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Figure 8.1.8.1 DEHNguard M TNC CI 275 FM – Figure 8.1.8.2 Inner structure of the DEHNguard M/S … CI (front and rear view)
Type 2 arrester with integrated
backup fuse

8.1.8 Surge arrester with integrated backup
fuse
When choosing backup fuses for surge protective devices, two
dimensioning criteria must be observed:
¨ Maximum value of the backup fuse specified by the manu-
facturer
¨ Impulse current carrying capability of the backup fuse
This can be effectively and easily implemented by using surge
protective devices with integrated backup fuse.

DEHN offers different type 1 and type 2 arresters where the
Figure 8.1.8.3 Considerably reduced space requirements – Com- backup fuse is already integrated in the surge protective de-
parison of the installation space of a conventional vice such as DEHNvenCI and DEHNguard M/S … CI (Figures
type 1 arrester with that of DEHNvenCI
8.1.8.1 to 5.1.8.3). These DIN rail mounted arresters offer
various benefits for the user:
¨ No need for an additional backup fuse since the backup
The availability of installations required by the IEC 61439-1 fuse is integrated in the arrester
(EN 60439-1) standard, even if surge protective devices oper- ¨ Considerably reduced space requirements (Figure 8.1.8.3)
ate, can be ensured by means of the “follow current suppres- ¨ Significantly less installation effort
sion” described before. Particularly for surge protective devices ¨ Monitoring of the integrated arrester backup fuse by means
with a low sparkover voltage which are supposed to ensure of an operating state / fault indication and remote signalling
lightning equipotential bonding and surge protection in the contact
installation, the performance of the follow current limitation
is more important than ever for the availability of the electri- ¨ Easy implementation of short connecting cable lengths
according to IEC 60364-5-53 (HD 60364-5-534)
cal installation. In Figure 8.1.7.11 it can be seen that even
in case of a prospective short-circuit current of 50 kA rms , the ¨ Available for all systems configurations (TNC, TNS, TT, sin-
let-through integral of the RADAX Flow spark gap is below the gle-pole systems)
minimum threshold value of a NH-gG fuse link with a rated Arresters with integrated backup fuse offer many advantages
current of 20 A. such as minimum space requirements and ease of installation.

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