THE NEED FOR GROUNDING

The Institute of Electrical and Electronics Engineers (IEEE) defines grounding as a conducting connection, whether intentional or accidental, by which an electric circuit or equipment is connected to the earth or to some conducting body of relatively large extent that serves in place of the earth. It is used for establishing and maintaining the potential of the earth (or of the conducting body) or approximately that potential, on conductors connected to it, and for conducting ground current to and from the earth (or the conducting body). Based on this definition, the reasons for grounding can be identified as:

• Personnel safety by limiting potentials between all noncurrent-carrying metal parts of an electrical distribution system.
• Personnel safety and control of electrostatic discharge (ESD) by limiting potentials between all noncurrent-carrying metal parts of an electrical distribution system and the Earth.

• Fault isolation and equipment safety by providing a low-impedance fault return path to the power source to facilitate the operation of over current devices during a ground fault.

The IEEE definition makes an important distinction between ground and earth. Earth refers to mother earth, and ground refers to the equipment grounding system, which includes equipment grounding conductors, metallic raceways, cable armor, enclosures, cabinets, frames, building steel, and all other noncurrent-carrying metal parts of the electrical distribution system.