IEC 60060-1:2010

High-voltage test techniques - Part 1: General definitions and test requirements

IEC 60060-1:2010 applies to dielectric tests with alternating voltage; dielectric tests with direct voltage; dielectric tests with impulse voltage and dielectric tests with combinations of the above. This document is applicable to tests on equipment having its highest voltage for equipment Um above 1 kV. The third edition cancels and replaces the second edition, published in 1989, and constitutes a technical revision. The major technical changes with respect to the previous edition are as follows:
- artifical pollution test procedures were removed as they are now described in IEC 60507,
- measurement of impulse current has been transferred to a new standard on current measurement (IEC 62475),
- the atmospheric correction factors are now presented as formulas.

Technique des essais à haute tension - Partie 1: Définitions et exigences générales

La CEI 60060-1:2010 S'applique aux essais diélectriques en tension alternative, aux essais diélectriques en tension continue, aux essais diélectriques en tension de choc et aux essais diélectriques combinant les essais ci-dessus. Ce document est applicable aux essais de matériels dont la tension la plus élevée Um pour le matériel est supérieure à 1 kV. Cette troisième édition annule et remplace la seconde édition publiée en 1989 et constitue une révision technique. Les changements techniques importants, par rapport à l'édition précédente, sont les suivants:
- les procédés de test de pollution artificielle ont été retirés car ils sont inclus dans la CEI 60507,
- la mesure de courant de choc a été transférée dans une nouvelle norme de mesure de courant (CEI 62475),
- les facteurs de correction atmosphérique sont présentés sous forme de formules.

General Information

• Status: Published
• Publication Date: 28-Sep-2010
• ICS: 17.220.20 - Measurement of electrical and magnetic quantities
• Technical Committee: TC 42 - High-voltage and high-current test techniques
• Drafting Committee: MT 4 - TC 42/MT 4
• Current Stage: PPUB - Publication issued
• Start Date: 29-Sep-2010
• Completion Date: 31-Oct-2010

Relations

• Revised: IEC 60060-1:2025 - High-voltage test techniques - Part 1: General terminology and test requirements
• Effective Date: 05-Sep-2023
• Revises: IEC 60060-1:1989 - High-voltage test techniques. Part 1: General definitions and test requirements
• Effective Date: 05-Sep-2023

Overview

IEC 60060-1:2010 is an international standard published by the International Electrotechnical Commission (IEC) focusing on high-voltage test techniques. Specifically, Part 1 covers general definitions and test requirements related to dielectric testing using alternating, direct, impulse, and combined voltages. This standard applies to electrical equipment with system voltages over 1 kV, ensuring the reliability and safety of high-voltage apparatus by defining test methodologies to evaluate insulation performance.

The 2010 edition (Edition 3.0) supersedes the previous 1989 version. Key revisions include removal of artificial pollution test procedures (now covered under IEC 60507), transfer of impulse current measurement techniques to IEC 62475, and expression of atmospheric correction factors in formula form to improve test accuracy and consistency.

This standard forms the basis for the consistent evaluation of insulation and withstand capabilities, helping manufacturers and testing laboratories comply with unified global voltage test requirements.

Key Topics

• Dielectric Test Types
  IEC 60060-1:2010 defines procedures for various dielectric tests on electrical equipment insulation, including:

  • Alternating voltage tests
  • Direct voltage tests
  • Impulse voltage tests (lightning and switching impulse)
  • Combined and composite voltage tests

• General Test Requirements
  Standardized general requirements cover:

  • Test object arrangement and clearances
  • Atmospheric conditions and correction factors for test results, accounting for pressure, humidity, and temperature variations
  • Measurement and generation of test voltages and currents
  • Test voltage tolerances and statistical evaluation of results

• Definitions and Classifications
  The standard provides comprehensive terminology for dielectric properties, test voltages, tolerance metrics, disruptive discharge characteristics, and classification of insulation systems to facilitate uniform understanding and reporting.

