And, depending on the weather, if it's foggy, or high humidity for instance, there will be some corona forming around where the connectors are at each of the poles where the cable stand-off's are. This can cause inteference because it radiates as a radio signal would. If you go near a power line in high humidity or foggy conditions, you can hear it..sounds like a sizzle.

I was on a LORAN "C" transmitting station in the Pacific. We put out about 2.3 million watts of RF energy. In the morning, when the humidity was the highest, we could see a blue light or "corona ring" form at each of the 16 "TLE's" or Top Loaded Elements.

It's everywhere when high voltage is concerned.

CGr.