A power plant is an installation capable of converting mechanical energy, obtained through other sources of primary energy, into electrical energy.
In general, mechanical energy comes from the transformation of the potential energy of water stored in a reservoir; of thermal energy supplied to water through the combustion of coal, natural gas, or fuel oil, or through the fission energy of uranium. This energy (in the form of water falling from a higher level or water vapour or combustion gas at high pressure) drives the impellers of a turbine.
To convert mechanical energy into electrical energy, machines called electric generators or alternators are used, which consist of two fundamental parts: the stator and the rotor.
The stator is a hollow, barrel-shaped metal cylinder whose interior surface has grooves that house an interconnected copper winding. The rotor is a solid shaft, also metallic, that lodges with a capacity of turn in the interior of the stator and whose surface also has grooves that lodge another winding of interconnected copper that acts like an electromagnet when a small continuous electrical current is applied to them coming from a third external team called an exciter.
The turbine, the alternator and the exciter are aligned and share the same axis of rotation. When the rotor rotates at the speed of 1,500 or 3,000 rpm (necessary to generate with a frequency of 50 Hz with which one works in Europe), driven by the shaft that shares with the turbine, an induced current is produced in the copper wires inside the stator. These currents provide the generator with the so-called electromotive force, capable of providing electrical power to any system connected to it.
This generated electrical energy is sent through a network of power lines to the places of consumption. At the output of the power plant, the voltage is 110 kV, 220 kV or 380 kV; that is to say, by means of a transformer a high voltage is obtained, so that the losses in the transport are minimal. Then, in the places of consumption, it is transformed again, through other transformers, to the known low voltages of 380 V and 220 V, which are what we usually use in our equipment and appliances.