Research on Multi-Functional Magnetic Shield Type Superconducting Fault Current Limiter

磁屏蔽型超导限流器是一种具有实际应用前景的限流器。通常使用Bi 2223或Bi 2212材料作为其磁屏蔽体。大量的材料必须用于屏蔽体，因为这些材料显示出1，000 A/cm^2的低Jc。因此，在故障期间仅通过焦耳热使材料的温度快速升高到其临界温度以上是不容易的。故障发生后，温度将缓慢下降到临界温度以下。这些都是实际应用的问题。本文提出了一种高性能磁屏蔽型故障限流器。一旦发生故障，它将自动快速启动。故障电流限制器（FCL）是一种新型的故障电流限制器，故障电流限制器可以在短时间内恢复到超导状态。几乎所有的设计都采用液体制冷剂冷却。虽然短路故障很少发生，一年最多只有一两次。我们必须始终提供液体冷冻剂，这将是昂贵和麻烦的。因此，从减少用于冷却的维护的观点来看，由制冷机冷却的传导冷却FCL将是期望的。本课题对传导冷却型故障限流器的稳定性、限流特性进行了理论和实验研究etc.in提出了一种带静止无功补偿器的超导故障限流器。

The magnetic shield type superconducting fault current limiter is thought to be one of the promising candidates for practical application. The Bi2223 or Bi2212 material will be used in general as its magnetic shielding body. A large quantity of the materials have to be used for the shielding body because those materials show such low Jc as 1,000〜1,500 A/cm^2. Accordingly, it is not easy to increase the temperature of the material quickly by joule heat only over its critical temperature during a fault. And the temperature will decrease slowly below the critical temperature after a fault. These are problems for practical application. in this project, a highperformance magnetic shield type fault current limiter has been proposed. it will be fast activated automatically in case of a fault. And it will be recovered to superconducting state in a short period of time after a fault.Various tyoes of fault current limiters(FCL)have been studied. Almost all designs adopt liquid cryogen cooling. Although the short-circuit failure will seldom occur, just once or twice a year at most. we must always provide liquid cryogen and it will be costly and troublesome. So, a conduction-cooling FCL cooled by a refrigerator will be desirable from a view point of reduction of maintenance for cooling. The theoretical and experimental studies on the stability, the current limiting characteristics etc.in the conduction-cooling FCL are conducted in this project.With relation to the multi-functional fault current limiter, the generation and control of inductive reactance are experimentally conducted by controlling actively the flux flow resistivity of the shielding body . A superconducting fault current limiter with the static var compensator is proposed.