Electromagnetic design of saturated iron core SFCL

The most attractive advantage of a saturated iron core SFCLs (SIC-SFCL) is that its impedance can change from very low in normal power transmission to very high for fault current limiting. This characteristic is achieved by varying the electromagnetic states in the main body of the device, including the iron cores, the ac working coils, and the dc bias coil. Usually, the dc coil and the ac coil are installed on different iron columns to facilitate the electrical insulation of the coils. Therefore, it is very important to understand how the dc bias magnetizing force can be effectively conducted to the iron column with the ac coils and how the ac current affects the magnetic field in the iron cores. This paper introduces our electromagnetic design method for a SIC-SFCL, in which a finite element computation is used to find the magnetic configurations among the dc bias coil, the ac working coils, and the iron cores. The design parameters of a 3-phase 220 kV SIC-SFCL are given as an example of this method.