1.2/5 0 voltage impulse
Voltage impulse with a nominal virtual front time of 1 .2 µs and a nominal time to half-value of 50µs
8/20 current impulse
Current impulse with a nominal virtual front time of 8 µs and a nominal time to half-value of 20 µs
Acceptance test
Contractual test to prove to the customer that the item meets certain conditions of its specification
Combination SPD
SPD that contains either at least one combination mode of protection or at least one voltage limiting mode of protection and one voltage switching mode of protection
Combination mode of protection
Mode of protection that incorporates both, voltage switching components and voltage limiting components
Combination wave
Wave characterized by defined voltage amplitude (Uoc) and wave shape under open-circuit conditions and a defined current amplitude (/cw) and wave shape under short-circuit conditions
Note 1 to entry : The voltage amplitude, current amplitude and waveform that is delivered to the SPD are determined by the combination wave generator ( CWG ) impedance Zf and the impedance of the DUT.
Combination wave generator short-circuit current
Icw
Prospective short-circuit current of the combination wave generator, at the point of connection of the device under test
Note 1 to entry : When the SPD is connected to the combination wave generator, the current that flows through the device is generally less than lcw.
Continuous Current
Ic
current flowing through the SPD's mode of protection while energized at Utest
Current Path
An electrical path designed to conduct at least a portion of the impulse current applied to a surge protective device (SPD) in its mode of protection
Note 1 to entry: An SPD's mode of protection may consist of either a single current path or multiple current paths when voltage-limiting and/or voltage-switching components are connected in parallel.
Note 2 to entry: Examples are provided in Annex B of IEC TR 61643-03 : 2024.
Decoupling Network
Electrical circuit designed to prevent surge energy from propagating to the power network during the energized testing of Surge Protective Devices (SPDs).
Note 1 to entry: This electrical circuit is sometimes referred to as a "back filter ."
Degradation (of Performance)
Undesired permanent deviation in the operational performance of equipment or a system from its intended performance
Degree of protection of enclosure
IP
Classification preceded by the symbol IP indicating the extent of protection provided by an enclosure against access to hazardous parts , against ingress of solid foreign objects and possibly harmful ingress of water
PE connection
Connection provided on an SPD and intended for the electric connection with the earthing arrangement
Electrically separated circuit
Electric circuit which is provided with terminations for connection to external circuits and insulated from the SPD main circuit(s) according to the requirements for simple or for protective separation
Note 1 to entry: Electrical circuits not provided with at least simple or even protective separation from the SPD main circuit (s) are considered as part of the main circuit (s).
Extra-low voltage
ELV
Voltage not exceeding the maximum value of the prospective touch voltage which is permitted to be maintained indefinitely under specified conditions of external influences
Note 1 to entry: According to IEC 61140, values for ELV stands for voltages below or equal to 50 VAC or 120 VDC.
[SOURCE : IEC 61140 : 2016,3.26 ]
Flush-mounted
Adjective qualifying a device mounted into a recess in a mechanical structure so that the shape of the mounting surface remains essentially unchanged
[SOURCE : IEC 60050-151 : 2001,151-16-40]
Follow current
If
Peak current supplied by the electrical power system and flowing through the SPD after a discharge current impulse
highest crest value of measured voltages
Umax
Highest value of voltage measured between the connections of the SPD during the application of impulses of specified wave shape and amplitude
Impulse discharge current
Limp
Crest value of a discharge current through an SPD’s mode of protection with specified charge transfer Q and specified specific energy W/R in the specified time
Note 1 to entry: This is used to characterize T1 SPDs or category D1(IEC61643-21)tested SPDs.
Isolation
Disconnection providing adequate insulation between electrical equipment, a system, an installation or part of an installation and their energy sources
[SOURCE : IEC 60050-195 : 2021,195-06-23]
Live part
Conductive part intended to be energized under normal operating conditions, including the neutral conductor and mid-point conductor, but excluding the PEN conductor, PEM conductor and PEL conductor
[SOURCE : IEC 60050-195 : 2021,195-02-19]
Load-side surge withstand capability (for a two-port SPD)
Ability of a two-port SPD to withstand surges on the output connections originating in circuitry
downstream of the SPD
Maximum continuous operating voltage
Uc
Maximum voltage, which may be continuously applied to the SPD's mode of protection
Note 1 to entry: Uc may exceed 1000VAC or 1500VDC.
