Besides unbalanced neutral current which is calculated by the three-phase root mean square (RMS) currents, there is still more neutral current that is zero sequence harmonic current.

Non-Linear Loads like SMPS, OA equipment, LED, etc., introduce third order harmonics. Third harmonic currents are in-phase on each of the supply phases and therefore will add into the neutral which can cause the neutral current in a wye system to exceed the phase currents.

A PQ Terminal dramatically eliminates the zero sequence harmonic current by removing about 95% of neutral current in a distribution board.