Electrical transmission and distribution lines are almost everywhere. Since most of these lines carry AC power that signal tends to radiate. If it were just the 50 or 60 Hertz power frequency that were the problem it would be easy enough to filter out. Unfortunately, non-linearities on the power lines like motors, bad insulators and all the other things we connect to them tend to generate harmonics all the way through the audible range. Of course these are fairly strong and in the same band of frequencies as the weaker Natural Radio signals that we want to hear. Although some filtering may help, the best solutions is to get away from the power lines.
You should be at least a couple of miles from high-voltage transmissions lines (These are the lines with big insulators that are usually on metal towers, but occasionally poles. They carry electricity from the power generating stations to the sub-stations.) You’ll want to be a half mile or more from distribution lines (These lines carry the power from the sub-stations to homes and businesses.)