- High winds blowing trees and branches onto power lines
- Vehicles striking and breaking utility poles
- High winds breaking utility poles
- High winds blowing lines into trees
- Cold-load pick-up problems
- Animals such as birds, snakes, and squirrels climbing poles and contacting both the pole and the power line
- Snow and ice build-up that causes power lines to break or touch tree branches
- Overloaded lines
- Problems at substations
