This paper presents the development and practical examples of an efficient method for the simultaneous solution of post-dynamic quasi-stationary states in each of the islands, using a unique numerical procedure, retaining the same node numeration which existed in the power system before its disintegration. At the same time, the developed method enables a simple incorporation of the effects of primary frequency and voltage control emergency control devices and a series of possible dispatch actions, both during the monitoring of the disintegration process and during power system restoration with island synchronization, if the necessary conditions are met.