Water stored behind the dam flows down huge pipes called penstocks . The flowing water turns a turbine, a set of blades that looks like a huge metal pinwheel. The rotating action of the turbine drives a generator , which converts the turbine's mechanical energy into electrical energy. Attached to the generator is a step-up transformer . This device converts the low-voltage electricity produced by the generator into a higher voltage, which is more efficient for the transmission lines to carry over long distances.
Voltage is the pressure that makes electricity flow.
Transmission Lines Transmission lines, usually supported by tall metal towers, carry high-voltage electricity over long distances to substations. Substation A substation is a system of transformers, circuit breakers, and control and protective devices. At the substation, the high transmission voltage is reduced to lower voltages for distribution to residential, commercial, and small and medium industries. Distribution Lines Distribution lines carry the lower-voltage electricity to customers. They are smaller and less complex-looking than transmission lines because they carry lower voltages.