JPH11113166A - Current limiter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make small the loss of to generate quenching over the whole length of a superconducting wire with a small loss without specifying its quenching position when it limits a current, by fastening only its both end to a fastening member via fastening fixtures, and by keeping the other parts noncontacting. SOLUTION: In a superconducting wire 1 constituting a current limiter element, applying longitudinally a constant tension to the wire 1, only its both ends are fastened to a fastening member 3 made of an insulation material via fastening fixtures 2a, 2b to keep noncontacting its portions other than both its end portions. Therefore, even though the superconducting wire 1 receives a magnetic field change by an AC current application in a stationary time, since the superconducting wire 1 has no portion contacted frictionally with other members, no heat generating phenomenon is caused by the friction to make small the loss of the current limiting element itself generated by the AC current application. Also, even when a large faulty current flows in the wire 1 by a shorting fault, etc., since such an unstable phenomenon as to break its superconducting state is not generated, the whole of the superconducting wire 1 is quenched in its critical current value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current limiting device for suppressing a fault current generated in an AC circuit, and more particularly to a current limiting device using a superconducting wire as a current limiting element.

[0002]

2. Description of the Related Art As is well known, when a short circuit fault or a ground fault fault occurs on an AC power line such as a distribution line, a fault current of several tens of kA flows. This fault current increases the equipment cost of the system and equipment. For this reason, attention has been paid to the insertion of a current limiting device for suppressing the maximum value of the fault current to a certain value or less in the distribution line, and research is being conducted by various research institutions.

[0003] There are various types of such current limiting devices, and recently, devices using superconducting technology have been proposed. In other words, the superconducting wire instantaneously transitions to the normal conduction transition (quenching) when a current exceeding the critical current flows through itself.
To increase the resistance value. Utilizing this resistance value increasing phenomenon, the superconducting wire itself is used as a current limiting element.

The resistance value when the superconducting wire is quenched is
It is proportional to the length of the superconducting wire. For example, when designing a current limiting element for a distribution system, it is necessary to use a superconducting wire of several tens of meters to several hundreds of meters. Since such a long superconducting wire is required, a current limiting device formed by winding the superconducting wire in a coil shape is usually incorporated to reduce the size of the current limiting device.

When a current limiting element is formed by winding a superconducting wire in a coil shape, it is necessary to adopt a multilayer winding structure in order to reduce the overall size. In this case, it is necessary to always cool the superconducting wire with cold soot typified by liquid helium, so a device different from the case of the normal conducting coil is required.

For this reason, conventionally, after a superconducting wire is wound around a winding core to form a first layer, a large number of dedicated spacers are arranged outside the first layer, and the superconducting wire is arranged outside this. Is wound to form a second layer, and then the third layer is formed in the same manner.
A method of forming a fourth layer and a fourth layer is employed.

However, with such a configuration,
Since a large number of spacers must be arranged in the winding process, there is a problem that not only a long time is required for manufacturing, but also a material having high mechanical strength cannot be manufactured.

As a method for solving such problems and satisfying cooling characteristics, mechanical strength, manufacturability, high pressure resistance and stability, a superconducting method disclosed in Japanese Patent Publication No. 7-118410 is disclosed. It has been proposed to employ a coil configuration.

In other words, this superconducting coil basically adopts a structure in which a plurality of layer coil elements formed by winding a superconducting wire around the outer peripheral surface of a cylindrical bobbin are concentrically stacked. Has a spiral groove for holding the superconducting wire on the outer peripheral surface and a plurality of refrigerant passage grooves deeper than the spiral groove intersecting with the spiral groove, and at least ones other than those located at the innermost layer in the circumferential direction. It has been split.

