Well, those balls are visibility markers. They weigh about 17 pounds each, and you will often find them near mountain passes, in deep valley areas, near major freeway crossings and around airports. Visibility markers are placed on power lines to make the conductor crossings visible to aircraft pilots.

Why are the balls on power lines different colors?

The coloured balls on overhead electricity cables act as visual warnings for low flying aircraft. They are most often used when cables cross major highways or deep gullies or valleys. To aid visibility, the colours are chosen to provide the greatest possible contrast with the background terrain.

What is the ball on a powerline for?

The main purpose of the marker balls is so that helicopters and low-flying planes don't hit electrical wires. They are an extra precaution since anything that flies isn't supposed to fly lower than the electrical towers.