IEC 61109:2025

IEC 61109 ®
Edition 3.0 2025-02
COMMENTED VERSION
INTERNATIONAL
STANDARD
Insulators for overhead lines – Composite suspension and tension insulators
with AC voltage greater than 1 000 V and DC voltage greater than 1 500 V –
Definitions, test methods and acceptance criteria
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IEC 61109 ®
Edition 3.0 2025-02
COMMENTED VERSION
INTERNATIONAL
STANDARD
Insulators for overhead lines – Composite suspension and tension insulators
with AC voltage greater than 1 000 V and DC voltage greater than 1 500 V –
Definitions, test methods and acceptance criteria
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.080.10 ISBN 978-2-8327-0286-4
– 2 – IEC 61109:2025 CMV © IEC 2025
CONTENTS
FOREWORD .5
INTRODUCTION .7
1 Scope and object .9
2 Normative references .9
3 Terms, definitions and abbreviated terms . 10
3.1 Terms and definitions . 10
3.2 Abbreviated terms . 13
4 Identification . 13
5 Environmental conditions . 14
6 Transport, storage and installation . 15
7 Hybrid insulators .
7 Tolerances . 15
8 Classification of tests . 15
8.1 Design tests . 15
8.2 Type tests . 16
8.3 Sample tests . 17
8.4 Routine tests . 17
9 Design tests . 20
9.1 General . 20
9.2 Test specimens for IEC 62217 . 20
9.2.1 Tests on interfaces and connections of end fittings . 20
9.2.2 Tracking and erosion test . 21
9.2.3 Tests on core material . 21
9.2.4 Tests on core with housing . 21
9.3 Product specific pre-stressing for IEC 62217 tests on interfaces and
connections of end fittings . 21
9.3.1 General . 21
9.3.2 Sudden load release . 21
9.3.3 Thermal-mechanical pre-stress . 22
9.4 Assembled core load-time tests . 22
9.4.1 Test specimens . 22
9.4.2 Mechanical load test . 23
10 Type tests . 23
10.1 General . 23
10.2 Electrical tests on string insulator units. 24
10.2.1 General . 24
10.2.2 Test specimens . 24
10.2.3 Mounting arrangements for electrical tests . 24
10.2.4 Dry lightning impulse withstand voltage test . 24
10.2.5 Wet power-frequency voltage tests. 24
10.2.6 Wet switching impulse withstand voltage test . 25
10.2.7 Corona and radio interference voltage (RIV) tests . 25
10.2.8 Power arc test . 25
10.3 Damage limit proof test and test of the tightness of the interface between
end fittings and insulator housing . 26
10.3.1 Test specimens . 26

10.3.2 Performance of the test . 26
10.3.3 Evaluation of the test . 28
11 Sample tests . 28
11.1 General rules. 28
11.2 Verification of dimensions (E1 + E2) . 29
11.3 Verification of the end fittings (E2) . 29
11.4 Verification of tightness of the interface between end fittings and insulator
housing (E2) and of the specified mechanical load, SML (E1) . 29
11.5 Galvanizing test (E2) . 30
11.6 Minimum sheath thickness (E1) . 30
11.7 Re-testing procedure . 30
12 Routine tests . 32
12.1 Mechanical routine test . 32
12.2 Visual examination . 33
Annex A (informative) Principles of the damage limit, load coordination and testing for
composite suspension and tension insulators . 34
A.1 Introductory remark . 34
A.2 Load-time behaviour and the damage limit. 34
A.3 Service load coordination . 35
A.4 Verification tests . 37
Annex B (informative) Example of two possible devices for sudden release of load . 39
B.1 Device 1 (Figure B.1) . 39
B.2 Device 2 (Figure B.2) . 39
Annex C (informative) Guidance on non-standard mechanical stresses and dynamic
mechanical loading of composite tension/suspension insulators . 41
C.1 Introductory remark . 41
C.2 Torsion loads. 41
C.3 Compressive (buckling) loads . 41
C.4 Bending loads . 42
C.5 Dynamic mechanical loads . 42
C.6 Limits . 43
Annex D (informative) Electric field control for AC . 44
Annex E (informative) Typical sketches for composite insulator assemblies . 46
Annex F (informative) Mechanical evaluation of the adhesion between core and
housing . 47
F.1 General . 47
F.2 Method A: Pull-off test . 48
F.2.1 General . 48
F.2.2 Specimens . 48
F.2.3 Procedure . 48
F.3 Method B: Peel test . 50
F.3.1 General . 50
F.3.2 Specimens . 50
F.3.3 Procedure . 51
F.4 Method C: Shear test . 52
F.4.1 General . 52
F.4.2 Specimens . 52
F.4.3 Procedure . 52
Annex G (informative) Applicability of design and type tests for DC applications. 53

