Lightning Protection, Grounding,
& Surge Suppression Glossary of Terms

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Earth Electrode System
See: Ground electrode system
Earth Termination System
See: Ground termination system
Earthing
See: Grounding
Effective Resistivity
A factor such that the conduction-current density is equal to the electric field in the material divided by the resistivity.
Effectively Grounded
Permanently connected to earth through a ground connection of sufficiently low impedance and having sufficient current carrying capacity that ground fault current which may occur cannot cause a voltage build up dangerous to personnel.
Efficiency
The output real power divided by the input real power.
Electric Potential
The potential difference between the point and some equipotential surface, usually the surface of the earth, which is arbitrarily chosen as having zero potential (remote earth).
Electrical Noise
Unwanted electrical signals that produce undesirable effects in the circuits of the control systems in which they occur.
Electromagnetic Compatibility (EMC)
The capability of equipments or systems to be operated in their intended environment, within designated levels of efficiency, without causing or receiving degradation due to unintentional electromagnetic interference. EMC is the result of an engineering planning process applied during the life cycle of the equipment. The process involves careful considerations of frequency allocation, design, procurement, production, site selection, installation, operation, and maintenance
Electromagnetic Interference
Any electrical or electromagnetic phenomenon, manmade or natural, either radiated or conducted, that results in unintentional and undesirable responses from, or performance degradation or malfunction of electronic equipment.
Electron Avalanche
An electron multiplication process due to electron-impact ionization of gas molecules. This is the initial stage in the development of an electrical discharge in air, e.g. a corona or streamer.
Electronic Multi-point Ground System
An electrically continuous network consisting of interconnected ground plates, equipment racks, cabinets, conduit, junction boxes, raceways, duct work, pipes and other normally non-current-carrying metal elements for electronic signals. It includes conductors, jumpers and straps that connect individual electronic equipment components to the electronic multipoint ground system.
Electronic Single-point Ground System
A single point ground system provides a single point reference in the facility for electronic signals. The single point ground system shall be installed in a trunk and branch arrangement to prevent conductive loops in the system. It shall be isolated from all other ground systems except for an interconnection, where applicable, to the multipoint ground system at the main ground plate. The single point ground system consists of insulated conductors, copper ground plates mounted on insulated stands, and insulated ground plates, buses, and/or signal ground terminals in the electronic equipment which are isolated from the frame of the equipment.
Elves
An acronym for Emissions of Light and Very Low Frequency Perturbations From Electromagnetic Pulse Sources, Elves often appear as a dim, flattened, expanding glow around 250 miles in diameter that lasts for, typically, just one millisecond. They occur in the ionosphere over thunderstorms.
EMI/RFI
The interference in a signal transmission or reception resulting from the radiation of undesirable electrical or magnetic and electrical fields.
Equalizer
A device to provide equipotential planes for resistance measurements.
Equipment Ground
A connection between a unit of electrical equipment and the facility ground network.
Equipment Grounding Conductor
The conductor used to connect non-current-carrying metal parts of equipment, raceways, or other enclosures to the system grounded conductor and/or grounding electrode conductor at the service entrance or at the source of a separately derived system.
Equipment Grounding Conductor (EGC)
The conductor used to connect the non-current-carrying parts of conduits, raceways, and equipment enclosures to the grounding electrode at the service equipment (main panel) or secondary of a separately derived system (e.g. isolation transformer).
Equipotential Line Or Contour
The locus of points having the same potential at a given time.
Equipotential Signal Reference Plane
An equipotential conducting plane designed to maintain a number of electrical/electronic units having a common signal reference at the same potential.
External Lightning Protection System
A system consisting of an air-termination system, a down conduction system and an earth termination system.
Extraterrestrial Lightning
Lightning requires the electrical breakdown of a gas, so it cannot exist in a visual form in the vacuum of space. However, lightning has been observed within the atmospheres of Venus, Jupiter and Saturn.