Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

arcing ground
a ground fault on a power line which alternately clears and restrikes, causing high, repetitive voltage surges.
background noise
the noise that typically affects a system but is produced independent of the system. This noise is typically due to thermal effects in materials, interpreted as the random motion of electrons, and the intensity depends on the temperature of the material. In radio channels, background noise is typically due to radiation that is inherent to the
universe and due mainly to radiation from astronomical bodies. There is a fundamental lower bound on the intensity of such noise which is solely dependent on the universe and independent of antenna and receiver design.

See thermal noise
counterpoise ground
buried conductor routed under transmission lines designed to achieve low earth electrode resistance.

(1) an earth-connected electrical conducting connection that may be designed or non-intentionally created.

(2) the electrical "zero" state, used as the reference voltage in computer systems.
ground bounce
a transient variation in the potential of the ground terminal of a logic device caused by variations in the supply current acting on the ground impedance of the circuit as seen by the device. Usually caused by simultaneous turnon of the pullup and pulldown sections of totem-pole outputs.
ground bounce noise
ground bounce occurs when a large number of semiconductor circuit components are mounted on a
common semiconductor chip substrate, so that they are imperfectly insulated from each other. In normal operation the substrate should act as an insulator; however, during certain unusual fluctuations in signal levels, the systems power and ground connections can experience fluctuations, which affect the performance of each component in a random way that has the characteristics of noise, much like capacitive coupling.
ground current
the current that flows in a power system in a loop involving earth and (in some usages) other paths apart from the three phases.
ground fault interrupter
a protective device used in commercial and residential wiring which monitors equipment connected to an electrical outlet and shuts off the power when a ground fault in the equipment is detected.
ground fault neutralizer
an inductor connected between the neutral of Y windings of a generator or transformer and ground. It is tuned to the machine's capacitance so as to minimize ground fault current.
ground lamp
indicator lamp on electrical distribution switchboards that darkens when a ground condition exists on one (or more) of the busses.
ground loop
an undesired conductive path between two conductive bodies in a radial grounding system that are connected to a common ground.
ground plane
a perfectly or highly conducting half space beneath an antenna. Also, an unetched layer of metal on a printed circuit board over which microstriplines and printed antennas are formed.
ground rod
a metallic, rod-type electrode designed to be driven into the earth. It serves as an earth connection for grounding purposes. Other types of earth electrodes include buried plates, rings, and grids. For buildings, its primary function is to keep the entire grounding system at earth potential.
ground wave
a vertically polarized TEM wave propagating close to the ground. It is one of the three modes of propagation (ground, sky, and space waves).
ground-fault circuit interrupter (GFCI)
a device designed to detect ground-fault current above a threshold value (several milliamperes) and then interrupt the source of electrical power by opening a circuit breaker or a set of contacts. GFCIs are designed for personnel protection and are generally available in the form of circuit breakers and receptacles.

See ground
grounding transformer
a transformer connected to an otherwise ungrounded three-phase system for the purpose of providing a path for ground current flow. Zig-zag transformers and grounded wye-delta transformers can be used as grounding transformers.
high-resistance grounded system
an electrical distribution system in which the neutral is intentionally grounded through a high resistance. The high-resistance grounded wye system is an alternative to solidly grounded and ungrounded systems.

High-resistance grounding will limit ground fault current to a few amperes, thus removing the potential for arcing damage inherent in solidly grounded systems.
reactance grounded
an electrical system in which the neutral is intentionally grounded through a reactance. Frequently used in the neutral of generators and transformers to limit the magnitude of line to ground fault currents.
resistance ground
a grounding scheme in which the neutral of Y-connected machines is connected to ground through a resistance such that ground-fault currents are limited.