Correct Answer - Option 2 : 4.6%
Concept:
In transformer voltage regulation is given by:
Voltage regulation = x (Rpu cosθ ± Xpu sinθ)
Where x = fraction of load
Rpu = resistance in pu (we can use % resistive drop in fraction)
Xpu = reactance in pu (we can use % reactive drop in fraction)
+ for lagging load
– for leading load
Calculation:
Given that, transformer is working at 0.8 lagging power factor at full load
⇒ cos θ = 0.8, sin θ = 0.6
x = 1
Rpu = 2%
Xpu = 5%
%V.R. = 1 × (2 × 0.8 + 5 × 0.6)
%V.R = 4.6%
