JP7444601B2 - Cooling system and cooling system control method - Google Patents

Description

The present disclosure relates to a cooling system and a method of controlling the cooling system.

Power cable systems using superconducting cables cool the superconducting cables by circulating a cryogenic coolant such as liquid nitrogen along the axial direction of the superconducting cables, thereby maintaining the superconducting state. In the unlikely event of an accident, when an excessive current exceeding the rated current flows through the power system and it attempts to transition to a normal conduction state, a current limiter is required that has the function of instantly interrupting the current. , there are not many examples in which a superconducting cable and a current limiter are used in combination.

Patent Document 1 (particularly FIG. 35) discloses a cooling system that combines a superconducting cable and a superconducting current limiter and maintains them at a temperature below the SN transition temperature (critical temperature). A superconducting current limiter is a device that suppresses current by utilizing the electrical resistance that occurs when a superconducting state is broken and transitions to a normal conducting state. Patent Document 2 discloses an example including a dedicated refrigerator for cooling a superconducting current limiting element that constitutes a superconducting current limiter.

International Publication No. 99/62127 (Figure 35) JP2007-317884A

Superconducting cables are cooled to a cooling temperature with a safety margin from the critical temperature so as not to exceed the critical temperature during operation. On the other hand, the superconducting current limiting element that constitutes the superconducting current limiter is required to immediately transfer and suppress the short circuit current when a short circuit current exceeding the rated current occurs in the superconducting cable. It is cooled to a temperature close to the critical temperature. As described above, since the cooling temperatures of the two types are different, it is generally thought that even when the two types are used in combination, a dedicated refrigerator must be provided for each type. Therefore, the cooling system may become complicated and expensive.

The present disclosure has been made in view of the above-mentioned problems, and when a superconducting cable and a superconducting current limiter are used in combination, the superconducting cable and the superconducting current limiter are cooled to a superconducting state at a temperature suitable for each. The purpose is to reduce the cost of cooling systems.

In order to achieve the above object, a cooling system according to the present disclosure is a cooling system for a superconducting cable and a superconducting current limiter electrically connected to the superconducting cable, and includes a refrigerator and a a circulation path for supplying a first refrigerant to the superconducting cable and returning it to the refrigerator; and a branch path branching from the circulation path, bypassing the superconducting cable, and passing through the superconducting current limiter. and a condenser provided on the branch path for cooling and condensing the second refrigerant vaporized by the superconducting current limiter with the first refrigerant.

Further, a method for controlling a cooling system according to the present disclosure is a cooling system for a superconducting cable and a superconducting fault current limiter electrically connected to the superconducting cable, the cooling system including a refrigerator and a first tube cooled by the refrigerator. a circulation path for supplying refrigerant to the superconducting cable and returning it to the refrigerator; a branch path branching from the circulation path, bypassing the superconducting cable, and passing through the superconducting current limiter; a condenser provided on the branch path for cooling and condensing a second refrigerant vaporized in the superconducting current limiter with the first refrigerant, the condenser being included in the superconducting current limiter. The second refrigerant for cooling the superconducting current limiting element is stored in the gas phase part of the refrigerant tank or in a space communicating with the gas phase part, and the condensed liquid liquefied in the condenser is transferred to the refrigerant tank. A method for controlling a cooling system including a liquid return flow path for returning the liquid to a liquid phase portion of the refrigerant tank, the method comprising: detecting a pressure value of a gas phase portion of the refrigerant tank or a space communicating with the gas phase portion; and a flow rate control step of controlling the flow rate of the first refrigerant flowing into the condenser according to the pressure value.

According to the cooling system according to the present disclosure, when a superconducting cable and a superconducting fault limiter are used in combination, a refrigerator dedicated to the superconducting fault limiter is not required, so the cooling system can be simplified and lowered in cost. The superconducting cable and the superconducting current limiter can be cooled to a superconducting state at temperatures suitable for each. Furthermore, according to the method for controlling the cooling system according to the present disclosure, the cooling temperature of the superconducting fault current limiter can be controlled to a temperature close to the transition temperature, so that the superconducting current limiter when a short circuit current higher than the rated current flows through the superconducting cable The responsiveness of the device can be improved.

