Application Note: Surge Tsting of unshielded

Application Note: Surge Tsting of unshielded
Application Note: Surge Testing of unshielded
Control and Data Lines
Surge testing on unshielded data and control lines is a very complex topic. This
application note will help you to get an overview, to select the suitable test equipment
and to perform a test properly.
Overview Coupling and Decoupling Networks for data- and control lines
Standard
Operating
Mode of the
EUT Lines
IEC 61000-4-5
asymmetrical
IEC 61000-4-12
symmetrical
asymmetrical / symmetrical
(*)
Impulse
Shapes
1,2/50µs8/20µs
1,2/50µs8/20µs
10/700µs5/320µs
Ring wave
100kHz with
Z=12Ω, 30Ω
and 200Ω
Damped
Oscillatory
Wave 100kHz
& 1MHz;
Ring wave
100kHz with
Z=200Ω
Coupling
Network
PCD 126
PCD 121
PCD 120
PCD 126
PCD 150
DEC 7
included in
PCD 150
Decoupling
Network
(*)
PCD 122
DEC 7
DEC 5
DEC 5
Communication ports with fast operating signals are tested without any CDN.
The test voltage is applied directly between the cabinets of the equipment
interconnected.
Standard
Operating
Mode of the
EUT Lines
Impulse
Shapes
Coupling
Network
Decoupling
Network
ITU K.44
TIA-968-A
(FCC Part 68)
Telcordia (Bellcore)
symmetrical
symmetrical
symmetrical
10/700µs
10/160µs
10/1000µs
10/360µs
10/560µs
10/360µs
12 pair
9/720µs
2/10µs
PCD 800
PCD 900
PIM 930
DEC 5
DEC 5
(DEC 5)
(DEC 5)
DEC 6
DEC 6
(**)
(**)
PCD 120
GR-1089-CORE
(PCD 122)
(**) Test impulses are applied with the system in an idle condition, that is not
transmitting or receiving data. However DC may be present on the EUT line.
The DEC 5 is used to decouple the auxiliary equipment in this idle state.
Coupling onto data and control lines
Several common standards describe the surge testing of control and data lines. Such
standards are e.g. IEC / EN 61000-4-5, IEC / EN 61000-4-12 and ITU-T K.44. These
basic standards only contain little information about selecting a suitable coupling
element. The following information will help you to decide which coupling element should
be used.
The given information can be used for symmetrical or asymmetrical operated lines.
There are some reasons to use coupling elements:
to protect the generator from the signals (AC and / or DC) present on the lines to be
tested
to isolate the lines to be tested from the load caused by the generator
to form a defined impulse shape and / or amplitude
As data rates in communication systems increase, the coupling element for
superimposing the surge onto control and data lines must be selected carefully. For this
reason it is necessary to know the characteristics of the most common coupling
elements.
Advantages
Disadvantages
Capacitors
Transzorbdiodes
(Avalanche
Breakdown
Diodes)
Gas Arrestors
no nonlinear
distortion
small capacitive load
to the lines to be
tested
nearly no capacitive
load to the lines to
be tested
heavy capacitive
load to the lines to
be tested
nonlinear distortion
Nonlinear distortion.
Causes short circuit
when ignited.
Influence on
If the proper value is
The diodes are
Impulse Amplitude selected (often given
limiting elements.
in the standards) no
The voltage drop
amplitude drop
must be taken into
account to select the
occurs.
impulse voltage at
the generator.
Since the voltage
across the ignited
arrestor is very low,
nearly no voltage
drop occur.
Application Fields
signal lines with high
data rates
control and signal
lines with low
frequencies (data
rates)
control and signal
lines with medium
frequencies (data
rates)
Which coupling element is used for a specific application should be defined in the relevant
product standard. If no information is given and the preferred type of coupling element
given in the basic standard does not work, the user has to decide which one he will use.
The table above gives guidance but no absolute rules to select a coupling element. When
the surge test system is connected to the EUT and it does not work any more, try it with
another coupling element.
The used coupling element has to be documented in the test protocol because different
types of coupling elements may produce different test results
Decoupling Auxiliary equipment from the EUT being tested
As data rates in communication systems increase, surge testing with a decoupling unit
between the EUT and the auxiliary equipment becomes more and more difficult or even
impossible. The following information helps you to decide which decoupling unit should
be used and what has to be done if no suitable decoupling unit exist.
With decoupling between EUT and Auxiliary Equipment according to e.g.
