JP2010263036A - Superconductive current-limiting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a series current-limiting element having an allowable electric field equivalent to that of a partial element between electrodes, in an internal series connection type thin-film current-limiting element wherein intermediate electrodes are arranged and external resistors are connected in parallel to the respective intermediate electrodes. <P>SOLUTION: In the internal series connection type current-limiting element, electrodes are formed by evaporating pure metal to both ends and an intermediate part of a superconductive thin film with an alloy shunt protective film; metal base material superconducting tapes are connected the electrodes through solder; and superconductive connection is carried out on the electrodes at both the ends, and also on the intermediate electrode. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a superconducting current limiting element that limits an excessive current such as a short-circuit current flowing in an electric circuit.

In the superconducting state, the superconductor can flow a large current with zero electric resistance, but an electric resistance is generated when a current larger than a predetermined current value (critical current I _c ) flows. When the current is further increased, the temperature of the superconductor rises due to the generated heat, and becomes a normal conducting state, resulting in a larger electric resistance.
A superconducting fault current limiter is known that takes advantage of such characteristics of a superconductor, normally having zero resistance and generating a large resistance in the event of a short circuit in the power system to suppress an increase in accident current.
A major issue in promoting the liberalization of electric power is the increase in short-circuit fault current associated with the distributed power supply interconnection. The most promising countermeasure is the introduction of a current limiter that suppresses the fault current, which is usually low impedance and high impedance in the event of a system fault. From the standpoint of promoting the liberalization of electric power, there is a very high social demand for the realization of a low-cost and highly reliable current limiter. Assuming that the superconducting thin film current limiter using a large area superconducting thin film is introduced into the power distribution system,
(1) Compact, (2) Instantaneous response to overcurrent, (3) Excellent in many respects, such as low constant AC loss, (4) Reliability and performance・ It is considered to be the best from the viewpoint of expandability to occupied capacity and large capacity.

The superconducting thin film current limiter has a thin film current limiting element that operates at a liquid nitrogen temperature (66-77.3 K) connected in series to the electric power system. The state is abruptly transferred (quenched) to the conductive state (N), and the system current is suppressed by the normal conductive resistance, which is also called an SN transfer resistance type current limiter. Conventionally, high-temperature superconducting oxidation such as YBa ₂ Cu ₃ O ₇ (hereinafter referred to as YBCO) is provided on an insulating substrate such as a sapphire substrate (alumina single crystal substrate) having higher thermal conductivity than that of metallic copper via a buffer layer. A large-area superconducting thin film produced from a thin film is used.
Immediately after the short-circuit accident, there is a hot spot phenomenon in which the temperature rapidly rises locally at the part where the normal conducting transition is first made and the thin film is broken. In the thin film current limiter, in order to prevent this, it is common to deposit a metal such as gold or silver on the high-temperature superconducting thin film to form a shunt protective layer at the time of normal conduction transition (Non-patent Document 1, 2).

However, when such a metal shunt layer is added, the electric resistance of the superconducting line is greatly reduced, and the heat generation at the time of current limiting when a predetermined voltage is applied is increased. However, since a long superconducting line is required, there is a problem that a large amount of expensive thin films are used.
On the other hand, a current-limiting element was devised, in which a gold-silver alloy having a resistivity nearly one digit higher than that of pure metal is deposited on the superconducting thin film to form a shunt protective layer, and an inexpensive non-inductive winding resistor is connected in parallel. _A permissible electric field four times higher than that of the conventional element called _peak / cm is obtained (see Patent Document 1, Non-Patent Documents 3 and 4). As a countermeasure against the seriousness of the hot spot phenomenon accompanying the increase in current capacity of the current limiting element of this system, it has been proposed to connect a small-capacitance capacitor in parallel with an external resistor (Patent Document 2, Non-Patent Document 5). reference).

The current limiter is used for suppressing the fault current of the power system, and the rated voltage assumed for the superconducting thin film current limiter is 6.6 kV _rms or more in the power distribution system. A rated voltage of 6.6 kV _rms is achieved even using the above-mentioned high-field type current limiting element (see Patent Document 1, Non-Patent Documents 3 and 4) having a very high allowable electric field of 40 V _peak / cm. In order to do so, the total length of the thin film of 2.3 m or more is required. For this reason, a YBCO thin film deposited on a relatively long rectangular sapphire substrate of 10 cm or more is used, but the normal conduction propagation velocity immediately after current limiting is 1-4 m / s, which is not so fast. The element unit length is set to about 5 cm so that the whole is normally conducted in two cycles (20-40 ms) and the temperature is equalized. For example, when a rectangular thin film having a length of 12 cm is used, an intermediate electrode is provided to provide an internal series connection type element. Is used, and an external resistor is connected in parallel to each of the partial thin films between the electrodes (see FIG. 7) (see Non-Patent Document 6).

