Dynamic Inductance in Saturated Cores Fault Current Limiters

The saturated cores Fault Current Limiter (FCL) is one of the leading candidates for providing a commercial robust solution to the fault current problem. Basically, the saturated cores FCL offers low impedance during normal grid operation due to its saturated cores state and high impedance in fault events due to cores desaturation. We developed a method to obtain the nonlinear inductance curve L(I) of the saturated cores FCL from which we show that the dynamic inductance component, dL/dt, contributes significantly to the FCL limiting capabilities. Specifically, we show that in some parts of the AC cycle, the dynamic inductance term dominates over the static inductance in contributing to the voltage drop across the device. We conclude that the design of saturated cores FCL should consider the dynamic inductance and calculate its contribution to the FCL voltage to benefit from better device performances.