Are you trying to silence the keyboard while you use it as a MIDI keyboard controller? If so, you don't want to set the velocity to 0, because a "Note On" event with a velocity of 0 is equivalent to a "Note Off" event. Instead, you want to set the "Local Control" function to "Off." See page 32 of the Operation Guide.
If you're trying to do something else, we need a bit more information and a context so we can better help you.