In order to further increase the capacity, a current limiting element module is manufactured by dividing a 2.7 cm × 20 cm rectangular thin film into three parts using two intermediate electrodes and paralleling them into two (see FIG. 8). (Refer nonpatent literature 7).
The internal series connection type superconducting thin film current limiting element 19 shown in FIG. 8 has a configuration in which a pair of rectangular superconducting thin film side-by-side bodies 20 and external resistors 3a and 3b connected in parallel therewith are provided.
The superconducting thin film juxtaposed body 20 is composed of rectangular superconducting thin films 20a and 20b.
Each of the superconducting thin films 20a and 20b is provided with a high-temperature superconducting thin film on a sapphire substrate via a buffer layer such as ceria, and a gold-silver alloy shunt layer is provided on the high-temperature superconducting thin film.

Four electrodes 15a1, 15b1, 15c1, 15d1 and 15a2, 15b2, 15c2, 15d2 are provided on the respective gold / silver alloy shunt layers at predetermined intervals in the length direction. The superconducting tapes 19a and 19b are soldered so as to short-circuit the end electrodes 15a1 and 15a2 and 15d1 and 15d2 located at both ends in the length direction of the gold-silver alloy shunt layer.
Each of the gold-silver alloy shunt layers of the superconducting thin films 20a and 20b is divided into four regions 15a1, 15b1, 15c1, 15d1 and 15a2, 15b2, 15c2, 15d2, and regions 4a1, 4b1, 4c1 and 4a2, 4b2, 4c2 Is defined.
The gold-silver alloy layer is formed as a deposited film made of an alloy of gold and silver.

The number of the electrodes can be appropriately set from the viewpoint of the propagation speed of quenching and dispersion of applied voltage.
The superconducting tape 19a is connected to the copper electrode 6a by an appropriate electrical wiring means such as a wire, and the superconducting tape 19b is connected to the copper electrode 6b by an appropriate electrical wiring means such as a wire.
The resistor 3a connects the non-inductive winding shunt resistors 11a1, 11b1, and 11c1 so as to be a continuous resistance by the copper electrodes 12a1 and 12b1 that are intermediate electrodes.
Similarly, the resistor 3b connects the non-inductive winding shunt resistors 11a2, 11b2, and 11c2 so as to be a continuous resistance by the copper electrodes 12a2 and 12b2 that are intermediate electrodes.

One end of the winding of the non-inductive winding shunt resistor 11a1, 11a2 is connected to the external connection electrode 6a, and the other end of the winding of the non-inductive winding shunt resistor 11a1, 11a2 is connected to the intermediate electrode 12a1, 12a2, respectively. The intermediate electrodes 12a1 and 12a2 are connected to the corresponding intermediate electrodes 15b1 and 15b2, respectively, and the intermediate electrodes 12a1 and 12a2 are short-circuited.
In the same manner, one end of the winding of the non-inductive winding shunt resistances 11b1 and 11b2 is connected to the intermediate electrodes 12a1 and 12a2, and the other end of the winding of the non-inductive winding shunt resistance 11b1 and 11b2 is intermediate. The electrodes are connected to the electrodes 12b1 and 12b2, the intermediate electrodes 12b1 and 12b are connected to the corresponding intermediate electrodes 15c1 and 15c2, respectively, and the intermediate electrodes 12b1 and 12b2 are short-circuited.

In the same manner, one end of the winding of the non-inductive shunt resistances 11c1 and 11c2 is connected to the intermediate electrodes 12b1 and 12b2, and the other end of the winding of the non-inductive shunt resistance 11c1 and 11c2 is externally connected. Connect to the connection electrode 6b.
By connecting in this way, the resistors 3 a and 3 b are connected in parallel to the superconducting thin film juxtaposed body 20.
Although not shown in FIG. 8, in this current limiting element, as a countermeasure against hot spots, a small-capacitance capacitor together with the non-inductive winding external resistance shown in FIG. (See Patent Document 2 and Non-Patent Document 5).