• Atmospheric Corrections
  Detailed guidance on applying atmospheric correction factors to dry, wet, and artificial pollution tests ensures test results can be reliably compared regardless of experimental environment variations.

• Test Procedures
  Clear procedural outlines include:

  • Withstand voltage tests to verify insulation strength
  • Disruptive-discharge voltage tests to determine breakdown thresholds
  • Assured disruptive-discharge voltage tests using statistical approaches to confirm insulation reliability

• Voltage Generation and Measurement
  The standard covers technical criteria for generating standard lightning-impulse and switching-impulse waveforms, measuring voltage wave shapes, amplitude, and current during impulse tests to assure quality and reproducibility.

Applications

• High-Voltage Equipment Testing
  Manufacturers and testing laboratories utilize IEC 60060-1:2010 to design and execute rigorous dielectric tests on transformers, switchgear, cables, insulators, and other equipment operating above 1 kV.

• Quality Assurance and Compliance
  This standard ensures consistent application of test voltages and conditions, helping stakeholders meet regulatory requirements and industry best practices for electrical safety and performance.

• Product Development
  During design validation, engineers use the defined test methods to verify insulation systems, enabling refinement of components to withstand specific voltage stresses encountered in service.

• Research and Development
  Researchers apply the standard’s measurement and atmospheric correction techniques to study insulation behavior under different voltage stressors and environmental conditions.

Related Standards

• IEC 60507 – Artificial pollution tests of high-voltage insulators now cover procedures removed from IEC 60060-1, providing detailed methodology for contamination impact assessment.

• IEC 62475 – Defines current measurement techniques for impulse testing, complementing the voltage test procedures detailed in IEC 60060-1.

• IEC 60060-2 – Focuses on measuring instruments and test equipment requirements for high-voltage testing, supporting the practical implementation of IEC 60060-1 methods.

• IEC 60694 – Standard on common specifications for high-voltage switchgear and controlgear, often tested according to IEC 60060 series protocols.

Adherence to IEC 60060-1:2010 ensures accurate, reliable, and comparable high-voltage dielectric test results, contributing to safer electrical infrastructure worldwide. For more information and access to the full standard, visit the official IEC website.

Standards Content (Sample)

IEC 60060-1 ®
Edition 3.0 2010-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
High-voltage test techniques –
Part 1: General definitions and test requirements

Technique des essais à haute tension –
Partie 1: Définitions et exigences générales

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IEC 60060-1 ®
Edition 3.0 2010-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
High-voltage test techniques –
Part 1: General definitions and test requirements

Technique des essais à haute tension –
Partie 1: Définitions et exigences générales

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
XB
CODE PRIX
ICS 17.220.20 ISBN 978-2-88912-185-4
– 2 – 60060-1 © IEC:2010
CONTENTS
FOREWORD.5
1 Scope.7
2 Normative references .7
3 Terms and definitions .7
3.1 Definitions related to characteristics of discharges .8
3.2 Definitions relating to characteristics of the test voltage .8
3.3 Definitions relating to tolerance and uncertainty .9
3.4 Definitions relating to statistical characteristics of disruptive-discharge
voltage values .9
3.5 Definitions relating to classification of insulation in test objects .10
4 General requirements .11
4.1 General requirements for test procedures.11
4.2 Arrangement of the test object in dry tests .11
4.3 Atmospheric corrections in dry tests .12
4.3.1 Standard reference atmosphere.12
4.3.2 Atmospheric correction factors for air gaps.12
4.3.3 Application of correction factors.13
4.3.4 Correction factor components .13
4.3.5 Measurement of atmospheric parameters .16
4.3.6 Conflicting requirements for testing internal and external insulation.17
4.4 Wet tests.18
4.4.1 Wet test procedure .18
4.4.2 Atmospheric corrections for wet tests .19
4.5 Artificial pollution tests .19
5 Tests with direct voltage.19
5.1 Definitions for direct voltage tests.19
5.2 Test voltage .20
5.2.1 Requirements for the test voltage .20
5.2.2 Generation of the test voltage.20
5.2.3 Measurement of the test voltage.20
5.2.4 Measurement of the test current .21
5.3 Test procedures .21
5.3.1 Withstand voltage tests .21
5.3.2 Disruptive-discharge voltage tests .22
5.3.3 Assured disruptive-discharge voltage tests .22
6 Tests with alternating voltage .22
6.1 Definitions for alternating voltage tests.22
6.2 Test Voltage.22
6.2.1 Requirements for the test voltage .22
6.2.2 Generation of the test voltage.23
6.2.3 Measurement of the test voltage.24
6.2.4 Measurement of the test current .25
6.3 Test procedures .25
6.3.1 Withstand voltage tests .25
6.3.2 Disruptive-discharge voltage tests .25
6.3.3 Assured disruptive-discharge voltage tests .25

