any Ydx transformer fed by a negative sequence (1U=C, 1V=B, 1W=A) will work as Ydy (where y is the working vectorial group and it is x (nameplate vect. group) mirrored over the 12-6 clock axis). i.e. an Yd1 fed by negative sequence will work as an Yd11; Yd3 as Yd9; ...