5 behind the separation the
PEN conductor.
Lightning current arrestor, type 1
Type lightning current arrestors and combination ar-
restors are used the 3-pin circuit (e.TBS
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3.g. With the 3+1 circuit,
the external conductors (L1, L2, L3) are connected to
the neutral conductor (N) via arrestors.
Surge arrestor type 2
Type surge protection devices (SPDs) are used in
the 3+1 circuit (e. Usage described IEC
60364-5-53.
TBS
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187
Chapter The internal lightning protection system
.: ÜSM-A). circuit protects the L
and lines with varistor circuits and makes the con-
nection the line through collective spark gap
(e.
System fuse F1
Cable length between arrestors
Circuit distribution board, e. The neutral
conductor (N) connected the protective earth via
a collective spark gap.g. V20 3+NPE).g.: MCF75-
3+FS).g.2.
Surge arrestor type 3
Type surge protection devices (SPDs) are used in
the device power circuits.3.3 Protection devices various power supply
systems
4-wire networks, TN-C network system
In the TN-C network system, the electrical unit sup-
plied through the three external lines (L1, L2, L3) and
the combined PEN line. sub-distributor
Final circuit
Main earthing busbar (MEB)
Local equipotential busbar (PAS), optional
Type (class surge protection devices (SPDs)
Type (class II) surge protection devices (SPDs)
Type (class III) surge protection devices (SPDs)
4-wire networks, TN-C network system and scope standards
An SPD used between the
neutral and protective conductors
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