IEC 62631-3-1:2016

Dielectric and resistive properties of solid insulating materials - Part 3-1: Determination of resistive properties (DC methods) - Volume resistance and volume resistivity - General method

IEC 62631-3-1:2016 covers a method of test for the determination of volume resistance and volume resistivity of electrical insulation materials by applying a DC voltage. This edition includes the following significant technical changes with respect to the second edition of IEC 60093:
a) IEC 60093 has been completely revised, both editorially and technically, and incorporated into the new IEC 62631 series;
b) test methods have been updated to current day state of the art;
c) volume and surface resistance and resistivity are now separated to appear in this part of IEC 62631 and in IEC 62631-3-2, respectively.

Propriétés diélectriques et résistives des matériaux isolants solides - Partie 3-1: Détermination des propriétés résistives (méthodes en courant continu) - Résistance transversale et résistivité transversale - Méthode générale

L'IEC 62631-3-1:2016 couvre une méthode d'essai pour déterminer la résistance transversale et la résistivité transversale de matériaux isolants électriques en appliquant une tension continue. Cette édition inclut les modifications techniques majeures suivantes par rapport à a deuxième édition de l'IEC 60093:
a) l'IEC 60093 a été entièrement révisée, au niveau éditorial et technique, et insérée dans la nouvelle série IEC 62631;
b) les méthodes d'essai ont été mises à jour à l'état actuel de la technique;
c) les résistances et les résistivités transversales et superficielles sont maintenant séparées pour figurer dans la présente partie de l'IEC 62631 et dans l'IEC 62631-3-2, respectivement.

General Information

• Status: Published
• Publication Date: 22-Mar-2016
• ICS: 17.220.99 - Other standards related to electricity and magnetism
• ICS: 29.035.01 - Insulating materials in general
• ICS: 29.120.99 - Other electrical accessories
• ICS: 29.240.99 - Other equipment related to power transmission and distribution networks
• ICS: 31.060.70 - Power capacitors
• Technical Committee: TC 112 - Evaluation and qualification of electrical insulating materials and systems
• Drafting Committee: WG 4 - TC 112/WG 4
• Current Stage: DELPUB - Deleted Publication
• Start Date: 23-Jan-2023
• Completion Date: 21-Dec-2018

Relations

• Revised: IEC 62631-3-1:2023 - Dielectric and resistive properties of solid insulating materials - Part 3-1: Determination of resistive properties (DC methods) - Volume resistance and volume resistivity - General method
• Effective Date: 05-Sep-2023

Overview

IEC 62631-3-1:2016 is an international standard published by the International Electrotechnical Commission (IEC) that specifies a method for determining the volume resistance and volume resistivity of solid insulating materials using direct current (DC) methods. This standard is part of the IEC 62631 series, which focuses on the dielectric and resistive properties of solid insulating materials. It replaces the earlier IEC 60093 standard with updated, state-of-the-art testing methodologies.

The standard provides comprehensive guidance on the general method for measuring volume resistive properties of electrical insulation materials by applying a DC voltage. It defines relevant terms, outlines equipment and testing procedures, and emphasizes repeatability and reproducibility, ensuring accurate evaluation of insulating materials for electrical applications.

Key Topics

• Scope and Purpose: The method focuses on the electrical characterization of solid insulating materials, essential for ensuring electrical isolation and mechanical integrity in electrical systems.

• Volume Resistance vs. Volume Resistivity:

  • Volume resistance is the measurable resistance due to conduction through the volume of an insulating material, expressed in ohms (Ω).
  • Volume resistivity is the intrinsic property relating volume resistance to the material’s geometry, expressed in ohm-meters (Ω·m).

• Testing Methodology:

  • Application of a DC voltage between electrodes placed on or through the test specimen.
  • Use of guarded electrodes to minimize leakage currents and stray influences.
  • Calibration requirements for accuracy and quality control of measuring equipment.
  • Sample preparation, including size, conditioning, and manufacturing considerations, to ensure consistent and representative results.

