JP2013038999A - Superconducting current-limiting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a superconducting current-limiting device in which deviation of occurrence spots of quench in a current-limiting coil is small and which is excellent in after-quench returning properties.SOLUTION: A superconducting current-limiting coil 11 is configured by winding two superconducting wires 13a, 13b corresponding to a first and a second coil 12a, 12b in a planar spiral form from outside toward inside of a radial direction in a state in which the superconducting wires 13a, 13b are arranged in the radial direction to make a first layer, winding each of the superconducting wires 13a, 13b arranged in the radial direction from inside toward outside of the radial direction in a planar spiral form to make a second layer, and letting one of terminal wires on both ends of each of the first and second coils 12a, 12b be connected at a connection part 15.

Description

  The present invention relates to a superconducting fault current limiter having a nonconducting winding superconducting current limiting coil.

  Conventionally, a current limiter that limits an overcurrent generated on an electric circuit is known. For example, an overcurrent generated in an electric power system due to a ground fault or a lightning strike is performed to connect to an electric power line or an electric power device. Current limiting devices that reduce the burden are known.

  One type of current limiter has a pair of first and second coils in which a superconducting wire is wound in a plane spiral shape as shown in Patent Document 1, for example, and the coils are arranged in opposite directions. There is a type using a superconducting current-limiting coil that is wound and has no induction winding.

  In the case of using such a current limiting coil, the electric resistance of the superconducting wire itself is extremely low in the superconducting state at the normal time (below the critical current value), and the first and second coils forming non-inductive winding mutually generate a magnetic field. In order to cancel, the inductance as a current limiting coil is also extremely small. That is, in normal times, the impedance of the current limiting coil is small, and the voltage drop at the current limiting device is very small.

  On the other hand, when an overcurrent is generated on the electric circuit and the input current to the current limiting coil increases, the critical current values of the first and second coils are naturally different or positively different, so that the critical current value is small. A so-called quench occurs in which the coil on the side first transitions from the superconducting state to the normal conducting state, and the inductance of the coil increases. Then, the other coil is also quenched in conjunction with the sudden increase in the inductance, and the inductance increases in the same manner. Thereby, since the impedance of the current limiting coil increases rapidly, the current limiting of the overcurrent input to the current limiting coil is performed.

JP 2001-251757 A

By the way, in a current limiter using a superconducting material, the superconducting material is brought into a sufficiently low temperature state by a cooling device and is maintained in a superconducting state below a critical current value.
The current limiting coil of Patent Document 1 has a structure in which superconducting wires are used to superimpose first and second coils that are reversely wound, and the radially inner ends are joined to each other by soldering or the like. For this reason, the joint portion on the radially inner side generates heat when energized by the connection resistance due to the joint, but since the heat generating joint portion is a spiral inner side, heat is likely to be trapped. In other words, the radially inner portion where there is a joint is likely to be at a temperature higher than the preferred temperature for maintaining the superconducting state, so that it is easier to quench than the other portions, and it takes time to recover after quenching. .

  The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a superconducting fault current limiter in which the occurrence of quenching in the current-limiting coil is small and the return characteristics after quenching are excellent. There is.

  In order to solve the above-mentioned problems, the invention described in claim 1 has a pair of first and second coils in which a superconducting wire is wound in a plane spiral shape, and each coil is configured by non-inductive winding. A superconducting fault current limiter comprising a superconducting current limiting coil and performing a current limiting when an input current becomes an overcurrent using a quench phenomenon of the superconducting current limiting coil, wherein the superconducting current limiting coil is the first current limiting coil. And two superconducting wires corresponding to each of the second coils are wound in a plane spiral shape from the radially outer side to the inner side in a state in which the two superconducting wires are aligned in the radial direction, and then the first layer is wound. The superconducting wires in a state of being arranged in the radial direction across the eyes are wound in a plane spiral shape from the radial inner side to the outer side to perform the second layer winding, and the terminal wires at both ends of the first and second coils The gist is that any one of the above is connected at the connecting portion.

