Marker balls: What are the bright ‘balloons’ hanging on power lines?

You have probably seen brightly-coloured balloon-like balls on power lines and wondered what they are.

They are called overhead wire markers, aerial marker balls, transmission visibility markers or sometimes aircraft warning spheres.

Big and usually yellow, orange, white or red, these marker balls are installed in transmission lines to enhance the visibility of conductor crossings.

You will mostly find them near mountain passes, water bodies, highway and railway crossings, deep valley areas, and around airports.

Marker balls are essentially ABS plastic shells clamped around the lines or mounted directly on top of the transmission poles, which can be difficult to see from the air.

Some are even fitted with conductor marking lights or strobe lights to improve visibility in bad weather or at night.

The markers also serve as deterrents to birds, protecting them from colliding with lines and minimising the risk of interference with the power lines.

According to the Kenya Power and Lighting Company, the balls weigh around seven kilograms each.

Recently, in the wake of heavy rains experienced in most of the country, Kenya Power said the markers along the GSU to Magadi power line in Kajiado County filled with water and increased the conductor's weight so much that it interrupted power transmission.

“This saturation increased the conductor's weight so much that it reduced the allowed clearance between the 66 kV phase-to-phase conductors and ultimately caused power interruption to our customers in Magadi,” the utility company said in a social media post.

Kenya Power’s maintenance team had to drain the warning balls to prevent the conductors from sagging further.