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SURGE PROTECTIVE DEVICES COMMITTEE
BIBLIOGRAPHY SUBCOMMITTEE
C62 SERIES DEFINITIONS
Approved October 04, 2006
Surge Protective Devices Committee
C62 Definitions
DEFINITIONS FROM C62 SERIES DOCUMENTS
SPDC Terms Glossary
Each entry in this glossary consists of the term, letter symbol (if any), definition(s) and document
source(s) in square brackets. When a term has multiple definitions, these are grouped under a single term.
Explanatory Comments
Definitions in bold indicate that there are two or more definitions for the same term and
the definition in bold is SPDC preferred.
Non-preferred definitions are shown as underlined.
Definitions in Italics are new since May, 2001.
Definitions followed by a superscript “a” are identical to a definition that appears in IEEE Std.
100-Seventh Edition, December 2000.
Definitions were taken from latest issues of the following Standards:
1.
C62.1
2.
C62.2
3.
C62.11
4.
C62.22
5.
C62.31
6.
C62.32
7.
C62.33
8.
C62.35
9.
C62.36
10.
C62.37
11.
C62.41
11.
C62.42
13.
C62.45
14.
C62.47
15.
C62.92.1
16.
C62.92.2
17.
C62.92.4
18.
C62.92.5
19.
IEEE STD 32-1990
1
Surge Protective Devices Committee
C62 Definitions
AC STANDBY POWER (VARISTOR)
Varistor ac power dissipation measured at rated rms voltage V m(ac).
[C62.33-1989]
ACCEPTANCE TEST
A test to demonstrate the degree of compliance of a device with purchaser's requirements.
[STD 32-1990]
AIR DISCHARGE METHOD
A method of ESD testing in which the charged electrode of the ESD simulator approaches the Unit Under Test (UUT)
or coupling plane. The discharge is actuated by a spark in air to the UUT or coupling plane.
[C62.38-1995]
AIR GAP SURGE ARRESTER
A gap or gaps, in air at ambient atmospheric pressure, designed to protect apparatus and personnel or both, from high
transient voltages.
[C62.32-1987]
AIR GAP SURGE PROTECTOR
A protective device, consisting of one or more air gap surge arresters; optional fuses, short-circuiting devices, etc; and
a mounting assembly, for limiting surge voltages on low voltage (600 V rms or less) electrical and electronic
equipment or circuits.
[C62.32-1987]
AIR INSULATION AND SWITCHGEAR
For air insulation and switchgear: 250 x 2500 µs.
[C62.2-1987]
AMBIENT TEMPERATURE
The temperature of the medium such as air, water, or earth into which the heat of the equipment is dissipated.
STD 32-90
ANODE
The electrode by which current enters the thyristor, when the thyristor is in the on-state with the gate open-circuited.a
[C62.3719-1996]
ANTISTATIC
A property of materials that resist triboelectric charging.
[C62.47-1992]
APPROACH SPEED
The rate at which the intruder approaches the receptor.
[C62.47-1992]
ARC CURRENT
The current that flows after breakdown when the circuit impedance allows a current that exceeds the glow-to-arc
transition current. Sometimes called arc mode current.
C62.31-1987
ARC VOLTAGE
The voltage drop across the arrester during arc current flow. Sometimes called arc mode voltage. C62.31-1987
ARRESTER DISCHARGE CURRENT
The surge current that passes through an arrester when sparkover occurs.
The current that flows through an arrester due to a surge.
[C62.2-1987]
[C62.22-1991]
ARRESTER DISCHARGE VOLTAGE
The voltage that appears across the terminals of an arrester during passage of discharge current. [C62.22-1991]
NOTE: Published discharge voltages are determined by tests using 8/20µs impulses.
[C62.2-1987]
ARRESTER DISCONNECTOR
A means for disconnecting an arrester in anticipation of or after, a failure in order to prevent a permanent fault on the
circuit and to give indication of a failed arrester. NOTE: Clearing of the power current through the arrester during
disconnection generally is a function of the nearest source-side overcurrent-protective device.
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Surge Protective Devices Committee
C62 Definitions
[C62.1-1989 & C62.11-1987]
ARRESTER DUTY CYCLE RATING
The designated maximum permissible root-mean-square (rms) value of power-frequency voltage between its line and
earth terminals at which it is designed to perform it's duty cycle.
[C62.22-1991]
ARRESTER RATING (for silicon carbide arresters only)
The designated maximum permissible operating voltage between an arrester's terminals at which it is designed to
perform it's duty cycle. It is the voltage rating specified on the nameplate.
[C62.1-1984, C62.2-1987]
ARRESTER RECOVERY VOLTAGE
The crest voltage that occurs across the terminals of an arrester following a unit operation.
[C62.2-1987]
ARRESTER SPARKOVER
A disruptive discharge between electrodes of an arrester.
[C62.2-1987]
ARRESTER UNIT
Any section of a multi-unit arrester.
[C62.11-1993]
ARRESTER, DEADFRONT TYPE
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 pad-mounted distribution equipment and circuits.
[C62.11-1993]
ARRESTER, DISTRIBUTION, HEAVY DUTY CLASS
An arrester normally used to protect overhead distribution systems exposed to severe lightning currents.
[C62.11-1993]
ARRESTER, DISTRIBUTION, LIGHT DUTY CLASS
An arrester normally 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. [C62.11-1993]
ARRESTER, DISTRIBUTION, NORMAL DUTY CLASS
An arrester normally used to protect overhead distribution systems exposed to normal lightning currents.
[C62.11-1993]
ARRESTER, RISER POLE TYPE
An arrester for pole mounting normally used to protect underground distribution cable and equipment.
[C62.11-1993]
BACK FILTER
A filter inserted in the power line feeding an equipment to be surge tested; this filter has a dual purpose: (1) To prevent
the applied surge from being fed back to the power source where it may (might according to the word usage in this
guide) cause damage. (2) To eliminate loading effects of the power source on the surge generator. See decoupling
network.
[C62.45-1992]
BACKUP AIR-GAP DEVICE
An air-gap device connected in parallel with a sealed gas-tube device, having a higher breakdown voltage than the gas
tube, which provides a secondary means of protection in the event of a venting to atmosphere by the primary gas-tube
device.
[C62.31-1987 & C62.32-1987]
BASIC IMPULSE INSULATION LEVEL (BIL)
A reference impulse insulation strength expressed in terms of the crest value of withstand voltage of standard full
impulse voltage wave. NOTE: See ANSI C92.1-1982
[C62.1-89 & C62.11-1987]
3
Surge Protective Devices Committee
C62 Definitions
BASIC LIGHTNING IMPULSE INSULATION LEVEL
The electrical strength of insulation expressed in terms of the crest value of a standard lightning impulse. The basic
lightning impulse insulation level (BIL) may be either a statistical BIL, or a conventional BIL, defined as follows; (see
ANSI C92.1-1982)
[C62.2-1987]
A specific insulation level expressed in terms of the crest value of a standard lightning impulse; (see ANSI C92.11982.)
[C62.22-1991]
BASIC SWITCHING IMPULSE INSULATION LEVEL
The electrical strength of insulation expressed in terms of the crest value of a standard switching impulse. The basic
switching impulse insulation level (BSL) may be either a statistical BSL, or a conventional BSL, defined as follows;
(see ANSI C92.2-82)
[C62.2-1987]
A specific insulation level expressed in terms of the crest value of a standard switching impulse; (see ANSI C92.182)
[C62.22-1991]
BIDIRECTIONAL THYRISTOR
A thyristor having substantially the same switching behavior in the first and third quadrants of the principal
voltage-current characteristic.
[C62.37-1996]
BLIND SPOT
A limited range within the total domain of application of a device, generally at values inferior to the maximum rating.
Operation of the equipment or of the protective device might fail in that limited range despite the device's
demonstration of satisfactory performance at maximum ratings.
[C62.45-1992]
BLOCKING
A term describing the state of a semiconductor device or junction that imposes high resistance to the passage of
current.
[C62.37-1996]
BODY/FINGER ESD
An electrostatic discharge from an intruding human finger or hand. Also called body /finger discharge. [C62.47-1992]
BODY/METAL ESD
See hand/metal ESD. Also called body/metal discharge.
[C62.47-1992]
BREAKDOWN
A phenomena occurring in a reverse biased semiconductor junction, the initiation of which is observed as a
transition from a region of high dynamic resistance to a region of substantially lower dynamic resistance for
increasing magnitude of reverse current.
[C62.37-1996]
BREAKDOWN
The abrupt transition of the gap resistance from a practically infinite value to a relatively low value. In the case of a
gap, this is sometimes referred to as sparkover or ignition. See: sparkover.
[C62.31-1987 & C62.32-1987]
BREAKDOWN CURRENT (I(BR))
The current through the device in the breakdown region.
[C62.37-1996]
BREAKDOWN REGION
The portion of the characteristic that starts with the transition from the high dynamic resistance off state to a
substantially lower dynamic resistance and extending to the switching point.
[C62.3 7-1996]
BREAKDOWN VOLTAGE (V(BR))
The voltage across the device in the breakdown region (prior to the switching point/ at a specified breakdown current,
I(BR).
[C62. 37-1996]
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Surge Protective Devices Committee
C62 Definitions
BREAKDOWN VOLTAGE, ac
The minimum rms value of a sinusoidal voltage at frequencies between 15 Hz and 62 Hz that results in arrester
sparkover.
[C62.31-1987]
BREAKDOWN VOLTAGE, dc
The minimum slowly rising do voltage that causes breakdown or sparkover when applied across the terminals of an
arrester.
[C62.31-1987 & C62.32-1987]
BREAKOVER CURRENT (I(BO))
The instantaneous current flowing at the breakover voltage, V(BO)
[C62.37-1996]
BREAKOVER POINT
Any point on the principal voltage-current characteristic for which the differential resistance is zero and where the
principal voltage reaches a maximum value.a
[C62.37-1996]
BREAKOVER VOLTAGE (V(BO))
The maximum voltage across the device in or at the breakdown region measured under specified voltage rate of rise
and current rate of rise.
[C62.37-1996]
BRUSH-BY
An electrostatic discharge from the human torso, such as from the hip or shoulder. Also called brush-by ESD or brushby discharge.
[C62.47-1992]
CAPACITANCE (VARISTOR)
Capacitance between the two terminals of the varistor measured at specified frequency and bias.
