This book focuses on polymer insulation as applied to HVDC transmission. It addresses both fundamental principles and engineering practice, with more weight placed on the latter. This is achieved by providing in-depth studies on a number of major topics such as DC insulation structure, DC insulation design, nanocomposites, modification, testing and performance evaluation. In turn, several typical HVDC insulation application cases are examined in detail, e.g. cables, cable accessories, GIS/GIL, and converter transformers. A comprehensive and systematic study on polymer insulation modification and ageing assessment is one of the book’s major features, making it particularly well suited for readers who are interested in learning about polymer insulation materials. Given its scope, it offers a valuable resource for researchers, engineers and graduate students in the fields of high-voltage and insulation technologies, electrical engineering, material engineering, etc.