  In the present invention, two superconducting wires corresponding to the first and second coils are wound in a plane spiral shape from the radially outer side to the inner side in a state where they are aligned in the radial direction, and the first layer is formed. From the inner side to the outer side in the radial direction, the superconducting wires arranged in the radial direction across the second layer are wound in a plane spiral shape to form the second layer. One of the terminal wires at both ends of the first and second coils is connected at the connection portion. In this way, the first and second coils having a non-inductive winding two-layer structure are formed, that is, a superconducting current-limiting coil is formed. That is, the non-inductive winding first and second coils have a two-layer structure, and the terminal wires at both ends of each coil (each superconducting wire) are led out radially outside the coil body. Can be connected at the radially outer portion of the coil body. For this reason, the terminal wire connecting portion, which is likely to be quenched due to the heat generated by the connection resistance, is positioned outside the coil body where heat does not accumulate, so that it is sufficiently cooled by the cooling device for maintaining the superconducting state at normal times. For this reason, it is possible to reduce an event in which the quench occurs first from the connection portion, and to reduce the bias of the occurrence location of the quench. Further, since the connecting portion is sufficiently cooled, the return time after quenching occurs in the connecting portion is short, and the return characteristics after quenching are excellent.

  According to a second aspect of the present invention, in the superconducting fault current limiter according to the first aspect, the superconducting current-limiting coil is composed of first and second layers of superconducting wires constituting the first and second coils. The first coil in the first layer and the second coil in the second layer are opposed to each other, and the second coil in the first layer and the first coil in the second layer are opposed to each other. The gist of this is

  In this invention, the arrangement of the superconducting wires of the first and second coils is switched between the first layer and the second layer, and the first coil of the first layer and the second coil of the second layer are opposed to each other. The second coil of the layer and the first coil of the second layer are configured to face each other. As a result, the magnetic fields generated by the first and second coils are canceled between the first layer and the second layer, so that further non-induction can be achieved.

  According to the present invention, it is possible to provide a superconducting fault current limiter having a small deviation in the occurrence of quenching in the current-limiting coil and having excellent return characteristics after quenching.

(A) and (b) are the block diagrams which show the current limiting coil of the current limiting device of this embodiment. It is a block diagram which shows the current limiting coil of the current limiting device in another example.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
As shown in FIG. 1A, the superconducting current limiting coil 11 provided in the superconducting current limiting device 10 of the present embodiment includes non-inductive winding first and second coils 12a and 12b whose winding directions are opposite to each other. Are connected in series. The first and second coils 12a and 12b have a two-layer structure and are configured by winding using two superconducting wires 13a and 13b.

  Specifically, the first and second coils 12a and 12b constituting the current limiting coil 11 are arranged in the first layer from the radially outer side by arranging two corresponding superconducting wires 13a and 13b in the radial direction. In this embodiment, it is wound four times in a plane spiral shape in the same direction. Next, the second end of the superconducting wires 13a and 13b is twisted once so that the positions of the superconducting wires 13a and 13b are interchanged, and the second layer is transferred. Next, in the second layer, two superconducting wires 13a and 13b whose positions are interchanged are similarly arranged in the radial direction and wound in a plane spiral shape in the same direction as the first layer from the radially inner side to the outer side. In the embodiment, it is wound four times in the same manner and overlapped in the axial direction so that the first layer and the second layer have the same winding diameter. When the terminal wires at the beginning of winding of the superconducting wires 13a and 13b are connected to the connecting terminals 14a and 14b for connection to the other, the terminal wires at the end of winding of the superconducting wires 13a and 13b are connected by soldering or the like. The current limiting coil 11 is configured in which the first and second coils 12a and 12b are directly connected to each other at the portion 15. Moreover, by winding in this way, the first and second coils 12a and 12b become non-inductive winding whose winding directions are opposite to each other.