[C62.33-1989]
CAPACITANCE
Capacitance between the two terminals of an avalanche surge suppressor measured at specific frequency and bias.
[C62.35-1987]
CATHODE
The electrode by which current leaves the thyristor, when the thyristor is in the on-state with the gate open-circuited.a
NOTE: This term does not apply to bi-directional thyristors.
[C62.37-1996]
CERTIFICATION TESTS
Tests made, when required, to verify selected performance characteristics of a product or representative
samples thereof.
[C62.1-1989]
CERTIFICATION TESTS
Tests run on a regular, periodic basis to verify that selected, key performance characteristics of a product or
representative samples thereof have remained within performance specifications.
[C62.11-1987]
CHARACTERISTIC
An inherent and measurable property of a device. Such a property may be electrical, mechanical, thermal, hydraulic,
electromagnetic, or nuclear, and can be expressed as a value for stated or recognized conditions. A characteristic
may also be a set of related values, usually shown in graphical form. a
[C62.37-1996]
CHARGE VOLTAGE
The voltage difference between the intruder and the receptor just prior to an ESD.
[C62.47-1992]
CIRCUIT PACK
A printed circuit board (PCB) populated with components, i.e. a PCB assembly, also called a Feature Card.
[C62.38-1995]
5
Surge Protective Devices Committee
C62 Definitions
CLAMPING FACTOR
Ratio of the measured clamping voltage (VC) at a specified peak pulse current IPP to breakdown voltage. CF=VC/V(BR)
[C62.35-1987]
CLAMPING VOLTAGE
Peak voltage across the SPD measured under conditions of a specified peak pulse current and specified wave
form.
NOTE-Peak voltage and peak current are not necessarily coincident in time.
[C62.37-1996]
CLAMPING VOLTAGE
Peak voltage across the varistor measured under conditions of a specified peak pulse current and specified waveform. a
[C62.33-1989]
NOTE: Peak voltage and peak current are not necessarily coincidental in time. a
CLASSES OF GROUNDING
A specific range of degree of grounding; for example, effectively and non-effectively.
[C62.92.1-1987]
CLASSIFICATION CURRENT
The designated current used to perform the classification tests.
[C62.11-1987]
CLASSIFICATION OF ARRESTERS
Arrester classification is determined by prescribed test requirements. These classifications are:
(1) Station arrester
(2) Intermediate arrester
(3) Distribution arrester
(a) Heavy duty
(b) Normal duty
(4) Secondary arrester
[C62.1-1989 & C62.11-1987]
CLEARING
The characteristic of some types of air gap surge arresters to exhibit a low resistance and then to revert to a high
resistance state as a result of an external influence. [C62.32-1987]
CLEARING SOURCE
A defined electrical source which is intentionally applied as a clearing stimulus to an air gap surge protective
device under laboratory test conditions. This stimulus is intended to stimulate conditions encountered during
normal usage.
[C62.32-1987]
COEFFICIENT OF GROUNDING
The ratio ELG/ELL, expressed as a percentage, of the highest root-mean-square line-to-ground power-frequency voltage
ELG, on a sound phase, at a selected location, during a fault to ground affecting one or more phases to the line-to-line
power-frequency voltage ELL which (that) would be obtained, at the selected location, with the fault removed.
[C62.2-1987 & C62.22-1991]
NOTES: (1)
Coefficients of grounding for three-phase systems are calculated from the phase-sequence
impedance components as viewed from the selected location. For machines, use the subtransient
reactance.
(2)
The coefficient of grounding is useful in the determination of an arrester rating for a selected
location.
(3)
A value not exceeding 80% is obtained approximately when, for all system conditions, the ratio of
zero-sequence reactance to positive-sequence reactance is positive and less than 3, and the ratio of
zero-sequence resistance to positive sequence reactance is positive and less than 1.
[C62.1-1989]
6
Surge Protective Devices Committee
C62 Definitions
COMPONENT SURGE-PROTECTIVE DEVICE (COMPONENT SPD)
A discrete surge protective device involving a single specific technology and intended to be installed as a component
within a surge protector or as a component housed within the equipment to be protected.
NOTE-- Examples are “component air gap surge-protective device”, “component gas tube surge-protective device”,
“component varistor surge-protective device” and “component avalanche junction semiconductor surge-protective
device”. The term surge arrester is also used to describe a single component.
[C62.42-2005]
COMPONENT SURGE-PROTECTIVE DEVICE – VOLTAGE LIMITING TYPE
A component surge-protective device that has a high impedance when no surge is present, but that can limit voltage
by progressively and smoothly reducing its impedance when responding to a surge. Examples are component varistor
and avalanche junction semiconductor surge-protective devices.
NOTE--also commonly referred to as a “voltage clamping” device.
[C62.42-2005]
COMPONENT SURGE-PROTECTIVE DEVICE – VOLTAGE SWITCHING TYPE
A component surge-protective device that has a high impedance when no surge is present, but that can have a sudden
voltage collapse to a low impedance state when responding to a surge. Examples are component air gap and gas tube
surge-protective devices.
NOTE--also commonly referred to as “crowbar” devices.
[C62.42-2005]
CONFORMANCE TEST
Tests made, when required, to demonstrate selected performance characteristics of a product or representative samples
thereof.
[C62.1-1989 & C62.11-1987]
CONTACT DISCHARGE METHOD
A method of ESD testing in which the electrode of the ESD simulator is in firm conductive contact with the UUT or
coupling plane prior to and during the discharge. The discharge is actuated by a switching device, e.g. a relay, within
the simulator.
[C 62.38 –1995]
CONVENTIONAL BIL
Applicable specifically to nonself-restoring insulations. The crest value of a standard lightning impulse for which the
insulation shall not exhibit disruptive discharge when subjected to a specific number of applications of this impulse
under specified conditions.
[C62.2-1987]
CONVENTIONAL BSL
Applicable specifically to nonself-restoring insulations. The crest value of a standard switching impulse for which the
insulation does not exhibit disruptive discharge when subjected to a specific number of applications of this impulse
under specific conditions.
[C62.2-1987]
COORDINATION OF INSULATION
The process of correlating the insulation strengths of electric equipment with expected overvoltages and with the
characteristics of surge protective devices: (see ANSI 92.1-82)
[C62.2-87 & C62.22-91]
COUPLER
A device, or combination of devices, used to feed a surge from a generator to powered equipment while limiting the
flow of current from the power source into the generator. See: coupling network.
[C62.45-1992]
COUPLING FACTOR
The ratio of the induced voltage to the inducing voltage on parallel conductors.
e.g. At the tower the shield or coupling wires and tower crossarms are at practically the same potential (because of
lightning stroke travel time). The stress across the insulator string is (1 minus coupling factor) multiplied by (tower top
potential)
Stress = (1. 0 - Kƒc) x VTT
where Kƒc is the coupling factor and VTT is the tower top voltage.
[C62.23 – 1995]
7
Surge Protective Devices Committee
C62 Definitions
COUPLING NETWORK
Electrical circuit for the purpose of transferring energy from one circuit to another. See: coupler. [C62.45-1992]
COUPLING WIRE
A conductor attached to the transmission line structure, and below the phase wires, with proper clearance, and
connected to the grounding system of the towers or pole supporting the line.
[C62.23 – 1995]
CREST (PEAK) VALUE (OF A WAVE, SURGE, OR IMPULSE)
The maximum value that it (an impulse) attains. [C62.1-1989 & C62.2-1987 & C62.11-1987 & C62.22-1991]
CREST (PEAK) VALUE (OF A WAVE, SURGE, OR IMPULSE)
The maximum value that it attains.
[C62.37-1996]
CRITICAL RATE OF RISE OF OFF-STATE VOLTAGE (dv/dt)
The maximum rate of rise of voltage (below VDRM) that will not cause switching from the off-state to the on-state.
[C62.37-96]
CRITICAL RATE OF RISE OF ON-STATE CURRENT (di/dt)
Rated value of the rate of rise of current which the device can withstand without damage.
[C62.37-1996]
CURRENT TURNOFF TIME
The time required for the arrester to restore itself to a nonconducting state following a period of conduction. This
applies only to a continuous specified dc potential under a specified circuit condition.
[C62.31-1987]
CURRENT TURNOFF TIME
The time required for the arrester to restore itself to a non-conducting state following a period of
conduction. This definition applies only to a condition where the arrester is exposed to a continuous
specified dc potential under a specified circuit condition.
[C62.32-1987]
DC HOLDOVER
In applications where 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. [C62.31-1987 & C62.32-1987]
DC HOLDOVER VOLTAGE
The maximum dc voltage across the terminals of an arrester under which it may be expected to clear and to return to the
high-impedance state after the passage of a surge, under specified circuit conditions.
[C62.31-1987 & C62.32-1987]
DC STANDBY CURRENT (VARISTOR)
Varistor current measured at rated voltage. V m(dc).
[C62.33-1989]
DECOUPLING NETWORK
Electrical circuit for the purpose of preventing an EFT signal applied to the equipment under test from affecting other
devices, equipment or systems which are not under test. See back filter.
[C62.45-1992]
DEFLECTOR
A means for directing the flow of the gas discharge from the vent of the arrester.
[C62.1-1989 & C62.11-1987]
DESIGN TESTS
Tests made by the manufacturer 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.
[C62.1-1989 & C62.11-1987]
DES
Discharge Electrostatic; an alternative name for ESD.
[C62.47-1992]
8
Surge Protective Devices Committee
C62 Definitions
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.a
[C62.37-1996]
DIRECT ESD EVENT
An ESD event taking place between an intruder and a receptor in which the intruder or the receptor, or both, is an
equipment victim.
[C62.47-1992]
DISCHARGE COUNTER
A means for recording the number of arrester discharge operations.
[C62.1-1989 & C62.11-1987]
DISCHARGE CURRENT
The surge current that flows through an arrester when sparkover occurs.
DISCHARGE CURRENT
The current that flows through an arrester when sparkover occurs.
[C62.1-1989]
[C62.31-87 & C62.32-1987]
DISCHARGE CURRENT
The surge current that flows through an arrester.
[C62.11-1987]
DISCHARGE INDICATOR
A means for indicating that the arrester has discharged.
[C62.1-1989 & C62.11-1987]
DISCHARGE VOLTAGE
The voltage that appears across the terminals of an arrester during the passage of discharge current.
