Out of step relaying using phasor measurement unit and equal area criterion

Significant changes of load as well as faults and their clearance in power systems, which disturb balance of energy in the system, often result in electromechanical oscillations. This causes variation in power flow between two areas which is usually called as power swing. An effective way to retaliate such a disturbance is through controlled islanding of the power system using out of step (OOS) protection systems. In this paper we use a method which is based on the well-known equal area criterion (EAC) and application of phasor measurement units to protect interconnected systems against loss of synchronism. System oscillation is modeled using the mth-order auto regressive model. Afterwards, using the phase difference values stability of the power system is determined using the equal area criterion