JP3977884B2 - Current limiting element, current limiter using oxide superconductor, and manufacturing method thereof - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は酸化物超電導体を用いた限流素子、限流器およびその製造方法に関するものである。
【０００２】
【従来の技術】
電力回路で短絡事故が発生すると、極めて大きな短絡電流が流れる。短絡電流は遮断機によって遮断されるが、短絡電流によって強い電磁力と多量のジュール熱が発生し、電力機器や電路が大きな機械的・熱的損傷を受ける。このような事故発生時の短絡電流を抑えて、遮断機の責務を軽減する事故時限流器（限流器）の開発が望まれている。また、このような限流器は各種送配電系統の安定化に帰する効果は極めて大きく限流器の早期実現が期待されている。
【０００３】
限流器には多くの方式のものが提案されているが、現状では実用性の高いものは少ない。比較的広く用いられているものに限流リアクトル、永久ヒューズ、限流電線、アーク式限流器があるが、負荷電流通電時の電気抵抗が高く発熱が多いあるいは、応答が遅いため限流性能が低いという問題点がある。
【０００４】
限流器に要求される事項として、正常負荷通電時には電気抵抗が低く発熱が少ないこと、短絡事故時には応答が早くかつ電気抵抗が高くなることなどが挙げられる。この点で超電導体を用いた限流器は理想的なものと考えられる。超電導限流器には超電導・常伝導転移型、リアクトル型、整流型、コイル型等が提案されている。この中で超電導・常伝導転移型限流器は超電導体の超電導・常伝導転移を最も直接的に利用したものである。負荷電流通電時には、超電導体には臨界電流以下の電流しか流れていないので、超電導体の抵抗は極めて小さい。しかし、短絡事故が発生した場合には、超電導体には臨界電流以上の電流が流れ、超電導体が超電導状態から常伝導状態に転移して電気抵抗が発生する。この抵抗により短絡電流が限流される。この超電導・常伝導転移型限流器は他の方式の超電導限流器に比べて、構造が簡単で小型であるという特徴を持つ。
【０００５】
上記超電導限流器には、金属系超電導体と酸化物系超電導体を用いたものがある。金属系超電導体は、常伝導状態での電気抵抗が低く、装置全体が大型化してしまうことや液体ヘリウム温度近傍で使用する必要があるため運転コストが大きくなり、さらには断熱の点からも装置が大型化してしまうという問題があった。そのため、常伝導状態での電気抵抗が高く、かつ、コストの安い液体窒素で超電導状態を維持できる酸化物超電導体を用いた限流器の開発が期待されている。
【０００６】
【発明が解決しようとする課題】
酸化物超電導材料を用いた超電導限流器には基板に薄膜の限流素子を形成した例（特開平2-281766）やバルクの焼結体を用いた例（平成７年電気学会電力・エネルギー部門大会予稿集p697）などが報告されている。薄膜を用いたものは臨界電流密度は高いものの断面積が小さいため実際の低圧系統で用いられるレベルの電流値までには達していない。一方焼結体は断面積は大きいが臨界電流密度が小さいため、同様のレベルにある。
【０００７】
また酸化物超電導体は比較的高温で使用されるため、４．２Ｋ近傍で用いられる金属系超電導線材にくらべ使用温度域での比熱が大きくなる。また熱伝導率は小さくなるため常伝導転移した部分が伝搬しにくく、局所的に高温になり溶断しやすい傾向にある。またこの溶断しやすい性質は酸化物超電導体が金属系線材に比較して、細線化および均一化しにくいことにも起因する。このように本発明はバルク超電導体を用いた溶断に対しての信頼性が高く、かつ高速でクエンチが均一に伝搬する限流素子、限流器およびその製造方法を提供することを目的とする。
【０００８】
【課題を解決するための手段】
（１） RE系（REはY、Pr、Nd、Sm、Eu、Gd、Dy、Ho、Er、Tm、Yb、Luおよびこれらの組み合わせ）酸化物超電導体を用いた限流素子において、REBa2Cu3O7-X中にRE2BaCuO5が微細分散した超電導バルク体を用いた超電導−常伝導転移型限流素子であって、前記超電導バルク体の少なくとも一部がダイヤモンド、サファイヤ、窒化アルミ、銅、銀又はアルミから選ばれる一種以上でコーティングされ、かつ、２個以上のシャント抵抗がある間隔で当該超電導バルク体と並列に電気的に接続されており、さらに、当該シャント抵抗がコイル状に巻かれており、これにより発生する磁場が周辺の前記超電導バルク体に印加されることを特徴とする限流素子。
