John Smith wrote:
"Better question might be, when a run of conductor just happens to be
resonant / impedance matched at 60 Hz, why isn`t massive amounts of 60
Hz ELF being radiated?"

The hot and neutral conductors are too close together to allow energy to
stray too far.

Certain antennas exhibit "power gain". Terman defines power gain as:
"the ratio of power that must be radiated by the comparison (reference)
antenna to develop a particular field strength in the direction of
maximum radiation to the power that must be radiated by the directional
antenna to obtain the same field strength in the same direction."

The definition implies more power required by the less directional
(reference) antenna to equal the signal produced by the directional
antenna which is said to have the "power gain" in a certain direction.

The constant is the power fed to both antennas, gain and reference. The
gain antenna is sending more of its power towards the target and not
wasting so much in undesired directions. If it wasted power like the
less directional antenna, it would eat more power in total to have a
power gain ? on its target. In fact, the directional antenna is just
making more effective use of the energy it receives, not sending out
opposing streams of coincident energy.

Best regards, Richard Harrison, KB5WZI