Hurricane Sandy has now made landfall along the central coast of New Jersey, and utility companies up and down the U.S. Eastern seaboard are scrambling to keep the lights on. Over the weekend, I spoke with Nicholas Abi-Samra, a 35-year veteran of the power industry and an expert on the effects of extreme weather on the electricity grid, to see how companies have been gearing up for this massive storm. Abi-Samra, chair of the IEEE Power & Energy Society’s San Diego chapter, is vice president of asset management at Quanta Technology, an energy consulting company headquartered in Raleigh, N.C.
Spectrum: From a grid operator’s perspective, what’s the biggest concern right now?
Nicholas Abi-Samra: This storm is packing three threats: high wind (even gale force), heavy rain, and high surges. High winds—and specifically their ability to bring down trees and produce airborne debris—are a threat to transmission and distribution lines and also to electricity poles. Studies show that tree-related failures increase exponentially when wind speeds are over 60 mph [100 km/h]. [At 9:00pm EDT on 29 October, Sandy had maximum sustained winds of 80 mph or 130 km/h.] Wind may cause conductors to slap together and short out. The fact that trees have not lost their leaves yet in a number of areas in the predicted path of the storm is a big concern, because they’re much heavier than bare branches, and so their impact on a power line or pole will be much greater. When you add rain, the leaves and branches become even heavier. Wind may blow tree limbs or entire trees into or across lines, either knocking them down and breaking them, or knocking them into each other and causing faults and interruption of service.
In the past 10 years, most utilities have made great strides in vegetation management—removing dead or diseased trees, so-called “hazard trees”—along their right-of-ways [the land immediately surrounding power lines and poles]. But in high wind situations, risk from airborne debris from trees outside the right-of-way (both “hazard” trees and normal-looking trees) can exceed the risk of trees within the right-of-way by a factor of 3 or even 4 to 1. This kind of secondary damage is really the prevalent cause of damage in many storms.
The expected storm surge is phenomenal, well above Hurricane Irene at the highest. And the storm’s coverage is way more extensive, as far west as Pittsburgh, so even lakes will be hit with high waves. Generating plants downstream from reservoirs or dams could be vulnerable. Flooding should be of concern to operators of coastal energy facilities, such as oil refineries and nuclear power plants. It’s not just power plants that might be affected, but also industrial facilities and of course residential areas.
Spectrum: What kinds of precautions do grid operators take at such times?
Nicholas Abi-Samra: Many utilities will take preemptive steps like shutting down some of their energy assets so that they can contain the damage. They will suspend routine and scheduled maintenance work and restore essential equipment that can be put back in service. They’ll move to storm operation mode, and they will arrange an off-site emergency communications control center just outside the storm area, in case it becomes too dangerous to remain on site. They’ll increase real and reactive reserves, have diesel-driven emergency generators at critical sites, and have emergency generators available for the pumps (and other important loads). They’ll also prepare for storm-related flooding, for example, by putting out sandbags.
For generator stations that are vulnerable to flood or sea-level surge, they’ll reduce the power output and be prepared to do a controlled shutdown of generating units ahead of the storm surge, to minimize damage and downtime. They’ll also be prepared to operate the units as an “island,” disconnecting from the rest of the grid, if all transmission is lost.
And they’ll take general precautions, like emptying and then securing dumpsters around substations, topping off the fuel tanks in utility vehicles, and making sure workers have spare batteries for their cell phones, since recharging may not be possible.
You really can’t do much about hardening the system at this point in the storm—and you can never harden 100 percent against extreme weather. Restoration is the important thing now, how to patch the system back together and minimize the outages resulting from Sandy. The affected utilities are getting assistance from other utilities. I know that employees from some of the west coast utilities, including here in San Diego, are deploying to the east. Our company does storm assistance, and we were contacted by some utilities as early as last week. And workers are coming in from neighboring states with trucks and tools, which is great. From past events like Hurricane Katrina, we know that mutual assistance is the king in terms of getting back on line. Otherwise you’re talking about outages that can last for weeks.
After Sandy, each utility will have to analyze the performance of its assets and how they fared.
Spectrum: You written about the dangers of substation flooding. Why is that a big concern and why is it so costly and difficult to recover from that kind of event?
Nicholas Abi-Samra: A power substation is basically a place where you get the power from the transmission grid and distribute it to the distribution feeders and hence the end users. You have a number of components all concentrated in the same place: power transformers, breakers, capacitors, and so on. The breaker (and its associated relays) is a form of protection, designed to break fault current—the large volume of current that flows when a fault is detected on the system. It also has a secondary function, allowing the system operator to switch circuits in and out. You also have a lot of lead-acid batteries on site. And there’s the control house, which is the brains of the substation, with a lot of electronic and computer equipment. So a substation is a concentration of equipment that’s essential for the operation of the grid. Floods may inundate substations, and some utilities may be forced to shut them down to prevent major damage to the equipment, and therefore accelerate the restoration after the storm.
Trying to get the substation back in service is a very lengthy and laborious process, much more so than replacing a broken pole after a wind storm. And if you lose a number of stations at the same time, that’s obviously much worse.
In a substation, even minute quantities of moisture and dirt contamination can render some electric equipment inoperable or lead to catastrophic failure. After a flood, large amounts of water and mud can remain trapped, making repair a sizable task and lengthening the restoration task. For example, if a breaker is submerged for a long time, it’s necessary to completely disassemble the mechanism and clean each part. That means all the bearings, pins, cylinders, rings, latches, and triggers.
Repairing a transformer can also be a lengthy and expensive process. It takes anywhere from 18 months to a couple years to get a new transformer. This is why in an event like this some utilities try to minimize the number of energized transformers and thus decrease the risk of a damaging close-in short circuit (or fault) caused by flying debris.
Spectrum: Are grid operators better prepared for severe storms than they were, say, five years ago?
Nicholas Abi-Samra: Yes, they are. Today we see better communication between the utilities and their work crews and customers. A number of utilities are using storm-tracking software. And they have much better situational awareness of where the outages are and what needs to be done to bring things back online. In the past, you’d have to call the utility and report a problem; now it’s automated. And utilities are much better at taking the lessons learned from past storms and figuring out how to restore the system as quickly as possible.
Spectrum: How can smart grid technology help in preventing or recovering from storm power outages?
Nicholas Abi-Samra: A smart grid introduces automation so that you don’t need somebody to go and close a switch or breaker. And if you have an area that has a fault, the system is designed to isolate that area and then restore power automatically. You may have heard the term “self-healing”: that means the system can reconfigure itself to deal with outages. At the moment, that works best if you just have a limited event, like the failure of just one feeder—it can automatically switch to another feeder. But when the problem is larger, it won’t be as effective. The smart grid will however speed up system restoration.
There are logical limits. Remember that the smart grid is not replacing the existing electricity infrastructure, and in many cases [in the United States] those systems are well beyond their expected service life. You have some utility poles that are more than 80 years old, for example. A smart grid cannot fix an old transformer or a utility pole that has been there for 80 or 90 years. And as electrical equipment and systems get older, they deteriorate, leading to higher failure rates and making them unable to perform as needed during periods of high stress, such as extreme events like Sandy.
PHOTO: FirstEnergy Corp.
UPDATE: This post was revised at 10:45pm on 29 October 2012.