– 4 – IEC 61109:2025 CMV © IEC 2025
Bibliography . 55
List of comments . 57

Figure 1 – Thermal-mechanical pre-stressing . 22
Figure 2 – Examples for 1 min SML withstand test . 27
Figure 3 – Location for minimum sheath thickness measurement . 30
Figure 4 – Method of re-testing at different stages . 32
Figure A.1 – Load-time strength and damage limit of a core assembled with fittings . 35
Figure A.2 – Graphical representation of the relationship of the damage limit to the
mechanical characteristics and service loads of an insulator with a 16 mm diameter
core and an SML rating of 133 kN . 36
Figure A.3 – Applied specific force relationship, example 1 . 36
Figure A.4 – Applied specific force relationship, example 2 . 37
Figure A.5 – Test loads . 38
Figure B.1 – Example of possible device 1 for sudden release of load. 39
Figure B.2 – Example of possible device 2 for sudden release of load. 40
Figure C.1 – Example of compression loads in V-string assemblies . 42
Figure C.2 – Buckling of composite insulator in a phase-to-phase configuration . 42
Figure D.1 – Example for electrical field vectors on a composite insulator . 45
Figure E.1 – Interface description for insulator with housing made by modular
assembly and external sealant . 46
Figure E.2 – Interface description for insulator with housing made by injection molding
and overmolded end fitting . 46
Figure F.1 – Example for type of housing separation . 47
Figure F.2 – Example of specimen mounted in a tensile test machine . 49
Figure F.3 – Example of test object for pull-off test and application clamping and force . 49
Figure F.4 – Relevant dimensions for the calculation of the area of the pull-off section . 50
Figure F.5 – Example of test specimen for peel test . 51
Figure F.6 – Method of peel test and tested specimens after peel test . 51
Figure F.7 – Method of shear test and tested samples after shear test with cohesive
bonding, sample passed the test. 52

Table 1 – Normal environmental conditions . 14
Table 2 – Tests to be carried out after design changes . 17
Table 3 – Design tests . 20
Table 4 – Application and mounting arrangements for electrical tests . 26
Table 5 – Sample sizes . 29
Table G.1 – Design and type tests for DC applications . 53

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INSULATORS FOR OVERHEAD LINES
COMPOSITE SUSPENSION AND TENSION INSULATORS
FOR A.C. SYSTEMS WITH A NOMINAL AC VOLTAGE GREATER THAN
1 000 V AND DC VOLTAGE GREATER THAN 1 500 V 1 –
DEFINITIONS, TEST METHODS AND ACCEPTANCE CRITERIA

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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9) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
respect thereof. As of the date of publication of this document, IEC had not received notice of (a) patent(s), which
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the latest information, which may be obtained from the patent database available at https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
This commented version (CMV) of the official standard IEC 61109:2025 edition 3.0 allows
the user to identify the changes made to the previous IEC 61109:2008 edition 2.0.
Furthermore, comments from IEC TC 36 experts are provided to explain the reasons of
the most relevant changes, or to clarify any part of the content.
A vertical bar appears in the margin wherever a change has been made. Additions are in
green text, deletions are in strikethrough red text. Experts' comments are identified by a
blue-background number. Mouse over a number to display a pop-up note with the
comment.
This publication contains the CMV and the official standard. The full list of comments is
available at the end of the CMV.

