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

磁屏蔽型超导限流器被认为是最有发展前途的实用限流器之一。Bi2223或Bi2212材料一般用作其磁屏蔽体。屏蔽体需要大量的材料，因为这些材料的Jc很低，只有1000~1500A/cm~2。因此，在故障期间，仅通过焦耳热来快速提高材料的温度是不容易的。发生故障后，温度会缓慢下降到临界温度以下。这些都是实际应用中的问题。本课题提出了一种高性能的磁屏蔽式故障限流器。一旦出现故障，它将被快速自动激活。故障后可在短时间内恢复到超导状态。研究了各种类型的故障限流器。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，但一年最多只发生一到两次。我们必须始终提供液体制冷剂，这将是昂贵和麻烦的。因此，从减少冷却维护的角度来看，由冰箱冷却的传导冷却整流柜是可取的。本项目对导冷式限流器的稳定性、限流特性等进行了理论和实验研究，并结合多功能故障限流器，通过主动控制屏蔽体的磁通流电阻率来实现感应电抗的产生和控制。提出了一种带有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.