Maximum discharge current
Imax
crest value of a current through a T2 SPD’s mode of protection having an 8/20 current impulse and magnitude according to the manufacturer's specification,which is equal to or greater than
In
Note 1 to entry: Imax can be withstood at least once.
means for short-circuiting the SPD
SC-means
Internal method for short-circuiting an SPD under specified conditions, with a current carrying capacity equal to the short-circuit current rating ISCCR of the SPD
Measured limiting voltage
Highest value of voltage measured between the connections of the SPD during the application of impulses of specified wave shape and amplitude
Minimum short-circuit current rating
ISCCRMIN
Minimum prospective short-circuit current from the power system for which the SPD, in conjunction with the internal disconnector (s) , is rated
Mode of protection
Intended circuitry between two connections, that contains one or more protective components, declared by the manufacturer
Note 1 to entry: Additional connections may be included within this circuitry.
Note 2 to entry: Such modes may be line to line, line to neutral, line to PE, neutral to PE, plus to minus, plus to PE and mi nus to PE.
Note 3 to entry: Examples are provided in Annex B of IEC TR 61643-03 : 2024.
Diversified SPD
SPD with more than one mode of protection , or a set of electrically interconnected SPDs offered as a unit
Nominal discharge current
In
crest value of an 8/20 current impulse through an SPD’s mode of protection
Note 1 to entry: This current impulse can be withstood multiple times.
Note 2 to entry: This is used to characterize T 2 SPDs or category E1 (IEC 61643-21) tested SPDs.
Nominal varistor voltage
U1mA
Voltage across the MOV measured at 1 mA DC
Nominal voltage of a system
Suitable approximate value of voltage used to designate or identify a system
[SOURCE : IEC 60050-601 : 1985,601-01-21]
One-port SPD
SPD having no intended series impedance
Note 1 to entry: A one -port SPD may have separate input and output connections.
Note 2 to entry: Over current protection devices e.g. fuses or CBs are not considered as specific intended series impedance.
Open-circuit mode
OCM
End-of-life behaviour whereby an SPDA changes to a permanent high impedance or open -circuit state under specified conditions
Note 1 to entry: A low impedance intermediate state is possible for a limited time until the final end-of-life mode is reached.
Open-circuit voltage
Uoc
Open-circuit voltage of the combination wave generator at the point of connection of the device under test
Note 1 to entry: This is used to characterize T3 SPDs.
Ordinary person
Person who is neither a skilled person nor an instructed person
[SOURCE : IEC 60050-195 : 2021,195-04-03 ]
Output contact
Contact included in a circuit separate from the main circuit of an SPD, and linked to a disconnector or status indicator
Over voltage category
Numeral defining a transient over voltage condition
Note 1 to entry: Further information on over voltage categories is provided in IEC 60364- 4-443.
[SOURCE: IEC 60050-581 : 2008, 581-21-02, modified-addition of Note 1 to entry ]
PELV system
Electric system in which the voltage cannot exceed the value of extra-low voltage :
– under normal conditions and
– under single fault conditions, except earth faults in other electric circuits
Note 1 to entry: PELV is the abbreviation for protective extra-low voltage.
Note 2 to entry: PELV has protective separation from all circuits other than PELV, SELV or earth.
[SOURCE : IEC60050-826 : 2022,826-12-32]
PEM conductor
PEM
Conductor combining the functions of both a protective earthing conductor and a mid- point conductor
[SOURCE : IEC 60050-195 : 2021,195-02-13]
PEN conductor
PEN
Conductor combining the functions of both a protective earthing conductor and a neutral conductor
[SOURCE : IEC 60050-195 : 2021,195-02-12]
Prospective short-circuit current
IP
Current which would flow at a given location in a circuit if it were short-circuited at that location by a link of negligible impedance
Protective conductor
PE
Conductor provided for purposes of electrical safety
[SOURCE : IEC 60050-195 : 2021,195-02-09]
Protective conductor current
IPE
Current expected to flow through the PE connection of the SPD
(electrically) protective separation
Separation of one electric circuit from another by means of:
--double insulation; or
--basic insulation and electrically protective screening (shielding); or
--reinforced insulation
[SOURCE : IEC 61140 : 2016, 3 .24]
Rated load current
IL
Maximum current that can be continuously conducted between the input and the output connections of the SPD
Note 1 to entry: This current does not influence the impedance of current-limiting components.
