The term "ground" refers solely to physical connections between conductive materials and the earth

The Term "ground"

We opened the text for "Alternating Current (AC) Ground System" with the statement, The term "ground" is probably one of the most misunderstood terms in electricity today. It really should read the terms - ground, grounded, grounded conductor, grounding, and grounding conductor are probably ............"

The American Heritage Dictionary - defines ground as: Electricity. a. A large conducting body, such as the earth or an electric circuit connected to the earth, used as an arbitrary zero of potential. b. A conducting object, such as a wire, that is connected to such a position of zero potential.

To some, the term ground refers solely to physical connections between conductive materials and the Earth. Whether or not this conducting connection carries current is irrelevant.

Years ago, in tugboat design, the definition for ground had its roots in terra firma - solid ground - dry land. Back then the term "Earth" was used instead ground. As tugboat electrical systems evolved the term positive ground systems came into play. Later, the positive ground systems gave way to negative ground systems. Eventually the water became real murky as to the true meaning of the term "ground".

For us, in the marine environment, we are going to limit our definition of the term ground to:

Ground - Ground applies to the voltage potential of the Earth's surface or some conducting body that serves in place of the Earth. This voltage potential will be considered zero.

Then we are going to add the following terms:

Grounded - Grounded is a normally conducting connection, whether intentional or accidental, between an electrical circuit or equipment and the Earth or some conducting body that serves in place of Earth. (Note: In the marine environment we need to include - any conductive part of the wetted surface of a hull.)

Grounded Conductor – A grounded conductor is a current carrying circuit conductor that is intentionally grounded (connected to Earth or to some conducting body that serves in place of the Earth) and maintained at ground potential.

The grounded conductor is referred to as the neutral conductor in AC electrical systems and is white or light blue in color. It is held to the Earth ground potential (zero volts).

The grounded conductor is referred to as the negative conductor in DC electrical systems.

In an non-insulated ground return DC system the negative conductor is the engine block or frame which is connected to the negative battery terminal.

In an insulated ground return DC system the negative conductor is connected to a negative buss bar which is tied to the negative battery terminal. The insulated negative conductor is normally black in color.

In both DC systems the battery's negative terminal is the ground zero reference point for the electrical system

Grounding - Grounding is where the Earth's voltage potential as a safety factor is realized. This voltage potential will be considered zero.

Grounding conductor - A grounding conductor is a normally non-conducting connection, which is intentionally connected between an electrical enclosure or equipment case and the Earth. Its sole function is to provide a low resistance path to ground. If a short develops between an electrical device's phase wire and its case or enclosure electrical current will take this low resistance path to ground. In the marine environment the grounding conductor is green or green with a yellow stripe. It is held to the Earth ground potential (zero volts).

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