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 PMUbuses
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