Network control is a young discipline and yet already a considerable number of textbooks have been published on the topic. The aim of this book is to give a comprehensive description of Energy Management Systems (EMS) from the operator's point of view, with regard to their hardware and to their software aspects. The scope of the book is restricted to network control of electrical transmission systems and emphasis is placed on systematic description of the different operational planning aspects. The book provides a framework within which EMS may be realised, considering both the present state of the art and future developments in this multidisciplinary field. A carefully edited glossary contains the most important terms used in the field of energy management systems.