EN 61952:2003

SLOVENSKI STANDARD
01-september-2004
Insulators for overhead lines - Composite line post insulators for alternative
current with a nominal voltage > 1000 V (IEC 61952:2002)
Insulators for overhead lines - Composite line post insulators for alternative current with a
nominal voltage > 1 000 V
Isolatoren für Freileitungen - Verbund-Freileitungsstützer für
Wechselspannungsfreileitungen mit einer Nennspannung über 1 000 V
Isolateurs pour lignes aériennes - Isolateurs composites rigides à socle pour courant
alternatif de tension nominale > 1 000 V
Ta slovenski standard je istoveten z: EN 61952:2003
ICS:
29.080.10 Izolatorji Insulators
29.240.20 Daljnovodi Power transmission and
distribution lines
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN 61952
NORME EUROPÉENNE
EUROPÄISCHE NORM January 2003

ICS 29.080.10; 29.240.20
English version
Insulators for overhead lines -
Composite line post insulators for alternative current
with a nominal voltage > 1 000 V
(IEC 61952:2002)
Isolateurs pour lignes aériennes - Isolatoren für Freileitungen -
Isolateurs composites rigides à socle Verbund-Freileitungsstützer
pour courant alternatif für Wechselspannungsfreileitungen
de tension nominale > 1 000 V mit einer Nennspannung über 1 000 V
(CEI 61952:2002) (IEC 61952:2002)

This European Standard was approved by CENELEC on 2002-12-01. 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, 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

© 2003 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 61952:2003 E
Foreword
The text of document 36B/208/FDIS, future edition 1 of IEC 61952, prepared by SC 36B, Insulators for
overhead lines, of IEC TC 36, Insulators, was submitted to the IEC-CENELEC parallel vote and was
approved by CENELEC as EN 61952 on 2002-12-01.

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) 2003-09-01

– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2005-12-01

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 annexes A, B and C are informative.
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61952:2002 was approved by CENELEC as a European
Standard without any modification.

In the official version, for Bibliography, the following note has to be added for the standard indicated:

IEC 60507 NOTE Harmonized as EN 60507:1993 (not modified).
__________
- 3 - EN 61952:2003
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 60383-1 1993 Insulators for overhead lines with a EN 60383-1 1996
nominal voltage above 1 kV A11 1999
Part 1: Ceramic or glass insulator units
for a.c. systems - Definitions, test
methods and acceptance criteria

IEC 60383-2 1993 Part 2: Insulator strings and insulator EN 60383-2 1995
sets for a.c. systems - Definitions, test
methods and acceptance criteria

IEC 60695-11-10 1999 Fire hazard testing EN 60695-11-10 1999
Part 11-10: Test flames - 50 W
horizontal and vertical flame test
methods
ISO 868 1985 Plastics and ebonite - Determination of EN ISO 868 1997
indentation hardness by means of a
durometer (Shore hardness)
ISO 3274 1996 Geometrical Product Specifications EN ISO 3274 1997
Cor 1 1998 (GPS) - Surface texture: Profile
method - Nominal characteristics of
contact (stylus) instruments
ISO 3452 Series Non-destructive testing - Penetrant - -
inspection
ISO 4287 1997 Geometrical Product Specifications EN ISO 4287 1998
Cor 1 1998 (GPS) - Surface texture: Profile
method - Terms, definitions and
surface texture parameters
ISO 4892-1 1999 Plastics - Methods of exposure to EN ISO 4892-1 2000
laboratory light sources
Part 1: General guidance
Publication Year Title EN/HD Year
ISO 4892-2 1994 Part 2: Xenon arc sources EN ISO 4892-2 1999

ISO 4892-3 1994 Part 3: Fluorescent UV lamps EN ISO 4892-3 1999

NORME CEI
INTERNATIONALE IEC
INTERNATIONAL
Première édition
STANDARD
First edition
2002-07
Isolateurs pour lignes aériennes –
Isolateurs composites rigides
à socle pour courant alternatif
de tension nominale >1 000 V
Insulators for overhead lines –
Composite line post insulators
for alternative current
with a nominal voltage >1 000 V
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électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from
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Pour prix, voir catalogue en vigueur
For price, see current catalogue