FIG. 1 is a system diagram showing a power cable system according to an embodiment using a combination of a superconducting cable and a superconducting current limiter. FIG. 1 is a cross-sectional view of a cooling system for a superconducting current limiter according to an embodiment. FIG. 1 is a cross-sectional view of a cooling system for a superconducting current limiter according to an embodiment. FIG. 3 is a process diagram of a method for controlling a cooling system for a superconducting current limiter according to an embodiment.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments or shown in the drawings are not intended to limit the scope of the present invention thereto, and are merely illustrative examples.
For example, expressions expressing relative or absolute positioning such as "in a certain direction,""along a certain direction,""parallel,""orthogonal,""centered,""concentric," or "coaxial" are strictly In addition to representing such an arrangement, it also represents a state in which they are relatively displaced with a tolerance or an angle or distance that allows the same function to be obtained.
For example, expressions such as "same,""equal," and "homogeneous" that indicate that things are in an equal state do not only mean that things are exactly equal, but also have tolerances or differences in the degree to which the same function can be obtained. It also represents the existing state.
For example, expressions expressing shapes such as squares and cylinders do not only refer to shapes such as squares and cylinders in a strict geometric sense, but also include uneven parts and chamfers to the extent that the same effect can be obtained. Shapes including parts, etc. shall also be expressed.
On the other hand, the expressions "comprising,""comprising,""comprising,""containing," or "having" one component are not exclusive expressions that exclude the presence of other components.

FIG. 1 is a system diagram of a cooling system 10 according to one embodiment. The cooling system 10 is applied to a power cable system that uses a combination of a superconducting cable 12 and a superconducting current limiter 16 electrically connected to the terminal 14 of the superconducting cable 12. This is a cooling system for cooling the flow vessel 16 to a superconducting state suitable for each cooling temperature. The cooling system 10 includes a circulation path 18 and a branch path 22, and the circulation path 18 is provided with a refrigerator 20 and a refrigerant pump 26. r1 (first refrigerant) is circulated through the circulation path 18 and branch path 22 by the refrigerant pump 26.

The circulation path 18 includes an outgoing path 18 (18a) formed from the terminal 14 inside the superconducting cable 12 along the axial direction of the superconducting cable 12, and a path separated from the superconducting cable 12 at the other end of the superconducting cable 12 to the refrigerator 20. and a return route 18 (18b). The refrigerant r1 cooled by the refrigerator 20 flows through the outgoing path 18 (18a), cools the superconducting cable 12 to a temperature below the SN transition temperature, and maintains the superconducting state. The branch path 22 is arranged so as to branch from the circulation path 18 on the upstream side of the superconducting cable 12, pass through the superconducting current limiter 16, bypass the superconducting cable 12, and return to the refrigerator 20.

2 and 3 are cross-sectional views showing a cooling system for a superconducting fault current limiter 16 according to some embodiments in the cooling system 10. As shown in FIG. 2 or 3, the branch path 22 is provided with a condenser 30 (30a, 30b) that constitutes a cooling system for the superconducting current limiter 16. The refrigerant r2 (second refrigerant) used to cool the superconducting current limiter 16 cools the superconducting current limiter 16 to a temperature close to the critical temperature, and therefore has a temperature close to the boiling point under atmospheric pressure, for example. Therefore, part of the refrigerant r2 evaporates during the operation of the superconducting current limiter 16. The condenser 30 cools and recondenses the refrigerant r2 vaporized by the superconducting current limiter 16 by exchanging heat with the refrigerant r1.

The superconducting current limiter 16 includes a superconducting current limiting element 50 and a refrigerant tank 52 in which refrigerant r2 for cooling the superconducting current limiting element 50 is stored. The superconducting current limiting element 50 is immersed in the refrigerant r2 stored in the refrigerant tank 52. The superconducting cable 12 is maintained at a low temperature with a safety margin from the critical temperature by the refrigerant r1 so as not to exceed the critical temperature. On the other hand, when a short circuit current exceeding the rated current occurs in the superconducting cable 12, the superconducting fault current limiter 16 is cooled to a temperature close to the critical temperature by the refrigerant r2 in order to immediately interrupt the short circuit current. Therefore, the cooling temperatures for both are different.

According to the embodiment described above, in the condenser 30, the refrigerant r2 evaporated in the refrigerant tank 52 is cooled and recondensed by the refrigerant r1, and the recondensed refrigerant r2 is used for cooling the superconducting fault current limiter 16. A dedicated refrigerator for cooling the flow vessel 16 is not required. Furthermore, since the gas phase G of the refrigerant r2 is in a saturated state, by controlling the pressure (saturation pressure) of the gas phase G of the refrigerant r2, the temperature of the liquid phase L of the refrigerant r2 (saturation temperature ) can be controlled. Since the temperature of the liquid phase portion L of the refrigerant r2 can be controlled, the superconducting current limiting element 50 cooled by the refrigerant r2 can be cooled to a temperature close to the critical temperature. In this way, even though the cooling temperatures of the superconducting cable 12 and the superconducting current limiter 16 are different, a refrigerator for cooling the superconducting current limiting element 50 is not required, and only one refrigerator is required for cooling the superconducting cable 12. Only by this, the superconducting cable 12 and the superconducting current limiter 16 can be cooled to a cooling temperature suitable for each.

