SPDC Terms beginning with D

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.
damage

A) Degradation or loss of function which is not recoverable due to damage of equipment (components) or software, or loss of data.
B) Temporary degradation or loss of function or performance which requires operator intervention or system reset.
[C62.41.1-2002]

dc holdover

In applications where a dc voltage exists on a line, a holdover condition is one in which a surge-protective device continues to conduct after it is subjected to an impulse large enough to cause breakdown. Factors that affect the time required to recover from the conducting state include the dc voltage and the dc current.
[C62.31-2006]

dc holdover voltage

The maximum dc voltage across the terminals of a gas tube under which it may be expected to clear and return to the high impedance state after the passage of a surge, under specified circuit conditions.
[C62.31-2006]

DC standby current (Varistor)

ID
Varistor current measured at rated voltage, Vm(dc)
[C62.33-1982]

deadfront type arrester

An arrester assembled in a shielded housing providing system insulation and conductive ground shield, intended to be installed in an enclosure for the protection of underground and padmounted distribution equipment and circuits.
[C62.22-2009]

deflector

A means for directing the flow of the gas discharge from the vent of the arrester.
[C62.11-2005]

degradation

Irreversible change in characteristics of any component beyond the specification limit.
[C62.62-2010]

design tests

Tests made on each design to establish the performance characteristics and to demonstrate compliance with the appropriate standards of the industry. Once made, they need not be repeated unless the design is changed so as to modify performance.
[C62.34-1996]

design tests

Tests made on each design to establish the performance characteristics and to demonstrate compliance with the appropriate standards of the industry. Once made, they need not be repeated unless the design is changed so as to modify performance.
[C62.11-2005]

device failure

An irreversible change in characteristic, resulting in an inability to perform as intended.
[C62.41.1-2002]

diode

A semiconductor device having two terminals and exhibiting a nonlinear voltage-current characteristic; in more-restricted usage, a semiconductor device that has the asymmetrical voltage-current characteristic exemplified by a single p-n junction.
[62.37-1996]

discharge counter

A means for recording the number of arrester discharge operations.
[C62.11-2005]

discharge current

The current that flows through a gas tube when sparkover occurs.
[C62.31-2006]

discharge indicator

A means for indicating that the arrester has discharged.
[C62.11-2005]

discharge voltage

The voltage that appears across the terminals of a gas tube during the passage of discharge current.
[C62.31-2006]

discharge voltage-current characteristic

The variation of the crest values of discharge voltage with respect to discharge current.
NOTE: This characteristic is normally shown as a graph based on three or more current-surge measurements of the same wave shape but of different crest values.
[C62.11-2005]

discharge withstand current

The specified magnitude and wave shape of a discharge current that can be applied to an arrester a specified number of times without causing damage to it.
[C62.11-2005]

discharge-voltage-current characteristic

The variation of the crest values of discharge voltage with respect to discharge current.
[C62.31-2006]

disruptive discharge

The sudden and large increase in current through an insulating medium, due to the complete failure of the medium under the electrostatic stress.
[C62.11-2005]

disruptive discharge

The sudden and large increase in current through an insulating medium due to the complete failure of the medium under electrical stress.
[C62.22-2009]

distribution arrester

(A) heavy duty class: An arrester most often used to protect overhead distribution systems exposed to severe lightning currents.
(B) light duty class: An arrester generally installed on and used to protect underground distribution systems where the major portion of the lightning stroke current is discharged by an arrester located at the overhead line/cable junction.
(C) normal duty class: An arrester generally used to protect overhead distribution systems exposed to normal lightning currents.
[C62.22-2009]

duty cycle test

A test to determine if a device can repeatedly function, extinguish follow current, and avoid thermal runaway.
[C62.34-1996]

duty-cycle voltage rating

The designated maximum permissible voltage between its terminals at which an arrester is designed to perform its duty cycle.
[C62.11-2005]

dynamic impedance (Varistor)

Zx
A measure of small signal impedance at a given operating point as defined by:
Zx = dVx/dIx
[C62.33-1982]