In short, this noise is due to a phenomenon called corona discharge, an energy discharge within the power lines themselves. When the surface of the conductor has a greater electric field strength than the surrounding air, this buzzing is more than likely to happen. Essentially, the power lines or associated hardware generate unwanted radio signals that override or compete with desired radio signals. Power-line noise can impact radio and TV reception, including cable TV head-end pick-up and Internet service. An overloaded circuit can. Virtually all power-line noise, originating from utility company equipment, is caused by a spark or arcing across some power-line related hardware. A breakdown and ionization of air occurs, and current flows between two conductors in a gap. The gap may be caused by broken or loose hardware such as. The audible noise you hear from high-voltage cables occurs because of the energy that is being discharged.
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