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In electrical engineering, ground or earth is a reference point in an electrical circuit from which voltages are measured, a common return path for electric current, or a direct physical connection to the Earth.
A high-voltage direct current (HVDC) electric power transmission system uses direct current (DC) for electric power transmission, in contrast with the more common alternating current (AC) transmission systems.
A galvanic anode, or sacrificial anode, is the main component of a galvanic cathodic protection system used to protect buried or submerged metal structures from corrosion.
Cathodic protection is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell. A simple method of protection connects the metal to be protected to a more easily corroded "sacrificial metal" to act as the anode. The sacrificial metal then corrodes instead of the protected metal. For structures such as long pipelines, where passive galvanic cathodic protection is not adequate, an external DC electrical power source is used to provide sufficient current.
Single-wire earth return (SWER) or single-wire ground return is a single-wire transmission line which supplies single-phase electric power from an electrical grid to remote areas at lowest cost. Its distinguishing feature is that the earth is used as the return path for the current, to avoid the need for a second wire to act as a return path.
An Earth battery is a pair of electrodes made of two dissimilar metals, such as iron and copper, which are buried in the soil or immersed in the sea. Earth batteries act as water activated batteries. If the plates are sufficiently far apart, they can tap telluric currents. Earth batteries are sometimes referred to as telluric power sources and telluric generators.
An earth-leakage circuit breaker (ELCB) is a safety device used in electrical installations with high Earth impedance to prevent shock. It detects small stray voltages on the metal enclosures of electrical equipment, and interrupts the circuit if a dangerous voltage is detected. Once widely used, more recent installations instead use residual-current devices which instead detect leakage current directly.
A transmission tower, also known as an electricity pylon or simply a pylon in British English and as a hydro tower in Canadian English, is a tall structure, usually a steel lattice tower, used to support an overhead power line.
The Pacific DC Intertie is an electric power transmission line that transmits electricity from the Pacific Northwest to the Los Angeles area using high voltage direct current (HVDC). The line capacity is 3,100 megawatts, which is enough to serve two to three million Los Angeles households and represents almost half of the Los Angeles Department of Water and Power (LADWP) electrical system's peak capacity.
Ground and neutral are circuit conductors used in alternating current electrical systems. The ground circuit is connected to earth, and neutral circuit is usually connected to ground. As the neutral point of an electrical supply system is often connected to earth ground, ground and neutral are closely related. Under certain conditions, a conductor used to connect to a system neutral is also used for grounding (earthing) of equipment and structures. Current carried on a grounding conductor can result in objectionable or dangerous voltages appearing on equipment enclosures, so the installation of grounding conductors and neutral conductors is carefully defined in electrical regulations. Where a neutral conductor is used also to connect equipment enclosures to earth, care must be taken that the neutral conductor never rises to a high voltage with respect to local ground.
An overhead power line is a structure used in electric power transmission and distribution to transmit electrical energy across large distances. It consists of one or more uninsulated electrical cables suspended by towers or poles.
A power cable is an electrical cable, an assembly of one or more electrical conductors, usually held together with an overall sheath. The assembly is used for transmission of electrical power. Power cables may be installed as permanent wiring within buildings, buried in the ground, run overhead, or exposed. Power cables that are bundled inside thermoplastic sheathing and that are intended to be run inside a building are known as NM-B.
A mercury-arc valve or mercury-vapor rectifier or (UK) mercury-arc rectifier is a type of electrical rectifier used for converting high-voltage or high-current alternating current (AC) into direct current (DC). It is a type of cold cathode gas-filled tube, but is unusual in that the cathode, instead of being solid, is made from a pool of liquid mercury and is therefore self-restoring. As a result, mercury-arc valves were much more rugged and long-lasting, and could carry much higher currents than most other types of gas discharge tube.
An electrode line is used in some high-voltage direct-current (HVDC) power transmission systems, to connect the converter stations to distant ground electrodes. Many long-distance HVDC systems use sea or ground return for the DC neutral current since this is considerably cheaper than providing a dedicated metallic return conductor on an overhead wire or cable. The ground electrode is separated from the converter station so that current returning through the ground electrode does not cause corrosion of parts of the station in contact with the earth.
A mast radiator is a radio mast or tower in which the metal structure itself is energized and functions as an antenna. This design, first used widely in the 1930s, is commonly used for transmitting antennas operating at low frequencies, in the LF and MF bands, in particular those used for AM radio broadcasting stations. The conductive steel mast is electrically connected to the transmitter. Its base is usually mounted on a nonconductive support to insulate it from the ground. A mast radiator is a form of monopole antenna.
An earthing system or grounding system (US) connects specific parts of an electric power system with the ground, typically the Earth's conductive surface, for safety and functional purposes. The choice of earthing system can affect the safety and electromagnetic compatibility of the installation. Regulations for earthing systems vary considerably among countries, though most follow the recommendations of the International Electrotechnical Commission (IEC). Regulations may identify special cases for earthing in mines, in patient care areas, or in hazardous areas of industrial plants.
In electrical engineering, earth potential rise (EPR) also called ground potential rise (GPR) occurs when a large current flows to earth through an earth grid impedance. The potential relative to a distant point on the Earth is highest at the point where current enters the ground, and declines with distance from the source. Ground potential rise is a concern in the design of electrical substations because the high potential may be a hazard to people or equipment.
A lightning rod or lightning conductor is a metal rod mounted on a structure and intended to protect the structure from a lightning strike. If lightning hits the structure, it will preferentially strike the rod and be conducted to ground through a wire, instead of passing through the structure, where it could start a fire or cause electrocution. Lightning rods are also called finials, air terminals, or strike termination devices.
Soil resistivity is a measure of how much the soil resists or conducts electric current. It is a critical factor in design of systems that rely on passing current through the Earth's surface. It is a very important parameter for finding the best location of a transmitter working on low frequiencies as such radio stations usually use ground as counterpole. An understanding of the soil resistivity and how it varies with depth in the soil is necessary to design the grounding system in an electrical substation, or for lightning conductors. It is needed for design of grounding (earthing) electrodes for substations and High-voltage direct current transmission systems. It was formerly important in earth-return telegraphy. It can also be a useful measure in agriculture as a proxy measurement for moisture content.
Galvanic corrosion is an electrochemical process in which one metal corrodes preferentially when it is in electrical contact with another, in the presence of an electrolyte. A similar galvanic reaction is exploited in primary cells to generate a useful electrical voltage to power portable devices.
References
- ↑ Electrical Engineer's Reference Book, Sixteenth edition by M. A. Laughton CEng., FIEE and D. J. Warne CEng., FIEE, Newnes, 2003, ISBN 0 7506 46373
- ↑ "Soil conditioning agents".
- ↑ "Achieving an Acceptable Ground in Poor Soil". October 1998.
- ↑ "Marconite".
- ↑ W.R. Jones, Bentonite Rods Assure Ground Rod Installation In Problem Soils, 1980, DOI: 10.1109/TPAS.1980.319556
- ↑ NACE/ASTM G193 – 10a Standard Terminology and Acronyms Relating to Corrosion 2010