IEC TS 61934:2011
(Main)Electrical insulating materials and systems - Electrical measurement of partial discharges (PD) under short rise time and repetitive voltage impulses
Electrical insulating materials and systems - Electrical measurement of partial discharges (PD) under short rise time and repetitive voltage impulses
IEC/TS 61934:2011(E) is applicable to the off-line electrical measurement of partial discharges (PD) that occur in electrical insulation systems (EIS) when stressed by repetitive voltage impulses generated from electronic power devices. Typical applications are EIS belonging to apparatus driven by power electronics, such as motors, inductive reactors and windmill generators. Excluded from the scope of this technical specification are:
- methods based on optical or ultrasonic PD detection,
- fields of application for PD measurements when stressed by non-repetitive impulse voltages such as lightning impulse or switching impulses from switchgear.
The principal changes with regard to the previous edition concern the addition of:
- an Introduction that provides some background information on the progress being made in the field of power electronics;
- impulse generators;
- PD detection methods;
- a new informative Annex C covering practical experience obtained from round-robin testing (RRT);
- example of noise levels, as shown in new informative Annex D.
General Information
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Standards Content (Sample)
IEC/TS 61934 ®
Edition 2.0 2011-04
TECHNICAL
SPECIFICATION
colour
inside
Electrical insulating materials and systems – Electrical measurement of partial
discharges (PD) under short rise time and repetitive voltage impulses
IEC/TS 61934:2011(E)
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by
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IEC/TS 61934 ®
Edition 2.0 2011-04
TECHNICAL
SPECIFICATION
colour
inside
Electrical insulating materials and systems – Electrical measurement of partial
discharges (PD) under short rise time and repetitive voltage impulses
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
U
ICS 17.220.99; 29.035.01; 29.080.30 ISBN 978-2-88912-479-4
– 2 – TS 61934 © IEC:2011(E)
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Measurement of partial discharge pulses during repetitive, short rise-time voltage
impulses and comparison with power frequency . 9
4.1 Measurement frequency . 9
4.2 Measurement quantities . 9
4.3 Test objects. 10
4.3.1 General . 10
4.3.2 Inductive test objects . 10
4.3.3 Capacitive test objects. 10
4.3.4 Distributed impedance test objects . 10
4.4 Impulse generators . 10
4.4.1 General . 10
4.4.2 Impulse waveforms . 11
4.5 Effect of testing conditions . 11
4.5.1 General . 11
4.5.2 Effect of environmental factors . 12
4.5.3 Effect of testing conditions and ageing . 12
5 PD detection methods . 12
5.1 General . 12
5.2 PD pulse coupling and detection devices . 12
5.2.1 Introductory remarks . 12
5.2.2 Coupling capacitor with multipole filter . 13
5.2.3 HFCT with multipole filter . 14
5.2.4 Electromagnetic couplers . 15
5.2.5 Charge measurements . 16
5.3 Source-controlled gating techniques . 17
6 Measuring instruments . 17
7 Sensitivity check of the PD measuring equipment . 17
7.1 General . 17
7.2 Test diagram for sensitivity check . 18
7.3 PD detection sensitivity check . 18
7.4 Background noise check . 19
7.5 Detection system noise check . 19
7.6 Sensitivity report . 19
8 Test procedure for increasing and decreasing the repetitive impulse voltage
magnitude . 19
9 Test report. 20
Annex A (informative) Voltage impulse suppression required by the coupling device . 22
Annex B (informative) PD pulses extracted from a supply voltage impulse through
filtering techniques . 24
Annex C (informative) Result of round-robin tests of RPDIV measurement . 26
Annex D (informative) Examples of noise levels of practical PD detectors . 28
TS 61934 © IEC:2011(E) – 3 –
Bibliography . 29
Figure 1 – Coupling capacitor with multipole filter . 13
Figure 2 – Example of voltage impulse and PD pulse frequency spectra before and
after filtering . 14
Figure 3 – HFCT between supply and test object with multipole filter . 14
Figure 4 – HFCT between test object and earth with multipole filter . 15
Figure 5 – Circuit using an electromagnetic coupler (for example an antenna) to
suppress impulses from the test supply. 15
Figure 6 – Circuit using an electromagnetic UHF antenna . 15
Figure 7 – Example of waveforms of repetitive bipolar impulse voltage and charge
accumulation for a twisted-pair sample . 16
Figure 8 – Charge measurements . 16
Figure 9 – Example of PD detection using electronic source-controlled gating (other
PD coupling devices can be used) . 17
Figure 10 – Test diagram for sensitivity check . 18
Figure 11 – Example of relation between the outputs of LVPG and PD detector . 19
Figure 12 – Example of increasing and decreasing the impulse voltage magnitude . 20
Figure A.1 – Example of overlap between voltage impulse and PD pulse spectra
(dotted area) . 22
