Potential energy stored in a water reservoir behind a dam is converted to kinetic energy when the water starts flowing down the penstock from the dam. This kinetic energy is used to turn a turbine. Generator Falling water strikes a series of blades attached around a shaft, converting kinetic energy to mechanical energy, thus causing the turbine to rotate. The shaft is attached to a generator, so that when the turbine turns, the generator is driven. The generator converts the turbine's mechanical energy into electric energy.
Voltage is the pressure that makes electricity flow.
Generators usually produce electricity with a low voltage. In order for the transmission lines to carry the electricity efficiently over long distances, the low generator voltage is increased to a higher transmission voltage by a step-up transformer. Grid high voltage transmission lines Grid transmission lines, usually supported by tall metal towers, carry high voltage electricity over long distances. Terminal Station Terminal stations control power flow on grid transmission lines and reduce the grid voltage to subtransmission voltage. Subtransmission lines supply power from terminal stations to large industrial customers or distribution substations.