Schneider Electric - Electrical installation guide 2009
J
© Schneider Electric - all rights reserved
Chapter J
Protection against voltage surges
in LV
Contents
General
J2
1.1 What is a voltage surge?
J2
1.2 The four voltage surge types
J2
1.3 Main characteristics of voltage surges
J4
1.4 Different propagation modes
J5
Overvoltage protection devices
J6
2.1 Primary protection devices (protection of installations
J6
against lightning)
2.2 Secondary protection devices (protection of internal
J8
installations against lightning)
Protection against voltage surges in LV
J
3.1 Surge protective device description
J11
3.2 Surge protective device standards
J11
3.3 Surge protective device data according to IEC 61643-1 standard J11
3.4 Lightning protection standards
J13
3.5 Surge arrester installation standards
J13
Choosing a protection device
J4
4.1 Protection devices according to the earthing system
J14
4.2 Internal architecture of surge arresters
J15
4.3 Coordination of surge arresters
J16
4.4 Selection guide
J17
4.5 Choice of disconnector
J22
4.6 End-of-life indication of the surge arrester
J23
4.7 Application example: supermarket
J24
2
3
4
Schneider Electric - Electrical installation guide 2009
J - Protection against voltage surges in LV
J2
© Schneider Electric - all rights reserved
General
. What is a voltage surge?
A voltage surge is a voltage impulse or wave which is superposed on the rated
network voltage (see Fig. J).
Voltage
Lightning type impulse
(duration = 100 µs)
"Operating impulse"
type dumped ring wave
(F = 100 kHz to 1 MHz)
Irms
Fig. J1 : Voltage surge examples
This type of voltage surge is characterised by ( see Fig. J2):
b The rise time (tf) measured in μs
b The gradient S measured in kV/μs
A voltage surge disturbs equipment and causes electromagnetic radiation.
Furthermore, the duration of the voltage surge (T) causes a surge of energy in the
electrical circuits which is likely to destroy the