SIST EN 60052:2004

Voltage measurement by means of standard air gaps

Applies to the construction and use of sphere-gaps for measuring the peak value of alternating, direct and both full standard and longer tail impulse voltages. Peak values of the disruptive voltages in air are given in tabular form. Note: - For high-voltage test techniques, see EN 60.

Spannungsmessungen mit Standard-Luftfunkenstrecken

Mesure de tension au moyen des éclateurs à sphères normalisés

Concerne la construction et l'utilisation d'éclateurs à sphères pour la mesure des valeurs de crête des tensions alternatives, des tensions continues et des tensions de choc pleines normales ainsi que des tensions de choc de plus grande durée de queue. Les valeurs de crête des tensions disruptives dans l'air sont données sous forme de tableaux. Note: - Pour les techniques des essais à haute tension voir la EN 60.

Voltage measurement by means of standard air gaps (IEC 60052:2002)

General Information

• Status: Published
• Publication Date: 31-Mar-2004
• ICS: 19.080 - Electrical and electronic testing
• Technical Committee: IVNT - High-voltage testing techniques
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Apr-2004
• Due Date: 01-Apr-2004
• Completion Date: 01-Apr-2004
• Ref Project: EN 60052:2002 - Voltage measurement by means of standard air gaps

Standards Content (Sample)

SLOVENSKI SIST EN 60052:2004

STANDARD
april 2004
Voltage measurement by means of standard air gaps (IEC 60052:2002)
ICS 19.080 Referenčna številka
SIST EN 60052:2004(en)
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

---------------------- Page: 1 ----------------------

EUROPEAN STANDARD EN 60052
NORME EUROPÉENNE
EUROPÄISCHE NORM November 2002

ICS 19.080


English version


Voltage measurement by means of standard air gaps
(IEC 60052:2002)


Mesure de tension au moyen  Spannungsmessungen mit
des éclateurs à sphères normalisés Standard-Luftfunkenstrecken
(CEI 60052:2002) (IEC 60052:2002)






This European Standard was approved by CENELEC on 2002-11-01. 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, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta,
Netherlands, Norway, Portugal, Slovakia, 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


© 2002 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 60052:2002 E

---------------------- Page: 2 ----------------------

EN 60052:2002 - 2 -
Foreword

The text of document 42/173/FDIS, future edition 3 of IEC 60052, prepared by IEC TC 42, High-voltage
testing techniques, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC
as EN 60052 on 2002-11-01.

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) 2003-08-01

– latest date by which the national standards conflicting
 with the EN have to be withdrawn (dow) 2005-11-01

Annexes designated "normative" are part of the body of the standard.
Annexes designated "informative" are given for information only.
In this standard, annex ZA is normative and annex A to D are informative.
Annex ZA has been added by CENELEC.
__________

Endorsement notice

The text of the International Standard IEC 60052:2002 was approved by CENELEC as a European
Standard without any modification.
__________

---------------------- Page: 3 ----------------------

- 3 - EN 60052:2002
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
IEC 60060-1 1989 High-voltage test techniques
+ corr. March 1990 Part 1: General definitions and test HD 588.1 S1 1991
requirements

IEC 60060-2 1994 Part 2: Measuring systems EN 60060-2 1994
A11 1998

---------------------- Page: 4 ----------------------

NORME CEI
INTERNATIONALE IEC
60052
INTERNATIONAL
Troisième édition
STANDARD
Third edition
2002-10
Mesure de tension au moyen des éclateurs
à sphères normalisés
Voltage measurement by means of
standard air gaps
© IEC 2002 Droits de reproduction réservés ⎯ Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in any
utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including
électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from
microfilms, sans l'accord écrit de l'éditeur. the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: [phone] Telefax: [phone] E-mail: [e-mail]  Web: www.iec.ch
CODE PRIX
U
Commission Electrotechnique Internationale PRICE CODE
International Electrotechnical Commission
ɆɟɠɞɭɧɚɪɨɞɧɚɹɗɥɟɤɬɪɨɬɟɯɧɢɱɟɫɤɚɹɄɨɦɢɫɫɢɹ
Pour prix, voir catalogue en vigueur
For price, see current catalogue

