Hi group .

Perhaps there is a coincidence here . 
"There were fluctuations hours before the failure" . Sounds like a
positive feedback effect caused the problem .

e.g. so many control systems trying to compensate for the original
glitch, due to the sheer size of the grid it began oscillating at a
low frequency which built up and finally caused a system failure .

Recall Tahoma Narrows bridge . Wind was just at the wrong speed to
induce resonance .

Perhaps a seismic event caused it ? Something caused a slow build-up
(perhaps current was being drawn in the right pattern + some other
event) causing the above scenario a couple of hours later .

Now , here is the interesting part . Earth lights are caused by
seismic activity , and the 1965 blackout was marked by a lot of UFO
reports . Connection maybe ?

The power failures seem to have originated in the same area, perhaps
the cause was indeed a seismic event ? Perhaps this is the missing
link .

-A