Figure A.2 – Example of voltage impulse and PD pulse spectra after filtering . 22
Figure A.3 – Example of impulse voltage damping as a function of impulse voltage
magnitude and rise time . 23
Figure B.1 – Power supply waveform and recorded signal using an antenna during
supply voltage commutation . 24
Figure B.2 – Signal detected by an antenna from the record of Figure B.1, using a
filtering technique (400 MHz high-pass filter) . 25
Figure B.3 – Characteristic of the filter used to pass from Figure B.1 to Figure B.2 . 25
Figure C.1 – The sequence of negative voltage impulses used for RRT . 26
Figure C.2 – PD pulses (under) corresponding to voltage impulses (above) . 26
Figure C.3 – Dependence of normalized RPDIV on 100 data (NRPIV/100) on relative
humidity (A-F indicates the participants of RRT) . 27
Table 1 – Example of parameter values of impulse voltage waveform without load . 11
Table D.1 – Examples of bandwidths and noise levels for practical PD sensors . 28
– 4 – TS 61934 © IEC:2011(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICAL INSULATING MATERIALS AND SYSTEMS –
ELECTRICAL MEASUREMENT OF PARTIAL DISCHARGES (PD)
UNDER SHORT RISE TIME AND REPETITIVE VOLTAGE IMPULSES
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
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
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Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
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with the International Organization for Standardization (ISO) in accordance with conditions determined by
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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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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.
The main task of IEC technical committees is to prepare International Standards. In
exceptional circumstances, a technical committee may propose the publication of a technical
specification when
• the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts, or
• the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
Technical specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC/TS 61934, which is a technical specification, has been prepared by IEC technical
committee 112: Evaluation and qualification of electrical insulating materials and systems.
This second edition cancels and replaces the first edition, published in 2006, and constitutes
a technical revision.
TS 61934 © IEC:2011(E) – 5 –
The principal changes with regard to the previous edition concern the addition of
• an Introduction that provides some background information on the progress being
made in the field of power electronics;
• impulse generators;
• PD detection methods;
• a new informative Annex C covering practical experience obtained from round-robin
testing (RRT);
• example of noise levels, as shown in new informative Annex D.
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
112/163/DTS 112/175/RVC
Full information on the voting for the approval of this technical specification 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.
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
• transformed into an International standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 6 – TS 61934 © IEC:2011(E)
INTRODUCTION
Power electronics has developed along with both control theory and semiconductor
technology. Switching is one of the essential features of power electronics control. For higher
efficiency and smoother operation, switching times of the latest devices such as insulated-
gate bipolar transistor (IGBT) tend to be shorter than microseconds. Such a short rise time
may cause transient overvoltage impulses or surges in the systems. When the voltage
impulses reach the breakdown strength of an air gap, partial discharge (PD) may occur. In
addition, the impulses are repetitive from power electronics modulation such as pulse width
modulation (PWM). Since PD may cause degradation of electrical insulation parts in the
system, it is one of the most important parameters to be measured.
The first edition of IEC/TS 61934 was issued in April 2006. Because of rapid development in
this field, the revision activity for the latest information was approved in TC112 at the Berlin
meeting in September 2006. In addition to technical and editorial changes, practical
experience obtained through round-robin test (RRT) is also presented in Annex C.
TS 61934 © IEC:2011(E) – 7 –
ELECTRICAL INSULATING MATERIALS AND SYSTEMS –
ELECTRICAL MEASUREMENT OF PARTIAL DISCHARGES (PD)
UNDER SHORT RISE TIME AND REPETITIVE VOLTAGE IMPULSES
1 Scope
IEC/TS 61934, which is a technical specification, is applicable to the off-line electrical
measurement of partial discharges (PD) that occur in electrical insulation systems (EIS) when
stressed by repetitive voltage impulses generated from electronic power devices.
Typical applications are EIS belonging to apparatus driven by power electronics, such as
motors, inductive reactors and windmill generators.
