Comment by ericd

Yeah, I've seen this with our own solar installation - when the grid frequency dips even a bit, our house cuts itself off from the grid, including whatever power it was feeding back. It seems like a recipe for instability - grid is overstrained, so the frequency dips, and suddenly tons of distributed solar generation drops off and makes the grid even more strained.

And with UPSes that beep when they kick on, it's become very apparent that this happens basically daily during the summer, when power demand for air conditioning is high.