In the aftermath of storms that knocked out power to millions, overheated residents and elected officials are demanding to know why it's taking so long to restring power lines and why they're not more resilient in the first place.
Q: WHY DOES THE POWER GO OUT IN A STORM?
A: Utilities transmit electricity to your home through a network of transmission lines, transformers, power poles and other, relatively delicate equipment that can be damaged in a storm. Heavy winds can push trees into power lines and snap poles in half. Rain can flood substations, submerging equipment that connects major transmission lines to cities and neighborhoods. Any break in the network can snuff out power to thousands of people at once.
Q: WHY DOES IT TAKE SO MUCH TIME TO REPAIR?
A: Power lines stretch in many directions for hundreds of miles. After a storm, someone needs to drive, or sometimes walk, along those lines to see what's wrong. The lights don't come back on until the power company can locate the problem, fix or replace the broken equipment, and reconnect it to the grid. This is a tedious process that can take days or weeks following a storm like the one that hit the Atlantic Coast last weekend. Power companies usually set priorities during a cleanup. They try to fix the biggest problems first in hopes of restoring power to the largest number of customers. That means they'll tend to the major transmission lines and substations before focusing on the outskirts of the grid. Smaller neighborhood lines are usually the last to get fixed.
Q: WHY DON'T UTILITIES BURY POWER LINES TO PROTECT THEM FROM STORMS?
A: The newest communities do. But many older communities have found that it's too expensive to replace their existing network.
To bury power lines, utilities need to take over city streets so they can cut trenches into the asphalt, lay down plastic conduits and then the power lines. They need to add manholes to connect power lines with each other. Burying power lines costs between $5 million and $15 million per mile, according to the Electric Power Research Institute, Inc., a nonprofit research and development group funded by electric utilities.
Those costs get passed on to residents in the form of higher electric bills, making the idea unpalatable for many communities.
North Carolina considered burying its lines in 2003, after a winter storm knocked out power to 2 million utility customers. The North Carolina Public Staff Utilities Commission eventually concluded that it was "prohibitively expensive" and time consuming. The commission estimated it would cost $41 billion and take 25 years to complete. Altogether, the commission concluded, doing so would raise residential electric bills by 125 percent.
David Lindsay, a specialist in underground power transmission for EPRI, said it also costs more money to maintain underground power lines since problems are hidden and harder to fix.
"You can't just drive around in a truck and find them," Lindsay said.