(Solved): A 33/66 kV, 5 MVA, three-phase star-connected transformer with short circuited secondary passes ful ...

A 33/66 kV, 5 MVA, three-phase star-connected transformer with short circuited secondary passes full-load current with 7 % primary potential difference and losses are 30 kW. With full potential difference on the primary and the secondary open circuited, the losses are 15 kW. What will be the efficiency of the transformer at full-load and 0.8 power factor?