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GLOVERSVILLE - Mention a circuit breaker and you would might think of the electric panel in your basement or garage. 

If the lights in one room go out, you check the circuit breaker to see if one of them has tripped, possibly to prevent an overload. After the proper precautions, you might unplug an appliance or two and switch it back on.

But imagine a circuit breaker  the size of a refrigerator that handles enough power for a small community or several neighborhoods. And consider that it’s running all the time and may be decades old. 

That’s what a utility substation is. And every few years, these jumbo arrays of circuit breakers need maintenance, replacement or upgrading.

But how does one do that without blacking out an entire neighborhood while the work is being done?

One way is through the use of portable power substations, like the one that a group of National Grid technicians were using earlier this summer here to replace the aging breakers currently in place at a substation on the edge of town.

National Grid has 24 of these trailer-sized substations in its upstate region and they are moved around as needed. 

“It’s everything you see here on a trailer,” Dan DeChiuaro, the upstate substation director for National Grid said during a recent tour.

Actually, visit would be a better description than tour, since the actual substation, about the size of two tennis courts, is behind a chain link fence for safety reasons. 

You have no doubt seen these substations scattered across the state, with power lines running into and out of them and the giant bulbous-shaped circuit breakers.

While they can pretty much run on their own, there is a schedule of maintenance and replacement that National Grid follows, meaning the workers and their portable substation are almost constantly on the move, going from one location to the next.

“It’s a never-ending plan,” DeChiaro said, adding that the improvements being done at this substation would take about a month and cost about $300,000 – which comes out of  the electric delivery charges on your National Grid bill. 

The job entails more than simply replacing the breaker, since there are other parts and wires that get swapped out as well. “You don’t replace three tires on your car when you get new tires,” said DeChiaro.

If not at a substation, the portable models act as what DeChiaro described as a “security blanket,” since they can quickly be moved to substations that have been damaged or disrupted by storms or other events.

That was done after damage during a 2008 ice storm, for instance, required substation repairs.

National Grid keeps some of these standby machines at strategic spots throughout the state, including the Riverside substation in Albany near the Huck Finn furniture store site.

According to Delta Star Inc., which manufactures the portable or mobile substation used here in Gloversville, the devices were first deployed in 1976 and they’ve since built more than 400 in use across the U.S. and Canada. They cost about $1.5 million each.

Some permanent substations date from before the 1970s.

Until recently, DeChiaro said, they had one substation in Cobleskill that was built in 1919.

Rick Karlin covers the environment and energy development for the Times Union. Has previously covered education and state government and wrote about natural resources and state government in Colorado and Maine. You can reach him at  rkarlin@timesunion.com or  518-454-5758.