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Q & A: Aerial markers on power lines

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Why are red spheres fixed with wires of high voltage electricity coming from the main power station?
- Suleiman (age 36)
Directorate of Education, Palestine
Here's an idea of what you may have been seeing: The power company puts big red plastic balls on their high-voltage transmission lines in order to keep airplanes from running into them. They usually need these on long stretches between the support towers, in places where the power lines cross a canyon or a ravine. Power lines are thin and may be difficult to see by even low-flying aircraft, and we donít want airplanes colliding with them. The big marker balls are there to warn airplanes of the power lines.

Alternatively, you could be talking about the transformers in a substation. These often have big insulators on top, separating the high-voltage lines from metal that is electrically connected to the ground (say, the metal side of the transformer). They also serve as lightning arrestors, since outside power lines sometimes get hit by lightning, and it is important that the transformers survive these strikes as much as possible. Usually these insulators look like stacks of disks, but I seem to remember some ball-like objects there too.


(republished on 07/13/06)

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