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Application note
IEC 61000-4-5 standard overview
Introduction
The objective of this document is to briefly explain the IEC 61000-4-5 standards and to
show the benefits of having a range of protection devices specified according to this
standard. For further details on IEC 61000-4-5 refer to the International Electrotechnical
Commission web site.
Industrial and consumer equipment are subjected to various surges. Here are the main
ones:
 IEC 61000-4-2: ESD surges affect most of consumer equipment. The more stressful ESD
standard is IEC 61000-4-2 (few tens of ns duration) but other standards such as human
body model (HBM), machine model (MM) exist.
 IEC 61000-4-4: This standard is made to check the capability of the equipment to survive
repetitive electrical fast transients and bursts.
 IEC 61000-4-5: Lightning and industrial surges modeled by IEC 61000-4-5. This is the
one we will describe in this document.
 Telecommunication lines are exposed to lightning either directly on the equipment or due
to induced effect because of ground potential change.
In addition to these surges, a telecommunication line may also be disturbed by either power
induction or power contact with main AC lines. Depending on the country, these surges
have been mainly modeled in:
– Telcordia GR-1089 core for America with 2/10 µs and 10/1000 µs surges
– ITU-T K series for the rest of the world with 10/700 µs surges
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IEC 61000-4-5
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IEC 61000-4-5
Power lines are subjected to switching and lightning transients.
1.1
Power system switching transients
Power system switching transients can be separated into transients associated with:
1.2

Major power system switching disturbances, such as capacitor bank switching

Minor local switching activity or load changes in the power distribution system

Resonating circuits associated with switching devices, such as thyristors

Various system faults, such as short circuits and arcing faults to the grounding system
of the installation
Lightning transients
The major mechanisms by which lightning produces surge voltages are the following:
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
Direct lightning strokes to outdoor circuits injecting high currents and producing over
voltages.

Indirect lightning strikes (i.e. strikes between or within clouds or to nearby objects
which produce electromagnetic fields) that induce voltages/currents on the conductors
outside and/or inside a building.

Lightning ground current flows resulting from nearby direct-to-earth discharges
coupling into the common ground paths of the grounding system of the installation. The
rapid change of voltages and flows of current which can occur as a result of the
operation of a lightning protection device can induce electromagnetic disturbances into
adjacent equipment.

Target of the IEC 61000-4-5 is to provide a model to simulate these surges and then to
be able to check if the equipment is able to survive them.
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IEC 61000-4-5 definition
2
IEC 61000-4-5 definition
2.1
Classes and voltage levels
The standard specifies different classes depending on where the equipment is installed. For
each class a corresponding peak voltage is applicable (see Table 1).
Table 1. Classes and voltage levels
Class
Environment
Voltage level
0
Well protected environment, often in a special room
25 V
1
Partially protected environment
500 V
2
Electrical environment where the cables are well
separated, even at short runs
1 kV
3
Electrical environment where power and signal cables
run in parallel
2 kV
4
Electrical environment where the interconnections
include outdoor cables along with the power cable, and
cables are used for both electronics and electric circuits
4 kV
5
Electrical environment for electronic equipment
connected to telecommunication cables and overhead
power lines in a non-densely populated area
Test level 4
Starting at a 500 V surge, it is generally required to protect the equipment with a specific
device.
2.2
Surge generator
The generator used to model the surge is described in Figure 1.
Figure 1. IEC 61000-4-5 surge generator
Rext
1.2 µs/50 µs surge generator source
Rout = 2 W
In open mode, the generator delivers a 1.2 µs/50 µs voltage waveform, and in short circuit,
the current waveform is 8/20 µs. This kind of generator is called a combination wave
generator. The surge is shown on Figure 2 and Figure 3.
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IEC 61000-4-5 definition
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Figure 2. Voltage waveform in open circuit
U
1,0
0,9
B
0,5
50 µs ± 20%
0,3
A
0,1
0,0
O1
T
t
30% max.
1,2 µs ± 30%
Figure 3. Current waveform in short circuit
I
1,0
B
0,9
0,5
20 µs ± 20 %
0,1
0,0
O1
C
T
30% max.
8 µs ± 20%
t
For the same environment, there is a distinction between power lines and data lines, and an
additional serial resistance (Rext) may be required between the DUT (device under test) and
the surge generator.
The selection of the source impedance (Rout + Rext) depends on the kind of equipment to be
protected:

The 2 impedance represents the source impedance of the low-voltage power supply
network. The generator is used alone with its effective output impedance of 2 . The
surge is applied in a differential mode.

The 12  (10 + 2 ) impedance represents the source impedance of the low-voltage
power supply network and ground (common mode). A generator with an additional
resistor of 10  in series is used.

