Improved Configuration of the Inductive Core-Saturation Fault Current Limiter with the Magnetic Decoupling

Due to the increasing levels of the short-circuit currents, the fault current limiters (FCLs) are expected to play an important role in the protection of the future power grids. The inductive FCLs, that have a dc winding that drives the core into saturation, are particularly interesting due to their inherent reaction on the fault. To avoid an over-voltage on the dc winding during a fault, FCL with decoupled ac and dc magnetic circuits has been proposed [5]. However, this FCL configuration reduces the value of the normal current, since its ac leg operates around saturation knee, i.e. the FCL impedance increases during the nominal operation. The size of the core and the peak value of the limited fault current have to be increased if the FCL impedance in the normal operation is to be diminished. This paper presents an improved version of the inductive FCL with magnetic decoupling of ac and dc circuits. The new FCL design reduces the device weight and size, while decreasing the FCL impedance to a low value during the normal operation. The increase of the peak value of the limited fault current is avoided. Comparison results are obtained through simulations in software SaberDesigner.