Japanese Patent Application No. 2006-528493 (see WO2006 / 001226) JP 2008-283106 A

B. Gromoll, G. Ries, W. Schmidt, H.-P. Kraemer, B. Seebacher, B. Utz, R. Nies, H.-W. Neumueller, E. Baltzer, S. Fischer and B. Heismann, “Resistive fault current limiters with YBCO films−100 kVA functional model,” IEEE Trans. Appl. Supercond. 9 (1999) 656-659 Ok-Bae Hyun, Hye-Rim Kim, J. Sim, Y.-H. Jung, K.-B. Park, J.-S. Kang, BW Lee, and I.-S. Oh, “6.6 kV resistive superconducting fault current limiter based on YBCO films, ”IEEE Trans. Appl. Supercond. 15 (2005) 2027-2030 H. Yamasaki, M. Furuse, and Y. Nakagawa, “High-power-density fault-current limiting devices using superconducting YBa2Cu3O7 films and high-resistivity alloy shunt layers,” Appl. Phys. Lett. 85 (2004) 4427-4429 H. Yamasaki, K. Arai, M. Furuse, K. Kaiho, and Y. Nakagawa, “Low-cost and high-power-density resistive fault-current limiting elements using YBCO thin films and Au-Ag alloy shunt layers,” J. Phys. Conf. Ser. 43 (2006) 937-941 K. Arai, H. Yamasaki, K. Kaiho, Y. Nakagawa, M. Sohma, W. Kondo, I. Yamaguchi, and T. Kumagai, “Methods to increase current capacity of superconducting thin-film fault current limiter using Au- Ag alloy shunt layers, ”IEEE Trans. Appl. Supercond., In press. K. Arai, H. Yamasaki, K. Kaiho, M. Furuse, Y. Nakagawa, M. Sohma, and I. Yamaguchi, “Normal zone propagation in superconducting thin-film fault current limiting elements with Au-Ag alloy shunt layers, ”J. Phys. Conf. Ser. 97 (2008) 12031 H. Yamasaki, K. Arai, K. Kaiho, Y. Nakagawa, M. Sohma, W. Kondo, I. Yamaguchi, and T. Kumagai, “Development of 500 V / 200 A fault-current-limiting modules made of large MOD-YBCO thin films with Au-Ag alloy shunt layers, ”Program & Abstracts of the 21st International Symposium on Superconductivity (2008) 163 J. Duron, L. Antognazza, M. Decroux, F. Grilli, S. Stavrev, B. Dutoit, and O. Fischer, “3-D finite element simulations of strip lines in a YBCO / Au fault current limiter,” IEEE Trans. Appl. Supercond. 15 (2005) 1998-2002

The inventors of the present invention have a 2.7 cm wide and 20 cm long high-temperature superconducting YBCO thin film (thickness 150 nm, expected direct current critical current ≧ 155 A _peak ), and a YBCO thin film of the same size (thickness 160 nm, expected) DC critical current ≧ 167 A _peak ) were connected in parallel using a metal substrate superconducting tape to produce a current limiting element as shown in FIG.
An alloy film having a composition of approximately gold-23 wt% silver was sputter-deposited on the thin film with a film thickness of about 60 nm, and then silver was evaporated at a width of 7-8 mm at both ends and the center to form an electrode (divided into three parts). (Effective length of each partial thin film is 5.7 cm). To prevent hot spots, an external shunt resistor made by non-inductive winding of an alloy wire and a 120 microfarad capacitor (not shown) are divided into three partial thin films. Connected in parallel. The connection between the external resistor and the capacitor and the two thin films in the intermediate electrode was performed using solder and a normal conductive copper lead. The external shunt resistance is 0.35 ohm for each partial thin film, and the resistance of the thin film is about 1.9 ohm. Therefore, when the thin film is quenched, most of the energized current is shunted to the external resistance.
FIG. 9 is a diagram showing a current limiting test result when the above current limiting element is used. As shown in the figure, the total current (I _total ) flowing through the current limiting element increases rapidly at a rate of 2.5 kA _rms without the current limiting element, but increases from around 604 A with the quenching of the superconducting thin film. As the speed decreased, the thin film voltage (V _film ) across the thin _film increased rapidly. And in the state which applied the alternating voltage of 590V _{peak to} the both ends of the high temperature superconducting thin film, electricity supply of 5 cycles (100 msec) was possible, without a thin film burning. At this time, the average electric field at an element effective length of 17 cm was E = 34.7 V / cm.

9, V1 is a voltage value between the electrodes 6a and 12a2 in FIG. 8, V2 is a voltage value between the electrodes 12a2 and 12b2 in FIG. 8, and V3 is a voltage value between the electrodes 12b2 and 6b in FIG. means. V _film means the voltage between the electrodes 6a and 6b in FIG. The total current I _total means the current between the electrodes 6a and 6b in FIG. The rising point of V2 is indicated by an arrow.
However, in the experiment shown in FIG. 10 in which a higher voltage was applied, the thin film was damaged in the central part (V2 section) where quenching occurred at the end of each of the three parts. The specified value (average electric field of 43 V / cm or more) could not be achieved.
In FIG. 10, V1 is a voltage value between the electrodes 6a and 12a2 in FIG. 8, V2 is a voltage value between the electrodes 12a2 and 12b2 in FIG. 8, and V3 is a voltage value between the electrodes 12b2 and 6b in FIG. means. V _film means the voltage between the electrodes 6a and 6b in FIG. The total current I _total means the current between the electrodes 6a and 6b in FIG. The rising point of V2 is indicated by an arrow.
A similar current limiting test was performed on a plurality of current limiting element modules shown in FIG. 8 manufactured using superconducting thin films having the same size but different critical current and homogeneity. In the applied voltage test, it was found that the thin film breakage occurred at the last quenching part, and as a result, the allowable electric field specification value (E> 43 V / cm) for the partial element could not be achieved with the configuration of FIG. It was.

