The development of power systems and their associations creates the increasing variety of structures and conditions of those united power systems. Under these conditions it is necessary simultaneously to achieve coordination of the automatic excitation control (AEC) gains at many stations and to provide the high quality of the transient processes. Practically this becomes possible only upon transfer from the analog regulator to digital, fulfiled on the microprocessor base. In this case the new principles of adaptive regulation in highest degree corresponding to the management tasks in the modern united power systems may be realized. By study of transient processes is understood the estimation of their quality and system stability during different disturbances of its regime. The providing of the best quality of the slightly turbulent regimes due to the selection of the parameters of the automatic regulation devices and first of all, AEC of the generators, is the task of the oscillatory stability analysis.