Millions Left in Dark After Irma

By Barbara Gutierrez

Millions Left in Dark After Irma

By Barbara Gutierrez
With power knocked out for millions of people throughout Florida after Hurricane Irma, does putting power lines underground make sense.

Dean Jean-Pierre Bardet South Florida did not receive a direct hit from Hurricane Irma, but after the storm passed, thousands were affected by power outages that lasted from days to long, sweltering weeks. Across Florida, millions of people were impacted. In the aftermath of Irma and with the prediction that hurricanes will become more powerful in the future, many are wondering whether burying power lines underground would help prevent future outages.

University of Miami College of Engineering Dean Jean-Pierre Bardet weighs in on that issue with UM News.

What are the challenges of overhead power lines?

JPB: Although overhead power lines are typically more economical, they are susceptible to damage from wind-borne tree branches, debris and high wind, and ice-loading conditions from extreme weather. The damage can cause extended power outages that, in extreme cases, cannot be restored for days or even weeks. The cost for repairing the physical damage can be in the billions of dollars. During long outages after a catastrophe, there are also associated intangible impacts to a utility's customers, such as despair, discomfort, anxiety and helplessness. In addition to the intangible impacts, there are considerable direct economic impacts to customers resulting from lost economic activity, food spoilage, looting, etc. These tangible and intangible impacts challenge the electric utility industry's attempts to justify the installation of overhead electric distribution and transmission systems.

What are the challenges of underground power lines?

JPB: The real issue comes down to cost. It can be ten times more expensive for underground versus aerial cables. The communication and power lines can be put underground throughout Florida. The issue of our shallow water table simply increases cost (initial, maintenance, repairs, etc.). Additionally, at some point, depending on the intensity of the storm, underground cables will come to the surface and can be vulnerable during a hurricane.

Can I request that my house’s cables be put underground?

JPB: That is one of Florida Power & Light’s most frequently asked questions. According to their website, “Florida Power & Light (FPL) is willing to bury cable as stated on the FAQ page.”

For system-reliability reasons, FPL will only convert the system to underground if one full block or more is converted at the same time. FPL’s typical underground system is a “looped” system, which means power can be supplied to the same transformer from two different directions. Depending on the location, more than one block may need to be converted in order to complete this loop.

Buried power lines are protected from tree damage and wind that are common causes of outages, and so they suffer fewer weather- or vegetation-related outages. However, buried lines are more vulnerable to flooding and can still fail due to equipment issues or lightning.