New Saturable-Core Fault Current Limiter Topology with Reduced Core Size

Fault current limiters (FCLs) are expected to play an important role in protection of future power grids. By inserting a limiting impedance in series with a line, they limit the increasing levels of the fault currents to acceptable values. Inductive FCLs based on core-saturation effect are particularly interesting due to their inherent reaction on a fault. However, some challenges are to be solved: too large amount of required material and induced over-voltage across the DC winding that is used to drive the core into saturation. This paper introduces a new configuration of the inductive FCLs, where the amount of the required material is reduced considerably and the induced over-voltage across the DC winding is decreased. The amount of magnetic material is reduced by employment of one core per-phase instead of two. The middle leg of the three-leg core is used as a shunt path for the AC flux. It enables a gap insertion in the AC magnetic circuit without influencing the DC magnetic circuit, i.e. the amount of DC winding material. Thus, a smaller core (less magnetic material) can be used for the same power level. Results obtained from the lab prototype match very well the one from simulations. (C) 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.