IEC TS 62896:2015

IEC TS 62896 ®
Edition 1.0 2015-11
TECHNICAL
SPECIFICATION
Hybrid insulators for a.c. and d.c. high-voltage applications – Definitions, test
methods and acceptance criteria

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IEC TS 62896 ®
Edition 1.0 2015-11
TECHNICAL
SPECIFICATION
Hybrid insulators for a.c. and d.c. high-voltage applications – Definitions, test

methods and acceptance criteria

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.080.10 ISBN 978-2-8322-3017-6

– 2 – IEC TS 62896:2015  IEC 2015

CONTENTS
FOREWORD . 3

INTRODUCTION . 5

1 Scope . 6

2 Normative references . 6

3 Definitions . 7

4 Identification . 9

5 Environmental conditions . 9
6 Tolerances . 9
7 Classification of tests . 10
7.1 Design tests . 10
7.2 Type tests . 10
7.3 Sample tests . 11
7.4 Routine tests . 11
8 Design tests . 12
8.1 General . 12
8.2 Tests on interfaces and connections of end fittings . 13
8.2.1 General . 13
8.2.2 Pre-stressing . 13
8.2.3 Verification tests . 14
8.3 Tests on Shed and Housing Material . 14
8.3.1 Hardness test . 14
8.3.2 Accelerated weathering test . 14
8.3.3 Tracking and erosion test . 15
8.3.4 Flammability test . 15
9 Type tests . 15
9.1 General . 15
9.2 Electrical tests . 15
9.3 Mechanical tests . 15
10 Sample tests . 15
11 Routine tests . 15
Annex A (informative) Comparison between hybrid insulators and glass fibre cored

polymeric housing and porcelain insulators. 16
A.1 History . 16
A.2 Comparison between porcelain and pultruded GFRP rod . 16
A.3 Advantages of hybrid insulators over conventional porcelain insulators . 16
A.4 Advantages of hybrid insulators over glass fibre cored insulators . 17
A.5 Problems shared with polymeric insulators . 17
A.6 Transport, storage and installation . 17
Bibliography . 18

Figure 1 – Thermal cycle test . 14

Table 1 – Required tests . 12
Table 2 – Design tests. 13

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
HYBRID INSULATORS FOR A.C. AND D.C. HIGH-VOLTAGE

APPLICATIONS – DEFINITIONS, TEST METHODS

AND ACCEPTANCE CRITERIA
FOREWORD
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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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The main task of IEC technical committees is to prepare International Standards. In

exceptional circumstances, a technical committee may propose the publication of a technical
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• the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts, or
• the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
Technical specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC TS 62896, which is a technical specification, has been prepared by IEC technical
committee 36: Insulators.
– 4 – IEC TS 62896:2015  IEC 2015

The text of this technical specification is based on the following documents:

Enquiry draft Report on voting

36/362/DTS 36/368/RVC
Full information on the voting for the approval of this technical specification can be found in the

report on voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

The committee has decided that the contents of this publication will remain unchanged until the
stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data related to
the specific publication. At this date, the publication will be
• transformed into an International standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
INTRODUCTION
Hybrid insulators consist of an insulating core, bearing the mechanical load protected by a

polymeric housing, the load being transmitted to the core by end fittings. Despite these

common features, the materials used and the construction details employed by different

manufacturers may be quite different. The core is made of ceramic or glass material.

Hybrid insulators are applied as overhead line, post or hollow core equipment insulators. In

order to perform the design tests, IEC 62217 shall be applied for the polymeric housing and the

interfaces between core and the housing. For the core, the test standards for the respective

ceramic product (IEC 60168, IEC 60383 and IEC 62155) shall be applied.

