IEC 62217:2025

Polymeric HV insulators for indoor and outdoor use - General definitions, test methods and acceptance criteria

IEC 62217:2025 is applicable to polymeric insulators for AC systems with a nominal voltage greater than 1 000 V (frequency less than 100 Hz) and DC systems with a nominal voltage greater than 1 500 V whose insulating body consists of one or various organic materials. Polymeric insulators covered by this document are intended for use both on HV overhead lines and in substations, in both indoor and outdoor applications. They include composite insulators with solid and hollow core and resin insulators. Hybrid insulators with ceramic core and polymeric housing are also included, while coated insulators (e.g. with RTV silicone rubber coatings) are not included in this standard. Electrical tests described in this document are done under AC voltage and are in general applicable to insulators to be used in DC systems too. Tests under DC voltage are intended to reflect up-to-date knowledge and experience. Only polymeric housing materials of hybrid insulators are specified in this document. Tests for core materials and the interfaces between housing and core of hybrid insulators are not included.
The object of this document is
- to define the common terms used for polymeric insulators;
- to prescribe common test methods for design tests on polymeric insulators;
- to prescribe acceptance or failure criteria, if applicable;
These tests, criteria and recommendations are intended to ensure a satisfactory lifetime under normal operating and environmental conditions. This document includes design tests intended to reject materials or designs which are inadequate under normal operating and environmental conditions. This document defines test methods and acceptance criteria. The applicable tests are given in the relevant product standard. This third edition cancels and replaces the second edition published in 2012. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) The scope of the document is specified to comprise composite insulators with solid and hollow core and resin insulators used for both AC and DC systems in indoor and outdoor applications of HV overhead lines and substations; hybrid insulators (defined in IEC TS 62896) with ceramic core and polymeric housing are also included, while coated insulators (e.g. with Room Temperature Vulcanized (RTV) silicone rubber coatings) are not considered in this document;
b) Steep-front impulse voltage test is modified to avoid unwanted flashovers between the leads of the electrodes;
c) Differences between hydrophobicity transfer material (HTM) and non-HTM housing materials are specified and relevant test methods and acceptance criteria for polymeric insulators with HTM housing are introduced;
d) The previous water diffusion test on core materials with or without housing is split into two tests. One is on core materials without housing, the other is on core materials with housing. The acceptance criteria are modified;
e) Stress corrosion test for core materials is introduced;
f) Annex B summarizes the test application for evaluating the quality of interfaces and connections of end fittings, housing materials and core materials;
g) Annex E is introduced to emphasize the need for control of electric fields of polymeric insulators for AC. The control of electric fields of polymeric insulators for DC is still under consideration.

Isolateurs polymériques à haute tension pour usage intérieur et extérieur - Définitions générales, méthodes d'essai et critères d'acceptation

