Tornadoes, earthquakes, hurricanes, unprecedented rainfalls and record-high 500-year flooding levels in 2011 have all together caused massive damage to the grid, homes, businesses and public infrastructure and billions in damage costs.
In the wake of recent disasters, the response of utility workers and electrical contractors has been nothing short of heroic. Round-the-clock restoration is tough work, always dangerous and occasionally fatal. Of course, since overhead transmission lines are susceptible to high winds, lightning, and falling trees and limbs, these natural disasters always beg the question of whether it would be better to run the lines underground.
Jim Leary is president of JBL Electric, South Plainfield, N.J., which, in August, dealt with severe flooding and downed trees that caused widespread outages. JBL contributes to storm restoration all over the country, but Leary said it was odd doing it in his own backyard.
“We don’t go into a lot of areas that have underground,” Leary said. “We skip them because high wind and falling trees don’t affect the underground network, so they don’t usually have any storm issues, just the overhead stuff that’s feeding it.”
Leary said JBL had up to 170 linemen assisting utilities with overhead transmission and distribution this summer.
“We’ve been working for PSE&G, Pepco, and First Energy here in New Jersey doing restoration. You have these massive, older trees that have landed on wires all over the streets. I don’t think we’ve run across any underground failures at all. You may run into a damaged riser pole, which feeds an underground system, but that’s about it. The one extreme is when there is a washout and a duct bank gets yanked out of a manhole, something severe. Otherwise, underground holds up very well.”
Leary said aesthetic appeal is one of the main draws for underground transmission; however, underground lines can be tougher to work on.
“In certain situations, it’s more dangerous for linemen. You can’t work it energized like overhead. In a manhole, things can blow up without warning, and guys have been killed by that. It’s always more difficult dealing with wires buried as opposed to wires you can observe.”
According to Tom Short, a technical executive at the Electric Power Research Institute, utilities may be moving toward a greater focus on building underground.
“Utilities are now putting in a lot of underground; I’d even say they are putting more in for new installations,” Short said. “If you are putting in a new development, they almost always want it underground, just to keep the wires out of the air. You may be able to make an argument for safety. You don’t have to worry about downed conductors energized and lying on the ground, although you still have the threat of contractors with backhoes digging into lines.”
Short said overhead systems are more prone to damage during storms. However, that doesn’t mean underground is immune to outages and the elements.
“One thing that kills underground cables over time is water, especially salt water, but they really try to design the systems to be as water-resistant as possible,” Short said. “The biggest advantage of overhead is lower cost. It varies widely depending on what you do underground, but overhead can often be half the cost. It’s also easier to make connections, add lines to poles and make taps off conductors, whereas with underground you have to dig things up to splice terminations, unless it’s a ducted system.”
With advances in sensor technology to isolate faults and the smart grid adding automated distribution systems, we are likely to see more utilities seeking shelter from the storms by going underground.