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Aerial bundled cables (also aerial bundled conductors or simply ABC) are overhead power lines using several insulated phase conductors bundled tightly together, usually with a bare neutral conductor. This contrasts with the traditional practice of using uninsulated conductors separated by air gaps. This variation of bundled conductors utilizes the same principles as overhead power lines, except that they are closer together to the point of touching but each conductor is surrounded by an insulating layer (except for the neutral line).
The main objections to the traditional design are that the multiple conductors are considered unappealing, and external forces (such as high winds) can cause them to touch and short circuit. The resultant sparks have been a cause of bushfires in drier climates. In the UK where some supplies to rural property are converted to PME/MEN from TT Earthing system concerns have been expressed that the lower conductor alone may be broken, (by high vehicle or falling tree for example) but with the upper phase conductors intact. This is a potentially dangerous fault condition. With ABC, a simultaneous disconnection of all conductors is more likely.
In moister climates, tree growth is a significant problem for overhead power lines. ABC will not arc over if touched by tree branches. Although persistent rubbing is still a problem, tree-trimming costs can be reduced.
Areas with large trees and branches falling on lines are a problem for ABC as the line degrades over time. Due to the very large strain forces cracking and breaking insulation can lead to short circuit failures which can then lead to ground fires due to dripping of molten insulation.
Low voltage ABC has already been developed in several countries across the globe and promises to be cheaper, safer, more reliable, require less tree clearing and pruning, be more aesthetic, be less labor-intensive, require less maintenance and eliminate bushfires being initiated by conductor clashing.
ABC have been introduced into Australian power systems progressively since 1983. [1] This was partly in response to bushfires sparked by old wires touching.
In some bushfire prone areas though, older ABC installations are now creating fires, particularly at points where the cables have damaged or been degraded over time.
In the Dandenong Ranges area Victoria 2014. Medium voltage (11-22 kV) ABC is being replaced with underground cable due to high failure rates of HV ABC, with life expectancy of just 10 years, when original life was expected to be approx 30 years. Due to degraded cable, cost of repairs & maintenance and bushfire risk.
Low voltage ABC lines were first installed on the rural Irish distribution networks in 1981. [2] It is not known where ABC was first installed.
K-Electric first introduced ABC, in Gulshan-e-Iqbal area of Karachi city with a pilot project was completed in March 2014. Following 90% theft loss reduction, the decision to roll out the new cabling across the entire K-Electric distribution network of Karachi.
Low voltage ABC lines are installed in urban distribution systems commonly.
An electrical insulator is a material in which electric current does not flow freely. The atoms of the insulator have tightly bound electrons which cannot readily move. Other materials—semiconductors and conductors—conduct electric current more easily. The property that distinguishes an insulator is its resistivity; insulators have higher resistivity than semiconductors or conductors. The most common examples are non-metals.
In electrical engineering, ground or earth may be 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.
An electrical cable is an assembly of one or more wires running side by side or bundled, which is used as an electrical conductor, i.e., to carry electric current. One or more electrical cables and their corresponding connectors may be formed into a cable assembly, which is not necessarily suitable for connecting two devices but can be a partial product. Cable assemblies can also take the form of a cable tree or cable harness, used to connect many terminals together.
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.
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.
A transmission tower is a tall structure, usually a lattice tower made of steel that is used to support an overhead power line. In electrical grids, transmission towers carry high-voltage transmission lines that transport bulk electric power from generating stations to electrical substations, from which electricity is delivered to end consumers; moreover, utility poles are used to support lower-voltage sub-transmission and distribution lines that transport electricity from substations to electricity customers.
In electrical engineering, ground and neutral are circuit conductors used in alternating current (AC) 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.
Electrical wiring is an electrical installation of cabling and associated devices such as switches, distribution boards, sockets, and light fittings in a structure.
Electrical wiring in the United Kingdom is commonly understood to be an electrical installation for operation by end users within domestic, commercial, industrial, and other buildings, and also in special installations and locations, such as marinas or caravan parks. It does not normally cover the transmission or distribution of electricity to them.
