There is no single fixed drying time for a 5 MVA transformer in a vacuum oven, because it depends strongly on initial moisture content, insulation thickness, and the applied temperature and vacuum level. In practice, for a mid-size 5 MVA unit, a typical drying cycle ranges from 48 to 120 hours. Well-prepared transformers with moderate moisture may be dried in 2-3 days, while heavily wetted insulation can require 5 days or more. The end point is defined by moisture evolution rate and insulation resistance, not by time alone.