My BX750MI-GR has saved my precious data on two occasions. Earlier this year, my seven year old, well used waffle iron shorted, popping loudly and sparking quite brightly in the process, probably because of all the gunk that had accumulated inside its less cleanable interior over the years. That not only made my breaker trip, but also blew the 16 amp main fuse. The UPS kicked in immediately, making a klick and a beep, which felt amazing. That was my first time ever.
As for the second time, see this post.
Will a UPS provide any benefit on a non-grounded outlet?
I’m not an expert, but I don’t think grounding gives or takes anything in this scenario. Grounding in wall outlets provides a path for current to flow into instead of human flesh in case there is a shortcut in devices connected to the outlet, or if the outlet itself shorts. Please correct me if I’m wrong!