SIST EN 60270:2002

SLOVENSKI STANDARD
01-september-2002
High-voltage test techniques - Partial discharge measurement (IEC 60270:2000)
High-voltage test techniques - Partial discharge measurements
Hochspannungs-Prüftechnik - Teilentladungsmessungen
Techniques des essais à haute tension - Mesure des décharges partielles
Ta slovenski standard je istoveten z: EN 60270:2001
ICS:
17.220.20 0HUMHQMHHOHNWULþQLKLQ Measurement of electrical
PDJQHWQLKYHOLþLQ and magnetic quantities
19.080 (OHNWULþQRLQHOHNWURQVNR Electrical and electronic
SUHVNXãDQMH testing
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN 60270
NORME EUROPÉENNE
EUROPÄISCHE NORM March 2001
ICS 17.220.20;19.080
English version
High-voltage test techniques -
Partial discharge measurements
(IEC 60270:2000)
Technique des essais à haute tension - Hochspannungs-Prüftechnik -
Mesure des décharges partielles Teilentladungsmessungen
(CEI 60270:2000) (IEC 60270:2000)
This European Standard was approved by CENELEC on 2000-12-01. CENELEC members are bound
to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,
Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway,
Portugal, Spain, Sweden, Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2001 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60270:2001 E
Foreword
The text of document 42/162/FDIS, future edition 3 of IEC 60270, prepared by IEC TC 42, High-
voltage testing techniques, was submitted to the IEC-CENELEC parallel vote and was approved by
CENELEC as EN 60270 on 2000-12-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2001-10-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2003-12-01
Annexes designated "normative" are part of the body of the standard.
Annexes designated "informative" are given for information only.
In this standard, annexes A and ZA are normative and annexes B to G are informative.
Annex ZA has been added by CENELEC.
The words in bold in the text of the standard are defined in clause 3.
__________
Endorsement notice
The text of the International Standard IEC 60270:2000 was approved by CENELEC as a European
Standard without any modification.
__________
- 3 - EN 60270:2001
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of
any of these publications apply to this European Standard only when incorporated in it by
amendment or revision. For undated references the latest edition of the publication referred to
applies (including amendments).
NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
1) 2)
IEC 60060-1 High-voltage test techniques HD 588.1 S1 1991
Part 1: General definitions and test
requirements
1) 2)
IEC 60060-2 Part 2: Measuring systems EN 60060-2 1994
CISPR 16-1 1993 Specification for radio disturbance and--
immunity measuring apparatus and
methods
Part 1: Radio disturbance and immunity
measuring apparatus
1)
undated reference.
2)
valid edition at date of issue.

INTERNATIONAL IEC
STANDARD 60270
Third edition
2000-12
High-voltage test techniques –
Partial discharge measurements
© IEC 2000 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.
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Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
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Международная Электротехническая Комиссия
For price, see current catalogue

60270 © IEC:2000 – 3 –
CONTENTS
Page
FOREWORD . 9
Clause
1 Scope . 13
2 Normative references . 15
3 Definitions. 15
4 Test circuits and measuring systems . 25
4.1 General requirements. 25
4.2 Test circuits for alternating voltages . 25
4.3 Measuring systems for apparent charge . 27
4.3.1 General. 27
4.3.2 Coupling device. 27
4.3.3 Pulse train response of instruments for the measurement
of apparent charge . 27
4.3.4 Wide-band PD instruments. 29
4.3.5 Wide-band PD instruments with active integrator . 31
4.3.6 Narrow-band PD instruments. 31
4.4 Requirements for measurements with digital PD-instruments. 31
4.4.1 Requirements for measurement of apparent charge q. 33
4.4.2 Requirements for measurement of test voltage magnitude and phase . 33
4.5 Measuring systems for derived quantities . 33
4.5.1 Coupling device. 33
4.5.2 Instruments for the measurement of pulse repetition rate n . 33
4.5.3 Instruments for the measurement of average discharge current I . 35
4.5.4 Instruments for the measurement of discharge power P. 35
4.5.5 Instruments for the measurement of quadratic rate D. 35
4.5.6 Instruments for the measurement of the radio disturbance voltage . 35
4.6 Ultra-wide-band instruments for PD detection . 37
5 Calibration of a measuring system in the complete test circuit. 37
5.1 General. 37
5.2 Calibration procedure. 37
6 Calibrators . 39
6.1 General. 39
6.2 Calibrators for the calibration of a measuring system in the complete test circuit. 39
6.3 Calibrators for performance tests on measuring systems . 41

