Professional grade protectors and battery backups have visual indicators if they are providing protection or not while many of the cheaper residential grade ones give no clues at all. For surge strips here - I use pretty much all APC brand ones with a few Tripp Lite mixed in. On battery backups - those are mostly APC while the big ones for the main design and rip system, servers, and the Mimaki are all Leibert GXT UPStations... 6000va for the printer and RIP, another of the same for the 2 servers, router, and switch, and a 1500va one for the main design system. All connect either directly to the computer via USB cable for status monitoring while the 2 big ones actually connect to the network and can be monitored in a browser.
About 6 years ago - the power lines behind our old building shorted together. Sparks literally shot out of the plug outlets in our building. Nearly every light got burned out, several surge ssupressors actually caught on fire, and all supressors got toasted. Interstingly - all of the quality suppressors and backups sacrificed themselves to protect the machines connected to them. We had several cheapo ones as well - every single one of those - the equipment connected got damaged. Fortunatley our electric company (took 4 months) actually paid for all of the damages though since it was their lines that had degraded and come loose causing the problems. They tried to deny it and said it was not possible at first.