On 25/07/2017 19:58, Bob Wilson wrote:

There is a lot yet to be fully understood about access to the LF bands
in the US. But if you are under a HV line, they might well be using the
line for carrying control signals for the power grid. The technology,
PLC, doesn't play nicely with ham usage.

If I remember correctly from my time working on the design of
grid control systems (40 years and counting), it's known as
Pilot Protection and its loss may be the first indication of
a line going down.