60270 © IEC:2000 – 5 –
Clause Page
7 Maintaining the characteristics of calibrators and measuring systems . 41
7.1 Schedule of tests . 41
7.2 Maintaining the characteristics of calibrators . 43
7.2.1 Type tests on calibrators . 43
7.2.2 Routine tests on calibrators . 43
7.2.3 Performance tests on calibrators . 43
7.2.4 Performance checks on calibrators. 43
7.2.5 Record of performance. 45
7.3 Maintaining the characteristics of measuring systems. 45
7.3.1 Type tests on PD measuring systems . 45
7.3.2 Routine tests on measuring systems. 47
7.3.3 Performance tests on measuring systems. 47
7.3.4 Performance checks for measuring systems . 47
7.3.5 Checks for additional capabilities of digital measuring systems . 49
7.3.6 Record of performance. 51
8 Tests . 51
8.1 General requirements. 51
8.2 Conditioning of the test object . 51
8.3 Choice of test procedure . 53
8.3.1 Determination of the partial discharge inception and extinction voltages. 53
8.3.2 Determination of the partial discharge magnitude at a specified
test voltage . 53
9 Measuring uncertainty and sensitivity. 55
10 Disturbances.55
11 Partial discharge measurements during tests with direct voltage . 57
11.1 General. 57
11.2 Quantities related to partial discharges. 57
11.3 Voltages related to partial discharges . 57
11.3.1 Partial discharge inception and extinction voltages . 57
11.3.2 Partial discharge test voltage. 59
11.4 Test circuits and measuring systems . 59
11.5 Tests . 59
11.5.1 Choice of test procedures. 59
11.5.2 Disturbances . 59
Annex A (normative)  Performance test on a calibrator. 71
Annex B (informative) Test circuits . 77
Annex C (informative) Measurements on cables, gas insulated switchgear, power
capacitors and on test objects with windings . 81
Annex D (informative) The use of radio disturbance (interference) meters for
the detection of partial discharges. 83
Annex E (informative) Guidelines to digital acquisition of partial discharge quantities. 87
Annex F (informative) Non-electrical methods of PD detection . 93
Annex G (informative) Disturbances. 95

60270 © IEC:2000 – 7 –
Page
Figure 1 – Basic partial discharge test circuits. 63
Figure 2 – Test circuit for measurement at a tapping of a bushing . 65
Figure 3 – Test circuit for measuring self-excited test objects. 65
Figure 4 – Connections for the calibration of the complete test arrangement . 69
Figure 5 – Correct relationship between amplitude and frequency to minimize integration
errors for a wide-band system. 69
Figure A.1 – Calibration of pulse calibrators . 75
Figure D.1 – Variation of CISPR radio disturbance meter reading f(N) with repetition
frequency N, for constant pulses. 85
Figure E.1 – Output voltage signals U of two different PD measuring systems
out
for apparent charge (double pulse) . 91
Table 1 – Pulse train response of PD instruments . 29
Table 2 – Tests required for calibrators. 45
Table 3 – Tests required for measuring systems . 49

60270 © IEC:2000 – 9 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
HIGH-VOLTAGE TEST TECHNIQUES –
PARTIAL DISCHARGE MEASUREMENTS
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International Organization
for Standardization (ISO) in accordance with conditions determined by agreement between the two
organizations.
2) The formal decisions or agreements of the 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 National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60270 has been prepared by IEC technical committee 42: High-
voltage test techniques.
This third edition cancels and replaces the second edition published in 1981 of which it
constitutes a technical revision.
The text of this standard is based on the following documents:
FDIS Report on voting
42/162/FDIS 42/165/RVD
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 3.
Annex A forms an integral part of this standard.
Annexes B, C, D, E, F and G are for information only.
bold roman type
Terms used throughout this standard which have been defined in clause 3: .