60060-1 © IEC:2010 – 3 –
7 Tests with lightning-impulse voltage .26
7.1 Definitions for lightning-impulse voltage tests .26
7.2 Test Voltage.33
7.2.1 Standard lightning-impulse voltage .33
7.2.2 Tolerances .34
7.2.3 Standard chopped lightning-impulse voltage.34
7.2.4 Special lightning-impulse voltages.34
7.2.5 Generation of the test voltage.34
7.2.6 Measurement of the test voltage and determination of impulse shape.34
7.2.7 Measurement of current during tests with impulse voltages .35
7.3 Test Procedures .35
7.3.1 Withstand voltage tests .35
7.3.2 Procedures for assured disruptive-discharge voltage tests .36
8 Tests with switching-impulse voltage .36
8.1 Definitions for switching-impulse voltage tests.36
8.2 Test voltage .38
8.2.1 Standard switching-impulse voltage.38
8.2.2 Tolerances .38
8.2.3 Time-to-peak evaluation .38
8.2.4 Special switching-impulse voltages.38
8.2.5 Generation of the test voltage.38
8.2.6 Measurement of test voltage and determination of impulse shape .39
8.2.7 Measurement of current during tests with impulse voltages .39
8.3 Test procedures .39
9 Tests with combined and composite voltages .39
9.1 Definitions for combined- and composite-voltage tests .39
9.2.4 Tolerances .42
9.2.5 Generation .42
9.2.6 Measurement.42
9.3 Composite test voltages .43
9.3.1 Parameters.43
9.3.2 Tolerances .43
9.3.3 Generation .43
9.3.4 Measurement.43
9.4 Test procedures .43
Annex A (informative) Statistical treatment of test results .45
Annex B (normative) Procedures for calculation of parameters of standard lightning-
impulse voltages with superimposed overshoot or oscillations .54
Annex C (informative) Guidance for implementing software for evaluation of lightning-
impulse voltage parameters .59
Annex D (informative) Background to the introduction of the test voltage factor for
evaluation of impulses with overshoot.62
Annex E (informative) The iterative calculation method in the converse procedure for
the determination of atmospheric correction factor.68
Bibliography.73

Figure 1 – Recommended minimum clearance D of extraneous live or earthed objects
to the energized electrode of a test object, during an a.c. or positive switching impulse

