This book is aimed at engineers in electrical power engineering as well as scientists and students in this field. It is particularly relevant in the areas of generation, transmission, and distribution of electrical energy. After an introduction to the necessary mathematical foundations, it provides a comprehensive treatment of electromechanical balancing processes in electrical energy systems. The precise modeling of the considered operating resources is presented. Investigations in different frequency ranges and special calculation methods, such as wave propagation theory and methods for examining transient stability, complete the subject matter. Practical examples illustrate the issues. This work includes the current state of research.