Single wire earth return (SWER) or single wire ground return is a single-wire transmission line for supplying single-phase electrical power from an electrical grid to remote areas at low cost. A single-wire transmission line (or single wire method) is a method of supplying electrical power through a single-wired electrical conductor In electrical engineering single-phase electric power refers to the distribution of Alternating current Electric power using a system in which all the voltages of Electric power is defined as the rate at which Electrical energy is transferred by an Electric circuit. Electric power transmission, a process in the delivery of Electricity to consumers is the bulk transfer of electrical power It is principally used for rural electrification, but also finds use for larger isolated loads such as water pumps, and light rail. Rural electrification is the process of bringing electrical power to Rural and remote areas For specific light rail systems many of which use the words "light rail" as part of their name see List of light-rail transit systems. Single wire earth return is also used for HVDC over submarine power cables. HVDC or high-voltage Direct current Electric power transmission systems contrast with the more common Alternating current systems as a means Submarine power cables are cables for electrical power running through the sea below the surface
SWER is a choice for a distribution system when conventional return current wiring would cost more than SWER’s isolation transformers and small power losses. Power engineers experienced with both SWER and conventional power lines rate SWER as equally safe, more reliable, less costly, but with slightly lower efficiency than conventional lines. 
Power is supplied to the SWER line by an isolating transformer of up to 300 kVA. A transformer is a device that transfers Electrical energy from one circuit to another through inductively coupled Electrical conductors This isolates the grid from ground or earth, and changes the grid voltage (typically 22 kilovolts line to line) to the SWER voltage (typically 12. Electrical tension (or voltage after its SI unit, the Volt) is the difference of electrical potential between two points of an electrical 7 or 19. 1 kilovolts line to earth).
The SWER line is a single conductor that may stretch for tens or even hundreds of kilometres, visiting a number of termination points. In Science and engineering, a conductor is a material which contains movable Electric charges. The kilometre ( American spelling: kilometer) symbol km is a unit of Length in the Metric system, equal to one thousand At each termination point, such as a customer's premises, current flows from the line, through the primary coil of a step-down transformer, to earth through an earth stake. In Electrical engineering, the term ground or earth has several meanings depending on the specific application areas From the earth stake, the current eventually finds its way back to the main step-down transformer at the head of the line, completing the circuit. An electrical network is an interconnection of Electrical elements such as Resistors Inductors Capacitors Transmission lines Voltage SWER is therefore a practical example of a phantom loop. A phantom loop is a suitably arranged Electrical network that includes within the number of conductive paths part of the Natural environment (which can be at the same
The secondary winding of the local transformer will supply the customer with either single ended single phase (N-0) or split phase (N-0-N) power in the region’s standard appliance voltages, with the 0 volt line connected to a safety earth that does not normally carry an operating current. A split phase Electricity distribution system is a 3-wire Single-phase distribution system commonly used in North America for single-family residential and light
A large SWER line may feed as many as 80 distribution transformers. Since the distribution system must carry reactive power (vars), as well as real power (watts), capacities are measured in volt-amperes, not watts. This article deals with power in AC systems See Mains electricity for information on utility supplied AC power A volt-ampere in electrical terms means the amount of Apparent power in an Alternating current circuit equal to a current of one Ampere at an The watt (symbol W) is the SI derived unit of power, equal to one Joule of energy per Second. The transformers are usually rated at 5 kVA, 10 kVA and 25 kVA. The load densities are usually below 0. 5 kVA per kilometer (0. 8 kVA per mile) of line. Any single customer’s maximum demand will typically be less than 3. 5 kVA, but larger loads up to the capacity of the distribution transformer can also be supplied.
Some SWER systems in the USA are conventional distribution feeders that were built without a continuous neutral (most likely obsoleted transmission lines that were refitted for rural distribution service). The substation feeding such lines has a grounding rod on each pole within the substation; then on each branch from the line, the span between the pole next to and the pole carrying the transformer would have a grounded conductor (giving each transformer two grounding points for safety reasons).