  In FIG. 1A, the number of turns (number) of the first coil 12a is indicated by a normal number, and the number of turns (number) of the second coil 12b is indicated by a round numeral. That is, when viewed from one connection terminal 14a, the first coil 12a spirals from the radially outer side to the inner side in the first layer, crosses the second layer at the inner end portion, and from there to the radially outer side again. It forms a spiral toward the connection part 15. The second coil 12b becomes the second coil 12b from the connecting portion 15 and spirals from the radially outer side to the inner side in the second layer, crosses the first layer at the inner end portion, and then spirals from there to the radially outer side again. To the other connection terminal 14b. Further, the first coil 12a in the first layer and the second coil 12b in the second layer face each other by being twisted so that the arrangement of the superconducting wires 13a and 13b is switched between the first layer and the second layer. The first coil 12b in the first layer and the first coil 12a in the second layer face each other. It should be noted that the superconducting wire 13a constituting the first coil 12a and the superconducting wire 13b constituting the second coil 12b are naturally different or positively different in critical current values leading to quenching (for example, wires made of the same superconducting material). The diameter is made different).

  In this way, the current-limiting coil 11 made of a superconducting material is maintained in a superconducting state in a normal state by, for example, a cooling device (not shown) formed by immersing it in liquid nitrogen and enclosing it in a case. It is maintained at a low temperature. As a feature of the current limiting coil 11 of the present embodiment, two superconducting wires 13a and 13b that form a pair are wound from the radially outer side to the inner side to form the first layer, and the radial direction is applied to the second layer. It is configured to be wound from the inner side toward the outer side and to be connected at the connecting portion 15. That is, since the installation position of the connection portion 15 is located on the outside in the radial direction of the coil 11 body where heat can be easily radiated, the connection portion 15 is sufficiently cooled by the previous cooling device, although connection resistance occurs in the connection portion 15. Will come to be. Therefore, the occurrence of quench in the connection portion 15 is suppressed from being biased.

  Such a current limiter 10 is used, for example, on an electric circuit of a power system, that is, each connection terminal 14a, 14b of the current limiting coil 11 is connected to a corresponding power line. Under normal conditions (below the critical current value), the superconducting wires 13a and 13b are in a superconducting state, so that the current limiting coil 11 has an extremely low impedance, and in addition, the current limiting coil 11 is non-inductively wound with the first and second coils 12a. , 12b, the slight magnetic fields generated in the coils 12a, 12b cancel each other, and the current-limiting coil 11 is further reduced in impedance. Therefore, in this normal time, highly efficient power transmission with a very small voltage drop in the current limiting coil 11 is possible.

  Further, when an overcurrent occurs due to a short circuit or lightning strike in the power system, the first and second coils 12a and 12b having different critical current values are increased based on the increase in the input current to the current limiting coil 11. Either one quenches first and transitions from the superconducting state to the normal conducting state. As a result, the inductance of one of the first and second coils 12a and 12b previously quenched increases, and in conjunction with this, the other coils 12a and 12b are also quenched, and similarly the inductance increases. Thereby, the impedance of the current limiting coil 11 increases rapidly, and the overcurrent input to the current limiting coil 11 is limited. By such an operation of the current limiter 10, the power line, the power device, and the like are protected from overcurrent.

  Incidentally, FIG. 1B shows a superconducting current-limiting coil 21 configured by connecting four current-limiting coils 11 shown in FIG. 1A as a minimum unit in series. That is, the current limiting coil 21 is formed by stacking four current limiting coils 11 of FIG. 1A in the axial direction, and connecting one adjacent connection terminal 14b and the other connection terminal 14a to each other. Thus, a current limiting coil 21 in which four sets of current limiting coils 11 are connected in series is configured. Also in this case, since the connection portion by the connection terminals 14a and 14b between the groups can be arranged on the outer side in the radial direction of the coil 11 body, it is sufficiently cooled by the cooling device and quenched to the connection portion by the connection terminals 14a and 14b. The occurrence of bias is suppressed. It should be noted that various current limiting coils can be configured by appropriately changing the number of current limiting coils 11 according to the application.

