Design guidelines of a flux‐lock superconducting fault current limiter with ac magnetic field coil for a 6.6‐kV distribution system

We have proposed a new type of fault current limiter, which consists of a flux-lock reactor with high-Tc superconducting (HTS) elements and an ac magnetic field coil (Flux-Lock-Type Fault Current Limiter: FLT-FCL). The FLT-FCL can increase both the current capacity and the limiting impedance by means of a transformer action and an ac magnetic field application mechanism. This paper reports the conceptual design of an FLT-FCL for application to a 6.6-kV/200-A distribution system. Theoretical expressions for the current limiting behavior are derived and the new concept of “quench power” is proposed in order to estimate the required number of HTS elements for two types of FLT-FCL and for a basic FCL type consisting only of HTS elements. Design guidelines for the FLT-FCL are derived from the calculation results. © 2001 Scripta Technica, Electr Eng Jpn, 135(4): 17–25, 2001