Don’t forget that with insulation-resistance testing you are charging the natural capacitor whose two “plates” are the normally grounded and normally ungrounded {er, “phase” conductors.} That stored energy can be discharged through you, and should not be dismissed as always harmless.
Another mode of stored energy might be the inductance in a winding should one mistakenly do a test where the instrument is paralleled not with a capacitor, but an inductor.
