Hi there
My first post on this forum, however I read many of the topics discussed.
I have been in the electrical profession for many years and I have a good understanding of the quirks of HV power etc.
HV power lines "normally" do not interfere with quads, however if you're the unlucky person to fly around HV lines that have dirty or cracked insulators and they are normally identified by a buzzing sound or crackling and sometimes no indicators at all.
The HV phase will track and create a current path to the structure earthing. The arcing emits a plethora of high frequency radio signals due to the tracking and may interfere or render your quad uncontrollable. A good experiment for those who wish to know how strong the electric fields around HV lines is to take a 4 foot fluorescent tube and stand under these power lines, obviously far away from the actual conductor cables, and wave the fluorescent around, in most cases the fluorescent tube will start to glow and sometimes they light up!
My advice - Stay clear of power lines.