For example, liquid nitrogen is used as the refrigerant r1 and the refrigerant r2. The refrigerator 20 supplies the superconducting cable 12 and the condenser 30 with liquid nitrogen at, for example, 67 K, which matches the cooling temperature of the superconducting cable 12 . When the superconducting current limiter 16 is maintained at atmospheric pressure, the liquid phase portion L of the refrigerant r2 is controlled to a temperature close to 77K, which is the boiling point of liquid nitrogen.

In one embodiment, as shown in FIG. 1, superconducting current limiter 16 is electrically connected to terminal 14 of superconducting cable 12 and electrically connected to a power system, such as power transmission facility 24.

In one embodiment, as shown in FIG. 1, the circulation path 18 is provided with a reservoir 28 for recovering the refrigerant r1 after passing through the superconducting cable 12 and the superconducting current limiter 16. When a short circuit current equal to or higher than the rated current flows through the superconducting cable 12, the superconducting current limiting element 50 included in the superconducting current limiter 16 is transferred, generates electrical resistance, and is heated. In response to an increase in the pressure of the refrigerant r2 caused by an increase in the temperature of the superconducting current limiting element 50, the flow rate of the refrigerant r1 flowing into the condenser 30 is increased to prevent the temperature of the refrigerant r2 from increasing. Even in this case, since the reservoir 28 is provided in this embodiment, the flow rate of the refrigerant r1 necessary for the cooling load is not affected by the flow rate or fluid pressure of the refrigerant r1 that passes through the superconducting cable 12 and flows into the reservoir 28. From the condenser 30 it can be returned to the reservoir 28.

In one embodiment, reservoir 28 is provided at the confluence of circulation path 18 and branch path 22 . Then, the refrigerant r1 in the branch path 22 is returned to the gas phase portion of the reservoir 28. If the circulation path 18 and the branch path 22 merge on the upstream side of the reservoir 28, there is a risk that the refrigerant r1 will flow back into the branch path 22 from the circulation path 18 where the flow rate of the refrigerant r1 is large. According to this embodiment, the circulation path 18 and the branch path 22 are connected to the reservoir 28, and the branch path 22 is returned to the gas phase portion of the reservoir 28, so there is no such fear.

In one embodiment, as shown in FIG. 2 or 3, the condenser 30 (30a, 30b) is connected to a gas phase portion G of a refrigerant tank 52 in which refrigerant r2 is stored or a space S communicating with the gas phase portion G. Placed. In the embodiment shown in FIG. 2, the condenser 30 (30a) is arranged in the gas phase section G of the refrigerant tank 52, and in the embodiment shown in FIG. 3, the condenser 30 (30b) communicates with the gas phase section G. It is placed in space S. Further, a liquid return passage 32 is provided for returning the condensed liquid of the refrigerant r2 liquefied in the condenser 30 to the liquid phase portion L of the refrigerant tank 52.

When the superconducting current limiter 16 transitions from a superconducting state to a normal conducting state, it is necessary to quickly return to the superconducting state, and when returning, the cooling load increases instantaneously. Therefore, in order to quickly restore the superconducting current limiter 16, it is necessary to efficiently recondense the refrigerant r2 vaporized in the condenser 30. According to this embodiment, the refrigerant r2 recondensed in the condenser 30 is quickly returned to the refrigerant tank 52 through the liquid return channel 32, so that the refrigerant r2 can be efficiently recondensed.

In the embodiment shown in FIG. 2, the condenser 30 (30a) is arranged in the gas phase part G of the refrigerant tank 52, so the condensed liquid re-liquefied in the condenser 30 (30a) is transferred to the gas phase part by gravity. It falls directly from G to the liquid surface of liquid phase part L. Therefore, in this embodiment, the liquid return channel 32 can be considered to be formed in the gas phase section G. Since the condenser 30 (30a) is arranged in the gas phase section G, it does not require a housing or the like, and therefore the condenser 30 (30a) can be simplified and reduced in cost.

