Single-wire transmission line
A single-wire transmission line is a way to send electrical power or signals using only one conductor. There is no second wire or ground return involved. The return path, if any, comes from the load’s own capacitance and other stray capacitances, not from a separate conductor.
Historically, most electrical devices relied on a complete circuit with a pair of wires. In the late 19th century, Nikola Tesla showed that by tuning a system to resonance, power could be transmitted with a single conductor, using the load and the line’s capacitance to complete the circuit in effect. Experiments in the 1890s demonstrated that motors and lamps could run on a single wire, though it wasn’t a true closed circuit in the ordinary sense. Large power could be sent if the impedance was matched and resonance was achieved.
Today, single-wire transmission isn’t practical with direct current or typical low-frequency power (like 50–60 Hz). It works at much higher frequencies, where the return path can be provided by the load’s self-capacitance and parasitic capacitances. By using a large inductor to create resonance, the capacitive reactance can be canceled, allowing significant current and power to flow through a single wire without an extra return conductor.
In 1899, Sommerfeld suggested that a surface wave could propagate energy along a single cylindrical wire at radio frequencies, potentially with lower loss than a two-wire system. However, practical issues—like the need for very long lines and sensitivity to nearby objects—made it challenging.
In 1950, Georg Goubau improved the idea by coating the wire with a dielectric and using a special launcher. This produces a surface wave that stays closer to the wire and reduces the surrounding field, cutting radiation losses. The practical line is called a G-line, and it works best at very high frequencies (UHF and above). It also requires a specific end-to-end launcher and connectors.
From 2003 to 2008, researchers explored versions using Sommerfeld’s bare wire with modern launchers, marketed in some cases as E-Line. These efforts aimed at non-radiating, high-speed communication over lines that would otherwise carry power.
Overall, single-wire transmission shows that, with the right frequency, a carefully designed single conductor and proper impedance matching, energy can be transmitted without a return wire. But it remains mainly a high-frequency, specialized concept rather than a mainstream method for ordinary power transmission.
This page was last edited on 3 February 2026, at 15:15 (CET).