 are not operated.

In this state, the control unit 100 may close the first and second water level control valves 131 and 132. In this case, the first and second pressure control valves 121 and 122 may be open. Therefore, each refrigerator inlet (201, 202) and the main chamber (231) of the refrigerant container (200) have first and second water level adjustment gas passages (271, 272) and first and second pressure adjustment passages (211, 212). They may be connected to each other through.

In this state, the control unit 100 may inject the insulating gas 230 into the main chamber 231 of the refrigerant container 200 until a preset pressure (3 BAR) is formed. In this case, as described above, each refrigerator inlet 201, 202 and the main chamber 231 of the refrigerant container 200 are connected to each other, so the insulating gas 230 filled in the main chamber 231 of the refrigerant container 200 When the pressure is 3 BAR, the insulating gas 230 having a pressure of 3 BAR may be filled in each refrigerator inlet 201 and 202. That is, each refrigerator inlet 201, 202 and the main chamber 231 of the refrigerant container 200 may be filled with the insulating gas 230 at the same pressure.

In this state, the control unit 100 can cool the liquid refrigerant 220 to drive the superconducting current limiter 10. To this end, the controller 100 may close the first and second pressure control valves 121 and 122 and open at least one of the first and second water level control valves. Then, the insulating gas filled in at least one of the first and second refrigerator inlets (201, 202) through at least one of the first and second water level control gas passages (271, 272) connected to the open water level control valve, It may be discharged depending on the air pressure difference with the outside of the current limiter tank 210.

Then, due to the discharge of the insulating gas, the level of the liquid refrigerant charged in at least one of the first and second refrigerator inlets 201 and 202 through which the insulating gas was discharged increases, and at the top of the refrigerator inlets 201 and 202. It may come into contact with the incoming cold head. In this case, the control unit 100 operates a cryogenic refrigerator with a cold head introduced into at least one of the first and second refrigerator inlets 201 and 202 from which the insulating gas is discharged, thereby keeping the liquid refrigerant 220 below the critical temperature. It can be cooled to a temperature of And when the liquid refrigerant 220 is cooled below the critical temperature, the plurality of HTS elements 213 accommodated in the liquid refrigerant 220 may have superconducting characteristics.

In this way, the state in which the plurality of HTS elements 213 have superconducting characteristics as the liquid refrigerant 220 is cooled below the critical temperature can be said to be a state in which the superconducting current limiter 10 is operating.

Meanwhile, when the superconducting current limiter 10 is in an operating state, the control unit 100 can detect the current load of the superconducting current limiter 10 (S400). As an example, the control unit 100 may detect the current load based on the detection result of the current detection unit 112, which detects the amount of current flowing through the superconducting current limiter 10. And it can be determined whether the detected current load is greater than or equal to a preset threshold (S402). And if the sensed current load is greater than a preset threshold, it may be determined that both the first and second cryogenic refrigerators 251 and 252 are required to be driven.

Here, the threshold value may be determined according to the size of the maximum current that can be passed in the superconducting current limiter 10, that is, the size of the rated current. For example, the threshold may be a current value closer to the rated current. That is, the control unit 100 may determine that operation of both the first and second cryogenic refrigerators 251 and 252 is necessary when the current load of the superconducting current limiter 10 is close to the rated current.

Then, the control unit 100 can open both the first and second water level control valves 131 and 132 while closing the first and second pressure control valves 121 and 122 (S404). Then, the insulating gas filled in the first and second refrigerator inlets 201 and 202 may be discharged through the first and second water level adjustment gas passages 271 and 272. Then, since the gas pressure in the first and second refrigerator inlets 202 becomes smaller than the pressure of the insulating gas 230 filled in the main chamber 231 of the refrigerant container 200, the insulating gas pressure in the main chamber 231 Accordingly, a greater amount of liquid refrigerant 220 may flow into each refrigerator inlet (201, 202). Therefore, as shown in FIG. 6, the level of the liquid refrigerant filled in each refrigerator inlet (201, 202) may rise.

Here, the volume of the main chamber 231 of the refrigerant container 200 may be large enough to ignore the volume of each refrigerator inlet 201 and 202. Therefore, even if a larger amount of liquid refrigerant flows into the freezer inlet, the change in the liquid refrigerant level in the main chamber 231 of the refrigerant container 200 may be small enough to be ignored.