NOTE 1 Use of this technical specification with specific products may require the application of additional
procedures.
NOTE 2 The procedures described in this technical specification are emerging technologies. Experience and
caution, as well as certain preconditions, are needed to apply it.
Excluded from the scope of this technical specification are
– methods based on optical or ultrasonic PD detection,
– fields of application for PD measurements when stressed by non-repetitive impulse
voltages such as lightning impulse or switching impulses from switchgear.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60034 (all parts), Rotating electrical machines
IEC 60270:2000, High-voltage test techniques – Partial discharge measurements
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
repetitive voltage impulses
voltage impulses which are used as test voltage for the evaluation of switching surges from
power electronic devices with a carrier or driven frequency
3.2
partial discharge
PD
electric discharge that only partially bridges the insulation between conductors
[IEC 60270:2000, 3.1, modified]
– 8 – TS 61934 © IEC:2011(E)
3.3
partial discharge pulse
current pulse in an object under test that results from a partial discharge occurring within the
object under test
NOTE 1 The pulse is measured using suitable detector circuits, which have been introduced into the test circuit
for the purpose of the test.
NOTE 2 A detector in accordance with the provisions of this technical specification produces a current or a
voltage signal at its output related to the PD pulse at its input.
[IEC 60270:2000, 3.2, modified]
3.4
repetitive partial discharge inception voltage
RPDIV
minimum peak-to-peak impulse voltage at which more than five PD pulses occur on ten
voltage impulses of the same polarity
NOTE This is a mean value for the specified test time and a test arrangement where the voltage applied to the
test object is gradually increased from a value at which no partial discharges can be detected.
3.5
repetitive partial discharge extinction voltage
RPDEV
maximum peak-to-peak impulse voltage at which less than five PD pulses occur on ten
voltage impulses of the same polarity
NOTE This is a mean value for a specified test time and a test arrangement where the voltage applied to the test
object gradually decreases from a voltage at which PD have been detected.
3.6
impulse voltage polarity
polarity of the applied impulse voltage with respect to earth
[IEC 62068-1:2003, 3.10]
3.7
unipolar impulse
repetitive voltage impulse, the polarity of which is either positive or negative
[IEC 62068-1:2003, 3.8, modified]
NOTE The magnitude of the oscillation of the opposite polarity has to be less than 20 %.
3.8
bipolar impulse
repetitive voltage impulse, the polarity of which changes
[IEC 62068-1:2003, 3.9, modified]
3.9
impulse voltage repetition rate
inverse of the average time between successive impulses of the same polarity, whether
unipolar or bipolar
[IEC 62068-1:2003, 3.11, modified]
3.10
impulse rise time
time for the voltage impulse to go from 0 % to 100 %
NOTE Unless otherwise stated, this is estimated as 1,25 times the time for the voltage to rise from 10 % to 90 %.
TS 61934 © IEC:2011(E) – 9 –
[IEC 62068-1:2003, 3.12, modified]
3.11
impulse decay time
time interval between the instants at which the instantaneous value of an impulse decreases
from a specified upper value to a specified lower value
NOTE Unless otherwise specified, the upper and lower values are fixed at 90 % and 10 % of the impulse
magnitude.
3.12
impulse width
interval of time between the first and last instants at which the instantaneous value of an
impulse reaches a specified fraction of impulse magnitude or a specified threshold
3.13
impulse duty cycle
ratio, for a given time interval, of the impulse width to the total time
3.14
peak partial discharge magnitude
largest magnitude of any quantity related to PD pulses observed in a test object at a specified
voltage following a specified conditioning and test
[IEC 60270:2000, 3.4 modified]
NOTE For impulse voltage tests, the peak magnitude of the PD pulse is the largest repeatedly occurring PD
magnitude.
4 Measurement of partial discharge pulses during repetitive, short rise-time
voltage impulses and comparison with power frequency
4.1 Measurement frequency
IEC 60270 describes the methods employed to measure the electrical pulses associated with
PD in test objects excited by DC and alternating voltages up to 400 Hz. The methods used to
measure PD pulses when the test object is subjected to supply voltage impulses have to be
modified from the standard narrow-band and wide-band frequency methods described in
IEC 60270.