L'IEC 62217:2025 s'applique aux isolateurs polymériques pour systèmes à courant alternatif de tension nominale supérieure à 1 000 V (fréquence inférieure à 100 Hz) et pour systèmes à courant continu de tension nominale supérieure à 1 500 V, dont le corps isolant est constitué d'un ou de plusieurs matériaux organiques. Les isolateurs polymériques couverts par le présent document sont destinés à être utilisés sur les lignes aériennes HT et dans les postes, en intérieur et en extérieur. Il s'agit d'isolateurs composites à noyau plein et à noyau creux, ainsi que d'isolateurs en résine. Les isolateurs hybrides constitués d'un noyau en céramique et d'un revêtement en polymère sont également inclus, tandis que les isolateurs revêtus (avec des revêtements en caoutchouc silicone vulcanisé à température ambiante (RTV), par exemple) ne sont pas couverts par la présente norme. Les essais électriques décrits dans le présent document sont effectués sous une tension alternative et s'appliquent généralement aux isolateurs destinés à être utilisés dans des systèmes à courant continu également. Les essais sous tension continue sont prévus pour refléter l'état actuel des connaissances et de l'expérience. Seuls les matériaux de revêtement en polymère des isolateurs hybrides sont spécifiés dans le présent document. Les essais pour les matériaux de noyau et les interfaces entre le revêtement et le noyau des isolateurs hybrides ne sont pas inclus.
L'objet du présent document est
- de définir les termes couramment utilisés pour les isolateurs polymériques.
- de spécifier des méthodes d'essai communes pour les essais de conception sur les isolateurs polymériques.
- de spécifier des critères d'acceptation ou de défaillance, le cas échéant.
Ces essais, critères et recommandations sont destinés à procurer une durée de vie satisfaisante des isolateurs dans les conditions normales d'exploitation et d'environnement (voir l'Article 5). Le présent document comprend des essais de conception destinés à rejeter les matériaux ou les conceptions qui ne conviennent pas dans des conditions normales d'exploitation et d'environnement. Le présent document définit les méthodes d'essai et les critères d'acceptation. Les essais applicables sont définis dans la norme de produit pertinente. Cette troisième édition annule et remplace la deuxième édition parue en 2012. Cette édition constitue une révision technique.
Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) le domaine d'application du document couvre les isolateurs composites à noyau plein ou creux, ainsi que les isolateurs en résine utilisés avec des systèmes à courant alternatif et à courant continu, en intérieur et en extérieur, sur les lignes aériennes HT et dans les postes; les isolateurs hybrides (définis dans l'IEC TS 62896) constitués d'un noyau en céramique et d'un revêtement en polymère sont également inclus, tandis que les isolateurs revêtus (avec des revêtements en caoutchouc silicone vulcanisé à température ambiante (RTV), par exemple) ne sont pas couverts par le présent document;
b) l'essai sous onde de choc à front raide a été modifié pour éviter des contournements indésirables entre les conducteurs des électrodes;
c) les différences entre le matériau de transfert d'hydrophobie (HTM - Hydrophobicity Transfer Material) et les matériaux de revêtement non HTM ont été spécifiées, et les méthodes d'essai et les critères d'acceptation pertinents pour les isolateurs polymériques avec revêtement HTM ont été ajoutés;
d) l'essai précédent de pénétration d'eau sur les matériaux de noyau avec ou sans le revêtement a été divisé en deux essais. L'un porte sur les matériaux de noyau sans le revêtement, l'autre sur les matériaux de noyau avec le revêtement. Les critères d'acceptation ont été modifiés;
e) l'essai de corrosion sous contrainte pour les matériaux de noyau a été ajouté;
f) l'Annexe B récapitule l'application de l'essai pour évaluer la qua

General Information

• Status: Published
• Publication Date: 05-Oct-2025
• ICS: 29.080.10 - Insulators
• Technical Committee: TC 36 - Insulators
• Drafting Committee: MT 19 - TC 36/MT 19
• Current Stage: PPUB - Publication issued
• Start Date: 06-Oct-2025
• Completion Date: 03-Oct-2025

Relations

• Revises: IEC 62217:2012 - Polymeric HV insulators for indoor and outdoor use - General definitions, test methods and acceptance criteria
• Effective Date: 05-Sep-2023

Overview

IEC 62217:2025 - "Polymeric HV insulators for indoor and outdoor use - General definitions, test methods and acceptance criteria" is the international standard that defines common terminology, design test methods and acceptance criteria for polymeric high-voltage (HV) insulators. It applies to polymeric insulators for AC systems with nominal voltage > 1 000 V (frequency < 100 Hz) and DC systems with nominal voltage > 1 500 V whose insulating body is made of organic materials. Covered product types include composite insulators (solid and hollow core) and resin insulators; hybrid insulators with a ceramic core and polymeric housing are included only for their polymeric housing materials. Coated insulators (e.g., RTV-coated) and core material/interface tests for hybrids are excluded.

This third edition (2025) is a technical revision of the 2012 edition and updates scope, test procedures and acceptance criteria to reflect current HV AC/DC applications and material developments.