• Environment and Conditioning:

  • Importance of controlling environmental factors such as temperature and humidity, as these significantly affect resistivity measurements.

• Measurement and Calculation:

  • Procedures for recording volume resistance over time, considering effects like dielectric polarization.
  • Calculations converting resistance values into volume resistivity for material comparison and qualification.

• Reporting and Verification:

  • Comprehensive test report requirements including specimen details, test conditions, equipment used, and observed measurement data.
  • Emphasis on repeatability and reproducibility to validate testing outcomes.

Applications

IEC 62631-3-1:2016 is vital for manufacturers, researchers, and quality control laboratories involved in the development and certification of electrical insulating materials. Key applications include:

• Material Selection: Assisting engineers in choosing appropriate solid insulating materials based on volume resistivity for specific electrical and environmental conditions.

• Quality Assurance: Verifying consistency and compliance of insulating materials during production to meet international electrical safety standards.

• Research and Development: Supporting innovation in advanced insulating materials that require precise electrical characterization.

• Electrical Equipment Manufacturing: Ensuring insulation components in transformers, cables, capacitors, and other electrical devices meet performance requirements.

Related Standards

IEC 62631-3-1:2016 references and is complemented by several other international standards, including:

• IEC 62631 Series:

  • Part 3-2 focuses on surface resistance and surface resistivity of insulating materials using DC methods.
  • Other parts address dielectric properties and test methods relevant to electrical insulation.

• IEC 60212: Specifies standard conditions during testing to ensure uniformity.

• IEC 60455 and IEC 60464: Address resin and varnish materials used for electrical insulation.

• IEC 61212: Covers industrial materials such as rigid laminated tubes and rods based on thermosetting resins.

• ISO 868: Details the determination of indentation hardness (Shore hardness) which can relate to mechanical characteristics of insulating materials.

These standards collectively provide a full framework for the evaluation, specification, and quality assurance of solid insulating materials used in electrical and electronic industries.

---

By adhering to IEC 62631-3-1:2016, stakeholders ensure reliable, internationally recognized methods for assessing the volume resistive properties of insulating materials-critical for safety, performance, and longevity in electrical applications. This standard promotes consistency and comparability in test results, enabling informed decisions and fostering innovation in electrical insulation technology.

Standards Content (Sample)

IEC 62631-3-1 ®
Edition 1.0 2016-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Dielectric and resistive properties of solid insulating materials –
Part 3-1: Determination of resistive properties (DC methods) – Volume
resistance and volume resistivity – General method

Propriétés diélectriques et résistives des matériaux isolants solides –
Partie 3-1: Détermination des propriétés résistives (méthodes en courant
continu) – Résistance transversale et résistivité transversale – Méthode générale

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IEC 62631-3-1 ®
Edition 1.0 2016-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Dielectric and resistive properties of solid insulating materials –

Part 3-1: Determination of resistive properties (DC methods) – Volume

resistance and volume resistivity – General method

Propriétés diélectriques et résistives des matériaux isolants solides –

Partie 3-1: Détermination des propriétés résistives (méthodes en courant

continu) – Résistance transversale et résistivité transversale – Méthode générale

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220.99; 29.035.01 ISBN 978-2-8322-3254-5

– 2 – IEC 62631-3-1:2016  IEC 2016
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references. 5
3 Terms and definitions . 5
4 Significance . 6
5 Method of test . 6
5.1 General . 6
5.2 Power supply, voltage . 6
5.3 Equipment . 7
5.3.1 Accuracy . 7
5.3.2 Guarding . 7
5.3.3 Electrodes . 8
5.4 Calibration . 10
5.5 Test specimen . 10
5.5.1 General . 10
5.5.2 Recommended dimensions of test specimens and electrode
arrangements . 10
5.5.3 Manufacturing of test specimens . 11
5.5.4 Number of test specimen . 11
5.5.5 Conditioning and pre-treatment of test specimen . 11
5.6 Procedures for specific materials . 11
6 Test procedure . 11
6.1 General . 11
6.2 Measurement of volume resistance . 11
6.3 Calculation of volume resistivity . 12
7 Test report. 12
8 Repeatability and reproducibility . 12
Bibliography . 13