---------------------- Page: 5 ----------------------

60052 © IEC:2002 – 3 –
CONTENTS
FOREWORD . 5
INTRODUCTION .7
1 Scope . 9
2 Normative references. 9
3 Definitions. 9
4 Standard sphere-gap. 9
4.1 Requirements on shape and surface conditions. 9
4.2 General arrangement of a sphere-gap for measurement.11
4.3 Connections.13
5 Use of the sphere-gap.15
5.1 Condition of the sphere surfaces .17
5.2 Irradiation .17
5.3 Voltage measurements .17
6 Reference values in tables 2 and 3.19
6.1 Accuracy of values in tables 2 and 3.21
6.2 Air density correction factor.21
6.3 Humidity correction factor .23
7 Standard rod-rod gap for measurement of direct voltage.23
7.1 General arrangement of a rod-rod gap .23
7.2 Reference values .23
7.3 Measurement procedure .23
8 Use of standard air gaps for performance checks of approved measuring systems .25
Annex A (informative) Range of experimental calibrations for sphere-gaps.45
Annex B (informative) Procedure by which the values in tables 2 and 3 have been
derived from national standards and other sources .47
Annex C (informative) Sources of irradiation .49
Annex D (informative) Uncertainty and calibration of sphere-gaps .51
Bibliography .53
Figure 1 – Vertical sphere-gap.39
Figure 2 – Horizontal sphere-gap.41
Figure 3 – Arrangement for rod-rod gap .43
Table 1 – Clearance limits .13
Table 2 – Peak values of disruptive discharge voltages (U values in impulse tests) in
50
kV for alternating voltages at power frequencies, full lightning and switching impulse
voltages of negative polarity and direct voltages of both polarities .27
Table 3 – Peak values of disruptive discharge voltages (U values in impulse tests)
50
in kV for full lightning and switching impulse voltages of positive polarity.33
Table A.1 – Experimental calibrations of the sphere-gap .45
Table B.1 – Rounding off of values in tables 2 and 3.47

---------------------- Page: 6 ----------------------

60052 © IEC:2002 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
VOLTAGE MEASUREMENT
BY MEANS OF STANDARD AIR GAPS
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 60052 has been prepared by IEC technical committee 42: High-
voltage testing techniques.
This third edition of IEC 60052 cancels and replaces the second edition, published in 1960, and
constitutes a technical revision.
The text of this standard is based on the following documents:
FDIS Report on voting
42/173/FDIS 42/175/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.
Annexes A, B, C and D are for information only.
The committee has decided that the contents of this publication will remain unchanged until
2012. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.

---------------------- Page: 7 ----------------------

60052 © IEC:2002 – 7 –
INTRODUCTION
Sphere-gaps have been used as a simple and reliable method for measurement of peak
voltage in many industrial test facilities for 75 years, and the values of tables I and II in the
second edition of IEC 60052 have been accepted as an International Consensus Standard of
Measurements. These tables appear in this standard as tables 2 and 3.
There is no information in the references (e.g. annex A) with regard to traceability to national
standards of measurement. However, the dispersion in the measured values of sparkover
voltages upon which tables 2 and 3 are based, does not exceed 3 % for a 95 % confidence
level.
In view of the long history of IEC 60052 as an International Consensus Standard of
Measurement, the values for disruptive discharge voltage in tables I and II of the second
edition of IEC 60052 are reproduced in this publication as tables 2 and 3. They are to be used
as mean values with an uncertainty of 3 % for a 95 % confidence level.
The material on rod-rod gaps for reliable measurement of high direct voltages has been
included here to form an integrated standard on high voltage measurements using standard
air gaps.
Four informative annexes are included:
Annex A gives the limits of voltage and frequency over which tables 2 and 3 have been derived
from experiments and can be presumed to be accurate within the limits specified in 4.1.
Annex B gives the procedure by which the values in tables 2 and 3 have been derived from
previous national standards and other sources.
Annex C provides information on additional irradiation, which may be needed in certain
situations.
Annex D provides information on the uncertainty and calibration of sphere-gaps.