Residual current device
RCD
Mechanical switching device or association of devices designed to make, carry and break currents under normal service conditions and to cause the opening of the contacts when the residual current attains a given value under specified conditions
[SOURCE : IEC 60050-442 : 1998,442-05-02]
Residual voltage
Ures
Crest value of voltage measured between the connections of the SPD during the passage of discharge current
Routine test
Conformity test made on each individual item during or after manufacture
[SOURCE: IEC 60050-151 : 2001;151-16-17]
SELV system
Electric system in which the voltage cannot exceed the value of extra-low voltage :
–under normal conditions and
–under single fault conditions, including earth faults in other electric circuits
Note 1 to entry: SELV is the abbreviation for safety extra -low voltage .
Note 2 to entry: SELV has simple separation from PELV, other SELV systems and earth, and protective separation from All other circuits.
[SOURCE: IEC 60050-195 : 2021,195-06-28 modified–addition of Note 2 to entry]
Short-circuit current rating
ISCCR
Maximum prospective short-circuit current from the power system for which the SPD , in conjunction with any external disconnector (s) specified, is rated
Note 1 to entry: The term SPD includes internal disconnect or s as well as any internal SC- means which are part of the SPD.
Short-circuit mode
SCM
End-of-life behaviour whereby an SPDA changes to an intended permanent low impedance or short-circuit state under specified conditions
Short-circuiting SPD
SPD which changes its characteristic by an SC-means to an intentional internal short- circuit due to an impulse according to the transition surge current rating
Simple separation
Separation between electric circuits or between an electric circuit and local earth by means of basic insulation
[SOURCE : IEC 60050 -195 : 2021,195-06-30]
Skilled person
Electrically skilled person
Person with relevant education and experience to enable him or her to perceive risks and to avoid hazards that electricity can create
[SOURCE : IEC 60050 - 195 : 2021 , 195-04-01]
Spark over voltage
maximum voltage value at which the sudden change from high to low impedance starts for a voltage switching SPD or combination SPD
SPD assembly
SPDA
One SPD or a set of SPDs, in both cases including all SPD disconnectors required by the SPD manufacturer, providing the required over voltage protection for a type of system earthing
[SOURCE : IEC 60364-5-53 : 2019,530 .3 .8]
SPD disconnector
Disconnector
Device for disconnecting an SPD, or part of an SPD, from the power system in the event of SPD end-of-life
Note 1 to entry: This disconnecting device is not required to have isolating capability for safety purposes. it is to prevent a persistent fault on the system and is used to give an indication of an SPD's end-of-life. Disconnectors can be internal (built in) or external (required by the manufacturer). There may be more than one disconnector function for example an over-current protection function and a thermal protection function. These functions may be in separate units.
Specific energy for T 1 SPD test
W/R
Unit dissipated by a unit resistance of 1Ώ with the impulse discharge current Iimp
Note 1 to entry: This is equal to the time integral of the square of the current (W/R=∫i2dt).
Status indicator
Means to indicate the operational status of an SPD, an SPD disconnect or, an SPDA or a part of an SPD
Note 1 to entry: Such indicators may be local with visual and / or audible alarms and / or may have remote signal and / or output contact capability.
Surge protective device
SPD
Device that contains at least one nonlinear component that is intended to limit surge voltages and divert surge currents
Note 1 to entry: An SPD is a complete unit or device, having appropriate connecting means.
Note 2 to entry: Secondary functions may be incorporated, such as current-limiting function.
Note 3 to entry: Nonlinear may be caused by frequency change.
Note 4 to entry: The IEC 61643- 3xx series of standards covers surge protective components.