As shown in FIG. 6, when the level of the liquid refrigerant charged in each refrigerator inlet 201, 202 rises, the water level of at least some of the cold heads 261, 262 of the inserted cryogenic freezer rises. May come into contact with liquid refrigerant.

Meanwhile, when the insulating gas filled in the first and second refrigerator inlets 202 is discharged by opening the first and second water level control valves 121 and 122, the control unit 100 operates the pressure sensing unit 111. Through this, the gas pressure within each refrigerator inlet (201, 202) can be sensed. In this case, the first and second pressure sensors (111-1, 111-2) are connected to each other between the water level control gas flow paths (271, 272) and the pressure control flow paths (211, 212), the water level control gas flow path ( 271, 272) and pressure control valves 121, 122. Therefore, when the pressure control valves 121 and 122 are closed, the gas pressure in the refrigerator inlets 201 and 202 can be detected through the water level control gas passages 271 and 272.

In this case, since the gas in each refrigerator inlet 201 and 202 is discharged as the first and second water level control valves 131 and 132 are opened, the pressure in the refrigerator inlet may continue to decrease. And, if the gas pressure at the refrigerator inlet continues to decrease and the level of the liquid refrigerant becomes higher than necessary, there is a risk that the liquid refrigerant will be discharged through the first and second water level adjustment gas passages 271 and 271.

Here, the level of the liquid refrigerant increases as the pressure of the insulating gas in the refrigerator inlet decreases, and the level of the liquid refrigerant may have a correlation inversely proportional to the insulating gas pressure in the refrigerator inlet. Therefore, the control unit 100 detects the insulating gas pressure in the refrigerator inlet through the pressure detection unit 111 (S406), and when the preset decompression pressure is reached, the first and second water level control valves 131 and 132 By closing, it is possible to prevent liquid refrigerant from being discharged through the first and second water level control gas passages 271 and 271 (S408).

Meanwhile, when the first and second water level control valves 131 and 132 are opened and the filled insulating gas is discharged, the liquid refrigerant level in each refrigerator inlet 201 and 202 rises, as shown in FIG. At least a portion of each of the cold heads 261 and 262 of the cryogenic refrigerators 251 and 252 introduced into each refrigerator inlet 201 and 202 may be in contact with the liquid refrigerant whose level has risen. Therefore, the control unit 100 can quickly cool the liquid refrigerant by driving both the first and second cryogenic refrigerators 251 and 252. Then, the control unit 100 can proceed again to step S400 and detect the current load.

Meanwhile, if the sensed current load is less than a preset threshold as a result of the determination in step S402, the control unit 100 closes the first and second pressure control valves 121 and 122 and adjusts the water level to one level. Only the control valve can be opened (S404). For convenience of explanation, the following description will be made on the assumption that only the first water level control valve is opened.

Then, the insulating gas filled in the first refrigerator inlet 201 can be discharged. Then, since the gas pressure in the first refrigerator inlet 201 becomes smaller than the pressure of the insulating gas 230 filled in the main chamber 231 of the refrigerant container 200, the liquid phase changes depending on the insulating gas pressure in the main chamber 231. Refrigerant 220 may flow into the first refrigerator inlet 201. Therefore, as shown in FIG. 7, the level of the liquid refrigerant charged in the first refrigerator inlet 201 may rise.

Then, the control unit 100 can detect the gas pressure in the first refrigerator inlet 201 through the pressure detection unit 111, that is, the first pressure sensor 111-1 (S414). In this case, since the gas in the first refrigerator inlet 201 is discharged, the pressure in the first refrigerator inlet 201 may continue to decrease. And when the pressure of the first refrigerator inlet 201 reaches the preset reduced pressure, the control unit 100 closes the first water level control valve 131, thereby allowing the liquid phase to flow through the first water level control gas flow path 271. Refrigerant can be prevented from being discharged (S416).