---------------------- Page: 8 ----------------------

60052 © IEC:2002 – 9 –
VOLTAGE MEASUREMENT
BY MEANS OF STANDARD AIR GAPS
1 Scope
IEC 60052 sets forth recommendations concerning the construction and use of standard air
gaps for the measurement of peak values of the following four types of voltage:
a) alternating voltages of power frequencies;
b) full lightning impulse voltages;
c) switching impulse voltages;
d) direct voltages.
Air gaps constructed and used in accordance with this standard represent IEC standard
measuring devices in accordance with IEC 60060-2 and are primarily intended for performance
checks of high voltage measuring systems.
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 60060-1:1989, High-voltage test techniques – Part 1: General definitions and test
requirements
IEC 60060-2:1994, High-voltage test techniques – Part 2: Measuring systems
3 Definitions
vacant
4 Standard sphere-gap
The standard sphere-gap is a peak voltage measuring device constructed and arranged in
accordance with this standard. The points on the two spheres which are closest to each other
are called the sparking points. Figures 1 and 2 show two arrangements, one of which is typical
of sphere-gaps with a vertical axis and the other of sphere-gaps with a horizontal axis.
4.1 Requirements on shape and surface conditions
The standard sphere-gap consists of two metal spheres of the same diameter D, their shanks,
operating gear, insulating supports, supporting frame and leads for connection to the point at
which the voltage is to be measured. Standard values of D are 2 – 5 – 6,25 – 10 – 12,5 – 15 –
25 – 50 – 75 – 100 –150 and 200 cm. The spacing between the spheres is designated S.

---------------------- Page: 9 ----------------------

60052 © IEC:2002 – 11 –
The spheres shall be carefully made so that their surfaces are smooth and their curvature is as
uniform as possible.
The tolerances on size and shape need usually only be checked when the spheres are first
supplied and any suitable instrument (e.g. spherometer) may be used.
The diameter of each sphere shall not differ by more than 2 % from the nominal value. The
spheres shall be reasonably free from surface irregularities in the region of the sparking point.
A medium grade mechanical surface finishing (roughness R below 10 µm) is considered to
max
be adequate. The region of the sparking point is defined by a circle such as would be drawn on
the spheres by a pair of dividers set to an opening of 0,3 D and centred in the sparking point.
When the sphere-gap is used, it will normally be sufficient to examine the surface by touch and
visual inspection.
NOTE Any minor damage on the non-adjacent hemispherical surfaces does not alter the sphere-gap performance.
4.2 General arrangement of a sphere-gap for measurement
4.2.1 Vertical gap
When the spheres are arranged vertically, the shank of the high-voltage sphere shall be free
from sharp edges or corners and the diameter of the shank shall not exceed 0,2 D over a
lengthD. This requirement is made in order to reduce the influence of the high-voltage shank
on the disruptive discharge voltage. If a stress distributor (corona shield) is used at the end of
the shank, its greatest dimension, perpendicular to the axis of the spheres, shall not exceed
0,5D and shall be at least 2 D from the sparking point of the high-voltage sphere.
The earthed shank and the operating gear have a smaller effect and their dimensions are
therefore less important.
Figure 1 gives the limits of size of the components of a typical vertical sphere-gap.
The sphere shanks should be visually in line.
4.2.2 Horizontal gap
When the spheres are arranged horizontally, the limiting dimensions of a typical sphere-gap
are given in figure 2. They are the same for both sides of the gap.
The sphere shanks should be visually in line.
4.2.3 Height of the spheres above the horizontal earth plane
The height A of the sparking point of the high-voltage sphere above the earth plane of the
laboratory floor shall be within the limits given in table 1.
If the sphere-gap is mounted with the earthed sphere nearest to the ceiling, and if other
surfaces such as walls and the floor are at a considerably greater distance, then the ceiling
shall be regarded as the horizontal plane, from which the distance A is measured downwards.

