Using the word "Neutral" sometimes causes confusion in the realm of NEMA vs IEC.
For a single secondary winding, single voltage ransformer, ground one end of the winding.
In NEMA land, for a single secondary, centertapped winding, ground the center tap.
For a multiple tapped, multiple voltage winding, ground the "0" volt tap. this may or may not be a neutral.
For a transformer with multiple secondary windings, ground each winding on it's own merits. Be aware that a seperate winding may be provided for a circuit that a designer specifically wants to isolate from ground.
Be aware that while the grounded circuit conductor and the neutral conductor are often the same conductor, there may be exceptions.
The final authority is the code or practice in the country of intended use.
respectfully