（２） （１）に記載の限流素子において、さらに少なくとも前記超電導バルク体の一部が銀でコーティングされていることを特徴とする限流素子。
（３） （１）に記載の限流素子において、銀の上に銀よりも高い比抵抗を有する金属又は合金が銀の膜厚以上にコーティングされていることを特徴とする限流素子。
（４） （１）〜（３）のいずれか１つに記載の限流素子が電気的に直列または並列に接続されていることを特徴とする限流器。
（５） REBa2Cu3O7-X（REはY、Pr、Nd、Sm、Eu、Gd、Dy、Ho、Er、Tm、Yb、Luおよびこれらの組み合わせ）中にRE2BaCuO5が微細分散した酸化物超電導材料の少なくとも一部をダイヤモンド、サファイヤ、窒化アルミ、銅、銀又はアルミから選ばれる一種以上でコーティングしてから、発生する磁場が周辺の超電導バルク体に印加されるようにコイル状に巻かれた複数のシャント抵抗を電気的に接続することを特徴とする限流器の製造方法。
前述のように、酸化物超電導体を用いた限流器を実現するには、高い臨界電流密度を有するバルク材が必要となる。このような材料にはＱＭＧと呼ばれる溶融法で作製された単結晶状バルク材料がある〔Physica C 235-240（1994）209-212〕。そこでまず、酸化物超電導体を転移型限流器に用いるにはREBa2Cu3O7-X中にRE2BaCuO5が微細分散した高臨界電流密度を有する超電導バルク体を用いることが重要である。
【０００９】
次に、常伝導転移時に溶断を防ぐ方法として超電導体を銀でコーティングし常伝導転移した部分の超電導体と電気的に並列の回路を設けることで溶断を回避することが重要である。このときのコーティングの厚さおよび面積は超伝導体の断面積との相対比較で、溶断を十分抑制できる範囲でかつ抵抗値を上げるために最小限に留めることが望ましい。膜厚は、超電導体のＪｃ特性および断面積によって変化するが、５ミクロン以上１００ミクロン以下が望ましい。
【００１０】
また、超電導体の表面を高い熱電導率を有する物質でコーティングすることによって、熱の拡散を大きくすることで温度上昇を抑制し溶断を回避することができる。これらのコーティングは超電導材の防湿等の保護膜の機能も果たす。高い熱電導率を有する物質としてはダイヤモンド、サファイヤ、窒化アルミのセラミックスや銅、銀、アルミの金属が挙げられる。電気抵抗を大きくする観点からはセラミックスコーティングが望ましい。
【００１１】
さらに、シャント抵抗をある間隔で超電導体と並列に電気的に接続されていることで銀とは別に常伝導転移した超電導部のバイパス回路を形成し溶断を回避することも重要である。また上記溶断を回避する方法を組み合わせ、かつこのような限流素子を電気的に直列および並列に接続しても有用であることはいうに及ばない。
【００１２】
【作用】
前述のように十分高Ｊｃを有するバルク材料を用いることは、所定の定格電流を超電導状態で抵抗無しに（交流の場合交流損失があるため、有限の抵抗値を有する）流すために必要である。また、限流素子を構成する超電導体の電流路断面を小さくすることができ、常伝導転移時の超電導体の単位長さ当たり抵抗値を大きくすることができるため、長さを短くすることができ、素子の小型化が容易になる。
【００１３】
一方、高Ｊｃを有する材料を用い線径を小さくした場合、超電導体のわずかな不均一が素子のクエンチ特性に大きく影響することになる。限流素子の超電導体が均一温度に冷却されていたとすると、大きな事故電流が流れた場合、有効断面積の小さい部分からクエンチの芽が発生しそれが伝搬して素子全体が常伝導転移し、限流動作をすることになる。不均一が大きいとクエンチの伝搬は遅くなり、さらには局部的に加熱され、ひいては溶断を招くことが多くなる。
【００１４】
このような溶断を回避するには、接触抵抗の小さな電極をつくり、かつ電流のバイパス回路を常伝導転移した超電導体と並列に形成することが有効である。このようなバイパスによって、異常電流の多くはクエンチした部分を迂回してバイパスを通るために、溶断を回避することか可能となる。Agがコーティングされた部分は適当な熱処理によって接触抵抗が１０-8ｍΩオーダーの良好な電極となる、また銀のコーティング自体バイパス回路となり溶断を抑制する働きを有する。
