SPDC Terms beginning with F

Terms and definitions extracted from current SPDC published documents
Click one of the capital letters above to advance the page to terms beginning with that letter.
fail-safe

Use of this term is not recommended. See device failure.
[C62.41.1-2002]

failure

The termination of the ability of an item to perform a required function.
NOTE 1 — "Failure" is an event, as distinct from "fault", which is a state.
NOTE 2 — A failure usually results in a fault state.
[C62.31-2006]

failure mode

See device failure.
[C62.41.1-2002]

failure mode

A manner in which failure occurs.
NOTE: A failure mode may be defined by the function lost or the state transition that occurred.
[C62.31-2006]

fault

A state causing inability to perform a required function.
NOTE 1: Inability during preventive maintenance or other planned actions, or due to lack of external resources does not constitute a fault state.
NOTE 2: A fault is often the result of a failure of the item itself, but may exist without prior failure.
[C62.31-2006]

fault current

A current that flows from one conductor to ground or to another conductor due to an abnormal connection (including an arc) between the two. A fault current flowing to ground may be called a ground fault current.
[C62.72-2007]

fault current

The current from the connected power system that flows in a short circuit.
[C62.41.1-2002]

fault current

The current from the connected power system that flows in a short circuit.
[C62.11-2005]

ferroresonance

Can also occur between the capacitance to ground of an ungrounded circuit and voltage transformers with primary windings that are grounded. This phenomenon is also possible in gas-insulated systems.
[C62.22-2009]

ferroresonance

A phenomenon usually characterized by overvoltages and very irregular wave shapes and associated with the excitation of one or more saturable inductors through capacitance in series with the inductor.
[C62.72-2007]

flashover

A disruptive discharge around or over the surface of a solid or liquid insulator.
[C62.22-2009]

flashover

A disruptive discharge around or over the surface of a solid or liquid insulator.
[C62.11-2005]

follow current

The current from the connected power source that flows through a gas tube during and following the passage of discharge current.
[C62.31-2006]

follow current (power)

A) The current from the connected power source that flows through an arrester during and following the passage of discharge current.
B) Current supplied by the electrical power system and flowing through the SPD after a discharge current impulse and significantly different from the continuous operating current (IC)
[C62.41.1-2002]

forced current zero (rotating electric machinery)

A current wave in the machine circuit forced to zero by an interrupter at other than a fundamental frequency current zero in the interrupted phase and with a forcing duration of several milliseconds but less than a half cycle of fundamental frequency.
Example: current-limiting fuse.
[C62.21-2003]

forward conducting region

The portion of the volt-ampere characteristic occurring in a forward-biased P-N junction where there is a low small-signal resistance to the passage of current.
[C62.35-2010]

forward current

IF
The current through the device in the forward conducting state.
[62.37-1996]

forward direction

1) The direction of current in a p-n junction that results when the p-type semiconductor region is at a positive potential relative to the n-type region.
2) The direction of current in a semiconductor device that results when the p-type semiconductor region connected to one terminal is at a positive potential relative to the n-type region connected to the other terminal.
NOTE: This definition does not apply if one or more junctions are connected in series with at least one other junction whose p and n regions are reversed.
[62.37-1996]

forward voltage

VF
The voltage across the device in the forward conducting state at a specified current IF.
[C62.35-2010]

forward voltage

VF
The voltage across the device in the forward conducting state at a specified current IF.
[62.37-1996]

forward-conducting diode thyristor surge protection device (SPD)

A two-terminal internally triggered thyristor SPD that switches only for negative terminal-2 (cathode) voltage and conducts large currents at positive terminal-2 voltages comparable in magnitude to the on-state voltage.
NOTE 1 - In conventional thyristor applications where the cathode is the common terminal, this device would be called a reverse-conducting diode thyristor.
NOTE 2 - When terminal 2 (cathode) is positive, the device characteristics are similar to those of a forward biased diode.
NOTE 3 - When terminal 2 (cathode) is negative, the device characteristics are similar to those of a breakover-triggered SCR.
[62.37-1996]

forward-conducting triode thyristor surge protection device (SPD)

A three-terminal thyristor SPD that switches only for negative main terminal-2 (cathode) voltage and conducts large currents at positive main terminal-2 voltages comparable in magnitude to the on-state voltage.
NOTE 1 - In conventional thyristor applications where the cathode is the common terminal, this device would be called a reverse-conducting triode thyristor.
NOTE 2 - Application of an appropriate fixed gate voltage allows switching to take place at voltages well below the intrinsic breakover value.
NOTE 3 - When main terminal 2 (cathode) is positive, the device characteristics are similar to those of a forward biased diode.
[62.37-1996]

forward/reverse conducting quadrant

A quadrant of the principal voltage-current characteristic in which the device exhibits a forward direction conduction state. This will be quadrant 1 for a forward conducting thyristor SPD and quadrant 3 for a reverse conducting thyristor SPD.
[62.37-1996]

front-of-wave impulse sparkover voltage

The impulse sparkover voltage with a wave front that rises at a uniform rate and causes sparkover on the wave front.
[C62.11-2005]

front-of-wave lightning impulse voltage shape

A voltage impulse, with a specified rate-of-rise, that is terminated intentionally by sparkover of a gap that occurs on the rising front of the voltage wave with a specified time to sparkover, and a specified minimum crest voltage.
[C62.82.1-2010]