In one embodiment, the condenser 30 (30b) is located above the refrigerant tank 52, as shown in FIG. The liquid return channel 32 is configured to drop the condensed liquid condensed in the condenser 30 (30b) into the liquid phase portion L of the refrigerant tank 52. The condensed liquid of the refrigerant r2 condensed in the condenser 30 (30b) is automatically dripped into the liquid phase portion L of the refrigerant tank 52 by gravity via the liquid return channel 32. Therefore, no power is required to return the recondensed refrigerant r2 to the refrigerant tank 52.

In one embodiment, as shown in FIG. 3, the condenser 30 (30b) includes a housing 34 provided above the refrigerant tank 52. A communication pipe 35 is provided as the liquid return flow path 32 to communicate the inside of the housing 34 and the inside of the refrigerant tank 52, and a lower end 35a of the communication pipe 35 protrudes below the ceiling surface 54 of the refrigerant tank 52. It is configured as follows. The recondensed refrigerant r2 in the condenser 30 (30b) passes through the communication pipe 35 and falls to the lower end 35a, so the recondensed refrigerant r2 does not touch the gas phase G but near the liquid level of the liquid phase L. Move up to. This makes it possible to suppress re-evaporation during falling. When the lower end 35a of the communication pipe 35 is not configured to protrude below the ceiling surface 54 of the refrigerant tank 52, there is a risk that the condensed liquid will re-vaporize while falling.

The condenser 30 (30b) shown in FIG. 3 is disposed above the top surface of the refrigerant tank 52 via the communication pipe 35, but in another embodiment, the housing 34 is placed in contact with the top surface of the refrigerant tank 52. You may arrange it so that it is placed.

In one embodiment, as shown in FIGS. 2 and 3, the condenser 30 (30a, 30b) includes a heat exchanger 36 that exchanges heat between the refrigerant r1 and the refrigerant r2, and further supplies the refrigerant r1 and r2 to the heat exchanger 36. The refrigerant r1 is provided with a flow rate adjustment valve 38 that controls the flow rate of the refrigerant r1. In this embodiment, by controlling the opening degree of the flow rate adjustment valve 38, the flow rate of the refrigerant r1 supplied to the heat exchanger 36 can be controlled, so the amount of condensation of the refrigerant r2 that exchanges heat with the refrigerant r1 can be controlled. . The refrigerant tank 52 is a container having a closed structure, and the inside of the refrigerant tank 52 is in a saturated state. Therefore, the saturation pressure of the refrigerant tank 52 can be controlled by controlling the amount of recondensation of the refrigerant r2. By controlling the saturation pressure, the saturation temperature that uniquely corresponds to the saturation pressure can be controlled. Thereby, the temperature of the refrigerant r2 can be controlled to a temperature suitable for cooling the superconducting current limiting element 50.

In the embodiment shown in FIGS. 2 and 3, the heat exchanger 36 is constituted by a heat exchange tube provided in the gas phase portion G or the communication space S of the refrigerant tank 52. The refrigerant r1 flows inside the heat exchange tube, a gas phase portion of the refrigerant r2 is formed outside the heat exchange tube, and the refrigerant r1 and the refrigerant r2 indirectly exchange heat through the heat exchange tube. Therefore, the gas phase portion G or the communication space S can form a closed space and can maintain a saturated state.

In the embodiment shown in FIG. 2 or 3, the flow regulating valve 38 is provided in the branch 22 upstream of the condenser 30, but it may instead be provided in the branch 22 downstream of the condenser 30. It's okay.
Further, in one embodiment, as shown in FIGS. 1 to 3, the pipes forming the circulation path 18 and the branch path 22 are covered with a heat insulating layer 44 to prevent heat from entering from the outside. Further, the liquid level of the liquid phase portion L stored inside the refrigerant tank 52 can be detected by a liquid level gauge 56. This makes it possible to grasp the amount of refrigerant in the liquid phase portion L.

In one embodiment, as shown in FIG. 2 or 3, a pressure sensor 40 is provided to detect the pressure in the gas phase portion G of the refrigerant tank 52 or the communication space S of the condenser 30 (30b). The detected value of the pressure sensor 40 is sent to the control section 42, and the control section 42 controls the opening degree of the flow rate adjustment valve 38 based on the detected value of the pressure sensor 40. By controlling the opening degree of the flow rate regulating valve 38 based on the detected value of the pressure sensor 40, the pressure in the gas phase portion G of the refrigerant tank 52 can be controlled to a desired pressure. Thereby, the temperature of the refrigerant r2 can be accurately controlled to a temperature suitable for cooling the superconducting current limiting element 50.

