Out of step detection using synchronized swing impedance and resistance measurement

Distance relays used for transmission line protection can mal-operate on power swing. This paper presents protection schemes for out of step detection based on synchronized phasor measurement. Voltages and currents at both the ends of a transmission line are used to derive the parameters required for designing these schemes. The proposed schemes can distinguish stable and unstable power swing and can prohibit tripping of distance relays on stable power swings. The schemes are also compared with conventional power swing detection schemes. Simulations are carried out on single machine infinite bus system (SMIB) using PSCAD.