Meanwhile, when the filled insulating gas is discharged as the first water level control valve 131 is opened, the liquid refrigerant level in the first refrigerator inlet 201 rises, as shown in FIG. 7, and the first refrigerator inlet ( At least a portion of the cold head 261 of the cryogenic refrigerator 251 introduced into the 201) may be in contact with the liquid refrigerant whose water level has risen. Then, the control unit 100 can cool the liquid refrigerant by operating only the first cryogenic refrigerator 251. That is, when a current load lower than the rated rectification is detected, the control unit 100 operates only one cryogenic refrigerator, thereby preventing unnecessary operation of the cryogenic refrigerator. In this case, unnecessary operation of the cryogenic refrigerator is prevented, thereby saving maintenance costs for the superconducting current limiter.

Meanwhile, in this case, the second cryogenic refrigerator 252 may not be driven. In this case, the control unit 100 closes the second water level control valve 132 to prevent gas discharge in the second refrigerator inlet 202, so that the liquid refrigerant is stored in the second cryogenic refrigerator 252, as shown in FIG. 7. It is possible to prevent contact with the cold head 262. In this case, since an insulating gas layer having a preset pressure exists between the second cold head 262 of the second cryogenic refrigerator 252 and the liquid refrigerant, the space between the second cold head 262 and the liquid refrigerant is insulated. , it is possible to prevent the second cryogenic refrigerator 252, which is not driven, from acting as a heat load of the liquid refrigerant.

Meanwhile, as shown in FIG. 6 according to the load current detection result, in a state in which both the first and second cryogenic refrigerators 251 and 252 are driven, only one cryogenic refrigerator (the first cryogenic refrigerator 251) can be driven. Of course it is possible. In this case, the controller 100 may close the second water level control valve 132 and open the first pressure control valve 122 in the state shown in FIG. 6 . Then, according to the pressure difference between the pressure of the insulating gas 230 filled in the main chamber 231 of the refrigerant container 200 and the pressure of the insulating gas in the second refrigerator inlet 202, the Insulating gas 230 may flow into the second refrigerator inlet 202. And in this case, the insulating gas is injected into the second freezer inlet (202) until the pressure of the insulating gas 230 filled in the main chamber 231 of the refrigerant container 200 becomes equal to the pressure of the insulating gas in the second freezer inlet 202. 202).

However, as described above, the volume of the main chamber 231 of the refrigerant container 200 may be large enough to ignore the volume of each of the refrigerator inlets 202 and 202. Therefore, even when the insulating gas in the main chamber 231 of the refrigerant container 200 flows into the second refrigerator inlet 202, the pressure of the insulating gas in the main chamber 231 of the refrigerant container 200 can be maintained as is. In this case, the main chamber 231 of the refrigerant container 200 may function as a pressure tank that supplies insulating gas to each refrigerator inlet 201 and 202.

Meanwhile, when the pressure of the insulating gas 230 filled in the main chamber 231 of the refrigerant container 200 becomes equal to the pressure of the insulating gas in the second refrigerator inlet 202 due to the inflow of the insulating gas, the increased gas pressure causes The level of liquid refrigerant may decrease. Therefore, as shown in FIG. 7, the liquid refrigerant can be separated from the second cold head 262. Then, heat transfer between the second cold head 262 and the liquid refrigerant may be blocked by the insulating gas. And the control unit 100 can stop driving the second cryogenic refrigerator 252.

Meanwhile, in the above description, a configuration for depressurizing or pressurizing each refrigerator inlet through the insulating gas filled in the main chamber 231 of the refrigerant container 200 was explained. However, of course, unlike this, a separate pressure tank may be provided to control the pressure of the insulating gas applied to each refrigerator inlet.

Figure 8 shows an example of a superconducting current limiter further including such a separate pressure tank.

Referring to FIG. 8 , if a pressure tank is further provided, the pressure tank may be connected to the first water level control gas flow path 271 and the second water level control gas flow path 272. Therefore, when at least one of the first water level control gas flow path 271 and the second water level control gas flow path 272 is opened according to the first water level control valve 131 and the second water level control valve 132, the pressure tank ( Based on the gas pressure applied through 130), the insulating gas filled in at least one of the first refrigerator inlet 201 and the second refrigerator inlet 202 is sucked into the pressure tank 130 or the pressure It may be discharged from the tank 130 to the first refrigerator inlet 201 and the second refrigerator inlet 202.