In the current limiting test of the current limiting element module configured as shown in FIG. 8, the thin film was damaged at the portion where the quenching occurred at the end. One reason for this is that, as can be seen from FIGS. 9 and 10, the energization current when the last quench occurs is larger than that during the first quench. The inventors of the present invention have other reasons such as the current flowing through the thin film almost linearly in the longitudinal direction of the thin film when the first quench occurs due to steady energization or when the current suddenly increases. At the time of the last quench, the current flowing into the thin film through the copper lead / intermediate electrode from the external resistor connected to the previously quenched partial thin film is linear in the longitudinal direction due to uneven connection resistance. (See FIG. 11).
For example, when the current path is not linear but bent at a right angle like the corner of an L-shaped thin film, it is stated that the thin film at the corner is easily damaged by the sudden increase in electric field during current limiting. (See Non-Patent Document 8). The inventors of the present invention have also conducted a current limiting test on a device in which a small notch is made in a rectangular thin film to reduce the critical current slightly, and if there is no notch, the thin film should not be damaged. When a voltage of 5 is applied, the thin film was damaged just outside the notch. From these experimental facts, it can be seen that the current path being bent rather than linear is a major factor that exacerbates the problem of hot spots.

  An object of the present invention is to provide a superconducting current limiting element that prevents hot spots from occurring in a long superconducting current limiting element in which an external resistor is connected to an intermediate electrode in the middle of a thin film. .

In the current limiting element module having a long thin film connecting an external resistor to the intermediate electrode in the middle of the thin film in FIG. 8, the quenched thin film is formed immediately after the first or second quench. Current flows into the thin film from the connected external resistor via the copper lead and intermediate electrode, but it is an experiment that the current does not flow linearly in the longitudinal direction due to uneven connection resistance. Inferred from the results.
In FIG. 11, when the quench 13 is generated in the region 4a1 of the high-temperature superconducting thin film with the gold-silver alloy layer, the current path 14 is formed in a biased manner as indicated by an arrow.
Therefore, in the same way as the parallel connection at both end electrodes of the thin film, the connection resistance becomes uniform and the second and third quenches occur in the intermediate electrode if the superconducting parallel connection is made using a metal base superconducting tape and solder. It was found that the current path can be made linear in the longitudinal direction of the thin film (see FIG. 12).
In the example of the present invention shown in FIG. 12, when the quench 13a is generated in the region 4a1 of the high-temperature superconducting thin film with the gold-silver alloy layer, the current paths 14a are formed in parallel as shown by the arrows.

In order to achieve the above object, the present invention takes the following aspects as basic forms for carrying out the invention.
(1) As a method of connecting two superconducting thin films in parallel, superconducting connection is performed not only at both ends but also at an intermediate electrode so as to have the element configuration of FIG.
Specifically, the current limiting element proposed in the present invention is a method in which pure metal is vapor-deposited on both ends and an intermediate portion of a superconducting thin film with a shunt protective film to form electrode portions, and a metal base material is formed on these electrode portions via solder. By connecting the superconducting tape, superconducting connection is made not only at the electrodes at both ends but also at the intermediate electrode, and an internal series connection type superconducting limit that connects an external shunt resistor to each partial thin film between the electrodes A flow element is used (see FIG. 1). In the superconducting current limiting element, capacitors can be connected in parallel as protection during current limiting.
(2) FIG. 1 is an example in which two thin films are connected in parallel, but even when only one thin film as shown in FIG. 2 is used, when connecting each electrode to an external shunt resistor, It can also be set as the structure which connects a metal base material superconducting tape to an electrode part via solder.
(3) In particular, the superconducting tape can be a tape made of a bismuth-based superconducting oxide using a sheath material made of silver or a silver alloy.
(4) The example of the high-temperature superconducting thin film current limiting element provided with the gold-silver alloy layer as the shunt protection layer has been described so far, but the present invention is not limited thereto, and the deposited film made of an alloy other than pure metal or gold-silver alloy It is also possible to use a high-temperature superconducting thin film having a shunt protective layer.