test at the maximum voltage U applied during test .12

– 4 – 60060-1 © IEC:2010
Figure 2 – k as a function of the ratio of the absolute humidity h to the relative air
density δ (see 4.3.4.2 for limits of applicability) .14
Figure 3 – Values of exponents m and w .16
Figure 4 – Absolute humidity of air as a function of dry- and wet-bulb thermometer
readings .17
Figure 5 – Full lightning-impulse voltage.26
Figure 6 – Test voltage function.28
Figure 7 – Full impulse voltage time parameters .29
Figure 8 – Voltage time interval .30
Figure 9 – Voltage integral.30
Figure 10 – Lightning-impulse voltage chopped on the front.31
Figure 11 – Lightning-impulse voltage chopped on the tail .32
Figure 12 – Linearly rising front chopped impulse .32
Figure 13 – Voltage/time curve for impulses of constant prospective shape .33
Figure 14 – Switching-impulse voltage .37
Figure 15 – Circuit for a combined voltage test .40
Figure 16 – Schematic example for combined and composite voltage .41
Figure 17 – Circuit for a composite voltage test .42
Figure 18 – Definition of time delay Δt.43
Figure A.1 – Example of a multiple-level (Class 1) test .48
Figure A.2 – Examples of decreasing and increasing up-and-down (Class 2) tests for
determination of 10 % and 90 % disruptive-discharge probabilities respectively.49
Figure A.3 – Examples of progressive stress (Class 3) tests .50
Figure B.1 – Recorded and base curve showing overshoot and residual curve.55
Figure B.2 – Test voltage curve (addition of base curve and filtered residual curve).55
Figure B.3 – Recorded and test voltage curves .56
Figure D.1 – “Effective” test voltage function in IEC 60060-1:1989.63
Figure D.2 – Representative experimental points from European experiments and test
voltage function .65
Figure E.1 – Atmospheric pressure as a function of altitude.69

Table 1 – Values of exponents, m for air density correction and w for humidity
correction, as a function of the parameter g .15
Table 2 – Precipitation conditions for standard procedure .19
Table A.1– Discharge probabilities in up-and-down testing .52
Table E.1 – Altitudes and air pressure of some locations .69
Table E.2 – Initial K and its sensitivity coefficients with respect to U for the example
t 50
of the standard phase-to-earth a.c. test voltage of 395 kV .70
Table E.3 – Initial and converged K values for the example of the standard phase-to-
t
earth a.c. test voltage of 395 kV .72

60060-1 © IEC:2010 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
HIGH-VOLTAGE TEST TECHNIQUES –

Part 1: General definitions and test requirements

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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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 IEC on technical matters express, as nearly as possible, an international
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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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6) All users should ensure that they have the latest edition of this publication.
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Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60060-1 has been prepared by IEC technical committee 42: High-
voltage test techniques.
This third edition of IEC 60060-1 cancels and replaces the second edition, published in 1989,
and constitutes a technical revision.
The significant technical changes with respect to the previous edition are as follows:
a) The general layout and text was updated and improved to make the standard easier to
use.
b) Artificial pollution test procedures were removed as they are now described in IEC 60507.
c) Measurement of impulse current has been transferred to a new standard on current
measurement (IEC 62475).
d) The atmospheric correction factors are now presented as formulas.

– 6 – 60060-1 © IEC:2010
e) A new method has been introduced for the calculation of the time parameters of lightning
impulse waveforms. This improves the measurement of the time parameters of lightning
impulses with oscillations or overshoot.
The text of this standard is based on the following documents:
FDIS Report on voting
42/277/FDIS 42/282/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 2
A list of all the parts in the IEC 60060 series, under the general title High-voltage test
techniques, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data
related to this specific publication. At this date, the publication will be:
• reconfirmed;
• withdrawn;
• replaced by a revised edition or
• amended.
60060-1 © IEC:2010 – 7 –
HIGH-VOLTAGE TEST TECHNIQUES –

