Power System

In large facilities where there are multiple service drops, it is not inconceivable for wiring mix-ups to occur. Loads that are powered from one panel may have their return path through the neutral of another panel or even another service drop.

To determine this, first check the neutral current waveform. If it is predominantly 180 Hz, then current distortion is the main cause. If it is still 60 Hz, and the panel's unbalance does not account for the current level, then improper system sharing is the next likely culprit.

This situation can be resolved by ensuring that the wiring in the facility is correct, and that loads are not powered inappropriately.

Parallel service ties, normally open, may have been closed allowing multiple return paths. If this is the case, restoring them to their correct operation will fix the problem.