Season One Research Files
Episode Nineten
6:00pm-7:00pm
POWER GRID
The power grid is a giant network of long-distance, high-voltage transmission lines and substations that covers the entire United States and much of Canada. They carry bulk electricity to local utilities for distribution to their customers. These wires are all interconnected at hundreds of substations, so power companies can buy and sell "product" from each other. Effectively it's a single machine to distribute electricity, stretching 3,000 miles from east to west, and 3,000 miles from north to south.
The grid has three main sections. The eastern part connects everything from the Rockies to the Atlantic, and from Florida up into Canada. The western network connects everything west of the Rockies from Mexico up to Canada. Most of Texas is on a grid of its own because back in the 1930s, Texas utilities didn't want to deal with interstate government controls. The grid is broken down into 150 smaller subsections, so that it can be monitored on a more local basis. But those subsections are only organizational. The wires are all interconnected. It is technically possible to light up a light bulb in Seattle with a watt that was generated in Tallahassee.
The whole grid idea wouldn't work without a unique property of electricity. Electricity will travel down whatever path provides the least resistance, kind of like water running downhill. Think of the grid as if it were a huge network of hoses that carry water, connected at lots of places so the water in one hose can flow into another. Pump some water up into one of those hoses and, because of all the interconnections, the water can find its way into any of the hoses as it goes on its way. This imaginary giant network of hoses holds a cumulative reservoir of water. The electric power grid is a giant network of thick aluminum wires that holds a reservoir of electricity. The individual watts in any one of those wires might have come from any of the generating stations pumping power into the grid.
Substations, the crossroads on the grid, take in the high-voltage juice from transmission lines, redirect some of it back out onto other high-power lines, and transform some of it into lower-voltage power that goes into distribution lines on those poles on the street and finally into your house. Every time you turn on anything plugged into the wall, you are drawing electrical power from the grid, at the speed of light -- 186,000 miles per second. When you switch on a lamp, it's like sucking on a straw. The lamp draws power out of the wall plug. That draws power from the wire in your wall between the plug and your circuit breaker box. That in turn draws power from the line that runs between your house and the distribution line out on the local power pole. That draws power from the distribution line itself, which then draws power from one of the high-voltage grid transmission lines feeding the substation.
The people at the 150 grid control stations spread across the United States and Canada are constantly watching for tiny variations in the frequencies of the electrical energy in the transmission wires, which tell them how to adjust things so the demand for electricity from consumers and the supply from the generators always matches. Balance in the grid is vital to protect it from failure. Imbalances can occur when too much electricity heats up a transmission wire and wipes out the entire grid. Also, a sudden loss of one major transmission line or substation can cause the same chain reaction. Too much demand and not enough supply (as is currently the case in California) can also lead to an imbalance. That may cause something called voltage collapse, which can shut down a major section of a regional grid. Since the balance between supply and demand is so important, bringing the grid back online after a big shutdown is more than a matter of just flipping a switch. They have to restore the system one transmission line at a time, so they don't suddenly shock things with more supply than there is demand. Which is why, after the 1965 blackout in the Northeast, it took nearly a day to restore power to everybody.
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