To measure the PD during repetitive short rise time voltage impulses, it is necessary to avoid
the induced current of the excited impulse voltage. One technique is current or
electromagnetic wave measurement at ultra-high frequency, that is, higher than that of the
impulse. Ultra-wide band (UWB) detection is often used with a high-pass filter for the
suppression of relatively lower frequency components of impulse voltage. In principle, narrow-
band measurement in the ultra-high frequency (UHF: 300 MHz to 3 GHz) region is also
effective for the suppression of the impulse voltage. The other method is the integration of PD
current at a very low frequency compared to that of the impulse voltage.
4.2 Measurement quantities
Measured quantities concern the RPDIV, the RPDEV, the peak partial discharge magnitude
and partial discharge pulse repetition rate.
RPDIV and RPDEV may depend on PD measurement sensitivity and measurement circuit
noise, so that normalization, as indicated in Clause 7, is needed. Moreover, they depend on
the test object and the pulse deformation from the discharge to the measurement point.
– 10 – TS 61934 © IEC:2011(E)
In this technical specification, PD readings are reported in units of mV. In all cases, a
sensitivity evaluation of the measuring system is necessary and shall be carried out according
to Clause 7.
4.3 Test objects
4.3.1 General
Test objects behave predominantly as inductive, capacitive or distributed equivalent
impedances according to the voltage supply frequency content. For some test objects,
whether they are predominantly inductive, capacitive or distributed impedances may depend
on the PD detection frequency range (not only on the voltage supply frequency). Test objects
with distributed behaviour have transmission line characteristics which may cause attenuation
and distortion of the PD pulses as the pulses propagate through the test object. The following
classification is effective only for low-frequency, narrow-band measurements.
4.3.2 Inductive test objects
Types of inductive test objects may include:
– stator and rotor windings;
– inductive reactors;
– transformer windings;
– motorettes and formettes (see the IEC 60034 series).
4.3.3 Capacitive test objects
Types of capacitive test objects may include:
– twisted pairs of winding wire;
– capacitors;
– packaging of switching devices;
– power electronic modules and substrates;
– isolated heat sinks;
– mainwall insulation models in stator coils and bars;
– printed circuit boards;
– optocouplers.
4.3.4 Distributed impedance test objects
The following test objects may have distributed equivalent impedance properties:
– cables;
– busbars;
– stator and rotor windings;
– transformer windings;
– turn insulation of stator and rotor windings.
– bushings with capacitive voltage stress control;
4.4 Impulse generators
4.4.1 General
Impulse generators used in this technical specification shall generate short rise time and
repetitive voltage impulses with a low noise level. For a short rise time of impulses,
TS 61934 © IEC:2011(E) – 11 –
semiconductor devices may be used for switching in addition to conventional sphere electrode
gaps. For repetitive impulses, the main capacitor shall be charged from a DC power supply in
a short period of time. The ranges of rise time, repetition frequency and other parameters are
described in 4.4.2.
The polarity of successive impulses is important for PD behaviour. To simulate the turn-to-
turn voltage of a motor driven by a PWM phase voltage, a bipolar repetitive impulse voltage is
preferable. When a bipolar generator is hard to obtain, a unipolar repetitive impulse generator
may be used.
For PD measurements, impulse generators shall suppress noise emission by means of
sufficient electromagnetic shielding.
4.4.2 Impulse waveforms
For the purpose of comparison between different insulating materials or design solutions,
partial discharge measurements can be performed using appropriate voltage supply
waveforms. The specification of the impulse generator shall include amongst other factors:
– impulse rise time;
– impulse voltage polarity;
– impulse voltage repetition rate;
– impulse width;
– impulse duty cycle.
Examples are given in Table1.
Table 1 – Example of parameter values of impulse voltage waveform without load
Characteristic Range
Rise time 0,04 µs to 1 μs
Repetition rate 1 Hz to 10 000 Hz
Impulse width 0,08 μs to 25 μs
Shape Square or triangular
Polarity Unipolar or bipolar (preferred)
The impulse waveform depends not only on the impulse generator specification but also on
sample impedance. The impulse waveform will change significantly with load. The impulse
generator needs to be designed to deliver the required wave shape to the load. As the
capacitance of the sample increases, the rise time of the voltage impulse increases in general.
On the other hand, the inductive test object, or distributed equivalent impedan
...
IEC/TS 61934 ®
Edition 2.0 2011-04
TECHNICAL
SPECIFICATION
colour
inside
Electrical insulating materials and systems – Electrical measurement of partial
discharges (PD) under short rise time and repetitive voltage impulses
IEC/TS 61934:2011(E)
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by
any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either IEC or
IEC's member National Committee in the country of the requester.
