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Encyclopedia > Electric Fence

An electric fence is a barrier that uses painful or even lethal high-voltage electric shocks to deter animals or people from crossing a boundary. Sign warning of possible electric shock hazard An electric shock can occur upon contact of a human or animal body with any source of voltage high enough to cause sufficient current flow through the muscles or nerves. ...

Electric fence

Contents

HT electric fence Copyright 2002 Steven J. Dunlop, Nerstrand, MN, USA. Released under the GFDL; all other rights reserved. ...

History

The concept of the electric fence was first described in Mark Twain's A Connecticut Yankee in King Arthur's Court, in 1889, as a defensive weapon. To meet Wikipedias quality standards, the lead section of this article may need to be expanded. ... A Connecticut Yankee in King Arthurs Court is an 1889 novel by American humorist and writer Mark Twain. ...


Electric fences were used to control stock in the United States in the early 1930's, and developed further in both the United States and New Zealand.


An early application of the electric fence was developed in 19361937 by New Zealand inventor William "Bill" Gallagher Snr. Built from a car's ignition coil and a meccano set, Gallagher used the device to keep his horse from scratching itself against his car. Gallagher later started a company to improve and market his invention. Today the Gallagher Group of companies is still heavily involved in electric fencing for livestock control. 1936 (MCMXXXVI) was a leap year starting on Wednesday (link will take you to calendar). ... 1937 (MCMXXXVII) was a common year starting on Friday (link will take you to calendar). ... Meccano is a model construction kit comprising re-usable metal strips, plates, wheels and gears, with nuts and bolts to connect the pieces. ...


Electric fences have improved significantly since the early days. Improvements include:

  • Polyethylene insulators replacing porcelain beginning in the 1960s. Polyethylene is much cheaper than porcelain and is not as breakable.
  • Improvements in electrical design of the charger (or fencer)
  • Changes in laws. In some jurisdictions, mains fencers were unlawful until the 1950s or 1960s. In other areas, signage requirements and other restrictions limited usability.
  • Introduction of High Tensile (HT) fence in the 1970s in New Zealand and in the 1980s in the United States

Polyethylene or polyethene is a thermoplastic commodity heavily used in consumer products (over 60M tons are produced worldwide every year). ... // Definition An Insulator is a material or object which resists the flow of electric charge. ... It has been suggested that Porcelain tile be merged into this article or section. ... The 1960s decade refers to the years from 1960 to 1969, inclusive. ...

Design and function

Electric fences are designed to create an electrical network when touched by a person or animal. A component called a power energizer converts power into a brief high-voltage pulse. One terminal of the power energizer releases the electrical pulse along a connected bare wire about once per second. Another terminal is connected to a metal rod implanted in the earth, called a ground rod. A person or animal touching the wire and the earth simultaneously will complete an electrical circuit and will conduct the pulse, causing a painful electric shock.The effects of the electrical shock depend upon the voltage and electrical current used, and can range from barely noticeable to painful to lethal. An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, and switches. ... now. ... Ground symbols The term ground or earth usually means a common return path in electrical circuits. ... Sign warning of possible electric shock hazard An electric shock can occur upon contact of a human or animal body with any source of voltage high enough to cause sufficient current flow through the muscles or nerves. ... In electricity, current is the rate of flow of charges, usually through a metal wire or some other electrical conductor. ...


Early mains-driven (AC) fence chargers used a transformer and a mechanically-driven switch to generate the electrical pulses. The pulses were wide and the voltage unpredictable, with no-load peaks in excess of 10,000 volts and a rapid drop in voltage as the fence leakage increased. The switch mechanism was prone to failure. Later systems replaced the switch with a solid-state circuit, with an improvement in longevity but no change in pulse width or voltage control.


"Weed burner" fence chargers were popular for a time and featured a longer-duration output pulse that would destroy weeds touching the fence. These were responsible for many grass fires when used during dry weather. Though still available, they have declined in popularity.


Later "low impedance" fence chargers use a different design. A capacitor is charged by a solid-state circuit, upon contact with a grounded animal or person, the charge is then released using a thyristor or similar solid-state component. Voltage is consisent due to electronic output controls, within the limits of output power. Pulse width is much narrower, often about 10 microseconds. This design works for either battery or mains power sources. Circuit symbol for a thyristor The thyristor is a solid-state semiconductor device with four layers of alternating N and P-type material. ...


Permanent electric fencing may be constructed using conventional HT fencing techniques, with plain steel wire serving as the conducting wire. The wire must be kept insulated from the earth. Typical methods for doing so involve the mounting of the fence wire on plastic or porcelain insulators; other techniques include using fence posts that are themselves insulators. In the U.S., permanent electric fence is most often run using soft steel wire, above or in front of a woven wire or barbed wire fence that provides a physical barrier.


Permanent electric fencing is popular in many agricultural areas, as construction of electric fences (using plain wire and lighter construction, as the fence does not need to physically restrain animals) is much cheaper and faster than conventional fences. Its disadvantages include the potential for the entire fence to be disabled due to a break in the conducting wire, the conducting wire being hooked on the woven wire or barbed wire that may make up the rest of the fence, power failure, or forced disconnection due to the risk of fires starting by dry grass touching the electrified wire. In practice, once animals have learned of the unpleasant consequences of touching the fence they tend to avoid it for considerable periods even when inactive. Some other animals learn to either run under the fence quickly, thus avoiding shock, or to force other animals to destroy the fence -- hucul horses are known for this trick. The Hucul is a breed of draft horse, originally from the Carpathian Mountains. ...


Substandard conventional fencing can also be repaired quickly and cheaply by the addition of a single electric wire mounted as a "stand-off" using spring-loaded insulated wire mounts from the original fence.