Key topics and technical requirements

• Scope & definitions: Common terms for polymeric insulators used across overhead lines and substations, indoor and outdoor.
• Classification of tests: Design, type, sample and routine tests with recommended application scenarios.
• Material and specimen requirements: Test specimen preparation and environmental conditioning for realistic ageing and performance evaluation.
• Electrical testing: AC-based electrical tests (generally applicable to DC use); updated procedures for steep-front impulse voltage tests to avoid unwanted electrode flashovers.
• Material-specific tests: Tracking and erosion, accelerated weathering, hardness, flammability, porosity (dye penetration), and water diffusion (now split into core-only and core-with-housing tests).
• Hydrophobicity: Distinction between hydrophobicity transfer material (HTM) and non-HTM housings; introduced test methods and acceptance criteria for HTM housings.
• Mechanical and interface evaluation: Annex B provides guidance for evaluating end-fitting interfaces, housing–core connections and related pre-stressing/immersion procedures.
• New tests: Stress corrosion test for core materials; enhanced acceptance criteria and electric field control considerations (Annex E for AC; DC under review).

Practical applications

• Use IEC 62217:2025 to:
  • Specify procurement and acceptance criteria for polymeric HV insulators.
  • Develop product test programs and type-test reports for manufacturers.
  • Guide independent test laboratories and certification bodies performing design and routine tests.
  • Inform utilities and asset managers assessing insulator selection, lifecycle risk and field performance.
• Ensures consistent evaluation to achieve satisfactory lifetime under typical operating and environmental conditions.

Who should use this standard

• Insulator manufacturers, design engineers, test laboratories, utilities, procurement/specification teams, certification bodies and regulatory authorities involved in HV insulation selection, testing and compliance.

Related standards

• IEC TS 62896 (definition and aspects of hybrid insulators) - referenced for hybrid insulator context.
• Relevant product and regional standards (see IEC 62217 product-specific references for applicable tests and criteria).

Standards Content (Sample)

IEC 62217 ®
Edition 3.0 2025-10
INTERNATIONAL
STANDARD
COMMENTED VERSION
Polymeric HV insulators for indoor and outdoor use - General definitions, test
methods and acceptance criteria
ICS 29.080.10 ISBN 978-2-8327-0765-4
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CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope and object . 7
2 Normative references . 7
3 Terms and definitions . 8
4 Identification . 12
5 Environmental conditions . 12
6 Information on transport, storage and installation . 14
7 Classification of tests . 14
7.1 General . 14
7.2 Design tests . 14
7.3 Type tests . 14
7.4 Sample tests . 14
7.5 Routine tests . 15
8 General requirements for insulator test specimens . 15
9 Design tests . 15
9.1 General . 15
9.2 Tests on interfaces and connections of end fittings . 16
9.2.1 General . 16
9.2.2 Test specimens . 16
9.2.3 Reference flashover voltage and reference temperature for verification
tests . 16
9.2.4 Reference dry power frequency test .
9.2.4 Reference flashover voltage test. 16
9.2.5 Product specific pre-stressing . 17
9.2.6 Water immersion pre-stressing . 17
9.2.7 Verification tests . 17
9.3 Tests on shed and housing material . 19
9.3.1 Hardness test . 19
9.3.2 Accelerated weathering test . 21
9.3.3 Tracking and erosion test – 1 000 h salt fog AC voltage test –
Procedure . 22
9.3.4 Flammability test . 25
9.3.5 Hydrophobicity transfer test . 25
9.4 Tests on core material . 26
9.4.1 General . 26
9.4.2 Porosity test (Dye penetration test) . 27
9.4.3 Water diffusion test . 29
9.4.4 Stress corrosion test . 31
9.5 Water diffusion test on core with housing . 31
9.5.1 General . 31
9.5.2 Test specimens . 32
9.5.3 Test procedure . 32
9.5.4 Acceptance criteria . 32
Annex CA (informative) Explanation of the concept of classes for the design tests . 33
Annex B (informative) Recommended test application of tests . 34
Annex C (informative) Tests for AC or DC application . 36
Annex AD (informative) Difference between the tracking and erosion and accelerated
ageing test on polymeric insulators . 37
Annex E (informative) Consideration of electric field control . 38
Bibliography . 40
List of comments. 41

