JP2012146821A - Superconductive coil device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a superconductive coil device which prevents short circuits between a superconductive coil and a container due to air bubbles generated in a cooling liquid.SOLUTION: A superconductive coil device incudes: a superconductive coil 10; a container 30 housing the superconductive coil 10 and a cooling liquid 20 maintaining the superconductive state of the superconductive coil 10; and a shield 40 which covers an upper surface and a side surface of the superconductive coil 10, is disposed in the cooling liquid 20 in the container 30, and is made of a conductive material.

Description

  The present invention relates to a superconducting coil device in which a superconducting coil using a superconducting material is disposed in a cooling liquid.

  As the power demand increases, the power system has become larger, so the fault current that flows during a short-circuit fault has also increased. For this reason, the performance improvement of the fault current limiter for suppressing a fault current is calculated | required so that the magnitude | size of a fault current may not exceed the capacity | capacitance of a circuit breaker. For example, a superconducting fault current limiter (SFCL) using a dislocation (S / N dislocation) between a superconducting state and a normal conducting state of a superconductor has been proposed.

  As a superconducting current limiting device, a method using a superconducting coil device in which a superconducting coil using a superconducting material is arranged in a cooling liquid has been studied (for example, see Patent Document 1). The superconducting fault current limiter is a superconducting coil that is normally in the superconducting state, and is transferred to the normal conducting state at the time of failure. Fulfill. The superconducting coil is arranged in a cooling liquid such as liquid nitrogen or liquid helium in order to maintain a superconducting state at normal times.

JP 2007-273740 A

  When the superconducting coil of the superconducting coil device shifts from the superconducting state to the normal conducting state, the superconducting coil generates heat due to the electric resistance generated in the superconducting coil and the current flowing through the superconducting coil. Due to the heat generated by the superconducting coil, the cooling liquid evaporates and bubbles are generated.

  For this reason, the superconducting coil device has a problem in that the superconducting coil and the container containing the cooling liquid are short-circuited through bubbles generated by evaporation of the cooling liquid, causing flashover, resulting in dielectric breakdown.

  In view of the above problems, an object of the present invention is to provide a superconducting coil device that can prevent a short circuit between a superconducting coil and a container caused by bubbles generated in a cooling liquid.

  According to one aspect of the present invention, (a) a superconducting coil, (b) a superconducting coil, and a container containing a cooling liquid that maintains the superconducting state of the superconducting coil, and (c) covering the upper surface and side surfaces of the superconducting coil. Thus, there is provided a superconducting coil device including a shield made of a conductive material disposed in a cooling liquid in a container.

  ADVANTAGE OF THE INVENTION According to this invention, the superconducting coil apparatus which can prevent the short circuit with a superconducting coil and a container resulting from the bubble which generate | occur | produces in a cooling liquid can be provided.

It is a schematic diagram which shows the structure of the superconducting coil apparatus which concerns on embodiment of this invention. It is a typical top view of a superconducting coil device concerning an embodiment of the present invention. It is a schematic diagram which shows the example of the bubble which generate | occur | produces between a superconducting coil and a container. It is a schematic diagram which shows the example which the bubble generate | occur | produced in the superconducting coil apparatus which concerns on embodiment of this invention. It is a schematic diagram which shows the example by which the superconducting coil of the superconducting coil apparatus which concerns on embodiment of this invention is divided | segmented. It is a schematic diagram which shows the example in which the superconducting coil apparatus which concerns on embodiment of this invention has a cooling system. It is a schematic diagram which shows the example which applied the superconducting coil apparatus which concerns on embodiment of this invention to the superconducting fault current limiter.

  Next, an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and different from the actual ones. Further, the following embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention is the material, shape, structure, and arrangement of component parts. Etc. are not specified below. The embodiment of the present invention can be variously modified within the scope of the claims.

  As shown in FIG. 1, a superconducting coil device 1 according to an embodiment of the present invention includes a superconducting coil 10, a superconducting coil 10, a container 30 containing a cooling liquid 20 that maintains the superconducting state of the superconducting coil 10, and a superconducting coil. 10, and a shield 40 made of a conductive material and disposed in the cooling liquid 20 in the container 30.

