IEC 60270:2025

IEC 60270 ®
Edition 4.0 2025-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
High-voltage test techniques – Charge-based measurement of partial discharges

Techniques des essais à haute tension – Mesurages des décharges partielles
fondés sur les charges
ICS 19.080, 17.220.20 ISBN 978-2-8327-0398-4

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– 2 – IEC 60270:2025 © IEC 2025
CONTENTS
FOREWORD . 6
1 Scope . 8
2 Normative references. 8
3 Terms and definitions . 9
4 Test circuits and measuring systems . 14
4.1 General requirements . 14
4.2 Test circuits for alternating voltages . 15
4.3 Measuring systems for apparent charge . 18
4.3.1 General . 18
4.3.2 Coupling device or ‘quadripole’ . 18
4.3.3 Pulse train response of instruments for the measurement of apparent
charge . 18
4.3.4 Wide-band PD measuring systems . 20
4.3.5 Wide-band PD instruments with active integrator . 20
4.3.6 Narrow-band PD instruments . 21
4.4 Requirements for measurements with digital PD-instruments . 21
4.4.1 General . 21
4.4.2 Requirements for measurement of apparent charge q . 22
4.4.3 Requirements for measurement of test voltage magnitude and phase . 22
4.5 Measuring systems for derived quantities . 22
4.5.1 Coupling device . 22
4.5.2 Instruments for the measurement of pulse repetition rate n . 22
4.5.3 Instruments for the measurement of average apparent discharge
current I . 22
4.5.4 Instruments for the measurement of apparent discharge power P . 23
4.6 Instruments for the measurement of the radio disturbance voltage. 23
4.7 Instrumentation for PD detection >1 MHz . 23
5 Calibration of a measuring system in the complete test circuit . 24
5.1 General . 24
5.2 Calibration procedure . 24
6 Calibrators. 26
6.1 General . 26
6.2 Calibrators for the calibration of a measuring system in the complete test
circuit . 27
6.3 Calibrators for performance tests on measuring systems . 28
7 Maintaining the characteristics of calibrators and measuring systems . 28
7.1 General . 28
7.2 Schedule of tests . 28
7.3 Maintaining the characteristics of calibrators . 29
7.3.1 Type tests on calibrators . 29
7.3.2 Routine tests on calibrators . 29
7.3.3 Performance tests on calibrators . 29
7.3.4 Performance checks on calibrators . 29
7.3.5 Record of performance . 30
7.4 Maintaining the characteristics of PD measuring systems . 30
7.4.1 General . 30
7.4.2 Type tests on PD measuring systems . 30

7.4.3 Routine tests on measuring systems . 31
7.4.4 Performance checks on PD measuring systems . 31
7.4.5 Checks for additional capabilities of digital measuring systems . 32
7.4.6 Record of performance . 32
8 Partial discharge measurements during tests with alternating voltage . 33
8.1 General . 33
8.2 Conditioning of the test object . 33
8.3 Choice of test procedure . 33
8.3.1 General . 33
8.3.2 Determination of the partial discharge inception and extinction voltages . 34
8.3.3 Determination of the partial discharge magnitude at a specified test
voltage . 34
9 Measuring uncertainty and sensitivity . 34
10 External disturbances and interference . 35
11 Partial discharge measurements during tests with direct voltage . 36
11.1 General . 36
11.2 PD quantities . 36
11.3 Voltages related to partial discharges . 37
11.3.1 Partial discharge inception and extinction voltages . 37
11.3.2 Partial discharge test voltage . 37
11.4 Test circuits and measuring systems . 37
11.5 Test procedures with regard to external disturbances . 37
11.5.1 Choice of test procedures . 37
11.5.2 Disturbances . 38
Annex A (normative) Performance tests on calibrators . 39
A.1 General . 39
A.2 Comparison method . 41
A.3 Numerical integration method . 41
A.4 Passive integration method . 43
A.5 Active integration method . 44
Annex B (informative) Test circuits . 46
Annex C (informative) Measurements on test objects with distributed or inductive
characteristics such as cables, gas-insulated switchgear, power capacitors, and on test
objects with windings: alternative methods . 48
C.1 General . 48
C.2 Attenuation and distortion phenomena . 50
C.3 Resonance phenomena, reflections . 51
C.4 Location of discharges . 51
Annex D (informative) The use of radio disturbance (interference) meters for the
detection of partial discharges . 52
Annex E (informative) PD measuring instruments . 54
E.1 General concept . 54
E.2 Correct acquisition of (charge) amplitude and polarity of PD signals . 57
E.3 Recommendations for recording test voltage, phase angle φ and time t of
i i
occurrence of a PD pulse . 58
E.4 Phase-resolved partial discharge (PRPD) pattern display algorithm . 59