With such a configuration, when winding the superconducting wire, the superconducting wire may be simply wound while being mounted in a spiral groove formed on the outer peripheral surface of the winding frame, thereby facilitating the winding operation. Becomes possible. Further, the spiral groove reliably fixes the superconducting wire while keeping the winding pitch of the superconducting wire constant. Therefore, the fixation of the superconducting wire is sufficiently ensured. Further, since the plurality of refrigerant passage grooves are formed deeper than the spiral groove and intersect with the spiral groove, the flow of the refrigerant near the superconducting wire can be sufficiently ensured even after the winding, and Good cooling becomes possible. Furthermore, since the winding frame is divided into a plurality of parts in the circumferential direction, the so-called crossover part between the layer coil elements can be set up from the boundary between the divided pieces, so that the overall structure is neat despite the multilayer structure. This enables a compact configuration. In addition, since the winding frame is divided into a plurality in the circumferential direction, it is possible to prevent the occurrence of a gap that easily occurs between the layer coil elements when the winding frame is formed in a cylindrical shape, and impairs cooling characteristics and manufacturability. The integration between the coil elements of the respective layers can be easily realized without performing. further,
Since the winding frame is divided into a plurality of parts in the circumferential direction, it is easy to dispose an insulating material such as a polymer film between the layers, and the pressure resistance can be improved.

However, the current limiting device constructed using the improved winding frame as described above has the following problems. In other words, heat is generated in the superconducting wire constituting the current limiting element because an alternating current flows in a steady state. This heat generation is due to both electromagnetic and mechanical sources.

The heat generated by the former mainly depends on the magnetic field of the superconducting wire, and in the case of a multilayer coil, it can be reduced by connecting the first layer and the second layer in such a way that the first layer and the second layer are energized in the reverse direction and de-inductive.

On the other hand, the latter heat is generated mainly by the friction of the portion in contact with the bobbin due to the superconducting wire vibrating due to the fluctuating magnetic field. The heat generated by this minute friction
It is believed to reach the order of ~ 1W. In a current limiting device using a superconducting wire as a current limiting element, it is originally desired that the superconducting wire be instantly quenched when a current exceeding the critical current flows through the superconducting wire. But,
The quench may occur in the superconducting wire due to the mechanical instability described above. Such mechanical instability changes depending on the state of contact between the superconducting wire and the bobbin. For this reason,
In the case where the superconducting wire is wound around the winding frame to constitute a current limiting element, the quench current value has a distribution over the entire element, that is, the length direction of the superconducting wire.

Even in a conventional current limiting device constructed using the improved bobbin, most of the superconducting wire is in contact with the bobbin. Therefore, the distribution of the quench current value still exists. When the quench current value has a distribution as described above, a portion exhibiting a low quench current at the time of current limiting transitions to normal conduction first to generate resistance. The fault current is limited by the resistance generated at this time. Therefore, when the distribution of the quench current value is large, only a part of the superconducting wire undergoes normal conduction transition, and only the part where the normal conduction transition has been performed consumes the input energy. Further, there is a risk of burning. Also,
Since there is a possibility that the resistance value generated every time of an accident changes, there is also a possibility that the stability of the system may be affected.

[0015]

As described above, in a conventional current limiting device using a superconducting wire wound around a bobbin as a current limiting element, the quench current value is a critical current value inherent to the superconducting wire. It is more likely to be determined by the mechanical instability of the portion where the superconducting wire is fixed than this, which may cause local deterioration and burning of the superconducting wire, as well as adversely affect the stability of the system.

Therefore, the present invention is capable of generating a quench over the entire superconducting wire with low loss and without specifying the quench location at the time of current limiting, and performing a reliable current limiting operation. It is an object of the present invention to provide a current limiting device capable of causing a current to flow.

[0017]

According to a first aspect of the present invention, there is provided a current limiting device using a superconducting wire as a current limiting element, wherein only the both ends of the superconducting wire are connected via fixing members. The superconducting wire is fixed to the fixing member, and portions other than the both ends of the superconducting wire are held in a non-contact manner.