【００１５】
しかしながら、通電容量が大きい場合、銀のコーティングはバイパス回路として比較的断面積が小さくなってしまうため溶断を防ぐには不十分になることがある。この場合、銀のコーティングは主に電極として用い、超電導体と並列にバルクの抵抗体を接続することが望ましい。さらにこのとき抵抗体は超電導体と両端間で接合するのではなく、ある間隔ごとに電極を設けて電気的に接続することが望ましい。これは、図１、図２のようにある箇所でクエンチが起きた場合、図２では図１より小さな抵抗で結ばれたバイパス回路を構成することができるため、より効果的にクエンチ部を迂回させることができる。また、電流が迂回するときには電極部の接触抵抗により発熱が生じ、クエンチをより早く伝搬させる働きもする。さらにこのように超電導体と接触していないバイパス回路を構成することで、超電導体からの発熱を低くし、事故電流が十分小さくなった時（事故の回復時）の超電導状態への回復時間を短縮することが可能にできる。
【００１６】
さらにバイパス回路がコイル状になっているので、このコイルが発生する磁界によって超電導バルク体の臨界電流値は低下するため、クエンチが周辺の超電導バルク体におよび限流動作速度を高める働きをする。また複数の超電導バルク体同士が電気的に並列に接続され互いにバイパス回路を形成しているので、一つの超電導バルク体のクエンチにより電流分布が変化しクエンチが高速で伝搬することもある。この現象はクエンチした部分に電圧が集中するのを防ぎその結果溶断を抑制する働きがある。
【００１７】
また溶断を回避する方法としては、熱電導率の大きな物質をコーティング又は接触させることが有効である。このような物質はクエンチ部の熱を超電導体に沿って伝えることによって、溶断を防ぐとともにクエンチ速度を高める働きもある。
【００１８】
さらに図３のように抵抗値を高く保ちかつ溶断を効果的に防止する方法としては超電導体と接触する抵抗率の低い銀の膜厚を極力薄くし(0.1ミクロン以下、望ましくは0.02ミクロン以下)、銀の膜の上に銀よりも高い比抵抗を有する金属（金、ニッケル、錫、鉛、等）あるいは合金を銀の膜厚以上の厚さにコーティングすることが有効である。このような状況では、銀は主に酸化物超電導体との接触抵抗を低減するためにのみ用い、銀の上のコーティングを主にバイパス回路として用いる。
【００１９】
【実施例】
比較例
YBa2Cu3O7-x中にY2BaCuO5が微細分散した直径４６ｍｍ、高さ１５ｍｍの単結晶状の超電導バルク材料を図４の様に厚さ１ｍｍにスライスし、さらに切れ込み加工を行い電流路断面積が２ｍｍ2の超電導体を作製した。そののち銀ペーストを電極部のみに塗布し酸素気流中で一旦９００℃まで昇温し１０分保持した後、６００℃まで２時間で降温さらに室温まで２０時間かけて徐冷した。両端の電極部に半田により銅のリード線を接続した後、液体窒素中で冷却した。パルス電源を用いて図５の様な回路を作り限流器を通さない場合、最大１５００Ａの瞬時値の電流が流れるように回路を設定した。このような回路に限流器を接続してパルス通電したところ、電極から約１０ｍｍ離れたところで限流素子が溶断した。
【００２３】
このようにして作製した２つの超電導体を渦巻きの方向が一致するように重ね、厚さ０．４ｍｍの窒化アルミの絶縁体をスペーサーとしてはさみ、中心部の電極で二つの超電導体を接続した。また、両端の電極部に半田により２本の銅のリード線を接続した。さらにこの超電導体に20mmごとに抵抗体を接続した。これを液体窒素中で冷却し、500Aの臨界電流（Ic）を直流通電により確認した。またパルス電源を用いて図３の様な回路を作り限流器を通さない場合、最大1500Aの瞬時値の電流が流れるように回路を設定した。このような回路に限流器を接続してパルス通電したところ電流の最大値は900Aに限流されていることが分かった。またこの時限流素子の溶断は無かった。
【００２４】
実施例
