A New Algorithm for Predicting Out-of-step Using Rotor Speed-acceleration Based on Phasor Measurement Units (PMU) Data

Transient instability is one of the major threats to system security which can cause out-of-step condition. Out-of-step condition can result in mechanical and thermal damage to generators. Therefore, in the case of out-of-step, early detection and disconnection of the generator from grid is essential. In this article, using generator rotor speed-acceleration ( - ) data obtained from phasor measurement units (PMU) measurements, a new algorithm for predicting out-of-step condition for generators is proposed. The trend of the movement of the ( - ) locus curve in the plane provides a measure for predicting and detecting out-of-step status. The predictive ability of this method enables early tripping of the unstable generator, thereby avoiding hazard damage. The proposed algorithm is examined using an IEEE 39 bus system. The simulation results demonstrate the ability of the proposed algorithm for correct prediction of various unstable power swing conditions, with sufficient early prediction compared with the actual instability time.