[C62.31-1987 & C62.1-1989 & C62.11-1987 & C62.32-1987]
DISCHARGE WITHSTAND CURRENT RATING
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.
[C62.1-1989 & C62.11-1987]
DISCHARGE-VOLTAGE-CURRENT CHARACTERISTIC
The variation of the crest values of discharge voltage with respect to discharge current.
[C62.31-1987]
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.
[C62.1-1989 & C62.11-1987][
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.
[C62.1-1989 & C62.2-1987 & C62.11-1987 & C62.22-1991]
DUTY CYCLE VOLTAGE RATING
The designated maximum permissible voltage between its terminals at which an arrester is designed to perform its
duty cycle.
[C62.11-1987]
DYNAMIC IMPEDANCE (VARISTOR)
A measure of small signal impedance at a given operating point as defined by: ZX=dVX/dIX.
[C62.33-1989]
EQUIPMENT UNDER TEST (EUT)
A representative component, unit or system to be used for evaluation purposes.
[C62.45-1992]
EQUIPMENT VICTIM
The electronic equipment or subassembly which is subjected to the effects associated with an ESD event. It may be the
intruder or receptor, or it may be in proximity to the discharge between the intruder and receptor, and therefore
subjected to the stress of ESD related electromagnetic fields.
[C62.47-1992]
9
Surge Protective Devices Committee
C62 Definitions
ESD CURRENT WAVE
The waveform of the discharge current between an intruder and a receptor.
[C62.47-1992]
ESD EVENT
Includes the ESD current, electromagnetic fields and corona effects before and during an ESD.
[C62.47-1992]
ESD
Electrostatic Discharge: the sudden transfer of charge between bodies of differing electrostatic potentials.
[C62.47-1992]
FAIL-SAFE
Use of this term is not recommended in C62 series documents.
[C62.32-1987]
FAST APPROACH
Approach speeds that engender short, sub-nanosecond rise-time ESD current waves. Fast approach speed depends on
the voltage difference between the intruder and receptor, e.g. for rounded electrodes of 8 mm diameter, greater than
0.05m/s, lm/s, and 10m/s at charge voltages of 4 kV, 8 kV and 16 kV respectively.
[C62.47-1992]
FAULT CURRENT
The current from the connected power system that flows in a short circuit.
[C62.1-1989 & C62.11-1987]
FAULT-CURRENT WITHSTAND
The maximum rms symmetrical fault current of a specified duration that a failed distribution class arrester will
withstand without an explosive fracture of the housing.
[C62.1-1989]
FLASHOVER
A disruptive discharge around or over the surface of a solid or liquid insulator.
[C62.1-1989 & C62.2-1987 & C62.11-1987 & C62.22-1991]
FOLLOW (POWER) CURRENT
The current from the connected power source that flows through an arrester during and following the passage of
discharge current.
[C62.31-1987 & C62.1-1989 & C62.2-1987 & C62.32-1987]
FORWARD CURRENT (IF)
The current through the device in the forward conducting state.
[C62.37-1996]
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.
[C62.37-1996]
FORWARD VOLTAGE (VF)
The voltage across the device in the forward conducting state at a specified current I F
[C62.37-1996]
FORWARD VOLTAGE
Peak voltage measured across the avalanche surge suppressor for a specified forward pulse current I FS. Applies to
asymmetrical bi-directional avalanche junction surge suppressor only.
[C62.35-1987]
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
10
Surge Protective Devices Committee
conducting thyristor SPD.
C62 Definitions
[C62.37-1996]
FORWARD-CONDUCTING DIODE THYRISTOR 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.
NOTES:
1-In conventional thyristor applications where the cathode is the common terminal, this device
would be called a reverse-conducting diode thyristor.
2-When terminal 2 (cathode) is positive, the device characteristics are similar to those of a forward
biased diode.
3-When terminal 2 (cathode) is negative, the device characteristics are similar to those of a
breakover-triggered SCR.
[C62.37-1996]
FORWARD-CONDUCTING TRIODE THYRISTOR 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.
NOTES:
1-In conventional thyristor applications where the cathode is the common terminal, this device
would be called a reverse-conducting triode thyristor.
2-Application of an appropriate fixed gate voltage allows switching to take place at voltages well
below the intrinsic breakover value. 3-When main terminal 2 (cathode) is positive, the device
characteristics are similar to those of a forward biased diode.
[C62.37-1996]
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.
[C62.11-1987]
FURNITURE ESD
An electrostatic discharge in which the intruder is an inanimate object such as a cart or chair, with or without a
human in electrical contact with the object.
[C62.47-1992]
GAPLESS
Not possessing gaps, series or parallel, as in "gapless arrester".
[C62.11-1987]
GAS-TUBE SURGE ARRESTER
A gap, or gaps, in an enclosed discharge medium, other than air at atmospheric pressure, designed to protect
apparatus or personnel, or both, from high transient voltages.
[C62.31-1987]
GATE
An electrode connected to one of the semiconductor regions to introduce a control current.
[C62.37-96]
GATE REVERSE CURRENT, ADJACENT TERMINAL OPEN
(IGAO, IGKO)
The current through the gate terminal when a specified gate bias voltage, V G, is applied and the cathode terminal
for a p-gate device or anode terminal for an n-gate device is open circuited.
[C62.37-1996]
GATE REVERSE CURRENT, FORWARD CONDUCTING STATE (IGAF, IGKF)
The current through the gate terminal when a specified gate bias voltage, V G, is applied and a specified forward
conduction current, IF, is flowing.
[C62.37-1996]
GATE REVERSE CURRENT, MAIN TERMINALS SHORT CIRCUITED
(IGAS, IGKS)
The current through the gate terminal when a specified gate bias voltage, V G, is applied and the cathode terminal for a
p-gate device or anode terminal for an n-gate device is short circuited to the third terminal.
[C62.37-1996]
GATE REVERSE CURRENT, ON-STATE (IGAT, IGKT)
The current through the gate terminal when a specified gate bias voltage, V G, is applied and a specified on-state
current, IT is flowing.
[C62.37-1996]
GATE SWITCHING CHARGE (QGS )
The charge through the gate terminal, under impulse conditions, during the transition from the off-state to the
11
Surge Protective Devices Committee
C62 Definitions
switching point, when a specified gate bias voltage, VG, is applied.
[C62.37-1996]
GATE-TO-ADJACENT TERMINAL BREAKOVER VOLTAGE (V GK(BO); VGA(BO))
The gate to cathode voltage for a p-type device or gate to anode voltage for an n-gate device at the breakover point.
This is equivalent to the voltage difference between the breakover voltage, V(BO), and the specified gate voltage, VG..
[C62.37-1996]
GATE-TO-ADJACENT TERMINAL PEAK OFF-STATE VOLTAGE (VGDM)
The maximum gate to cathode voltage for a p-gate device or gate to anode voltage for an n-gate device that may be
applied such that a specified off-state current, ID, at a rated off-state voltage, VD, is not exceeded. [C62.37-1996]
GLOW CURRENT
The current that flows after breakdown when circuit impedance limits the follow current to a value less than the glowto-arc transition current. It is sometimes called the glow mode current.
[C62.31-1987]
GLOW VOLTAGE
The voltage drop across the arrester during glow-current flow. It is sometimes called the glow mode voltage.
[C62.31-1987]
GLOW-TO-ARC TRANSITION CURRENT
The current required for the arrester to pass from the glow mode into the arc mode.
[C62.31-1987]
GPR
Acronym for ground potential rise. see: ground potential rise.
[C62.23 – 1995]
GRADING OR CONTROL RING
A metal part, usually circular or oval in shape, mounted to modify electrostatically the voltage gradient or
distribution.
[C62.1-1989 & C62.11-1987]
GROUND END (OF A NEUTRAL GROUNDING DEVICE)
The end or terminal that is grounded directly or through another device.
[STD 32-1990]
GROUND POTENTIAL RISE
The voltage that a station grounding grid may attain relative to distant grounding point assumed to be at the
potential of remote earth.
[C62.23 – 1995]
GROUND TERMINAL
The conducting part provided for connecting the arrester to ground.
GROUNDED PARTS
Parts that are intentionally connected to ground.
[C62.1-1989 & C62.11-1987]
STD 32-1990
GROUNDED SYSTEM
An electric system in which at least one conductor or point (usually the neutral conductor or neutral point of
transformer or generator windings) is intentionally grounded, either solidly or through a grounding device.
[C62.1-1989]
A system of conductors in which at least one conductor or point (usually the neutral conductor or neutral point of
transformer or generator windings) is intentionally grounded, either solidly or through a current-limiting device.
[STD 32 - 1990 & C62. 1991]
GROUND-FAULT NEUTRALIZER GROUNDED
Reactance grounded through such values of reactance that, during a fault between one of the conductors and earth. the
rated-frequency current flowing in the grounding reactances and the rated-frequency capacitance current flowing
between the unfaulted conductors and earth shall be substantially equal. In the fault, these two components of fault
current will be substantially 180 degrees out of phase.
NOTE: When a system is ground-fault neutralizer grounded, it is expected that the quadrature component of the
12
Surge Protective Devices Committee
C62 Definitions
rated-frequency single-phase-to-ground fault current will be so small that an arc fault in air will be self
extinguishing.
[STD 32-1990]
GROUND-FAULT NEUTRALIZER
A grounding device that provides an inductive component of current in a ground fault that is substantially equal to
and therefore neutralizes the rated-frequency capacitive component of the ground-fault current, thus rendering the
system resonant grounded.
[STD 32-1990]
GROUNDING DEVICE
An impedance device used to connect conductors of an electric system to ground for the purpose of controlling the
ground current or voltage to ground.
NOTE: The grounding device may consist of a grounding transformer or a neutral grounding device, or a
combination of these. Protective devices, such as lightning arresters, may also be included as an integral part of
the device.
[STD 32-1990]
GROUNDING TRANSFORMER
A transformer intended primarily to provide a neutral point for grounding purposes.
NOTE: It may be provided with a delta winding in which resistors or reactors may be connected. [STD 32-1990]
HAND/METAL ESD
An electrostatic discharge from an intruding human hand which occurs from an intervening metal object such as a
ring, tool, key, etc. Also called hand/metal discharge.