In one embodiment, the control unit 42 is configured to control the cooling temperature of the superconducting current limiting element 50 by the refrigerant r2 to a temperature within a set range close to the transition temperature. Thereby, the responsiveness of the superconducting fault current limiter 16 when a short circuit current equal to or higher than the rated current flows through the superconducting cable 12 can be improved.

As shown in FIG. 4, the method for controlling the cooling system 10 according to one embodiment first detects the pressure value of the gas phase portion G or communication space S of the refrigerant tank 52 (pressure detection step S10). Next, the flow rate of the refrigerant r1 flowing into the condenser 30 is controlled according to the detected pressure value (flow rate control step S12). Since the gas phase portion G or communication space S of the refrigerant tank 52 can be set to the target pressure, the cooling temperature of the superconducting current limiting element 50 can be controlled to a temperature close to the transition temperature by the liquid phase portion L of the refrigerant tank 52. Thereby, the responsiveness of the superconducting fault current limiter 16 when a short circuit current equal to or higher than the rated current flows through the superconducting cable 12 can be improved.

The inside of the refrigerant tank 52 is maintained in a saturated state with the refrigerant r2. In one embodiment, in the flow rate control step S12, the refrigerant r1 flowing into the condenser 30 is adjusted such that the refrigerant r2 in the refrigerant tank 52 has a target pressure Pg that uniquely corresponds to the cooling target temperature Tg under a saturated state. Control the flow rate. The target pressure is the pressure of the refrigerant r2 in the refrigerant tank 52, which is easy to control as a control parameter, and the flow rate of the refrigerant r1 flowing into the condenser 30 is controlled so that the pressure of the refrigerant r2 becomes the target pressure Pg. It is possible to precisely control the cooling target temperature Tg of the refrigerant r2 that uniquely corresponds to the temperature Tg of the refrigerant r2.

FIG. 4 explains an example of a method of controlling the pressure in the gas phase portion G or the communication space S by controlling the opening degree of the flow rate regulating valve 38 in the embodiment shown in FIG. 2 or 3. In addition, in FIG. 4, the symbol V indicates the opening degree (%) of the flow rate adjustment valve 38. In this control example, the target pressure Pg of the gas phase portion G or the communication space S is set within the pressure range P1 to P2.
The purpose of the pressure control here is to cool the liquid temperature of the refrigerant r2 stored for cooling the superconducting current limiting element 50 included in the superconducting current limiter 16 to the cooling target temperature Tg. If the cooling target temperature Tg of the refrigerant r2 is within the range of T1≦cooling target temperature Tg≦T2, the target pressure Pg of the pressure value corresponding to the saturation pressure can be within the range of P1≦target pressure Pg≦P2. The temperature T1 is the lower limit of the cooling target temperature Tg, and the pressure P1 is a pressure that uniquely corresponds to the temperature T1 under a saturated state. Further, the temperature T2 is the upper limit value of the cooling target temperature Tg, and the pressure P2 is a pressure that uniquely corresponds to the temperature T2 under a saturated state.

In addition, in FIG. 4, the relationship between the detected value P of the pressure sensor 40, the target pressure Pg (pressure width P1 to P2), the pressure values P1 and P2 during control, and the range of the opening degree V (%) of the flow rate regulating valve 38 are shown. is as follows.
Target pressure: P1≦Pg≦P2
Conditions below target pressure: P<P1
Condition exceeding target pressure: P2<P
0≦V≦100

First, the pressure value P of the gas phase portion G or the communication space S is detected by the pressure sensor 40 (step S10). Next, when the pressure value P decreases below the target pressure Pg (pressure range P1 to P2) (P<P1) (step 12a), the pressure of the refrigerant r2 decreases and the liquid temperature of the refrigerant r2 is low. The opening degree V of the flow rate adjustment valve 38 is decreased to reduce the flow rate of the refrigerant r1 flowing into the condenser 30 (step S14a). When the pressure value P is stable within the target pressure Pg range (P1≦Pg≦P2) (step S12b), the opening degree V of the flow rate regulating valve 38 remains constant and is not changed (step S14b). When the pressure value P increases (P2<P) (step S12c), the liquid temperature of the refrigerant r2 increases due to the increase in the pressure of the refrigerant r2, so the opening degree V of the flow rate regulating valve 38 is increased and the flow into the condenser 30 is increased. The flow rate of the refrigerant r1 is increased (step S14c). By performing such an operation, the pressure in the gas phase portion G or the communication space S can be maintained at the target pressure Pg. Further, the target pressure Pg can be set near atmospheric pressure.

