A Wide-Area Back-Up Protection Scheme for Discrimination of Symmetrical Faults from Power Swing and Load Encroachment

As the recent power systems operate in a low stability margin due to the economic and environmental issues, any misinterpretation might lead the power system to cascading outage and catastrophic blackouts. In these circumstances, stressed conditions such as power swing, voltage instability, and load encroachment, which have a similar nature with the symmetrical faults, might mistakenly interpret as fault situations and cause the mis-operation of the distance protection systems. This issue causes the power system stability margin leads toward much more lower than the before and, even to a blackout. With these considerations, in this paper, a PMU-based wide-area back-up protection scheme is proposed for avoiding of the distance protection systems mis-operation. In the proposed method, first, an equivalent circuit between each two PMU-buses in the determined vulnerable area is obtained. Then, based on the behavior of the equivalent circuit variables during the disturbance, the symmetrical fault is discriminated from the other events. The validation of the introduced method is evaluated on the two-area power system in MATLAB/SIMULINK.