[C62.47-1992]
HAND-TO-METAL IMPEDANCE
The impedance between the human hand and the metal object with which it is associated in a hand/metal ESD. The
metal object is usually the intruder discharge electrode. Examples of hand-to-metal impedance include resistance and
capacitance between the fingers and a key, between the wrist and a metal watch or bracelet, and between the hand and
screwdriver.
[C62.47-1992]
HOLDING CURRENT (IH)
The minimum current required to maintain the device in the on-state.
[C62.37-1996]
IMPEDANCE GROUNDED
Grounded through impedance.
NOTE: The components of the impedance need not be at the same location.
[STD 32-1990]
IMPEDANCE VOLTAGE
Comprises an effective resistance component corresponding to the impedance losses, and a reactance component
corresponding to the flux linkages of the winding.
[STD 32-1990]
IMPULSE
A surge of unidirectional polarity. a [C62.1-1989 & C62.2-1987 & C62.11-1987 & C62.22-1987 & 62.37-1996]
IMPULSE FLASHOVER VOLTAGE
The crest voltage of an impulse causing a complete disruptive discharge through the air between electrodes of a
test specimen.
[STD 32-1990]
IMPULSE PROTECTIVE LEVEL
For a defined wave shape, the higher of the maximum sparkover value or the corresponding discharge-voltage
value.
[C62.11-1987]
IMPULSE PROTECTIVE VOLT-TIME CHARACTERISTIC
The discharge-voltage time response of the device to impulses of a designated wave shape and polarity, but of
varying magnitudes.
[C62.11-1987]
IMPULSE RESET TIME t(Reset)
The time taken for a device to switch back into the off-state, in the presence of a specified value of dc short-circuit
13
Surge Protective Devices Committee
C62 Definitions
current, after being switched into the on state by a specified impulse.
[C62.37-1996]
IMPULSE SPARKOVER VOLTAGE
The highest value of voltage attained by an impulse of a designated wave shape and polarity applied across the
terminals of an arrester (that will cause sparkover) prior to the flow of discharge current. Sometimes referred to as
surge or impulse breakdown voltage.
[C62.31-1987 & C62.32-1987 & C62.1-1989 & C62.11-1987]
IMPULSE SPARKOVER VOLTAGE-TIME CURVE (ARRESTER)
A curve that relates the impulse sparkover voltage to the time to sparkover.
[C62.31-1987]
IMPULSE SPARKOVER VOLT-TIME CHARACTERISTIC
The (gap) sparkover response of the device to impulses of a designated wave shape and polarity, but of varying
magnitudes.
NOTE: For an arrester, this characteristic is shown by a graph of values of crest voltage plotted against time to
sparkover.
[C62.1-1989 & C62.11-1987]
IMPULSE TESTS
Dielectric tests in which the voltage applied is an impulse voltage of specified wave shape. The wave shape of an
impulse test wave is the graph of the wave as a function of time or distance.
NOTE: It is customary in practice to express the wave shape by a combination of two numbers, the first part of
which represents the wave front and the second the time between the beginning of the impulse and the instant at
which one-half crest value is reached on the wave tail, both values being expressed in microseconds, such as a 1.2
x 50 microsecond wave.
[STD 32-1990]
IMPULSE WAVE
A unidirectional wave of current or voltage of very short duration containing no appreciable oscillatory components. a
NOTE - In the case of the 8/20 wave an opposite polarity wave tail underswing of up to 30% is allowed. a
[C62.37-1996]
IMPULSE WITHSTAND VOLTAGE
The crest value of an impulse that, under specified conditions, can be applied without causing a disruptive discharge.
[C62.1-1989 & C62.11-1987]
The crest value of an applied impulse voltage which does not cause a flashover, puncture, or disruptive
discharge on the test specimen.
[STD 32-1990]
INCREMENTAL SURGE RESISTANCE
R
S

V
V
C2
C1
I
 I
PP2
PP1
Resistance composed of thermal and nonlinear avalanche characteristics calculated between two instantaneous sets of
values for peak pulse current (Ipp) and clamping voltage (VC) with a specified waveform.
[C62.35-1987]
INDIRECT ESD EVENT
An ESD event taking place between an intruder and a receptor, in proximity to equipment which is the victim.
[C62.47-1992]
INDOOR ARRESTER
An arrester that, because of its construction, shall (must) be protected from the weather. [C62.1-1989 & C62.11-1987]
INDUCED-POTENTIAL TEST
A dielectric test in which the test voltage is an alternating voltage of suitable frequency, applied or induced
between the terminals.
[STD 32-1990]
INERT GAS-PRESSURE SYSTEM
A method of oil preservation in which the interior of the tank is sealed from the atmosphere, over the temperature
range specified, by means of a positive pressure of inert gas maintained from a separate inert-gas source and
14
Surge Protective Devices Committee
reducing-valve system.
C62 Definitions
[STD 32-1990]
INHIBITED OIL
Mineral transformer oil to which a synthetic oxidation inhibitor has been added.
[STD 32-1990]
INITIAL CURRENT PULSE
The sub-nanosecond rise time, and <1 to perhaps 3 nanosecond duration pulse that can occur at the start of the
current wave from an ESD. Also called initial pulse, initial spike and fast discharge mode. Its leading edge is the
initial slope.
[C62.47-1992]
INITIAL SLOPE
The slope, in Amps per nanosecond (A/ns), which occurs at the start of the ESD current wave. Also termed rising
slope.
[C62.47-1992]
INSULATION CLASS (OF A GROUNDING DEVICE)
A number that defines the insulation levels of the device.
[STD 32-1990]
INSULATION LEVEL
A combination of voltage values (both power-frequency and impulse) that characterize the insulation of an equipment
with regard to its capability of withstanding dielectric stresses.
[C62.22-1991]
INSULATION RESISTANCE
The equivalent insulation resistance of the device, computed by: VD / ID
[C62.37-1996]
INTRUDER ELECTRODE GEOMETRY
The size and shape of that surface of the intruder, termed the intruder electrode, at which the ESD takes place.
[C62.47-1992]
INTRUDER
The body which is in motion in an ESD event. The intruder is usually but not necessarily charged relative to its
surroundings. It is always at a potential different from that of the receptor.
[C62.47-1992]
IONIZATION CURRENT
The electric current resulting from the movement of electric charges in an ionized medium, under the influence of an
applied electric field.
[C62.1-1989 & C62.11-1987]
IONIZATION VOLTAGE
A high-frequency voltage appearing at the terminals of an arrester, generated by all sources, but particularly by
ionization current within the arrester, when a power-frequency voltage is applied across the terminals.
[C62.1-1989 & C62.11-1987]
LET-THROUGH SPARKOVER
A measure of the highest lightning surge an arrester is likely to withstand without sparkover in 3 µs or less. The value
determined by a 1.2/50 µs impulse sparkover test: see ANSI/IEEE C62.1-1984
[C62.2-1987]
LIFETIME RATED PULSE CURRENTS (VARISTOR)
Derated values of Itm for impulse durations exceeding that of an 8/20 µs wave shape, and for multiple pulses which
may be applied over device's rated lifetime.
[C62.33-1989]
LIFETIME RATED PULSE CURRENTS
Rated values of the peak impulse current, Ipp, as a function of the number of pulses and wave shape, which may
be applied over the device rated lifetime.
[C62.37-1996]
LIGHTNING OVERVOLTAGE
The crest voltage appearing across an arrester or insulation caused by a lightning surge. [C62.2-1987 & C62.22-1991]
LIGHTNING SURGE
15
Surge Protective Devices Committee
C62 Definitions
A transient electric disturbance in an electric circuit caused by lightning.
[C62.1-1989 & C62.2-1987 & C62.11-1987 & C62.22-1991]
LIGHTNING
An electric discharge that occurs in the atmosphere between clouds or between clouds and ground.
[C62.1-1989 & C62.11-1987]
LINE END (OF A NEUTRAL GROUNDING DEVICE)
The end or terminal of the device that is connected to the line circuit directly or through another device. STD 32-1990
LINE TERMINAL
The conducting part provided for connecting the arrester to the circuit conductor.
C62.11-1987
NOTE: When a line terminal is not supplied as an integral part of the arrester, and the series gap is obtained by
providing a specified air clearance between the line end of the arrester and a conductor, or arcing electrode, etc., the
words line terminal used in the definition refer to the conducting part that is at line potential and that is used as the line
electrode of the series gap.
[C62.1-1989]
LONGITUDINAL (COMMON) MODE VOLTAGE
The voltage common to all conductors of a group as measured between that group at a given location and an arbitrary
reference (usually earth).
[C62.31-1987]
LOSSES (OF A GROUNDING DEVICE)
The I²R loss in the windings, core loss, dielectric loss, loss due to stray magnetic fluxes in windings and other metallic
parts of the device, and, in cases involving parallel windings, losses due to circulating currents.
NOTES:
(1) The losses as here defined do not include any losses produced by the device in adjacent apparatus
or materials not a part of the device.
(2) Losses will normally be considered at the rated thermal current but in some cases may be
required at other current ratings, if more than one rating is specified, or at no load, as for grounding
transformers. The losses may be given at 25 ºC or 75 ºC.
[STD 32-1990]
MAIN DISCHARGE CURRENT WAVE
The relatively long portion of the ESD current wave that follows the initial current pulse, or that occurs by itself when
the initial current pulse doesn't exist. It may be unidirectional or oscillatory; its initial slope may be fast or slow.
[C62.47-1992]
MAINS
The ac power source available at the point of use in a facility. It consists of the set of electrical conductors (referred to
by terms including "service entrance", "feeder", or "branch circuit") for delivering power to connected loads at the
utilization voltage level.
[C62.41-1991]
MAIN TERMINALS
The two terminals through which the principal current flows.a
[C62.37-1996]
NOTE: The main terminals may be named by application usage. In telecommunications, terminals may be named
after the line connections of R(ing), T(ip), and G(round) or A, B, and C(ommon).
MAIN TERMINAL 1
The main terminal that is named 1 by the device manufacturer.
[C62.37-1996]
MAIN TERMINAL 2
The main terminal that is named 2 by the device manufacturer.
[C62.37-1996]
MAXIMUM (HIGHEST) SYSTEM VOLTAGE
The highest voltage at which a system is operated.