Next, characteristic effects of the present embodiment will be described.
(1) Non-inductive winding The first and second coils 12a and 12b have a two-layer structure, and both terminal wires at both ends of each coil 12a and 12b (each superconducting wire 13a and 13b) are arranged on the radially outer side of the coil 11 body. The terminal wire is connected at the radially outer portion of the main body of the coil 11 by adopting the derived configuration. For this reason, since the terminal wire connection portion 15 that is likely to be quenched due to heat generated by the connection resistance is located outside the coil 11 main body where heat does not accumulate, a cooling device (not shown) for maintaining the superconducting state at the normal time is used. It is possible to reduce the phenomenon in which the cooling is sufficiently performed and the quench first occurs from the connection portion 15, and the deviation of the occurrence of the quench in the current limiting coil 11 can be reduced. In addition, since the connection portion 15 is sufficiently cooled, the return time after the quench occurs in the connection portion 15 is short, and the return characteristics after quenching of the current limiting coil 11 are excellent. Can do.

  (2) The arrangement of the superconducting wires 13a, 13b of the first and second coils 12a, 12b is switched between the first layer and the second layer, and the first coil 12a in the first layer and the second coil in the second layer. The second coil 12b in the first layer and the first coil 12a in the second layer are opposed to each other. Thereby, since the magnetic field generated in the first and second coils 12a and 12b is canceled between the first layer and the second layer, the current limiting coil 11 can be made more non-inductive. .

In addition, you may change embodiment of this invention as follows.
In the above embodiment, the arrangement of the superconducting wires 13a and 13b is switched between the first layer and the second layer in order to make the current-limiting coil 11 non-inductive, but the superconducting current-limiting coil 31 shown in FIG. Thus, it is good also as a structure which is not replaced. In the current limiting coil 31, the superconducting wires 13a of the first coil 12a and the superconducting wires 13b of the second coil 12b face each other in the first and second layers. This eliminates the need to replace (twist) the superconducting wires 13a and 13b in the first and second layers.

  Incidentally, a plurality of sets of current limiting coils with the current limiting coil 31 shown in FIG. 2 as a minimum unit can be configured similarly to FIG. Also, a plurality of sets of current limiting coils in which the current limiting coil 11 of FIG. 1A and the current limiting coil 31 of FIG. 2 are mixed can be configured.

  -Current limiting device 10 of the above-mentioned embodiment may be installed not only in the electric power system but also in other electric devices.

  DESCRIPTION OF SYMBOLS 10 ... Superconducting current limiting device, 11, 21, 31 ... Superconducting current limiting coil, 12a ... 1st coil, 12b ... 2nd coil, 13a, 13b ... Superconducting wire, 15 ... Connection part.

Claims (2)

A superconducting current-limiting coil having a pair of first and second coils in which a superconducting wire is wound in a plane spiral shape, each coil being configured by non-inductive winding, and using the quench phenomenon of the superconducting current-limiting coil A superconducting current limiter that performs current limiting when the input current becomes overcurrent,
The superconducting current-limiting coil is formed in a first layer by winding two superconducting wires corresponding to the first and second coils in a planar spiral shape from the outer side in the radial direction to the inner side in the radial direction. After the second winding, the superconducting wires arranged in the radial direction across the second layer are wound in a plane spiral shape from the inner side to the outer side in the radial direction, and the second layer is wound. A superconducting fault current limiter characterized in that either one of terminal wires at both ends of the first and second coils is connected at a connection portion. The superconducting fault current limiter of claim 1,
In the superconducting current-limiting coil, the arrangement of superconducting wires constituting the first and second coils is switched between the first layer and the second layer, and the first coil in the first layer and the first coil in the second layer 2. A superconducting current limiting device, wherein two coils are opposed to each other, and the second coil in the first layer and the first coil in the second layer are opposed to each other.

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