As a method of connecting two thin films in parallel, superconducting connection is performed not only at the electrodes at both ends but also at all electrodes including the intermediate electrode so as to have the element configuration of FIG.
The current limiting element proposed in the present invention forms electrode parts by vapor-depositing pure metal on both ends and the middle part of a superconducting thin film with a shunt protection film, and a metal substrate superconducting tape is connected to these electrode parts via solder. In this way, superconducting connections are made not only at the electrodes at both ends but also at intermediate electrodes, and an internal series connection type superconducting limit that connects an external shunt resistor to each thin film corresponding to the region between the electrodes. Current element (see FIG. 1). In the superconducting current limiting element, capacitors can be connected in parallel as protection during current limiting.
Thus, pure metal is vapor-deposited on both ends and middle portion of the superconducting thin film with a shunt protective film to form electrode portions, and the metal base superconducting tape is connected to these electrode portions via solder, thereby providing electrodes on both ends. In addition, by producing an internal series connection type current limiting element that performs superconducting parallel connection not only in an intermediate electrode, a series current limiting element having an allowable electric field equivalent to that of a partial element can be produced.
FIG. 1 shows an example in which two thin films are connected in parallel. However, even when only one thin film as shown in FIG. 2 is used, the electrodes are connected to each electrode and an external shunt resistor. It can also be set as the structure which connects a metal-base superconducting tape via solder | pewter. In this way, the connection resistance with the current lead can be reduced and made uniform, the current path has the effect of being linear, and the current limiting characteristics can be improved.
In particular, a tape made of a bismuth-based superconducting oxide using a sheath material made of silver or a silver alloy can also be used. In this case, since solder can be easily welded, the metal base superconducting tape used in the current limiting element proposed in this patent can be made preferable.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of the internal series connection type superconducting thin film current limiting element which is Example 1 of this invention. It is a block diagram of an internal series connection type superconducting thin film current limiting element having one superconducting thin film of the present invention. It is D1-D2 sectional drawing of FIG. It is a current limiting test result of the superconducting thin film current limiting element of the internal series connection type proposed in this patent using two superconducting thin films of 2.7 cm width and 20 cm length. It is a principal part enlarged view of the short time immediately after generation | occurrence | production of quenching in FIG. This is an internal series connection type superconducting thin film current limiting element proposed in this patent, using a circular superconducting thin film. It is a block diagram of the superconducting thin film current limiting element which used one superconducting thin film. It is a conceptual diagram of the internal series connection type superconducting thin film current limiting element proposed in Non-Patent Document 7. It is a current-limiting test result of the internal series connection type superconducting thin film current limiting element proposed in Non-Patent Document 7 using two superconducting thin films of 2.7 cm width and 20 cm length. 10 shows a current limiting test result when a voltage slightly higher than that in FIG. 9 is applied. It is explanatory drawing at the time of quench generation | occurrence | production in the case of FIG. It is explanatory drawing at the time of quench generation | occurrence | production in the case of FIG.

In order to achieve the above object, the present invention takes the following aspects as basic forms for carrying out the invention.
(1) As a method of connecting two thin films in parallel, superconducting connection is performed in all electrodes including not only electrodes at both ends but also intermediate electrodes so as to have the element configuration of FIG.
In the current limiting element proposed in the present invention, pure metal is vapor-deposited on both ends and an intermediate portion of a superconducting thin film with a shunt protective film, and electrodes are formed by connecting a metal substrate superconducting tape to these electrodes via solder. Is an internal series connection type superconducting current limiting element in which an external shunt resistor is connected to each partial thin film between the electrodes as shown in FIG. 1). In the superconducting current limiting element, capacitors can be connected in parallel as protection during current limiting.
(2) FIG. 1 is an example in which two thin films are connected in parallel, but even when only one thin film as shown in FIG. 2 is used, when connecting each electrode to an external shunt resistor, It can also be set as the structure which connects a metal base material superconducting tape to an electrode part via solder.
(3) In particular, the superconducting tape may be a tape produced by using a sheath material made of bismuth-based superconducting oxide made of silver or a silver alloy.
(4) The example of the high-temperature superconducting thin film current limiting element provided with the gold-silver alloy layer as the shunt protection layer has been described so far, but the present invention is not limited thereto, and the deposited film made of an alloy other than pure metal or gold-silver alloy It is also possible to use a high-temperature superconducting thin film having a shunt protective layer.

