For shock hazard the distance is dependent on voltage level. At 480/277V the limited approach boundary would be 42", the restricted approach boundary 12". For arc flash hazard it is dependent on the results of an arc flash analysis.
If the worker is task-qualified for the task being performed, there is no minimum distance. An "un-escorted" or unqualified person (or person lacking the required protective equipment) would remain at the further of the limited approach boundary or the arc flash boundary. As Kent has indicated for 480V (3 phase) the limited (shock) approach boundary is 42" (3'6" or 1m). If this were single phase (277V or 120V), the same shock boundary will apply. The arc flash boundary should be calculated using an engineering study, since it is largely dependant on fault current and fault clearing time. The further of the two boundaries is the "safe" zone.