The 2014 NEC adds two definitions that appear on different pages in Art. 100, don’t cross-reference each other, and differ only by one word. Both are electrically conductive paths from the point of ground fault to the electrical supply source. The difference is in whether the path is intended.
Any path back to the electrical source can be a ground fault current path. You don’t want equipment, for example, to be part of that path; this modality is a major cause of motor bearing failure and it presents lethal shock hazard.
The effective ground fault current path is one that is there by design. It’s intentionally constructed to be the preferred path for the current that arises from a ground fault. It also facilitates the operation of the overcurrent protective device and/or ground fault detectors.
For this path to be the preferred path (and thus “effective”), it must have very low impedance. This path is effective not because electricity seeks the path of least resistance (it doesn’t), but because the impedance is so low that the path “effectively” serves as a shunt to the other paths in parallel with it. Electricity flows in inverse proportion to the impedances presented to it.
