> A passively actuated gripping mechanism grasps the powerline cable during landing after which a control circuit regulates the magnetic field inside a split-core current transformer to provide sufficient holding force as well as battery recharging.
When the grippers close they probably close the loops of a coil that wraps around the wire. So it's harvesting the ever changing magnetic field that arises from AC current, independent of voltage. You can still get some power from coils that aren't wrapped around the wire but are still parallel. I think that's how wireless phone chargers work.
You can also take power using a capacitor instead of an inductor, from the changing voltage (not current) in an AC line. Like when you hold a florescent tube vertical under a hi-power line, and it lights up.
This would vaporize the drone, the wire, and anyone or anything nearby, sending flaming battery and electronics shrapnel in many directions. High tension does not mess around.
There's nothing gentle about 38kV. You're not going to lower down a line and bleed off some charge. Once there's a viable path to ground, current will flow all over whatever is making that path, including the very air around it. The entire drone, wire, and the air it is inside of will turn into vaporized plasma as if hit by a bolt of lightning. And 38kV is low voltage in the high-tension world.
Creating current flows from a field is what induction is, so if you're imagining that you could just generate electricity from a field, well, that's what they're already doing. It doesn't take lowering a probe. You can just use an inductor.
That is exactly opposite of what would keep the drone safe. In a power transmission network the earth is a conductive path. Touching a phase and touching earth allows the grid to push as much power through you as your impedance and grpund contact will allow.
