Voltage regulation in transformers is the difference between the no load voltage and the full load voltage. This is usually expressed in terms of percentage. For example: A transformer delivers 100 volts at no load and the voltage drops to 95_volts at full load, the regulation would be 5%. dry type distribution transformers generally have regulation from 2% to 4%, depending on the size and the application for which they are used.The change in secondary terminal voltage from no load to full load expressed as a percentage of no load or full load voltage istermed as regulation.
%regulation =E2-V2/E2 *100
%regulation = voltage drop in transformer/ no load voltage of transformer
V2>E2 for leading p.f load
V2<E2 for lagging p.f load