61952  IEC:2002 – 3 –
CONTENTS
FOREWORD . 5
INTRODUCTION .7
1 Scope and object .11
2 Normative references.11
3 Definitions .13
4 Identification .17
5 Classification of tests.17
5.1 Design tests .17
5.2 Type tests.21
5.3 Sample tests.21
5.4 Routine tests .21
6 Design tests.21
6.1 General .21
6.2 Tests on interfaces and connections of end fittings.21
6.3 Assembled core load tests.25
6.4 Tests of shed and housing material .27
6.5 Tests for the core material .33
7 Type tests.35
7.1 Verification of dimensions.37
7.2 Electrical tests .37
7.3 Mechanical tests.39
8 Sample tests.41
8.1 General rules.41
8.2 Verification of dimensions (E1 + E2) .41
8.3 Galvanizing test (E1 + E2) .41
8.4 Verification of the SCL (E1) .41
8.5 Re-testing procedure .43
9 Routine tests .43
9.1 Tensile load test .43
9.2 Visual examination .43
Annex A (informative) Notes on the mechanical loads and tests.51
Annex B (informative) Determination of the equivalent bending moment
caused by combined loads.55
Annex C (informative) Explanation of the concept of classes for the design tests .61
Bibliography.63
Figure 1 – Thermal-mechanical pre-stressing test –Typical cycles .45
Figure 2 – Example of a boiling container for the water diffusion test .47
Figure 3 – Electrodes for the voltage test .49
Figure 4 – Typical circuit for the voltage test .49
Figure B.1 – Combined loads applied to unbraced insulators.57
Figure B.2 – Combined loads applied to braced insulators .59

61952  IEC:2002 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INSULATORS FOR OVERHEAD LINES –
COMPOSITE LINE POST INSULATORS FOR ALTERNATIVE CURRENT
WITH A NOMINAL VOLTAGE >>1 000 V
>>
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 61952 has been prepared by subcommittee 36B: Insulators for
overhead lines, of IEC technical committee 36: Insulators.
The text of this standard is based on the following documents:
FDIS Report on voting
36B/208/FDIS 36B/209/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, and C are for information only.
The committee has decided that the contents of this publication will remain unchanged until
2004. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
61952  IEC:2002 – 7 –
INTRODUCTION
Composite line post insulators consist of a cylindrical solid insulating core, bearing the
mechanical load, protected by an elastomer housing, the loads being transmitted to the core
by metal fittings. Despite these common features, the materials used and the construction
details employed by different manufacturers may be different.
Some tests have been grouped together as "design tests" to be performed only once for
insulators of the same design. Design tests are performed in order to eliminate designs and
materials not suitable for high-voltage applications. The influence of time on the electrical and
mechanical properties of the complete composite line post insulator and its components (core
material, housing material, interfaces, etc.) has been considered in specifying the design tests
in order to ensure a satisfactory lifetime under normal service conditions.
The approach for mechanical testing under bending loads used in this standard is based on
the work of CIGRE. This approach uses the concept of a damage limit which is the maximum
stress which can be developed in the insulator before damage begins to occur. Annex A gives
some notes on the mechanical loads and tests used in this standard.
Line post insulators are often used in braced structures whose geometry varies from line to
line. A combined loading test to reproduce the complex loading cases in such structures is
outside the scope of this standard and it would be very difficult to specify a general test which
covers the majority of geometry and loading cases. In order to give some guidance, annex B
explains how to calculate the moment in the insulators resulting from combined loads. This
moment can then be equated to an equivalent bending load or stress for design purposes.
Compression load tests are not specified in this standard. The mechanical loads expected
from service stress acting on line post insulators are mostly combined loads, These loads will
cause some deflection on the insulator. Compression loads applied on pre-deflected
insulators will lead to results largely dependent on the pre-deflection. Therefore a pure
compression test has little meaning since the deflection prior to the cantilever load test cannot
be specified.
Pollution tests, as specified in IEC 60507, are not included in this standard, their applicability
to composite line post insulators not having been proven. Such pollution tests performed on
insulators made of non-ceramic materials do not correlate with experience obtained from
service. Specific pollution tests for non-ceramic insulators are under consideration.
The tracking and erosion test given in this standard is based on the test specified in
IEC 61109. However, when this standard was drafted, it had been decided to study the
possibility of preparing a general standard on tracking, erosion and ageing tests for all types
of composite insulators. The prescriptions concerning the 1 000 h and alternative tests for
severe environmental conditions are therefore given as a temporary measure until such time
as the general standard is issued by the IEC.

