Objects seen spaced at regular intervals decorating the wires athwart the power line:

(1) Above power lines; Large ball on ground wire

(2) Below power lines; flat, squarish, metallic, vented by slots; half fold along diagonal axis, to accommodate cable, possibly phone. End-on has triangular aspect

While the ones on top are for the benefit of air traffic, one can only speculate on the ones below; as it's hard to feature a light-plane pilot dumb enough to try swooping below

But conicidentally, do you know any nicknames for these objects

dalehileman