Section 90.2(A) of the National Electrical Code, “Practical Safeguarding,” contains the Code’s purpose, which is to provide the practical safeguarding of people and property from hazards associated with the use of electricity. Chapter 2, “Wiring and Protection,” is where the general grounding and bonding requirements are located, specifically in Article 250.

Grounding and bonding are necessary for protection and safe electrical wiring installation and systems. Electrical installations include safety circuits that accomplish grounding and bonding simultaneously. One function complements and supports the other. Bonding and grounding functions are accomplished when noncurrent-­carrying conductive equipment parts are bonded together and then connected to the ground. This results in improved electrical safety.

Digging into history

From the beginning, the discovery and use of electricity brought many challenges and questions, including about electrical grounding. Today, DC  system use and installation are significantly more common in applications such as small- and large-scale energy storage systems. After much debate and experimentation, grounding electrical equipment and systems prevailed as the most effective method of building safety into electrical systems, at least in North America.

Arguments have been made for and against electrical system grounding. For example, without grounding, the possibility of completing an electrical circuit through the human body is reduced. However, the earth is included in the electrical circuit in a grounded system, making shock hazards more likely. And then, on the other hand, grounded electrical systems and equipment offer the advantage of circuit protection by causing overcurrent protective devices to operate during ground-fault conditions, clearing the faulted circuit.

To accomplish grounding of equipment or systems, a connection to earth must be made. This connection is established through a grounding electrode or system of electrode(s).

If electrical equipment or systems are grounded, the earth is included in the circuit and connected to the electrical system. The terms “ground” and “grounded (grounding)” are defined in Article 100. One of the most elementary concepts to remember is that throughout the NEC, “electrical grounding” refers to a connection to earth. This is accomplished by using a “grounding electrode.”

Earth is a large but a somewhat poor conductor. It should never be relied on to carry any current, be it normal or fault. The earth offers significant opposition to current in circuits, including grounding and bonding ones. This opposition is known as resistance in DC circuits or impedance in AC.

Start at the beginning

To understand electrical grounding concepts and performance, getting back to basics is necessary. Grounding is a function of connecting to earth. Buildings and structures depend on a good connection to earth through a sufficient foundation or footing. Electrical systems are built on a similar one, and the foundation of a grounded electrical system and grounded equipment is the grounding electrode or grounding electrode system.

When an object qualifies as a grounding electrode, any connection to it renders a grounding function. Since the NEC defines “ground” simply as the earth, if equipment or a system is grounded, it must be connected to the planet Earth (i.e., soil or bedrock). So, contrary to what many people think, the frame of an automobile does not qualify as ground because there is no connection to the earth. It is connected to the negative side of the vehicle battery, not ground. The same holds true for an aircraft. The frame of a jet airliner may be used as the reference for the 400-cycle power system onboard, but it is not grounded, as some people might claim. If there is no connection to the ground (the earth), there is no grounding.

To accomplish grounding of equipment or systems, a connection to earth must be made. This connection is established through a grounding electrode or system of electrode(s).

Grounding is a function that results from conductive equipment, parts or systems connected to ground. The definitions of these terms in Article 100 provide a common (Code) means of communication when applying the rules to installations and systems.

Electrical bonding, by definition, is a connection, because bonding is the process of connecting conductive objects together. When there is bonding, two or more conductive objects become one, electrically establishing conductivity and continuity between them.

Stay tuned for the second part of this series, which will address electrical grounding and bonding performance.