NOTE: This is generally considered to be the maximum system voltage as prescribed in ANSI C84.1-1989
[C62.1-1989 & C62.11-1987 & C62.22-1991]
The highest rms phase-to-phase voltage that occurs on the system under normal operating conditions, and the highest
rms phase-to-phase voltage for which equipment and other system components are designed for satisfactory
16
Surge Protective Devices Committee
C62 Definitions
continuous operation without derating of any kind. (This voltage excludes voltage transients and temporary
overvoltages caused by abnormal system conditions such as faults, load rejection, and so forth.) [C62.2-1987]
MAXIMUM CONTINUOUS OPERATING VOLTAGE (MCOV)
The maximum designated root-mean-square (rms) value of power frequency voltage that may be applied
continuously between the terminals of the arrester.
[C62.11-1987 & C62.22-1991]
MAXIMUM JUNCTION TEMPERATURE (T JM)
The maximum value of permissible junction temperature, due to self heating, which a Thyristor SPD can withstand
without degradation.
[C62.37-1996]
MAXIMUM RATING; ABSOLUTE MAXIMUM RATING
A rating that establishes either a limiting capability or a limiting condition beyond which damage to the device
may occur. NOTE - A limiting condition may be either a maximum or a minimum.
[C62.37 –1996]
MEANS OF GROUNDING
The generic agent by which various degrees of grounding are achieved; for example, inductance grounding,
resistance grounding, and resonant grounding.
[C62.92.1-1987]
MECHANICAL LIMIT
The rated maximum instantaneous value of current, in amperes, that the device will withstand without mechanical
failure.
[STD 32-1990]
METAL-OXIDE SURGE ARRESTER (MOSA)
A surge arrester utilizing valve elements fabricated from nonlinear resistance metal-oxide materials. [C62.11-1987]
METHODS (OR TYPES) OF GROUNDING
The equipment, procedure, or scheme used for attaining the particular means.
[C62.92.1-1987]
MINIMUM IMPULSE FLASHOVER VOLTAGE
The crest value of the lowest voltage impulse at a given wave shape and polarity that causes flashover. [STD 32-1990]
MULTIPLE ESD EVENT
An ESD event in which more than one discharge occurs. The time interval between successive discharges may be
several microseconds to several tens of milliseconds. Related terms include multiple ESD, multiple discharge and
multiple normalized peak ESD current. Ratio of peak current to charge voltage (e.g. 5a/kV).
[C62.47-1992]
NEGATIVE DIFFERENTIAL-RESISTANCE (REGION)
The region of the principal voltage-current characteristic in the switching quadrant where the differential resistance is
negative and the thyristor is switching between the breakdown and on-state regions.
[C62.37-1996]
NEGATIVE-BREAKDOWN RESISTANCE THYRISTOR SPD
A thyristor SPD, whose static breakdown characteristic has a net negative-resistance slope prior to switching.
[C62.37-1996]
NEUTRAL GROUND CAPACITOR
A neutral grounding device, the principal element of which is capacitance.
[STD 32-1990]
NEUTRAL GROUNDING DEVICE
A grounding device used to connect the neutral point of a system of electric conductors to earth.
NOTE: The device may consist of a resistance, inductance, or capacitance element, or a combination of them.
[STD 32-1990]
NEUTRAL GROUNDING IMPEDOR
A neutral grounding device comprising an assembly of at least two of the elements, resistance, inductance, or
capacitance.
[STD 32-1990]
17
Surge Protective Devices Committee
C62 Definitions
NEUTRAL GROUNDING REACTOR
A neutral grounding device, the principal element of which is inductive reactance.
[STD 32-1990]
NEUTRAL GROUNDING RESISTOR
A neutral grounding device, the principal element of which is resistance.
[STD 32-1990]
NEUTRAL GROUNDING WAVE TRAP
A neutral grounding device comprising a combination of inductance and capacitance designed to offer a very high
impedance to a specified frequency or frequencies.
NOTE: The inductances used in neutral grounding wave traps should meet the same requirements as neutral grounding
reactors.
[STD 32-1990]
N-GATE THYRISTOR
A three-terminal thyristor in which the gate terminal is connected to the n-region adjacent to the region to which
the anode is connected and that is normally switched to the on state by applying a negative signal between the
gate and anode terminals.
[C62.37-1996]
NOMINAL RATE OF RISE (OF AN IMPULSE WAVE FRONT)
(For a wave front,) The slope of the line that determines the virtual zero. It is usually expressed in volts or amperes per
microsecond.
[C62.1-1989 & C62.2-1987 & C62.11-1987 & C62.22-1991]
NOMINAL SYSTEM VOLTAGE
A nominal value assigned to designate a system of a given voltage class.
NOTE: See ANSI C84.1-1989
[C62.1-1989 & C62.11-1987]
The system voltage by which the system may be designated, and to which certain operating characteristics of the
system are related. (The nominal voltage of a system is near the voltage level at which the system normally
operates and provides a per-unit base voltage for system study purposes. To allow for operating contingencies,
systems generally operate at voltage levels about 5 to 10% below the maximum system voltage for which the
system components are designed.)
[C62.2-1987 & C62.22-1991]
NOMINAL VARISTOR VOLTAGE
Voltage across the varistor measured at a specified pulsed dc current, I N(dc), of specific duration. IN(dc) is specified by
the varistor manufacturer.
[C62.33-1989]
NONLINEAR EXPONENT
A measure of varistor nonlinearity between two given operating currents, I 1 and I2, as described by I = k V where k is
a device constant, Il < I < I2, and
12 
log I 2 I1
log V2 V1
[C62.33-1989]
NON-REPETITIVE CURRENT RATING
A maximum rating that may be applied to the device for a minimum of 100 times over the life of the device without
failure. During the rated condition, the device is permitted to exceed its maximum rated junction temperature for
short periods of time. The device is not required to block voltage or retain any gate control during or immediately
following this rated condition until the device returned to the original thermal equilibrium conditions. This rated
condition may be repeated after the device has returned to the original thermal equilibrium conditions.
[C62.37-1996]
NON-REPETITIVE PEAK FORWARD CURRENT (IFSM)
Rated maximum (peak) value of ac power frequency forward surge current of specified waveshape and frequency
which may be applied for a specified time or number of ac cycles.
[C62.37-1996]
NON-REPETITIVE PEAK ON-STATE CURRENT (ITSM)
Rated maximum (peak) value of ac power frequency on-state surge current of specified waveshape and frequency
which maybe applied for a specified time or number of ac cycles.
[C62.37-1996]
18
Surge Protective Devices Committee
C62 Definitions
NON-REPETITIVE PEAK PULSE CURRENT (IPPS)
Rated maximum value of peak impulse pulse current of specified amplitude and waveshape that may be applied.
[C62.37-1996]
NORMALIZED RISING SLOPE
Ratio of the initial slope to charge voltage (e.g. 3.75 A/ns/kV).
[C62.47-1992]
OFF STATE OF A THYRISTOR SPD
The state of a thyristor SPD, in a quadrant in which switching can occur, that corresponds to the high dynamicresistance portion of the characteristic between the origin and the beginning of the breakdown region. [C62.37-1996]
OFF-STATE CAPACITANCE (CO)
The capacitance in the off-state measured at specified frequency, f, amplitude, V d and dc bias, VD.
[C62.37-1996]
OFF-STATE CURRENT (ID)
The dc value of current that results from the application of the off-state voltage, VD.
[C62.37-1996]
OFF-STATE VOLTAGE (VD)
The dc voltage when the device is in the off-state.
[C62.37-1996]
OIL-IMMERSED (FOR A GROUNDING DEVICE)
Means that the windings are immersed in an insulating oil.
[STD 32-1990]
OIL
Includes synthetic insulating liquids as well as mineral transformer oil.
[STD 32-1990]
ON-STATE CURRENT (IT)
The current through the device in the on-state condition.
[C62.37-1996]
ON-STATE (REGION)
The condition of the thyristor corresponding to the low-resistance low-voltage portion of the principal voltage-current
characteristic in the switching quadrants(s).a
[C62.37-1996]
ON-STATE VOLTAGE (VT)
The voltage across the device in the on-state condition at a specified current IT.
OPERATING DUTY CYCLE
One or more unit operations, as specified.
[C62.37-1996]
[C62.1-1989 & C62.11-1987]
OSCILLATORY SURGE
A surge that includes both positive and negative polarity values.
[C62.1-89 & C62.11-1987]
OUTDOOR ARRESTER
An arrester that is designed for outdoor use.
[C62.1-89 & C62.11-1987]
OVERSHOOT DURATION (VARISTOR)
The time between the point at which the wave exceeds the clamping voltage level (V C) and the point at which the
voltage overshoot has decayed to 50% of its peak. For the purpose of this definition, clamping voltage is defined with
an 8/20 µs current waveform of the same peak current amplitude as the waveform used for this overshoot duration.
[C62.33-1989]
OVERSHOOT DURATION
The time between the point at which the wave exceeds the clamping voltage level V C and the point at which the
voltage overshoot has decayed to 50% of its peak.
[C62.35-1987]
19
Surge Protective Devices Committee
C62 Definitions
OVERVOLTAGE
Abnormal voltage between two points of a system that is greater than the highest value appearing between the same
two points under normal service conditions. Overvoltages may be low-frequency, temporary, and transient (surge).
[C62.2-1987 & C62.22-1991]
PARAMETER
A device descriptor that is measurable or quantifiable, such as a characteristic or rating.
[C62.37-1996]
PEAK FORWARD RECOVERY VOLTAGE (VFRM)
The maximum value of forward conduction voltage across the device upon the application of a specified voltage
rate of rise and current rate of rise following a zero or specified reverse-voltage condition.
[C62.37-1996]
PEAK GATE SWITCHING CURRENT (IGSM)
The maximum value of current through the gate terminal during the transition from the off-state to the switching point,
when a specified gate bias voltage, VG, is applied.
[62.37-1996]
PEAK NOMINAL VARISTOR VOLTAGE
Voltage across the varistor measured at a specified peak ac current, I N(ac), of specific duration. IN(ac) is specified by the
varistor manufacturer.
[C62.33-1989]
PEAK OFF-STATE GATE CURRENT (IGDM)
The maximum gate current that results from the application of the peak off-state gate voltage, VGDM. [C62.37-1996]
PEAK PULSE IMPULSE CURRENT (IPPM)
Rated maximum value of peak impulse pulse current (I PP) applied for 10 pulses with 10 X 1000µs waveform and
maximum duty factor of 0. 0l % without causing failure.