At the end of the 19th century, Nikola Tesla demonstrated that only a single wire was necessary for power systems, with no need for a wired return conductor (using the Earth instead). The 19th century of the Common Era began on January 1, 1801 and ended on December 31, 1900, according to the Gregorian calendar There have already been discussions about Tesla's ethnicity on the talk page A single-wire transmission line (or single wire method) is a method of supplying electrical power through a single-wired electrical conductor  Lloyd Mandeno fully developed SWER in New Zealand around 1925 for rural electrification. Year 1925 ( MCMXXV) was a Common year starting on Thursday (link will display the full calendar of the Gregorian calendar. Although he termed it “Earth Working Single Wire Line” it was often called “Mandeno’s Clothesline”. More than 200,000 kilometres have now been installed in Australia and New Zealand. It is considered safe, reliable and low cost, provided that safety features and earthing are correctly installed. The Australian standards are widely used and cited. It has been applied in Saskatchewan, Brazil, Africa, portions of the Upper Midwest, and SWER interties have been proposed for Alaska and prototyped. Saskatchewan (səˈskætʃəwən) is a prairie province in Canada, which has an area of 588276
SWER violates common wisdom about electrical safety, because it lacks a traditional metallic return to a neutral shared by the generator. SWER’s safety is instead assured because transformers isolate the ground from both the generator and user. However, certain pressure groups claim that stray voltages from SWER can injure livestock. " Stray voltage " is a term commonly used throughout the electric utility industry to describe when infrastructure devices such as lamp posts manholes gratings and junction
Grounding is critical because of the significant currents on the order of 8 amperes that flow through the ground near the earth points, so a good-quality earth connection is needed to prevent risk of electric shock due to earth potential rise near this point. The ampere, in practice often shortened to amp, (symbol A is a unit of Electric current, or amount of Electric charge per second In Electrical engineering, the term ground or earth has several meanings depending on the specific application areas "Electrocute" redirects here For the band see Electrocute (band. 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 Separate grounds for power and safety are also used. Duplication of the ground points assures that the system is still safe if either of the grounds is damaged.
A good earth connection is normally a 6 m stake of copper-clad steel driven vertically into the ground, and bonded to the transformer earth and tank. A good ground resistance is 5–10 ohms.
Other standard features include automatic reclosing circuit breakers (reclosers). In Electric power distribution, an autorecloser is a Circuit breaker equipped with a mechanism that can automatically close the breaker after it has been opened due Most faults (overcurrent) are transient. Since the network is rural, most of these faults will be cleared by the recloser. Each service site needs a rewirable drop out fuse for protection and switching of the transformer. The transformer secondary should also be protected by a standard high-rupture capacity (HRC) fuse or low voltage circuit breaker. A surge arrestor (spark gap) on the high voltage side is common, especially in lightning-prone areas.
Bare-wire or ground-return telecommunications can be compromised by the ground-return current if the grounding area is closer than 100 m or sinks more than 10 A of current. Modern radio, optic fibre channels and cell phone systems are unaffected.
SWER’s main advantage is its low cost. It is often used in sparsely populated areas where the cost of building an isolated distribution line cannot be justified. Capital costs are roughly 50% of an equivalent two-wire single-phase line. They can be 70% less than 3-wire three-phase systems. Maintenance costs are roughly 50% of an equivalent line.
SWER also reduces the largest cost of a distribution network, the number of poles. Conventional 2-wire or 3-wire distribution lines have a higher power transfer capacity, but can require seven poles per kilometre, with spans of 100 m to 150 m. SWER’s high line voltage and low current permits the use of low-cost galvanized steel wire. Hot-dip galvanizing is a form of Galvanization. It is the process of coating Iron or Steel with a thin Zinc layer by passing the steel Steel’s greater strength permits spans of 400 m or more, reducing the number of poles to 2. 5/km.
Reinforced concrete poles have been traditionally used in SWER lines because of their low cost, low maintenance, and resistance to water damage, termites and fungus. Reinforced concrete is Concrete in which reinforcement bars (" Rebars quot or fibers have been incorporated to strengthen a material that would otherwise be The termites are a group of Social Insects usually classified at the taxonomic rank of order Isoptera (but see also taxonomy A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ Local labor can produce them in most areas, further lowering costs.
SWER can be used in a grid or loop, but is usually arranged in a linear or radial layout to save costs. In the customary linear form, a single-point failure in a SWER line causes all customers further down the line to lose power. However, since it has fewer components in the field, SWER has less to fail. For example, since there is only one line, winds can’t cause lines to clash, removing a source of damage, as well as a source of rural brush fires.
Since the line can't clash in the wind, and the bulk of the transmission line has low resistance attachments to earth, excessive ground currents from shorts and geomagnetic storms are far more rare than in conventional metallic-return systems. A geomagnetic storm or solar storm is a temporary disturbance of the Earth 's Magnetosphere caused by a disturbance in Space weather. So, SWER has fewer ground-fault circuit-breaker openings to interrupt service.
SWER lines tend to be long, with high impedance, so the voltage drop along the line is often a problem, causing poor regulation. Variations in demand cause variation in the delivered voltage. To combat this, some installations have automatic variable transformers at the customer site to keep the received voltage within legal specifications.