Part 1: General definitions and test requirements

1 Scope
This part of IEC 60060 is applicable to:
– dielectric tests with direct voltage;
– dielectric tests with alternating voltage;
– dielectric tests with impulse voltage;
– dielectric tests with combinations of the above.
This part is applicable to tests on equipment having its highest voltage for equipment U
m
above 1 kV.
NOTE 1 Alternative test procedures may be required to obtain reproducible and significant results. The choice of
a suitable test procedure should be made by the relevant Technical Committee.
NOTE 2 For voltages U above 800 kV meeting some specified procedures, tolerances and uncertainties may not
m
be achievable.
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 60060-2, High-voltage test techniques – Part 2: Measuring systems
IEC 60270, High-voltage test techniques – Partial discharge measurements
IEC 60507:1991, Artificial pollution tests on high-voltage insulators to be used on a.c.
systems
IEC 61083-1, Instruments and software used for measurement in high-voltage impulse tests –
Part 1: Requirements for instruments
IEC 61083-2, Digital recorders for measurements in high-voltage impulse tests – Part 2:
Evaluation of software used for the determination of the parameters of impulse waveforms
IEC 62475, High-current test techniques: Definitions and requirements for test currents and
measuring systems
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

– 8 – 60060-1 © IEC:2010
3.1 Definitions related to characteristics of discharges
3.1.1
disruptive discharge
failure of insulation under electric stress, in which the discharge completely bridges the
insulation under test, reducing the voltage between electrodes to practically zero
NOTE 1 Non-sustained disruptive discharge in which the test object is momentarily bridged by a spark or arc may
occur. During these events the voltage across the test object is momentarily reduced to zero or to a very small
value. Depending on the characteristics of the test circuit and the test object, a recovery of dielectric strength may
occur and may even allow the test voltage to reach a higher value. Such an event should be interpreted as a
disruptive discharge unless otherwise specified by the relevant Technical Committee.
NOTE 2 A disruptive discharge in a solid dielectric produces permanent loss of dielectric strength; in a liquid or
gaseous dielectric the loss may be only temporary.
3.1.2
sparkover
disruptive discharge that occurs in a gaseous or liquid dielectric
3.1.3
flashover
disruptive discharge that occurs over the surface of a dielectric in a gaseous or liquid
dielectric
3.1.4
puncture
disruptive discharge that occurs through a solid dielectric
3.1.5
disruptive-discharge voltage value of a test object
value of the test voltage causing disruptive discharge, as specified, for the various tests, in
the relevant clauses of the present standard
3.1.6
non-disruptive discharge
discharge between intermediate electrodes or conductors where the test voltage does not
collapse to zero
NOTE 1 Such an event should not be interpreted as a disruptive discharge unless so specified by the relevant
Technical Committee.
NOTE 2 Some non-disruptive discharges are termed “partial discharges” and are dealt with in IEC 60270.
3.2 Definitions relating to characteristics of the test voltage
3.2.1
prospective characteristics of a test voltage
characteristics which would have been obtained if no disruptive discharge had occurred.
When a prospective characteristic is used, this shall always be stated.
3.2.2
actual characteristics of a test voltage
those characteristics which occur during the test at the terminals of the test object
3.2.3
value of the test voltage
as defined in the relevant clauses of this standard

