This book offers a compact guide to IEC61850 systems, including wide-area implementation, as it has been applied to real substations worldwide. It utilises technical brochures and papers based on existing practice of IEC61850 systems that give stakeholders from different disciplines an understanding of systems in use, their features, how they are applied, and approach for implementation. The book offers a holistic practical view considering all relevant interfaces and possibilities. It includes the different applications, practical implementation considerations and choices made for IEC61850 PACS (Protection Automation & Control System) designs. Power system engineers, planners, technicians and researchers will find the book useful for exploring, developing and delivering these systems. This second edition of the book includes publication quality corrections. The technical content remains unaltered.