Most of us take the click of a switch for granted. We don’t think much about what makes the lights come on, the music play, the coffee brew. Likewise, when the power goes out, most of us don’t have a clear idea of what has happened, beyond a basic, oh well, the lights are out.

So where does the power come from?  How does it get here? Why does it falter?  Why does it take so long to restore it?

The flow of electricity across the country is controlled by one of several regional transmission organizations (RTO). The RTO for western Pennsylvania is called PJM. PJM, based outside of Philadelphia, oversees the grid in all or parts of Delaware, Illinois, Indiana, Kentucky, Maryland, Michigan, New Jersey, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia and the District of Columbia.

Electricity is generated at a power plant by a variety of methods, such as burning coal, oil or natural gas, or using nuclear, hydroelectric, or wind-generated power. From the power plants, the electricity is transmitted along high voltage power lines to where it is distributed. Distribution is the last leg of the journey, from the high voltage lines to a power substation, where transformers increase or decrease the amount of electricity delivered to customers, according to demand.  From the power station, the electricity runs along power lines to homes and businesses. The transformer regulates the amount of power that goes to operate local lines.

To use an analogy brazenly stolen from PJM, the electrical grid is like a road system, with the high voltage power lines acting as interstate highways for the electricity, and the distribution power lines, the ones we see on our streets, are the local roads that bring the electricity home.

While PJM directs the flow of electricity across our section of the grid, Duquesne Light is responsible for transmission and distribution in most of Allegheny and Beaver counties.  If you have a device that’s not dependent on a power source, you can track the progress of power outage repairs online. Along with the company’s website, www.duquesnelight.com, Duquesne Light also uses Facebook and Twitter to keep customers in the loop. The website also offers tips on how to deal with power outages, including ways to stay informed and track the progress of repairs in affected areas.

As crews move out to repair outages, automated equipment can minimize the size of the disruption. “A lot of our transmission and distribution systems are automated, even some of the distribution lines in neighborhoods,” says Joseph Vallarian, manager of media and community relations for Duquesne Light. Sectionalizers—sensors that automatically detect changes in current flow—allow the power company to better isolate outages. “If a tree crashes down and takes out a power line between two poles, sectionalizers allow us to pick up the load, isolate where that fault is and supply people upstream and downstream from the site of the accident,” says Vallarian.

Vallarian says the main causes of power outages are trees and vegetation. What appears to be brutal trimming by Duquesne Light of trees entwined with power lines along our roadways is part of their effort to reduce power disruptions.  Many of the trees that affect power lines are not located in the utility company’s right of way, however.  “We’re not allowed to go onto private property to trim trees,” he says. “It’s really incumbent on the property owner.”

And as with anything else, some property owners are more proactive than others, when it comes to keeping their trees away from power lines.

So if trees are such a big problem, why not run the lines underground?

Aside from the prohibitive cost of rerouting existing power lines underground, which can run as high as $8 million per mile in some locations, the truth is, it’s still not the answer in a built-out community like Mt. Lebanon.

“Underground electric makes sense in new developments where all the utilities are installed at the same time and trees can be planted out of the right of way,” says Tom Kelley, Mt. Lebanon Public Works Director. “It does not make economic or common sense to dig up established residential areas to bury electric lines.”

In addition to the cost, each property owner would be responsible for paying t to install their own underground connection from their home to the utility’s underground distribution boxes. And it’s not a perfect solution. Underground vaults flood, and buried conduits can be cut during excavation by gas, water, communication, and sewer contractors who will be sharing the same utility right of way area.

“Conduit is installed either by direct burial or by tunneling,” says Kelley, “so every tree along the street would be affected. Also, the risk of hitting gas lines, which are located in the utility right of way, would be astronomical.”

Other weather-related causes for power outages include: lightning strikes to electrical equipment; strong wind that can cause power lines to touch, resulting in a short circuit or even cause the lines to snap or the utility poles to break; snow and ice, which can accumulate on lines and weigh them down, causing them to break or to sag enough to bring the poles down, and rain and flooding, which can damage underground and aboveground equipment.

Aside from weather, the biggest cause of power outages is vehicle-utility pole accidents. More than 900 Duquesne Light poles are damaged every year by vehicles. A more grisly source of power interruption happens when squirrels or other small animals climbs on equipment, sometimes completing an electrical circuit, electrocuting themselves and causing equipment to fail.

Some of these outages can just be short circuits, which can often clear automatically, as a breaker on the line will de-energize the circuit and interrupt the power flow. About 30 percent of short circuits clear this way.

Vallarian says Duquesne Light does not track outages by community, only by service address, so he says he has no figures on how many outages occurred in Mt. Lebanon over the past year or so.

Wherever the power goes out, the utility follows the same protocol. First priority is to work with fire and police to eliminate any safety hazards, such as downed lines or burning equipment. Once it’s safe to work, the power is restored to “critical customers,” hospitals, emergency service providers, water and sanitary authorities, nursing homes and assisted living facilities. After that come the major circuits, that serve the largest number of consumers, and finally to individual homes.

So why are your lights still out when the house down the street is back on the grid? Different circuits may serve different parts of the same neighborhood. In some cases, houses on the same street might be served by different circuits or different transformers. Getting back to 100 percent restoration can sometimes take a while.

“It all depends on the severity of the storm, the amount of damage, how extensive the repairs are, if there are multiple broken poles, downed wires, lots of trees down, etc,” Vallarian says. “In any storm, in any neighborhood, there will always be single homes that will be the last to come back on, because until we do repairs to power that comes into a neighborhood or particular street, repairing the service drop to a single home will do no good.”

—mjantz@mtlebanon.org