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Total Solution to Earthing & Lightning Protection |
9AKK106354A3360
10/3
10
Protection against lightning and switching transients
IEC/BS EN 62305 takes account of protection measures on
metallic service lines (typically power, signal and telecom
lines) using transient overvoltage or surge protective devices
(SPDs) against both direct lightning strikes as well as the
more common indirect lightning strikes (often described as
the secondary effects of lightning) and switching transients.
Standards such as BS EN 61643 series define the
characteristics of lightning currents and voltages to enable
reliable and repeatable testing of SPDs (as well as
lightning protection components).
Although these waveforms may differ from actual transients,
the standardized forms are based upon years of
observation and measurement (and in some cases simulation).
In general they provide a fair approximation of the real
world transient.
Transient waveforms have a fast rising edge and a longer tail.
They are described through their peak value (or magnitude),
rise time and their duration (or fall time). The duration is
measured as the time taken for the test transient to decay
to half its peak value.
10/350 μs Waveform
I
imp @t = 10 μs
The common current and voltage waveforms
used to test SPDs for mains, signal and telecom lines
Surge Current
(kA)
30
20
10
0
200 400 600 800 1000
Time
t (μs)
Surge Voltage
(kV)
40
30
20
10
0
300 600 900 1200 1500
Time
t (μs)
I
max @t = 8 μs
V
peak @t = 1.2 μs
V
peak @t = 10 μs
Ii
mp @t = 350 μs
2
Vpeak
@t = 700 μs
2
10/700 μs Waveform
Vpeak
@t = 50 μs
2
1.2/50 μs Waveform
8/20 μs Waveform
Imax
@t = 20 μs
2
1 Transient overvoltage damage to a circuit board | 2 Most damage is barely visible
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