The growing share of power electronic/converter interfaced generation is decreasing the total system rotational inertia. The reduced rotational inertia in the power system has important impact on the electro-mechanical processes, the power angle and frequency evolution time are quicker resulting in faster transient processes. Rapid response of the protection systems shall be applied, in order to clear the faults in the power systems. This paper aims to identify the roots/mechanism of critical

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... earing time reduction/deterioration by determining/analyzing the trajectories of the critical clearing time (CCT) in low rotational inertia power systems. In this paper, the equal area criterion (EAC) is used for analysis purposes. Theoretical and practical findings demonstrate the increase of the rotational inertia increases the CCT.