grounded
Of or pertaining to an electrical conductor which is connected to earth; earthed.
grounded: connected to earth for safety
A grounded conductor is one that has been intentionally connected to earth, or to a conductor that reaches earth, to provide a low-resistance path for electrical current. In practical terms, this means a copper wire or conductive rod driven into the soil, or a metal water pipe, serves as the reference point at zero volts against which all other voltages in a system are measured. This connection is the foundation of electrical safety.
Grounding serves two distinct purposes. First, it establishes a reference potential: all circuit voltages are defined relative to ground, which is assigned a potential of 0 volts. Second, it provides a return path for fault currents. If insulation fails and current leaks from a live conductor to a metal enclosure or frame, that grounding path allows the fault current to flow safely to earth rather than through a person who touches the enclosure.
Equipment grounding versus system grounding
Equipment grounding connects the non-current-carrying metal parts of machines, panels, and enclosures to ground. A typical installation uses a bare or green-jacketed copper conductor running alongside the power cables in a conduit. In North America, a standard equipment ground in a 120/240 volt single-phase service is a number 10 AWG or larger copper wire. System grounding, by contrast, connects one point of the power source itself, usually the neutral conductor in an AC system, to earth. Both must be present for a complete protection scheme.
The effectiveness of grounding depends on the resistance of the earth connection itself. A typical ground rod of 5/8 inch diameter copper-clad steel, driven 8 feet into soil, should achieve a resistance below 25 ohms. In high-resistivity soils or rocky terrain, multiple rods connected in parallel, or chemical treatments, may be necessary to reach acceptable resistance values. Poor grounding is a common cause of safety failures.
The term is also used adjectivally to describe circuits, systems, or equipment that have been properly connected to ground. A grounded outlet, one with a third round or U-shaped hole for the ground prong, provides a path for equipment grounding current. An ungrounded or floating system, by contrast, offers no intentional earth reference and is used in specialized applications like isolated medical power supplies, where leakage current must be carefully monitored rather than safely discharged.