Chapter A General rules of electrical installation design

J22
© Schneider Electric - all rights reserved
J - Protection against voltage surges in LV
1
Equipment to be
protected
2
Determine the
architecture of the
building
3
Risk level of
the impact of a
lightning strike
Choice of type of
surge arrester
Heavy equipment
Type 2
65 kA
Single
switchboard,
main
switchboard
Type 1
25 kA
+
Type 2
40 kA
Type 1
25 kA
or
35 kA
+
Type 2
40 kA
Medical, production,
or heavy computer
processing infrastructure,
etc.
Type 1
25 kA
or
35 kA
+
Type 2
40 kA
Distribution
board
Type 2
20 KA
Schneider Electric - Electrical installation guide 2008
Dedicated
protection,
more than
30 m from a
switchboard
Note:
Type 1: very high discharge capacity surge arrester used with a lightning conductor with an impact level of and .
Type 2: surge arrester used in cascade behind a type 1 surge arrester or alone in zone and .
Fig. J35 : Heavy equipment
Lightning can also propagate through
telecommunications and computer networks.
It can damage all the equipment connected
to these networks: telephones, modems,
computers, servers, etc.
4 Choosing a protection device
Type 2
8 kA
Protection of telecommunications and computer equipment
Choice of surge arresters PRC PRI
Analogue telephone networks < 200 V b
Digital networks, analogue lines < 48 V
Digital networks, analogue lines < 6 V
VLV load supply < 48 V
b
b