An overhead power line is a structure used in electric power transmission and distribution to transmit electrical energy along large distances. It consists of one or more conductors suspended by towers or poles. Since most of the insulation is provided by air, overhead power lines are generally the lowest-cost method of power transmission for large quantities of electric energy.
In electric power distribution, automatic circuit reclosers (ACRs) are a class of switchgear designed for use on overhead electricity distribution networks to detect and interrupt transient faults. Also known as reclosers or autoreclosers, ACRs are essentially rated circuit breakers with integrated current and voltage sensors and a protection relay, optimized for use as a protection asset. Commercial ACRs are governed by the IEC 62271-111/IEEE Std C37.60 and IEC 62271-200 standards. The three major classes of operating maximum voltage are 15.5 kV, 27 kV and 38 kV.
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.
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 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.
Mineral-insulated copper-clad cable is a variety of electrical cable made from copper conductors inside a copper sheath, insulated by inorganic magnesium oxide powder. The name is often abbreviated to MICC or MI cable, and colloquially known as pyro. A similar product sheathed with metals other than copper is called mineral insulated metal sheathed (MIMS) cable.
Knob-and-tube wiring is an early standardized method of electrical wiring in buildings, in common use in North America from about 1880 to the 1930s. It consisted of single-insulated copper conductors run within wall or ceiling cavities, passing through joist and stud drill-holes via protective porcelain insulating tubes, and supported along their length on nailed-down porcelain knob insulators. Where conductors entered a wiring device such as a lamp or switch, or were pulled into a wall, they were protected by flexible cloth insulating sleeving called loom. The first insulation was asphalt-saturated cotton cloth, then rubber became common. Wire splices in such installations were twisted together for good mechanical strength, then soldered and wrapped with rubber insulating tape and friction tape, or made inside metal junction boxes.
In an electric power system, a fault or fault current is any abnormal electric current. For example, a short circuit is a fault in which a live wire touches a neutral or ground wire. An open-circuit fault occurs if a circuit is interrupted by a failure of a current-carrying wire or a blown fuse or circuit breaker. In three-phase systems, a fault may involve one or more phases and ground, or may occur only between phases. In a "ground fault" or "earth fault", current flows into the earth. The prospective short-circuit current of a predictable fault can be calculated for most situations. In power systems, protective devices can detect fault conditions and operate circuit breakers and other devices to limit the loss of service due to a failure.
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 flow in the power system. Large voltages can appear on the enclosures of electrical equipment due to a fault in the electrical power system, such as a failure of insulation.
In civil engineering, undergrounding is the replacement of overhead cables providing electrical power or telecommunications, with underground cables. It helps in wildfire prevention and in making the power lines less susceptible to outages during high winds, thunderstorms or heavy snow or ice storms. An added benefit of undergrounding is the aesthetic quality of the landscape without the powerlines. Undergrounding can increase the capital cost of electric power transmission and distribution but may decrease operating costs over the lifetime of the cables.
An aerial cable or air cable is an insulated cable usually containing all conductors required for an electrical distribution system or a telecommunication line, which is suspended between utility poles or electricity pylons. As aerial cables are completely insulated there is no danger of electric shock when touching them and there is no requirement for mounting them with insulators on pylons and poles. A further advantage is they require less right of way than overhead lines for the same reason. They can be designed as shielded cables for telecommunication purposes. If the cable falls, it may still operate if its insulation is not damaged.
A high-voltage cable is a cable used for electric power transmission at high voltage. A cable includes a conductor and insulation. Cables are considered to be fully insulated. This means that they have a fully rated insulation system that will consist of insulation, semi-con layers, and a metallic shield. This is in contrast to an overhead line, which may include insulation but not fully rated for operating voltage. High-voltage cables of differing types have a variety of applications in instruments, ignition systems, and alternating current (AC) and direct current (DC) power transmission. In all applications, the insulation of the cable must not deteriorate due to the high-voltage stress, ozone produced by electric discharges in air, or tracking. The cable system must prevent contact of the high-voltage conductor with other objects or persons, and must contain and control leakage current. Cable joints and terminals must be designed to control the high-voltage stress to prevent the breakdown of the insulation.