60270 © IEC:2000 – 11 –
The committee has decided that the contents of this publication will remain unchanged until
2008. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
The contents of the corrigendum of October 2001 have been included in this copy.

60270 © IEC:2000 – 13 –
HIGH-VOLTAGE TEST TECHNIQUES –
PARTIAL DISCHARGE MEASUREMENTS
1 Scope
This International Standard is applicable to the measurement of partial discharges which
occur in electrical apparatus, components or systems when tested with alternating voltages up
to 400 Hz or with direct voltage.
This standard
– defines the terms used;
– defines the quantities to be measured;
– describes test and measuring circuits which may be used;
– defines analogue and digital measuring methods required for common applications;
– specifies methods for calibration and requirements of instruments used for calibration;
– gives guidance on test procedures;
– gives some assistance concerning the discrimination of partial discharges from external
interference.
The provisions of this standard should be used in the drafting of specifications relating to
partial discharge measurements for specific power apparatus. It deals with electrical
measurements of impulsive (short-duration) partial discharges, but reference is also made to
non-electrical methods primarily used for partial discharge location (see annex F).
Diagnosis of the behaviour of specific power apparatus can be aided by digital processing of
partial discharge data (see annex E) and also by non-electrical methods that are primarily
used for partial discharge location (see annex F).
This standard is primarily concerned with electrical measurements of partial discharges made
during tests with alternating voltage, but specific problems which arise when tests are made
with direct voltage are considered in clause 11.
The terminology, definitions, basic test circuits and procedures often also apply to tests with
other frequencies, but special test procedures and measuring system characteristics, which are
not considered in this standard, may be required.
Annex A provides normative requirements for performance tests on calibrators.

