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

What are Marker Balls and Why They are used for on Power Lines?

Almost all of us have seen those colored (mostly orange, yellow, red or white) balls on transmission and distribution power lines. If you ever wonder what they are and why it is used for? Let discuss in detail and don’t spoil the post as there is no rocket science everywhere.

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What are those Balls?

They are called “Marker Balls” and known as “Aerial Visibility Marker Balls”. They weight about 7.7kg (17 Pounds) each. Mostly used color for marker ball is “International Danger Orange” ( British STD. 381C-1964-No. 557 or U.S. Engineer’s Spec. 595-121197) however, yellow, red or white are also can be used in specific situation depending on the surrounding for clear visibility recommended by FFA (Federal Aviation Administration).

The diameter of the marker balls used on power lines and less extensive catenary wires (those wires crossing a river, lake, canyon etc) ) below 15m (50 feet) should not be less than 51cm (20 inch). For extensive catenary wires and power lines, the size should not less than 91cm (36 Inches).

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What they are used for?

Aerial marker Balls are used for safety. It saves lives and infrastructure by making guy wire and power lines (Transmission, distribution and communication lines) visible to the low flying helicopters, aircraft and plans according to the Federal Aviation Administration(FFA ).

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

The power lines conductors and skyline become almost invisible against the terrain as the human eye start to loos its visual acuity at just a few degrees off dead center. Other reasons to unable to notice the  power lines for pilots are light condition and dirty windscreens etc.

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That is the exact reason why marker balls are installed on the power lines especially in case of the overhead cables and wires crossing the major highways, freeways, valleys, deep gullies and mostly fly low while landing at airports.

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Next time, when you see those colored balls on power lines, remember that they are used for safety to save lives and aircraft and expensive electrical power system network and infrastructure.

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