For those wh've experienced over-voltage events in their aircraft (and for
those who likely will) check out Bob Nuckols over-voltage protection
device - commonly referred to as a "over-voltage crowbar". I know he has one
for 12 volt systems, not sure about 28 volt though.

Simple device, easily installed and will pop the alternator field (if I
remember right) breaker in micro seconds before the buss voltage exceeds
dangerous levels. The indication that this has happened is a flashing yellow
"low voltage" indicator telling you that the alternator is off line. If the
condition was just a transient, resetting the field breaker will allow the
alternator to come back on line. In the event of a hard (high voltage)
failure, the crowbar will pop the breaker again.

Pretty cool device as some of the stuff in our panels do not take kindly to
excessive input voltage.

Dan Schaefer