Out-of-step protection using equal area criterion in time domain

This paper proposes the out-of-step (OOS) protection system, which operation principle is based on combination of two approaches: equal area criterion, implemented in time domain, is used for generators first swing stability assessment and generation sources electromotive forces (emf) vectors angle control is used for multi swing instability detection. The paper focuses on possibilities of practical implementation of the above mentioned approaches within real time operating OOS protection system. Protection system structure and principles of operation addressed in the paper.