If you have any questions about IEC copyright or have an enquiry about obtaining additional rights to this publication,
please contact the address below or your local IEC member National Committee for further information.
Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de la CEI ou du Comité national de la CEI du pays du demandeur.
Si vous avez des questions sur le copyright de la CEI ou si vous désirez obtenir des droits supplémentaires sur cette
publication, utilisez les coordonnées ci-après ou contactez le Comité national de la CEI de votre pays de résidence.
IEC Central Office
3, rue de Varembé
CH-1211 Geneva 20
Switzerland
Email: inmail@iec.ch
Web: www.iec.ch
About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.
Catalogue of IEC publications: www.iec.ch/searchpub
The IEC on-line Catalogue enables you to search by a variety of criteria (reference number, text, technical committee,…).
It also gives information on projects, withdrawn and replaced publications.
IEC Just Published: www.iec.ch/online_news/justpub
Stay up to date on all new IEC publications. Just Published details twice a month all new publications released. Available
on-line and also by email.
Electropedia: www.electropedia.org
The world's leading online dictionary of electronic and electrical terms containing more than 20 000 terms and definitions
in English and French, with equivalent terms in additional languages. Also known as the International Electrotechnical
Vocabulary online.
Customer Service Centre: www.iec.ch/webstore/custserv
If you wish to give us your feedback on this publication or need further assistance, please visit the Customer Service
Centre FAQ or contact us:
Email: csc@iec.ch
Tel.: +41 22 919 02 11
Fax: +41 22 919 03 00
IEC/TS 61934 ®
Edition 2.0 2011-04
TECHNICAL
SPECIFICATION
colour
inside
Electrical insulating materials and systems – Electrical measurement of partial
discharges (PD) under short rise time and repetitive voltage impulses
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
U
ICS 17.220.99; 29.035.01; 29.080.30 ISBN 978-2-88912-479-4
– 2 – TS 61934 © IEC:2011(E)
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Measurement of partial discharge pulses during repetitive, short rise-time voltage
impulses and comparison with power frequency . 9
4.1 Measurement frequency . 9
4.2 Measurement quantities . 9
4.3 Test objects. 10
4.3.1 General . 10
4.3.2 Inductive test objects . 10
4.3.3 Capacitive test objects. 10
4.3.4 Distributed impedance test objects . 10
4.4 Impulse generators . 10
4.4.1 General . 10
4.4.2 Impulse waveforms . 11
4.5 Effect of testing conditions . 11
4.5.1 General . 11
4.5.2 Effect of environmental factors . 12
4.5.3 Effect of testing conditions and ageing . 12
5 PD detection methods . 12
5.1 General . 12
5.2 PD pulse coupling and detection devices . 12
5.2.1 Introductory remarks . 12
5.2.2 Coupling capacitor with multipole filter . 13
5.2.3 HFCT with multipole filter . 14
5.2.4 Electromagnetic couplers . 15
5.2.5 Charge measurements . 16
5.3 Source-controlled gating techniques . 17
6 Measuring instruments . 17
7 Sensitivity check of the PD measuring equipment . 17
7.1 General . 17
7.2 Test diagram for sensitivity check . 18
7.3 PD detection sensitivity check . 18
7.4 Background noise check . 19
7.5 Detection system noise check . 19
7.6 Sensitivity report . 19
8 Test procedure for increasing and decreasing the repetitive impulse voltage
magnitude . 19
9 Test report. 20
Annex A (informative) Voltage impulse suppression required by the coupling device . 22
Annex B (informative) PD pulses extracted from a supply voltage impulse through
filtering techniques . 24
Annex C (informative) Result of round-robin tests of RPDIV measurement . 26
Annex D (informative) Examples of noise levels of practical PD detectors . 28
TS 61934 © IEC:2011(E) – 3 –
Bibliography . 29
Figure 1 – Coupling capacitor with multipole filter . 13
Figure 2 – Example of voltage impulse and PD pulse frequency spectra before and
after filtering . 14
Figure 3 – HFCT between supply and test object with multipole filter . 14
Figure 4 – HFCT between test object and earth with multipole filter . 15
Figure 5 – Circuit using an electromagnetic coupler (for example an antenna) to
suppress impulses from the test supply. 15
Figure 6 – Circuit using an electromagnetic UHF antenna . 15
Figure 7 – Example of waveforms of repetitive bipolar impulse voltage and charge
accumulation for a twisted-pair sample . 16
Figure 8 – Charge measurements . 16
Figure 9 – Example of PD detection using electronic source-controlled gating (other
PD coupling devices can be used) . 17
Figure 10 – Test diagram for sensitivity check . 18
Figure 11 – Example of relation between the outputs of LVPG and PD detector . 19
