Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

temporary fault
a fault that will not reoccur if the equipment is deenergized and then reenergized. An example of a temporary fault is when a lightning stroke causes an uninsulated overhead line to arc over an insulator, with no equipment damage.
temporary interruption
a loss of voltage of less than 0.1 pu for a duration of 3 seconds to 1 minute.
terahertz (THz)
a frequency unit, 1012 hertz.
terminal bushing

See bushing
termination
a circuit element or device placed at the end of a transmission line that reflects and/or absorbs signal energy.
terminator
(1) a device connected to the physical end of a signal line that prevents the unwanted reflection of the signal back to its source.

(2) a data item in a stream that marks the end of some portion or all of the data.
tertiary winding
a third winding on a transformer. A tertiary winding may be used to obtain a second voltage level from the transformer. For example, in a substation it may be necessary to have low voltage power for the substation equipment in addition to the distribution voltage. Another application of a tertiary winding is in a wye-wye three-phase transformer. Here the tertiary is connected in delta, to provide a path for the triple harmonic components of the exciting current and prevent distortion of the phase voltages.
tesla
a unit of magnetic flux density equal to one weber per square meter, i.e., one volt-second per square meter. Denoted by T. The unit is named in honor of Nikola Tesla, an early pioneer in the electric industry, who is most commonly credited with building the first practical induction motor.
Tesla
Tesla, Nikola (1856-1943) Born: Smiljan, Croatia

is best known as the electrical pioneer who championed the use of alternating current. When Tesla first came to the
United States he worked for Edison. He soon split with Edison, because Tesla approached invention from a theoretical standpoint, whereas Edison was a "trial and error" type experimentalist. Together with his financial backer, George Westinghouse, they battled with Edison, who championed the use of direct current for electrifying the world. Tesla is also known for his many inventions including the Tesla coil and the AC induction motor. It was Westinghouse who made a fortune from Tesla's inventions. Tesla was known for his eccentricities and died a recluse in New York City.
THD

See total harmonic distortion
thermal control

See thermal management
thermal expansion mismatch
the absolute difference in thermal expansion of two components.
thermal fin
an extension of the surface are in contact with a heat transfer fluid, usually in the form of a cylinder or rectangular prism protruding from the base surface.
thermal light
light generated by spontaneous emission, such as when a group of excited atoms or molecules drops to a lower energy state in a random and independent manner emitting photons in the process; contrasted with laser light.
thermal management
the process or processes by which the temperature of a specified component or system is maintained at the desired level. Also called thermal control.
thermal reactor
a reactor which maintains a critical reaction with thermal neutrons.
thermal resistance
a thermal characteristic of a heat flow path, establishing the temperature drop required to transport heat across the specified segment or surface; analogous to electrical resistance.
thermionics
direct conversion of thermal energy into electrical energy by using the Edison effect (thermionic emission).
thermit welding
a welding process that produces coalescence of metals by heating them with superheated liquid metal from a chemical reaction between a metal oxide and aluminum with or without the application of pressure.
third rail
a method of transmitting power to an electric locomotive. An insulated steel rail is laid along the railbed just outside the traction rails. This third rail is maintained at (typically) 600 volts DC by the railroad power supply, and contact is made to the locomotive by a shoe which slides atop the rail. Ground return is through the traction rails.
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