図４の様な比較例と同様の形状を有するHo-Y系の超電導バルク材料を作製した。そののち銀ペーストを表面に塗布し酸素気流中で一旦９００℃まで昇温し１０分保持した後、６００℃まで２時間で降温さらに室温まで２０時間かけて徐冷した。このようにして作製した３つの超電導体を両端の電極部に半田により直列に接続し、さらに２本の銅のリード線を接続した。そしてこの超電導体に１５ｍｍごとに抵抗体でできた直径６ｍｍのコイルを接続し、隣接する超電導体に磁場が印加されるようにした。これを液体窒素中で冷却し、５００Ａの臨界電流（Ic）を直流通電により確認した。またパルス電源を用いて図５の様な回路を作り限流器を通さない場合、最大１５００Ａの瞬時値の電流が流れるように回路を設定した。このような回路に限流器を接続してパルス通電したところ電流の最大値は８５０Ａに限流されていることが分かった。またこの時限流素子の溶断は無かった。
【００２６】
【発明の効果】
本発明によれば、限流器の溶断を回避し、かつ迅速な限流動作を実現する限流器システムを提供することができ、その工業的効果は甚大である。
【図面の簡単な説明】
【図１】一つのバイパス回路を有する限流素子
【図２】複数のバイパス回路を有する限流素子
【図３】銀のコーティングの上に比抵抗の大きい金属をコーティングした限流器
【図４】ミアンダ構造を有する超電導導体
【図５】通電実験に用いた電気回路
【図６】 (a) 渦巻き状超電導導体、(b) 渦巻き状超電導導体の断面の様子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a current limiting device using an oxide superconductor, a current limiting device, and a method for manufacturing the current limiting device .
[0002]
[Prior art]
When a short circuit accident occurs in the power circuit, a very large short circuit current flows. The short-circuit current is interrupted by the circuit breaker, but the short-circuit current generates a strong electromagnetic force and a large amount of Joule heat, and the power equipment and the electric circuit are seriously damaged mechanically and thermally. It is desired to develop an accident time limiter (current limiter) that suppresses the short circuit current at the time of such an accident and reduces the duty of the circuit breaker. In addition, such a current limiter is extremely effective in stabilizing various power transmission and distribution systems, and is expected to be realized at an early stage.
[0003]
Many types of current limiters have been proposed, but at present there are few that are highly practical. Current-limiting reactors, permanent fuses, current-limiting wires, and arc-type current limiters are widely used, but current-limiting performance is high due to high electrical resistance when the load current is applied and high heat generation or slow response. There is a problem that is low.
