Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

active power line conditioner

a device which senses disturbances on a power line and injects compensating voltages or currents to restore the line's proper waveform.

air-gap line
the line that is obtained by continuing the linear portion of the saturation curve of a synchronous machine or a DC machine. The figure shows a plot of generated voltage vs. field current at constant machine speed. Initially, an increase in field current yields a linear increase in the generated voltage, but as the iron becomes saturated, the voltage rolls off. The air-gap line gives the voltage that would be obtained without saturation.
asymmetric digital subscriber line (ADSL)
a digital subscriber line (DSL) in which the rate from central switching office (CO) to customer premise is much faster than the rate from customer premise to CO.
balanced line
symmetric multiconductor transmission line in which the voltage on each conductor along the transmission line
has the same magnitude, but the phases are such that the voltage would sum to zero. In a two conductor transmission line, the voltages would be equal and 180 degrees out of phase. This is the equivalent of a virtual ground plane or zero E-field plane at the geometric center plane of the transmission line cross section, or balanced with respect to virtual ground. Balanced wiring configurations are often used to prevent noise problems such as ground loops. Contrast with unbalanced line.
branch line coupler
coupler comprised of four transmission lines, each of 90. electrical length, arranged in a cascaded configuration with the end of the last transmission line section connected to the beginning of the first transmission line to form a closed path. The input, coupled, direct, and isolated ports are located at the connection point of one transmission line with the next one.
coupled line filter
a type of microstrip or stripline filter that is composed of parallel transmission lines. Bandwidth is controlled by adjusting the transmission line spacing. Wider bandwidths are obtained by tighter coupling. A two-port circuit is formed by terminating two of the four ports in either open or short circuits, which leaves ten possible combinations. Different combinations are used to synthesize low-pass, bandpass, all pass, and all stop frequency responses.
coupled lines
the electromagnetic field of two unshielded transmission lines in proximity can interact with each other to form coupled lines. Usually three conductors are needed. Examples of coupled lines are coupled microstrip lines and coupled striplines.
electronic nonlinear response
the nonlinear optical response resulting from the motion of bound electrons. It is characterized by moderately large response and very short (several fs) response times.
flux line

See direction line
a line of the mercury spectrum corresponding to a wavelength of about 436 nm.
hot line work
work performed on energized electric power lines. See glove, hot stick, bare-hand.
a line of the mercury spectrum corresponding to a wavelength of about 365 nm.
(1) on a bus structure, one wire of the bus, which may be used for transmitting a datum, a bit of an address, or a control signal.

(2) in a cache, a group of words from successive locations in memory stored in cache memory together with an associated
tag, which contains the starting memory reference address for the group.

(3) a power-carrying conductor or group of conductors. line broadening nonzero spectral width of an absorbing or emitting transition; caused by many physical effects.
line conditioner

See power conditioner
line drop compensator
a multiply-tapped autotransformer equipped with a load-sensing relay which will adjust the line voltage to compensate for the impedance drop in the circuit between the device and the load center.
line impedance stabilization network (LISN)
a network designed to present a defined impedance at high frequency to a device under test, to filter any existing noise on the power mains, and to provide a 50 Ω impedance to the noise receiver.
line of sight (LOS)
the shortest possible straight line that can be envisioned, regardless of possible obstacles in the way, between a transmitter and a receiver. If a line of sight between transmitter and receiver is not blocked, the strongest signal will be received from the line-of-sight direction.
line outage distribution factor
a ratio used in contingency analysis. Given two parallel lines in a power system called x and y, assume that line y is removed from service. The line outage distribution factor of line x for the outage of line y is the ratio of the change in power flow on line x to the flow on line y before the outage.
line to line fault
a fault on a three phase power line in which two conductors have become connected.
line-connected reactor

See shunt reactor