How Does That Work?

Ice has weighty effect on power lines

Lightning, thunderstorms and tornadoes aren’t the only threats to OPPD’s electrical infrastructure. In the winter, ice and wind can be just as dangerous and damaging to power lines, leading to disruptions in service. 

Each drop of freezing rain adds weight to power lines and their structures, also increasing pressure and strain. 

A blizzard that raged for eight hours through eastern Nebraska on March 19, 2025, illustrated just how damaging ice can be. Over the course of the storm, heavy ice – 3-5 inches thick in some areas – built up on power lines, pulling down lines and power poles and knocking out power to 106,000 customers. 

Record-setting damage

The storm was the fifth-largest in OPPD’s history as measured by the number of outages. But it was the biggest by far in terms of damage to the utility’s infrastructure. 

OPPD replaced 1,524 distribution poles and 71 transmission poles during the restoration. By contrast, during OPPD’s largest-ever outage in July 2024, workers replaced 433 poles after hurricane-force winds devastated the Omaha metro and surrounding areas.  

To better understand just how damaging ice on wires can be, check out the infographic below. It explains in more detail the stress ice puts on power lines and infrastructure.  

Designing for bad weather

OPPD uses guidelines in the National Electrical Safety Code (NESC) and various weather condition scenarios to determine the design criteria for ice load on overhead power lines.

Distribution lines are designed to handle up to 1/2-inch of ice and 40-mph winds. New OPPD transmission lines are designed to handle 1 1/4 inches of ice with no wind, or winds of up to 90 miles-per-hour (equivalent to a weak EF1 tornado) with no ice.

Galloping

As ice accumulates on power lines, it forms a teardrop shape.

When wind blows, wires can start to move up and down in an oscillating motion. In essence, the wires encased in ice act like an aerodynamic airplane wing. This is known as “galloping.”

Galloping can cause wires to eventually touch, resulting in a fault or subsequent power outage. The increased movement can also cause cross-arms to break, bringing lines to the ground.

To reduce galloping and its dangers, you may see twisted wire or metal pieces attached to certain power lines. The video below shows how that works.