250.4 General Requirements for Grounding and Bonding
(A) Grounded Systems.
(5) Effective Ground-Fault Current Path. Electrical equipment and other electrically conductive material likely to become energized must be installed in a manner that creates a permanent, low-impedance circuit capable of safely carrying the maximum ground-fault current likely to be imposed on it from where a ground-fault may occur to the grounded (neutral) terminal at the electrical supply source, see definition 250.2.
The earth cannot be used as the sole equipment grounding conductor or effective ground-fault current path. Figure 250–7Intent: The changes to this section should make it much easier to understand the grounding and bonding requirements contained in Article 250. The most significant change includes the explanation that, in order to clear a fault, the fault current must have an effective low-impedance ground-fault current path back to the grounded (neutral) terminal at the power supply.
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