The electrical power system is the largest system ever created and controlled by man. The management of “machinery” of such size requires solid knowledge and well-trained engineers, as its functioning depends on complex control, careful design and appropriate maintenance. Ever greater electricity consumption, the introduction of modern technologies, new energy sources, the establishment of the electricity market and the consideration given to sustainable development are all factors that continuously alter the electrical power sector. All of this engineering work has resulted in an efficient and reliable power system, enabling consumers a continuous supply of one of the most flexible forms of energy: electricity.