Substation1
Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

ANSI
American National Standards Institute, a body which administers numerous industrial standards in the USA including several which pertain to electric utility construction practices.
See American National Standards Institute
antenna
a device used to couple energy from a guiding structure (transmission line, waveguide, etc.) into a propagation medium, such as free space, and vice versa. It provides directivity and gain for the transmission and reception of electromagnetic waves.
antenna beamwidth
the effective angular extent of the antenna radiation pattern usually specified between points of fixed amplitude relative to the main lobe gain (e.g., -3 dB points).

antenna gain
the maximum ratio of an antenna's ability to focus or receive power in a given direction relative to a standard; the standard is usually an isotropic radiator or a dipole. The gain includes the efficiency of the antenna.
antenna Q
ratio of the energy stored to the energy dissipated (ohmically or via radiation) per cycle.

antifuse
a fuse-like device that when activated becomes low-impedance.

antiparticle
a particle having the same mass as a given fundamental particle, but whose other properties, while having the same magnitude, may be of opposite sign. Each particle has a partner called an antiparticle. For example, electrical charge in the case of the electron and positron, magnetic moment in the case of the neutron and antineutron. On collision a particle and its antiparticle may mutually annihilate with the emission of radiation. Some properties of the antiparticle will be identical in magnitude but opposite in sign to the particle it is paired with.

antipodal
symmetry created by simultaneously mirroring an object in both the X and Y axes.

antireflection coating
See antireflective coating
antireflective coating (ARC)
a coating placed on top or below the layer of photoresist to reduce the reflection of light, and hence reduce the detrimental effects of standing waves or thin film interference.
AOA
See angle of arrival
aperiodic waveform
a phrase is used to describe a waveform that does not repeat itself in a uniform, periodic manner. Compare with periodic waveform.
aperture
(1) an opening to a cavity, or wave-guide, from which radiation is either received or transmitted. Typically used as antenna or a coupling element.
(2) a physical space available for beam to occupy in a device. Aperture limitations are the physical size of the vacuum chamber; a magnetic field anomaly may deflect the beam so that the full available aperture cannot be used.
aperture antenna
an antenna with a physical opening, hole, or slit.

apparent power
(1) in an AC system, the product of voltage, Eand current, I. Apparent power (or total power) is composed of
two mutually independent components — an active component (real power), and a reactive component (imaginary power). Apparent power is denoted by S, and has the unit of voltamperes.
(2) the scalar product of the voltage and current delivered to the load. It can also be expressed as the vector S = P + jQ, where P = real power and Q = reactive power.
arc fault interrupter
the mechanism that breaks the fault current arc in a power circuit breaker.

arc lamp
lamp made by driving a high current across a gap between two electrodes. Some types operate in air consuming the electrode, for example, a carbon arc in which the electrode material is made as a rod and fed into the discharge to replace what is consumed. Others operate in a vacuum envelop that reduces the electrode consumption.
arc resistance
period of time that the surface of an insulating material can be submitted to the action of an electrical arc without becoming conductive.
arcing fault
See arcing ground
arcing ground
a ground fault on a power line which alternately clears and restrikes, causing high, repetitive voltage surges.