IEC TS 62073:2003

TECHNICAL IEC
SPECIFICATION
TS 62073
First edition
2003-06
Guidance on the measurement of wettability
of insulator surfaces
Mesure de l'hydrophobicité
de la surface des isolateurs
Reference number
IEC/TS 62073:2003(E)
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TECHNICAL IEC
SPECIFICATION
TS 62073
First edition
2003-06
Guidance on the measurement of wettability
of insulator surfaces
Mesure de l'hydrophobicité
de la surface des isolateurs
 IEC 2003  Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
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International Electrotechnical Commission
Международная Электротехническая Комиссия
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– 2 – TS 62073  IEC:2003(E)
CONTENTS
FOREWORD . 4
INTRODUCTION .6
1 Scope and object . 7
2 Terms and definitions. 7
3 Methods for measurement of wetting properties. 9
4 Method A – Contact angle method.10
4.1 General .10
4.2 Equipment .10
4.3 Measurement procedure .10
4.4 Evaluation.11
5 Method B – Surface tension method .11
5.1 General .11
5.2 Safety precautions .12
5.3 Equipment and reagents .12
5.4 Measurement procedure .12
5.5 Evaluation.13
6 Method C – The spray method.13
6.1 General .13
6.2 Equipment .13
6.3 Measurement procedure .13
6.4 Evaluation.14
7 Documentation.15
Annex A (normative) Guidelines regarding the applicability and comments on the
limitations of the different methods described in this technical specification.16
Annex B (normative) Method A – Contact angle method.18
Annex C (normative) Method B – Surface tension method.19
Annex D (normative) Method C – Spray method.21
Figure 1 – Definition of the static contact angle. 8
Figure 2 – Definition of the advancing angle (θ ) and the receding angle (θ )
a r
inside a liquid drop resting on an inclined solid surface . 9
Figure 3 – Measurements of the advancing angle (θ ) and the receding angle (θ )
a r
by adding or withdrawing water from a droplet.11
Figure B.1 – Measurement of the advancing angle (θ ) and the receding angle (θ )
a r
by using the captive bubble technique.18

TS 62073  IEC:2003(E) – 3 –
Table 1 – Criteria for the determination of wettability class (WC).14
Table C.1 – Concentrations of ethylene-glycol-monoethyl-ether (cellosolve), formamide
mixtures used in measuring surface tension of insulator surfaces in the range 30 mN/m
to 56 mN/m (T = 20 °C).19
Table C.2 – Concentrations of distilled water and formamide mixture used in measuring
surface tension of insulator surfaces in the range 58 mN/m to 73 mN/m (T = 20 °C) .20
Table C.3 – Concentrations of distilled water and sodium chloride in mixtures used
in measuring surface tension of insulator surfaces in the range 73 mN/m to 82 mN/m
(T = 20 °C) .20

– 4 – TS 62073  IEC:2003(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
GUIDANCE ON THE MEASUREMENT OF WETTABILITY
OF INSULATOR SURFACES
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 technical specification may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
The main task of IEC technical committees is to prepare International Standards. In excep-
tional circumstances, a technical committee may propose the publication of a technical
specification when
• 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 62073, which is a technical specification, has been prepared by IEC technical committee
36: Insulators.
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
36/185/DTS 36/197A/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.

TS 62073  IEC:2003(E) – 5 –
The committee has decided that the contents of this publication will remain unchanged until
2006. At this date, the publication will be
• transformed into an International standard;
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
– 6 – TS 62073  IEC:2003(E)
INTRODUCTION
The wetting properties of a surface by water are commonly described by the terms hydrophobic
(or hydrophobicity) and hydrophilic (or hydrophilicity). A hydrophobic surface is water-repellent,
while a surface that is easily wetted by water is hydrophilic.
The wetting phenomenon of a surface is complex and many different parameters can influence
its apparent wettability. Some important parameters include: type of insulator material, surface
roughness, heterogeneities of the surface, chemical composition (e.g. due to ageing) and
presence of pollution. For some of the insulator materials in common use, the wetting
properties can change over time, due to the influence of the ambient conditions. This change
can be either reversible or irreversible. Thus, the result of the measurement of the wettability
may be influenced by the ambient conditions and the HV corona or dry-band arcing to which
the insulator has been previously exposed. This dynamic wetting behaviour is more or less
specific to different insulator materials.
The dynamic wetting behaviour exhibited by insulator materials is due to their chemical
composition. Different processes such as oxidation, hydrolysis, migration of low molecular
weight compounds, formation of complex compounds between e.g. siloxanes and water,
rotation of flexible polymer chains, inter- and intra-molecular rearrangements, microbial growth,
deposition of contaminants, adhesion and encapsulation of contaminant particles, may take
place at different rates, depending on material and ambient conditions. Thus, wettability along
and around an insulator can vary, due to differences in the exposure to solar radiation, rain,
corona discharges, deposited pollution, etc. Therefore, wettability measurement of insulators
should be performed on several separate areas of the insulator.
Measurement of the wettability of a surface is readily performed in the laboratory on well
defined, homogeneous, smooth and planar surfaces of prepared specimens. In the case of
insulators, for which non-destructive measurements are usually required (and where cut-out of
material samples is usually not desired), these conditions do not exist and measurement with
high precision is a difficult task. This is especially true when the measurement has to be
performed on an insulator installed in an overhead line, substation or even in a high voltage
test set-up in the laboratory.

TS 62073  IEC:2003(E) – 7 –
GUIDANCE ON THE MEASUREMENT OF WETTABILITY
OF INSULATOR SURFACES
1 Scope and object
The methods described in this technical specification can be used for the measurement of the
wettability of the shed and housing material of composite insulators for overhead lines,
substations and equipment or ceramic insulators covered or not covered by a coating. The
obtained value represents the wettability at the time of the measurement.
The object of this standard is to describe th
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