Power engineering or power systems engineering is a subfield of electrical engineering that focuses on the generation, transmission, distribution, and use of electricity. Much of the field concerns itself with three-phase AC power (the contemporary standard for large-scale power transmission and distribution), the conversion between AC and DC power, and the development of specialized power systems for specific uses such as for aircraft or electric railway networks. This subfield is thus critical to keeping our 21st-century infrastructure running, and will assure any hardworking graduate a well-paid and well-respected job safe from economic ups and downs.