[C62.35-1987] [6]
PERMANENTLY GROUNDED DEVICE
A grounding device designed to be permanently connected to ground, either solidly or through current transformers
and/or another grounding device.
[STD 32-1990]
P-GATE THYRISTOR
A three-terminal thyristor in which the gate terminal is connected to the p-region adjacent to the region to which
the cathode is connected and that is normally switched to the on state by applying a positive signal between the
gate and cathode terminals.
[C62.37-1996]
POSITIVE-BREAKDOWN-RESISTANCE THYRISTOR SPD
A thyristor SPD whose static breakdown characteristic has a net positive-resistance slope prior to switching.
[C62. 37-1996]
POWER-FREQUENCY SPARKOVER VOLTAGE
The root-mean-square value of the lowest power-frequency sinusoidal voltage that will cause sparkover when applied
across the terminals of an arrester.
[C62.1-1989 & C62.11-1987]
POWER-FREQUENCY WITHSTAND VOLTAGE
A specified root-mean-square test voltage at power frequency that will not cause a disruptive discharge.
[C62.1-1989 & C62.11-1987]
PRINCIPAL CURRENT
A generic term for the current through the device excluding any gate current.
NOTE - It is the current through both main terminals.
20
[C62.37-1996]
Surge Protective Devices Committee
C62 Definitions
PRINCIPAL VOLTAGE
The voltage between the main terminals.a
[C62.37-1996]
NOTES:
1In the case of reverse blocking and reverse conducting thyristors, the principal voltage is called positive
when the anode potential is higher than the cathode potential, and called negative when the anode potential is lower
than the anode potential.a
2For bi-directional thyristor, the principal voltage is called positive when the potential of main terminal 2 is
higher than the potential of main terminal 1.a
3For forward-conducting thyristors the principal voltage is called positive when the cathode potential is
higher than the anode potential, and called negative when the cathode potential is lower than the anode potential.
PRINCIPAL VOLTAGE-CURRENT CHARACTERISTIC
The function, usually represented graphically, relating the principal voltage to the principal current. Syn: principal
characteristic.
[C62.37-1996]
PRORATED SECTION
A complete, suitably housed part of an arrester, comprising all necessary components, including gaseous medium,
in such a proportion as to accurately represent, for a particular test, the characteristics of a complete arrester.
[C62.1-1989 & C62.11-1987]
PROXIMITY ESD
See indirect ESD event. Also called proximity discharge.
[C62.47-1992]
QUADRANT
When the principal voltage-current characteristic is expressed graphically, the voltage, v, and current, I, axes
create four areas called quadrants. These quadrants are numbered counter clockwise as 1 through 4. The
characteristic occurs in quadrant 1, +v and +i, and quadrant 3, -v and -i.
[C62.37-1996]
RADIO INFLUENCE VOLTAGE (RIV)
A high-frequency voltage, generated by all sources of ionization current, that appears at the terminals of electric-power
apparatus or on power circuits.
[C62.1-1989 & C62.11-1987]
RATED AVERAGE POWER DISSIPATION
Maximum average power dissipation in the device due to repetitive pulses at a specified current and temperature
without causing device failure.
[C62.35-1987]
RATED CONTINUOUS CURRENT
The current expressed in amperes, root mean square, that the device can carry continuously under specified service
conditions without exceeding the allowable temperature rise.
[STD 32-1990]
RATED CURRENT (OF A NEUTRAL DEVICE) (CURRENT RATING)
The rated thermal current of a neutral device.
[STD 32-1990]
RATED DC VOLTAGE (VARISTOR)
Maximum continuous dc voltage which may be applied.
[C62.33-1989]
RATED FORWARD SURGE CURRENT
Maximum single peak current for an 8.3 ms, half sine wave, without causing device failure. Applies to asymmetrical
bi-directional avalanche junction surge suppressors only.
[C62.35-1987]
RATED FREQUENCY (OF A GROUNDING DEVICE)
The frequency of the alternating current for which a device is designed.
21
[STD 32-1990]
Surge Protective Devices Committee
C62 Definitions
RATED MULTIPLE PEAK PULSE POWER DISSIPATION
Peak pulse power dissipation resulting from the pulse current.
[C62.35-1993]
IPP.PPPM = VC X IPPM
RATED PEAK SINGLE PULSE TRANSIENT CURRENT (VARISTOR)
Maximum peak current which may be applied for a single 8/20 µs impulse, with rated line voltage also applied,
without causing device failure.
[C62.33-1989]
RATED RECURRENT PEAK VOLTAGE (VARISTOR)
Maximum recurrent peak voltage which may be applied for a specified duty cycle and waveform. [C62.33-1989]
RATED RMS VOLTAGE (VARISTOR)
Maximum continuous sinusoidal rms voltage which may be applied.
[C62.33-1989]
RATED SINGLE PULSE TRANSIENT ENERGY (VARISTOR)
Energy which may be dissipated for a single impulse of maximum rated current at a specified wave shape, with rated
rms voltage or rated dc voltage also applied, without causing device failure.
[C62.33-1989]
RATED THERMAL CURRENT
The rms neutral current in amperes which the device is rated to carry under standard operating conditions for rated
time without exceeding temperature limits.
[STD 32-1990]
RATED TIME (TIME RATING)
The time during which the device will carry its rated thermal current (or, for certain resistors, withstand its rated
voltage) under standard operating conditions, without exceeding the limitations established by these standards.
[STD 32-1990]
RATED TIME TEMPERATURE RISE (FOR A GROUNDING DEVICE)
The maximum temperature rise above ambient attained by the winding of a device as the result of the flow of rated
thermal current (or, for certain resistors, the maintenance of rated voltage across the terminals) under standard
operating conditions, for rated time and with a starting temperature equal to the steady-state temperature. It may be
expressed as an average or a hot-spot winding rise. [STD 32-1990]
RATED TRANSIENT AVERAGE POWER DISSIPATION (VARISTOR)
Maximum average power which may be dissipated due to a group of pulses occurring within a specified isolated time
period, without causing device failure.
[C62.33-1989]
RATED VOLTAGE
The rms voltage, at rated frequency, which may be impressed between the terminals of the device under standard
operating conditions for rated time (continuously for grounding transformers) without exceeding the limitations
established by these standards.
[STD 32-1990]
RATING
The designation of an operating limit for a device.
[C62.1-1989]
The nominal value of any electrical, thermal, mechanical, or environmental quantity assigned to define the
operating conditions under which a component, machine, apparatus, electronic device, etc., is expected to give
satisfactory service.
NOTE - Rating is a generic term, but also see maximum rating.
[C62.37-1996]
REACTANCE GROUNDED
Grounded through impedance, the principal element of which is reactance.
NOTE: The reactance may be inserted either directly, in the connection to ground, or indirectly by increasing the
reactance of the ground return circuit. The latter may be done by intentionally increasing the zero-sequence reactance
22
Surge Protective Devices Committee
C62 Definitions
of apparatus connected to ground, or by omitting some of the possible connections from apparatus neutrals to ground.
[STD 32-1990]
RECEPTOR ELECTRODE GEOMETRY
The size and shape of that surface of the receptor, termed the receptor electrode, at which the ESD takes place.
[C62.47-1992]
RECEPTOR
The body which is at rest in an ESD event. The receptor is usually but not necessarily at the same potential as its
surroundings. It is always at a potential different from that of the intruder.
[C62.47-1992]
RECOVERY VOLTAGE
That voltage that occurs across the terminals of a pole of circuit-interrupting device upon the interruption of the
current.
NOTE: For an arrester, this occurs as a result of interruption of the follow current.
[C62.1-1989]
REMOTE EARTH (POTENTIAL)
The location outside the influence of local grounds, and always assumed to be at zero potential.
[C62.23 – 1995]
REPETITIVE PEAK FORWARD CURRENT (IFRM)
Rated maximum (peak) value of ac power frequency forward current of specified waveshape and frequency which
may be applied continuously.
[C62.37-1996]
REPETITIVE PEAK OFF-STATE CURRENT (IDRM)
The maximum (peak) value of off-state current that results from the application of the repetitive peak off-state voltage.
[C62.37-1996]
REPETITIVE PEAK OFF-STATE VOLTAGE (VDRM)
Rated maximum (peak) continuous voltage that may be applied in the off-state conditions including all dc and
repetitive alternating voltage components.
[C62.37-1996]
REPETITIVE PEAK ON-STATE CURRENT (ITRM)
Rated maximum (peak) value of ac power frequency on-state current of specified waveshape and frequency which
may be applied continuously.
[C62.37-1996]
REPETITIVE PEAK REVERSE CURRENT (I RRM)
The maximum (peak) value of reverse current that results from the application of the repetitive peak reverse voltage,
VRRM.
[C62.37-1996]
REPETITIVE PEAK REVERSE VOLTAGE (VRRM)
Rated maximum (peak) continuous voltage that may be applied in the reverse blocking direction including all dc and
repetitive alternating voltage components.
[C62.37-1996]
REPETITIVE RATING
A maximum rating that may be continuously applied to the thyristor.
[C62.37-1996]
RESEAL VOLTAGE RATING OF AN ARRESTER
The maximum arrester recovery voltage permitted for a specified time following one or more unit operation(s) with
discharge currents of specified magnitude and duration.
[C62.2-1987]
RESISTANCE (VARISTOR)
Static resistance of the varistor at a given operating point as defined by: Rx = dVx/dIx.
RESISTANCE GROUNDED
Grounded through impedance, the principal element of which is resistance.
23
[C62.33-1989]
Surge Protective Devices Committee
C62 Definitions
NOTE: The resistance may be inserted either directly, in the connection to the ground, or indirectly, as, for example, in
the secondary of a transformer, the primary of which is connected between neutral and ground, or in series with the
delta-connected secondary of a wye-delta grounding transformer.
[STD 32-1990]
RESISTANCE METHOD OF TEMPERATURE DETERMINATION
The determination of the temperature by comparison of the resistance of a winding at the temperature to be
determined, with the resistance at known temperature.
[STD 32-1990]
RESPONSE TIME (VARISTOR)
The time between the point at which the wave exceeds the clamping voltage level (VC) and the peak of the voltage
overshoot. For the purpose of this definition, clamping voltage is defined with a 8/20 µs current waveform of the same
peak current amplitude as the waveform used for this response time.