  The superconducting coil 10 has a structure in which, for example, a superconducting wire 12 is wound around the outer periphery of a cylindrical insulator 11. In general, the temperature at which the superconducting wire 12 undergoes S / N transition from a state having electrical resistance (normal conducting state) to a superconducting state is referred to as a critical temperature. The magnitude of the current that can be passed through the superconducting wire 12 in the superconducting state is called a critical current value.

  The cooling liquid 20 is, for example, liquid nitrogen or liquid helium. As the cooling liquid 20, a liquid whose boiling point is equal to or lower than the critical temperature at which the superconducting wire 12 used in the superconducting coil 10 undergoes S / N dislocation is employed. For this reason, when the current flowing through the superconducting coil 10 is less than the critical current value, the superconducting wire 12 in the cooling liquid 20 is in a superconducting state. For example, when a high-temperature superconductor that is in a superconducting state at the liquid nitrogen temperature is used as the superconducting wire 12 of the superconducting coil 10, liquid nitrogen can be adopted as the cooling liquid 20.

  The container 30 is made of a conductive material and is grounded when used. Since the cooling liquid 20 is an insulator, the container 30 and the shield 40 are electrically insulated.

  A conductive metal material or the like can be used for the shield 40. For example, inexpensive and lightweight aluminum (Al) is suitable for the material of the shield 40. As will be described later, bubbles generated by evaporation of the cooling liquid 20 due to heat generated by the superconducting coil 10 remain inside the shield 40.

  FIG. 2 shows a plan view of the superconducting coil device 1. FIG. 1 is a cross-sectional view taken along the II direction of FIG.

  The shape of the shield 40 viewed from above is circular as shown in FIG. 2, and the shape of the shield 40 viewed from the side is an inverted U shape as shown in FIG. That is, the shield 40 has a hollow cylindrical shape with the upper surface closed, and covers the upper surface and side surfaces of the superconducting coil 10. 1 and 2 show an example in which the shape of the shield 40 is a cylindrical shape, but what is the shape of the shield 40 as long as the bubbles stay inside the shield 40 and the bubbles do not leak outside the shield 40? It may be a simple shape. For example, the shield 40 may have a cubic shape.

  Here, a case where an excessive current flows through the superconducting coil 10 is considered. For example, when the magnitude of the current flowing through the superconducting coil 10 exceeds the critical current value of the superconducting coil 10 at the time of a short circuit failure of the power system using the superconducting coil device 1, the superconducting coil 10 changes from the superconducting state to the normal conducting state. Rearrange. As a result, an electrical resistance is generated in the superconducting coil 10. The phenomenon in which electric resistance is generated in the superconductor is called quenching.

When an electrical resistance is generated in the superconducting coil 10, a heat quantity Q shown in the following formula (1) is generated in the superconducting coil 10:

Q = I ² × R × t (1)

In Equation (1), I is the value of current flowing through the superconducting coil 10, R is the magnitude of the electrical resistance generated in the superconducting coil 10, and t is the time during which current flows through the superconducting coil 10.

  Due to heat generation in the superconducting coil 10, the cooling liquid 20 evaporates around the superconducting coil 10, and bubbles are generated in the cooling liquid 20. Bubbles rise in the cooling liquid 20.

  The container 30 is grounded in use. For this reason, for example, as shown in FIG. 3, when the shield 40 is not disposed in the container 30, the bubbles 21 are cooled between the superconducting coil 10 and the container 30 while the voltage is applied to the superconducting coil 10. When this occurs in 20, as indicated by an arrow, the superconducting coil 10 and the side surface of the container 30 are short-circuited via the bubble 21, and flashover occurs.

  However, in the superconducting coil device 1, when bubbles 21 are generated around the superconducting coil 10 due to heat generated by the superconducting coil 10, a conductor is not formed between the bubbles 21 and the side surface of the container 30 as shown in FIG. 4. There is a shield 40. For this reason, flashover does not occur in the superconducting coil device 1.

  In many cases, a potential difference of several tens of thousands to several hundred thousand V is generated between the superconducting coil 10 and the container 30, and a flashover may occur immediately after the bubbles 21 are generated around the superconducting coil 10. However, in the superconducting coil device 1, since the shield 40 exists between the bubble 21 and the container 30, flashover does not occur immediately after the bubble 21 is generated on the side surface of the superconducting coil 10.