IEC 61000-4-5 or ITU-T K.44
asymmetrically operated lines
symmetrically operated lines
control lines up
to few 100Hz
data lines above
some 100Baud
low data
transfer rate up
to 10kBaud
medium data
transfer rate up
to 100kBaud
high data
transfer rate up
to 10MBaud
e.g. control lines
for relays or
20mA current
interface
e.g. RS-232 or
20mA current
interface
e.g. analog
telecom lines
e.g. RS-422 or
RS-485
e.g. ISDN or
Ethernet lines
DEC 7
DEC 6
DEC 5
DEC 5
DEC 6
PCD 150
PCD 150 (*)
(*) The PCD 150 can be used only up to some 100Baud
If the system is not working correctly with a decoupling unit between the EUT and
auxiliary equipment, surge tests must be made without any decoupling as described
below.
Surge Tests without Decoupling between the EUT and the Auxiliary Equipment
The standards Telcordia (Bellcore) GR-1089-CORE and IEC 61000-4-5 Edition 2 describe
test procedures when no suitable decoupling unit is available. Such tests may be
performed as described below.
EUT survival test
Surges have high energy and can destroy insufficient protected electric equipment. It is
important to ensure that the protection circuits of the EUT are working properly. This is
verified with this test. No information about the system behavior due to surges can be
gained from this test.
Test procedure:
- Functional test of the whole system (EUT connected with auxiliary equipment)
- Testing the EUT alone (no connection to the auxiliary equipment) with surges
- Functional test of the whole system (EUT connected with auxiliary equipment again)
Test result: The EUT has survived / not survived the test
System test
The data will always be interrupted or corrupted when a surge is applied. Data bits are
typically a few volts or lower, and a surge is up to several thousand volts. Therefore it is
important to know how the system response to the surge is, e.g. are there any software
latch-ups?
Test procedure:
- Whole system in action, EUT is connected to the auxiliary equipment without a
decoupling unit
- Testing the whole system with surges through a coupling network
Test result: The system has passed / not passed the test
Ordering Information for Haefely Equipment
Type
Article No.
Short description
PCD 120
249941
Automatic coupling network for symmetrical lines.
Optimized for ITU-T K.44. Can also be used for
IEC 61000-4-5 (impulse shape 10/700us).
PCD 121
249801
Manually coupling network for symmetrical lines
according IEC 61000-4-5
(combination wave 1.2/50us - 8/20us).
PCD 122
249802
Manually coupling network for symmetrical lines.
Optimized for IEC 61000-4-5 (impulse shape 10/700us).
Can also be used for ITU K.44
PCD 126
249803
Manually coupling network for asymmetrical lines
according to IEC 61000-4-5
(combination wave 1.2/50us - 8/20us) and
IEC 61000-4-12 (ring wave 100kHz).
PCD 150
249804
Manually coupling and decoupling network according
IEC 61000-4-12 (damped oscillatory waves 100kHz and
1MHz).
PCD 800
249908
Automatic coupling network for symmetrical lines
according TIA-968-A (FCC Part 68)
PCD 900
249930
Automatic coupling network for symmetrical lines
according Telcordia (Bellcore) GR-1089-CORE
PIM 930
249933
Impulse module with integrated automatic coupling
network for symmetrical lines (12 pair) according
Telcordia (Bellcore) GR-1089-CORE
DEC 5
249014
Decoupling network with current compensated inductors
for symmetrical lines according IEC 61000-4-5
(combination wave 1.2/50us - 8/20us and 10/700us)
and ITU-T K.44
DEC 6
249015
Decoupling network with resistors for symmetrical lines
according ITU-T K.44
DEC 7
249016
Decoupling network with single inductors for
asymmetrical lines according IEC 61000-4-5
(1.2/50us - 8/20us) and IEC 61000-4-12
(ring wave 100kHz).
Headquarters
Haefely Test AG
Lehenmattstrasse 353
CH-4052, Basel
Switzerland
Locate your local
sales representative at
www.haefelyEMC.com
+ 41 61 373 41 11
+ 41 61 373 45 99
EMC-sales@haefely.com
Haefely has a policy of continuous product improvement. Therefore we reserve the right to change design and specification without notice.
North American Office
Hipotronics Inc.
Haefely EMC Division
1650 Route 22
Brewster, NY 10509
++1 845 279 3644 x264
++1 845 279 2467
EMCsales@hubbell-haefely.com
AN_surgetesting_unshielded_control&data_lines_2006-09-20.doc
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