Bonding & Grounding Definitions as per NEC Code

[ali hassan]

The terms Bonding & Grounding are often confused or misused. Bonding
should not be mistaken for Grounding since their definitions are
different as follows:

Bonding:
It is the connection of two or more conductive objects to one another
by means of a conductor such as a wire to provide continuity and
conductivity.

Grounding / Earthing:
It is the attachment of a bonded metallic system to earth, typically
through ground rods or other suitable grounding electrodes for
ensuring zero voltage.
Note: grounding is American standard term is equivalent to earthing
which is IEC standard term.
For a Comparison table between bonding and grounding Please review the
topic included in Understanding NFPA 70 (National electrical code)
course EC-1 titled “NEC Article 100 - Part Three”
Ground:
The ground is now simply the planet earth.
Grounded:
It means connected to the ground (planet earth), either directly or
through a conductive body that extends the ground connection.

Grounded Conductor:
A grounded conductor is the conductor of an electrical system that is
intentionally connected to earth via a grounding electrode conductor
and a grounding electrode at the service of premises, at a transformer
secondary, or at a generator or other source of electric power. It is
most commonly a neutral conductor of a single-phase, 3-wire system or
3-phase, 4-wire system but may be one of the phase legs—as in the case
of a corner-grounded delta system.


Grounded conductor in different system types:
In 3-wire, single-phase systems, the midpoint of the transformer
Winding, the point from which the system neutral is derived, is
grounded.

For grounded 3-phase, 4-wire wiring systems, the neutral point of the
wye-connected transformer(s) or generator is usually the point
connected to ground.

In delta-connected transformer hookups, grounding of the system can be
effected by grounding one of the three phase legs, by grounding a
center-tap point on one of the transformer windings (as in the 3-
phase, 4-wire “red-leg” delta system), or by using a special grounding
transformer which establishes a neutral point of a wye-connection
which is grounded.

The need for a grounded conductor:
It limits the voltage upon the circuit that might otherwise occur
through exposure to lightning or other voltages higher than that for
which the circuit is designed.

It limits the maximum voltage to ground under normal operating
conditions.

It provides automatic opening procedure of the circuit if an
accidental or fault ground occurs on one of its ungrounded conductors.

Grounding Conductor, Equipment:
Equipment grounding is the intentional electrical interconnection of
all metal enclosures that contain electrical wires or equipment with
the grounding electrode conductor (all systems) and with the grounded
conductor of the system (grounded systems only).

The term equipment grounding conductor includes bare or insulated
conductors, metal raceways [rigid metal conduit, intermediate metal
conduit, electrical metallic tubing (EMT)], and metal cable jackets
where the Code permits such metal raceways and cable enclosures to be
used for equipment grounding—which is a basic Code-required concept.

Equipment grounding function:

When the insulation failure occurs on a grounded system, equipment
grounding serves to ensure adequate current flow to cause the affected
circuit’s over-current protective device to “open,” . This prevents
the enclosures from remaining energized, which would otherwise
constitute a shock or fire hazard.

Grounding Electrode:

The grounding electrode is any one of the building or structural
elements that is in actual physical contact with the earth.
Metal Underground Water Pipe
Metal Frame of the Building or Structure
Concrete-Encased Electrode
Ground Ring
Rod and Pipe Electrodes
Plate Electrodes
Other Local Metal Underground Systems or Structures (such as piping
systems and underground tanks.)

Grounding Electrode Conductor:

It is the connection between either the grounded conductor of a
grounded electrical system (typically the neutral) and the grounding
electrode system, or the connection between the equipment ground bus
and the grounding electrode system for ungrounded systems.

The conductor that runs from the bonded neutral block or busbar or
ground bus at service equipment, separately derived systems, or main
building disconnects to the system grounding electrode is clearly and
specifically identified as the “grounding electrode conductor.”