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The Grid Grows Up

The nation’s electric grid is the largest man-made system on the planet, and an amazing success story.

Generators and wires and transformers make electricity available at the flip of a switch in homes, farms, offices, schools, factories, hospitals – everywhere people live and work. The grid delivers the energy we need where we want it, when we want it, day and night.

But the grid is showing its age.

Each piece of the grid is doing fine because of regular maintenance and replacement. Stronger wires, larger transformers, better poles, bigger generators – new parts are always being added.

What’s old about the electric grid is how all its pieces work together. And that has a lot of people talking about a new, “smart” grid.

The electricity grid is mostly a one-way system. Centralized generating plants mass-produce electricity and long transmission lines ship the power over large geographic areas.

But that one-size-fits-all approach may give way to a network that tailors electricity to the way it’s used by each individual business or residential consumer. Many experts are talking about using cutting-edge technology that would allow people to choose from a variety of electric services and prices.

The smart grid the experts have in mind is a system that includes two big changes.

The first change involves new ways for power system managers to monitor and control the flow of electricity. The second change would provide new opportunities for individual electricity users to make choices about how and when they use electricity based on the price.

These two new smart grid concepts are becoming more important because of a third change. As interest in energy efficiency and renewable energy grows, bringing these new methods of generating electricity into wider use will require a lot of changes.

America’s power grid is a vast infrastructure of more than 5.7 million miles of transmission and distribution lines worth more than 1 trillion dollars.

Among the most important features of the grid is the way it connects utilities across large regions of the country. A power plant in Kentucky can send electricity hundreds of miles within the Bluegrass State – or across the Ohio River into Indiana and Illinois. A power plant in Tennessee can provide electricity to Kentucky customers. Events in Michigan or Pennsylvania can affect what power plant and systems operators within Kentucky need to do to keep the flow of electricity reliable within our state.

That far-flung network of wires, power plants, transformers, and equipment to route that electricity where it needs to go safely also has to be more reliable than ever before. Power surges and voltage drops, once something only factory managers worried about, are now a concern for anybody with a home computer or big-screen TV. Sensitive equipment in hospitals, airports, even the traffic signals on the town square can be affected by changes in the amount of electricity flowing through the grid. A flicker of even a fraction of a second in the flow of electricity can disrupt today’s sophisticated electronics.

The Electric Power Research Institute, a group of about 800 utility industry researchers, says that today’s grid is 99.99 percent reliable. That means that, on average, the grid in any particular area will function perfectly for all but one hour during an entire year.

Engineers believe that a smart grid with new computer devices could help them achieve a new goal, a standard known as “9-nines.” That kind of reliability would make the electric power grid 99.9999999 percent dependable.

Improving our huge, centrally managed electric power grid to make it super-reliable is only part of the push for a smarter grid.

For example, a tiny localized distribution network for electricity from a small rooftop solar generating plant may be an economical choice within a suburban neighborhood. Yet that little system will still need to be both interconnected with an existing electric utility and capable of being isolated from it during certain other times.

And what if it makes more economic sense for an individual electric consumer to choose when to use certain amounts of electricity based on prices that vary throughout any 24-hour period?

Clearly, there won’t be a “one device does it all” solution to making the electric grid smarter in the future.


There is currently no efficient, cost-effective way to store electricity long-term. High-voltage transmission lines are used to deliver electricity from generation plants to consumers.

High-Voltage Transmission Lines
Large amounts of power are delivered by transmission lines. These lines are energized with very high voltage in order to move the power long distances with minimal losses. Insulators on the towers prevent the power from flowing to the towers or the ground.

Electric cooperatives own and maintain 65,000 miles (6 percent) of the nation’s transmission lines!

Substations and Sub-Transmission Lines
Transformers at transmission substations reduce the voltage from transmission levels to sub-transmission levels, typically ranging from 115,000 volts to 34,500 volts. Sub-transmission lines deliver power over short distances to industrial sites and distribution substations.

The lines also deliver electricity to distribution substations, where transformers reduce the voltage to a lower level, typically 34,500 volts, 25,000 volts, or 12,500 volts.

Distribution Lines
The lines typically seen along rural roads and next to homes are generally single-phase distribution lines, energized at 7,200 or 14,400 volts. Transformers on the power poles lower the voltage to between 120 and 480 volts to serve residential homes and small businesses.

Electric cooperatives own and maintain 2.5 million miles (42 percent) of the nation’s distribution lines!

Source: National Rural Electric Cooperative, Iowa Association of Electric Cooperatives


To learn more about the most important engineering project of the 20th century, visit this Web site for photos and descriptions of the way the nation’s electric grid took shape:



Read how the nation’s electric grid grew from an 1888 New York City curiosity to a sophisticated nationwide network bringing power to all parts of the country, go to grid growth.

Next month: How you’ll talk to the smart grid

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