Dynamic Desaturation Process in Saturated Cores Fault Current Limiters

The process of driving the magnetic core of saturated-cores fault-current-limiters (SCFCL) out of saturation has been studied numerically using finite elements calculations. The de-saturated core section was found to grow dynamically starting from the central region below the AC coils and gradually expanding towards the coil edges with increasing AC current amplitude. During the transition, the core volume underneath the coils is non-homogeneously magnetized and the system is highly non-linear. An effective core volume that contributes to the SFCL impedance during fault can be defined for different current amplitudes. Two “open core” SCFCL models have been studied and compared for their dynamic de-saturation process. The results demonstrate the importance of the dynamic effective volume size to the current limiting process and suggest that prior art approximations based on full core desaturation are not sufficient for a detailed SFCL design.