Alternating current limiting apparatus

Abstract

An alternating current limiting apparatus is disclosed which includes first, second, and third circuit. The first circuit is formed of a winding means such as transformer, autotransformer, or reactor and a capacitor serially connected to the winding means and is connected between two different kinds of power systems. The second circuit is formed of a series combination of a closing device composed of, e.g. a gap, mechanical or semiconductor switch, or a non-linear resistive element, and a resistor. The second circuit is connected across the output terminals of the winding means. The third circuit is formed of a reactor and a second resistor serially connected to the reactor. The third circuit is connected in parallel with the first circuit. The closing device is normally kept in its open state to form a series resonance circuit of the transformer and the capacitor, thereby directly interconnecting the systems with null impedance therebetween. Upon a system fault, the closing device is closed to switch the impedance as seen from the primary side of the winding means over to a small value to detune the series resonance, thereby forming a parallel resonance circuit between the combination of the small impedance with the capacitor and the third circuit including the reactor to enlarge the total impedance between the systems so that an overcurrent therebetween due to the fault may be suppressed.