Page 11 - Surge-Protection-E_0.pdf

Terms and Definitions

Surge Protective Devices (SPDs) actiVsense
Surge protective devices are devices consisting mainly of voltage-con- The actiVsense technology is integrated in universal combined arrest-
trolled resistors (varistors, suppressor diodes) and / or spark gaps (dis- ers for protecting information technology installations and devices. The
charge paths). Surge protective devices are used to protect other electrical arrester automatically detects the signal voltage applied and optimally
equipment and installations against impermissibly high surges and / or to adapts the voltage protection level to it. This makes the arrester univer-
establish equipotential bonding. sally applicable at different interfaces and provides the best possible
protection for the devices and system circuits connected to it in case of
Surge protective devices are classified: failure.
a) according to their use into:
• Surge protective devices for power supply systems and Breaking capacity, follow current extinguishing capability Ifi
equipment (Red / Line product family) The breaking capacity is the uninfluenced (prospective) r.m.s. value of
for nominal voltage ranges up to 1000 V the mains follow current which can automatically be extinguished by
– according to EN 61643-11:2012 in type 1 / 2 / 3 SPDs the surge protective device when connecting UC. It can be verified in an
operating duty test according to IEC / EN 61643-11.
– according to IEC 61643-11:2011 in class I / II / III SPDs
• Surge protective devices for IT systems and equipment Categories according to IEC 61643-21:2012
(Yellow / Line product family) A number of impulse voltages and impulse currents are described in IEC
for protecting modern electronic systems in telecommunications 61643-21:2012 for testing the current carrying capability and voltage
and signal-processing networks with nominal voltages up to limitation of impulse interference. Table 3 of this standard puts these into
1000 V a.c. [root-mean-square value (rms)] and 1500 V d.c. against categories and provides preferred values. In Table 2 of the IEC 61643-22
the indirect and direct effects of lightning strikes and other transi- standard the sources of transients are assigned to the different impulse
ents. categories according to the decoupling mechanism. Category C2 includes
– according to IEC 61643-21:2012, EN 61643-21:2013 and inductive coupling (surges), category D1 galvanic coupling (lightning cur-
DIN VDE 0845-3-1. rents). The relevant category is specified in the technical data.
DEHN surge protective devices surpass the values in the specified catego-
• Isolating spark gaps for earth-termination systems or equi-
potential bonding (Red / Line product family) ries. Therefore, the exact value for the impulse current carrying capability
is indicated by the nominal discharge current (8/20 μs) and the lightning
• Surge protective devices for use in photovoltaic installations impulse current (10/350 μs).
(Red / Line product family)
for nominal voltage ranges up to 1500 V Combination wave UOC
– according to EN 50539-11:2013 as type 1 / 2 SPDs A combination wave is generated by a hybrid generator (1.2/50 μs,
8/20 μs) with a fictitious impedance of 2 Ω. The open-circuit voltage of
b) according to their impulse current discharge capacity and protec- this generator is referred to as UOC. UOC is a preferred indicator for type 3
tive effect into: arresters since only these arresters may be tested with a combination
• Lightning current arresters / Coordinated lightning current wave (according to IEC / EN 61643-11).
arresters Cut-off frequency fG
for interference resulting from direct or nearby lightning strikes for The cut-off frequency defines the frequency-dependent behaviour of an
protecting installations and equipment [for use at the boundaries arrester. The cut-off frequency is equivalent to the frequency which in-
between lightning protection zones (LPZ) 0A and 1]. duces an insertion loss (aE) of 3 dB under certain test conditions (see EN
• Surge arresters 61643-21:2013). Unless otherwise indicated, this value refers to a 50 Ω
for remote lightning strikes, switching overvoltages as well as elec- system.
trostatic discharges for protecting installations, equipment and ter-
minal devices (for use at the boundaries downstream of LPZ 0B). Degree of protection
The IP degree of protection corresponds to the protection categories de-
• Combined lightning current and surge arresters scribed in IEC / EN 60529.
for interference resulting from direct or nearby lightning strikes for
protecting installations, equipment and terminal devices (for use at Direct Current Disconnection
the boundaries between LPZ 0A and 1 as well as 0A and 2). When using surge arresters in d.c. applications, disconnection must be
reliably ensured even if there are no zero crossings. The specifically de-
Technical data veloped DC Disconnection (DCD) technology acts as a wedge similar to
The technical data of surge protective devices comprise information de- a blocking valve and interrupts the direct current. Consequently, the de-
fining their conditions of use according to: vices of the DEHNguard SE DC series are capable of safely interrupting
• use (e.g. installation, power supply conditions, temperature) direct currents, thus preventing fire damage caused by d.c. switching arcs.
• performance in case of interference (e.g. impulse current discharge
capacity, follow current extinguishing capability, voltage protection Disconnecting time ta
level, response time) The disconnecting time is the time which passes until the power supply is
• performance during operation (e.g. nominal current, attenuation, in- automatically disconnected in case of a failure of the circuit or equipment
to be protected. The disconnecting time is an application-specific value
sulation resistance) resulting from the intensity of the fault current and the characteristics of
• performance in case of failure (e.g. backup fuse, disconnection device, the protective device.
fail-safe, remote signalling option).
Energy coordination of SPDs
Energy coordination is the selective and coordinated interaction of cas-
caded protection elements (= SPDs) of an overall lightning and surge
protection concept. This means that the total load of the lightning im-
pulse current is split between the SPDs according to their energy carrying
capability. If energy coordination does not work, downstream SPDs are
not sufficiently relieved by the upstream SPDs as they intervene too late,
insufficiently or not at all. Consequently, downstream SPDs as well as the
terminal equipment to be protected may be destroyed.
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