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tages. The space gain, lower wiring effort, integrated fuse Maximum discharge current I max
monitoring and the increased protective effect due to short- The maximum discharge current is the maximum peak value
er connecting cables are clear advantages of this concept of the 8/20 μs impulse current which the device can safely dis-
which is integrated in the DEHNvenCI, DEHNbloc Maxi S, charge.
DEHNguard … CI and V(A) NH product families.
Maximum transmission capacity
LifeCheck The maximum transmission capacity defines the maximum
Repeated discharge processes which exceed the specification high-frequency power which can be transmitted via a coaxial
of the device can overload arresters in information technology surge protective device without interfering with the protection
systems. In order to ensure high system availability, arresters component.
should therefore be subjected to systematic tests. LifeCheck
allows quick and easy testing of arresters. Nominal discharge current I n
The nominal discharge current is the peak value of a 8/20 μs
impulse current for which the surge protective device is rated
Lightning impulse current I imp
The lightning impulse current is a standardised impulse current in a certain test programme and which the surge protective
curve with a 10/350 μs wave form. Its parameters (peak value, device can discharge several times.
charge, specific energy) simulate the load caused by natural
lightning currents. Lightning current and combined arresters Nominal load current (nominal current) I L
must be capable of discharging such lightning impulse cur- The nominal load current is the maximum permissible operat-
rents several times without being destroyed. ing current which may permanently flow through the corre-
sponding terminals.
Mains-side overcurrent protection / arrester backup
fuse Nominal voltage U N
Overcurrent protective device (e.g. fuse or circuit breaker) lo- The nominal voltage stands for the nominal voltage of the sys-
cated outside of the arrester on the infeed side to interrupt tem to be protected. The value of the nominal voltage often
the power-frequency follow current as soon as the breaking serves as type designation for surge protective devices for in-
formation technology systems. It is indicated as an r.m.s. value
capacity of the surge protective device is exceeded. No addi- for a.c. systems.
tional backup fuse is required since the backup fuse is already
integrated in the SPD.
N-PE arrester
Surge protective devices exclusively designed for installation
Maximum continuous operating voltage U C between the N and PE conductor.
The maximum continuous operating voltage (maximum
permissible operating voltage) is the r.m.s. value of the maxi-
mum voltage which may be connected to the corresponding Operating temperature range T U
The operating temperature range indicates the range in
terminals of the surge protective device during operation. This which the devices can be used. For non-self-heating devices,
is the maximum voltage on the arrester in the defined non- it is equal to the ambient temperature range. The temperature
conducting state, which reverts the arrester back to this state rise for self-heating devices must not exceed the maximum
after it has tripped and discharged. The value of U C depends value indicated.
on the nominal voltage of the system to be protected and the
installer’s specifications (IEC 60364-5-534). Protective circuit
Protective circuits are multi-stage, cascaded protective devices.
Maximum continuous operating voltage U CPV for a The individual protection stages may consist of spark gaps,
photovoltaic (PV) system varistors, semiconductor elements and gas discharge tubes
Value of the maximum d.c. voltage that may be permanently (see Energy coordination).
applied to the terminals of the SPD. To ensure that U CPV is
higher than the maximum open-circuit voltage of the PV sys- Protective conductor current I PE
tem in case of all external influences (e.g. ambient tempera- The protective conductor current is the current which flows
ture, solar radiation intensity), U CPV must be higher than this through the PE connection when the surge protective device
maximum open-circuit voltage by a factor of 1.2 (according to is connected to the maximum continuous operating voltage
CLC/TS 50539-12). This factor of 1.2 ensures that the SPDs are U C , according to the installation instructions and without load-
not incorrectly dimensioned. side consumers.

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