A transformer has positive voltage regulation when its load power factor is:

Correct option is C

$$\bullet \ \text{The positive regulation produces a voltage drop in the winding while a negative regulation produces a voltage rise in the winding.} \\[6pt]\bullet \ \text{Voltage regulation is the measure of how well a transformer can maintain a constant secondary voltage under varying load conditions, as the output secondary voltage may not be what we expect.} \\[8pt]\bullet \ \text{Voltage regulation of single-phase transformers is the percentage (or per unit value) change in its secondary terminal voltage compared to its original no-load voltage under varying secondary load conditions.} \\[8pt]\bullet \ \text{In other words, regulation determines the variation in secondary terminal voltage which occurs inside the transformer as a result of variations in the transformer connected load thereby affecting its performance and efficiency if these losses are high and the secondary voltage becomes too low.} \\[8pt]\bullet \ \text{A leading power factor (capacitive load), the output terminal voltage will rise.} \\[8pt]\bullet \ \text{Voltage regulation for the transformer is given by the ratio of change in secondary terminal voltage from no load to full load to no-load secondary voltage.} \\[6pt]\text{Voltage regulation} = \frac{(E_2 - V_2)}{E_2} \\[8pt]\text{It can also be expressed as,} \\[4pt]\text{Regulation} = \frac{(I_2 R_{02} \cos \phi_2 \pm I_2 X_{02} \sin \phi_2)}{E_2} \\[10pt]\bullet \ + \text{ sign is used for lagging loads} \\[6pt]\bullet \ - \text{ sign is used for leading loads}$$​​