Loss of a phase can cause interesting things to happen to the voltages.
The line that feeds me kind of wanders along the river's edge for 15 miles or so. It was originally installed for irrigation from the river but has not been heavily used for that. Only a few residences powered from it and loosing a phase isn't all that unusual and will often go un-noticed for several hours or even a day or two. Since I only use it in the storage shed/summer shop it isn't a big deal and hasn't really caused any equipment malfunctions. Of course, the 3-phase motors don't run when a phase is lost. Depending on which phase is lost, the 120V lights may be slightly dimmer or lots dimmer. Compact fluorescents may not even light if the right phase is gone. Switching power supply in the shop computer keeps right on working but some instances will cause the CRT monitor to have a pretty small picture. The drill press with the VFD seems to work as long as power is coming down the wires -- regardless of which phase is missing.