Book excerpt: This book provides an overview of a power transformer infrastructure and comprehensive digital protection of it. It presents various protective methodologies available to protect the transformer from disturbances by taking care of mal-operation due to external disturbances and providing fine protection to the transformer. Though there are many protection methodologies available in the practice. However, these existing methodologies may mal-operate during external disturbances such as inrush, over-fluxing and short circuits. Hence, further research is needed in addition to the existing methods of protection in terms of more fault prediction accuracy, speedy operation, and lower protection cost with zero error in the detection of faults. The book will be useful reference for practitioners from academia and industrial applications. .