60270 © IEC:2000 – 15 –
2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this International Standard. For dated references, subsequent
amendments to, or revisions of, any of these publications do not apply. However, parties to
agreements based on this International Standard are encouraged to investigate the possibility
of applying the most recent editions of the normative documents indicated below. For undated
references, the latest edition of the normative document referred to applies. Members of IEC
and ISO maintain registers of currently valid International Standards.
IEC 60060-1, High-voltage test techniques – Part 1: General definitions and test requirements.
IEC 60060-2, High-voltage test techniques – Part 2: Measuring systems
CISPR 16-1:1993, Specification for radio disturbance and immunity measuring apparatus and
methods – Part 1: Radio disturbance and immunity measuring apparatus
3 Definitions
For the purpose of this International Standard, the following definitions apply.
3.1
partial discharge (PD)
localized electrical discharge that only partially bridges the insulation between conductors and
which can or can not occur adjacent to a conductor
NOTE 1 Partial discharges are in general a consequence of local electrical stress concentrations in the
insulation or on the surface of the insulation. Generally, such discharges appear as pulses having a duration of
much less than 1 µs. More continuous forms can, however, occur, such as the so-called pulse-less discharges in
gaseous dielectrics. This kind of discharge will normally not be detected by the measurement methods described in
this standard.
NOTE 2 "Corona" is a form of partial discharge that occurs in gaseous media around conductors which are
remote from solid or liquid insulation. "Corona" should not be used as a general term for all forms of PD.
NOTE 3 Partial discharges are often accompanied by emission of sound, light, heat, and chemical reactions.
For further information, see annex F.
3.2
partial discharge pulse (PD pulse)
current or voltage pulse that results from a partial discharge occurring within the object under
test. The pulse is measured using suitable detector circuits, which have been introduced into
the test circuit for the purpose of the test
NOTE A partial discharge which occurs in the test object produces a current pulse. A detector in accordance with
the provisions of this standard produces a current or a voltage signal at its output, proportional to the charge of the
current pulse at its input.
60270 © IEC:2000 – 17 –
3.3
quantities related to partial discharge pulses
3.3.1
apparent charge q
of a PD pulse is that charge which, if injected within a very short time between the terminals of
the test object in a specified test circuit, would give the same reading on the measuring
instrument as the PD current pulse itself. The apparent charge is usually expressed in
picocoulombs (pC)
NOTE The apparent charge is not equal to the amount of charge locally involved at the site of the discharge,
which cannot be measured directly.
3.3.2
pulse repetition rate n
ratio between the total number of PD pulses recorded in a selected time interval and the
duration of this time interval
NOTE In practice, only pulses above a specified magnitude or within a specified range of magnitudes are
considered.
3.3.3
pulse repetition frequency N
number of partial discharge pulses per second, in the case of equidistant pulses
NOTE Pulse repetition frequency N is associated with the situation in calibration.
3.3.4
phase angle φ and time t of occurrence of a PD pulse
i i
is
φ = 360 (t /T)
i i
where t is the time measured between the preceding positive going transition of the test
i
voltage through zero and the partial discharge pulse and T is the period of the test voltage
The phase angle is expressed in degrees (°).
3.3.5
average discharge current I
derived quantity and the sum of the absolute values of individual apparent charge magnitudes
q during a chosen reference time interval T divided by this time interval:
i ref
I =()q + q + . + q
2 i
T
ref
The average discharge current is generally expressed in coulombs per second (C/s) or in
amperes (A).
60270 © IEC:2000 – 19 –
3.3.6
discharge power P
derived quantity that is the average pulse power fed into the terminals of the test object due to
apparent charge magnitudes q during a chosen reference time interval T :
i ref
P =()q u + q u + . + q u
1 1 2 2 i i
T
ref
where u , u . u are instantaneous values of the test voltage at the instants of occurrence t of
1 2 i i
the individual apparent charge magnitudes q . The sign of the individual values must be
i
observed
The discharge power is generally expressed in watts (W).
3.3.7
quadratic rate D
derived quantity that is the sum of the squares of the individual apparent charge magnitudes
q during a chosen reference time interval T divided by this time interval:
i ref
2 2 2
D =()q + q + . + q
m
1 2
T
ref
2 2
The quadratic rate is generally expressed in (coulombs) per second (C /s).
3.3.8
radio disturbance meter
quasi-peak measuring receiver for frequency band B in accordance with the provisions of
CISPR 16-1:1993
NOTE This type of instrument was earlier called a radio interference (or influence) meter.
3.3.9
radio disturbance voltage U
RDV
derived quantity that is the reading of a radio disturbance meter when used for indicating the
apparent charge q of partial discharges. For further information, see 4.5.6 and annex D
The radio disturbance voltage U is generally expressed in µV.
RDV
3.4
largest repeatedly occurring PD magnitude
largest magnitude recorded by a measuring system which has the pulse train response as
specified in 4.3.3
The concept of the largest repeatedly occurring PD magnitude is not applicable to tests with
direct voltage.
3.5
specified 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 procedure. For alternating voltage tests, the
specified magnitude of the apparent charge q is the largest repeatedly occurring PD
magnitude
NOTE The magnitude of any PD pulse quantity can vary stochastically in successive cycles and also show a
general increase or decrease with time of voltage application. The specified PD magnitude, the test procedure and
also the test circuit and instrumentation should therefore be appropriately defined by the relevant technical
committees.
60270 © IEC:2000 – 21 –
3.6
background noise
signals detected during PD tests, which do not originate in the test object
NOTE Background noise can be composed of either white noise in the measurement system, broadcast radio or
other continuous or impulsive signals. For further information, see annex G.
3.7
applied test voltages related to partial discharge pulse quantities
as defined in IEC 60060-1. The following voltage levels are of particular interest
3.7.1
partial discharge inception voltage U
i
applied voltage at which repetitive partial discharges are first observed in the test object,
when the voltage applied to the object is gradually increased from a lower value at which no
partial discharges are observed
In practice, the inception voltage U is the lowest applied voltage at which the magnitude of a
i
PD pulse quantity becomes equal to or exceeds a specified low value.
NOTE For tests with direct voltage, the determination of U needs special considerations. See clause 11.
i
3.7.2
partial discharge extinction voltage U
e
applied voltage at which repetitive partial discharges cease to occur in the test object, when
the voltage applied to the object is gradually decreased from a higher value at which PD pulse
quantities are observed
In practice, the extinction voltage U is the lowest applied voltage at which the magnitude of a
e
chosen PD pulse quantity becomes equal to, or less than, a specified low value.
NOTE For tests with direct voltage, the determination of U needs special considerations. See clause 11.
e
3.7.3
partial discharge test voltage
specified voltage, applied in a specified partial discharge test procedure, during which the test
object should not exhibit PD exceeding a specified partial discharge magnitude
3.8
partial discharge measuring system
system consisting of a coupling device, a transmission system and a measuring instrument
3.9
measuring system characteristics
The following definitions refer to measuring systems as specified in 4.3
3.9.1
transfer impedance Z(f)
ratio of the output voltage amplitude to a constant input current amplitude, as a function of
frequency f, when the input is sinusoidal

