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SCI SCI

Figure 9.18.9 Modular DEHNguard M YPV SCI … (FM) type 2 surge
arrester with fault-resistant Y circuit and three-step
d.c. switching device

Figure 9.18.11 DEHNguard type 2 SPD integrated in the inverter
for the a.c. and d.c. side

The numerous technologies combined in these arresters pre-
vent damage to the surge protective device due to insula-
tion faults in the PV circuit, the risk of fire of an overloaded
arrester and puts the arrester in a safe electrical state with-
out disrupting the operation of the PV system. Thanks to
the protective circuit, the voltage-limiting characteristic of
varistors can be fully used even in the d.c. circuits of PV
systems. In addition, the permanently active surge protec-
tive device minimises numerous small voltage peaks. Thus,
Figure 9.18.10 Ready-to-install type 2 DEHNcube YPV SCI 1000 1M
surge arrester the SCI technology increases the service life of the entire
d.c.-side PV system.
ful technology that allows to discharge partial lightning cur- Selection of SPDs according to the voltage
rents in case of d.c. PV systems. Thanks to its spark gap tech- protection level U p
nology and a d.c. extinction circuit which allow to efficiently The operating voltage on the d.c. side of PV systems dif-
protect downstream electronic systems, this arrester series fers from system to system. At present, values up to 1500 V
has an extremely high lightning current discharge capacity d.c. are possible. Consequently, the dielectric strength of ter-
I total of 50 kA (10/350 µs) which is unique on the market. minal equipment also differs. To ensure that the PV system is
reliably protected, the voltage protection level U p of the SPD
Type 2 d.c. arrester for use in PV systems: DEHNguard must be lower than the dielectric strength of the PV system
M YPV SCI … (FM) and DEHNcube YPV SCI ... it is supposed to protect. The CENELEC CLC/TS 50539-12
Reliable operation of SPDs in d.c. PV circuits is also indis- standard requires that U p is at least 20 % lower than the
pensable when using type 2 surge protective devices. To this dielectric strength of the PV system. Type 1 or type 2 SPDs
end, the DEHNguard M YPV SCI … (FM) and DEHNcube YPV must be energy-coordinated with the input of terminal
SCI ... surge arresters also feature a fault-resistant Y protec- equipment. If SPDs are already integrated in terminal equip-
tive circuit and the SCI technology (Figure 9.18.9 and ment, coordination between the type 2 SPD and the input
9.18.10) and are also connected to PV generators up to circuit of terminal equipment is ensured by the manufac-
1000 A without additional backup fuse. turer (Figure 9.18.11).

www.dehn-international.com LIGHTNING PROTECTION GUIDE 367