Electrical power system is a real-time energy delivery system. Real-time means that electric power is generated, transmitted, distributed and supplied the moment you turn on the light switch. Electric power systems are not storage systems like water systems and gas systems. Instead, generators produce the energy as the demand calls for it.
The above figure shows the fundamental building blocks of an electrical power system. The system starts with the generation of electrical energy. By that electrical energy produced within the power plant is transformed to high-voltage electrical energy using transformer that’s more suitable for economical long-distance energy transmission.
The power plants at the generation station transforms other sources of energy in the process of generating electrical energy i.e. heat, mechanical, hydraulic, chemical, solar, wind, geothermal, nuclear and many other energy sources are used in the generation of electrical energy at generation station.
High voltage (HV) power lines in the transmission system efficiently transmit electrical energy over long distances to the consumption locations. Finally, substations transform this HV electrical energy into lower-voltage energy that is transmitted over distribution power lines that are more suitable for the distribution of electrical energy to its destination, where it is again transformed for residential, commercial, and industrial consumption.
A full-scale actual interconnected electrical power system is much more complex than that shown in above figure. However the basic principles, concepts, theories, and terminologies are all the same.