What Are The Orange Balls On Power Lines?

We've all seen them, or maybe seen them but not really consciously noticed them. Maybe you're driving along a rural route aside a big, empty field with some mountains in the distance. The only other things in sight are those metal, daisy-chained power line towers with semi-sagging lines connecting them. Maybe there's some birds sitting on the lines, maybe not. But also, strangely enough, maybe a string of bright orange balls sits on those lines looking like beads on an abacus. What gives?

The answer to this question lives in the illustration above: You can see the bright orange balls much more easily than the thin power lines. Known by a variety of names — spherical markers to the Federal Aviation Administration (FAA), line markers, aerial markers, aviary balls, bird diverters, and more — these orange, yellow, or white balls were originally intended to prevent planes flying at low altitude from hitting power lines. You might think, "How the heck could a plane get low enough to hit a power line?," but the point is: The safer, the better. This was the conclusion reached by the FAA in the 1950's following a series of aircraft-to-power line crashes, presumably from smaller, personal planes and not big commercial jets.

Since then, spherical markers have gone through several upgrades, including a change of material from glass to plastic. They've also become the subject of conspiracy theories, with some claiming that they're surveillance devices, weather sensors, and more.  

There's a deeper rabbit hole than you might think when it comes to spherical markers on power lines. First off, all rules related to spherical markers, aerial markers, aviary balls — whatever the term — fall under the purview of the Federal Aviation Administration (FAA) -0. Although other countries basically follow the same rules, like Canada, the UK, and Ghana, doubtlessly because there needs to be a universal, global system that all pilots can follow. Secondly, the FAA's very extensive Aeronautical Information Manual (AIM) classifies power line balls as a type of unlit daytime marker rather than a lit-up nighttime marker. Furthermore, they're referred to as "obstruction lights," presumably because they obstruct the line of sight. Simply put, and as we mentioned, "Obstructions are marked/lighted to warn airmen of their presence during daytime and nighttime conditions." 

Beyond that, the color of the spheres isn't accidental. The FFA's AIM specifically calls out orange and white as the color combination for daytime markers, as opposed to flashing red lights (at a rate of 20 to 40 flashes per minute) or constant glowing red at night. There's a litany of other rules and types of markers, too, including different lights to denote high terrain, obstructions, landmarks, airports, heliports, airstrips, the direction of the airstrips, and more. Some spherical markers on lines can be lit during the day, too, called "catenary lighting," where "catenary" refers to the wire sag we talked about before. This extra layer of safety is used only for wires that are 69KV (kilovolts) or stronger.  

When we said that spherical line markers provided a deeper rabbit hole than you'd expect, we weren't kidding. To illustrate, we can look to the Federal Aviation Administration's 2016 Advisory Circular meant to clarify and update the subject of obstruction marking and lighting. It's 91 pages long. See? You'll never look at power lines the same.

Remember we mentioned the 69KV cut-off for swapping out unlit orange and white balls for day-lit catenary (sagging wire) lighting? Well, page 17 of the Advisory Circular breaks down the specifics of non-69KV spherical markers either on catenary or overhead (non-sagging) wires. Each ball has to be at least 36 inches in diameter, which is bigger than it might look from the ground. However, 20-inch balls are okay if the power line is less than 50 feet high and if the line is located within 1,500 feet of the end of an airport runway.

Other rules get even more detailed. Spherical markers need to be spaced 200 feet apart, or 30 to 50 feet at the end of runways. But if there are multiple wires that reach the highest point at a tower, then the markers need to be staggered. On and on it goes, including specifics related to the color pattern on the ball, the allowable sag of wires taking wind, temperature, and wire weight into account, the proximity of one set of markers to another, and loads of other stuff you might have never thought about. 

Now that we know some of the ins and outs of power line balls, power line ball conspiracies ought to seem just as absurd as they are. But still: There's always going to be that one guy who's like, "Dude, they're totally spying on us!" or something.

Power line ball conspiracy number one is just that: The balls that are made from hollow plastic and attached to conductive aluminum wires also somehow contain electronics that, uh ... Check your driving speed? Listen to your music selection on Spotify? Generally surveil innocent citizens for nefarious governmental purposes? You're not that important. Sorry.

Power line ball conspiracy number two is less insidious than number one, and potentially makes some sense: The balls are weights meant to keep the lines in place or prevent them from hitting each other. While it's true that power lines can "gallop" or jump around in high-speed winds, it would take some truly heavy balls to lock them in place in winds of that speed — heavy enough to be impractical, practically impossible to install, and put strain on towers or poles.

Power line ball conspiracy number three is also decidedly non-insidious, but doesn't make any sense: The balls are weather sensors. "Weather sensor," as Earth Networks says, is a terribly vague term that doesn't begin to cover all aspects of weather that require monitoring: temperature, wind speed, wind direction, precipitation, humidity, solar radiation, atmospheric pressure, humidity, etc. Power line balls don't have any sensors at all, and why would we need sensors every 200 feet, anyway?  

Finally, we come to the last piece of the power line ball puzzle: How do those things get up there, anyway? As we can watch in the video on T&D World (via YouTube) we now come to the most impressive and surprising part of the whole spherical marker saga: helicopters — at least for balls in the mountains or forests. For spherical markers easier to access, a truck with a hydraulic ladder/lift should cut it.

Either way, you need balls of, erm ... plastic to do the job. These plastic balls have a clamshell design with a little opening on either side that closes over a wire, and each ball weighs about 20 pounds. For remote power lines, an installation dude sits on a special seat attached to a helicopter's landing skids and another dude hands him a ball. Then the helicopter flies right up to the wire and the installation guy closes the clamshell over the wire and power screws the ball closed. Each ball also comes with a short, twisted wire pre-slid through its holes, which the installer winds around the power cable to cinch the marker into place. And, this happens one at a time, back and forth to fetch a new ball. It's a weird blend of brilliantly inventive and bizarrely crude. But, at least the installer wears a harness to keep safe.

So the next time you're driving down the highway and notice some power cables? Keep an eye out for the spherical markers, and remember all the regulatory minutiae and physical labor needed to get those balls into place.