[C62.33-1989]
RESPONSE TIME
The time between the point at which the wave exceeds the clamping level (V C) and the peak of the voltage overshoot.
[C62.35-1987]
REVERSE BLOCKING QUADRANT
Quadrant 3 of the principal voltage-current characteristic in which the device exhibits a reverse blocking state.
[C62.37-1996]
REVERSE DIRECTION
(1) The direction of current in a p-n junction that results when the n-type semiconductor region is at a positive
potential relative to the p-type region. (2) The direction of current in a semiconductor device that results when the ntype semiconductor region connected to one terminal is at a positive potential relative to the p-type region connected
to the other terminal.
NOTE-This definition may not apply if one or more junctions are connected in series with at least one other
junction whose p and n regions are reversed.
[C62.37-1996]
REVERSE-BLOCKING DIODE THYRISTOR SPD
A two-terminal thyristor SPD that exhibits a blocking state for positive cathode voltage.
[C62.37-1996]
REVERSE-BLOCKING TRIODE THYRISTOR SPD
A three-terminal thyristor SPD that exhibits a blocking state for positive cathode voltage.
[C62.37-1996]
ROUTINE TESTS
Tests made by the manufacturer on every device or representative samples, or on parts or materials, as
required, to verify that the product meets the design specifications.
[C62.1-1989 & C62.11-1987]
A test made for quality control by the manufacturer on every device, on representative samples, or on parts or
materials as required to verify during production that the product meets the design specifications.
[STD 32-1990]
SAG
A rms reduction in the ac voltage, at the power frequency, for durations from a half-cycle to a few seconds.
[C62.48-1995]
SEALED TANK SYSTEM
A method of oil preservation in which the interior of the tank is sealed from the atmosphere and in which the gas plus
the oil volume remains constant over the temperature range.
[STD 32-1990]
SED
Static Electric Discharge; an alternate name for ESD.
[C62.47-1992]
SERIES GAP
24
Surge Protective Devices Committee
C62 Definitions
An intentional gap(s) between spaced electrodes: it is in series with the valve elements of the arrester, substantially
isolating the element from line or ground, or both, under normal line-voltage conditions. [C62.1-1989 & C62.2-1987]
An intentional gap(s) between spaced electrodes in series with the valve elements across which all or part of the
impressed arrester terminal voltage appears.
[C62.11-1987 & C62.22-1991]
SHORT CIRCUIT
An abnormal connection of relatively low impedance, whether made accidentally or intentionally, between two points
of different potential in a circuit.
[C62.31-1987]
NOTE: The term is often applied to the group of phenomena that accompany a short circuit.
[C62.32-1987]
SHORT TIME RATING (OF A GROUNDING DEVICE)
A rated time of ten minutes or less.
[STD 32-1990]
SHUNT GAP
An intentional gap(s) between spaced electrodes that is electrically in parallel with one or more valve elements.
[C62.11-1987]
SOLIDLY GROUNDED
Grounded through an adequate ground connection in which no impedance has been inserted intentionally.
NOTE: Adequate as used here means suitable for the purpose intended.
[STD 32-1990]
SPARKOVER
A disruptive discharge between electrodes of a measuring gap, voltage control gap, or protective device.
[C62.31-1987 & C62.1-1989 & C62.11-1987 & C62.32-1987]
STANDARD LIGHTNING IMPULSE
The wave shape of standard impulse used (when it is not in conflict with product standards) is 1.2/50µs.
[C62.2-1987 & C62.22-1991]
STANDARD SWITCHING IMPULSES
The wave shapes of standard impulse tests depend on equipment being tested.
[C62.2-1987 & C62.22-1991]
STARTING TEMPERATURE (FOR A GROUNDING DEVICE)
The winding temperature at the start of the flow of thermal current.
[STD 32-1990]
STATIC DISSIPATIVE
Having a level of resistivity that typically leads to charge dissipation.
[C62.47-1992]
STATISTICAL BIL
Applicable specifically to self-restoring insulations. The crest value of a standard lightning impulse for which the
insulation exhibits a 90% probability of withstand (or a 10% probability of failure) under specified conditions.
[C62.2-1987]
STATISTICAL BSL
Applicable specifically to self-restoring insulations. The crest value of a standard switching impulse for which the
insulation exhibits a 90% probability of withstand (or a 10% probability of failure) under specified conditions.
[C62.2-1987]
STEADY-STATE TEMPERATURE RISE (FOR A GROUNDING DEVICE)
The maximum temperature rise above ambient which will be attained by the winding of a device as the result of the
flow of rated continuous current under standard operating conditions. It may be expressed as an average or a hot spot
winding rise.
[STD 32-1990]
SUBASSEMBLY
Subassemblies are items, not completed equipment or individual components, that have an identifiable function.
25
Surge Protective Devices Committee
C62 Definitions
[C62.38-1995]
SURGE (SURGE-PROTECTIVE DEVICE)
A transient wave of current, potential, or power in an electric circuit a.
C62.11-87 & C62.22-91
NOTE: The use of this term to describe a momentary overvoltage consisting of a mere increase of the mains voltage
for several cycles is deprecated. See swell.
[C62.41-1991 & C62.1-1989 & C62.2-1987 & C62.37-1996]
A transient wave of voltage or current. The duration of surge is not tightly specified but is usually less than a
few milliseconds.
[C62.48-1995]
SURGE ARRESTER
A protective device for limiting surge voltages on equipment by discharging or bypassing surge current; it
prevents continued flow of follow current to ground, and is capable of repeating these functions as specified.
[C62.22-1991]
A protective device for limiting surge voltages on equipment by diverting surge current and returning the device to its
original status. It is capable of repeating these functions as specified.
[C62.11-1987]
NOTE: Hereafter, the term arrester as used in this standard shall be understood to mean surge arrester.
[C62.1-1989 & C62.2-1987]
SURGE LET-THROUGH
That part of the surge that passes by a surge-protective device with little or no alteration. See: surge remnant.
[C62.45-1992]
SURGE-PROTECTIVE DEVICE
The generic term used to describe a device by its protective function, regardless of technology used, ratings,
packaging, point of application, etc.
[C62.45-1992]
SURGE PROTECTOR (SPD)
A specific complete surge-protective device, as opposed to a component of a surge protector or a generic surgeprotective device.
[C62.42-2005]
SURGE PROTECTOR
A protective device, consisting of one or more surge arresters, a mounting assembly, optional fuses and shortcircuiting devices, etc, which is used for limiting surge voltages on low-voltage (<1000 Vrms or 1200 Vdc) electrical
and electronic equipment or circuits.
[C62.31-1987]
The term used to refer to a specific complete device (generally the equipment under test in the context of the present
guide), as opposed to a component of the surge protector or a generic surge-protective device.
[C62.45-1992]
An assembly of protective devices consisting of one or more series, parallel, or any combination of elements used to
limit surge voltages, currents, or both to a specified level. Syn: protector.
[C62.36-1991]
SURGE REMNANT
That part of an applied surge that remains downstream of one or several protective devices. See: surge let-through and
surge response voltage.
[C62.45-1992]
SURGE RESPONSE VOLTAGE
The voltage profile appearing at the output terminals of a surge protective device and applied to downstream loads,
during and after a specified impinging surge, until normal, stable conditions are reached.
[C62.45-1992]
SUSCEPTIBILITY
The inability of a device, equipment, or system to resist an electromagnetic disturbance. Note: Susceptibility is the
lack of immunity.
[C62.45-1992]
SWELL
26
Surge Protective Devices Committee
C62 Definitions
A momentary increase in the power frequency voltage delivered by the mains, outside of the normal tolerances, with a
duration of more than one cycle and less than a few seconds. See surge.
[C62.41-1991]
SWITCHING CURRENT (IS)
The instantaneous current flowing through the device at the switching voltage, VS.
[C62.37-1996]
SWITCHING OVERVOLTAGE
Any combination of switching surge(s) and temporary overvoltage(s) associated with a single switching episode.
[C62.2-1987 & C62.22-1991]
SWITCHING POINT
The point in the principal voltage-current characteristic which the thyristor regenerates and initiates switching into the
on-state. This point occurs at the termination of the breakdown region and the start of the negative differentialresistance region.
[C62.37-1996]
SWITCHING QUADRANT
A quadrant of the principal voltage-current characteristic in which the device is intended to switch between the
off-state and the on-state. For a bi-directional thyristor the switching quadrants will be 1 and 3. For a reverse
blocking or reverse conducting thyristor the switching quadrant will be quadrant 1. For a forward conducting
thyristor the switching quadrant will be quadrant 3. [C62.37-1996]
SWITCHING RESISTANCE (RS)
The equivalent slope resistance of the breakdown region, R S, computed by:
V S  V( BO )
I S  I ( BO )
[C62.37-1996]
SWITCHING SURGE
A heavily damped transient electrical disturbance associated with switching. System insulation flashover may precede
or follow the switching in some cases but not all.
C62.2-87 & C62.22-91
SWITCHING VOLTAGE (VS)
The instantaneous voltage across the device at the final point in the breakdown region prior to switching into the onstate.
[C62.37-1996]
SYSTEM (CIRCUIT) VOLTAGE
The root-mean-square power-frequency voltage from line to line as distinguished from the voltage from line to neutral.
[C62.1-1989 & C62.11-1987 & C62.22-1991]
The root mean square (rms) phase-to-phase power frequency voltage on a three-phase alternating-current
electric system.
[C62.2-1987]
TAP
An available connection which permits changing the active portion of the device in the circuit.
[STD 32-1990]
TEMPERATURE COEFFICIENT OF BREAKDOWN VOLTAGE
The ratio of the change in breakdown voltage, V(BR), to changes in temperature. Expressed as either millivolts
per degree Celsius (mV/ºC) or percent per degree Celsius (%/ºC) with reference to the 25 ºC value of breakdown
voltage.
[C62.37-1996]
TEMPERATURE COEFFICIENT OF BREAKDOWN VOLTAGE
 V ( BR)  dV( BR) / dTJ 
The ratio of the change in breakdown voltage [V(BR)] to changes in temperature. Expressed as either millivolts per
degree Celsius (mV/°C) or percent per degree Celsius (%/°C).
