A groundbed is an
array
An array is a systematic arrangement of similar objects, usually in rows and columns.
Things called an array include:
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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 a gas). In electrochemical cells, electrodes are essential parts that can consist of a varie ...
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 possessing an electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by Maxwel ...
path to
ground 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 equipment's conductive surface, for safety and functional purposes. The choice of earthing system can ...
.
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 of iron and carbon that demonstrates improved mechanical properties compared to the pure form of iron. Due to steel's high Young's modulus, elastic modulus, Yield (engineering), yield strength, Fracture, fracture strength a ...
with a
copper
Copper is a chemical element; it has symbol Cu (from Latin ) 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 pinkish-orang ...
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
file:Sample cross-section of high tension power (pylon) line.jpg, 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 d ...
. 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:
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Ufer ground
The Ufer ground is an electrical Ground (electricity), 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.
...
*
Bentonite
Bentonite ( ) is an Absorption (chemistry), 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 swelli ...
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 " sacrifi ...
, the
anode
An anode usually is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, which is usually an electrode of the device through which conventional current leaves the devic ...
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 substance that conducts electricity through the movement of ions, but not through the movement of electrons. This includes most soluble Salt (chemistry), salts, acids, and Base (chemistry), bases, dissolved in a polar solven ...
.
[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 uses direct current (DC) for electric power transmission, in contrast with the more common alternating current (AC) transmission systems. Most HVDC links use voltages betwe ...
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
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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 by the normal current fl ...
*
Earth potential rise
References
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Electric power