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Equipotential Bonding (EPB)

Last updated: December 20, 2021

What Does Equipotential Bonding (EPB) Mean?

Equipotential bonding (EPB) is the process of electrically connecting metalwork and conductive parts, both exposed and extraneous, such that the voltage is the same throughout these various parts. EPB is used to reduce the risk of equipment damage and personal injury.

Equipotential bonding is sometimes simply referred to as bonding.

Safeopedia Explains Equipotential Bonding (EPB)

Two charged objects can be hazardous when they have different potential voltages. That variance in the voltages creates a circuit between the two points, since energy will flow from the higher potential point to the lowest potential point.

When a person comes into contact with one of these objects, that current flows through them, resulting in an electric shock.

Grounding the objects eliminates this hazard by connecting both to the Earth's conductive surface.

Grounding and Bonding

Grounding and bonding have the fundamental goal of safety and electromagnetic compatibility (EMC). Safety is achieved by limiting the touch voltage and the return path of fault currents while EMC is achieved by avoiding differences in potential and providing a screening effect. Grounding and bonding are essential parts of any electrical system.

Grounding works by limiting the duration of voltages while EPB works by limiting the magnitude of the voltages. Grounding minimizes the risk of an electric shock if metal parts are touched when a fault is present while bonding protects equipment and people by reducing the current flow between pieces of equipment at different potentials.

Equipotential Bonding Zone

The use of equipotential bonding zones is required by OSHA for individuals working with power generation, transmission, and distribution equipment under standard number 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.

Equipotential bonding of grounded 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. An equipotential work zone should protect an individual under the worst-case scenario.

The IEEE’s standards for an equipotential work zone, as defined in IEEE Standard 524a, Sub-clause 2.2 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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