Figure 1 – Basic connection for guarded electrodes . 8
Figure 2 – Specimen with liquid electrodes . 9

Table 1 – Test specimen . 10

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DIELECTRIC AND RESISTIVE PROPERTIES
OF SOLID INSULATING MATERIALS –

Part 3-1: Determination of resistive properties (DC methods) –
Volume resistance and volume resistivity – General method

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62631-3-1 has been prepared by IEC technical committee TC 112:
Evaluation and qualification of electrical insulating materials and systems.
This first edition of IEC 62631-3-1 cancels and replaces the second edition of IEC 60093,
published in 1980. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the second
edition of IEC 60093:
a) IEC 60093 has been completely revised, both editorially and technically, and incorporated
into the new IEC 62631 series;
b) test methods have been updated to current day state of the art;
c) volume and surface resistance and resistivity are now separated to appear in this part of
IEC 62631 and in IEC 62631-3-2, respectively.

– 4 – IEC 62631-3-1:2016  IEC 2016
The text of this standard is based on the following documents:
FDIS Report on voting
112/339/FDIS 112/350/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 62631 series, published under the general title Dielectric and
resistive properties of solid insulating materials, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
DIELECTRIC AND RESISTIVE PROPERTIES
OF SOLID INSULATING MATERIALS –

Part 3-1: Determination of resistive properties (DC methods) –
Volume resistance and volume resistivity – General method

1 Scope
This part of IEC 62631 covers a method of test for the determination of volume resistance and
volume resistivity of electrical insulation materials by applying a DC voltage.
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 60212, Standard conditions for use prior to and during the testing of solid electrical
insulating materials
IEC 60455 (all parts), Resin based reactive compounds used for electrical insulation
IEC 60464 (all parts), Varnishes used for electrical insulation
IEC 61212 (all parts), Industrial materials – Industrial rigid round laminated tubes and rods
based on thermosetting resins for electrical purposes
ISO 868, Plastics and ebonite – Determination of indentation hardness by means of a
durometer (Shore hardness)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
volume resistance
part of the insulation resistance which is due to conduction through the volume
Note 1 to entry: Volume resistance is expressed in the unit of Ω.
3.2
volume resistivity
volume resistance of a material related to its volume
Note 1 to entry: Volume resistivity is expressed in the unit of Ωm.
Note 2 to entry: For insulating materials, the volume resistivity is usually determined by means of measuring
electrodes arranged on a sheet of the material.
Note 3 to entry: According to IEC 60050-121: Electromagnetism, “conductivity” is defined as “scalar or tensor
quantity, the product of which by the electric field strength in a medium is equal to the electric current density” and
“resistivity” as “the inverse of the conductivity when this inverse exists”. Measured in this way, the volume

