Rock Doc column: Behind the hum of electrical power

By E. Kirsten Peters, College of Agricultural, Human & Natural Resource Sciences

peters-e-k-2010-80PULLMAN, Wash. – Think about the most complicated machine you’ve dealt with in the past year. Was it a beeping monitor tethered to a high-tech device in an emergency room? Or was it a superfast computer you used at work?

Actually, the most complicated machine you’ve interacted with was the one you used this morning when you switched on a light or plugged in your coffee machine. The entire power grid has to balance supply (generation) and demand (load) on a second by second basis. We take it for granted most of the time, but it’s a marvel when you stop to think about it.

Web of complexity

“The U.S. grid is the most complicated machine on the planet,” Bob Morris recently told me. He is an engineer who works at Schweitzer Engineering Laboratories (SEL), which sells electronic relays and other devices that help the grid function more safely and reliably.

Morris showed me a map of the backbone of the grid in the U.S. It looks a bit like a national highway map with oodles of lines running across states. Those big power lines feed into smaller and smaller ones, all the way down to your house.

You can see some of the grid’s complexity right in your neighborhood. Transformers at your local substation or hanging from power poles speak to some of what’s going on in the grid. And relays like the kind SEL manufactures control circuit breakers in the power lines.

Robust redundancy

There’s a lot of redundancy in the grid. That means there are backup routes through which power can flow if part of the grid is lost. Even if a power plant suddenly goes offline for some reason, the grid is designed to compensate for that and get power from other sources to where it’s needed.

“Our grid is amazingly robust,” Morris told me. “We have the most reliable power in the world.”

Pinpointing faults, delivering fixes

Just like cell phones, the grid has been getting “smarter” in recent years. Companies like SEL sell relays and other electronic devices that have added new capabilities to the grid.

In the old days, when a line went down or shorted out, workers had to go out in trucks or helicopters to look for where the problem was. But increasingly, because of devices like SEL’s products, relays connected to the wires tell the utility company how far from a substation the fault is. This means that responses and repairs can be made much more quickly.

When there is a problem in the grid, it’s the job of protective relays to isolate the faulted area. The instant there’s a fault or short-circuit, the current in the line jumps way up.

“The relays are programmed to look for that and open a circuit breaker,” Morris said. “It all happens in less than a tenth of a second.”

As the grid gets smarter, it’s getting more reliable, even as it continues to grow. That’s the good news – a fact I hope you’ll remember the next time you turn on a light.


Dr. E. Kirsten Peters, a native of the rural Northwest, was trained as a geologist at Princeton and Harvard. This column is a service of the College of Agricultural, Human and Natural Resource Sciences at Washington State University.