[0004]
The requirements for the current limiter include a low electrical resistance when the normal load is energized and little heat generation, and a quick response and a high electrical resistance when a short circuit accident occurs. In this respect, a current limiter using a superconductor is considered ideal. For the superconducting fault current limiter, a superconducting / normal conducting transition type, a reactor type, a rectifying type, a coil type and the like have been proposed. Among them, the superconducting / normal conducting transition type fault current limiter is the most direct use of the superconducting / normal conducting transition of the superconductor. When a load current is applied, only a current below the critical current flows through the superconductor, so the resistance of the superconductor is extremely small. However, when a short-circuit accident occurs, a current exceeding the critical current flows through the superconductor, and the superconductor changes from the superconducting state to the normal conducting state, and an electric resistance is generated. This resistance limits the short circuit current. This superconducting / normal conducting transition type fault current limiter is characterized by its simple structure and small size compared to other types of superconducting current limiters.
[0005]
Some of the superconducting fault current limiters use metal superconductors and oxide superconductors. Metal-based superconductors have low electrical resistance in the normal conduction state, which increases the overall size of the equipment and requires operation near the liquid helium temperature. There has been a problem of increasing the size. Therefore, the development of a current limiter using an oxide superconductor capable of maintaining a superconducting state with liquid nitrogen having high electric resistance in a normal conducting state and low cost is expected.
[0006]
[Problems to be solved by the invention]
Examples of superconducting fault current limiters that use oxide superconducting materials include thin-film current-limiting elements formed on substrates (Japanese Patent Laid-Open No. 2-281766) and examples using bulk sintered bodies (1995 IEEJ Power and Energy Section conference proceedings, p. 697) have been reported. Those using thin films have a high critical current density but a small cross-sectional area, so that they do not reach the level of current used in an actual low-voltage system. On the other hand, the sintered body has a large cross-sectional area but a small critical current density, and therefore is at the same level.
[0007]
In addition, since the oxide superconductor is used at a relatively high temperature, the specific heat in the operating temperature range is larger than that of the metal-based superconducting wire used in the vicinity of 4.2K. Further, since the thermal conductivity is small, the portion where the normal conduction transition has occurred is difficult to propagate, and the temperature tends to be locally high, so that it tends to melt. Further, this property of being easily melted is caused by the fact that oxide superconductors are less likely to be thinned and made uniform than metal-based wires. Thus, the present invention aims to provide a current limiting device, current limiter and a manufacturing method reliable and the quenching at high speed to uniformly propagate against blown using a bulk superconductor .
[0008]
[Means for Solving the Problems]
(1) RE-based (RE is Y, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu and combinations thereof) In the current limiting element using an oxide superconductor, REBa 2 A superconducting-normal conduction transition type current limiting device using a superconducting bulk body in which RE 2 BaCuO 5 is finely dispersed in Cu 3 O 7-X , wherein at least a part of the superconducting bulk body is diamond, sapphire, aluminum nitride Coated with at least one selected from copper, silver or aluminum, and two or more shunt resistors are electrically connected in parallel with the superconducting bulk body at a certain interval , and the shunt resistor is coiled limiting device wound and, the magnetic field generated by this, characterized in Rukoto is applied to the superconducting bulk body near to.
(2) The current limiting element according to (1), wherein at least a part of the superconducting bulk body is coated with silver.
( 3 ) The current limiting element according to (1), wherein a metal or alloy having a specific resistance higher than that of silver is coated on silver so as to have a film thickness greater than that of silver.
( 4 ) A current limiter, wherein the current limiting element according to any one of (1) to ( 3 ) is electrically connected in series or in parallel.
( 5 ) REBa 2 Cu 3 O 7-X (RE is fine in RE 2 BaCuO 5 in Y, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu and combinations thereof) Coil at least a part of the dispersed oxide superconducting material with at least one selected from diamond, sapphire, aluminum nitride, copper, silver or aluminum, and then the generated magnetic field is applied to the surrounding superconducting bulk body A method of manufacturing a current limiter, comprising electrically connecting a plurality of shunt resistors wound in a shape .
