Single-wire transmission line
Encyclopedia
A single-wire transmission line (or single wire method) is a method of supplying electrical power through a single electrical conductor.
noticed the phenomenon of electrical conductivity. Essentially, electric currents may be transmitted from one body to another along a conductor, and all conductors contain movable charges of electricity. At the end of the 19th century, Tesla
demonstrated that by using an electrical network
tuned to resonance
and using, what at the time would be called, "high frequency AC" and today would be low frequency
AC, only a single wire was necessary for power systems, with no need for a metal or Earth return conductor. Tesla called it the "transmission of electrical energy through one wire without return".
In 1891 and 1892, Tesla gave demonstration lectures with electrical oscillators before the American Institute of Electrical Engineers at Columbia College, N.Y. and the Institution of Electrical Engineers, London, showing that electric motors and single-terminal incandescent lamps can be operated through a single wire without a return conductor. Electrical capacitance serves to complete the circuit by "electrostatic induction."
In 1893 Tesla stated,
A one-wire transmission system was protected in 1897 by , "Electrical Transformer". This patent shows a one-wire with earth return circuit.
In 1901 Tesla stated,
intended for use at UHF and microwave
wavelengths. The line itself consists of a single conductor coated with dielectric material. Coupling to and from the G-line is done with conical metal "launchers" or "catchers," with their narrow ends connected for example to the shield of coaxial feed line, and with the transmission line passing through a hole in the conical tips.
Planar Goubau Lines with applications at terahertz frequencies have also been demonstrated recently.
Contrary to Goubau's assertions, it has been shown both possible and practical to launch a surface wave around an uninsulated conductor without special conditioning and without reducing the wave velocity, while still using launchers of practical size. Conductors much larger than those used by Goubau have been shown to be completely adequate. Furthermore, "a nearby conductor other than the line itself may provide a termination point and thereby reduce energy coupled into the TM wave." This has relevance to Tesla's 1891-1893 table-top demonstrations.
Common uninsulated single or multistrand overhead power conductor may be used to support very low attenuation propagation over the entire frequency range from below 50 MHz to above 20 GHz while employing a launch device of only 15–20 cm in diameter. This makes the installed base of overhead powerlines available for very high rate information transport. Propagation velocity for this line operating in air has been measured to be within 0.1% of that of a free wave in air. The effects of line taps, bends, insulators and other impairments normally found on power distribution systems have proven to be predictable and manageable.
Numerical solutions of Maxwell's equations for three dimensional models of simple launcher devices coupling to an ideal, smooth conductor have confirmed the low attenuation, high bandwidth, high propagation velocity and that the vast majority of the propagated energy remains quite close to the conductor surface, all in agreement with measurement.
History
In 1729, the English physicist Stephen GrayStephen Gray (scientist)
Stephen Gray was an English dyer and amateur astronomer, who was the first to systematically experiment with electrical conduction, rather than simple generation of static charges and investigations of the static phenomena....
noticed the phenomenon of electrical conductivity. Essentially, electric currents may be transmitted from one body to another along a conductor, and all conductors contain movable charges of electricity. At the end of the 19th century, Tesla
Nikola Tesla
Nikola Tesla was a Serbian-American inventor, mechanical engineer, and electrical engineer...
demonstrated that by using an electrical network
Electrical network
An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources and switches. An electrical circuit is a special type of network, one that has a closed loop giving a return path for the current...
tuned to resonance
Resonance
In physics, resonance is the tendency of a system to oscillate at a greater amplitude at some frequencies than at others. These are known as the system's resonant frequencies...
and using, what at the time would be called, "high frequency AC" and today would be low frequency
Low frequency
Low frequency or low freq or LF refers to radio frequencies in the range of 30 kHz–300 kHz. In Europe, and parts of Northern Africa and of Asia, part of the LF spectrum is used for AM broadcasting as the longwave band. In the western hemisphere, its main use is for aircraft beacon,...
AC, only a single wire was necessary for power systems, with no need for a metal or Earth return conductor. Tesla called it the "transmission of electrical energy through one wire without return".
In 1891 and 1892, Tesla gave demonstration lectures with electrical oscillators before the American Institute of Electrical Engineers at Columbia College, N.Y. and the Institution of Electrical Engineers, London, showing that electric motors and single-terminal incandescent lamps can be operated through a single wire without a return conductor. Electrical capacitance serves to complete the circuit by "electrostatic induction."
In 1893 Tesla stated,
- "Thus coils of the proper dimensions might be connected each with only one of its ends to the mains from a machine of low E. M. F., and though the circuit of the machine would not be closed in the ordinary acceptance of the term, yet the machine might be burned out if a proper resonance effect would be obtained.
A one-wire transmission system was protected in 1897 by , "Electrical Transformer". This patent shows a one-wire with earth return circuit.
