Good info! I hadn't considered 3-phase power issues in a commercial building or high-rise, but it makes perfect sense for them to use it.

An undervolt (a.k.a. brownout) condition is really, really hard on equipment. Motors and older-style power supplies can overheat and eventually fail, or in the worst case, start to smoke/burn.

I have always felt that a reliable multimeter and some basic understanding of its use is an extremely important tool in many of the disaster scenarios we consider.