As described above, a bulk material having a high critical current density is required to realize a current limiting device using an oxide superconductor. One such material is a single crystal bulk material produced by a melting method called QMG [Physica C 235-240 (1994) 209-212]. Therefore, it is important to use a superconducting bulk material having a high critical current density in which RE 2 BaCuO 5 is finely dispersed in REBa 2 Cu 3 O 7-X in order to use an oxide superconductor for a transition type current limiter. is there.
[0009]
Next, as a method for preventing fusing at the normal conduction transition, it is important to avoid fusing by coating the superconductor with silver and providing a circuit in parallel with the superconducting portion of the normal conduction transition. It is desirable that the thickness and area of the coating at this time be kept to a minimum in order to increase the resistance value within a range in which fusing can be sufficiently suppressed by relative comparison with the cross-sectional area of the superconductor. The film thickness varies depending on the Jc characteristics and the cross-sectional area of the superconductor, but is preferably 5 microns to 100 microns.
[0010]
Further, by coating the surface of the superconductor with a material having a high thermal conductivity, the temperature rise can be suppressed and fusing can be avoided by increasing the diffusion of heat. These coatings also function as protective films such as moisture-proofing of the superconducting material. As the substance having a high thermal conductivity diamond, sapphire, nitride Aluminum ceramics, copper, silver, Aluminum metal can be mentioned up. Ceramic coating is desirable from the viewpoint of increasing electrical resistance.
[0011]
Furthermore, it is also important to avoid a fusing by forming a bypass circuit of the superconducting part that is normally conducted in addition to silver by electrically connecting the shunt resistor in parallel with the superconductor at a certain interval. Further, it goes without saying that it is useful to combine the methods for avoiding the above-mentioned fusing and electrically connect such current limiting elements in series and in parallel.
[0012]
[Action]
As described above, it is necessary to use a bulk material having a sufficiently high Jc in order to allow a predetermined rated current to flow without resistance in a superconducting state (since there is an AC loss in the case of AC, it has a finite resistance value). . In addition, the current path cross section of the superconductor constituting the current limiting element can be reduced, and the resistance value per unit length of the superconductor at the normal conduction transition can be increased, so that the length can be shortened. This makes it easy to reduce the size of the device.
[0013]
On the other hand, the reduction in use of wire diameter of materials having a high Jc, so that slight uneven super conductors greatly affects the quenching characteristics of the device. When super conductors of current limiting device has been cooled to a uniform temperature, large if the fault current flows, a small portion buds quench occurs from then it propagates the entire device is normal conducting transition in the effective area The current limiting operation will be performed. When the non-uniformity is large, the propagation of the quench is slow, and further, it is locally heated, and as a result, often causes fusing.
[0014]
To avoid such blown, creating a small electrode contact resistance, and it is effective to form a bypass circuit of the current in parallel with the super-conductors were normal-conducting transition. By such a bypass, it is possible to avoid fusing because many of the abnormal currents bypass the quenched part and pass through the bypass. The portion coated with Ag becomes a good electrode with a contact resistance of the order of 10 −8 mΩ by an appropriate heat treatment, and the silver coating itself functions as a bypass circuit and functions to suppress fusing.
[0015]
However, when the current carrying capacity is large, the silver coating may be insufficient to prevent fusing because the cross-sectional area becomes relatively small as a bypass circuit. In this case, the coating of silver is mainly used as an electrode, it is desirable to connect the bulk of the resistor in parallel with the super-conductors. Further this time resistor instead of bonding between super conductors and two ends, it is desirable to electrically connect is provided an electrode for each certain interval. This is because when a quench occurs at a certain location as shown in FIG. 1 and FIG. 2, a bypass circuit connected with a smaller resistance than in FIG. 1 can be configured in FIG. Can be made. Further, heat generation caused by contact resistance of the electrode portion when the current is bypassed, also serves to propagate faster quench. By further forming such a bypass circuit that is not in contact with the super-conductors, low heat generation from super conductors, when the fault current has become sufficiently small (recovery of an accident) to the superconducting state The recovery time can be shortened.
