Fundamental performance of superconducting fault current limiter with two air core coils

In this paper, we theoretically compared the fundamental characteristics of fault current limiter (FCL) with high-Tc superconductor (HTS) and two coaxial air-core coils based on steady-state analysis. Two types of FCL are possible. One is parallel type and the other is transformer type. The parallel type can be divided into two types according to the combination of the winding direction of coils. That is, there are two cases that the coils are wound so that the magnetic fluxes induced by coils reduce and increase each other. In this paper, we called them parallel type 1 and 2, respectively. There is no significant difference in the HTS volume required to satisfy both the specified limiting impedance ZFCL and initial current Iini in limiting operation among those three FCLs although the HTS in each type of FCL has different length and cross-sectional area. In the cases of those FCLs, we can improve the current limiting performance by arranging the HTS in the coils and applying the magnetic flux to the HTS in the limiting operation. The magnitudes of the magnetic flux density are almost the same. From the viewpoint of the FCL impedance in normal operation, parallel type 1 has the most desirable structure. On the other hand, transformer type is the best to eliminate the magnetic flux applied to the HTS in the normal operation. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(3): 29–36, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20477