This book is about infrastructure asset management, which can be expressed as the combination of management, financial, economic, engineering, applied to physical assets, with the objective of providing the required level of service in the most cost-effective manner. It includes management of the whole lifecycle of a physical asset from design, construction, commission, operation, maintenance, modification, decommissioning, and disposal. Moreover, there are typically constraints, for example, in budget, which result in the need for a strategy for performing asset management. There is a long history of applying infrastructure asset management, for example, in the military and aviation sectors. This book focuses on asset management of an energy infrastructure, that is, the electric power system. Electricity has been appointed as one of the greatest inventions. The launch of the light bulb in 1879, which is listed as one of ten most important inventions of all time, revolutionized society by using electricity. Electricity provides energy in applications for transport, heating, lighting, communications, and computation. The electric power system is the infrastructure that manages the electricity from generation, delivery, to consumption. The electric power system is currently undergoing a major reconstruction, captured in the concept of Smart Grid. Main drivers for this change are the climate and energy goals towards a sustainable energy system. There are, however, also crucial drivers for cost efficiency and efficient use of resources—in this context the tools of infrastructure asset management become one of the important solutions. Moreover, new technology developments open up for new solutions for asset management of the electric power system. A general trend is in new possibilities for control and operation, forexample, with Phasor Measurements Units, generally located in the transmission grid providing measurements of voltage and current with accuracy up to30–120 times per second, or smart meters placed at the end consumer, whichenables integration of small-scale electricity generation, for example, fromsolar cells, electrical vehicles, and energy storage, and a distributed controlof energy use. Another trend is the development of diagnostic measurement techniques for assessing the insulation condition and prediction of lifetime of physical assets, and new methods for condition monitoring, for example, using sensor networks. These different trends have in common an overall development towards access to large volumes of data for handling and analysis, and another concept growing in interest is referred to as Big Data—which provides new means for infrastructure asset management.