If it helps...here's a story...
A customer of mine had assorted power quality problems. I worked in the building for over a year, doing other jobs, when one Thanksgiving half the surge supressors fried, and the local UPS's kicked in. (Walking into the place was like entering a cricket convention.... chirp...chirp...).
While checking the assorted panels, trying to discover the cause, my partner was smart enough to back away, relax, and look at it all from a new perspective. Something just didn't seem right. After much headscratching, he noticed the "obvious;" ther was NO neutral wire! That's right, the panel was fed from a panel next to it, and the neutral bus was bonded to the case. 20 years of rust and vibration had finally loosened a locknut.
We ran a proper neutral, and a ground wire, removed that green screw... and the building now had amazingly "clean" power!
So- the 'moral' is... before getting into all sorts of fancy theories, check your basics. Just maybe, someone got careless....
