Question

Neutral Displacement voltage occurs in:
(1) Unbalanced delta connected loads.
(2) Unbalanced star connected loads with neutral grounded
(3) Balanced star connected loads with neutral grounded.
(4) Unbalanced star connected loads with ungrounded neutral

Answer 1

There is ordinarily no “neutral point” in a delta connection, as there is no neutral connection - only the three phase conductors attached to the the corners of the delta, and the equipment ground, which is not considered a “neutral” in that unbalanced phase currents do not normally flow in it.
In an (ungrounded) delta transformer connection, all voltages are line-to-line, and all currents flow from line-to-line - there is no measurable current flow between the corners of the delta and ground . While it is possible to measure line-ground voltages in a delta system, these are phantom voltages resulting from the parasitic impedances that exist between the corners of the delta and the (grounded) equipment enclosure.