Figure 12 – Example of increasing and decreasing the impulse voltage magnitude . 20
Figure A.1 – Example of overlap between voltage impulse and PD pulse spectra
(dotted area) . 22
Figure A.2 – Example of voltage impulse and PD pulse spectra after filtering . 22
Figure A.3 – Example of impulse voltage damping as a function of impulse voltage
magnitude and rise time . 23
Figure B.1 – Power supply waveform and recorded signal using an antenna during
supply voltage commutation . 24
Figure B.2 – Signal detected by an antenna from the record of Figure B.1, using a
filtering technique (400 MHz high-pass filter) . 25
Figure B.3 – Characteristic of the filter used to pass from Figure B.1 to Figure B.2 . 25
Figure C.1 – The sequence of negative voltage impulses used for RRT . 26
Figure C.2 – PD pulses (under) corresponding to voltage impulses (above) . 26
Figure C.3 – Dependence of normalized RPDIV on 100 data (NRPIV/100) on relative
humidity (A-F indicates the participants of RRT) . 27
Table 1 – Example of parameter values of impulse voltage waveform without load . 11
Table D.1 – Examples of bandwidths and noise levels for practical PD sensors . 28
– 4 – TS 61934 © IEC:2011(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICAL INSULATING MATERIALS AND SYSTEMS –
ELECTRICAL MEASUREMENT OF PARTIAL DISCHARGES (PD)
UNDER SHORT RISE TIME AND REPETITIVE VOLTAGE IMPULSES
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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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
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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.
The main task of IEC technical committees is to prepare International Standards. In
exceptional circumstances, a technical committee may propose the publication of a technical
specification when
• the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts, or
• the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
Technical specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC/TS 61934, which is a technical specification, has been prepared by IEC technical
committee 112: Evaluation and qualification of electrical insulating materials and systems.
This second edition cancels and replaces the first edition, published in 2006, and constitutes
a technical revision.
TS 61934 © IEC:2011(E) – 5 –
The principal changes with regard to the previous edition concern the addition of
• an Introduction that provides some background information on the progress being
made in the field of power electronics;
• impulse generators;
• PD detection methods;
• a new informative Annex C covering practical experience obtained from round-robin
testing (RRT);
• example of noise levels, as shown in new informative Annex D.
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
112/163/DTS 112/175/RVC
Full information on the voting for the approval of this technical specification 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.
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
• transformed into an International standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 6 – TS 61934 © IEC:2011(E)
INTRODUCTION
Power electronics has developed along with both control theory and semiconductor
technology. Switching is one of the essential features of power electronics control. For higher
efficiency and smoother operation, switching times of the latest devices such as insulated-
gate bipolar transistor (IGBT) tend to be shorter than microseconds. Such a short rise time
may cause transient overvoltage impulses or surges in the systems. When the voltage
impulses reach the breakdown strength of an air gap, partial discharge (PD) may occur. In
addition, the impulses are repetitive from power electronics modulation such as pulse width
modulation (PWM). Since PD may cause degradation of electrical insulation parts in the
system, it is one of the most important parameters to be measured.
The first edition of IEC/TS 61934 was issued in April 2006. Because of rapid development in
this field, the revision activity for the latest information was approved in TC112 at the Berlin
meeting in September 2006. In addition to technical and editorial changes, practical
experience obtained through round-robin test (RRT) is also presented in Annex C.
TS 61934 © IEC:2011(E) – 7 –
ELECTRICAL INSULATING MATERIALS AND SYSTEMS –
ELECTRICAL MEASUREMENT OF PARTIAL DISCHARGES (PD)
UNDER SHORT RISE TIME AND REPETITIVE VOLTAGE IMPULSES
1 Scope
IEC/TS 61934, which is a technical specification, is applicable to the off-line electrical
measurement of partial discharges (PD) that occur in electrical insulation systems (EIS) when
stressed by repetitive voltage impulses generated from electronic power devices.