– 6 – IEC 61109:2025 CMV © IEC 2025
IEC 61109 has been prepared by subcommittee 36B: Insulators for overhead lines, of IEC
technical committee 36: Insulators. It is an International Standard.
This third edition cancels and replaces the second edition published in 2008. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) extension of this document to apply both to AC and DC systems;
b) modifications of Clause 3, Terms, definitions and abbreviations;
c) removal of Clause 7, Hybrid insulators, from this document;
d) modifications of tests procedures recently included in IEC 62217 (hydrophobicity transfer
test, stress corrosion, water diffusion test on the core with housing);
e) modifications on environmental conditions;
f) modifications on classification of tests and include the relevance of the interfaces;
g) clarification and modification of the parameters determining the need to repeat design and
type tests;
h) revision of Table 1;
i) revision of electrical type tests;
j) revision of re-testing procedure of sample test;
k) addition of a new Annex D on electric field control for AC;
l) addition of a new Annex E on typical sketch for composite insulators assembly;
m) addition of a new Annex F on mechanical evaluation of the adhesion between core and
housing;
n) addition of a new Annex G on applicability of design- and type tests for DC applications.
The text of this International Standard is based on the following documents:
Draft Report on voting
36/609/FDIS 36/611/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
This International Standard is to be used in conjunction with IEC 62217:2012.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
INTRODUCTION
Composite suspension and tension 2 insulators (in the following the term "composite insulator"
is used) consist of fibreglass insulating core, bearing the mechanical load protected by a
polymeric housing, the load being transmitted to the core by metallic end fittings. Despite these
common features, the materials used and the construction design details and manufacturing
process used by different manufacturers may differ.
Some tests have been grouped together as "Design tests", to be performed only once on
insulators which satisfy the same design conditions. For all design tests of these composite
suspension and tension insulators, the appropriate common clauses defined in IEC 62217 are
applied. As far as practical, the influence of time on the electrical and mechanical properties of
its components (core material, housing, interfaces etc.) and of the complete composite
insulators has been considered in specifying the design tests to ensure a satisfactory lifetime
under normally known stress conditions of transmission lines. Explanation of the principles of
the damage limit, load coordination and testing are presented in Annex A.
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 need to 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 document, however, does not
exclude the possibility of a power arc test by agreement between the user and manufacturer
and customer. IEC 61467 gives details on AC power arc testing of complete insulator sets, that
match their configuration with actual protective and string fittings, to recreate the real
electromagnetic field affecting the arc movement.
Composite insulators are used in both a.c. and d.c. applications. In spite of this fact, a specific
tracking and erosion test procedure for d.c. applications as a design test has not yet been
defined and accepted. The 1 000 h a.c. tracking and erosion test of IEC 62217 is used to
establish a minimum requirement for the tracking resistance of the housing material.
The mechanism of brittle fracture has been investigated by CIGRE B2.03 and conclusions are
published in [2, 3]. Brittle fracture is a result of stress corrosion induced by internal or external
acid attack on the resin bonded glass fibre core. CIGRE D1.14 has developed a test procedure
for core materials based on time-load tests on assembled cores exposed to acid, along with
chemical analysis methods to verify the resistance against acid attack [4]. In parallel IEC
TC36WG 12 is studying preventive and predictive measures.
This document covers both AC and DC composite insulators. Before the appropriate standard
for DC applications is issued, the majority of tests listed in this document can also be applicable
for DC (Annex G). Due to the difference in AC and DC tracking performance, a specific tracking
and erosion test procedure for DC applications as a design test is planned to be developed.
The 1 000 h AC tracking and erosion test of IEC 62217 can be used only to establish a minimum
requirement for the tracking and erosion resistance. This 1 000 h salt fog tracking and erosion
test is considered as a screening test intended to reject materials in combination with the design
which are inadequate. Tracking and erosion tests are not intended to evaluate long term
performance of insulators. Such tests, e.g. the 5 000 h multiple stress test and wheel test in
IEC TR 62730 [1] , or other tests intended for research or sometimes used as a supplementary
design test, are not considered in this document.
Composite suspension and tension insulators are, in general, not intended for torsion or other
non-tensile loads. However, due to consideration to non-standard applications (interphase
___________
International Council on Large High Voltage Electric Systems: Working Group B2.03.
Numbers in square brackets refer to the bibliography.

