Restoration in extreme cold
Different conditions, different process
Entergy uses a methodical and calculated process in bringing customers back online after an outage in very cold weather, regardless of whether the initial cause of the outage was specifically weather-related.
Careful work due to peak load
In extremely cold conditions, what our customers may notice is that if an outage occurs, regardless of the cause, restoration follows a different process.
- Rather than simply energizing an entire power line all at once, we must bring customers back online one section at a time to avoid damage to our system and make the situation worse.
- The reason for the different process involves how much power is being used. During temperature extremes, hot or cold, customers tend to use a lot of electricity, either keeping the heat on or air conditioning or other devices running. Electric heaters in particular will often run continuously and not power off and on, creating too much constant power demand.
- Homes that have both electric heat and air conditioning along with other electrical appliances use more power than a comparable one using just air conditioning (like in the summer). And when power is disrupted during winter, many customers leave their heating systems and appliances turned on, creating too much energy demand all at once when we try to restore power.
- When an outage occurs, restoring all the customers on a given feeder (power conductor line) has the potential to create large, instantaneous power demands. And that power demand could be higher than the built-in protective devices on a line can handle, meaning equipment could trip offline or cause more damage.
- We have devices in place that are designed to protect our system during times of normal, day-to-day operations and power demand and most weather and other contingencies. But during weather extremes, we must change our processes to make sure we protect our system and also do the right thing by our customers. That means restoring power in a way that best ensures safety and reliability for them as well as our employees.
- During extreme cold weather conditions, these specific restoration challenges are experienced not just by Entergy, but throughout the industry and the country.
Ice causes hazards above us
The most dangerous part of a storm is often just after it has passed. Extreme cold temperatures make many materials like wood and metal brittle, and the extra weight of snow and ice accumulation on power lines and trees can make them snap. Ice is particularly harmful to electrical lines and can increase the weight of branches by 30 times, so be sure to stay clear of falling ice or debris from above and keep your distance from working crews. More on extreme cold safety can be found here.
- 1/8” of ice accumulation can cause small limbs and lines to become coated and may cause outages due to breaking limbs hanging over power lines.
- 1/4” of ice accumulation can worsen conditions. Younger evergreen trees will start to become so heavy that they may lean onto distribution lines, causing more outages.
- 1/2” of ice accumulation on power lines can add 500 pounds of extra weight.
A little ice can impact transmission lines in a big way
It’s called galloping
When cold, icy weather strikes, our transmission lines can experience galloping, which is the slow, “skipping rope” motion of power lines. Galloping occurs when rain freezes to the power lines, and then steady winds cause adjacent lines to move and sometimes contact one another. This can cause an outage.
Some compare this phenomenon to an airplane, where the ice freezes to the wire, creating a wing-type effect and making the lines move up and down. Wind blows across the conductor, which creates lift. With the right conditions, this will cause the lines to gallop. Minor galloping generally has no negative effect, but moderate galloping can cause adjacent conductors to contact and cause a fault. If severe enough the conductor can cause serious structural damage.
While we can’t prevent lines from galloping, there are a number of ways our engineers try to prevent the impact of galloping lines. This includes controlling the tension in the conductor during the initial installation and installing dampers at certain locations on the line. Selecting the damper location is normally done using software that considers conductor size, span lengths and tension.
Other helpful links
- Learn more about how we restore.
- Learn more about extreme winter weather preparation.
- The impact of ice on transmission lines.
- Get money-saving tips on energy usage.
- See information about your personal energy usage.
- Get the latest Entergy storm updates.
Call 1-800-9OUTAGE (1-800-968-8243) to report downed power lines