What Are the Colored Aerial Marker Balls on Power Lines For?

Electrical Technology

What Are Marker Balls and Why Are They Used on Power Lines?

Almost all of us have seen colored balls (usually orange, yellow, red, or white) on transmission and distribution power lines. Ever wondered what they are and why they’re used? Let’s discuss in detail – no need to overthink it, as there’s no rocket science involved.

What are the Colored Aerial Marker Balls on Power Lines For

What are Those Balls?

These are called “Marker Balls,” also known as “Aerial Visibility Marker Balls.” They typically weigh around 7.7 kg (17 pounds) each. The most commonly used color is “International Danger Orange” (British Standard 381C-1964-No. 557 or U.S. Engineer’s Spec. 595-121197). However, depending on the surroundings and visibility needs, yellow, red, or white balls may also be used, as recommended by the Federal Aviation Administration (FAA).

The diameter of marker balls used on power lines and less extensive catenary wires (those crossing rivers, lakes, canyons, etc.) below 15 meters (50 feet) should be at least 51 cm (20 inches). For more extensive catenary wires and power lines, the diameter should be no less than 91 cm (36 inches).What are Marker Balls and Why They are used for on Power Lines

What are They Used For?

Aerial marker balls are used for safety. They help save lives and protect infrastructure by making guy wires and power lines (transmission, distribution, and communication lines) visible to low-flying helicopters, aircraft, and planes, as required by the Federal Aviation Administration (FAA).

Some marker balls glow due to the electric field surrounding the power lines. In some cases, flashing marker balls are installed on transmission poles, towers, and power lines for increased visibility.

Power lines and sky wires can become nearly invisible against the terrain, as the human eye loses visual acuity when looking slightly off-center. Other factors like lighting conditions and dirty windscreens further hinder pilots’ ability to notice the lines.

Red Balls on Power Lines

This is precisely why marker balls are installed, particularly on overhead cables and wires crossing major highways, freeways, valleys, deep gullies, and areas near airports where aircraft tend to fly lower during landing.

Next time you see those colored balls on power lines, remember that they’re there for safety, protecting lives, aircraft, and the valuable electrical power system infrastructure.

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