A lost neutral?
480 Volts is unlikely, as is the suggestion that supplies were connected in series to give 480V. Entirely possible when a fault or mistake happens during synchronising three phase generators to the mains or another 3 phase supply, is a lost or floating neutral, which usually results in phases being substantially under or over or voltage by anything from near zero change to near 240V. If your are lucky you just fry equipment but less than a month ago such an incident also burnt down a pair of semidetached houses
Biting the hand that feeds IT
