Some notes on AC power line conditions.
 

While intended more for the Audiophile, this PDF is still worth
reading to gain an appreciation
of how AC power reaches our homes, and what can happen to degrade it
on the way.

The data on harmonics is very revealing.

http://www.smartdev.com/pdf/ac_power.pdf

FWIW, in a conversation with the chief engineer of Touch Stone Energy,
I found out that for most
residential areas, the primary feeding the "pole pig", or pole mounted
transformer, or the transformer
mounted on a concrete pedestal is either 7.2KV or 14.4KV. Voltages can
vary by 5 to 10%.

These voltages are low enough so that Corona Discharge is seldom an
issue.

Terry