A three-phase two-winding transformer has a voltage transformation ratio \(\dfrac{V_P}{V_S} = 0.866 + j0.5\), where \(V_P\) is the primary side voltage in p.u., and \(V_S\) is the secondary side voltage in p.u. \(I_P\) and \(I_S\) represent the currents injected into the primary and secondary sides of the transformer, respectively. The admittance corresponding to the leakage impedance of the transformer referred to the secondary is \(y_t\) p.u. Neglect the magnetizing branch.
The Y bus representation of this transformer is: