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Illustrated Changes to the NEC, 2002 Edition - Part 1

Article 250


250.2 Definitions

The following definitions were added to Article 250:

Effective Ground-Fault Current Path. An intentionally constructed, permanent, low-impedance path designed and intended to carry fault current from the point of a line-to-case fault on a wiring system to the grounded (neutral) at the electrical supply source, see 250.4(A)(5). Figure 250–1

Author Comment: An effective ground-fault current path is created when all electrically conductive materials that are likely to be energized are bonded together and to the grounded (neutral) at the electrical supply. Effective bonding is accomplished through the use of equipment grounding conductors, bonding jumpers, metallic raceways, connectors and couplings, metallic sheathed cable and cable fittings, and other approved devices recognized for the purpose. A ground-fault path is effective when it is properly sized so that it will safely carry the maximum ground-fault current likely to be imposed on it.
Intent: The addition of these definitions will be very helpful for the Code user to understand the performance requirements contained in Article 250. Defining the words or terms will help the users more readily understand the requirements of Article 250.
Ground-Fault. A ground-fault is an unintentional electrical connection between an ungrounded (hot) conductor and metal enclosures, raceways, equipment, or earth. Figure 250-2

Ground-Fault Current Path. An electrically conductive path from the point of a line-to-case fault on a wiring system through conductors, equipment, or the earth extending to the grounded (neutral) terminal at the electrical supply source.

FPN: The ground-fault current paths could consist of equipment grounding conductors, metallic raceways, metallic cable sheaths, electrical equipment, and other electrically conductive material such as metallic water and gas piping, steel framing members, stucco mesh, metal ducting, reinforcing steel, shields of communications cables, or the earth itself.

Author’s Comment: These definitions originated from the Usability Task Group recommendations for clearly describing what grounding and bonding is intended to accomplish.

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