The contents described in each of the above embodiments can be understood as follows, for example.

(1) A cooling system (10) according to one embodiment is a cooling system for a superconducting cable (12) and a superconducting fault current limiter (16) electrically connected to the superconducting cable, and includes a refrigerator (20) and a circulation path (18) for supplying the first refrigerant (r1) cooled by the refrigerator to the superconducting cable (12) and returning it to the refrigerator (20) , and from the circulation path ( 18). a branch path (22) provided to branch and bypass the superconducting cable (12) and pass through the superconducting current limiter (16) ; and a branch path (22) provided on the branch path (22) to bypass the superconducting current limiter (16); and a condenser (30) for cooling and condensing the second refrigerant (r2) vaporized in the container (16) with the first refrigerant (r1) .

According to such a configuration, since the second refrigerant evaporated in the condenser is cooled and recondensed by the first refrigerant, a refrigerator for cooling the second refrigerant is not required. Further, since the gas phase portion of the second refrigerant is in a saturated state, the temperature (saturation temperature) of the second refrigerant can be controlled by controlling the saturation pressure of the gas phase portion of the second refrigerant. Therefore, the liquid phase portion of the second refrigerant can be adjusted to a desired temperature by controlling the flow rate of the first refrigerant supplied to the condenser and controlling the pressure of the gas phase portion of the second refrigerant. Thereby, the superconducting current limiting element cooled by the second coolant can be cooled to a temperature close to the critical temperature. In this way, when a superconducting cable and a superconducting fault limiter are used in combination, only one refrigerator for cooling the superconducting cable can cool the superconducting cable and the superconducting fault limiter to the appropriate cooling temperature for each. .

(2) The cooling system (10) according to another aspect is the cooling system according to (1), which is provided in the circulation path (18) , and includes the superconducting cable (12) and the superconducting current limiter ( 16) for collecting the first refrigerant (r1) after passing through the refrigerant.

When a short circuit current greater than the rated current flows through the superconducting cable, the superconducting current limiting element included in the superconducting current limiter is transferred, generating electrical resistance and heating. This increases the pressure of the second refrigerant, but in this case, the flow rate of the first refrigerant flowing into the condenser is increased to prevent the temperature of the second refrigerant from rising. Even in this case, according to the above configuration, the amount of the first refrigerant required for the cooling load of the superconducting cable is transferred from the condenser to the reservoir without being affected by the flow rate or fluid pressure of the first refrigerant that passes through the superconducting cable and flows into the reservoir. can be returned to.

(3) A cooling system (10) according to yet another aspect is the cooling system according to (1) or (2), in which the condenser (30) is included in the superconducting current limiter (16). the gas phase part (G) of the refrigerant tank (52) in which the second refrigerant (r2 ) for cooling the superconducting current limiting element (50) is stored, or the space ( S ) communicating with the gas phase part (G); ) for returning the condensed liquid liquefied in the condenser (30) to the liquid phase portion (L) of the refrigerant tank (52) .

According to such a configuration, during the operation of the superconducting current limiter, a portion of the second refrigerant evaporates due to heat received from the superconducting current limiting element, and the second refrigerant that is recondensed in the condenser quickly passes through the liquid return channel. Since the second refrigerant is returned to the refrigerant tank, the second refrigerant can be efficiently recondensed.

(4) A cooling system (10) according to still another aspect is the cooling system according to (3), in which the condenser (30) is disposed above the refrigerant tank (52) , and the liquid return The flow path (32) is configured to drop the condensed liquid into the liquid phase portion (L) of the refrigerant tank (52) .

According to such a configuration, since the condenser is disposed above the refrigerant tank, the recondensed second refrigerant automatically returns to the liquid phase portion of the refrigerant tank by gravity. Therefore, no power is required to return the recondensed second refrigerant to the refrigerant tank.

(5) A cooling system (10) according to yet another aspect is the cooling system according to (4), in which the condenser (30 (30b)) is provided above the refrigerant tank (52). a housing (34) , and a communication pipe (35) that communicates between the housing and the refrigerant tank (52) , the lower end (35a ) of the communication pipe (35) is connected to the refrigerant tank (52). is configured to protrude downward from the ceiling surface (54) of.