Embodiment 1 of the present invention will be described in detail with reference to the drawings.
In order to demonstrate the current limiting element disclosed in the present invention, two thin films having characteristics similar to those of the two thin films obtained in FIGS. 9 and 10 are used, and solder is used not only at both ends but also at an intermediate electrode. The element module of the structure of FIG. 1 which produced the superconducting parallel connection of the two thin films by connecting the metal substrate superconducting tape through the electrode was manufactured.
A specific example is as follows: a 2.7 cm wide and 20 cm long YBCO thin film 22 a (see FIG. 3: film thickness 160 nm, expected direct current critical current ≧ 160 A _peak ), and the same YBCO thin film 22b of a size (not shown: film thickness 160 nm, expected direct current critical current ≧ 155 A _peak ) and alloy films 21 a and 21 b having a composition of approximately gold-23 wt% silver are formed to a film thickness of approximately 60 nm. After sputter deposition, silver is deposited at a width of 7-8 mm at both ends and the center to form an electrode (effective length of each of the three divided thin films is 5.7 cm). In addition, two thin films were connected in parallel to each other by connecting a metal substrate superconducting tape via solder. In order to prevent hot spots, an external shunt resistor (0.35 ohm) produced by non-inductive winding of an alloy wire and a 120 microfarad capacitor (not shown) corresponding to each region divided into three by electrodes. Connected to the partial thin film in parallel. The metal base superconducting tape used is a tape made of a bismuth-based superconducting oxide using a sheath material made of silver.

FIG. 1 is a configuration diagram of an internal series connection type superconducting thin film current limiting element, which is Embodiment 1 of the present invention.
FIG. 2 is a block diagram of an internal series connection type superconducting thin film current limiting element having a single superconducting thin film composed of the upper half of FIG.
FIG. 3A shows a cross-sectional view taken along D1-D2 in FIG. FIG. 3B shows a cross-sectional view of another embodiment.
The internal serial connection type superconducting thin film current limiting element 1 shown in FIG. 1 includes a superconducting thin film juxtaposed body 2 composed of a pair of superconducting thin films 2a and 2b, and external resistors 3a and 3b connected in parallel therewith. Have
However, without being limited to the embodiment of FIG. 1, the superconducting thin film juxtaposed body 2 of the present invention may be composed of a single superconducting thin film 2a as shown in FIG.
The same components are denoted by the same reference numerals and description thereof is omitted.
In the superconducting thin film 2a, a high-temperature superconducting thin film 22a is provided on a sapphire substrate 7a via a buffer layer 23a such as ceria, and a gold-silver alloy shunt layer 21a is provided on the high-temperature superconducting thin film 22a.
On the gold-silver alloy shunt layer, electrodes are provided at predetermined intervals in the length direction. The number of electrodes is provided in relation to the hot spot.
End electrodes 5a1 and 5d1 are provided at both ends in the length direction of the gold-silver alloy shunt layer, and a required number of intermediate electrodes 5b1 and 5c1 are provided inside both ends. Superconducting tapes 9a, 9b, 9c and 9d are soldered on these electrodes.
The superconducting thin film 2b is provided in the same manner as the superconducting thin film 2a.
The superconducting tapes 9a, 9b, 9c and 9d are connected between corresponding electrodes of the superconducting thin film 2a and the superconducting thin film 2b, that is, the electrodes 5a1 and 5a2 are connected by the superconducting tape 9a, and the electrodes 5b1 and 5b2 are connected by the superconducting tape 9b. The electrodes 5c1 and 5c2 are connected by the superconducting tape 9c, and the electrodes 5d1 and 5d2 are connected by the superconducting tape 9d.

The gold-silver alloy shunt layers 21a and 21b are formed as vapor deposition films made of an alloy of gold and silver.
Superconducting tapes 9a, 9b, 9c and 9d are formed as metal-based superconducting tapes, and are produced using a bismuth-based superconducting oxide as a sheath material made of silver or a silver alloy.
In the gold-silver alloy layer on the high-temperature superconducting thin films 22a and 22b, regions 4a1, 4b1, and 4c1 are defined by electrodes 5a1 and 5b1, 5b1 and 5c1, 5c1 and 5d1, respectively, and electrodes 5a2 and 5b2, 5b2 and 5c2, 5c2 and Regions 4a2, 4b2, and 4c2 are defined by 5d2. The number of electrodes is determined in relation to the hot spot.
The superconducting tape 9a is connected to the copper electrode 6a by an appropriate electrical wiring means such as a wire, and the superconducting tape 9d is connected to the copper electrode 6b by an appropriate electrical wiring means such as a wire.

Copper electrodes 6a and 6b constitute external connection electrodes.
The resistor 3a connects the non-inductive winding shunt resistors 11a1, 11b1, and 11c1 so as to be a continuous resistance by the copper electrodes 12a1 and 12b1.
Similarly, the resistor 3b connects the non-inductive winding shunt resistors 11a2, 11b2, and 11c2 so as to be a continuous resistance by the copper electrodes 12a2 and 12b2.
One end of the winding of the non-inductive winding shunt resistor 11a1, 11a2 is connected to the external connection electrode 6a, and the other end of the winding of the non-inductive winding shunt resistor 11a1, 11a2 is connected to the copper electrode 12a1, 12a2, respectively. The copper electrodes 12a1 and 12a are connected to the corresponding superconducting tapes 9b.

