Analysis of Magnetic Circuit and Leakage Magnetic Field of a Saturated Iron-Core Superconducting Fault Current Limiter

The saturated iron-core superconducting fault current limiter (SISFCL) is considered to be an effective solution to reduce the impact of fault current and increase the reliability of the power grid. This paper presents the basic structure and the electromagnetic analysis of SISFCL. In order to study the leakage magnetic flux distribution of the SISFCL, two approaches have been used to model the transient behavior of such device. The leakage magnetic flux distribution of the limiter was calculated, respectively, by using the finite element method (FEM) and the magnetic field division method. By considering the SISFCL as a controlled voltage source dominated by the flux through the ac coils, we establish a magnetic circuit. With the magnetic circuits, we calculate the steady-state impedance. Comparing the results with the FEM model, we verify the validity of the equivalent magnetic circuit model.