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Why We Lose Power in Very Cold Weather – Boston, Providence, Hartford

Joseph Coupal - Wednesday, February 05, 2014

The extreme cold temperatures have highlighted the vulnerability of power systems equipment in very cold weather. Snowstorms can lead to power outages in the Northeast, but cold weather alone can be enough to cause problems. Power companies ask customers to conserve energy to prevent a cold-weather outage. The average person might ask, ‘why would my power go out when it’s just cold outside?’

The electric system consists of thousands of components with lots of moving parts. These systems work best when they operate at the right temperature and moisture/humidity range they were designed for. When they are new, these devices are designed and rated to operate correctly in even extreme temperatures. But as they age—and much of our infrastructure is well beyond it’s life span—they may not operate well in extreme conditions.

Most of the time, when power system equipment is subjected to extreme cold or hot weather, all is well as long as it is not subjected to stress. When it gets too cold, hot, or moist, many of these devices operate slower, faster, or less predictably than they normally would—especially when they are called upon to perform really hard work, such as a circuit breaker or switch opening fast enough to protect the system from a short circuit caused by a tree branch falling on a line.

Anyone who has lost electricity during a storm with high winds knows that trees and other nearby items can pose a threat to power lines. But even if there is no snow and ice to send branches tumbling onto the above-ground lines, tree roots can cause problems by providing a pathway for ice to build up around lines underground. In both cases the lines are already stiffer than usual from the cold, making them more vulnerable.

Wind can also cause malfunctions in the power system by blowing tree limbs into lines or rocking trees hard enough to have the roots of the trees rub against the underground lines. Over 40% percent of outages come from trees, and another 20% come from animals.

Another issue with extreme temperatures is that consumer demand for energy is usually higher. Heat pumps are operating almost continuously, emergency heat systems and electric space heaters may be running as well. If temperature extremes are worse than forecast and/or happen faster than forecast, the utilities may not have planned for or had enough time to bring sufficient generation online to support the demand.  This can result in local or widespread overloads that may cause service to some neighborhoods to go offline automatically or switch to rotating blackouts.

In an age when more homeowners are using solar panels to generate their own electricity, bad weather usually limits the output of these devices and increases the amount of energy the utility must supply, making the problem even worse. Self-generation of electricity by customers essentially hides the true energy demand of a residence or building from the utility, making it difficult for them to know how much energy they must be able to supply instantaneously when those self-generation sources go offline or are substantially reduced.

There are many things that utilities can do to minimize the impact of extreme cold or hot weather on power system operation. Ensuring that power plants are properly insulated so that their support equipment is working.  Replacing aging infrastructure, adding additional status monitoring equipment, and improving load forecasting for given weather environments can also help.

All of these measures come at a cost—especially the replacement of aging infrastructure—and unfortunately, few are willing to see their electricity rates go up to pay for such improvements. At some point, aging infrastructure starts to fail more often and more catastrophically, resulting in more inconvenience for longer periods of time at much higher cost.

For more information on power line and infrastructure repair during extreme weather, contact ElecComm.

National Geographic

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