60060-1 © IEC:2010 – 9 –
3.2.4
withstand voltage of a test object
specified prospective voltage value which characterizes the insulation of the object with
regard to a withstand test
NOTE 1 Unless otherwise specified, withstand voltages are referred to standard reference atmospheric conditions
(see 4. 3. 1 ) .
NOTE 2 This applies to external insulation only.
3.2.5
assured disruptive-discharge voltage of a test object
specified prospective voltage value which characterizes its performance with regard to a
disruptive-discharge test
3.3 Definitions relating to tolerance and uncertainty
3.3.1
tolerance
constitutes the permitted difference between the measured value and the specified value
NOTE 1 This difference should be distinguished from the uncertainty of a measurement.
NOTE 2 A pass/fail decision is based on the measured value, without consideration of the measurement
uncertainty.
3.3.2
uncertainty (of measurement)
parameter, associated with the result of a measurement, that characterizes the dispersion of
the values that could be reasonably attributed to the measurand
[IEV 311-01-02]
NOTE 1 In this standard, all uncertainty values are specified at a level of confidence of 95 %.
NOTE 2 Uncertainty is positive and given without sign.
NOTE 3 It should not be confused with the tolerance of a test-specified value or parameter.
3.4 Definitions relating to statistical characteristics of disruptive-discharge voltage
values
3.4.1
disruptive-discharge probability of a test object
p
probability that one application of a certain prospective voltage value of a given shape will
cause disruptive discharge in the test object
NOTE The parameter p may be expressed as a percentage or a proper fraction.
3.4.2
withstand probability of a test object
q
probability that an application of a certain prospective voltage value of a given shape does not
cause a disruptive discharge on the test object
NOTE If the disruptive-discharge probability is p, the withstand probability q is (1 – p).
3.4.3
p % disruptive-discharge voltage of a test object
U
p
prospective voltage value which has p % probability of producing a disruptive discharge on
the test object
– 10 – 60060-1 © IEC:2010
NOTE 1 Mathematically the p % disruptive-discharge voltage is the quantile of the order p (or p quantile) of the
breakdown voltage.
NOTE 2 U is called the “statistical withstand voltage” and U is called the “statistical assured disruptive-
10 90
discharge voltage”.
3.4.4
50 % disruptive-discharge voltage of a test object
U
prospective voltage value which has a 50 % probability of producing a disruptive discharge on
the test object
3.4.5
arithmetic mean value of the disruptive-discharge voltage of a test object,
U
a
n
U = U
a ∑ i
n
i=1
where
U is the measured disruptive-discharge voltage and
i
n is the number of observations (discharges).
NOTE For symmetric distributions U is identical to U .
a 50
3.4.6
standard deviation of the disruptive voltage of a test object
s
a measure of the dispersion of the disruptive voltage estimated by
n
()
s = U − U
∑ i a
n − 1
i=1
where
th
U is the i measured disruptive voltage and
i
U is the arithmetic mean of the disruptive voltages (in most cases it is identical to U ).
a 50
n is the number of observations (discharges).
NOTE 1 It can also be evaluated by the difference between the 50 % and 16 % disruptive-discharge voltages (or
between the 84 % and 50 % disruptive-discharge voltages). It is often expressed in per unit or percentage value
referred to the 50 % disruptive-discharge voltage.
NOTE 2 For successive disruptive-discharge tests the standard deviation s is defined by the formula. For multiple
level and up-and-down tests it is defined by the difference of the quantiles. The methods are equivalent because,
between p = 16 % and p = 84 % all distribution functions are nearly identical.
3.5 Definitions relating to classification of insulation in test objects
3.5.1
external insulation
air insulation and the exposed surfaces of solid insulation of the equipment, which are subject
both to dielectric stresses and to the direct effects of atmospheric and other external
conditions
3.5.2
internal insulation
internal solid, liquid or gaseous elements of the insulation of equipment protected from the
direct effects of external conditions such as pollution, humidity and vermin

