Textbook in PDF format This book aims to provide readers with practical knowledge of the fundamentals of the “digital transition” concept, tools for designing and managing the operation of smart grids and substations, and critical issues in modernizing the energy sector. The inevitable transformation of the electric power industry is moving toward digitalization, which has taken the form of the concept of "Intelligent (smart) grids" (sometimes called "Digital Transition"). This has required coordinated work not only from the energy industry, but also from other stakeholders (government agencies, private firms, utilities, scientific and educational institutions, etc.) to solve numerous problems that arise during the transition to this advanced technology. It is obvious that the development of new components of energy systems, such as smart meters, monitoring and geolocation equipment, new disaster recovery systems, and energy storage systems, should be supplemented by the creation of the necessary communication infrastructure, modernization of existing network components, implementation of relevant regulations, training of highly qualified personnel