60270 © IEC:2000 – 23 –
3.9.2
lower and upper limit frequencies f and f
1 2
frequencies at which the transfer impedance Z(f) has fallen by 6 dB from the peak pass-band
value
3.9.3
midband frequency f and bandwidth ∆f
m
for all kinds of measuring systems, the midband frequency is defined by:
f + f
1 2
f =
m
and the bandwidth is defined by:
∆f = f – f
2 1
3.9.4
superposition error
caused by the overlapping of transient output pulse responses when the time interval between
input current pulses is less than the duration of a single output response pulse. Superposition
errors can be additive or subtractive depending on the pulse repetition rate of the input
pulses. In practical circuits, both types will occur due to the random nature of the pulse
repetition rate. However, since measurements are based on the largest repeatedly
occurring PD magnitude, usually only the additive superposition errors will be measured
NOTE Superposition errors can attain levels of 100 % or more depending on the pulse repetition rate and the
characteristics of the measuring system.
3.9.5
pulse resolution time T
r
shortest time interval between two consecutive input pulses of very short duration, of same
shape, polarity and charge magnitude for which the peak value of the resulting response will
change by not more than 10 % of that for a single pulse
The pulse resolution time is in general inversely proportional to the bandwidth ∆f of the
measuring system. It is an indication of the measuring system's ability to resolve successive
PD events.
NOTE It is recommended that the pulse resolution time be measured for the whole test circuit, as well as for the
measuring system, as superposition errors can be caused by the test object, for example reflections from cable
ends. The relevant technical committees should specify the procedure for handling superposition errors and
particularly, the allowable tolerances including their signs.
3.9.6
integration error
error in apparent charge measurement which occurs when the upper frequency limit of the PD
current pulse amplitude-spectrum is lower than
• the upper cut-off frequency of a wideband measuring system; or
• the mid-band frequency of a narrow-band measuring system.
See figure 5.
NOTE If required for a special type of apparatus, the relevant technical committees are urged to specify more
restrictive values for f and f to minimize the integration error.
1 2
60270 © IEC:2000 – 25 –
3.10
digital partial discharge instruments
considered in this standard are in general based on analogue measuring systems or
instruments for the measurement of apparent charge q, followed by a digital acquisition and
processing system. The digital part of a digital PD-instrument is used to process analogue
signals for further evaluation, to store relevant quantities and to display test results. See also
annex E.
NOTE A digital PD-instrument can also be based on a coupling device and a digital acquisition system without
the analogue signal processing front end. This standard does not provide specific information applicable to this type
of instrument.
3.11
scale factor k
factor by which the value of the instrument reading is to be multiplied to obtain the value of the
input quantity (IEC 60060-2:1994, 3.5.1)
4 Test circuits and measuring systems
4.1 General requirements
In this clause, basic test circuits and measuring systems for partial discharge quantities are
described, and information on the operating principle of these circuits and systems is provided.
The test circuit and measuring system shall be calibrated as specified in clause 5 and shall
meet the requirements specified in clause 7. The technical committee may also recommend a
particular test circuit to be used for particular test objects. It is recommended that the technical
committees use apparent charge as the quantity to be measured wherever possible, but other
quantities may be used in particular specific situations.
If not otherwise specified by the relevant technical committee, any of the test circuits
mentioned in 4.2 and any of the measuring systems as specified in 4.3 are acceptable. In each
case, the most significant characteristics of the measuring system (f , f , T , see 3.9.2
1 2 r
and 3.9.5) as applied, shall be recorded.
For tests with direct voltage, see clause 11.
4.2 Test circuits for alternating voltages
Most circuits in use for partial discharge measurements can be derived from one or other of
the basic circuits, which are shown in figures 1a to 1d. Some variations of these circuits are
shown in figures 2 and 3. Each of these circuits consists mainly of
– a test object, which can usually be regarded as a capacitor C (see, however, annex C);
a
– a coupling capacitor C , which shall be of low inductance design, or a second test object
k
C , which shall be similar to the test object C . C or C should exhibit a sufficiently low
a1 a k a1
level of partial discharges at the specified test voltage to allow the measurement of the
specified partial discharge magnitude. A higher level of partial discharges can be
tolerated if the measuring system is capable of distinguishing the discharges from the test
object and the coupling capacitor and measuring them separately;
– a measuring system with its input impedance (and sometimes, for balanced circuit arrange-
ments, a second input impedance);

