2.3.g.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
0. The neutral
conductor (N) connected the protective earth via
a collective spark gap. Usage described IEC
60364-5-53.: ÜSM-A).
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Chapter The internal lightning protection system
.g. V20 3+NPE).5 behind the separation the
PEN conductor.
System fuse F1
Cable length between arrestors
Circuit distribution board, e.TBS
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3. circuit protects the L
and lines with varistor circuits and makes the con-
nection the line through collective spark gap
(e.
Surge arrestor type 3
Type surge protection devices (SPDs) are used in
the device power circuits.
Lightning current arrestor, type 1
Type lightning current arrestors and combination ar-
restors are used the 3-pin circuit (e.
Surge arrestor type 2
Type surge protection devices (SPDs) are used in
the 3+1 circuit (e.g.: MCF75-
3+FS). With the 3+1 circuit,
the external conductors (L1, L2, L3) are connected to
the neutral conductor (N) via arrestors.g
