Distinguish Between "Bonding" and "Grounding"
The terms “bonding” and “grounding” are often employed interchangeably as general terms in the electrical industry to imply or mean that a specific piece of electrical equipment, structure, or enclosure is somehow referenced to earth. In fact, “bonding” and “grounding” have completely different meanings and employ different electrical installation methodologies.
“Bonding” is a method by which all electrically conductive materials and metallic surfaces of equipment and structures, not normally intended to be energized, are effectively interconnected together via a low-impedance conductive means and path in order to avoid any appreciable potential difference between any separate points. The bonded interconnections of any specific electrically conductive materials, metallic surfaces of enclosures, electrical equipment, pipes, tubes, or structures via a low impedance path are completely independent and unrelated to any intended contact or connection to the Earth. For example, airplanes do not have any connection to Earth when they are airborne.
However, it is extremely important for the safety and welfare of passengers, crew, and aircraft that all metallic parts and structures of an airplane are effectively bonded together. The laboratories and satellites orbiting in space above the planet Earth obviously have no direct connection with the surface of our planet. However, all of the conductive surfaces of these orbiting laboratories and satellites must be effectively bonded together in order to avoid differences of potential from being induced across their surfaces from the countless charged particles and magnetic waves traveling through space.
The common method to effectively bond together different metallic surfaces of enclosures, electrical equipment, pipes, tubes, or structures is with a copper conductor, rated lugs, and the appropriate bolts, fasteners, or screws. Other bonding methods between different metallic parts and pieces might employ brackets, clamps, exothermic bonds, or welds to make effective connections.
In addition to preventing potential differences that may result in hazards, effectively bonded equipment can also be employed to adequately and safely conduct phase-to-ground fault current, induced currents, surge currents, lightning currents, or transient currents during such abnormal conditions.
“Grounding” is a term used rather exclusively in North America to indicate a direct or indirect connection to the planet Earth or to some conducting body that serves in place of the Earth. The connection(s) to Earth can be intentional or unintentional by an assortment of metallic means.
A designated grounding electrode is the device that is intended to establish the direct electrical connection to the earth. A common designated grounding electrode is often a copper-clad or copper-flashed steel rod. However, the designated grounding electrode might be a water pipe, steel columns of a building or structure, concrete encased steel reinforcement rods, buried copper bus, copper tubing, galvanized steel rods, or semiconductive neoprene rubber blankets. Gas pipes and aluminum rods cannot be employed as grounding electrodes.
The grounding electrode conductor is the designed conductor that is employed to connect the grounding electrode(s) to other equipment.
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