---------------------- Page: 10 ----------------------

60052 © IEC:2002 – 13 –
4.2.4 Clearance around the spheres
The distance from the sparking point of the high-voltage sphere to any extraneous objects
(such as ceiling, walls, and any energized or earthed equipment), and also to the supporting
frame work for the spheres, if this is made of conducting material, shall not be less than the
value of distance B in table 1. Except as permitted below, B should not be less than 2 D,
regardless of the value of S.
Supporting frameworks for the spheres made of insulating material are exempt from this
requirement, provided that they are clean and dry and that the spheres are used for the
measurement of alternating or impulse voltages only. The distance B between the sparking
point of the high-voltage sphere and the framework may then be less than is prescribed in
table 1, however, it shall not be less than 1,6 D.
The peak values of disruptive discharge voltages in tables 2 and 3 are valid for clearances
around the spheres within the limits given in table 1.
Table 1 – Clearance limits
Sphere diameter D Minimum value of Maximum value of Minimum value of
cm
height A height A distance B
7 D 9 D 14 S
Up to 6,25
6 D 8 D 12 S
10 -15
25 5 D 7 D 10 S
50 4 D 6 D 8 S
75 4 D 6 D 8 S
100 3,5 D 5 D 7 S
150
3 D 4 D 6 S
200
3 D 4 D 6 S
The test conditions may make it impossible for the values of A and B to comply with the
minimum requirements. Such sphere-gaps can be used, providing that, either the conventional
deviation z meets the requirements of clause 5, or, that the uncertainty in the values for
disruptive discharge in tables 2 and 3 are suitably increased. Such sphere-gaps could be
calibrated under laboratory conditions as indicated in annex D.
The circuit should be arranged so that at the test voltage there is
– no disruptive discharge to other objects,
– no visible leader discharge from the high-voltage lead or the shank within the space defined
by B,
– no visible discharge from other earthed objects extending into the space defined by B.
4.3 Connections
The sphere-gap shall be connected in accordance with the requirements specified in
IEC 60060-2.
4.3.1 Earthing
One sphere normally shall be connected directly to earth. Low ohmic shunts may be connected
between the sphere and earth for special purposes.

---------------------- Page: 11 ----------------------

60052 © IEC:2002 – 15 –
4.3.2 High-voltage conductor
The high-voltage conductor, including any series resistor not in the shank itself, shall be
connected to a point on the shank at least 2 D away from the sparking point of the high-voltage
sphere.
Within the region where the distance to the sparking point of the high-voltage sphere is less
than B, the high-voltage conductor (including the series resistor, if any) must not pass through
the plane normal to the axis of the sphere-gap and situated at a distance 2 D from the sparking
point of the high-voltage sphere. See figures 1 and 2 where the plane is shown.
4.3.3 Protective resistor for measurement of alternating and direct voltages
Precautions should be taken to minimize pitting of the spheres and to prevent superimposed
oscillations, which may cause erratic disruptive discharges. For this purpose, a resistance of
0,1 MΩ to 1 MΩ shall be connected in series with the sphere-gap. This range of resistance
values applies to measurements of direct voltages and of alternating voltages at power
frequencies, because the values of the resistance results in a negligible voltage drop.
The protective resistor should be placed as near as possible to the shank of the sphere and
connected directly to it.
When streamer discharges are present in the test circuit, series resistance is particularly
important in order to reduce the effect of the consequent transient over-voltage on the
operation of the sphere-gap. When these discharges are not present either in the test circuit or
in the test specimen, the value of resistance may be reduced to a value which prevents
excessive burning of the spheres by disruptive discharges.
4.3.4 Protective series resistor for measurement of impulse voltages
Series resistance is needed with large diameter spheres to eliminate oscillations in the sphere-
gap circuit which may cause a higher voltage to occur between the spheres and, if connected,
across the test object. This phenomenon is usually of minor importance for smaller spheres,
unless they are used with long connecting leads. Series resistance may also be needed to
reduce the steepness of the voltage collapse which might introduce undesirable stresses in the
test object.
The resistor shall have a non-inductive construction (not more than 30 µH) and its resistance
should not exceed 500 Ω. For the position of the resistor in the circuit, see 4.3.2.
5 Use of the sphere-gap
A sphere-gap is an IEC standard measuring device when the conventional deviation z (4.4.5 of
IEC 60060-1) at the time of use is less than 1 % for alternating voltages at power frequency
and lightning impulse voltages and less than 1,5 % for switching impulse voltages. The
conventional deviation z is affected by the condition of the sphere surfaces, the availability of
free electrons (sufficient irradiation), the dust contained in the air and the measurement
procedures.