– 8 – IEC 61109:2025 CMV © IEC 2025
spacers etc.) loads during handling and installation have to be considered in the design.
Guidance on non-standard loads is given in Annex C.
Wherever possible, IEC Guide 111 [2] has been followed for the drafting of this document.

INSULATORS FOR OVERHEAD LINES
COMPOSITE SUSPENSION AND TENSION INSULATORS
FOR A.C. SYSTEMS WITH A NOMINAL AC VOLTAGE GREATER THAN
1 000 V AND DC VOLTAGE GREATER THAN 1 500 V –
DEFINITIONS, TEST METHODS AND ACCEPTANCE CRITERIA

1 Scope and object
This International Standard applies to composite suspension/tension insulators for overhead
lines consisting of a load-bearing cylindrical insulating solid core consisting of fibres – usually
glass – in a resin-based matrix, a housing (outside surrounding the insulating core) made of
polymeric material and metal end fittings permanently attached to the insulating core.
Composite insulators covered by this document are intended for use as suspension/tension line
insulators, but it should be noted that these insulators can could occasionally be subjected to
compression or bending, for example when used as phase interphase-spacers. Guidance on
such loads is outlined in Annex C.
This standard can be applied in part to hybrid composite insulators where the core is made of
a homogeneous material (porcelain, resin), see Clause 8.
The object of this document is to
– define the terms used,
– prescribe specify test methods,
– prescribe specify acceptance criteria.
This document does not include requirements dealing with the choice of insulators for specific
operating conditions or environments beyond normal environmental conditions defined in
Table 1.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60060-1, High-voltage test techniques – Part 1: General definitions and test requirements
IEC 60383-1, Insulators for overhead lines with a nominal voltage above 1000 V – Part 1:
Ceramic or glass insulator units for AC systems – Definitions, test methods and acceptance
criteria
IEC 60383-2, Insulators for overhead lines with a nominal voltage above 1 000 V – Part 2:
Insulator strings and insulator sets for AC systems – Definitions, test methods and acceptance
criteria
IEC 60437, Radio interference test on high-voltage insulators
IEC 61284, Overhead lines – Requirements and tests for fittings

– 10 – IEC 61109:2025 CMV © IEC 2025
IEC 61466-1, Composite string insulator units for overhead lines with a nominal voltage greater
than 1 000 V – Part 1: Standard strength classes and end fittings
IEC 61467, Insulators for overhead lines – Insulator strings and sets for lines with a nominal
voltage greater than 1 000 V – AC power arc tests
IEC 62217:2005— , Polymeric HV insulators for indoor and outdoor use with a nominal voltage
> 1 000 V – General definitions, test methods and acceptance criteria
IEC 62231, Composite station post insulators for substations with AC voltages greater than
1 000 V up to 245 kV – Definitions, test methods and acceptance criteria
ISO 3452 (all parts), Non-destructive testing – Penetrant testing
3 Terms, definitions and abbreviated terms
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
Note 1 to entry: Certain terms from IEC 62217:2012 are reproduced here for ease of reference. Additional
definitions applicable to insulators can be found in IEC 60050-471 [3].
3.1 Terms and definitions
3.1.1
polymeric insulator
insulator whose insulating body consists of at least one organic based material
Note 1 to entry: Polymeric insulators are also known as non-ceramic insulators.
Note 2 to entry: Coupling devices may be attached to the ends of the insulating body.
[SOURCE: IEC 60050-471:2007, 471-01-13]
3.1.2
composite insulator
insulator made of at least two insulating parts, namely a core and a housing equipped with
metal end fittings
Note 1 to entry: Composite insulators can consist either of individual sheds mounted on the core, with or without
an intermediate sheath, or alternatively, of a housing directly moulded or cast in one or several pieces on to the core.
[SOURCE: IEC 60050-471:2007, 471-01-02]
3.1.3
core (of a composite an insulator)
internal insulating part of a composite insulator which is designed to ensure the mechanical
characteristics
NOTE The core usually consists of either fibres (e.g. glass) which are positioned in a resin-based matrix or a
homogeneous insulating material (e.g. porcelain or resin).
___________
Under preparation. Stage at the time of publication: IEC/RFDIS 62217:2025.

