Strategies for detection of out-of-step phenomenon for power system protection and control

Power systems, nowadays, are subjected to severe oscillations during the post disturbance span of time because of its operation at very narrow stability margins. Out-of-step condition is a consequence of transient instability and protection against out-of-step condition is a major issue for the power industry. In order to operate a system safely and to protect from the damages caused to system components such as generators, transmission lines and switching equipment, proper out-of-step detection and necessary protective action has to be provided. This paper explains the various out-of-step detection strategies which can be augmented to the numerical relaying algorithms, their computational simplicity and reliability and also discusses the issues and challenges related to implementation.