[0016]
Further, since the bypass circuit is turned coiled, the critical current value of the superconducting bulk body by the magnetic field the coil generates is to decrease, which works to increase the bulk superconductors near quench and current limiting operation speed. Since each other a plurality of superconducting bulk body forms an electrically connected in parallel by path circuit together, sometimes one superconducting bulk quench current distribution is changed by quenching propagates at a high speed. This phenomenon prevents the voltage from concentrating on the quenched part and consequently suppresses fusing.
[0017]
As a method for avoiding fusing, it is effective to coat or contact a substance having a high thermal conductivity. By transmitting such materials heat quench along super conductors, also serves to increase the quench rate while preventing blowout.
[0018]
Furthermore, as shown in Fig. 3, as a method for keeping the resistance value high and preventing fusing effectively, the silver film having a low resistivity contacting the superconductor is made as thin as possible (less than 0.1 microns, preferably less than 0.02 microns). It is effective to coat a metal (gold, nickel, tin, lead, etc.) or an alloy having a specific resistance higher than that of silver on the silver film so as to have a thickness greater than that of silver. In such situations, silver is mainly used only to reduce the contact resistance with the oxide superconductor, and the coating on silver is mainly used as a bypass circuit.
[0019]
【Example】
Comparative example
YBa 2 Cu 3 O in 7-x Y 2 diameter BaCuO 5 is finely dispersed 46 mm, the single crystal form of the superconducting bulk material height 15mm sliced to a thickness of 1mm as shown in FIG. 4, further subjected to cut processing current path cross-sectional area to produce a super conductors of 2 mm 2. After that, the silver paste was applied only to the electrode part , heated once to 900 ° C. in an oxygen stream and held for 10 minutes, then cooled to 600 ° C. in 2 hours and then gradually cooled to room temperature over 20 hours. A copper lead wire was connected to the electrode portions at both ends by soldering, and then cooled in liquid nitrogen . If impervious to make fault current limiter circuits, such as in FIG. 5 using the pulse power supply was set circuit to flow a current instantaneous value of the maximum 1500A. When a current limiting device was connected to such a circuit and pulsed electricity was supplied, the current limiting element was blown away at a distance of about 10 mm from the electrode .
[0023]
The two superconductors thus produced were overlapped so that the spiral directions coincided, and an aluminum nitride insulator having a thickness of 0.4 mm was sandwiched as a spacer, and the two superconductors were connected by a central electrode. Two copper lead wires were connected to the electrode portions at both ends by solder. Furthermore, a resistor was connected to this superconductor every 20 mm. This was cooled in liquid nitrogen and a critical current (Ic) of 500 A was confirmed by direct current application. In addition, when a circuit as shown in Fig. 3 was made using a pulse power supply and the current limiter was not passed, the circuit was set so that a maximum current of 1500A would flow. When a current limiter was connected to such a circuit and pulsed energization, it was found that the maximum current was limited to 900A. Moreover, there was no fusing of this time-current element.
[0024]
Example A Ho-Y superconducting bulk material having the same shape as the comparative example shown in FIG. 4 was produced. After that, the silver paste was applied to the surface, heated up to 900 ° C. in an oxygen stream and held for 10 minutes, then cooled down to 600 ° C. in 2 hours and then gradually cooled to room temperature over 20 hours. The three superconductors thus produced were connected in series to the electrode portions at both ends by soldering, and two copper lead wires were further connected. A coil having a diameter of 6 mm made of a resistor is connected to the superconductor every 15 mm so that a magnetic field is applied to the adjacent superconductor. This was cooled in liquid nitrogen, and a critical current (Ic) of 500 A was confirmed by direct current application. In addition, when a circuit as shown in FIG. 5 is formed using a pulse power source and the current limiter is not passed, the circuit is set so that a current of a maximum value of 1500 A flows. When a current limiter was connected to such a circuit and pulsed energization, it was found that the maximum current value was limited to 850A. Moreover, there was no fusing of this time-current element.