– 6 – IEC 62631-3-1:2016  IEC 2016
resistivity is an average of the resistivity over possible heterogeneities in the volume incorporated in the
measurement; it includes the effect of possible polarization phenomena at the electrodes.
3.3
stray current
leakage current in the earth or in metallic structures buried in the ground and resulting from
their intended or unintended earthing
4 Significance
Insulating materials are used in general to electrically isolate components of an electrical
system from each other and from earth. Solid insulating material may also provide mechanical
support. For these purposes it is generally desirable to have the insulation resistance as high
as possible, consistent with acceptable mechanical, chemical and heat resistance properties.
Volume resistance is a part of the insulating resistance.
Volume resistivity can be used as an aid in the choice of an insulating material for a specific
application. The change in resistivity with temperature and humidity may be great and has to
be known when designing for operation conditions.
When a direct voltage is applied between electrodes in contact with a specimen, the current
through it decreases asymptotically towards a steady-state value. The decrease of current
with time may be due to dielectric polarization and the sweep of mobile ions to the electrodes.
For materials having volume resistivity less than about 10 Ωm the steady state is generally
reached within 1 min and the resistance is determined after this time of electrification. For
materials with higher volume resistivity the current may continue decreasing for several
minutes, hours, days or even weeks. For such materials, therefore, longer electrification times
may be necessary.
NOTE For very high electric field strengths different behaviour can occur.
5 Method of test
5.1 General
This general method describes common values for general measurements. If a method for a
specific type of material is described in this standard, the specific method shall be used.
The measurement of volume resistance (and volume resistivity respectively) shall be carried
out carefully and taking into account the electric properties of the measuring circuit as well as
the specific electric properties of the material.
To carry out the test, in most cases the use of high voltages is necessary. Care shall be taken
to prevent electric shock.
Polarization effects can influence the measurement. Therefore it is not acceptable to achieve
the measured resistance twice in two consecutive experiments without a sufficient space of
time in-between.
NOTE For materials with volume resistance of not more than 10 Ω a period of 1 h after voltage application might
be sufficient.
5.2 Power supply, voltage
A source of very steady direct voltage is required. This may be provided either by batteries or
by rectified and stabilized power supply. The degree of stability required is such that the
change in current due to any change in voltage is negligible compared with the current to be
measured.
-5
NOTE 1 The ripple of the voltage source is important. A typical value for 100 V is <5 × 10 peak to peak.
Commonly specified test voltages to be applied to the complete specimen are 10 V, 100 V,
500 V, 1 000 V, and 10 000 V.
If not otherwise stipulated, a voltage of 100 V is to be used.
NOTE 2 In air, below 340 V no partial discharges will occur. Partial discharge can lead to erroneous
measurements of the resistance when a specific inception voltage is exceeded.
5.3 Equipment
5.3.1 Accuracy
Any suitable equipment may be used. The measuring device should be capable of
determining the unknown resistance with an overall accuracy of at least
• ±10 % for resistances below 10 Ω,
10 14
• ±20 % for resistances between 10 Ω and 10 Ω,
• ±50 % for values higher than 10 Ω.
5.3.2 Guarding
The insulation of the measuring circuit is composed of materials which, at best, have
properties comparable with those of the material under test. Errors in the measurement of the
specimen may arise from:
• stray current from spurious external voltages which are usually unknown in magnitude and
often sporadic in character;
• inadequate shunting of the specimen resistance, reference resistors or the current
measuring device by insulation, having resistance of unknown, and possibly variable
magnitude;
• the surface resistance may be lower than the volume resistance by one order of
magnitude.
An approximate correction of these difficulties may be obtained by making the insulation
resistance of all parts of the circuit as high as possible under the conditions of use. This may
lead to unwieldy apparatus which is still inadequate for measurement of insulation resistances
higher than the magnitude of some hundred MΩ. A more satisfactory correction is obtained by
using the technique of guarding.
Guarding depends on interposing, in all critical insulated parts, guard conductors which
intercept all stray currents that might otherwise cause errors. The guard conductors are
connected together, constituting the guard system and forming with the measuring terminals a
three terminal network. When suitable connections are made, stray currents from spurious
external voltages are shunted away from the measuring circuit by the guard system, the
insulation resistance from either measuring terminal to the guard system shunts a circuit
element which should be of very much lower resistance, and the specimen resistance
constitutes the only direct path between the measuring terminals. By this technique the
probability of error is considerably reduced. The basic connections for guarded electrodes
used for volume resistance is shown in Figure 1.