Figure 1 – Illustration of different types of insulators . 9
Figure 2 – Illustration of the electrodes position and axial length . 18
Figure 2 3 – – Example of boiling container for the water diffusion test . 21
Figure 1 4 – Examples of test specimen for core material . 27
Figure 5 – Example of porosity test specimen with certain areas not being allowed to
be sealed . 29
Figure 3 – Electrodes for the voltage test .
Figure 4 – Voltage test circuit .
Figure E.1 – Typical sealing area description for composite insulator . 39

Table 1 – Normal environmental conditions . 13
Table 2 – Initial NaCI content of the water as a function of the specimen dimensions . 24
Table 3 – Flammability requirements . 25
Table B.1 – Application on interfaces and connections of end fittings. 34
Table B.2 – Application on housing materials . 35
Table B.3 – Application on core materials . 35
Table B.4 – Application on core with housing . 35
Table C.1 – Tests for AC or DC application . 36

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Polymeric HV insulators for indoor and outdoor use -
General definitions, test methods and acceptance criteria

FOREWORD
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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)
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shall not be held responsible for identifying any or all such patent rights.
This commented version (CMV) of the official standard IEC 62217:2025 edition 3.0 allows the
user to identify the changes made to the previous IEC 62217:2012 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.
IEC 62217 has been prepared by IEC technical committee 36: Insulators. It is an International
Standard.
This third edition cancels and replaces the second edition published in 2012. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) The scope of the document is specified to comprise composite insulators with solid and
hollow core and resin insulators used for both AC and DC systems in indoor and outdoor
applications of HV overhead lines and substations; hybrid insulators (defined in
IEC TS 62896) with ceramic core and polymeric housing are also included, while coated
insulators (e.g. with Room Temperature Vulcanized (RTV) silicone rubber coatings) are not
considered in this document;
b) Steep-front impulse voltage test is modified to avoid unwanted flashovers between the leads
of the electrodes;
c) Differences between hydrophobicity transfer material (HTM) and non-HTM housing
materials are specified and relevant test methods and acceptance criteria for polymeric
insulators with HTM housing are introduced;
d) The previous water diffusion test on core materials with or without housing is split into two
tests. One is on core materials without housing, the other is on core materials with housing.
The acceptance criteria are modified;
e) Stress corrosion test for core materials is introduced;
f) Annex B summarizes the test application for evaluating the quality of interfaces and
connections of end fittings, housing materials and core materials;
g) Annex E is introduced to emphasize the need for control of electric fields of polymeric
insulators for AC. The control of electric fields of polymeric insulators for DC is still under
consideration.
The text of this International Standard is based on the following documents:
Draft Report on voting
36/612/FDIS 36/631/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.
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
Polymeric insulators consist either of one insulating material (resin insulators) or two or several
insulating materials (composite insulators). The insulating materials are generally cross-linked
organic materials synthesised from carbon or silicon chemistry and form the insulating body.
Insulating materials can be composed from organic materials containing various inorganic and
organic ingredients, such as fillers and extenders. End fittings are often used at the ends of the
insulating body to transmit mechanical loads. Despite these common features, the materials
used and the construction details employed by different manufacturers may be widely different
might differ significantly.
The tests given in this document are those which are, in general, common to a great majority
of insulator designs and materials, whatever their final application. Considering the increasing
applications of polymeric insulators, the scope of this document specifies technical
requirements for solid core, hollow core and resin insulators used in AC and DC systems, in
indoor and outdoor, in applications of HV overhead lines and substations to ensure proper
insulator performance under normal operating conditions. The technical requirements have
been regrouped in this document to avoid repetition of the relevant product standards and drift
between procedures as the various product standards are drafted or revised.