[C62.35-1987]
27
Surge Protective Devices Committee
C62 Definitions
TEMPERATURE DERATING
Derating with temperature above a specified base temperature, expressed as a percentage, such as may be applied
to peak pulse current
[C62.37-1996]
TEMPERATURE DERATING
Derating with temperature above specified base temperature, expressed as a percentage, such as may be applied to
peak pulse power and peak pulse current.
[C62.35-1987]
TEMPORARY OVERVOLTAGE
An oscillatory overvoltage associated with switching of relatively long duration, which is undamped or slightly
damped.
[C62.2-1987]
An oscillatory overvoltage, associated with switching or faults (for example, load rejection, single phase faults) or
from non-linearities (ferro-resonance effects, harmonics) or both, of relatively long duration, which is undamped or
slightly damped.
[C62.22-1991]
TERMINALS
The conducting parts provided for connecting the arrester across the insulation to be protected.
[C62.1-1989 & C62.11-1987]
THERMAL CURRENT RATING
For resistors whose rating is based on constant voltage, the initial rms symmetrical value of the current that will flow
when rated voltage is applied.
[STD 32-1990]
THERMAL RESISTANCE
Junction to ambient, case, or lead temperature rise per unit input of applied power expressed as degree Celsius per
Watt.
[C62.35-1987]
THERMAL RESISTANCE (RΘJL; RΘJC; R JA)
The effective temperature rise per unit power dissipation of a designated junction, above the temperature of a stated
external reference point (lead, case, or ambient) under conditions of thermal equilibrium.
[C62.37-1996]
THERMOMETER METHOD OF TEMPERATURE DETERMINATION
The determination of the temperature by mercury, alcohol, resistance, or thermocouple thermometers, any of these
instruments being applied to the hottest accessible part of the device.
[STD 32-1990]
THYRISTOR
A bi-stable semiconductor device comprising three or more junctions that can be switched from the off-state to the onstate or vice versa, such switching occurring within at least one quadrant of the principal voltage-current
characteristic.a
[C62.37-1996]
TIME TO IMPULSE SPARKOVER
The time between virtual zero of the voltage impulse causing sparkover and the point on the voltage wave at which
sparkover occurs.
[C62.1-1989 & C62.11-1987]
TRANSFER TIME
The time duration of the transverse voltage.
[C62.31-1987]
TRANSIENT THERMAL IMPEDANCE (ZΘJL (t); ZΘJC(t); ZΘJA(t))
The change in the difference between the virtual junction temperature and the temperature of a specified reference
point or region (lead, case, or ambient) at the end of a time interval divided by the step function change in power
dissipation at the beginning of the same time interval that causes the change of temperature-difference.
[C62.37-1996]
TRANSITION CURRENT
28
Surge Protective Devices Committee
C62 Definitions
The current required at a given temperature and duration to cause a current-protective device to change state.
[C62.36-1991]
TRANSITION TIME
The time required for the voltage across a conducting gap to drop into the arc region after the gap initially begins to
conduct.
[C62.31-1987]
TRANSVERSE (DIFFERENTIAL) MODE VOLTAGE
The voltage at a given location between two conductors of a group.
[C62.31-1987 & C62.32-1987]
TRAVELING WAVE
The resulting wave when an electrical variation in a circuit such as a transmission line takes the form of translation of
energy along a conductor, such energy being always equally divided between current and potential forms.
[C62.2-1987 & C62.22-1987]
TRIBOELECTRIC CHARGING
The generation of electrostatic charges when two pieces of material are brought into intimate contact and are then
separated. Also termed triboelectrification.
[C62.47-1992]
TRIBOELECTRIC SERIES
A list of substances in an order of relative positive to negative charging as a result of the triboelectric charging effect.
[C62.47-1992]
UNGROUNDED
Without an intentional connection to ground except through potential indicating of measuring devices or other veryhigh-impedance devices.
[STD 32-1990]
UNIDIRECTIONAL THYRISTOR SPD
A thyristor SPD that has switching characteristics in only quadrant.
NOTE-The main unidirectional thyristor SPDs are the reverse-blocking, reverse conducting and forward
conducting thyristor SPDs.
[C62.37-1996]
UNINHIBITED OIL
Mineral transformer oil to which no synthetic oxidation inhibitor has been added.
[STD 32-1990]
UNIT OPERATION
Discharging a surge through an arrester while the arrester is energized.
[C62.1-1989 & C62.2-1987 & C62.11-1987 & C62.22-1991]
VALVE ARRESTER
An arrester that includes a valve elements.
[C62.1-1989 & C62.2-1987 & C62.11-1987 & C62.22-1991]
VALVE ELEMENT
A resistor that, because of its nonlinear current-voltage characteristic, limits the voltage across the arrester terminals
during the flow of discharge current and contributes to the limitation of follow current at normal power
frequency voltage.
[C62.1-1989 & C62.2-1987 & C62.11-1987 & C62.22-1991]
VARIATION OF HOLDING CURRENT WITH TEMPERATURE
The change in holding current, IH, with changes in temperature. It is shown as a graph.
[C62.37-1996]
VARISTOR VOLTAGE
Voltage across the varistor measured at a given current, I X.
[C62.33-1989]
VENT
An intentional opening for the escape of gases to the outside.
VIRTUAL DURATION OF WAVE FRONT (OF AN IMPULSE)
29
[C62.1-1989 & C62.11-1987]
Surge Protective Devices Committee
C62 Definitions
The virtual value for the duration of the wave front is as follows:
For voltage waves with wave front duration less than 30 μs, either full or chopped on the front, crest, or
tail, 1.67 times the time for the voltage to increase from 30% to 90% of its crest value. a
(2)
For voltage waves with wave front duration of 30 μs or more, the time taken by the voltage to increase
from actual zero to maximum crest value. a
(3)
For current waves, 1.25 times the time for the current to increase from 10% to 90% of crest value. a
[C62.1-1989 & C62.2-1987 & C62.11-1987 & C62.22-1991 & C62.37-1996]
(VIRTUAL) JUNCTION TEMPERATURE (T J)
A theoretical temperature representing the temperature of the junction(s) calculated on the basis of a simplified model
of the thermal and electrical behavior of the device.
[C62.37-1996]
VIRTUAL ZERO POINT (OF AN IMPULSE)
The intersection with the zero axis of a straight line drawn through points on the front of the current wave at 10% and
90% crest value, or through points on the front of the voltage wave at 30% and 90% crest value.
[C62.1-1989 & C62.2-1987 & C62.11-1987 & C62.22-1991 & C62.37-1996]
VOLTAGE CLAMPING RATIO (VARISTOR)
A figure of merit measure of the varistor clamping effectiveness as defined by the symbols V C/Vm(ac), VC/Vm(dc).
[C62.33-1989]
VOLTAGE CLAMPING RATIO
A figure of merit, which determines the clamping effectiveness of an avalanche surge suppressor as defined by the
symbols.
[C62.35-1987]
VOLTAGE OVERSHOOT (VARISTOR)
The excess voltage above the clamping voltage of the device for a given current that occurs when current waves of less
than 8 μs virtual front duration are applied. This value may be expressed as a % of the clamping voltage (V C) for an
[C62.33-1989]
VOLTAGE OVERSHOOT
The excess voltage above the clamping voltage (VC) of the device for a given current that occurs when current waves
of less than 10 μs virtual front duration are applied. This value may be expressed as a percentage of the clamping
voltage (VC) for a 10 X 1000 μs current wave.
[C62.35-1987]
VOLTAGE RATING
The designated maximum permissible operating voltage between its terminals at which an arrester is designed to
perform its duty cycle. It is the voltage rating specified on the nameplate.
[C62.1-1989]
VOLTAGE TO GROUND
The voltage between any live conductor of a circuit and the earth.
NOTE: Where safety considerations are involved, the voltage to ground that may occur in an ungrounded circuit is
usually the highest voltage normally existing between the conductors of the circuit, but in special circumstances higher
voltages may occur.
[STD 32-1990]
VULNERABILITY
The characteristic of a device for being damaged by an external influence, such as a surge.
[C62.45-1992]
WAVEFORM
A manifestation or representation (that is, graph, plot, oscilloscope presentation, equation(s), table of co-ordinate or
statistical data, etcetera) or a visualization of a wave, pulse or transition. a
[C62.37-1996]
WAVEFRONT (OF A SURGE OR IMPULSE)
That part (of an impulse) which occurs prior to the crest value. a
[C62.1-1989 & C62.11-1987 & C62.22-1991 & C62.37-1996]
WAVE SHAPE (OF AN IMPULSE TEST WAVE)
30
Surge Protective Devices Committee
C62 Definitions
The graph of the wave as a function of time.a
[C62.1-1989 & C62.2-1987 & C62.11-1987 & C62.22-1991 & C62.37-1996]
WAVE SHAPE DESIGNATION (OF AN IMPULSE)
The wave shape of an impulse (other than rectangular) of a current or voltage as designated by a combination of two
numbers. The first, an index of the wave front, is the virtual duration of the wave front in microseconds. The second,
an index of the wave tail, is the time in microseconds from virtual zero to the instant at which one-half of the crest
value is reached on the wave tail. Examples are 1.2/50 and 8/20 waves.
[C62.1-1989 & C62.2-1987 & C62.11-1987 & C62.37-1996]
The wave shape of a rectangular impulse of current or voltage is designated by two numbers. The first designates the
minimum value of current or voltage that is sustained for the time in microseconds designated by the second number.
An example is the 75A X 1000 µs wave.
[C62.2-1987 & C62.22-1991 & C62.37-1996]
WAVE SHAPE OF A RECTANGULAR IMPULSE OF CURRENT OR VOLTAGE
This wave is designated by two numbers. The first designates the minimum value of current or voltage which is
sustained for the time in microseconds designated by the second number. An example is the 75A X l000 µs wave.
[C62.1-1989]
WAVE TAIL (OF AN IMPULSE)
That part between the crest value and the end of the impulse.a
[C62.1-1989 & C62.2-1987 & C62.11-1987 & C62.22-1991 & C62.37-1996]
WAVE
The variation with time of current, potential, or power at any point in an electric circuit. a
[C62.1-1989 & C62.11-1987 & C62.37-1996]
WITHSTAND VOLTAGES
The voltage that electric equipment is capable of withstanding without failure or disruptive discharge when tested
under specified conditions; (see ANSI C92.1-1982) [C62.2-1987 & C62.22-1991]
31