60270 © IEC:2000 – 27 –
– a high-voltage supply, with sufficiently low level of background noise (see also clauses 9
and 10) to allow the specified partial discharge magnitude to be measured at the
specified test voltage;
– high-voltage connections, with sufficiently low level of background noise (see also
clauses 9 and 10) to allow the specified partial discharge magnitude to be measured at
the specified test voltage;
– an impedance or a filter can be introduced at high voltage to reduce background noise
from the power supply.
NOTE For each of the basic PD test circuits shown in figures 1 and 3, the coupling device of the measuring
system can also be placed at the high-voltage terminal side, so that the positions of the coupling device with C or
a
C are exchanged; then, optical links are used for the interconnection of the coupling device with the instrument, as
k
indicated in figure 1a.
Additional information and particular characteristics of the different test circuits are considered
in annexes B and G.
4.3 Measuring systems for apparent charge
4.3.1 General
Partial discharge measuring systems can be divided into the subsystems: coupling device,
transmission system (for example, connecting cable or optical link) and measuring instrument.
In general, the transmission system does not contribute to the circuit characteristics and will
thus not be taken into consideration.
4.3.2 Coupling device
The coupling device is an integral part of the measuring system and test circuit, with
components specifically designed to achieve the optimum sensitivity with a specific test circuit.
Different coupling devices may thus be used in conjunction with a single measuring instrument.
The coupling device is usually an active or passive four-terminal network (quadripole) and
converts the input currents to output voltage signals. These signals are transmitted to the
measuring instrument by a transmission system. The frequency response of the coupling
device, defined by output voltage to input current, is normally chosen at least so as to
effectively prevent the test voltage frequency and its harmonics from reaching the instrument.
NOTE 1 Though the frequency response of an individual coupling device is not of general interest, the magnitude
and frequency characteristics of the input impedance are of importance as this impedance interacts with C and C
k a
and is thus an essential part of the test circuit.
NOTE 2 Interconnection leads between the coupling device and the test object should be kept as short as
practical so as to minimize effects on the detection bandwidth.
4.3.3 Pulse train response of instruments for the measurement of apparent charge
Provided the amplitude frequency spectrum of the input pulses is constant at least within the
bandwidth ∆f of the measuring system (see figure 5), the response of the instrument is a
voltage pulse with a peak value proportional to the (unipolar) charge of the input pulse. The
shape, duration and the peak value of this output pulse are determined by the transfer
impedance Z(f) of the measuring system. Thus, the shape and duration of the output pulse
can be completely different from that of the input signal.