The majority of these tests have been grouped together as "Design tests", to be performed only
once for insulators of the same design. The design tests are intended to eliminate insulator
designs, materials or manufacturing technologies which are not suitable for high voltage (HV)
applications. The influence of time on the electrical properties of the complete polymeric
insulator and its components (core material, housing, interfaces etc.) has been considered in
specifying the design tests in order to ensure a satisfactory lifetime under normal operating and
environmental conditions. To ensure quality and reliable long-term performance of insulators,
the requirements on the modification of certain test procedures as well as the introduction of
new tests were identified.
Pollution tests, according to IEC 60507 or IEC TS 61245 [1] , are not included in this document,
the applicability of their methodology to composite insulators not having been proven and still
requiring study by CIGRE. The results of such pollution tests performed on insulators made of
polymeric materials do not correlate with experience obtained from service. Specific pollution
tests for polymeric insulators are still under consideration of IEC, indications for design
considering pollution are given in IEC TS 60815-1, IEC TS 60815-3 [2] and IEC TS 60815-4 [3].
The 1 000 hour salt-fog tracking and erosion test given in this second edition of IEC 62217 is
considered as a screening test intended to reject materials or designs which are inadequate.
This test is not intended to predict long term performance for insulator designs under cumulative
service stresses. For more information, see Annex C. The first edition of IEC 62217 (2005)
included two other alternative tracking and erosion tests (a 5 000 hour multi-stress test and a
tracking wheel test) which were based on tests developed by CIGRE and utilities. These tests
are no longer given as normative alternatives following the results of a study/questionnaire by
TC 36 on the relative merits of all three tracking and erosion tests. The 5 000 hour multi-stress
test and a tracking wheel test are described in IEC/TR 62730 (2012).
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 hour a.c. tracking and erosion test described in this standard
is used to establish a minimum requirement for the tracking resistance of the housing material.
Before the appropriate standard for DC applications will be issued, the majority of tests listed
in this document can also be applied to DC insulators. The 1 000 h AC salt fog tracking and
erosion test is considered as a design test in this document to reject materials in combination
with the design which are inadequate. For the time being, the 1 000 h AC salt fog tracking and
___________
Numbers in square brackets refer to the Bibliography.
erosion test is used to establish a minimum requirement for the tracking and erosion resistance,
for both AC and DC 1. For DC applications, a specific DC tracking and erosion test procedure
as a design test has not been developed. Further tracking and erosion test methods such as
the 5 000 hour and the tracking wheel test are described in IEC TR 62730 [4] and can be used
for research or other purposes. Tracking and erosion tests are not intended to evaluate long
term performance of insulators in harsh environments by the simulation of multiple
environmental factors. It is therefore necessary to carry out ageing tests for insulator designs
under cumulative service stresses. These aging tests do not form part of this present document.
For polymeric insulators with hydrophobicity transfer property, relevant test procedures are
introduced. In this document the hydrophobicity transfer test is intended to distinguish the HTM
from non-HTM rather than differentiate between different HTMs degrees.
The water diffusion test is divided into two tests. The first one is for the core (as earlier), the
second one is for the core with housing. The water diffusion test on core with housing addresses
the interface between the core and the housing. The acceptance criteria are modified and
harmonized for both tests.
Stress corrosion test for insulators mainly subjected to tensile loads is introduced to minimize
the risks of brittle fractures.
Annex B summarizes the test application for evaluating the quality of interfaces and
connections of end fittings, housing materials and core materials.
Annex E is introduced to emphasize the need for the control of electric field of polymeric
insulators under AC voltage.
IEC Guide 111 has been followed wherever possible during the preparation of this document.
1 Scope and object
This International Standard is applicable to polymeric insulators for AC systems with a nominal
voltage greater than 1 000 V (frequency less than 100 Hz) and DC systems with a nominal
