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Equipotential Bonding

Last updated: September 26, 2018

What Does Equipotential Bonding Mean?

Equipotential bonding, commonly just called bonding, is used to reduce the risk of equipment damage and personal injury.

It involves joining together all metalwork and conductive items that are connected to an earthing system (also called a grounding system) so that they all have the same potential energy (voltage).

Safeopedia Explains Equipotential Bonding

Earthed materials are materials that are connected to the Earth’s conductive surface, often for the safety purpose of directing faulty current into the ground (tripping a fuse in the process) or dissipating potentially hazardous static discharges. Bonding multiple earthed items limits the magnitude of their voltages and prevents the existence of a dangerous potential difference (different voltages) between them. This eliminates the risk of a worker being shocked by a harmful electric charge flowing from one earthed item and through the worker, toward another earthed item of different voltage.

When two different objects hold different potential energy, they can be hazardous if a worker makes contact with both objects at the same time. This is because when a circuit is created between two points of varying potential energy/voltage, the energy will flow from the higher potential point to the lower potential point as fast as possible. This energy flow results in a current that will travel through the worker, which can be fatal if it is large enough. Equipotential bonding of earthed equipment ensures that the worker in an equipotential zone is protected because there is a nearly identical level of electrical potential between all points of the body.

The use of equipotential bonding zones is required by OSHA for individuals working with power generation, transmission, and distribution equipment under standard 1910.269. OSHA recognizes the methods prescribed by recognized standards organizations, such as the Institute of Electrical and Electronics Engineers’ IEEE Guide for Protective Grounding of Power Lines (IEEE Standard 1048), as complying with the requirements of OSHA’s standard.

An equipotential work zone should protect an individual under worst-case conditions. The IEEE’s standards for an equipotential work zone, as defined in IEEE Standard 524a, define such a work zone as one in which all equipment is interconnected by jumpers or grounding instruments, such that there will be an acceptable potential difference between all parts of the zone under a worst-case scenario of energization.


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