60270 © IEC:2000 – 29 –
Display of the individual output voltage pulses on the screen of an oscilloscope can assist in
recognizing the origin of partial discharges and in distinguishing them from disturbances (see
clause 10). The voltage pulses should be displayed either on a linear time-base which is
triggered by the test voltage, or on a sinusoidal time base synchronized with the test voltage
frequency or an elliptical time-base which rotates synchronously with the test voltage
frequency.
In addition, it is particularly recommended that an indicating instrument or recorder should be
used to quantify the largest repeatedly occurring PD magnitude. The reading of such
instruments, when used in testing with alternating voltage, should be based on an analogue
peak detection circuit, or digital peak detection by software, with a very short electrical charge
time constant and an electrical discharge time constant not larger than 0,44 s. Independent of
the type of display used in such instruments, the following requirements apply:
The response of the system to a pulse train consisting of equally large equidistant pulses q
with a known pulse repetition frequency N, shall be such that the reading R of the instrument
indicates magnitudes as given in the following table. The range and gain of the instrument is
assumed to be adjusted to read full scale or 100 % for N = 100. The calibrator used to produce
the pulses shall conform to the requirements of clause 5.
Table 1 – Pulse train response of PD instruments
N (1/s): 1 2 5 10 50
≥100
R (%): 35 55 76 85 94 95
min
R (%): 45 65 86 95 104 105
max
NOTE 1 This characteristic is necessary to establish compatibility of readings obtained with different types of
instruments. The requirement is to be fulfilled on all ranges. Instruments already in use at the date of issue of this
standard are not required to comply with these requirements; however, the actual values for R(N) should be given.
NOTE 2 The measured quantity can be indicated, for example, on pointer instruments, digital displays or
oscilloscopes.
NOTE 3 The specified response may be obtained either by analogue or by digital signal processing.
NOTE 4 The pulse train response defined in this subclause is not appropriate for direct voltage tests.
NOTE 5 The relevant technical committee may specify a different response tailored to a particular apparatus.
4.3.4 Wide-band PD instruments
In combination with the coupling device, this type of instrument constitutes a wide-band PD
measuring system which is characterized by a transfer impedance Z(f) having fixed values
of the lower and upper limit frequencies f and f , and adequate attenuation below f and
1 2 1
above f . Recommended values for f , f and ∆f are
2 1 2
30 kHz ≤ f ≤ 100 kHz;
f ≤ 500 kHz;
100 kHz ≤ ∆f ≤ 400 kHz.
NOTE Combinations of different coupling devices with the measuring instrument can alter the transfer
impedance. The overall response should, however, always fulfil the recommended values.

60270 © IEC:2000 – 31 –
The response of these instruments to a (non-oscillating) partial discharge current pulse is in
general a well-damped oscillation. Both the apparent charge q and polarity of the PD current
pulse can be determined from this response. The pulse resolution time T is small and is
r
typically 5 µs to 20 µs.
4.3.5 Wide-band PD instruments with active integrator
This type of instrument consists of a very wide-band amplifier followed by an electronic
integrator which is characterized by the time constant of its integrating capacitor and resistor
network. The response of the integrator to a PD pulse is a voltage signal increasing with the
instantaneous sum of charge. The final amplitude of the signal is thus proportional to the total
charge, assuming that the time constant of the integrator is much larger than the duration
of the PD pulse. In practice, time constants in the range of 1 µs are typical. The pulse
resolution time for consecutive PD pulses is less than 10 µs.
NOTE A corresponding upper limit frequency of some hundred kilohertz can be attributed to such instruments,
calculated from the time constant of the combination of the amplifier and active integrator.
4.3.6 Narrow-band PD instruments
These instruments are characterized by a small bandwidth ∆f and a midband frequency f ,
m
which can be varied over a wide frequency range, where the amplitude frequency spectrum of
the PD current pulse is approximately constant. Recommended values for ∆f and f are
m
9 kHz ≤ ∆f ≤ 30 kHz
50 kHz ≤ f ≤ 1 MHz.
m
It is further recommended that the transfer impedance Z(f) at frequencies of f ± ∆f should be
m
20 dB below the peak pass-band value.
NOTE 1 During actual apparent charge measurements, midband frequencies f > 1 MHz should only be applied
m
if the readings for such higher values do not differ from those as monitored for the recommended values of f .
m
NOTE 2 In general, such instruments are used together with coupling devices providing high-pass characteristics
f
within the frequency range of the instrument. If resonance coupling devices are used, has to be tuned and fixed
m
to the resonance frequency of the coupling device and the test circuit to provide a constant scale factor of the
circuit.
NOTE 3 Radio disturbance meters with quasi-peak response are not qualified under this standard for the
measurement of the apparent
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