Measured Impedance by Distance Relay in Presence of Resistive Fault Current Limiter

Distance relays are widely in use as main and back-up protective devices for transmission lines. Their operation is based on impedance measurement at the relaying point, which can be affected by several factors. Continued demand for electricity energy leads to increase in the short circuit levels along the network, which itself causes new problems. One of the proposed solutions for this problem is the utilization of fault current limiter (FCL), which imposes further changes on the measured impedance at the relaying point. This paper presents the effects of resistive superconductor FCL, on the measured impedance at the relaying point. In addition to its limitation degree, its installation point also affects the measured impedance. The variation of the ideal tripping characteristic due to presence of FCL for different installation points would be investigated.