In this case, when the insulating gas is sucked into the pressure tank 130, the level of the liquid refrigerant in at least one refrigerator inlet into which the insulating gas is sucked rises, and when the insulating gas is discharged from the pressure tank 130, the discharged insulating gas The level of the liquid refrigerant in at least one refrigerator inlet into which the gas flows may be lowered.

Depending on the level of the liquid refrigerant, the liquid refrigerant inside comes into contact with the cold head of a running cryogenic freezer and receives cold air directly from the freezer inlet, or the liquid refrigerant inside comes into contact with the freezer inlet from the cold head of a stopped cryogenic freezer. It can be separated and insulated.

Meanwhile, in the above description, it has been described as an example that the control unit 100 operates only some cryogenic refrigerators or all cryogenic refrigerators according to the detection result of the current detection unit 112. However, unlike this, it goes without saying that all or only some of the cryogenic refrigerators may be operated depending on the operation policy of the superconducting current limiter or the driver's settings.

In this case, of course, the control unit 100 may control the valve unit 120 based on the driven cryogenic refrigerator without the detection result of the current detection unit 112. For example, if all cryogenic refrigerators are operated according to the operation policy or driver settings, the control unit 100 may control the valve unit 120 so that the liquid refrigerant level in all refrigerator inlets increases. Therefore, liquid refrigerant can come into contact with the cold head of all cryogenic refrigerators. On the other hand, if some of the cryogenic refrigerators are driven according to the operation policy or the driver's settings, the control unit 100 operates the valve unit 120 so that the liquid refrigerant level in the refrigerator inlet where the driven portion of the cryogenic refrigerators is introduced increases. can be controlled. Therefore, liquid refrigerant can only come into contact with the cold head of some operated cryogenic refrigerators.

The detailed description of the present invention described above should not be construed as restrictive in any respect and should be considered illustrative. The scope of the present invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the present invention are included in the scope of the present invention.

[Explanation of symbols]

10: Superconducting current limiter 100: Control unit

111-1: first pressure sensor 111-2: second pressure sensor

121: first pressure control valve 122: second pressure control valve

131: first water level control valve 132: second water level control valve

200: Refrigerant container 201: First refrigerator inlet

202: Second refrigerator inlet 210: Current limiter tank

211: first pressure control flow path 212: second pressure control flow path

213: plural HTS elements 220: liquid refrigerant

230: Insulating gas 231: Refrigerant container main compartment

240: External connection 251: First cryogenic freezer

252: second cryogenic refrigerator 261: first cold head

262: second cold head 271: first water level control gas flow path

272: Second water level control gas flow path 350: Bulkhead

Claims (21)

1. Current limiter tank with sealed interior;

   A cryogenic refrigerator that is cooled to a very low temperature and has a cold head that is introduced into a current limiter tank;

   A refrigerant container that is sealed inside the current limiter tank and includes a liquid refrigerant filled to a height higher than the height at which the superconductor element is installed, and an insulating gas having a preset pressure and filled on the liquid refrigerant;

   The cold head is introduced at the top, the liquid refrigerant and the insulating gas are filled, and the insulating gas is filled in the refrigerant container by the liquid refrigerant formed on one side of the refrigerant container and filled with one side of the refrigerant container. A freezer inlet forming a space separated from the main room;

   A water level control gas flow path connected to the freezer inlet to discharge the insulating gas in the freezer inlet or to allow the insulating gas to flow into the freezer inlet, and a water level control valve that opens or closes the water level control gas flow path. ;

   a pressure control flow path connecting the main chamber of the refrigerant container and the level control gas flow path, and a pressure control valve that opens or closes the pressure control flow path; and,

   When the cryogenic refrigerator is operated, the water level control valve and the pressure control valve are controlled to change the level of the liquid refrigerant filled in the refrigerator inlet, so that the liquid refrigerant comes into contact with the cold head of the cryogenic refrigerator, or from the cold head. A superconducting current limiter comprising a control unit that separates the liquid refrigerant.
2. The method of claim 1, wherein the control unit,