60060-1 © IEC:2010 – 11 –
3.5.3
self-restoring insulation
insulation which completely recovers its insulating properties after a disruptive discharge
caused by the application of a test voltage
[IEV 604-03-04, modified]
3.5.4
non-self-restoring insulation
insulation which loses its insulating properties, or does not recover them completely, after a
disruptive discharge caused by the application of a test voltage
[IEV 604-03-05, modified]
NOTE In high-voltage apparatus, parts of both self-restoring and non-self-restoring insulation are always
operating in combination and some parts may be degraded by repeated or continued voltage applications. The
behaviour of the insulation in this respect should be taken into account by the relevant Technical Committee when
specifying the test procedures to be applied.
4 General requirements
4.1 General requirements for test procedures
The test procedures applicable to particular types of test objects, for example, the test
voltage, the polarity to be used, the preferred order if both polarities are to be used, the
number of applications and the interval between applications shall be specified by the
relevant Technical Committee, having regard to such factors as:
– the required accuracy of the test results;
– the random nature of the observed phenomena;
– any polarity dependence of the measured characteristics and
– the possibility of progressive deterioration with repeated voltage applications.
At the time of a test, the test object shall be complete in all essential details, and it should
have been processed in the normal manner for similar equipment.
At the time of a test, the test object should have become acclimatised as much as practicable
to the ambient atmospheric conditions of the test area. The period allocated to reach
equilibrium should be recorded.
4.2 Arrangement of the test object in dry tests
The disruptive-discharge characteristics of a test object with external insulation may be
affected by its general arrangement (for example, proximity effects such as distance in air
from other live or earthed structures, height above ground level and the arrangement of its
high-voltage lead). The general arrangement should be specified by the relevant Technical
Committee.
NOTE 1 A clearance to extraneous structures not less than 1,5 times the length of the shortest possible discharge
path on the test object usually makes such proximity effects negligible. In wet or pollution tests, or wherever the
voltage distribution along the test object and the electric field around its energized electrode are sufficiently
independent of external influences, smaller clearances may be acceptable, provided that discharges do not occur
to extraneous structures.
NOTE 2 In the case of a.c. or positive switching-impulse voltage tests above 750 kV (peak) the influence of an
extraneous structure may be considered as negligible if its distance from the energized electrode is also not less
than the height of this electrode above the ground plane. A guide for recommended minimum clearance is given in
Figure 1, as a function of the highest test voltage. Significant shorter clearances may be suitable in individual

– 12 – 60060-1 © IEC:2010
cases. However, an experimental adaptation or a field calculation, taking into account a voltage dependent
maximum field strength as described in the literature [1, 2] , is recommended.