– 8 – IEC 62631-3-1:2016  IEC 2016

IEC
Figure 1 – Basic connection for guarded electrodes
NOTE Dimensions of specimen are given in 5.5
Voltages (e.g. electrochemically or thermally induced) between guard and guarded terminals
can be compensated if they are small. Care shall be taken so that such voltages do not
introduce significant errors in the measurements.
Errors in the measurement of current may result from the fact that the current-measuring
device is shunted by the resistance between the guarded terminal and the guard system. To
ensure satisfactory operation of the equipment, a measurement should be made with the lead
from the voltage source to the specimen disconnected. Under this condition, the equipment
should indicate infinite resistance within its sensitivity. If suitable standards of known values
are available, they may be used to test the operation of the equipment.
5.3.3 Electrodes
5.3.3.1 General
The electrodes for insulating materials should be of a material that is readily applied, allows
intimate contact with the specimen surface and introduces no appreciable error because of
electrode resistance or contamination of the specimen. The electrode material should be
corrosion resistant under the conditions of the test. The electrodes shall be used with suitable
backing plates of the given form and dimensions. It may be advantageous to use two different
electrode materials or two methods of application to see if any significant error is introduced.
The following are typical electrode materials that may be used.
5.3.3.2 Conductive silver paint
Certain types of commercially available, high-conductivity silver paints, either air-drying or
low-temperature-baking varieties are sufficiently porous to permit diffusion of moisture
through them and thereby allow the test specimens to be conditioned after application of the
electrodes. This is a particularly useful feature in studying resistance-humidity effects as well
as changes with temperature. However, before conductive paint is used as an electrode
material, it should be established that the solvent in the paint does not affect the electrical
properties of the specimen. Reasonably smooth edges of guard electrodes may be obtained
with a fine-bristle brush. However, for circular electrodes, sharper edges may be obtained by
the use of a compass for drawing the outline circles of the electrodes and filling in the
enclosed areas by brush. Clamp-on masks may be used if the electrode paint is sprayed on.
5.3.3.3 Evaporated or sputtered metal
Evaporated or sputtered metal can be used where it can be shown that the material is not
affected by ion bombardment, temperature stress or vacuum treatment.

5.3.3.4 Liquid electrodes
Liquid electrodes can be used and give satisfactory results. The liquid forming the upper
electrode should be confined, for example, by stainless steel rings, each of which should have
its lower rim reduced to a sharp edge by bevelling on the side away from the liquid. Figure 2,
shows the electrode arrangement. Alloys e.g. containing gallium, indium and tin which are
liquid at room temperature had been proved as suitable. Mercury is not recommended.
IEC
Key
1 Measurement electrode
2 Specimen
3 Guard electrode
4 Liquid metal electrode
Figure 2 – Specimen with liquid electrodes
5.3.3.5 Colloidal graphite
Colloidal graphite dispersed in water or other suitable medium, may be used under the same
conditions as given for conductive silver paint.
5.3.3.6 Conducting rubber
Conducting rubber may be used as an electrode material. It has the advantage that it can be
applied and removed from the specimen quickly and easily. As the electrodes are applied only
during the time of measurement they do not interfere with the conditioning of the specimen.
The resistance of the rubber electrode shall be less than 1 000 Ω.
The conducting rubber material shall be soft enough to ensure that effective contact to the
specimen is obtained when a reasonable pressure, for example 2 kPa (0,2 N/cm ), is applied.
Shore A hardness according to ISO 868 in the range of 65 to 85 has been found suitable.
NOTE Results of resistivity measurements obtained with the application of electrodes made of conducting rubber
are always higher (few tens to few hundreds %) in comparison to that obtained for metallic electrodes.
5.3.3.7 Metal foil
Metal foil can be applied to specimen surfaces as electrodes for volume resistance
measurement, but it is not suitable for surface resistance measurement. Aluminum and tin foil
are in common use. They are usually attached to the specimen by a minimum quantity of
petrolatum, silicone grease, oil or other suitable material, as an adhesive.