[0026]
【The invention's effect】
According to the present invention, it is possible to provide a current limiter system that avoids fusing of the current limiter and realizes a rapid current limit operation , and its industrial effect is enormous.
[Brief description of the drawings]
FIG. 1 Current limiting element having one bypass circuit FIG. 2 Current limiting element having a plurality of bypass circuits FIG. 3 Current limiting device in which a metal having a large specific resistance is coated on a silver coating ] Superconducting conductor with meander structure [Fig. 5] Electrical circuit used in energization experiment [Fig. 6] (a) Spiral superconducting conductor, (b) Spiral superconducting section
Claims (5)
さらに少なくとも前記超電導バルク体の一部が銀でコーティングされていることを特徴とする限流素子。The current limiting element according to claim 1,
Further, at least a part of the superconducting bulk body is coated with silver.
銀の上に銀よりも高い比抵抗を有する金属又は合金が銀の膜厚以上にコーティングされていることを特徴とする限流素子。The current limiting element according to claim 1,
A current limiting element characterized in that a metal or alloy having a specific resistance higher than that of silver is coated on silver so as to have a thickness greater than that of silver.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP29988996A JP3977884B2 (en) | 1996-10-25 | 1996-10-25 | Current limiting element, current limiter using oxide superconductor, and manufacturing method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP29988996A JP3977884B2 (en) | 1996-10-25 | 1996-10-25 | Current limiting element, current limiter using oxide superconductor, and manufacturing method thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH10136563A JPH10136563A (en) | 1998-05-22 |
| JP3977884B2 true JP3977884B2 (en) | 2007-09-19 |
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| JP29988996A Expired - Fee Related JP3977884B2 (en) | 1996-10-25 | 1996-10-25 | Current limiting element, current limiter using oxide superconductor, and manufacturing method thereof |
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Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6762673B1 (en) * | 1998-02-10 | 2004-07-13 | American Superconductor Corp. | Current limiting composite material |
| KR100382286B1 (en) * | 2000-10-17 | 2003-05-01 | 한국전력공사 | Superconducting faulting current limiter using thin films having semiconductor switch |
| EP1353339B1 (en) * | 2001-01-16 | 2017-12-27 | Nippon Steel & Sumitomo Metal Corporation | Low resistance conductor, method of producing the same, and electric component using the same |
| DE112005001495B4 (en) * | 2004-06-24 | 2011-06-16 | National Institute Of Advanced Industrial Science And Technology | Superconducting fault current limiting element and method for producing the same |
| JP2006319101A (en) * | 2005-05-12 | 2006-11-24 | Kyushu Institute Of Technology | Superconductor apparatus using oxide superconductor |
| JP4851814B2 (en) * | 2006-03-01 | 2012-01-11 | 株式会社東芝 | Power system |
| KR100912273B1 (en) * | 2007-05-14 | 2009-08-17 | 한국전력공사 | Low temperature resistance switch contact manufacturing method for superconduction fault current limiter |
| KR100903349B1 (en) * | 2007-05-14 | 2009-06-23 | 한국전력공사 | Low temperature conduction switch contact for supre conducting fault current limiter |
| JP5028222B2 (en) * | 2007-11-01 | 2012-09-19 | 株式会社フジクラ | High resistance material composite oxide superconducting tape |
| JP2012150914A (en) * | 2011-01-17 | 2012-08-09 | Fujikura Ltd | High-resistance material composite oxide superconducting wire material |
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| JPH10136563A (en) | 1998-05-22 |
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