61952  IEC:2002 – 9 –
For insulators intended for use in severe environmental conditions, a supplementary multi-
stress ageing test may be considered (such as the 5 000 h ageing test in annex C of
IEC 61109). However CIGRE and IEC are currently studying the representativity, repeatability
and reproducibility of ageing tests and will issue guidance in the future. In the meantime, it is
recommended that particular care be taken when specifying the type and parameters of such
tests.
It has not been considered useful to specify a power arc test as a mandatory test. The test
parameters are manifold and can have very different values depending on the configurations
of the network and the supports and on the design of arc-protection devices. The heating
effect of power arcs should be considered in the design of metal fittings. Critical damage to
the metal fittings, resulting from the magnitude and duration of the short-circuit current can be
avoided by properly designed arc-protection devices. This standard, however, does not
exclude the possibility of a power arc test if agreed between the user and manufacturer.
IEC 61467 gives details of a.c. power arc testing of insulator sets.
Radio interference and corona tests are not specified in this standard since the RIV and
corona performance are not characteristics of the insulator alone.
Composite, hollow core, line post insulators are currently not dealt with in this standard.
IEC 61462 gives details of tests on hollow core, composite insulators, many of which can be
applied to such line post insulators.
Torsion loads are not dealt with in this standard since they are usually negligible in the
configuration in which line post insulators are generally used. Specific applications where high
torsion loads can occur are outside the scope of this standard.

61952  IEC:2002 – 11 –
INSULATORS FOR OVERHEAD LINES –
COMPOSITE LINE POST INSULATORS FOR ALTERNATIVE CURRENT
WITH A NOMINAL VOLTAGE >>>>1000 V
1 Scope and object
This International Standard applies to composite line post insulators consisting of a load-
bearing, cylindrical, insulating solid core made up of fibres – usually glass – in a resin-based
matrix, a housing (outside the insulating core) made of elastomer material (e.g. silicone or
ethylene-propylene) and end fittings permanently attached to the insulating core.
Composite line post insulators covered by this standard are subjected to cantilever, tensile
and compressive loads, when supporting the line conductors.
They are intended for use on a.c. overhead lines with a rated voltage greater than 1 000 V
and a frequency not greater than 100 Hz.
The object of this standard is to
– define the terms used,
– prescribe test methods,
– prescribe acceptance or failure criteria.
This standard does not include requirements dealing with the choice of insulators for specific
operating conditions.
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 60383-1:1993, Insulators for overhead lines with a nominal voltage above 1 000 V –
Part 1: Ceramic or glass insulator units for a.c. systems – Definitions, test methods and
acceptance criteria
IEC 60383-2:1993, Insulators for overhead lines with a nominal voltage above 1 000 V –
Part 2: Insulator strings and insulator sets for a.c. systems – Definitions, test methods and
acceptance criteria
IEC 60695-11-10:1999, Fire hazard testing – Part 11-10: Test flames – 50 W horizontal and
vertical flame test methods
ISO 868:1985, Plastics and ebonite – Determination of indentation hardness by means of
a durometer (Shore hardness)
61952  IEC:2002 – 13 –
ISO 3274:1996, Geometrical Product Specifications (GPS) – Surface texture: Profile method –
Nominal characteristics of contact (stylus) instruments
ISO 3274:1996/Cor. 1:1998
ISO 3452 (all parts), Non-destructive testing – Penetrant inspection
ISO 4287:1997, Geometrical Product Specifications (GPS) – Surface texture: Profile method –
Terms, definitions and surface texture parameters
ISO 4287:1997/Cor. 1:1998
ISO 4892-1:1999, Plastics – Methods of exposure to laboratory light sources – Part 1:
General guidance
ISO 4892-2:1994, Plastics – Methods of exposure to laboratory light sources – Part 2: Xenon-
arc sources
ISO 4892-3:1994, Plastics – Methods of exposure to laboratory light sources – Part 3:
Fluorescent UV lamps
3 Definitions
For the purposes of this International Standard, the following definitions apply.
3.1
composite line post insulator
insulator consisting of a load-bearing cylindrical insulating solid core, a housing and end
fittings attached to the insulating core. It is intended to be subjected to cantilever, tensile
and compressive loads
3.2
core
internal insulating part of a composite line post insulator designed to ensure the mechanical
characteristics. The core usually consists of glass-fibres in a resin-based matrix
3.3
housing
external insulating part of composite line post insulator providing necessary creepage
distance and protecting core from environment. An intermediate sheath made of insulating
material may be part of the housing
3.4
housing profile
shape and dimensions of the housing which include the following:
– shed overhang(s)
– shed thickness at the base and at the tip
– shed spacing
– shed repetition
– shed inclination(s).
61952  IEC:2002 – 15 –
3.5
shed
projecting part of the housing intended to increase the creepage distance
3.6
interface
surface between different materials. Various interfaces occur in most composite line post
insulators, e.g.
– between glass fibres and impregnating resin,
– between core and housing,
– between various parts of the housing, e.g. between sheds or between sheds and sheath,
– between housing, core and end fittings
3.7
end fittings of a composite line post insulator
devices forming an integral and permanent part of the insulator intended to connect it to a
supporting structure or to conductor hardware. The base end fitting of a composite line post
insulator is where the maximum cantilever stress usually occurs. The line end fitting is where
the cantilever load is usually applied
3.8
connection zone
zone where the mechanical load is transmitted between the core and the end fitting
3.9
coupling zone
part of the end fitting which transmits the load to the hardware external to the composite line
post insulator
3.10
tracking
irreversible degradation consisting of the formation of conductive paths starting and
developing on the surface of an insulating material. These paths are conductive even under
dry conditions. Tracking can occur on surfaces in contact with air and also on the interfaces
between different insulating materials
3.11
erosion
irreversible and non-conducting degradation of the surface of the insulator that occurs by loss
of material. This can be uniform, localized or tree-shaped
NOTE Light surface traces, commonly tree-shaped, can occur on composite line post insulators, as on ceramic
insulators, after partial flashover. These traces are not considered to be objectionable as long as they are non-
conducting. When they are conducting they are classed as tracking.
3.12
delamination of the core
irreversible loss of bonding within fibre laminates perceivable by the naked eye
3.13
crack
any internal fracture or surface fissure of depth greater than 0,1 mm