In 1901 Tesla stated,
- Some ten years ago, I recognized the fact that to convey electric currents to a distance it was not at all necessary to employ a return wire, but that any amount of energy might be transmitted by using a single wire. I illustrated this principle by numerous experiments, which, at that time, excited considerable attention among scientific men.
Goubau line
A Goubau line, or G-line for short, is a type of single wire transmission lineTransmission line
In communications and electronic engineering, a transmission line is a specialized cable designed to carry alternating current of radio frequency, that is, currents with a frequency high enough that its wave nature must be taken into account...
intended for use at UHF and microwave
Microwave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
wavelengths. The line itself consists of a single conductor coated with dielectric material. Coupling to and from the G-line is done with conical metal "launchers" or "catchers," with their narrow ends connected for example to the shield of coaxial feed line, and with the transmission line passing through a hole in the conical tips.
Planar Goubau Lines with applications at terahertz frequencies have also been demonstrated recently.
E-Line
While Goubau-Line, which uses a conductor having an outer dielectric or special surface conditioning provided to reduce the velocity of the wave on the conductor, has long been known, a more general transverse-magnetic (TM) mode does not have this limitation. Marketed as E-Line, it is similar to Goubau-Lines in its use of launchers to couple to and from a radially symmetric wave propagating in the space around a single conductor but different in that it can operate on insulation-free conductors, including those that are polished and completely unfeatured. The propagation velocity of the wave is not reduced and is accordingly quite close to that of a wave traveling in the same medium in the absence of any conductor at all.Contrary to Goubau's assertions, it has been shown both possible and practical to launch a surface wave around an uninsulated conductor without special conditioning and without reducing the wave velocity, while still using launchers of practical size. Conductors much larger than those used by Goubau have been shown to be completely adequate. Furthermore, "a nearby conductor other than the line itself may provide a termination point and thereby reduce energy coupled into the TM wave." This has relevance to Tesla's 1891-1893 table-top demonstrations.
Common uninsulated single or multistrand overhead power conductor may be used to support very low attenuation propagation over the entire frequency range from below 50 MHz to above 20 GHz while employing a launch device of only 15–20 cm in diameter. This makes the installed base of overhead powerlines available for very high rate information transport. Propagation velocity for this line operating in air has been measured to be within 0.1% of that of a free wave in air. The effects of line taps, bends, insulators and other impairments normally found on power distribution systems have proven to be predictable and manageable.
Numerical solutions of Maxwell's equations for three dimensional models of simple launcher devices coupling to an ideal, smooth conductor have confirmed the low attenuation, high bandwidth, high propagation velocity and that the vast majority of the propagated energy remains quite close to the conductor surface, all in agreement with measurement.
See also
- Power line communicationPower line communicationPower line communication or power line carrier , also known as power line digital subscriber line , mains communication, power line telecom , power line networking , or broadband over power lines are systems for carrying data on a conductor also used for electric power transmission.A wide range...
- Single wire earth returnSingle wire earth returnSingle wire earth return 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...
- Surface waveSurface waveIn physics, a surface wave is a mechanical wave that propagates along the interface between differing media, usually two fluids with different densities. A surface wave can also be an electromagnetic wave guided by a refractive index gradient...
- Wireless energy transferWireless energy transferWireless energy transfer or wireless power is the transmission of electrical energy from a power source to an electrical load without artificial interconnecting conductors. Wireless transmission is useful in cases where interconnecting wires are inconvenient, hazardous, or impossible...
Patents
, " Art of Transmitting Electrical Energy Through The Natural Mediums" Nikola Tesla, "Surface wave transmission line". George J. E. Goubau, "Launching and receiving of surface waves". George J. E. Goubau., "Method and apparatus for single line electrical transmission". Avramenko, et al., "Method and apparatus for launching a surfacewave onto a single conductor transmission line using a slotted flared cone". Glenn E. Elmore, " Surface wave transmission system over a single conductor having E-fields terminating along the conductor " Glenn E. ElmoreFurther reading
- N. Tesla, "The True Wireless". Electrical ExperimenterElectrical ExperimenterThe Electrical Experimenter was a technical science magazine that was published monthly. It was first published in May 1913, as the successor to Modern Electrics, a combination of a magazine and mail-order catalog that had been published by Hugo Gernsback starting in 1908...
(May 1919). - J.J. O'Neill, Prodigal Genius, The life of Nikola Tesla (Neville Spearman 1968) pp. 70–73, 128-133.
- John O'Neill, "Electrical Prometheus" (History of Technology ("Molodaya Gvardiya") 1959).
- Toby Grotz, "Wireless Transmission of Power, An Attempt To Verify Nikola Tesla's 1899 Colorado Springs Experiments, Results Of Research And Experimentation". Proceedings of the 26th IECEC Conference, vol. 4 (1991).