Application of equal area criterion conditions in the time domain for out-of-step protection

A new procedure for out-of-step protection by mapping the equal area criterion conditions to the time domain is proposed in this paper. The classification between stable and out-of-step swings is done using the accelerating and decelerating energies, which represents the area under the power-time curve. The proposed methodology is simple and overcomes some of the difficulties associated with the previous techniques. The proposed approach is based only on the local electrical quantities available at the relay location, and does not depend on the network configuration and parameters. The proposed algorithm has been tested on a single machine infinite bus and a three machine infinite bus system using software simulations. A digital prototype of the relay has also been implemented on the hardware and its performance has been assessed in a closed loop mode using a Real-Time Digital Simulator. The simulation results and the hardware testing results confirm the validity of the approach presented.