Fault current limiting by means of loss-less resistor

The concepts of the loss-less resistor (LLR) and LLR-based fault current limiter (LLR-FCL) are proposed. LLR is a new circuit element with resistive V-I characteristic, but without average power loss. There are two kinds of LLR developed. Namely, the inductor-emulated linear conductive element G/sub L/(t) and the capacitor-emulated linear resistive element R/sub C/(t). G/sub L/(t) is realized by a switching network with an ideal inductor, while R/sub c/(t) is realized by a switching network with an ideal capacitor. The LLR-FCL consists of G/sub L/(t), R/sub c/(t) and ZnO-arrester in parallel. The resistance of LLR-FCL equals zero at the normal condition of electric system, so there is no voltage drop and power loss caused by it. During a short circuit fault occurs, the resistance of LLR-FCL rises up automatically to a large value to limit the short circuit current within a given level. It is also no power loss produced by LLR-FCL as the fault current passing through it.