   When the cryogenic refrigerator is driven, the pressure control valve is controlled to close the pressure control passage, and the water level control valve is controlled in a state in which the pressure control passage is closed to discharge the insulating gas in the freezer inlet, A superconducting current limiter, characterized in that the liquid refrigerant level in the refrigerator inlet is adjusted using the difference between the gas pressure in the refrigerator inlet, which is reduced due to the discharged insulating gas, and the insulating gas pressure in the main chamber of the refrigerant container.
3. The method of claim 2, wherein the control unit,

   When the operation of the cryogenic refrigerator is stopped, the water level control valve is controlled to close the water level control gas flow path, and when the water level control gas flow path is closed, the insulating gas filled in the main chamber of the refrigerant container flows through the pressure control flow path. A superconducting current limiter, characterized in that the pressure control flow path is opened by controlling the pressure control valve so that the pressure control valve flows into the refrigerator inlet.
4. According to paragraph 1,

   It further includes a pressure sensor that detects the gas pressure in the refrigerator inlet through the pressure of the water level control gas flow path,

   The control unit,

   Based on the gas pressure in the refrigerator inlet according to the detection result of the pressure sensor, the liquid refrigerant level in the refrigerator inlet is determined, and the water level control valve is controlled according to the determined liquid refrigerant level to open the water level control gas flow path. A superconducting current limiter characterized by closing.
5. According to paragraph 1,

   The cryogenic freezer is plural,

   A superconducting current limiter further comprising the refrigerator inlet corresponding to each of the plurality of cryogenic refrigerators, the water level control gas flow path and water level control valve, and the pressure control flow path and pressure control valve.
6. The method of claim 5, wherein the control unit,

   Among the plurality of cryogenic refrigerators, at least one of a plurality of water level control valves and at least one of a plurality of pressure control valves are allowed to contact the liquid refrigerant to each of the at least one driven cold head, or to separate the liquid refrigerant from each cold head. A superconducting current limiter, characterized in that the level of the liquid refrigerant filled in at least one refrigerator inlet is changed by controlling each of them.
7. According to clause 6,

   It further includes a current sensor that detects a current load applied to the superconducting current limiter,

   The control unit,

   A superconducting current limiter, characterized in that driving at least one of the plurality of cryogenic refrigerators according to the detection result of the current sensor.
8. The method of claim 1, wherein the liquid refrigerant charged in the refrigerant container is:

   A superconducting current limiter that accommodates at least a portion of one side of the refrigerant container forming one side of the refrigerator inlet, and is filled so that the cold head of the refrigerator inlet has a water level lower than the inlet height.
9. According to paragraph 1,

   One side of the refrigerant container forming one side of the refrigerator inlet is at least partially separated into one side of the refrigerant container and one side of the refrigerator inlet, and one side of the separated refrigerant container and one side of the refrigerator inlet are separated. A superconducting current limiter characterized by being spaced apart from each other by a space formed between one side.
10. The method of claim 1, wherein the cryogenic freezer,

    A superconducting current limiter, characterized in that the cold head is introduced into the current limiter tank in the direction of gravity so that it is installed in the direction of gravity.
11. The method of claim 1, wherein the liquid refrigerant charged in the refrigerator inlet is,

    When the water level rises according to the control of the water level control valve and the pressure control valve of the control unit and comes into contact with the cold head introduced into the refrigerator inlet, the cold air discharged from the cryogenic refrigerator is directly discharged through at least a portion of the contacted cold head. A superconducting current limiter characterized by receiving transmission.
12. The method of claim 1, wherein the liquid refrigerant is:

    A superconducting current limiter characterized by supercooled liquid nitrogen.
13. The method of claim 1, wherein the insulating gas is:

    The insulating gas is a mixed gas of gaseous nitrogen and gaseous non-condensable gas,

    A superconducting current limiter, wherein the non-condensable gas is any one of hydrogen, helium, and neon, which has a vaporization point lower than nitrogen.
14. In the control method of the superconducting current limiter of claim 7,

    detecting a current load of the superconducting current limiter based on a detection result of the current sensor;

    If the detected current load is above the preset threshold, all gas pressures in the plurality of refrigerator inlets are changed to increase the level of all liquid refrigerants in the plurality of refrigerator inlets so that the cold head of the cryogenic refrigerator reaches the inlet height. raising step; and,