– 4 – IEC 60270:2025 © IEC 2025
Annex F (informative) Alternative methods of PD detection . 61
F.1 General . 61
F.2 Electromagnetic detection . 61
F.3 Acoustic detection . 61
F.4 Chemical detection . 61
F.5 Optical detection . 62
Annex G (informative) Disturbances – Interference and noise . 63
G.1 Sources of disturbances . 63
G.2 Detecting disturbances . 63
G.3 Disturbance levels . 64
G.4 Suggestions for reducing disturbances . 64
G.4.1 Basic earthing, bonding, and filtering . 64
G.4.2 Balanced circuits . 64
G.4.3 Electronic signal processing . 65
G.5 Further interference mitigation methods . 66
Annex H (informative) Evaluation of PD test results during tests with direct voltage . 67
Bibliography . 69

Figure 1 – Basic partial discharge test circuits . 16
Figure 2 – Test circuit for measurement at a bushing tap . 17
Figure 3 – Test circuit for measuring self-excited test objects . 17
Figure 4 – Correct relationship between amplitude and frequency to minimize
integration errors for a wide-band system . 19
Figure 5 – Connections for the calibration of the complete test arrangement . 25
Figure 6 – Output waveform of the calibrator step voltage generator . 26
Figure 7 – Minimum realistic specified PD magnitude versus noise level . 35
Figure A.1 – Measurement of calibrator characteristics . 39
Figure A.2 – Indicative range of applicability for different methods . 40
Figure A.3 – Performance test of calibrator using the numerical integration method . 41
Figure A.4 – Calibration pulses u (t) of a typical calibrator using integration
m
resistances R = 33 Ω and R = 200 Ω respectively (q = 100 pC) . 42
m m
Figure A.5 – Performance test of calibrator using the passive integration method . 43
Figure A.6 – Performance test of calibrator using the active integration method . 44
Figure C.1 – Partial discharge measurements in different test objects versus frequency . 49
Figure D.1 – CISPR radio disturbance meter readings . 53
Figure E.1 – Block diagram of an analog PD instrument equipped with an electronic
integrator . 54
Figure E.2 – Block diagrams of digital PD instruments . 55
Figure E.3 – Conceptual diagram of phase-resolved PD pattern (PRPD) . 56
Figure E.4 – Detection of PD pulse amplitude and polarity . 58
Figure E.5 – Examples of some phase-resolved PRPD patterns . 60
Figure H.1 – Display modes of apparent pulses against measuring time . 67
Figure H.2 – Histograms of PD pulse count n against apparent charge intervals . 68

Table 1 – Pulse train response of PD instruments . 19
Table 2 – Tests required for calibrators . 30
Table 3 – Tests required for measuring systems . 32
Table A.1 – Three methods for determining PD calibrator output charge . 40
Table C.1 – PD measurement application areas with selected references. 49

– 6 – IEC 60270:2025 © IEC 2025
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
HIGH-VOLTAGE TEST TECHNIQUES – CHARGE-BASED
MEASUREMENT OF PARTIAL DISCHARGES