Typical applications are EIS belonging to apparatus driven by power electronics, such as
motors, inductive reactors and windmill generators.
NOTE 1 Use of this technical specification with specific products may require the application of additional
procedures.
NOTE 2 The procedures described in this technical specification are emerging technologies. Experience and
caution, as well as certain preconditions, are needed to apply it.
Excluded from the scope of this technical specification are
– methods based on optical or ultrasonic PD detection,
– fields of application for PD measurements when stressed by non-repetitive impulse
voltages such as lightning impulse or switching impulses from switchgear.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60034 (all parts), Rotating electrical machines
IEC 60270:2000, High-voltage test techniques – Partial discharge measurements
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
repetitive voltage impulses
voltage impulses which are used as test voltage for the evaluation of switching surges from
power electronic devices with a carrier or driven frequency
3.2
partial discharge
PD
electric discharge that only partially bridges the insulation between conductors
[IEC 60270:2000, 3.1, modified]
– 8 – TS 61934 © IEC:2011(E)
3.3
partial discharge pulse
current pulse in an object under test that results from a partial discharge occurring within the
object under test
NOTE 1 The pulse is measured using suitable detector circuits, which have been introduced into the test circuit
for the purpose of the test.
NOTE 2 A detector in accordance with the provisions of this technical specification produces a current or a
voltage signal at its output related to the PD pulse at its input.
[IEC 60270:2000, 3.2, modified]
3.4
repetitive partial discharge inception voltage
RPDIV
minimum peak-to-peak impulse voltage at which more than five PD pulses occur on ten
voltage impulses of the same polarity
NOTE This is a mean value for the specified test time and a test arrangement where the voltage applied to the
test object is gradually increased from a value at which no partial discharges can be detected.
3.5
repetitive partial discharge extinction voltage
RPDEV
maximum peak-to-peak impulse voltage at which less than five PD pulses occur on ten
voltage impulses of the same polarity
NOTE This is a mean value for a specified test time and a test arrangement where the voltage applied to the test
object gradually decreases from a voltage at which PD have been detected.
3.6
impulse voltage polarity
polarity of the applied impulse voltage with respect to earth
[IEC 62068-1:2003, 3.10]
3.7
unipolar impulse
repetitive voltage impulse, the polarity of which is either positive or negative
[IEC 62068-1:2003, 3.8, modified]
NOTE The magnitude of the oscillation of the opposite polarity has to be less than 20 %.
3.8
bipolar impulse
repetitive voltage impulse, the polarity of which changes
[IEC 62068-1:2003, 3.9, modified]
3.9
impulse voltage repetition rate
inverse of the average time between successive impulses of the same polarity, whether
unipolar or bipolar
[IEC 62068-1:2003, 3.11, modified]
3.10
impulse rise time
time for the voltage impulse to go from 0 % to 100 %
NOTE Unless otherwise stated, this is estimated as 1,25 times the time for the voltage to rise from 10 % to 90 %.
TS 61934 © IEC:2011(E) – 9 –
[IEC 62068-1:2003, 3.12, modified]
3.11
impulse decay time
time interval between the instants at which the instantaneous value of an impulse decreases
from a specified upper value to a specified lower value
NOTE Unless otherwise specified, the upper and lower values are fixed at 90 % and 10 % of the impulse
magnitude.
3.12
impulse width
interval of time between the first and last instants at which the instantaneous value of an
impulse reaches a specified fraction of impulse magnitude or a specified threshold
3.13
impulse duty cycle
ratio, for a given time interval, of the impulse width to the total time
3.14
peak partial discharge magnitude
largest magnitude of any quantity related to PD pulses observed in a test object at a specified
voltage following a specified conditioning and test
[IEC 60270:2000, 3.4 modified]
NOTE For impulse voltage tests, the peak magnitude of the PD pulse is the largest repeatedly occurring PD
magnitude.
4 Measurement of partial discharge pulses during repetitive, short rise-time
voltage impulses and comparison with power frequency
4.1 Measurement frequency
IEC 60270 describes the methods employed to measure the electrical pulses associated with
PD in test objects excited by DC and alternating voltages up to 400 Hz. The methods used to
measure PD pulses when the test object is subjected to supply voltage impulses have to be
modified from the standard narrow-band and wide-band frequency methods described in
IEC 60270.
