BDH, I think the power company might fix your [problem since you have PS Audio monitoring your line. That gives them data (proof) that you do have a problem. But,finding that pesky motor is the main issue. It might just be as simple as changing out the motor for a new one which should not do that to your power lines. I worked with 440 volt AC power supplies for 300 volt motors (DC) and the excess power from when the motor became a generator was fed back into the AC lines. It did not affect the AC lines in our building at all and our units slammed the lines with excess power quite often. It was all designed and made to take it with no problems. So, I think something is not right causing that spike and when you can figure it out, it will be a fairly easy fix. Good Luck. I hope Duke takes care of you as I have Duke here in Florida too.
PS Audio support made it clear that these things are usually very difficult to run down because while it could be in our house, it just as easily could be in a neighbors house. Also, while they said that it could be a motor, they also said it could be a simple as a bad dimmer. I suppose I could go around swapping out our dimmers, I don't really want to be swapping out motors... especially if it turns out to be from something down the street.
Does anyone know what these DC spikes do to electronics over time? If Duke Energy either doesn't help, OR they can't find/fix the issue, I guess I can put a DC blocker on the feed to my P20 (the only piece of equipment that seems to be having a problem with these spikes, at least that I am 'aware of'). But what about all the other electronics in the house... do I need to put DC blockers on my mono blocks, my rear subs, and my projector (the only devices not served by my P20 in the main system)... or how about the upstairs system, or even our Macs? Also, since my limited data shows the spikes hitting (mostly) in the middle of the night when our systems are off, should I even care about these spikes (other than messing with my P20 that is)? If I make the move to tube equipment in the future, would tubes be more (or less susceptible to these spikes)?
All I really want to do is bring the best music possible to our home and I am starting to feel like I need to go back and get an engineering degree!