The electric transmission system ends and the distribution
system begins at a substation. A substation is essentially a series of transformers
surrounded by circuit breakers and other safety and protective devices. The substation
transformers "step down" the voltage from high-power, long-distance
transmission lines, by reducing it from as much as 765,000 volts to less than
39,000 volts. This makes the electricity easier and safer to handle.
Distribution lines carry the electricity from
the substation to transformers mounted on poles or in metal boxes on the ground
for underground lines. These transformers further reduce the voltage, to the
120 or 240 volts used by most homes and businesses.
Wires carry the electricity from the transformers
to residential, commercial, and industrial customers.