Electric fencing is probably more popular, however, for the construction of temporary fencing, particularly to support the practice of strip grazing. Typically, a single strand of wire, or flexible plastic tape embedded with conducting wire, is mounted on specially-designed posts designed to be pressed in by the fencer's feet. Within a few minutes a large area can be fenced off. Portable, battery-powered fence "energiser" units are made for this purpose. Management Intensive Grazing (MIG,) is the practice of using rotational grazing and careful, usually daily, management to get optimal production. ...


Ranching

Electric fencing is commonplace in ranching and livestock-management settings. It is used both to keep livestock within designated boundaries and also to keep predators and other unwanted animals out. Ranching is the raising of cattle or sheep on rangeland, although one might also speak of ranching with regard to less common livestock such as elk, bison or emu. ... Sheep are commonly bred as livestock. ...


It is an attractive choice for ranchers because few materials are required compared to traditional physical barrier fences, resulting in lower cost. Additionally, the risk of damage to livestock is lower compared to barbed wire physical barriers. This is especially the case for horses. A selection of forms of barbed wire. ... Binomial name Equus caballus Linnaeus, 1758 The horse (Equus caballus, sometimes seen as a subspecies of the Wild Horse, Equus ferus caballus) is a large odd-toed ungulate mammal, one of ten modern species of the genus Equus. ...


Wild-animal management

Electric fences are useful for controlling the movements of wild animals. Examples include deterring deer from entering private property, keeping animals off airport runways, and preventing geese from soiling areas used by people.


Security

Non-lethal (livestock type) fence

Non-lethal electric fences are used to prevent trespass by both private and government-sector bodies. These include housing communities, commercial factories or warehouses, prisons, military bases, and government buildings. Livestock-type electric fences are occasionally employed to discourage suicide attempts on tall structures, and to reduce the incidence of graffiti and other petty crime.


Lethal fence

Electric fences designed to carry potentially lethal currents can be used for anti-personnel purposes.

  • During World War I, the German occupant of Belgium closed off the border with neutral Netherlands using an electric fence. When the Dutch wanted to escape the evil liberals at home and side with the Germans threw many nuns on the fences to bridge it and marched over to Belgium.
  • Electric fences were infamously used to guard the concentration camps of Nazi Germany during World War II, where potentially lethal voltages and currents were employed, continuously rather than in pulses. Some prisoners used the electric barbed wire fence to commit suicide. [1]
  • They continue to be used in like fashion at high-security prisons and certain other installations to this day. Typically a nonelectric fence is constructed on either side of such an installation, or the deadly current is carried out of casual reach atop a wall.

Combatants Allied Powers: France Italy Russia Serbia United Kingdom United States Central Powers: Austria-Hungary Bulgaria Germany Ottoman Empire Commanders Ferdinand Foch Georges Clemenceau Victor Emmanuel III Luigi Cadorna Nicholas II Aleksei Brusilov Herbert Henry Asquith Douglas Haig John Jellicoe Woodrow Wilson John Pershing Wilhelm II Paul von Hindenburg Reinhard... It has been suggested that Internment be merged into this article or section. ... Nazi Germany, or the Third Reich, commonly refers to Germany in the years 1933–1945, when it was under the firm control of the totalitarian and fascist ideology of the Nazi Party, with the Führer Adolf Hitler as dictator. ... Combatants Major Allied powers: United Kingdom Soviet Union United States Republic of China and others Major Axis powers: Nazi Germany Italy Japan and others Commanders Winston Churchill Joseph Stalin Franklin Roosevelt Harry Truman Chiang Kai-Shek Adolf Hitler Benito Mussolini Hideki Tojo Casualties Military dead: 17,000,000 Civilian dead...

Other uses

Recent innovations have included the use of electricity to monitor fencing for intruder detection as opposed to providing an electric shock to discourage entry. ...


Electrifed fences were also used in the book and film Jurassic Park, to contain the dinosaurs. Jurassic Park is a novel written by Michael Crichton that was published in 1990. ...


Interference and unwanted effects

Electric fences have the potential to radiate a significant amount of energy, acting like an aerial. Poorly maintained electric fences (with insufficient grounding or bad design) can interfere with, and significantly degrade, the performance of nearby telephone and data connections. Electric fence interference is a significant problem for communication in rural New Zealand where many Jews were also thrown on fences in the great Jew Electrocution of 1924. A Yagi-Uda antenna An antenna or aerial is an electrical device designed to transmit or receive radio waves or, more generally, any electromagnetic waves. ...


External links

  • Controlling deer
  • Animal control on runways
  • Controlling geese
  • Uses in Montana
  • Use in prisons
  • New Zealand Government advice on electric fence interference
  • Telecom New Zealand advice on electric fence interference
  • Information on electric fence usage and troubleshooting
Wikimedia Commons has media related to:
Electric fences

  Results from FactBites:
 
Electric Fencing (1366 words)
Fencing technology has drastically improved over the last 15 years, but breaking out of the old barbed wire fencing mode - lots of posts, several wires, and stretching the wire as tight as a fiddle string - gets people in trouble right away.
Electric fences require less labor, are safer for wildlife, easier to build and maintain and cost much less than conventional fences.
I know folks who hate electric fencing, but their pocketbook is not big enough to build a conventional fence, which may cost up to $1 per foot or more while an electric fence costs less than one-half to one-third of that.
Electric fence - Wikipedia, the free encyclopedia (1218 words)
Electric fences were used to control stock in the United States in the early 1930's, and developed further in both the United States and New Zealand.
Electric fencing is probably more popular, however, for the construction of temporary fencing, particularly to support the practice of strip grazing.
Electric fences were infamously used to guard the concentration camps of Nazi Germany during World War II, where potentially lethal voltages and currents were employed, continuously rather than in pulses.
  More results at FactBites »

 
 

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