61952  IEC:2002 – 17 –
3.14
specified cantilever load (SCL)
cantilever load which can be withstood by the insulator at the line end fitting when tested
under the prescribed conditions. This value is specified by the manufacturer
3.15
maximum design cantilever load (MDCL)
load level above which damage to the core begins to occur and which is the ultimate limit for
service loads. This value and direction of the load are specified by the manufacturer
3.16
specified tensile load (STL)
tensile load which can be withstood by the insulator when tested under the prescribed
conditions. This value is specified by the manufacturer
3.17
failing load of a composite line post insulator
maximum load that is reached when tested under the prescribed conditions
NOTE Damage to the core is likely to occur at loads lower than the insulator failing load.
4 Identification
The manufacturer’s drawing shall show the relevant dimensions and values necessary for
identifying and testing the insulator in accordance with this standard. The drawing shall also
show applicable manufacturing tolerances. In addition, the relevant IEC designation shall
figure on the drawing.
Each insulator shall be marked with the name or trade mark of the manufacturer and the year
of manufacture. In addition, each insulator shall be marked with the MDCL or with the relevant
IEC designation. These markings shall be legible and indelible.
NOTE At present there is no IEC standard giving designations of composite line post insulators.
5 Classification of tests
The tests are divided into four groups as follows:
5.1 Design tests
These tests are intended to verify the suitability of the design, materials and method of
manufacture (technology). A composite line post insulator design is defined by
− materials of the core, housing and manufacturing method,
− material of the end fittings, their design and method of attachment,
− layer thickness of the housing over the core (including a sheath where used),
− diameter of the core.
When changes in the design occur, re-qualification shall be carried out in accordance with
table 1.
61952  IEC:2002 – 19 –
Table 1 – Tests to be carried out after design changes
THEN the following design tests shall be repeated:
6.2 6.3 6.4.1 6.4.2 6.4.3 6.4.4 6.5.1 6.5.2
IF the change in insulator design concerns: .
1 Housing materials x xxx x
a b
2 Housing profile x x
3 Core material xx xx
4 Core diameter xx xx
5 Manufacturing process xx xxx xx
6 End fitting material xx
7a End fitting connection zone design xx
7b Base end fitting coupling design x
7c Core/housing/end fitting interface design x
8 End fitting method of attachment to core xx
a
Variations of the profile within following tolerances do not constitute a change:
Overhang: ±15 %
+15
Diameter: %
Thickness at base and tip: ±15 %
Spacing : ±25 %
Mean shed inclination: ±3 %
Shed repetition: Identical
b
Except 6.2.2.1 and 6.2.3.3.
When a composite line post insulator is submitted to the design tests, it becomes a parent
insulator for a design class and the results shall be considered valid for the whole class.
Annex C gives information on the design class concept. This tested parent insulator defines a
design class of insulators which have the following characteristics:
A same materials for the core and housing and same manufacturing method;
B same material for the end fittings, same design and same method of attachment;
C same or greater minimum layer thickness of the housing over the core (including an
intermediate sheath where used) within a tolerance of ±15 %;
D same or smaller ratio of all mechanical loads to the smallest core diameter between
fittings;
E same or greater diameter of the core;
F same housing profile parameters within a tolerance of ±15 %, except for spacing where
the tolerance is ±25 %.
Interfaces and
connections of
end fittings
Assembled
core load tests
Hardness test
Accelerated
weathering test
Tracking and
erosion test
Flammability
test
Dye
penetration
test
Water diffusion
test
61952  IEC:2002 – 21 –
5.2 Type tests
These tests are intended to verify the main characteristics of a composite line post insulator
which depend mainly on its shape and size. Type tests shall be applied to composite
insulators belonging to an already qualified design class. The type tests shall be repeated
only when the type of the composite insulator is changed (see clause 7 for more details of
insulator types).
5.3 Sample tests
These tests are intended to verify the characteristics of composite line post insulators which
depend on the quality of manufacture and materials used. They shall be made on insulators
taken at random from lots offered for acceptance.
5.4 Routine tests
These tests are intended to eliminate composite line post insulators with manufacturing
defects. They shall be made on every composite line post insulator to be supplied.
6 Design tests
6.1 General
The design tests shall be performed only once and the results shall be recorded in a test
report. Each part can be performed independently on new test specimens where appropriate.
The composite line post insulator of a particular design shall be deemed accepted only when
all insulators or test specimens have satisfied all the design tests.
6.2 Tests on interfaces and connections of end fittings
6.2.1 Test specimen
For this series of tests four insulators assembled on the production line shall be selected.
One of these is reserved as reference for the dry power-frequency voltage test described
in 6.2.3.3. The insulation length (metal to metal spacing) shall be at least 15 times the
core diameter.
If the manufacturer only has facilities to produce insulators shorter than 15 times the core
diameter, the design tests may be performed on insulators of those lengths available to him.
However the results are only valid for up to the lengths tested.
If not already routine tested, the insulators shall be examined visually and their conformity
with the drawing shall be checked. They shall then be subjected to the tensile load routine
test according to 9.1.
6.2.2 Pre-stressing
The pre-stressing shall be carried out on three specimens in the sequence indicated below.

