Resolving inconsistencies in three-phase current measurements

It is widely assumed that any unbalance between phase currents in 4-wire distribution circuits will equal the neutral current; that is that the sum of currents is zero. In practice, however, measurements made at distribution substations often show significant inconsistency. Several possible explanations for this are explored, showing that calculations of the voltage drop and losses are more accurate if harmonics are included. More generally, feeder configurations are described in which the currents may not sum to zero.