– 10 – IEC 62631-3-1:2016  IEC 2016
All adhesive materials may be of influence to the measurement results and should be
minimized.
NOTE A pharmaceutically obtainable jelly of the following composition is suitable as a conductive adhesive:
– anhydrous polyethylene glycol of molecular mass 600 to 800 parts by mass;
– water: 200 parts by mass;
– soft soap (pharmaceutical quality): 1 part by mass;
– potassium chloride: 10 parts by mass;
Soft soap is a non-corrosive, neutral soap used for medical purposes.
The electrodes shall be applied under a smoothing pressure sufficient to eliminate all wrinkles
and to work excess adhesive towards the edge of the foil where it can be wiped off with a
cleansing tissue. Rubbing with a soft material such as the finger, has been used successfully.
This technique can be used satisfactorily only on specimens that have very smooth surfaces.
With care, the adhesive film can be reduced to 0,002 5 mm or less.
5.4 Calibration
The equipment shall be calibrated in the magnitude of the volume resistance measured.
NOTE Calibration resistors in the range up to 100 TΩ are commercially available.
5.5 Test specimen
5.5.1 General
The specimen under test shall have a thickness close to their application.
If not otherwise specified, a plate ≥ 100 mm × ≥ 100 mm × (1 mm ± 0,5 mm) is recommended.
5.5.2 Recommended dimensions of test specimens and electrode arrangements
If not otherwise stipulated in the relevant product standard, the following dimensions, as
shown in Table 1, for test specimens are recommended:
Table 1 – Test specimen
Type of product Recommended dimensions Remarks
of test specimen
Thermoplastic moulding
components
Thermosetting moulding
components
Long fibre reinforced polyester and
100 mm × 100 mm × (3 to 5) mm
vinyl ester moulding components
(SMB BMC)
Epoxy based sheets and laminates
Impregnating resins and varnishes See IEC 62631-3-11 Materials described in
IEC 60455 and IEC 60464
Casting resins Materials described in IEC 60455
Pipes, bars, rods Materials described in IEC 61212
Elastomeric material 100 mm × 100 mm × 3 mm

5.5.3 Manufacturing of test specimens
The production and shape of the test specimens shall be determined by the relevant
standards for the material. During removal and production of the specimens the condition of
the material shall not be changed and the specimen shall not be damaged.
If the surface of the test specimen is machined at the contact areas of the electrodes, the type
of machining shall be specified in the test report. The test specimens shall have a
geometrically simple shape (e.g. plate with parallel measuring areas, cylinder etc.).
Specimens from products shall be prepared with the product thickness, if possible.
5.5.4 Number of test specimen
The number of specimens to be tested shall be determined by the relevant product standards.
If no such data is available, at least three specimens shall be tested.
5.5.5 Conditioning and pre-treatment of test specimen
Conditioning and any other pre-treatment of the test specimens shall be carried out according
to the relevant product standard. If no product standard exists, conditioning shall be done for
at least 4 days at 23 °C and 50 % r.h. according to IEC 60212 (standard climate B).
5.6 Procedures for specific materials
Specific materials are described in material specifications. IEC 60455-2, IEC 60464-2 and
IEC 61212-2 contain methods of test. If a specific procedure for a specified material exists,
this specification shall be used.
6 Test procedure
6.1 General
A number of specimens as described in the relevant specification shall be prepared. If not
otherwise specified, 3 specimens shall be tested. Thickness of the sample should be
measured at least at 5 points before application of the electrodes. The thickness of the
specimens and electrode dimensions shall be measured with an accuracy of ±1 %.
6.2 Measurement of volume resistance
Before measurement, the specimen shall be brought into an electrically stable condition. To
obtain this, short-circuit the measuring electrodes of the specimen through the measuring
device and observe the changing short-circuit current, while increasing the sensitivity of the
current measuring device. The short-circuit current shall attain a fairly constant value. If not
otherwise stipulated, the volume resistance shall be determined after a fixed time of
electrification of 1 min. Before the measurement, the specimen shall be stored for at least
24 h under climate conditions
It is not allowed to repeat the measurement unless the specimen is brought into a stable
condition again.
Where the time-dependent behavior of the material under test is of interest, apply the
specified direct voltage and start a timing device simultaneously. Unless otherwise specified,
a measurement is taken after each of the following times of electrification: 1 min, 2 min,
5 min, 10 min, 50 min and 100 min. If two successive measurements give the same results,
the test shall be terminated.
– 12 – IEC 62631-3-1:2016  IEC 2016
6.3 Calculation of volume resistivity
The volume resistivity shall be calculated from the following formula:
A
ρ= R ×
x
h
where
ρ is the volume resistivity in Ωm;
R is the volume resistance measured in Ω;
x
A is the effective area of the electrode in m ;
h is the thickness of the specimen in m (average).
7 Test report
The test report shall include the following:
– complete identification and description of the material tested, including source and
manufacturer’s code;
– shape and thickness of test specimens;
– test voltage;
– accuracy of the instrument and calibration method, depending on the measured values of
resistance, if necessary;
– curing conditions of the material and any pre-treatment;
– conditioning of samples and climatic conditions under test;
– description of test set-up and instrument used for the test;
– number of samples;
– date of test;
– each single value and the median of volume resistance and volume resistivity,
respectively;
– ambient conditions during testing;
– any other important observations if applicable.
8 Repeatability and reproducibility
Measurements of volume resistance and volume resistivity are dependent on numerous
aspects. Experience have shown that the reproducibility is in the range of > 50 % (of the
measured value).
The repeatability is between 20 % and 50 %.
NOTE Repeatability and reproducibility are under consideration. IEC TC112 WG4 is going to perform a round
robin test to specify the repeatability and reproducibility with more precision.

