Comparative Study of Transformer Type Superconducting Fault Current Limiters Considering Magnetic Saturation of Iron Core

The paper reports on the transient performances of the transformer type superconducting fault current limiter (SCFCL). This type of fault current limiters (FCL) consists of a transformer in series with the transmission line and a superconducting current limiting device connected to the transformer. The performances are analysed through simulation during a short-circuit fault in the presence and absence of the shunt inductor. Magnetic saturation of the transformer iron core was compared to clarify its influence on current limiting characteristics of these SCFCLs. The magnetization curve of the transformer core is expressed by Froehlich´s formula and the time dependence of resistance R(t) of the current limiting device during its S-N transition (transition from superconducting to normal-conducting state) is considered. It was shown that magnetic saturation deteriorates the current limiting characteristics of this FCL.