A comparative assessment of power swing detection techniques

Distance relays, which respond to changes in impedance, may mal-operate due to power swings. For maintaining security, power swing blocking (PSB) function is utilized in modern distance relays to avoid unintended operation during power swing. However, if fault occurs during power swing, distance relays must operate. This paper reviews the shortcomings in the existing power swing detection techniques of distance relays. The concentric impedance characteristics scheme, the Vcosφ, the decreased resistance and the superimposed current methods are the conventional techniques for power swing detection for which a comparative assessment is carried out.