Preferably, the superconducting wire is fixed to the fixing member via the fixing tool in a state where tension is applied. In order to achieve the above objective,
The invention according to claim 3 is a current limiting device using a superconducting wire as a current limiting element, wherein both ends of the superconducting wire are fixed to a fixing member, and both ends of the superconducting wire attached to the fixing member. And a plurality of intermediate supports for supporting a plurality of portions between the portions with the tension applied to the superconducting wire.

It is preferable that each of the intermediate supports supports both ends of the superconducting wire at substantially equal intervals. Further, each of the intermediate supports may support between the both ends of the superconducting wire in a meandering form.

[0020] Each of the intermediate supports may be formed in a drum shape having a smaller diameter at the center than at both ends. Also,
Each of the intermediate supports may be rotatably provided with respect to the fixing member.

In the current limiting device according to the first aspect, only both ends of the superconducting wire constituting the current limiting element are fixed,
Non-contact is maintained between both ends. In particular, when both ends of the superconducting wire are fixed in a state where tension is applied to the superconducting wire, the superconducting wire is stretched in a straight line, so that it is easy to hold the two ends of the superconducting wire in a non-contact manner. For this reason, even if the superconducting wire receives a fluctuating magnetic field, that is, a fluctuating electromagnetic force due to alternating current in a steady state, the superconducting wire does not have a portion that comes into frictional contact with another member, so that a heat generation phenomenon due to friction does not occur. Therefore, the loss of the element itself due to the alternating current is negligibly small.

On the other hand, even when a large fault current is about to flow due to a short circuit fault or the like, an unstable phenomenon such as frictional heating that breaks the superconducting state at a value lower than the critical current value of the superconducting wire occurs. Therefore, a high quench current is exhibited and a uniform quench current value is exhibited over the entire device. In other words, the entire element simultaneously transitions to the normal conduction state, so that the entire element becomes a resistor. Therefore, in a steady state, the circuit current flows with almost zero resistance, and in the event of a short circuit or the like, the fault current can be limited by the resistance value of the entire element.

In the current limiting device according to the third aspect, both ends of the superconducting wire constituting the current limiting element are fixed to the fixing member, and a plurality of portions between both ends of the superconducting wire are added to the superconducting wire by the intermediate support. Since the element is supported by the applied tension, the volume of the entire element can be reduced by, for example, supporting the superconducting wire with an intermediate support so as to meander.

In this current limiting device, a heat generation phenomenon such as friction may occur in a portion supported by the intermediate support. Therefore, although quench may occur at a location supported by the intermediate support, it is possible to limit the quench occurrence location to the above-mentioned support location, and to control a heat generation phenomenon such as friction at the support location. This makes it possible to control the quench current of the entire device.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a main part of the current limiting device according to the first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a superconducting wire constituting a current limiting element. This superconducting wire 1 has a fixed tension applied in the longitudinal direction, and only two ends of the superconducting wire 1
It is fixed to a fixing member 3 made of an insulating material via 2b, and portions other than the above both ends are held in a non-contact manner. Electrodes 4a, 4b connected to both ends of superconducting wire 1 are fixed to fixtures 2a, 2b.

In order to properly set the tension and the frictional force applied to the superconducting wire 1, the wire expands as the temperature decreases as shown by solid arrows 3 'and 2' in the figure, or shows a characteristic that hardly changes. Members, in other words arrows 3 ', 2'
The thermal expansion coefficient of the superconducting wire 1 when the thermal expansion coefficient in the direction is −1 × 10 ⁻⁵ [1 / K] or more (generally, about 9 × 10 ⁻⁶ [1 /
K]) The fixing member 3 and the fixing tools 2a and 2b may be formed from the following materials.

The fixtures 2a and 2b are made of a material such as ethylene tetrafluoride having a static or kinetic friction coefficient of 0.2 or less with metal in order to suppress frictional heating with the superconducting wire 1 and accompanying quench. It may be formed of a low-friction material or a low-friction material (having a coefficient of static or kinetic friction with a metal of 0.1.
2 or less) may be formed of a material provided only on the surface.

