There are numerous potential benefits associated with electrified aircraft propulsion (EAP). Achieving economical and safe EAP in transport aircraft would constitute an enormous leap forward in aviation. However, as with all potential engineering breakthroughs, the devil is in the details. This chapter begins to examine some of these details by introducing the electric power system (EPS) and summarizing its design, control, and protection functions. With the electrification of propulsion systems, EPS power levels (i.e., generation, distribution, and loads) are expected to increase by at least an order of magnitude, with far-reaching implications on the overall system design. Since all aspects of the EPS will be impacted, a thorough understanding and appreciation of the EPS and its functions is necessary to fully comprehend the challenges ahead. Several key EPS components and functions are described, and the solid foundation provided by the material in this chapter prepares the reader for the focused discussions of individual system components that follow in subsequent chapters.

Chapter 5 deals with electrical issues and is broadly divided in two. The first half explains the operating principles of the several different types of generator found on wind turbines and their influence on dynamics and electrical power quality. Generator types are illustrated schematically and their characteristics explained using simple physical principles. Geared and gearless (direct drive) generators are discussed, and there is a brief historical review of generator developments. The second half of the chapter deals with electrical networks and further examines the issue of power quality. The importance of reactive power and how modern generators can manipulate it to aid voltage stability are explained; the role of external devices such as Statcoms, SVCs, and pre-insertion resistors is also discussed in this context. Measurements from a MW-scale wind turbine illustrate voltage control via reactive power management over a period of several days. The challenge of low grid strength is illustrated with a practical example of a small wind farm development on a rural network with low fault level. The chapter concludes with a brief discussion of wind turbine lightning protection.