[IEV 471-01-03, modified]
central insulating part of an insulator which provides the mechanical characteristics
Note 1 to entry: The housing and sheds are not part of the core.
[SOURCE: IEC 60050-471:2007, 471-01-03]
3.1.4
insulator trunk
central insulating part of an insulator from which the sheds project
Note 1 to entry: Also known as shank on smaller insulators.
[SOURCE: IEC 60050-471:2007, 471-01-11]
3.1.5
housing
external insulating part of composite insulator providing the necessary creepage distance and
protecting protects the core from the environment
Note 1 to entry: An intermediate sheath made of insulating material may be part of the housing.
[SOURCE: IEC 60050-471:2007, 471-01-09]
3.1.6
shed (of an insulator)
insulating part, projecting from the insulator trunk, intended to increase the creepage distance
Note 1 to entry: The shed can be with or without under-ribs.
[SOURCE: IEC 60050-471:2007, 471-01-15]
3.1.7
interface
contact surface between the different materials
Note 1 to entry: Various interfaces exist in composite insulators, e.g.:
– between housing and fixing devices end fittings;
– between various parts of the housing; e.g. between separately manufactured sheds, or between sheath and
sheds;
– between core and housing;
– between sealant and core;
– between sealant and end fittings.
(Annex E: Typical sketches for composite insulator assemblies)
[Definition 3.10 of IEC 62217]
[SOURCE: IEC 62217:—, 3.11, modified – "contact" added in definition, Note 1 to entry
modified]
3.1.8
end fitting
integral component or formed part of an insulator intended to connect it to a supporting
structure, or to a conductor, or to an item of equipment, or to another insulator
Note 1 to entry: Where the end fitting is metallic, in general the term "metal fitting" is used.
Note 2 to entry: Standard end fittings are defined in IEC 61466-1.

– 12 – IEC 61109:2025 CMV © IEC 2025
[SOURCE: IEC 60050-471:2007, 471-01-06]
3.1.9
connection zone
zone where the mechanical load is transmitted between the insulating body core and the end
fitting
[Definition 3.12 of IEC 62217]
[SOURCE: IEC 62217:2012, 3.13, modified – "insulating body and the fixing device" replaced
by "core and the end fitting"]
3.1.10
coupling
part of the end fitting which transmits the load to the accessories external to the insulator
[Definition 3.13 of IEC 62217, modified]
[SOURCE: IEC 62217:2012, 3.14, modified – "fixing device" replaced by "end fitting",
"hardware" replaced by "accessories"]
3.1.11
creepage distance
shortest distance or the sum of the shortest distances along the surface on an insulator between
two conductive parts which normally have the operating voltage between them
[SOURCE: IEC 60050-471:2007, 471-01-04]
3.1.12
arcing distance
shortest distance in the air external to the insulator between the metallic parts which normally
have the operating voltage between them
Note 1 to entry: The term "dry arcing distance" is also used.
[SOURCE: IEC 60050-471:2007, 471-01-01]
3.1.13
specified mechanical load
SML
withstand load, specified by the manufacturer, which is used for mechanical tests in this
document
3.1.14
routine test load
RTL
load applied to all assembled composite insulators during a routine mechanical test
3.1.15
mechanical failing load
maximum load that is reached when the insulator is tested under the prescribed standard
conditions
[SOURCE: IEC 60050-471:2007, 471-01-12, modified – "prescribed" replaced by "standard",
Note 1 to entry removed]
3.1.16
insulator set
assembly of one or more insulator strings suitably connected together, complete with end
fittings and protective devices as required in service
Note 1 to entry: The terms "arcing and field grading devices" is also used for protective devices.
[SOURCE: IEC 60050-471:2007, 471-03-02]
3.1.17
string insulator unit
cap and pin insulator or long rod insulator of which the end fittings are suitable for flexible
attachment to other similar string insulator units or to connecting accessories
Note 1 to entry: Cap and pin insulators are not composite insulators and are not part of this document.
[SOURCE: IEC 60050-471:2007, 471-03-08]
3.1.18
sealing
method for providing the ability of a component to resist the ingress of contaminants
Note 1 to entry: Contaminants include pollution and moisture.
[SOURCE: IEC 60050-581:2008, 581-23-16]
3.1.19
sealant
additional material used for sealing
Note 1 to entry: Typically RTV-silicones are used for composite insulators.
Note 2 to entry: See sealant in Annex E: Typical principles sketch for composite insulators assembly.
3.1.20
grading/corona ring
protective devices made from metal attached to the composite insulator end fitting or
intermediate string fitting intended to keep the electric field anywhere along the surface of
composite insulator below the specified maximum value
3.2 Abbreviated terms
The following abbreviated terms are used in this document:
E1, E2 Sample sets for sample tests
M Average 1 min failing load of the core assembled with fittings
AV
RTL Routine test load
RTV Room-temperature-vulcanizing silicone
SML Specified mechanical load
4 Identification
In addition to the requirements of IEC 62217, each insulator shall be marked with the SML.
It is recommended that each insulator is marked or labelled by the manufacturer to show that it
has passed the routine mechanical test.

