Innovative electromagnetic dynamic fault current limiter operating at ambient temperature for smart grids

Design and performance of dynamic fault current limiter (DFCL) operating at ambient temperature is presented. DFCL has incremental impedance due to incremental permeability in the electromagnetic circuit of device. DFCL limits currents for first peak and also subsequent rms value of short circuit. Electro-dynamic stresses due to peak current and thermal stresses due to rms current are limited to safe values for network. Let through current is limited to within 9 kA, preventing cascade tripping but a value high enough for relay coordination. After protective devices operate and short circuit is isolated, current through DFCL reduces and DFCL instantaneously and automatically resets to low impedance. Variable impedance of DFCL ensures that even for a high impedance fault, hanging is avoided. DFCL can thermally withstand three short circuits of three seconds duration, coming in quick succession. DFCL have been fully tested and are operational in the field, with actual fault data recorded.