Page 12 - Surge-Protection-E_0.pdf

Terms and Definitions

DIN CLC/TS 61643-12:2010 describes how to verify energy coordination. Maximum discharge current Imax
Spark-gap-based type 1 SPDs offer considerable advantages due to their The maximum discharge current is the maximum peak value of the
voltage-switching characteristic (see WAVE BREAKER FUNCTION). 8/20 μs impulse current which the device can safely discharge.
Follow current extinguishing capability Ifi: Maximum transmission capacity
Prospective short-circuit current that an SPD is able to interrupt inde- The maximum transmission capacity defines the maximum high-frequen-
pendently without disconnection (source: IEC 61643-11). cy power which can be transmitted via a coaxial surge protective device
without interfering with the protection component.
Frequency range
The frequency range represents the transmission range or cut-off frequen- Nominal discharge current In
cy of an arrester depending on the described attenuation characteristics. The nominal discharge current is the peak value of a 8/20 μs impulse
current for which the surge protective device is rated in a certain test
Insertion loss programme and which the surge protective device can discharge several
With a given frequency, the insertion loss of a surge protective device is times.
defined by the relation of the voltage value at the place of installation
before and after installing the surge protective device. Unless otherwise Nominal load current (nominal current) IL
indicated, the value refers to a 50 Ω system. The nominal load current is the maximum permissible operating current
which may permanently flow through the corresponding terminals.
Integrated backup fuse
According to the product standard for SPDs, overcurrent protective devic- Nominal voltage UN
es / backup fuses must be used. This, however, requires additional space in The nominal voltage stands for the nominal voltage of the system to be
the distribution board, additional cable lengths, which should be as short protected. The value of the nominal voltage often serves as type designa-
as possible according to IEC 60364-5-53, additional installation time (and tion for surge protective devices for information technology systems. It is
costs) and dimensioning of the fuse. A fuse integrated in the arrester indicated as an r.m.s. value for a.c. systems.
ideally suited for the impulse currents involved eliminates all these disad-
vantages. The space gain, lower wiring effort, integrated fuse monitoring N-PE arrester
and the increased protective effect due to shorter connecting cables are Surge protective devices exclusively designed for installation between
clear advantages of this concept which is integrated in the DEHNvenCI, the N and PE conductor.
DEHNbloc Maxi S, DEHNguard … CI and V(A) NH product families.
Operating temperature range TU
LifeCheck The operating temperature range indicates the range in which the devic-
Repeated discharge processes which exceed the specification of the de- es can be used. For non-self-heating devices, it is equal to the ambient
vice can overload arresters in information technology systems. In order to temperature range. The temperature rise for self-heating devices must
ensure high system availability, arresters should therefore be subjected not exceed the maximum value indicated.
to systematic tests. LifeCheck allows quick and easy testing of arresters
(see page 240).
Permanent short-circuit current Ik
The r.m.s. value of the short-circuit current in low-voltage or high-volt-
Lightning impulse current I imp age three-phase systems which remains after all compensation processes
The lightning impulse current is a standardised impulse current curve [based on IEC 60909-0].
with a 10/350 μs wave form. Its parameters (peak value, charge, specific
energy) simulate the load caused by natural lightning currents. Lightning Protective circuit
current and combined arresters must be capable of discharging such Protective circuits are multi-stage, cascaded protective devices. The indi-
lightning impulse currents several times without being destroyed.
vidual protection stages may consist of spark gaps, varistors, semicon-
ductor elements and gas discharge tubes (see energy coordination).
Mains-side overcurrent protection / arrester backup fuse
Overcurrent protective device (e.g. fuse or circuit breaker) located outside
of the arrester on the infeed side to interrupt the power-frequency follow Protective conductor current IPE
current as soon as the breaking capacity of the surge protective device is The protective conductor current is the current which flows through the
exceeded. No additional backup fuse is required since the backup fuse is PE connection when the surge protective device is connected to the max-
already integrated in the SPD (see relevant section). imum continuous operating voltage UC, according to the installation in-
structions and without load-side consumers.
Maximum continuous operating voltage UC
The maximum continuous operating voltage (maximum permissible op- Remote signalling contact
erating voltage) is the r.m.s. value of the maximum voltage which may be A remote signalling contact allows easy remote monitoring and indica-
connected to the corresponding terminals of the surge protective device tion of the operating state of the device. It features a three-pole terminal
during operation. This is the maximum voltage on the arrester in the de- in the form of a floating changeover contact. This contact can be used as
fined non-conducting state, which reverts the arrester back to this state a break and / or make contact and can thus be easily integrated in the
after it has tripped and discharged. The value of UC depends on the nomi- building control system, controller of the switchgear cabinet, etc.
nal voltage of the system to be protected and the installer’s specifications
(IEC 60364-5-534). Response time tA
Response times mainly characterise the response performance of individ-
Maximum continuous operating voltage UCPV for a photovoltaic ual protection elements used in arresters. Depending on the rate of rise
(PV) system du/dt of the impulse voltage or di/dt of the impulse current, the response
Value of the maximum d.c. voltage that may be permanently applied to times may vary within certain limits.
the terminals of the SPD. To ensure that UCPV is higher than the maximum
open-circuit voltage of the PV system in case of all external influences (e.g. Return loss
ambient temperature, solar radiation intensity), UCPV must be higher than this In high-frequency applications, the return loss refers to how many parts
maximum open-circuit voltage by a factor of 1.2 (according to CLC/TS 50539- of the “leading“ wave are reflected at the protective device (surge point).
12). This factor of 1.2 ensures that the SPDs are not incorrectly dimensioned. This is a direct measure of how well a protective device is attuned to the
characteristic impedance of the system.

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