  In the superconducting coil device 1, since the shield 40 is provided so as to cover the entire upper surface and side surfaces of the superconducting coil 10, the bubbles 21 generated around the superconducting coil 10 are not scattered in the cooling liquid 20. That is, the bubbles 21 rise inside the shield 40 and gather below the upper portion of the shield 40. The bubbles 21 accumulated in the shield 40 are cooled and recondensed by heat exchange with the surrounding cooling liquid 20 or the like.

  Therefore, the bubble 21 is held between the superconducting coil 10 and the shield 40, and the bubble 21 does not rise to the surface of the cooling liquid 20. For this reason, in the superconducting coil device 1, the superconducting coil 10 and the container 30 are not short-circuited via the bubbles 21 on the surface of the cooling liquid 20, and flashover does not occur.

  Further, no bubbles 21 can exist between the shield 40 and the container 30. For this reason, the electrical insulation between the shield 40 and the container 30 is maintained by the insulating cooling liquid 20.

  In addition, as shown in FIG. 5, when the superconducting coil 10 is divided into superconducting coils 10a to 10c and arranged in the cooling liquid 20, the upper surfaces and side surfaces of the superconducting coils 10a to 10c are shields 40a to 40c. Covered by each.

  An example in which the superconducting coil device 1 has a cooling system 50 for the shield 40 is shown in FIG. The cooling system 50 illustrated in FIG. 6 includes a cooling device 51 disposed outside the container 30 and a cooling pipe 52 disposed on the upper surface of the shield 40 and connected to the cooling device 51.

  By cooling the cooling pipe 52 by the cooling device 51, the bubbles 21 accumulated below the shield 40 can be efficiently cooled via the shield 40. For example, when the cooling liquid 20 is liquid nitrogen, the bubbles 21 are supercooled by cooling the cooling pipe 52 to about 50K. Thereby, the bubble 21 returns to the liquid and is stored in the container 30 as a part of the cooling liquid 20. Therefore, it is preferable to use a material with good thermal conductivity for the shield 40.

  As described above, in the superconducting coil device 1 according to the embodiment of the present invention, the bubbles 21 generated by the evaporation of the cooling liquid 20 due to the heat generated by the superconducting coil 10 are stored inside the shield 40. For this reason, flashover between the superconducting coil 10 and the container 30 due to the bubbles 21 does not occur. That is, the superconducting coil device 1 that can prevent a short circuit between the superconducting coil 10 and the container 30 caused by the bubbles 21 generated in the cooling liquid 20 can be realized.

  The superconducting coil device 1 according to the embodiment is used in, for example, a superconducting fault current limiter 100 shown in FIG. The superconducting fault current limiter 100 will be described below.

  In the superconducting current limiter 100 shown in FIG. 7, the superconducting coil device 1 and the commutation switch 2 are connected in series, and the parallel coil 3 is connected in parallel with the series connection of the superconducting coil device 1 and the commutation switch 2. A shunt-type superconducting fault current limiter having a configuration.

  As already described, the superconducting current limiter is a current limiting device that utilizes the S / N dislocation of the superconductor, and uses a superconducting coil device that normally has a low impedance but has a high impedance when a failure occurs. Further, in the superconducting current limiter 100, the current flowing through the superconducting coil device 1 is interrupted by opening the commutation switch 2 using the energy generated when an excessive current flows through the parallel coil 3.

  For the commutation switch 2, for example, a configuration in which a vacuum valve 210 and an electromagnetic repulsion plate 220 as shown in FIG. 7 are connected in series can be employed. The vacuum valve 210 has a fixed part 211 connected to the superconducting coil device 1 and a movable part 212 connected to the electromagnetic repulsion plate 220.

  The operation of superconducting fault current limiter 100 will be described below. During normal energization, the superconducting coil 10 of the superconducting coil device 1 is in a superconducting state, and a current flows through the electric path via the superconducting coil device 1 and the commutation switch 2. When an excessive current flows through the superconducting coil device 1 due to a short circuit accident or the like, the superconducting coil 10 shifts from the superconducting state to the non-superconducting state (high resistance state). As a result, the superconducting fault current limiter 100 becomes high impedance.

