Page 478 - 35_DS702_E_2014_Lightning_Protection_Guide

¨ Application (e.g. installation, mains conditions, tempera- Total discharge current I total
ture) Current which flows through the PE, PEN or earth connection
¨ Performance in case of interference (e.g. impulse current of a multi-pole SPD during the total discharge current test. This
discharge capacity, follow current extinguishing capability, test is used to determine the total load if current simultane-
voltage protection level, response time) ously flows through several protective paths of a multipole
¨ Performance during operation (e.g. nominal current, at- SPD. This parameter is decisive for the total discharge capacity
which is reliably handled by the sum of the individual paths
tenuation, insulation resistance) of an SPD.
¨ Performance in case of failure (e.g. backup fuse, disconnec-
tor, fail-safe, remote signalling option) Voltage protection level U p
The voltage protection level of a surge protective device is the
Short-circuit withstand capability maximum instantaneous value of the voltage at the terminals
The short-circuit withstand capability is the value of the pro- of a surge protective device, determined from the standardised
spective power-frequency short-circuit current handled by the individual tests:
surge protective device when the relevant maximum backup ¨ Lightning impulse sparkover voltage 1.2/50 μs (100 %)
fuse is connected upstream. ¨ Sparkover voltage with a rate of rise of 1kV/μs

Short-circuit rating I SCPV of an SPD in a photovoltaic ¨ Measured limit voltage at a nominal discharge current I n
(PV) system The voltage protection level characterises the capability of a
Maximum uninfluenced short-circuit current which the SPD, surge protective device to limit surges to a residual level. The
alone or in conjunction with its disconnection devices, is able voltage protection level defines the installation location with
to withstand. regard to the overvoltage category according to IEC 60664-1
in power supply systems. For surge protective devices to be
Temporary overvoltage (TOV) used in information technology systems, the voltage protec-
Temporary overvoltage may be present at the surge protective tion level must be adapted to the immunity level of the equip-
device for a short period of time due to a fault in the high-volt- ment to be protected (IEC 61000-4-5: 2001).
age system. This must be clearly distinguished from a transient
caused by a lightning strike or a switching operation, which Wave breaker function
last no longer than about 1 ms. The amplitude U T and the Due to the technical design of type 1 SPDs,
duration of this temporary overvoltage are specified in energy coordination of SPDs considerably
EN 61643-11 (200 ms, 5 s or 120 min.) and are individually varies. Experience has shown that even small
tested for the relevant SPDs according to the system config- amplitudes of the 10/350 μs lightning im-
pulse current overload downstream SPDs
uration (TN, TT, etc.). The SPD can either a) reliably fail (TOV or even destroy them if varistor-based type
safety) or b) be TOV-resistant (TOV withstand), meaning that 1 lightning current arresters are used. In case of spark-gap-
it is completely operational during and following temporary based type 1 arresters, in contrast, virtually the total current
overvoltages. flows through the type 1 arrester. Similar to a wave breaker
the energy is reduced to an acceptable level. The advantage
Thermal disconnector is that the time to half value of the 10/350 μs impulse current
Surge protective devices for use in power supply systems is reduced due to the reduction of the impulse time and the
equipped with voltage-controlled resistors (varistors) mostly switching behaviour of type 1 SPDs. This considerably relieves
feature an integrated thermal disconnector that disconnects downstream SPDs.
the surge protective device from the mains in case of overload All devices of the DEHN + SÖHNE Red/Line and Yellow/Line
and indicates this operating state. The disconnector responds product family are energy-coordinated. Moreover, all type 1
to the “current heat“ generated by an overloaded varistor and arresters of the Red/Line family are based on spark gaps and
disconnects the surge protective device from the mains if a thus feature this WAVE BRAKER FUNCTION.
certain temperature is exceeded. The disconnector is designed
to disconnect the overloaded surge protective device in time Yellow/Line SPD class
to prevent a fire. It is not intended to ensure protection against All DEHN arresters for use in information technology systems
indirect contact. The function of these thermal disconnectors are categorised into a Yellow/Line SPD class and are marked
can be tested by means of a simulated overload / ageing of with the corresponding symbol in the datasheet and on the
the arresters. rating plate.

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