perhaps I was doing some trivial writes during the poweroutage
As far as RAID is concerned, there's no such thing as a "trivial write". A write is a write, and if the RAID goes down in an unclean state, where there's a strong possibility that a write didn't get properly written everywhere it needed to, it's going to do a full resync to make sure things are healthy.
To prevent this, use a hardware RAID controller with a battery-backed write cache. Short of changing to a hardware RAID controller, at least get yourself a UPS with a long enough capacity to make it through short power outages. Good quality UPSes can also be configured to automatically shut down your servers gracefully in the event of a power outage. This would also prevent your RAID and filesystem going down hard.