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 hybrid insulators,
the common clauses defined in IEC 62217 are applied. As far as practical, the influence of time
on the electrical and mechanical properties of the components (core material, housing,
interfaces etc.) and of the complete hybrid insulators has been considered in specifying the
design tests to ensure a satisfactory life-time under normally known stress conditions in
service.
Polymeric housing materials that show the hydrophobicity transfer mechanism (HTM) are
preferred for hybrid insulators. They are applied as a countermeasure against severe polluted
service conditions. For the time being, no ageing or pollution tests have been developed for the
verification of this property, but CIGRE Technical Brochure No. 442 is available for the
evaluation of the retention of the hydrophobicity and the HTM of polymeric housing materials.
Artificial pollution tests for insulators with polymeric housings under AC and DC voltage stress
are presently under development by CIGRE.

– 6 – IEC TS 62896:2015  IEC 2015

HYBRID INSULATORS FOR A.C. AND D.C. HIGH-VOLTAGE

APPLICATIONS – DEFINITIONS, TEST METHODS

AND ACCEPTANCE CRITERIA
1 Scope
This technical specification applies to hybrid insulators for a.c. and d.c. applications consisting

of a load-bearing insulating solid or hollow core consisting of ceramic or glass, a housing
(defined geometry, outside the insulating core) made of polymeric material and end fittings
permanently attached to the insulating core.
Hybrid insulators covered by this technical specification are intended for use as
suspension/tension line insulators, line post insulators, station post insulators and hollow core
insulators for apparatus.
The object of this technical specification is to:
• define the terms used;
• prescribe test methods;
• prescribe acceptance criteria.
Silicone or other functional coatings (CIGRE Technical Brochure No. 478, Appendix B), booster
sheds, shed extenders and rain deflectors are not within the scope of this technical
specification.
This technical specification does not include requirements dealing with the choice of insulators
for specific operating conditions.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. 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 – Part 471: Insulators

IEC 60168, Tests on indoor and outdoor post insulators of ceramic material or glass for
systems with nominal voltages greater than 1000 V
IEC 60383-1, Insulators for overhead lines with a nominal voltage above 1000 V – Part 1:
Ceramic or glass insulator units for a.c. systems – Definitions, test methods and acceptance
criteria
IEC 60383-2, Insulators for overhead lines with a nominal voltage above 1000 V – Part 2:
Insulator strings and insulator sets for a.c. systems – Definitions, test methods and acceptance
criteria
IEC 62155, Hollow pressurized and unpressurized ceramic and glass insulators for use in
electrical equipment with rated voltages greater than 1 000 V

IEC 62217, Polymeric HV insulators for indoor and outdoor use – General definitions, test

methods and acceptance criteria

3 Definitions
For the purpose of this document the terms and definitions given in IEC 60050-471 and the

following apply (some definitions from IEC 62217 are reproduced here for ease of reference).

3.1
high voltage
HV
voltage over 1 000 V a.c. or over 1 500 V d.c. or over 1 500 V peak value
3.2
polymeric insulator
insulator whose insulating body consists of only polymer containing materials, to the ends of
which coupling devices may be attached
Note 1 to entry: Polymeric insulators are also known as non-ceramic insulators.
3.2.1
resin insulator
polymeric insulator whose insulating body consists of a solid shank and sheds protruding from
the shank made from only one organic based housing material (e.g. cycloaliphatic epoxy)
3.2.2
composite insulator
polymeric insulator made of at least two polymeric insulating parts, namely a core and a
housing, equipped with metal 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.
3.3
hybrid insulator
insulator that consists of a ceramic or glass core and a polymeric housing, equipped with one
or more metal fittings
Polymeric insulator Ceramic / glass insulator

Resin Composite
Hybrid insulator
insulator insulator
IEC
Note 1 to entry: The mechanical functions are mainly characterised by the core, the 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.

– 8 – IEC TS 62896:2015  IEC 2015

3.4
core of a hybrid insulator
the internal insulating part, consisting of ceramic or glass, of a hybrid insulator which is

designed to ensure the mechanical characteristics

Note 1 to entry: The core for composite insulators is defined in IEC 62217.

3.5
shank of a hybrid insulator
the section between two adjacent sheds (also known as trunk on larger insulators)

3.6
housing
external insulating part which is made of polymeric material providing necessary creepage
distance and protecting the core from environment
3.7
shed
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]
3.8
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]
3.9
arcing distance
s
...