Protection Technologies of Ultra-High-Voltage AC Transmission Systems considers the latest research on UHV, UHV transmission line electromagnetic field, transmission line parameters, and tower structures, with a focus on protective relaying of UHV transmission systems. This book gives insights into protective relaying of UHV AC transmission systems and sheds light on the conundrum of protective relaying for the EHV systems. In addition, it elaborates on both traditional relaying and the application of new type current differential protection, distance protection and automatic reclosing, as well as protective schemes for transformers and reactors in UHV transmission systems. This resource will serve as an important reference for technical personnel in network design and operation, as well as students and engineers in related engineering areas.