what I see is that, at the power drop time miner encountered issues, such as probably pool connection problem and the likes,
try to check your miner Logs, well it depends on what miner you're using, check timings on when it drop and check logs what happen on your miner at that moments event.
Mining power will obviously dropped when it does not mine or mining and will resume upon recovery.
Rgr, I was thinking about the worse case scenario - as it in having to deal with my hardware/software. Didn't think about miner/pool. Thanks