Further, in order to suppress an increase in heat generation and quench due to a current concentration in the electrode portion, when connecting the superconducting wire 1 to the electrodes 4a and 4b, a cylindrical terminal plate 21 as shown in FIG. You may. In FIG. 7, as an example, 6
A × 6 secondary conductor 23 is considered. The secondary conductor 23 is divided into the primary conductors 22 and the primary conductors 22 are soldered to the surface of the cylindrical terminal plate 21 in parallel at equal intervals of 60 degrees. In addition, the (n-1) secondary conductor 22 is the (n-1) secondary conductor 2
2 (360 / s) on the surface of the cylindrical terminal plate 21.
The soldering may be performed in parallel at intervals of degrees.

The main part thus constructed is a superconducting wire 1
Can be cooled as a current limiting device by being immersed in a refrigerant capable of cooling below the critical temperature, for example, liquid helium or liquid nitrogen, or cooled through the fixing member 3, the fixing tools 2a, 2b, and the like.

With such a configuration, even if the superconducting wire 1 receives a fluctuating magnetic field due to alternating current in a steady state, the superconducting wire 1
Since there is no portion that comes into frictional contact with other members, heat generation due to friction does not occur. Therefore, the loss of the element itself due to the alternating current is negligibly small.

Further, even when a large fault current is caused to flow due to a short circuit fault or the like, an unstable phenomenon such as frictional heating that breaks the superconducting state at a value lower than the critical current value of the superconducting wire occurs. Therefore, the entire superconducting wire 1 is quenched at the critical current value. That is, since the entire superconducting wire 1 simultaneously transitions to the normal conducting state, the entire element becomes a resistor. Therefore, in a steady state, the circuit current flows with almost zero resistance, and the fault current can be limited in the event of a short circuit fault or the like. FIG. 2 shows a main part of the current limiting device according to the second embodiment of the present invention. Is shown in a partially cutaway perspective view.

In the figure, reference numeral 11 denotes a refrigerant tank. In the coolant tank 11, a fixing member 12 made of an insulating material is arranged along the inner surface of the side wall of the coolant tank 11. A bushing 13a serving also as a fixture is provided on the upper wall of the refrigerant tank 11.
13b are provided at predetermined intervals between each other and penetrate in a liquid-tight manner.

The electrode 14 of each bushing 13a, 13b
Both ends of the superconducting wire 15 constituting the current limiting element are electrically and mechanically fixed to the ends of the superconducting wires 15 a and 14 b located in the refrigerant tank 11. On the side surface of the fixing member 12, there are provided a plurality of intermediate supports 16 for supporting the superconducting wire 15 at substantially equal intervals between both ends thereof, in a meandering manner, and with a constant tension applied to the superconducting wire 15. Installed. The intermediate support 16 is formed in a drum shape having a smaller diameter at the center than at both ends, and is attached with the axis thereof orthogonal to the side surface of the fixing member 12. In addition,
The handle of the drum of the intermediate support 16 may be V-shaped.

With such a configuration, the superconducting wire 15
Are supported by the intermediate support 16 in a state where a constant tension is applied and the both ends are equally spaced and meandering, so that heat generated due to electromagnetic causes due to non-induction is generated. It has been suppressed. Such a meandering arrangement can reduce the size of the entire device.

In the current limiting device according to this embodiment, since the superconducting wire 15 is supported by the intermediate support 16, a heat generation phenomenon such as friction may occur in the portion supported by the intermediate support 16. Therefore, quenching may occur at a location supported by the intermediate support member 16, but rather, the quench location can be limited to the above-described support location, so that heat generation phenomena such as friction at the support location can be controlled. By doing so, the quench current of the entire device can be controlled.

In the example shown in FIG. 2, the superconducting wire 15 serving as a current limiting element is arranged in a meandering state along one side surface of the fixing member 12. In addition, a configuration in which the superconducting wires are arranged in a meandering state may be adopted.

