Substation1
Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

fail safe
pertaining to a circuit, for a set of faults, if and only if for any fault in this set and for every valid input code either the output is correct or assumes some defined safe state.
fail-stop processor
a processor that does not perform incorrect computation in the event of a fault. Self-checking logic is often used to approximate fail-stop processing.
failure
manifestation of an error at system level. It relates to execution of wrong actions, nonexecution of correct actions, performance degradation, etc.
failure mechanism
a physical or chemical defect that results in partial degradation or complete failure of a product.
farad
the basic unit of measure in capacitors. A capacitor charged to 1 volt with a charge of 1 coulomb (1 ampere flowing for 1 second) has a capacitance of 1 farad.
Faraday effect
the rotation of the plane of polarization of a high-frequency signal (microwave RF, optical field) in the presence of a magnetic field.
Faraday rotation
(1) rotation in the direction of polarization experienced by a wave traveling through an anisotropic medium. Important examples of media in which the phenomenon occurs include the earth's ionosphere and ferrites biased by a static magnetic field.

(2) depolarization caused in a plasma (e.g., the ionosphere) resulting from interaction between the ions of the plasma and the magnetic field of the wave.

(3) rotation in the polarization vector experienced by a wave after it propagates through a gyromagnetic medium.
Faraday rotator a magneto-optical device that changes the orientation plane of polarized light when it passes parallel to a
magnetic field through a substance with pronounced absorption lines.
Faraday shield
an electrostatic (E field) shield made up of a conductive or partially conductive material or grid. A Faraday cage or screen room is effective for protecting inside equipment from outside radiated RF energies.
Faraday's law
one of Maxwell's equations that describes the fundamental relationship between induced voltage and a time-varying magnetic field. For a conducting coil, the induced voltage is proportional to the time rate of change in the magnetic flux linking the coil. This change may be produced either by actual variation of field strength or by relative motion between coil and field. See also Maxwell's equations.
fault
(1) in hardware, a physical defect or imperfection of hardware. Typical circuit faults are shorts opens in conductor, defects in silicon, etc. See also disturbance.

(2) in software, the manifestation of an error. fault avoidance a technique used to prevent or limit fault occurrence (for example, with signal shielding, fan-out limitation, and power dissipation decrease).
fault confinement
technique that limits the spread of fault effects to some area of the system and prevents propagation of these effects to other areas.
fault coverage
the measure of test quality expressed as the percentage of detected faults.
fault detection
based on circuit duplication and comparison. One module is designed using positive logic and the other module uses negative logic. This assures detecting common mode faults.
fault detection
the process of locating distortions or other deviations from the ideal, typically during the process of automated visual inspection, e.g., in products undergoing manufacture.
fault indicator
a small indicating unit equipped with a permanent magnet and pivoting pointer which is hung on a transmission line suffering intermittent faults of unknown origin. After a fault occurs, fault indicators are inspected. Each shows the presence and direction of a fault, thus allowing the defect to be located.
fault kva
fault kilovolt-amps (kva) is the fault level expressed in terms of volt-amps rather than amps. One advantage of using volt-amps rather than amps is that the same flow is experienced on both sides of a transformer when expressed in volt-amps, while the flow changes due to the transformer turns ratio when it is expressed in amps. Volt-amps for a three-phase fault are expressed as 1.73 x rms line-line voltage x rms symmetrical fault current. Volt-amps for a single phase fault are defined as 1.73 x rms line-line voltage x rms symmetrical current in the faulted phase.
fault latency
the length of time between the occurrence of a fault and the appearance of an error.
fault masking
a technique that hides the effects of faults with the use of redundant circuitry or information.
fault mva
fault megavolt-amps (mva) is the fault level expressed in terms of volt-amps rather than amps. One advantage of using volt-amps rather than amps is the same flow is experienced on both sides of a transformer when expressed in volt-amps, while the flow changes due to the transformer turns ratio when it is expressed in amps. Volt-amps for
a three-phase fault are expressed as 1.73 x rms line-line voltage x rms symmetrical fault current. Volt-amps for a single phase fault are defined as 1.73 x rms line-line voltage x rms symmetrical current in the faulted phase.
fault prevention
any technique or process that attempts to eliminate the possibility of having a failure occur in a hardware device or software routine.