When used with distributed generation, SWER is substantially more efficient than when it is operated as a single-ended system. Distributed generation, also called on-site generation, dispersed generation, embedded generation, decentralized generation, decentralized For example, some rural installations can offset line losses and charging currents with local solar power, wind power, small hydro or other local generation. Solar energy is the Light and radiant heat from the Sun that powers Earth 's Climate and Weather and sustains Life Wind Power is the conversion of wind energy into a useful form such as electricity using Wind turbines At the end of 2007 worldwide capacity of wind-powered generators was Small hydro is the development of Hydroelectric power on a scale serving a small community or industrial plant This can be an excellent value for the electrical distributor, because it reduces the need for more lines. (Kashem and Ledwich)
After some years of experience, the inventor (Mandeno, below) advocated a capacitor in series with the ground of the main isolation transformer to counteract the inductive reactance of the transformers, wire and earth return path. A capacitor is a passive electrical component that can store Energy in the Electric field between a pair of conductors The plan was to improve the power factor, reduce losses and improve voltage performance due to reactive power flow. The power factor of an AC electric power system is defined as the Ratio of the real power to the apparent power, and is a number between 0 and This article deals with power in AC systems See Mains electricity for information on utility supplied AC power Though theoretically sound, this is not standard practice.
As demand grows, a well-designed SWER line can be substantially upgraded without new poles. The first step may be to replace the steel wire with more expensive copper-clad or aluminum-clad steel wire.
If more capacity is needed, a second SWER line can be run on the same poles to provide two SWER lines 180 degrees out of phase. This requires more insulators and wire, but doubles the power without doubling the poles. Many standard SWER poles have several bolt holes to support this upgrade. This configuration causes most ground currents to cancel, reducing shock hazards, and interference with communication wirelines.
Conventional two phase service is also possible with a two-wire upgrade: Though less reliable, it is more efficient. Two-phase electrical power was an early 20th century polyphase Alternating current electric power distribution system As more power is needed the lines can be upgraded to match the load, from single wire SWER to two wire, single phase and finally to three wire, three phase. This ensures a more efficient use of capital and makes the initial installation more affordable.
Customer equipment installed before these upgrades will all be single phase, and can be reused after the upgrade. If moderate amounts of three-phase are needed, it can be economically synthesized from two-phase with on-site equipment. This article deals with where how and why "three phase" is used
Many national electrical regulations (notably the U. S. ) require a metallic return line from the load to the generator. In these jurisdictions, each SWER line must be approved by exception.
In 1981 a high-power 8. 5 mile prototype SWER intertie was successfully installed from a coal plant in Bethel, Alaska to Napakiak, Alaska. Bethel ( Mamterilleq in Central Alaskan Yup'ik) is a city located near the west coast of the U Napakiak is a city in Bethel Census Area, Alaska, United States. It operates at 80 kV, and has special lightweight fiberglass poles that form an A-frame. The poles can be carried on lightweight snow machines, and most poles can be installed with hand-tools on permafrost without extensive digging. Erection of “anchoring” poles still required heavy machinery, but the cost savings were dramatic.
The phase conductor also carries a bundle of optic fibres within the steel armor wire, so the system supplies telecommunications as well as power.
Researchers at the University of Alaska Fairbanks estimate that a network of such interties, combined with coastal wind turbines, could substantially reduce Alaska’s dependence on increasingly expensive diesel fuel for power generation. The University of Alaska Fairbanks, located in Fairbanks, Alaska, USA is the flagship campus of the University of Alaska System, and is abbreviated as A wind turbine is a rotating machine which converts the Kinetic energy in Wind into Mechanical energy.  Alaska’s state economic energy screening survey advocated further study of this option, in order to use more of the state’s underutilized power sources. 
Many HVDC systems using submarine power cables are (or were until their expansion to bipolar schemes) single wire earth return systems. HVDC or high-voltage Direct current Electric power transmission systems contrast with the more common Alternating current systems as a means Submarine power cables are cables for electrical power running through the sea below the surface In order to avoid electrochemical corrosion, the ground electrodes of such systems are situated apart from the converter stations and not in the proximity of the transmission cable. The electrodes can be situated in the sea or on land. As cathodes, bare copper wires can be used in the sea or on land. As anodes, graphite rods dug in the ground, or titanium grids in the sea are used. In order to avoid electrochemical corrosion (and passivation of titanium surfaces) the current density at the surface of the electrodes may be only small and therefore large electrodes are required. Passivation is the process of making a material "passive" in relation to another material prior to using the materials together
The advantage of such schemes is saving money for a second conductor, because the saltwater is an excellent conductor. Some ecologists claim bad influences of electrochemical reactions, but they do not occur on very large underwater electrodes.