According to such a configuration, the second refrigerant recondensed in the condenser can travel through the communication pipe and fall near the liquid level of the liquid phase portion of the second refrigerant stored in the refrigerant tank. In this manner, by passing through the communication pipe, contact with the gas phase portion of the second refrigerant can be avoided as much as possible, and re-evaporation during falling can be suppressed.

(6) A cooling system (10) according to yet another aspect is the cooling system according to any one of (3) to (5), wherein the condenser (30) is configured to use the first refrigerant (r1). and the second refrigerant (r2) , the flow rate adjustment valve ( 38) controlling the flow rate of the first refrigerant (r1) supplied to the heat exchanger (36). ) .

According to such a configuration, by controlling the flow rate of the first refrigerant supplied to the heat exchanger with the flow rate adjustment valve, the amount of recondensation of the second refrigerant in the condenser can be controlled. By controlling the amount of recondensation of the second refrigerant, it is possible to control the pressure in the saturated refrigerant tank, and thereby the saturation temperature of the second refrigerant can be controlled, so the second refrigerant is used to cool the superconducting current limiting element. The temperature can be precisely controlled to the appropriate temperature.

(7) A cooling system (10) according to yet another aspect is the cooling system according to (6), in which the gas phase part (G) or the gas phase part (G ) of the refrigerant tank (52 ) a pressure sensor ( 40 ) for detecting the pressure in the space (S) communicating with the space ( S ), and a control unit ( 42) .

According to such a configuration, the pressure sensor detects the saturation pressure of the gas phase portion of the refrigerant tank, and the opening degree of the flow rate adjustment valve is controlled based on this detected value, thereby controlling the second refrigerant to the superconducting current limit. The temperature can be precisely controlled to the appropriate temperature for cooling the element.

(8) A cooling system (10) according to yet another aspect is the cooling system according to (7), in which the control unit ( 42) controls the superconducting fault current limiter ( 16) is configured to control the cooling temperature within a set range close to the transition temperature .

According to such a configuration, by controlling the cooling temperature of the superconducting current limiter to a temperature within a set range, the responsiveness of the superconducting fault current limiter is improved when a short circuit current exceeding the rated current flows through the superconducting cable. be able to.

(9) A method for controlling a cooling system according to the present disclosure is a cooling system for a superconducting cable (12) and a superconducting fault current limiter ( 16) electrically connected to the superconducting cable (12) , 20) , a circulation path (18) for supplying the first refrigerant ( r1) cooled by the refrigerator (20) to the superconducting cable (12) and returning it to the refrigerator (20 ); a branch path (22) that branches from the path (18) and is provided so as to bypass the superconducting cable (12) and pass through the superconducting current limiter (16) ; and a branch path ( 22) that is provided on the branch path (22). , a condenser (30 ) for cooling and condensing the second refrigerant (r2) vaporized in the superconducting current limiter (16) with the first refrigerant (r1 ), the condenser (30) is the gas phase portion (G) of the refrigerant tank (52) in which the second refrigerant (r2) for cooling the superconducting current limiting element (50) included in the superconducting current limiter (16) is stored; A liquid return flow that is arranged in a space (S) communicating with the gas phase part (G) and returns the condensed liquid liquefied in the condenser (30) to the liquid phase part (L) of the refrigerant tank (52). A method for controlling a cooling system comprising a passage (32) , the pressure detecting a pressure value of a gas phase portion (G) of the refrigerant tank (52) or a space (S) communicating with the gas phase portion (G). The method includes a detection step (S10) , and a flow rate control step (S12) for controlling the flow rate of the first refrigerant flowing into the condenser according to the pressure value.

According to such a configuration, the gas phase portion of the refrigerant tank or the space communicating with the gas phase portion can be set as the target pressure, so that the cooling temperature of the superconducting current limiting element can be adjusted to the transition temperature by the liquid phase portion of the refrigerant tank. The temperature can be controlled close to . This makes it possible to improve the responsiveness of the superconducting current limiter when a short-circuit current higher than the rated current flows through the superconducting cable.

(10) A method for controlling a cooling system according to one aspect is the method for controlling a cooling system according to (9), wherein the second refrigerant (r2 ) maintains the inside of the refrigerant tank (52 ) in a saturated state. In the flow rate control step (S12) , the condenser (30 ) the flow rate of the first refrigerant (r1) flowing into the refrigerant (r1) is controlled.

According to such a configuration, the pressure of the second refrigerant in the refrigerant tank, which is easy to control as a control parameter, is targeted, and the flow rate of the first refrigerant flowing into the condenser is controlled so that the pressure becomes the target pressure Pg. Therefore, it is possible to accurately control the cooling target temperature Tg of the second refrigerant that uniquely corresponds to the target pressure Pg.