voltage greater than 1 500 V whose insulating body consists of one or various organic materials.
Polymeric insulators covered by this standard include both solid core and hollow insulators.
They are intended for use on HV overhead lines and in indoor and outdoor equipment. Polymeric
insulators covered by this document are intended for use both on HV overhead lines and in
substations, in both indoor and outdoor applications 2. They include composite insulators with
solid and hollow core and resin insulators. Hybrid insulators with ceramic core and polymeric
housing are also included, while coated insulators (e.g. with RTV silicone rubber coatings) are
not included in this standard 3. Electrical tests described in this document are done under AC
voltage and are in general applicable to insulators to be used in DC systems too. Tests under
DC voltage are intended to reflect up-to-date knowledge and experience.
NOTE Only polymeric housing materials of hybrid insulators are specified in this document. Tests for core materials
and the interfaces between housing and core of hybrid insulators are not included. 4
The object of this document is
– to define the common terms used for polymeric insulators;
– to prescribe common test methods for design tests on polymeric insulators;
– to prescribe acceptance or failure criteria, if applicable;
These tests, criteria and recommendations are intended to ensure a satisfactory lifetime under
normal operating and environmental conditions (see Clause 5). This standard shall only be
applied in conjunction with the relevant product standard. This document includes design tests
intended to reject materials or designs which are inadequate under normal operating and
environmental conditions. This document defines test methods and acceptance criteria. The
applicable tests are given in the relevant product standard.
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 60050-471:2007, International Electrotechnical Vocabulary (IEV) - Part 471: Insulators
IEC 60060-1, High-voltage test techniques - Part 1: General definitions and test requirements
IEC 60068-2-11, Environmental testing – Part 2: Tests. Test KA: Salt mist
IEC 60507:2013+COR1:2018, Artificial pollution tests on high-voltage ceramic and glass
insulators to be used on a.c. systems
IEC 60695-11-10, Fire hazard testing - Part 11-10: Test flames - 50 W horizontal and vertical
flame test methods
IEC 60721-1, Classification of environmental conditions - Part 1: Environmental parameters and
their severities
IEC TS 60815-1, Selection and dimensioning of high-voltage insulators intended for use in
polluted conditions - Part 1: Definitions, information and general principles
IEC TR 62039:2021, Selection guidelines for polymeric materials for outdoor use under HV
stress
ISO 868, Plastics and ebonite - Determination of indentation hardness by means of a durometer
(Shore hardness)
ISO 4287, Geometrical product specifications (GPS) – Surface texture: Profile method – Terms,
definitions and surface texture parameters
ISO 4892-1, Plastics – Methods of exposure to laboratory light sources – Part 1: General
Guidance
ISO 4892-2, Plastics - Methods of exposure to laboratory light sources - Part 2; Xenon-arc
lamps
ISO 21920-2, Geometrical product specifications (GPS) Surface texture: Profile - Part 2: Terms,
definitions and surface texture parameters
3 Terms and definitions 5
For the purposes of this document, the terms and definitions given in IEC 60050-471:2007 and
the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1
high voltage
HV
voltage over 1 000 V AC or over 1 500 V DC or over 1 500 V peak value
3.2
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]
3.3
resin insulator
polymeric insulator whose insulating body consists of a solid shank insulator trunk and sheds
protruding from the shank insulator trunk made from only one organic based housing material
(e.g. cycloaliphatic epoxy)
3.4
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, for example, 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]
3.5
hybrid insulator
insulator that consists of a ceramic core and a polymeric housing, equipped with one or more
metal fittings
Figure 1 – Illustration of different types of insulators
SEE: Figure 1.
Note 1 to entry: According to IEC TS 62896 [5].
Note 2 to entry: The mechanical functions are mainly characterised by the core, the external electrical functions
are mainly characterised by the polymeric housing. The housing may cover the core completely or partly. In the latter
case the exposed portions of the ceramic core are usually covered by glaze.
3.6
composite insulator with fibre reinforced plastic (FRP) solid core
composite insulators of which the core, covered by polymeric housing, is made of solid
insulating polymeric material reinforced by fibres such as glass fibres
3.7
composite hollow insulator