– 14 – IEC 61109:2025 CMV © IEC 2025
5 Environmental conditions 3
The normal environmental conditions to which insulators are submitted in service are defined
in IEC 62217 and shown in Table 1. Terms are defined as follows:
• Indoor environment: installation within a building or other construction where the insulators
are protected against wind, rain, snow, periodical fast-built pollution deposits, abnormal
condensation, ice and hoar frost.
• Outdoor environment: installation in open air outside any building or shelter, where the
insulators are submitted to wind, rain, snow, periodical fast-built pollution deposits, high
condensation, ice and hoar frost.
If service conditions of polymeric insulators deviate significantly from the parameters in Table 1,
the insulator is to be designed or evaluated according to agreement between the customer and
manufacturer. Alternatively, if positive service experience ("i.e. no failures") is available for a
specific environment and specific insulator design (including material and profile), the insulator
can be used for this specific environment, deviating from normal environmental conditions.
Table 1 – Normal environmental conditions
Indoor insulation Outdoor insulation
a
Does not exceed 40 °C and its average value measured over a period of
Maximum ambient air temperature
24 h does not exceed 35 °C
b
−25 °C −40 °C
Minimum ambient air temperature
Vibration Negligible vibration due to causes external to the insulators or to earth
c
tremors .
d 2
Not applicable
Solar radiation Up to a level of 1 120 W/m
e
No significant pollution by dust, Pollution by dust, smoke, corrosive
Site pollution severity
smoke, corrosive and/or
gases, vapours or salt occurs.
flammable gases, vapours, or salt. Pollution does not exceed SPS class
"heavy" as defined in
IEC TS 60815-1 [5].
f
No rain, snow, abnormal humidity, Rain, snow, abnormal humidity,
Humidity
condensation, ice and hoar frost condensation, ice and hoar frost
occur.
a
If exceeded, follow the recommendations of IEC TR 62039 [5] for the core and adhesive materials (like glue) in
"glass transition temperature" section.
b
In general, temperatures below −40 °C are non-critical for service. However, for handling and installation the
crystallization temperature of the polymeric housing is to be considered. For line installations with temperatures
below −20 °C, special steel grades with low ductile transition temperature can be specified.
c
Vibration due to external causes can be dealt with in accordance to IEC 60721-1 [6].
d 2
For outdoor application, the influence of deviation from the assumed level of 1 120 W/m .
depends on the insulator material. If service conditions of polymeric insulators deviate significantly from the
parameters in Table 1, the insulator is to be designed/evaluated taking into account relevant service experience.
In the absence of significant service experience, special tests simulating the solar radiation condition of the
installation area have to be carried out.
e
In general, pollution is not an issue for indoor insulators. In particular cases, such as DC.
indoor conditions, the insulators can accumulate some contamination due to DC electrical field. However, the
pollution flashover phe
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