61952  IEC:2002 – 23 –
6.2.2.1 Thermal-mechanical pre-stressing
The three specimens shall be submitted to a mechanical load in two opposite directions and
to temperature cycles as described in figure 1. The 24 h temperature cycle shall be repeated
twice. Each temperature cycle has two temperature levels with a duration of at least 8 h, one
at +50 °C ± 5 K, the other at –35 °C ± 5 K. The cold period shall be at a temperature at least
85 K below the value actually applied in the hot period. The pre-stressing can be conducted in
air or any other suitable medium.
The load applied to the specimens shall correspond to the MDCL.
The load shall be applied perpendicularly to the insulator's axis as near as possible to the
normal load application point, either directly at the normal conductor position or at a hardware
attachment point. When the load is not applied at the normal application point, it shall be
corrected to produce the same bending moment at the base of the insulator as the one
exerted by the MDCL.
The direction of the cantilever load applied to the specimens shall be reversed once,
generally at the cooling passage through ambient temperature as described in figure 1.
The cycles may be interrupted for the load direction reversal and for maintenance of the test
equipment for a total duration of 2 h. The starting point after any interruption shall be the
beginning of the interrupted cycle.
NOTE The temperatures and loads in this pre-stressing are not intended to represent service conditions; they are
designed to produce specific reproducible stresses in the interfaces on the insulator.
6.2.2.2 Water immersion pre-stressing
The specimens shall be kept immersed in boiling de-ionized water with 0,1 % by weight of
NaCl, for 42 h. Alternatively, tap water may be used with salt added to obtain a conductivity
of 1 650 µS/cm ± 50 µS/cm at 20 °C to 25 °C.
At the end of boiling, the specimens are allowed to cool and shall remain in water until the
verification tests start in the following sequence. If transport is necessary in this period,
the wet insulators may be put in sealed plastic bags or another suitable container for
a maximum of 12 h.
6.2.3 Verification tests
The time interval between the following individual tests: 6.2.3.1, 6.2.3.2 and 6.2.3.3, shall be
such that the verification tests are completed within 48 h.
6.2.3.1 Visual examination
The housing of each specimen shall be inspected visually. No cracks are permissible.
6.2.3.2 Steep-front impulse voltage test
6.2.3.2.1 Test procedure
The test specimens shall be fitted with sharp-edged electrodes (consisting of clips, e.g. made
of a copper strip approximately 20 mm wide and less than 1 mm thick). These electrodes are
fitted firmly around the housing between sheds and positioned to form sections of axial length
of about 500 mm or smaller. The voltage shall be applied to the end fittings in the case of
insulators with a distance between end fittings smaller than, or equal to, 500 mm.

