When it comes to transmission and distribution grid improvements, headlines tend to use the word smart. However, following a range of natural disasters, from hurricanes to floods to wildfires, many utilities also are pursuing some decidedly less cutting-edge approaches to keeping their systems up and running during and after such events.
These infrastructure-hardening improvements are seen as increasingly important investments in the face of a rapidly changing climate. In November, the U.S. Global Change Research Program, led by the National Oceanic and Atmospheric Administration, published its “Fourth National Climate Assessment,” which reviewed current and anticipated climate change effects. Among the findings, the report states global sea levels will rise at least several inches in just the next 15 years. Daily tidal flooding is becoming an increasing problem in 25 Atlantic and Gulf Coast cities. In the Western United States and Alaska, the incidence of large forest fires also is on the rise.
Utilities see hardening as a natural complement to other measures to improve grid resilience. Resilience is meant to minimize outages and hasten system restoration. It includes broader use of smart meters, which provide utilities with instant knowledge of power outage locations. In addition, line sensors and other devices can help reroute power around damaged transformers, so issues with one piece of equipment don’t take down entire circuits.
Hardening is meant to prevent outages and minimize system damage by addressing physical vulnerabilities. It involves examining ways the wires, poles and other infrastructure can better survive high winds, floods and wildfires. It can be expensive, but in the aftermath of several recent storms, the investments have proved to be worth their cost.
Stronger poles and wires
In 2005, Hurricane Wilma damaged more than 12,400 of Florida Power & Light’s power-line poles. As a result, the utility began a $3 billion program to harden lines throughout its service territory. In areas most vulnerable to hurricanes, concrete poles have replaced wooden units, and throughout its system, the utility is working to shorten the distance between poles. While these moves haven’t eliminated storm-related outages, fewer poles are going down. For instance, 2017’s Hurricane Irma knocked out power to 90 percent of the utility’s customers, but with only a total of 4,600 poles going down, recovery time was shorter than past storms of similar magnitude.
Southern California Edison (SCE) is upping its hardening efforts in the wake of 2017 and 2018 wildfires tied to the company’s equipment. Among the risks the utility is hoping to reduce are the overheating and sparking from overhead lines that can occur during the hot, dry fire season. Replacing bare overhead lines with insulated conductors is a major element in the fire-mitigation plan SCE filed with the California Public Utilities Commission in February 2019. According to that filing, the utility has proposed almost 600 miles of line for replacement by the end of 2020. The utility also hopes to replace an additional 3,400 miles of line between 2021 and 2025 and will request approval for that effort in an upcoming general rate case.
Burying lines underground—“undergrounding” in utility jargon—is another option some utilities are taking to reduce the risks high wind and fires can pose. Pepco, the utility serving Washington, D.C., received approval in March 2019 to begin the first phase of a project to move some of its distribution lines underground. Starting with six of the system’s lines, the larger plan envisions burying up to 30 of the system’s most vulnerable lines in the next six to eight years. The strategy also is part of plans both SCE and Pacific Gas & Electric have developed to reduce wildfire risks in especially vulnerable wilderness areas.
However, undergrounding can pose its own problems. Burying lines is expensive and repairing buried lines is more expensive still. Houston learned this lesson following Hurricane Harvey’s devastating flooding in 2017. The city’s underground distribution system had kept downtown lights on after 2008’s Hurricane Ike put most of the rest of the city in the dark, but underground vaults flooded during Harvey, creating widespread outages and the need for costly repairs.
Stronger and higher substations
Substation flooding vulnerability became abundantly clear in the aftermath of 2012’s Hurricane Sandy. That storm knocked out power to much of New Jersey and New York, including almost all of Manhattan. Sandy proved the need for greater substation protection In addition to giving an enormous boost to the then-nascent microgrid industry.
New York utility Con Ed invested heavily in fortifying perimeter walls and raising equipment as part of its $1 billion investment to strengthen its system against future storms. Similarly, New Jersey’s Public Service Electric and Gas has proposed a $428 million effort to raise and harden 14 substations and eliminate two substations in flood-prone locations as part of a $2.5 billion rate case related to improving its system’s reliability and resilience.