To measure the PD during repetitive short rise time voltage impulses, it is necessary to avoid
the induced current of the excited impulse voltage. One technique is current or
electromagnetic wave measurement at ultra-high frequency, that is, higher than that of the
impulse. Ultra-wide band (UWB) detection is often used with a high-pass filter for the
suppression of relatively lower frequency components of impulse voltage. In principle, narrow-
band measurement in the ultra-high frequency (UHF: 300 MHz to 3 GHz) region is also
effective for the suppression of the impulse voltage. The other method is the integration of PD
current at a very low frequency compared to that of the impulse voltage.
4.2 Measurement quantities
Measured quantities concern the RPDIV, the RPDEV, the peak partial discharge magnitude
and partial discharge pulse repetition rate.
RPDIV and RPDEV may depend on PD measurement sensitivity and measurement circuit
noise, so that normalization, as indicated in Clause 7, is needed. Moreover, they depend on
the test object and the pulse deformation from the discharge to the measurement point.
– 10 – TS 61934 © IEC:2011(E)
In this technical specification, PD readings are reported in units of mV. In all cases, a
sensitivity evaluation of the measuring system is necessary and shall be carried out according
to Clause 7.
4.3 Test objects
4.3.1 General
Test objects behave predominantly as inductive, capacitive or distributed equivalent
impedances according to the voltage supply frequency content. For some test objects,
whether they are predominantly inductive, capacitive or distributed impedances may depend
on the PD detection frequency range (not only on the voltage supply frequency). Test objects
with distributed behaviour have transmission line characteristics which may cause attenuation
and distortion of the PD pulses as the pulses propagate through the test object. The following
classification is effective only for low-frequency, narrow-band measurements.
4.3.2 Inductive test objects
Types of inductive test objects may include:
– stator and rotor windings;
– inductive reactors;
– transformer windings;
– motorettes and formettes (see the IEC 60034 series).
4.3.3 Capacitive test objects
Types of capacitive test objects may include:
– twisted pairs of winding wire;
– capacitors;
– packaging of switching devices;
– power electronic modules and substrates;
– isolated heat sinks;
– mainwall insulation models in stator coils and bars;
– printed circuit boards;
– optocouplers.
4.3.4 Distributed impedance test objects
The following test objects may have distributed equivalent impedance properties:
– cables;
– busbars;
– stator and rotor windings;
– transformer windings;
– turn insulation of stator and rotor windings.
– bushings with capacitive voltage stress control;
4.4 Impulse generators
4.4.1 General
Impulse generators used in this technical specification shall generate short rise time and
repetitive voltage impulses with a low noise level. For a short rise time of impulses,
TS 61934 © IEC:2011(E) – 11 –
semiconductor devices may be used for switching in addition to conventional sphere electrode
gaps. For repetitive impulses, the main capacitor shall be charged from a DC power supply in
a short period of time. The ranges of rise time, repetition frequency and other parameters are
described in 4.4.2.
The polarity of successive impulses is important for PD behaviour. To simulate the turn-to-
turn voltage of a motor driven by a PWM phase voltage, a bipolar repetitive impulse voltage is
preferable. When a bipolar generator is hard to obtain, a unipolar repetitive impulse generator
may be used.
For PD measurements, impulse generators shall suppress noise emission by means of
sufficient electromagnetic shielding.
4.4.2 Impulse waveforms
For the purpose of comparison between different insulating materials or design solutions,
partial discharge measurements can be performed using appropriate voltage supply
waveforms. The specification of the impulse generator shall include amongst other factors:
– impulse rise time;
– impulse voltage polarity;
– impulse voltage repetition rate;
– impulse width;
– impulse duty cycle.
Examples are given in Table1.
Table 1 – Example of parameter values of impulse voltage waveform without load
Characteristic Range
Rise time 0,04 µs to 1 μs
Repetition rate 1 Hz to 10 000 Hz
Impulse width 0,08 μs to 25 μs
Shape Square or triangular
Polarity Unipolar or bipolar (preferred)
The impulse waveform depends not only on the impulse generator specification but also on
sample impedance. The impulse waveform will change significantly with load. The impulse
generator needs to be designed to deliver the required wave shape to the load. As the
capacitance of the sample increases, the rise time of the voltage impulse increases in general.
On the other hand, the inductive test object, or distributed equivalent impedance mentioned in
4.3.4, can cause damped oscillation after the impu
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