Brochure/Catalogue
RCD circuit breaker If a fault current exceeds a certain threshold, then the RCD switches off within
0.2 seconds.
Recommended fuse The nominal value of the fuse recommended by the manufacturer and specied
by the technical data sheet.
Remote signalling contact (FM)
A volt-free contact for the power products for signalling triggered/defective
arresters. For the measurement/control SPD/VSPC products, this connection
with the VSPC CONTROL UNIT is required to produce a signal. The Weidmüller
diagrams show this with the letter R which stands for “remote signal contact”.
Requirement class B / T 1 / Type I For the purpose of lightning protection equipotential bonding according to DIN
VDE 0185-1, also see Type I.
Requirement class C / T 2 / Type II For the purpose of surge protection in the xed facility, preferably for use in
impulse withstand voltage category III, also see Type II.
Requirement class D / T 3 / Type III For the purpose of surge protection in the xed facility, preferably for use in
impulse withstand voltage category II, also see Type III.
RSU Surge protection on clip-on base with gas discharge tube, varistor and suppressor
diode for 6-A and 10-A current loops
Short-circuit withstand rating Maximum prospective short-circuit current that the surge protection device can
withstand.
Sparkover time Response times can vary between a few µs to ps, depending on the type and
construction of the protective components.
SPD Surge protective device (lightning and surge protection device).
Suppressor diode Voltage-dependent, fast-switching semiconductor diode.
Surge protection (OVP/SPD) Switching circuitry/wiring of a circuit used to limit the output voltage; and the
sum of all lightning protection measures used to protect the technical equipment
against lightning currents and surge voltages.
Surge protection device (SPD) Device with at least one non-linear component, used to limit the surge voltages
and to discharge the surge currents.
Surge protection equipment (SPE) Surge protection devices and surge protection equipment for a facility, including
the cables associated with the surge protection .
Surge voltage Unwanted continuous or short-term differences in potential between the
conductors or between conductor and earth which create interference or
destruction.
Surge voltage protection classes Classication of electrical equipment in accordance with their dielectric strength
relative to the nominal voltage, EN 50178.
Symmetric interference voltage Voltage between the outward and return conductors (differential-mode voltage).
TAZ See suppressor diode.
TN power grid Power grid as a 4- or 5-wire system; 3 phases and the PEN come into the
building. PE from the building and PE from power system are connected to each
other.
Glossary
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The basics of lightning and surge protection
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