The effective 42  (40  + 2 ) impedance represents the source impedance between
all other lines and ground. A generator with an additional resistance of 40  in series is
used.
As protection devices are sized with the surge current, Table 2 shows the maximum peak
current values depending on voltage level and Rext when surge generator is short circuited.
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IEC 61000-4-5 definition
Table 2. Maximum peak current values depending on voltage level and Rext
Class 0
Class 1
Class 2
Class 3
Class 4
25 V
500 V
1 kV
2 kV
4 kV
Req = 42 
0.6 A
12 A
24 A
48 A
96 A
Req = 12 
2.1 A
42 A
84 A
167 A
334 A
Req = 2 
12.5 A
250 A
500 A
1000 A
2000 A
Test schematics are shown in Figure 4 and Figure 5.
Figure 4. Differential mode test set-up
Combination
wave generator
Rext = 0 Ω
Decoupling network
L
Equipment
under test
AC (DC)
N
power supply network
PE
Figure 5. Common mode test set-up
Combination
wave generator
Rext = 10 Ω
Decoupling network
L
Equipment
under test
AC (DC)
power supply network N
PE
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IEC 61000-4-5 definition
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Figure 4 and Figure 5 show the test schematics when the equipment is connected to power
lines.
For other types of lines, the decoupling network is slightly different on both line-to-line and
line-to-ground tests. Furthermore the test must be done with Rext = 40 (see Figure 6).
Figure 6. IEC 61000-4-5 multi-line test set-up
Combination
wave generator
Rext = 40 Ω
Protection
equipment
Auxillary
equipment
Decoupling network
Equipment
under test
In practice, this surge is applied to equipment and not to a specific protection device.
If the protection device is directly located at the input of the equipment, the protection device
has to withstand the complete surge. In some cases, the protection device is not located at
the input but somewhere in the middle of a board and then the protection device sees a
slightly different surge.
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3
Protection devices
Protection devices
The device used to protect against IEC 61000-4-5 is generally a clamping device located in
parallel with the circuit to be protected. This protection device limits the voltage to a
specified value VCL (Clamping voltage) by absorbing the surge current. Its surge current
capability is specified in its datasheet: IPP (peak pulse current).
Figure 7 gives the I/V characteristics of a clamping device.
Figure 7. I/V characteristics of a unidirectional clamping devices
I
Working area
in case of
positive surges
VCL
VRM
V
IRM
Working area
in case of
negative surges
Off-state area
Ipp
The goal of a protection device is to survive the surge (IPP), and to protect the equipment by
limiting the surge voltage (VCL) below the maximum admissible voltage of the
equipment/circuit.
IPP protection
The IPP of the protection must be defined according to the surge. In order to withstand a
surge, a protection device should have an IPP (8/20 µs surge) higher than the peak current
generated by the standard. It is worthless to choose a protection defined by a 10/1000 µs
surge (this surge is dedicated to telecommunication lines) when the standard requires to
comply with 8/20 µs.
ST has been specifying its protection devices with 10/1000 µs and 8/20 µs surges for years.
Trends toward optimized protection in cost and in size leads us to produce dedicated
protection devices specified according to IEC 61000-4-5.
VCL protection
To protect a circuit from a surge, the protection device should have a VCL (8/20 µs surge)
lower than the maximum voltage the circuit can withstand.
Using a unidirectional device is safer as clamping voltage will be limited to VCL in one
direction and to a forward voltage on the other direction.
Bidirectional device must be used only if the application requires to accept a reverse plug-in
(on DC power lines) or if located on AC lines.
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PEP01-5841 as an example
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PEP01-5841 as an example
This device is dedicated to the protection of power supplies of PoE in PSE side. Typically
PoE power supply is 0 to -48 V. This protection device embeds 4 cells to protect against
IEC 61000-4-5 1 kV under 42 which leads to a 24 A surge current.Topology is given on
Figure 8.
Figure 8. PEP01-5841 functional diagram
Gnd PS1
2-3-6-7
1
PS2
4
PS3
5
PS4
8
All Gnd pins must be connected to Gnd
As the PEP01-5841 has been designed to protect against IEC61000-4-5, specified current
capability (IPP) of each cell is 24 A (Figure 8).
This complies with the IPP protection requirement (capability to withstand the surge).
Table 3. Electrical characteristics - values (Tamb = 25 °C)
8/20 µs
VBR @IR (1)
IRM max @ VRM
VCL @IPP
RD(2)
Type
PEP01-5841
25 °C
85 °C
min.
µA
µA
V
V
0.2
1
58
64.4
typ.
67.8
max.
71.2
max.
mA
V
A

1
100
24
1.2
1. Pulse test: tp < 50 ms
2. To calculate maximum clamping voltage at other surge level, use the following formula:
VCLmax = RD x IPP + VBRmax
The capability to protect is achieved with the VCL max limited to 100 V. The reason for the
100 V max is to avoid failure of the Pmos or the PSE controller generally using a technology
typically around 110 or 120 V rated 100 V in the datasheet.
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Conclusion
Conclusion
In most countries it is mandatory to comply with the IEC 61000-4 series.
Most of the protection devices are rated with ESD capability but only a few of them are rated
with the surge corresponding to IEC 61000-4-5. Using the correct protection designed to
comply with IEC 61000-4-5 is an insurance to get reliable equipment and to avoid costly
quality field returns to keep a good brand image.
ST has developed a range of devices rated according to IEC 61000-4-5. For more
information, go to the ST.COM web site and follow the links to the products for power
discretes and modules for protection devices. IEC 61000-4-5 compliant devices are listed
under EOS 8/20 microsecond surge protection (see Figure 9).
Figure 9. EOS 8/20 µs surge protection
The use of an IEC 61000-4-5 rated protection limits the number of tests to be performed
before certification, saves cost and time and reduces the number of quality returns.
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Revision history
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Revision history
Table 4. Document revision history
10/11
Date
Revision
06-Aug-2013
1
Changes
Initial release.
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