Grounding and bonding requirements are designed to protect staff and equipment from undesired surges and buildup of electrical current. Properly grounded and bonded circuits and equipment provide a return path for electrical current caused by the buildup of static electricity, accidental contact with higher-voltage lines, lightning strikes, line surges, and excess voltage that could otherwise cause arcing or other electrical dangers.
Defining Grounding and Bonding
Grounding and bonding are often treated as if they describe the same process. In fact, the terms describe two different situations. According to the National Electrical Code, the two terms are described as follows:
Grounding: “Connecting to earth or to some connecting body that serves in place of the earth.” The grounding material provides a conducting path to the earth independent of the current-carrying path within the wiring or equipment.
Bonding: “The permanent joining of metallic parts to form an electrically conductive path.” Bonded materials are not intended or designed to carry electricity. Giving all bonded materials the same electric potential allows the bonded items to be connected to the earth, providing them with earth potential and reducing the risk of electric shock.
Types of Grounding
Two types of grounding exist: electrical circuit / system grounding and electrical equipment grounding.
In electrical circuit grounding, one of the circuit’s conductors is connected to earth to protect against unintentional high voltage strikes, including lightning strikes. Electrical system grounding stabilizes the voltage in a system, keeping voltage levels at normal levels during normal conditions.
Electrical equipment grounding grounds the entirety of a piece of equipment’s metal frame or enclosure with a permanent bond. The equipment’s grounding conductor offers a path for excess current to return to the ground at the circuit’s supply source if installation failure occurs. In this case, the grounding conductor is the current path that triggers circuit breakers, fuses, and other protective devices in the event of a fault.
The type of grounding conductor used varies, and can include wiring, metallic conduits, electrical tubing, and flexible conduits with approved fittings. When wire is used, copper is the material of choice.
If the electrical system has a neutral, the circuit will be grounded there. For systems with no neutral, grounding can occur at any point in the system. AC power systems are grounded at the source to:
Limit the potential difference across insulation materials
Allow circuit protective devices time to operate.
Grounding and Bonding Training
Understanding grounding and bonding requirements is vital if you want to keep your electrical systems in compliance with OSHA and the National Electric Code. While the basic concept seems simple enough, proper grounding and bonding training is needed to fully understand, maintain, and troubleshoot grounded systems.