In the same manner, one end of the winding of the non-inductive winding shunt resistors 11b1 and 11b2 is connected to the copper electrodes 12a1 and 12a2, and the other end of the winding of the non-inductive winding shunt resistors 11b1 and 11b2 is connected to the copper. The electrodes 12b1 and 12b2 are connected, and the copper electrodes 12b1 and 12b are connected to the corresponding superconducting tapes 9c, respectively.
In the same manner, one end of the winding of the non-inductive winding shunt resistor 11c1, 11c2 is connected to the superconducting tape 9c, and the other end of the winding of the non-inductive winding shunt resistor 11c1, 11c2 is for external connection. Connect to electrode 6b.
By connecting in this way, the resistors 3 a and 3 b are connected in parallel to the superconducting thin film juxtaposed body 2.

FIG. 2 shows an embodiment constituted by one superconducting thin film 2a in the upper half of the construction of FIG.
In FIG. 2, the same reference numerals as those in FIG. 1 use the description of FIG.
FIG. 3A shows a cross-sectional view taken along D1-D2 in FIG. FIG. 3B shows a cross-sectional view of another embodiment.
In FIG. 3A, in the superconducting thin film 2a, a high-temperature superconducting thin film 22a is provided on a sapphire substrate 7a via a buffer layer 23a such as ceria, and a gold-silver alloy shunt layer 21a is provided on the high-temperature superconducting thin film 22a.
An electrode (silver or gold) 5a1 is provided on the gold-silver alloy shunt layer 21a. Superconducting tape 9a is soldered to a predetermined location on electrode (silver or gold) 5a1.
The superconducting thin film 2b has the same configuration as the superconducting thin film 2a, although not shown.
FIG. 3B shows another example in which the electrode 5a1 in the example of FIG. 3A is provided directly on the high-temperature superconducting thin film 22a without using the gold-silver alloy shunt layer 21a.

FIG. 4 is a diagram showing a current limiting test result when the current limiting element of FIG. 1 is used. As shown in the figure, the total current flowing through the current limiting element (I _total ) increases rapidly at an increasing rate (gradient of time variation of the total current) of 2.26 kA _rms without the current limiting element. Along with the quench, the rate of increase in current became moderate from the middle, and the thin film voltage (V _film ) at both ends of the thin _film increased rapidly. In a state where an AC voltage is applied to _V film _{= 778V peak} across the high-temperature superconducting thin film, the thin film became possible to energization of 5 cycles (100 msec) without burning.
At this time, the average electric field at an element effective length of 17 cm was E = 45.8 V / cm.
4, V1 is a voltage value between the electrodes 6a and 12a2 in FIG. 1, V2 is a voltage value between the electrodes 12a2 and 12b2 in FIG. 1, and V3 is a voltage value between the electrodes 12b2 and 6b in FIG. means. V _film means a voltage between the electrodes 6a and 6b in FIG. The total current I _total means the current between the electrodes 6a and 6b in FIG.
FIG. 5 is an enlarged view of a main part of a short time graph immediately after the occurrence of quenching in FIG.
FIG. 5 is an enlarged view of the characteristics of FIG. 4 in a time width of 130 ms to 152 ms. It can be seen from FIG. 5 that quenching is finally generated in the V2 section.
V1 in FIG. 5 is a voltage value between the electrodes 6a and 12a2 in FIG. 1, V2 is a voltage value between the electrodes 12a2 and 12b2 in FIG. 1, and V3 is a voltage value between the electrodes 12b2 and 6b in FIG. To do. V _film means a voltage between the electrodes 6a and 6b in FIG. The total current I _total means the current between the electrodes 6a and 6b in FIG.
From this result, it was proved that according to the superconducting thin film current limiting element module of this configuration, an internal series connection type superconducting thin film current limiting element having a high allowable electric field of 45 V _peak / cm or more can be manufactured. The rated voltage of this module is 500 Vrms, the rated current is 200 Arms, and the 8 series is 4 kVrms and 200 Arms, constituting one phase of a 3φ6.6 kV / 200 A current limiter.

FIG. 6 is a configuration diagram of Embodiment 2 of the present invention.
FIG. 6 shows a 5 inch diameter YBCO thin film current limiting element module.
In FIG. 6, a high-temperature superconducting thin film 4f with a gold-silver alloy layer having a substantially uniform width is provided in a spiral shape on a 5-inch disk-like sapphire substrate 7c via a buffer layer. The intermediate electrodes 5h, 5i, and 5j are provided with appropriate intervals in the length direction (spiral direction). The number of intermediate electrodes is determined in relation to the hot spot.
End electrodes 5k and 5g are provided at both ends of the high-temperature superconducting thin film 4f with a gold-silver alloy layer, and intermediate electrodes 5h, 5i and 5j are provided at both ends.
Superconducting tapes 9g, 9h, 9i, 9j, and 9k are soldered on the electrodes 5k, 5g, 5h, 5i, and 5j.
The example of FIG. 6 is a module with a rated voltage of 1.27 kVrms and a rated current of 100 Arms.