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
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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) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
respect thereof. As of the date of publication of this document, IEC had not received notice of (a) patent(s), which
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the latest information, which may be obtained from the patent database available at https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
IEC 60270 has been prepared by IEC technical committee 42: High-voltage and high-current
test techniques. It is an International Standard.
This fourth edition cancels and replaces the third edition published in 2000 and
Amendment 1:2015. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) Title modified.
b) Use with alternating voltages up to 500 Hz or with direct voltage.
c) Clear focus on charge-based partial discharge measurements.
d) Streamlined performance checks for partial discharge measurement system components.
e) Improved normative Annex A for performance tests on calibrators.
f) Revised and new informative Annexes.

The text of this International Standard is based on the following documents:
Draft Report on voting
42/452/FDIS 42/456/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
In a future revision, this document will seek horizontal publication status in accordance with
IEC Guide 108.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
– 8 – IEC 60270:2025 © IEC 2025
HIGH-VOLTAGE TEST TECHNIQUES – CHARGE-BASED
MEASUREMENT OF PARTIAL DISCHARGES

1 Scope
This document is applicable to the charge-based measurement of partial discharges which
occur in electrical apparatus, components or systems when tested with alternating voltages
(AC) up to 500 Hz or with direct voltage (DC).
This document:
– defines the terms used;
– defines the quantities to be measured;
– describes the measurement frequencies as well as the 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 document are 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 document is primarily concerned with electrical measurement of partial discharge in terms
of apparent charge for specific power apparatus 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 at other
PD measurement frequencies, but special test procedures and measuring system
characteristics which are not considered in this document may be required. For measurements
at higher frequency ranges, see IEC TS 62478 [5] .
Annex A provides normative requirements for performance tests on calibrators.
NOTE This document defines and provides guidance for charge-based direct electrical PD measurements at the
terminals of the equipment under test, differentiating from other PD measurement and detection methods, e.g.
acoustic PD techniques or electromagnetic methods in elevated frequency ranges, e.g. ultra-high frequency (UHF).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
___________
Numbers in square brackets refer to the Bibliography.

For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60060-2, High-voltage test techniques – Part 2: Measuring systems
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1
partial discharge
PD
localized electrical discharge that only partially bridges the insulation between conductors and
which can occur adjacent to a conductor
Note 1 to entry: 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
document.
Note 2 to entry: "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 to entry: Partial discharges are accompanied by emission of acoustic transients (sound), electromagnetic
waves, optical signals (light), heat, and associated chemical reactions. For further information, see Annex F.
3.2
partial discharge pulse
PD pulse
signal produced by a partial discharge occurring within the object under test, measured using
suitable detector circuits introduced into the test circuit
Note 1 to entry: A partial discharge which occurs in the test object produces a current pulse at its origin. A detector
in accordance with the provisions of this document produces a current or a voltage signal at its output proportional
to the charge of the PD pulse.
3.3
quantities related to partial discharge pulses
3.3.1
apparent charge
q
charge which, if injected between the terminals of the test object in a specified
test circuit, would result in the same reading on the measuring instrument as the PD pulse itself,
typically expressed in units of picocoulombs (pC) or nanocoulombs (nC)
Note 1 to entry: The apparent charge is not equal to the amount of charge locally involved at the site of the
discharge, which cannot be measured directly.