Further, in the example shown in FIG. 2, a flat fixing member is used, but as shown in FIGS. 3 (a) and 3 (b), a cylindrical or columnar fixing member 12a is used. The superconducting wire 15 may be provided along the outer peripheral surface of the fixing member 12a so as to be supported by the intermediate support 16 and arranged in a meandering manner. 3A and 3B, 17a, 1
Reference numeral 7b denotes a fixing tool for fixing both ends of the superconducting wire 15 constituting the current limiting element to the fixing member 12a or a wall of a refrigerant tank (not shown) which also serves as a fixing member.

With such a configuration, the impedance of the entire device can be further reduced. In order to properly set the tension and the frictional force applied to the superconducting wire 15, as shown in FIG. 4, the wire expands as the temperature decreases, as shown by a solid line arrow 18 in the drawing, or shows a characteristic that hardly changes. The fixing member 12 (12a) may be formed of a member, in other words, a material having a coefficient of thermal expansion in the direction of the arrow of −1 × 10 ⁻⁵ [1 / K] or more and a coefficient of thermal expansion of the superconducting wire 15 or less. Also, as shown in FIG. 5, a member that expands as shown by a solid line arrow 20 in the figure with a decrease in temperature, or shows a characteristic that hardly changes, in other words, a coefficient of thermal expansion in the arrow direction is −1 × 10 ^−5. The intermediate support 16 may be formed of a material that is not less than [1 / K] and not more than the thermal expansion coefficient of the superconducting wire 15. Further, in order to suppress the occurrence of quench due to frictional heat generated in the intermediate support 16, the intermediate support 16 is formed of a low friction material such as ethylene tetrafluoride having a coefficient of static or dynamic friction with metal of 0.2 or less. Or low friction material (static or kinetic friction coefficient with metal is 0.2 or less)
The intermediate support 16 may be formed of a material having only the surface. In addition, as shown by a solid line arrow 20 'in the drawing, the intermediate support 16 may be provided so as to be rotatable about the axis. Further, the electrodes 14a, 14
For connection to the terminal b, a cylindrical terminal plate 21 shown in FIG. 7 may be used.

The unit configured as shown in FIG. 2 is referred to as a unit U, and the unit U is configured as shown in FIG.
A plurality may be arranged in one vacuum vessel 19 so as to cope with a three-phase electric circuit.

Here, an experimental example of the example shown in FIG. 3 will be described. Outer diameter 250mm, inner diameter 200mm, height 300mm
Fixing member 1 made of glass fiber reinforced plastic
2a 50mm from the top and 50mm from the bottom
A superconducting wire 15 as a current limiting element was stretched on a drum-shaped intermediate support 16 having an outer diameter of 20 mm at both ends and a phase shift of 45 degrees vertically at 45 ° intervals. The total length of the superconducting wire 15 was 7 m, and the tension at the time of winding was 10 kg / mm ² . 400m outside diameter
A superconducting wire was stretched over a similar fixing member having a diameter of 300 m, an inner diameter of 300 mm, and a height of 300 mm. Both were concentrically overlapped and connected in parallel to form a current limiting element. The superconducting wire is a superconducting wire for alternating current having a diameter of 0.2 mm and Cu-30 having the same diameter.
% Ni wire is stranded around the primary conductor of Cu
-Six secondary conductors twisted around the Ni wire were used.
Quench current Iq at 50 Hz AC in a short length of this conductor
Was 3000 A peak value. In this example, the superconducting wire is connected to the electrodes 14a and 14b in order to avoid the occurrence of quench due to an increase in heat generation due to current concentration at the electrodes 14a and 14b.
When connecting to a and 14b, as shown in FIG. 7, the secondary conductor 23 was divided into six primary conductors 22 and soldered in parallel to the surface of the cylindrical terminal board 21 made of copper at equal intervals.

For comparison, the same superconducting wire is spirally wound around two winding frames formed of the same size as the above two types of fixing members made of glass fiber reinforced plastic, and these are concentrically arranged. A current limiting element was prepared. The electrode section had the same configuration as in FIG.

