A groundbed is an
array
An array is a systematic arrangement of similar objects, usually in rows and columns.
Things called an array include:
{{TOC right
Music
* In twelve-tone and serial composition, the presentation of simultaneous twelve-tone sets such that the ...
of
electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials de ...
s, installed in the ground to provide a low
resistance electrical
Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by ...
path to
ground
Ground may refer to:
Geology
* Land, the surface of the Earth not covered by water
* Soil, a mixture of clay, sand and organic matter present on the surface of the Earth
Electricity
* Ground (electricity), the reference point in an electrical c ...
or earth. A groundbed is a component in an
earthing system
An earthing system (UK and IEC) 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 affec ...
.
Each electrode is called a ground rod or an earth electrode.
Grounding systems
For building electrical grounding systems or earthing systems, there is a low resistance conductor bonding the metalwork and this is connected to a groundbed. The electrodes for electrical grounding are often called ''ground rods'' and are often made from
steel
Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistant ty ...
with a
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
clad surface – typically 1 to 2 m long and in diameter. These are driven vertically into the ground and bonded together with bare copper
wire
Overhead power cabling. The conductor consists of seven strands of steel (centre, high tensile strength), surrounded by four outer layers of aluminium (high conductivity). Sample diameter 40 mm
A wire is a flexible strand of metal.
Wire is c ...
. Other grounding electrodes may include buried solid plates, or a grid of buried wires, where soil conditions do not favor driven ground rods. Buried metallic piping systems, well casings or the reinforcing bars of concrete slabs in contact with the earth have all been used as grounding electrodes.
Soil conditioning
Various materials may be placed around the ground rod to improve conductivity. These include:
*
Ufer ground The Ufer ground is an electrical earth grounding method developed during World War II. It uses a concrete-encased electrode to improve grounding in dry areas. The technique is used in construction of concrete foundations.
History
During World W ...
*
Bentonite
Bentonite () is an absorbent swelling clay consisting mostly of montmorillonite (a type of smectite) which can either be Na-montmorillonite or Ca-montmorillonite. Na-montmorillonite has a considerably greater swelling capacity than Ca-mon ...
clay
Marconite
Cathodic protection
In
cathodic protection
Cathodic protection (CP; ) 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 "sacrific ...
, the
anode
An anode is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, an electrode of the device through which conventional current leaves the device. A common mnemonic is ...
groundbed is the arrangement of anodes in the ground or water and it provides the path for protective current to leave the anodes and enter to
electrolyte
An electrolyte is a medium containing ions that is electrically conducting through the movement of those ions, but not conducting electrons. This includes most soluble salts, acids, and bases dissolved in a polar solvent, such as water. Upon dis ...
.
[NACE/ASTM G193 – 10a Standard Terminology and Acronyms Relating to Corrosion 2010]
High voltage direct current systems
In a
high voltage direct current
A high-voltage direct current (HVDC) electric power transmission system (also called a power superhighway or an electrical superhighway) uses direct current (DC) for electric power transmission, in contrast with the more common alternating curren ...
transmission system, each converter station may be equipped with a substantial ground bed to facilitate earth return operation of the system. In normal operation of a bipolar HVDC system, current is carried on the two wires of the transmission line, but if a line fails or one converter fails, the earth return can be used to maintain partial operation. Ground beds must be designed to accept considerable current ( on the order of 1000 amperes) for extending times, without drying out. Ground return operation may cause objectionable earth currents that cause corrosion of other buried services such as pipelines. A short overhead power line may be run from the converter station to obtain the best location for a ground bed.
See also
*
Stray voltage
Stray voltage is the occurrence of electrical potential between two objects that ideally should not have any voltage difference between them. Small voltages often exist between two grounded objects in separate locations, due to normal current flo ...
*
Earth potential rise
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 poi ...
References
{{reflist
Electric power