– 10 – IEC 60270:2025 © IEC 2025
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 1 to entry: 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
3.3.4
phase angle φ and time t
i i
given by
φ = 360 (t /T)
i i
where:
t is the time measured between the preceding positive going zero crossing of the test voltage
i
and the partial discharge pulse, and
T is the period of the test voltage, with the phase angle being expressed in degrees (°)
3.3.5
average apparent discharge current
I
derived quantity consisting of 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 qq+++. q
( )
12 i
T
ref
Note 1 to entry: Average apparent discharge current is generally expressed in coulombs per second (C/s) or in
amperes (A).
3.3.6
apparent discharge power
P
derived quantity consisting of 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++. qu
( )
11 2 2 ii
T
ref
where u , u . u are the instantaneous values of the test voltage at the instants of occurrence
1 2 i
t of the individual apparent charge magnitudes q ;
i i
Note 1 to entry: The sign of the individual values shall be observed
Note 2 to entry: Apparent discharge power is generally expressed in watts (W).
=
=
3.3.7
radio interference
radio disturbance meter
specialized measurement receiver utilizing weighted quasi-peak RF measurements on
frequency B in accordance with CISPR 16-1
Note 1 to entry: This type of instrument was commonly known as ‘RIV’ or ‘radio interference voltage’ or ‘radio
influence voltage’ meter in earlier times, having been applied to search for HV equipment producing high levels of
corona which in turn would interfere with LW and MW broadcast transmission.
3.3.8
radio disturbance voltage
U
RDV
output reading of a radio interference meter
Note 1 to entry: See 4.6 and Annex D.
Note 2 to entry: Radio disturbance voltage is generally expressed in µV.
3.4
largest repeatedly occurring PD magnitude
Q
IEC
value recorded by a measuring system which has the pulse train response as specified in 4.3.3,
commonly realized by a quasi-peak detector or a digital emulation of such a circuit, applicable
for AC voltages
3.5
peak apparent charge
Q
pk
largest value recorded by a PD measuring system, commonly realized by a peak detector or a
digital emulation of such circuit, applicable for DC voltages
3.6
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
Note 1 to entry: For alternating voltage tests, this is the largest repeatedly occurring apparent charge Q
IEC
Note 2 to entry: 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 equipment
committee(s).
3.7
background noise and interference/disturbances
extraneous signals detected during PD tests, which are not of interest because they are not
signals caused by PD originating in the test object
Note 1 to entry: Background or electrical noise is defined as originating in the PD measurement equipment itself,
e.g. thermal, shot, 1/f noise in resistors and amplifiers.
Note 2 to entry: Interference or disturbances can originate from external sources such as motor drives, thyristor
control circuits, terrestrial AM broadcast stations, etc. Moreover, external interference can also arise due to partial
discharges external to the test object; such PD-like interference can be extremely challenging to differentiate from
PD signals within the test object. Refer to Annex G for further information.
3.8
test voltages related to partial discharge pulse quantities
Note 1 to entry: Voltages as defined in e.g. IEC 60060-1.