---------------------- Page: 12 ----------------------

60052 © IEC:2002 – 17 –
5.1 Condition of the sphere surfaces
The surfaces of the spheres in the neighbourhood of the sparking points shall be cleaned and
dried but need not be polished. In normal use the surfaces of the spheres become roughened
and pitted. The surface should be rubbed with fine abrasive paper and the resulting dust
removed with lint-free cloth; any trace of oil or grease should be removed with a solvent. If the
spheres become excessively roughened or pitted in use, they shall be repaired or replaced.
Moisture may condense on the surface of the sparking points in conditions of high relative
humidity causing measurements to become erratic.
Minor damage to the surface of the sphere beyond the region of sparking point (see 4.1) is not
likely to affect the use of the sphere as a measuring device.
NOTE The requirement for the conventional deviation z ensures that the requirements for surface conditions have
been met.
5.2 Irradiation
The disruptive discharge voltage of a sphere-gap depends upon the availability of free
electrons in the gap between the spheres at the moment of application of voltage. Actions
should be taken if the requirements for conventional deviation are not met.
Direct exposure of a sphere-gap to the light from the impulse generator gaps, or to negative
polarity corona of the used or separate source, may be sufficient.
Irradiation is usually required for measurements below 50 kV peak for all sphere diameters,
and for measurement of voltages with spheres of 12,5 cm diameter and less for all voltage
shapes. Methods of arranging irradiation are described in annex C.
NOTE When sufficient irradiation is not available, the uncertainty associated with the values for disruptive
discharge in the tables 2 and 3 should be increased.
5.3 Voltage measurements
A measurement of voltage by means of sphere-gap consists of establishing the relation
between a voltage in the test circuit, as measured by the standard air gap, and the indication of
a voltmeter in the control circuit, or the peak value of the voltage obtained from a suitable
measuring or recording device connected to the low voltage side of a measuring system. The
spacing between the spheres shall be measured by a method consistent with the overall
uncertainty of the voltage measurement. Unless the contrary can be shown, this relation
ceases to be valid if the circuit is altered in any respect other than due to a change of the
spacing of the spheres.
5.3.1 Measurement of peak value of alternating voltage at power frequency
The voltage shall be applied with an amplitude low enough not to cause disruptive discharge
when the supply is energized, and it is then raised sufficiently slowly for the low-voltage
indicator to be read accurately at the instant of disruptive discharge of the gap.
A minimum number of 10 successive disruptive discharge voltages shall be recorded in order
that the mean value and conventional deviation z can be evaluated. The value of the
conventional deviation z shall be less than 1 % of the mean value.
The interval between voltage applications should be not less than 30 s.

---------------------- Page: 13 ----------------------

60052 © IEC:2002 – 19 –
5.3.2 Measurement of peak value of full lightning and switching impulse voltages
The 50 % disruptive discharge voltage U and the conventional deviation z shall be
50
determined. The value of the conventional deviation z shall be not more than 1 % for full
lightning impulse voltages and not more than 1,5 % for switching impulse voltages.
This can be done by a multiple level test. A minimum of 10 voltage applications at each of five
voltage levels in approximately 1 % steps of the expected disruptive discharge value is needed
to obtain U and to check the conventional deviation z.
50
It can also be done by an up-and-down-test with a minimum number of 20 voltage applications
at approximately 1 % steps of the expected U voltage.
50
The criterion for the conventional deviation z shall be checked by applying 15 impulses at a
voltage level of U -1 % for lightning impulse voltages and U -1,5 % for switching impulse
50 50
voltages. There shall be not more than two disruptive discharges.
The interval between voltage applications shall be not less than 30 s.
NOTE If, in a particular test, the sphere-gap is used over a gap spacing range, the criterion for the conventional
deviation z should be checked for the smallest and largest gap distances.
5.3.3 Measurement of direct voltages
Sphere-gaps are not recommended for the measurement of direct voltages because of the
erratic behaviour of these gaps due to fibrous particles in the air which cause erratic disruptive
discharges at low voltages. The rod-rod gap is recommended for the measurement of direct
–3 –3
voltage in a humidity range from 1 gm to 13 gm .
When a rod-rod-gap cannot be used, the following procedure for sphere-gaps is recommended.
A constant air flow of at least 3m/s should be maintained across the gap. The voltage shall
then be
...