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Standard EN 61643-11:2012 IEC 61643-11:2011
Type / designation
Lightning current arrester / combined arrester Type 1 SPD Class I SPD
Surge arrester for distribution boards, sub-distribution boards, fixed installations Type 2 SPD Class II SPD
Surge arrester for socket outlets / terminal devices Type 3 SPD Class III SPD
Table 8.1.1 Classification of surge protective devices according to IEC and EN

voltage which may be applied to the correspondingly labelled 230/400 V three-phase system only applies to equipment of
terminals of the surge protective device during operation. It is the fixed electrical installation. Equipment in the final cir-
the maximum voltage applied to the arrester in the defined cuits supplied by this installation requires a voltage protec-
non-conductive state which ensures that this state is restored tion level which is much lower than 2.5 kV.
after the operation and discharge process. IEC 60364-5-53 (HD 60364-5-534) also requires a minimum
The value U c depends on the nominal voltage of the sys- voltage protection level of 1.5 kV for a 230/400 V low-
tem to be protected and the requirements of the installation voltage consumers‘ installation – for consumers according
standard (IEC 60364-5-53 (HD 60364-5-534)). Taking into to overvoltage category I. This minimum voltage protection
account a 10 % voltage tolerance for TN and TT systems, the level can be achieved by means of a coordinated system
maximum continuous operating voltage U c for 230/400 V of type 1 and type 2 SPDs or by using a type 1 combined
systems is 253 V. arrester.

Lightning impulse current I imp Short-circuit withstand capability I SCCR
This is a standardised impulse current curve with a 10/350 μs This is the value of the prospective power-frequency short-
wave form. Its parameters (peak value, charge, specific ener- circuit current which the surge protective device can safely
gy) simulate the stress caused by natural lightning currents. handle in case it is provided with an upstream backup fuse
Lightning impulse currents (10/350 μs) apply to type 1 SPDs. (backup protection).
They must be able to discharge such lightning impulse cur-
rents several times without destructing the equipment. Follow current extinguishing capability I fi (at U c )
The follow current extinguishing capability is the unaffected
Nominal discharge current I n (prospective) rms value of the mains follow current which
The nominal discharge current I n is the peak value of the can be automatically extinguished by the surge protective
current flowing through the surge protective device (SPD). device when U c is applied.
It has an 8/20 μs impulse current wave form and is rated for According to IEC 62305-3 (EN 62305-3) and IEC 60364-5-53
classifying the test of type 2 SPDs. (HD 60364-5-534), the follow current extinguishing capabil-
ity of the SPDs should be equal to the maximum prospective
Voltage protection level U p short-circuit current at the place of installation of the SPDs.
The voltage protection level of an SPD denotes the maxi- In case of distribution boards in industrial plants with too
mum instantaneous value of the voltage on the terminals of high short-circuit currents, an adequate backup fuse which
an SPD while at the same time characterising their capacity interrupts the mains follow current by means of the protec-
to limit surges to a residual level. tive device must be chosen for the protective device.
According to IEC 60364-5-53 (HD 60364-5-534) and
Depending on the type of SPD, the voltage protection level IEC 61643-11 (EN 61643-11), the SPDs which are connected
is determined by means of the following individual tests:
between the neutral and PE conductor and where a power-
¨ Impulse sparkover voltage 1.2/50 μs (100 %) frequency follow current may occur after they have oper-
¨ Residual voltage U res at nominal discharge current (in ac- ated (e.g. spark gaps) have a follow current extinguishing
cordance with IEC 61643-11 (EN 61643-11)) capability I fi ≥ 100 A rms .

The surge protective device appropriate to the place of in- Follow current limitation (in case of spark-gap-
stallation is chosen in accordance with the overvoltage cat- based type 1 SPDs)
egories described in IEC 60664-1 (EN 60664-1). It must be Follow current limitation is the capability of a spark-gap-
observed that the required minimum value of 2.5 kV for a based SPD to limit any mains follow currents which arise to

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