  In a normal state, the fixed portion 211 and the movable portion 212 of the vacuum valve 210 are in contact with each other, and a current flows through the commutation switch 2. However, when an excessive current flows through the superconducting coil device 1 and the superconducting coil 10 enters a normal conducting state, an excessive current flows through the parallel coil 3. In this case, the electromagnetic repulsion plate 220 moves in a direction away from the vacuum valve 210 by the electromagnetic repulsion force generated between the parallel coil 3. For this reason, the fixed part 211 and the movable part 212 of the vacuum valve 210 are separated, the commutation switch 2 is opened, and no current flows through the superconducting coil device 1.

  That is, in the superconducting fault current limiter 100 shown in FIG. 7, the energy generated in the parallel coil 3 when an excessive current flows through the parallel coil 3 at the time of a short circuit failure or the like is used as energy for opening the commutation switch 2. . Thereby, the energy consumed in the superconducting coil device 1 is reduced by interrupting the current flowing through the superconducting coil device 1.

  In addition, since the commutation switch 2 is opened by the energy generated in the parallel coil 3, the current flowing in the superconducting coil device 1 is cut off in a short time such as an alternating half-wave flowing in the parallel coil 3.

  As described above, the superconducting fault current limiter 100 does not require an external power source for driving the commutation switch 2. For this reason, the superconducting fault current limiter 100 does not require a complicated operation mechanism for opening the commutation switch 2, and can operate at high speed.

  In the superconducting fault current limiter 100 shown in FIG. 7, when a current exceeding the critical current value flows through the superconducting coil 10 of the superconducting coil device 1 due to, for example, a lightning strike or contact between cables of the power system, the superconducting coil 10. Rearranges from the superconducting state to the normal conducting state. As a result, the superconducting coil 10 generates heat, and the cooling liquid 20 evaporates around the superconducting coil 10 to generate bubbles 21. However, by using the superconducting coil device 1 in which the shield 40 is disposed between the generated bubble 21 and the container 30 for the superconducting current limiter 100, flashover occurring between the superconducting coil 10 and the container 30 can be prevented. . For this reason, the reliability of the superconducting fault current limiter 100 can be improved.

  In power systems in areas where power demand is growing, such as in urban areas, the short-circuit current is expected to exceed the rating of existing power equipment due to the increase in power supply capacity. For this reason, measures are taken by increasing the breaking current of the circuit breaker or dividing the system. However, as a more fundamental measure against the future increase in short-circuit current, a method of suppressing the short-circuit current by installing a superconducting current limiting device is also being studied. If the superconducting fault current limiter is applied to the electric power system, the cost for taking measures such as increasing the capacity of the system protective circuit breaker and system separation / reorganization can be greatly reduced. Then, by applying the superconducting fault current limiter to the power system, useful effects such as improved reliability and ensuring system stability can be expected.

  For example, according to the superconducting fault current limiter 100 as shown in FIG. 7 using the superconducting coil device 1 according to the embodiment of the present invention, the superconducting limit in which the short circuit between the superconducting coil 10 and the container 30 caused by the bubbles 21 is prevented. The flow device can be generated without an external power source for driving the commutation switch 2. For this reason, the cost of the superconducting fault current limiter 100 is reduced.

  As mentioned above, although this invention was described by embodiment, it should not be understood that the description and drawing which form a part of this indication limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art. That is, it goes without saying that the present invention includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

DESCRIPTION OF SYMBOLS 1 ... Superconducting coil apparatus 2 ... Commutation switch 3 ... Parallel coil 10 ... Superconducting coil 11 ... Insulator 12 ... Superconducting wire 20 ... Cooling liquid 21 ... Bubble 30 ... Container 40 ... Shield 50 ... Cooling system 51 ... Cooling device 52 ... Cooling Pipe 100 ... Superconducting current limiting device 210 ... Vacuum valve 211 ... Fixed part 212 ... Movable part 220 ... Electromagnetic repulsion plate

Claims (3)

A superconducting coil;
A container for containing the superconducting coil and a cooling liquid for maintaining the superconducting state of the superconducting coil;
A superconducting coil device comprising: a shield made of a conductive material that covers an upper surface and a side surface of the superconducting coil and is disposed in the cooling liquid in the container.   2. The superconducting device according to claim 1, wherein the superconducting coil is divided and arranged in the cooling liquid, and an upper surface and a side surface of each of the divided superconducting coils are respectively covered with the plurality of shields. Coil device.   The superconducting coil device according to claim 1, further comprising a cooling system for cooling the shield.

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