10 Cooling system 12 Superconducting cable 14 Terminal 16 Superconducting current limiter 18 Circulation path 20 Refrigerator 22 Branch path 24 Power transmission equipment 26 Refrigerant pump 28 Reservoir 30 (30a, 30b) Condenser 32 Liquid return channel 34 Housing 35 Communication pipe 35a Lower end Part 36 Heat exchanger 38 Flow rate adjustment valve 40 Pressure sensor 42 Control part 44 Heat insulating layer 50 Superconducting current limiting element 52 Refrigerant tank 54 Ceiling surface 56 Level gauge r1 Refrigerant (first refrigerant)
r2 refrigerant (second refrigerant)
G Gas phase part L Liquid phase part S Communication space

Claims (10)

A cooling system for a superconducting cable and a superconducting current limiter electrically connected to the superconducting cable, the cooling system comprising:
A refrigerator and
a circulation path for supplying a first refrigerant cooled by the refrigerator to the superconducting cable and returning it to the refrigerator;
a branch path branching from the circulation path, bypassing the superconducting cable and passing through the superconducting current limiter;
a condenser provided on the branch path for cooling and condensing the second refrigerant vaporized by the superconducting current limiter with the first refrigerant;
Cooling system with. The cooling system according to claim 1, further comprising a reservoir provided in the circulation path and for recovering the first refrigerant after passing through the superconducting cable and the superconducting current limiter. The condenser is disposed in a gas phase part of a refrigerant tank in which the second refrigerant for cooling a superconducting current limiting element included in the superconducting current limiter is stored or in a space communicating with the gas phase part,
a liquid return channel for returning the condensed liquid liquefied in the condenser to the liquid phase part of the refrigerant tank;
The cooling system according to claim 1 or 2, comprising: the condenser is located above the refrigerant tank;
4. The cooling system according to claim 3, wherein the liquid return channel is configured to drip the condensed liquid into the liquid phase portion of the refrigerant tank. The condenser is
a housing provided above the refrigerant tank;
a communication pipe that communicates between the housing and the refrigerant tank;
Equipped with
5. The cooling system according to claim 4, wherein a lower end of the communication pipe is configured to protrude below a ceiling surface of the refrigerant tank. The condenser includes a heat exchanger that exchanges heat between the first refrigerant and the second refrigerant,
The cooling system according to any one of claims 3 to 5, further comprising a flow rate adjustment valve that controls the flow rate of the first refrigerant supplied to the heat exchanger. a pressure sensor for detecting the pressure of the gas phase portion of the refrigerant tank or the space communicating with the gas phase portion;
a control unit that controls the opening degree of the flow rate adjustment valve based on the detected value of the pressure sensor;
The cooling system according to claim 6, comprising: The cooling system according to claim 7, wherein the control unit is configured to control the cooling temperature of the second refrigerant by the first refrigerant to a temperature within a set range close to a transition temperature . A cooling system for a superconducting cable and a superconducting current limiter electrically connected to the superconducting cable, the cooling system comprising:
A refrigerator and
a circulation path for supplying a first refrigerant cooled by the refrigerator to the superconducting cable and returning it to the refrigerator;
a branch path branching from the circulation path, bypassing the superconducting cable and passing through the superconducting current limiter;
a condenser provided on the branch path for cooling and condensing the second refrigerant vaporized by the superconducting current limiter with the first refrigerant;
Equipped with
The condenser is disposed in a gas phase portion of a refrigerant tank in which the second refrigerant for cooling a superconducting current limiting element included in the superconducting current limiter is stored or in a space communicating with the gas phase portion, and A method for controlling a cooling system comprising a liquid return passage for returning condensed liquid liquefied in a condenser to a liquid phase part of the refrigerant tank, the method comprising:
a pressure detection step of detecting a pressure value in a gas phase portion of the refrigerant tank or a space communicating with the gas phase portion;
a flow rate control step of controlling the flow rate of the first refrigerant flowing into the condenser according to the pressure value;
A method for controlling a cooling system comprising: The second refrigerant is maintained in a saturated state inside the refrigerant tank,
In the flow rate control step, the flow rate of the first refrigerant flowing into the condenser is controlled so that the second refrigerant in the refrigerant tank has a target pressure Pg that uniquely corresponds to the cooling target temperature Tg. 10. The method for controlling a cooling system according to item 9.

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