Bibliography
IEC 60050-121, International Electrotechnical Vocabulary – Part 121: Electromagnetism
(available at http://www.electropedia.org)
IEC 62631-3-11, Dielectric and resistive properties of solid insulating materials – Part 3-11:
Determination of resistive properties (DC methods) – Volume resistance and volume
resistivity – Method for impregnation and coating materials

_____________
______________
Under consideration.
– 14 – IEC 62631-3-1:2016  IEC 2016
SOMMAIRE
AVANT-PROPOS . 15
1 Domaine d'application . 17
2 Références normatives . 17
3 Termes et définitions . 17
4 Portée . 18
5 Méthode d’essai . 18
5.1 Généralités . 18
5.2 Tension d'alimentation . 19
5.3 Equipements . 19
5.3.1 Précision . 19
5.3.2 Dispositifs de garde . 19
5.3.3 Electrodes . 20
5.4 Étalonnage . 22
5.5 Spécimen d'essai . 22
5.5.1 Généralités . 22
5.5.2 Dimensions recommandées pour les spécimens d'essai et les
agencements des électrodes . 22
5.5.3 Fabrication de spécimens d'essai . 23
5.5.4 Nombre de spécimens d'essai . 23
5.5.5 Conditionnement et prétraitement du spécimen d'essai . 23
5.6 Procédures pour matériaux spécifiques . 23
6 Procédure d'essai . 24
6.1 Généralités . 24
6.2 Mesure de la résistance transversale . 24
6.3 Calcul de la résistivité transversale . 24
7 Rapport d'essai . 24
8 Répétabilité et reproductibilité . 25
Bibliographie . 26

Figure 1 – Connexions de base d'électrodes gardées . 20
Figure 2 – Spécimen avec électrodes liquides . 21

Tableau 1 – Spécimen d'essai . 23

COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE
____________
PROPRIÉTÉS DIÉLECTRIQUES ET
RÉSISTIVES DES MATÉRIAUX ISOLANTS SOLIDES –

Partie 3-1: Détermination des propriétés
résistives (méthodes en courant continu) –
Résistance transversale et résistivité transversale – Méthode générale

AVANT-PROPOS
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de brevets et de ne pas avoir signalé leur existence.
La Norme internationale IEC 62631-3-1 a été établie par le comité d'études 112 de l’IEC:
Evaluation et qualification des systèmes et matériaux d'isolement
...