The big orange balls found on some high power lines are designed to alert lower flying aircraft of the presence of these lines. Typically, these warning balls often are fashioned out of aluminum. In some cases, they are red in color.
The big orange balls placed on high power lines serve three primary objectives. First, the contribute to aviation safety by alerting aircraft (and their crews and passengers) of these potential hazards. Second, these warning balls protect expensive high power lines and related equipment from damage. Finally, these balls work to protect the power supply to a neighborhood or community.