What is the difference between 460 or 480 volt?

The difference between 460 volts and 480 volts is 20 volts. They are not the same but all voltages have a nominal and a tolerance on each side of it. For example US household is 115 (or 117 or 118) nominal, and it can be between 110 and 120, or sometimes between 105 and 125 volts.