– 12 – IEC 60270:2025 © IEC 2025
3.8.1
partial discharge inception voltage
U
i
applied voltage at which repetitive partial discharges are first observed in the test object, after
being gradually increased from a lower value at which no partial discharges are observed
Note 1 to entry: In practice, the lowest applied voltage at which the magnitude of a PD pulse quantity becomes
equal to or exceeds a specified minimum value
Note 2 to entry: For tests with direct voltage, special considerations are necessary for the determination of U . See
i
Clause 11.
3.8.2
partial discharge extinction voltage
U
e
applied voltage at which repetitive partial discharges cease to occur in the test object, after
being gradually decreased from a higher value at which PD pulse quantities are observed
Note 1 to entry: In practice, the applied voltage at which the magnitude of a chosen PD pulse quantity becomes
equal to, or less than, a specified low value
Note 2 to entry: For tests with direct voltage, special considerations are necessary for the determination of U . See
e
Clause 11.
3.8.3
partial discharge test voltage
specified voltage, applied in a specified partial discharge test procedure, during which the test
object shall not produce PD exceeding a specified partial discharge magnitude
Note 1 to entry: Partial discharges are usually measured at AC sinusoidal waveform. In real conditions, the test
voltage also contains harmonics that modify the shape of the voltage waveform and can thus be considered as a
disturbance affecting the PD pulse parameters and PD phase-resolved patterns. Such disturbances should be taken
into account and documented during PD measurements. See Annex G for further information.
3.9
partial discharge measuring system
coupling device, a transmission system and a partial discharge measuring instrument
3.10
measuring system characteristics
3.10.1
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
3.10.2
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
3.10.3
mid-band frequency
f
m
given by:
ff+
f =
m
3.10.4
mid-band frequency bandwidth
∆f
given by:
∆f = f – f
2 1
3.10.5
superposition error
error caused when successive PD pulses overlap one another due to the time interval between
successive pulses being less than the duration (settling time) of a single pulse response
Note 1 to entry: Superposition error is also known as 'pulse pile-up'. See Annex E.
Note 2 to entry: Superposition errors can be additive or subtractive depending on the pulse repetition rate of the
incoming pulses in combination with the transient response of the detector circuit elements. 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 3 to entry: Superposition errors can attain levels of 100 % or more depending on the pulse repetition rate and
the characteristics of the measuring system.
3.10.6
pulse resolution time
t
res
shortest time interval between two consecutive PD pulses within which the PD measurement
instrument is still able to resolve two separate pulses and for which the peak value of the
resulting response does not change by more than 10 % of the value for a single pulse
Note 1 to entry: The pulse resolution time t is an indication of the PD measuring system's ability to resolve
res
successive PD pulses and is inversely proportional to the lower cut-off frequency f of the PD measurement
bandwidth.
Note 2 to entry: 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. Specifying the procedure for handling superposition errors and particularly, the allowable tolerances
including their signs, is the responsibility of the relevant equipment technical committee(s).
3.10.7
dead time
t
DT
time period following successful digital acquisition of a PD pulse during which the instrument
does not accept or acquire signals or neglect detected pulses
Note 1 to entry: Dead time is closely related to pulse resolution time.
Note 2 to entry: Especially for strongly oscillatory input signals, dead time is introduced in order to avoid false or
repeat triggering on successive oscillatory remnants of the same pulse.
3.10.8
noise modulation
superimposition of an actual PD pulse with a simultaneously occurring noise signal leading to
an incorrect registering of the peak amplitude of the PD signal
Note 1 to entry: Such noise modulation occurs when calibrating and measuring low amplitude PD pulses close to
the noise floor and can cause apparent non-linearities in such cases.

– 14 – IEC 60270:2025 © IEC 2025
3.10.9
integration error of apparent charge measurement
error 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 4.
Note 1 to entry: If required for a special type of apparatus, the relevant equipment committee(s) are urged to specify
more restrictive values for f and f to minimize the integration error.
1 2
3.11
digital partial discharge instruments
digital signal processing techniques used for acquisition and evaluation of PD pulses
Note 1 to entry: See Annex E.
3.12
scale factor
k
factor by which the value of the instrument reading is to be multiplied to obtain the value of the
input quantity
Note 1 to entry: In modern digital PD measurement instruments, the scale factor is usually automatically calculated
and set internally. After calibration, the instruments display the result of the multiplication with the internal scale
factor k.
3.13
accumulated apparent charge
q
a
sum of the apparent charge q of all individual pulses exceeding a specified threshold level, and
occurring during a specified time interval ∆t
3.14
PD pulse count
m
total number of PD pulses which exceed a specified threshold level within a specified time
interval ∆t
3.15
phase-resolved PD pattern
PRPD pattern
display of the apparent charge q versus the phase angle φ of the PD pulses recorded during a
i
specified time interval ∆t
Note 1 to entry: See Annex E Figure E.3.
4 Test circuits and measuring systems
4.1 General requirements
Basic test circuits and measuring systems for partial discharge quantities are described in
Clause 4, 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 relevant equipment committee(s) might also recommend a particular test circuit to be used
for particular test objects. It is recommended that the equipment committee(s) use apparent
charge as the quantity to be measured wherever possible, but other derived quantities may be
used in p
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