Some in the Town of Chevy Chase think there is no debate as to the reliability of underground power lines compared to the overhead ones that now line the streets.
In a report by Town Councilmembers Al Lang and John Bickerman about the idea of undergrounding power lines in the town, the two wrote the high cost of the process would be worthwhile, pending a more complete analysis from a hired consultant.
“Underground power lines are more reliable. There is no serious debate to suggest otherwise,” the report states. “The unassailable conclusion is that customers with underground service will be without power for far less time and far less frequently than those with overhead service.”
Others don’t see the issue as so clear-cut.
“Five years of underground and overhead reliability comparisons for North Carolina’s investor-owned electric utilities – Duke Energy, Progress Energy and Dominion – found that the frequency of outages on underground systems was 50% less than for overhead systems, but the average duration of an underground outage was 58% longer,” according to one report from a South Carolina utility company.
“Because those repair times are typically much longer, customers served by underground lines are usually among the last to have power restored. Long term reliability is also an issue. As underground lines get older, they become less reliable. In fact, a Maryland utility found that customers served by 40-year-old overhead lines had better reliability than those served by 20-year-old underground lines,” the report stated.
“You’re not really eliminating risk completely when you underground the power lines. You’re simply trading off one type of risk for another,” a utility researcher told NPR in 2011 after Hurricane Irene wiped out power for millions on the east coast. “Yes, you’ve mitigated the risk of losing power because of a failure in the pole or a tree getting blown into the lines. But you’ve traded that risk off for outages due to storm surge or to flooding.”
Lang and Bickerman’s report estimated the cost of undergrounding power lines would range from $313,300 per mile to $2,420,000 per mile, depending on terrain and other factors. There would also be a roughly $1,500 cost per household to changing the connection for each home.
The report lays out exactly how power gets from power plants to the home, through a grid that includes transmission wires, distribution substations and the distribution lines common to residential neighborhoods.
The report does address the increased difficulty of finding problems in underground lines compared to finding problems in overhead lines:
Because of the time and difficulty of locating faults on underground distribution, the preferred design incorporates an open loop arrangement (permitting supply from two directions). Thus, when a cable fails, the faulted section is first identified and the sectionalizing point allows the faulted section to be isolated until service can be restored.
The report also claims it would mean quicker power restoration from Pepco:
However, PEPCO follows an algorithm for restoring power. It deploys crews on a “bang for your buck” approach, sending crews out to fix outages that will result in the most customers having their power restored. Consequently, because the Town would have approximately 1,000 affected households without power, PEPCO would place restoration of the Town’s power near the front of the queue. Town residents could expect to be without power for shorter durations than their neighbors who are served by overhead lines.
The Town Council is attempting to find uses for a growing surplus of $8.2 million. A proposal to provide a shuttle for residents to access downtown Bethesda was thrown out earlier this year. The Town this week decided to hire two consultants to respond to the state’s Final Environmental Impact Statement on the Purple Line. The Town has not said how much that work will cost.