insulator consisting of at least two insulating parts, namely a tube-shaped core, and a housing
Note 1 to entry: The housing may consist either of individual sheds mounted on the tube, with or without an
intermediate sheath, or directly applied in one or several pieces onto the tube. A composite hollow insulator unit is
permanently equipped with fixing devices or end fittings.
3.8
core
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]
3.9
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]
3.10
housing
external insulating part of a composite insulator providing the necessary creepage distance and
protecting core from 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]
3.11
sheath
uniform and continuous tubular covering made of insulating material
[SOURCE: IEC 60050-151:2001, 151-12-41]
3.12
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 ribs.
[SOURCE: IEC 60050-471:2007, 471-01-15]
3.13
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
Note 1 to entry: The surface of cement or of any other non-insulating jointing material is not considered as forming
part of the creepage distance.
Note 2 to entry: If a high resistance coating is applied to parts of the insulating part of an insulator, such parts are
considered to be effective insulating surfaces and the distance over them is included in the creepage distance.
[SOURCE: IEC 60050-471:2007, 471-01-04, modified (removal of Note 2 to entry)]
3.14
arcing distance
shortest distance in air external to the insulator between the metallic parts which normally have
the operating voltage between them
[SOURCE: IEC 60050-471:2007, 471-01-01]
3.15
interfaces
surface between the different materials
Note 1 to entry: Various interfaces occur exist in most 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
3.16
end fitting
fixing device
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, the term "metal fitting" is normally used.
[SOURCE: IEC 60050-471:2007, 471-01-06, modified by the addition of a synonym]
3.13
connection zone
zone where the mechanical load is transmitted between the insulating body and the fixing device
3.17
coupling
part of the fixing device end fitting which transmits load to the hardware external to the insulator
3.18
tracking
process which forms irreversible degradation by formation of conductive paths (tracks) starting
and developing on the surface of an insulating material.
progressive formation of conductive paths, which are produced on the surface or within a solid
insulating material, due to the combined effects of electric stress and electrolytic contamination
Note 1 to entry: Tracking paths are conductive even under dry conditions.
[SOURCE: IEC 60050-212:2010, 212-11-56, modified (addition of Note 1 to entry)]
3.19
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
loss of material by electrical discharge
Note 1 to entry: Light Surface traces, commonly tree-shaped, can occur on composite insulators as on ceramic and
glass insulators, after partial flashover exposure to surface discharges. These traces are not considered to be
objectionable as long as they are non-conductive. When they are conductive they are classified as tracking.
3.20
crack
any internal fracture or surface fissure of depth greater than 0,1 mm
3.21
puncture
permanent loss of dielectric strength due to a disruptive discharge passing through the solid
insulating material of an insulator
[SOURCE: IEC 60050-471:2007, 471-01-14, modified to define puncture as the result of a
discharge, rather than the discharge itself]
3.22
hydrophobicity
surface of a solid insulating material characterized by its capacity to repel water or aqueous
electrolyte solutions
Note 1 to entry: Hydrophobicity of a polymeric insulating material is, in general, a volume property by means of the
chemical composition of a material at its surface.
Note 2 to entry: Nonetheless, hydrophobicity is strongly affected by surface effects such as:
 surface structure (i. e. roughness);
 chemical interaction between water and the solid surface (adsorption, absorption, swelling of the solid material
in contact with water);
 an accumulated pollution layer.
Note 3 to entry: Furthermore, the conditions during an evaluation of hydrophobicity (temperature, pressure,
humidity), and the method for cleaning or electrostatic charges can affect the measured degree of hydrophobicity.
[SOURCE: IEC TR 62039: 2021, 3.1, modified (deleting of "climatic" in Note 3 to entry)]
3.23
hydrophobicity transfer
phenomenon of a transfer of hydrophobicity from the bulk of the housing material to pollution
layer on its surface
3.24
hydrophobicity transfer material
HTM
polymeric material which exhibits hydrophobicity and the capability to transfer hydrophobicity
onto the layer of pollution, which is a combined dynamic behaviour of retention and transfer of
hydrophobicity specific to different insulator materials
