Stray-impedance, but ideal magnetic coupling, i.e. zero magnetisation current.
SI-input: values for stray and coupling impedances winding dependent.
r[k] = R[k] x[k] = omega_nom*L[k]
pu-input: values for stray and coupling impedances winding-reduced to primary side.
r[k] = R[k]/R_nom[k] x[k] = omega_nom*L[k]/R_nom[k]
with
R_nom[k] = V_nom[k]^2/S_nom, k = 1(primary), 2(secondary)