Performance of protection relays during stable and unstable power swings

Power swings and loss of synchronism are complex events which occur during severe system disturbances. Many protection functions may respond during such events, but not always in an intended, expected, or coordinated manner. This paper aims to present an overview of the scenarios which give rise to power swings, how protection devices response, and how the implementation of protection algorithms by different manufacturers can cause similar relays functions to react in different ways.