About every eight poles, there was one that had this arrangement of wires- one connected to each power leg, then an insulator, then all connected to (ground?):
Could it be a common lightning arrestor?
Can’t quite make them out from your photo…
I think that’s possible.
Sorry about the photo, we were zooming down the highway…
I’ve never seen that, but it seems like a logical setup when there isn’t a static line running above all the other conductors.
Basically for lightning protection. Seems the term of art is line surge arrestor. They can protect from other faults, but lightning is the main problem. They can be complicated - internally containing a MOV to adsorb energy, and an external spark gap to let serious overvoltages get to ground. And also, in the event they fail as a short circuit, a small explosive charge that disconnects the ground connection. Not sure if the smaller one have all of this. They appear on the really big transmission lines as well, and really need to behave safely.
The key idea seems to prevent lightning induced surges from getting far enough that they trip out the system. Lightning can lead to saturation of transformers, which doesn’t play nice with their operation. There is a lot of protection in the grids to avoid damage. But you similarly want to try to avoid the problem in the first place, so surge arrestors.
Excellent. The very last photo on this page appears to be basically the same thing, though wired slightly differently.