In the case of the example, for example, non-inductive winding parallel resistors 11a3, 11b3, 11c3 and 113d are connected every approximately 11 cm of the superconducting line of the high-temperature superconducting thin film 4f with a gold-silver alloy layer.
For example, in order to set the current limiting current flowing between the external connection electrodes 5k and 5g to 200 Arms, one parallel resistance value is slightly over 1.6Ω.
The external resistor is connected to the superconducting tape provided on the high-temperature superconducting thin film 4f with the gold-silver alloy layer so as to divide resistance.

6 is an example in which a YBCO thin film is provided on a 5-inch diameter sapphire substrate. The YBCO large-area thin film is easier to make uniform in film quality than the circular one with a rectangular shape.
A large area thin film of YBCO can be patterned by wet etching.
A gold-silver alloy thin film is deposited on the YBCO superconducting thin film, electrodes 5g, 5h, 5i, 5j, and 5k made of silver or a gold layer are deposited on the gold-silver alloy thin film, and a superconducting tape for each electrode is soldered. Provide.
The 5 inch diameter YBCO thin film element current limiting module shown in FIG. 6 is disposed on a 9 inch × 9 inch FRP plate, for example.
The high-temperature superconducting thin film 4f with a substantially uniform width of the gold-silver alloy layer has a width perpendicular to the spiral direction of, for example, about 1.6 cm, and a length along the spiral of, for example, about 45 cm.
Rated current of the thin film element current limiting module 1 element in FIG. 6, for example, in 90 × 1.6 / √2, about _{102A rms,} the allowable voltage at _0.04 × _45kV peak ₌ 1.8kV _peak, About 1.27 kV _rms can be expected.
The maximum voltage between YBCO large-area thin film patterns is about 1.2 kV _peak , and if the distance between the patterns is set to 8 mm, the dielectric breakdown voltage is almost satisfied. is necessary).
(Other examples)
The high-temperature superconducting thin film with the gold-silver alloy shunt layer of the present invention has an arbitrary shape, for example, a three-dimensional spiral shape, a spherical shape, etc., as long as it has a length that allows resistance division with a substantially uniform width. Can be taken.

1 Superconducting thin film current limiting element 2a, 2b Superconducting thin film 3a, 3b External resistor 4a1, 4b1, 4c1, 4a2, 4b2, 4c2 Region 5a1, 5b1, 5c1, 5d1, 5a2, 5b2, 5c2, 5d2 Electrodes 6a, 6b External connection Copper electrodes 7a, 7b Sapphire substrate (alumina single crystal substrate)
9a, 9b, 9c, 9d Superconducting tape 11a1, 11b1, 11c1, 11a2, 11b2, 11c2 Non-inductive shunt resistance 12a1, 12b1, 12a2, 12b2 Copper electrode 21a Gold-silver alloy shunt layer 22a High-temperature superconducting thin film 23a Buffer layer 24a such as ceria Solder

Claims (6)

A superconducting thin film having electrodes made of a plurality of gold or silver layers spaced apart in the longitudinal direction, and a resistor connected between the electrodes via a superconducting tape,
The superconducting thin film is provided with a high-temperature superconducting thin film on a sapphire substrate via a buffer layer, and a gold-silver alloy shunt layer is provided on the high-temperature superconducting thin film,
A silver or gold layer is provided on the gold-silver alloy shunt layer as an electrode for dividing,
A superconducting thin film current limiting element, wherein a superconducting tape is soldered on the electrode layer. 2. The superconducting thin film current limiting element according to claim 1, wherein the electrode layer is provided directly on the high temperature superconducting thin film without using a gold-silver alloy shunt layer. A superconducting thin film juxtaposed body is formed by juxtaposing the superconducting thin films,
2. A superconducting thin film current limiting element according to claim 1, wherein the superconducting thin film has a common superconducting tape. The superconducting tape is formed as a metal-based superconducting tape, and is a bismuth-based superconducting oxide produced by using a sheath material made of silver or a silver alloy. The superconducting thin film current limiting element described in the item. The superconducting thin film current limiting element according to any one of claims 1 to 3, wherein the gold-silver alloy layer formed on the superconducting thin film is a vapor deposition film made of a pure metal or an alloy. 6. The superconducting thin film current limiting element according to claim 1, wherein a capacitor is connected in parallel to the electrode.