Measured impedance by distance relay for inter phase faults in presence of resistive Fault Current Limiter

Distance relays are widely used as main and back-up protection for transmission lines. Their operation is based on impedance measurement at the relaying point, which can be affected by several factors, including pre-fault line loading and short circuit levels at the line ends. Continues demand for electricity energy leads to increase of 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 investigates the effects of resistive superconductor FCL, on the measured impedance at the relaying point, in the case of inter phase, phase to phase and three phase, faults. In addition to limitation degree, its installation point also affects the measured impedance. The variation of the ideal tripping characteristic for different installation points will be investigated.