On Oct. 29, 2012, Hurricane Sandy made landfall in the Northeast United States. Although Sandy was only a Category 1, it was the largest Atlantic hurricane on record with winds spanning 1,100 miles (1,770 km). Sandy affected the entire East Coast, with particularly extensive damage in New Jersey and New York. Sandy caused power interruptions to more than 6 million people, with more than 1 million still out of power a week after landfall.
The public is understandably frustrated whenever an extreme weather event results in power restoration times of a week or more. In these situations, it is common for the media and politicians to criticize utilities for old and unmaintained infrastructure, poor storm preparation, inefficient restoration processes and inadequate communication with a variety of stakeholders. Valid or not, these attacks put pressure on utilities to develop action plans so things will be better when the next storm hits.
Alternatives to Consider
When considering alternatives for improving storm performance, it is natural to think about historical approaches used to improve normal-weather and minor-storm reliability. Unfortunately, these are not always effective. Much of the utility system was not designed for extreme weather and different rules often apply. It reminds me of a classic “Seinfeld” episode where George Costanza turns his life around by doing the opposite of his instincts. For a utility to turn its storm performance around, it must recognize that the effects of many improvement initiatives are counterintuitive.
Here are four examples when initial instincts may not translate into the best storm-improvement approach:
Put it underground — not!
After a major storm, it is a safe bet utilities will be urged to put all of their lines underground. Overhead-to-underground conversion has been examined dozens of times by states, cities, professional organizations and consultants. The answer is always the same. Unless there are special circumstances, overhead-to-underground conversion is far too expensive to justify the benefits. Worse, underground systems result in less reliability near coastal areas subject to storm surges. Underground systems near the coast are less reliable during major storms, not more.
Trim the trees — not!
Utilities are often scolded after a major storm because they are behind on their tree-pruning cycle. Cycle pruning focuses on conductor clearances, which is important for clear-weather reliability but less so for major storms. Most tree damage during storms results from large branches and entire trees falling into wires, often from outside of the right-of-way. To improve storm performance, vegetation management needs to focus on removing dead and diseased trees, removing tall trees (and perhaps replacing them with short trees), and removing all branches that overhang the conductors.
Replace wood poles — not!
After seeing broken and leaning poles, utilities often are asked why they do not switch to stronger poles made out of steel, concrete or composites. In fact, the average strength of a wood pole for a given grade of construction is higher than these alternatives. New wood poles are one-third stronger to allow for degradation, and have a higher safety factor to compensate for higher-strength variability. Sometimes it makes sense to use non-wood poles, such as to reduce weight. However, a strong storm will snap a non-wood pole just as easily as a wood pole of the same strength.
Replace small wire — not!
Old copper wire does not stand much of a chance against falling trees, and nobody likes to see broken conductor on the ground. Consequently, it can be tempting to proactively replace small conductor with something larger and stronger. Although stronger conductors are less likely to break, they often can cause a bigger problem than they solve. When trees fall into large conductors, the full force is transferred to nearby utility poles, resulting in broken hardware, crossarms and often the pole itself. Needless to say, it is easier to splice a broken conductor than replace a broken pole. Some utilities have begun using wire ties that will fail before the conductor breaks or structural damage occurs. When the tie fails, the conductor simply drops to the ground and can be rehung during restoration.
When it comes to storm strategies, initial instincts may not always be wrong. However, most rules of thumb and accepted approaches are based on non-storm situations and may not translate well to storm situations. Storm performance requires different thinking, and considering counterintuitive outcomes will ensure that all actions result in the desired benefits.
Imagine taking the stand at post-storm hearings. Instead of defending mediocre results with “everybody does it this way,” you can tout superior results because “most do it this way, but we do it the right way.”
Richard Brown is the vice president of power networks for WorleyParsons in the United States. He is also a fellow of the IEEE.