Three single-phase, two-winding transformers, each rated 450 MVA, 20 kV/288.7 kV, with leakage reactance Xeq = 0.10 per unit, are connected to form a three-phase bank. The high-voltage windings are connected in Y with a solidly grounded neutral. Draw the per-unit equivalent circuit if the low-voltage windings are connected
(a) in Δ with American standard phase shift,
(b) in Y with an open neutral. Use the transformer ratings as base quantities. Winding resistances and exciting current are neglected.