[SOURCE: IEC TS 60815-4:2016 [3], 3.1.4, modified (addition of text from "which is …")]
4 Identification
The manufacturer's drawing shall show the relevant dimensions and information necessary for
identifying and testing the insulator in accordance with this document and the applicable IEC
product standard(s). The drawing shall also show applicable manufacturing tolerances.
Each insulator shall be marked with the name or trademark of the manufacturer and the year of
manufacture. In addition, each insulator shall be marked with the rated characteristics specified
in the relevant IEC product standards. These markings shall be legible, indelible and their
fixings (if any) weather- and corrosion-proof.
5 Environmental conditions
The normal environmental conditions to which insulators are submitted in service are defined
according to Table 1. Terms are defined as follows:
When special environmental conditions prevail at the location where insulators are to be put in
service, they shall be specified by the user by reference to IEC 60721-1.
Table 1 – Normal environmental conditions 6
Indoor insulation Outdoor insulation
Maximum ambient air Does not exceed 40 °C and its average value measured over a period of
a
24 h does not exceed 35 °C
temperature
b
−25 °C −40 °C
Minimum ambient air temperature
Negligible vibration due to causes external to the insulators or to earth
Vibration
c
tremors .
bd 2
To be neglected Not applicable
Solar radiation Up to a level of 1 000 1 120 W/m
Pollution of the ambient air Site No significant pollution by dust, Pollution by dust, smoke, corrosive
e
smoke, corrosive and/or gases, vapors or salt may occur
pollution severity
flammable gases, vapors, or salt. occurs. Pollution does not exceed
"heavy" SPS class as defined in
IEC TS 60815-1.
f
The average value of the relative Rain, snow, abnormal humidity,
Humidity
humidity, measured over a period condensation, ice and hoar frost
of 24 h, does not exceed 95 % occur.
and measured over a period of
one month, does not exceed
95 %. For these conditions,
condensation may occasionally
occur. No rain, snow, abnormal
humidity, condensation, ice and
hoar frost
a
If exceeded, follow the recommendations of IEC TR 62039 for the core and adhesive materials (like glue) in
"glass transition temperature" section.
b
Details of solar radiation are given in IEC 60721-1.
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 during wintertime
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 with IEC 60721-1.
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 electric field. However, the pollution flashover
phenomena cannot develop when the humidity is controlled. For outdoor conditions the requirements of this
document are specified for stresses arising in relatively harsh but not extreme environments (see e.g. for
hydrophobicity verification and tracking and erosion tests for which criteria are provided in IEC TR 62039).
f
Insulator for indoor applications can also be used in presence of limited deviations from the above conditions
if sufficient proven field experience is available and condensation occurs only occasionally. To limit
condensation-related phenomena, the average value of the relative humidity condition, measured over a period
of 24 h, shall not exceed 95 % and when measured over a period of one month, shall not exceed 90 %.
Exceeding these values is considered as abnormal humidity condition.
• 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 capable to withstand 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 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. 7
6 Information on transport, storage and installation
Manufacturers of insulators shall provide appropriate instructions and information covering
general conditions during transport, storage and installation of the insulators. These instructions
can include recommendations for cleaning or maintenance and correct positioning and
installation of the corona rings.
7 Classification of tests
7.1 General
The tests are divided into four groups as follows:
7.2 Design tests
The design tests are intended to verify the suitability of the design, materials and method of
manufacturing (technology).
A polymeric insulator design is generally 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).
Additional parameters defining design may be given in the relevant product standard.
When changes in the design of a polymeric insulator occur, re-qualification shall be carried out
according to the prescriptions of the relevant product standard. Typically, only part of the tests
is repeated. A survey of the tests is given in Annex C. Explanation of the concept of classes for
the design tests is provided in Annex A.
When a polymeric insulator is submitted to the design tests, it becomes a parent insulator for a
design class and the results shall
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