IEC TS 61934:2006

TECHNICAL IEC
SPECIFICATION TS 61934
First edition
2006-04
Electrical insulating materials and systems –
Electrical measurement of partial discharges (PD)
under short rise time and repetitive voltage
impulses
Reference number
IEC/TS 61934:2006(E)
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TECHNICAL IEC
SPECIFICATION TS 61934
First edition
2006-04
Electrical insulating materials and systems –
Electrical measurement of partial discharges (PD)
under short rise time and repetitive voltage
impulses
 IEC 2006  Copyright - all rights reserved
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 the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
PRICE CODE
Commission Electrotechnique Internationale S

International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue

– 2 – TS 61934  IEC:2006(E)
CONTENTS
FOREWORD.4

1 Scope.6
2 Normative references .6
3 Terms and definitions .6
4 Measurement of partial discharge pulses during repetitive, short-rise time, voltage
impulses and comparison with power frequency .8
4.1 Measurement frequency .8
4.2 Measurement quantities .9
4.3 Test objects.9
4.4 Effect of testing conditions .10
5 PD detection methods .11
5.1 General .11
5.2 PD pulse coupling and detection devices.11
5.3 Source-controlled gating techniques.15
6 Display methods.15
7 Sensitivity of PD measurement .16
8 Test circuits.17
9 Test procedures .17
10 Test report.17

Annex A (informative) Indications on the voltage impulse suppression action required
by the coupling device .18
Annex B (informative) PD pulses extracted from a supply voltage impulse through
filtering techniques .20

Bibliography.22

Figure 1 – Coupling capacitor with multipole filter .12
Figure 2 – Example of voltage impulse and PD pulse frequency spectra before and
after filtering .12
Figure 3 – HFCT with multipole filter .13
Figure 4 – HFCT between test object and earth with multipole filter .13
Figure 5 – Circuit using an electromagnetic coupler (for example an antenna) to
suppress impulses from the test supply.13
Figure 6 – Example of waveforms of repetitive bipolar impulse voltage and charge
accumulation for on twisted-pair sample .14
Figure 7 – Charge measurements .14
Figure 8 – Example of PD detection using electronic source-controlled gating (other
PD coupling devices can be used) .15

TS 61934  IEC:2006(E) – 3 –
Figure A.1 – Schematic example of overlap between voltage impulse and PD pulse
spectra (dotted area) .18
Figure A.2 – Schematic example of voltage impulse and PD pulse spectra after filtering.18
Figure A.3 – Example of impulse voltage damping as a function of impulse voltage
magnitude and rise time.19
Figure B.1 – Power supply waveform and recorded PD pulses measured using an
antenna during supply voltage commutation.20
Figure B.2 – Partial discharge pulses detected by an antenna from the record of
Figure B.1, using a filtering technique (400 MHz high-pass filter).21
Figure B.3 – Characteristic of the filter used to pass from Figure B.1 to Figure B.2 .21

– 4 – TS 61934  IEC:2006(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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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.
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The main task of IEC technical committees is to prepare International Standards. In
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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 61934, which is a technical specification, has been prepared by IEC technical
committee 112: Evaluation and qualification of electrical insulating materials and systems .
———————
Provisional title.
TS 61934  IEC:2006(E) – 5 –
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
112/13/DTS 112/25/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.
A bilingual version of this publication may be issued at a later date.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result 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.
– 6 – TS 61934  IEC:2006(E)
ELECTRICAL INSULATING MATERIALS AND SYSTEMS –
ELECTRICAL MEASUREMENT OF PARTIAL DISCHARGES (PD)
UNDER SHORT RISE TIME AND REPETITIVE VOLTAGE IMPULSES

1 Scope
This 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 having a rise time of 50 µs or less.
Typical applications are EIS belonging to apparatus driven by power electronics, such as
motors.
NOTE 1 Use of this document with specific products may require specification of additional procedures.
NOTE 2 Those described in the TS are emerging technologies, so that experience and cautions, as well as
certain preconditions, are needed to apply this TS.
Excluded are
– methods based on optical or ultrasonic PD detection,
– fields of application for PD measurements when stressed by non-repetitive impulse
voltages.
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 60270:2000, High voltage test techniques – Partial discharge measurements
IEC 62068-1:2003, Electrical insulation systems – Electrical stresses produced by repetitive
impulses – Part 1: General method of evaluation of electrical endurance
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply, some of which
are taken from IEC 60270 and IEC 62068-1.
3.1
repetitive voltage impulses
impulses that occur when switching of power electronic devices at a carrier or driven
frequency
3.2
partial discharge
PD
electric discharge that only partially bridges the insulation between conductors
[IEC 60270:2000, Definition 3.1, modified]

TS 61934  IEC:2006(E) – 7 –
3.3
partial discharge pulse
PD pulse
current or voltage pulse at the terminal of the object under test that results from a partial
discharge occurring within the object under test
NOTE The pulse is measured using suitable detector circuits, which have been introduced into the test circuit for
the purpose of the test.
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, Definition 3.2, modified]
3.4
repetitive partial discharge inception voltage
RPDIV
minimum peak-to-peak voltage at which partial discharges occur with a repetition rate of 1 or
more PD pulses per every 2 voltage impulses
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 voltage at which partial discharges occur with a repetition rate of less
than 1 PD pulse per 2 voltage impulses
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, Definition 3.10]
3.7
unipolar impulse
repetitive voltage impulse, the polarity of which is either positive or negative
[IEC 62068-1:2003, Definition 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, Definition 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, Definition 3.11, modified]
3.10
PD pulse repetition rate
inverse of the average time between successive PD pulses of the same polarity
[IEC 62068-1:2003, Definition 3.11, modified]

– 8 – TS 61934  IEC:2006(E)
3.11
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 %.
[IEC 62068-1:2003, Definition 3.12, modified]
3.12
rate of impulse voltage rise
impulse voltage magnitude divided by the rise time, defined in 3.11

3.13
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 pulse magnitude.
3.14
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
3.15
impulse duty cycle
ratio, for a given time interval, of the impulse width to the total time
3.16
peak partial discharge magnitude
largest magnitude of any quantity related to PD pulses permitted in a test object at a specified
voltage following a specified conditioning and test
[IEC 60270:2000, Definition 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 should
normally 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, the detector circuit shall
be of the ultra-wide band (UWB) type (see 4.6. of IEC 60270, i.e. >400 kHz), where the
operating detection range is such that the exciting impulse voltage is strongly suppressed
while the PD pulse is not significantly suppressed. IEC 60270 does not suggest specific ultra-
wide band detection methods. For the purposes of this technical specification, specific
detection methods are required. Types of couplers other than conventional capacitors are
permitted in this document.
TS 61934  IEC:2006(E) – 9 –
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.
In this technical specification, PD readings are reported in units of mV. In any case, a
sensitivity evaluation of the measuring system is necessary and should 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 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.
4.3.2 Inductive test objects
Types of inductive test objects may include
• stator and rotor windings;
• transformer windings;
• motorettes and formettes (see IEC 60034).
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 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.

– 10 – TS 61934  IEC:2006(E)
4.4 Effect of testing conditions
4.4.1 General
PD pulses can occur during the rise time of a voltage impulse or the remaining period of the
impulse. PD depends on the testing conditions, including supply voltage impulse,
environmental factors, as well as from ageing extent. For this reason, comparative
evaluations should be carried out using test circuits and generators having the same
characteristics (see IEC 62068-1), and comparable environmental conditions. Measurement of
PD quantities at different times during the service life of a test object can be used as a
diagnos
...