Temporary over voltage test value
UT
Test voltage applied to the SPD for a specific duration tT , to simulate the stress under temporary over voltage (TOV) conditions
Test current
Itest
Test current derived from specific application conditions
Note 1 to entry: This parameter is only used for test purposes .
Test voltage
Utest
Test voltage derived from the system voltage
Note 1 to entry: This parameter is only used for test purposes.
Thermal equilibrium
State reached when the temperature of the parts of a component or equipment operating in a given environment no longer varies faster than a specified limit
[SOURCE : IEC 60050-151 : 2001,151-16-33]
Thermal stability
Condition of the SPD when the current flowing into the SPD or the power dissipation does not increase during a defined time of application of the maximum continuous operating voltage Uc
Total discharge current
Total
Current which flows through the PE connection of a multi-mode SPD during the total discharge current test
Note 1 to entry: The aim is to take into account cumulative effects that occur when multiple modes of protection of a multi-mode SPD conduct at the same time.
Note 2 to entry: Total is particularly relevant for T1 SPDs and is used for the purpose of lightning protection equipotential bonding according to lEC 62305 series.
Note 3 to entry: This is sometimes called "Total surge current".
Note 4 to entry: The PE connection is sometimes called "common connection C".
Note 5 to entry: A multi-mode SPD is sometimes called multi-connection SPD.
Transition surge current rating
Itrans
Crest value of an 8 / 2 0 current impulse for T 2 SPD or an impulse discharge current for T 1 SPD, that will force a short-circuiting SPD into an intended short-circuit
Two - port SPD
SPD having a specific series impedance connected between separate input and output connections
Type of SPD
T1 SPD
SPD that is tested with the impulse discharge current Iimp, with an 8/20 current impulse having
a crest value equal to the crest value of Iimp, and, if relevant, with a 1,2/50 voltage impulse
Note 1 to entry: This was called class I test in IEC 61643-11 : 2011.
T2 SPD
SPD that is tested with the nominal discharge current In, and, if relevant, with a 1,2/50 voltage impulse
Note 1 to entry: This was called class II test in IEC 61643-11 : 2011.
T3 SPD
SPD that is tested with the combination wave with an open circuit voltage Uoc
Note 1 to entry: This was called class III test in IEC 61643 - 11 : 2011.
Type test
Conformity test made on one or more items representative of the production
[SOURCE: IEC 60050-151 : 2001,151-16-16]
Voltage fluctuation
Series of voltage changes or a continuous variation of the RMS or peak value of the voltage
Voltage limiting SPD
Voltage clamping SPD
SPD that contains only voltage limiting mode (s) of protection (voltage clamping mode (s) of protection)
Note 1 to entry: The term voltage limiting SPD is used in the power area.
Note 2 to entry: The term voltage clamping SPD is used in the Telecommunication and Signaling area.
Voltage limiting mode of protection
Voltage clamping mode of protection
Mode of protection that has a high shunt impedance when no surge is present, but will reduce it continuously with increased surge current and voltage
Note 1 to entry: Common examples of components used in voltage limiting mode of protection are Varistor (e .g .MOVs) and avalanche breakdown diodes (ABDs). These are sometimes called "clamping" components.
Note 2 to entry: The term voltage clam ping mode of protection is used in IEC 61643-21.
Voltage protection level
UP
Maximum voltage to be expected at the SPD connections due to an impulse stress with defined voltage steepness and an impulse stress with a discharge current with given amplitude and waveform
Voltage rate of rise ( of a two-port SPD )
Rate of change of voltage with time measured at the output connections of a two port SPD under specified test conditions
Voltage switching SPD
SPD that contains only voltage switching mode (s) of protection
Voltage switching mode of protection
Mode of protection that has a high impedance when no surge is present, but can have a sudden reduction in impedance in response to a voltage surge
Note 1 to entry: Common examples of components used in voltage switching modes of protection are spark gaps, gas discharge tubes (GDTs) and Semiconductor thyristor surge suppressors (TSS).
Abbreviated terms and symbols
Table 1 provides the list of abbreviated terms and symbols used in this document.
English 