61952  IEC:2002 – 25 –
An impulse voltage with a steepness of at least 1 000 kV/µs shall be applied between two
neighbouring electrodes or between the metal fitting and the neighbouring electrode,
respectively. Each section shall be stressed individually with 25 impulses of positive and
25 impulses of negative polarity.
6.2.3.2.2 Acceptance criteria
Each impulse shall cause external flashover between the electrodes. No puncture of any part
of the insulator shall occur. The electrodes used to form sections shall be removed.
6.2.3.3 Dry power-frequency voltage test
6.2.3.3.1 Test procedure
The dry power-frequency flashover voltage shall be determined by averaging five flashover
voltages on each specimen. The average flashover voltage shall be corrected to normal
standard atmospheric conditions in accordance with IEC 60060-1. The flashover voltage shall
be obtained by increasing the voltage linearly from zero within 1 min.
Using the same method, determine the value of the reference flashover voltage using the
additional reference insulator.
The three test specimens and the reference insulator shall then be allowed to reach thermal
equilibrium with the surrounding atmosphere.
The three test specimens and the reference insulator shall then be continuously subjected for
30 min to 80 % of the reference flashover voltage.
The temperature of the shank of the three test specimens and of the reference insulator shall
be measured immediately after the removal of the test voltage.
6.2.3.3.2 Acceptance criteria
The flashover voltage of each of the three test insulators shall be greater than or equal to
90 % of the reference flashover voltage.
No puncture of any part of the insulator shall occur and the temperature rise of the insulator
shank with respect to the temperature of the reference insulator shall be less than 10 K.
6.3 Assembled core load tests
6.3.1 Test for the verification of the maximum design cantilever load (MDCL)
6.3.1.1 Test specimens and test procedure
Three insulators made on the production line using the standard end fittings shall be selected.
The overall length of the insulators shall be between 15 and 18 times the diameter of the
core, unless the manufacturer does not have facilities to make such a length. In this case, the
length of insulator shall be as near as possible to the prescribed length range.
If not already routine tested, the insulators shall be examined visually and their conformity
with the drawing shall be checked. They shall then be subjected to the tensile load routine
test according to 9.1.
61952  IEC:2002 – 27 –
The insulator shall be gradually loaded to 1,1 times the MDCL at a temperature of 20 °C ± 10 K.
This load shall be maintained for 96 h. The load shall be applied to the insulator at the
conductor position in the specified direction, and perpendicular to the core of the insulator.
After removal of the load, the steps below shall be followed:
– visually inspect the base end fitting for cracks or permanent deformation,
– check that threads of the end fitting are re-usable.
Cut each insulator at 90° to the axis of the core and about 50 mm from the base end fitting,
then cut the base end fitting longitudinally into two halves in the plane of the previously
applied cantilever load. The cut surfaces shall be smoothed by means of fine abrasive cloth
(grain size 180). Then:
– visually inspect the cut halves for cracks and delamination,
– perform a dye penetration test according to ISO 3452 to the cut surfaces to reveal cracks.
6.3.1.2 Acceptance criteria
Non-compliance with any of the above points shall constitute failure.
6.3.2 Tensile load test
6.3.2.1 Test procedure
Three insulators made on the production line using the standard end fittings shall be selected.
If not already routine tested, the insulators shall be examined visually and their conformity
with the drawing shall be checked. They shall then be subjected to the tensile load routine
test according to 9.1.
The tensile load shall be applied in line with the axis of the core of the insulator, at or near the
intended service attachment point. The load shall be increased rapidly but smoothly from zero
to approximately 75 % of the STL and shall then be gradually increased in a time between
30 s and 90 s until the STL is reached. If the STL is reached in less than 90 s, the load shall
be maintained for the remainder of the 90 s.
6.3.2.2 Acceptance criteria
The test shall be regarded as passed if there is no evidence of
– pull-out of the core from the end fitting,
– breakage of the end fitting.
6.4 Tests of shed and housing material
6.4.1 Hardness test
6.4.1.1 Test procedure
Two specimens of the housing material of a size, shape and thickness appropriate for the
hardness measurement method given in ISO 868 shall be taken from the housing of two
insulators. If the shed shape or thickness is inappropriate, then samples may be made
separately using the same manufacturing process and parameters.