750 1 000 1 250 1 500 1 750 2 000
U peak  (kV)
IEC  2204/10
Figure 1 – Recommended minimum clearance D of extraneous live or earthed objects to
the energized electrode of a test object, during an a.c. or positive switching impulse
test at the maximum voltage U applied during test
If not otherwise specified by the relevant Technical Committee, the test should be made at
ambient atmospheric conditions in the test area without extraneous precipitation or pollution.
The procedure for voltage application shall be as specified in the relevant clauses of this
standard.
4.3 Atmospheric corrections in dry tests
4.3.1 Standard reference atmosphere
The standard reference atmosphere is:
– temperature t = 20 °C ;
– absolute pressure p = 1 013 hPa (1 013 mbar) ;
3.
– absolute humidity h = 11 g/m
NOTE 1 An absolute pressure of 1 013 hPa corresponds to the height of 760 mm of the mercury column in a
mercury barometer at 0 °C. If the barometer height is H mm of mercury, the atmospheric pressure in hectopascal is
approximately:
p = 1,333 H hPa
Correction for temperature with respect to the height of the mercury column is considered to be negligible.
NOTE 2 Instruments automatically correcting pressure to sea level are not suitable and should not be used.
4.3.2 Atmospheric correction factors for air gaps
The disruptive discharge of external insulation depends upon the atmospheric conditions.
Usually, the disruptive-discharge voltage for a given path in air is increased by an increase in
either air density or humidity. However, when the relative humidity exceeds about 80 %, the
disruptive-discharge voltage becomes irregular, especially when the disruptive discharge
occurs over an insulating surface.
___________
Numbers in square brackets refer to the Bibliography.
D  (m)
60060-1 © IEC:2010 – 13 –
NOTE Atmospheric corrections do not apply to flashover, only to sparkover.
The disruptive-discharge voltage is proportional to the atmospheric correction factor K that
t
results from the product of two correction factors:
– the air density correction factor k (see 4. 3. 4. 1) ;
– the humidity correction factor k (see 4. 3.4 . 2 ) .
K = k k
t 1 2
4.3.3 Application of correction factors
4.3.3.1 Standard procedure
By applying correction factors, a disruptive-discharge voltage measured in given test
conditions (temperature t, pressure p, humidity h) may be converted to the value, which would
have been obtained under the standard reference atmospheric conditions (t , p , h ).
0 0 0
Disruptive-discharge voltages, U, measured at given test conditions are corrected to U
corresponding to standard reference atmosphere by dividing by K :
t
U = U K
0 t
The test report shall always contain the actual atmospheric conditions during the test and the
correction factors applied.
4.3.3.2 Converse procedure
Conversely, where a test voltage is specified for standard reference conditions, it shall be
converted into the equivalent value under the test conditions and this may require an iterative
procedure.
If not otherwise specified by the relevant Technical Committee, the voltage U to be applied
during a test on external insulation is determined by multiplying the specified test voltage U
by K ;
t
U = U K
0 t
However, as U enters into the calculation of K , an iterative procedure might have to be used
t
(see A n nex E) .
NOTE 1 The test for the correct choice of U for the calculation of K is to divide U by K . If the result is the
t t
specified test voltage, U , then a correct choice of U has been made. If U is too high, U has to be reduced but if it
0 0
is too low, it has to be increased.
NOTE 2 When K is close to unity, iterative calculation is not necessary.
t
NOTE 3 In correcting power-frequency voltage the peak value has to be used, because the discharge behaviour
is based on the peak value.
4.3.4 Correction factor components
4.3.4.1 Air density correction factor, k
The air density correction factor k depends on the relative air density δ and can be generally
expressed as:
m
k = δ
– 14 – 60060-1 © IEC:2010
where m is an exponent given in 4. 3. 4. 3.
When the temperatures t and t are expressed in degrees Celsius and the atmospheric
pressures p and p are expressed in the same units, the relative air density is:
t
p 273+
δ = ×
p 273 + t
The correction is considered reliable for 0,8 < k < 1,05.
4.3.4.2 Humidity correction factor, k
The humidity correction factor may be expressed as:
w
k = k
where w is an exponent given in 4. 3. 4. 3 a nd k is a parameter that depends on the type of test
voltage and may be obtained as a function of the ratio of absolute humidity, h, to the relative
air density, δ, using the following equations (Figure 2):
3 3
DC  for 1 g/m < h/δ < 15 g/m
k = 1 + 0,014()h δ − 11 − 0,00022()h δ − 11
3 3
AC k = 1 + 0, 012()h δ − 11 for 1 g/m < h/δ < 15 g/m
3 3
Impulse k = 1 + 0,010()hδ − 11  for 1 g/m < h/δ < 20 g/m
NOTE The impulse equation is based on experimental results for positive lightning-impulse waveforms. This
equation also applies to negative lightning-impulse voltages and switching-impulse voltages.

1,2
1,15
1,1
1,05
DC
AC
1,0
Impulse
0,95
0,9
0,85
0,8
0 5 10 15 20 25 30
h/δ  (g/m )
IEC  2205/10
Figure 2 – k as a function of the ratio of the absolute humidity h to the relative air
density δ (see 4.3.4.2 for limits of applicability)
k
60060-1 © IEC:2010 – 15 –
For U below 72,5 kV (or approximately gap lengths l < 0,5 m) no humidity correction can at
m
present be specified.
NOTE For specific apparatus, the relevant Technical Committee has specified other procedures (e.g. IEC 62271-
1).
4.3.4.3 Exponents m and w
As the correction factors depend on the type of pre-discharges, this fact can be taken into
account by considering the parameter:
U
g =
500 Lδ k
where U is the 50 % disruptive-discharge voltage (measured or estimated) at the actual
atmospheric conditions, in kilovolt peak,
L is the minimum discharge path in m,
δ is the relative air density and
k is the dimension less parameter defined in 4 . 3. 4. 2.
In the case of a withstand test where an estimate of the 50 % disruptive-discharge voltage is
not available, U can be assumed to be 1,1 times the test voltage, U .
50 0
The exponents, m and w, are obtained from Table 1 for the specified ranges of g (Figure 3).
Table 1 – Values of exponents, m for air density correction and w for humidity
correction, as a fun
...