50 Hz is too low a frequency to be a problem i think.
Also how would you get higher than 10 m?
If anything they’ll just block some part of the sky a little bit.
But they should have enough air in between to allow signals through.
If you have other buildings or trees around you, placing the antenna higher than them will definitely help.
Be sure to check this thread out: What is the Maximum Range I can Get?
Seeing the horizon from where the antenna is, that’s what you want.
Très Haute Tension THT (French) = Extra High Voltage EHV (English)
Due to safety requirements, the minimum distance to ground at lowest point of conductor of a EHV line should be greater than about 9m. This is the lowest point on the sag. At supports, it is much higher (about 20m), as the wire is a catanary due to long span (250m ~ 400m between towers)
I have my Antenna on the top of my roof (it’s a house), i used a 1090 filter and an Amplificator (this one : the Uptronic 1090MHz ADS-B Ceramic Filtered Preamp).
In fact I asked myself this question because I noticed that in the axis of the high voltage lines, I capture less well, while it’s this axis which is totally cleared (fields) and without any obstacle apart from the power lines.
You can get problems if an insulator on the power line is failing and starting to arc over. This acts as a spark transmitter radiating wide band interference.
It will affect lower frequencies more than high frequencies and I would think it is unlikely to cause a problem with ADSB. Usually you can hear an insulator that is failing especially if it is misty. Power companies are usually pretty good (in the UK at least) at replacing failing insulators if reported. They don’t want them to fail catastrophically and then have a power outage. Power outages cost them money in fines from the regulators.