Try plugging your rig into the socket/outlet directly. You may have a bad surge protector or it's designed to shut off at specific loads we have no idea about.
I had the exact same problem a few months back. I tried changing everything from drivers, to risers, to cables, to PSUs. Turns out that the problem was that my extension cord / surge protector for some reason automatically turns itself of. Never would have noticed it until i sat beside it for an hour and saw it right before my eyes, the surge protector's switch simply turned itself off.
I've since them switched to an extension cord without any switches at all. Been running a stable rig ever since.
I suspect the surge protector thing could be the culprit too. It's a slightly beefier version of just a box standard one. The tricky thing is that even though the rig is beside a 2-outlet socket on the wall, space is tricky. I have a powerline plug for the network cable that won't work on a powerbar, and the next nearest outlet is quite a bit away. I think you might be right though that the one powerbar is essentially getting overloaded. I'll test it tomorrow.
using a 20A 2000W surge protector.
You mean simple extension with MOV (varistor) iniside or proper one? What are psu's model and how does they connected?
I think it's the first option. The PSUs are 2xRosewill Hive 1000W. I think it's the powerbar thing though.
Cheers for the ideas, both of you.