How an Electrical Network Works
Electrical networks distribute electricity from the point of generation to points of consumption. A collection of networks is called a "grid." The network begins at the power-generating plant. Traditional generating plants used large turbines driven by water or fossil fuels. Beginning in the late 1950s, nuclear-powered generators began supplying energy, and today, solar and wind power are in the first stages of becoming major sources of generating power.
As each new source is developed, a new way to distribute power to subscribers---a network---must be built. From the generating plant, millions of volts of electricity are "packaged" by transmission substations to travel in several directions over high-voltage carrier lines that may carry from 300 to 800 kilovolts of electricity. The transmission lines end at distribution substations. Each substation contains a main "transformer" that packages or "steps down" the voltage from the high-voltage energy necessary to propel it over long distances. Another device called a "bus" divides the electricity, now measuring 10 kilovolts or fewer, for local distribution.
In order for electricity to be used in machines and household appliances, it must behave in certain ways. American electricity, for example, is produced in a three-phase alternating cycle (AC) current and travels in three lines (the fourth wire is a ground wire) along transmission and distribution lines. As the electricity is distributed, "regulators" manage the electricity in each wire to keep the voltage from suddenly increasing or dropping, causing power surges or brown-outs. At the point where electricity is drawn off the distribution line to a set of users, one or two of the distribution lines are "tapped" to carry electricity to a group of users or neighborhood. These lines are tapped again to run through drum-shaped transformers that finally step down the voltage to 240 volts---the voltage that enters most individual services.
In many older neighborhoods, these wires and transformers are mounted in the air on poles. In newer neighborhoods, distribution lines are being installed underground in cables---transformers are installed at the entrance to each customer along with entrance bridges for telephone and cable services.
Today, as more networks are established and old ones are connected in ways not thought of by the original builders, grids have become increasingly complex and unstable. As more energy sources are developed, the need for efficient interface between dozens of electrical networks will increase so that an event on one network does not overload or crash others, leading to a "cascade" of failures and area-wide blackouts.
New "smart" networks are setting precedents for future restructuring of the larger grid. These networks control transmission and routing with computerized management that controls flow and forestalls the kind of overloads and blackouts that can be caused by as something as simple as bird droppings or a lightning strike. An interconnected, automatically managed grid is the way to make sure that networks can share their surpluses but keep their problems to themselves.