    When the detected current load is less than a preset threshold, the gas pressure of some of the plurality of refrigerator inlets is changed to increase the liquid refrigerant level in some of the refrigerator inlets so that the cold head of the cryogenic refrigerator reaches the inlet height. A control method of a superconducting current limiter comprising the step of raising the current limiter.
15. According to clause 14,

    The step of raising the level of all liquid refrigerants in the plurality of refrigerator inlets is,

    controlling the plurality of water level control valves and the plurality of pressure control valves so that all of the plurality of pressure control flow paths are closed and all of the plurality of water level control gas flow paths are open while the plurality of pressure control flow paths are all closed;

    Checking whether the gas pressure in each refrigerator inlet detected by pressure sensors that detect the gas pressure in the refrigerator inlet through the pressure of the water level control gas flow path has reached a preset pressure;

    controlling the plurality of water level control valves so that all of the open water level control gas passages are closed according to the check results; and,

    A control method for a superconducting current limiter, comprising the step of driving all of the plurality of cryogenic refrigerators.
16. According to clause 14,

    A water level control valve that closes the pressure control flow path connected to a part of the refrigerator inlet and opens a part of the water level control gas flow path connected to the part of the freezer inlet while the part of the pressure control flow path is closed; controlling some pressure regulating valves;

    Checking whether the gas pressure in the partial refrigerator inlet reaches a preset pressure from at least one pressure sensor that detects the gas pressure in the partial refrigerator inlet;

    controlling the part of the water level control valve to close the part of the open water level control gas passage according to the check result; and,

    A method of controlling a superconducting current limiter, comprising the step of driving at least one cryogenic refrigerator introduced into the partial refrigerator inlet.
17. The method of claim 14, wherein the preset threshold is:

    A control method of a superconducting current limiter, characterized in that it is determined based on the rated current of the superconducting current limiter.
18. In a superconducting current limiter comprising a refrigerant container containing a liquid refrigerant and an insulating gas, and containing a superconductor inside the liquid refrigerant,

    The refrigerant container is,

    It is provided with a refrigerant container main chamber and a freezer inlet into which a cryogenic freezer is introduced,

    The refrigerant container main chamber and the refrigerator inlet are connected to each other to allow the liquid refrigerant to flow,

    The superconducting current limiter,

    At least one pressure regulator provided in at least one of the refrigerant container main chamber and the refrigerator inlet, and capable of adjusting the pressure of the insulating gas contained in at least one of the refrigerant container main chamber and the refrigerator inlet; and

    A superconducting current limiter comprising a control unit that controls the at least one pressure control unit to adjust the level of the liquid refrigerant contained in the refrigerator inlet.
19. According to clause 18,

    The at least one pressure regulator includes a pressure control valve provided in the main chamber of the refrigerant container,

    The control unit,

    The pressure control valve is controlled to provide additional insulating gas pressure to the refrigerant container main chamber so that a portion of the liquid refrigerant contained in the refrigerant container main chamber is pushed into the refrigerator inlet and the liquid refrigerant level in the refrigerator inlet increases. A superconducting current limiter.
20. According to clause 18,

    The at least one pressure regulator includes a water level control valve provided at the refrigerator inlet,

    The control unit,

    Superconducting current-limiting current, characterized in that controlling the water level control valve to lower the pressure of the insulating gas in the refrigerator inlet so that a portion of the liquid refrigerant contained in the main chamber of the refrigerant container is drawn to the refrigerator inlet and the liquid refrigerant level in the refrigerator inlet increases. energy.
21. According to clause 18,

    The at least one pressure regulator includes a pressure control valve provided in the main chamber of the refrigerant container and a water level control valve provided in the refrigerator inlet,

    The control unit,

    The pressure control valve is controlled so that a portion of the liquid refrigerant contained in the main chamber of the refrigerant container flows into the refrigerator inlet and the liquid refrigerant level in the refrigerator inlet increases, thereby providing additional insulating gas pressure to the main chamber of the refrigerant container. A superconducting current limiter, characterized in that it lowers the insulating gas pressure at the refrigerator inlet by controlling the water level control valve.

Images