IEC 60243-3:2013

IEC 60243-3 ®
Edition 3.0 2013-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electric strength of insulating materials – Test methods –
Part 3: Additional requirements for 1,2/50 µs impulse tests

Rigidité diélectrique des matériaux isolants – Méthodes d’essai –
Partie 3: Exigences complémentaires pour les essais
aux ondes de choc 1,2/50 µs
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IEC 60243-3 ®
Edition 3.0 2013-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electric strength of insulating materials – Test methods –

Part 3: Additional requirements for 1,2/50 µs impulse tests

Rigidité diélectrique des matériaux isolants – Méthodes d’essai –

Partie 3: Exigences complémentaires pour les essais

aux ondes de choc 1,2/50 µs
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX J
ICS 17.220.99; 29.035.01 ISBN 978-2-8322-1201-1

– 2 – 60243-3 © IEC:2013
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Significance of the test . 6
5 Electrodes and test specimens . 7
6 Conditioning before tests . 7
7 Surrounding medium . 7
8 Electrical apparatus . 7
8.1 Voltage source . 7
8.2 Voltage measurement . 8
9 Procedure . 8
10 Application of voltage . 8
10.1 Breakdown test . 8
10.2 Proof tests . 8
11 Criterion of breakdown . 9
12 Number of tests . 9
13 Report . 9

Figure 1 – Full impulse-voltage wave . 6

60243-3 © IEC:2013 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRIC STRENGTH OF INSULATING MATERIALS –
TEST METHODS –
Part 3: Additional requirements for 1,2/50 µs impulse tests

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60243-3 has been prepared by technical committee 112: Evaluation
and qualification of electrical insulation materials and systems.
This third edition cancels and replaces the second edition, published in 2001, and constitutes
an editorial revision.
This part of IEC 60243 shall be read in conjunction with IEC 60243-1.
The text of this standard is based on the following documents:
CDV Report on voting
112/246/CDV 112/267A/RVC
– 4 – 60243-3 © IEC:2013
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 60243 series, published under the general title Electric strength of
insulating materials – Test methods, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until the
stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data related to
the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
60243-3 © IEC:2013 – 5 –
ELECTRIC STRENGTH OF INSULATING MATERIALS –
TEST METHODS –
Part 3: Additional requirements for 1,2/50 µs impulse tests

1 Scope
This part of IEC 60243 gives requirements additional to those in IEC 60243-1 for the
determination of the electric strength of solid insulating materials under 1,2/50 µs impulse
voltage stress.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments)
applies.
IEC 60243-1:2013, Electric strength of insulating materials – Test methods – Part 1: Tests at
power frequencies
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60243-1, together
with the following, apply.
3.1
full impulse-voltage wave
aperiodic transient voltage that rises rapidly to a maximum value, then falls less rapidly to zero
(see Figure 1)
3.2
peak value (of an impulse-voltage wave)
U
P
maximum value of voltage
3.3
virtual peak value (of an impulse-voltage wave)
U
value derived from a recording of an impulse-voltage wave on which high-frequency
oscillations, or overshoot of a limited magnitude, may be present
3.4
virtual origin (of an impulse-voltage wave)
O
point of intersection O with the line of zero voltage of a line drawn through the points of 0,3
and 0,9 times the virtual peak value on the front of an impulse-voltage wave (see Figure 1)

– 6 – 60243-3 © IEC:2013
3.5
virtual front time (of an impulse-voltage wave)
t
equal to 1,67 times the interval t between the instants when the voltage is 0,3 and 0,9 times
f
the peak value (t , Figure 1)
f
3.6
virtual time to half-value
t
between the virtual origin O and the instant on the tail when the voltage has
time interval t
2 1
decreased to half the peak value
3.7
impulse breakdown voltage
nominal peak voltage that the wave causing breakdown would have reached if breakdown had
not occurred
3.8
withstand voltage
highest nominal peak voltage of a set of three impulses which did not cause breakdown
U/U
p
1,0
0,9
B
0,5
0,3 A
O
t
1 t
f
t
t
t = 1,67 t IEC  1085/01
1 f
Figure 1 – Full impulse-voltage wave
4 Significance of the test
In addition to the information of Clause 4 of IEC 60243-1:2013, the following points are of
importance in connection with impulse-voltage tests.
High-voltage equipment may be subjected to transient voltage stresses resulting from such
causes as nearby lightning strokes. This is particularly true of apparatus such as transformers
and switchgears used in electrical power transmission and distribution systems. The ability of
insulating materials to withstand these transient voltages is important in establishing the
reliability of apparatus insulated with these materials.
Transient voltages caused by lightning may be of either positive or negative polarity. In a
symmetrical field between identical electrodes, the polarity has no effect on the electric