61952  IEC:2002 – 29 –
Measure and record the ambient temperature and the hardness of the two samples in
accordance with ISO 868 with a Shore A durometer.
The samples shall then be kept immersed in boiling water as defined in 6.2.2.2, for 42 h. The
boiling container shown in figure 2 is suitable for this boiling.
At the end of the boiling period, the samples shall be allowed to cool and, within 3 h, their
hardness shall be measured again at the same temperature as that of the pre-boiling
measurements ±5 K.
6.4.1.2 Acceptance criteria
The hardness of each specimen shall not change from the pre-boiled value by more than
20 %.
6.4.2 Accelerated weathering test
6.4.2.1 Test procedure
Select three specimens of shed and housing materials for this test (with markings included, if
applicable).
The insulator housing shall be subjected to a 1 000 h UV light test using one of the following
test methods. Markings on the housing, if any, shall be directly exposed to UV light.
• Xenon-arc methods: ISO 4892-1 and ISO 4892-2 using
− method A without dark periods,
− standard spray cycle,
− black-standard/black panel temperature of 65 °C,
− an irradiance of around 550 W/m².
• Fluorescent UV Method: ISO 4892-1 and ISO 4892-3, using
− type I fluorescent UV lamp,
− exposure method 2.
Test without water are not permitted.
6.4.2.2 Acceptance criteria
After the test, markings on shed or housing material shall still be legible; surface degradations
such as cracks and blisters are not permitted.
In case of doubt concerning such degradation, two surface roughness measurements shall be
made on each of the three specimens. The crack depth, R as defined in ISO 4287, shall be
z
measured along a sampling length of at least 2,5 mm. R shall not exceed 0,1 mm.
z
NOTE ISO 3274 give details of surface roughness measurement instruments.

61952  IEC:2002 – 31 –
6.4.3 Tracking and erosion test
6.4.3.1 Test specimens
Two test insulators with a creepage distance between 480 mm and 690 mm shall be taken
from the production line. If such insulators cannot be taken from the production line, special
test specimens shall be cut from other insulators so that the creepage distance falls between
the given values. These special test specimens shall be fitted with standard production end
fittings.
6.4.3.2 Test procedure
The test is a time-limited continuous test in salt fog at constant power-frequency voltage in
the range of 14 kV to 20 kV. The test voltage in kilovolts is determined by dividing the
creepage distance in millimetres by 34,6 (equal to a specific creepage distance of 20 mm/kV).
The test shall be carried out in a moisture-sealed, corrosion-proof chamber, the volume of
3 2
which shall not exceed 10 m . An aperture of
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