Comment by KaiserPro

I would guess that its just a coil thats near the cable. however I can't imagine its actually that much power, as the field isn't that strong.

_but_ at 33kv, you start to get corona discharge, which gives you a potential difference, so that might be the mechanism they get power.

(thats a wild guess. )

Edit I did some more digging, induction appears to be magnetic induction, long cables do produce a magnetic field, but not that much (unless you put it in a coil)

Capacitive coupling is much more effective at high voltage.