60243-3 © IEC:2013 – 7 –
strength. However, with dissimilar electrodes, there may be a pronounced polarity effect. When
asymmetrical electrodes are used for testing materials with which the tester has no previous
experience or knowledge, it is recommended that comparative tests be made with both
directions of polarity.
The standard wave shape is a 1,2/50 µs wave, reaching peak voltage in approximately
1,2 µs, and decaying to 50 % of peak value in approximately 50 µs after the beginning of the
wave. This wave is intended to simulate a lightning stroke that may strike a system without
breakdown.
NOTE If the object being tested has appreciable inductive characteristics, it may be difficult or impossible to attain
the specified wave shape with less than 5 % oscillations, as prescribed in 8.2. However, the procedures given in
this standard are expected ordinarily to be applied to configurations of test specimens and electrodes which are
primarily capacitive. Testing of more complex configurations, such as between coils of completed apparatus or
models of such apparatus, should be performed in accordance with the specifications for that apparatus.
Because of the short time involved, dielectric heating, other thermal effects and the influence
of injected space-charges may be reduced during impulse testing of most materials. Thus,
impulse tests usually give higher values than the peak voltage of short-term ac tests. From
comparisons of the impulse electric strength with the values drawn from longer time tests,
inferences may be drawn as to the modes of failure under the various tests for a given
material.
5 Electrodes and test specimens
Clause 5 of IEC 60243-1:2013 is applicable.
6 Conditioning before tests
Clause 6 of IEC 60243-1:2013 is applicable.
7 Surrounding medium
Clause 7 of IEC 60243-1:2013 is applicable.
8 Electrical apparatus
8.1 Voltage source
The test voltage applied to the electrodes shall be provided by an impulse generator having the
following characteristics.
A choice of either positive or negative polarity shall be provided, one of the connections to the
electrodes being earthed.
Controls within the generator shall be capable of adjusting the shape of the wave applied to the
test specimen under test to have a virtual front time t of (1,2 ± 0,36) µs, and virtual time to
half-value t of (50 ± 10) µs (see Figure 1).
The voltage capability and energy-storage capacity of the generator shall be sufficient to apply
impulse waves of the proper shape to any test specimens to be tested, up to the breakdown
voltage or specified proof voltage of the material.
The peak value of the voltage is taken as the virtual peak value, provided that the conditions of
8.2 are satisfied.
– 8 – 60243-3 © IEC:2013
8.2 Voltage measurement
Provisions shall be made for recording the voltage wave as applied to the test specimen, and
for measuring the virtual peak voltage, the virtual front time and the virtual time to half-value
within ±5 % of the true values.
If the voltage wave has oscillations with a magnitude of no more than 5 % of the peak value,
and a frequency of at least 0,5 MHz, a mean curve may be drawn, the maximum amplitude of
which is the virtual peak value. If the oscillations are of greater magnitude, or of lower
frequency, the voltage wave is not acceptable for a standard test.
9 Procedure
Clause 9 of IEC 60243-1:2013 is applicable. However, the application of the voltage shall be as
shown in Clause 10.
10 Application of voltage
10.1 Breakdown test
Breakdown tests shall be in accordance with Clause 11 of IEC 60243-1:2013.
The voltage impulses shall be applied in an increasing series of sets of three waves of equal
peak voltages. The peak voltage of the initial set should be approximately 70 % of the expected
breakdown voltage.
Increase the peak voltage of successive sets by 5 % to 10 % of the peak value of the first set.
Table 1 of IEC 60243-1:2013 is applicable.
Allow sufficient time between successive impulses for the generator to become completely
charged. Normally, a time of three times the charging time constant for the generator is
sufficient.
Sufficient time shall also be allowed between successive impulses to allow dissipation of any
injected space-charge. For many materials, the charging time of the generator will cover this
eventuality. For materials having a longer space-charge retention time, the necessary time
shall be specified in the material specification sheet. If this information is not known, but a long
space-charge retention period is suspected, then additional tests should be run with longer
intervals between impulses, to determine if a significant difference in breakdown values is
obtained.
A valid test on a test specimen is one in which impulse waves are applied at at least two
voltage levels without breakdown, before breakdown occurs at the third or a subsequent level.
The electric strength shall be based on the virtual peak voltage of the last set of three waves
which was applied without breakdown. The breakdown voltage is the nominal voltage of the
next set of waves causing breakdown.
When using asymmetrical electrode systems, preliminary tests shall be conducted to determine
the polarity which yields the lower breakdown voltage. If significant differences are obtained,
the polarity giving the lower test results should be used.
10.2 Proof tests
One set of three impulses of specified proof voltage (virtual value) shall be applied to the test
specimen in accordance with Clause 11 of IEC 60243-1:2013. When necessary for calibration

60243-3 © IEC:2013 – 9 –
purposes, up to
...