First, a current was continuously supplied at 1000 A (rms), and the calorific value at this time was measured.
In contrast to 00 mW, it was 10 mW in the experimental example. In addition, when the quench currents of both were measured, the comparative example had a peak value of 2000 A at the beginning, increased with the number of times of quench and almost saturated at the peak value of 2800 A, whereas the experimental example first showed a peak value of 4500 A, The two quench times showed a peak value of 5600 A corresponding to the critical current Ic of the conductor. Furthermore, the resistance value of the element at this time was 1.0Ω, indicating that the entire superconducting wire was uniformly quenched.

[0044]

As described above, according to the present invention,
In addition to reducing the steady-state loss, it is possible to prevent the quench current value from being determined by the mechanical instability of the part that fixes the superconducting wire more than the critical current value inherent to the superconducting wire,
A current limiting device that excels in stability can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of a current limiting device according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a main part of a current limiting device according to a second embodiment of the present invention, with a part cut away.

FIG. 3A is a perspective view of a main part of a current limiting device according to a third embodiment of the present invention, and FIG. 3B is a view taken along line AA in FIG.

FIG. 4 is a view for explaining a modification of the fixing member.

FIG. 5 is a view for explaining a modification of the intermediate support.

FIG. 6 is a conceptual diagram of a current limiting device for a three-phase circuit.

7A is a perspective view of a cylindrical terminal plate used for connection to an electrode, and FIG. 7B is a view taken along the line BB in FIG. 7A.

[Explanation of symbols]

 1, 15 ... superconducting wire 2a, 2b, 13a, 13b, 17a, 17b ... fixture 3, 12, 12a ... fixing member 4a, 4b ... electrode 11 ... refrigerant tank 13a, 13b ... bushing 14a, 14b ... electrode 16 ... middle Support 19: Vacuum container 2 ', 3', 20: Direction of elongation against temperature drop 20 ': Direction of rotation 21: Cylindrical terminal plate 22: (n-1) -order conductor 23: n-order conductor

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshihiro Iwata 4-1 Egasaki-cho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Within the Electric Power Research Laboratory, Tokyo Electric Power Co., Inc. No. 1, Komukai Toshiba, Toshiba R & D Center (72) Inventor Eriko Yoneda No. 1, Komukai Toshiba, Kochi, Kawasaki, Kanagawa, Japan Toshiba R & D Center (72) Inventor Nobuhisa Takezawa, Kanagawa 1 Toshiba R & D Center, Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi (72) Inventor ▲ Tsuru ▼ Kazuyuki Naga Eighth Toshiba-cho, Fuchu-shi, Tokyo Toshiba Corporation Fuchu Plant, Inc. Body 1-1-1, Shibaura, Minato-ku, Tokyo Inside the Toshiba head office

Claims (7)

[Claims] 1. A current limiting device using a superconducting wire as a current limiting element, wherein only both ends of the superconducting wire are fixed to a fixing member via a fixture, and portions other than the both ends of the superconducting wire are in non-contact. A current limiting device, characterized in that the current limiting device is held. 2. The current limiting device according to claim 1, wherein the superconducting wire is fixed to the fixing member via the fixing tool in a state where tension is applied. 3. A current limiting device using a superconducting wire as a current limiting element, wherein both ends of said superconducting wire are fixed to a fixing member, and said fixing member is attached to said fixing member and is provided between said two ends of said superconducting wire. A current limiting device, comprising: a plurality of intermediate supports for supporting a plurality of locations with tension applied to the superconducting wire. 4. The current limiting device according to claim 3, wherein each of said intermediate supports supports said both ends of said superconducting wire at substantially equal intervals. 5. The current limiting device according to claim 3, wherein each of the intermediate supports supports the both ends of the superconducting wire in a meandering form. 6. A limiter according to claim 3, wherein each of said intermediate supports is formed in a drum shape having a smaller diameter at a center portion than at both end portions. Flow device. 7. The current limiting device according to claim 3, wherein each of the intermediate supports is rotatably provided with respect to the fixing member. .