Equal area criterion and angle control-based out-of-step protection

The article is devoted to wide-area measurements-based out-of-step (OOS) protection system which comprises of several protection terminals exchanging information in real time. Protection system structure and principles of operation described as also operation algorithm presented. OOS regime detection relies on simultaneous implementation of two approaches: generator angles differences are used for multi-swing instability detection while equal area criterion-based (EAC) approach is used for first-swing instability detection. Several deficiencies of EAC-based method, applied to multi-machine environment were revealed by the simulations and the algorithm was proposed to avoid those deficiencies.