An Improved Field Suppression System for SISFCL

Saturated iron-core superconducting fault current limiters (SISFCL) are becoming increasingly well known for their effective and reliable current limiting capabilities. The device is capable of producing very low impedance during normal operation and substantially high impedance during fault. Its ability of changing impedance can be attributed to the change of magnetic state of the ferromagnetic core of the device from saturation to unsaturation. The SISFCL employs a dc source to maintain the saturated state of the core for normal operation with the help of a superconducting coil. The high ac ampere turns during fault not only bring the core to unsaturation, but also cause alarmingly high voltage to develop across the dc source. Hence, the protection of the dc source is of great concern as the high voltage is capable of destroying the source and additionally, force the superconducting material to quench. In this paper, the SISFCL is analyzed using the finite element method and the field suppression method of dc source protection is discussed and shortcomings are pointed. The novelty of the paper lies in the use of shorted winding for the improved performance of the field suppression system. For the finite element method (FEM) analysis, the ANSYS Maxwell 2D software is utilized.