Power transformers are a key asset for electricity utilities around the globe. However, aging populations of large power transformers require reliable monitoring and diagnostics techniques to extend the asset's lifetime and minimise the possibility of catastrophic failure. This book describes the most popular power transformer condition monitoring techniques from principles to practice. Topics covered include concepts and challenges in power transformer condition monitoring and diagnosis; dissolved gas analysis, measurements and interpretations; moisture analysis for power transformers; assessing degree of polymerisation value considering thermal ageing and paper moisture; frequency response analysis; monitoring of power transformers by mechanical oscillations; lifecycle management of power transformers in a new energy era; and other topics in power transformer asset management and remnant life. Each chapter covers the fundamentals and theory of the topic, and conveys techniques to measure relevant parameters and assess or interpret the results. Power Transformer Condition Monitoring and Diagnosis is essential reading for researchers in academia and industry involved with power transformer R&D, engineers in utilities working with equipment monitoring techniques, and advanced students in power engineering.