I need to add a comment related to Subsynchronous Resonance conditions, which imply a rather sustained condition, as opposed to a shorter duration or somewhat transient event.
Another potentially disastrous effect on generators and electrical transmission is an Out-Of-Step condition. SSR is typically thought of as a more oscillatory/periodic condition {like waves on a lake.} OOS is sort of the severe rotating-shaft equivalent of stripped gears that couple the hypothetical water wheel to the giant shaft.
