Three Single-Phase Transformers, Each Rated $10 \mathrm{MVA}, 66.4 / 12.5 \mathrm{kV}, 60 \mathrm{~Hz}$

Essay

Three single-phase transformers, each rated $10 \mathrm{MVA}, 66.4 / 12.5 \mathrm{kV}, 60 \mathrm{~Hz}$ , with an equivalent series reactance of 0.12 per unit divided equally between primary and secondary, are connected in a three-phase bank. The high-voltage windings are Y connected and their terminals are directly connected to a $115-\mathrm{kV}$ three-phase bus. The secondary terminals are all shorted together. Find the currents entering the high-voltage terminals and leaving the low-voltage terminals if the low-voltage windings are (a) $\mathrm{Y}$ connected, (b) $\Delta$ connected.