2. A three-phase Y-Y transformer is rated at 25 MVA, 13.8-kV:69-kV and has a single- phase equivalent series impedance 62+ 388 mQ What are the possible vector groups? referred to the low-voltage winding a. b. Draw the transformer per phase equivalent circuit in per unit. c. A three-phase short circuit is applied to the low-voltage winding. Calculate the voltage applied to the high-voltage winding which will result in rated current into the short circuit. d. The short circuit is removed and a three-phase load is connected to the low-voltage winding. With rated voltage applied to the high-voltage winding, the input power to the transformer is observed to be 18 MW at 0.75 power-factor lagging. Calculate the line-to- line terminal voltage at the load. e. Calculate the transformer efficiency at the conditions specified in part (d). f. Calculate the transformer voltage regulation at full load conditions. g. Draw the phasor diagram. (10 Marks)