Aviation Ball Marker on Overhead Line

[wbd]

Hello,
We are looking at adding some of the orange aviation ball markers on an overhead line that we own, primarily to improve visibility for equipment that may work in that area. One concern that was raised was the additional loading on the line. I have looked thru the NESC C2 and could not find any references to aviation ball markers. Is there any design considerations or is it such a small item that it is inconsequential?
Thank you

 

[stevenal]

Look at 251B. Markers would be "equipment that it supports." The additional cross sectional area to the wind or surface area to ice may not be inconsequential even if the dry weight is.

 

[bacon4life]

They can definitely have an impact. We have one long span vertical crossing where only the top wire has marker balls. The added weight from the marker balls reduced the top phase to middle phase clearance by a couple of feet.

If you need vibration dampeners or armor rod at the marker ball locations, be sure to include the weight of those as well.

 

[lookintomyeyes]

I'm not in the USA so I can't comment on NESC, but yes, the effect of wind and/or ice can affect the sag on the conductor.
As well, they are essentially a concentrated point load on the conductor, so armor rods are often added to provide mechanical strength/protection.
Your local aviation standards likely specify the size and spacing of the markers.

I've heard of some utilities using aerial marker CONES rather than spheres as some (older? bolted?) designs were prone to coming apart, leaving only half a cone in the air.

You may want to consider/checking loads created by maintenance people in the future. Eg, conductor carts are often used by maintenance people to inspect the markers over the waterway. Is your conductor in good condition, are your structure supports and hardware sufficient to support that load? If not, can/do you perform helicopter maintenance?